Role of p53/miR-155-5p/sirt1 loop in renal tubular injury of diabetic kidney disease

Role of p53/miR-155-5p/sirt1 loop in renal tubular injury of diabetic kidney disease Background: Diabetic kidney disease is a renal microvascular disease caused by diabetes, known as one of the most serious and lethal complications of diabetes. Early renal hypertrophy is the main pathological feature, which gradually leads to the deposition of glomerular extracellular matrix and tubulointerstitial fibrosis, eventually developing irrevers‑ ible structural damage to the kidneys. Autophagy is a cell self‑ homeostatic mechanism that is activated under stress conditions and may serve as a protective response to the survival of renal fibrogenic cells. MicroRNA (miRNA) network may be involved in the regulation of fibrosis. The purpose of this study is to assess how miRNAs regulate diabetic kidney disease and autophagy and fibrosis in renal proximal tubular cells under high glucose conditions. Methods: Human renal proximal tubular (HK‑ 2) cells were exposed to high glucose in vitro. Bioinformatic analy‑ sis was used to select the candidate gene for potential target regulation of miR‑ 155, Sirt1. ATG5, ATG7 is the key to autophagosome formation, regulated by Sirt1. p53 regulates miR‑ 155 expression as a transcription factor. MiR‑ 155 overexpression and inhibition were achieved by transfection of miR‑ 155 mimic and inhibit to evaluate its effect on Sirt1 and autophagy and fibrosis markers. Dual luciferase reporter assays were used to confirm the direct interaction of Sirt1 with miR‑ 155. Overexpression and inhibition of Sirt1 gene were achieved by transfection of Sirt1 plasmid and Sirt1 si to observe its effect on P53. Chip assay experiments confirmed the direct regulation of P53 on miR ‑ 155. Results: Under high glucose conditions, miR‑ 155 was detected in HK‑ 2 cells in concentration gradient, increased expression of p53 and down‑ regulated expression of sirt1 and autophagy‑ associated proteins LC3II, ATG5 and ATG7. Dual luciferase reporter assays indicate that miR‑ 155 can target its binding to the Sirt1 3′UTR region to reduce its expression. Under high glucose conditions, over expression of miR‑ 155 decreased the expression of LC3‑ II and ATG5 in HK‑ 2 cells, while inhibition of miR‑ 155 reversed this effect. Using chip assay testing in HK ‑ 2 cells, we demonstrated that p53 binds directly to miR‑ 155. Conclusions: The signaling axis of p53, miR‑ 155‑ 5p, and sirt1 in autophagic process might be a critical adapting mechanism for diabetic kidney injury. Keywords: Diabetic kidney disease, HK‑ 2, miRNA, miR‑ 155‑ 5p, Sirt1, p53, Autophagy postpone the development of diabetic kidney disease is Background particularly important. Despite the control of blood glu- Diabetic kidney disease (DKD) is one of the most com- cose, blood pressure and blood lipids, such as proteinu- mon and devastating complications of diabetes [1]. It ria and other comprehensive treatment, but the current is also the high risk factors of end-stage renal disease clinical efficacy is still poor. Because of the complicated (ESRD) and significantly increases the risk of diabetes metabolic disorder in patients, it is more difficult for Patient’s mortality rate. Diabetes has become a global DKD to progress to end-stage treatment, which is one of health problem, for the prevention of complications, the important reason of death in patients [2]. Therefore, looking for an earlier and more effective new target for *Correspondence: xueyaoming999@126.com prevention and treatment of diabetic nephropathy, pre- Department of Endocrinology and Metabolism, Nanfang Hospital, venting or delaying the progress of DKD is a problem that Southern Medical University, Guangzhou, Guangdong, China © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/ publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Wang et al. J Transl Med (2018) 16:146 Page 2 of 9 the medical profession has so far failed to solve, exploring Methods the pathogenesis of DKD in search of new and effective Cell culture prevention and treatment methods has important medi- 10% FBS (Gibco, NZL) was supplemented in MEM cal and social research value [3, 4]. (Gibco, Invitrogen) and human renal proximal tubule MicroRNA is a single-stranded, non-coding RNA (HK-2) cells were cultured at 37 °C and 5% The medium about 22-24 nucleotides in length that can degrade or was changed every 2 days, waiting for HK-2 cells to grow inhibit protein translation by specifically binding to the to 60% and then starved for 24  h in a medium supple- 3 ‘non-coding region of the target gene mRNA. The bind - mented with MEM (Gibco, Invitrogen) supplemented ing mechanism is very flexible and complex [5]. Recent with 2% FBS (Gibco, NZL). Group 1: (normal glucose) research, miR-155-5p is observed significantly increased normal glucose concentration (5.5  mmol/l) medium in Diabetic kidney disease patients’ kidney tubules [6] as a control. Group 2: normal cell culture medium sup- and can aggravate renal fibrosis in patients with acute plemented with high glucose (11  mM) medium. Group kidney injury [7]. The mechanism of microRNA expres - 3: normal cell culture medium supplemented with high sion changes is focused on the control of transcriptional glucose (20  mM) medium. Group 4: normal cell cul- activity by the binding of transcription factors to promot- ture medium supplemented with high glucose (30  mM) ers. It is noteworthy that there is literature describing that medium as high glucose stimulation group. All cells were p53 promotes the expression of miR-155-5p in tumor incubated with medium for 72 h. To observe the expres- cells and tissues [8]. Therefore, we hypothesize that the sion of miR-155-5p in all groups. And to observe the p53/miR-155-5p loop may be involved in the regulation expression of Sirt1, P53, autophagy and fibrosis related of the injury process of renal tubular cells under high glu- factors in both 1 and 4 groups. cose conditions. MicroRNA regulates gene expression by inhibiting the Quantitative real‑time RT‑PCR translation process, cutting and degrading mRNA, and We extracted total RNA from HK-2 cells using a phenol– reducing mRNA stability. We tried to find the target gene chloroform extraction protocol and used to determine for miR-155-5p [9]. There is growing evidence that Sirt1 the purity and concentration of RNA after NANODROP is under the control of microRNAs such as miR-199 [10], 2000 DEPC water was zeroed. After RNA was uni- miR-200 [11] and miR-22 [12]. We predicted the exist- formly diluted to 100  ng/μl, cDNA was reverse tran- ence of binding sites between the miR-155-5p and Sirt1 scribed. Quantitative real-time RT-PCR was performed 3′UTR regions by the online bioinformatics analysis (Tar- on a LightCycler 480 (Roche, CH). PCR reaction system getScan) [13]. for 1 μl cDNA, 0.2 nM of each primer, 3.6 μl SBRE then Sirt1 is the most famous member of the silent informa- RNase-free water to make a total amount of 10 μl. Using tion regulator 2 family,when we detect patients with dia- GAPDH as an internal control, the resulting CT values betic nephropathy (DKD) or study DKD animal models, for Sirt1, p53 and autophagy-related markers of fibrosis. we find that the expression of Sirt1 in renal cells tends to The primers we used are showed in Table 1. decrease, and further studies have found that increasing the expression of SIRT1 can be constructed well. Kid- Western blotting ney protection is provided in animal models with DKD Using western blotting to detect the expression level of disease [14, 15]. SIRT1 can exert anti-apoptosis, anti- Sirt1 and P53 and the expression of autophagy-related oxidation and anti-inflammatory effects in cell injury proteins LC3II and p62. Briefly, the extracted protein and protect cells by regulating mitochondrial biogenesis, samples were mixed with SDS-PAGE and boiled in boil- autophagy and metabolism in response to cellular energy ing water for 5  min to denature. The isolated protein and redox state. Specifically, SIRT1 can directly de-acety - was then electrophoretically transferred to a polyvi- late key proteins (Atg) of autophagy, such as Atg5, Atg7, nylidene difluoride (PVDF) membrane (0.45  mm) (Mil - and Atg8, to remove them from the inhibitory state, lipore, USA). Incubate with 5% skim milk in TBS for 1 h thereby promoting autophagy [16]. At the same time, to block non-specific proteins. The primary antibodies SIRT1 can also deactivate transcriptional activity of p53, used include the following: Sirt1, p53, LC3 II, p62, FN, thereby inhibiting its function. Col-1 and GAPDH. After incubating for 2 h at room tem- In summary, we investigated the mechanism of p53/ perature with pre-prepared rabbit secondary antibody miR-155-5p/Sirt1 loop in high glucose-induced tubular (1: 5000; Santa Cruz biotechnology, USA) and mouse epithelial cell injury in vitro. secondary antibody (1: 5000; Santa Cruz biotechnology, Wang et al. J Transl Med (2018) 16:146 Page 3 of 9 Table 1 Sequences of primers for qRT-PCr in this study plasmid or Sirtl si was mixed with 250 μl Opti-MEM at a 1  μg target dose (plasmid group supplemented Gene Sequences with 10 μl P3000TM Reagent/well). The two mixtures Sirt1 Sense 5′‑AGT TCC AGC CGT CTC TGT GT‑3′ were then mixed for 5  min and then added to the Antisense 5′‑CTC CAC GAA CAG CTT CAC AA‑3′ cell culture medium for further 48 h at 37 °C in a 5% Atg5 Sense 5′‑TGT GCT TCG AGA TGT GTG GTT‑3′ CO incubator. Protein or total RNA was extracted Antisense 5′‑ACC AAC GTC AAA TAG CTG ACTC‑3′ from the cell collection plate for subsequent experi- Atg7 Sense 5′‑ACC CAG AAG AAG CTG AAC GA‑3′ ments. The changes of Sirt1 expression were verified Antisense by western blot and q-PCR. The expression of p53, 5′‑CTC ATT TGC TGC TTG TTC CA‑3′ ATG5, LC3 II, p62 and fibrosis related genes were Col‑1 Sense 5′‑TCA AGA CAC GTT CCC GTG AG‑3′ observed after validation. Antisense 5′‑GCC AAC TTC TCC AGC GGT A‑3′ GAPDH Sense 5′‑GAA CGG GAA GCT CAC TGG ‑3′ Antisense 5′‑GCC TGC TTC ACC ACC TTC T‑3′ Luciferase reporter gene assay miR‑155‑5p Sense 5′‑GCC TCC AAC TGA CTC CTA CA‑3′ We used PCR to amplify the miR-155-5p and Sirt1′ 3′ Antisense Universal reverse primer ( Tiangen, Beijing, UTR binding sites (primer: forward: 5′-CCG CTC GAG China) TGT AAT AAT TGT GCA GGT ACA G-3′; reverse: 5′-ATT U6 Sense 5′‑CTC GCT TCG GCA GCACA‑3′ T G C G G C C G C A A A GT T A GT GT T GA G T T T GTA C - Antisense Universal reverse primer ( Tiangen, Beijing, 3′) from HK-2 cell genomic DNA. The amplified Sirt1 China) 3′UTR fragment was inserted into the psi-Check2 vec- tor (Ribobio, Guangzhou, China) respectively, using the XhoI and NotI restriction sites. HK-2 cells were setted in USA) and using chemiluminescence (ECL) Imaging 24-well plates at 60% density treated by MEM medium Analysis System Exposure photography. Relative protein containing 2% Gibico fetal calf serum for 24 h. After this, stripe density through the image inspection software cells were co-transfected with psi-Check2 (0.5  μg) con- quantity one for testing and analysis. structed with Sirt1 and miR-155-5p binding sites with miR-155-5p mimics/inhibitors, MEM medium contain- Transfection ing 30 nm d-glucose and 10% Gibico fetal bovine serum 1. To effect changes in miR-155-5p expression, HK-2 was used to groom. Cells were harvested 48 h after trans- cells were treated with miR-155-5p mimic/inhibit fection, dual luciferase assay system was used to analyze (bought from ribobio Biotechnology company, the luminescence. Guangzhou China) using both LipofectamineTM 3000 as a transfection reagent and a non-sense strand negative control (NC) as a control. Briefly, Chip assay cells were starved overnight in 12-well plates at 60% The presence of p53 binding sites in the promoter density prior to transfection. Lipofectamine 3000 region of miR-155-5p was predicted by software. Using was mixed with 50  μl Opti-MEM, meanwhile, miR- a Chip assay, in brief, cells were treated with 1% forma- 155-5p mimic/inhibit was mixed with 100  μl Opti- lin and sonicated to collect soluble chromatin superna- MEM. The two mixtures were then mixed for 5 min tants at 14,000g for 10  min at 4  °C. Anti-p53 antibodies and then added to the cell culture medium and left to (Santa Cruz Biotechnology, USA.) Overnight, mouse incubate for 48 h at 37 °C in 5% CO . Collect cells for IgG immunoprecipitated as a negative control. Immune protein or total RNA extraction. q-PCR was used to complexes were washed and DNA samples were obtained validate the up-regulation of miR-155-5p. After veri- with a QIAquick Gel Extraction Kit (QIAGEN, Ger). We fication, the expression of Sirt1, p53, ATG5, LC3II, use qRT-PCR to analysis the recovered DNA by using p62 and fibrosis related genes were detected by west - primers containing the miR-155-5p promoter region and ern blot and q-PCR. the P53 binding site. (primer: forward: 5′-CCG CAT GTG 2. To achieve changes in Sirt1 expression, HK-2 cells CAT ACA CAA AC-3′; reverse: 5′-CAT TTA GGA TAC were treated with Sirt1 plasmid or Sirt1 si using TAC TGA TAA ATC -3′). LipofectamineTM 3000 as transfection reagent and non-sense strand negative control (NC) as controls. Statistical analysis Similar to the experiment described in the previous All of the experimental data obtained in this study were phase, cells were starved overnight in 6-well plates entered using Excel spreadsheet software. Use SPSS 20 at 60% density prior to transfection. Lipofectamine software to accomplish statistical analysis. Statistical 3000 was mixed with 125  μl Opti-MEM while Sirtl results were expressed as mean ± standard error of mean. Wang et al. J Transl Med (2018) 16:146 Page 4 of 9 Use independent means t test to compare the mean of (30  mM). P53 expression was increased by stimulat- the two samples. Use One-way ANOVA to compare mul- ing high concentrations of glucose (30  mM). Western tiple groups. P < 0.05 was statistically significant. blot results showed that after high glucose stimulation (30  mM), we observed changes in autophagy-related Results expression, with a significant decrease in LC3 II and a High glucose stimulates the general measurement of HK2 significant increase in p62. After high glucose stimulation cells (30 mM), the fibrosis index FN, Col-1 also increased sig - The expression of miR-155-5p is significantly increased nificantly (Fig. 1). in patients with diabetic nephropathy. Explore what role miR-155-5p plays in renal tubular injury. We chose HK-2 MiR‑155‑5p directly regulates Sirt1 cells as an in  vitro experimental model. The test was Aberrant expression of miR-155-5p was confirmed divided into four groups, the normal glucose (5.5  mM) in HK-2 cells, and we then verified whether Sirt1 was group and the gradient high glucose group (11  mM, directly regulated by miR-155-5p expression. We 20 nM, 30 mM). After culturing the HK-2 cells for 72 h, change miR-155-5p expression level by Transferring total RNA and protein were extracted for analysis. We miR-155-5p mimic or inhibit into HK-2 cells. After found that the expression level of MiR-155-5p in HK-2 transferring miR-155-5p mimic in HK-2 cells, miR- cells was gradually up-regulated with the increase of glu- 155-5p levels were significantly increased by 61.006- cose concentration (11  mM, 20  nM, 30  mM) compared fold, whereas the Sirt1 mRNA and protein expression to the cells treated with normal glucose (5.5  mM). Sirt1 was diminished contrast with the NC group (Fig.  2a). expression was significantly inhibited by high glucose The reverse trend was discovered in HK-2 cells after Fig. 1 High glucose can promote the expression of miR‑155‑5p in HK ‑2 cells in concentration gradient, a inhibit the expression of Sirt1, autophagy‑related index, promote P53 and promote the expression of fibrosis molecules. b QRT ‑PCR and c western blot with d quantitative analysis of Sirt1, P53, LC3 II, p62, FN and Col‑1 expression in HK ‑2 cells treated with high glucose (30 mM) for 72 h. Results are presented as mean ± SEM of three independent experiments. *P < 0.05 vs NG, NG normal glucose (5.5 mM) Wang et al. J Transl Med (2018) 16:146 Page 5 of 9 Wang et al. J Transl Med (2018) 16:146 Page 6 of 9 (See figure on previous page.) Fig. 2 MiR‑155‑5p promote Sirt1‑inhibited fibrosis in HK ‑2 cells via inhibiting autophagy activity. a miR‑155‑5p mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with miR‑155‑5p mimics/inhibit. b–e miR‑155‑5p inhibit decreased the expression levels of Sirt1, Atg5, Atg7, Col‑1, on the contrary, miR‑155‑5p inhibit increased the expression levels of Sirt1, Atg5, Atg7, Col‑1 by qRT ‑PCR and f the influence of miR‑155‑5p mimics/inhibitor on Sirt1, LC3II and p62, FN, Col‑1 expression level measured by western blot with (f–i) quantitative analysis. Results are presented as mean ± SEM of three independent experiments. *P < 0.05. miR-NC miRNA negative control, miR-155-5p-m miR‑155‑5p mimics, miR-155-5p-i miR‑155‑5p inhibitor Sirt1 direct regulation P53 in high glucose cultured HK‑2 miR-155-5p inhibit. As shown (Fig.  2), levels of miR- cells 155-5p are reduced by a factor of 100, while expression To confirm that Sirt1 directly inhibits P53 expression of Sirtl mRNA and protein is increased. Subsequently, in high glucose cultured HK-2 cells, we transfected we constructed psi-Check2, a dual luciferase plasmid HK-2 cells with LipofectamineTM 3000 to overexpress carrying the Sirt1 fragment and co-transfected with or suppress the Sirt1 gene to determine the effect of miR-155-5p mimic and inhibit. The results showed that Sirt1 on P53. As shown in Fig. 4, Sirt1 plasmid transfec- the psi-Check2 fluorescence ratio co-transfected with tion confirmed that Sirt1 gene was overexpressed and miR-155-5p mimic significantly decreased, whereas the its expression was increased by 79.12-fold. After Sirt1 reverse significantly increased, suggesting that Sirt1 gene overexpression, Sirt1 gene expression was sig- and miR-155-5p binding (Fig. 3). nificantly inhibited by P53 expression. By q-PCR and Western blotting, we observed that P53 expression was significantly reduced after Sirt1 overexpression in high glucose conditions, and this effect was reversed after Sirt1 was inhibited. The data demonstrate that in high glucose treated HK-2 cells sirtl can directly inhibit P53 expression (Fig. 4). P53 binds to miR‑155‑5p We use chip assay to assess whether p53 directly regu- lar miR-155-5p gene expression in HK-2 cell cultured by high glucose. High glucose can stimulate P53 and miR-155-5p promoter region binding. The phenom - enon was then confirmed by qRT-PCR analysis, as shown in Fig.  5, with a significant up-regulation of P53 and miR-155-5p promoter binding sites after high glu- cose stimulation, with statistical significance. It shows that P53 pathway-upregulated miR-155-5p expression exists in high glucose group. We demonstrated that P53 can direct increase the expression of miR-155-5p (Fig. 5). Discussion The early manifestations of diabetic nephropathy are renal hypertrophy, glomerular and tubular basement membrane thickening and other obvious pathological features. As the disease progresses, it gradually evolves Fig. 3 The Sirt1 3′UTR is regulated by miR‑155‑5p. a MiR‑155‑5p and into glomerular extracellular matrix accumulation of its putative binding sequence in the 3′UTR of Sirt1. Luciferase assay tubulointerstitial fibrosis and eventually Irreversible of HK‑2 cells co ‑transfected with miR‑155 inhibitors (b) or mimics damage to the kidney structure. Some studies have sug- (c) and the luciferase reporter. The experiments were performed gested that the changes in tubules may precede the glo- in triplicate. The data are expressed as the mean ± SEM. *P < 0.005. miR‑155‑i miR‑155 inhibitor, miR‑inhibit‑NC miRNA inhibit negative meruli, suggesting that tubules may be a key player in control, miR‑155‑m miR‑155 mimics, miR‑mimic‑NC miRNA mimic the development of DKD [17]. Therefore, renal tubular negative control Wang et al. J Transl Med (2018) 16:146 Page 7 of 9 Fig. 4 The Sirt1 regulate expression of P53. a Sirt1 mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with pCMV ‑Sirt1 plasmid, and confirmed by d western blot with e quantitative analysis. b Sirt1 over expression increased the levels of Atg5, Atg7, LC3 II and decreased the expression levels of P53, P62, FN, Col‑1 by qRT ‑PCR and h western blot with i quantitative analysis. a Sirt1 mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with si‑Sirt1, and confirmed by f western blot, g quantitative analysis. c Inhibition of expression of Sirt1 gene increased the levels of P53, P62, FN, Col‑1 and decreased the expression levels of Atg5, Atg7, LC3 II by qRT ‑PCR and j western blot with k quantitative analysis. The experiments were performed in triplicate. The data are expressed as the mean ± SED. *P < 0.05. pCMV-Sirt1 Sirt1 over expression, pCMV-control Sirt1 over expression negative control Wang et al. J Transl Med (2018) 16:146 Page 8 of 9 of patients with diabetic nephropathy, which contrib- uted to its important role in the development of dia- betic nephropathy. In the same year, another investigator discovered that the expression of miR-155-5p was sig- nificantly elevated in the serum of patients with chronic kidney disease and nocturnal hypertension, suggesting that miR-155-5p played a role in renal tubular disease and even renal tubular injury in diabetic nephropathy, important role. In our study, we demonstrated for the first time that the expression of miR-155-5p increased with the increase of high glucose concentration in Fig. 5 High glucose promote P53 binds to miR‑155‑5p promoter HK-2 cells. miR-155-5p is transcriptionally regulated by region. P53 and miR‑155‑5p promoter binding region was detected p53 and participates in the regulation of cell cycle, cell by qRT‑PCR analysis DNA from Chip assay in HK ‑2 cells treated by growth, differentiation and apoptosis. We speculate that High glucose (30 mM) group complete with normal glucose (5.5 mM) miR-155-5p up-regulation may inhibit Sirt1, activate P53 group. The data are expressed as the mean ± SEM. *P < 0.005. LG and form a positive feedback loop. Although it has been normal glucose (5.5 mM), HG high glucose (30 mM) reported that miR-155-5p is involved in the promotion of renal fibrosis under hypoxic conditions, the existence injury has become an important area of DKD research of the p53/miR-155-5p/Sirt1 loop and its mechanism of in recent years, and autophagy dysfunction, especially action in renal tubular injury and renal fibrosis in dia - impaired autophagy, plays an important role in renal betic nephropathy clear. In this study, we demonstrated tubular injury [18]. Previous studies have found that for the first time that the expression of miR-155-5p Sirt1 is a protective factor of tubular cells and that Sirt1 increased with the increase of high glucose concentration expression was increased in both human and animal in HK-2 cells. miR-155-5p is transcriptionally regulated models of diabetic nephropathy (DKD) and confirmed by p53 and participates in the regulation of cell cycle, cell to be protective in DKD kidneys [19]. Specifically, it growth, differentiation and apoptosis. We speculate that can exert its deacetylation, freeing the key proteins of miR-155-5p up-regulation may inhibit Sirt1, activate P53 autophagy from acetylation inhibition, thereby promot- and form a positive feedback loop. Although miR-155-5p ing autophagy activity and improving adaptability to is reported to be involved in the promotion of renal fibro - stress environments. Our experiments also confirmed sis under hypoxic conditions, the presence of the p53/ that high glucose stimulation can induce renal tubules. miR-155-5p/Sirt1 loop and its role in renal tubular injury Cell Sirt1 expression was decreased, autophagy was and renal fibrosis are clear in diabetic nephropathy. In impaired, tubular cell injury was induced [20], and this study, we investigated the presence and function of P53 was also involved [21] as downstream regulator of p53/miR-155-5p/Sirt1 loop in renal tubular cells stimu- sirt1 [22, 23]. In contrast, in a mouse model of diabe- lated by high glucose, providing a new idea for the mech- tes, improving tubular autophagy can reduce tubular anism of diabetic tubular injury. cell oxidative stress and reverse renal tubular injury in diabetic mice [24]. Due to the complex mechanism of Conclusion renal tubular injury in DKD, the study of renal tubular • miR-155-5p is a microRNA that was found to have injury, especially tubular autophagy, has become the significantly increased renal tubular specificity in core of DKD tubular injury. patients with diabetic nephropathy last year. According to the analysis software predictive search, • Our data broaden the scope of the study of miR- we found that the target binding site of miR-155-5p on 155-5p, confirming its role in high glucose-induced Sirt1 3′UTR region is very interesting. miR-155-5p is tubular injury. a transcription product of tumor gene BIC. It has been • Our data revealed, for the first time, the existence of widely studied in the tumor field in the past. This year it a new signaling loop p53/miR-155-5p/Sirt1 that miR- was found to have a promoting effect on lung and liver 155-5p is involved in regulating,this is a new mecha- fibrosis, and was gradually introduced into the study of nism of high glucose-induced renal tubular damage renal fibrosis. In 2015, it was discovered that MiR-155-5p and provides evidence that miR-155-5p over expres- promotes fibrosis of proximal tubule cells and EMT by sion inhibits the sirt1-regulated autophagy path- modulating TGF-β1 under hypoxic conditions [7]. In way and serves as a therapeutic target for diabetic 2017, Baker et  al. [6] found that the expression of miR- nephropathy. 155-5p was significantly increased in the renal tubules Wang et al. J Transl Med (2018) 16:146 Page 9 of 9 Abbreviations 4. Dalla VM, et al. Structural involvement in type 1 and type 2 diabetic DKD: diabetic kidney disease; HK‑2 cells: human renal proximal tubular cells; nephropathy. Diabetes Metab. 2000;26(Suppl 4):8–14. Sirt1: sirtuin type 1; p53: tumor protein 53; LC3: autophagy marker light chain 5. Kato M, Arce L, Natarajan R. MicroRNAs and their role in progressive 3; p62: autophagy substrate protein 62; ATG5: autophagy related genes 5; kidney diseases. Clin J Am Soc Nephrol. 2009;4(7):1255–66. ATG7: autophagy related genes 7; FN: fibronectin; Col‑1: collagen I; GAPDH: 6. Baker MA, et al. Tissue‑specific MicroRNA expression patterns in four glyceraldehyde‑3‑phosphate dehydrogenase; NC: negative control; EMT: types of kidney disease. J Am Soc Nephrol. 2017;28(10):2985–92. epithelial–mesenchymal transition; 3′UTR : 3′untranslated region. 7. Xie S, et al. Hypoxia‑induced microRNA‑155 promotes fibrosis in proximal tubule cells. Mol Med Rep. 2015;11(6):4555–60. Authors’ contributions 8. Neilsen PM, et al. Mutant p53 drives invasion in breast tumors through YW completed all experiments and was a major contributor to writing this up‑regulation of miR‑155. Oncogene. 2013;32(24):2992–3000. paper, ZZ, Y‑jJ, Y ‑lY, Y ‑mX given a valuable and selfless guidance in the experi‑ 9. Hasegawa K, et al. Renal tubular Sirt1 attenuates diabetic albuminuria by mental process and article writing. All authors read and approved the final epigenetically suppressing Claudin‑1 overexpression in podocytes. Nat manuscript. Med. 2013;19(11):1496–504. 10. Wang D, et al. Targeting of microRNA‑199a‑5p protects against Acknowledgements pilocarpine‑induced status epilepticus and seizure damage via SIRT1‑p53 Not applicable. cascade. Epilepsia. 2016;57(5):706–16. 11. Zhang P, et al. Beraprost sodium, a prostacyclin analogue, reduces Competing interests fructose‑induced hepatocellular steatosis in mice and in vitro via the The authors declare that they have no competing interests. microRNA‑200a and SIRT1 signaling pathway. Metabolism. 2017;73:9–21. 12. Lu H, Wang B. SIRT1 exerts neuroprotective effects by attenuating Availability of data and materials cerebral ischemia/reperfusion‑induced injury via targeting p53/micro ‑ All data generated or analysed during this study are included in this published RNA‑22. Int J Mol Med. 2017;39(1):208–16. article. 13. Bordone L, Guarente L. Calorie restriction, SIRT1 and metabolism: under‑ standing longevity. Nat Rev Mol Cell Biol. 2005;6(4):298–305. Consent for publication 14. Yacoub R, Lee K, He JC. The role of SIRT1 in diabetic kidney disease. Front Not applicable. Endocrinol (Lausanne). 2014;5:166. 15. Kume S, et al. Anti‑aging molecule, Sirt1: a novel therapeutic target for Ethics approval and consent to participate diabetic nephropathy. Arch Pharm Res. 2013;36(2):230–6. Not applicable. 16. Ma L, et al. Sirt1 is essential for resveratrol enhancement of hypoxia‑ induced autophagy in the type 2 diabetic nephropathy rat. Pathol Res Funding Pract. 2016;212(4):310–8. This work was supported by research Grants from the National Natural Science 17. Kimura T, et al. Autophagy protects the proximal tubule from degenera‑ Foundation of China (Grant Nos. 81570724, 81628004 and 81700730) and the tion and acute ischemic injury. J Am Soc Nephrol. 2011;22(5):902–13. Natural Science Foundation of Guangdong (Grant No. 2017A030313555). 18. Liu S, et al. Autophagy plays a critical role in kidney tubule maintenance, aging and ischemia‑reperfusion injury. Autophagy. 2012;8(5):826–37. 19. Luo J, et al. Negative control of p53 by Sir2alpha promotes cell survival Publisher’s Note under stress. Cell. 2001;107(2):137–48. Springer Nature remains neutral with regard to jurisdictional claims in pub‑ 20. Kitada M, et al. Dietary restriction ameliorates diabetic nephropathy lished maps and institutional affiliations. through anti‑inflammatory effects and regulation of the autophagy via restoration of Sirt1 in diabetic Wistar fatty (fa/fa) rats: a model of type 2 Received: 16 February 2018 Accepted: 17 April 2018 diabetes. Exp Diabetes Res. 2011;2011:908185. 21. Peng J, et al. Hyperglycemia, p53, and mitochondrial pathway of apopto‑ sis are involved in the susceptibility of diabetic models to ischemic acute kidney injury. Kidney Int. 2015;87(1):137–50. 22. Cohen HY, et al. Calorie restriction promotes mammalian cell survival by References inducing the SIRT1 deacetylase. Science. 2004;305(5682):390–2. 1. Shi Y, Hu FB. The global implications of diabetes and cancer. Lancet. 23. Smith J. Human Sir2 and the ‘silencing’ of p53 activity. Trends Cell Biol. 2014;383(9933):1947–8. 2002;12(9):404–6. 2. Sun YM, et al. Recent advances in understanding the biochemical and 24. Xiao L, et al. The mitochondria‑targeted antioxidant MitoQ ameliorated molecular mechanism of diabetic nephropathy. Biochem Biophys Res tubular injury mediated by mitophagy in diabetic kidney disease via Commun. 2013;433(4):359–61. Nrf2/PINK1. Redox Biol. 2017;11:297–311. 3. Kanwar YS, et al. Diabetic nephropathy: mechanisms of renal disease progression. Exp Biol Med (Maywood). 2008;233(1):4–11. Ready to submit your research ? Choose BMC and benefit from: fast, convenient online submission thorough peer review by experienced researchers in your field rapid publication on acceptance support for research data, including large and complex data types • gold Open Access which fosters wider collaboration and increased citations maximum visibility for your research: over 100M website views per year At BMC, research is always in progress. Learn more biomedcentral.com/submissions http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Translational Medicine Springer Journals

Role of p53/miR-155-5p/sirt1 loop in renal tubular injury of diabetic kidney disease

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/lp/springer_journal/role-of-p53-mir-155-5p-sirt1-loop-in-renal-tubular-injury-of-diabetic-3RZd0N7TaJ
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BioMed Central
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Copyright © 2018 by The Author(s)
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Biomedicine; Biomedicine, general; Medicine/Public Health, general
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1479-5876
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10.1186/s12967-018-1486-7
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Abstract

Background: Diabetic kidney disease is a renal microvascular disease caused by diabetes, known as one of the most serious and lethal complications of diabetes. Early renal hypertrophy is the main pathological feature, which gradually leads to the deposition of glomerular extracellular matrix and tubulointerstitial fibrosis, eventually developing irrevers‑ ible structural damage to the kidneys. Autophagy is a cell self‑ homeostatic mechanism that is activated under stress conditions and may serve as a protective response to the survival of renal fibrogenic cells. MicroRNA (miRNA) network may be involved in the regulation of fibrosis. The purpose of this study is to assess how miRNAs regulate diabetic kidney disease and autophagy and fibrosis in renal proximal tubular cells under high glucose conditions. Methods: Human renal proximal tubular (HK‑ 2) cells were exposed to high glucose in vitro. Bioinformatic analy‑ sis was used to select the candidate gene for potential target regulation of miR‑ 155, Sirt1. ATG5, ATG7 is the key to autophagosome formation, regulated by Sirt1. p53 regulates miR‑ 155 expression as a transcription factor. MiR‑ 155 overexpression and inhibition were achieved by transfection of miR‑ 155 mimic and inhibit to evaluate its effect on Sirt1 and autophagy and fibrosis markers. Dual luciferase reporter assays were used to confirm the direct interaction of Sirt1 with miR‑ 155. Overexpression and inhibition of Sirt1 gene were achieved by transfection of Sirt1 plasmid and Sirt1 si to observe its effect on P53. Chip assay experiments confirmed the direct regulation of P53 on miR ‑ 155. Results: Under high glucose conditions, miR‑ 155 was detected in HK‑ 2 cells in concentration gradient, increased expression of p53 and down‑ regulated expression of sirt1 and autophagy‑ associated proteins LC3II, ATG5 and ATG7. Dual luciferase reporter assays indicate that miR‑ 155 can target its binding to the Sirt1 3′UTR region to reduce its expression. Under high glucose conditions, over expression of miR‑ 155 decreased the expression of LC3‑ II and ATG5 in HK‑ 2 cells, while inhibition of miR‑ 155 reversed this effect. Using chip assay testing in HK ‑ 2 cells, we demonstrated that p53 binds directly to miR‑ 155. Conclusions: The signaling axis of p53, miR‑ 155‑ 5p, and sirt1 in autophagic process might be a critical adapting mechanism for diabetic kidney injury. Keywords: Diabetic kidney disease, HK‑ 2, miRNA, miR‑ 155‑ 5p, Sirt1, p53, Autophagy postpone the development of diabetic kidney disease is Background particularly important. Despite the control of blood glu- Diabetic kidney disease (DKD) is one of the most com- cose, blood pressure and blood lipids, such as proteinu- mon and devastating complications of diabetes [1]. It ria and other comprehensive treatment, but the current is also the high risk factors of end-stage renal disease clinical efficacy is still poor. Because of the complicated (ESRD) and significantly increases the risk of diabetes metabolic disorder in patients, it is more difficult for Patient’s mortality rate. Diabetes has become a global DKD to progress to end-stage treatment, which is one of health problem, for the prevention of complications, the important reason of death in patients [2]. Therefore, looking for an earlier and more effective new target for *Correspondence: xueyaoming999@126.com prevention and treatment of diabetic nephropathy, pre- Department of Endocrinology and Metabolism, Nanfang Hospital, venting or delaying the progress of DKD is a problem that Southern Medical University, Guangzhou, Guangdong, China © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/ publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Wang et al. J Transl Med (2018) 16:146 Page 2 of 9 the medical profession has so far failed to solve, exploring Methods the pathogenesis of DKD in search of new and effective Cell culture prevention and treatment methods has important medi- 10% FBS (Gibco, NZL) was supplemented in MEM cal and social research value [3, 4]. (Gibco, Invitrogen) and human renal proximal tubule MicroRNA is a single-stranded, non-coding RNA (HK-2) cells were cultured at 37 °C and 5% The medium about 22-24 nucleotides in length that can degrade or was changed every 2 days, waiting for HK-2 cells to grow inhibit protein translation by specifically binding to the to 60% and then starved for 24  h in a medium supple- 3 ‘non-coding region of the target gene mRNA. The bind - mented with MEM (Gibco, Invitrogen) supplemented ing mechanism is very flexible and complex [5]. Recent with 2% FBS (Gibco, NZL). Group 1: (normal glucose) research, miR-155-5p is observed significantly increased normal glucose concentration (5.5  mmol/l) medium in Diabetic kidney disease patients’ kidney tubules [6] as a control. Group 2: normal cell culture medium sup- and can aggravate renal fibrosis in patients with acute plemented with high glucose (11  mM) medium. Group kidney injury [7]. The mechanism of microRNA expres - 3: normal cell culture medium supplemented with high sion changes is focused on the control of transcriptional glucose (20  mM) medium. Group 4: normal cell cul- activity by the binding of transcription factors to promot- ture medium supplemented with high glucose (30  mM) ers. It is noteworthy that there is literature describing that medium as high glucose stimulation group. All cells were p53 promotes the expression of miR-155-5p in tumor incubated with medium for 72 h. To observe the expres- cells and tissues [8]. Therefore, we hypothesize that the sion of miR-155-5p in all groups. And to observe the p53/miR-155-5p loop may be involved in the regulation expression of Sirt1, P53, autophagy and fibrosis related of the injury process of renal tubular cells under high glu- factors in both 1 and 4 groups. cose conditions. MicroRNA regulates gene expression by inhibiting the Quantitative real‑time RT‑PCR translation process, cutting and degrading mRNA, and We extracted total RNA from HK-2 cells using a phenol– reducing mRNA stability. We tried to find the target gene chloroform extraction protocol and used to determine for miR-155-5p [9]. There is growing evidence that Sirt1 the purity and concentration of RNA after NANODROP is under the control of microRNAs such as miR-199 [10], 2000 DEPC water was zeroed. After RNA was uni- miR-200 [11] and miR-22 [12]. We predicted the exist- formly diluted to 100  ng/μl, cDNA was reverse tran- ence of binding sites between the miR-155-5p and Sirt1 scribed. Quantitative real-time RT-PCR was performed 3′UTR regions by the online bioinformatics analysis (Tar- on a LightCycler 480 (Roche, CH). PCR reaction system getScan) [13]. for 1 μl cDNA, 0.2 nM of each primer, 3.6 μl SBRE then Sirt1 is the most famous member of the silent informa- RNase-free water to make a total amount of 10 μl. Using tion regulator 2 family,when we detect patients with dia- GAPDH as an internal control, the resulting CT values betic nephropathy (DKD) or study DKD animal models, for Sirt1, p53 and autophagy-related markers of fibrosis. we find that the expression of Sirt1 in renal cells tends to The primers we used are showed in Table 1. decrease, and further studies have found that increasing the expression of SIRT1 can be constructed well. Kid- Western blotting ney protection is provided in animal models with DKD Using western blotting to detect the expression level of disease [14, 15]. SIRT1 can exert anti-apoptosis, anti- Sirt1 and P53 and the expression of autophagy-related oxidation and anti-inflammatory effects in cell injury proteins LC3II and p62. Briefly, the extracted protein and protect cells by regulating mitochondrial biogenesis, samples were mixed with SDS-PAGE and boiled in boil- autophagy and metabolism in response to cellular energy ing water for 5  min to denature. The isolated protein and redox state. Specifically, SIRT1 can directly de-acety - was then electrophoretically transferred to a polyvi- late key proteins (Atg) of autophagy, such as Atg5, Atg7, nylidene difluoride (PVDF) membrane (0.45  mm) (Mil - and Atg8, to remove them from the inhibitory state, lipore, USA). Incubate with 5% skim milk in TBS for 1 h thereby promoting autophagy [16]. At the same time, to block non-specific proteins. The primary antibodies SIRT1 can also deactivate transcriptional activity of p53, used include the following: Sirt1, p53, LC3 II, p62, FN, thereby inhibiting its function. Col-1 and GAPDH. After incubating for 2 h at room tem- In summary, we investigated the mechanism of p53/ perature with pre-prepared rabbit secondary antibody miR-155-5p/Sirt1 loop in high glucose-induced tubular (1: 5000; Santa Cruz biotechnology, USA) and mouse epithelial cell injury in vitro. secondary antibody (1: 5000; Santa Cruz biotechnology, Wang et al. J Transl Med (2018) 16:146 Page 3 of 9 Table 1 Sequences of primers for qRT-PCr in this study plasmid or Sirtl si was mixed with 250 μl Opti-MEM at a 1  μg target dose (plasmid group supplemented Gene Sequences with 10 μl P3000TM Reagent/well). The two mixtures Sirt1 Sense 5′‑AGT TCC AGC CGT CTC TGT GT‑3′ were then mixed for 5  min and then added to the Antisense 5′‑CTC CAC GAA CAG CTT CAC AA‑3′ cell culture medium for further 48 h at 37 °C in a 5% Atg5 Sense 5′‑TGT GCT TCG AGA TGT GTG GTT‑3′ CO incubator. Protein or total RNA was extracted Antisense 5′‑ACC AAC GTC AAA TAG CTG ACTC‑3′ from the cell collection plate for subsequent experi- Atg7 Sense 5′‑ACC CAG AAG AAG CTG AAC GA‑3′ ments. The changes of Sirt1 expression were verified Antisense by western blot and q-PCR. The expression of p53, 5′‑CTC ATT TGC TGC TTG TTC CA‑3′ ATG5, LC3 II, p62 and fibrosis related genes were Col‑1 Sense 5′‑TCA AGA CAC GTT CCC GTG AG‑3′ observed after validation. Antisense 5′‑GCC AAC TTC TCC AGC GGT A‑3′ GAPDH Sense 5′‑GAA CGG GAA GCT CAC TGG ‑3′ Antisense 5′‑GCC TGC TTC ACC ACC TTC T‑3′ Luciferase reporter gene assay miR‑155‑5p Sense 5′‑GCC TCC AAC TGA CTC CTA CA‑3′ We used PCR to amplify the miR-155-5p and Sirt1′ 3′ Antisense Universal reverse primer ( Tiangen, Beijing, UTR binding sites (primer: forward: 5′-CCG CTC GAG China) TGT AAT AAT TGT GCA GGT ACA G-3′; reverse: 5′-ATT U6 Sense 5′‑CTC GCT TCG GCA GCACA‑3′ T G C G G C C G C A A A GT T A GT GT T GA G T T T GTA C - Antisense Universal reverse primer ( Tiangen, Beijing, 3′) from HK-2 cell genomic DNA. The amplified Sirt1 China) 3′UTR fragment was inserted into the psi-Check2 vec- tor (Ribobio, Guangzhou, China) respectively, using the XhoI and NotI restriction sites. HK-2 cells were setted in USA) and using chemiluminescence (ECL) Imaging 24-well plates at 60% density treated by MEM medium Analysis System Exposure photography. Relative protein containing 2% Gibico fetal calf serum for 24 h. After this, stripe density through the image inspection software cells were co-transfected with psi-Check2 (0.5  μg) con- quantity one for testing and analysis. structed with Sirt1 and miR-155-5p binding sites with miR-155-5p mimics/inhibitors, MEM medium contain- Transfection ing 30 nm d-glucose and 10% Gibico fetal bovine serum 1. To effect changes in miR-155-5p expression, HK-2 was used to groom. Cells were harvested 48 h after trans- cells were treated with miR-155-5p mimic/inhibit fection, dual luciferase assay system was used to analyze (bought from ribobio Biotechnology company, the luminescence. Guangzhou China) using both LipofectamineTM 3000 as a transfection reagent and a non-sense strand negative control (NC) as a control. Briefly, Chip assay cells were starved overnight in 12-well plates at 60% The presence of p53 binding sites in the promoter density prior to transfection. Lipofectamine 3000 region of miR-155-5p was predicted by software. Using was mixed with 50  μl Opti-MEM, meanwhile, miR- a Chip assay, in brief, cells were treated with 1% forma- 155-5p mimic/inhibit was mixed with 100  μl Opti- lin and sonicated to collect soluble chromatin superna- MEM. The two mixtures were then mixed for 5 min tants at 14,000g for 10  min at 4  °C. Anti-p53 antibodies and then added to the cell culture medium and left to (Santa Cruz Biotechnology, USA.) Overnight, mouse incubate for 48 h at 37 °C in 5% CO . Collect cells for IgG immunoprecipitated as a negative control. Immune protein or total RNA extraction. q-PCR was used to complexes were washed and DNA samples were obtained validate the up-regulation of miR-155-5p. After veri- with a QIAquick Gel Extraction Kit (QIAGEN, Ger). We fication, the expression of Sirt1, p53, ATG5, LC3II, use qRT-PCR to analysis the recovered DNA by using p62 and fibrosis related genes were detected by west - primers containing the miR-155-5p promoter region and ern blot and q-PCR. the P53 binding site. (primer: forward: 5′-CCG CAT GTG 2. To achieve changes in Sirt1 expression, HK-2 cells CAT ACA CAA AC-3′; reverse: 5′-CAT TTA GGA TAC were treated with Sirt1 plasmid or Sirt1 si using TAC TGA TAA ATC -3′). LipofectamineTM 3000 as transfection reagent and non-sense strand negative control (NC) as controls. Statistical analysis Similar to the experiment described in the previous All of the experimental data obtained in this study were phase, cells were starved overnight in 6-well plates entered using Excel spreadsheet software. Use SPSS 20 at 60% density prior to transfection. Lipofectamine software to accomplish statistical analysis. Statistical 3000 was mixed with 125  μl Opti-MEM while Sirtl results were expressed as mean ± standard error of mean. Wang et al. J Transl Med (2018) 16:146 Page 4 of 9 Use independent means t test to compare the mean of (30  mM). P53 expression was increased by stimulat- the two samples. Use One-way ANOVA to compare mul- ing high concentrations of glucose (30  mM). Western tiple groups. P < 0.05 was statistically significant. blot results showed that after high glucose stimulation (30  mM), we observed changes in autophagy-related Results expression, with a significant decrease in LC3 II and a High glucose stimulates the general measurement of HK2 significant increase in p62. After high glucose stimulation cells (30 mM), the fibrosis index FN, Col-1 also increased sig - The expression of miR-155-5p is significantly increased nificantly (Fig. 1). in patients with diabetic nephropathy. Explore what role miR-155-5p plays in renal tubular injury. We chose HK-2 MiR‑155‑5p directly regulates Sirt1 cells as an in  vitro experimental model. The test was Aberrant expression of miR-155-5p was confirmed divided into four groups, the normal glucose (5.5  mM) in HK-2 cells, and we then verified whether Sirt1 was group and the gradient high glucose group (11  mM, directly regulated by miR-155-5p expression. We 20 nM, 30 mM). After culturing the HK-2 cells for 72 h, change miR-155-5p expression level by Transferring total RNA and protein were extracted for analysis. We miR-155-5p mimic or inhibit into HK-2 cells. After found that the expression level of MiR-155-5p in HK-2 transferring miR-155-5p mimic in HK-2 cells, miR- cells was gradually up-regulated with the increase of glu- 155-5p levels were significantly increased by 61.006- cose concentration (11  mM, 20  nM, 30  mM) compared fold, whereas the Sirt1 mRNA and protein expression to the cells treated with normal glucose (5.5  mM). Sirt1 was diminished contrast with the NC group (Fig.  2a). expression was significantly inhibited by high glucose The reverse trend was discovered in HK-2 cells after Fig. 1 High glucose can promote the expression of miR‑155‑5p in HK ‑2 cells in concentration gradient, a inhibit the expression of Sirt1, autophagy‑related index, promote P53 and promote the expression of fibrosis molecules. b QRT ‑PCR and c western blot with d quantitative analysis of Sirt1, P53, LC3 II, p62, FN and Col‑1 expression in HK ‑2 cells treated with high glucose (30 mM) for 72 h. Results are presented as mean ± SEM of three independent experiments. *P < 0.05 vs NG, NG normal glucose (5.5 mM) Wang et al. J Transl Med (2018) 16:146 Page 5 of 9 Wang et al. J Transl Med (2018) 16:146 Page 6 of 9 (See figure on previous page.) Fig. 2 MiR‑155‑5p promote Sirt1‑inhibited fibrosis in HK ‑2 cells via inhibiting autophagy activity. a miR‑155‑5p mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with miR‑155‑5p mimics/inhibit. b–e miR‑155‑5p inhibit decreased the expression levels of Sirt1, Atg5, Atg7, Col‑1, on the contrary, miR‑155‑5p inhibit increased the expression levels of Sirt1, Atg5, Atg7, Col‑1 by qRT ‑PCR and f the influence of miR‑155‑5p mimics/inhibitor on Sirt1, LC3II and p62, FN, Col‑1 expression level measured by western blot with (f–i) quantitative analysis. Results are presented as mean ± SEM of three independent experiments. *P < 0.05. miR-NC miRNA negative control, miR-155-5p-m miR‑155‑5p mimics, miR-155-5p-i miR‑155‑5p inhibitor Sirt1 direct regulation P53 in high glucose cultured HK‑2 miR-155-5p inhibit. As shown (Fig.  2), levels of miR- cells 155-5p are reduced by a factor of 100, while expression To confirm that Sirt1 directly inhibits P53 expression of Sirtl mRNA and protein is increased. Subsequently, in high glucose cultured HK-2 cells, we transfected we constructed psi-Check2, a dual luciferase plasmid HK-2 cells with LipofectamineTM 3000 to overexpress carrying the Sirt1 fragment and co-transfected with or suppress the Sirt1 gene to determine the effect of miR-155-5p mimic and inhibit. The results showed that Sirt1 on P53. As shown in Fig. 4, Sirt1 plasmid transfec- the psi-Check2 fluorescence ratio co-transfected with tion confirmed that Sirt1 gene was overexpressed and miR-155-5p mimic significantly decreased, whereas the its expression was increased by 79.12-fold. After Sirt1 reverse significantly increased, suggesting that Sirt1 gene overexpression, Sirt1 gene expression was sig- and miR-155-5p binding (Fig. 3). nificantly inhibited by P53 expression. By q-PCR and Western blotting, we observed that P53 expression was significantly reduced after Sirt1 overexpression in high glucose conditions, and this effect was reversed after Sirt1 was inhibited. The data demonstrate that in high glucose treated HK-2 cells sirtl can directly inhibit P53 expression (Fig. 4). P53 binds to miR‑155‑5p We use chip assay to assess whether p53 directly regu- lar miR-155-5p gene expression in HK-2 cell cultured by high glucose. High glucose can stimulate P53 and miR-155-5p promoter region binding. The phenom - enon was then confirmed by qRT-PCR analysis, as shown in Fig.  5, with a significant up-regulation of P53 and miR-155-5p promoter binding sites after high glu- cose stimulation, with statistical significance. It shows that P53 pathway-upregulated miR-155-5p expression exists in high glucose group. We demonstrated that P53 can direct increase the expression of miR-155-5p (Fig. 5). Discussion The early manifestations of diabetic nephropathy are renal hypertrophy, glomerular and tubular basement membrane thickening and other obvious pathological features. As the disease progresses, it gradually evolves Fig. 3 The Sirt1 3′UTR is regulated by miR‑155‑5p. a MiR‑155‑5p and into glomerular extracellular matrix accumulation of its putative binding sequence in the 3′UTR of Sirt1. Luciferase assay tubulointerstitial fibrosis and eventually Irreversible of HK‑2 cells co ‑transfected with miR‑155 inhibitors (b) or mimics damage to the kidney structure. Some studies have sug- (c) and the luciferase reporter. The experiments were performed gested that the changes in tubules may precede the glo- in triplicate. The data are expressed as the mean ± SEM. *P < 0.005. miR‑155‑i miR‑155 inhibitor, miR‑inhibit‑NC miRNA inhibit negative meruli, suggesting that tubules may be a key player in control, miR‑155‑m miR‑155 mimics, miR‑mimic‑NC miRNA mimic the development of DKD [17]. Therefore, renal tubular negative control Wang et al. J Transl Med (2018) 16:146 Page 7 of 9 Fig. 4 The Sirt1 regulate expression of P53. a Sirt1 mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with pCMV ‑Sirt1 plasmid, and confirmed by d western blot with e quantitative analysis. b Sirt1 over expression increased the levels of Atg5, Atg7, LC3 II and decreased the expression levels of P53, P62, FN, Col‑1 by qRT ‑PCR and h western blot with i quantitative analysis. a Sirt1 mRNA expression was detected by qRT‑PCR analysis in HK ‑2 cells transfected with si‑Sirt1, and confirmed by f western blot, g quantitative analysis. c Inhibition of expression of Sirt1 gene increased the levels of P53, P62, FN, Col‑1 and decreased the expression levels of Atg5, Atg7, LC3 II by qRT ‑PCR and j western blot with k quantitative analysis. The experiments were performed in triplicate. The data are expressed as the mean ± SED. *P < 0.05. pCMV-Sirt1 Sirt1 over expression, pCMV-control Sirt1 over expression negative control Wang et al. J Transl Med (2018) 16:146 Page 8 of 9 of patients with diabetic nephropathy, which contrib- uted to its important role in the development of dia- betic nephropathy. In the same year, another investigator discovered that the expression of miR-155-5p was sig- nificantly elevated in the serum of patients with chronic kidney disease and nocturnal hypertension, suggesting that miR-155-5p played a role in renal tubular disease and even renal tubular injury in diabetic nephropathy, important role. In our study, we demonstrated for the first time that the expression of miR-155-5p increased with the increase of high glucose concentration in Fig. 5 High glucose promote P53 binds to miR‑155‑5p promoter HK-2 cells. miR-155-5p is transcriptionally regulated by region. P53 and miR‑155‑5p promoter binding region was detected p53 and participates in the regulation of cell cycle, cell by qRT‑PCR analysis DNA from Chip assay in HK ‑2 cells treated by growth, differentiation and apoptosis. We speculate that High glucose (30 mM) group complete with normal glucose (5.5 mM) miR-155-5p up-regulation may inhibit Sirt1, activate P53 group. The data are expressed as the mean ± SEM. *P < 0.005. LG and form a positive feedback loop. Although it has been normal glucose (5.5 mM), HG high glucose (30 mM) reported that miR-155-5p is involved in the promotion of renal fibrosis under hypoxic conditions, the existence injury has become an important area of DKD research of the p53/miR-155-5p/Sirt1 loop and its mechanism of in recent years, and autophagy dysfunction, especially action in renal tubular injury and renal fibrosis in dia - impaired autophagy, plays an important role in renal betic nephropathy clear. In this study, we demonstrated tubular injury [18]. Previous studies have found that for the first time that the expression of miR-155-5p Sirt1 is a protective factor of tubular cells and that Sirt1 increased with the increase of high glucose concentration expression was increased in both human and animal in HK-2 cells. miR-155-5p is transcriptionally regulated models of diabetic nephropathy (DKD) and confirmed by p53 and participates in the regulation of cell cycle, cell to be protective in DKD kidneys [19]. Specifically, it growth, differentiation and apoptosis. We speculate that can exert its deacetylation, freeing the key proteins of miR-155-5p up-regulation may inhibit Sirt1, activate P53 autophagy from acetylation inhibition, thereby promot- and form a positive feedback loop. Although miR-155-5p ing autophagy activity and improving adaptability to is reported to be involved in the promotion of renal fibro - stress environments. Our experiments also confirmed sis under hypoxic conditions, the presence of the p53/ that high glucose stimulation can induce renal tubules. miR-155-5p/Sirt1 loop and its role in renal tubular injury Cell Sirt1 expression was decreased, autophagy was and renal fibrosis are clear in diabetic nephropathy. In impaired, tubular cell injury was induced [20], and this study, we investigated the presence and function of P53 was also involved [21] as downstream regulator of p53/miR-155-5p/Sirt1 loop in renal tubular cells stimu- sirt1 [22, 23]. In contrast, in a mouse model of diabe- lated by high glucose, providing a new idea for the mech- tes, improving tubular autophagy can reduce tubular anism of diabetic tubular injury. cell oxidative stress and reverse renal tubular injury in diabetic mice [24]. Due to the complex mechanism of Conclusion renal tubular injury in DKD, the study of renal tubular • miR-155-5p is a microRNA that was found to have injury, especially tubular autophagy, has become the significantly increased renal tubular specificity in core of DKD tubular injury. patients with diabetic nephropathy last year. According to the analysis software predictive search, • Our data broaden the scope of the study of miR- we found that the target binding site of miR-155-5p on 155-5p, confirming its role in high glucose-induced Sirt1 3′UTR region is very interesting. miR-155-5p is tubular injury. a transcription product of tumor gene BIC. It has been • Our data revealed, for the first time, the existence of widely studied in the tumor field in the past. This year it a new signaling loop p53/miR-155-5p/Sirt1 that miR- was found to have a promoting effect on lung and liver 155-5p is involved in regulating,this is a new mecha- fibrosis, and was gradually introduced into the study of nism of high glucose-induced renal tubular damage renal fibrosis. In 2015, it was discovered that MiR-155-5p and provides evidence that miR-155-5p over expres- promotes fibrosis of proximal tubule cells and EMT by sion inhibits the sirt1-regulated autophagy path- modulating TGF-β1 under hypoxic conditions [7]. In way and serves as a therapeutic target for diabetic 2017, Baker et  al. [6] found that the expression of miR- nephropathy. 155-5p was significantly increased in the renal tubules Wang et al. J Transl Med (2018) 16:146 Page 9 of 9 Abbreviations 4. Dalla VM, et al. Structural involvement in type 1 and type 2 diabetic DKD: diabetic kidney disease; HK‑2 cells: human renal proximal tubular cells; nephropathy. Diabetes Metab. 2000;26(Suppl 4):8–14. 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Dietary restriction ameliorates diabetic nephropathy lished maps and institutional affiliations. through anti‑inflammatory effects and regulation of the autophagy via restoration of Sirt1 in diabetic Wistar fatty (fa/fa) rats: a model of type 2 Received: 16 February 2018 Accepted: 17 April 2018 diabetes. Exp Diabetes Res. 2011;2011:908185. 21. Peng J, et al. Hyperglycemia, p53, and mitochondrial pathway of apopto‑ sis are involved in the susceptibility of diabetic models to ischemic acute kidney injury. Kidney Int. 2015;87(1):137–50. 22. Cohen HY, et al. Calorie restriction promotes mammalian cell survival by References inducing the SIRT1 deacetylase. Science. 2004;305(5682):390–2. 1. Shi Y, Hu FB. The global implications of diabetes and cancer. Lancet. 23. Smith J. Human Sir2 and the ‘silencing’ of p53 activity. Trends Cell Biol. 2014;383(9933):1947–8. 2002;12(9):404–6. 2. Sun YM, et al. Recent advances in understanding the biochemical and 24. Xiao L, et al. The mitochondria‑targeted antioxidant MitoQ ameliorated molecular mechanism of diabetic nephropathy. Biochem Biophys Res tubular injury mediated by mitophagy in diabetic kidney disease via Commun. 2013;433(4):359–61. Nrf2/PINK1. Redox Biol. 2017;11:297–311. 3. Kanwar YS, et al. Diabetic nephropathy: mechanisms of renal disease progression. Exp Biol Med (Maywood). 2008;233(1):4–11. Ready to submit your research ? Choose BMC and benefit from: fast, convenient online submission thorough peer review by experienced researchers in your field rapid publication on acceptance support for research data, including large and complex data types • gold Open Access which fosters wider collaboration and increased citations maximum visibility for your research: over 100M website views per year At BMC, research is always in progress. Learn more biomedcentral.com/submissions

Journal

Journal of Translational MedicineSpringer Journals

Published: May 30, 2018

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