Neurotoxic Mechanism of Arsenic: Synergistic Effect of Mitochondrial Instability, Oxidative Stress, and Hormonal-Neurotransmitter Impairment

The interaction effect of metals exposure and dietary habit on cognitive function in Chinese older adult cohort

BACKGROUND

As the important factors in cognitive function, dietary habits and metal exposures are interactive with each other. However, fewer studies have investigated the interaction effect of them on cognitive dysfunction in older adults.

METHODS

2,445 registered citizens aged 60-85 years from 51 community health centers in Luohu District, Shenzhen, were recruited in this study based on the Chinese older adult cohort. All subjects underwent physical examination and Mini-cognitive assessment scale. A semi quantitative food frequency questionnaire was used to obtain their food intake frequency, and 21 metal concentrations in their urine were measured.

RESULTS

Elastic-net regression model, a machine learning technique, identified six variables that were significantly associated with cognitive dysfunction in older adults. These variables included education level, gender, urinary concentration of arsenic (As) and cadmium (Cd), and the frequency of monthly intake of egg and bean products. After adjusting for multiple factors, As and Cd concentrations were positively associated with increased risk of mild cognitive impairment (MCI) in the older people, with OR values of 1.19 (95% CI: 1.05-1.42) and 1.32 (95% CI: 1.01-1.74), respectively. In addition, older adults with high frequency of egg intake (≥30 times/month) and bean products intake (≥8 times/month) had a reduced risk of MCI than those with low protein egg intake (<30 times/month) and low bean products intake (<8 times/month), respectively. Furthermore, additive interaction were observed between the As exposure and egg products intake, as well as bean products. Cd exposure also showed additive interactions with egg and bean products intake.

CONCLUSIONS

The consumption of eggs and bean products, as well as the levels of exposure to the heavy metals Cd and As, have been shown to have a substantial influence on cognitive impairment in the elderly population.

Arsenic Induced Oxidative Neural-Damages in Rat are Mitigated by Tea-Leave Extract via MMPs and AChE Inactivation, Shown by Molecular Docking and in Vitro Studies with Pure Theaflavin and AChE

BACKGROUND

Chronic arsenic-exposure causes neuromuscular disorders and other health anomalies. Damage to DNA and cytoskeletal/extracellular matrix is brought on by reactive-oxygen-species (ROS)-induced intrinsic antioxidant depletion (thiols/urate). Therapeutic chelating-agents have multiple side-effects.

OBJECTIVES

The protection of (Camellia sinensis) tea-extract and role of uric-acid (UA) or allopurinol (urate-depletor) on arsenic-toxicity were verified in rat model.

METHODS

Camellia sinensis (CS dry-leaves), UA or allopurinol was supplemented to arsenic-intoxicated rats for 4-weeks. Purified theaflavins and their galloyl-ester were tested in-vitro on pure AChE (acetylcholinesterase) and their PDB/PubChem 3-D structures were utilized for in-silico binding studies. The primary chemical components were evaluated from CS-extracts. Biochemical analysis, PAGE-zymogram, DNA-stability comet analysis, HE-staining was performed in arsenic-exposed rat brain tissues.

RESULTS

Animals exposed to arsenic showed symptoms of erratic locomotion, decreased intrinsic antioxidants (catalase/SOD1/uric acid), increased AChE, and malondialdehyde. Cerebellar and cerebrum tissue damages were shown with increased levels of matrix-metalloprotease (MMP2/9) and DNA damage (comets). Allopurinol- supplemented group demonstrated somewhat similar biochemical responses. In the CS-group brain tissues especially cerebellum is considerably protected which is evident from endogenous antioxidant and DNA and cytoskeleton protection with concomitant inactivation of MMPs and AChE. Present study indicates theaflavin-digallate (TFDG) demonstrated the highest inhibition of purified AChE (IC50 = 2.19 µg/ml with the lowest binding free-energy; -369.87 kcal/mol) followed by TFMG (IC50 = 3.86 µg/ml, -347.06 kcal/mol) suggesting their possible restoring effects of cholinergic response.

CONCLUSIONS

Favorable responses in UA-group and adverse outcome in allo-group justify the neuro-protective effects of UA as an endogenous antioxidant. Role of flavon-gallate in neuro protection mechanism may be further studied.

The Neglected Sibling: NLRP2 Inflammasome in the Nervous System

While classical NOD-like receptor pyrin domain containing protein 1 (NLRP1) and NLRP3 inflammasomal proteins have been extensively investigated, the contribution of NLRP2 is still ill-defined in the nervous system. Given the putative significance of NLRP2 in orchestrating neuroinflammation, further inquiry is needed to gain a better understanding of its connectome, hence its specific targeting may hold a promising therapeutic implication. Therefore, bioinformatical approach for extracting information, specifically in the context of neuropathologies, is also undoubtedly preferred. To the best of our knowledge, there is no review study selectively targeting only NLRP2. Increasing, but still fragmentary evidence should encourage researchers to thoroughly investigate this inflammasome in various animal- and human models. Taken together, herein we aimed to review the current literature focusing on the role of NLRP2 inflammasome in the nervous system and more importantly, we provide an algorithm-based protein network of human NLRP2 for elucidating potentially valuable molecular partnerships that can be the beginning of a new discourse and future therapeutic considerations.

AuNPs with Cynara scolymus leaf extracts rescue arsenic-induced neurobehavioral deficits and hippocampal tissue toxicity in Balb/c mice through D1R and D2R activation

The present study was designed to evaluate whether AuNPs (gold nanoparticles) synthesized with the Cynara scolymus (CS) leaf exert protective and/or alleviative effects on arsenic (As)-induced hippocampal neurotoxicity in mice. Neurotoxicity in mice was developed by orally treating 10 mg/kg/day sodium arsenite (NaAsO2) for 21 days. 10 µg/g AuNPs, 1.6 g/kg CS, and 10 µg/g CS-AuNPs were administered orally simultaneously with 10 mg/kg As. CS and CS-AuNPs treatments showed down-regulation of TNF-α and IL-1β levels. CS and CS-AuNPs also ameliorated apoptosis and reduced the alterations in the expression levels of D1 and D2 dopamine receptors induced by As. Simultaneous treatment with CS and CS-AuNPs improved As-induced learning, memory deficits, and motor coordination in mice assessed by water maze and locomotor tests, respectively. The results of this study provide evidence that CS-AuNPs demonstrated neuroprotective roles with antioxidant, anti-inflammatory, and anti-apoptotic effects, as well as improving D1 and D2 signaling, and eventually reversed neurobehavioral impairments.

Heavy Metals Bioaccumulation in Mytilus galloprovincialis and Tapes decussatus from Faro Lake (Messina), Italy

The aim of this study was to evaluate the potential bioaccumulation of arsenic (As), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb) and mercury (Hg) in the haemolymph and corpus of Mytilus galloprovincialis and Tapes decussatus from Lake Faro. The lake is particularly prone to the accumulation of substances that are potentially toxic to aquatic organisms, due to the input of pollutants from urban and agricultural sources and the low rate of water exchange. The combination of saltwater from the Tyrrhenian Sea, the Strait of Messina and freshwater from hilly aquifers has created brackish conditions in the lake, resulting in an area of high commercial shellfish productivity. As, Cd, Cu, Pb and Zn were determined using a single quadrupole inductively coupled plasma mass spectrometer; Hg was determined using a direct mercury analyser (DMA-80). Physicochemical parameters of the water from Lake Faro were also performed. Statistical analysis was carried out using GraphPad Prism 9.0 (GraphPad Software, Inc., Boston, MA, USA) and Shapiro-Wilk normality was applied. Concentrations of Cd, Hg and Pb below the permitted MRLs in Mytilus galloprovincialis and Tapes decussatus used as ''biological indicators'' show that Lake Faro is not at risk of contamination by these pollutants and, moreover, is free of health problems for the consumer based on regulatory limits.

A protein-miRNA biomic analysis approach to explore neuroprotective potential of nobiletin in human neural progenitor cells (hNPCs)

Chemical-induced neurotoxicity is increasingly recognized to accelerate the development of neurodegenerative disorders (NDs), which pose an increasing health burden to society. Attempts are being made to develop drugs that can cross the blood-brain barrier and have minimal or no side effects. Nobiletin (NOB), a polymethoxylated flavonoid with anti-oxidative and anti-inflammatory effects, has been demonstrated to be a promising compound to treat a variety of NDs. Here, we investigated the potential role of NOB in sodium arsenate (NA)-induced deregulated miRNAs and target proteins in human neural progenitor cells (hNPCs). The proteomics and microRNA (miRNA) profiling was done for different groups, namely, unexposed control, NA-exposed, NA + NOB, and NOB groups. Following the correlation analysis between deregulated miRNAs and target proteins, RT-PCR analysis was used to validate the selected genes. The proteomic analysis showed that significantly deregulated proteins were associated with neurodegeneration pathways, response to oxidative stress, RNA processing, DNA repair, and apoptotic process following exposure to NA. The OpenArray analysis confirmed that NA exposure significantly altered miRNAs that regulate P53 signaling, Wnt signaling, cell death, and cell cycle pathways. The RT-PCR validation studies concur with proteomic data as marker genes associated with autophagy and apoptosis (HO-1, SQSTM1, LC-3, Cas3, Apaf1, HSP70, and SNCA1) were altered following NA exposure. It was observed that the treatment of NOB significantly restored the deregulated miRNAs and proteins to their basal levels. Hence, it may be considered one of its neuroprotective mechanisms. Together, the findings are promising to demonstrate the potential applicability of NOB as a neuroprotectant against chemical-induced neurotoxicity.

Proteomic-miRNA Biomics Profile Reveals 2D Cultures of Human iPSC-Derived Neural Progenitor Cells More Sensitive than 3D Spheroid System Against the Experimental Exposure to Arsenic

The iPSC-derived 3D models are considered to be a connective link between 2D culture and in vivo studies. However, the sensitivity of such 3D models is yet to be established. We assessed the sensitivity of the hiPSC-derived 3D spheroids against 2D cultures of neural progenitor cells. The sub-toxic dose of Sodium Arsenite (SA) was used to investigate the alterations in miRNA-proteins in both systems. Though SA exposure induced significant alterations in the proteins in both 2D and 3D systems, these proteins were uncommon except for 20 proteins. The number and magnitude of altered proteins were higher in the 2D system compared to 3D. The association of dysregulated miRNAs with the target proteins showed their involvement primarily in mitochondrial bioenergetics, oxidative and ER stress, transcription and translation mechanism, cytostructure, etc., in both culture systems. Further, the impact of dysregulated miRNAs and associated proteins on these functions and ultrastructural changes was compared in both culture systems. The ultrastructural studies revealed a similar pattern of mitochondrial damage, while the cellular bioenergetics studies confirm a significantly higher energy failure in the 2D system than to 3D. Such a higher magnitude of changes could be correlated with a higher amount of internalization of SA in 2D cultures than in 3D spheroids. Our findings demonstrate that a 2D culture system seems better responsive than a 3D spheroid system against SA exposure.

Arsenic Exposure Induces Neuro-immune Toxicity in the Cerebral Cortex and the Hippocampus via Neuroglia and NLRP3 Inflammasome Activation in C57BL/6 Mice

This study aimed to examine the immuntoxic effects of arsenic in the nervous system. Our results showed that arsenic increased corticocerebral and hippocampal weights (p < 0.05). Morris water maze tests revealed that arsenic significantly increased the time spent in latency to platform on the fourth day in 50 mg/L arsenic exposure and the fifth day in 25 and 50 mg/L arsenic exposure, as well as reduced the path length in target quadrant, time spent in target quadrant, and crossing times of the platform (p < 0.05). Hematoxylin-eosin staining showed that the vacuolated degeneration and pyknosis was found in the cerebral cortex and hippocampus of arsenic-treated mice. The mRNA levels of corticocerebral and hippocampal brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) were decreased in the 50 mg/L arsenic-treated group (p < 0.05). In addition, immunofluorescence staining showed that 25 and 50 mg/L arsenic all increased the expression of CD11b and glial fibrillary acidic protein (GFAP) in the cerebral cortex and hippocampus (p < 0.05). Arsenic markedly raised antigen-presenting molecule MHCII and CD40 mRNA levels in the cerebral cortex and hippocampus and upregulated the cell chemokine receptor 5 (CCR5) and CCR7 mRNA levels in the cerebral cortex at the 50 mg/L arsenic group, and increased the CCR7 mRNA levels in the hippocampus at the 25 and 50 mg/L arsenic groups (p < 0.05). Arsenic activated the nucleotide-binding domain-like receptor protein-3 (NLRP3) inflammasome, and enhanced its upstream promoter NF-κB protein level and downstream regulators IL-18 mRNA levels. Collectively, these results provide new evidences for the neuro-immune toxicity of arsenic.

Selenium and zinc protect against heavy metal mixture-induced, olfactory bulb and hippocampal damage by augmenting antioxidant capacity and activation of Nrf2-Hmox-1 signaling in male rats

PURPOSE/AIM OF THE STUDY

Heavy metals and metalloids have been implicated in neurodenerative diseases. Present study has evaluated the potential protective effects of Se and Zn on heavy metals and metalloids mixture-induced (Cd, Pb, Hg and As) toxicity in the hippocampus and olfactory bulb in male rats.

MATERIALS AND METHODS

Five groups of Wistar rats were randomly divided in to: controls, toxic metals mixture (TMM) exposed rats (PbCl2, 20 mg·kg-1; CdCl2, 1.61 mg·kg-1; HgCl2, 0.40 mg·kg-1 and NaAsO3, 10 mg·kg-1)), TMM + Zn, TMM + Se and TMM-+Zn + Se groups and were orally treated for 60 days.

RESULTS

We found that in hippocampus and olfactory bulb, TMM generated increased lipid peroxidation and diminished antioxidant capacity. These adverse effects induced by TMM were alleviated by Zn and Se co-treatment; moreover, essential trace elements (Zn and Se) decreased activity of acetylcholinesterase, reduced Cd, Pb, Hg and As bioaccumulation in hippocampus and olfactory bulb and decreased levels of TNF-α in the hippocampus. TMM treated rats had lower levels of Hmox-1 (hippocampus), higher levels of Nrf2 (olfactory bulb and hippocampus) and NF-kB (olfactory bulb). TMM treated rats showed significantly highest time in locating the escape hole. Histopathological examination revealed hypertrophied granule cells in OB of TMM exposed rats.

CONCLUSION

Zn and Se supplementation can reverse quaternary mixture-induced (Cd, Pb, Hg and As) toxicity in hippocampus and OB in male albino rats.

Effect of Arsenic on Fluoride Tolerance in Microbacterium paraoxydans Strain IR-1

Fluoride (F) and arsenic (As) are two major contaminants of water and soil systems around the globe, causing potential toxicity to humans, plants, animals, and microbes. These contaminated soil systems can be restored by microorganisms that can tolerate toxic stress and provide rapid mineralization of soil, organic matter, and contaminants, using various tolerance mechanisms. Thus, the present study was undertaken with the arsenic hyper-tolerant bacterium Microbacterium paraoxydans strain IR-1 to determine its tolerance and toxicity to increasing doses of fluoride, either individually or in combination with arsenic, in terms of growth inhibition using a toxicity unit model. The minimum inhibitory concentration (MIC)and half maximal inhibitory concentration (IC50) values for fluoride increased, from 9 g/L to 11 g/L and from 5.91 ± 0.1 g/L to 6.32 ± 0.028 g/L, respectively, in the combination (F + As) group. The statistical comparison of observed and expected additive toxicities, with respect to toxicity unit (TU difference), using Student's t-test, was found to be highly significant (p < 0.001). This suggests the antagonistic effect of arsenic on fluoride toxicity to the strain IR-1. The unique stress tolerance of IR-1 ensures its survival as well as preponderance in fluoride and arsenic co-contaminated sites, thus paving the way for its possible application in the natural or artificial remediation of toxicant-exposed degraded soil systems.

Arsenic exposure induced anxiety-like behaviors in male mice via influencing the GABAergic Signaling in the prefrontal cortex

Arsenic contamination in drinking water causes a global public health problem. Emerging evidence suggests that arsenic may act as an environmental risk factor for anxiety disorders. However, the exact mechanism underlying the adverse effects has not been fully elucidated. This study aimed to evaluate the anxiety-like behaviors of mice exposed to arsenic trioxide (As2O3), to observe the neuropathological changes, and to explore the link between the GABAergic system and behavioral manifestations. For this purpose, male C57BL/6 mice were exposed to various doses of As2O3 (0, 0.15, 1.5, and 15 mg/L) through drinking water for 12 weeks. Anxiety-like behaviors were assessed using the open field test (OFT), light/dark choice test, and elevated zero maze (EZM). Neuronal injuries in the cerebral cortex and hippocampus were assessed by light microscopy with H&E and Nissl staining. Ultrastructural alteration in the cerebral cortex was assessed by transmission electron microscope (TEM). The expression levels of GABAergic system-related molecules (i.e., glutamate decarboxylase, GABA transporter, and GABAB receptor subunits) in the prefrontal cortex (PFC) were determined by qRT-PCR and western blotting. Arsenic exposure showed a striking anxiogenic effect on mice, especially in the group exposed to 15 mg/L As2O3. Light microscopy showed neuron necrosis and reduced cell counts. TEM revealed marked ultrastructural changes, including the vacuolated mitochondria, disrupted Nissl bodies, an indentation in the nucleus membrane, and delamination of myelin sheath in the cortex. In addition, As2O3 influenced the GABAergic system in the PFC by decreasing the expression of the glutamate decarboxylase 1 (GAD1) and the GABAB2 receptor subunit, but not the GABAB1 receptor subunit. To sum up, sub-chronic exposure to As2O3 is associated with increased anxiety-like behaviors, which may be mediated by altered GABAergic signaling in the PFC. These findings shed light on the mechanisms responsible for the neurotoxic effects of arsenic and therefore more cautions should be taken.

Fenugreek seed powder protects mice against arsenic-induced neurobehavioral changes

The current study was designed to evaluate the protective effect of fenugreek seed powder against As-induced neurobehavioral and biochemical perturbations using a mouse model. Mice exposed to arsenic at 10 mg/kg body weight showed development of anxiety-like behavior and memory impairment compared to control mice in elevated plus maze and Morris water maze tests, respectively. A significantly decreased acetyl and butyrylcholinesterase, superoxide dismutase and glutathione reductase activities and brain-derived neurotrophic factor levels were found in the brain of arsenic-exposed mice compared to control mice. Interestingly, supplementation of fenugreek seed powder to arsenic-treated mice significantly restored the activity of cholinesterase and antioxidant enzymes (e.g. superoxide dismutase, glutathione reductase) as well as brain-derived neurotrophic factor levels in the brain tissue of arsenic-exposed mice. Consequently, reduced anxiety-like behavior, improved learning and memory were observed in fenugreek supplemented arsenic treated mice compared to only arsenic-exposed mice group. Thus, this study suggests that fenugreek seed powder reduces arsenic-induced neurotoxicity in mice.

Heavy metal toxicity in poultry: a comprehensive review

Arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) have been recognized as most toxic heavy metals that are continuously released into the environment, both from natural sources and from anthropogenic production of fertilizers, industrial activities, and waste disposal. Therefore, As, Cd, Hg, and Pb are found in increasing concentrations in bodies of water, fodder, feed, and in the tissues of livestock, including poultry, in the surroundings of industrial areas, leading to metabolic, structural, and functional abnormalities in various organs in all animals. In poultry, bioaccumulation of As, Pb, Cd, and Hg occurs in many organs (mainly in the kidneys, liver, reproductive organs, and lungs) as a result of continuous exposure to heavy metals. Consumption of Cd lowers the efficiency of feed conversion, egg production, and growth in poultry. Chronic exposure to As, Pb, Cd, and Hg at low doses can change the microscopic structure of tissues (mainly in the brain, liver, kidneys, and reproductive organs) as a result of the increased content of these heavy metals in these tissues. Histopathological changes occurring in the kidneys, liver, and reproductive organs are reflected in their negative impact on enzyme activity and serum biochemical parameters. Metal toxicity is determined by route of exposure, length of exposure, and absorbed dosage, whether chronic and acute. This review presents a discussion of bioaccumulation of As, Cd, Pb, and Hg in poultry and the associated histopathological changes and toxic concentrations in different tissues.

Nephroprotective Effects of Selenium Nanoparticles Against Sodium Arsenite-Induced Damages

Introduction

The potential effects of selenium nanoparticles (SeNPs) administration on arsenic exposure-mediated nephrotoxicity by alleviating fibrosis, inflammation, oxidative stress-related damage, and apoptosis remains more detailed investigations.

Methods

After the synthesis of selenium nanoparticles (SeNPs) by sodium selenite (Na₂SeO₃) through a versatile and green procedure, the biosafety of SeNPs was assessed by assaying renal functions and inflammation in mice. Subsequently, nephroprotective effects of SeNPs against sodium arsenite (NaAsO₂)-induced damages were confirmed by biochemical, molecular, and histopathological assays, including renal function, histological lesion, fibrosis, inflammation, oxidative stress-related damage, and apoptosis in mice renal tissues and renal tubular duct epithelial cells (HK2 cells).

Results

The excellent biocompatibility and safety of SeNPs prepared in this study were confirmed by the non-significant differences in the renal functions and inflammation levels in mice between the negative control (NC) and 1 mg/kg SeNPs groups (p>0.05). The results of biochemical, molecular, and histopathological assays confirmed that daily administration of 1 mg/kg SeNPs for 4 weeks not only ameliorated renal dysfunctions and injuries caused by NaAsO₂ exposure but also inhibited the fibrosis, inflammation, oxidative stress-related damage, and apoptosis in the renal tissues of NaAsO₂-exposed mice. In addition, altered viability, inflammation, oxidative stress-related damage, and apoptosis in the NaAsO₂-exposed HK2 cells were effectively reversed after 100 μg/mL SeNPs supplementation.

Conclusion

Our findings authentically confirmed the biosafety and nephroprotective effects of SeNPs against NaAsO₂ exposure-induced damages by alleviating inflammation, oxidative stress-related damage, and apoptosis.

Mitigation of maternal fecal microbiota transplantation on neurobehavioral deficits of offspring rats prenatally exposed to arsenic: Role of microbiota-gut-brain axis

It is established that gut microbiota dysbiosis is implicated in arsenic (As)-induced neurotoxic process, however, the underlying mode of action remains largely unclear. Here, through remodeling gut microbiota on As-intoxicated pregnancy rats using fecal microbiota transplantation (FMT) from Control rats, neuronal loss and neurobehavioral deficits in offspring prenatally exposed to As were significantly alleviated after maternal FMT treatment. In prenatal As-challenged offspring after maternal FMT treatment, remarkably, suppressed expression of inflammatory cytokines in tissues (colon, serum, and striatum) were observed along with reversed mRNA and protein expression of tight junction related molecules in intestinal barrier and blood-brain barrier (BBB); Further, expression of serum lipopolysaccharide (LPS), toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (Myd88) and nuclear transcription factor-κB (NF-κB) in colonic and striatal tissues were repressed with activation of astrocytes and microglia inhibited. In particular, tightly correlated and enriched microbiomes were identified such as higher-expressed g_Prevotella, g_UCG_005, and lower-expressed p_Desulfobacterota, g_Eubacterium_xylanophilum_group. Collectively, our results first demonstrated that reconstruction of normal gut microbiota by maternal FMT treatment alleviated prenatal As-induced overall inflammatory state and impairments of intestinal barrier and BBB integrity by impeding LPS-mediated TLR4/Myd88/NF-κB signaling pathway through microbiota-gut-brain axis, which provides a novel therapeutic avenue for developmental arsenic neurotoxicity.

Minocycline as a Neuroprotective Agent in Arsenic-Induced Neurotoxicity in PC12 Cells

Arsenic is a naturally occurring metalloid that exists in water, soil, food, and air. Humans can be exposed to arsenic through occupational, medical, or nutritional routes. Both acute and chronic forms of toxicity with severe outcomes are likely following arsenic exposure. Neurotoxicity is one of the serious manifestations of arsenic toxicity. In our study, the effect of minocycline, a widely used antimicrobial agent with antioxidant aspects and the ability to cross the blood-brain barrier, was evaluated against arsenic-induced neurotoxicity. PC12 cell line was used as the cellular model of this study. Cells were pre-treated with minocycline (50 nM-1 µM) for 2 h, and then incubated for 24 h after adding sodium arsenite (10 µM). The MTT assay and fluorimetry were performed to study cytotoxicity and reactive oxygen species generation, respectively. Finally, Western blotting was done to determine the levels of caspase-8, Bax, Bcl-2, and caspase-3. Once exposed to arsenic, the cell viability was significantly reduced, the intracellular oxidative balance was significantly disrupted, and the levels of proteins caspase-8, Bax/Bcl-2, and caspase-3 were significantly increased. Minocycline not only attenuated arsenic-induced cytotoxicity and reduced oxidative stress, but also led to lower levels of caspase-8, Bax/Bcl-2, and caspase-3 proteins compared with the arsenic-treated cells. Minocycline can significantly protect cells against arsenic-induced neurotoxicity by antioxidant and anti-apoptosis properties via both intrinsic and extrinsic caspase-dependent apoptotic pathways; therefore, at this point, it's worth considering it as a promising agent for the treatment of arsenic toxicity.

Insufficient evidence to link human exposure to heavy metals with biomarkers of glioma

Information on molecular mechanisms has implicated potential association between the concentrations of heavy metals and incidences of glioma, but experimental data on human brain tissue remain sparse. To address this data gap, 13 heavy metals were measured in 137 glioma and 35 non-glioma samples collected from 161 alive patients in Guangdong Province, China in 2019 - 2020. All target heavy metals were detected, suggesting they could cross the blood-brain barrier. Concentrations of Mn, Cu, and Zn were higher in glioma than in non-glioma samples, while those of Ni and Se were higher in non-glioma samples, probably suggesting that these five heavy metals are more prone to be altered by changing pathological conditions. In addition, Cu/Zn, Cr/Mn, Cr/Se, Ni/Se, Pb/Mn, and Pb/Se were statistically different between glioma and non-glioma samples by a difference test and a multiple logistic regression model. These concentration ratios may serve as chemical markers to assist pathological analysis for differentiating between tumor and healthy tissues. However, no direct link between heavy metal concentrations or concentration ratios and biomarkers of glioma (i.e., tumor grade, P53, and Ki-67) was observed. No sufficient evidence was obtained to implicate the role of heavy metals in inducing glioma, largely caused by the limited number of samples. Different concentrations and concentration ratios of heavy metals may be the consequence rather than the cause of pathological changes in brain tumors.

The protective effect of natural or chemical compounds against arsenic-induced neurotoxicity: Cellular and molecular mechanisms

Arsenic is a notorious metalloid that exists in the earth's crust and is considered toxic for humans and the environment. Both cancerous and non-cancerous complications are possible after arsenic exposure. Target organs include the liver, lungs, kidney, heart, and brain. Arsenic-induced neurotoxicity, the main focus of our study, can occur in central and peripheral nervous systems. Symptoms can develop in a few hours, weeks, or years depending on the quantity of arsenic and the duration of exposure. In this review, we aimed to gather all the compounds, natural and chemical, that have been studied as protective agents in cellular, animal, and human reports. Oxidative stress, apoptosis, and inflammation are frequently described as destructive mechanisms in heavy metal toxicity. Moreover, reduced activity of acetylcholinesterase, the altered release of monoamine neurotransmitters, down-regulation of N-methyl-D-aspartate receptors, and decreased brain-derived neurotrophic factor are important underlying mechanisms of arsenic-induced neurotoxicity. As for neuroprotection, though some compounds have yet limited data, there are others, such as curcumin, resveratrol, taurine, or melatonin which have been studied more deeply and might be closer to a reliable protective agent. We collected the available information on all protective agents and the mechanisms by which they fight against arsenic-induced neurotoxicity.

The potential neuroprotective effects of stingless bee honey

Tropical Meliponini bees produce stingless bee honey (SBH). Studies have shown beneficial properties, including antibacterial, bacteriostatic, anti-inflammatory, neurotherapeutic, neuroprotective, wound, and sunburn healing capabilities. High phenolic acid and flavonoid concentrations offer SBH its benefits. SBH can include flavonoids, phenolic acids, ascorbic acid, tocopherol, organic acids, amino acids, and protein, depending on its botanical and geographic origins. Ursolic acid, p-coumaric acid, and gallic acid may diminish apoptotic signals in neuronal cells, such as nuclear morphological alterations and DNA fragmentation. Antioxidant activity minimizes reactive oxygen species (ROS) formation and lowers oxidative stress, inhibiting inflammation by decreasing enzymes generated during inflammation. Flavonoids in honey reduce neuroinflammation by decreasing proinflammatory cytokine and free radical production. Phytochemical components in honey, such as luteolin and phenylalanine, may aid neurological problems. A dietary amino acid, phenylalanine, may improve memory by functioning on brain-derived neurotrophic factor (BDNF) pathways. Neurotrophin BDNF binds to its major receptor, TrkB, and stimulates downstream signaling cascades, which are crucial for neurogenesis and synaptic plasticity. Through BDNF, SBH can stimulate synaptic plasticity and synaptogenesis, promoting learning and memory. Moreover, BDNF contributes to the adult brain's lasting structural and functional changes during limbic epileptogenesis by acting through the cognate receptor tyrosine receptor kinase B (TrkB). Given the higher antioxidants activity of SBH than the Apis sp. honey, it may be more therapeutically helpful. There is minimal research on SBH's neuroprotective effects, and the related pathways contribute to it is unclear. More research is needed to elucidate the underlying molecular process of SBH on BDNF/TrkB pathways in producing neuroprotective effects.

Genetic Approaches for Iron and Zinc Biofortification and Arsenic Decrease in Oryza sativa L. Grains

Rice is the staple diet to half of the world's population, being a major source of carbohydrates, vitamins, and some essential elements. However, rice naturally contains low amounts of essential minerals such as iron (Fe) and zinc (Zn), which are drastically decreased after milling. Thus, populations that consume mostly rice may have micronutrient deficiency, which is associated with different diseases. On the other hand, rice irrigated by flooding has a high ability to accumulate arsenic (As) in the grain. Therefore, when rice is grown in areas with contaminated soil or irrigation water, it represents a risk factor for consumers, since As is associated with cancer and other diseases. Different strategies have been used to mitigate micronutrient deficiencies such as Fe and Zn and to prevent As from entering the food chain. Each strategy has its positive and its negative sides. The development of genetically biofortified rice plants with Fe and Zn and with low As accumulation is one of the most promising strategies, since it does not represent an additional cost for farmers, and gives benefits to consumers as well. Considering the importance of genetic improvement (traditional or molecular) to decrease the impact of micronutrient deficiencies such as Fe and Zn and contamination with As, this review aimed to summarize the major efforts, advances, and challenges for genetic biofortification of Fe and Zn and decrease in As content in rice grains.

Arsenic Induces GSK3β-dependent p-tau, neuronal apoptosis and cognitive impairment via an interdependent hippocampal ERα and IL-1/IL-1R1 mechanism in female rats

Arsenic is an environmental contaminant with potential neurotoxicity. We previously reported that arsenic promoted hippocampal neuronal apoptosis, inducing cognitive loss. Here, we correlated it with tau pathology. We observed that environmentally relevant arsenic exposure increased tau phosphorylation and the principal tau kinase, glycogen synthase kinase-3 beta (GSK3β), in the female rat hippocampal neurons. We detected the same in primary hippocampal neurons. Since a regulated estrogen receptor (ER) level and inflammation contributed to normal hippocampal functions, we examined their levels following arsenic exposure. Our ER screening data revealed that arsenic down-regulated hippocampal neuronal ERα. We also detected an up-regulated hippocampal interleukin-1 (IL-1) and its receptor, IL-1R1. Further, co-treating arsenic with the ERα agonist, 4,4',4''-(4-Propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), or IL-1R antagonist (IL-1Ra) resulted in reduced GSK3β and p-tau, indicating involvement of decreased ERα and increased IL-1/IL-1R1 in tau hyperphosphorylation. We then checked whether ERα and IL-1/IL-1R1 had linkage, and detected that while PPT reduced IL-1 and IL-1R1, the IL-1Ra restored ERα, suggesting their arsenic-induced interdependence. We finally correlated this pathway with apoptosis and cognition. We observed that PPT, IL-1Ra and the GSK3β inhibitor, LiCl, reduced hippocampal neuronal cleaved caspase-3 and TUNEL+ve apoptotic count, and decreased the number of errors during learning and increased the saving-memory for Y-Maze Test and retention performance for Passive avoidance test in arsenic-treated rats. Thus, our study reveals a novel mechanism of arsenic-induced GSK3β-dependent tau pathology via interdependent ERα and IL-1/IL-1R1 signaling. It also envisages the protective role of ERα agonist and IL-1 inhibitor against arsenic-induced neurotoxicity.

Cortex metabolome and proteome analysis reveals chronic arsenic exposure via drinking water induces developmental neurotoxicity through hnRNP L mediated mitochondrial dysfunction in male rats

Lots of people are at the risk of arsenic-contaminated drinking water. Arsenic exposure was confirmed to be closely linked to neurocognitive deficits, particularly during childhood. The multi-omics approaches are known be well suitable for toxicological research. Thus, this study aimed to explore the molecular mechanisms of arsenic-induced learning and memory function impairments through the integrative proteome and metabolome analysis of cortex in rats. The weaned rats were exposed to arsenic-contaminated drinking water for six months to mimic the developmental exposure. 220 differential proteins and 19 differential metabolites were identified in the cortex, and nine potential biomarkers were found to be related to impaired Morris water maze (MWM) indicators. Chronic arsenic exposure affected the cognitive function by inducing the overproduction of amyloid-β (Aβ) peptides and the redox imbalance in the mitochondria. Glycolysis and tricarboxylic acid (TCA) cycle enhancement driven by the increased heterogeneous nuclear ribonucleoprotein L (hnRNP L) is a low-dose protective mechanism against arsenic-induced ATP deficiency and oxidative stress. Moreover, apoptosis is another important pathway of arsenic-induced neurotoxicity. This study provides new evidence about the alterations of proteins and metabolites in the cortex of the exposed rats under arsenic toxicity. These findings suggest hnRNP L could be a potential target for the treatment of arsenic-induced neurotoxicity.

Assessment of Metal Intake by Selected Food Supplements Based on Beehive Products

The aim of this study was to determine the quantity of particular toxic metals (Pb, Cd, As, Hg) and micronutrients (Cr, Fe, Co, Ni, Cu, Zn, Se) in the recommended daily dose of 51 food supplements based on beehive products. Samples taken from the Croatian market were submitted for the identification/quantification of studied metals and micronutrients. It was carried out by means of inductively coupled plasma mass spectrometry (ICP-MS). Eleven samples (21.57%) showed an increased concentration of total arsenic, three samples (5.88%) contained an increased concentration of total iron, and eight samples (15.68%) had an increased concentration of total nickel. Three samples (5.88%) contained an increased concentration of zinc, while one sample (1.96%) contained an increased concentration of selenium. Increased levels of certain toxic metals and micronutrients do not pose a danger to human health because the amount identified was less than what can cause toxic effects in humans. All other analysed metals and micronutrients fell within the defined literature values. Despite certain increases in particular parameters, all samples met the established toxicity criteria. This study evidenced their safety if consumed in the recommended daily dose.

Fluorescent Indicators For Biological Imaging of Monatomic Ions

Monatomic ions play critical biological roles including maintaining the cellular osmotic pressure, transmitting signals, and catalyzing redox reactions as cofactors in enzymes. The ability to visualize monatomic ion concentration, and dynamic changes in the concentration, is essential to understanding their many biological functions. A growing number of genetically encodable and synthetic indicators enable the visualization and detection of monatomic ions in biological systems. With this review, we aim to provide a survey of the current landscape of reported indicators. We hope this review will be a useful guide to researchers who are interested in using indicators for biological applications and to tool developers seeking opportunities to create new and improved indicators.

Arsenic Induces Differential Neurotoxicity in Male, Female, and E2-Deficient Females: Comparative Effects on Hippocampal Neurons and Cognition in Adult Rats

We earlier reported that arsenic induced hippocampal neuronal loss, causing cognitive dysfunctions in male rats. This neuronal damage mechanism involved an altered bone morphogenetic protein (BMP2)/Smad and brain-derived neurotrophic factor (BDNF)/TrkB signaling. Susceptibility to toxicants is often sex-dependent, and hence we studied the comparative effects of arsenic in adult male and female rats. We observed that a lower dose of arsenic reduced learning-memory ability, examined through passive avoidance and Y-maze tests, in male but not female rats. Again, male rats exhibited greater learning-memory loss at a higher dose of arsenic. Supporting this, arsenic-treated male rats demonstrated larger reduction in the hippocampal NeuN and %-surviving neurons, together with increased apoptosis and altered BMP2/Smad and BDNF/TrkB pathways compared to their female counterparts. Since the primary female hormone, estrogen (E2), regulates normal brain functions, we next probed whether endogenous E2 levels in females offered resistance against arsenic-induced neurotoxicity. We used ovariectomized (OVX) rat as the model for E2 deficiency. We primarily identified that OVX itself induced hippocampal neuronal damage and cognitive decline, involving an increased BMP2/Smad and reduced BDNF/TrkB. Further, these effects appeared greater in arsenic + OVX compared to arsenic + sham (ovary intact) or OVX rats alone. The OVX-induced adverse effects were significantly reduced by E2 treatment. Overall, our study suggests that adult males could be more susceptible than females to arsenic-induced neurotoxicity. It also indicates that endogenous E2 regulates hippocampal BMP and BDNF signaling and restrains arsenic-induced neuronal dysfunctions in females, which may be inhibited in E2-deficient conditions, such as menopause or ovarian failure.

Life-long arsenic exposure damages the microstructure of the rat hippocampus

Epidemiological studies demonstrate that arsenic exposure is associated with cognitive dysfunction. Experimental arsenic exposure models showed learning and memory deficits and molecular changes resembling the functional and pathologic neurodegeneration features. The present work focuses on hippocampal pathological changes in Wistar rats induced by continuous arsenic exposure from in utero up to 12 months of age, evaluated by magnetic resonance imaging along with immunohistochemistry. Diffusion-weighted images revealed age-related lower fractional anisotropy and higher radial-axial and mean diffusivity at 6 and 12 months, indicating that arsenic exposure leads to hippocampal demyelination. These structural alterations were paralleled by immunohistochemical changes that showed a significant loss of myelin basic protein in CA1 and CA3 regions accompanied by increased glial fibrillary acidic protein expression at all time-points studied. Concomitantly, arsenic exposure induced an altered morphology of astrocytes at all studied ages, whereas increased synaptogenesis was only observed at two months of age. These results suggest that environmental arsenic exposure is linked to impaired hippocampal connectivity and perhaps early glial senescence, which together might resemble a premature aging phenomenon leading to cognitive deficits.

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.

Resveratrol Attenuates Learning, Memory, and Social Interaction Impairments in Rats Exposed to Arsenic

Arsenic (As) toxicity has deleterious effects on human health causing disorder in the brain. The aim of this study was to investigate the possible neuroprotective effect of resveratrol (RSV) on arsenic-induced neurotoxicity in rats. Neurotoxicity in rats was developed by treating As 10 mg/kg/day for 21 days orally. Animals were put into seven groups: control, vehicle, As, As+RSV10, As+RSV20 mg/kg, RSV10, and RSV20 mg/kg. Behavioral assessments such as the social interaction test, novel object recognition test, elevated plus maze, open field, the Morris water maze, in addition to assessment of biomarkers such as ferric reducing ability of plasma assay, glutathione assay, and malondialdehyde assay, were used to evaluate the effects of RSV on cognitive impairment and molecular changes induced by As. The results showed that cognitive performance impaired in As rats. RSV20 mg/kg significantly could ameliorate behavioral changes like spatial learning in days 3 and 4 (p < 0.05), recognition learning and memory (p < 0.01), disabilities in motor coordination and stress (p < 0.05), increased anxiety (p < 0.05), and social interaction deficit (sociability (p < 0.001) and social memory (p < 0.05)). RSV20 mg/kg also attenuated molecular modifications like decreased antioxidant power (p < 0.001), reduced glutathione content (p < 0.05), and increased malondialdehyde level (p < 0.05) induced by As. In addition to oxidative stress assessments, RSV10 mg/kg could significantly increase FRAP (p < 0.01) and GSH (p < 0.05); however, MDA was not significantly increased. Our current behavioral findings suggest that RSV has neuroprotective effects against AS toxicity.

The modulatory potential of herbal antioxidants against oxidative stress and heavy metal pollution: plants against environmental oxidative stress

Free radicals, principally reactive oxygen species (ROS), contribute to oxidative stress in human beings. Free radicals have different mechanisms of action and affect lipids, proteins, and DNA. Heavy metals including cadmium (Cd), lead (Pb), and arsenic are environmental pollutants that may induce oxidative stress and produce ROS, leading to harmful effects on different body systems such as the liver and brain. On the other side, antioxidants can have protective effects against oxidative stress and decrease their toxicity. Herbal antioxidants have potential antioxidative effects. These antioxidants positively affect neurodegenerative diseases, atherosclerotic diseases, lung fibrosis, kidney injuries, and liver toxicities induced by oxidative agents, including heavy metals. In this manuscript, we explained the mechanisms of oxidative stress, and also discussed heavy metals which contribute to human oxidative stress. We further discussed different herbal antioxidants, their mechanisms of action, and their clinical use for various diseases.

Molecular Mechanism of Arsenic-Induced Neurotoxicity including Neuronal Dysfunctions

Arsenic is a key environmental toxicant having significant impacts on human health. Millions of people in developing countries such as Bangladesh, Mexico, Taiwan, and India are affected by arsenic contamination through groundwater. Environmental contamination of arsenic leads to leads to various types of cancers, coronary and neurological ailments in human. There are several sources of arsenic exposure such as drinking water, diet, wood preservatives, smoking, air and cosmetics, while, drinking water is the most explored route. Inorganic arsenic exhibits higher levels of toxicity compared its organic forms. Exposure to inorganic arsenic is known to cause major neurological effects such as cytotoxicity, chromosomal aberration, damage to cellular DNA and genotoxicity. On the other hand, long-term exposure to arsenic may cause neurobehavioral effects in the juvenile stage, which may have detrimental effects in the later stages of life. Thus, it is important to understand the toxicology and underlying molecular mechanism of arsenic which will help to mitigate its detrimental effects. The present review focuses on the epidemiology, and the toxic mechanisms responsible for arsenic induced neurobehavioral diseases, including strategies for its management from water, community and household premises. The review also provides a critical analysis of epigenetic and transgenerational modifications, mitochondrial oxidative stress, molecular mechanisms of arsenic-induced oxidative stress, and neuronal dysfunction.

Theaflavin-3'-O-gallate a Black-tea Constituent Blocked SARS CoV-2 RNA dependant RNA Polymerase Active-site with Better Docking Results than Remdesivir

BACKGROUND

Replication of SARS-CoV-2 depends on viral RNA-dependent RNA-polymerase (RdRp). Remdesivir, the broad-spectrum RdRp inhibitor acts as nucleoside-analogues (NAs). Remdesivir has initially been repurposed as a promising drug against SARS-CoV-2 infection with some health hazards like liver damage, allergic reaction, low blood-pressure, and breathing-shortness, throat-swelling. In comparison, theaflavin-3'-O-gallate (TFMG), the abundant black tea component has gained importance in controlling viral infection. TFMG is a non-toxic, non-invasive, antioxidant, anticancer and antiviral molecule.

RESULTS

Here, we analyzed the inhibitory effect of theaflavin-3'-O-gallate on SARS CoV-2 RdRp in comparison with remdesivir by molecular-docking study. TFMG has been shown more potent in terms of lower Atomic-Contact-Energy (ACE) and higher occupancy of surface area; -393.97 Kcal/mol and 771.90 respectively, favoured with lower desolvation-energy; -9.2:  Kcal/mol. TFMG forms more rigid electrostatic and H-bond than remdesivir. TFMG showed strong affinity to RNA primer and template and RNA passage-site of RdRp.

CONCLUSIONS

TFMG can block the catalytic residue, NTP entry site, cation binding site, nsp7-nsp12 junction with binding energy of -6. 72 Kcal/mol with Ki value of 11.79, and interface domain with binding energy of -7.72 and -6.16 Kcal/mol with Ki value of 2.21 and 30.71 µM. And most importantly, TFMG shows antioxidant/anti-inflammatory/antiviral effect on human studies.

Microglia-derived IL-1β promoted neuronal apoptosis through ER stress-mediated signaling pathway PERK/eIF2α/ATF4/CHOP upon arsenic exposure

Arsenic is the leading toxicant of hazardous environmental chemicals, which is linked with neurotoxicity including cognitive dysfunction, neurodevelopmental alterations and neurodegenerative disorders. It has been suggested that sustained pro-inflammatory response is one of the triggering factors of arsenic-induced neurotoxicity. Microglia, the immune cells in the central nervous system, response to physiological and pathological stress, and release a large array of pro-inflammatory cytokines if activated excessively. Several studies indicated that arsenic was capable of inducing microglia activation, however, the role of the subsequently released pro-inflammatory cytokines in arsenic-induced neurotoxicity remains to be elucidated. Our findings demonstrated that arsenic-induced cognitive dysfunction, microglia activation, up-regulation and release of IL-1β and ER stress-mediated apoptosis could be attenuated by minocycline, a recognized inhibitor of microglia activation. In addition, the IL-1 receptor antagonist IL-1ra diminished arsenic-induced activation of ER stress-mediated apoptotic pathway PERK/eIF2α/ATF4/CHOP and neuronal apoptosis. Our findings provided evidences that arsenic-induced microglia activation also contributed to neuronal apoptosis through pro-inflammatory cytokine. Microglia-derived IL-1β promoted hippocampal neuronal apoptosis through ER stress-mediated PERK/eIF2α/ATF4/CHOP apoptotic pathway. Neuronal apoptosis induced by prolonged activation of microglia was partially involved in the arsenic-induced cognitive dysfunction.

Exposure to Environmental Arsenic and Emerging Risk of Alzheimer's Disease: Perspective Mechanisms, Management Strategy, and Future Directions

Alzheimer’s disease (AD) is one of the most prevailing neurodegenerative diseases, characterized by memory dysfunction and the presence of hyperphosphorylated tau and amyloid β (Aβ) aggregates in multiple brain regions, including the hippocampus and cortex. The exact etiology of AD has not yet been confirmed. However, epidemiological reports suggest that populations who were exposed to environmental hazards are more likely to develop AD than those who were not. Arsenic (As) is a naturally occurring environmental risk factor abundant in the Earth’s crust, and human exposure to As predominantly occurs through drinking water. Convincing evidence suggests that As causes neurotoxicity and impairs memory and cognition, although the hypothesis and molecular mechanism of As-associated pathobiology in AD are not yet clear. However, exposure to As and its metabolites leads to various pathogenic events such as oxidative stress, inflammation, mitochondrial dysfunctions, ER stress, apoptosis, impaired protein homeostasis, and abnormal calcium signaling. Evidence has indicated that As exposure induces alterations that coincide with most of the biochemical, pathological, and clinical developments of AD. Here, we overview existing literature to gain insights into the plausible mechanisms that underlie As-induced neurotoxicity and the subsequent neurological deficits in AD. Prospective strategies for the prevention and management of arsenic exposure and neurotoxicity have also been discussed.

Antioxidant Effect of Hydroxytyrosol, Hydroxytyrosol Acetate and Nitrohydroxytyrosol in a Rat MPP+ Model of Parkinson's Disease

3,4-Dihydroxyphenyl ethanol, known as hydroxytyrosol (HTy), is a phenylpropanoid found in diverse vegetable species. Several studies have demonstrated that HTy is a potent antioxidant. Thus, our study is aimed to evaluate the antioxidant effect of HTy and its derivatives, hydroxytyrosol acetate (HTyA) and nitrohydroxytyrosol (HTyN), in a model of oxidative stress induced by 1-methyl-4-phenylpyridinium (MPP⁺) in rats. Rats were administered intravenously (i.v.) in the tail with 1 mL saline solution or polyphenol compound (1.5 mg/kg) 5 min before intrastriatal infusion of 10 µg MPP⁺/8 µL. We found that rats injured with MPP⁺, pretreatment with HTy, HTyA or HTyN significantly decreased ipsilateral turns. This result was consistent with a significant preservation of striatal dopamine levels and decreased lipid fluorescence products (LFP), a marker of oxidative stress. Brain GSH/GSSG ratio, from rats pretreated with HTy or HTyN showed a significant preservation of that marker, decreased as a consequence of MPP⁺-induced oxidative damage. These results show an antioxidant effect of HTy, HTyA and HTyN in the MPP⁺ model of Parkinson's disease in the rat.

Sodium arsenite induces spatial learning and memory impairment associated with oxidative stress and activates the Nrf2/PPARγ pathway against oxidative injury in mice hippocampus

Arsenic (As) is a ubiquitous environmental and industrial toxin with known correlates of oxidative stress and cognitive deficits in the brain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcriptional factor that represents a central cellular antioxidant defense mechanism and transcribes many antioxidant genes. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a well-known nuclear receptor to regulate lipid metabolism in many tissues, and it has been also associated with the control of oxidative stress, neuronal death, neurogenesis and differentiation. The role of Nrf2 and PPARγ in As-induced neurotoxicity is still debated. The present study was designed to investigate the neurobehavioral toxic effect of sub-chronic and middle-dose sodium arsenite exposure in mice hippocampus, as well as the response of Nrf2/PPARγ expression and influence on protein expression levels of their downstream antioxidant genes. Our results showed that mice treated with intraperitoneal injection of sodium arsenite (50 mg/kg body wt.) twice a week for 7 weeks resulted in increased generation of reactive oxygen species and impairment of spatial cognitive function. The present study also found a positive association between Nrf2/PPARγ expression in hippocampus of mice, and activation of antioxidant defenses by the evidently upregulated expression of their downstream genes, including superoxide dismutase, heme oxygenase-1 and glutathione peroxidase-3. Therefore, our findings were helpful for further understanding the role of Nrf2/PPARγ feedback loop in As-induced neurobehavioral toxicity.

Different mechanisms of arsenic related signaling in cellular proliferation, apoptosis and neo-plastic transformation

Arsenic is a toxic heavy metal vastly dispersed all over the earth crust. It manifests several major adverse health issues to millions of arsenic exposed populations. Arsenic is associated with different types of cancer, cardiovascular disorders, diabetes, hypertension and many other diseases. On the contrary, arsenic (arsenic trioxide, As₂O₃) is used as a chemotherapeutic agent in the treatment of acute promyelocytic leukemia. Balance between arsenic induced cellular proliferations and apoptosis finally decide the outcome of its transformation rate. Arsenic propagates signals via cellular and nuclear pathways depending upon the chemical nature, and metabolic-fates of the arsenical compounds. Arsenic toxicity is propagated via ROS induced stress to DNA-repair mechanism and mitochondrial stability in the cell. ROS induced alteration in p53 regulation and some mitogen/ oncogenic functions determine the transformation outcome influencing cyclin-cdk complexes. Growth factor regulator proteins such as c-Jun, c-fos and c-myc are influenced by chronic arsenic exposure. In this review we have delineated arsenic induced ROS regulations of epidermal growth factor receptor (EGFR), NF-ĸβ, MAP kinase, matrix-metalloproteinases (MMPs). The role of these signaling molecules has been discussed in relation to cellular apoptosis, cellular proliferation and neoplastic transformation. The arsenic stimulated pathways which help in proliferation and neoplastic transformation ultimately resulted in cancer manifestation whereas apoptotic pathways inhibited carcinogenesis. Therapeutic strategies against arsenic should be designed taking into account all these factors.

Environmental neurotoxic pollutants: review

Environmental pollutants are recognized as one of the major concerns for public health and responsible for various forms of neurological disorders. Some of the common sources of environmental pollutants related to neurotoxic manifestations are industrial waste, pesticides, automobile exhaust, laboratory waste, and burning of terrestrial waste. Among various environmental pollutants, particulate matter, ultrafine particulate matter, nanoparticles, and lipophilic vaporized toxicant (acrolein) easily cross the blood-brain barrier, activate innate immune responses in the astrocytes, microglia, and neurons, and exert neurotoxicity. Growing shreds of evidence from human epidemiological studies have correlated the environmental pollutants with neuroinflammation, oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, myelin sheath disruption, and alterations in the blood-brain barrier anatomy leading to cognitive dysfunction and poor quality of life. These environmental pollutants also considerably cause developmental neurotoxicity, exhibit teratogenic effect and mental growth retardance, and reduce IQ level. Until now, the exact mechanism of pollutant-induced neurotoxicity is not known, but studies have shown interference of pollutants with the endogenous antioxidant defense system, inflammatory pathway (Nrf2/NF-kB, MAPKs/PI3K, and Akt/GSK3β), modulation of neurotransmitters, and reduction in long-term potentiation. In the current review, various sources of pollutants and exposure to the human population, developmental neurotoxicity, and molecular mechanism of different pollutants involved in the pathogenesis of different neurological disorders have been discussed.

Variations in Mineral/heavy Metals Profiling and Preventive Role of Trichomes in Peach Fruits Treated with CaC2

BACKGROUND

Phytonutrients in peach fruits have health-promoting antioxidants against various chronic diseases. However, there is no extensive data to show the nutritional values of Local peach cultivars after post-harvest treatments.

OBJECTIVE

Mainly this study was objective to determine the effect of calcium carbide on nutritional value and quality of fruits of Pakistani peach cultivars.

METHODS

The peach fruits were collected from three different peach orchids of KPK and the fruits were divided into 4 groups while 5th group was collected from a local fruit shop. Each experimental group was treated with different concentrations of calcium carbide whereas control group was not treated. The peel and pulp samples were oven dried and ground to fine powder separately. The elemental compositions were determined using Particle Induced X-ray emission and Pelletron Tandem Accelerator.

RESULTS

Sixteen elements were identified in peach fruits and the elements were Al, P, S, Cl, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, and Se. In peel, the concentration of some elements increased or decreased after treatment with CaC₂ while in pulp the conc. of nearly all detected elements was increased in treated samples. We found a significantly higher amount of heavy metals traces, including As, Se, Co, Si, and P in peach fruits treated with CaC₂ Interestingly, the presence of trichomes in peach skin prevents the transfer of these heavy metals deep into the pulp which was also verified by the elemental profiling of nectarines.

CONCLUSION

Conclusively, the artificial ripening with CaC₂ changed the nutritional value of peach fruits that has higher health risks if consume with the peel. According to our best knowledge, this is the first report that highlights the effects of CaC₂ which deteriorate the nutritional value of peach fruits in Pakistan.