Taurine and Glutathione Alleviate <scp> <i>Aeromonas hydrophila</i> </scp> Infection by Inhibiting Inflammation and Ferroptosis via <scp>ROS</scp> / <scp>NF</scp> ‐ <scp>κB</scp> Pathway in Fishes

Aeromonas hydrophila-induced bacterial sepsis is a major threat to aquaculture, characterised by excessive inflammation, ferroptosis (an iron-dependent lipid peroxidation-driven cell death) and oxidative damage, which collectively lead to high mortality. Taurine (TAU) and glutathione (GSH) have been demonstrated to have potential therapeutic efficacy against ferroptosis-associated pathologies through redox modulation. However, their combined effects and underlying mechanisms in alleviating A. hydrophila infection remain unclear. In this study, we investigated the protective roles of TAU, GSH and their combination in vitro using yellow catfish (Pelteobagrus fulvidraco) macrophages and grass carp (Ctenopharyngodon idella) kidney (CIK) cells and in vivo using yellow catfish challenged with A. hydrophila. The results showed that TAU and GSH, either alone or in combination, alleviated oxidative stress by significantly reducing reactive oxygen species (ROS) accumulation and inhibited nuclear factor-κB (NF-κB) pathway activation. This led to downregulated expression of pro-inflammatory cytokines (IL-1β and TNF-α) and upregulated anti-inflammatory cytokines (IL-10 and TGF-β), accompanied by alleviated ferroptosis. In vivo, dietary supplementation with TAU (10 g/kg) or GSH (350 mg/kg) alone improved survival rates (51.7% and 38.3%, respectively), reduced tissue bacterial loads and protected intestinal and hepatic tissues by preserving mucosal barrier function. However, the TAU + GSH combination unexpectedly decreased survival (28.3%) due to excessive immunosuppression (overproduction of IL-10 and TGF-β) and impaired mucosal barrier, which exacerbated pathogen colonisation. Together, our findings demonstrate that TAU and GSH alleviate A. hydrophila-induced oxidative stress by reducing mitochondrial ROS overproduction and disrupting the ROS/NF-κB signalling pathway, thereby attenuating inflammatory cytokine storms and ferroptosis. These results provide novel insights into the pathological mechanisms of bacterial sepsis in fish and develop sustainable strategies to improve disease resistance in aquaculture.