Differential cytokine-mediated modulation of endocytosis in rat liver endothelial cells

We have studied the effects of exogenous tumor necrosis factor-alpha, interleukin-1 beta, and lipopolysaccharide-induced interleukin-1 beta on receptor-mediated endocytosis in primary cultures of liver sinusoidal endothelial cells. Tumor necrosis factor-alpha and interleukin-1 beta enhanced endocytosis via the scavenger and mannose receptors in a dose-time dependent manner, while the function of the collagen receptor remained unaffected. The modulatory effects of the cytokines were blocked by adding specific inhibitors for both cytokines. Results from studies on binding (4 degrees C) and internalization and degradation (37 degrees C) of ligands indicate that the increased scavenger capacity of liver sinusoidal endothelial cells resulting from exposure to the inflammatory mediators was due to increased rate of intracellular transport of endocytosed ligands to lysosomes, rather than to increased binding to receptors.