Hematological changes and cytogenotoxicity in the tilapia Oreochromis niloticus caused by sub-chronic exposures to mercury and selenium

Partial immune responses in Sichuan bream (Sinibrama taeniatus) after starvation

Background

Food deprivation is a severe stress across multiple fields and it might be a challenge to immune system.

Methods

In the present study, adult male Sinibrama taeniatus were deprived of feed for 7 to 28 days. We explored the effects of starvation on immunity in S. taeniatus through hematological analysis, antioxidant capacity analysis, detection of the content or activity of immune factors in plasma, and transcriptomic analysis.

Results

The results indicated that biometric indexes significantly decreased in the fish after starvation, the proportion of thrombocyte, neutrophil and monocyte increased and, conversely, the proportion of lymphocyte decreased. The antioxidant indexes (SOD and CAT) and innate immune parameters (LZM, C3) were upregulated in fish suffering from a short period of starvation, while adaptive immune parameter (IgM) conversely declined. The transcriptome analysis revealed the changes of various metabolic regulatory pathways involved in fatty acids and amino acids, as well as the immune responses and antioxidant capacity.

Conclusions

Taken together, this research in the present study suggested an induced innate immunity while a partly suppressed adaptive immunity under a short period starvation.

Mercury chloride toxicity in juveniles Prochilodus argenteus a species from southeastern Brazil

The aim of this study was to determine the 96-h LC₅₀ (lethal concentration for 50% of the test population in 96 h of observation) of mercury chloride (HgCl₂) and evaluated its absorption in the gills, liver, and muscle of juvenile "curimatã-pacu," Prochilodus argenteus. The fish were exposed for 4 days to different concentrations of HgCl₂: 0.000, 0.0375, 00.075, 0.150, 0.225, 0.300, and 0.400 mg L^-1 to get the 96-h LC₅₀, and the concentration of Hg in the tissues. The fish were exposed to different levels of HgCl2 (0.000, 0.0375, 00.075, 0.150, 0.225, and 0.300 mg L^-1), for 4 and 7 days, when different tissues (gills, liver, and muscle) were sampled. The mercury concentration values obtained were compared between tissues, days, and concentration of mercury in the water. The 96-h LC₅₀ for P. argenteus was 0.339 mg L^-1 of HgCl₂, within the range found for other neotropical and tropical species, showing a medium sensitivity. The concentration of Hg in the tissues increased from the muscle to the gills and liver, and according to the increasing concentration of HgCl₂ in the water. The fish liver is the most suitable tissue for environmental monitoring and for the evaluation of the consumed fished. Despite being the tissue that least accumulated mercury, the muscle must be evaluated because it is the part consumed by the population.

Thermal stress accelerates mercury chloride toxicity in Oreochromis niloticus via up-regulation of mercury bioaccumulation and HSP70 mRNA expression

Mercury (Hg) is an environmental pollutant that threatens aquatic life. Many environmental factors, including water temperature, are reported to influence the toxicity of dissolved chemicals in the aquatic ecosystem. Therefore, we investigated the impact of thermal stress on Hg-induced subchronic toxicity in Nile tilapia (Oreochromis niloticus). Fish were randomly allocated into five groups. Group I served as the control and kept at 25 °C. Groups II, III, IV, and V were reared at 25, 28, 31, and 34 °C, respectively, and co-exposed to HgCl₂ (1/10 LC₅₀) for 42 days. Blood and tissue samples were collected after 21 and 42 days. All HgCl₂-exposed groups exhibited significant elevations in serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, and creatinine, along with decreases in the serum total protein and albumin. In addition, marked reductions in antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSPx), were observed. Remarkable increases in Hg tissue concentrations were detected along with increases in heat shock protein (HSP) 70 mRNA expression. Interestingly, the patterns data that were recorded were more coincident with the water temperature than the period of exposure. In conclusion, water temperature and exposure period are two crucial factors modulating HgCl₂-induced toxicity and bioaccumulation in Nile tilapia. Our findings provide new insights concerning the impact of thermal stress as an environmental factor on Hg toxicity and bioaccumulation in Nile tilapia and, in turn, on fish and fish consumer health.

Multidisciplinary haematology as prognostic device in environmental and xenobiotic stress-induced response in fish

The variations of haematological parameters hematocrit, hemoglobin concentration, leukocyte and erythrocyte count have been used as pollution and physiological indicators of organic dysfunction in both environmental and aquaculture studies. These parameters are commonly applied as prognostic and diagnostic tools in fish health status. However, there are both extrinsic and intrinsic factors to consider when performing a blood test, because a major limitation for field researchers is that the "rules" for animal or human haematology do not always apply to wildlife. The main objective of this review is to show how some environmental and xenobiotic factors are capable to modulating the haematic cells. Visualizing the strengths and limitations of a haematological analysis in the health assessment of wild and culture fish. Finally, we point out the importance of the use of mitochondrial activities as part of haematological evaluations associated to environment or aquaculture stress.

Human exposure to mercury and its hematological effects: a systematic review

Mercury is a metal found in the environment from natural and anthropogenic sources. It is highly toxic to ecosystems and living beings. Most human exposures come from ingestion of contaminated seafood, outgassing from dental amalgam or occupational exposure (e.g. gold mining), among other cases. Large populations are exposed to mercury, making it a very important issue from the public health perspective. Adverse health effects are commonly seen in the nervous system, but every organ is a potential target, such as the bone marrow. The main goal of this study was to assess the available evidence on human exposure to mercury and its hematological effects. A search strategy was constructed, including key terms (MeSH, text word and equivalents) for querying 2 repositories of master dissertation and PhD thesis (Fiocruz/ARCA and University of São Paulo) and 4 different electronic databases: BVS/LILACS, MEDLINE/PubMed, Scopus and TOXLINE/NIH, for articles published from 1950 to February 2018. There was no language restriction and a tool (EPHPP) was used to assess the quality of included studies. According to pre-established criteria, 80 studies were retrieved, all of them observational (48 case reports, 24 cross-sectional, 6 case series and 2 cohorts), comprising 9,284 people. Despite the fact that most exposed ones (6,012) had normal blood cell count and mercury hematological effects did not seem very usual (1,914 cases: 14 severe and 29 deaths), three studies reported association (β) for anemia, lymphopenia, neutrophilia and basophilia. We concluded that the gathered information pointed to mercury hematotoxic effects, some of them may be serious and even fatal.

Charting a path towards non-destructive biomarkers in threatened wildlife: A systematic quantitative literature review

Threatened species are susceptible to irreversible population decline caused by adverse sub-lethal effects of chemical contaminant exposure. It is therefore vital to develop the necessary tools to predict and detect these effects as early as possible. Biomarkers of contaminant exposure and effect are widely applied to this end, and a significant amount of research has focused on development and validation of sensitive and diagnostic biomarkers. However, progress in the use biomarkers that can be measured using non-destructive techniques has been relatively slow and there are still many difficulties to overcome in the development of sound methods. This paper systematically quantifies and reviews studies that have aimed to develop or validate non-destructive biomarkers in wildlife, and provides an analysis of the successes of these methods based on the invasiveness of the methods, the potential for universal application, cost, and the potential for new biomarker discovery. These data are then used to infer what methods and approaches appear the most effective for successful development of non-destructive biomarkers of contaminant exposure in wildlife. This review highlights that research on non-destructive biomarkers in wildlife is severely lacking, and suggests further exploration of in vitro methods in future studies.

Addressing the impact of mercury estuarine contamination in the European eel (Anguilla anguilla L., 1758) - An early diagnosis in glass eel stage based on erythrocytic nuclear morphology

The decline of the European eel (Anguilla anguilla L., 1758) population throughout Europe has been partially attributed to pollution. As glass eel estuarine migration may represent a considerable threat, the impact of mercury (Hg) contamination at this stage was evaluated through an in situ experiment (7days). Total Hg (tHg) bioaccumulation was evaluated concomitantly with erythrocytic nuclear morphology alterations: erythrocytic nuclear abnormalities assay (ENA), frequency of immature erythrocytes (IE) and the erythrocytic maturity index (EMI). The ENA results suggested a genotoxic pressure at the most contaminated sites, in line with the tHg increase. The EMI data, together with IE frequency, showed that fish exposed to high levels of Hg exhibited alterations of haematological dynamics, translated into an erythropoiesis increment. Despite the presence of these compensatory mechanisms, the present findings suggest a harmful impact of Hg on genome integrity at this early development stage, potentially affecting eels' condition and ultimately the population sustainability.

Hair Mercury Level is Associated with Anemia and Micronutrient Status in Children Living Near Artisanal and Small-Scale Gold Mining in the Peruvian Amazon

Anemia has been widely studied in global health contexts because of severe nutritional deficiency, and more recently, inflammatory status, but chemical exposures are rarely considered. Until recently, "anemia" was used synonymously with "iron deficiency anemia (IDA)" in global health settings. However, only 50% of anemia cases worldwide are IDA. Environmental toxicology studies of anemia risk have generally focused on populations in developed countries, albeit with high exposure to environmental toxicants, such as lead or cadmium. In the developing world, toxicant exposures commonly coexist with other risk factors for anemia. In particular, artisanal and small-scale gold mining (ASGM) communities are at risk for dietary methylmercury exposure through contaminated fish consumption, and for anemia due to food insecurity and infectious and chronic diseases. Here, we report analysis of total hair mercury content, hemoglobin, and serum micronutrient levels in children < 12 years of age (N = 83) near ASGM in the Peruvian Amazon. Forty-nine percent (N = 29/59) of those aged < 5 years were anemic (< 11 g/dL) and 52% (N = 12/23) of those aged 5-11 years (< 11.5 g/dL). Few children were stunted, wasted, or micronutrient deficient. Median total hair mercury was 1.18 μg/g (range: 0.06-9.70 μg/g). We found an inverse association between total mercury and hemoglobin (β = -0.12 g/dL, P = 0.06) that persisted (β = -0.14 g/dL, P = 0.04) after adjusting for age, sex, anthropometrics, and vitamin B₁₂ in multivariate regression. This study provides preliminary evidence that methylmercury exposure is associated with anemia, which is especially relevant to children living near ASGM.

Sublethal effects of pulp and paper mill effluent on two commonly cultured carps: a SEM- and EDS-based hematological biomarker analysis

Blood being a vehicle for the transport of industrial pollutants in living system, fish hematology is considered as potent biomarker. In the present study, we investigated respective sublethal effects of pulp and paper mill effluents on hematology of two commonly cultured carps, Cyprinus carpio and Ctenopharyngodon idella, using optical, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Irrespective of species, results showed significant decrease in erythrocyte, hematocrit and hemoglobin contents while an increase in white blood cell counts (P < 0.05). We observed an increasing trend of MCV (170.0 ± 3.07 to 193.16 ± 2.5) and MCH (34.31 ± 1.89 to 38.71 ± 3.61) up to 28th day in C. carpio (P < 0.05), while, in C. idella, the highest percent increase in MCV (180.8 ± 2.19) and MCH (32.9 ± 0.62) was observed on seventh exposure day, which subsequently declined, respectively, to 173.1 ± 17.1 and 27.9 ± 2.45 on 28th day. Unlike C. carpio, significant and progressive MCHC declining trend (18.23 ± 0.28 to 16.13 ± 0.31) was observed in C. idella. The most commonly observed abnormalities under SEM include echinocytes, cytoplasmic blebbing, cytoplasmic ring, spherocytes, lobopodial projections and acanthocytes in red blood cells of exposed fishes. EDS further revealed the presence of aluminum, antimony, arsenic, cadmium, mercury, tungsten, zinc and titanium; some of these metals were not even detected in the effluent samples, suggesting the probable metal bio-concentration in fish tissue, and subsequent jeopardization is a major concern particularly in the industrial area. Our study further suggested the use of sensitive and specific techniques like SEM and EDS in fish hematological biomarker analysis along with the conventional approach.