Abstract
Injury associated with neuroinflammation has been linked with several kinds of neurodegenerative diseases. The activation of the NLRP3 inflammasome plays an important role in microglia-mediated inflammation. Phoenixin (PNX)-20 is a newly discovered neuropeptide with pleiotropic effects involved in the regulation of reproductive and cognitive function, depression, and food uptake. This study investigated whether PNX-20 possesses a protective effect against lipopolysaccharide (LPS)-induced activation of the NLRP3 inflammasome in microglia. Firstly, our results show that the PNX-20 treatment significantly prevented LPS-induced expression of NADPH oxidase 4 (NOX-4) and the generation of reactive oxygen species (ROS). Secondly, PNX-20 mitigated LPS-induced upregulation of TxNIP, an upstream regulator of NLRP3 inflammasome activation. Thirdly, further evaluation of the major components of the NLRP3 inflammasome revealed that PNX-20 inhibited LPS-mediated upregulation of NLRP3, ASC, and cleaved caspase-1 (P10). Notably, based on our results, the inhibitory effect of PNX-20 on the NLRP3 inflammasome results in the inhibition of IL-1β and IL-18 secretions. Finally, we found that PNX-20 ameliorated the reduction in SIRT1 expression induced by LPS. When microglial SIRT1 was inhibited by nicotine, PNX-20 lost its suppressive effect on the expression of NLRP3, ASC, and caspase-1, as well as the secretion of IL-1β and IL-18. As a result of these findings, we draw the conclusion that the neuroprotective effect of PNX-20 is dependent on SIRT1. Collectively, the study shows that PNX-20 has a regulatory effect via modulation of neuroinflammation.