Arsenic induces reactive oxygen species-caused neuronal cell apoptosis through JNK/ERK-mediated mitochondria-dependent and GRP 78/CHOP-regulated pathways

Arsenic-Induced Inflammatory Response via ROS-Dependent Activation of ERK/NF-kB Signaling Pathways: Protective Role of Natural Polyphenol Tannic Acid

Arsenic (As), a highly toxic metalloid, is present throughout our environment as a result of both natural and human-related activities. Furthermore, As exposure could lead to a persistent inflammatory response, which may facilitate the pathogenesis of several diseases in various organs. This study was performed to investigate the As-induced inflammatory response and the underlying molecular mechanisms in vitro. Further, the anti-inflammatory effects of a natural dietary polyphenol tannic acid (TA) were also explored. In human normal bronchial (BEAS-2B), adenocarcinoma alveolar basal (A549), and murine macrophages (J774) cell lines, a trivalent form of As (as As3+) exposure markedly induced the expression of various pro-inflammatory mediators (cytokines and chemokines). Additionally, it was found that As3+ exposure induced reactive oxygen species (ROS) generation and activation of the nuclear factor-kappa B (NF-kB) p65 and extracellular signal-regulated kinase (ERK)1/2 pathways in BEAS-2B cells. As expected, the blockade of either ERK1/2 (PD98059) or NF-kB p65 (IMD0354), or both pathways attenuated As3+-induced pro-inflammatory mediators release. Interestingly, pre-treatment with ROS inhibitor N-acetylcysteine (NAC) attenuated activation of ERK/NF-kB pathways, suggesting that ROS have a critical role in pathway's activation and subsequent inflammatory response. Further, TA pre-treatment effectively attenuated As3+-induced inflammatory response by suppressing ROS production and ERK/NF-kB signaling pathways activation. Therefore, this study provides scientific evidence for the anti-inflammatory activities of TA and the underlying molecular mechanisms.

Effects of Arsenic-induced Diabetic Vascular Diseases through Mitogen-activated Protein Kinase Signaling Pathway: In vitro and In vivo Studies

ABSTRACT

Arsenic (As) is an environmental pollutant that causes endocrine disruption. Diabetes increases the risk of Blackfoot disease, which is a peripheral artery disease caused by chronic exposure to As through drinking water in Taiwan and Bangladesh; however, the mechanism underlying this increased risk remains unclear. Therefore, in this study, we aimed to investigate the mechanisms underlying vascular damage in hyperglycemic conditions caused by As exposure using in vivo and in vitro studies. We utilized an animal model of streptozotocin-induced diabetes that was exposed to As through drinking water for 8 weeks. Subsequently, blood and organ samples of the animals were collected for follow-up analysis. Further, we cultured endothelial cells that were treated with As treatment in glucose condition and detected their biomarkers. The findings revealed that both the diabetes and diabetes + As groups exhibited insulin resistance, weight gain, and increased plasma triglyceride and total cholesterol levels. The diabetes + As group had lower antioxidant activity, which caused the arteries to exhibit prominent luminal narrowing with increased thickness. In vivo study revealed that glucose + As group-induced cell cycle arrest, a 98.80% increase in reactive oxygen species (ROS) levels, and decreased cell viability and mitochondrial membrane potential (MMP). However, in glucose + As group, treatment with SP600125 and U10126 treatment decreased ROS production by 80.5% and 84%, respectively, and restored MMP and cell viability. The glucose-regulated protein 78 level increased in the As as well as glucose + As groups. Our findings demonstrate that As exacerbates vascular damage in individuals with diabetes and its associated complications through the activation of the mitogen-activated protein kinase signaling pathway.

Effect of 2,5-hexanedione on rat ovarian granulosa cell apoptosis involves endoplasmic reticulum stress-dependent m-TOR signaling pathway

Occupational exposure to N-hexane/2,5-hexanedione (2,5-HD) was found to adversely affect reproductive functions in females. However, there are few studies regarding the mechanisms underlying reproductive system damage initiated by 2,5-HD. Several studies demonstrated that 2,5-HD exerts hormonal dysfunctions in females by promoting apoptosis using rat ovarian granulosa cells (GCs) as a model. The endoplasmic reticulum (ER) plays a key role in cellular processes such as protein folding and modification, Ca2+ storage, and lipid synthesis, which are known to involve the activation of stress (ERS)-dependent m-TOR signaling pathway. Thus, the aim of this study was to examine the effects of 2,5-HD on ER and the associated activation of stress (ERS)-dependent m-TOR signaling pathway resulting in consequent apoptosis of ovarian GCs. Data demonstrated that after intraperitoneal treatment with 100, 200, or 400 mg/kg 2,5-HD for 6 consecutive weeks, 5 times per week, a decrease in body weight, ovarian weight, and relative ovary weight was found. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay showed that 2,5-HD promoted apoptosis of ovarian GCs, which involved enhanced relative protein expression levels of m-TOR/p-mTOR. Our findings demonstrated that 2,5-HD (1) elevated expression levels of pro-apoptosis-related genes Bax and Caspase 3, (2) decreased expression levels of the anti-apoptosis gene Bcl-2, and (3) activated the protein expression of glucose-regulatory protein 78 (GRP78), inositol-requiring enzyme-1 (IRE1), and c-Jun terminal kinase (JNK) associated with increased apoptosis. Evidence indicates that chronic exposure to 2,5-HD induced apoptosis of ovarian GCs, and the possible mechanism underlying this effect involves the ERS-dependent m-TOR signaling pathway.

Synthesis, Biological Evaluation, Molecular Docking, and In Silico ADME Predictions of Huperzine: A Derivative for the Novel Protective Application Against Neurodegenerations

To date, there has been no effective treatment available for the Alzheimer's disease (AD); hence, novel compounds with AD inhibitory effects are highly desirable. Huperzine A (HupA), a natural Lycopodium alkaloid, is a potent acetylcholinesterase (AChE) inhibitor for AD treatment. In this study, HupA derivatives, huperzil, N-hippurylhuperzine A, pyrrolhuperzine A, maleicamide-huperzine A and phthaleicamide-huperzine A, were synthesized and their in silico computation as the central nervous system (CNS) drug was performed. All derivatives exhibited lower anti-AChE activity than HupA. However, we found other non-cholinergic functions in AD-mimicking models using differentiated SH-SY5Y. HupA and derivatives significantly suppressed the Aβ25-35 cytotoxicity and showed recovery effects against arsenic- induced AD pathologies including reactive oxygen species generation, neurite outgrowth shortening, amyloid precursor protein suppression and the elevation of β-secretase, endogenous Aβ peptide, and Tau and neurofilament light proteins. In summary, we prepared three potential compounds with dual-AChE cholinergic and non-cholinergic functions. Further development of these compounds will be beneficial for the future use as an alternate compound against AD.

New advances in Traditional Chinese Medicine interventions for epilepsy: where are we and what do we know?

Epilepsy, one of the most common neurological diseases, affects more than 70 million people worldwide. Anti-seizure drugs targeting membrane ion channels or GABAergic neurotransmission are the first choices for controlling seizures, whereas the high incidence of pharmacoresistance and adverse effects largely restrict the availability of current anti-seizure drugs (ASDs). Traditional Chinese Medicine (TCM) has shown historical evidence-based therapeutic effects for neurological diseases including epilepsy. But until the late 1990s, great efforts in both clinical and experimental fields advanced TCM interventions for epilepsy from evidence-based practices to more systematic neuropharmacological significance, and show new lights on preferable management of epilepsy in the last decade. This review summarized the advances of applying TCM interventions (ranging from herbal medicines and their active ingredients to other strategies such as acupuncture) for epilepsy, followed by associated mechanism theories. The therapeutic potential of TCM interventions for epilepsy as well as its comorbidities turns from somehow debatable to hopeful. Finally, some prospects and directions were proposed to drive further clinical translational research. The future directions of TCM should aim at not only deriving specific anti-epileptic molecules but also illustrating more precise mechanisms with the assistance of advanced multifaceted experimental tools.

Ferulic acid ameliorates bisphenol A (BPA)-induced Alzheimer's disease-like pathology through Akt-ERK crosstalk pathway in male rats

OBJECTIVES

This study investigated the neuroprotective effect of ferulic acid (FA) against bisphenol A (BPA) induced Alzheimer's disease-like pathology in male rats.

METHODS

Rats were allocated into four groups, control, BPA, BPA + FA, and FA, respectively, for 40 days. Spatial working memory and recognition memory were evaluated. Moreover, the brain levels of oxidative stress biomarkers, proinflammatory cytokines, extracellular signal-regulated kinase (ERK), and phosphorylated serine/threonine protein kinase (p-Akt) were measured. We also determined the brain neuropathological protein levels, including Beta-Amyloid 1-42, total Tau (tTau), and phosphorylated Tau (pTau) proteins. Furthermore, brain levels of Acetylcholinesterase (AChE) and Beta-secretase (BACE) were assessed. Brain histological investigation and immunohistochemistry determination of glial fibrillar acidic protein (GFAP) were also performed. Moreover, docking simulation was adapted to understand the inhibitory role of FA on AChE, BACE-1, and ERK1/2.

RESULTS

Interestingly, the BPA + FA treated group showed a reversal in the cognitive impairments induced by BPA, which was associated with improved brain redox status. They also exhibited a significant decrease in brain inflammatory cytokines, ERK, and p-Akt levels. Moreover, they revealed a decline in beta-amyloid 1-42 and a significant improvement in tTau expression and pTau protein levels in the brain tissue. Further, the brain levels of AChE and BACE were substantially reduced in BPA + FA rats. The neuroprotective effect of FA was confirmed by restoring the normal architecture of brain tissue, which was associated with decreasing GFAP.

CONCLUSION

FA could be a potent neuroprotectant agent against AD with a possible prospect for its therapeutic capabilities and nutritional supplement value due to its antioxidant and antiapoptotic properties.

Targeting Nrf2/HO-1 signaling by crocin: Role in attenuation of arsenic trioxide-induced neurotoxicity in mice

ETHNOPHARMACOLOGY RELEVANCE

Saffron is a valued herb, obtained from the stigmas of the C.sativus Linn (Iridaceae). Pharmacopoeias have described it as having a variety of actions, such as stimulant, anti-carcinogen, and anti-depressant. As a folk medicine, crocin has been reported to have anti-cardiotoxicity and anti-hepatotoxicity effects. This paper focuses on crocin, one of the bioactive molecules found in saffron that are known to have therapeutic effects. Crocin has been shown in numerous experimental studies to be beneficial in treating depression, however, there aren't many studies on its neurotoxicity.

AIM OF THE STUDY

Applications of arsenic trioxide (ATO) in medical settings is limited by its side effects. This study aims to examine crocin's protective effect against ATO-induced neurotoxicity and understand its potential molecular mechanism. Materialandmethods: A neurotoxicity model was created by administering ATO (4 mg/L/d). To counteract this, mice were intraperitoneally injected with crocin (100, 200 mg/kg/d). After 60 days, biochemical, histopathological, transmission electron microscopy, ELISA, and western blotting analyses were then performed.

RESULTS

Our results indicated that crocin decreased neuronal death and loss caused by ATO, countered oxidative stress damage, and mitigated pro-inflammatory cytokines. Mice treated with crocin also displayed positive signs of brain tissue recovery. Additionally, crocin reduced the protein expressions of NLRP1, apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1, GRP78, CHOP, and ATF4.

CONCLUSIONS

This study attests that crocin can reduce ATO-induced neurotoxicity by safeguarding nerves from oxidative stress, inflammation, and apoptosis, possibly through the activation of the Nrf2/HO-1 signaling pathway.

Inorganic arsenic modulates cell apoptosis by regulating Argonaute 2 expression via the p53 pathway

This study explores the role of Argonaute 2 (AGO2) in the induction of apoptosis by arsenic in 16HBE cells and investigates the association between AGO2 expression and arsenic exposure in a human population. By silencing AGO2 with siRNA, we examined its impact on cell viability and apoptosis using CCK-8, HO-PI, and JC-1 assays, complemented by qRT-PCR and Western blot analyses for gene and protein expressions. Our findings revealed a significant correlation between AGO2 expression and levels of exposure to inorganic arsenic (iAs), which was more pronounced than with other arsenic forms such as monomethylarsonic (MMA) and dimethylarsinic acids (DMA). The results showed that silencing AGO2 not only reduced cell viability but also intensified apoptosis, highlighting its role in activating the p53 pathway. This was further supported by increased phosphorylation of p53 at Ser392 and Thr55, reinforcing AGO2's involvement in apoptotic processes. The study underscores the potential of AGO2 as a therapeutic target in arsenic-related pathologies and highlights the critical need for managing occupational exposure to arsenic.

Isolinderalactone suppresses pancreatic ductal adenocarcinoma by activating p38 MAPK to promote DDIT3 expression and trigger endoplasmic reticulum stress

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies worldwide, and its incidence rate is increasing. PDAC patients are prone to acquired chemotherapy resistance, necessitating the development of novel drugs to provide alternative treatment options. In recent years, traditional folk medicine and its active ingredients have garnered increasing attention for their effectiveness in treating tumors. Here, we discovered that isolinderalactone (ILL), a sesquiterpenoid compound extracted from the traditional Chinese medicine Lindera aggregata (Sims) Kosterm., possesses anti-PDAC pharmacological activity. Our results revealed that ILL decreased the proliferative capacity of PDAC cells in a time- and dose-dependent manner. The migration and invasion abilities of tumor cells were significantly suppressed due to the inhibition of epithelial-to-mesenchymal transition (EMT). Additionally, the cell cycle was arrested in the G2/M phase, leading to apoptosis, and inhibiting inflammatory responses. Mechanistically, bioinformatics analysis of molecular expression changes combined with in vivo and in vitro experiments demonstrated that ILL induces persistent ER stress by activating p38 MAPK signaling pathway, thus promoting the expression of DDIT3, and ultimately suppressing progression-related cell behaviors. Animal experiments confirmed that ILL also inhibited PDAC development in vivo with minimal toxicity. In summary, our study identified ILL as a potential therapeutic compound for PDAC treatment.

C11orf58 (Hero20) Gene Polymorphism: Contribution to Ischemic Stroke Risk and Interactions with Other Heat-Resistant Obscure Chaperones

Background: Recently identified Hero proteins, which possess chaperone-like functions, are promising candidates for research into atherosclerosis-related diseases, including ischemic stroke (IS). Methods: 2204 Russian subjects (917 IS patients and 1287 controls) were genotyped for fifteen common SNPs in Hero20 gene C11orf58 using probe-based PCR and the MassArray-4 system. Results: Six C11orf58 SNPs were significantly associated with an increased risk of IS in the overall group (OG) and significantly modified by smoking (SMK) and low fruit/vegetable intake (LFVI): rs10766342 (effect allele (EA) A; P(OG = 0.02; SMK = 0.009; LFVI = 0.04)), rs11024032 (EA T; P(OG = 0.01; SMK = 0.01; LFVI = 0.036)), rs11826990 (EA G; P(OG = 0.007; SMK = 0.004; LFVI = 0.03)), rs3203295 (EA C; P(OG = 0.016; SMK = 0.01; LFVI = 0.04)), rs10832676 (EA G; P(OG = 0.006; SMK = 0.002; LFVI = 0.01)), rs4757429 (EA T; P(OG = 0.02; SMK = 0.04; LFVI = 0.04)). The top ten intergenic interactions of Hero genes (two-, three-, and four-locus models) involved exclusively polymorphic loci of C11orf58 and C19orf53 and were characterized by synergic and additive (independent) effects between SNPs. Conclusions: Thus, C11orf58 gene polymorphism represents a major risk factor for IS. Bioinformatic analysis showed the involvement of C11orf58 SNPs in molecular mechanisms of IS mediated by their role in the regulation of redox homeostasis, inflammation, vascular remodeling, apoptosis, vasculogenesis, neurogenesis, lipid metabolism, proteostasis, hypoxia, cell signaling, and stress response. In terms of intergenic interactions, C11orf58 interacts most closely with C19orf53.

Neuroprotective Effects of Morin Against Cadmium- and Arsenic-Induced Cell Damage in PC12 Neurons

Arsenic and cadmium, both toxic metals and widespread environmental pollutants, can trigger apoptosis and oxidative stress in various tissues and cells. Morin, a natural flavonoid with diverse biological properties, has been found to protect neurons from oxidative stress and apoptosis-induced damage. This research aimed to examine the protective properties of morin against neurotoxicity caused by arsenic and cadmium, utilizing PC12 cells as a model for nerve cells. The cells were pre-treated with different concentrations of morin and then exposed to arsenic and cadmium, after which cell viability and reactive oxygen species (ROS) production were assessed. Additionally, western blotting was performed to evaluate the protein levels of the Bax/Bcl-2 ratio and cleaved-caspase-3. Following exposure to arsenic and cadmium, there were significant increases in ROS, Bax/Bcl-2 ratio, and cleaved-caspase-3. However, the results of the study demonstrated the beneficial effects of morin at various concentrations, as it increased cell viability and decreased ROS production. Furthermore, morin at a concentration of 10 µM was found to reduce the elevated levels of cleaved-caspase-3 induced by arsenic and diminish the increased Bax/Bcl-2 ratio after exposure to arsenic and cadmium. The findings of this study suggest that morin can effectively protect cells from arsenic and cadmium-induced neurotoxicity through its antioxidant and anti-apoptotic effects. Thus, morin should be considered a promising agent for treating arsenic and cadmium toxicity.

The Role of Endoplasmic Reticulum Stress on Reducing Recombinant Protein Production in Mammalian Cells

Therapeutic recombinant protein production relies on industrial scale culture of mammalian cells to produce active proteins in quantities sufficient for clinical use. The combination of stresses from industrial cell culture environment and recombinant protein production can overwhelm the protein synthesis machinery in the endoplasmic reticulum (ER). This leads to a buildup of improperly folded proteins which induces ER stress. Cells respond to ER stress by activating the Unfolded Protein Response (UPR). To restore proteostasis, ER sensor proteins reduce global protein synthesis and increase chaperone protein synthesis, and if that is insufficient the proteins are degraded. If proteostasis is still not restored, apoptosis is initiated. Increasing evidence suggests crosstalk between ER proteostasis and DNA damage repair (DDR) pathways. External factors (e.g., metabolites) from the cellular environment as well as internal factors (e.g., transgene copy number) can impact genome stability. Failure to maintain genome integrity reduces cell viability and in turn protein production. This review focuses on the association between ER stress and processes that affect protein production and secretion. The processes mediated by ER stress, including inhibition of global protein translation, chaperone protein production, degradation of misfolded proteins, DNA repair, and protein secretion, impact recombinant protein production. Recombinant protein production can be reduced by ER stress through increased autophagy and protein degradation, reduced protein secretion, and reduced DDR response.

Induction of oxidative- and endoplasmic-reticulum-stress dependent apoptosis in pancreatic cancer cell lines by DDOST knockdown

The dolichyl-diphosphooligosaccharide-protein glycosyltransferase non-catalytic subunit (DDOST) is a key component of the oligosaccharyltransferase complex catalyzing N-linked glycosylation in the endoplasmic reticulum lumen. DDOST is associated with several cancers and congenital disorders of glycosylation. However, its role in pancreatic cancer remains elusive, despite its enriched pancreatic expression. Using quantitative mass spectrometry, we identify 30 differentially expressed proteins and phosphopeptides (DEPs) after DDOST knockdown in the pancreatic ductal adenocarcinoma (PDAC) cell line PA-TU-8988T. We evaluated DDOST / DEP protein-protein interaction networks using STRING database, correlation of mRNA levels in pancreatic cancer TCGA data, and biological processes annotated to DEPs in Gene Ontology database. The inferred DDOST regulated phenotypes were experimentally verified in two PDAC cell lines, PA-TU-8988T and BXPC-3. We found decreased proliferation and cell viability after DDOST knockdown, whereas ER-stress, ROS-formation and apoptosis were increased. In conclusion, our results support an oncogenic role of DDOST in PDAC by intercepting cell stress events and thereby reducing apoptosis. As such, DDOST might be a potential biomarker and therapeutic target for PDAC.

N-acetylcysteine attenuates sodium arsenite-induced oxidative stress and apoptosis in embryonic fibroblast cells

In recent years, the increase in environmental pollutants has been one of the most important factors threatening human and environmental health. Arsenic, a naturally occurring element found in soil, water, and air, easily enters the human body and leads to many metabolic disorders. In this study, we focused on the possible protective effects of N-acetylcysteine (NAC) against sodium arsenite (As)-induced toxic effects on embryonic fibroblast cells. The effects of As and NAC treatment on cells were evaluated, including cytotoxicity, oxidative stress, and apoptosis. Embryonic fibroblast cells were exposed to As (ranging from 0.01 μM to 10 μM) and NAC (at a concentration of 2 mM) for 24 h. The assessment of cytotoxicity markers, such as cell viability and lactate dehydrogenase (LDH), showed that As significantly reduced cell viability and increased LDH levels. Furthermore, we observed that As increased the amount of reactive oxygen species (ROS) in the cell, decreased the activity of antioxidant enzymes, and triggered apoptosis in cells. Additionally, our research revealed that the administration of NAC mitigates the detrimental effects of As. The results showed that As exerted hazardous effects on embryonic fibroblast cells through the induction of oxidative stress and apoptosis. In this context, our study provides evidence that NAC may have a protective effect against the toxicity of As in embryonic fibroblast cells.

Analysis of arsenic-modulated expression of hypothalamic estrogen receptor, thyroid receptor, and peroxisome proliferator-activated receptor gamma mRNA and simultaneous mitochondrial morphology and respiration rates in the mouse

Arsenic has been identified as an environmental toxicant acting through various mechanisms, including the disruption of endocrine pathways. The present study assessed the ability of a single intraperitoneal injection of arsenic, to modify the mRNA expression levels of estrogen- and thyroid hormone receptors (ERα,β; TRα,β) and peroxisome proliferator-activated receptor gamma (PPARγ) in hypothalamic tissue homogenates of prepubertal mice in vivo. Mitochondrial respiration (MRR) was also measured, and the corresponding mitochondrial ultrastructure was analyzed. Results show that ERα,β, and TRα expression was significantly increased by arsenic, in all concentrations examined. In contrast, TRβ and PPARγ remained unaffected after arsenic injection. Arsenic-induced dose-dependent changes in state 4 mitochondrial respiration (St4). Mitochondrial morphology was affected by arsenic in that the 5 mg dose increased the size but decreased the number of mitochondria in agouti-related protein- (AgRP), while increasing the size without affecting the number of mitochondria in pro-opiomelanocortin (POMC) neurons. Arsenic also increased the size of the mitochondrial matrix per host mitochondrion. Complex analysis of dose-dependent response patterns between receptor mRNA, mitochondrial morphology, and mitochondrial respiration in the neuroendocrine hypothalamus suggests that instant arsenic effects on receptor mRNAs may not be directly reflected in St3-4 values, however, mitochondrial dynamics is affected, which predicts more pronounced effects in hypothalamus-regulated homeostatic processes after long-term arsenic exposure.

Camellia sinensis polysaccharide attenuates inflammatory responses via the ROS-mediated pathway by endocytosis

Polysaccharide CSTPs extracted from Camellia sinensis tea-leaves possessed unique against oxidative damage by scavenging ROS. Herein, acid tea polysaccharide CSTPs-2 with tightly packed molecular structure was isolated, purified and characterized in this research. Furthermore, the effects of CSTPs-2 on ROS-involved inflammatory responses and its underlying mechanisms were investigated. The results suggest that CSTPs-2 dramatically reduced the inflammatory cytokines overexpression and LPS-stimulated cell damage. CSTPs-2 could trigger the dephosphorylation of downstream AKT/MAPK/NF-κB signaling proteins and inhibit nuclear transfer of p-NF-κB to regulate the synthesis and release of inflammatory mediators in LPS-stimulated cells by ROS scavenging. Importantly, the impact of CSTPs-2 in downregulating pro-inflammatory cytokines and mitigating ROS overproduction is associated with clathrin- or caveolae-mediated endocytosis uptake mechanisms, rather than TLR-4 receptor-mediated endocytosis. This study presents a novel perspective for investigating the cellular uptake mechanism of polysaccharides in the context of anti-inflammatory mechanisms.

Prosopis africana exerts neuroprotective activity against quaternary metal mixture-induced memory impairment mediated by oxido-inflammatory response via Nrf2 pathway

The beneficial effects of Prosopis africana (PA) on human health have been demonstrated; however, its protective effects against heavy metals (HM) are not yet understood. This study evaluated the potential neuroprotective effects of PA in the cerebral cortex and cerebellum. To accomplish this, we divided 35 albino Sprague Dawley rats into five groups. Group I did not receive either heavy metal mixture (HMM) or PA. Group II received a HMM of PbCl2 (20 mg/kg), CdCl2 (1.61 mg/kg), HgCl2 (0.40 mg/kg), and NaAsO3 (10 mg/kg) orally for a period of two months. Groups III, IV, and V received HMM along with PA at doses of 500, 1000, and 1500 mg/kg, respectively. PA caused decreased levels of HM accumulation in the cerebral cortex and cerebellum and improved performance in the Barnes maze and rotarod tests. PA significantly reduced levels of IL-6 and TNF-α. PA increased concentrations of SOD, CAT, GSH, and Hmox-1 and decreased the activities of AChE and Nrf2. In addition, levels of MDA and NO decreased in groups III, IV, and V, along with an increase in the number of live neurons. In conclusion, PA demonstrates a complex neuroprotective effect with the potential to alleviate various aspects of HM-induced neurotoxicity.

Endoplasmic reticulum stress responses and epigenetic alterations in arsenic carcinogenesis

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

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.

New Insight into the Potential Protective Function of Sulforaphene against ROS-Mediated Oxidative Stress Damage In Vitro and In Vivo

Sulforaphene (SFE) is a kind of isothiocyanate isolated from radish seeds that can prevent free-radical-induced diseases. In this study, we investigated the protective effect of SFE on oxidative-stress-induced damage and its molecular mechanism in vitro and in vivo. The results of cell experiments show that SFE can alleviate D-gal-induced cytotoxicity, promote cell cycle transformation by inhibiting the production of reactive oxygen species (ROS) and cell apoptosis, and show a protective effect on cells with H2O2-induced oxidative damage. Furthermore, the results of mice experiments show that SFE can alleviate D-galactose-induced kidney damage by inhibiting ROS, malondialdehyde (MDA), and 4-hydroxyalkenals (4-HNE) production; protect the kidney against oxidative stress-induced damage by increasing antioxidant enzyme activity and upregulating the Nrf2 signaling pathway; and inhibit the activity of pro-inflammatory factors by downregulating the expression of Toll-like receptor 4 (TLR4)-mediated inflammatory response. In conclusion, this research shows that SFE has antioxidant effects, providing a new perspective for studying the anti-aging properties of natural compounds.

SIRT1/P53 pathway is involved in the Arsenic induced aerobic glycolysis in hepatocytes L-02 cells

Arsenic is a known human carcinogen. Low doses of arsenic can induce cell proliferation, but the mechanism remains elusive. Aerobic glycolysis, also known as the Warburg effect, is one of the characteristics of tumour cells and rapidly proliferating cells. P53 is a tumour suppressor gene that has been shown to be a negative regulator of aerobic glycolysis. SIRT1 is a deacetylase that inhibits the function of P53. In this study, we found that P53 was involved in low dose of arsenic-induced aerobic glycolysis through regulating HK2 expression in L-02 cells. Moreover, SIRT1 not only inhibited P53 expression but also decreased the acetylation level of P53-K382 in arsenic-treated L-02 cells. Meanwhile, SIRT1 influenced the expression of HK2 and LDHA, which then promoted arsenic-induced glycolysis in L-02 cells. Therefore, our study demonstrated that the SIRT1/P53 pathway is involved in arsenic-induced glycolysis, thereby promoting cell proliferation, which provides theoretical basis for enriching the mechanism of arsenic carcinogenesis.

Nanoplastics promote arsenic-induced ROS accumulation, mitochondrial damage and disturbances in neurotransmitter metabolism of zebrafish (Danio rerio)

As a carrier, nanoplastics (NPs) can adsorb other toxic substances and thus modify their biological toxicity. Numerous studies have investigated the neurotoxic of high concentrations of arsenic (As, 2.83 mg/L-5 mg/L). However, it is still unknown whether the relatively low environmentally relevant concentrations of As (200 μg/L) can damage the structure and function of fish brains with the presence of NPs. In this study, zebrafish were exposed to polystyrene NPs, As and their mixture for 30 days respectively. Firstly, we found that the presence of NPs promoted the accumulation of As in zebrafish brains. Thereby the co-exposure of NPs and As further promoted the production of reactive oxygen species (ROS) in zebrafish brains compared with the single exposure of NPs or As, resulting in severe oxidative stress. Moreover, accumulated ROS directly damaged the mitochondrial membrane and mtDNA in zebrafish brains. Moreover, the mitochondrial damage was further aggravated due to inhibited mitochondrial fusion and activated mitochondrial division and mitophagy. Ultimately, the co-exposure led to mitochondrial damage in the zebrafish brain. Damaged mitochondria may not meet the high energy metabolic requirement for neuronal function. As a result, the normal function of nerve cells was adversely affected and eventually cell apoptosis may occur. Besides, the co-exposure caused more significant structural alterations in zebrafish brain tissue. Finally, the co-exposure of NPs and As caused abnormal biosynthesis and degradation of dopamine and acetylcholine. These resulted in decreased dopamine levels and increased acetylcholine levels in zebrafish brains. In conclusion, the presence of NPs promoted the accumulation of As, thereby inducing severe oxidative stress, which caused structural alterations and mitochondrial damage in the zebrafish brain, thus disordering neuromodulation, which may ultimately cause neurological dysfunction in zebrafish. This study will provide a risk assessment for evaluating the biotoxicity of NPs and As to fish and even other animals.

The 28-day repeated arsenic exposure increases tau phosphorylation in the rat brain

Herein, we examined whether prolonged arsenic exposure altered tau phosphorylation in the brain of Sprague Dawley rats expressing endogenous wild-type tau. The results showed that daily intraperitoneal injections of 2.5 mg/kg BW sodium arsenite over 28 days caused arsenic accumulation in the rat brain. Interestingly, we found an increase in tau phosphorylation at the Tau 1 region (189-207) and S202 in the hippocampus, S404 in the cerebral cortex, and S396 and S404 in the cerebellum of arsenic-treated rats. Additionally, arsenic increased active ERK1/2 phosphorylation at T202/Y204 in the hippocampus, cerebral cortex, and cerebellum. Meanwhile, we detected increasing active JNK phosphorylation at T183/Y185 in the hippocampus and cerebellum. Moreover, p35, a neuron-specific activator of CDK5, was also elevated in the cerebellum of arsenic-treated rats, suggesting that CDK5 activity may be increased by arsenic. These results suggested that arsenic may induce tau phosphorylation through the activation of tau kinases, ERK1/2, JNK, and CDK5. Together, the findings from this study demonstrated that prolonged arsenic exposure is implicated in neurodegeneration by promoting tau phosphorylation in the rat brain and points toward a possible prevention strategy against neurodegeneration induced by environmental arsenic exposure.

Ethanolic extract of Coleus aromaticus leaves impedes the proliferation and instigates apoptotic cell death in liver cancer HepG2 cells through repressing JAK/STAT cascade

Liver cancer or hepatocellular carcinoma (HCC) has become a leading cause for cancer burden across the globe, and incidences have tripled since the last two decades. Poor diagnosis of primary liver cancer and limited treatment strategies aggravate the challenges. Researchers globally have shown a steep inclination toward the exploration of plant-based compounds for their nutraceutical and anticancer potential to fit into the role of novel chemotherapeutics. Coleus aromaticus is a well-known culinary herb that earlier has been reported for several medicinal attributes. The current investigation deals with exploring the anticancer potential of ethanolic leaf extract of C. aromaticus (CoL-EtOH) against hepatocellular carcinoma HepG2 cell line. The observations made it evident that CoL-EtOH extract impeded the viability of HepG2 at 400 μg/ml (p < .01). Additionally, the extract also succeeded in escalating ROS production (p < .01) which aided dissipation of mitochondrial membrane potential and disruption of nuclear morphology. CoL-EtOH further activated caspase-8, -9, and -3 which was reaffirmed by increase in apoptosis at 400 μg/ml (p < .01). Moreover, post treatment with CaLEt-OH extract significantly reduced the expression of JAK-1 & STAT-3 genes (p < .01) along with regulated expression of Mcl1, Bcl-2, cyclinD1, p21, and p27 within HepG2 cells. This evidence portrays the promising anticancer potential of CoL-EtOH projecting it as a novel chemotherapeutic agent against HCC. PRACTICAL APPLICATIONS: The herb Coleus aromaticus belonging to Lamiaceae family and Coleus genus is known by various names in different regions of the world and several language-specific vernacular names. The herb has been used in therapeutic and medicinal applications as well as in culinary preparations. Various attributes of the nutritional strength and functional characteristics of the leaves in terms of carotenoids, minerals, phenols, dietary fiber, and antioxidant activity have been reported by several researchers. Carvacrol and thymol are majorly found in the plant, while chlorogenic acid and rosmarinic acid etc. as the phenolic components. The herb has been used in therapeutic and medicinal implications as well as in culinary preparations.

Arabinogalactan derived from Larix gmelinii (Rupr.) Kuzen. Alleviates cisplatin-induced acute intestinal injury in vitro and in vivo through IRE1α/JNK axis mediated apoptotic signaling pathways

Many dietary polysaccharides have been shown to protect against various harmful external stimuli by protecting the integrity of the intestinal barrier. Arabinogalactan (AG) is a high molecular weight polysaccharide composed of arabinose and galactose, which has good immunomodulatory, antioxidant and intestinal conditioning activities. Gastrointestinal injury caused by cisplatin (CP) is an inevitable damage during CP chemotherapy. This research explored the ameliorative effect of AG on cisplatin-induced intestinal toxicity and its possible molecular targets and mechanisms. The results showed that AG (200, 400 mg/kg) could significantly reverse the intestinal histopathological changes and oxidative stress injury caused by CP. Meantime, AG could target the IRE1α/JNK axis to inhibit the expression of apoptosis-related proteins and block the apoptotic cascade, thus reducing intestinal damage. In vitro, AG (10, 20, and 40 μg/mL) could regulate the IRE1α/JNK axis, inhibit apoptosis, and restore the antioxidant defense system damaged by CP to play a protective role in the intestine. In addition, 4-phenylbutyrate (4-PBA), a specific inhibitor of endoplasmic reticulum stress, was used to verify that AG also affected protein expression levels by regulating the IRE1α/JNK pathway-mediated endoplasmic reticulum stress signaling pathway, thereby alleviating CP-induced gastrointestinal dysfunction. Therefore, AG may be a potential drug to prevent CP-induced intestinal damage.

TNF-α derived from arsenite-induced microglia activation mediated neuronal necroptosis

Arsenic, an identified environmental toxicant, poses threats to the health of human beings through contaminated water and food. Recently, increasing reports focused on arsenic-induced nerve damage, however, the underlying mechanism remains elusive. Microglia are important immune cells in the nervous system, which produce a large number of inflammatory factors including TNF-α when activated. Recent reports indicated that TNF-α is involved in the process of necroptosis, a new type of programmed cell death discovered recently. Although there were evidences suggested that arsenic could induce both microglia activation and TNF-α production in the nervous system, the mechanism of arsenic-induced neurotoxicity due to microglia activation is rarely studied. In addition, the role of microglia-derived TNF-α in response to arsenic exposure in necroptosis has not been documented before. In this study, we found that arsenite induced microglial activation through p38 MAPK signaling pathway, leading to the production of TNF-α. Microglia-derived TNF-α further induced necroptosis in the neuronal cells. Our findings suggested that necroptosis induced by microglia-derived TNF-α upon arsenite exposure partially played a role in arsenic-induced cell death which underlie the fundamental event of arsenic-related neurotoxicity.

Norketamine, the Main Metabolite of Ketamine, Induces Mitochondria-Dependent and ER Stress-Triggered Apoptotic Death in Urothelial Cells via a Ca2+-Regulated ERK1/2-Activating Pathway

Ketamine-associated cystitis is characterized by suburothelial inflammation and urothelial cell death. Norketamine (NK), the main metabolite of ketamine, is abundant in urine following ketamine exposure. NK has been speculated to exert toxic effects in urothelial cells, similarly to ketamine. However, the molecular mechanisms contributing to NK-induced urothelial cytotoxicity are almost unclear. Here, we aimed to investigate the toxic effects of NK and the potential mechanisms underlying NK-induced urothelial cell injury. In this study, NK exposure significantly reduced cell viability and induced apoptosis in human urinary bladder epithelial-derived RT4 cells that NK (0.01–0.5 mM) exhibited greater cytotoxicity than ketamine (0.1–3 mM). Signals of mitochondrial dysfunction, including mitochondrial membrane potential (MMP) loss and cytosolic cytochrome c release, were found to be involved in NK-induced cell apoptosis and death. NK exposure of cells also triggered the expression of endoplasmic reticulum (ER) stress-related proteins including GRP78, CHOP, XBP-1, ATF-4 and -6, caspase-12, PERK, eIF-2α, and IRE-1. Pretreatment with 4-phenylbutyric acid (an ER stress inhibitor) markedly prevented the expression of ER stress-related proteins and apoptotic events in NK-exposed cells. Additionally, NK exposure significantly activated JNK, ERK1/2, and p38 signaling and increased intracellular calcium concentrations ([Ca²⁺]_i). Pretreatment of cells with both PD98059 (an ERK1/2 inhibitor) and BAPTA/AM (a cell-permeable Ca²⁺ chelator), but not SP600125 (a JNK inhibitor) and SB203580 (a p38 inhibitor), effectively suppressed NK-induced mitochondrial dysfunction, ER stress-related signals, and apoptotic events. The elevation of [Ca²⁺]_i in NK-exposed cells could be obviously inhibited by BAPTA/AM, but not PD98059. Taken together, these findings suggest that NK exposure exerts urothelial cytotoxicity via a [Ca²⁺]_i-regulated ERK1/2 activation, which is involved in downstream mediation of the mitochondria-dependent and ER stress-triggered apoptotic pathway, consequently resulting in urothelial cell death. Our findings suggest that regulating [Ca²⁺]_i/ERK signaling pathways may be a promising strategy for treatment of NK-induced urothelial cystitis.

Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway

Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.

Protective Effects of Alpha Lipoic Acid Against Arsenic Induced Oxidative Stress in Isolated Rat Liver Mitochondria

Arsenic as a heavy metal and toxic pollutant has been established that has the hepatotoxic effect in animal and human models. Previous studies showed that mitochondria as the first target of arsenic toxicity has a pathogenic role in liver diseases. This study investigated alpha lipoic acid (ALA) as an antioxidant could ameliorate against liver toxicity induced by arsenic in rat mitochondria. First, mitochondria were isolated by the liver tissue centrifugation protocol. Then, isolated mitochondria were exposed with different concentrations of ALA and arsenic in different times for receiving the optimum dose and time. Finally, mitochondria were pretreated with the optimum concentrations and times of ALA and then treated with optimum concentration and time of arsenic (160 μg/ml; 30 min). The results demonstrated a significant decrease in total mitochondrial dehydrogenase activity (mitochondrial complex II) by 3, 4 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay after arsenic exposure. Mitochondria treated with arsenic also showed a significant increase in ROS generation, MMP, and MDA levels. The activity of mitochondrial catalase and mitochondrial GSH significantly decreased after exposure of mitochondria with arsenic. Pretreatment of mitochondria with ALA improved mitochondrial complex II activity; decreased mitochondrial membrane damage, MDA, and ROS amounts; and ameliorated mitochondrial GSH levels and mitochondrial catalase activity. These findings revealed that arsenic induced oxidative stress and mitochondria dysfunction, while ALA improved mitochondrial function through increasing of antioxidant defense or preserving of complex II, but suggested that ALA could prevent from mitochondria dysfunction.

Investigating the Neurotoxic Impacts of Arsenic and the Neuroprotective Effects of Dictyophora Polysaccharide Using SWATH-MS-Based Proteomics

Arsenic (As) is one of the most important toxic elements in the natural environment. Currently, although the assessment of the potential health risks of chronic arsenic poisoning has received great attention, the research on the effects of arsenic on the brain is still limited. It has been reported that dictyophora polysaccharide (DIP), a common bioactive natural compound found in dietary plants, could reduce arsenic toxicity. Following behavioral research, comparative proteomics was performed to explore the molecular mechanism of arsenic toxicity to the hippocampi of SD (Sprague Dawley) rats and the protective effect of DIP. The results showed that exposure to arsenic impaired the spatial learning and memory ability of SD rats, while DIP treatment improved both the arsenic-exposed rats. Proteomic analysis showed that arsenic exposure dysregulated the expression of energy metabolism, apoptosis, synapse, neuron, and mitochondria related proteins in the hippocampi of arsenic-exposed rats. However, DIP treatment reversed or restored the expression levels of these proteins, thereby improving the spatial learning and memory ability of arsenic-exposed rats. This study is the first to use high-throughput proteomics to reveal the mechanism of arsenic neurotoxicity in rats as well as the protective mechanism of DIP against arsenic neurotoxicity.

Polyphenolics with Strong Antioxidant Activity from Acacia nilotica Ameliorate Some Biochemical Signs of Arsenic-Induced Neurotoxicity and Oxidative Stress in Mice

Neurotoxicity is a serious health problem of patients chronically exposed to arsenic. There is no specific treatment of this problem. Oxidative stress has been implicated in the pathological process of neurotoxicity. Polyphenolics have proven antioxidant activity, thereby offering protection against oxidative stress. In this study, we have isolated the polyphenolics from Acacia nilotica and investigated its effect against arsenic-induced neurotoxicity and oxidative stress in mice. Acacia nilotica polyphenolics prepared from column chromatography of the crude methanol extract using diaion resin contained a phenolic content of 452.185 ± 7.879 mg gallic acid equivalent/gm of sample and flavonoid content of 200.075 ± 0.755 mg catechin equivalent/gm of sample. The polyphenolics exhibited potent antioxidant activity with respect to free radical scavenging ability, total antioxidant activity and inhibition of lipid peroxidation. Administration of arsenic in mice showed a reduction of acetylcholinesterase activity in the brain which was counteracted by Acacia nilotica polyphenolics. Similarly, elevation of lipid peroxidation and depletion of glutathione in the brain of mice was effectively restored to normal level by Acacia nilotica polyphenolics. Gallic acid methyl ester, catechin and catechin-7-gallate were identified in the polyphenolics as the major active compounds. These results suggest that Acacia nilotica polyphenolics due to its strong antioxidant potential might be effective in the management of arsenic induced neurotoxicity.

The role of Fas-FasL-FADD signaling pathway in arsenic-mediated neuronal apoptosis in vivo and in vitro

The molecular mechanisms underlying arsenic-induced neurotoxicity have not been completely elucidated. Our study aimed to determine the role of the Fas-FasL-FADD signaling pathway in arsenic-mediated neuronal apoptosis. Pathological and molecular biological tests were performed on the cerebral cortex of arsenic-exposed rats and SH-SY5Y neuroblastoma cells. Arsenic induced apoptosis in the cortical neurons, which corresponded to abnormal ultrastructural changes. Mechanistically, arsenic activated the Fas-FasL-FADD signaling pathway and the downstream caspases both in vivo and in vitro. ZB4 treatment reversed the apoptotic effects of arsenic on the SHSY5Y cells. Taken together, arsenic induces neurotoxicity by activating the Fas-FasL-FADD signaling pathway.

Diphenylarsinic acid induced activation of MAP kinases, transcription factors, and oxidative stress-responsive factors and hypersecretion of cytokines in cultured normal human cerebellar astrocytes

Diphenylarsinic acid (DPAA) is a non-natural pentavalent organic arsenic and was detected in well water in Kamisu, Ibaraki, Japan in 2003. Individuals that had consumed this arsenic-contaminated water developed cerebellar symptoms such as myoclonus. We previously revealed that DPAA exposure in rats in vitro and in vivo specifically affected astrocytes rather than neurons among cerebellar cells. Here, we evaluated adverse effects of DPAA in cultured normal human cerebellar astrocytes (NHA), which were compared with those in normal rat cerebellar astrocytes (NRA) exposed to DPAA at 10 μM for 96 h, focusing on aberrant activation of astrocytes; increase in cell viability, activation of MAP kinases (ERK1/2, p38MAPK, and SAPK/JNK) and transcription factors (CREB, c-Jun, and c-Fos), upregulation of oxidative stress-responsive factors (Nrf2, HO-1, and Hsp70), and also hypersecretion of brain cytokines (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6) as reported in NRA. While DPAA exposure at 10 μM for 96 h had little effect on NHA, a higher concentration (50 μM for 96 h) and longer exposure (10 μM for 288 h) induced similar aberrant activation. Moreover, exposure to DPAA at 50 μM for 96 h or 10 μM for 288 h in NHA induced hypersecretion of cytokines induced in DPAA-exposed NRA (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6), and IL-8 besides into culture medium. These results suggested that aberrantly activated human astrocytes by DPAA exposure might play a pivotal role in the pathogenesis of cerebellar symptoms, affecting adjacent neurons, microglia, brain blood vessels, or astrocyte itself through these brain cytokines in human.

Changes in metabolomics and lipidomics in brain tissue and their correlations with the gut microbiome after chronic food-derived arsenic exposure in mice

Arsenic can cause neurodegenerative diseases of the brain, but the definite mechanism is still unknown. In this study, to discuss the disturbances on brain metabolome and lipidome under subchronic arsenic exposure, we treated mice with the arsenic-containing feed (concentration of total arsenic = 30 mg/kg) prepared in accordance with the proportion of rice arsenicals for 16 weeks and performed metabolomics and lipidomics studies respectively using UHPLC-Triple-TOF-MS/MS and UHPLC-Q Exactive Focus MS/MS on mice brain. In addition, the distributions of arsenical metabolites along the feed-gut-blood-brain chain were analyzed by ICP-MS and HPLC-ICP-MS, and fecal microbial variations were investigated by 16 s sequencing. The data showed that although only a tiny amount of arsenic (DMA=0.101 mg/kg, uAs=0.071 mg/kg) enters the brain through the blood-brain barrier, there were significant changes in brain metabolism, including 118 metabolites and 17 lipids. These different metabolites were involved in 30 distinct pathways, including glycometabolism, and metabolisms of lipid, nucleic acid, and amino acid were previously reported to be correlated with neurodegenerative diseases. Additionally, these different metabolites were significantly correlated with 12 gut bacterial OTUs, among which Lachnospiraceae, Muribaculaceae, Ruminococcaceae, and Erysipelotrichaceae were also previously reported to be related to the distortion of metabolism, indicating that the disturbance of metabolism in the brain may be associated with the disturbance of gut microbes induced by arsenic. Thus, the current study demonstrated that the brain metabolome and lipidome were significantly disturbed under subchronic arsenic exposure, and the disturbances also significantly correlated with some gut microbiome and may be associated with neurodegenerative diseases. Although preliminary, the results shed some light on the pathophysiology of arsenic-caused neurodegenerative diseases.

NAC antagonizes arsenic-induced neurotoxicity through TMEM179 by inhibiting oxidative stress in Oli-neu cells

Arsenic is one of the most common environmental pollutants. Neurotoxicity induced by arsenic has become a major public health concern. However, the effects of arsenic-induced neurotoxicity in the brain and the underlying molecular mechanisms are not well understood. N-acetyl-cysteine (NAC) is a thiol-based antioxidant that can antagonize heavy metal-induced neurotoxicity by scavenging reactive oxygen species (ROS). Here, we used the mouse oligodendrocyte precursor cell (OPC) line Oli-neu to explore the neurotoxic effects of arsenic and the protective effects of NAC. We found that arsenic exposure decreased cell viability, increased oxidative stress, caused mitochondrial dysfunction, and led to apoptosis of Oli-neu cells. Furthermore, we revealed that NAC treatment reversed these neurotoxic effects of arsenic. TMEM179, a key membrane protein, was found highly expressed in OPCs and to be an important factor in maintaining mitochondrial functions. We found that TMEM179 played a critical role in mediating the neurotoxic effects of arsenic and the protective role of NAC. PKCβ is a downstream factor through which TMEM179 regulates the expression of apoptosis-related proteins. This study improves our understanding of the neurotoxic effects and mechanisms of arsenic exposure and the protective effects of NAC. It also identifies a potential molecular target, TMEM179, for the treatment of arsenic-induced neurotoxicity.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

ERK: A Double-Edged Sword in Cancer. ERK-Dependent Apoptosis as a Potential Therapeutic Strategy for Cancer

The RAF/MEK/ERK signaling pathway regulates diverse cellular processes as exemplified by cell proliferation, differentiation, motility, and survival. Activation of ERK1/2 generally promotes cell proliferation, and its deregulated activity is a hallmark of many cancers. Therefore, components and regulators of the ERK pathway are considered potential therapeutic targets for cancer, and inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic. Notably, ERK1/2 kinases also have pro-apoptotic functions under certain conditions and enhanced ERK1/2 signaling can cause tumor cell death. Although the repertoire of the compounds which mediate ERK activation and apoptosis is expanding, and various anti-cancer compounds induce ERK activation while exerting their anti-proliferative effects, the mechanisms underlying ERK1/2-mediated cell death are still vague. Recent studies highlight the importance of dual-specificity phosphatases (DUSPs) in determining the pro- versus anti-apoptotic function of ERK in cancer. In this review, we will summarize the recent major findings in understanding the role of ERK in apoptosis, focusing on the major compounds mediating ERK-dependent apoptosis. Studies that further define the molecular targets of these compounds relevant to cell death will be essential to harnessing these compounds for developing effective cancer treatments.

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.

Mechanisms of Metal-Induced Mitochondrial Dysfunction in Neurological Disorders

Metals are actively involved in multiple catalytic physiological activities. However, metal overload may result in neurotoxicity as it increases formation of reactive oxygen species (ROS) and elevates oxidative stress in the nervous system. Mitochondria are a key target of metal-induced toxicity, given their role in energy production. As the brain consumes a large amount of energy, mitochondrial dysfunction and the subsequent decrease in levels of ATP may significantly disrupt brain function, resulting in neuronal cell death and ensuing neurological disorders. Here, we address contemporary studies on metal-induced mitochondrial dysfunction and its impact on the nervous system.

Arsenic induces autophagy-dependent apoptosis via Akt inactivation and AMPK activation signaling pathways leading to neuronal cell death

Inorganic arsenic (As³⁺), a well-known worldwide industrial and environmental pollutant, has been linked to neurodegenerative disorders (NDs). Autophagy plays an important role in controlling neuronal cell survival/death. However, limited information is available regarding the toxicological mechanism at the interplay between autophagy and As³⁺-induced neurotoxicity. The present study found that As³⁺ exposure induced a concomitant activation of apoptosis and autophagy in Neuro-2a cells, which was accompanied with the increase of phosphatidylserine exposure on outer membrane leaflets and apoptotic cell population, and the activation of caspase-3, -7, and PARP as well as the elevation of protein expressions of LC3-II, Atg-5, and Beclin-1, and the accumulation of autophagosome. Pretreatment of cells with autophagy inhibitor 3-MA, but not that of Z-VAD-FMK (a pan-caspase inhibitor), effectively prevented the As³⁺-induced autophagic and apoptotic responses, indicating that As³⁺-triggered autophagy was contributing to neuronal cell apoptosis. Furthermore, As³⁺ exposure evoked the dephosphorylation of Akt. Pretreatment with SC79, an Akt activator, could significantly attenuated As³⁺-induced Akt inactivation as well as autophagic and apoptotic events. Expectedly, inhibition of Akt signaling with LY294002 obviously enhanced As³⁺-triggered autophagy and apoptosis. Exposure to As³⁺ also dramatically increased the phosphorylation level of AMPKα. Pretreatment of AMPK inhibitor (Compound C) could markedly abrogate the As³⁺-induced phosphorylated AMPKα expression, and autophagy and apoptosis activation. Taken together, these results indicated that As³⁺ exerted its cytotoxicity in neuronal cells via the Akt inactivation/AMPK activation downstream-regulated autophagy-dependent apoptosis pathways, which ultimately lead to cell death. Our findings suggest that the regulation of Akt/AMPK signals may be a promising intervention to against As³⁺-induced neurotoxicity and NDs.

N-trans-Feruloyloctopamine Wakes Up BBC3, DDIT3, CDKN1A, and NOXA Signals to Accelerate HCC Cell Apoptosis

N-trans-Feruloyloctopamine (FO), a natural compound, was reported in our previous study to inhibit a tumor cell malignant phenotype by AKT- and EMT-related signals and might be used as a promising drug for HCC treatment. However, the specific targets and detailed mechanisms still need to be clarified. Screening with RNA-Seq in Huh7 cells treated with FO revealed that 317 genes were modulated, of which 188 genes were upregulated and 129 genes were downregulated. Real-time cell analyzer and flow cytometry data reveal that tumor cell proliferation and apoptosis were impacted by FO. DAVID bioinformatic data showed that most of the biological process GO terms are related to proliferation and apoptosis. KEGG enrichment analysis showed that FO mainly regulates PI3K-AKT- and apoptosis-related signals, in which BBC3, DDIT3, NOXA, and CDKN1A on the surface serve as the novel targets of FO inducing HCC cell apoptosis. The result implied that FO might exacerbate HCC cell apoptosis by regulating BBC3, DDIT3, CDKN1A, and NOXA signals. The obstacle effect of FO can provide new targets and new credibility for the treatment of liver cancer.

4-Methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene, a Major Active Metabolite of Bisphenol A, Triggers Pancreatic β-Cell Death via a JNK/AMPKα Activation-Regulated Endoplasmic Reticulum Stress-Mediated Apoptotic Pathway

4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), a major active metabolite of bisphenol A (BPA), is generated in the mammalian liver. Some studies have suggested that MBP exerts greater toxicity than BPA. However, the mechanism underlying MBP-induced pancreatic β-cell cytotoxicity remains largely unclear. This study demonstrated the cytotoxicity of MBP in pancreatic β-cells and elucidated the cellular mechanism involved in MBP-induced β-cell death. Our results showed that MBP exposure significantly reduced cell viability, caused insulin secretion dysfunction, and induced apoptotic events including increased caspase-3 activity and the expression of active forms of caspase-3/-7/-9 and PARP protein. In addition, MBP triggered endoplasmic reticulum (ER) stress, as indicated by the upregulation of GRP 78, CHOP, and cleaved caspase-12 proteins. Pretreatment with 4-phenylbutyric acid (4-PBA; a pharmacological inhibitor of ER stress) markedly reversed MBP-induced ER stress and apoptosis-related signals. Furthermore, exposure to MBP significantly induced the protein phosphorylation of JNK and AMP-activated protein kinase (AMPK)α. Pretreatment of β-cells with pharmacological inhibitors for JNK (SP600125) and AMPK (compound C), respectively, effectively abrogated the MBP-induced apoptosis-related signals. Both JNK and AMPK inhibitors also suppressed the MBP-induced activation of JNK and AMPKα and of each other. In conclusion, these findings suggest that MBP exposure exerts cytotoxicity on β-cells via the interdependent activation of JNK and AMPKα, which regulates the downstream apoptotic signaling pathway.

Inorganic arsenic induces sex-dependent pathological hypertrophy in the heart

Arsenic exposure though drinking water is widespread and well associated with adverse cardiovascular outcomes, yet the pathophysiological mechanisms by which iAS induces these effects are largely unknown. Recently, an epidemiological study in an American population with a low burden of cardiovascular risk factors found that iAS exposure was associated with altered left ventricular geometry. Considering the possibility that iAS directly induces cardiac remodeling independently of hypertension, we investigated the impact of an environmentally relevant iAS exposure on the structure and function of male and female hearts. Adult male and female C56BL/6J mice were exposed to 615 μg/L iAS for 8 wk. Males exhibited increased systolic blood pressure via tail cuff photoplethysmography, left ventricular wall thickening via transthoracic echocardiography, and increased plasma atrial natriuretic peptide via enzyme immunoassay. RT-qPCR revealed increased myocardial RNA transcripts of Acta1, Myh7, and Nppa and decreased Myh6, providing evidence of pathological hypertrophy in the male heart. Similar changes were not detected in females, and nitric oxide-dependent mechanisms of cardioprotection in the heart appeared to remain intact. Further investigation found that Rcan1 was upregulated in male hearts and that iAS activated NFAT in HEK-293 cells via luciferase assay. Interestingly, iAS induced similar hypertrophic gene expression changes in neonatal rat ventricular myocytes, which were blocked by calcineurin inhibition, suggesting that iAS may induce pathological cardiac hypertrophy in part by targeting the calcineurin-NFAT pathway. As such, these results highlight iAS exposure as an independent cardiovascular risk factor and provide biological impetus for its removal from human consumption.NEW & NOTEWORTHY This investigation provides the first mechanistic link between an environmentally relevant dose of inorganic arsenic (iAS) and pathological hypertrophy in the heart. By demonstrating that iAS exposure may cause pathological cardiac hypertrophy not only by increasing systolic blood pressure but also by potentially activating calcineurin-nuclear factor of activated T cells and inducing fetal gene expression, these results provide novel mechanistic insight into the theat of iAS exposure to the heart, which is necessary to identify targets for medical and public health intervention.

Roles of ERK/Akt signals in mitochondria-dependent and endoplasmic reticulum stress-triggered neuronal cell apoptosis induced by 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene, a major active metabolite of bisphenol A

Bisphenol A (BPA) is recognized as a harmful pollutant in the worldwide. Growing studies have reported that BPA can cause adverse effects and diseases in human, and link to a potential risk factor for development of neurodegenerative diseases (NDs). 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), which generated in the mammalian liver after BPA exposure, is a major active metabolite of BPA. MBP has been suggested to exert greater toxicity than BPA. However, the molecular mechanism of MBP on the neuronal cytotoxicity remains unclear. In this study, MBP exposure significantly reduced Neuro-2a cell viability and induced apoptotic events that MBP (5-15 μM) exhibited greater neuronal cytotoxicity than BPA (50-100 μM). The mitochondria-dependent apoptotic signals including the decrease in mitochondrial membrane potential (MMP) and the increase in cytosolic apoptosis-induced factor (AIF), cytochrome c release, and Bax protein expression were involved in MBP (10 μM)-induced Neuro-2a cell death. Exposure of Neuro-2a cells to MBP (10 μM) also triggered endoplasmic reticulum (ER) stress through the induction of several key molecules including glucose-regulated protein (GRP)78, C/EBP homologous protein (CHOP), X-box binding protein (XBP)-1, protein kinase R-like ER kinase (PERK), eukaryotic initiation factor 2α (eIF2α), inositol-requiring enzyme(IRE)-1, activation transcription factor(AFT)4 and ATF6, and caspase-12. Pretreatment with 4-PBA (an ER stress inhibitor) and specific siRNAs for GRP78, CHOP, and XBP-1 significantly suppressed the expression of these ER stress-related proteins and the activation of caspase-12/-3/-7 in MBP-exposed Neuro-2a cells. Furthermore, MBP (10 μM) exposure dramatically increased the activation of extracellular regulated protein (ERK)1/2 and decreased Akt phosphorylation. Pretreatment with PD98059 (an ERK1/2 inhibitor) and transfection with the overexpression of activation of Akt1 (myr-Akt1) effectively suppressed MBP-induced apoptotic and ER stress-related signals. Collectively, these results demonstrate that MBP exposure exerts neuronal cytotoxicity via the interplay of ERK activation and Akt inactivation-regulated mitochondria-dependent and ER stress-triggered apoptotic pathway, which ultimately leads to neuronal cell death.

Cistanches deserticola PhG-RE through Inhibiting ERS Apoptosis Mechanism to Protect Myocardial Cell Apoptosis from H2O2-Induced Endoplasmic Reticulum Stress

The herb Cistanche deserticola has some myocardial protective effects. This study attempted to explain the mechanism by which PhG-RE protects myocardial cells and verify if this protection occurs through regulating the apoptosis mechanism associated with endoplasmic reticulum stress (ERS). Rat myocardial cells were exposed to 150 μg·mL⁻¹ PhG-RE for 24 h and then to 100 μmol·mL⁻¹ H₂O₂ for 18 h to induce ERS and establish a cell damage model. Thapsigargin (TG), a specific ERS activator, and 4-phenylbutyric acid (4-PBA), an ERS inhibitor, were used to validate the accuracy of the experiment. Our results demonstrated that PhG-RE significantly improved cell viability, protected cells, and reduced cell damage and apoptosis. PhG-RE played a role similar to that of the ERS inhibitor 4-PBA in protecting myocardial cells against apoptosis and damage induced by ER stress. Furthermore, PhG-RE significantly attenuated the mRNA expression of the ERS-associated apoptotic factors GRP78, CHOP, and Caspase-12 and the protein expression of the ERS-associated apoptotic factors GRP78, CHOP, Caspase-12, and p-JNK. Taken together, these findings suggest that PhG-RE can effectively protect myocardial cells and reduce cell apoptosis and damage, which may be related to the regulation of ERS-associated apoptosis.

Co-exposure to Arsenic-Fluoride Results in Endoplasmic Reticulum Stress-Induced Apoptosis Through the PERK Signaling Pathway in the Liver of Offspring Rats

Arsenic and fluoride are two of the major groundwater pollutants. To better understand the liver damage induced during development, 24 male rats exposed to fluoride (F), arsenic (As), and their combination (As + F) from the prenatal stage to 90 days after birth were selected for analysis. Histopathological results showed vacuolar degeneration in the As and As + F groups. Compared to those in the control group, aspartate aminotransferase and alanine aminotransferase levels were significantly increased in the combined group. Catalase activity significantly decreased in the treatment groups compared to that in the controls, and the malondialdehyde content in the As and As + F groups was significantly higher than those in the control group. We further evaluated whether this damage is linked to endoplasmic reticulum stress and its related pathways. The mRNA expression levels of PERK, GRP78, EIF2α, ATF4, and CHOP as well as the protein levels of CHOP was significantly increased in the As + F group compared with the control group. These results demonstrate that As, F, and their combination could lead to liver function damage and reduce the antioxidant capacity of the liver to cause oxidative damage to tissues. Moreover, the combination of As and F triggers endoplasmic reticulum stress-induced apoptosis in liver cells by activating the PERK pathway in the unfolded protein response. As and F seem to have different independent effects, whereas their combination resulted in more severe effects overall.

The critical role of PPARα in the binary switch between life and death induced by endoplasmic reticulum stress

Endoplasmic reticulum stress (ER stress) just like a double-edged sword depending on different conditions in the development of multiple hepatic diseases. But the molecular mechanisms of functional conversion during ER stress have not been fully elucidated. In this study, we aim to illustrate the role of PPARα and the subtle mechanism in the functional conversion of ER stress. Tunicamycin (TM) and thapsigargin (TG), as ER stress inducers, were used to induce ER stress in AML12 cells. During the ER stress, qRT-PCR and immunoblotting was used to measure the expression levels of GRP78 and CHOP which show a gradually increasing trend, while PPARα and autophagy was significantly activated in the early stage but was inhibited in the late stage. Moreover, PPARα inhibition by siRNA promoted cell injury in the mild-ER stress and PPARα activation by WY-14643 reduced cell apoptosis in the serious ER stress. In the mild-ER stress with PPARα knocked down, activation of autophagy by rapamycin significantly improved cell survival, in the serious ER stress with PPARα activation, inhibition of autophagy by 3-MA aggravate cell injury. In addition, in the mild-ER stress with PPARα knocked down, CHOP knocked down by siRNA reduced cell apoptosis, in the serious ER stress activated PPARα, CHOP over-expression mediated by lentiviral vector contributed to serious cell injury. Furthermore, C57BL/6 mice was used to induce ER stress with TM intraperitoneal injection, PPARα and autophagy was upregulated in the mild-ER stress while downregulated in the serious ER stress, measured by qRT-PCR and immunoblotting, further confirmed the finding in vitro. Our results firstly demonstrated that PPARα is a key molecule in the functional conversion of ER stress: protective effects in the mild ER stress was mediated by PPARα-autophagy pathway and destructive effects in the serious ER stress was mediated by PPARα-CHOP pathway.