Long-term alcohol exposure changes sensitivity of rat Kupffer cells to lipopolysaccharide

Background: Chronic ethanol treatment enhances Kupffer cell sensitivity to lipopolysaccharide (LPS). In this model, CD14 in Kupffer cells was increased significantly 4 weeks after ethanol. Moreover, it was shown that prostaglandin E-2 produced by activated Kupffer cells participated in the mechanism of ethanol-induced fatty liver. This study was designed to elucidate the temporal effect of chronic ethanol exposure on Kupffer cell sensitization to LPS. Methods: Rats were given ethanol every 24 hr intragastrically for up to 12 weeks, and Kupffer cells were isolated 24 hr after the final ethanol administration and cultured in RPMI 1640 with 10% fetal bovine serum. After addition of LPS to Kupffer cells, intracellular calcium ([Ca2+](i)) was measured. Results: CD14 in Kupffer cells was increased approximately 2-fold, and then it decreased and returned to control levels. The LPS-induced increases in [Ca2+](i) and tumor necrosis factor-alpha by Kupffer cells were also increased approximately 3-fold over control values, but they also returned to control levels. Triglyceride content increased with the duration of chronic ethanol treatment. At 8 weeks, prostaglandin E-2 produced by Kupffer cells increased approximately 3-fold over control values and triglycerides by approximately 4-fold before gradually decreasing to basal levels. After 12 weeks of ethanol exposure, LPS-induced increases in [Ca2+](i) and tumor necrosis factor-a production were only approximately 50% as high as peak levels at 4 weeks. Liver triglyceride content at 12 weeks was reduced significantly compared with values at 8 weeks. Conclusions: Kupffer cells at the early stage of chronic ethanol exposure exhibited sensitization to LPS, but this sensitivity was blunted later. This correlated with triglyceride accumulation in the liver. These data indicate that long-term alcohol exposure changes the sensitivity of rat Kupffer cells to LPS but that the magnitude of the effect is time dependent.