Roles of H2S and NO in regulating the antioxidant system of Vibrio alginolyticus under norfloxacin stress

Antioxidant system is of great importance for organisms to regulate the level of excessive reactive oxygen species (ROS) under the environmental stresses including antibiotics stress. Effects of norfloxacin (NOR) on cystathionine-β-synthase (CBS), nitric oxide synthase (NOS) and antioxidant enzymes were investigated, and interaction between NO and H2S and their regulation on the antioxidant system of Vibrio alginolyticus under NOR were determined as well in the present study. After treated with 2 µg/mL NOR (1/2 MIC), CBS content, H2S and NO contents decreased while H2O2 accumulation and the antioxidant-related genes mRNA level increased. Additionally, the endogenous H2S content in V. alginolyticus was increased by the exogenous NO, while H2O2 accumulation and the relative expression level of SOD (Superoxide dismutase gene) decreased under exogenous NO or H2S. And the content of endogenous NO and NOS in V. alginolyticus increased under the exogenous H2S as well. Taken together, these results showed that anti-oxidative ability in V. alginolyticus was respectively enhanced by the gas molecules of H2S and NO under NOR-induced stress, and there may be a crosstalk regulative mechanism between H2S and NO. These results lay a foundation for the research of regulation network of H2S and NO, and provide a hint to synthesize anti-vibrio drugs in the future.