The cardiac glycoside ouabain activates NLRP3 inflammasomes and promotes cardiac inflammation and dysfunction

Cardiac glycosides such as digoxin are Na+/K+-ATPase inhibitors that are widely used for the treatment of chronic heart failure and cardiac arrhythmias; however, recent epidemiolog- ical studies have suggested a relationship between digoxin treatment and increased mortal- ity.Wepreviously showed that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes, which regulate caspase-1- dependent interleukin (IL)-1β release, mediate the sterile cardiovascular inflammation. Because the Na+/K+–ATPase is involved in inflammatory responses, we investigated the role of NLRP3 inflammasomes in the pathophysiology of cardiac glycoside-induced cardiac inflammation and dysfunction. The cardiac glycoside ouabain induced cardiac dysfunction and injury in wild-type mice primed with a low dose of lipopolysaccharide (LPS), although no cardiac dysfunction was observed in mice treated with either ouabain or LPS alone. Oua- bain also induced cardiac inflammatory responses, such as macrophage infiltration and IL- 1β release, when mice were primed with LPS. These cardiac manifestations were all signifi- cantly attenuated in mice deficient in IL-1β. Furthermore, deficiency of NLRP3 inflamma- some components, NLRP3 and caspase-1, also attenuated ouabain-induced cardiac dysfunction and inflammation. In vitro experiments revealed that ouabain induced NLRP3 inflammasome activation as well as subsequent IL-1β release from macrophages, and this activation was mediated by K+ efflux. Our findings demonstrate that cardiac glycosides pro- mote cardiac inflammation and dysfunction through NLRP3 inflammasomes and provide new insights into the mechanisms underlying the adverse effects of cardiac glycosides.