Oxidative stress and inflammatory responses mediate the high mortality of Takifugu obscurus under combined hypoxia and Vibrio parahaemolyticus stress

Abstract

In the complex marine environment, hypoxia stress and bacterial infection pose significant threats to the survival of marine fish. Extensive research has been conducted on the adaptive mechanisms of fish in response to individual hypoxia stress or bacterial infection. However, limited knowledge exists regarding the mechanisms underlying the immune response of fish to the simultaneous stress of hypoxia and bacterial infection. In this study, we investigated the immune response of Takifugu obscurus to the combined stress of hypoxia and Vibrio parahaemolyticus infection. Both in vivo and in vitro experiments were conducted, revealing the upregulation of hypoxia-related genes and their downstream factors in the T. obscurus under hypoxic conditions. Moreover, the expression of inflammatory factors and inflammasome-related genes exhibited significant increases under hypoxia stress, V. parahaemolyticus infection, and the combined stress. Notably, respiratory burst, lactate dehydrogenase (LDH) enzyme activity, lysozyme activity, cell apoptosis, and other indicators demonstrated substantial increases, while antioxidant enzyme activity exhibited a significant decrease. Comparative analysis with individual stressors demonstrated noteworthy alterations in liver injury, cell apoptosis, antioxidant capacity, and expression of inflammatory genes in the T. obscurus under the dual stress. These factors likely contribute to the accelerated mortality observed under combined stress conditions. In conclusion, this study explores the immune response of the T. obscurus to the concurrent stress of hypoxia and V. parahaemolyticus infection, thereby providing novel insights for the advancement of stress resistance and disease control techniques in fish.