CsNOSIP Reverses NLRP3 Inflammasome Activation Induced by CsESPs via Inducing iNOS and NO Expression and Inhibiting NF-κB Signaling Pathway in Macrophages

Excretory/secretory products from parasites (ESPs) can act as pathogen-associated molecular patterns (PAMPs) to activate innate immunity. Parasites may achieve immune evasion by modulating the interaction between PAMPs and the nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing three (NLRP3) inflammasome. Previous studies have suggested that some components of ESPs from Clonorchis sinensis (CsESPs) can induce the host’s immune responses, but the components that balance immunopathology and maintain chronic infection in chronic Clonorchis sinensis (C. sinensis) remain unclear. We previously found that the iNOS-interacting protein from C. sinensis (CsNOSIP), a component of CsESP, stimulates macrophages to produce reactive oxygen species (ROS) and nitric oxide (NO), both of which inhibit NLRP3 inflammasome activation. Therefore, this study investigated the effects of CsESP and CsNOSIP on inflammasome activation using RT-PCR, Western blot, and ELISA. This study showed that CsESPs promoted NLRP3 inflammasome activation in RAW264.7 cells, while CsNOSIP inhibited LPS-induced IL-1β secretion through an NLRP3-caspase-1-dependent pathway and reversed the CsESPs-induced activation through the iNOS/NO–NF-κB pathway. These results reveal the antagonistic effects of CsESPs and CsNOSIP in inflammasome regulation, suggesting that this balance contributes to the regulation of the host’s immunity and the promotion of chronic infection of C. sinensis, providing potential targets for prevention and treatment.