Abstract
Innate immunity is the first line of defense against pathogen-associated molecular patterns (PAMPs) and endogenous danger-associated molecular patterns (DAMPs) in the central nervous system (CNS) and the peripheral immune system. CNS injury involves cellular damage that is at least in part caused by an innate inflammatory response induced by extracellular ATP. Pattern recognition receptors (PRRs), including NOD-like receptors (NLRs), are involved in signaling cascades that regulate innate immune responses to CNS injury. However, their exact mechanism of action currently remains largely undefined. In this doctoral thesis, I investigated the expression of the NLR protein 2 (NLRP2) inflammasome in cortical human astrocytes in vitro and evaluated whether ATP activates the NLRP2 inflammasome. The NLRP2 inflammasome is a multiprotein complex that consists of NLRP2, the adaptor protein apoptosis-speck-like protein containing a caspase recruitment domain (ASC) and caspase-1. The NLRP2 inflammasome interacts with the P2X7 receptor and the pannexin 1 channel and that stimulation of human astrocytes with ATP results in activation of the NLRP2 inflammasome, leading to the processing of inflammatory caspase-1 and interleukin-1β (IL-1β). ATP-induced activation of the NLRP2 inflammasome was inhibited by the pannexin 1 inhibitor probenecid and by the P2X7 receptor antagonist brilliant blue G (BBG). Moreover, siRNA knockdown of NLRP2 significantly decreased levels of NLRP2 and caspase-1 proteins in human astrocytes in response to ATP. Collectively, my findings suggest that the astrocytic NLRP2 inflammasome may be an important component of the CNS inflammatory response and that the NLRP2 inflammasome may be a therapeutic target to inhibit inflammation induced by CNS injury.