Induction of nitric oxide synthesis: A strategy to defend against the high environmental ammonia-induced oxidative stress in primary hepatocytes of air-breathing catfish, Clarias magur

Abstract

Air-breathing magur catfish (Clarias magur) regularly face the problem of exposure to high environmental ammonia (HEA) as one of the major pollutants in their natural habitats that causes considerable toxic effects at the cellular level, including that of oxidative stress. The major objective of the present study was to demonstrate the antioxidant activity of endogenously produced nitric oxide (NO) to defend against ammonia-induced oxidative stress in primary hepatocytes of magur catfish during exposure to HEA. Exposure to NH 4 Cl (5 mmol l −1) led to a significant increase in intracellular ammonia concentration with a sharp rise of hydrogen peroxide (H 2 O 2) and malondialdehyde (MDA) concentrations within 3 h in primary hepatocytes, which decreased gradually at later stages of treatment. This phenomenon was accompanied by a significant increase in superoxide dismutase (SOD) and catalase (CAT) activity as a consequence of induction of corresponding genes. HEA exposure also led to the stimulation of NO production due to induction of inducible nitric oxide synthase (iNOS) activity, as a consequence of up-regulation of the nos2 gene. Most interestingly, when NO production by hepatocytes under ammonia stress was blocked by adding certain inhibitors [aminoguanidine and 3-(4methylphenylsulfonyl)-2-propenenitrile] to the culture medium, there was a further rise of H 2 O 2 and MDA concentrations in hepatocytes. These were accompanied by the lowering of SOD and CAT activity with less expression of corresponding genes. Thus, it can be contemplated that magur catfish use the strategy of stimulation of NO production, which ultimately induces the SOD-CAT enzyme system to defend against ammonia-induced oxidative stress.

Nitric oxide synthase (NOS) inhibitor L‐NAME activates inducible NOS/NO system and drives multidimensional regulation of Na+/K+‐ATPase in ionocyte epithelia of immersion‐stressed air‐breathing fish (Anabas testudineus Bloch)

“…In addition, hypoxia has been shown to activate iNOS expression in brown trout (Jensen et al, 2015). Moreover, a protective role of iNOS against oxidative stress and ammonia tolerance has been reported in the hepatocytes of Magur catfish (Hasan et al, 2020).…”

“…As a short‐lived free radical, nitric oxide (NO) acts as gasotransmitter and performs autocrine/paracrine function to impose physiological actions in mammals and fishes (Ally et al, 2020; Althaus, 2012; Cioni et al, 2019; Jensen et al, 2015; Hasan et al, 2020). The enzymatic actions of nitric oxide synthases (NOS) on l ‐arginine release NO in the presence of molecular oxygen and NADPH (Griffith & Stuehr, 1995).…”

“…The NOS/NO system of fish responds to many environmental stressors such as hyperammonia (Choudhury & Saha, 2012a), temperature elevation (Jorgensen et al, 2014), desiccation stress (Choudhury & Saha, 2012b; Garofalo et al, 2015), hyperosmotic stress (Gerber et al, 2018) and hypoxia/anoxia (Imbrogno et al, 2014; Jensen et al, 2015; Sandvik et al, 2012; Hansen et al, 2016). Similarly, a role for NO in stress acclimation has been reported in fishes (Fago & Jensen, 2015; Hasan et al, 2020). Likewise, cortisol has been shown to modify the NO production and the pattern of nNOS and iNOS expression in the osmoregulatory tissues of rainbow trout (Gerber et al, 2017).…”

Molecular characterization of superoxide dismutase and catalase genes, and the induction of antioxidant genes under the zinc oxide nanoparticle-induced oxidative stress in air-breathing magur catfish (Clarias magur)

“…More recently, the antioxidant activity of NO against the ammonia-and ZnO NP-induced oxidative stress has been demonstrated in primary hepatocytes of magur catfish (Koner et al 2019;Hasan et al 2020).…”

“…This finding was further supplemented by the observations made on the stimulation of iNOS activity, up-regulation of the nos2 gene, and more abundance of its translated enzyme protein at variable levels in different tissues of magur catfish. In our previous studies, we have fairly demonstrated that the induction of both SOD and CAT genes under ammonia-and NP-induced oxidative was mediated by the NO, the production of which was stimulated via the NFκBmediated induction of NO/NOS system, as an antioxidant strategy (Koner et al 2019;Hasan et al 2020). The induction of NO synthesis via the NOS/NO system has also been reported in non-hepatic tissues of this magur catfish under hyper-ammonia stress, and also while treating with lipopolysaccharide (Choudhury et al 2018;Kumari et al 2019).…”