Evaluation of the hepatotoxic risk caused by lead acetate via skin exposure using a proteomic approach

Rapid Review of Dermal Penetration and Absorption of Inorganic Lead Compounds for Occupational Risk Assessment

Lead (Pb) exposure continues to be a significant public health issue in both occupational and non-occupational settings. The vast majority of exposure and toxicological studies have focused on effects related to inhalation and gastrointestinal exposure routes. Exposure to inorganic Pb compounds through dermal absorption has been less well studied, perhaps due to the assumption that the dermal pathway is a minor contributor to aggregate exposures to Pb compounds. The aim of this rapid review was to identify and evaluate published literature on dermal exposures to support the estimation of key percutaneous absorption parameters (Kp, flux, diffusion rate) for use in occupational risk assessment. Eleven articles were identified containing information from both in vitro and in vivo systems relevant to percutaneous absorption kinetics. These articles provided 24 individual study summaries and information for seven inorganic Pb compounds. The vast majority of study summaries evaluated (n = 22, 92%) reported detectable amounts of dermal absorption of inorganic Pb. Data were identified for four Pb compounds (Pb acetate, Pb nitrate, Pb oxide, and Pb metal) that may be sufficient to use in evaluating physiologically based pharmacokinetic models. Average calculated diffusion rates for the pool of animal and human skin data ranged from 10-7 to 10-4 mg cm-2 h-1, and Kp values ranged from 10-7 to 10-5 cm h-1. Study design and documentation were highly variable, and only one of the studies identified was conducted using standard test guideline-compliant methodologies. Two studies provided quality estimates on the impacts of dermal absorption from water-insoluble Pb compounds on blood Pb levels. These two studies reported that exposures via dermal routes could elevate blood Pb by over 6 µg dl-1. This estimation could represent over 100% of 5 µg dl-1, the blood Pb associated with adverse health effects in adults. The utility of these estimates to occupational dermal exposures is limited, because the confidence in the estimates is not high. The literature, while of limited quality, overall strongly suggests inorganic Pb has the potential for dermal uptake in meaningful amounts associated with negative health outcomes based on upper bound diffusion rate estimates. Future standard test guideline-compliant studies are needed to provide high-confidence estimates of dermal uptake. Such data are needed to allow for improved evaluation of Pb exposures in an occupational risk assessment context.

Watermelon rind ethanol extract exhibits hepato-renal protection against lead induced-impaired antioxidant defenses in male Wistar rats

Lead acetate associated tissue injury has been linked to altered antioxidant defenses, hyperuricemia and inflammation. We hypothesized that watermelon rind extract, would ameliorate lead acetate-induced hepato-renal injury. Thirty Male Wistar rats received distilled water, lead acetate (Pb; 5 mg/kg) with or without watermelon rind extract (WM; 400 mg/kg; WM + Pb; 15 days of WM pretreatment); Pb + WM (15 days of WM post treatment) and simultaneous treatment (WM-Pb) for 30 days. Lead toxicity led to elevated serum malondialdehyde, creatinine, urea, uric acid, lactate dehydrogenase, liver injury enzymes, as well as decreased body weight. Decreased serum levels of reduced glutathione, nitric oxide, total protein and glutathione peroxidase activity was also observed. However, these alterations were ameliorated by watermelon rind extract in lead acetate-treated rats. Watermelon rind ethanol extract protects against lead acetate-induced hepato-renal injury through improved antioxidant defenses at least in part, via uric acid/nitric oxide-dependent pathway signifying the health benefits of this agricultural waste and a potential for waste recycling while limiting environmental pollution.

Rapid Speciation of Lead in Human Blood and Urine Samples Based on MWCNTs@DMP by Dispersive Ionic Liquid-Suspension-Micro-Solid Phase Extraction

An efficient sorbent based on 2,3-dimercapto-1-propanol immobilized on multi-wall carbon nanotubes (MWCNTs@DMP) was developed for separation/speciation of organic and inorganic lead (alkyl-Pb, Pb²⁺) in human blood, urine, and water samples by dispersive ionic liquid-suspension-micro-solid phase extraction (DIL-S-μ-SPE). By procedure, the MWCNTs@DMP as solid phase, acetone, and ionic liquid (IL, [HMIM][PF₆]) were mixed and injected to 10 mL of the liquid phase at pH = 6.5. After shaking, the Pb(II) was extracted in MWCNTs@DMP and settled down in a conical tube with IL by centrifuging (Pb²⁺→: SH-SiO₂@CNTs). The lead (Pb²⁺) was back-extracted from sorbent/IL in acidic pH and measured by atom trap atomic absorption spectrometry (AT-AAS). In addition, the organic lead (R-Pb, alkyl lead) converted to Pb(II) and total lead (T-Pb) was determined in the same conditions by UV radiation in 95 °C. Under the optimal conditions, the linear range (9.5-480 μg L^-1), LOD (3.2 μg L^-1), and enrichment factor (10.4) were obtained (RSD < 5%). The adsorption capacity of the MWCNTs@DMP and MWCNTs was achieved as 191.6 mg g^-1 and 25.8 mg g^-1, respectively. The method was validated by standard reference materials (SRM 1643d, SRM 955, and SRM 2668), ET-AAS, and ICP-MS analysis in real samples. Graphical abstract.

Zinc ameliorates lead toxicity by reducing body Pb burden and restoring Pb-induced haematological and biochemical derangements

Background:

Studies on nutritional factors, including zinc in ameliorating the deleterious effects of potentially toxic elements have been scarce and the findings have been inconsistent.

Aim:

The aim of the present study was to evaluate the ameliorative potential of zinc against lead-induced toxicity in rats.

Materials and methods:

Male albino rats (n = 24) assigned into four groups of six/group: normal control (NC), zinc control (ZnC; 20 mg/kg ZnCl2), lead control (PbC; 50 mg/kg PbCl2) and lead plus zinc (Pb + Zn; 50 mg/kg PbCl2plus 20 mg/kg ZnCl2), respectively were investigated. All administrations were through oral route and lasted for 42 days after which blood samples were collected for haematological and biochemical analyses using standard techniques.

Results:

Results showed that packed cell volume (PCV), haemoglobin concentration (HBC), red blood cell count (RBC) were significant (p < 0.05) reduced while total white blood cell count (TWBC), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and platelets were significantly elevated in PbC group in comparison with NC and ZnC. Also liver and renal function parameters as well as the liver and kidney malondialdehyde (MDA) were elevated while antioxidant enzymes; catalase (CAT) and superoxide dismutase (SOD) were significantly (p < 0.05) reduced in PbC group in comparison with NC and ZnC. Concentrations of lead were in the order: blood > liver > kidney in the PbC group. In addition to restoration of the altered parameters, administration of zinc in Pb + Zn group significantly reduced the raised lead concentrations in the plasma and organs.

Conclusion:

Reduction in body Pb burden and restoration of Pb-induced derangements in haematological and biochemical parameters by Zn strongly support the ameliorative property of Zn against Pb-induced toxicity.

The Comparison of the Plasma Levels of the Lead Element in Patients with Gastrointestinal Cancers and Healthy Individuals

Back ground and Aim:

Heavy metals are considered as risk factors in the development of some types of cancers. In this context, the lead (Pb) along with its biological impacts on the human body has raised significant concerns in public health. The aim of this study was to compare the plasma levels of the lead element in patients with gastrointestinal (GI) cancer and healthy subjects to examine whether this element has a role in the susceptibility of cancer.

Methods:

In a case-control study conducted between March 2016 to February 2017, the plasma levels of the lead were assessed. One-hundred patients with upper and lower GI cancers, as well as one-hundered healthy subjects who were age- and sex-matched participated in our study. A classic flame atomic absorption spectroscopy (FAAS) method was employed for the determination of the lead element in plasma levels of all subjects.

Results:

The mean age of patients was 53.8±10.6 years old. The patient group consisted of 51 male and 49 female patients. The results showed that the concentrations of Pb were lower than the defined toxic levels. The comparison of the mean levels of Pb between the case and control groups revealed that there was no statistically significant difference even when the gender, age, and history of smoking were included in the statistical analysis. Our findings showed that the concentration of Pb is significantly associated with the type of cancer (p<0.003) and the location of the tumor (whether upper or lower tract was affected) (p<0.003).

Conclusion:

Lead may contributes to the pathology and progression of GI cancers but we can not conclude that it involved in the causation or susceptibility of healthy individuals to develop GI cancer.

Lead facilitates foci formation in a Balb/c-3T3 two-step cell transformation model: role of Ape1 function

Several possible mechanisms have been examined to gain an understanding on the carcinogenic properties of lead, which include among others, mitogenesis, alteration of gene expression, oxidative damage, and inhibition of DNA repair. The aim of the present study was to explore if low concentrations of lead, relevant for human exposure, interfere with Ape1 function, a base excision repair enzyme, and its role in cell transformation in Balb/c-3T3. Lead acetate 5 and 30 μM induced APE1 mRNA and upregulation of protein expression. This increase in mRNA expression is consistent throughout the chronic exposure. Additionally, we also found an impaired function of Ape1 through molecular beacon-based assay. To evaluate the impact of lead on foci formation, a Balb/c-3T3 two-step transformation model was used. Balb/c-3T3 cells were pretreated 1 week with low concentrations of lead before induction of transformation with n-methyl-n-nitrosoguanidine (MNNG) (0.5 μg/mL) and 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.1 μg/mL) (a classical two-step protocol). Morphological cell transformation increased in response to lead pretreatment that was paralleled with an increase in Ape1 mRNA and protein overexpression and an impairment of Ape1 activity and correlating with foci number. In addition, we found that lead pretreatment and MNNG (transformation initiator) increased DNA damage, determined by comet assay. Our data suggest that low lead concentrations (5, 30 μM) could play a facilitating role in cellular transformation, probably through the impaired function of housekeeping genes such as Ape1, leading to DNA damage accumulation and chromosomal instability, one of the most important hallmarks of cancer induced by chronic exposures.

Systematic revelation of the protective effect and mechanism of Cordycep sinensis on diethylnitrosamine-induced rat hepatocellular carcinoma with proteomics

Cordyceps sinensis (C. sinensis) has been reported to treat liver diseases. Here, we investigated the inhibitory effect of C. sinensis on hepatocarcinoma in a diethylnitrosamine (DEN)-induced rat model with functional proteome tools.In the DEN-exposed group, levels of serum alanine aminotransferase and aspartate aminotransferase were increased while C. sinensis application remarkably inhibited the activities of these enzymes. Histopathological analysis also indicated that C. sinensis could substantially restore hypertrophic hepatocytes caused by DEN, suggesting that C. sinensis is effective in preventing DEN-induced hepatocarcinogenesis.We therefore comprehensively delineated the global protein alterations using a proteome platform. The most meaningful changes were found among proteins involved in oxidative stress and detoxification. Meanwhile, C. sinensis application could attenuate the carbonylation level of several enzymes as well as chaperone proteins. Network analysis implied that C. sinensis could obviously alleviate hepatocarcinoma via modulating redox imbalance, protein ubiquitination and tumor growth-associated transcription factors.Our findings provide new insight into the potential effects of C. sinensis in preventing carcinogenesis and might help in developing novel therapeutic strategies against chemical-induced hepatocarcinoma.

Association of changes in ER stress-mediated signaling pathway with lead-induced insulin resistance and apoptosis in rats and their prevention by A-type dimeric epigallocatechin-3-gallate

A-type dimeric epigallocatechin-3-gallate (A-type-EGCG-dimer, AEd), a new proanthocyanidins dimer from persimmon fruits, has been shown to have health benefit effects. However, A-type-EGCG-dimer affects gluose metabolism in the liver and the underlying mechanism is not clarified. The present study aims to examine the protective effects of A-type-EGCG-dimer on Pb-induced hepatic insulin resistance, endoplasmic reticulum (ER) stress and apoptosis in rats. Male wistar rats exposed to 0.05% w/v Pb acetate in the drinking water with or without A-type-EGCG-dimer coadministration (200 mg/kg body weight/day, intragastrically) for three months. We found that A-type-EGCG-dimer and pioglitazone supplementation significantly deceased glucose and insulin levels in plasma as compared with the Pb group. A-type-EGCG-dimer markedly prevents Pb-induced oxidative stress, ER stress and apoptosis in livers. A-type-EGCG-dimer and pioglitazone reduced the expression levels of the GRP78, PEPCK, G6Pase, p-PERK, p-IRE1, p-JNK, ATF4, CHOP and increased p-AKT in livers of the Pb group. Moreover, A-type-EGCG-dimer reduced ROS production and restored the activities of SOD and GPx in livers. A-type-EGCG-dimer decreased Bax, cytosolic cytochrome c and cleaved caspase-3 and increased Bcl-2 in livers of Pb-exposed rats. Our results suggest that A-type-EGCG-dimer might be a potential natural candidate for the prevention of hepatic insulin resistance and apoptosis induced by Pb.

Grape seed procyanidin extract ameliorates lead-induced liver injury via miRNA153 and AKT/GSK-3β/Fyn-mediated Nrf2 activation

Lead-induced hepatotoxicity is characterized by an extensive oxidative stress. Grape seed procyanidin extract (GSPE) possesses abundant biological activities. Herein, we investigated the protective role of GSPE against lead-induced liver injury and determined the potential molecular mechanisms. In vivo, rats were treated with/without lead acetate (PbAc) (0.05%, w/v) in the presence/absence of GSPE (200 mg/kg). In vitro, hepatocytes were pretreated with/without GSPE (100 μg/ml) in the presence/absence of PbAc (100 μM). PbAc administration to rats resulted in anemia, liver dysfunction, lead accumulation in the bone and liver, oxidative stress, DNA damage and apoptosis. GSPE significantly attenuated these adverse effects, except lead accumulation in liver. GSPE also decreased the expression of miRNA153 and increased the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and levels of its downstream protein, and protein kinase B (AKT) phosphorylation in PbAc-induced liver injury. In primary hepatocytes treated with PbAc, GSPE increased hepatocyte viability and decreased lactate dehydrogenase release and reactive oxygen species levels. Dietary GSPE attenuated PbAc-induced liver injury in rats via an integrated mechanism associated with the miRNA153 and AKT/glycogen synthase kinase 3 beta/Fyn-mediated Nrf2 activation.

Differential proteomic expression of human placenta and fetal development following e-waste lead and cadmium exposure in utero

Prenatal exposure to lead (Pb) and cadmium (Cd) has been associated with a series of physiological problems resulting in fetal growth restriction. We aimed to investigate the effects of Pb and Cd exposure on placental function and the potential mechanisms involved in fetal development. Placental specimens and questionnaires were collected from an e-waste area and a reference area in China. Two-dimensional electrophoresis combined with MALDI-TOF-MS/MS and molecular network relationship were performed to analyze differentially expressed proteins using a compositing sample pool. Compared with the reference group, the exposed group exhibited significantly higher levels of placental Pb and Cd (p<0.01), shorter body length and higher gestational age (p<0.01). After bivariate adjustment in a linear regression model, decreases of 205.05g in weight and 0.44cm in body length were associated with a 10ng/g wt increase in placental Cd. Pb showed a negative trend but lacked statistical significance. Proteomic analysis showed 32 differentially-expressed proteins and were predominantly involved in protein translocation, cytoskeletal structure, and energy metabolism. Fumarate hydratase was down-regulated in the exposed placenta tissues and validated by ELISA. Alterations in placental proteome suggest that imbalances in placental mitochondria respiration might be a vital pathway targeting fetal growth restriction induced by exposure to Cd.

Herbal formula, Scutellariae radix and Rhei rhizoma attenuate dimethylnitrosamine-induced liver fibrosis in a rat model

The bioactive components extracted from Scutellariae radix and Rhei rhizoma (SR) have been commonly used to treat liver diseases. The aim of this study was to verify the underlying mechanisms and antifibrotic effects of ethanol extract from the herbal combinatorial formula (SRE) in a dimethylnitrosamine (DMN)-administered rat model, with functional proteome tools. Our results indicated that the hepatic collagen content and alpha-smooth muscle actin expression were obviously alleviated by treatment with SRE. Comprehensive proteomics revealed global protein changes, and the network analysis implied that SRE application would attenuate oxidative stress and cytoskeleton dysregulation caused by DMN exposure. Next, marked downregulation of antioxidant enzymes mediated by DMN treatment was restored in the presence of SRE, while SRE treatment contributed to decreased MDA content. Moreover, protein carbonylation and DNA adduction induced by oxidative stress finally leading to liver injury were also reduced under SRE administration. These findings demonstrate that SRE could effectively prevent hepatic fibrosis mainly through regulating the redox status, and subsequently modulating the modification of intracellular molecules. Our experiments might help in developing novel therapeutic strategies against oxidation-caused liver diseases.

Lead toxicity: a review

Lead toxicity is an important environmental disease and its effects on the human body are devastating. There is almost no function in the human body which is not affected by lead toxicity. Though in countries like US and Canada the use of lead has been controlled up to a certain extent, it is still used vehemently in the developing countries. This is primarily because lead bears unique physical and chemical properties that make it suitable for a large number of applications for which humans have exploited its benefits from historical times and thus it has become a common environmental pollutant. Lead is highly persistent in the environment and because of its continuous use its levels rise in almost every country, posing serious threats. This article reviews the works listed in the literature with recent updates regarding the toxicity of lead. Focus is also on toxic effects of lead on the renal, reproductive and nervous system. Finally the techniques available for treating lead toxicity are presented with some recent updates.