Aldehydes potentiate α2(I) collagen gene activity by JNK in hepatic stellate cells

Hepatic stellate cells (HSCs) are responsible for type I collagen deposition in liver fibrosis that leads to cirrhosis. The purpose of this study was to examine potential molecular signals that lead to increased α2(I) collagen gene expression by acetaldehyde, the primary metabolite of alcohol and malondialdehyde (MDA), a lipid peroxidation product known to be associated with chronic liver injury. MDA and the combination of MDA and acetaldehyde were employed to determine the effect on α2(I) collagen gene expression as assessed by transient transfection analysis and reverse transcriptase polymerase chain reaction (RT-PCR). Immunoblot and subsequent immunoprecipitation analysis examined stress-activated protein kinase (SAPK) activity. Cotransfection with a dominant negative mutant for c-jun nuclear kinase (dnJNK1) was also employed with the α2(I) collagen promoter. MDA increased α2(I) collagen gene expression nearly 2.5- to 3-fold, however there was no synergistic effect of the combination of acetaldehyde and MDA on α2(I) collagen gene activation and expression. Acetaldehyde, MDA, or both significantly increased JNK activity when compared to untreated stellate cells. The dnJNK1 expression vector abrogated α2(I) collagen transgene activity. In conclusion, JNK activation appears to be critical in the signaling cascade of oxidative metabolites of chronic alcohol-related liver injury and collagen gene activation.