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Minamoto, Kanji; Pinsky, David J.; Fujita, Tomoyuki; Naka, Yoshifumi
doi: 10.1165/ajrcmb.26.1.4649pmid: 11751199
Nitroglycerin (NTG) given to donor lungs improves lung preservation for transplantation, but the mechanism(s) underlying this therapeutic benefit remain incompletely understood. Furthermore, it is not known whether the therapeutic window of opportunity for NTG administration is temporally-restricted. Because endothelin-1 (ET-1), a potent vasoconstrictor, and nitric oxide (NO) are reciprocally regulated in vitro, we hypothesized that early administration of the NO donor NTG may suppress ET-1 and thereby improve lung preservation. Using an isogeneic rat left lung transplantation model, four groups were studied (n = 12 transplant/group): (1) NTG given during flush/ preservation (Early NTG); (2) NTG given in the ex vivo flush (Late NTG); (3) No NTG; and (4) a nonselective ET-receptor antagonist (PD156252) given during flush/preservation. Early NTG decreased vascular tone in lung grafts measured ex vivo as well as in vivo following lung transplantation, and resulted in improved survival (100%) and gas exchange (pO2 209 ± 19 mm Hg) compared with Late (17%, 62 ± 16 mm Hg) or No NTG (25%, 59 ± 9 mm Hg) (P < 0.05 for Early NTG versus all other groups for both survival and pO2). PD156252 was associated with an intermediate level of survival (50%) and function (104 ± 23 mm Hg). Transplanted lung graft ET-1 mRNA, measured by Northern blotting and in situ hybridization, and protein, measured by Western blotting and immunohistochemistry, were suppressed only with Early NTG (P < 0.05 versus all other groups). Post-transplantation benefits of NTG are restricted to lung grafts which received NTG during the early harvest and immersion periods, and are coincident with suppression of graft ET-1 expression. When viewed in the context of improved graft survival and function with ET-1 receptor blockade, these data suggest that early administration of NTG to donor lungs improves primary graft function, in part, by suppressing graft ET-1 expression.
Zulueta, Javier J.; Sawhney, Raneeta; Kayyali, Usamah; Fogel, Michael; Donaldson, Cameron; Huang, Hailu; Lanzillo, Joseph J.; Hassoun, Paul M.
doi: 10.1165/ajrcmb.26.1.4510pmid: 11751200
The effects of hypoxia on the regulation of inducible nitric oxide synthase (NOS) 2 expression were examined in cultured rat pulmonary microvascular endothelial cells (EC). EC did not express NOS 2 mRNA or protein when exposed to normoxia or hypoxia unless they were pretreated with interleukin (IL)-1 β and/or tumor necrosis factor (TNF)- α for 24 h. Induction of NOS 2 by IL-1 β+ TNF- α was significantly attenuated by concomitant exposure of EC to hypoxia or treatment of EC with antioxidants such as tiron, diphenyliodonium, and catalase, suggesting that NOS 2 expression is dependent on the production of reactive oxygen species. Degradation of I κ B and activation of NF- κ B, which were both induced by treatment of EC with cytokines, were not altered when the cells were exposed to hypoxia, suggesting that the modulation of NOS 2 expression by hypoxia is unrelated to NF- κ B activation. Following stimulation with IL-1 β+ TNF- α for 24 h, incubation of EC in normoxia resulted in a progressive decline in NOS 2 expression and a calculated half-life of approximately 6 h for NOS 2 mRNA. Hypoxia significantly prolonged the half-life of NOS 2 mRNA (17 h, P < 0.05 versus normoxic EC). The half-life of NOS 2 mRNA was also prolonged by actinomycin D treatment (19.5 and 29.5 h for normoxic and hypoxic EC, respectively), suggesting that transcription of an RNA destabilizing factor or RNAse contributes to NOS 2 mRNA degradation. In EC transiently transfected with the rat NOS 2 promoter, hypoxia and the combination of IL-1 β+ TNF- α independently increased promoter activity 2.2- and 3-fold, respectively. As opposed to the attenuating effect that hypoxia had on IL-1 β+ TNF- α – dependent induction of NOS 2 gene expression, the concomitant treatment with IL-1 β+ TNF- α and hypoxia synergistically increased NOS 2 promoter activity 17.6-fold. Taken together, these results suggest that hypoxia alone does not induce NOS 2 expression in cultured pulmonary microvascular EC, but may modulate cytokine induction of this enzyme at pretranscriptional, transcriptional, and posttranscriptional levels.
Sekhon, Harmanjatinder S.; Keller, Jennifer A.; Proskocil, Becky J.; Martin, Ellen L.; Spindel, Eliot R.
doi: 10.1165/ajrcmb.26.1.4170pmid: 11751201
The recent identification of nicotinic acetylcholine receptors (nAChR) in pulmonary fibroblasts suggests that in utero nicotine exposure may alter collagen expression by these cells in the developing lung. To test this hypothesis, timed-pregnant rhesus monkeys were administered nicotine (1–1.5 mg/kg/d, subcutaneously) using osmotic minipumps from Days 26–134 or 26–160 of gestation (term = 165 d). In utero nicotine exposure significantly increased airway wall area per unit epithelial basement membrane. Collagen type I and III mRNA expression and immunostaining were significantly increased in the airway and alveolar walls of the nicotine-treated group. Elastin mRNA expression increased, but protein expression in parenchyma remained unchanged. Dual labeling studies colocalized α 7 nAChR and collagen to the same cells in airway wall cells, and colocalization of α 7 nAChR and collagen was confirmed in isolated pulmonary fibroblasts. These findings suggest that nicotine may directly interact with α 7 nAChR to increase collagen accumulation in airway and alveolar walls following in utero nicotine exposure. These data suggest that passage of nicotine across the placenta to increase collagen deposition and therefore increase airway wall dimensions in fetal lung may partially explain the observed alterations in lung mechanics in the infants of mothers who smoke during pregnancy.
Cho, Hye-Youn; Jedlicka, Anne E.; Reddy, Sekhar P. M.; Zhang, Liu-Yi; Kensler, Thomas W.; Kleeberger, Steven R.
doi: 10.1165/ajrcmb.26.1.4536pmid: 11751202
A strong role for reactive oxygen species (ROS) has been proposed in the pathogenesis of a number of lung diseases. Hyperoxia ( > 95% oxygen) generates ROS and extensive lung damage, and has been used as a model of oxidant injury. However, the precise mechanisms of hyperoxia-induced toxicity have not been completely clarified. This study was designed to identify hyperoxia susceptibility genes in C57BL/6J (susceptible) and C3H/HeJ (resistant) mice. The quantitative phenotypes used for this analysis were pulmonary inflammatory cell influx, epithelial cell sloughing, and hyperpermeability. Genome-wide linkage analyses of intercross (F2) and recombinant inbred cohorts identified significant and suggestive quantitative trait loci on chromosomes 2 (hyperoxia susceptibility locus 1 [Hsl1]) and 3 (Hsl2), respectively. Comparative mapping of Hsl1 identified a strong candidate gene, Nfe2l2 (nuclear factor, erythroid derived 2, like 2 or Nrf2) that encodes a transcription factor NRF2 which regulates antioxidant and phase 2 gene expression. Strain-specific variation in lung Nrf2 messenger RNA expression and a T → C substitution in the B6 Nrf2 promoter that cosegregated with susceptibility phenotypes in F2 animals supported Nrf2 as a candidate gene. Results from this study have important implications for understanding the mechanisms through which oxidants mediate the pathogenesis of lung disease.
Meshi, Bernard; Vitalis, Timothy Z.; Ionescu, Diana; Elliott, W. Mark; Liu, Chun; Wang, Xiang-Dong; Hayashi, Shizu; Hogg, James C.
doi: 10.1165/ajrcmb.26.1.4253pmid: 11751203
This study was designed to test the hypothesis that cigarette smoke–induced inflammation and emphysema are amplified by the presence of latent adenoviral (Ad) infection, and to determine whether this emphysematous process can be reversed by all-trans-retinoic acid (RA) treatment. The results confirm that in guinea pigs, chronic cigarette-smoke exposure caused lesions similar to human centrilobular emphysema. They also show that latent Ad infection combined with cigarette-smoke exposure caused an excess increase in lung volume (P < 0.001), air-space volume (P < 0.001), and lung weight (P < 0.01), and further decrease in surface-to-volume ratio (P < 0.001) compared with smoke exposure alone. RA treatment failed to reverse these emphysematous changes. Analysis of inflammatory response in parenchymal and airway tissue showed that smoking caused an increase of polymorphonuclear leukocytes (PMNs) (P < 0.0002), macrophages (P < 0.001), and CD4 cells (P < 0.0009), and that latent Ad infection independently increased PMNs (P < 0.001), macrophages (P = 0.003), and CD8 cells (P < 0.001). We conclude that latent Ad infection amplifies the emphysematous lung destruction and increases the inflammatory response produced by cigarette-smoke exposure. In this study, the increase in CD4 was associated with cigarette smoke and the increase in CD8 cells with latent Ad infection.
Coulter, Kristin R.; Doseff, Andrea; Sweeney, Patricia; Wang, Yijie; Marsh, Clay B.; Wewers, Mark D.; Knoell, Daren L.
doi: 10.1165/ajrcmb.26.1.4285pmid: 11751204
Tissue repair is determined by many signals provided in the local environment. Central to this process is the commitment of the parenchymal cell to undergo apoptosis, survive, or proliferate following inflammation. We hypothesize that lung epithelial cell apoptosis is influenced by exposure to cytokines released into the alveolar microenvironment during the inflammatory process. In this investigation we demonstrate that interferon (IFN)- γ and interleukin (IL)-1 β have opposing effects on Fas-mediated apoptosis in A549 cells, a human lung epithelial cell line. Exposure to IFN- γ before Fas activation significantly increased caspase activity, caspase processing of CK-18, a key cytoskeletal protein in epithelial cells, and increased the appearance of apoptotic nuclei. Induction of Fas-mediated death by IFN- γ was 3-fold higher than with Fas activation alone. In contrast, pretreatment with IL-1 β before Fas activation completely inhibited apoptosis. Furthermore, our results demonstrate that IFN- γ and IL-1 β induce opposite effects at multiple checkpoints during Fas-mediated apoptosis. Most striking, IL-1 β prevented the activation of caspases involved in Fas-mediated death by inducing an anti-apoptotic effect proximal to or at the point of caspase-8 activation. Finally, our investigation demonstrates that the differential impact of IL-1 β and IFN- γ on Fas-mediated apoptosis are in part dependent on modulation of the PI 3-K/Akt survival pathway.
Hind, Matthew; Corcoran, Jonathan; Maden, Malcolm
doi: 10.1165/ajrcmb.26.1.4575pmid: 11751205
Alveoli are formed postnatally in the rat, mouse, and human. The molecular signals controlling the patterning of this developmental process are not well understood. Here we describe immunohistochemical studies that label proliferating alveolar wall cells which suggest two distinct patterns of alveologenesis: (1) a low grade, peripheral subpleural parenchymal process which occurs from P1 through to P15; and (2) a dramatic increase in central cell proliferation from P4 which is complete by P15, corresponding to the well described period of alveolar septation. We describe the temporal and spatial expression of the retinoid-synthesizing enzymes Aldh-1 and Raldh-2 in the postnatal mouse lung. Both enzymes are upregulated during the period of maximal alveolar wall cell proliferation. Aldh-1 is located in the bronchial epithelium and alveolar parenchyma, and Raldh-2 is restricted to the bronchial epithelium and pleural mesothelial cells. High-pressure liquid chromatography (HPLC) reveals that rapidly septating lungs have relatively simple chromatographic profiles; in contrast, the adult lungs have a complex profile that includes many novel retinoids. These data suggest two patterns of alveolar proliferation with temporal and spatial association of the enzymes Aldh-1 and Raldh-2 and a dynamic role for different retinoids in both the septating and adult mouse lung.
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