Integrative multi-omics analysis of magnesium-mediated alleviation of nitrite toxicity in Litopenaeus vannamei

Nitrite accumulation represents a major stressor in the intensive aquaculture of Litopenaeus vannamei. Increasing water salinity (by NaCl supplementation) is one of the conventional alleviation strategies. However, this study found that under conditions providing equivalent Cl^- concentration, MgCl₂ was more effective than NaCl in alleviating nitrite toxicity. To elucidate the specific protective mechanism of magnesium ions (Mg²⁺), a stress experiment under an equimolar chloride background was designed, including NaCl and MgCl₂ treatment groups. Survival analysis, histopathology, oxidative stress indicators, and combined transcriptomic and metabolomic approaches were comprehensively employed for evaluation. The results demonstrated that, compared with the NaCl group, MgCl₂ treatment significantly improved shrimp survival, reduced hepatopancreatic tissue damage and apoptosis, and accelerated the clearance of nitrite in vivo. At the molecular level, the beneficial effect of Mg²⁺ was primarily achieved through a dual synergistic pathway: First, it systematically up-regulated genes and metabolites related to cofactor biosynthesis, providing critical support for cellular metabolism under stress. Second, it directed adaptive reprogramming of the glycerophospholipid metabolism pathway, enhancing resistance to oxidative damage by stabilizing cell membrane structure. This coordinated regulation of metabolic support systems and membrane stability enabled the organism to manage oxidative stress via an economical and efficient "prevention-stabilization" mode, rather than passively activating high-energy-consuming antioxidant defenses. This study reveals, at both physiological and multi-omics levels, the unique cytoprotective mechanism of Mg²⁺ against acute aquatic toxicants in crustaceans, providing an important theoretical foundation for developing novel and efficient nitrite alleviation strategies based on Mg²⁺ regulation.