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 sodium‐taurocholate‐cotransporting polypeptide (ntcp). We hypothesized that stimulated macrophages are essential transducers for down‐regulating hepatocellular bile salt uptake in response to endotoxin (lipopolysaccharide [LPS]) exposure. Using an in vitro model, we exposed mouse macrophages (IC‐21 cell line) to LPS for 24 hours. Concentrations of cytokines tumor necrosis factor‐α (TNF‐α), interleukin (IL)‐1β, and IL‐6 increased 10.6‐fold, 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 cells were incubated with either CM or UM or treated directly with medium containing recombinant TNF‐α, IL‐1β, and IL‐6. [3H]Taurocholate ([3H]TC) uptake decreased in WIF‐B cells exposed to either TNF‐α (54% of control), IL‐1β (78%), IL‐6 (55%) as single additives, or in triple combination (TCC) (43%). A virtually identical decrease was observed after exposing WIF‐B cells to CM (52%, P < .001). LPS had no direct effect on [3H]TC uptake. CM treatment did not decrease L‐alanine transport in WIF‐B cells. Blocking antibodies against TNF‐α, IL‐1β, and IL‐6 restored the diminished [3H]TC uptake in cells exposed to TCC and CM to 87% and 107% of controls, 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‐α (68%, 14%, and 29% of control, respectively). We conclude that macrophages and their ability to secrete the cytokines TNF‐α, IL‐1β, and IL‐6 may be essential in mediating the endotoxin‐induced cholestatic effect of decreased hepatocellular bile salt uptake.