Pollution induced nitrative stress and heat shock protein 70 overexpression in fish liver mitochondria

The effects of sodium butyrate (NaB) combination with soy saponin dietary supplementation on the growth parameters, intestinal performance and immune-related genes expression of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)

Soy saponins are generally known to have negative effects on growth and the intestines of aquatic animals, and appropriate levels of sodium butyrate (NaB) may provide some mitigating effects. We investigated the effects of low and high levels of soy saponin and the protective effects of NaB (based on high level of soy saponin) on growth, serum cytokines, distal intestinal histopathology, and inflammation in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). The experiment included four groups: fishmeal group (FM, 0.00% saponin and 0.00% NaB), low saponin group (SL, 0.30% saponin and 0.00% NaB), high saponin group (SH, 1.50% saponin and 0.00% NaB) and high saponin with NaB group (SH-NaB, 1.50% saponin and 0.13% NaB). The results showed compared to FM, the final body weight (FBW) and weight gain (WG) were significantly higher and lower in SL and SH, respectively (P < 0.05). Compared to SH, the FBW and WG were significant higher in SH-NaB (P < 0.05). In the serum, compared to FM, the interferon γ (IFN-γ) and interleukin-1β (IL-1β) levels in SH were significantly increased (P < 0.05). Compared to SH, the IFN-γ level was significantly decreased in SH-NaB (P < 0.05). In the distal intestine, based on Alcian Blue-Periodic Acid-Schiff (AB-PAS) observation, the goblet cell/μm was significantly increased and decreased in the SL and SH, respectively, compared to FM. The intestinal diameter/plica height ratio in the SH was significantly higher than those in the FM, SL and SH-NaB (P < 0.05). The NO and ONOO- levels in the SH were significantly higher than that in FM and SL (P < 0.05). At the transcriptional level in the distal intestine, compared to FM, the mRNA levels of tumor necrosis factor (tnfα), il1β, interleukin-8 (il8) and ifnγ were significantly up-regulated in the SH (P < 0.05). Compared to the SH, tnfα, il8 and ifnγ were significantly down-regulated in the SH-NaB (P < 0.05). Compared to the FM, the mRNA levels of claudin3, claudin15, zo2 and zo3 were significantly up-regulated in the SL (P < 0.05). The mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly down-regulated in the SH compared to the FM (P < 0.05). Additionally, compared to the SH, the mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly up-regulated in the SH-NaB (P < 0.05). After the 7-day Vibrio parahaemolyticus challenge test, the survival was significantly higher and lower in the SL and SH, respectively, compared to FM (P < 0.05). Overall, low and high levels of soy saponins had positive and negative effects on growth, disease resistance, serum cytokines, and distal intestinal development and anti-inflammation, respectively, in hybrid grouper. NaB effectively increased disease resistance and improved distal intestinal inflammation in hybrid grouper, but the effects of NaB were mainly observed in improving distal intestinal tight junctions.

Roundup® disrupts tissue architecture, attenuates Na+/K+-ATPase expression, and induces protein oxidation/nitration, cellular apoptosis, and antioxidant enzyme expressions in the gills of goldfish, Carassius auratus

Extensive agricultural activities to feed the growing population are one major driving force behind aquatic pollution. Different types of pesticides are used in farmlands to increase crop production and wash up into water bodies. Glyphosate-based herbicide Roundup® is one of the most used pesticides in the United States; however, its effects on teleost species are still poorly understood. This study focused on the effects of environmentally relevant concentrations of Roundup exposure (low- and high-dose: 0.5 and 5 μg/L for 2-week) on Na+/K+-ATPase (NKA, a biomarker for sodium‑potassium ion pump efficacy), cytochrome P450-1A (CYP1A, a monooxygenase enzyme), 2,4-dinitrophenyl protein (DNP, a biomarker for protein oxidation), 3-nitrotyrosine protein (NTP, a biomarker for protein nitration), superoxidase dismutase (SOD, an antioxidant enzyme), catalase (CAT, an antioxidant enzyme) expressions, and cellular apoptosis in the gills of goldfish. Histopathological and in situ TUNEL analyses showed widespread tissue damage, including lamellar fusion, loss of gill architecture, club shape of primary lamellae, mucous formation, and distortion in the epithelium layer, as well as apoptotic nuclei in gills. Immunohistochemical and qRT-PCR analyses provided insights into the expressions of molecular indicators in gills. Fish exposed to Roundup exhibited a significant (P < 0.05) downregulation of NKA expression in gills. Additionally, we observed upregulation of CYP1A, DNP, NTP, SOD, and CAT expressions in the gills of goldfish. Overall, our results suggest that exposure to Roundup causes disruption of gill architecture, induces protein oxidation/nitration and cellular apoptosis, and alters prooxidant-antioxidant homeostasis in tissues, which may lead to reduced fitness and survivability of teleost species.

Molecular and biochemical biomarkers in the American oyster Crassostrea virginica exposed to herbicide Roundup® at high temperature

Aquatic organisms are frequently exposed to various environmental stressors. Thus, the effects of high temperatures and herbicides on aquatic organisms are a major subject of interest. In this study, we studied the effects of short-term exposure (1 week) to Roundup®, a glyphosate-based herbicide (concentrations: 0.5 and 5 µg/L), on the morphology of gills, digestive glands, and connective tissues, and the expression of heat shock protein-70 (HSP70, a chaperone protein), cytochrome P450 (CYP450, a biomarker of environmental contaminants), dinitrophenyl protein (DNP, a biomarker of protein oxidation), nitrotyrosine protein (NTP, a biomarker of protein nitration), antioxidant enzymes such as superoxidase dismutase (SOD) and catalase (CAT) in tissues of American oyster, Crassostrea virginica (Gmelin, 1791) maintained at high temperature (30 °C). Histological analyses showed an increase in mucous production in the gills and digestive glands, and in hemocyte aggregation in the connective tissues as well as a structural change of lumen in the digestive glands of oysters exposed to Roundup. Immunohistochemical and quantitative RT-PCR analyses showed significant (P < 0.05) increases in HSP70, CYP450, DNP, NTP, CAT, and SOD mRNA and protein expressions in the tissues of oysters exposed to Roundup. Taken together, these results suggest that exposure to Roundup at high temperature induces overproduction of reactive oxygen species/reactive nitrogen species which in turn leads to altered prooxidant-antioxidant activity in oyster tissues. Moreover, our results provide new information on protein oxidation/nitration and antioxidant-dependent mechanisms for HSP70 and CYP450 regulations in oysters exposed to Roundup at high temperature.

Toxic effect of heavy metals on ovarian deformities, apoptotic changes, oxidative stress, and steroid hormones in rainbow trout

BACKGROUND

As is well known, the pollution in the aquatic environment in which fish grow has a direct impact on aquaculture practices. Pollution in aquatic systems because of multiple adverse effects on fish metabolic processes, especially the reproductive systems.

AIM

The goal of this study was to assess the severity of pollution impact in two different hatcheries, Verinag hatchery, Site 1 (S1) and Panzath hatchery, Site 2 (S2) in Anantnag region, using histopathological, ultrastructural, oxidative stress, genotoxic, and hormonal analysis in rainbow trout gonad (ovary). M&M: Fish were collected between May 2018 and April 2019 from two locations, Verinag hatchery (S1) and Panzath hatchery (S2), which were affected by heavy metals.

RESULTS

The histological and ultrastructural examination of rainbow trout ovaries from the Verinag hatchery (S1) revealed normal structure in growing oocytes in rainbow trout at various stages based on morphological features while the fish ovaries in the Panzath hatchery (S2) showed various deformities and irregularly shaped oocytes. The surfaces of some of these oocytes were wrinkled, rough, or distorted. Apoptotic studies revealed that the frequency of apoptotic cells collected from S2 water was significantly increased in ovarian cells (P < 0.05). The activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were found to be increased in fish collected from S1 but decreased in fish collected from S2. In S2 caught fish, malondialdehyde (MDA) levels were found to increase gradually, and the degree of heavy metal stress was positively correlated (p < 0.05). The comet assay was used to determine the induction of DNA damage in ovarian cells. The induction of DNA damage was found to be significantly higher (p < 0.05) in S2 fish specimens compared to fish from S1. On comparing the DNA damage of the rainbow trout from the two sampling sites, it was revealed that the fish is much more sensitive to aquatic contaminants. Regarding steroid hormones, higher levels of progesterone and estrogen were reported in the fish samples collected from S1 as compared to S2 captured fish.

CONCLUSION

In conclusion, the comparative study of fish from two different sites viz. Verinag hatchery (S1) and Panzath hatchery (S2) revealed that S2 sampled fish suffered more heavy metal damage, including cellular deformities, apoptosis, oxidative damage, and altered steroid hormones.

Potential mechanisms of Na+/K+-ATPase attenuation by heat and pesticides co-exposure in goldfish: role of cellular apoptosis, oxidative/nitrative stress, and antioxidants in gills

In this study, we examined the dose-dependent effects of an environmentally relevant pesticide cocktail (metalachlor, linuron, isoproturon, tebucanazole, aclonifen, atrazine, pendimethalin, and azinphos-methyl) and temperature change (22 vs. 32 °C for 4-week exposure) on Na⁺/K⁺-ATPase, 3-nitrotyrosine protein (NTP), dinitrophenyl protein (DNP), catalase (CAT), and superoxide dismutase (SOD) expressions in gills of goldfish (Carassius auratus). Histopathological analysis showed widespread damage to gill in elevated temperature (32 °C) and pesticide co-exposure groups, including fusion of secondary lamellae, club-shaped primary lamellae, rupture of epithelial layer, loss of normal architecture, and hemorrhaging. Immunohistochemical and qRT-PCR analyses showed significant decreases in Na⁺/K⁺-ATPase protein and mRNA expressions in gills exposed to higher temperature and pesticides; however, combined exposure to heat and pesticides significantly increases NTP, DNP, CAT, and SOD expressions. In situ TUNEL assay revealed elevated levels of apoptotic cells in response to combined exposure. Collectively, our results suggest the combined effects of heat and pesticide stress cause cellular damage, upregulate oxidative/nitrative stress biomarkers, and increase apoptotic cells, downregulate Na⁺/K⁺-ATPase expression in gills. This provides new evidence for oxidant/antioxidant-dependent mechanisms for downregulation of Na⁺/K⁺-ATPase expression in gills during combined exposure.

Interactive effects of high temperature and pesticide exposure on oxidative status, apoptosis, and renin expression in kidney of goldfish: Molecular and cellular mechanisms of widespread kidney damage and renin attenuation

One of many noteworthy consequences of increasing societal reliance on pesticides is their predominance in aquatic environments. These pernicious chemicals interact with high temperatures from global climate change, heat waves, and natural variations to create unstable environments that negatively impact organisms' health. To understand these conditions, we examined the dose-dependent effects of environmentally relevant pesticide mixtures (metolachlor, linuron, isoproturon, tebuconazole, aclonifen, atrazine, pendimethalin, and azinphos-methyl) combined with elevated temperatures (22 control vs. 32°C for 4-week exposure) on renin, dinitrophenyl protein (DNP, an indicator of reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS), superoxidase dismutase (SOD, an antioxidant), and catalase (CAT, an antioxidant) expressions in the kidneys of goldfish (Carassius auratus). Histopathological analysis showed widespread damage to kidney tissues in high temperature and pesticide co-exposure groups, including rupture of the epithelial layer, hemorrhaging, and degeneration of tubular epithelium. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical analyses demonstrated significant declines in renin receptor-like mRNA and protein expressions in kidney tissues under combined exposure to high temperature and pesticides compared with controls; conversely, expression of DNP, NTP, SOD, and CAT increased in kidney tissues under the same conditions. Apoptotic cells were also increased in co-exposure groups as assessed by in situ terminal deoxynucleotidyl transferase dUTP nick labeling (TUNEL) assay. The enhanced apoptosis in kidneys of heat and pesticides co-exposed fish was associated with increased caspase-3 (a protease enzyme) mRNA levels. Our results demonstrated that high temperature and pesticides induced oxidative/nitrative stress (i.e., ROS/RNS), damaged tissues, increased cellular apoptosis, and suppressed renin expression in kidneys of goldfish.

Effects of benzo[a]pyrene exposure on black rockfish (Sebastes schlegelii): EROD activity, CYP1A protein, and immunohistochemical and histopathological alterations

Cytochrome P450 1A (CYP1A) is the major phase I of metabolic enzyme that plays essential roles in the detoxification of drugs and biotransformation of environmental pollutants. This study investigated CYP1A enzyme induction using EROD activity, CYP1A protein levels, and immunohistochemistry, along with histopathology of the liver, gills, kidneys, and intestine from the black rockfish, Sebastes schlegelii, exposed to benzo[a]pyrene (B[a]P). S. schlegelii has high risks of ingestion of sediment and absorption of heavy crude oil after accidental oil spills in Korea. This study thus exposed fish to B[a]P at 2, 20, and 200 μg/g body weight. EROD activity and CYP1A protein levels in hepatic microsomes had a positive correlation with the concentration of B[a]P (2-200 μg/g); in particular, exposure to 200 μg/g of B[a]P resulted in a 4- and 6-fold increase in hepatic EROD activity and CYP1A protein level, respectively. Hyperplasia of primary lamellar epithelium and atrophy of renal tubules were observed in the gills and kidney, respectively, following exposure to B[a]P at 200 μg/g. In contrast, severe histological alteration was not seen in intestinal tissues. Immunohistochemical analysis of the distribution of cellular CYP1A in four tissues showed strong immunostaining in the cytoplasm and nuclear membranes of the liver against B[a]P at 200 μg/g. Polycyclic aromatic hydrocarbons (PAHs), such as B[a]P, cause adverse histological changes in tissues of fish and provide evidence that PAH metabolism is inducible in fish liver, leading to increased CYP1A induction. Furthermore, the CYP1A induction in specific tissues might assist in monitoring and field assessment of marine ecosystems.

Nickel nanoparticles induce hepatotoxicity via oxidative and nitrative stress-mediated apoptosis and inflammation

Nickel nanoparticles (Ni NPs) are utilized extensively in various industrial applications. However, there are increasing concerns about potential exposure to Ni NPs and consequent health effects. The aim of this study was to assess Ni NPs-induced liver toxicity in Sprague Dawley rats. Twenty-five rats were exposed to Ni NPs via intraperitoneal injection at doses of 15, 30, and 45 mg/kg per body weight for 28 days. Results from ICP-MS analysis showed an increase in the concentration of Ni NPs in a dose-dependent manner. The liver dysfunction was indicated by considerable production of ALT, AST, ALP, LDH, and TB in Ni NPs-treated rats. Histological examination demonstrated liver injuries (inflammatory cells, congestion, necrosis, and pyknosis) in exposed rats with dose-dependent severity of pathologies by semi-quantitative histograding system. To explore the toxicological pathways, we examined oxidative stress biomarkers and detected Ni NPs significantly elevated the levels of MDA and LPO while decreasing the levels of CAT and GSH. All the changes in biomarkers were recorded in a dose-dependent relationship. In addition, we found upregulated NF-kβ indicating activation of inflammatory cytokines. ELISA results of serum revealed a remarkable increase of nitrative stress markers (iNOS and NO), ATPase activity, inflammatory cytokine (IL-6, IL-1β, and TNF-α), and apoptotic mediators (caspase-3 and caspase-9) in Ni NPs-treated groups than the control. In summary, the result of this study provided evidence of hepatotoxicity of Ni NPs and insightful information about the involved toxic pathways, which will help in health risk assessment and management, related preventive measures for the use of Ni-NPs materials.

Toxic effects of waterborne ammonia exposure on hematological parameters, oxidative stress and stress indicators of juvenile hybrid grouper, Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀

Juvenile hybrid grouper, Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀ (mean weight: 26.5 ± 2.8 g, mean length: 11.8 ± 1.3 cm) were exposed to different, sub-lethal levels of waterborne ammonia (0, 1, 2, 4, and 8 mg NH₄⁺/L) for 2 weeks. We assessed the hematological parameters, antioxidant enzymes, and stress responses of juvenile hybrid grouper after 1 week and after 2 weeks. Hematological parameters such as hemoglobin and hematocrit levels, were significantly decreased by ammonia exposure. Plasma components such as the magnesium and total protein contents, and the glutamic oxaloacetic transaminase and glutamic pyruvic transaminase activities were significantly altered by ammonia exposure; however, no changes in the magnesium levels were detected. Antioxidant responses, such as superoxide dismutase and glutathione S-transferase activities, were also significantly affected by ammonia exposure. Stress indicator levels, i.e., plasma cholesterol and heat shock protein 70 levels, were significantly increased by ammonia exposure. The results of this study indicated that ammonia exposure has toxic effects on juvenile hybrid grouper and affects their hematological parameters, antioxidant enzymes, and stress responses.

Waterborne zinc induced lobe-dependent effect on oxidative stress and energy metabolism in hepatopancreas of Larimichthys crocea

The study aimed to compare differences in oxidative stress and energy metabolism between the left and right lobe of hepatopancreas in large yellow croaker Larimichthys crocea exposed to 0 (control), 20, and 100 μM Zn for 96 h. Tipical biomarkers were examined including the proportion of white hepatopancreas, lipid content, malondialdehyde (MDA) level, glutathione (GSH) content, activity levels of enzymes (Cu/Zn-superoxide dismutase, Cu/Zn-SOD; catalase, CAT; glutathione peroxidase, GPx; glutathione reductase, GR; mitochondrial ATP synthase, F-ATPase; malate dehydrogenase, MDH; succinate dehydrogenase, SDH; hepatic lipase, HTGL; lipoprotein lipase, LPL), mRNA levels of genes encoding these enzymes (sod1, cat, gpx1a, gr, atp5b, mdh, sdh, htgl, and lpl), and gene expression of signaling molecules the NF-E2-related nuclear factor 2 (nrf2) and Kelch-like ECH-associated protein 1 (keap1). A whitish color in the left lobe of hepatopancreas was observed in the control and Zn-exposed fish. Contrarily, the right lobe of hepatopancreas tended towards red with increasing Zn levels. The phenomenon was further confirmed by that lipid content was reduced in the right lobe and was not significantly affected in the left lobe by Zn. The right lobe showed higher energy consumption than the left lobe as reflected by the up-regulation of activity levels of HTGL, LPL, F-ATPase, MDH, and SDH. Lipid peroxidation declined by 20 μM Zn and was unchanged by 100 μM Zn in both lobes, which could be explained by increased activity levels of Cu/Zn-SOD and GPx. However, the magnitude of increase in Cu/Zn-SOD activity was greater in the right lobe than that in the left one. The difference in enzyme activity between two lobes may be involved in changes in mRNA levels of sod1, gr, atp5b, sdh, htgl, lpl, and nrf2, which was further confirmed by positive relationships between enzyme activity and gene expression. Our data also showed positive correlations between nrf2 expression and mRNA levels of its target genes, suggesting that Nrf2 was required for the protracted induction of these genes. Our results demonstrated the potential molecular mechanism of Zn-induced differences between lobes of hepatopancreas, suggesting that the sampling part of hepatopancreas should be considered with caution when assessing metal contamination.

Negative impacts of elevated nitrate on physiological performance are not exacerbated by low pH

Multiple environmental stressors, including nutrient effluents (i.e. nitrates [NO₃^-]) and altered pH regimes, influence the persistence of freshwater species in anthropogenically disturbed habitats. Independently, nitrate and low pH affect energy allocation by increasing maintenance costs and disrupting oxygen uptake, which ultimately results in impacts upon whole animal performance. However, the interaction between these two stressors has not been characterised. To address this, the effects of nitrate and pH and their interaction on aerobic scope and physiological performance were investigated in the blueclaw crayfish, Cherax destructor. Crayfish were exposed to a 2 × 3 factorial combination, with two pH levels (pH 5.0 and 7.0) and three nitrate concentrations (0, 50 and 100 mg L^-1NO₃^-). Crayfish were exposed to experimental conditions for 65 days and growth and survival were monitored. Aerobic scope (i.e. maximal - standard oxygen uptake) was measured at six time points (1, 3, 5, 7, 14, and 21 days) during exposure to experimental treatments. Crayfish performance was assessed after 28 days, by measuring chelae strength and whole animal activity capacity via the righting response. Survival was reduced in crayfish exposed to pH 5.0, but there was no exacerbation of this effect by exposure to high nitrate levels. Aerobic scope was compromised by the interaction between low pH and nitrate and resulted in prolonged elevations of standard oxygen uptake rates. Exposure to nitrate alone affected aerobic scope, causing a 59% reduction in maximum oxygen uptake. Reduced aerobic capacity translated to reduced chelae strength and righting capacity. Together, these data show that low pH and elevated nitrate levels reduce aerobic scope and translate to poorer performance in C. destructor, which may have the potential to affect organismal fitness in disturbed habitats.

Role of oxidative stress in liver toxicity induced by nickel oxide nanoparticles in rats

The aim of the present study was to explore the role of oxidative stress in liver toxicity induced by nickel oxide nanoparticles (nano‑NiO) in rats. Male Wistar rats received saline (control), nano‑NiO [0.015, 0.06 or 0.24 mg/kg body weight (b.w.)] or micro‑NiO (0.24 mg/kg b.w.) by intratracheal instilling twice a week for 6 weeks. Liver tissues were then collected and examined for biomarkers of nitrative and oxidative stress, as well as mRNA expression of heme oxygenase (HO)‑1 and metallothionein (MT)‑1. The results demonstrated that the NiO exposure groups had increased liver wet weight and coefficient to body weight, as well as liver pathological changes, evidenced as cellular edema, hepatic sinus disappeara-nce and binucleated hepatocytes. The activities of total nitric oxide synthase and inducible nitric oxide synthase, and the nitric oxide content, were increased in the 0.24 mg/kg nano‑NiO group compared with the control group. The MT‑1 mRNA expression levels were downregulated, while HO‑1 mRNA was upregulated in the 0.24 mg/kg nano‑NiO exposure group compared with the control group. In addition, abnormal changes of hydroxyl radical, lipid peroxidation, catalase, glutathione peroxidase, total superoxide dismutase and total antioxidative capacity were observed in the liver tissues of the 0.24 mg/kg nano‑NiO exposure group, compared with the control group. The present results therefore indicated that nano‑NiO‑induced liver toxicity may be associated with nitrative and oxidative stress in rats.

Organ-specific effects of low-dose zinc pre-exposure on high-dose zinc induced mitochondrial dysfunction in large yellow croaker Pseudosciaena crocea

The study was carried out to evaluate the effects of low-dose zinc (Zn) pre-exposure on survival rate, new Zn accumulation, and mitochondrial bioenergetics in the liver and spleen of large yellow croaker exposed to high-dose Zn. To the end, fish were pre-exposed to 0 and 2 mg L^-1 Zn for 48 h and post-exposed to 0 and 12 mg L^-1 Zn for 48 h. Twelve milligrams Zn per liter exposure alone reduced survival rate, but the effect did not appear in the 2 mg L^-1 Zn pre-exposure groups. Two milligrams per liter Zn pre-exposure also ameliorated 12 mg Zn L^-1 induced new Zn accumulation, reactive oxygen species (ROS) levels, and mitochondrial swelling in the liver. However, these effects did not appear in the spleen. In the liver, 2 mg L^-1 Zn pre-exposure apparently relieved 12 mg L^-1 Zn induced down-regulation of activities of ATP synthase (F-ATPase), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH). The mRNA levels of these genes remained relatively stable in fish exposed to 12 mg L^-1 Zn alone, but increased in fish exposed to 12 mg L^-1 Zn with 2 mg L^-1 Zn pre-treatment. In the spleen, 2 mg Zn L^-1 pre-exposure did not mitigate the down-regulation of mRNA levels of genes and activities of relative enzymes induced by 12 mg L^-1 Zn. In conclusion, our study demonstrated low-dose zinc pre-exposure ameliorated high-dose zinc induced mitochondrial dysfunction in the liver but not in the spleen of large yellow croaker, indicating an organ-specific effect.

Putative Roles for Metallothionein and HSP70 Genes in Relation with Heavy Metal Accumulation and Parasitic Cymothoid in the Fish Nemipterus furcosus

To assess stress level induced by multiple stressors in aquatic organism, biomarkers have been adopted as early warning indicator due to their high accuracy, rapidity, and sensitivity. We investigated the effects of ectoparasitic isopod infection on heavy metal bioaccumulation (Fe, Cu, Zn, and Cd) in the fish Nemipterus furcosus and profiled the expression of metallothionein (MT) and heat shock proteins 70 (HSP70) genes of the fish host. Sixty individuals (parasitized and nonparasitized with Cymothoa truncata) were collected from three sites differing in the levels of anthropogenic activities off the South China Sea. Our results revealed no significant difference in heavy metal concentrations between infected and nonparasitized fish. We observed a positive correlation between heavy metal bioaccumulation in the fish host and anthropogenic activities. Accordingly, expression analysis of MT genes in fish liver showed significant differences in expression level between sampling sites, with lowest level in the least exploited site (Batu Rakit). A reverse pattern in HSP70 gene expression was demonstrated in fish muscle, showing the highest expression at Batu Rakit. While cymothoid infection in N. furcosus had no significant impact on fish MT gene expression, it resulted in a reduction of HSP70 level in liver of parasitized fish. These findings highlight the putative roles of MT in heavy metal assessment. Future studies should determine the kinetics of cymothoid infection and other potential stressors in characterizing the HSP70 gene expression profile.

Heat Shock Protein 70 Expression is Increased in the Liver of Neonatal Intrauterine Growth Retardation Piglets

Intrauterine growth retardation (IUGR) leads to the dysfunction in digestive system, as well as the alteration in the expression of some functional proteins. Heat shock protein 70 (Hsp70) could be induced by various stress factors, but whether Hsp70 expression is changed in neonatal IUGR infants has not been demonstrated. This study was conducted to explore the expression of Hsp70 in the liver by using the IUGR piglet model. Liver and plasma samples were obtained from IUGR and normal birth weight (NBW) piglets at birth. The neonatal IUGR piglets had significantly lower liver weight than their counterparts. The activities of aspartate aminotransferase and alanine aminotransferase in serum were enhanced significantly in IUGR indicating liver dysfunction. The activities of superoxide dismutase (p<0.01), glutathione peroxidase (p<0.01) and catalase (p>0.05) were lower and the level of malondialdehybe was higher (p<0.05) in IUGR liver compared with in NBW. According to the results of histological tests, fatty hepatic infiltrates and cytoplasmic vacuolization were present in the liver of IUGR piglets, but not in NBW liver. The expression of Hsp70 protein was significantly higher (p<0.05) in IUGR piglet liver than in NBW. Similar to where the hepatic injuries were observed, location of Hsp70 was mostly in the midzonal hepatic lobule indicating that oxidative stress might be responsible for the increased expression of Hsp70.

Effects of heavy metals on antioxidants and expression of HSP70 in different tissues of Milk fish (Chanos chanos) of Kaattuppalli Island, Chennai, India

Distribution of heavy metals and its associated oxidative stress, ultrastructure and expression of HSP 70 were studied in varies tissues of Chanos chanos collected from polluted sites compared with the fish collected from less polluted sites of Kaattuppalli Island. The concentrations of copper, lead, zinc, cadmium, manganese and iron were quantified in gills and liver. The results showed marked differences between the two sites as well as significant variations within the tissues. The decreasing trend of metals in the tissues of fish sampled from both polluted and less polluted sites was in the order of Fe>Mn>Zn>Cu>Pb>Cd. Overall, the highest metal concentrations were found in the fish collected from polluted sites. Similarly increase of antioxidant enzymes biomarkers due to heavy metals was also evident in gills and liver of the fish collected from polluted sites. These tissues were further investigated by scanning and electron microscopy and the results were compared with the reference less polluted sites. The presence of large lipid droplets in liver and increase of mucous cells in gills were some of the most noticeable alterations observed and were related to heavy metal contaminants. It is concluded that scanning, ultrastructural and useful of HSP70 biomarkers for heavy metal induced oxidative stress, and demonstrate that precautions need to be taken in polluted sites of Kaattuppalli Island in order to prevent heavy metal pollution that can occur in the future.

Mitochondrial HSP70 cognate-mediated differential expression of JNK1/2 in the pollution stressed grey mullets, Mugil cephalus

Cells have evolved different networks of cellular stress responses to adapt during environmental changes and survive combating wide variety of stress. Mitochondrial heat shock protein 70 (mtHSP70) are essential for maintaining cellular homeostasis. c-Jun-N terminal kinase (JNK), a subfamily of MAPK, plays a key role in the transmission of extracellular signal for survival and death. In the present investigation, the differential expression of phosphorylated JNK1/2 with corresponding increases in heat shock transcription factor-1 (HSF-1) under high levels of B-cell lymphoma 2 (Bcl-2), HSP70 transcripts (twofold) and mtHSP70 has been correlated with fish survival in polluted Ennore estuary. This study suggests that in Ennore sample, the amplification in HSP70 transcripts along with corresponding mtHSP70 overexpression might be due to activation of JNK1/2 and HSF-1. This would influence the expression of Bcl-2 protein involved in mitochondrial survival under pollution-stressed condition.

Zebrafish: a model animal for analyzing the impact of environmental pollutants on muscle and brain mitochondrial bioenergetics

Mercury, anthropogenic release of uranium (U), and nanoparticles constitute hazardous environmental pollutants able to accumulate along the aquatic food chain with severe risk for animal and human health. The impact of such pollutants on living organisms has been up to now approached by classical toxicology in which huge doses of toxic compounds, environmentally irrelevant, are displayed through routes that never occur in the lifespan of organisms (for instance injecting a bolus of mercury to an animal although the main route is through prey and fish eating). We wanted to address the effect of such pollutants on the muscle and brain mitochondrial bioenergetics under realistic conditions, at unprecedented low doses, using an aquatic model animal, the zebrafish Danio rerio. We developed an original method to measure brain mitochondrial respiration: a single brain was put in 1.5 mL conical tube containing a respiratory buffer. Brains were gently homogenized by 13 strokes with a conical plastic pestle, and the homogenates were immediately used for respiration measurements. Skinned muscle fibers were prepared by saponin permeabilization. Zebrafish were contaminated with food containing 13 μg of methylmercury (MeHg)/g, an environmentally relevant dose. In permeabilized muscle fibers, we observed a strong inhibition of both state 3 mitochondrial respiration and cytochrome c oxidase activity after 49 days of MeHg exposure. We measured a dramatic decrease in the rate of ATP release by skinned muscle fibers. Contrarily to muscles, brain mitochondrial respiration was not modified by MeHg exposure although brain accumulated twice as much MeHg than muscles. When zebrafish were exposed to 30 μg/L of waterborne U, the basal mitochondrial respiratory control ratio was decreased in muscles after 28 days of exposure. This was due to an increase of the inner mitochondrial membrane permeability. The impact of a daily ration of food containing gold nanoparticles of two sizes (12 and 50 nm) was investigated at a very low dose for 60 days (40 ng gold/fish/day). Mitochondrial dysfunctions appeared in brain and muscle for both tested sizes. In conclusion, at low environmental doses, dietary or waterborne heavy metals impinged on zebrafish tissue mitochondrial respiration. Due to its incredible simplicity avoiding tedious and time-consuming mitochondria isolation, our one-pot method allowing brain respiratory analysis should give colleagues the incentive to use zebrafish brain as a model in bioenergetics. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.

Mitochondrial membrane potential is a suitable candidate for assessing pollution toxicity in fish

Fish inhabiting polluted estuaries are highly exposed to severe stress characterized by an oxidant-antioxidant imbalance. The aim of the study was to explore the use of stress parameters such as adenosine triphosphate/adenosine diphosphate (ATP/ADP) ratio, mitochondrial membrane potential (∆ψm) and total protein expression patterns as biomarkers against oxidant exposures in hepatocytes of Mugil cephalus living in either a contaminated (Test; Ennore) or uncontaminated (Control; Kovalam) estuary. Earlier, the pollutant stress impact was determined through light and electron microscopy studies. The ATP/ADP ratio was measured using high performance liquid chromatography; ∆ψm by fluorescent probe 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethyl benzimidazolcarbocyanine iodide (JC-1) dye and total protein expression patterns by protein profiling. The preponderance of stress impact was confirmed through microscopy studies that featured cytological alterations, disturbances in the surface morphology and in the cell organelles at the ultrastructural levels. Hepatocytes of test fish demonstrated a decrease in ATP and an increase in ADP and thereby alteration in ATP/ADP ratio (p<0.05; 20.75%). A significant disturbance (p<0.05; 26.57%) in ∆ψm with a ratio of J-aggregates/JC-1 monomer of 1 was observed for test fish hepatocytes compared to control group with a J-aggregates/JC-1 monomer ratio of 1.5. Quantitative assessment of protein expression levels also revealed enhanced induction of both low and high molecular weight proteins in test fish hepatocytes. The findings highlight the use of these parameters as the highly sensitive biomarkers in response to contaminant exposure compared to the routinely used antioxidant and oxidant stress parameters in biomonitoring programs. Among the measured parameters, the determination of ∆ψm may be suggested as a novel candidate as a biomarker because of its greater specificity and rapid quantitative risk assessment of pollutant exposures.

Evaluation of oxidative stress biomarkers in Zosterisessor ophiocephalus from the Venice Lagoon, Italy

Several studies carried out in the last years have demonstrated the presence of a wide range of contaminants in some areas of the Venice Lagoon. Many of these contaminants are able to drive free radical reactions, which lead to oxidative stress and can potentially affect fish health. In the present study, oxidative stress biomarkers were examined in three different sites (Porto Marghera, Val di Brenta and Caroman) of the Venice Lagoon and their levels monitored in Zosterisessor ophiocephalus, one of the most common fish species present in the lagoon. Schmorl's staining revealed the presence of melanomacrophage centres in spleen and head kidney, and the highest number of melanomacrophage centres was observed in the animals sampled at the Porto Marghera (Porto Marghera vs Val di brenta and Caroman: p<0.01). The cellular localization of HNE and NT, investigated through an immunohistochemical approach, showed that immunopositivity was mainly localized in melanomacrophage centres of spleen and kidney. It is relevant that the animals of the detoxified control group did not exhibit any immunoreactivity. By Western blot, the antibodies against HNE and NT recognized in the liver polypeptides damaged by oxidative stress with molecular weights under 66kDa. Comparing the relative densities, animals from the Val di Brenta site exhibited the lowest levels of HNE adducts (p<0.05), whereas animals from the Porto Marghera site exhibited the highest levels of NT adducts (p<0.05). MDA levels, measured spectrophotometrically by TBARS assay did not exhibit any statistical difference among sites.

Stress response of heavy metal mixture present in wastewater and leachate on heat-shock protein 47-transfected cells

Heavy metals present in water environment and hazardous sites as single compounds or mixture may drastically affect human health. In the present work, we investigated the risk assessment of wastewater effluents and leachate with a focus on three heavy metals-nickel (Ni), cadmium (Cd), and lead (Pb)-and their combined effect on mammalian cells, using Chinese hamster ovary cells transfected with the heat-shock protein (HSP) 47 promoter. The heavy metal mixture model was designed based on the concentrations of metals in wastewater effluents and leachate sampled in Tunisia. Using a ternary diagram, we investigated the stress response of the interaction model. This research indicated that the single heavy metals induced the stress response on HSP(+) cells even at concentrations lower than the local and international guidelines. Differences in water quality likely influenced the metal responses such that the organic composition of the leachate increased the stress response induced by the heavy metals exclusively, whereas the effluents included organic compounds that were able to mask the heavy metal effect. The mixture characterization discovered the key role played by the high levels of Ni or combination of Cd and Pb to induce the highest stress response following 3-h incubation. Heat-shock protein 47 has proven its effectiveness for assessing the heavy metal mixture effect even at low concentrations. Furthermore, the combination of a bioassay system with a statistical model proved extremely useful for better understanding the major contributors to the stress response of the mixture.

Heat-shock protein (Hsp70) and cytochrome P-450 (CYP1A) in the white mullet Mugil curema (Pisces:Mugilidae) as biomarkers to assess environmental quality in coastal lagoons

Biomarkers have been useful tools to monitor some effects of pollution in coastal environments. Hepatic expression of heat-shock protein 70 (Hsp70) and cytochrome P450 1A (CYP1A) were analyzed in white mullet (Mugil curema) by RT-PCR from July, 2005 until July, 2006 in three coastal lagoons located in the southern Gulf of California, Mexico. These three coastal systems receive contaminants derived from local anthropogenic activities. Heat-shock proteins function to maintain protein integrity in the presence of stressors (such as heat or chemicals) and can be used as biomarkers of homeostatic alterations in polluted environments, whereas cytochrome P450 family members participate in steroid hormone synthesis and metabolism, and in xenobiotic transformation as a detoxification mechanism. The expression levels of both genes showed consistency in time and space, and presented a high overall correlation (r = 0.731, P < 0.001). Regardless of a high individual variability, both genes presented higher expression levels in the Urias Estuary (P < 0.001 and P < 0.05 for CYP1A and Hsp70, respectively), which was considered the most polluted among the three systems, especially during the rainy season (summer to fall). Gene expression levels were significantly associated with non-halogenated hydrocarbon concentrations in sediments during the sampling period (r = 0.686, P = 0.019 for CYP1A and r = 0.91, P < 0.001 for Hsp70), suggesting that both genes respond to chemicals in the environment. The results indicate that Mugil curema is a good candidate species to implement biomonitoring programs in tropical coastal environments.

Physiological adaptations of stressed fish to polluted environments: role of heat shock proteins

Fish are subjected to a wide variety of environmental stressors. Stressors affect fish at all life stages and the stress-specific responses that occur at the biochemical and physiological levels affect the overall health and longevity of such animals. In this review, the organ-specific alterations in fish that inhabit polluted environments are addressed in detail. Fish,like other vertebrates, have evolved strategies to counteract stress-mediated effects. Among the key strategies that fish have developed is the induction of HSPs. The primary functions of HSPs are to promote the proper folding or refolding of proteins, to prevent potentially damaging interactions with proteins, and aiding in the disassembly of formations of protein aggregates. Stress, a state of unbalanced tissue oxidation, causes a general disturbance in the cellular antioxidant and redox balance and evokes HSP70 overexpression. Distinct families of HSPs have diverse physiological functions, and their induction, which is regulated at the transcriptional level, is mediated by the activation of heat shock factors. Interestingly, HSPs also interact with a wide variety of signaling molecules that modulate stress-mediated apoptotic effects. Hence, HSP induction is of major importance for maintenance of cell homeostasis. HSP-mediated adaptation processes are regarded as a fundamental protective mechanism that decreases cellular sensitivity to damaging events. Thus, the adaptive expression of HSPs is a protective response that helps combat stress-induced conformational damage to proteins. Additional research is needed to gain further information on the functional significance and role of individual HSPs and to enhance the understanding of the molecular mechanisms by which they act. In addition, field studies are needed to allow comprehensive evaluation of the potential use of HSPs as biomarkers for environmental monitoring. Furthermore, the expression of HSPs in fish fluctuates in response to seasonal variation. Because HSPs serves as a tool for assessing the stressed state of individuals and/or populations, the impact of seasonal influences on constitutive and inducible factors of these proteins should also be elucidated. Such research will lead to a fundamental improvement in the understanding of the functional role of HSPs in response to natural environmental changes and may allow correlation of the action of HSPs at the molecular level with the whole organismal stress response, which, so far, remains unexplained.

Modulation of ASK1 expression during overexpression of Trx and HSP70 in stressed fish liver mitochondria

Mitochondrial heat shock protein 70 (mtHSP70) is found to play a primary role in cellular defense against physiological stress like exposure to environmental contaminants and helpful in the maintenance of cellular homeostasis by promoting the cell survival. In the present investigation, the environmental-stress-induced increase in mtHSP70 levels along with the quantification of apoptosis signal regulating kinase 1 (ASK1) and thioredoxin (Trx) were measured in the liver mitochondria of grey mullets (Mugil cephalus) collected from the polluted Ennore estuary and the unpolluted Kovalam estuary for a period of 2 years. The results showed elevated lipid peroxide (LPO) and decreased total antioxidant capacity along with the decrease in mitochondrial viability percentage. Mitochondrial HSP70, ASK1, and Trx levels were increased under this stress condition. A 42% increase in LPO levels and 18% decrease in mitochondrial survivality were observed in the polluted-site fish liver mitochondria when compared to the results of unpolluted estuary. We also report that, under observed oxidative stress condition in Ennore fish samples, the ASK1 levels are only moderately elevated (13% increase). This may be due to mitochondrial-HSP70-induced adaptive tolerance signaling for the activation of Trx (22% increase) which suppresses the ASK1 expression thereby promoting the cell survival that leads to the maintenance of the cellular homeostasis.