Up-regulation of CD14 in liver caused by acute ethanol involves oxidant-dependent AP-1 pathway

Ethanol is known to cause both tolerance and sensitization to endotoxin (lipopolysaccharide). It is also known that ethanol modulates the expression and activity of several intracellular signaling molecules and transcription factors in monocytes and Kupffer cells, the resident hepatic macrophages. Expression of CD14, the endotoxin receptor, is up-regulated following chronic exposure to endotoxin and ethanol. Ethanol-induced oxidative stress is important in the regulation of transcription factor activation and cytokine production by Kupffer cells. Thus, it was hypothesized that acute ethanol increases CD14 expression through a mechanism dependent upon oxidant production. This hypothesis was tested by overexpression of superoxide dismutase via recombinant adenovirus. Mice were infected with adenovirus (3 x 10(9) plaque-forming units, intravenously) containing either Cu,Zn superoxide dismutase (Ad.SOD1) or beta-galactosidase (Ad.lacZ), which caused significant expression of Cu,Zn-SOD in hepatocytes and Kupffer cells. Three days post-infection, mice were given saline or ethanol (5 g/kg, intragastrically). A significant increase in CD14 mRNA was observed 3 h after ethanol, and this increase was almost completely blocked in mice overexpressing Cu,Zn-SOD. Additionally, overexpression of SOD also blunted ethanol-induced activation of redox-sensitive transcription factors NFkappaB and AP-1 and production of cytokines. However, only inhibition of AP-1 with dominant-negative TAK1 but not NFkappaB by dominant-negative IkappaBalpha significantly blunted ethanol-induced increases in CD14, suggesting that AP-1 is important for CD14 transcriptional regulation. It is also shown here that NADPH oxidase is important in the increase in CD14 due to ethanol. Moreover, these data suggest that acute ethanol causes sensitization to endotoxin through mechanisms dependent upon oxidative stress.