Involvement of the epidermal growth factor receptor in Pb²+-induced activation of cPLA₂/COX-2 genes and PGE₂ production in vascular smooth muscle cells

Combined exposure to multiple metals on abdominal aortic calcification: results from the NHANES study

Exposure to metals increases the risk of many diseases and has become a public health concern. However, few studies have focused on the effect of metal on abdominal aortic calcification (AAC), especially the combined effects of metal mixtures. In this study, we aim to investigate the combined effect of metals on AAC risk and determine the key components in the multiple metals. We tried to investigate the relationship between multiple metal exposure and AAC risk. Fourteen urinary metals were analyzed with five statistical models as follows: generalized linear regression, weighted quantile sum regression (WQS), quantile g-computation (Qgcomp), and Bayesian kernel machine regression (BKMR) models. A total of 838 participants were involved, of whom 241 (28.8%) had AAC. After adjusting for covariates, in multiple metal exposure logistic regression, cadmium (Cd) (OR = 1.364, 95% CI = 1.035-1.797) was positively associated with AAC risk, while cobalt (Co) (OR = 0.631, 95% CI = 0.438-0.908) was negatively associated with AAC risk. A significant positive effect between multiple metal exposure and AAC risk was observed in WQS (OR = 2.090; 95% CI = 1.280-3.420, P < 0.01), Qgcomp (OR = 1.522, 95% CI = 1.012-2.290, P < 0.05), and BKMR models. It was found that the positive association may be driven primarily by Cd, lead (Pb), uranium (U), and tungsten (W). Subgroups analysis showed the association was more significant in participants with BMI ≥ 25 kg/m2, abdominal obesity, drinking, and smoking. Our study shows that exposure to multiple metals increases the risk of AAC in adults aged ≥ 40 years in the USA and that Cd, Pb, U, and W are the main contributors. The association is stronger in participants who are obese, smoker, or drinker.

Influence of lead-induced toxicity on the inflammatory cytokines

Lead (Pb2+) is a hazardous heavy metal that is pervasive in the human environment as a result of anthropogenic activity, and poses serious health risks, particularly in children. Due to its innumerable unique physical and chemical properties, it has various applications; therefore, it has become a common environmental pollutant. Lead may cause oxidative stress, and accumulating evidence indicates that oxidative stress influences the pathophysiology of lead poisoning, also called plumbism. The immune system is continually exposed to various environmental pathogens and xenobiotics, including heavy metals such as lead, and appears to be one of the most vulnerable targets. After being exposed to lead, cells are subjected to oxidative stress as a result of reactive oxygen species (ROS) production. When the generation and consumption of ROS are out of equilibrium, various cell structures, particularly phospholipids are disrupted leading to lipid peroxidation. Various inflammatory signalling pathways are activated as a consequence, along with reduced disease resistance, inflammation, autoimmunity, sensitization and disruption of the cell-mediated and humoral immune systems. Lead negatively affects the metabolism of cytokines, including the interleukins IL-2, IL-1b, IL-6, IL-4, IL-8, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN), as well as the expression and functioning of inflammatory enzymes such as cyclooxygenases. However, the cause of toxicity depends on the kind of lead, dosage, route of entry, exposure period, age, host and genetic predisposition.

Higher Blood Lead Level Is Associated With Increased Likelihood of Abdominal Aortic Calcification

Aims: This study aimed to evaluate the association between blood lead level (BLL) and abdominal aortic calcification (AAC) in US adults aged ≥40 years.

Methods: We obtained data from 2013 to 2014 National Health and Nutrition Examination Survey (NHANES). Participants missing the data of BLL and AAC scores were excluded. BLL was measured using inductively coupled plasma mass spectrometry directly. AAC scores were quantified by Kauppila score system, and severe AAC was defined as AAC score >6. Weighted multivariable regression analysis and subgroup analysis were conducted to explore the independent relationship between BLL with AAC score and severe AAC.

Results: A total of 1,530 participants were included with the mean BLL of 1.45 ± 1.31 ng/dl and mean AAC score of 1.40 ± 3.13. The prevalence of severe AAC was 7.98% overall, and participants in higher BLL quartile showed higher prevalence of severe AAC (Quartile 1: 3.55%, Quartile 2: 7.28%, Quartile 3: 9.88%, Quartile 4: 12.58%, P < 0.0001). BLL was positively associated with higher AAC score (β = 0.15, 95% CI: 0.02, 0.27, P = 0.021) and increased risk of severe AAC (OR = 1.11; 95% CI: 1.00–1.22; P = 0.047). Subgroup analysis and interaction test indicated that the association between BLL and AAC was similar in different population settings.

Conclusions: Higher BLL was associated with higher AAC score and increased risk of severe AAC. Lead burden should be considered for people with AAC in clinical settings.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

Relations of blood lead levels to echocardiographic left ventricular structure and function in preschool children

Lead (Pb) has been proved to exert adverse effect on human cardiovascular system. However, the cardiotoxicity of Pb on children is still unclear. The aim of this study was to evaluate left ventricular (LV) structure and function, by using echocardiographic indices, in order to elucidate the effect of Pb on low-grade inflammation related to left ventricle in healthy preschool children. We recruited a total of 486 preschool children, 310 from Guiyu (e-waste-exposed area) and 176 from Haojiang (reference area). Blood Pb levels, complete blood counts, and LV parameters were evaluated. Associations between blood Pb levels and LV parameters and peripheral leukocyte counts were analyzed using linear regression models. The median blood level of Pb and the counts of white blood cells (WBCs), monocytes, and neutrophils were higher in exposed group. In addition, the exposed group showed smaller left ventricle (including interventricular septum, LV posterior wall, and LV mass index) and impaired LV systolic function (including LV fractional shortening and LV ejection fraction) regardless gender. After adjustment for confounding factors, elevated blood Pb levels were significantly associated with higher counts of WBCs and neutrophils, and lower levels of LV parameters. Furthermore, counts of WBCs, monocytes, and neutrophils were negatively correlated with LV parameters. Taken together, smaller left ventricle and impaired systolic function were found in e-waste-exposed children and associated with chronic low-grade inflammation and elevated blood Pb levels. It indicates that the heart health of e-waste-exposed children is at risk due to the long-term environmental chemical insults.

Developing a Health Impact Model for Adult Lead Exposure and Cardiovascular Disease Mortality

BACKGROUND

Lead (Pb) is a highly toxic pollutant. Evidence suggests it is associated with cardiovascular disease (CVD)-related mortality.

OBJECTIVES

We present a rigorous approach for identifying concentration-response functions that relate adult Pb exposures to CVD mortality to inform a health impact model (HIM). We then use the model in a proof-of-concept example.

METHODS

Building on previously conducted government literature reviews and a de novo supplemental literature review, we compiled and evaluated the available data on Pb and CVD mortality in humans. We applied a set of predefined selection criteria to identify studies that would be most useful in understanding the impact of Pb exposure on CVD mortality risk in adults. Once we identified the studies, we derived a HIM and used each study's concentration-response function in a proof-of-concept example.

RESULTS

Our literature search identified 15 studies for full-text review. Of those 15 studies, 4 fit our criteria for use in the HIM. Using population and CVD mortality rates for 40- to 80-y-olds in 2014, we estimated that 34,000-99,000 deaths have been avoided due to the lowering of blood Pb levels from 1999 to 2014. Based on these values we estimated that approximately 16%-46% of the decreased CVD-related death rate from 1999 to 2014 may be attributable to decreased blood Pb levels.

CONCLUSION

Our results demonstrate that decreases in Pb exposure can result in large benefits for the adult population. We have provided a HIM that can be used in a variety of applications from burden-of-disease estimates to regulatory impact assessments and have demonstrated its sensitivity to the choice of concentration-response function. https://doi.org/10.1289/EHP6552.

Elevated, sustained, and yet reversible biotoxicity effects of lead on cessation of exposure: Melatonin is a potent therapeutic option

Melatonin (Mel) is known to prevent and mitigate lead (Pb)-induced gonadotoxicity. However, there is no report in literature on the endogenous levels of different biomarkers after the cessation of Pb exposure, with or without treatment with Mel. Fifty adult male Wistar rats were divided into five groups (N = 10), which included control ((vehicle (normal saline) - treated) - 0.1 ml/day); lead chloride (PbCl₂) untreated (3 weeks vehicle + 3 weeks Pb); Pb recovery (3 weeks Pb + 3 weeks vehicle); Pb + Mel (3 weeks Pb + 3 weeks Mel); and Mel (3 weeks vehicle + 3 weeks Mel) groups. Pb and Mel were administered at 50 and 10 mg/kg B.W. (p.o.), respectively. The results showed that Pb caused significant decreases in total bilirubin (TB), phospholipids (PLP), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (TAC), but significant elevations in alkaline phosphatase (ALP), aspartate aminotransferase (AST), triglyceride (TG), and malondialdehyde (MDA). Although the adverse effects of Pb on TB, ALP, AST, SOD, MDA, and TAC were sustained after the cessation of exposure, a reversal was observed in total cholesterol (TC), TG, PLP, CAT, and c-reactive protein (CRP) results. Nevertheless, the detrimental effects of Pb on alanine aminotransferase (ALT), albumin, and globulin were only expressed post-exposure. Treatment with Mel caused no significant effect on TB and albumin levels. However, unlike TAC and CRP, the hormone significantly reduced ALP, AST, ALT, TC, low-density lipoprotein cholesterol, PLP, SOD, CAT, MDA, and globulin to levels comparable to the control group. In conclusion, following the cessation of Pb exposure, alterations in physiological balance could be elevated, sustained, or reversible. However, Mel enhanced the reestablishment homeostatic status after Pb administration.

Angiogenesis and lead (Pb): is there a connection?

Lead (Pb) is a toxic heavy metal ubiquitously distributed around the world, especially in industrial areas. Occupational and environmental exposures to Pb have detrimental effects on human health. Pb affects functioning of many systems of the human body, including the cardiovascular system. Angiogenesis, the process of new blood vessel formation, which makes critical contribution throughout life is deranged in various diseases. Excessive angiogenesis may result in different diseases including cancer. On the other spectrum, insufficient angiogenesis is observed in many diseases, such as atherosclerosis, hypertension, and cardiovascular disease. These disorders are also associated with occupational Pb exposure. In this paper, epidemiological and experimental studies are reviewed selectively for evidence in support of this hypothesis, that is, interactions between Pb and angiogenesis. We discuss the evidence for the possible mechanism of Pb impact on concentrations of angiogenic factors. Studies suggested that Pb exposure affects the level of angiogenic factors associated with angiogenesis regulation and promotion. Further research is needed, especially in the mechanisms in which Pb-induced vascular endothelial growth factor (VEGF) disregulation is present. We believe that characterizing the connection between Pb and angiogenesis will provide helpful information for the development of intervention strategies to reduce the adverse effects of Pb exposure.

Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA₂ and 15d-PGJ₂) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.

Fatty acid levels alterations in THP-1 macrophages cultured with lead (Pb)

OBJECTIVE

As cardiovascular events are one of the main causes of death in developed countries, each factor potentially increasing the risk of cardiovascular disease deserves special attention. One such factor is the potentially atherogenic effect of lead (Pb) on lipid metabolism, and is significant in view of the still considerable Pb environmental pollution and the non-degradability of Pb compounds.

METHODS

Analysis of saturated fatty acids (SFA) (caprylic acid (C8:0), decanoic acid (C10:0), lauric acid (C12:0), tridecanoic acid (C13:0), myristic acid (C14:0), pentadecanoic acid (C15:0), palmitic acid (C16:0), heptadecanoic acid (C17:0), stearic acid (C18:0), and behenic acid (C22:0)), monounsaturated fatty acid (MUFA) (palmitoleic acid (C16:1), oleic acid (18:1w9), trans-vaccenic acid (C18:1 trans11)), and polyunsaturated fatty acid (PUFA) (linoleic acid (C18:2n6), gamma-linolenic acid (C18:3n6), arachidonic acid (C20:4n6)), was conducted by gas chromatography. Analysis of stearoyl-CoA desaturase (SCD), fatty acid desaturase 1 (FADS1) and fatty acid desaturase 2 (FADS2) expression was performed using qRT-PCR. Oxidative stress intensity (malondialdehyde - MDA concentration) was measured using spectrophotometric method. Intracellular generation of reactive oxygen species (ROS) in macrophages was visualized by fluorescence microscopy and quantitatively measured by plate reader.

RESULTS

Pb caused quantitative alterations in FAs profile in macrophages; the effect was Pb-concentration dependent and selective (i.e. concerned only selected FAs). In general, the effect of Pb was biphasic, with Pb levels of 1.25 μg/dL and 2.5 μg/dL being stimulatory, and 10 μg/dL being inhibitory on concentrations of selected FAs. The most potent Pb concentration, resulting in increase in levels of 9 FAs, was 2.5 μg/dL, the Pb-level corresponding to the mean blood Pb concentrations of people living in urban areas not contaminated by Pb. Pb was found to exert similar, biphasic effect on the expression of FADS1. However, Pb decreased, in a concentration-dependent manner, the expression of SCD and FADS2. Pb significantly increased MDA and ROS concentration in macrophages.

CONCLUSION

Environmental Pb exposure might be a risk factor resulting in alterations in FAs levels, oxidative stress and increased MDA concentration in macrophages, which might lead to the formation of foam cells and to inflammatory reactions.

The effect of subacute lead exposure on selected blood inflammatory biomarkers and angiogenetic factors

Objectives:

The aim of the study was to examine blood levels of selected pro-inflammatory cytokines, C reactive protein (CRP), and selected factors that influence angiogenesis in workers exposed to lead for a short period of time.

Methods:

The study population consisted of 36 male workers (mean age 41 ± 14 years) exposed to lead for 40 days.

Results:

The mean blood lead level (BLL) was 10.7 ± 7.67 μg/dl at the beginning of the study, and increased to 49.1 ± 14.1 μg/dl at the end of the study period. The levels of macrophage inflammatory protein 1-α (MIP-1α) were significantly higher after the studied exposure to lead compared to the baseline by 71%. Similarly, the values of CRP increased by 35%. Conversely, the values of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and fibroblast growth factor-basic (FGF-basic) decreased by 14% and 21%, respectively. After the examined period of lead exposure, analysis of correlations showed positive correlations between vascular endothelial growth factor (VEGF) levels and the levels of interleukin 1β (IL-1β) (R = 0.39), interleukin 6 (IL-6) (R = 0.42), and MIP-1α (R = 0.54). Positive correlations were identified between MIP-1α and FGF-basic (R = 0.38), soluble angiopoietin receptor (sTie-2) (R = 0.41), and sVEGFR-1 (R = 0.47).

Discussion:

Short-term exposure to lead induces the inflammatory response; however, these mechanisms seem to be different from those observed in chronic lead exposure. Subacute exposure to lead may dysregulate angiogenesis via modifications in the levels of angiogenic factors.

Lead (Pb) Exposure Enhances Expression of Factors Associated with Inflammation

The human immune system is constantly exposed to xenobiotics and pathogens from the environment. Although the mechanisms underlying their influence have already been at least partially recognized, the effects of some factors, such as lead (Pb), still need to be clarified. The results of many studies indicate that Pb has a negative effect on the immune system, and in our review, we summarize the most recent evidence that Pb can promote inflammatory response. We also discuss possible molecular and biochemical mechanisms of its proinflammatory action, including the influence of Pb on cytokine metabolism (interleukins IL-2, IL-4, IL-8, IL-1b, IL-6), interferon gamma (IFNγ), and tumor necrosis factor alpha (TNF-α); the activity and expression of enzymes involved in the inflammatory process (cyclooxygenases); and the effect on selected acute phase proteins: C-reactive protein (CRP), haptoglobin, and ceruloplasmin. We also discuss the influence of Pb on the immune system cells (T and B lymphocytes, macrophages, Langerhans cells) and the secretion of IgA, IgE, IgG, histamine, and endothelin.

The influence of occupational chronic lead exposure on the levels of selected pro-inflammatory cytokines and angiogenic factors

The aim of the study was to determine the effect of occupational exposure to lead on the blood levels of pro-inflammatory cytokines and selected factors that influence angiogenesis. The study population was divided into two groups. The first group consisted of 56 male workers chronically exposed to lead. The second group (control) was comprised of 24 male administrative workers. The serum levels of interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) were significantly higher in the group of workers chronically exposed to lead compared to control values by 38%, 68%, and 57%, respectively. Similarly, the values of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and fibroblast growth factor-basic (FGF-basic) were higher by 19% and 63%, respectively. In the group of workers chronically exposed to lead, there were positive correlations between the levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and angiogenic factors (VEGF, FGF-basic, sVEGFR-1, and soluble angiopoietin receptor). In the control group, there were no correlations between the levels of the abovementioned parameters. Results of the present study indicate that chronic occupational lead exposure promotes inflammatory processes via induction of pro-inflammatory cytokines, modulates angiogenesis, and elicits interdependencies between the immune response and angiogenic factors.

Folic acid protects against lead acetate-induced hepatotoxicity by decreasing NF-κB, IL-1β production and lipid peroxidation mediataed cell injury

Folic acid plays an important role in cellular metabolic activities. The present study was designed to investigate the protective effect of folic acid against lead acetate-induced hepatotoxicity. Twenty four male Wistar albino rats were randomly divided into four groups, six animals each. Negative control group received the vehicle, positive control group received 1mg/kg folic acid for five consecutive days/week for 4 weeks orally, lead-exposed group received 10mg/kg lead acetate intraperitoneally (IP) for five consecutive days/week for 4 weeks, and lead-treated group received 10mg/kg lead acetate IP and 1mg/kg folic acid orally for five consecutive days/week for 4 weeks concurrently. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ- glutamyltransferase (GGT) were measured. Hepatic total peroxide and interleukin-1β (IL-1β) were also investigated. Histopathological studies using hematoxylin-eosin (H&E) and periodic acid shiff's (PAS) were carried out. The expression of nuclear factor kappa B (NF-κB) was evaluated using immunohistochemistry. Serum AST, ALT and GGT and hepatic total peroxide and IL-1β were significantly increased in lead-exposed group and were positively correlated with hepatic lead level. Moreover, lead-exposed rats showed hydropic degeneration, nuclear vesiculation, high lymphocytic infiltration, depletion of glycogen content and NF-κB expression. Concomitant folic acid administration resulted in a significant alleviation of biochemical and structural alteration-induced by lead. This was associated with reduction of hepatic total peroxide and IL-1β and reduction of NF-κB expression. In conclusion, folic acid protects against lead acetate-induced hepatotoxicity by decreasing NF-κB, IL-1β production and lipid peroxidation mediataed cell injury.

Antagonistic effect of selenium on lead-induced inflammatory injury through inhibiting the nuclear factor-κB signaling pathway and stimulating selenoproteins in chicken hearts

In the chicken model of Pb and Se, Se alleviated Pb-induced the changes of inflammatory factors, selenoproteins, and histology. Se alleviated Pb-induced inflammatory injury through inhibiting NF-κB signaling pathway and stimulating selenoproteins in the chicken hearts.

The Antagonistic Effect of Selenium on Lead-Induced Inflammatory Factors and Heat Shock Proteins mRNA Expression in Chicken Livers

The aim of this study was to investigate the effect of lead (Pb) poisoning on nitric oxide (NO) content, inducible nitric oxide synthase (iNOS) activity, the messenger RNA (mRNA) levels of inflammatory factors (nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), prostaglandin E synthases (PTGEs), and iNOS), heat shock proteins (HSPs) (HSP27, HSP40, HSP60, HSP70, and HSP90), and the antagonistic effect of selenium (Se) on Pb in chicken livers. One hundred eighty 7-day-old male chickens were randomly divided into four groups and were fed commercial diet and drinking water, Na2SeO3-added commercial diet and drinking water, commercial diet and (CH3OO)2Pb-added drinking water, and Na2SeO3-added commercial diet and (CH3OO)2Pb-added drinking water, respectively, for 30, 60, and 90 days. Then, NO content, iNOS activity, and the mRNA levels of NF-κB, TNF-α, COX-2, PTGEs, iNOS, HSP27, HSP40, HSP60, HSP70, and HSP90 were examined in chicken livers. The results showed that Pb poisoning induced NO content, iNOS activity, and mRNA expression of inflammation factors and HSPs in chicken livers. In addition, Se alleviated Pb-induced increase of inflammation factor and HSP expression in chicken livers.

Involvement of L-type Ca²⁺ channel and toll-like receptor-4 in nickel-induced interleukin-8 gene expression

The metal nickel (Ni(2+)) is found everywhere in our daily lives, including coins, costume jewelry, and even nuts and chocolates. Nickel poisoning can cause inflammatory reactions, respiratory diseases, and allergic contact dermatitis. To clarify the mechanism by which nickel induces mediators of inflammation, we used the human acute monocytic leukemia THP-1 cell line as a model. Interleukin (IL)-8 promoter activity as well as gene expression were tested by luciferase assay and real-time polymerase chain reaction. The underlying mechanisms of nickel-induced IL-8 were investigated. We found that nickel induced IL-8 gene expression via the L-type Ca(2+) channel, Toll-like receptor-4 (TRL-4) and nuclear factor NF-κB signal transduction pathways. Nickel activated NF-κB expression through extracellular signal-regulated kinase 1/2 phosphorylation and then increased IL-8 expression. Thus, the L-type Ca(2+) channel and TRL-4 play important roles in nickel-induced inflammatory gene expressions.

Functional role of inorganic trace elements in angiogenesis part III: (Ti, Li, Ce, As, Hg, Va, Nb and Pb)

Many essential elements exist in nature with significant influence on human health. Angiogenesis is vital in developmental, repair, and regenerative processes, and its aberrant regulation contributes to pathogenesis of many diseases including cancer. Thus, it is of great importance to explore the role of these elements in such a vital process. This is third in a series of reviews that serve as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. Here we will review the roles of titanium, lithium, cerium, arsenic, mercury, vanadium, niobium, and lead in these processes. The roles of other inorganic elements in angiogenesis were discussed in part I (N, Fe, Se, P, Au, and Ca) and part II (Cr, Si, Zn, Cu, and S) of these series. The methods of exposure, structure, mechanisms, and potential activities of these elements are briefly discussed. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. These elements can promote and/or inhibit angiogenesis through different mechanisms. The anti-angiogenic effect of titanium dioxide nanoparticles comes from the inhibition of angiogenic processes, and not from its toxicity. Lithium affects vasculogenesis but not angiogenesis. Nanoceria treatment inhibited tumor growth by inhibiting angiogenesis. Vanadium treatment inhibited cell proliferation and induced cytotoxic effects through interactions with DNA. The negative impact of mercury on endothelial cell migration and tube formation activities was dose and time dependent. Lead induced IL-8 production, which is known to promote tumor angiogenesis. Thus, understanding the impact of these elements on angiogenesis will help in development of new modalities to modulate angiogenesis under various conditions.

Function of DNA methyltransferase 3a in lead (Pb(2+) )-Induced Cyclooxygenase-2 gene

Lead ions (Pb(2+) ) are toxic industrial pollutants associated with chronic inflammatory diseases in humans and animals. Previously, we found that Pb(2+) ions induce COX-2 gene expression via the EGF receptor/nuclear factor-κB signal transduction pathway in epidermoid carcinoma cell line A431. In this study, to see whether Pb(2+) ions affect COX-2 expression by epigenetic mechanisms, we looked at the mRNAs of DNA methyltransferases (DNMTs) using real-time PCR of total RNA from these cells. Cells exposed to Pb(2+) had low levels of DNMT3a mRNA, whereas the levels of DNMT1 and DNMT3b mRNAs remained unchanged. Pretreatment of cells with DNMT inhibitor 5-aza-2'-deoxycytidine (5 μM) followed by Pb(2+) (1 μM) significantly increased levels of COX-2 mRNA compared with cells treated with Pb(2+) alone. Overexpression of tumor suppressor gene Rb correlated with an increase in COX-2 mRNA and a decrease in DNMT3a mRNA. Conversely, overexpression of transcription factor E2F1 correlated with a decrease in COX-2 mRNA and an increase in DMNT3a mRNA. Pretreatment with EGFR inhibitors AG1478 and PD153035 significantly limited Pb(2+) -induced reduction in DNMT3a mRNA. In addition, gene knockdown of DNMT3a with short hairpin RNA correlated with increased COX-2 mRNA induced by Pb(2+) . Our findings suggest Pb(2+) ions induce COX-2 expression indirectly by reducing DNMT3a methylation of the COX-2 promoter via transcription factors Rb and E2F1.

Pb²⁺ induced IL-8 gene expression by extracellular signal-regulated kinases and the transcription factor, activator protein 1, in human gastric carcinoma cells

Divalent lead (Pb(2+) ) is a common industrial pollutant epidemiologically associated with gastric cancers. Pb(2+) was found to promote tumorigenesis, which may include interleukin (IL)-8, a pro-inflammatory chemokine that promotes angiogenesis and tumor metastasis. Given that the gastrointestinal tract is a major route of Pb(2+) exposure, we investigated the ability of Pb(2+) to induce IL-8 expression in gastric carcinoma cells and its underlying mechanism. At a concentration of 0.1 μM, Pb(2+) induced IL-8 gene activation in gastric carcinoma AGS cells. Using a IL-8 promoter-deletion analysis, transcription factor activator protein 1 (AP-1) was identified as a necessary component of Pb(2+) -induced IL-8 gene activation. Upregulation of the IL-8 gene was abrogated by the MEK inhibitor, PD98059, and partially suppressed by the epidermal growth factor receptor inhibitors, AG1478 and PD153035. Furthermore, c-Jun protein expression was induced in cells treated with Pb(2+) , and overexpression of c-Jun enhanced Pb(2+) -induced IL-8 activation. Collectively, our findings highlight the pivotal roles of AP-1 and extracellular signal-regulated kinase in signal transduction of Pb(2+) -induced IL-8 gene activation. These molecules may be potential therapeutic targets for Pb(2+) -related inflammation leading to stomach carcinogenesis. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 315-322, 2015.

Pb2+ induces gastrin gene expression by extracellular signal-regulated kinases 1/2 and transcription factor activator protein 1 in human gastric carcinoma cells

Divalent lead ions (Pb(2+) ) are toxic environmental pollutants known to cause serious health problems in humans and animals. Absorption of Pb(2+) from air, water, and food takes place in the respiratory and digestive tracts. The ways in which absorbed Pb(2+) affects cell physiology are just beginning to be understood at the molecular level. Here, we used reverse transcription PCR and Western blotting to analyze cultures of human gastric carcinoma cells exposed to 10 μM lead nitrate. We found that Pb(2+) induces gastrin hormone gene transcription and translation in a time-dependent manner. Promoter deletion analysis revealed that activator protein 1 (AP1) was necessary for gastrin gene transcription in cells exposed to Pb(2+) . MitogIen-activated protein kinase (MAPK)/ERK kinase inhibitor PD98059 suppressed the Pb(2+) -induced increase in messenger RNA. Epidermal growth factor receptor (EGFR) inhibitors AG1478 and PD153035 reduced both transcription and phosphorylation by extracellular signal-regulated kinase (ERK1/2). Cells exposed to Pb(2+) also increased production of c-Jun protein, a component of AP1, and over-expression of c-Jun enhanced activation of the gastrin promoter. In sum, the findings suggest the EGFR-ERK1/2-AP1 pathway mediates the effects of Pb(2+) on gastrin gene activity in cell culture.

The effect of occupational lead exposure on blood levels of zinc, iron, copper, selenium and related proteins

The study objective was to evaluate the effect of occupational lead exposure on blood concentrations of zinc, iron, copper, selenium and proteins related to them, such as transferrin, caeruloplasmin and haptoglobin. The examined group consisted of 192 healthy male employees of zinc-lead works. By the degree of lead exposure, the exposed group was subdivided into three subgroups. The control group was composed of 73 healthy male administrative workers. The markers of lead exposure (blood levels of lead and zinc protoporphyrin) were significantly elevated in the exposed group compared with the control group. Additionally, concentrations of copper and caeruloplasmin were raised. The significant increase in haptoglobin level was observed only in the low exposure group. Selenium levels were significantly decreased, whereas iron, zinc and transferrin levels were unchanged in the exposed group compared with the control group. There were positive correlations between the lead toxicity parameters and the copper and caeruloplasmin levels. In conclusion, the effect of occupational exposure to lead on the metabolism of trace metals appears to be limited. However, significant associations between lead exposure and levels of copper and selenium were shown. Changed levels of positive acute-phase proteins, such as caeruloplasmin and haptoglobin, were also observed.