Contemporary Comprehensive Review on Arsenic-Induced Male Reproductive Toxicity and Mechanisms of Phytonutrient Intervention

Oral arsenite exposure induces inflammation and apoptosis in pulmonary tissue: acute and chronic evaluation in young and adult mice

Inorganic arsenic is a well-known environmental toxicant, and exposure to this metalloid is strongly linked with severe and extensive toxic effects in various organs including the lungs. In the present study, we aimed to investigate the acute and chronic effects of arsenite exposure on pulmonary tissue in young and adult mice. In brief, young and adult female Balb/C mice were exposed to 3 and 30 ppm arsenite daily via drinking water for 30 and 90 days. Subsequently, the animals were sacrificed and various histological and immunohistochemistry (IHC) analyses were performed using lung tissues. Our findings showed arsenite was found to cause dose-dependent pathological changes such as thickening of the alveolar septum, inflammatory cell infiltrations and lung fibrosis in young and adult mice. In addition, arsenite exposure significantly increased the expression of inflammatory markers NF-κB and TNF-α, indicating that arsenite-exposed mice suffered from severe lung inflammation. Moreover, the IHC analysis of fibrotic proteins demonstrated an increased expression of TGF-β1, α-SMA, vimentin and collagen-I in the arsenite-exposed mice compared to the control mice. This was accompanied by apoptosis, which was indicated by the upregulated expression of caspase-3 in arsenite-exposed mice compared to the control. Adult mice were generally found to be more prone to arsenite toxicity during chronic exposure relative to their younger counterparts. Overall, our findings suggest that arsenite in drinking water may induce dose-dependent and age-dependent structural and functional impairment in the lungs through elevating inflammation and fibrotic proteins.

Reproductive and Developmental Effects of Sex-Specific Chronic Exposure to Dietary Arsenic in Zebrafish (Danio rerio)

The present study investigated the reproductive and developmental effects of sex-specific chronic exposure to dietary arsenic in zebrafish. Adult zebrafish (Danio rerio) were exposed to environmentally realistic doses of arsenic via diet [0 (control; no added arsenic), 30 (low), 60 (medium), and 100 (high) μg/g dry weight, as arsenite] for 90 days. Following exposure, arsenic-exposed females from each dietary treatment were mated with control males, and similarly, arsenic-exposed males from each dietary treatment were mated with control females. In females, arsenic exposure resulted in a dose-dependent decrease in reproductive performance (fecundity, fertilization success, and hatching success). Moreover, a dose-dependent increase in developmental toxicity (larval deformities and larval mortality) was observed with maternal exposure to arsenic. In contrast, in males, arsenic exposure also induced similar reproductive and developmental toxicity; however, the adverse effects were mainly evident only in the medium and high dietary arsenic treatment groups. We also examined the sex-specific effects of dietary arsenic exposure on the expression of genes that regulate the hypothalamus-pituitary-gonadal-liver (HPG-L) axis in fish. The gene expression results indicated the downregulation of HPG-L axis genes in females irrespective of the arsenic treatment dose; however, the reduced expression of HPG-L axis genes in males was recorded only in the medium and high arsenic treatment groups. These observations suggest that chronic arsenic exposure in either females or males causes reproductive and developmental toxicity in zebrafish. However, these toxic effects are markedly higher in females than in males. Our results also suggest that arsenic can act as an endocrine disruptor and mediate reproductive and developmental toxicity by disrupting the HPG-L axis in zebrafish.

n-Butanol fraction of moringa seed attenuates arsenic intoxication by regulating the uterine inflammatory and apoptotic pathways

The adverse effects of arsenic-chelating drugs make it essential to replace invasive chelating therapy with non-invasive oral therapy for arsenic poisoning. The goal of the current investigation was to determine whether the uterine damage caused by arsenization could be repaired by the n-butanol fraction of Moringa oleifera seed (NB). The rats were orally administered with arsenic (10 mg/kg BW) for the initial 8 days, followed by NB (50 mg/kg) for the next 8 days without arsenic. The probable existence of different components in NB was evaluated by HPLC-MS. Pro and anti-inflammatory indicators were assessed by RT-PCR and western blot. ESR-α was detected via immunostaining. Arsenic-exposed rats had significantly increased lipid peroxidation and decreased antioxidant enzyme activity, which were markedly reduced after NB treatment. Weaker ESR-α expression and distorted uterine histomorphology following arsenication were retrieved significantly by NB. Meaningful restoration by NB was also achieved for altered mRNA and protein expression of various inflammatory and apoptotic indicators. Molecular interaction predicted that glucomoringin and methyl glucosinolate of moringa interact with the catalytic site of caspase-3 in a way that limits its activity. However, NB was successful in restoring the arsenic-mediated uterine hypofunction. The glucomoringin and methyl glucosinolate present in n-butanol fraction may play a critical role in limiting apoptotic event in the arsenicated uterus.

hnRNPA2B1 represses the disassembly of arsenite-induced stress granules and is essential for male fertility

Although the composition and assembly of stress granules (SGs) are well understood, the molecular mechanisms underlying SG disassembly remain unclear. Here, we identify that heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1) is associated with SGs and that its absence specifically enhances the disassembly of arsenite-induced SGs depending on the ubiquitination-proteasome system but not the autophagy pathway. hnRNPA2B1 interacts with many core SG proteins, including G3BP1, G3BP2, USP10, and Caprin-1; USP10 can deubiquitinate G3BP1; and hnRNPA2B1 depletion attenuates the G3BP1-USP10/Caprin-1 interaction but elevates the G3BP1 ubiquitination level under arsenite treatment. Moreover, the disease-causing mutation FUSR521C also disassembles faster from SGs in HNRNPA2B1 mutant cells. Furthermore, knockout of hnRNPA2B1 in mice leads to Sertoli cell-only syndrome (SCOS), causing complete male infertility. Consistent with this, arsenite-induced SGs disassemble faster in Hnrnpa2b1 knockout (KO) mouse Sertoli cells as well. These findings reveal the essential roles of hnRNPA2B1 in regulating SG disassembly and male mouse fertility.

Heavy Metal Levels in Males With Idiopathic Hypogonadotropic Hypogonadism

INTRODUCTION

The toxic effects of heavy metals on biological systems are being investigated with increasing interest day by day. Our purpose was to investigate heavy metals such as aluminum (Al), cadmium (Cd), arsenic (As), lead (Pb), and nickel (Ni) in males with idiopathic hypogonadotropic hypogonadism (IHH) and to determine whether there is a relationship between heavy metals and testosterone levels.

METHODS

Twenty-six male patients with IHH aged 18-50 and 22 healthy males aged 21-50 admitted to the Outpatient Department of Endocrinology for follow-up were enrolled. BMIs were calculated by measuring the height and weight of all participants. Al, Cd, As, Pb, and Ni levels were measured and compared between groups. Testosterone levels were measured to investigate whether there was a correlation with heavy metal levels.

RESULTS

Al, Cd, As, Pb, and Ni levels were statistically higher in the patient group compared to the control group (p<0.001). A moderately strong significant negative correlation was detected between the patients' testosterone and As levels (p=0.001, r=-0.609, R2=0.371). Decreased As and Cd levels were observed as the patients' ages increased (p=0.013, r=-0.471).

CONCLUSION

Heavy metals might play potential roles in IHH. We hope that investigating heavy metal levels in IHH and adding toxicity-preventive treatments to hormonal therapies will be beneficial in the multifaceted management of the disease in clinical practice.

Casein and pea enriched high-protein diet attenuates arsenic provoked apoptosis in testicles of adult rats

Arsenic toxicity is a major health issue that also threats male reproductive system leading to impairment of fertility. The antioxidant capacity of casein and pea enriched formulated high-protein diet (FHPD) is found to be effective in different toxicity management. The present study was endeavored to investigate the mitigatory aspect of FHPD on arsenic stimulated testicular apoptosis. Adult male rats were maintained on either normal diet as control (Gr I, n = 8) and arsenic (As2O3) treated at a dose of 3 mg/kg/rat/day (Gr II, n = 8) or on isocaloric FHPD as supplemented (Gr III, n = 8) with same dose of arsenic for 30 consecutive days. Testicular histomorphometry, spermatokinetics, testicular functional marker enzymes, serum gonadotrophins, oxidative stress markers, testicular deoxyribonucleic acid (DNA) damage, and apoptosis markers were evaluated to assess the reprotoxicity of arsenic and subsequent protection by FHPD. FHPD protected the histopathological alterations and also restored normal spermatogenesis. Altered enzymatic activities of testicular functional markers like lactate dehydrogenase, γ-glutamyl transferase, acid phosphatase, and alkaline phosphatase were also regularized. FHPD also reinstated the normal level of follicle stimulating hormone (FSH), luteinising hormone (LH), and also normalized the enzymatic activities of testicular glutathione peroxidase and glutathione reductase. Testicular DNA damage was also prevented by FHPD supplementation. Testicular apoptosis marked by the altered messenger ribonucleic acid and protein expression of apoptotic markers like Bax, Bcl-2, caspase 9, and caspase 3 were also attenuated upon FHPD supplementation along with diminution of arsenic accumulation in testicular tissues. FHPD not only mitigated the adverse effects of arsenic induced gonadotoxicity but also helped in sustaining the normal reproductive functions.

The Polymorphisms in GSTO Genes (GSTO1 rs4925, GSTO2 rs156697, and GSTO2 rs2297235) Affect the Risk for Testicular Germ Cell Tumor Development: A Pilot Study

Members of the omega class of glutathione transferases (GSTs), GSTO1, and GSTO2, catalyze a range of reduction reactions as a part of the antioxidant defense system. Polymorphisms of genes encoding antioxidant proteins and the resultant altered redox profile have already been associated with the increased risk for testicular germ cell cancer (GCT) development. The aim of this pilot study was to assess the individual, combined, haplotype, and cumulative effect of GSTO1rs4925, GSTO2rs156697, and GSTO2rs2297235 polymorphisms with the risk for testicular GCT development, in 88 patients and 96 matched controls, through logistic regression models. We found that carriers of the GSTO1*C/A*C/C genotype exhibited an increased risk for testicular GCT development. Significant association with increased risk of testicular GCT was observed in carriers of GSTO2rs2297235*A/G*G/G genotype, and in carriers of combined GSTO2rs156697*A/G*G/G and GSTO2rs2297235*A/G*G/G genotypes. Haplotype H7 (GSTO1rs4925*C/GSTO2rs2297235*G/GSTO2rs156697*G) exhibited higher risk of testicular GCT, however, without significant association (p > 0.05). Finally, 51% of testicular GCT patients were the carriers of all three risk-associated genotypes, with 2.5-fold increased cumulative risk. In conclusion, the results of this pilot study suggest that GSTO polymorphisms might affect the protective antioxidant activity of GSTO isoenzymes, therefore predisposing susceptible individuals toward higher risk for testicular GCT development.

Chronic dietary exposure to arsenic at environmentally relevant concentrations impairs cognitive performance in adult zebrafish (Danio rerio) via oxidative stress and dopaminergic dysfunction

The current study was designed to evaluate the effects of chronic dietary arsenic exposure on the cognitive performance of adult zebrafish and uncover probable pathways by which arsenic mediates such neurotoxic effects. Adult zebrafish were treated with 3 different dietary arsenic concentrations (30, 60, and 100 μg/g dry weight (dw), as arsenite) in addition to control for 60 days. A latent learning paradigm, which employs a complex maze, was used to assess the cognitive performance of fish. Our results demonstrated that dietary treatment with arsenic, especially at medium (60 μg/g dw) and high (100 μg/g dw) exposure dose levels, significantly impaired the performance of fish in various latent learning tasks evaluated in the present study. Concomitant with cognitive dysfunction, chronic dietary exposure to arsenic was also found to increase arsenic accumulation and dopamine levels, and induce oxidative stress (reduced thiol redox, increased lipid peroxidation and expression of antioxidant enzyme genes) in the brain of zebrafish in a dose-dependent manner. Dopaminergic system in the brain is known to play a critical role in regulating cognitive behaviours in fish, and our observations suggested that chronic dietary treatment with medium and high arsenic doses leads to significant alterations in the expression of genes involved in dopamine signalling (dopamine receptors), synthesis (thyroxine hydroxylase) and metabolism (monoamine oxidase) in the zebrafish brain. Moreover, we also recorded significant downregulation of genes such as the brain-derived neurotrophic factor (BDNF) and ectonucleotidases (entpd2_mg, entpd2_mq, and 5'-nucleotidase), which are critical for learning and memory functions, in the zebrafish brain following chronic dietary exposure to arsenic. Overall, the present study suggests that chronic environmentally relevant dietary exposure to arsenic can impair the cognitive performance in zebrafish, essentially by inducing oxidative stress and disrupting the dopaminergic neurotransmission in the brain.

The interplay of arsenic, silymarin, and NF-ĸB pathway in male reproductive toxicity: A review

Arsenic toxicity is one of the most trending reasons for several malfunctions, particularly reproductive toxicity. The exact mechanism of arsenic poisoning is a big question mark. Exposure to arsenic reduces sperm count, impairs fertilization, and causes inflammation and genotoxicity through interfering with autophagy, epigenetics, ROS generation, downregulation of essential protein expression, metabolite changes, and hampering several signaling cascades, particularly by the alteration of NF-ĸB pathway. This work tries to give a clear idea about the different aspects of arsenic resulting in male reproductive complications, often leading to infertility. The first part of this article explains the implications of arsenic poisoning and the crosstalk of the NF-ĸB pathway in male reproductive toxicity. Silymarin is a bioactive compound that exerts anti-cancer and anti-inflammatory properties and has demonstrated hopeful outcomes in several cancers, including colon cancer, breast cancer, and skin cancer, by downregulating the hyperactive NF-ĸB pathway. The next half of this article thus sheds light on silymarin's therapeutic potential in inhibiting the NF-ĸB signaling cascade, thus offering protection against arsenic-induced male reproductive toxicity.