CD14 expression on Kupffer cells during the course of carbon tetrachloride-mediated liver injury.

OBJECTIVE:  To investigate the expression of CD14 on Kupffer cells during the course of carbon tetrachloride (CCl4)-mediated liver injury and its role in the activation of Kupffer cells. METHODS:  Rats were administered CCl4 twice weekly for up to 8 weeks. Kupffer cells were isolated from normal and CCl4-treated rats by the combined ‘collagenase-pronase’ perfusion method, discontinuous density gradient centrifugation. On the day after isolation, the cells were incubated with RPMI-1640 containing varying doses of lipopolysaccharide (LPS) for 6 h. Supernatants were then collected for measuring the concentration of tumor necrosis factor-alpha (TNF-α) by enzyme-linked immunosorbent assay (ELISA). The expression of CD14 mRNA on Kupffer cells were determined by RT-PCR. The plasma concentrations of endotoxin were determined by chromogenic substrate Limulus amebocyte lysate assay. RESULTS:  Basic TNF-α production of Kupffer cells isolated from CCl4-treated rats at 4 and 6 weeks was significantly higher than that of normal (P < 0.05). Following LPS stimulation the production of TNF-α was markedly increased in Kupffer cells from the 2-, 4- and 6-week treatment groups (P < 0.05). Moreover, LPS-induced TNF-α production was dose-dependent. CD14 mRNA expression on Kupffer cells isolated from CCl4-treated rats was elevated following 2 weeks of CCl4 administration and the maximum elevation occurred at 6 weeks. Gene expression was decreased in Kupffer cells after 8 weeks of CCl4 treatment. CCl4 administration elicited extensive changes in liver morphology, including steatosis, inflammation and necrosis. The plasma concentrations of endotoxin of CCl4-treated rats were increased during the time of liver injury. CONCLUSION:  Up-regulation of CD14 expression in Kupffer cells during CCl4-mediated chronic liver injury indicates cell activation and that they are more sensitive to LPS stimulation. Kupffer cells are critical effector cells in the early stage of liver injury.