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 alpha(1)(I) collagen mRNA in stellate cells exposed to 200 mu mol/liter of acetaldehyde. The purpose of these studies was to determine whether PKC activation plays a role in transcriptional activation of the alpha(2)(I) collagen gene. Cultured stellate cells were exposed to 200 mu mol/liter of acetaldehyde. PKC, inositol triphosphate, diacylglycerol (DAG), and intracellular free calcium (Ca-i(2+)) were measured. alpha(1)(I) and alpha(2)(I) collagen messages were determined by reverse transcriptase-polymerase chain reaction. Activation of the alpha(2)(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 Ca-i(2+), or inositol triphosphate but increased DAG levels at 20 min and 3 hr, Acetaldehyde increased both the alpha(1)(I) and alpha(2)(I) collagen messages in stellate cells. Calphostin C, a specific PKC inhibitor, which blocks DAG binding, eliminated both activation of the alpha(2)(I) collagen promoter by acetaldehyde and mRNA production by reverse transcriptase-polymerase chain reaction analysis, Similarly, D609, an inhibitor of DAG production, also inhibited alpha(2)(I) collagen gene expression. This study shows that collagen production by acetaldehyde is mediated by a calcium-independent PKC mechanism.