Bile acids: Trying to understand their chemistry and biology with the hope of helping patientsHofmann, Alan F.
doi: 10.1002/hep.22789pmid: 19296471
An informal review of the author's five decades of research on the chemistry and biology of bile acids in health and disease is presented. The review begins with a discussion of bile acid structure and its remarkable diversity in vertebrates. Methods for tagging bile acids with tritium for metabolic or transport studies are summarized. Bile acids solubilize polar lipids in mixed micelles; progress in elucidating the structure of the mixed micelle is discussed. Extensive studies on bile acid metabolism in humans have permitted the development of physiological pharmacokinetic models that can be used to simulate bile acid metabolism. Consequences of defective bile acid biosynthesis and transport have been clarified, and therapy has been developed. Methods for measuring bile acids have been improved. The rise and fall of medical and contact dissolution of cholesterol gallstones is chronicled. Finally, principles of therapy with bile acid agonists and antagonists are given. Advances in understanding bile acid biology and chemistry have helped to improve the lives of patients with hepatobiliary or digestive disease. (HEPATOLOGY 2009.)
Hepatitis C virus persisting after clinically apparent sustained virological response to antiviral therapy retains infectivity in vitroMacParland, Sonya A.; Pham, Tram N. Q.; Guy, Clifford S.; Michalak, Tomasz I.
doi: 10.1002/hep.22802pmid: 19177592
Hepatitis C virus (HCV) can persist in the liver, lymphoid cells, and serum of individuals with apparently complete spontaneous or therapy‐induced resolution of hepatitis C and can replicate in vivo and in vitro in human T cells. The current study was aimed at assessing the infectivity of HCV persisting at very low levels using the previously established HCV infection system in human T cells. Naive lymphoid cells were exposed to plasma and/or supernatants from cultured peripheral blood mononuclear cells from nine individuals with apparent sustained virological response after completion of antiviral therapy. Exposed cells were analyzed for HCV RNA–positive and HCV RNA–negative strands and, in selected cases, for HCV nonstructural protein 5a (NS5a), the appearance of HCV variants, and the release of virions by immunoelectron microscopy (IEM). The results showed that 11 of the 12 established cultures became HCV RNA–positive strand–reactive, whereas 4 also expressed the virus replicative strand. NS5a protein was detected in the de novo infected cells, and clonal sequencing revealed HCV variants not found in inocula. IEM demonstrated enveloped HCV particles in plasma used as inocula and in culture supernatant from T cells exposed to that plasma. Overall, HCV carried in three of the nine individuals studied elicited productive infection in vitro. Conclusion: HCV persisting at very low levels long after therapy‐induced resolution of chronic hepatitis C can remain infectious. The retained biological competence of the virus might have implications with respect to the mechanisms of its persistence and the epidemiology of HCV infection. (HEPATOLOGY 2009.)
Elevations in alanine aminotransferase levels late in the course of antiviral therapy in hepatitis C virus RNA–negative patients are associated with virological relapseBasso, Monica; Giannini, Edoardo G.; Torre, Francesco; Blanchi, Sabrina; Savarino, Vincenzo; Picciotto, Antonino
doi: 10.1002/hep.22810pmid: 19350657
The incidence and clinical meaning of elevated alanine aminotransferase (ALT) in chronic hepatitis C patients who are hepatitis C virus (HCV)‐RNA negative during pegylated interferon (PEG‐IFN) and ribavirin therapy have not been completely characterized. In this study our aim was to assess the incidence, pattern, predictive factors, and clinical meaning of elevated ALT in a cohort of 173 chronic hepatitis C patients who obtained viral clearance during either PEG‐IFNα2a or α2b and weight‐based ribavirin therapy. Patients were defined sustained viral responders (SVRs) or relapser responders (RRs) on the basis of a serum HCV‐RNA result at 24‐week follow‐up. SVR and RR were obtained in 141 (58%) and 32 patients (13%), respectively. Among the 173 study patients, 57 patients (33%) had undetectable serum HCV‐RNA and elevated ALT in at least one evaluation (weeks 2, 4, 12, 24 in all genotypes, and week 48 in HCV genotype 1 and 4 alone), and this phenomenon was not differently distributed between SVRs and RRs. No pretreatment demographic (age, gender), clinical (ALT levels, histological grade and stage, body mass index) and viral (load, genotype) parameter was associated with this phenomenon. The incidence of elevated ALT levels was not associated with type of PEG‐IFN and ribavirin dose. Elevated ALT levels showed a different longitudinal pattern, occurring more frequently between week 12 and the end of treatment in RR as compared to SVR patients (90% versus 9%, P = 0.000001). Conclusion: The occurrence of elevated ALT levels in HCV‐RNA‐negative patients during PEG‐IFN and ribavirin therapy is a fairly frequent and unpredictable phenomenon. Although ALT elevation per se is not associated with a greater risk of relapse, its occurrence in the later phases of therapy is more common in relapsing patients. (HEPATOLOGY 2009.)
Seroconversion to hepatitis C virus alternate reading frame protein during acute infectionMorice, Yoann; Ratinier, Maxime; Miladi, Ahmed; Chevaliez, Stéphane; Germanidis, Georgios; Wedemeyer, Heiner; Laperche, Syria; Lavergne, Jean‐Pierre; Pawlotsky, Jean‐Michel
doi: 10.1002/hep.22821pmid: 19350656
The existence of hepatitis C virus (HCV) proteins encoded by alternate reading frames overlapping the core‐encoding region has been suggested. Several mechanisms of production have been postulated, and the functions of these proteins in the HCV life cycle remain unknown. We analyzed cases of seroconversion to an alternate reading frame protein in a group of 17 patients infected by one of the two HCV genotype 1b strains during an outbreak in a hemodialysis unit. Three patients seroconverted, and antibodies were transiently detected in another patient. Three of these patients were infected by one of the two HCV strains, whereas the strain infecting the remaining patient could not be identified. Quasispecies sequence analysis of the core‐coding region showed no differences in the core or +1 reading frame sequences that could explain alternate reading frame protein seroconversion in some but not all of the patients infected by one of the HCV strains, and no such difference was found between the two strains. Because differences in the structure of RNA elements could play a role in frameshift events, we conducted a predictive analysis of RNA folding. No difference was found between the patients who did and did not seroconvert to alternate reading frame protein. Conclusion: Our findings prove that alternate reading frame proteins can be produced during acute HCV infection. However, seroconversion does not occur in all patients for unknown reasons. Alternate reading frame protein could be generated by minority quasispecies variants or variants that occur transiently. (HEPATOLOGY 2009.)
Hepatitis C virus core protein triggers hepatic angiogenesis by a mechanism including multiple pathwaysHassan, Mohamed; Selimovic, Denis; Ghozlan, Hanan; Abdel‐kader, Ola
doi: 10.1002/hep.22849pmid: 19235829
Chronic hepatitis C virus (HCV) infection is associated with the production of serum cytokines, including transforming growth factor (TGF)‐β2. Despite the occurrence of hepatic angiogenesis in liver conditions, the role of HCV proteins in this context is currently unknown. We demonstrated that the development of hepatic neoangiogenesis in patients infected with HCV is associated with the expression of TGF‐β2 and vascular endothelial growth factor (VEGF) and with activation of endothelial cells, as evidenced by CD34 expression. The analysis of liver biopsies of HCV‐positive and HCV‐negative patients using immunostaining showed significant elevation of TGF‐β2, VEGF, and CD34 expression in patients who were HCV‐positive. Using an HCV established culture system, we confirmed further the production of both TGF‐β2 and VEGF proteins, in the hepatoma cell lines HepG2 and Huh7 by transfection with full‐length HCV RNA (JFH1) or by the regulated expression of core. In addition, regulated expression of core protein in HepG2 or Huh7 cells was found to induce expression and activation of the transcription factor E2F1 and apoptosis signal‐regulating kinase 1 (ASK1), activation of c‐jun‐N‐terminal kinase (JNK) and p38, and extracellular‐regulated kinase (ERK), and transcription factors activator protein 1 (AP‐1), activating transcription factor 2 (ATF‐2), cyclic adenosine monophosphate response element binding (CREB), E2F1, hypoxia inducing factor 1 alpha (HIF‐1α), and specificity protein 1. Furthermore, data obtained from inhibitor experiments revealed the importance of E2F1 and ASK1 in the modulation of core‐induced activation of JNK and p38 pathways and suggested an essential role for JNK, p38, and ERK pathways in the regulation of core‐induced production of TGF‐β2 and VEGF proteins. Thus, our data provide insight into the molecular mechanisms whereby core protein mediates the development of hepatic angiogenesis in patients with chronic HCV infection. (HEPATOLOGY 2009.)