P2X7 receptor blockade reduces pyroptotic inflammation and promotes phagocytosis in Vibrio vulnificus infection.

Abstract

Vibrio vulnificus, a gram-negative bacterium, causes serious wound infections and septicemia. Once it develops into early phase sepsis, hyperinflammatory immune responses result in poor prognosis in patients. The present study aimed to examine the possible underlying pathogenic mechanism and explore potential agents that could protect against V. vulnificus cytotoxicity. Here, we report that infection of mouse macrophages with V. vulnificus triggers antiphagocytic effects and pyroptotic inflammation via ATP-mediated purinergic P2X7 receptor (P2X7R) signaling. V. vulnificus promoted P2X7-dependent nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 translocation, modulating the expression of the inflammasome sensor NLR family pyrin domain containing 3 (NLRP3), adaptor apoptosis-associated speck-like protein containing a card (ASC), and pyroptotic protein gasdermin D (GSDMD) in mouse macrophages. V. vulnificus induced the NLRP3/caspase-1 inflammasome signaling complex expression that drives GSDMD transmembrane pore formation and secretion of interleukin (IL)-1β, IL-18, and macrophage inflammatory protein-2 (MIP-2). This effect was blocked by P2X7R antagonists, indicating that the P2X7R mediates GSDMD-related pyroptotic inflammation in macrophages through the NF-κB/NLRP3/caspase-1 signaling pathway. Furthermore, blockade of P2X7R reduced V. vulnificus-colony-forming units in the spleen, immune cell infiltration into the skin and lung tissues, and serum concentrations of IL-1β, IL-18, and MIP-2 in mice. These results indicate that P2X7R plays a vital role in mediating phagocytosis by macrophages and pyroptotic inflammation during V. vulnificus infection and provides new opportunities for therapeutic intervention in bacterial infections.