Abstract

Nitrite accumulation poses a serious threat to aquatic animals in intensive aquaculture systems. Although the antioxidant role of the Nrf2-Keap1 pathway is well established, its regulatory mechanisms under nitrite stress in crustaceans remain poorly understood. This investigation focused on the protective impact of N-acetylcysteine (NAC) on Marsupenaeus japonicus exposed to nitrite toxicity. Shrimp were injected with NAC or PBS and then exposed to 100 mg/L of nitrite nitrogen for 72 h. The findings revealed that pretreatment with NAC markedly reduced tissue damage in both the hepatopancreas and gills, in comparison to the PBS control group. Additionally, the NAC-treated M. japonicus exhibited upregulated mRNA levels of Nrf2 and its associated antioxidant genes including NQO1 , HO-1 , CAT , GPx , GST , and SOD , while Keap1 expression was notably suppressed. Additionally, the NAC group downregulated endoplasmic reticulum stress (ERS)-related genes ( PERK , eIF2α , ATF4 , GRP78 , CHOP , IRE1 , XBP1 , ATF6 ) and apoptosis-related genes ( Caspase-3 , Caspase-9 , p53 , Bax , Apaf-1 ), while upregulating Bcl-2 . Additionally, the NAC group improved total antioxidant capacity (T-AOC) and SOD activity, reduced malondialdehyde (MDA) content and Caspase-3 activity, and decreased the apoptosis rate in the hepatopancreas. The results indicate that NAC alleviates oxidative stress, ERS, and apoptosis triggered by nitrite in M. japonicus . This protective effect is associated with the activation of the Nrf2-Keap1 signaling pathway, suggesting its potential as a therapeutic strategy for nitrite toxicity in crustacean aquaculture.