Zinc modulates hypothalamo-pituitary-gonadal-liver axis to impair reproduction in female Mystus vittatus (Bloch, 1794).

The present study investigated the effects of zinc on the hypothalamo-pituitary-gonadal-liver (HPGL) axis of the bagrid catfish Mystus vittatus. Female fish (pre-ovulatory and ovulatory phases) were exposed to zinc sulphate at 1/10th of LC50 (5.62 mg/L) for 60 days and sacrificed at every 15-day interval to collect tissues. Zinc concentration in all tissues was significantly higher in the metal-exposed group at all exposure durations compared to control for both phases. Metallothionein (MT) levels increased in the brain, liver and ovary of fish from both phases with exposure duration. Reactive oxygen species (ROS) generation in the brain, liver and ovary tissues increased with exposure duration at both reproductive phases while serum cortisol levels in ovulatory fish increased significantly compared to pre-ovulatory. Condition factor, gonadosomatic index and hepatosomatic index decreased in Zn-exposed fish. Brain GnRH and kisspeptin levels decreased significantly in the Zn-exposed group for both phases. GnIH was significantly higher in Zn-exposed fish. Serum FSH levels in pre-ovulatory and LH levels in ovulatory fish decreased gradually with an increase in the duration of exposure. Zn exposure reduced vitellogenin (Vtg) and estradiol (E2) in the liver and ovary with an increase in duration from both phases. Ovary maturation-inducing hormone (MIH) levels showed a decrease with exposure duration in ovulatory fish. Moreover, Zn-exposed ovulatory fish showed a degenerated oocyte nucleus due to the disintegration of the nuclear membrane. It might be inferred that Zn altered the HPGL regulatory system of M. vittatus reproduction at both the pre-ovulatory and ovulatory phases.

The chimera of S1 and N proteins of SARS-CoV-2: can it be a potential vaccine candidate for COVID-19?

INTRODUCTION: Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has emerged as one of the biggest global health issues. Spike protein (S) and nucleoprotein (N), the major immunogenic components of SARS-CoV-2, have been shown to be involved in the attachment and replication of the virus inside the host cell. AREAS COVERED: Several investigations have shown that the SARS-CoV-2 nucleoprotein can elicit a cell-mediated immune response capable of regulating viral replication and lowering viral burden. However, the development of an effective vaccine that can stop the transmission of SARS-CoV-2 remains a matter of concern. Literature was retrieved using the keywords COVID-19 vaccine, role of nucleoprotein as vaccine candidate, spike protein, nucleoprotein immune responses against SARS-CoV-2, and chimera vaccine in PubMed, Google Scholar, and Google. EXPERT OPINION: We have focussed on the use of chimera protein, consisting of N and S-1 protein components of SARS-CoV-2, as a potential vaccine candidate. This may act as a polyvalent mixed recombinant protein vaccine to elicit a strong T and B cell immune response, which will be capable of neutralizing the wild and mutated variants of SARS-CoV-2, and also restricting its attachment, replication, and budding in the host cell.

Crosstalk between heat shock proteins, NRF2, NF-κB and different endogenous antioxidants during lead-induced hepatotoxicity in Puntius ticto.

Present study aims to investigate interaction of molecular chaperons (heat shock protein 70, heat shock protein 90) with transcriptional factors (nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to evaluate their role during metal induced stress in fish hepatocytes. Adult Puntius ticto were exposed to lead nitrate at 0 mg/l (control), 1/50th (0.04 mg/l) and 1/20th (0.12 mg/l) of LC50 for 30 days and sacrificed to collect liver tissues. Activity of selected liver enzymes, antioxidants and metallothionein were analyzed. Levels of heat shock protein 70, heat shock protein 90, nuclear factor kappa B, nuclear factor E2-related factor 2 and Kelch-like ECH-associated protein 1 were also measured. Liver enzymes showed a significant increase (p < 0.05) in both Pb exposed groups indicating that the liver might be at risk of damage. Increased level of lipid peroxidation due to metal stress was marked by significant increase (p < 0.05) in malondialdehyde level in fish exposed to the higher Pb concentration compared to control (+ 13.7 %). Significant increase (p < 0.05) in gluthathione reductase (+ 35 %, + 39.2 %), glutathione s-transferase (+ 22.4 %, + 50.4 %) activities and decrease in reduced glutathione level (- 6.75 %, - 12.25 %) in fish exposed to both lower and higher Pb concentration compared to control also indicated metal induced oxidative damage in fish liver. Super oxide dismutase and catalase activities increased significantly (p < 0.05) during exposure to lower Pb concentration, while decreased significantly (p < 0.05) during exposure to higher Pb concentration compared to those in control. Significant (P < 0.05) increase (+ 52.63 %, + 89.47 %) in metallothionein in Pb exposed groups confirmed its role in detoxification process of the metal. Heat shock protein 70 and heat shock protein 90 expression levels increased significantly (p < 0.05) during metal exposure indicating their role as modulator of stress-induced antioxidant protein remodelling. A positive correlation between nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1 with gluthathione regulatory enzymes (gluthathione reductase and glutathione s-transferase) was noted. Current study effectively illuminates the critical role of different factors (heat shock proteins/nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to influence the expression and synthesis of antioxidants and other functional enzymes in lead-exposed fish liver.

Enzymatic, non enzymatic antioxidants and glucose metabolism enzymes response differently against metal stress in muscles of three fish species depending on different feeding niche.

Current study aims to determine difference in metal accumulation pattern in muscle of Liza parsia (pelagic, omnivore), Amblypharyngodon mola (surface feeder, herbivore) and Mystus gulio (benthic, carnivore) depending on their niche and feeding habit and how it affects the endogenous antioxidants and glucose metabolism in fish muscle. Fishes were collected from Malancha, Diamond Harbour and Chandanpiri, West Bengal, India. Concentrations of lead, zinc, cadmium, chromium were measured in water, sediment and fish muscle. Metal pollution index (MPI) and bioconcentration factor (BCF) was calculated to evaluate the ability of fish to accumulate specific metals in muscle tissue from the aquatic environment. Metal concentrations were found significantly higher (P < 0.05) in water, sediment, fish muscles from Malancha than Chandanpiri and Diamond Harbour. L. parsia (MPI: 0.4-1.6) showed highest metal deposition in their muscle followed by A. mola (MPI: 0.37-1.38) and M. gulio (MPI: 0.2-1.2). Malondealdehyde, superoxide dismutase, catalase, glutathione S transferase, glutathione reductase and cortisol levels increased in case of L. parsia from Malancha and Chandanpiri. Succinate dehydrogenase, lactate dehydrogenase, Ca+2 ATPase and cytochrome C oxidase levels were significantly (P < 0.05) lower at Malancha and Chandanpiri than Diamond Harbour. Heat shock protein (HSP70) expression was significantly (P < 0.05) higher in all fish species at Malancha followed by Chandanpiri and Diamond Harbour. Glucose, glycogen, hexokinase, phosphofructokinase and glycogen phosphorylase levels varied between sites and selected fish species. Serum cortisol level was measured and found to be the highest in L. parsia from Malancha (2.94 ± 0.12 ng/ml) and the lowest in M. gulio from Diamond Harbour (0.7 ± 0.05 ng/ml). The results indicate that metal toxicity alters antioxidant levels, oxidative status and energy production in fish in species specific manner. Our results also indicate that Mystus has the highest degree of adaptability in response to metal toxicity possibly due to its specific food habit and niche position. Therefore, it can be concluded that maintenance of oxidative and metabolic status to combat metal-induced oxidative load will be helpful for the fishes to acquire better resistance under such eco-physiological stress. Alteration of niche and interactive segregation in aquatic organism may be one of the key modulator of resistance against such stress.

Impact of Metal Toxicity on Oxidative Balance and Mitochondrial Enzyme Function in Muscle of Tilapia.

Present study investigates the effect of metal accumulation on antioxidant level and mitochondrial enzymes function in muscle of Oreochromis mossambicus. Metal accumulation in muscle upregulated stress marker malondialdehyde and the activity of different antioxidant enzymes with no significant alteration in glutathione system. Metal exposure to fish muscle decreased the activity of mitochondrial enzymes. AMP deaminase, aldolase, cytochrome C oxidase and lipoamide reductase showed positive correlation with acetylcholinesterase, glutathione reductase, reduced glutathione and glutathione peroxidase, but negative correlation with superoxide dismutase, catalase, glutathione S-transferase and thiobarbituric acid reactive substance. Analysis of these biomarkers clearly indicates the change in oxidative load in muscle tissues and provides insight to muscle response to the metal exposure. Therefore, the study outlines the potential use of biomarkers in context of muscle mitochondrial enzymes relating to oxidative processes that take place in the fish muscle following metal exposure and toxicity.

Effect of heavy metals on tissue-specific antioxidant response in Indian major carps.

Concentrations of heavy metals (Cu, Ni, Zn, Cd and Pb) were measured in sediments, water and liver and kidney tissues of three Indian major carps (Labeo rohita, Catla catla and Cirrhinus cirrhosus), belonging to two different weight groups (250 and 500 g), collected from ponds at two different sites (Nalban bheri and Diamond Harbour). The tissues were analysed for the levels of different antioxidant defence systems such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRd), glutathione S-transferase (GST), glutathione (GSH) and malondialdehyde (MDA). Concentrations of all the metals were significantly higher (P < 0.05) in sediment, water and the tissues from Nalban bheri compared to those in Diamond Harbour. Metal concentrations were the lowest in C. cirrhosus, which increased with an increase in fish weight, and the liver accumulated higher amount of metals than the kidney. Activities of all enzymatic and non-enzymatic antioxidant parameters except GPx and GRd were significantly higher (P < 0.05) in the tissues from Nalban bheri than those in Diamond Harbour. Significant multicollinearity was found in the values of SOD, CAT, GST, GRd, GPx and MDA with Pb, Cu and Ni in all three fish species at Nalban and with Cd in L. rohita and C. catla. Principal component analysis results revealed that stress response in a polluted site was directly regulated by an amalgamation of GSH profile and the levels of MDA in a synchronized manner. The study indicated a tissue-specific and species-specific difference for heavy metal-induced oxidative stress response in fish and a correlation between different heavy metals and individual oxidative stress markers.