Luteolin alleviates inorganic mercury-induced liver injury in quails by resisting oxidative stress and promoting mercury ion excretion

BackgroundInorganic mercury is a well-known toxic substance that can cause oxidative stress and liver damage. Luteolin (Lut) is a kind of natural antioxidant, which is widely found in plants. Therefore, we focused on exploring the alleviative effect of Lut on liver injury induced by mercuric chloride (HgCl₂), and the potential molecular mechanism of eliminating mercury ions in quails.Methods and resultsTwenty-one-day-old male quails were randomly split into four groups: control group, Lut group, HgCl₂ group, and HgCl₂ + Lut group. The test period was 12 weeks. The results showed that Lut could significantly ameliorate oxidative stress, the release of inflammatory factors, and liver damage caused by HgCl_2, and reduce the accumulation of Hg²⁺ in quail liver. Furthermore, Lut evidently increased the levels of protein kinase C α (PKCα), nuclear factor-erythroid-2-related factor 2 (Nrf2), and its downstream proteins, and inhibited nuclear factor-kappaB (NF-κB) production in the liver of quails treated by HgCl₂.ConclusionsTo sum up, our results suggest that Lut not only reduces the levels of oxidative stress and inflammation, but also promotes the excretion of Hg²⁺ by promoting the PKCα/Nrf2 signaling pathway to alleviate HgCl₂-induced liver injury in quails.

Mitigative effect of green tea extract against mercury(II) chloride toxicity in Allium cepa L. model

Mercury (Hg) is a highly toxic heavy metal for all organisms. In the present study, the mitigative role of 190 mg/L and 380 mg/L doses of green tea extract (GTex) against mercury(II) chloride (HgCI₂)-induced toxicity was evaluated in Allium cepa L. For this aim, selected physiological, genotoxicity, and biochemical parameters as well as meristematic cell injuries in the roots were investigated. Ratios of catechin and caffeine in GTex were determined by HPLC analysis. Also, free radical scavenging activity of GTex was tested against superoxide and hydrogen peroxide radicals. As a result of HgCI₂ application, germination percentage, root elongation, weight gain, and mitotic index (MI) declined, while the frequency of micronucleus (MN), chromosomal abnormalities (CAs), and meristematic cell damages increased. HgCI₂ administration also led to a significant increase in malondialdehyde content, superoxide dismutase, and catalase activities which are signs of oxidative stress. On contrary, applications of GTex together with HgCI₂ reduced HgCI₂-induced adverse effects in all parameters in a dose-dependent manner. Antioxidant components in GTex were listed as caffeine, epigallocatechin gallate, epigallocatechin, epicatechin gallate, and catechin according to their abundance. GTex exhibited a strong scavenging ability in the presence of superoxide and hydrogen peroxide radicals. The present study revealed the strong protective capacity of GTex against HgCI₂-induced toxicity in A. cepa owing to its high antioxidant content with a multifaceted perspective. With this study, a reliable starting point was established for future studies investigating the more common and diverse use of GTex against toxic substances.

Harmful Effects of Inorganic Mercury Exposure on Kidney Cells: Mitochondrial Dynamics Disorder and Excessive Oxidative Stress

Mercury is widely used in industry and has caused global environmental pollution. Inorganic mercury accumulates in the body causes damage to many organs, and the kidney is the most susceptible to the toxic effects of mercury. However, the underlying specific molecular mechanism of renal injury induced by inorganic mercury remains unclear at the cellular level. Therefore, in order to understand its molecular mechanism, we used in vitro method. We established experimental models by treating human embryonic kidney epithelial cell line (HEK-293 T) cells with HgCl₂ (0, 1.25, 5, and 20 µmol/L). We found that HgCl₂ can lead to a decrease in cell viability and oxidative stress of HEK-293 T, which may be mediated by upregulation mitochondrial fission. In addition, HgCl₂ exposure resulted in the mitochondrial disorder of HEK-293 T cells, which was mediated by downregulating the expression of silent information regulator two ortholog 1 (Sirt1)/peroxisome proliferator-activated receptor coactivator-1α (PGC-1α) signaling pathway. In summary, our results suggest that HgCl₂ induces HEK-293 T cell toxicity through promoting Sirt1/PGC-1α axis-mediated mitochondrial dynamics disorder and oxidative stress. Sirt1/PGC-1α may be an appealing pharmaceutical target curing HgCl₂-induced kidney injury.

Effect of inorganic mercury exposure on reproductive system of male mice: Immunosuppression and fibrosis in testis

Mercury as a toxic heavy metal will accumulate in the body and induce various diseases through the food chain. However, it is unknown that the detailed mechanism of reproductive disorder induced by inorganic mercury in male mice to date. This study investigated the toxicological effect of mercuric chloride (HgCl₂ ) exposure on reproductive system in male mice. Male Kunming mice received normal saline daily or HgCl₂ (3 mg/kg bodyweight) by intraperitoneal injection for a week. The reproductive function was evaluated, and the HgCl₂ exposure induced the decline of sperm quality, pregnancy rate, mean litter size, and survival rate. Notably, we firstly found the HgCl₂ -induced immunosuppression and fibrosis in mice testis according to the results of RNA sequencing. Collectively, these findings demonstrate that HgCl₂ exposure disrupts the reproductive system and induces testicular immunosuppression and fibrosis via inhibition of the CD74 signaling pathway in male mice.

Multi-protective role of Echinacea purpurea L. water extract in Allium cepa L. against mercury(II) chloride

Mercury (Hg) is a persistent and dangerous heavy metal with genotoxic properties. Echinacea purpurea L. is a well-known therapeutic plant with anti-inflammatory, antioxidant, and anti-tumor properties. In this study, multi-protective role of Echinacea purpurea L. extract against toxicity caused by mercury(II) chloride (HgCI2) on Allium cepa L. investigated in a multifaceted way. As a consequence of 100 mgL-1 HgCI2 administration, root elongation, weight increase, germination rate, and mitotic index were reduced, whereas micronucleus frequency, chromosomal abnormalities frequency, meristematic cell injuries severity, malondialdehyde level, catalase, and superoxide dismutase activity were increased. On the other hand, co-administration of increasing doses of E. purpurea extract (265 mgL-1 and 530 mgL-1) and HgCI2 gradually alleviated all observed toxic effects of HgCI2. Protective role of E. purpurea extract against HgCI2-toxicity on A. cepa were clearly demonstrated in this study. The results of this study will lead to future researches investigating use of E. purpurea extract against genotoxic contaminants.

Neurotoxicity of β-HgS differs from environmental mercury pollutants (MeHgCl and HgCl2) in Neuro-2a cell

β-HgS, differing from environmental mercury pollutants (MeHgCl and HgCl₂) in chemical form, is used as traditional medicine in Asian countries for thousands of years. In this study, Neuro-2a cells were exposed to β-HgS, MeHgCl and HgCl₂ (5 µM) for 6-24 h. The cell viability of β-HgS was higher than MeHgCl with 25.9% and 72.4% in 12 h and 24 h respectively. As the incubation time increased, MeHgCl had obvious damage to cell morphology, decreased the ratio of Bcl-2 and Bak and increased the expressions of TNF-α, IL-6 and IL-1β significantly. Furthermore, the expressions of IL-1β and IL-6 in HgCl₂ group were increased significantly in 6 h and 24 h. The apoptotic rates in MeHgCl and HgCl₂ group were respectively higher than β-HgS with 32.2% and 7.30% in 24 h. Our findings indicate that β-HgS is much less neurotoxicity than MeHgCl and HgCl₂ in Neuro-2a cells.

New Insights into Alterations in PL Proteins Affecting Their Binding to DNA after Exposure of Mytilus galloprovincialis to Mercury-A Possible Risk to Sperm Chromatin Structure?

Mercury (Hg) is a highly toxic and widespread pollutant. We previously reported that the exposure of Mytilus galloprovincialis for 24 h to doses of HgCl2 similar to those found in seawater (range 1-100 pM) produced alterations in the properties of protamine-like (PL) proteins that rendered them unable to bind and protect DNA from oxidative damage. In the present work, to deepen our studies, we analyzed PL proteins by turbidimetry and fluorescence spectroscopy and performed salt-induced release analyses of these proteins from sperm nuclei after the exposure of mussels to HgCl2 at the same doses. Turbidity assays indicated that mercury, at these doses, induced PL protein aggregates, whereas fluorescence spectroscopy measurements showed mercury-induced conformational changes. Indeed, the mobility of the PLII band changed in sodium dodecyl sulphate-polyacrylamide gel electrophoresis, particularly after exposure to 10-pM HgCl2, confirming the mercury-induced structural rearrangement. Finally, exposure to HgCl2 at all doses produced alterations in PL-DNA binding, detectable by DNA absorption spectra after the PL protein addition and by a decreased release of PLII and PLIII from the sperm nuclei. In conclusion, in this paper, we reported Hg-induced PL protein alterations that could adversely affect mussel reproductive activity, providing an insight into the molecular mechanism of Hg-related infertility.

Zuotai (β-HgS)-containing 70 Wei Zhen-Zhu-Wan differs from mercury chloride and methylmercury on hepatic cytochrome P450 in mice

Background: Zuotai (mainly β-HgS)-containing 70 Wei-Zhen-Zhu-Wan (70W, Rannasangpei) is a famous Tibetan medicine for treating cardiovascular and gastrointestinal diseases.  We have shown that 70W protected against CCl 4 hepatotoxicity.  CCl 4 is metabolized via cytochrome P450 (CYP) to produce reactive metabolites. Whether 70W has any effect on CYPs is unknown and such effects should be compared with mercury compounds for safety evaluation.   Methods: Mice were given clinical doses of 70W (0.15-1.5 g/kg, po), Zuotai (30 mg/kg, po), and compared to HgCl 2 (33.6 mg/kg, po) and MeHg (3.1 mg/kg, po) for seven days. Liver RNA and protein were isolated for qPCR and Western-blot analysis. Results: 70W and Zuotai had no effects on hepatic mRNA expression of Cyp1a2, Cyp2b10, Cyp3a11, Cyp4a10 and Cyp7a1, and corresponding nuclear receptors [aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptor-α (PPARα); farnesoid X receptor (FXR)]. In comparison, HgCl 2 and MeHg increased mRNA expression of Cyp1a2, Cyp2b10, Cyp4a10 and Cyp7a1 except for Cyp3a11, and corresponding nuclear receptors except for PXR. Western-blot confirmed mRNA results, showing increases in CYP1A2, CYP2B1, CYP2E1, CYP4A and CYP7A1 by HgCl 2 and MeHg only, and all treatments had no effects on CYP3A. Conclusions: Zuotai and Zuotai-containing 70W at clinical doses had minimal influence on hepatic CYPs and corresponding nuclear receptors, while HgCl 2 and MeHg produced significant effects.  Thus, the use of total Hg content to evaluate the safety of HgS-containing 70W is inappropriate.

Zuotai (β-HgS)-containing 70 Wei Zhen-Zhu-Wan differs from mercury chloride and methylmercury on hepatic cytochrome P450 in mice

Background: Zuotai (mainly β-HgS)-containing 70 Wei-Zhen-Zhu-Wan (70W, Rannasangpei) is a famous Tibetan medicine for treating cardiovascular and gastrointestinal diseases.  We have shown that 70W protected against CCl 4 hepatotoxicity.  CCl 4 is metabolized via cytochrome P450 (CYP) to produce reactive metabolites. Whether 70W has any effect on CYPs is unknown and such effects should be compared with mercury compounds for safety evaluation.   Methods: Mice were given clinical doses of 70W (0.15-1.5 g/kg, po), Zuotai (30 mg/kg, po), and compared to HgCl 2 (33.6 mg/kg, po) and MeHg (3.1 mg/kg, po) for seven days. Liver RNA and protein were isolated for qPCR and Western-blot analysis. Results: 70W and Zuotai had no effects on hepatic mRNA expression of Cyp1a2, Cyp2b10, Cyp3a11, Cyp4a10 and Cyp7a1, and corresponding nuclear receptors [aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptor-α (PPARα); farnesoid X receptor (FXR)]. In comparison, HgCl 2 and MeHg increased mRNA expression of Cyp1a2, Cyp2b10, Cyp4a10 and Cyp7a1 except for Cyp3a11, and corresponding nuclear receptors except for PXR. Western-blot confirmed mRNA results, showing increases in CYP1A2, CYP2B1, CYP2E1, CYP4A and CYP7A1 by HgCl 2 and MeHg only, and all treatments had no effects on CYP3A. Conclusions: Zuotai and Zuotai-containing 70W at clinical doses had minimal influence on hepatic CYPs and corresponding nuclear receptors, while HgCl 2 and MeHg produced significant effects.  Thus, the use of total Hg content to evaluate the safety of HgS-containing 70W is inappropriate.

Mercury Chloride but Not Lead Acetate Causes Apoptotic Cell Death in Human Lung Fibroblast MRC5 Cells via Regulation of Cell Cycle Progression

Heavy metals are important for various biological systems, but, in excess, they pose a serious risk to human health. Heavy metals are commonly used in consumer and industrial products. Despite the increasing evidence on the adverse effects of heavy metals, the detailed mechanisms underlying their action on lung cancer progression are still poorly understood. In the present study, we investigated whether heavy metals (mercury chloride and lead acetate) affect cell viability, cell cycle, and apoptotic cell death in human lung fibroblast MRC5 cells. The results showed that mercury chloride arrested the sub-G₁ and G₂/M phases by inducing cyclin B1 expression. In addition, the exposure to mercury chloride increased apoptosis through the activation of caspase-3. However, lead had no cytotoxic effects on human lung fibroblast MRC5 cells at low concentration. These findings demonstrated that mercury chloride affects the cytotoxicity of MRC5 cells by increasing cell cycle progression and apoptotic cell death.

Spermatozoa Transcriptional Response and Alterations in PL Proteins Properties after Exposure of Mytilus galloprovincialis to Mercury

Mercury (Hg) is an environmental pollutant that impacts human and ecosystem health. In our previous works, we reported alterations in the properties of Mytilus galloprovincialis protamine-like (PL) proteins after 24 h of exposure to subtoxic doses of toxic metals such as copper and cadmium. The present work aims to assess the effects of 24 h of exposure to 1, 10, and 100 pM HgCl₂ on spermatozoa and PL proteins of Mytilus galloprovincialis. Inductively coupled plasma–mass spectrometry indicated accumulation of this metal in the gonads of exposed mussels. Further, RT-qPCR analyses showed altered expression levels of spermatozoa mt10 and hsp70 genes. In Mytilus galloprovincialis, PL proteins represent the major basic component of sperm chromatin. These proteins, following exposure of mussels to HgCl₂, appeared, by SDS-PAGE, partly as aggregates and showed a decreased DNA-binding capacity that rendered them unable to prevent DNA damage, in the presence of CuCl₂ and H₂O₂. These results demonstrate that even these doses of HgCl₂ exposure could affect the properties of PL proteins and result in adverse effects on the reproductive system of this organism. These analyses could be useful in developing rapid and efficient chromatin-based genotoxicity assays for pollution biomonitoring programs.

Potential Whole-Cell Biosensors for Detection of Metal Using MerR Family Proteins from Enterobacter sp. YSU and Stenotrophomonas maltophilia OR02

Cell-based biosensors harness a cell's ability to respond to the environment by repurposing its sensing mechanisms. MerR family proteins are activator/repressor switches that regulate the expression of bacterial metal resistance genes and have been used in metal biosensors. Upon metal binding, a conformational change switches gene expression from off to on. The genomes of the multimetal resistant bacterial strains, Stenotrophomonas maltophilia Oak Ridge strain 02 (S. maltophilia 02) and Enterobacter sp. YSU, were recently sequenced. Sequence analysis and gene cloning identified three mercury resistance operons and three MerR switches in these strains. Transposon mutagenesis and sequence analysis identified Enterobacter sp. YSU zinc and copper resistance operons, which appear to be regulated by the protein switches, ZntR and CueR, respectively. Sequence analysis and reverse transcriptase polymerase chain reaction (RT-PCR) showed that a CueR switch appears to activate a S. maltophilia 02 copper transport gene in the presence of CuSO₄ and HAuCl₄·3H₂O. In previous studies, genetic engineering replaced metal resistance genes with the reporter genes for β-galactosidase, luciferase or the green fluorescence protein (GFP). These produce a color change of a reagent, produce light, or fluoresce in the presence of ultraviolet (UV) light, respectively. Coupling these discovered operons with reporter genes has the potential to create whole-cell biosensors for HgCl₂, ZnCl₂, CuSO₄ and HAuCl₄·3H₂O.

Conversion of Isocyanide to Amine in The Presence of Water and Hg(II) Ions: Kinetics and Mechanism as Detected by Fluorescence Spectroscopy and Mass Spectrometry

Aromatic isocyanides including isocyanonaphthalene derivatives have been proven to be very effective fluorescent sensors for the quantification of Hg(II) ions in water. Thus, the reaction of 1,5-isocyanoaminonaphthalene (1,5-ICAN), which is one of the most important members of this family, with water and HgCl2 as the oxidation agents, was studied by fluorescence spectroscopy and mass spectrometry in order to get deeper insight into the kinetics and mechanistic details of this complex reaction. The reactions of 1,5-ICAN with water and HgCl2 were performed in various water/co-solvent mixtures of different compositions. The co-solvents used in this study were both aprotic solvents including tetrahydrofuran, acetonitrile and N,N-dimethylformamide and protic solvents, such as ethanol and 2-propanol. It was found that in aprotic solvents the conversion of the isocyano group to amino moiety takes place, while in protic solvents the corresponding carbamate (urethane) group is formed in addition to the amino moiety. The variation of the resulting fluorescence intensities versus time curves were described using an irreversible, consecutive reaction model, in which the formation of isocyanate and carbamic acid intermediates, as well as diamino and carbamate (in the case of protic solvents) products were assumed. The formation of these intermediates and products was unambiguously confirmed by mass spectrometric measurements. Furthermore, by fitting the model to the experimental fluorescence versus time curves, the corresponding rate coefficients were determined. It was observed that the overall rate of transformation of the isocyano group to amino moiety increased with the water concentration and the polarity of the co-solvent. It was also supported that formation of diamino and carbamate derivatives in protic solvents takes place simultaneously and that the ratio of the amino to the carbamate function increased with the increasing water concentration. In addition, with an extension, the model presented herein proved to be capable of describing the kinetics of the transformation of 1,5-diisocyanonaphthalene (1,5-DIN) into 1,5-diaminonaphthalene (1,5-DAN) in the mixtures of water/aprotic solvents.

Promotional removal of gas-phase Hg0 over activated coke modified by CuCl2

Impregnating CuCl₂ on AC (activated coke) support to synthesize xCuCl₂/AC showed superior activity with higher 90% Hg⁰ removal efficiency at 80-140 °C, as well as a lower oxygen demand of 2% O₂ for Hg⁰ removal. The acceleration on Hg⁰ removal was observed for NO and SO₂. The BET, SEM, XRD, XPS, TPD, and FT-IR characterizations revealed that the larger surface area, sufficient active oxygen species and co-existence of Cu⁺ and Cu²⁺ may account for the efficient Hg⁰ removal. In addition, the low demand of gaseous O₂ was contributed to higher content of active oxygen and formed active Cl. After adsorbing on Cu sites, Cl sites, and surface functional groups, the Hg⁰_(ads) removal on xCuCl₂/AC was proceeded through two ways. Part of Hg⁰_(ads) was oxidized by active O and formed Hg⁰, and the other part of Hg⁰ combined with the active Cl, which was formed by the activation of lattice Cl with the aid of active O, and formed HgCl₂. Besides, the Hg²⁺ detected in outlet gas through mercury speciation conversion and desorption peak of HgCl₂ and Hg⁰ further proved it. As displayed in stability test and simulated industrial application test, CuCl₂/AC has a promising industrial application prospect.

The protective role of ascorbic acid in the hepatotoxicity of cadmium and mercury in rabbits

The liver is one of the vital and sensitive organs which are usually exposed against the toxicity of mercury (Hg) and cadmium (Cd). The main objective of the current study was to evaluate the potential toxicological effects of both Cd and Hg as individual and combined. Hepatotoxicity was evaluated by monitoring the biochemical parameters of the liver and their accumulation in the liver as well as therapeutic role of vitamin C in said toxicity in rabbits (Oryctolagus cuniculus). In this research, cadmium chloride (1.5 mg/kg), mercuric chloride (1.2 mg/kg), and vitamin C (150 mg/kg of body weight) were orally administered to treatment groups of the rabbits for 28 alternative days. Various biochemical parameters of the liver such as lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), bilirubin, alanine aminotransferase (ALAT), total protein, and gamma glutamyl transferase (GGT) were estimated using blood samples. Some biochemical parameters like ASAT, ALAT, LDH, GGT, and bilirubin were significantly elevated (P ≤ 0.001) in individual Cd and Hg treatment groups, while the level of total protein was found to be significantly declined. The effects of Cd and Hg in the presence of vitamin C on these biochemical parameters were low as compared to metals-treated groups. Similar results were found when rabbits were treated with co-administration of both metals and vitamin C. Accumulation of Cd and Hg found to be higher in the liver. However, chemoprevention and chemotreatment with vitamin C significantly (P ≤ 0.01) minimized the toxicological effects of both metals but not regained the accumulation similar to that of the control group. The findings of this study provide awareness on accumulation of metals in the liver in rabbits and their toxicity tested through biochemical parameters as well as the therapeutic role of vitamin C in such alterations.

Dietary luteolin attenuates chronic liver injury induced by mercuric chloride via the Nrf2/NF-κB/P53 signaling pathway in rats

Mercury exposure is a common cause of metal poisoning which is biotransformed to highly toxic metabolites thus eliciting biochemical alterations and oxidative stress. Luteolin, a phenolic compound found in many natural products, has multiple biological functions. Our study was aimed to explore the biological effects of luteolin in a liver injury model induced in rats by mercuric chloride (HgCl₂). Criteria for injury included liver enzyme, glutathione and malondialdehyde levels, histopathology, TUNEL assay, hepatocyte viability and reactive oxygen species levels. The results showed that luteolin protected against HgCl₂-induced liver injury. Luteolin increased total nuclear factor-erythroid-2-related factor 2 (Nrf2) levels in the presence of HgCl₂. Upregulation of its downstream factors, heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1, was also observed. This suggested that protection by luteolin against HgCl₂-induced liver injury involved Nrf2 pathway activation. Luteolin also decreased expression of nuclear factor-κB (NF-κB) and P53. HgCl₂ exposure led to increased Bcl-associated X protein (Bax), and decreased Bcl-2-related protein long form of Bcl-x (Bcl-xL) and B-cell leukemia/lymphoma-2 (Bcl-2) expression, leading to an increased Bax/Bcl-2 ratio. Taken together, our data suggested that decreasing oxidative stress is a protective mechanism of luteolin against development of HgCl2-induced liver injury, through the Nrf2/NF-κB/P53 signaling pathway in rats.

Protective effect of Rheum turkestanicum root against mercuric chloride-induced hepatorenal toxicity in rats

OBJECTIVE

The present study was designed to investigate the protective effects of hydroalcoholic extract of Rheum turkestanicum against HgCl₂ hepatorenal toxicity in rats.

MATERIALS AND METHODS

Animals were randomly divided into five groups (n= 6 in each group) and received HgCl₂ and plant's extract, intraperitoneally. Group1 received saline (1 mL/kg/day), group 2 received extract (200 mg/kg/day), group 3 was treated with HgCl₂ (5 mg/kg/day,) and groups 4 and 5 received the extract (100 and 200 mg/kg/day, respectively), 1 hr before HgCl₂ administration. All injections last for 3 days. Blood samples and specimens of the liver and kidney were collected 24 hr after the last injection.

RESULTS

Data showed that HgCl₂ significantly increases liver malondialdehyde (MDA) level, reduces total sulfhydryl content and increases serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, compared to control group. The histopathological changes such as inflammatory cells infiltration was observed in HgCl₂-treated group while plant's extract partially improved histological changes. The extract (100 and 200 mg/kg/day) improved the liver functions as reflected by significant reductions in AST and ALT levels in serum, MDA decreased and the content of total sulfhydryl elevated. Also, the extract improved necrosis and atrophy of the kidney induced byHgCl₂. Pretreatment with the extract reduced creatinine and urea in serum, and glucose and protein concentrations in urine, compared to HgCl₂- treated group (group III). The extract significantly reversed HgCl₂-induced depletion in thiol content and elevation in MDA content.

CONCLUSION

Therefore, oxidative stress may play an important role in HgCl₂-induced hepatorenal injury and R. turkestanicum extract may be regarded as a useful to protect the kidney and liver against HgCl₂-induced oxidative damage.

Mercury accumulation and its effects on molecular, physiological, and histopathological responses in the peacock blenny Salaria pavo

For humans, fish consumption is the major source of mercury (Hg) exposure. The aim of this study was to assess the effect of Hg in the peacock blenny Salaria pavo, a species of the family of blennies that was used as indicator of water pollution. We performed a sublethal contamination of fish to 66 μg HgCl₂ L^-1 during 1, 4, 10 and 15 days but Hg concentration measured in the experimental water was much lower than the nominal concentration. Hg was also measured in both gill and liver tissues and displays a significant increase of its concentration in gills after 1 day of exposure followed by a decrease throughout the experiment. In the liver, Hg burden reaches its maximum at day 4 followed also by a decrease. Partial-length cDNA of mt1, mt2, gpx, cat, mnsod and cuznsod was characterized. Results from mRNA expression levels displayed an up-regulation of mt1, gpx and mnsod while a downregulation of cat was observed. Several biomarker activities were determined in gills and liver and exposure to Hg affected all antioxidant enzymes in gills. EROD, GST and GPx significantly decreased, while CAT levels increased from 4 days of Hg exposure. No lipid peroxidation (LPO) induction was observed in gills of exposed fish. Regarding the liver, the activity of all enzymes increased significantly from the beginning of the experiment. LPO induction was, however, induced after 4 days only. The histological analysis also performed indicated that fish exhibited several damages in gills and liver, mainly in relation to circulatory disturbances in the gills and regressive changes in the liver. All biomarkers assessed showed that peacock blennies are able to detoxify Hg from gill and liver tissues by developing various defense mechanisms.

Developmental toxicity from exposure to various forms of mercury compounds in medaka fish (Oryzias latipes) embryos

This study examined developmental toxicity of different mercury compounds, including some used in traditional medicines. Medaka (Oryzias latipes) embryos were exposed to 0.001–10 µM concentrations of MeHg, HgCl2, α-HgS (Zhu Sha), and β-HgS (Zuotai) from stage 10 (6–7 hpf) to 10 days post fertilization (dpf). Of the forms of mercury in this study, the organic form (MeHg) proved the most toxic followed by inorganic mercury (HgCl₂), both producing embryo developmental toxicity. Altered phenotypes included pericardial edema with elongated or tube heart, reduction of eye pigmentation, and failure of swim bladder inflation. Both α-HgS and β-HgS were less toxic than MeHg and HgCl₂. Total RNA was extracted from survivors three days after exposure to MeHg (0.1 µM), HgCl₂ (1 µM), α-HgS (10 µM), or β-HgS (10 µM) to examine toxicity-related gene expression. MeHg and HgCl₂ markedly induced metallothionein (MT) and heme oxygenase-1 (Ho-1), while α-HgS and β-HgS failed to induce either gene. Chemical forms of mercury compounds proved to be a major determinant in their developmental toxicity.

Mercury (II) reduction and co-precipitation of metallic mercury on hydrous ferric oxide in contaminated groundwater

Mercury (Hg) speciation and sorption analyses in contaminated aquifers are useful for understanding transformation, retention, and mobility of Hg in groundwater. In most aquifers hydrous ferric oxides (HFOs) are among the most important sorbents for trace metals; however, their role in sorption or mobilization of Hg in aquifers has been rarely analyzed. In this study, we investigated Hg chemistry and Hg sorption to HFO under changing redox conditions in a highly HgCl2-contaminated aquifer (up to 870μgL(-1) Hg). Results from aqueous and solid phase Hg measurements were compared to modeled (PHREEQC) data. Speciation analyses of dissolved mercury indicated that Hg(II) forms were reduced to Hg(0) under anoxic conditions, and adsorbed to or co-precipitated with HFO. Solid phase Hg thermo-desorption measurements revealed that between 55 and 93% of Hg bound to HFO was elemental Hg (Hg(0)). Hg concentrations in precipitates reached more than 4 weight %, up to 7000 times higher than predicted by geochemical models that do not consider unspecific sorption to and co-precipitation of elemental Hg with HFO. The observed process of Hg(II) reduction and Hg(0) formation, and its retention and co-precipitation by HFO is thought to be crucial in HgCl2-contaminated aquifers with variable redox-conditions regarding the related decrease in Hg solubility (factor of ~10(6)), and retention of Hg in the aquifer.

Assessment of gill pathological responses in the tropical fish yellowfin seabream of Persian Gulf under mercury exposure

Gill histomorphological alterations were used to assess the effects of chronic exposure to HgCl₂ on the yellowfin seabream, Acanthopagrus latus. In this regard, 90 A. latus were exposed to sublethal concentrations of HgCl₂ (10, 20, 35 and 50 μg/L) for 3 weeks. Treated fish were erratic and showed respiratory distress. The most common morphological abnormalities included: filaments disorganization, increase of mucus secretion, debris and blood plaques on the filaments, losing or shortening of some filaments. The most frequent histopathological changes detected in the gills included extensive lifting of the lamellar epithelium and edema of lamellae with enlarged sub-epithelial spaces, exfoliated epithelium of lamellae, telangiectasia, hypertrophy and hyperplasia of the epithelial cell resulted in partial fusion of the secondary lamellae and a reduction of the water space, club shaping of gill lamellae, blood congestion. Some more severe alternations found in the gill of fish exposed to higher levels of HgCl₂ (35 and 50 μg/L) included lamellar aneurysm and hemorrhages with rupture of the lamellar epithelium. According to the results of the present study, mercuric chloride could cause major histomorphological changes in the gill of A. latus, decreasing its gas exchange capability. Two mercury concentrations (10 and 20 μg/L) used in the present study were in agreement with the concentration of mercury in the water of different parts of Mahshahr creeks (the north of Persian Gulf) (3.66 to 15 μg/L). Therefore, based on the results the presence of pathological alteration in A. latus inhibited in the natural environment (Mahshahr creeks) seems to be logical.