Involvement of phosphatidylinositol 3-kinase and extracellular-regulated kinase in hepatic stellate cell antioxidant response and myofibroblastic transdifferentiation.
Liver fibrogenesis is dependent upon transdifferentiation of hepatic stellate cells to a profibrogenic phenotype. Prooxidant stress purportedly stimulates both an antioxidant response and myofibroblastic transdifferentiation with fibrogenic gene expression; however, mechanisms by which oxidative stress mediates stellate cell activation remain unclear. To this end, stellate cells were treated with tert-butylhydroquinone (tBHQ), a known inducer of antioxidant response genes. As anticipated, tBHQ induced expression of antioxidant response element (ARE)-regulated genes via the transcription factor Nrf2. Further, tBHQ promoted transdifferentiation of quiescent stellate cells cultured on Engelbreth-Holm-Swarm extracellular matrix. Pretreatment of cultured stellate cells with a phosphatidylinositol 3-kinase (PI3K) inhibitor blocked tBHQ-mediated ARE-dependent gene induction as well as stellate cell transdifferentiation. In contrast, extracellular signal-regulated kinase, which was demonstrated to be prominently phosphorylated following tBHQ treatment, was not found to affect either induction of the antioxidant response nor stellate cell transdifferentiation. These data implicate involvement of PI3K pathways in tBHQ-mediated stellate cell activation and demonstrate a requirement for PI3K in the antioxidant response of hepatic stellate cells.
Reichard
John F
JF
Department of Pharmaceutical Sciences, Molecular Toxicology and Environmental Health Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Petersen
Dennis R
DR
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002070:Butadienes / Q000494:pharmacology; D002454:Cell Differentiation; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004790:Enzyme Induction; D005109:Extracellular Matrix / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D006873:Hydroquinones / Q000494:pharmacology; D008099:Liver / Q000166:cytology; D008103:Liver Cirrhosis / Q000473:pathology; D009025:Morpholines / Q000494:pharmacology; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D018384:Oxidative Stress; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020218:Response Elements; D015533:Transcriptional Activation
D000975:Antioxidants; D002070:Butadienes; D002867:Chromones; D048049:Extracellular Signal-Regulated MAP Kinases; D006873:Hydroquinones; D009025:Morpholines; D051267:NF-E2-Related Factor 2; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C495637:Nfe2l2 protein, rat; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C018855:2-tert-butylhydroquinone