Effects of chronic lead exposure on bone mineral properties in femurs of growing rats

Melatonin or vitamin C attenuates lead acetate-induced testicular oxidative and inflammatory damage in mice by inhibiting oxidative stress mediated NF-κB signaling

Lead (Pb) acts as an environmental endocrine disruptor and has negative effects in animals; excessive accumulation of lead causes reproductive dysfunction in male animals. Oxidative stress plays a vital role in Pb-induced injury. However, the mechanisms underlying chronic testicular toxicity of Pb remain unclear. In this study, we aimed to determine the effects of lead acetate on reproductive function in male mice, identify the underlying mechanisms, and test counter measures to alleviate the toxic effects. Male mice were dosed with lead acetate (500 mg/L) in free drinking water for 12 weeks, and administered melatonin (5 mg/kg) or vitamin C (500 mg/kg) by intraperitoneal injection. Blood from the eyeball, testicles, and sperm from the caudal epididymis were collected after 12 weeks and analyzed. Pb exposure reduced sperm count and motility, increased sperm malformation (P < 0.01), disrupted testicular morphology and structure, and decreased the expression of steroid hormone synthesis-related enzymes and serum testosterone concentration (P < 0.01). Pb also increased the number of inflammatory cells and the levels of the pro-inflammatory cytokines TNF-α and IL-6 (P < 0.01), and activated NF-κB signaling. Furthermore, the ROS yield and oxidation indicators LPO and MDA were significantly increased (P < 0.01), and the antioxidant indicators T-AOC, SOD, and GSH were significantly reduced (P < 0.01). Treatment with melatonin or vitamin C reversed the effects of lead acetate; vitamin C was more effective in restoring SOD activity (P < 0.01) and enhancing ZO-1 protein levels (P < 0.01). Thus, long-term exposure to lead acetate at low concentrations could adversely affect sperm quality and induce inflammatory damage by oxidative stress mediated NF-κB signaling. Vitamin C could act as a protective agent and improve reproductive dysfunction in male animals after lead accumulation.

Associations between exposure to different heavy metals and self-reported erectile dysfunction: a population-based study using data from the 2001-2004 National Health and Nutrition Examination Survey

Heavy metals are ubiquitous and nonbiodegradable pollutants that are widely distributed in the environment. Heavy metal exposure can damage various biological tissues and cause several diseases. This study aimed to investigate the association between blood and urinary cadmium, lead, and mercury levels and erectile dysfunction (ED) based on data from the 2001-2004 National Health and Nutrition Examination Survey. In total, 3681 participants were included in the analysis. Results showed that participants with ED had high blood cadmium, mercury, creatinine, urinary lead, cadmium levels, low blood lead, serum cotinine, and urinary mercury levels. Multivariate logistic regression analysis showed that only blood cadmium level was an independent risk factor of ED (tertile [T]2 vs T1: odds ratio = 1.495, 95% confidence interval: 1.181-1.892, p = 0.001; T3 vs T1: odds ratio = 2.089, 95% confidence interval: 1.554-2.809, p < 0.001). The dose-response curve showed a positive nonlinear association between blood cadmium and lead levels and ED and a negative nonlinear association between blood and urinary mercury levels and ED after propensity score matching. In conclusion, heavy metal exposure is closely correlated with the development of ED, and a high blood cadmium level is an independent risk factor of ED.

Bone manganese is a sensitive biomarker of ongoing elevated manganese exposure, but does not accumulate across the lifespan

Studies have established associations between environmental and occupational manganese (Mn) exposure and executive and motor function deficits in children, adolescents, and adults. These health risks from elevated Mn exposure underscore the need for effective exposure biomarkers to improve exposure classification and help detect/diagnose Mn-related impairments. Here, neonate rats were orally exposed to 0, 25, or 50 mg Mn/kg/day during early life (PND 1-21) or lifelong through ∼ PND 500 to determine the relationship between oral Mn exposure and blood, brain, and bone Mn levels over the lifespan, whether Mn accumulates in bone, and whether elevated bone Mn altered the local atomic and mineral structure of bone, or its biomechanical properties. Additionally, we assessed levels of bone Mn compared to bone lead (Pb) in aged humans (age 41-91) living in regions impacted by historic industrial ferromanganese activity. The animal studies show that blood, brain, and bone Mn levels naturally decrease across the lifespan without elevated Mn exposure. With elevated exposure, bone Mn levels were strongly associated with blood Mn levels, bone Mn was more sensitive to elevated exposures than blood or brain Mn, and Mn did not accumulate with lifelong elevated exposure. Elevated early life Mn exposure caused some changes in bone mineral properties, including altered local atomic structure of hydroxyapatite, along with some biomechanical changes in bone stiffness in weanlings or young adult animals. In aged humans, blood Mn ranged from 5.4 to 23.5 ng/mL; bone Mn was universally low, and decreased with age, but did not vary based on sex or female parity history. Unlike Pb, bone Mn showed no evidence of accumulation over the lifespan, and may not be a biomarker of cumulative long-term exposure. Thus, bone may be a useful biomarker of recent ongoing Mn exposure in humans, and may be a relatively minor target of elevated exposure.

Associations between Plasma Folate and Vitamin B12, Blood Lead, and Bone Mineral Density among Adults and Elderly Who Received a Health Examination

This study hypothesized that plasma folate and vitamin B₁₂ levels modified the association between blood lead and cadmium and total urinary arsenic levels and bone loss. A total of 447 study subjects who received a physical examination at the Wanfang Hospital Medical Center were recruited. Bone loss was defined as a calcaneus bone mineral density T-score less than -1. Blood cadmium and lead concentrations were measured by ICP-MS. Urinary arsenic species were determined using HPLC-HG-AAS. A SimulTRAC-SNB radioassay was used to measure plasma folate, vitamin B₁₂, and homocysteine levels. Total urinary arsenic and blood lead concentration were positively correlated with the odds ratio (OR) for bone loss in a dose-response manner. The OR and 95% confidence interval (CI) for bone loss in participants with blood lead concentrations > 56.14 versus ≤33.82 μg/dL were 1.82 and 1.10-3.01. No correlation between plasma folate and vitamin B₁₂ levels alone and bone loss was observed. However, this study is the first observational study to find that blood lead concentrations tend to increase the OR of bone loss in a low plasma folate and plasma vitamin B₁₂ group with multivariate ORs (95% CI) of 2.44 (0.85-6.96).

Chronic exposure to lead acetate promotes changes in the alveolar bone of rats: microstructural and physical-chemical characterization

There are a few data relating to the effects of lead (Pb) exposure on the alveolar bone, which has very distinct morphophysiological characteristics and is of great importance in the oral cavity. In this context, the aim of this study was to investigate the changes promoted after long-term exposure to Pb in the microstructure of the alveolar bone of rats. Twenty adult Wistar rats were exposed to 50 mg/kg/day of lead acetate for 55 days. These animals were euthanized and had their mandible removed. Each mandible was divided into hemimandibles, and the alveolar bone was used for bone lead quantification, crystallinity analysis, microstructure evaluation by the percentage of bone volume (BV/TV), number of trabeculae (Tb.N), thickness of the trabecular (Tb.Th), and trabecular space (Tb.Sp). Morphometric analysis of the exposed root area was also performed. Long-term exposure to Pb resulted in high levels of Pb in the alveolar bone but showed no changes in the organization of crystallinity. The microstructural analyses showed a reduction of BV/TV, Tb.Th, and Tb.N and increase of Tb.Sp parameters, resulting in an increase in the exposed root area and an alveolar bone loss in height. The findings of this study reveal the ability of Pb to alter the alveolar bone microstructure after long-term exposure to the metal, possibly due to changes in tissue homeostasis, contributing to the reduction of bone quality.

Association of plasma lead, cadmium and selenium levels with hearing loss in adults: National Health and Nutrition Examination Survey (NHANES) 2011-2012

To determine the association between hearing loss and environmental Pb, Cd and Se exposure, a total of 1503 American adults from National Health and Nutrition Examination Survey (NHANES) (2011-2012) were assessed. The average of four audiometric frequencies (0·5, 1, 2 and 4 kHz) was used to identify speech-frequency hearing loss (SFHL), while the average of 3 audiometric frequencies (3, 4 and 6 kHz) was used to identify high-frequency hearing loss (HFHL). HFHL adjusted OR determined by comparing the highest and lowest blood Pb and Cd quartiles were 1·98 (95 % CI: 1·27, 3·10) and 1·81 (95 % CI: 1·13, 2·90), respectively. SFHL was significantly associated with blood Cd with the OR = 2·42 for the highest quartile. When further stratified by age, this association appeared to be limited to adults aged 35-52 years. After stratified by gender, except for Pb and Cd, we observed that blood Se showed a dose-dependent association with SFHL in men. In women, only Cd showed a dose-dependent association with speech and high-frequency hearing loss. Hearing loss was positively associated with blood levels of Pb and Cd. Additionally, our study provided novel evidence suggesting that excessive Se supplement would increase SFHL risk in men.

Plant Polyphenols: Potential Antidotes for Lead Exposure

Lead is one of the most common heavy metal elements and has high biological toxicity. Long-term lead exposure will induce the contamination of animal feed, water, and food, which can cause chronic lead poisoning including nephrotoxicity, hepatotoxicity, neurotoxicity, and reproductive toxicity in humans and animals. In the past few decades, lead has caused widespread concern because of its significant threat to health. A large number of in vitro and animal experiments have shown that oxidative stress plays a key role in lead toxicity, and endoplasmic reticulum (ER) stress and the mitochondrial apoptosis pathway can also be induced by lead toxicity. Therefore, plant polyphenols have attracted attention, with their advantages of being natural antioxidants and having low toxicity. Plant polyphenols can resist lead toxicity by chelating lead with their special chemical molecular structure. In addition, scavenging active oxygen and improving the level of antioxidant enzymes, anti-inflammatory, and anti-apoptosis are also the key to relieving lead poisoning by plant polyphenols. Various plant polyphenols have been suggested to be useful in alleviating lead toxicity in animals and humans and are believed to have good application prospects.

Long-term exposure to fine particulate matter and osteoporotic fracture: A case-control study in Taiwan

Few studies have explored the relationship between long-term exposure to particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and osteoporotic fracture, particularly in high PM_2.5 level areas. The aim of this study was to assess the association between long-term exposure to PM_2.5 and osteoporotic fracture. We performed a matched case-control study of 16,175 participants obtained from a hospital registry during 2005-2014 in Taiwan. A major osteoporotic fracture was defined as a fracture of the spine, hip, proximal humerus, and forearm. We applied satellite-based spatiotemporal models with 1-km resolution to individually calculate the 1-year average PM_2.5 concentration before the index date which was defined as the first visit date for the osteoporotic fracture. Logistic regression models with and without potential confounding factors were used to estimate odds ratios (OR) and 95% confidence intervals (CI) between PM_2.5 and osteoporotic fracture, whereas a restricted cubic spline model was used to estimate the dose-response relationship. The sample's median age was 44.7 years (interquartile range: 30.7, 63.1 years). We observed that long-term PM_2.5 exposure was associated with osteoporotic fracture, the OR was 1.12 (95% CI: 1.03, 1.22) per 10-μg/m³ increase in PM_2.5 in women. In the dose-response association, the OR of osteoporotic fracture was significantly increased for PM_2.5 exposures more than 41 μg/m³. We did not find a significant association between PM_2.5 (per 10-μg/m³ increase) and osteoporotic fracture among overall population (adjusted OR, 1.02 [95% CI, 0.97 to 1.08]) and men (adjusted OR, 0.94 [95% CI, 0.86 to 1.02]). The results of the stratified analysis showed that women were more sensitive to the adverse impact of PM2.5 that were men, and evidence was obtained of sex-based effect modification (P for interaction = 0.002). Our findings suggest that long-term exposure to PM_2.5 is associated with osteoporotic fracture, particularly among women.

Protective Effect of Opuntia dillenii Haw Fruit against Lead Acetate-Induced Hepatotoxicity: In Vitro and In Vivo Studies

Lead is one of the most common environmental contaminants in the Earth's crust, which induces a wide range of humans biochemical changes. Previous studies showed that Opuntia dillenii (OD) fruit possesses several antioxidant and anti-inflammatory properties. The present study evaluates OD fruit hydroalcoholic extract (OHAE) hepatoprotective effects against lead acetate- (Pb-) induced toxicity in both animal and cellular models. Male rats were grouped as follows: control, Pb (25 mg/kg/d i.p.), and groups 3 and 4 received OHAE at 100 and 200 mg/kg/d + Pb (25 mg/kg/d i.p.), for ten days of the experiment. Thereafter, we evaluated the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST), catalase (CAT) activity and malondialdehyde (MDA) in serum, and liver histopathology. Additionally, the cell study was also done using the HepG2 cell line for measuring the direct effects of the extract on cell viability, oxidative stress MDA, and glutathione (GSH) and inflammation tumor necrosis factor-α (TNF-α) following the Pb-induced cytotoxicity. Pb significantly increased the serum levels of ALT, AST, ALP, and MDA and liver histopathological scores but notably decreased CAT activity compared to the control group (p < 0.001 for all cases). OHAE (100 and 200 mg/kg) significantly reduced the levels of serum liver enzyme activities and MDA as well as histopathological scores while it significantly increased CAT activity compared to the Pb group (p < 0.001-0.05 for all cases). OHAE (20, 40, and 80 μg/ml) concentration dependently and significantly reduced the levels of MDA and TNF-α, while it increased the levels of GSH and cell viability in comparison to the Pb group (p < 0.001-0.05 for all cases). These data suggest that OHAE may have hepatoprotective effects against Pb-induced liver toxicity both in vitro and in vivo by its antioxidant and anti-inflammatory activities.

Long-Term Accumulation of Metals in the Skeleton as Related to Osteoporotic Derangements

The concentrations of metals in the environment are still not within the recommended limits as set by the regulatory authorities in various countries because of human activities. They can enter the food chain and bioaccumulate in soft and hard tissues/organs, often with a long half-life of the metal in the body. Metal exposure has a negative impact on bone health and may result in osteoporosis and increased fracture risk depending on concentration and duration of metal exposure and metal species. Bones are a long-term repository for lead and some other metals, and may approximately contain 90% of the total body burden in birds and mammals. The present review focuses on the most common metals found in contaminated areas (mercury, cadmium, lead, nickel, chromium, iron, and aluminum) and their effects on bone tissue, considering the possibility of the long-term bone accumulation, and also some differences that might exist between different age groups in the whole population.

Metabolic adaptability in liver and gastrocnemius muscle of mice following subacute lead toxicity

Lead (Pb) is one of several environmental pollutants that adversely affect human health by producing toxicity at the tissue level. The aim of the study was to understand the effects of Pb on the metabolic profiles of liver and gastrocnemius muscle of mice in relation to carbohydrate and fat metabolisms. Swiss albino mice were chosen and divided into two groups, control and Pb-treated. The Pb-treated animals were exposed to Pb at a dose of 5 mg/kg body weight for 30 days orally, which resulted in hypoglycemia, glycosuria, and increased glycogenolysis in the liver and gastrocnemius muscle of treated mice. Pyruvic acid, the end product of glycolysis decreased in muscular tissue and increased in the liver. Additionally, the activity of G-6Pase was depressed in the liver, whereas lactate dehydrogenase activity was increased in skeletal muscle only. An adaptive mechanism was initiated by stimulating glycogenolytic and retarding glycolytic activity in the liver and also by alteration of liver and muscle pyruvate dehydrogenase activity along with increased activity of malate dehydrogenase in skeletal muscle. There was enhancement of succinate dehydrogenase and nicotinamide adenine dinucleotide phosphate oxidase activities in the studied tissues. Interestingly, cholesterol, high-density lipoprotein, and low-density lipoprotein levels were elevated, whereas those of triglycerides were decreased in Pb-treated mice serum. The activities of fatty acid synthase and glyceraldehyde 3 phosphate dehydrogenase were depressed in Pb-treated mice livers. Pb also significantly altered the morphological features of the liver, skeletal muscle, and pancreas. These data suggested that subacute Pb exposure was responsible for metabolic modulation in an adaptive fashion in the liver and skeletal muscle of mice.

Long-Term Exposure to Low-Dose Lead Induced Deterioration in Bone Microstructure of Male Mice

The aim of this study was to investigate the long-term effects of low-dose lead exposure on bone microstructure in mice. Ten SPF 12-week-old male C57BL/6J mice were randomly divided into two groups: control (deionized water) and lead exposure (150 ppm of lead acetate in drinking water). After 24 weeks treatment, mice were weighed and the left femurs were collected and stored at - 80 °C. The right femurs of the mice were scanned by Micro-CT for three-dimensional reconstruction, and bone mineral density, bone volume fraction, trabeculae thickness, trabeculae number, and trabeculae separation were measured. The right tibia was collected to investigate histopathological changes in H&E-stained sections. The gene expression of osteoprotegerin (OPG), RANKL, and runt-related transcription factor 2 (Runx2) was determined using real-time PCR. The bone density of femoral cancellous bone and the number of cancellous bone trabeculae in the lead exposure group were both significantly decreased compared with the control group. Bone marrow stromal cell numbers were decreased following lead administration, and lipid droplet vacuoles were observed in the lead group. Levels of OPG were significantly decreased in the lead group, and lead also inhibited the expression of Runx2 compared with the control group. Long-term exposure to low doses of lead can cause bone damage without inducing other obvious symptoms through decreasing bone density and the number of cancellous bone trabeculae, further suppressing bone formation. It suggests that lead may exacerbate bone loss and osteoporosis, especially in the elderly.

Variability in the Clearance of Lead Oxide Nanoparticles Is Associated with Alteration of Specific Membrane Transporters

Lead oxide nanoparticles (PbONPs), upon their entry into the lungs via inhalation, induce structural changes in primary and secondary target organs. The fate and ultrastructural localization of PbONPs in organs is known to be dependent on the specific organ. Here, we focused on the differences in the ability to clear the inhaled PbONPs from secondary target organs and on molecular and cellular mechanisms contributing to nanoparticle removal. Mice were exposed to PbONPs in whole-body inhalation chambers. Clearance of ionic lead and PbONPs (Pb/PbONPs) from the lungs and liver was very effective, with the lead being almost completely eliminated from the lungs and the physiological state of the lung tissue conspicuously restored. Kidneys exposed to nanoparticles did not exhibit serious signs of damage; however, LA-ICP-MS uncovered a certain amount of lead located preferentially in the kidney cortex even after a clearance period. The concentration of lead in femurs, as representatives of the axial skeleton, was the highest among studied organs at all designated time points after PbONP exposure, and the clearance ability of lead from the femurs was very low in contrast to other organs. The organ-specific increase of ABC transporters expression (ABCG2 in lungs and ABCC3 in the liver) was observed in exposed animals, suggesting their involvement in removing Pb/PbONPs from tissues. Moreover, the expression of caveolins and clathrin displayed a tissue-specific response to lead exposure. Our results uncovered high variability among the organs in their ability to clear Pb/PbONPs and in the transporters involved in this process.

The association between body lead levels and childhood rickets: A meta-analysis based on Chinese cohort

China has serious lead pollution and a high incidence of childhood rickets. High lead levels have been reported in childhood rickets, but the results were inconsistent.To evaluate the association between body lead levels and childhood rickets.After a systematic literature search, we identified 15 studies determining body lead levels between rickets children and healthy controls, and 4 studies focusing on the cases of different disease severity. Standard mean differences (SMD) and the corresponding 95% confidence intervals (CI) were pooled to compare the lead levels between different groups.Sixteen case-control studies were included with a total of 5082 cases and 6054 controls. Compared with healthy controls, the body lead levels in rickets children were significantly higher (SMD (95%CI): 0.67 (0.41-0.93)), and subgroup analyses showed consistent results. The cases with moderate-to-severe disease activity also had a significantly higher lead level than mild-to-moderate cases (SMD (95%CI): 0.64 (0.31-0.97)).This meta-analysis suggested an association between body lead levels and childhood rickets, and lead exposure might be a risk factor for rickets.

Clinical and Experimental Evidences of Hydrogen Sulfide Involvement in Lead-Induced Hypertension

Lead- (Pb-) induced hypertension has been shown in humans and experimental animals and cardiovascular effects of hydrogen sulfide (H₂S) have been reported previously. However, no studies examined involvement of H₂S in Pb-induced hypertension. We found increases in diastolic blood pressure and mean blood pressure in Pb-intoxicated humans followed by diminished H₂S plasmatic levels. In order to expand our findings, male Wistar rats were divided into four groups: Saline, Pb, NaHS, and Pb + NaHS. Pb-intoxicated animals received intraperitoneally (i.p.) 1st dose of 8 μg/100 g of Pb acetate and subsequent doses of 0.1 μg/100 g for seven days and sodium hydrosulfide- (NaHS-) treated animals received i.p. NaHS injections (50 μmol/kg/twice daily) for seven days. NaHS treatment blunted increases in systolic blood pressure, increased H₂S plasmatic levels, and diminished whole-blood lead levels. Treatment with NaHS in Pb-induced hypertension seems to induce a protective role in rat aorta which is dependent on endothelium and seems to promote non-NO-mediated relaxation. Pb-intoxication increased oxidative stress in rats, while treatment with NaHS blunted increases in plasmatic MDA levels and increased antioxidant status of plasma. Therefore, H₂S pathway may be involved in Pb-induced hypertension and treatment with NaHS exerts antihypertensive effect, promotes non-NO-mediated relaxation, and decreases oxidative stress in rats with Pb-induced hypertension.