Biochemical Adaptation Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, India; Department of Biotechnology, Assam Don Bosco University, Assam 782402, India.
Biochemical Adaptation Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, India.
Gene. 2018 Jun 5;658:18-27. doi: 10.1016/j.gene.2018.03.018. Epub 2018 Mar 7.
The magur catfish (Clarias magur) is a facultative air-breather and regularly encounters with various environmental changes along with exposure to various bacterial pathogens in its natural habitats. Occurrence of various biochemical adaptational strategies related to nitrogen metabolism in magur catfish is already known. The present investigation aimed at determining the possible induction of inducible nitric oxide synthase (inos) gene and stimulation of nitric oxide (NO) production in this catfish while challenging with lipopolysaccharide (LPS, a bacterial endotoxin) treatment, and also to determine the involvement of nuclear factor kappa B (NFkB) in induction of inos gene. Intra-peritoneal injection of LPS led to more production and accumulation of NO in different body tissues of magur catfish as a consequence of induction of iNOS activity. The induction of iNOS activity was associated with the induction of inos gene as evidenced by more expression of inos mRNA and more abundance of iNOS enzyme protein in different tissues of magur catfish with certain variations in zonal specific expression patterns. Similar observations related to more production of NO and induction of inos gene were also made when the isolated hepatocytes were treated with LPS in vitro condition. LPS treatment also led to activation of NFĸB in hepatic cells. However, in presence of a specific inhibitor of NFkB, the LPS-mediated induction of inos gene and extra production of NO were almost blocked, thereby suggesting that the induction of inos gene due to LPS treatment was mediated via the NFkB in magur catfish. It is hypothesized that the induction of iNOS activity, and more synthesis and accumulation of NO could serve as indicators to determine the pathophysiological conditions of the fish living in bacterial contaminated water bodies. Further, it can be contemplated that more synthesis of NO through iNOS enzyme probably serves as an important pharmacological tool against fish pathogen and also plays an important role in host defense mechanisms in this unique group of magur catfish.
麦哲伦海豚（Clarias magur）是一种兼性空气呼吸者，在其自然栖息地中经常会遇到各种环境变化，并暴露于各种细菌病原体。麦哲伦海豚已经存在与氮代谢相关的各种生化适应策略。本研究旨在确定在受到脂多糖（LPS，细菌内毒素）处理时，这种鱼是否可能诱导诱导型一氧化氮合酶（inos）基因的表达并刺激一氧化氮（NO）的产生，并确定核因子 kappa B（NFkB）是否参与inos 基因的诱导。LPS 的腹腔注射导致麦哲伦海豚不同身体组织中 NO 的产生和积累增加，这是由于 iNOS 活性的诱导。iNOS 活性的诱导与 inos 基因的诱导有关，这表现在麦哲伦海豚不同组织中 inos mRNA 的表达增加和 iNOS 酶蛋白的丰度增加，并且在不同组织中有特定的区域特异性表达模式。当分离的肝细胞在体外条件下用 LPS 处理时，也观察到与 NO 产生和 inos 基因诱导相关的类似现象。LPS 处理还导致 NFĸB 在肝细胞中激活。然而，在存在 NFkB 的特异性抑制剂的情况下，LPS 介导的 inos 基因诱导和额外的 NO 产生几乎被阻断，这表明 LPS 处理诱导 inos 基因是通过 NFkB 在麦哲伦海豚中进行的。研究人员假设，iNOS 活性的诱导以及更多的 NO 合成和积累可以作为指示物，用于确定生活在受细菌污染的水体中的鱼类的病理生理状况。此外，通过 iNOS 酶合成更多的 NO 可能被认为是一种对抗鱼类病原体的重要药理学工具，并在这群独特的麦哲伦海豚的宿主防御机制中发挥重要作用。
