Intracellular behavior of Nocardia seriolae and its apoptotic effect on RAW264.7 macrophages

Frontiers in Cellular and Infection Microbiology

Cellular and Infection Microbiology

Aiping Tan¹  Fei Zhao¹  Ouqing Chang¹  Yingtiao Lai¹  Zhibin Huang¹  Fang Wang¹  Wenwen Liu²  Yuting Deng³ 

[1] Key Laboratory of Fishery Drug Development of Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China;Guangdong Provincial Key Laboratory of Aquatic Animal Immunology and Sustainable Aquaculture, Guangzhou, China;Key Laboratory of Fishery Drug Development of Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China;Guangdong Provincial Key Laboratory of Aquatic Animal Immunology and Sustainable Aquaculture, Guangzhou, China;College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China;Key Laboratory of Fishery Drug Development of Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China;Guangdong Provincial Key Laboratory of Aquatic Animal Immunology and Sustainable Aquaculture, Guangzhou, China;Key Laboratory of Control of Quality and Safety for Aquatic Products of Ministry of Agriculture and Rural Affairs, Chinese Academy of Fishery Sciences, Beijing, China;

关键词: Nocardia seriolae;    macrophages;    intracellular bacteria;    apoptosis;    survival mechanism;   

DOI  :  10.3389/fcimb.2023.1138422

 received in 2023-01-05, accepted in 2023-02-17,  发布年份 2023

来源: Frontiers

【 摘 要 】

Nocardia seriolae, an intracellular gram-positive pathogen, is prone to infecting immunocompromised and surface-damaged fish, causing serious losses to the aquaculture industry. Although a previous study has demonstrated that N. seriolae infects macrophages, the persistence of this bacterium in macrophages has not been well characterized. To address this gap, we used the macrophage cell line RAW264.7, to investigate the interactions between N. seriolae and macrophages and deciphered the intracellular survival mechanism of N. seriolae. Confocal and light microscopy revealed that N. seriolae entered macrophages 2 hours post-inoculation (hpi), were phagocytosed by macrophages at 4–8 hpi, and induced the formation of multinucleated macrophages by severe fusion at 12 hpi. Flow cytometry, evaluation of mitochondrial membrane potential, release of lactate dehydrogenase, and observation of the ultrastructure of macrophages revealed that apoptosis was induced in the early infection stage and inhibited in the middle and later periods of infection. Additionally, the expression of Bcl-2, Bax, Cyto-C, Caspase-3, Capase-8, and Caspase-9 was induced at 4 hpi, and then decreased at 6–8 hpi, illustrating that N. seriolae infection induces the activation of extrinsic and intrinsic apoptotic pathways in macrophages, followed by the inhibition of apoptosis to survive inside the cells. Furthermore, N. seriolae inhibits the production of reactive oxygen species and releases large amounts of nitric oxide, which persists in macrophages during infection. The present study provides the first comprehensive insight into the intracellular behavior of N. seriolae and its apoptotic effect on macrophages and may be important for understanding the pathogenicity of fish nocardiosis.

【 授权许可】

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Copyright © 2023 Liu, Deng, Tan, Zhao, Chang, Wang, Lai and Huang