Abstract
The deduced amino acid sequences from the complete cDNA coding sequences of three antioxidant enzyme genes (sod1, sod2, and cat) demonstrated that phylogenetically the magur catfish (Clarias magur) is very much close to other bony fishes with complete conservation of active site residues among piscine, amphibian, and mammalian species. The three-dimensional structures of three antioxidant enzyme proteins are very much similar to mammalian counterparts, thereby suggesting the functional similarities of these enzymes. Exposure to ZnO NPs resulted in an oxidative stress as evidenced by an initial sharp rise of intracellular concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) but decreased gradually at later stages. The level of glutathione (GSH) also increased gradually in all the tissues examined after an initial decrease. Biochemical and gene expression analyses indicated that the magur catfish has the ability to defend the ZnO NP-induced oxidative stress by inducing the SOD/CAT enzyme system and also the GSH-related enzymes that are mediated through the activation of various antioxidant-related genes both at the transcriptional and translational levels in various tissues. Furthermore, it appeared that the stimulation of NO, as a consequence of induction nos2 gene, under NP-induced oxidative stress serves as a modulator to induce the SOD/CAT system in various tissues of magur catfish as an antioxidant strategy. Thus, it can be contemplated that the magur catfish possesses a very efficient antioxidant defensive mechanisms to defend against the oxidative stress and also from related cellular damages during exposure to ZnO NPs into their natural environment.
Highlights
Parallel to the increase of application of nanotechnology in recent years, more utilization of metal oxide nanoparticles (NPs) have received significant attention mainly because of their remarkable and multidimensional potentials
We have fairly demonstrated that the induction of both superoxide dismutase (SOD) and CAT genes under ammonia- and NP-induced oxidative was mediated by the nitric oxide (NO), the production of which was stimulated via the NFκB- mediated induction of NO/nitric oxide synthase (NOS) system, as an antioxidant strategy (Koner et al 2019; Hasan et al 2020)
The sequence alignment of amino acids of these three antioxidant enzyme proteins of magur catfish showed a high degree of sequence homology with that of other bony fishes along with complete conservation of active site residues in all the three enzyme proteins among piscine, amphibian and mammalian species
Summary
Parallel to the increase of application of nanotechnology in recent years, more utilization of metal oxide nanoparticles (NPs) have received significant attention mainly because of their remarkable and multidimensional potentials. NPs are taken up by fish and transported to the various tissues and organs through the blood (Handy et al 2008) In both in vitro and in vivo studies, it was demonstrated that ZnO NPs could induce oxidative stress by triggering ROS formation (Shahzad et al 2019; Yang et al 2020). Teleosts might have evolved a wide array of enzymatic and nonenzymatic antioxidant defense systems to convert ROS to harmless metabolites to protect and restore normal cellular homeostasis and functions (Lushchak et al 2001; Sinha et al 2015). The role of NO in defending against the NP-induced oxidative stress in different cellular systems of teleost fish is yet to be established except the recent report in primary hepatocytes of magur catfish under in vitro condition (Koner et al 2019)
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