Integrated histological, physiological, and transcriptome analysis reveals the post-exposure recovery mechanism of nitrite in Litopenaeus vannamei.

ABSTRACT

Nitrite is one of the most common toxic pollutants in intensive aquaculture and is harmful to aquatic animals. Recovery mechanisms post exposure to nitrite in shrimp have rarely been investigated. This study focuses on the effect of nitrite exposure and post-exposure recovery on the histological and physiological aspects of Litopenaeus vannamei and utilizes transcriptome sequencing to analyze the molecular mechanisms of adaptation to nitrite exposure. The results showed that histopathological damage to the hepatopancreas and gills caused by short-term nitrite exposure resolved with recovery. The total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) of shrimp were significantly reduced during nitrite exposure and returned to the control level after recovery, malondialdehyde (MDA) levels were opposite to them. Restoration of the antioxidant system after exposure mitigated oxidative damage. Nitrite exposure results in reduced activity of the immuno-enzymes acid phosphatase (ACP) and alkaline phosphatase (AKP), which can be recovered to the control level. L. vannamei can adapt to nitrite exposure by regulating Na+/K+-ATPase (NKA) activity. Transcriptome analysis revealed that activation of glutathione metabolism and peroxisomal pathways facilitated the mitigation of oxidative damage in L. vannamei during the recovery period. Excessive oxidative damage activates the apoptosis and p53 pathways. Additionally, Sestrin2 and STEAP4 may have a positive effect on recovery in shrimp. These results provide evidence for the damage caused by nitrite exposure and the recovery ability of L. vannamei. This study can complement the knowledge of the mechanisms of adaptation and recovery of shrimp under nitrite exposure.