Leptin induces increased alpha2(I) collagen gene expression in cultured rat hepatic stellate cells.
Leptin is a 16-kDa hormone with an array of biologic actions. We, and others, have demonstrated that leptin is critical to the development of liver fibrogenesis both in vitro and in the lean littermates of ob/ob mice exposed to carbon tetrachloride (CCl(4)). Controversy exists as to whether leptin can act as a direct cytokine in the development of increased collagen expression, and whether ob/ob mice are resistant to potential injury from CCl(4). Here, we provide evidence that strongly suggests that leptin acts to increase nascent production of mRNA for the alpha2(I) collagen gene based upon ribonuclease protection analysis (RPA). Actinomycin D, but not cyclohexamide, or the pan-neutralizing antibody to transforming growth factor beta one (TGFbeta1), significantly diminished the effect of leptin on total alpha2(I) collagen mRNA levels. Further evidence that leptin acts directly on HSCs to alter gene expression in liver wounding is demonstrated by enhanced binding of phosphorylated signal transduction and activator of transcription factor 3 (pStat3) to a cis-inducible element (SIE) oligonucleotide by electrophoretic mobility shift assay (EMSA). This consensus sequence is responsible for production of a critical collagen transcription factor, AP-1. Finally, we have demonstrated from the ob/ob mouse model that these animals are at least as sensitive to CCl(4) as their respective lean animals as assessed by serum alanine aminotransferase (ALT) measurements. Taken together, the current data provide a continued framework that leptin is a profibrogenic cytokine and plays a key role in liver fibrosis.
Saxena
Neeraj K
NK
Hepatology Section, Division of Gastroenterology, Department of Medicine, University of Maryland School of Medicine, Room N3W50, 22 South Greene Street, Baltimore, Maryland 21201, USA.
Saliba
George
G
Floyd
Jeffrey J
JJ
Anania
Frank A
FA
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D002251:Carbon Tetrachloride / Q000633:toxicity; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics*; D024042:Collagen Type I; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D020738:Leptin / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D016212:Transforming Growth Factor beta / Q000276:immunology
D024042:Collagen Type I; D020738:Leptin; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D003609:Dactinomycin; D003094:Collagen; D003513:Cycloheximide; D002251:Carbon Tetrachloride; D000410:Alanine Transaminase