Molecular identification and functional delineation of a glutathione reductase homolog from disk abalone (Haliotis discus discus): Insights as a potent player in host antioxidant defense

Impacts of high-dose riboflavin on cytotoxicity, antioxidant, growth, reproductive gene expressions, and genotoxicity in the rainbow trout gonadal cells

Riboflavin (vitamin B2 found in food) is a precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which study as coenzymes for a variety of cellular processes including biosynthesis, homocysteine metabolism, detoxification, and various oxidation and reduction reactions. Although studies on the symptoms resulting from riboflavin deficiency are intense, studies on the effects of high doses of riboflavin are almost absent. This report aimed to examine the actions of riboflavin on cell viability, the transcriptional expressions of antioxidant enzyme (gsr and gpx1a), growth (gh1, igf1, and igf2), the reproductive (bol) genes and DNA damage in the rainbow trout gonad cells (RTG-2) for 48 h. All concentrations of riboflavin (3.125, 6.25, 12.5, 25, 50, and 100 μM) significantly reduced the RTG-2 cell viability. Riboflavin (LD50: 12.5 μM) significantly downregulated the transcriptional expressions of gpx1a, igf1, and bol genes, while it non-significantly upregulated or downregulated the transcriptional expression of gsr, igf2, and gh1 genes in the RTG-2 cells in comparison to the control group for 48 h. The comet assay demonstrated that riboflavin significantly raised tail DNA% >10% DMSO (positive control). Based on the outcomes, high doses of riboflavin exhibit the potential to have a role in cellular mechanisms, including especially reproduction, DNA damage, and cell death.

Glutathione reductase, a biomarker of pollutant and stress in Pacific abalone

Abalone are frequently exposed to several environmental factors including heavy metal toxicity, thermal stress, H2O2-stress, starvation, viral and bacterial infection that can induce oxidative stress. Glutathione reductase is a vital enzyme in the antioxidant defense system that catalyzes the reduction of oxidized glutathione to reduced glutathione. The present study aimed to identify and localize glutathione reductase in Pacific abalone (Hdh-GR) and assess its potential role in stress physiology, heavy metal toxicity, immune response, gonadal development, and metamorphosis. The mRNA expression of Hdh-GR was upregulated in response to thermal stress, starvation, H2O2-stress, and cadmium-exposed toxicity. The induced mRNA expression was also quantified in immune-challenged abalone. Moreover, the Hdh-GR expression was significantly higher during metamorphosis. The Hdh-GR mRNA expression showed an inverse relationship with ROS production in heat stressed Pacific abalone. These results suggest that Hdh-GR has central role in the stress physiology, immune response, gonadal development, and metamorphosis of Pacific abalone.

Updating the use of biochemical biomarkers in fish for the evaluation of alterations produced by pharmaceutical products

The evaluation of toxic effects in stressful environmental conditions can be determined through the imbalance between exogenous factors (environmental contaminants) and enzymatic and non-enzymatic defenses in biological systems. The use of fish for the identification of alterations in biochemical biomarkers provides a comprehensive vision of the effects that pharmaceutical products cause in the aquatic ecosystem, as they are organisms with high sensitivity to contaminants, filtering capacity, and potential for environmental toxicology studies. A wide range of pharmaceuticals can stimulate or alter a variety of biochemical mechanisms, such as oxidative damage to membrane lipids, proteins, and changes in antioxidant enzymes. This review includes a summary of knowledge of the last 20 years, in the understanding of the different biochemical biomarkers generated by exposure to pharmaceuticals in fish, which include different categories of pharmaceutical products: NSAIDs, analgesics, antibiotics, anticonvulsants, antidepressants, hormones, lipid regulators and mixtures. This review serves as a tool in the design of studies for the evaluation of the effects of pharmaceutical products, taking into account the most useful biomarkers, type of matrix, enzyme alterations, all taking the pharmaceutical group of interest.

Molecular and functional characterization of a mitochondrial glutathione reductase homolog from redlip mullet (Liza haematocheila): Disclosing its antioxidant properties in the fish immune response mechanism

Glutathione reductase (GSHR) is a biologically important enzyme involved in the conversion of oxidized glutathione (GSSG) into its reduced form, reduced glutathione (GSH), with the catalytic activity of NADPH. Most animals and aquatic organisms, including fish, possess high levels of this enzyme system to neutralize oxidative stress in cells. The current study was conducted to broaden our knowledge of GSHR in fish by identifying a mitochondrial isoform of this enzyme (LhGSHRm) in redlip mullet, Liza haematocheila, and clarifying its structure and function. The complete open reading frame of LhGSHRm consists of 1527 base pairs, encoding 508 amino acids, with a predicted molecular weight of 55.43 kDa. Multiple sequence alignment revealed the conservation of important amino acids in this fish. Phylogenetic analysis demonstrated the closest evolutionary relationship between LhGSHRm and other fish GSHRm counterparts. In tissue distribution analysis, the highest mRNA expression of LhGSHRm was observed in the gill tissue under normal physiological conditions. Following pathogenic challenges, the LhGSHRm transcription level was upregulated in a time-dependent manner in the gill and liver tissues, which may modulate the immune reaction against pathogens. rLhGSHRm showed considerable glutathione reductase activity in an enzyme assay. Further, the biological activity of rLhGSHRm in balancing cellular oxidative stress was observed in both disk diffusion and DPPH assays. Collectively, these results support that LhGSHRm has profound effects on modulating the immune reaction in fish to sustain precise redox homeostasis.

Mercury and Atherosclerosis: Cell Biology, Pathophysiology, and Epidemiological Studies

Today atherosclerosis is considered as a main cause of death in the worldwide. There is a significant association between heavy metal exposure and atherosclerosis. In this study, we discussed the scientific literature about the effect of mercury on the pathogenesis of atherosclerosis. We also considered the epidemiological studies on mercury as a risk factor for atherosclerosis. Web of Science, Google Scholar, Medline, PubMed, and Scopus were searched by using the following keywords to 2019: (cardiovascular diseases OR atherosclerosis OR endothelial dysfunction) AND (mercury). Mercury has the potential to act as one of the novel risk factors for atherosclerosis development. The findings have indicated the role of mercury in the pathogenesis of atherosclerosis, vascular endothelial dysfunction, oxidative stress, inflammation, and dyslipidemia. Mercury can induce atherosclerosis indirectly via increasing the total cholesterol, triglycerides, and LDL-C levels as well as decreasing the HDL-C level. Mercury can be considered as a risk factor in the atherosclerosis progression. However, more studies are required to find the exact mechanisms involved in the pathogenesis of atherosclerosis induced by mercury.