Genipin protects D-galactosamine and lipopolysaccharide-induced hepatic injury through suppression of the necroptosis-mediated inflammasome signaling
Acute liver failure (ALF) is a life-threatening syndrome resulting from massive inflammation and hepatocyte death. Necroptosis, a programmed cell death controlled by receptor-interacting protein kinase (RIP) 1 and RIP3, has been shown to play an important role in regulating inflammation via crosstalk between other intracellular signaling. The inflammasome is a major intracellular multiprotein that induces inflammatory responses by mediating immune cell infiltration, thus potentiating injury. Genipin, a major active compound of the gardenia fruit, exhibits anti-inflammatory, antioxidant, and anti-apoptotic properties. This study investigated the hepatoprotective mechanisms of genipin on D-galactosamine (GalN) and lipopolysaccharide (LPS)-induced ALF, particularly focusing on interaction between necroptosis and inflammasome. Mice were given an intraperitoneal injection of genipin (25, 50, and 100 mg/kg) or necrostatin-1 (Nec-1, a necroptosis inhibitor; 1.8 mg/kg) 1 h prior to GalN (800 mg/kg)/LPS (40 μg/kg) injection and were killed 3 h after GalN/LPS injection. Genipin improved the survival rate and attenuated increases in serum aminotransferase activities and inflammatory cytokines after GalN/LPS injection. Genipin reduced GalN/LPS-induced increases in RIP3, phosphorylated RIP1 and RIP3 protein expression, and RIP1/RIP3 necrosome complex, similar to the effects of Nec-1. GalN/LPS significantly increased serum levels of high-mobility group box 1 and interleukin (IL)-33, which were attenuated by genipin and Nec-1. Moreover, similar to Nec-1, genipin attenuated GalN/LPS-induced increases in the protein expression levels of NLRP3, ASC, and caspase-1, inflammasome components, and levels of liver and serum IL-1β. Taken together, our findings suggest that genipin ameliorates GalN/LPS-induced hepatocellular damage by suppressing necroptosis-mediated inflammasome signaling.