Origin of the phagocytic respiratory burst and its role in gut epithelial phagocytosis in a basal chordate |
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| Affiliation: | 1. State Key Laboratory of Biocontrol, Guangdong Key Laboratory of Pharmaceutical Functional Genes, College of Life Sciences, Sun Yat-sen University, Guangzhou 510275, People׳s Republic of China;2. Beijing University of Chinese Medicine, Beijing 100029, People׳s Republic of China;1. Clincial Immunology and Allergy Unit, Department of Medicine Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden;2. Department of Clinical Science and Education, Karolinska Institutet, and Sachs’ Children and Youth Hospital, Södersjukhuset, Stockholm, Sweden;3. Department of Cell and Molecular Biology and Pathogenic Bioagents, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil;1. Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China;2. National Laboratory for Marine Science and Technology, Qingdao 266071, China;3. Shanghai Ocean University, Shanghai, China;4. Dalian Ocean University, Dalian, China;1. Department of Immunology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran;2. Payame Nour University of Malekan, Malekan, Iran;1. Department of Physiology and Pathophysiology, University of Manitoba, Canada;2. Biology of Breathing Group, Children’s Hospital Research Institute of Manitoba, Canada |
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| Abstract: | The vertebrate phagocytic respiratory burst (PRB) is a highly specific and efficient mechanism for reactive oxygen species (ROS) production. This mechanism is mediated by NADPH oxidase 2 (NOX2) and used by vertebrate phagocytic leukocytes to destroy internalized microbes. Here we demonstrate the presence of the PRB in a basal chordate, the amphioxus Branchiostoma belcheri tsingtauense (bbt). We show that using the antioxidant NAC to scavenge the production of ROS significantly decreased the survival rates of infected amphioxus, indicating that ROS are indispensable for efficient antibacterial responses. Amphioxus NOX enzymes and cytosolic factors were found to colocalize in the epithelial cells of the gill, intestine, and hepatic cecum and could be upregulated after exposure to microbial pathogens. The ROS production in epithelial cell lysates could be reconstructed by supplementing recombinant cytosolic factors, including bbt-p47phox, bbt-p67phox, bbt-p47phox, and bbt-Rac; the restored ROS production could be inhibited by anti-bbt-NOX2 and anti-bbt-p67phox antibodies. We also reveal that the gut epithelial lining cells of the amphioxus are competent at bacterial phagocytosis, and there is evidence that the PRB machinery could participate in the initiation of this phagocytic process. In conclusion, we report the presence of the classical PRB machinery in nonvertebrates and provide the first evidence for the possible role of PRB in epithelial cell immunity and phagocytosis. |
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| Keywords: | Amphioxus Phagocytic respiratory burst NOX ROS Phagocytosis Free radicals |
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