An immunomodulatory ochratoxin analogue from marine Aspergillus sp. potentiates macrophage defense against Edwardsiella tarda via AIFM1-mediated necroptosis inhibition.

Edwardsiella tarda is an intracellular pathogen capable of surviving within macrophages, evading immune surveillance, and inducing apoptosis and necrosis, leading to systemic infections in both aquatic animals and humans. Unlike traditional ochratoxins-mycotoxins known for nephrotoxic, hepatotoxic, and immunotoxic effects-we identified a novel hydroxy-containing ochratoxin derivative, ochratoxin E (1), along with three known ochratoxins (2-4), from the marine fungus Aspergillus sp. NBU1109. The structure and absolute configuration of compound 1 were elucidated using HRESIMS, NMR, ECD calculations, and single-crystal X-ray diffraction. Crucially, compound 1 showed no cytotoxicity in human LX-2 or murine RAW 264.7 cells, in contrast to the toxic effects of compounds 2-4. Functionally, compound 1 enhanced macrophage phagocytosis and bactericidal activity against E. tarda, and suppressed apoptosis and necrosis. Mechanistically, drug-affinity responsive target stability (DARTS), molecular docking, and cellular thermal shift assays (CETSA) confirmed that compound 1 directly binds AIFM1. This interaction blocked the AIFM1-RIP3 association, reduced RIP3 nuclear translocation, and inhibited apoptotic-necroptotic signaling. These results delineate a unique, non-toxic ochratoxin derivative that targets the AIFM1/RIP3 axis to bolster macrophage defense, highlighting its promise as a lead compound for anti-E. tarda therapy development.