Microplastics and Nitrite Stress Affect Physiological and Metabolic Functions of the Hepatopancreas in Marine Shrimp

Nitrite is a common toxic substance in aquaculture, and microplastics are environmental pollutants capable of adsorbing small molecules/particles. Shrimp rely mainly on the hepatopancreas to accomplish detoxification metabolism. In this study, we investigated the individual and combined effects of nitrite and microplastics on the physiological function of the <i>P. vannamei</i> hepatopancreas. The results demonstrated that both nitrite and microplastics induced morphological damage, with the combined stress exacerbating tissue damage. Oxidative stress biochemical indicators were disrupted, and most enzyme activities and gene expression levels were upregulated to varying degrees in each experimental group. The expression levels of immune genes (<i>cytC</i>, <i>CASP-3</i>, <i>Crus</i>, <i>ALF</i>, and <i>proPO</i>), detoxification metabolism genes (<i>CYP450</i>, <i>EH1</i>, <i>SULT</i>, and <i>UGT</i>), and oxidative-stress-related genes (<i>ROMO1</i>, <i>SOD</i>, <i>GPx</i>, and <i>Trx</i>) exhibited different fluctuations. Nitrite and microplastic stress resulted in altered hepatopancreatic function, mainly involving amino acid biosynthesis and metabolism, ABC transporters, oxidative phosphorylation, and the mTOR pathway. We identified 17 metabolic biomarkers, including 6 lipids (Oleic acid, Prostaglandin G2, Linoleic acid, Palmitic acid, Docosahexaenoic acid, Docosapentaenoic acid), 6 amino acids (L-Leucine, Agmatine, L-Arginine, L-Tyrosine, Ornithine, N-Acetylornithine), and 5 carbohydrates (Glyceric acid, Citric acid, D-Mannose, Sorbitol, Fumaric acid). These findings suggest that nitrite and microplastic stresses cause hepatopancreatic tissue damage and induce oxidative stress, physiological and metabolic dysfunction in the shrimp <i>P. vannamei</i>, thereby impacting its normal physiological functions.