The role of intracellular calcium in antimony-induced toxicity in cultured cardiac myocytes

Cardiovascular Effects of Environmental Metal Antimony: Redox Dyshomeostasis as the Key Pathogenic Driver

Significance: Cardiovascular diseases (CVDs) are the leading cause of death worldwide, which may be due to sedentary lifestyles with less physical activity and over nutrition as well as an increase in the aging population; however, the contribution of pollutants, environmental chemicals, and nonessential metals to the increased and persistent CVDs needs more attention and investigation. Among environmental contaminant nonessential metals, antimony has been less addressed. Recent Advances: Among environmental contaminant nonessential metals, several metals such as lead, arsenic, and cadmium have been associated with the increased risk of CVDs. Antimony has been less addressed, but its potential link to CVDs is being gradually recognized. Critical Issues: Several epidemiological studies have revealed the significant deleterious effects of antimony on the cardiovascular system in the absence or presence of other nonessential metals. There has been less focus on whether antimony alone can contribute to the pathogenesis of CVDs and the proposed mechanisms of such possible effects. This review addresses this gap in knowledge by presenting the current available evidence that highlights the potential role of antimony in the pathogenesis of CVDs, most likely via antimony-mediated redox dyshomeostasis. Future Directions: More direct evidence from preclinical and mechanistic studies is urgently needed to evaluate the possible roles of antimony in mitochondrial dysfunction and epigenetic regulation in CVDs. Antioxid. Redox Signal. 38, 803-823.

Electrocardiogram abnormalities in antimony exposed workers in the automotive brake lining manufacturing industry: a case report

Background

Antimony is used in catalysts, pesticides, brake systems, pharmaceuticals, and synthetic fire retardants in the plastic, paint, and rubber industries. Accumulation of trivalent antimony compounds in the body can cause cardiotoxic effects and increase the risk of electrocardiogram (ECG) abnormalities and sudden death. Antimony exposure can result in action potential prolongation, causing a cardiac repolarization delay, which appears as QTc prolongation and T-wave abnormalities on the ECG. There are no studies on antimony-associated cardiac toxicity in Korea.

Case presentation

Accordingly, the present study reports cases of ECG abnormalities in workers handling antimony trisulfide at a company located in the Gyeongsangbuk-do region. Nineteen workers employed at an automobile brake lining manufacturer were exposed to antimony trisulfide dust through thermoforming, grinding, and drilling processes. In 2020, the workers were reported to work 12-hour shifts, 5 days a week. The time-weighted average (TWA) of antimony trisulfide exposure measured in workers was 0.0028 mg/m³. Two workers were excluded from the analysis due to pre-existing medical conditions (cardiovascular disease). Of the remaining 17 workers, ECG abnormalities were found in 41% (seven out of 17: four with QTc prolongation and T-wave abnormalities; two with only T-wave abnormalities; and one with only QTc prolongation).

Conclusions

This case report outlines the first few cases in Korea in which potential cardiac toxicity caused by occupational exposure to antimony was identified. However, data regarding cardiac toxicity caused by antimony exposure are still lacking in Korea; thus, additional studies are needed to identify causal relationships.

A comparative study of the typical toxic metals in serum by patients of schizophrenia and healthy controls in China

Toxic metals are ubiquitous environmental pollutants, and their potential risks associated with the development of schizophrenia remain a subject of debate. In this study, we investigated the associations between six typical toxic metals (mercury, lead, chromium, silver, antimony, and uranium) in serum with the risk of schizophrenia using a case-control study design. In total, 109 patients with schizophrenia (cases) and 106 normal subjects (controls) from Shandong Province, China were recruited. Fasting blood samples were collected from all participants, as well as serum samples from the cases before and after medical treatment. The six metals were analyzed by inductively coupled plasma mass spectrometry. Only three metals (antimony, silver and uranium) had acceptable detection rates of >80%. The concentrations of antimony and uranium were significantly higher in the cases than in the controls, while no significant difference for silver. Moreover, the serum concentrations of antimony and uranium were significantly lower after medical treatment. Clear dose-response relationships between serum metal concentrations and the risk of schizophrenia were observed, even after adjusting for potential covariates. This suggests that higher levels of antimony and uranium may be one of the factors associated with an elevated risk of schizophrenia.

Environmental Metals and Cardiovascular Disease in Adults: A Systematic Review Beyond Lead and Cadmium

Published systematic reviews concluded that there is moderate to strong evidence to infer a potential role of lead and cadmium, widespread environmental metals, as cardiovascular risk factors. For other non-essential metals, the evidence has not been appraised systematically. Our objective was to systematically review epidemiologic studies on the association between cardiovascular disease in adults and the environmental metals antimony, barium, chromium, nickel, tungsten, uranium, and vanadium. We identified a total of 4 articles on antimony, 1 on barium, 5 on chromium, 1 on nickel, 4 on tungsten, 1 on uranium, and 0 on vanadium. We concluded that the current evidence is not sufficient to inform on the cardiovascular role of these metals because of the small number of studies. Few experimental studies have also evaluated the role of these metals in cardiovascular outcomes. Additional epidemiologic and experimental studies, including prospective cohort studies, are needed to understand the role of metals, including exposure to metal mixtures, in cardiovascular disease development.

Lipid peroxidation in workers exposed to aluminium, gallium, indium, arsenic, and antimony in the optoelectronic industry

OBJECTIVE

The objective of this study was to investigate whether exposure to aluminum, gallium, indium, arsenic, and antimony induces lipid peroxidation in humans.

METHODS

Whole blood and urine levels of 103 exposed electronic industry workers and 67 referents were analyzed by use of inductively coupled plasma mass spectrometry. Malondialdehyde (MDA), the product of lipid peroxidation, was determined by high-performance liquid chromatography.

RESULTS

The mean plasma MDA level in the 103 workers was significantly higher than that in 67 referents. The levels of MDA in the exposed workers were correlated significantly with the levels of urinary gallium and arsenic.

CONCLUSIONS

Malondialdehyde as an index of lipid peroxidation can be induced by gallium and arsenic exposure. By reducing exposure to these metals, biologic effects such as lipid peroxidation may also be diminished.

Cardiovascular effects of fine and ultrafine particles

Epidemiological studies of the past decades have provided a strong body of evidence that elevated levels of ambient particulate air pollution (PM) are associated with increased cardiovascular and respiratory morbidity and mortality. Exacerbations of ischemic and/or arrhythmic cardiac diseases have been linked to PM exposure. At a workshop held at the GSF- National Center for Environment and Health in November 2003, relevant epidemiological and toxicological data of the past 5 years were compiled and potential biological pathways discussed. Available clinical and experimental evidence lends support to the following mechanisms mediating cardiovascular effects of inhaled ambient particles: (i) pulmonary and/or systemic inflammatory responses inducing endothelial dysfunction, a pro-coagulatory state and promotion of atherosclerotic lesions, (ii) dysfunction of the autonomic nervous system in response to direct reflexes from receptors in the lungs and/or to local or systemic inflammatory stimuli, and (iii) cardiac malfunction due to ischemic responses in the myocardium and/or altered ion-channel functions in myocardial cells. While an increasing number of studies addressing these questions support the notion that PM exposure is associated with cardiovascular effects, these studies at present provide only a fragmentary and at times inconclusive picture of the complex biological pathways involved. The available data are consistent with the occurrence of a systemic inflammatory response and an alteration of autonomic cardiac control, but evidence on endothelial dysfunction, pro-coagulatory states, and PM-related myocardial malfunction is as yet scarce. Further studies are therefore needed to substantiate our current understanding of the pathophysiological links between PM exposure and adverse cardiovascular outcomes.

Antimony-induced cardiomyopathy in guinea-pig and protection by L-carnitine

Antimony (Sb) is the mainstay for the treatment of Leishmaniasis. It has serious, often lethal, cardiovascular side effects. The objective of this study was to examine the effects of Sb treatment upon the electrocardiogram (ECG), myocyte contractility (assessed by monitoring sarcomere length during field stimulation), whole-cell action potential (AP) and calcium current (I(Ca)) of the guinea-pig and to evaluate L-carnitine as a cardioprotective agent. Guinea-pigs received daily injections of either saline, Sb(V), Sb(III), L-carnitine or L-carnitine with Sb(III). Eight lead ECGs were recorded under halothane anaesthesia every 4 days. At the end of each treatment regime, animals were killed and ventricular myocytes were enzymatically isolated. Treatment with Sb(V) for 26 days prolonged the QT interval of the ECG. Treatment with Sb(III) was lethal within 2 days for approximately 50% of the animals. The survivors showed ECG alterations similar to those described in man: T wave flattening and/or inversion, depression of the ST segment, and elongation of RR and QT intervals. Their ventricular myocytes showed impaired contraction responses to changes in stimulus frequency, elongated AP and reduced I(Ca). Combined treatment with L-carnitine and Sb(III) delayed mortality. Prior treatment with L-carnitine followed by combined treatment with L-carnitine and Sb(III) reduced mortality to <10% over 12 days and these animals showed normal ECG. Their myocytes showed normal contractility and AP. It is concluded that L-carnitine has a preventive cardioprotective role against antimony-induced cardiomyopathy. The mechanism of action of L-carnitine may be to counter oxidative stress caused by Sb(III).

Biological monitoring of exposures to aluminium, gallium, indium, arsenic, and antimony in optoelectronic industry workers

The main objective of this study was to investigate aluminum, gallium, indium, arsenic, and antimony exposures on blood and urine levels in the optoelectronic workers. One hundred seventy subjects were enrolled in this cohort study. Whole blood and urine levels were determined by inductively coupled plasma-mass spectrometry. Blood indium and urine gallium and arsenic levels in the 103 workers were significantly higher than that in 67 controls during the follow-up period. In regression models, the significant risk factors of exposure were job title, preventive equipment, Quetelet's index, sex, and education level. The findings of this study suggest that gallium, indium, and arsenic exposure levels may affect their respective levels in blood and urine. The use of clean, preventive equipment is recommended when prioritizing the administration of safety and hygiene in optoelectronics industries.

Induction of stress proteins in rat cardiac myocytes by antimony

The effects of nonlethal concentrations of potassium antimonyl tartrate (PAT) were examined in cultured neonatal rat cardiac myocytes. PAT (5, 10 microM) significantly increased cellular reduced glutathione (GSH) and heme oxygenase activity after 18 h. GSH levels and heme oxygenase activity were increased 2.5- and 5.4-fold, respectively, by 10 microM PAT after 18 h. In addition, total cytochrome P450 levels were decreased by PAT after an 18-h exposure. PAT exposures were associated with the induction of specific stress proteins. Nonlethal concentrations of PAT produced a dose-dependent increase in HO-1, HSP70, and HSP25/27 protein levels but did not increase HSP60 levels. Pretreatment of cardiac myocytes with low concentrations of PAT (0.5-10 microM) protected against a subsequent lethal concentration of PAT (200 microM). This protection was blocked if cells were treated with the protein synthesis inhibitor cycloheximide. Results demonstrate that low concentrations of PAT increase GSH levels and stress protein synthesis, which may be responsible for the protection that low-level PAT exposure offers against the subsequent toxicity of higher concentrations of PAT.

Antimony trichloride induces DNA damage and apoptosis in mammalian cells

Antimony compounds are widely used in various manufacturing and semiconducting industries. Previously, it has been shown that antimony trichloride (SbCl3) elevates sister chromatid exchange (SCE) rates in V79 cells after a 28-h incubation. However, only limited data on its genotoxic effects are available so far. The present results demonstrate that a 4-h exposure to > 50 microM SbCl3 could induce micronuclei (MN) formation in cultured Chinese hamster ovary (CHO-K1) cells, human bronchial epithelial (BES-6) cells and human fibroblasts (HF). The order of sensitivity to SbCl3 determined by Sulforhodamine B (SRB)-staining survival assay is HF > BES-6 cells > CHO-K1 cells, with LD50 values in these cells being approximately 40, 80 and 180 microM, respectively. Apoptosis and DNA fragmentation was not found in cells immediately following 4-h SbCl3 treatment. However, DNA fragmentation was detected in CHO-K1 cells after 4-h SbCl3 treatment and a 16 h or more post incubation in fresh medium by 1.5% agarose gel electrophoresis. The delayed apoptosis was also observed under microscopic examination in HF, BES-6 and CHO-K1 cells after similar treatment protocol. In addition, an increase in calcium accumulation appeared in CHO-K1 cells and HF immediately after a 4-h SbCl3 treatment, or after a 24-h post incubation in fresh medium. The present results provide important genotoxic and cytotoxic information characterizing the cellular changes induced by short-term SbCl3 exposure in rodent and human cells.

Altered Ca2+ mobilization during excitation-contraction in cultured cardiac myocytes exposed to antimony

Industrial exposure and pharmaceutical use of antimony compounds have been linked to altered cardiovascular function and pathology. Antimony compounds induce hypotension, bradycardia, and cardiac arrhythmias, all of which can arise from aberrations in myocyte regulation of intracellular free calcium concentration ([Ca2+]i). To determine if trivalent antimony affects [Ca2+]i during excitation-contraction, we developed an in vitro cardiac myocyte model that was exposed for 24 hr to potassium antimonyl tartrate (PAT) at 0-10 microM. Control myocytes received sodium potassium tartrate. Concentrations of up to 10 microM PAT were without effect on total DNA and protein content of cultures, indicating that PAT exposures were not overtly toxic. However, spontaneous beating rates of myocytes were significantly reduced by 5 and 10 microM PAT. Myocytes were paced by electric field stimulation at 0.5 Hz, and the effect of PAT on [Ca2+]i transients during excitation-contraction was monitored with fura-2. PAT (2-8 microM) significantly reduced systolic [Ca2+]i in a concentration-dependent fashion, but was without effect on diastolic [Ca2+]i or on the first derivative of the transient rise (d[Ca2+]i/dt). Myocytes from control cells responded to epinephrine (10(-8)-10(-5) m) in concentration-dependent fashion with elevated systolic [Ca2+]i and an increase in the rate of decay of transients. In PAT-exposed myocytes, the systolic response was blunted while the decay rate was enhanced. PAT-exposed cells also exhibited a reduced basal [Ca2+]i when depolarized by 90 mm KCl and a reduced caffeine-releasable Ca2+ pool of the sarcoplasmic reticulum. Both control and PAT-treated cells responded to ryanodine in a comparable fashion. Results indicate that a nonlethal exposure to PAT reduces Ca2+ availability during excitation-contraction. Decreased influx of Ca2+ across the sarcolemma and enhanced removal of Ca2+ appear to be responsible.