Effects of sub-lethal and chronic lead concentrations on blood and liver ALA-D activity and hematological parameters in Nile tilapia

Hematological Parameters of Gasoline Station Workers at Hosanna Town, Southwest Ethiopia: A Comparative Cross-Sectional Study

Background

Human exposure to benzene is associated with many adverse health effects. It is mainly related to impairment of the hematopoietic system and bone marrow suppression, causing abnormalities in hematological parameters. However, the reports obtained from different studies are contradictory, and there are little data regarding the hematological parameters of gas station workers in the study area. Therefore, this study aimed to evaluate the hematological parameters of gas station workers in Hosanna town, southwest Ethiopia, from May 01 to June 15, 2020.

Methods

A comparative cross-sectional study was conducted by involving 180 (60 gas-stations workers and 120 controls) participants. Socio-demographic and related data of the study participants were collected using a pre-tested structured questionnaire through face-to-face-interviews. All phases of quality assurance were maintained, and hematological parameters were determined using Uni-Cel DxH 800 automated hematological analyzer. Independent sample T-test, Mann-Whitney U-test, and one-way ANOVA were used for data analysis. Statistical significance was declared at P<0.05.

Results

Statistically significant difference was observed in hematological parameters of gasoline-workers and control groups. The mean of red blood cell count among gasoline-workers was significantly reduced as compared to control groups (p=0.007). In addition, the median of hemoglobin levels among gasoline-workers was significantly decreased as compared to the control groups (p=0.001). In contrast, a significant increase was observed in median of absolute eosinophil count among the gasoline-workers as compared to control groups (p=0.01). The mean of mean cell volume was significantly decreased with respect to the duration of work experience (p=0.04).

Conclusion

In this study, a statistically significant difference was observed in some hematological parameters of gas station workers compared to the control group. Therefore, medical observation and periodic medical check-ups of the hematological profile should be considered to prevent the development of medical complications.

Curcumin and cinnamon mitigates lead acetate-induced oxidative damage in the spleen of rats

Lead toxicity is a common occupational and environmental health hazard that exerts many toxic effects on animals and humans, including immunotoxicity. Curcumin (CUR) and cinnamon (CIN) are common medicinal herbs with immunostimulatory and antioxidant properties. Therefore, this study investigated the protective effect of curcumin and cinnamon against lead acetate (LA)-induced splenotoxicity in rats via hemato-biochemical, immunological, oxidative stress marker, CYP-2E1 expression, histological, and immunohistological evaluations. Four groups of seven rats each were used: the control group received corn oil as a vehicle; the lead acetate group received (100 mg/kg), the CUR + LA group received curcumin (400 mg/kg) plus lead acetate, and the CIN + LA group received cinnamon (200 mg/kg) plus lead acetate orally for 1 month. LA exposure induced macrocytic hypochromic anemia, leukocytosis, neutrophilia, monocytosis, and lymphopenia. Additionally, significant elevations in serum iron, ferritin levels, and transferrin saturation percentage with significant decline of total and unsaturated iron binding capacities (TIBC and UIBC), transferrin, and immunoglobulin G and M levels were recorded. In addition, lead acetate significantly upregulated splenic CYP-2E1 expression, that was evident by significant depletion of reduced glutathione (GSH) activity and elevation of malondihyde (MDA), nitric oxide (NO), and protein carbonyl (PC) concentrations in the spleen. Histologically, hyperplasia of lymphoid follicles, hemosiderin deposition, and disturbance of CD3 and CD68 immuno-expressions were evident in the spleen from the lead acetate group. However, curcumin and cinnamon administration restored the hemato-biochemical, immunological, and oxidative stress parameters as well as histological and immunohistological pictures toward normalcy. In conclusion, curcumin and cinnamon can partially ameliorate LA-induced oxidative damage in the spleen, possibly through their antioxidant, immunomodulatory, and gene-regulating activities.

Exposure to Lead Nitrate Alters Growth and Haematological Parameters of Milkfish (Chanos chanos)

To date, the effects of lead on the growth and haematological parameters of milkfish are still not well understood. For this reason the present study seeks to explain this conundrum. Sub-adult female milkfish were exposed to four concentrations of lead nitrate (0 mg/l, 42.64 mg/l, 63.97 mg/l and 85.29 mg/l) for 40 days. Results revealed that exposure to lead nitrate caused significant changes in growth and haematological parameters of milkfish. Weight gain, length gain, specific growth rate, feed efficiency, and feed conversion ratio of milkfish declined significantly at the highest concentration treatment. Moreover, lead nitrate exposure significantly decreased the value of red blood cells, hemoglobin, hematocrit, and mean corpuscular hemoglobin concentration, along with a marked increase in mean corpuscular volume and mean corpuscular hemoglobin. Several erythrocyte malformations to cells including swelling, deformation, doubling, binucleus, laceration of the membrane, hemolyzation and vacuolation were all observed.

Tissue-specific genotoxicity and antioxidant imbalance of titanium dioxide nanoparticles (NPTiO2) and inorganic lead (PbII) in a neotropical fish species

The aquatic environment is the major recipient of wastes containing nanoparticles and other contaminants. Titanium dioxide nanoparticles (NPTiO₂) are one of the most produced and used nanoparticle worldwide. This study investigated the toxicity of NPTiO₂, as well as the toxicity interaction between NPTiO₂ and lead (Pb), in response to genetic and biochemical biomarkers using freshwater fish Rhamdia quelen, as an animal model. The results showed genotoxicity in blood and kidney tissues. No effect of NPTiO₂ alone or in co-exposure with Pb on liver genotoxicity were observed. Alterations in the antioxidant hepatic enzymes activities, as well as alterations in glutathione levels indicated that NPTiO₂ alone or in co-exposure with Pb can cause antioxidant imbalance. The lipid peroxidation was also raised after exposure to NPTiO₂. In general, the results of this study indicated that both NPTiO₂ alone and their co-exposure with Pb are capable of producing significant toxic effects in short-term exposure.

Antioxidative properties of Ocimum gratissimum alters Lead acetate induced oxidative damage in lymphoid tissues and hematological parameters of adult Wistar rats

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Chronic lead toxicity was induced in male rats by oral administration of lead acetate.

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Effect of Ocimum gratissimum in lead acetate toxicity on spleen, thymus, and blood.

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Oral lead acetate administration led to oxidative damage in spleen, thymus and blood.

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Ocimum gratissimum extract reversed oxidative stress and enhanced antioxidant enzymes.

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Ocimum gratissimum averts lead acetate-induced toxicity in the blood, thymus and spleen.

Lead exposure is a well-known environmental hazard. Its accumulation in humans may pose a danger to health. The present study investigated the beneficial effect of Ocimum gratissimum extract (OG) in reducing lead acetate (LA) induced oxidative damage in the spleen, thymus, and hematological indices. We employed an in vivo model of LA induced Wistar rats and administered 125 mg/kg/bw and 250 mg/kg/bw of OG extracts respectively. Our control groups were divided into 2; the first group received normal saline, feed, and water while the second group was administered OG extracts only. We assessed the levels of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) in the thymus and spleen and estimated percentages of blood cells. Our results showed that LA induces oxidative damage by significantly elevating MDA and diminishing GSH levels, SOD, and CAT activities. LA administration led to a significant decline in blood parameters. However, co-administration with OG compensated oxidative stress by significantly reducing MDA, increasing GSH, SOD, and CAT. Oral administration of OG to rats attenuated anemia, thrombocytopenia, leucocytosis, eosinophilia, monocytosis, and neutropenia induced by LA. The present study indicates that LA induced Spleen, thymus, and blood toxicity, which was reversed by oral OG administration.

Exposure to Pb-halide perovskite nanoparticles can deliver bioavailable Pb but does not alter endogenous gut microbiota in zebrafish

Lead-halide perovskite nanoparticles (NPs) are a new technology, and investigation of toxicity is of considerable importance due to the potential lead (Pb) release into the environment. The aim of the study was to investigate aqueous and dietary toxicity of Pb-halide perovskite NP and Pb in zebrafish Danio rerio. Perovskite NP toxicity was evaluated in zebrafish by mortality, gene expression, histopathology, and phylogenetic analysis of gut microbiota. Zebrafish larvae were exposed to five Pb-halide perovskite NPs in parallel with Pb(NO₃)₂ exposures, and zebrafish adults were exposed to the three perovskite NPs that caused the strongest effect and Pb(NO₃)₂. No median lethal concentration (LC₅₀) was observed for zebrafish larvae exposed to up to 200 mg/L of perovskite NPs for 96 h. Mortality, metallothionein 2 (mt2) and δ-aminolevulinic acid dehydratase (ala-d) gene expression (24-h exposure) in zebrafish larvae after aqueous perovskite NPs exposures did not differ from total Pb concentration - response curves. The lack of differences in mortality and gene expression between perovskite NPs and soluble Pb after aqueous exposure suggest that toxicity from perovskite NPs can be attributed to bioavailable Pb rather than nano-specific effects. Induction of mt2 and reduction of ala-d expression levels in liver tissues showed Pb bioavailability after 2-d and 4-d dietary exposure to perovskite-spiked feeds. Changes in gut microbiota of adult zebrafish were detected after 14-d exposure to Pb-spiked food, but no changes were detected from perovskite-NP spiked food. The phylogenetic analysis identified different microbiome profiles of Pb-fed fish compared to perovskite-fed fish suggesting a different mechanism of toxicity. Exposure to Pb-halide perovskite NPs led to absorption of Pb likely from release of Pb ions rather than absorption of NPs. Pb-halide perovskite NPs can release bioavailable Pb and this needs to be considered during the development of this technology.

Principles of problem-based learning for training and professional practice in ecotoxicology

Problem-based learning (PBL) is a protagonist of constructivism widely used successfully in higher education. PBL is a learner-centered instructional and curricular approach that can use real problems for the development of the teaching and learning process. On the other hand, the complexity of knowledge of Ecotoxicology, as well as the importance of this field for Environmental Health and society demand reflections and proposals for the training of professionals who work in this field. Therefore, in accordance with the principles of PBL, this strategy can effectively contribute to the training and professional practice of ecotoxicologists. We report herein the importance of the principles of PBL for the training of ecotoxicologists, including the discussion of a case study using fish biomarkers for the development of this teaching strategy. Teaching ecotoxicology through PBL principles allowed students to develop several advantages for Ecotoxicology training through the discussion of an authentic, real life problem that engaged them in its discussion, functioning as a stimulus for learning. The students were able to develop laboratory skills, group work competences, understand basic concepts and fundamentals of Ecotoxicology and become empowered regarding skills and competences for future practice.

Heavy metals in farmed and wild milkfish (Chanos chanos) and wild mullet (Mugil cephalus) along the coasts of Tanzania and associated health risk for humans and fish

In 2016, farmed milkfish (Chanos chanos) from Tanzania mainland (Mtwara), and Zanzibar islands (Pemba and Unguja) and wild milkfish and mullet (Mugil cephalus) from the Indian Ocean were collected for analyses of heavy metals (Pb, Cd, Hg, As, Al, Fe, Zn, Cu, Ni, Co and Cr) in muscles and livers. High concentrations of Pb were detected in muscles and livers from wild and farmed milkfish and wild mullet from all sites. The highest concentration of Pb was detected in wild milkfish liver from Mtwara (47.4 mg/kg ww). The Pb concentrations in fish muscle exceeded maximum levels (ML) set by FAO/WHO (0.3 mg/kg ww) in 100% of the analysed fish. Concentrations of Pb were higher in wild fish than in farmed fish. Cd concentrations were generally low. The comparison of the Hg concentration with EQS_Biota indicated that Hg might pose potential health risk to 22% of the analysed fish. Median concentrations of Fe in livers from farmed milkfish from Jozani and Shakani, Zanzibar, were 40-80 times higher than the other sites. Assessment of human health risk and exposure to heavy metals indicated no potential risk from consuming the fish from the present study locations. However, the Pb concentrations exceeding ML in the fish suggests that Pb may affect the health of fish. Future investigations should include regular monitoring of heavy metals in farmed and wild fish in Tanzania for further development of sustainable aquaculture and the welfare of the wild fish stock in the coastal waters.

Toxicological responses on cytochrome P450 and metabolic transferases in liver of goldfish (Carassius auratus) exposed to lead and paraquat

As the producer of reactive oxygen species (ROS), both lead (Pb) and paraquat (PQ) can generate serious oxidative stress in target organs which result in irreversible toxic effects on organisms. They can disturb the normal catalytic activities of many enzymes by means of different toxicity mechanism. The changed responses of enzymes are frequently used as the biomarkers for indicating the relationship between toxicological effects and exposure levels. In this work, goldfish was exposed to a series of test groups containing lead and paraquat in the range of 0.05-10mg/L, respectively. Four hepatic enzyme activities, including 7-ethoxyresorufinO-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin-O-debenzyloxylase (BFCOD), glutathione S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were determined after 1, 7, 14, 28 days exposure. The results showed that the activities of EROD and BFCOD in fish were significantly inhibited in response to paraquat at all exposure levels during the whole experiment. Similarly, the inhibitory effects of lead exposure on BFCOD activity were found in our study, while different responses of lead on EROD were observed. There were no significant differences on EROD activity under lower concentrations of lead (less than 0.1mg/L) before 14 days until an obvious increase was occurred for the 0.5mg/L lead treatment group at day 14. Furthermore, lead showed stronger inhibition on GST activity than paraquat when the concentrations of the two toxicants were more than 0.5mg/L. However, the similar dose and time-dependent manners of UGT activity were found under lead and paraquat exposure. Our results indicated that higher exposure levels and longer accumulations caused inhibitory effects on the four enzymes regardless of lead or paraquat stress. In addition, the responses of phase I enzymes were more sensitive than that of phase II enzymes and they may be served as the acceptable biomarkers for evaluating the toxicity effects of both lead and paraquat.

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.

Evaluation of a Brain Acetylcholinesterase Extraction Method and Kinetic Constants after Methyl-Paraoxon Inhibition in Three Brazilian Fish Species

Acetylcholinesterase (AChE) is an important enzyme in the control of the neuronal action potential and sensitive to organophosphate inhibition. Brain fish AChE is less sensitive to organophosphate inhibition than AChE from terrestrial animals, although this sensitivity is variable among species and has not yet been fully evaluated in fish species. In this setting, inhibition kinetic constants for progressive irreversible inhibition of brain acetylcholinesterase due to methyl-paraoxon exposure were determined in three fish species (Mugil liza, Genidens genidens and Lagocephalus laevigatus) and hen (Gallus domesticus). Enzyme extraction using a detergent was shown to be adequate, and samples presented activity inhibition in high substrate concentrations and suppression of inhibition by methyl-paraoxon in the presence of the substrate, similar to kinetic patterns from purified enzyme preparations. Catfish (G. genidens) AChE presented the highest sensitivity among the evaluated fish species (IC50 = 1031.20 nM ± 63.17) in comparison to M. liza and L. laevigatus (IC50: 2878.83 ± 421.94 and 2842.5 ± 144.63 nM respectively). The lower dissociation constant (K_d = 20.3 ± 2.95 μM) of catfish AChE showed greater enzyme affinity for methyl-paraoxon, explaining this species higher sensitivity to organophosphates. Hen AChE presented higher k_i (900.57 ± 65.3 mM^-1min^-1) and, consequently, greater sensitivity to methyl-paraoxon, explained by a lower K_d (0.6 ± 0.13 μM). Furthermore, hen AChE did not differentiate between the propionylthiocholine and acetylthiocholine substrates, indicating easier access of methyl-paraoxon to the hen enzyme activity site. The results obtained herein indicate a suitable extraction of AChE and, despite different inhibition kinetic constants, demonstrate that fish AChE is less sensitive to methyl-paraoxon, probably due to reduced access to the catalytic center which provides greater enzyme substrate selectivity.