Arsenic-induced abnormalities in glucose metabolism: Biochemical basis and potential therapeutic and nutritional interventions

Restoration of skin mucosal immune responses, cyto-genotoxicity and histological alterations in arsenic exposed Labeo rohita by Moringa oleifera supplementation

Arsenic (As) residue is present predominantly in aquatic ecosystem and fishery products globally, which is critically hazardous to both fish and consumer health beyond its permissible limit. Therefore, finding effective ways to mitigate As toxicity has become a priority. Hence, Moringa oleifera (M. oleifera), a medicinal plant containing several pharmacological properties, was evaluated for reducing adverse effects of sub-lethal concentration of As (1/3rd of 96 h LC50 = 6.75 mgL-1) in Labeo rohita (Rahu). Briefly, healthy acclimatized individual of L. rohita were allotted into four aquariums and named as T1, T2, T3 and T4. Each group had three replicates (10 fish in each aquarium). T1 group served as control, exposed with no As and fed with basal diet. T2, T3 and T4 groups were exposed to As and treated with 0, 2 and 4 % M. oleifera leaf extract supplemented diet respectively, for 28 days. Fish exposed to As and fed a diet with 0 % M. oleifera leaf extract exhibited increased histological alterations, elevated levels of liver enzymes, cortisol, antioxidant status, and relative expression of the cytochrome P450 gene, while showing significant decreases in skin mucosal immune responses (lysozyme, protease, antiprotease, and peroxidase activities). However, As exposed fish group fed with diets containing 2 % or 4 % M. oleifera leaf extract, the histological alterations were reduced, level of liver enzymes, cortisol, upregulation of anti-oxidant enzyme, relative expression of cytochrome P450 gene and skin mucosal immune responses were normalized, with (4 %) M. oleifera leaf extract supplemented diet showing more prominent effects. These results suggest the protective and therapeutic roles of M. oleifera as a feed supplement in L. rohita against As induced toxicity.

Integrated application of selenium and silica reduce arsenic accumulation and enhance the level of metabolites in rice grains

In this study, rice plants were co-exposed to selenium (Se) and silica (Si) under arsenic (As) stress to evaluate As accumulation in rice grains, associated cancer risk, and its impact on the types and numbers of grain metabolites. A total of 58 metabolites were identified, of which, 19 belong to sugars, and drastically altered during different treatments. Arsenic exposure significantly reduced monosaccharides, i.e., D-glucose (83%) >D-galactose (60%) >D-fructose (57%) >D-ribose (29%) but increased that monosaccharide units which have antioxidant properties (i.e. α-D-glucopyranoside and melibiose). However, the levels of D-galactose, fructose, and ribose were significantly increased during co-supplementation of selenite (SeIV) and Si under As stress. Other groups of rice grain metabolites, like sugar alcohols, organic acids, polyphenols, carboxylic acids, fatty acids, and phytosterols, were also significantly altered by As exposure and increased in grains of SeIV and Si supplemented rice compared to alone As exposure. In brief, rice growing in As-affected areas may have a low level of different metabolites. However, supplementation by selenite (SeIV) with Si not only increased metabolites and amylose/amylopectin ratio but also reduced ∼90% of As accumulation in grains. Thus, the use of SeIV with Si might be advantageous for the locals to provide a healthy diet of rice and limit As-induced cancer risk up to 10-fold.

Association of Arsenic and Nickel with Markers of Insulin Resistance and Beta Cell Dysfunction: A Case-Control Study in Indo Gangetic Plain

Environmental exposure to toxic metals/metalloids (TM) has been linked to type 2 diabetes mellitus (T2DM) via mechanisms involving insulin resistance and beta cell dysfunction, especially in regions with significant industrial and agricultural activities. This study assessed the relationship between serum toxic element levels and glycemic markers, including HbA1c, insulin resistance (HOMA-IR), and beta cell function (HOMA-β%). In total, 783 participants (480 T2DM patients and 303 controls) were recruited. TM (Ni, As, Al, Pb, Cd, and Hg) was quantified using inductively coupled plasma mass spectrometry. HbA1c was measured using ion exchange high-performance liquid chromatography, while fasting insulin and glucose levels were measured using a Cobas 6000 Roche autoanalyzer to calculate HOMA-IR and HOMA-β%. Among the tested TM, As (72.2%) and Ni (66.2%) were the most prevalent and associated with T2DM. On multivariate analysis, Ni and As levels were significantly positively correlated with HbA1c (Ni: β = 0.13, As: β = 0.16) and IR (Ni: β = 0.31, As: β = 0.24), and negatively correlated with β-cell function (Ni: β = -0.09, As: β = -0.19). A significant decline in beta cell function (Ni: Q1:55.96, Q4:34.27; As: Q1:58.61, Q4:27.88) and increased IR (Ni: Q1:2.75, Q4:3.97; As: Q1:2.77, Q4:3.76) was observed across exposure quartiles. Nonfiltered water consumption and smoking were associated with higher levels of Ni, As, and IR. The risk (adjusted odds ratio) of T2DM increased 2.18-fold and 6.81-fold with Ni and As exposure, respectively. The district with the highest exposure (Bahraich) to Ni (82%) and As (88%) had the highest prevalence (82%) of T2DM among the study population. Arsenic and nickel exposure are strongly associated with impaired glycemic markers in T2DM and correspond to drinking water in the Indo-Gangetic Plain. Smoking was also associated with high Ni and As levels.

Host-microbiota interplay in arsenic metabolism: Implications on host glucose homeostasis

Arsenic (As), a naturally occurring element with unique properties, has been recognized as the largest mass poisoning in the world by the World Health Organization (WHO). Approximately 200 million people worldwide are exposed to toxic levels of arsenic due to natural and anthropogenic activities. This widespread exposure necessitates a deeper understanding of microbe-arsenic interactions and their potential influence on host exposure and health risks. It is a major causative factor for metabolic diseases, including diabetes. Arsenic exposure has been linked to dysfunction in various cell types and tissues, notably affecting pancreatic islet cells. Numerous mechanisms have been identified to be responsible for arsenic exposure under both in vitro and in vivo conditions. These mechanisms contribute to the regulation of processes underlying diabetes etiology, such as glucose-stimulated insulin secretion from pancreatic beta cells. Unlike other toxic elements, arsenic undergoes metabolism by living organisms, including microbes, plants, and animals. Other toxic elements like Lead (Pb) and mercury (Hg) are generally not metabolized in the same way as Arsenic in microbes, plants and animals. In this review, we strive to initiate a dialogue by reviewing known aspects of microbe-arsenic interactions and placing it in the context of the potential for influencing host exposure and health risks. This review provides an up-to-date insight into arsenic metabolism by the human body and its associated microbiota, as well as the deciphered molecular pathways linking the different species of arsenic in the etiology of diabetes. Additionally, the future perspectives of mitigation and detoxification of arsenic in translational medicine and limitations in current scenarios are discussed. The comprehensive review presented here underscores the importance of exploring the complex interplay between arsenic metabolism, host-microbiota interactions, and their implications on glucose homeostasis and metabolic diseases. It emphasizes the need for continued research to develop effective strategies for mitigating arsenic-related health risks and fostering better translational medicine approaches.

Zingerone effects on arsenic-induced glucose intolerance and hepatotoxicity in mice via suppression of oxidative stress-mediated hepatic inflammation and apoptosis

BACKGROUND

Arsenic (As), a poisonous metalloid, is widely distributed in air, water, and soil and has been associated with the occurrence of diabetes and liver toxicity. Zingerone (ZNG), one of the active compounds in ginger, has several pharmacological benefits such as antioxidant and anti-inflammatory characteristics. The objective of this research was to assess the protective role of ZNG against arsenic (As)-induced glucose intolerance (GI) and hepatotoxicity in mice.

METHODS

Male NMRI mice were treated with ZNG (25, 50, and 100 mg/kg, oral gavage for 29 days) before As administration (10 mg/kg, oral gavage for 29 days). On the 29th day, fasting blood glucose (FBG) and glucose tolerance test were measured. The animals were euthanized (day 30), and samples from blood and tissue (liver and pancreas) were gathered for further evaluations.

RESULTS

Administration of ZNG inhibited As-induced elevation of FBG and GI. Moreover, hepatic tissue damage and decreased Langerhans islets' diameter caused by As administration were improved by ZNG treatment. Pretreatment with ZNG attenuated the elevation of serum liver enzymes induced by As (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase). Also, the reduction in total thiol content, as well as the decline in antioxidant enzyme activities (catalase, superoxide dismutase, and glutathione peroxidase) and the increase in lipid peroxidation marker (thiobarbituric acid reactive substances) in the liver tissue of As-exposed mice were reversed in ZNG-treated mice. Furthermore, ZNG prevented the increase of hepatic inflammatory markers (nitric oxide and tumor necrosis factor-alpha levels, and protein expression of nuclear factor-kappa B) and apoptosis-related marker (caspase-3 protein expression) in As-treated mice.

CONCLUSIONS

This study has provided evidence indicating that ZNG can act as a beneficial agent in preventing As-induced hepatotoxicity and diabetes.

Mechanisms of Staphylococcus aureus survival of trimethoprim-sulfamethoxazole-induced thymineless death

Trimethoprim-sulfamethoxazole (SXT) is commonly used to treat diverse Staphylococcus aureus infections, including those associated with cystic fibrosis (CF) pulmonary disease. Studies with Escherichia coli found that SXT impairs tetrahydrofolate production, leading to DNA damage, stress response induction, and accumulation of reactive oxygen species (ROS) in a process known as thymineless death (TLD). TLD survival can occur through the uptake of exogenous thymidine, countering the effects of SXT; however, a growing body of research has implicated central metabolism as another potentially important determinant of bacterial survival of SXT and other antibiotics. Here, we conducted studies to better understand the mechanisms of TLD survival in S. aureus. We found that thymidine abundances in CF sputum were insufficient to prevent TLD of S. aureus, highlighting the importance of alternative survival mechanisms in vivo. In S. aureus cultured in vitro with SXT and low thymidine, we frequently identified adaptive mutations in genes encoding carbohydrate, nucleotide, and amino acid metabolism, supporting reduced metabolism as a common survival mechanism. Although intracellular ROS levels rose with SXT treatment in vitro, survival was not improved in the presence of ROS scavengers, unlike in E. coli. SXT challenge induced the SOS response, which was alleviated by added thymidine. Finally, an inactivating mutation in the phosphotransferase gene ptsI conferred both limitation in cellular ATP and improved survival against TLD. Collectively, these results suggest that alterations in core metabolic functions, particularly those that reduce ATP levels, predominantly confer S. aureus survival and persistence during SXT treatment, potentially identifying novel targets for co-treatment.IMPORTANCEStaphylococcus aureus is a ubiquitous organism and one of the leading causes of human infections, many of which are difficult to treat due to persistence, antibiotic resistance, or antibiotic tolerance. As our arsenal of effective antibiotics dwindles, the need for improved treatments becomes increasingly urgent, necessitating a better understanding of the precise mechanisms by which pathogens evade our most critical antimicrobial agents. Here, we report a systematic characterization of the mechanisms of S. aureus survival to treatment with the first-line antistaphylococcal antibiotic trimethoprim-sulfamethoxazole, identifying pathways and candidate targets for enhancing the efficacy of available antimicrobial agents.

Protective Effects of Xanthine Derivatives Against Arsenic Trioxide-Induced Oxidative Stress in Mouse Hepatic and Renal Tissues

In this study, the protective efficacy of pentoxifylline (PTX) as a xanthine derivative against arsenic trioxide (ATO)-induced kidney and liver damage in mice was investigated. Thirty-six mice were divided into six groups, receiving intraperitoneal injections of saline, ATO, PTX, or a combination for four weeks. Blood samples were analyzed for serum biochemistry, while hepatic tissue underwent examination for histopathological changes and assessment of oxidative stress markers and antioxidant gene expression through Real-Time PCR. ATO exposure significantly increased serum markers (creatinine, ALT, BUN, ALP, AST) and induced histopathological changes in the liver. Moreover, it elevated renal and hepatic nitric oxide (NO) and lipid peroxidation (LPO) levels, and reduced antioxidant enzyme expression (CAT, GSR, GPx, MPO, SOD), total thiol groups (TTGs), and total antioxidant capacity (TAC). Conversely, PTX treatment effectively lowered serum hepatic and renal markers, improved antioxidant markers, and induced histopathological alterations. Notably, PTX did not significantly affect renal and hepatic NO levels. These findings suggest that PTX offers therapeutic potential in mitigating liver and acute kidney injuries induced by various insults, including exposure to ATO.

Metabolomics Analysis and Biochemical Profiling of Arsenic-Induced Metabolic Impairment and Disease Susceptibility

Our study aimed to conduct a comprehensive biochemical profiling and metabolomics analysis to investigate the effects of arsenic-induced metabolic disorders, with a specific focus on disruptions in lipid metabolism, amino acid metabolism, and carbohydrate metabolism. Additionally, we sought to assess the therapeutic potential of resveratrol (RSV) as a remedy for arsenic-induced diabetes, using metformin (MF) as a standard drug for comparison. We measured the total arsenic content in mouse serum by employing inductively coupled plasma mass spectrometry (ICP-MS) after administering a 50-ppm solution of sodium arsenate (50 mg/L) in purified water. Our findings revealed a substantial increase in total arsenic content in the exposed group, with a mean value of 166.80 ± 8.52 ppb (p < 0.05). Furthermore, we investigated the impact of arsenic exposure on various biomarkers using enzyme-linked immunosorbent assay (ELISA) methods. Arsenic exposed mice exhibited significant hyperglycemia (p < 0.001) and elevated levels of homeostatic model assessment of insulin resistance (HOMA-IR), hemoglobin A1c (Hb1Ac), Inflammatory biomarkers as well as liver and kidney function biomarkers (p < 0.05). Additionally, the levels of crucial enzymes linked to carbohydrate metabolism, including α-glucosidase, hexokinase, and glucose-6-phosphatase (G6PS), and oxidative stress biomarkers, such as levels of glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), catalase, and superoxide dismutase (SOD), were significantly reduced in the arsenic-exposed group compared to the control group (p < 0.05). However, the level of MDA was significantly increased. Molecular analysis of gene expression indicated significant upregulation of key enzymes involved in lipid metabolism, such as carnitine palmitoyl-transferase-I (CPT-I), carnitine palmitoyl-transferase-II (CPT-II), lecithin-cholesterol acyltransferase (LCAT), and others. Additionally, alterations in gene expression related to glucose transporter-2 (GLUT-2), glucose-6-phosphatase (G6PC), and glucokinase (GK), associated with carbohydrate metabolism, were observed. Amino acid analysis revealed significant decreases in nine amino acids in arsenic-exposed mice. Metabolomics analysis identified disruptions in lipid metabolomes, amino acids, and arsenic metabolites, highlighting their involvement in essential metabolic pathways. Histopathological observations revealed significant changes in liver architecture, hepatocyte degeneration, and increased Kupffer cells in the livers of arsenic-exposed mice. In conclusion, these findings enhance our comprehension of the impact of environmental toxins on metabolic health and offer potential avenues for remedies against such disruptions.

Disease-associated metabolic pathways affected by heavy metals and metalloid

Increased exposure to environmental heavy metals and metalloids and their associated toxicities has become a major threat to human health. Hence, the association of these metals and metalloids with chronic, age-related metabolic disorders has gained much interest. The underlying molecular mechanisms that mediate these effects are often complex and incompletely understood. In this review, we summarize the currently known disease-associated metabolic and signaling pathways that are altered following different heavy metals and metalloids exposure, alongside a brief summary of the mechanisms of their impacts. The main focus of this study is to explore how these affected pathways are associated with chronic multifactorial diseases including diabetes, cardiovascular diseases, cancer, neurodegeneration, inflammation, and allergic responses upon exposure to arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), and vanadium (V). Although there is considerable overlap among the different heavy metals and metalloids-affected cellular pathways, these affect distinct metabolic pathways as well. The common pathways may be explored further to find common targets for treatment of the associated pathologic conditions.

Metabolic and genetic derangement: a review of mechanisms involved in arsenic and lead toxicity and genotoxicity

Urbanisation and industrialisation are on the rise all over the world. Environmental contaminants such as potentially toxic elements (PTEs) are directly linked with both phenomena. Two PTEs that raise greatest concern are arsenic (As) and lead (Pb) as soil and drinking water contaminants, whether they are naturally occurring or the consequence of human activities. Both elements are potential carcinogens. This paper reviews the mechanisms by which As and Pb impair metabolic processes and cause genetic damage in humans. Despite efforts to ban or limit their use, due to high persistence both continue to pose a risk to human health, which justifies the need for further toxicological research.

Enhancing an Oxidative "Trojan Horse" Action of Vitamin C with Arsenic Trioxide for Effective Suppression of KRAS-Mutant Cancers: A Promising Path at the Bedside

The turn-on mutations of the KRAS gene, coding a small GTPase coupling growth factor signaling, are contributing to nearly 25% of all human cancers, leading to highly malignant tumors with poor outcomes. Targeting of oncogenic KRAS remains a most challenging task in oncology. Recently, the specific G12C mutant KRAS inhibitors have been developed but with a limited clinical outcome because they acquire drug resistance. Alternatively, exploiting a metabolic breach of KRAS-mutant cancer cells related to a glucose-dependent sensitivity to oxidative stress is becoming a promising indirect cancer targeting approach. Here, we discuss the use of a vitamin C (VC) acting in high dose as an oxidative "Trojan horse" agent for KRAS-mutant cancer cells that can be potentiated with another oxidizing drug arsenic trioxide (ATO) to obtain a potent and selective cytotoxic impact. Moreover, we outline the advantages of VC's non-natural enantiomer, D-VC, because of its distinctive pharmacokinetics and lower toxicity. Thus, the D-VC and ATO combination shows a promising path to treat KRAS-mutant cancers in clinical settings.

Arsenolipids reduce butyrate levels and influence human gut microbiota in a donor-dependent way

Arsenolipids are organic arsenic species with variable toxicity. Accurate assessment of the risks derived from arsenic-contaminated seafood intake requires studying the interplay between arsenolipids and the human gut microbiota. This research used the in vitro mucosal simulator of the human intestinal microbial ecosystem (M-SHIME) to assess the effect of defined chemical standards of arsenolipids (AsFA 362 and AsHC 332) on a simulated healthy human gut microbiota (n = 4). Microbial-derived metabolites were quantified by gas chromatography and microbiota structure was characterized by 16S rRNA gene sequencing. A specific reduction in butyrate production (control=5.28 ± 0.3 mM; AsFAs=4.56 ± 0.4 mM; AsHC 332=4.4 ± 0.6 mM, n = 4 donors), concomitant with a reduction in the abundance of Lachnospiraceae UCG-004 group and the Faecalibacterium genus was observed, albeit in a donor-dependent manner. Furthermore, an increase in Escherichia/Shigella, Proteobacteria and Fusobacterium abundance was observed after arsenolipid treatments, depending on individual microbiota background. These alterations in microbial functionality and microbial community structure suggest a detrimental effect of arsenolipids intake towards the commensal gut microbiome, and consequently, on human health.

Arsenic Exposure, Blood DNA Methylation, and Cardiovascular Disease

BACKGROUND

Epigenetic dysregulation has been proposed as a key mechanism for arsenic-related cardiovascular disease (CVD). We evaluated differentially methylated positions (DMPs) as potential mediators on the association between arsenic and CVD.

METHODS

Blood DNA methylation was measured in 2321 participants (mean age 56.2, 58.6% women) of the Strong Heart Study, a prospective cohort of American Indians. Urinary arsenic species were measured using high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry. We identified DMPs that are potential mediators between arsenic and CVD. In a cross-species analysis, we compared those DMPs with differential liver DNA methylation following early-life arsenic exposure in the apoE knockout (apoE-/-) mouse model of atherosclerosis.

RESULTS

A total of 20 and 13 DMPs were potential mediators for CVD incidence and mortality, respectively, several of them annotated to genes related to diabetes. Eleven of these DMPs were similarly associated with incident CVD in 3 diverse prospective cohorts (Framingham Heart Study, Women's Health Initiative, and Multi-Ethnic Study of Atherosclerosis). In the mouse model, differentially methylated regions in 20 of those genes and DMPs in 10 genes were associated with arsenic.

CONCLUSIONS

Differential DNA methylation might be part of the biological link between arsenic and CVD. The gene functions suggest that diabetes might represent a relevant mechanism for arsenic-related cardiovascular risk in populations with a high burden of diabetes.

Arsenic Exposure through Dietary Intake and Associated Health Hazards in the Middle East

Dietary arsenic (As) contamination is a major public health issue. In the Middle East, the food supply relies primarily on the import of food commodities. Among different age groups the main source of As exposure is grains and grain-based food products, particularly rice and rice-based dietary products. Rice and rice products are a rich source of core macronutrients and act as a chief energy source across the world. The rate of rice consumption ranges from 250 to 650 g per day per person in South East Asian countries. The source of carbohydrates through rice is one of the leading causes of human As exposure. The Gulf population consumes primarily rice and ready-to-eat cereals as a large proportion of their meals. Exposure to arsenic leads to an increased risk of non-communicable diseases such as dysbiosis, obesity, metabolic syndrome, diabetes, chronic kidney disease, chronic heart disease, cancer, and maternal and fetal complications. The impact of arsenic-containing food items and their exposure on health outcomes are different among different age groups. In the Middle East countries, neurological deficit disorder (NDD) and autism spectrum disorder (ASD) cases are alarming issues. Arsenic exposure might be a causative factor that should be assessed by screening the population and regulatory bodies rechecking the limits of As among all age groups. Our goals for this review are to outline the source and distribution of arsenic in various foods and water and summarize the health complications linked with arsenic toxicity along with identified modifiers that add heterogeneity in biological responses and suggest improvements for multi-disciplinary interventions to minimize the global influence of arsenic. The development and validation of diverse analytical techniques to evaluate the toxic levels of different As contaminants in our food products is the need of the hour. Furthermore, standard parameters and guidelines for As-containing foods should be developed and implemented.

Arsenic-Induced Sex Hormone Disruption: An Insight into Male Infertility

Arsenic (As) is one of the most potent natural as well as anthropogenic metalloid toxicants that have various implications in the everyday life of humans. It is found in several chemical forms such as inorganic salt, organic salt, and arsine (gaseous form). Although it is mostly released via natural causes, there are many ways through which humans come in contact with As. Drinking water contamination by As is one of the major health concerns in various parts of the world. Arsenic exposure has the ability to induce adverse health effects including reproductive problems. Globally, around 15% of the couples are affected with infertility, of which about 20-30% are attributed to the male factor. Arsenic affects the normal development and function of sperm cells, tissue organization of the gonads, and also the sex hormone parameters. Stress induction is one of the implications of As exposure. Excessive stress leads to the release of glucocorticoids, which impact the oxidative balance in the body leading to overproduction of reactive oxygen species (ROS). This may in turn result in oxidative stress (OS) ultimately interfering with normal sperm and hormonal parameters. This study deals with As-induced OS and its association with sex hormone disruption as well as its effect on sperm and semen quality.

Biochemical Investigation of Therapeutic Potential of Resveratrol Against Arsenic Intoxication

Arsenic has been reported to cause damaging effects on different body organs. This study was designed to evaluate the protective effect of resveratrol (RSV) against arsenic trioxide (ATO)–induced intoxication in experimental animals. Twenty-four Wistar rats were allocated in 4 groups: group 1: control group, received normal diet; group 2: received ATO (3 mg/kg); group 3: received RSV (8 mg/kg) 30 minutes before administration of ATO; and group 4: received ascorbic acid (25 mg/kg) 30 minutes before administration of ATO. Treatments were given to experimental rats daily for consecutive 8 days. At the end of experimental period, bioaccumulation of arsenic in liver and kidney was assessed by hydride generation-atomic absorption spectrophotometer to investigate the association of arsenic accumulation with histological aberrations. Following parameters were also investigated: serum biochemical profile (alanine aminotransferase, aspartate transaminase, alkaline phosphatase, blood urea nitrogen, and creatinine) for evaluation of liver and kidney functions and lipid peroxidation and oxidative stress (malondialdehyde, glutathione, superoxide dismutase, catalase, and glutathione peroxidase) in tissue homogenates of liver and kidney for estimation of oxidative status. The findings of this study indicate that RSV remarkably ameliorated the hepatic and renal toxicity in arsenic-exposed rat model due to its strong antioxidant potential.

Persister cells: formation, resuscitation and combative therapies

Persister cells, or superfits, have been strongly implicated in the recalcitrance and recurrence of chronic bacterial infection through the dormant (metabolically reduced) phenotype they display and the tolerance to antimicrobial agents this dormancy grants them. The complex biochemical events that lead to the formation of persister cells are not completely understood, though much research has linked the degradation of type II toxin/antitoxin systems and reduced cellular ATP levels to the rise in stress response molecules (where (p)ppGpp is of particular interest), which induce this dormant state. The equally complex mechanism of resuscitation is initiated by the cells’ ability to sense nutrient availability via chemotaxis systems. Levels of secondary messenger proteins (i.e., cAMP) within the cell are reduced to allow the resuscitation of ribosomes, by ribosomal resuscitation factor HflX, to reinstate protein synthesis and, therefore, growth to re-populate. Techniques of superfit eradication utilise one, or more, of three approaches (i) direct killing, (ii) re-sensitising persister cells to conventional antimicrobials, or (iii) prevention of persister formation though few laboratory findings have been translated to clinical practice. This work will outline current findings in the field with a critical approach, where possible.

Effects of arsenic and heavy metals on metabolic pathways in cells of human origin: Similarities and differences

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There are distinctive overlaps in different heavy metal affected metabolic pathways.

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Affected pathways vary according to the tissue origin and maturity of the cell.

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Arsenic appears to have relatively more pleiotropic effects on metabolic pathways.

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Some of the arsenic affected pathways are associated with diabetes.

Various anthropogenic and natural events over the years have gradually increased human exposure to various heavy metals. Several of these heavy metals including cadmium, mercury, nickel, chromium, and the metalloid arsenic among others, have created major public health concerns for their high level of toxicities. Identification of the general as well as the differentially affected cellular metabolic pathways will help understanding the molecular mechanism of different heavy metal-induced toxicities. In this study, we analyzed 25 paired (control vs. treated) transcriptomic datasets derived following treatment of various human cells with different heavy metals and metalloid (arsenic, cadmium, chromium, iron, mercury, nickel and vanadium) to identify the affected metabolic pathways. The effects of these metals on metabolic pathways depend not only on the metals per se, but also on the nature of the treated cells. Tissue of origin, therefore, must be considered while assessing the effects of any particular heavy metal or metalloid. Among the metals and metalloid, arsenic appears to have relatively more pleiotropic influences on cellular metabolic pathways including those known to have association with diabetes. Although only two stem cell derived datasets are included in the current study, effects of heavy metals on these cells appear to be different from other mature cells of similar tissue origin. This study provides useful information about different heavy metal affected pathways, which may be useful in further exploration using wet-lab based techniques.

Effect of Time Interval on Arsenic Toxicity to Paddy Field Cyanobacteria as Evident by Nitrogen Metabolism, Biochemical Constituent, and Exopolysaccharide Content

Arsenic poisoning in aquatic ecosystem is a global concern that obstructs the productivity of agricultural lands (paddy fields) by targeting the growth of cyanobacteria. The cyanobacteria also tolerate and accumulate elevated concentration of arsenic (As) inside the cell and excrete out from cells in less toxic forms after the successive time interval. Thus to validate this, the study was carried out at two different time intervals, i.e., 48 h and 96 h. Two redox forms of As arsenate (As^V) and arsenite (As^III) at different concentrations (50, 100, and 150 mM As^V; 50, 100, and 150 μM As^III) caused substantial reduction in growth, pigments (Chl a/Car and phycobiliproteins: phycocyanin, allophycocyanin, and phycoerythrin), inorganic nitrogen ( nitrate (NO₃^-) and nitrite (NO₂^-)) uptake, activity of enzymes (NR, NiR, GS, and GOGAT) of nitrogen metabolism, biochemical constituents (protein, carbohydrate, and exopolysaccharide (EPS) contents of Nostoc muscorum, and Anabaena sp. PCC7120. The tested doses of As^V and As^III after 48 h of exposure exhibited adverse impact on these parameters, but after 96 h with lower doses of As^V (50 mM and 100 mM) and As^III (50 μM and 100 μM), significant recovery was recorded. Contrary to this, at higher dose of As^V (150 mM) and As^III (150 μM), the adverse impact was further aggravated with increasing time exposure. Contrary to the activity of NR, NiR, GS, and GOGAT, GDH activity (alternative NH₃⁺ assimilating enzyme) was found to increase, and after 96 h, the activity showed declining trend but still higher than the control. The biochemical constituent EPS (first protective barrier) under scanning electron microscope showed more accumulation of dry adsorbent in the case of As^III stress hence displayed more toxic nature of As^III than As^V. The study concludes that with increasing time exposure, the recovery in growth and related parameters mainly at lower doses of As^V and As^III points toward adaptability of cyanobacteria which was more pronounced in Nostoc muscorum.

Protective effect of Mucuna pruriens against arsenic-induced liver and kidney dysfunction and neurobehavioral alterations in rats

BACKGROUND AND AIM

Intoxication of arsenic in rats is known to result in neurological effects as well as liver and kidney dysfunction. Mucuna pruriens has been identified for its medicinal properties. The aim of the study was to investigate the protective effect of aqueous seed extract of M. pruriens on sodium arsenite-induced memory impairment, liver, and kidney functions in rats.

MATERIALS AND METHODS

The experiment was divided into short-term treatment (45 days) and long-term treatment (90 days), with each group divided into nine sub-groups consisting of six animals each. Sub-groups 1 and 2 served as normal, and N-acetylcysteine (NAC) controls, respectively. Sub-groups 3-9 received sodium arsenite in drinking water (50 mg/L). In addition, sub-group 4 received NAC (210 mg/kg b.wt) orally once daily, sub-groups 5-7 received aqueous seed extract of M. pruriens (350 mg/kg b.wt, 530 mg/kg b.wt, and 700 mg/kg b.wt) orally once daily and sub-groups 8 and 9 received a combination of NAC and aqueous seed extract of M. pruriens (350 mg/kg b.wt and 530 mg/kg b.wt) orally once daily. Following the treatment, the blood was drawn retro-orbitally to assess the liver (serum alanine transaminase [ALT], serum aspartate transaminase, and serum alkaline phosphatase) and kidney (serum urea and serum creatinine) functions. Learning and memory were assessed by passive avoidance test. Animals were sacrificed by an overdose of ketamine, and their Nissl stained hippocampal sections were analyzed for alterations in neural cell numbers in CA1 and CA3 regions.

RESULTS

In the short-term treatment, groups administered with M. pruriens 530 mg/kg b.wt alone and combination of NAC + M. pruriens 350 mg/kg b.wt exhibited a significant improvement in memory retention, less severe neurodegeneration, and decrease in serum ALT levels. In long-term treatment, groups administered with M. pruriens 700 mg/kg b.wt alone and combination of NAC+M. pruriens 350 mg/kg b.wt, respectively, showed better memory retention, decreased neural deficits, and reduced levels of kidney and liver enzymes.

CONCLUSION

The seed extract of M. pruriens showed significant enhancement in memory and learning. The number of surviving neurons in the CA1 and CA3 regions also increased on treatment with M. pruriens. Serum ALT, serum urea, and serum creatinine levels showed significant improvement on long-term treatment with M. pruriens.

Arsenic concentrations, diversity and co-occurrence patterns of bacterial and fungal communities in the feces of mice under sub-chronic arsenic exposure through food

BACKGROUND

Arsenic, a global pollutant and a threshold-free primary carcinogen, can accumulate in rice. Previous studies have focused on arsenic poisoning in drinking water and the effects on gut microbes. The research on arseniasis through food, which involves the bio-transformation of arsenic, and the related changes in gut microbiome is insufficient.

METHOD

Mice were exposed from animal feed prepared with four arsenic species (iAs^III, iAs^V, MMA, and DMA) at a dose of 30 mg/kg according to the arsenic species proportion in rice for 30 days and 60 days. The levels of total arsenic (tAs) and arsenic species in mice feces and urine samples were determined using ICP-MS and HPLC-ICP-MS, respectively. 16S rRNA and ITS gene sequencing were conducted on microbial DNA extracted from the feces samples.

RESULTS

At 30 days and 60 days exposure, the tAs levels excreted from urine were 0.0092 and 0.0093 mg/day, and tAs levels in feces were 0.0441 and 0.0409 mg/day, respectively. We found significant differences in arsenic species distribution in urine and feces (p < 0.05). In urine, the predominant arsenic species were iAs^III (23% and 14%, respectively), DMA (55% and 70%, respectively), and uAs (unknown arsenic, 14% and 10%, respectively). In feces, the proportion of major arsenic species (iAs^V, 26% and 21%; iAs^III, 16% and 15%; MMA, 14% and 14%; DMA, 19% and 19%; and uAs, 22% and 29%, respectively) were evenly distributed. Microbiological analysis (MRPP test, α- and β-diversities) showed that diversity of gut bacteria was significantly related to arsenic exposure through food, but diversity of gut fungi is less affected. Manhattan plot and LEfSe analysis showed that arsenic exposure significantly changes microbial taxa, which might be directly associated with arsenic metabolism and diseases mediated by arsenic exposure, such as Deltaproteobacteria, Polynucleobacter, Saccharomyces, Candida, Amanitaceae, and Fusarium. Network analysis was used to identify the changing hub taxa in feces along with arsenic exposure. Function predicting analysis indicated that arsenic exposure might also significantly increase differential metabolic pathways and would disturb carbohydrates, lipid, and amino acids metabolism of gut bacteria.

CONCLUSIONS

The results demonstrate that subchronic arsenic exposure via food significantly changes the gut microbiome, and the toxicity of arsenic in food, especially in staples, should be comprehensively evaluated in terms of the disturbance of microbiome, and feces might be the main pathway through which arsenic from food exposure is excreted and bio-transformed, providing a new insight into the investigation of bio-detoxification for arseniasis.

Anti-diabetic Effect of Emblica-officinalis (Amla) Against Arsenic Induced Metabolic Disorder in Mice

Chronic exposure to arsenic through drinking water and occupational exposure has been found to be associated with the diabetic symptoms. Earlier, we reported that arsenic induced enhanced oxidative stress, inflammation, dislipidemia and hepatotoxicity in mice have been protected by treatment with Emblica officinalis (amla). The present study has therefore been focused to investigate the efficacy of amla in mitigation of arsenic induced hyperglycemia in mice. Arsenic exposure (3 mg/kg b.w./day for 30 days) in mice altered glucose homeostasis and significantly decreases hepatic glucose regulatory enzyme, glucokinase (43%), glucose-6 phosphate dehydrogenase (38%), malic enzyme (60%) and significantly increases the level of glucose-6 phosphates (65%), phosphoenolpyruvate carboxykinase (43%), lactate, (59%) Na+ (6.8%) Cl- (10.4%), anion gap (13.9%) and pancreatic (IL-1β, TNF-α) inflammation markers (52%, 53%) as compared to controls. Arsenic exposure also significantly decreased serum insulin (44%) and c-peptide protein (38%) in mice as compared to controls. Co-administration of arsenic and amla (500 mg/kg b.w./day for 30 days) balanced blood sugar level, hepatic glucose regulatory enzyme (glucokinase, glucose-6 phosphate dehydrogenase, malic enzyme (68%, 37%, 45%) and significantly decreases glucose-6 phosphatase (25%), phosphoenolpyruvate carboxykinase (22%), blood ion concentration and also lactate, Na+, Cl- and anion gap (20%, 4.6%, 6.7%, 5.2%), pancreatic (IL-1β, TNF-α) inflammation marker (21%, 24%) and significantly increased the serum insulin (57%) and c-peptide protein (31%) as compared to those treated with arsenic alone. Results of the present study suggests that the hypoglycemic and antioxidant property of amla could be responsible for its protective efficacy in arsenic induced hyperglycemia.

Role of cadmium and arsenic as endocrine disruptors in the metabolism of carbohydrates: Inserting the association into perspectives

Endocrine disrupting chemicals (EDCs) have widespread environmental distribution originated from both natural and anthropogenic sources. From the last few decades, their contamination has been raised dramatically owing to continuous discharge in sewage and untreated industrial effluents. They have rapidly gained a considerable attention due to their critical role in the development of multiple endocrine-related disorders notably diabetes mellitus (DM). Cadmium and arsenic, among the most hazardous EDCs, are not only widely spread in our environment, but they are also found to be associated with wide range of health hazards. After entering into the human body, they are preferably accumulated in the liver, kidney and pancreas where they exhibit deleterious effects on carbohydrate metabolism pathways notably glycolysis, glucogenesis and gluconeogenesis through the modification and impairment of relevant key enzymes activity. Impairment of hepatic glucose homeostasis plays a crucial role in the pathogenesis of DM. Along with compromised function of pancreas and muscles, diminished liver and kidney functions also contribute considerably to increase the blood glucose level. These metals have potential to bring conformational changes in these enzymes and make them inactive. Additionally, these metals also disturb the hormonal balance, such as insulin, glucocorticoids and catecholamines; by damaging pancreas and adrenal gland, respectively. Moreover, these metals also enhance the production of reactive oxygen species and depress the anti-oxidative defense mechanism with subsequent disruption of multiple organs. In this article, we have briefly highlighted the impact of arsenic and cadmium on the metabolism of carbohydrates and the enzymes that are involved in carbohydrate metabolism and glucose homeostasis.

Inactivation of Laccase by the Attack of As (III) Reaction in Water

Laccase is a multicopper oxidase containing four coppers as reaction sites, including one type 1, one type 2, and two type 3. We here provide the first experimental data showing that As (III) can be effectively removed from water and transformed to As (V) through reactions mediated by laccase with the presence of oxygen. To this end, the As (III) removal, As (V) yields, total protein, active laccase, and copper concentrations in the aqueous phase were determined, respectively. Additionally, electron paramagnetic resonance spectra and UV-vis spectra were applied to probe possible structural changes of the laccase during the reaction. The data offer the first evidence that laccase can be inactivated by As (III) attack thus leading to the release of type 2 copper. The released copper has no reactivity with the As (III). These findings provide new ideas into a significant pathway likely to master the environmental transformation of arsenite, and advance the understanding of laccase inactivation mechanisms, thus providing a foundation for optimization of enzyme-based processes and potential development for removal and remediation of arsenite contamination in the environment.

Inhibition of Setaria cervi protein tyrosine phosphatases by Phenylarsine oxide: A proteomic and biochemical study

Phenylarsine oxide (PAO), a specific protein tyrosine phosphatase (PTP) inhibitor significantly decreased the motility and viability of Setaria cervi ultimately leading to its death. The PTP activity present in the cytosolic and detergent soluble fractions as well as on surface of these parasites was significantly inhibited by PAO. A marked alteration in protein spots abundance after proteomic analysis showed 14 down-regulated and 9 upregulated spots in the treated parasites as compared to the control. The PTP inhibition led to increase in the cytosolic and mitochondrial calpain activity in these parasites. PAO also blocked the ATP generation in the parasite depicted by reduced activity of phosphoglycerate kinase and expression of enolase. An increased ROS level, induced lipid peroxidation/protein carbonyl formation and decreased activity of different antioxidant enzymes like thioredoxin reductase, glutathione reductase and glutathione transferases was also observed in the PAO treated parasites. PAO, thus disturbs the overall homeostasis of the filarial parasite by inhibiting PTPs. Thereby suggesting that these molecules could be used as a good chemotherapeutic target for lymphatic filariasis.

Heavy Metals and Human Health: Mechanistic Insight into Toxicity and Counter Defense System of Antioxidants

Heavy metals, which have widespread environmental distribution and originate from natural and anthropogenic sources, are common environmental pollutants. In recent decades, their contamination has increased dramatically because of continuous discharge in sewage and untreated industrial effluents. Because they are non-degradable, they persist in the environment; accordingly, they have received a great deal of attention owing to their potential health and environmental risks. Although the toxic effects of metals depend on the forms and routes of exposure, interruptions of intracellular homeostasis include damage to lipids, proteins, enzymes and DNA via the production of free radicals. Following exposure to heavy metals, their metabolism and subsequent excretion from the body depends on the presence of antioxidants (glutathione, α-tocopherol, ascorbate, etc.) associated with the quenching of free radicals by suspending the activity of enzymes (catalase, peroxidase, and superoxide dismutase). Therefore, this review was written to provide a deep understanding of the mechanisms involved in eliciting their toxicity in order to highlight the necessity for development of strategies to decrease exposure to these metals, as well as to identify substances that contribute significantly to overcome their hazardous effects within the body of living organisms.