Lead-dependent effects on arachidonic acid accumulation and the proliferation of vascular smooth muscle

Association between Mixed Heavy Metal Exposure and Arterial Stiffness, with Alkaline Phosphatase Identified as a Mediator

Elevated arterial stiffness has been associated with exposure to heavy metals such as lead (Pb) and cadmium (Cd). However, the collective impact of multiple metals and the underlying mechanisms are not fully elucidated. The purpose of this study was to assess the combined effects of exposure to nine heavy metals on arterial stiffness and explore whether serum alkaline phosphatase (ALP) acts as a mediator in this relationship. In the retrospective analysis, data from 8,700 participants were retrieved from the National Health and Nutrition Examination Survey (NHANES) spanning from 1999 to 2018. Arterial stiffness was measured by estimated pulse wave velocity (ePWV). The cumulative impact of exposure to multiple metals was examined using adaptive elastic-net, environmental risk score, weighted quantile sum regression, and quantile g-computation. Additionally, mediation analysis was conducted to explore the potential mediating role of serum ALP. We found that combined exposure to multiple metals was consistently associated with elevated ePWV, with Ba, Pb, and Sb exhibiting the greatest contributions. Notably, serum ALP partially mediated the associations between individual (Pb, Sb) and mixed metal exposure with ePWV, with mediation proportions at 10.76% for Pb, 18.22% for Sb, and 11.07% for mixed metal exposure. In conclusion, this study demonstrates a clear association between exposure to heavy metals, either individually or in combination, and heightened arterial stiffness. Furthermore, the findings suggest that serum ALP activity may act as a mediator in these relationships.

Insight into the effect of a heavy metal mixture on neurological damage in rats through combined serum metabolomic and brain proteomic analyses

The heavy metals lead (Pb), cadmium (Cd), and mercury (Hg) that cause neurocognitive impairment have been extensively studied. These elements typically do not exist alone in the environment; they are often found with other heavy metals and can enter the body through various routes, thereby impacting health. Our previous research showed that low Pb, Cd, and Hg levels cause neurobehavioral impairments in weaning and adult rats. However, little is known about the biomarkers and mechanisms underlying Pb, Cd, and Hg mixture-induced neurological impairments. A combined analysis of metabolomic and proteomic data may reveal heavy metal-induced alterations in metabolic and protein profiles, thereby improving our understanding of the molecular mechanisms underlying heavy metal-induced neurological impairments. Therefore, brain tissue and serum samples were collected from rats exposed to a Pb, Cd, and Hg mixture for proteomic and metabolomic analyses, respectively. The analysis revealed 363 differential proteins in the brain and 206 metabolites in serum uniquely altered in the Pb, Cd, and Hg mixture exposure group, compared to those of the control group. The main metabolic impacted pathways were unsaturated fatty acids biosynthesis, linoleic acid metabolism, phenylalanine metabolism, and tryptophan metabolism. We further identified that the levels of arachidonic acid (C20:4 n-3) and, adrenic acid (C22:4 n-3) were elevated and that kynurenic acid (KA) and quinolinic acid (QA) levels and the KA/QA ratio, were decreased in the group exposed to the Pb, Cd, and Hg mixture. A joint analysis of the proteome and metabolome showed that significantly altered proteins such as LPCAT3, SLC7A11, ASCL4, and KYAT1 may participate in the neurological impairments induced by the heavy metal mixture. Overall, we hypothesize that the dysregulation of ferroptosis and kynurenine pathways is associated with neurological damage due to chronic exposure to a heavy metal mixture.

Alteration of hepato-lipidomic homeostasis in A/J mice fed an environmentally relevant PFAS mixture

In the present study, we have investigated liver lipid homeostasis and corresponding changes in transcript and functional product levels in A/J mice exposed to environmental relevant concentration of per- and polyfluoroalkyl substances (PFAS) mixture. Mice were fed environmentally relevant concentrations of a PFAS mixture during a period of 10 weeks. The concentrations of the 8 individual PFAS in the mixture were chosen based on measured concentrations in earthworms at a Norwegian skiing area. Our data show high liver accumulation of ∑PFAS in exposed mice, which paralleled significant elevation in body weight and hepatosomatic index (HSI) of male mice. UPC2 -MS/MS analysis in both positive and negative mode, respectively, indicated significant differences between control and exposure groups in the liver of exposed mice. Principal component analysis (PCA) of the features revealed separation of control and exposure groups in both sexes. From the significantly differential 207 lipids, only 72 were identified and shown to belong to eight different lipid classes. PCA of fatty acids (FAs) profile showed a clear separation between control and PFAS exposure groups in both female and male mice, with differential abundant levels of 5 and 4 hydrolyzed FAs, respectively. Transcript and protein analysis of genes associated with lipid homeostasis (ppar-α and β, lxr-α and β, rxr, fasn and srebp) showed that PFAS exposure produced sex- and individual response related alterations. Glutathione reductase (Gr) activity showed exposure-related changes in both female and male mice, compared with controls. Overall, the present study has demonstrated changes in lipid metabolism after PFAS exposure, showing that PFAS accumulation in the liver resulted to hepatotoxic effects, potential interference with membrane lipid profile and homeostasis, and oxidative stress. Given the structural similarity with FAs, interaction between PFAS and nuclear receptors such as PPARs may have severe consequences for general health and physiology in exposed animals and humans.

Low-Level Metal Contamination and Chelation in Cardiovascular Disease-A Ripe Area for Toxicology Research

Cardiovascular disease remains the leading cause of death worldwide. In spite of cardiovascular prevention, there is residual risk not explicable by traditional risk factors. Metal contamination even at levels previously considered safe in humans may be a potential risk factor for atherosclerosis. This review examines evidence that 2 metals, lead, and cadmium, demonstrate sufficient toxicological and epidemiologic evidence to attribute causality for atherosclerotic disease. Basic science suggests that both metals have profound adverse effects on the human cardiovascular system, resulting in endothelial dysfunction, an increase in inflammatory markers, and reactive oxygen species, all of which are proatherosclerotic. Epidemiological studies have shown both metals to have an association with cardiovascular disease, such as peripheral arterial disease, ischemic heart disease, and cardiovascular mortality. This review also examines edetate disodium-based chelation as a possible pharmacotherapy to reduce metal burden in patients with a history of cardiovascular disease and thus potentially reduce cardiovascular events.

Retrospection on the Role of Soluble Guanylate Cyclase in Parkinson's Disease

Soluble guanylate cyclase (sGC) is an important transducing enzyme of cyclic guanosine monophosphate (cGMP) signaling pathway in striatum which has been considered as a potential target for the treatment of Parkinson's disease. Etiology of Parkinson's disease is multifactorial, finally resulting in abnormal proteinopathies causing degeneration of nigrostriatal pathways. Understanding the pathological basis of Parkinson's disease at molecular level is still an achievable target for the researchers and clinical practitioners. sGCs may be one of the causative factors resulting in Parkinson's disease due to glutamate toxicity or other event. This review presents the literature from articles of past five decades nearly as still this enzyme protein and its role in Parkinson's disease is not that clearly understood or presented till date. Recent interventions of this protein inhibition in the treatment of Parkinson's disease preclinically gave a chance to review the literature about this enzyme and its correlation with factors causing Parkinson's disease. We explored literature using PubMed and EMBASE for the role of sGC in Parkinson's disease. Databases were searched using the following terms: Parkinson's disease, neurotoxins, guanylate cyclase, sGC-cGMP pathway, and neurodegeneration. This review listed out the factors that have probability for stimulating sGC which already have been listed as a neurotoxins causing Parkinson's disease.

Real-time Assay of Toxic Lead in In Vivo Living Plant Tissue

A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL(-1)-20 mgL(-1) with preconcentration time of 100, 200, and 400 sec at the concentration of mgL(-1), μgL(-1), and ngL(-1), respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 μgL(-1) under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL(-1) (2.6 × 10(-8) M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses.

Changes in morphometry and association between whole-body fatty acids and steroid hormone profiles in relation to bioaccumulation patterns in salmon larvae exposed to perfluorooctane sulfonic or perfluorooctane carboxylic acids

In the present study, we have used salmon embryos whose continuous exposure to waterborne PFOA or PFOS at 100 μg/L started as freshly fertilized eggs, and lasted for a total of 52 days. PFOS and PFOA were dissolved in methanol (carrier vehicle) whose concentration never exceeded 0.01% of total tank volume. Samples were collected at day 21, 28, 35, 52, 49 and 56 after the start of the exposure. Note that days 49 and 56 represent end of exposure and 1 week after a recovery period, respectively. Tissue bioaccumulations were determined by HPLC/MS/MS, steroid hormones, fatty acids (FAs) and lipids were determined by GC-MS, while mRNA expression levels of genes were determined by qPCR in whole body homogenate. We observed that PFOS and PFOA showed a steady increase in whole body burden during the exposure period, with a slight decrease after the recovery period. Calculated somatic indexes showed that PFOA produced increases in heart-, thymus-, liver- and kidney somatic indexes (HSI, TSI, LSI and KSI). PFOA and PFOS exposure produced significant decreases in whole body dehydroepiandrosterone (DHEA), estrone and testosterone at sampling day 21 and a strong increase of cortisol and cholesterol at the end of recovery period (day 56). PFOA and PFOS effects differed with DHEA and estrone. While PFOS decreased DHEA levels, PFOA produced an increase at day 49, and while PFOS decreased estrone, PFOA produced a slight increase at day 56. We observed changes in FA composition that predominantly involved increases in FA methyl esters (FAMEs), mono- and poly-unsaturated FA (MUFA and PUFA) and a decrease in n-3/n-6 PUFA ratio by both PFOA and PFOS. Particularly, an increase in - pentadecenoic MUFA (15:1), two n-3 PUFAs α-linolenic acid [ALA: 18:3 n3] and eicosapentaenoic acid [EPA: 20:5 n-3] and n-6 PUFA: arachidonic acid [ARA: 20:4 n6], docosapentaenoic acid (DPA) by PFOA and PFOS were observed. These effects were associated with changes in mRNA expression of FA elongase (FAE), Δ5-desaturase (FAD5) and Δ6-desaturase (FAD6) genes. In summary, the changes in hormonal and FA profiles may represent cellular and/or physiological adaptation to continuous PFOS and PFOA exposure by increasing membrane fluidity, and/or overt developmental effects. The present findings provide some potential insights and basis for a better understanding on the possible mechanisms of PFCs toxicity in fish.

Impaired endothelial function assessed by flow-mediated vasodilatation in workers occupationally exposed to lead

The aim of the study was to examine endothelial function in workers occupationally exposed to lead by means of FMD (flow-mediated dilatation). 44 men professionally exposed to lead, smelters and refiners, employees working at copper smelter and control group of 41 healthy men were enrolled into the study. Within the group of men occupationally exposed to lead the absolute increase in diameter after ischaemia (BAD, brachial artery diameter) and flow-mediated dilation were statistically less significant when compared to those of the control group. There was a negative linear correlation between FMD and lead concentration in copper smelters (r=-0.64). Multivariate backward step-wise regression analysis showed that blood lead concentration in copper smelters independently influenced the impairment of endothelial function expressed as decreased FMD value. In conclusion, results of our study suggest that endothelial function assessed by flow-mediated dilatation was impaired in workers occupationally exposed to lead.

Mechanisms of lead-induced hypertension and cardiovascular disease

Lead is a ubiquitous environmental toxin that is capable of causing numerous acute and chronic illnesses. Population studies have demonstrated a link between lead exposure and subsequent development of hypertension (HTN) and cardiovascular disease. In vivo and in vitro studies have shown that chronic lead exposure causes HTN and cardiovascular disease by promoting oxidative stress, limiting nitric oxide availability, impairing nitric oxide signaling, augmenting adrenergic activity, increasing endothelin production, altering the renin-angiotensin system, raising vasoconstrictor prostaglandins, lowering vasodilator prostaglandins, promoting inflammation, disturbing vascular smooth muscle Ca(2+) signaling, diminishing endothelium-dependent vasorelaxation, and modifying the vascular response to vasoactive agonists. Moreover, lead has been shown to cause endothelial injury, impede endothelial repair, inhibit angiogenesis, reduce endothelial cell growth, suppress proteoglycan production, stimulate vascular smooth muscle cell proliferation and phenotypic transformation, reduce tissue plasminogen activator, and raise plasminogen activator inhibitor-1 production. Via these and other actions, lead exposure causes HTN and promotes arteriosclerosis, atherosclerosis, thrombosis, and cardiovascular disease. In conclusion, studies performed in experimental animals, isolated tissues, and cultured cells have provided compelling evidence that chronic exposure to low levels of lead can cause HTN, endothelial injury/dysfunction, arteriosclerosis, and cardiovascular disease. More importantly, these studies have elucidated the cellular and molecular mechanisms of lead's action on cardiovascular/renal systems, a task that is impossible to accomplish using clinical and epidemiological investigations alone.

Influence of lead (Pb2+) on the reactions of in vitro cultured rat aorta to 5-hydroxytryptamine

Although several studies demonstrated that lead induced abnormal vascular responses in low level lead exposed animals, investigations of the direct effects of lead on blood vessels are limited. In this study we tested the hypothesis that lead was able to directly affect the contractile reactivities of vessels. Male Wistar rat aortae were removed and cultured in PMRI 1640 with 1 ppm lead acetate for 0.5, 6, 12, 24 and 48 h, and then their responses to norepinephrine bitartrate (NE) and serotonin (5-hydroxytryptamine, 5-HT) were examined. The contractile responses to 5-HT of lead exposed aortae were significantly increased when the aortae were cultured for 24 and 48 h. Denudation of endothelium was able to abolish the increased contractile response completely. Diphenyleneiodonium (DPI), an inhibitor of the NAD(P)H oxidase, could abolish the increased contractile response to 5-HT. However, Vitamin C (VC) enhanced the contractile response of both groups to higher dosages of 5-HT. The expression of 5-HT(2B) receptor was not significantly altered by incubation with 1 ppm lead for 24 h. These data suggest that exposure to low levels of lead can directly increase the contraction of aorta to 5-HT. This effect is endothelium dependent, which is not mediated by increased expression of the 5-HT 2B receptor. The increased contraction to 5-HT may be related to increased production of superoxide (O2*-) induced by lead exposure.