Immune-protection and therapeutic effects of neuropeptide Y on largemouth bass infected with Aeromonas Hydrophila

Introduction. Neuropeptide Y (NPY) is a crucial neuroregulatory factor known to mediate diverse physiological functions in mammals, including the regulation of brain activity, vasoconstriction, feeding behavior, lipid metabolism, and immune responses. Our previous studies have demonstrated that NPY plays a significant regulatory role in the immune systems of fish. For the next，we further want to know whether NPY can be used for treatment when fish are infected with pathogenic bacteria in aquaculture. Methods. In this study, we examined the impact of A. hydrophila infection on inflammatory responses, cellular apoptosis, and intestinal morphology in juvenile largemouth bass (Micropterus salmoides). And then, for the first time, we explored the immune-protective and therapeutic effects of NPY on largemouth bass infected with A. hydrophila. Results. It was observed that A. hydrophila infection caused severe damage to juvenile largemouth bass, including intestinal injury, mortality elevation and inflammatory factors significant deterioration. Notably, in A. hydrophila infected largemouth bass, intraperitoneal administration of NPY reduced the overexpression of pro-inflammatory immune factors, TNF-α, enhanced resistance to inflammatory stimuli, and mitigated tissue inflammatory damage and cellular apoptosis induced by A. hydrophila. Conclusion. Our results demonstrate that NPY has a therapeutic effect on fish infected with bacteria by eliminating inflammation.