Endoplasmic reticulum stress responses and epigenetic alterations in arsenic carcinogenesis

Arsenic is a well-known human carcinogen whose environmental exposure via drinking water, food, and air impacts millions of people across the globe. Various mechanisms of arsenic carcinogenesis have been identified, ranging from damage caused by excessive production of free radicals and epigenetic alterations to the generation of cancer stem cells. A growing body of evidence supports the critical involvement of the endoplasmic stress-activated unfolded protein response (UPR) in promoting as well as suppressing cancer development/progression. Various in vitro and in vivo models have also demonstrated that arsenic induces the UPR via activation of the PERK, IRE1α, and ATF6 proteins. In this review, we discuss the mechanisms of arsenic-induced endoplasmic reticulum stress and the role of each UPR pathway in the various cancer types with a focus on the epigenetic regulation and function of the ATF6 protein. The importance of UPR in arsenic carcinogenesis and cancer stem cells is a relatively new area of research that requires additional investigations via various omics-based and computational tools. These approaches will provide interesting insights into the mechanisms of arsenic-induced cancers for prospective target identification and development of novel anti-cancer therapies.

Arsenic and polystyrene-nano plastics co-exposure induced testicular toxicity: Triggers oxidative stress and promotes apoptosis and inflammation in mice

Co-existing of polystyrene-nano plastics (PSNPs) and arsenic (As) in the environment caused a horrendous risk to human health. However, the potential mechanism of PSNPs and As combination induced testicular toxicity in mammals has not been elucidated. Therefore, we first explore the testicular toxicity and the potential mechanism in male Kunming mice exposed to As or/and PSNPs. Results revealed that compared to the As or PSNPs group, the combined group showed more significant testicular toxicity. Specifically, As and PSNPs combination induced irregular spermatozoa array and blood-testis barrier disruption. Simultaneously, As and PSNPs co-exposure also exacerbated oxidative stress, including increasing the MDA content, and down-regulating expression of Nrf-2, HO-1, SOD-1, and Trx. PSNPs and As combination also triggered testicular apoptosis, containing changes in apoptotic factors (P53, Bax, Bcl-2, Cytc, Caspase-8, Caspase-9, and Caspase-3). Furthermore, co-exposed to As and PSNPs aggravated inflammatory damage characterized by targeted phosphorylation of NF-κB and degradation of I-κB. In summary, our results strongly confirmed As + PSNPs co-exposure induced the synergistic toxicity of testis through excessive oxidative stress, apoptosis, and inflammation, which could offer a new sight into the mechanism of environmental pollutants co-exposure induced male reproductive toxicity.

Alternations of Fertility Parameters by Graded Dose of Inorganic Arsenic in Adult Male White Pekin Ducks

A significant health issue, reproductive toxicity is mostly linked to exposure to various environmental heavy metals. A pervasive toxin that occurs naturally in the environment is arsenic (As). This research was done to determine the effects of various doses of inorganic As supplements on the reproductive organs of adult male white Pekin ducks. A total of 240 numbers of 14-days-old male white Pekin ducks were weighed and randomly assigned into 4 experimental groups with six replicates (10 ducklings in each replicate). The experimental groups were as follows: (T-1) basal diet along with normal drinking water (control group); (T-2 to T-4) basal diet along with As in the form of sodium-meta-arsenite at 7, 14, and 28 ppm of drinking water respectively. The results showed reduction in body weight and testicular weight, disruption of spermatogenesis, reduction in follicular-stimulating hormone (FSH), leutinizing hormone (LH), and testosterone levels and histopathological alterations as compared to control. Additionally, there was not only a significant decrease in various antioxidant parameters in testis tissue, like catalase (CAT), reduced glutathione (GSH), super oxide dismutase (SOD), and ferric-reducing antioxidant power (FRAP), but also a significant increase in oxidative parameters of testis like lipid peroxidation (LPO), myloperoxidase (MPO), nitric oxide (NO), and super oxide anion radical (O2-) in As-treated groups, in comparison with T-1. A significantly higher level of As content in testis was observed in all the 3 As-treated groups, with highest level recorded in T-4 birds. Besides that, there was upregulation of nuclear factor kappa B (NF-κB), heat shock proteins (Hsps) and pro-inflammatory cytokines like interlukin (IL) series, i.e., IL-2, IL-6, IL-18, IL-1β and tumor necrosis factor- α (TNF-α) levels, whereas anti-inflammatory parameters like IL-4 and IL-10 levels showed downregulation in testis of As-treated groups. Together, these findings provide deeper understandings of the roles played by oxidative stress, NF-κB and Hsps in the progression of testicular injury, which may help to explain how the As induced male sterility, in ducks, due to exposure.

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.

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

Arsenic (As) is a poisonous metalloid that is toxic to both humans and animals. Drinking water contamination has been linked to the development of cancer (skin, lung, urinary bladder, and liver), as well as other disorders such as diabetes and cardiovascular, gastrointestinal, neurological, and developmental damage. According to epidemiological studies, As contributes to male infertility, sexual dysfunction, poor sperm quality, and developmental consequences such as low birth weight, spontaneous abortion, and small for gestational age (SGA). Arsenic exposure negatively affected male reproductive systems by lowering testicular and accessory organ weights, and sperm counts, increasing sperm abnormalities and causing apoptotic cell death in Leydig and Sertoli cells, which resulted in decreased testosterone synthesis. Furthermore, during male reproductive toxicity, several molecular signalling pathways, such as apoptosis, inflammation, and autophagy are involved. Phytonutrient intervention in arsenic-induced male reproductive toxicity in various species has received a lot of attention over the years. The current review provides an in-depth summary of the available literature on arsenic-induced male toxicity, as well as therapeutic approaches and future directions.

Gallic acid ameliorates sodium arsenite-induced renal and hepatic toxicity in rats

Chronic exposure to toxic inorganic arsenic results in the adverse health effects including skin lesions, cardiovascular diseases, diabetes, neurological disorders, and liver and kidney diseases. Gallic acid (GA) is an important phenolic compound, which could protect different tissues from oxidative stress induced damage. The present study investigated effects of GA against sodium arsenite (SA)-induced renal and hepatic toxicity. Thirty-five rats were randomly divided in to five groups; group 1 was treated with normal saline (2 ml/kg/day, p.o.; for 21 days); group 2 was exposed to SA (10 mg/kg/day, p.o.; for 14 days); groups 3 and 4 were treated with GA (10 and 30 mg/kg/day, respectively; for 7 days) prior to exposure to SA, and treatment was continued up to 21 days in parallel with SA administration; group 5 was treated with GA (30 mg/kg/day, p.o.; for 21 days). The level of MDA, IL-1β, NO and glutathione (GSH) and the activity of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were evaluated in kidney and liver tissues. Histopathological parameters and serum levels of ALT, AST, ALP, Cr and BUN were also assessed. Treatment with GA remarkably improved SA-induced alteration of hematological and histopathological parameters; these protective effects were associated with the reduction of SA-induced elevation of MDA, IL-1β and NO levels as well as reduction of GSH level and GPx, SOD and CAT activity. Our results suggest that GA may inhibit SA-induced kidney and liver toxicity through scavenging reactive free radicals and increasing intracellular antioxidant capacity.

Ameliorative effect of gallic acid on sodium arsenite-induced spleno-, cardio- and hemato-toxicity in rats

AIM

Arsenic is an important toxic chemical affecting millions of people around the world. Exposure to inorganic arsenic results in various health problems including skin lesions, hypertension, hematological disturbance, cardiovascular disease, spleen enlargement and cancer. Gallic acid (GA) is an important phenolic compound possessing various pharmacological properties including anti-inflammatory, antioxidant and free radical scavenging activities. The present study investigated effects of GA against sodium arsenite (SA)-induced spleno-, cardio- and hemato-toxicity.

MAIN METHODS

Thirty-five adult male Wistar rats were randomly divided into five groups; group I received normal saline (2 ml/kg/day, p.o.) for 21 days, group II received SA (10 mg/kg/day, p.o.) for 14 days, group III and IV were treated with GA (10 and 30 mg/kg/day, respectively) for 7 days prior to receive SA and treatment was continued up to 21 days in parallel with SA administration, group V received GA (30 mg/kg/day, p.o.) for 21 days. The level of MDA, NO and glutathione (GSH) and the activity of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase were measured in heart and spleen tissues. Creatine kinase-MB (CK-MB) activity and hematological and histopathological parameters were also assessed.

KEY FINDINGS

GA significantly decreased SA-induced elevation of MDA and NO levels and reduction of GSH level and GPx and SOD activity in heart and spleen tissues. Furthermore, GA improved SA-induced alteration in hematological and histopathological parameters and reduced SA-induced elevation of serum CK-MB activity.

SIGNIFICANCE

Our results suggest that GA inhibits SA-induced spleno-, cardio- and hemato-toxicity through reducing oxidative stress.

Protective Effect of Agaricus blazei Polysaccharide Against Cadmium-Induced Damage on the Testis of Chicken

Cadmium (Cd) exposure can cause reproductive toxicity through oxidative stress and inflammatory response. A polysaccharide extract of the edible mushroom Agaricus blazei Murill has been isolated and exhibits antioxidant activity and immunoregulatory effect. The aim of this study was to investigate the protective role of Agaricus blazei polysaccharide (ABP) against Cd-induced damage in chicken testis through enhancing antioxidant activity and alleviating inflammatory response. One hundred twenty healthy 7-day-old Hy-Line male chickens (Harbin, China) were randomly divided into four groups, and each group consisted of 30 chickens: Normal control was fed daily with full feed and 0.2 mL distilled water per day via oral gavage; Cd-treated group was fed daily with full feed that contained 140 mg/kg CdCl₂ and 0.2 mL distilled water per day by gavage; Polysaccharide-treated group was fed daily with full feed with 0.2 mL ABP(30 mg/ml) solution per day via oral gavage; Cd/polysaccharide-treated group was fed daily with full feed containing 140 mg/kg CdCl₂ and 0.2 mL ABP(30 mg/ml) solution per day by gavage. On the 20, 40, and 60 days, the testis was immediately removed. The contents of Cd in the testis, activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), malondialdehyde (MDA) production, messenger RNA (m RNA) levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6), protein expressions of heat shock proteins (HSPs) (HSP60, HSP70, and HSP90), and the histopathological changes of the testis were determined. The results indicated that ABP improved Cd-caused testicular tissue damage by increasing the SOD and GSH-Px activities: decreasing the Cd accumulation and MDA content, mRNA levels of TNF-α, IL-1β, and IL-6, and protein expressions of HSP60, HSP70, and HSP90. Results suggest that ABP for the mitigation of damage induced by cadmium in chicken testis through enhancing antioxidant activity and alleviating Inflammatory response.

Ellagic acid: A promising protective remedy against testicular toxicity induced by arsenic

Chronic exposure to arsenic, an inducer of oxidative stress, is one of the major causes of male infertility. Therefore, the present study investigated the protective role of Ellagic acid (EA), as a natural antioxidant, against testicular toxicity evoked by arsenic. Thirty-five male Wistar rats were divided into 5 treatment groups. Group 1 served as control, group 2 were orally exposed to sodium arsenite (SA, 10 mg/kg; 21 days), groups 3 and 4 were initially exposed to SA for 7 days and then were treated with both EA (10 and 30 mg/kg) and SA up to 21 days, and group 5 was treated with EA for 14 days. After this period, biochemical and histopathological parameters were evaluated in serum samples and testicular tissue. SA markedly reduced levels of serum testosterone, total antioxidant capacity, reduced glutathione as well as the activity of antioxidant enzymes. Furthermore, SA enhanced levels of malondialdehyde, tumor necrosis factor-α, interleukin-1β and nitric oxide in testes. Treatment with EA was found to reduce testicular arsenic accumulation and oxidative stress parameters. In addition, EA improved the serum testosterone level, testicular antioxidant markers and histological parameters after exposure to SA. EA may emerge as a promising therapeutic option to protect testes from arsenic-induced toxicity through reducing oxidative stress and inflammatory responses.