Mechanism of Biphasic Activation of NLRP3 Inflammasome in the Fat Greenling (Hexagrammos otakii) Under Hypoxic Stress: From Inflammatory Defense to Pyroptosis Execution

Hypoxic stress is an important environmental challenge for aquatic organisms, which is detrimental to fish survival and growth. Specifically, the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) has emerged as a pivotal regulator, with accumulating evidence underscoring its central role in inflammatory processes. However, the regulatory functions of NLRP3 during hypoxic stress in fat greenling (Hexagrammos otakii) remain elusive. In this study, we systematically analyzed the molecular features of HoNLRP3 and elucidated its biphasic regulatory mechanism under hypoxic stress in H. otakii using phylogenetic analysis, qRT-PCR, Western blot, and immunofluorescence. Its phylogeny is significantly different from that of mammals and carries FISNA and related motifs specific to bony fishes. Hypoxia induced predominant nlrp3 expression in the brain, peaking at 12–24 h, with strong positive correlation to hif-1α activation. NLRP3-ASC-Caspase1 inflammasomes assembly drove IL-1β maturation, while prolonged hypoxia (48 h) activated Caspase3/GSDME-mediated pyroptosis, accompanied by elevated LDH activity. Reoxygenation partially reversed inflammatory and pyroptosis markers, indicating that NLRP3 balances defense and injury through a biphasic regulatory mechanism. This study provides new insights into the hypoxic adaptation mechanisms in bony fish.