NLRP3 inflammasome as a target of berberine in experimental murine liver injury: interference with P2X7 signaling.

Berberine (BRB) is commonly used in herbal medicine, but its mechanisms of action are poorly understood. In this study we tested BRB in steatohepatitis induced by a methionine and choline-deficient (MCD) diet, in acute acetaminophen intoxication, and in cultured murine macrophages. BRB markedly improved parameters of liver injury and necroinflammation induced by the MCD diet, although increased mortality was observed by mechanisms independent of bacterial infections or plasma levels of BRB. The MCD diet induced up-regulation of all components of NLRP3 inflammasome, and increased hepatic levels of mature IL-1β. All these parameters were significantly reduced in mice treated with BRB. In mice administered an acetaminophen overdose, a model dependent on inflammasome activation, BRB reduced mortality and ALT elevation, and limited the expression of inflammasome components. In vitro, LPS-induced activation of NLRP3 inflammasome in RAW 264.7 murine macrophages was markedly decreased by preincubation with BRB. BRB significantly limited the activation of the purinergic receptor P2X7, involved in the late phases of inflammasome activation. Upon P2X7 knockdown, the ability of BRB to block LPS-induced secretion of IL-1β was lost. These data indicate that administration of BRB ameliorates inflammation and injury in two unrelated murine models of liver damage. We demonstrate for the first time that BRB interferes with activation of the NLRP3 inflammasome pathway in vivo and in vitro, through a mechanism based on interference with activation of P2X7, a purinergic receptor involved in inflammasome activation.