Hepatocyte-Derived Extracellular Vesicles Deliver miR-328-3p to Trigger PP2A-B56δ-Mediated p-NLRP3S295-Dependent Metaflammation in Macrophages upon Microcystin-LR Exposure

Microcystin-LR (MC-LR) exacerbates metabolic dysfunction-associated steatotic Liver Disease (MASLD) by inducing histopathological damage and Lipid Metabolism disorders. Inducible hepatocyte-derived extracellular vesicles (iHD-EVs) released after xenobiotic exposure activate the macrophage NOD-like Receptor protein 3 (NLRP3) inflammasome. Suppression of NLRP3 phosphorylation at serine 295 (p-NLRP3^S295) is previously shown to alleviate MASLD progression. Here, it is demonstrated that microcystin-LR (MC-LR)-induced iHD-EVs reduced deliver of miR-328-3p to Macrophages, thereby upregulating protein Phosphatase 2A (PP2A)-B56δ. Consequent PP2A-B56δ activation disrupts inositol 1,4,5-triphosphate receptor and voltage-dependent anion channel 1 coupling, evokes mitochondria-associated endoplasmic reticulum membrane (MAM) calcium (CA²⁺) overload, and recruits p-NLRP3^S295 into the inflammasome. Neutralization of p-NLRP3^S295 with a site-specific monoclonal antibody (anti-p-NLRP3^S295 mAb) markedly attenuates liver inflammation and injury in MC-LR-exposed mice. Collectively, the miR-328-3p/PP2A-B56δ/p-NLRP3^S295 axis is identified as a crucial driver of metaflammation and establishes circulating EV-miR-328-3p as a novel biomarker and anti-p-NLRP3^S295 mAbs as translational tools for MC-LR-associated MASLD.