Endotoxin-stimulated macrophages decrease bile acid uptake in WIF-B cells,a rat hepatoma hybrid cell line

Endotoxemia leads to cytokine-mediated alterations of the hepatocellular so dium-taurocholate-cotransporting polypeptide (ntcp). We hypothesized that s timulated macrophages are essential transducers for down-regulating hepatoc ellular bile salt uptake in response to endotoxin (lipopolysaccharide [LPS] ) exposure, Using an in vitro model, we exposed mouse macrophages (IC-21 ce ll line) to LPS for 24 hours. Concentrations of cytokines tumor necrosis fa ctor-alpha (TNF-alpha), interleukin (IL)-1 beta, and IL-6 increased 10.6-fo ld, 12.5-fold, and 444-fold, respectively, in LPS-conditioned IC-21 medium (CM) versus unconditioned IC-21 medium (UM), WIF-B rat hepatoma hybrid cell s were incubated with either CM or UM or treated directly with medium conta ining recombinant TNF-alpha, IL-1 beta, and IL-6. [H-3]Taurocholate ([H-3]T C) uptake decreased in WIF-B cells exposed to either TNF-alpha (54% of cont rol), IL-1 beta (78%), IL-6 (55%) as single additives, or in triple combina tion (TCC) (43%), A virtually identical decrease was observed after exposin g WIF-B cells to CM (52%, P <.001). LPS had no direct effect on [H-3]TC upt ake. CM treatment did not decrease L-alanine transport in WIF-B cells. Bloc king antibodies against TNF-alpha, IL-1 beta, and IL-6 restored the diminis hed [H-3]TC uptake in cells exposed to TCC and CM to 87% and 107% of contro ls, respectively. Northern blotting revealed that ntcp messenger RNA (mRNA) expression was significantly reduced in WIF-B cells after exposure to CM, and in primary rat hepatocytes exposed to CM or TNF-alpha (68%, 14%, and 29 % of control, respectively). We conclude that macrophages and their ability to secrete the cytokines TNF-alpha, IL-1 beta, and IL-6 may be essential i n mediating the endotoxin-induced cholestatic effect of decreased hepatocel lular bile salt uptake.