Acetaldehyde enhances murine α₂(I) collagen promoter activity by Ca²⁺-independent protein kinase C activation in cultured rat hepatic stellate cells

Protein kinase C (PKC) inhibitors decrease α₁(I) collagen mRNA in stellate cells exposed to 200 μmol/liter of acetaldehyde. The purpose of these studies was to determine whether PKC activation plays a role in transcriptional activation of the α₂(I) collagen gene. Cultured stellate cells were exposed to 200 μmol/liter of acetaldehyde. PKC, inositol triphosphate, diacylglycerol (DAG), and intracellular free calcium (Ca²⁺(i)) were measured. α₁(I) and α₂(I) collagen messages were determined by reverse transcriptase-polymerase chain reaction. Activation of the α₂(I) collagen promoter was determined in transiently transfected stellate cells. Acetaldehyde exposure enhanced PKC activity translocation to the particulate fraction at 20 min. Acetaldehyde did not increase Ca²⁺(i), or inositol triphosphate but increased DAG levels at 20 min and 3 hr. Acetaldehyde increased both the α₁(I) and α₂(I) collagen messages in stellate cells. Calphostin C, a specific PKC inhibitor, which blocks DAG binding, eliminated both activation of the α₂(I) collagen promoter by acetaldehyde and mRNA production by reverse transcriptase-polymerase chain reaction analysis. Similarly, D609, an inhibitor of DAG production, also inhibited α₂(I) collagen gene expression. This study shows that collagen production by acetaldehyde is mediated by a calcium-independent PKC mechanism.