Pathophysiological roles of interleukin-18 in inflammatory liver diseases

Innate immune response to microbes sometimes determines the nature of the Following specific immune response. Kupffer cells, a potent constituent of innate immunity, play a key role in developing the type 1 immune response by interleukin (IL)-12 production. Furthermore, Kupffer cells have the potential to induce liver injury by production of IL-1.8. Propionibacterium acnes-primed lipopolysaccharide (LPS)-challenged Liver injury is the prototype of IL-18-induced tissue injury, in which IL-18 acts on natural killer cells to increase Fas ligand (FasL) that causes liver injury by induction of Fas-dependenet hepatocyte apoptosis. LPS induces IL-18 secretion from Kupffer cells in a caspase-1-dependent manner. Indeed, caspase-1-deficient mice are resistant to P. acnes and LPS-induced liver injury. However, administration of soluble Fast induces acute: liver injury in P. acnes-primed caspase-1-deficient mice bur: does not do so in IL-18-deficient mice, indicating that IL-18 release in a caspase-1-independent fashion is essential for this liver injury. Therefore, a positive feedback loop between Fast and IL-18 plays an important role in the pathogenesis of endotoxin-induced liver injury.