Heavy Metal Status and Oxidative Stress in Diesel Engine Tuning Workers of Central Indian Population

Sub-chronic cadmium and lead compound exposure induces reproductive toxicity and development of testicular germ cell neoplasia in situ in murine model: Attenuative effects of resveratrol

Cadmium and lead are widespread, nonbiodegradable heavy metals of perpetual environmental concerns. The present study aimed to evaluate whether sub-chronic exposure to cadmium chloride (CdCl₂ ) and lead acetate [Pb(CH₃ COO)₂ ] induces reproductive toxicity and development of testicular germ cell neoplasia in situ (GCNIS) in swiss albino mice. The effects of resveratrol to reverse the metal-induced toxicity were also analyzed. The mice were randomly divided into four groups for metal treatments and two groups received two different doses of each metal, CdCl₂ (0.25 and 0.5 mg/kg) and Pb(CH₃ COO)₂ (3 and 6 mg/kg). The fourth group received oral doses of 20 mg/kg resveratrol in combination with 0.5 mg/kg CdCl₂ or 6 mg/kg Pb(CH₃ COO)₂ for 16 weeks. Toxic effects of both metals were estimated qualitatively and quantitatively by the alterations in sperm parameters, oxidative stress markers, testicular histology, and protein expressions of the treated mice. Pronounced perturbation of sperm parameters, cellular redox balance were observed with severe distortion of testicular histo-architecture in metal exposed mice. Significant overexpression of Akt cascade and testicular GCNIS marker proteins were recorded in tissues treated with CdCl₂ . Notable improvements were observed in all the evaluated parameters of resveratrol cotreated mice groups. Taken together, the findings of this study showed that long-term exposure to Cd and Pb compounds, induced acute reproductive toxicity and initiation of GCNIS development in mice. Conversely, resveratrol consumption abrogated metal-induced perturbation of spermatogenesis, testicular morphology, and the upregulation of Akt cascade proteins along with GCNIS markers, which could have induced the development of testicular cancer.

Low levels of lead and glutathione markers of redox status in human blood

Exposure to lead (Pb) is implicated in a plethora of health threats in both adults and children. Increased exposure levels are associated with oxidative stress in the blood of workers exposed at occupational levels. However, it is not known whether lower Pb exposure levels are related to a shift toward a more oxidized state. To assess the association between blood lead level (BLL) and glutathione (GSH) redox biomarkers in a population of healthy adults, BLL and four GSH markers (GSH, GSSG, GSH/GSSG ratio and redox potential E h ) were measured in the blood of a cross-sectional cohort of 282 avid seafood-eating healthy adults living on Long Island (NY). Additionally, blood levels of two other metals known to affect GSH redox status, selenium (Se) and mercury (Hg), and omega-3 index were tested for effect modification. Regression models were further adjusted for demographic and smoking status. Increasing exposure to Pb, measured in blood, was not associated with GSSG, but was associated with lower levels of GSH/GSSG ratio and more positive GSH redox potential E h , driven by its association with GSH. No effect modification was observed in analyses stratified by Hg, Se, omega-3 index, sex, age, or smoking. Blood Pb is associated with lower levels of GSH and the GSH/GSSG ratio in this cross-sectional study of healthy adults.

The protective effect of polysaccharide extracted from Portulaca oleracea L. against Pb-induced learning and memory impairments in rats

This paper studied the extraction of polysaccharide from Portulaca oleracea L. (POP) by hot water extraction and ethanol precipitation. Structural properties of the extracted polymers were determined. POP was composed of rhamnose, arabinose and galactose in ratios of 1: 2.34: 3.07 with a molecular weight of 1.55 × 10⁷ Da. The neuroprotective effect of POP on Pb-induced neuronal toxicity was then evaluated in vitro and in vivo test. Treatment with POP markedly increased the survival of PC12 cells and repressed the generation of reactive oxygen species following Pb exposure. In Morris water maze analysis, Pb exposure led to an increase in escape latency and a decrease in platform crossing times of rats in the probe test, which could be attenuated by POP treatment. Additionally, the Pb-induced loss of dendritic spine was recovered after feeding rats with POP at 600 mg/kg/day. These results indicated that Pb-induced cognitive impairments could be inhibited by POP.

Environmental toxin-induced acute kidney injury

Human beings are exposed to various potentially toxic agents and conditions in their natural and occupational environments. The kidney, due to its concentrating ability and excretory function, is highly vulnerable to the effects of environmental toxins. Identifying the precise cause and mechanisms of environmentally induced renal injury remains a challenge for which various scientific disciplines need to be involved. Investigations in this field are confronted with the apparent infinite types of toxins, their mutual interaction, handling/metabolization by the body, ways of exposure, etc. Although interdisciplinary efforts and persistence are required to identify, mechanistically unravel and tackle environmental toxin-induced pathologies, research eventually pays off in ameliorated working/living conditions and development of preventive/therapeutic strategies. This review was compiled to particularly emphasize the need for a maintained awareness of environmental threats in general and those targeting the kidney. Different mechanisms of renal toxicity are illustrated and discussed, thereby focusing on three types of environmental toxins, namely aristolochic acid, melamine and heavy metals.

Blood metal levels and third trimester maternal plasma matrix metalloproteinases (MMPs)

While it is known that in utero exposure to environmental toxicants, namely heavy metals, can adversely affect the neonate, there remains a significant paucity of information on maternal biological changes specific to metal exposures during pregnancy. This study aims at identifying associations between maternal metal exposures and matrix metalloproteinases (MMPs) that are known to be engaged in pregnancy process. Third trimester maternal plasma (n = 1533) from a pregnancy cohort (Maternal-Infant Research on Environmental Chemicals Study, MIREC) were analyzed for MMP-1,-2,-7,-9 and -10 by affinity-based multiplex protein array analyses. Maternal metal concentrations (mercury, cadmium, lead, arsenic and manganese) in 1st and 3rd trimesters exhibited strong correlations (p < 0.05). Multivariate regression models were used to estimate odds ratio (OR) for the association between metal concentrations in quartiles and high (90%) and low (10%) maternal MMP levels. Significant (p < 0.05) metal exposure-related effects were observed with the different MMP isoform responses. MMP profiles were specific to the trimester at which the maternal blood metals were analyzed. Our findings suggest that the profiles of these MMP isoforms vary with the type of metal exposure, blood metal concentrations and the trimester at which metal levels were determined. These new findings on maternal metal-MMP relationships can guide future explorations on toxicity mechanisms relevant to metal exposure-mediated adverse birth outcomes.

The role of Nrf2 in protection against Pb-induced oxidative stress and apoptosis in SH-SY5Y cells

Lead exerts severe adverse effects on the nervous system in which oxidative stress might mediate impairments. In this study, we focused on Nrf2, which has been identified to significantly influence the protection of a cellular system against many xenobiotic compounds. We found that PbAc exhibited neurotoxicity mainly through oxidant-based processes and could be inhibited by NAC and DPI in SH-SY5Y cells. As a defense response, Nrf2 was activated when exposed to PbAc, thereby inducing a rapid increase in Nrf2 nuclear accumulation, as well as Nrf2-ARE binding activities in a ROS-dependent manner. Analysis of Nrf2-regulated gene expression and protein showed that PbAc could induce the mRNA transcription of HO-1, GSTα1, GCLM, GCLC, and NQO1, as well as the protein expression of HO-1 and γ-GCS. The responses of these genes to PbAc were regulated by Nrf2. Silencing Nrf2 expression in SH-SY5Y cells inhibited PbAc-induced gene transcription and protein expression. Overexpression of Nrf2 led to decreased ROS production and cell apoptosis, as well as increased cell viability under PbAc exposure. These results indicated that the Nrf2-ARE system exhibited a protective role in Pb-induced neurotoxicity, providing potential therapeutic strategies for the prevention and treatment of Pb-related diseases.

Co-exposure to lead increases the renal response to low levels of cadmium in metallurgy workers

PURPOSE

Research on the effect of co-exposure to Cd and Pb on the kidney is scarce. The objective of the present study was to assess the effect of co-exposure to these metals on biomarkers of early renal effect.

METHODS

Cd in blood (Cd-B), Cd in urine (Cd-U), Pb in blood (Pb-B) and urinary renal biomarkers, i.e., microalbumin (μ-Alb), beta-2-microglobulin (β₂-MG), retinol binding protein (RBP), N-acetyl-β-d-glucosaminidase (NAG), intestinal alkaline phosphatase (IAP) were measured in 122 metallurgic refinery workers examined in a cross-sectional survey.

RESULTS AND CONCLUSIONS

The median Cd-B, Cd-U, Pb-B were: 0.8 μg/l (IQR = 0.5, 1.2), 0.5 μg/g creatinine (IQR = 0.3, 0.8) and 158.5 μg/l (IQR = 111.0, 219.3), respectively. The impact of Cd-B on the urinary excretion of NAG and IAP was only evident among workers with Pb-B concentrations ≥ 75th percentile. The association between Cd-U and the renal markers NAG and RBP was also evidenced when Pb-B ≥ 75th percentile. No statistically significant interaction terms were observed for the associations between Cd-B or Cd-U and the other renal markers under study (i.e., μ-Alb and β2-MG). Our findings indicate that Pb increases the impact of Cd exposure on early renal biomarkers.

Relation of blood cadmium, lead, and mercury levels to biomarkers of lipid peroxidation in premenopausal women

Exposures to cadmium, lead, and mercury are associated with adverse health effects, including cardiovascular disease, which may be promoted by lipid peroxidation. The authors examined cadmium, lead, and mercury in relation to plasma levels of F(2)-8α isoprostanes (isoprostane), 9-hydroperoxy-10,12-octadecadienoic acid (9-HODE), 13-hydroxy-9,11-octadecadienoic acid (13-HODE), and thiobarbituric acid reactive substances (TBARS) in 252 women from western New York State (2005-2007). Healthy premenopausal women were followed for ≤2 menstrual cycles, with biomarkers of lipid peroxidation being assessed ≤8 times per cycle. Metals were measured at baseline in whole blood. Linear mixed models were used to estimate the association between cadmium, lead, and mercury and lipid peroxidation biomarkers. Median cadmium, lead, and mercury levels were 0.30 μg/L, 0.86 μg/dL, and 1.10 μg/L, respectively. Blood cadmium, lead, and mercury were not associated with increases in isoprostane, TBARS, 9-HODE, or 13-HODE levels. Isoprostane levels decreased 6.80% (95% confidence interval: -10.40, -3.20) per 1% increase in mercury. However, after adjustment for a simulated strong confounding factor, such as precisely measured fish consumption, the observed association was attenuated, suggesting that this unexpected association could be attributable to unmeasured confounding. In this population of healthy premenopausal women with low exposure levels, cadmium, lead, and mercury were not associated with elevated lipid peroxidation biomarkers.