CYP2E1-mediated oxidative stress induces collagen type I expression in rat hepatic stellate cells

Hepatic stellate cells (HSCs) are a major source of extracellular matrix, which, during fibrogenesis, undergo a process of "activation" characterized by increased proliferation and collagen synthesis. Oxidative stress can stimulate HSC proliferation and collagen synthesis in vitro. Cytochrome P4502E1 (CYP2E1) is an effective producer of reactive oxygen species. To study how intracellular oxidative stress modulates alpha 2 collagen type I (COL1A2) gene induction, a rat HSC line (HSC-T6) was transfected with human CYP2E1 complementary DNA in the sense and antisense orientation and with empty vector, and stable cell lines were generated. The cells expressing CYP2E1 displayed elevated production of reactive oxygen species and showed a 4-fold increase in COL1A2 messenger RNA (mRNA) levels; expression of this mRNA among different clones appeared to correlate with the level of CYP2E1. COL1A2 expression was decreased by vitamin E treatment or transfection with manganese superoxide dismutase, and was further increased after treatment with L-buthionine sulfoximine (BSO) to lower GSH levels. Thus, CYP2E1-dependent oxidative stress plays a major role in the elevation of COL1A2 mRNA levels in this system. Nuclear run-on assay showed a 3-and-a-half-fold increase in COL1A2 transcription in the cells expressing CYP2E1; stabilization of COL1A2 mRNA was also observed. These results indicate that under oxidative stress conditions, COL1A2 mRNA expression is regulated both transcriptionally and through mRNA stabilization. The CYP2E1-expressing HSC appear to be a valuable model for the sustained generation of reactive oxygen species and may allow the elucidation of signaling pathways responsible for oxidant stress-mediated collagen gene induction.