Galectin-3 regulates inflammasome activation in cholestatic liver injury

Macrophage activation is an important feature of primary biliary cholangitis (PBC) pathogenesis and other cholestatic liver diseases. Galectin-3 (Gal3), a pleiotropic lectin, is produced by monocytic cells and macrophages. However, its role in PBC has not been addressed. We hypothesized that Gal3 is a key to induce NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in macrophages and in turn to propagate proinflammatory IL-17 signaling. In liver tissues from patients with PBC and dnTGF-beta RII mice, a model of autoimmune cholangitis, the expression of Gal3, NLRP3, and the adaptor protein adaptor apoptosis-associated speck-like protein was induced, with the down stream activation of caspase-1 and IL-1 beta. In wild-type hepatic macrophages, deoxycholic acid induced the association of Gal3 and NLRP3 with direct activation of the inflammasome, resulting in an increase in IL-1b. Downstream retinoid-related orphan receptor C mRNA, IL-17A, and IL-17F were induced. In Gal3(-/-) macrophages, no inflammasome activation was detected. To confirm the key role of Gal3 in the pathogenesis of cholestatic liver injury, we generated dnTGF-bRII/galectin-3(-/-) (dn/Gal3(-/-)) mice, which showed impaired inflammasome activation along with significantly improved inflammation and fibrosis. Taken together, our data point to a novel role of Gal3 as an initiator of inflammatory signaling in autoimmune cholangitis, mediating the activation of NLRP3 inflammasome and inducing IL-17 proinflammatory cascades. These studies provide a rationale to target Gal3 in autoimmune cholangitis and potentially other cholestatic diseases.