Peroxynitrite is key to Cylindrospermopsin-mediated MASLD to MASH progression via triggering TXNIP binding to NLRP3 and subsequent inflammasome activation.

Harmful algal bloom (HAB) toxins are shown to be associated with Metabolic dysfunction-associated steatohepatitis (MASH) progression. Several studies link the HAB toxin microcystin to hepatic inflammasome activation, but the role of cylindrospermopsin (CYN) in Metabolic dysfunction-associated steatotic liver disease (MASLD) pathology remains unknown. Using a mouse model of MASLD, we show that CYN exposure served as a second hit for MASLD to MASH progression, as shown by histopathology and NAS scoring. The pathology was attenuated by the use of NADPH oxidase 2 (NOX2) inhibitor apocynin and peroxynitrite inhibitor phenylboronic acid. Inhibition of peroxynitrite and other redox signaling processes decreased stellate cell activation and fibronectin protein in the hepatic lobules, thus confirming the involvement of the above nitrosative moiety in early fibrotic remodeling, crucial for MASH progression. Redox inhibitors also decreased the endothelial Nitric Oxide Synthase (eNOS)/inducible Nitric Oxide Synthase (iNOS) protein ratio, thus raising the yield of inducible nitric oxide and facilitating the uncoupling of eNOS. Mechanistically, peroxynitrite inhibitors coupled with attenuation of redox processes prevented Thioredoxin-interacting protein (TXNIP) colocalization with NLRP3 and resulted in the inhibition of NLRP3 inflammasome activation, a crucial mediator of hepatic inflammation in MASH. Hepatocyte-hepatic macrophage crosstalk, crucial for MASH progression, was shown to induce NOX2 activation, the generation of 3-nitrotyrosine in close proximity to iNOS, a predictive nitric oxide source, thus confirming the role of these cells in activating the inflammation cascade. The results show a crucial role of peroxynitrite in TXNIP-NLRP3 induced inflammasome activation and can be a crucial therapeutic target in treating MASH etiology from environmental exposure.