Desensitization to LPS after ethanol involves the effect of endotoxin on voltage-dependent calcium channels

Hepatic macrophages are sensitized to alcohol in 24 h due to increases in t he endotoxin receptor, CD14; however, desensitization to lipopolysaccharide (LPS), which occurred earlier, could not be explained by changes in CD14. Therefore, the purpose of this work was to attempt to understand factors re sponsible for ethanol-induced desensitization to LPS in hepatic macrophages . Rats were given ethanol (5 g/kg body wt) intragastrically, and hepatic ma crophages were isolated 2 h later. After addition of endotoxin, intracellul ar Ca2+ concentration ([Ca2+](i)) was measured using fura 2 and tumor necro sis factor (TNF)-alpha was measured by ELISA. Ethanol given 2 h before inje ction of LPS totally prevented liver injury and blunted LPS-induced increas es in [Ca2+](i) and TNF-alpha in hepatic macrophages. Furthermore, the prot ein kinase C (PKC) agonist phorbol 12-myristate 13-acetate and acute ethano l treatment both activated PKC and largely prevented the influx of [Ca2+](i ) caused by LPS. Sterilization of the gut with antibiotics completely block ed all effects of ethanol on [Ca2+](i) and TNF-alpha release. Thus ethanol- induced desensitization of hepatic macrophages correlates with gut-derived endotoxin after ethanol and involves the effect of PKC on voltage-dependent Ca2+ channels.