Nano­zinc enhances gene regulation of non­specific immunity and antioxidative status to mitigate multiple stresses in fish.

The toxicity of ammonia surged with arsenic pollution and high temperature (34 °C). As climate change enhances the pollution in water bodies, however, the aquatic animals are drastically affected and extinct from nature. The present investigation aims to mitigate arsenic and ammonia toxicity and high-temperature stress (As + NH3 + T) using zinc nanoparticles (Zn-NPs) in Pangasianodon hypophthalmus. Zn-NPs were synthesized using fisheries waste to developing Zn-NPs diets. The four isonitrogenous and isocaloric diets were formulated and prepared. The diets containing Zn-NPs at 0 (control), 2, 4 and 6 mg kg-1 diets were included. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-s-transferase (GST) were noticeably improved using Zn-NPs diets in fish reared under with or without stressors. Interestingly, lipid peroxidation was significantly reduced, whereas vitamin C and acetylcholine esterase were enhanced with supplementation of Zn-NPs diets. Immune-related attributes such as total protein, globulin, albumin, myeloperoxidase (MPO), A:G ratio, and NBT were also improved with Zn-NPs at 4 mg kg-1 diet. The immune-related genes such as immunoglobulin (Ig), tumor necrosis factor (TNFα), and interleukin (IL1b) were strengthening in the fish using Zn-NPs diets. Indeed, the gene regulations of growth hormone (GH), growth hormone regulator (GHR1), myostatin (MYST) and somatostatin (SMT) were significantly improved with Zn-NPs diets. Blood glucose, cortisol and HSP 70 gene expressions were significantly upregulated by stressors, whereas the dietary Zn-NPs downregulated the gene expression. Blood profiling (RBC, WBC and Hb) was reduced considerably with stressors (As + NH3 + T), whereas Zn-NPs enhanced the RBC, WBC, and Hb count in fish reread in control or stress conditions. DNA damage-inducible protein gene and DNA damage were significantly reduced using Zn-NPs at 4 mg kg-1 diet. Moreover, the Zn-NPs also enhanced the arsenic detoxification in different fish tissues. The present investigation revealed that Zn-NPs diets mitigate ammonia and arsenic toxicity, and high-temperature stress in P. hypophthalmus.

Health risk assessment and metal contamination in fish, water and soil sediments in the East Kolkata Wetlands, India, Ramsar site.

East Kolkata Wetlands (EKW) is an important site for fish culture in sewage-fed areas, which are major receivers of pollutants and wastages from Kolkata. EKW is internationally important as the Ramsar site was declared on Aug 2002 with an area of 125 km2. EKW is a natural water body where wastewater-fed natural aquaculture has been practiced for more than 70 years. It is ecologically vulnerable due to the discharge of toxic waste through sewage canals from cities. Assessing the EKW to understand the inflow and load of the toxic metal (s) in fish, water, and sediments samples is essential. The field (samples collection from 13 sites) and lab (determination of toxic level of metals) based research were carried out to assess metal toxicity and health risk assessment in EKW. The levels of eighteen metals (18), namely Chromium, Vanadium, Cobalt, Manganese, Copper, Nickel, Zinc, Silver, Molybdenum, Arsenic, Selenium, Tin, Gallium, Germanium, Strontium, Cadmium, Mercury, and Lead, were determined using Inductively coupled plasma mass spectrometry (ICP-MS) in five fish tissues viz. muscle, liver, kidney, gill and brain, along with the water samples and soil sediments in 13 sampling sites. The bioaccumulation and concentration of metals in fish tissues, soil sediments, and water samples were well within the safe level concerning the recommendation of different national and international agencies except for a few metals in a few sampling sites like Cd, As, and Pb. The geoaccumulation index (Igeo) was also determined in the soil sediments, indicating moderate arsenic, selenium, and mercury contamination in a few sites. The contamination index in water was also determined in 13 sampling sites. The estimated daily intake (EDI), reference dose (RfD), target hazard quotient (THQ), slope factor and cancer risk of Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd, Pb and Hg from fish muscle were determined. Based on the results of the present investigation, it is concluded that fish consumption in the East Kolkata Wetland (EKW) is safe. The effects of bioaccumulation of metals in muscle tissue were well within the safe level for consumption as recommended by WHO/FAO.

Metal determination and biochemical status of marine fishes facilitate the biomonitoring of marine pollution.

In the present study, the bioaccumulation of chromium, manganese, cobalt, copper, zinc, selenium, arsenic, strontium, cadmium, tin, antimony and lead in tissues of thirty marine fish species collected from New Ferry Whorf, Sassoon dock and Versova fishing harbour in Mumbai, India, were analysed. The bioaccumulation patterns of these twelve elements were determined to assess pollution biomarkers based on cellular and oxidative stresses. Catalase, superoxide dismutase and glutathione-s-transferase, glycolytic enzymes viz. lactate dehydrogenase and malate dehydrogenase, protein metabolism enzymes viz. aspartate transferase and alanine transferase, and lipid peroxidation were significantly higher in muscle and gill tissues. The activities of the neurotransmitter enzyme acetylcholine esterase in muscle and brain tissues was inhibited due to pollution. This study suggested that biochemical attributes such as oxidative stress enzymes, cellular biomarkers, neurotransmitter enzymes and metal and metalloid contamination could be successfully employed, even at low concentrations, as reliable biomarkers for biomonitoring of contaminated marine ecosystems.

Mitigation potential of selenium nanoparticles and riboflavin against arsenic and elevated temperature stress in Pangasianodon hypophthalmus.

Climate change impact has disturbed the rainfall pattern worsening the problems of water availability in the aquatic ecosystem of India and other parts of the world. Arsenic pollution, mainly through excessive use of groundwater and other anthropogenic activities, is aggravating in many parts of the world, particularly in South Asia. We evaluated the efficacy of selenium nanoparticles (Se-NPs) and riboflavin (RF) to ameliorate the adverse impacts of elevated temperature and arsenic pollution on growth, anti-oxidative status and immuno-modulation in Pangasianodon hypophthalmus. Se-NPs were synthesized using fish gill employing green synthesis method. Four diets i.e., Se-NPs (0 mg kg-1) + RF (0 mg kg-1); Se-NPs (0.5 mg kg-1) + RF (5 mg kg-1); Se-NPs (0.5 mg kg-1) + RF (10 mg kg-1); and Se-NPs (0.5 mg kg-1) + RF (15 mg kg-1) were given in triplicate in a completely randomized block design. The fish were treated in arsenic (1/10th of LC50, 2.68 mg L-1) and high temperature (34 °C). Supplementation of the Se-NPs and RF in the diets significantly (p < 0.01) enhanced growth performance (weight gain, feed efficiency ratio, protein efficiency ratio, and specific growth rate), anti-oxidative status and immunity of the fish. Nitroblue tetrazolium (NBT), total immunoglobulin, myeloperoxidase and globulin enhanced (p < 0.01) with supplementation (Se-NPs + RF) whereas, albumin and albumin globulin (A:G) ratio (p < 0.01) reduced. Stress biomarkers such as lipid peroxidation in the liver, gill and kidney, blood glucose, heat shock protein 70 in gill and liver as well as serum cortisol reduced (p < 0.01) with supplementation of Se-NPs and RF, whereas, acetylcholine esterase and vitamin C level in both brain and muscle significantly enhanced (p < 0.01) in compared to control and stressors group (As + T) fed with control diet. The fish were treated with pathogenic bacteria after 90 days of experimental trial to observe cumulative mortality and relative survival for a week. The arsenic concentration in experimental water and bioaccumulation in fish tissues was also determined, which indicated that supplementation of Se-NPs and RF significantly reduced (p < 0.01) bioaccumulation. The study concluded that a combination of Se-NPs and RF has the potential to mitigate the stresses of high temperature and As pollution in P. hypophthalmus.

Synergistic effect of zinc nanoparticles and temperature on acute toxicity with response to biochemical markers and histopathological attributes in fish.

In the present study, an experiment was carried out to delineate the lethal concentration of (LC50) zinc nanoparticles (Zn-NPs) alone and with concurrent to high temperature (34 °C) in Pangasianodon hypophthalmus. The lethal concentration of Zn-NPs alone and with high temperature was estimated as 21.89 and 19.74 mg/L respectivey in P. hypophthalmus. The lethal concentration was decided with the help of definite concentration via 16, 18, 20, 22, 24, 26, 28 and 30 mg/L. The Zn-NPs were significantly alter the biochemical and histopathology of different fish tissues. The stress biomarkers such as oxidative stress (catalase superoxide dismutase and glutathione-s-transferase, lipid peroxidation) was studied in the liver, gill and kidney tissue, which was noticeable (p < 0.01) enhanced with higher concentration in both condition (Zn-NPs alone and Zn-NPs-T) in dose dependent manners. The carbohydrate (lactate dehydrogenase and malate dehydrogenase) and protein metabolic enzymes (alanine amino transferase and aspartate amino transferase) were also remarkable enhanced (p < 0.01) with higher concentration of Zn-NPs and Zn-NPs-T. The neurotransmitter (acetylcholine esterase) activities were significant inhibited (p < 0.01) with exposure to Zn-NPs and Zn-NPs-T and digestive enzymes such as protease and amylase were non-significant (p > 0.01) with the exposure of Zn-NPs and Zn-NPs-T, further, lipase were significantly reduced (p < 0.01) with exposure to Zn-NPs and temperature exposure group. The histopathological alteration were also observed in the liver and gill tissue. The present investigation suggested that, essential trace elements at higher concentration in acute exposure led to pronounced deleterious alteration on histopathology and cellular and metabolic activities in fish.

Synergistic effect of dietary selenium nanoparticles and riboflavin on the enhanced thermal efficiency of fish against multiple stress factors.

An experiment was designed to delineate the efficacy of a dietary mixture of selenium nanoparticles (Se-NPs) and riboflavin (RF) on the thermal efficiency/tolerance of Pangasianodon hypophthalmus reared under arsenic (2.8 mg/L) and high-temperature (34 °C) stress. A green synthesis method was employed for the synthesis of Se-NPs using fish gills, which are normally discarded as by-products. Four isocaloric and iso-nitrogenous experimental diets were used, namely, a control diet (Se-NPs and RF @ 0 mg/kg diet) and diets containing RF @ 5, 10 or 15 mg/kg diet and Se-NPs @ 0.5 mg/kg diet, and feeding was performed for 95 days. At the end of the feeding trial, the thermal tolerance was evaluated by determination of the following parameters: critical thermal minimum (CTMin), lethal thermal minimum (LTMin), critical thermal maximum (CTMax), and lethal thermal maximum (LTMax). The anti-oxidative status in the form of catalase (CAT), glutathione-s-transferase (GST) and glutathione peroxidase (GPx) activities was significantly (p < 0.01) enhanced upon concurrent exposure to arsenic and high temperature at LTMin and LTMax, whereas a non-significant (p > 0.05) change in superoxide dismutase (SOD) activity was observed in the brain at LTMin and brain, gill and kidney at LTMax. Supplementation with Se-NPs @ 0.5 mg/kg diet and RF @ 5, 10 or 15 mg/kg diet significantly (p < 0.01) improved the anti-oxidative status with or without stressors. AChE activity in the brain was significantly (p < 0.01) inhibited upon concurrent exposure to arsenic and high temperature and improved in the treatment group supplemented with Se-NPs and RF. The arsenic concentration in muscle and experimental water and Se concentration in muscle and experimental feed were analysed. Overall, the results indicated that supplementation with RF @ 5 mg/kg diet and Se-NPs @ 0.5 mg/kg diet could confer protection to the fish against arsenic and thermal stress and led to enhanced thermal efficiency/tolerance of P. hypophthalmus.

Lipotropes protect against pathogen-aggravated stress and mortality in low dose pesticide-exposed fish.

The decline of freshwater fish biodiversity corroborates the trends of unsustainable pesticide usage and increase of disease incidence in the last few decades. Little is known about the role of nonlethal exposure to pesticide, which is not uncommon, and concurrent infection of opportunistic pathogens in species decline. Moreover, preventative measures based on current knowledge of stress biology and an emerging role for epigenetic (especially methylation) dysregulation in toxicity in fish are lacking. We herein report the protective role of lipotropes/methyl donors (like choline, betaine and lecithin) in eliciting primary (endocrine), secondary (cellular and hemato-immunological and histoarchitectural changes) and tertiary (whole animal) stress responses including mortality (50%) in pesticide-exposed (nonlethal dose) and pathogen-challenged fish. The relative survival with betaine and lecithin was 10 and 20 percent higher. This proof of cause-and-effect relation and physiological basis under simulated controlled conditions indicate that sustained stress even due to nonlethal exposure to single pollutant enhances pathogenic infectivity in already nutritionally-stressed fish, which may be a driver for freshwater aquatic species decline in nature. Dietary lipotropes can be used as one of the tools in resurrecting the aquatic species decline.