Characterization of the cellular effects and mechanism of arsenic trioxide-induced hepatotoxicity in broiler chickens

Arsenic induces hepatotoxicity in chickens via PANoptosis pathway

Environmental pollution caused by arsenic or its compounds is called arsenic pollution. Arsenic pollution mainly comes from people's mining and smelting of arsenic compounds. In addition, the widespread use of arsenic compounds, such as the use and production of arsenic-containing pesticides, is also a source of arsenic contamination. Arsenic contamination leads to an increased risk of arsenic exposure, and the multi-organ toxicity induced by arsenic exposure is a global health problem. As a non-mammalian vertebrate with high nutrient levels, chickens readily absorb and accumulate arsenic from their food. Relevant studies have shown that arsenic exposure induces hepatotoxicity in chickens, and there has been a steady stream of research into the specific mechanisms involved. PANoptosis, a newly discovered and unique mode of programmed cell death (PCD) characterized by both apoptosis, cellular pyroptosis, and necroptosis. There are no studies to indicate whether chicken liver toxicity due to arsenic is associated with PANoptosis. Therefore, we established chicken animal models and chicken primary hepatocyte models exposed to different arsenic concentrations to dissect the role and mechanism of PANoptosis in arsenic exposure-induced hepatotoxicity in chickens. Our histopathological results showed that arsenic treatment caused dose-dependent damage to chicken liver structure. Meanwhile, different doses of arsenic treatment groups caused significant up-regulation of the protein level of ZBP1, a key factor of PANoptosis. And then consequently triggered the abnormal gene and protein expression levels of apoptosis-associated factors (Caspase-8, Caspase-7, Caspase-3), cellular pyroptosis-associated factors (NLRP3, ASC, GSDMD) and necroptosis-associated factors (RIPK1, RIPK3, MLKL). In conclusion, our study revealed that PANoptosis is involved in arsenic-induced chicken hepatotoxicity. Our findings provide a new perspective on the pathogenesis of arsenic exposure-induced hepatotoxicity in chickens.

Effects of organophosphorus flame retardant EHDPP on mouse retinal photoreceptor cells: Oxidative stress, apoptosis, and proinflammatory response

2-Ethylhexyl diphenyl phosphate (EHDPP) is a frequently utilized organophosphorus flame retardant (OPFR) and has been extensively detected in environmental media. Prolonged daily exposure to EHDPP has been linked to potential retinal damage, yet the adverse impacts on the retina are still generally underexplored. In this research, we explored oxidative stress, inflammation, and the activating mechanisms initiated by EHDPP in mouse retinal photoreceptor (661 W) cells following a 24 h exposure period. Our research demonstrated that EHDPP led to a decline in cell viability that was directly proportional to its concentration, with the median lethal concentration (LC50) being 88 µM. Furthermore, EHDPP was found to elevate intracellular and mitochondrial levels of reactive oxygen species (ROS), trigger apoptosis, induce cell cycle arrest at the G1 phase, and modulate the expression of both antioxidant enzymes (Nrf2, HO-1, and CAT) and pro-inflammatory mediators (TNF-α, IL-1β, and IL-6) within 661 W cells. These findings indicate that retinal damage triggered by EHDPP exposure could be mediated via the Nrf2/HO-1 signaling pathway in these cells. Collectively, our investigation revealed that oxidative stress induced by EHDPP is likely a critical factor in the cytotoxic response of 661 W cells, potentially leading to damage in retinal photoreceptor cells.

Co-exposure of arsenic and polystyrene-nanoplastics induced kidney injury by disrupting mitochondrial homeostasis and mtROS-mediated ferritinophagy and ferroptosis

Arsenic (As) and polystyrene nanoplastics (PSNPs) co-exposure induced biotoxicity and ecological risks have attracted wide attention. However, the combined effects of As and PSNPs on the kidney and their underlying mechanisms of toxicities remain to be explored. Here, we investigated the effects of As and PSNPs co-exposure on structure and function in mice kidney, and further explored the possible mechanisms. In this study, we identified that co-exposure to As and PSNPs exhibited conspicuous renal structural damage and pathological changes, accompanied by renal tissue fibrosis (increased protein expression of Collagen I and α-SMA and deposition of collagen fibers), whereas alone exposure to As or PSNPs does not exhibit nephrotoxicity. Subsequently, our results further showed that combined action of As and PSNPs induced mitochondrial oxidative damage and impaired mitochondrial dynamic balance. Furthermore, co-treatment with As and PSNPs activated NCOA4-mediated ferritinophagy and ferroptosis in mice kidney and TCMK-1 cells, which was confirmed by the changes in the expression of ferritinophagy and ferroptosis related indicators (NCOA4, LC3, ATG5, ATG7, FTH1, FTL, GPX4, SLC7A11, FSP1, ACSL4 and PTGS2). Meaningfully, pretreatment with the mtROS-targeted scavenger Mito-TEMPO significantly attenuated As and PSNPs co-exposure induced mitochondrial damage, ferritinophagy and ferroptosis. In conclusion, these findings demonstrated that mtROS-dependent ferritinophagy and ferroptosis are important factors in As and PSNPs co-exposure induced kidney injury and fibrosis. This study provides a new insight into the study of combined toxicity of nanoplastics and heavy metal pollutants.

Arsenic exposure induces small intestinal toxicity in mice by barrier damage and inflammation response via activating RhoA/ROCK and TLR4/Myd88/NF-κB signaling pathways

Numerous studies have shown that arsenic (As) is an important hazardous metalloid that is commonly considered to have systemic toxicity. The main pathway of arsenic exposure is oral; however, many of the events that occur during its passage through the gastrointestinal tract are unclear, and there are few reports on the effect of arsenic on small intestinal mucosal barrier. This study aimed to investigate arsenic-induced mucosal barrier damage in the small intestine of mice induced by oral exposure and its potential mechanisms. In the present study, histomorphometric and immunohistochemical analyses showed that arsenic-treated mice exhibited signs of irregularly arranged and atrophied small intestinal villi, reduced villus lengths, inflammatory cells infiltration, along with up-regulated expression of inflammatory factors TNF-α, IL-6 and IL-1β in the small intestine of mice. The myeloperoxidase (MPO) activity was also increased in As-exposed mice. Transmission electron microscopy (TEM) analysis demonstrated that intestinal epithelial tight junctions (TJs) were impaired in the small intestines of mice in As group. In addition, arsenic down-regulated mRNA levels of TJ-related genes (ZO-1, ZO-2, occludin, claudin-1, and claudin-7) and protein levels of ZO-1, occludin and claudin-1 were significantly reduced in arsenic-treated groups, while arsenic also increased levels of TLR4, Myd88, NF-κB, RhoA, and ROCK mRNA and protein expression. In summary, these results indicate that the small intestine toxicity in mice evoked by arsenic was correlated with the activation of TLR4/Myd88/NF-κB and RhoA/ROCK pathways.

Nanocarrier-based delivery of arsenic trioxide for hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) poses a severe threat to human health and economic development. Despite many attempts at HCC treatment, most are inevitably affected by the genetic instability and variability of tumor cells. Arsenic trioxide (ATO) has shown to be effective in HCC. However, time-consuming challenges, especially the optimal concentration in tumor tissue and bioavailability of ATO, remain to be overcome for its transition from the bench to the bedside. To bypass these issues, nanotechnology-based delivery systems have been developed for prevention, diagnosis, monitoring and treatment in recent years. This article is a systematic overview of the latest contributions and detailed insights into ATO-loaded nanocarriers, with particular attention paid to strategies for improving the efficacy of nanocarriers of ATO.

Linking the Low-Density Lipoprotein-Cholesterol (LDL) Level to Arsenic Acid, Dimethylarsinic, and Monomethylarsonic: Results from a National Population-Based Study from the NHANES, 2003–2020

Arsenic (As) contamination is a global public health problem. Elevated total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) are risk factors for cardiovascular diseases, but data on the association of urinary arsenic species’ level and LDL-C are limited. We performed an association analysis based on urinary arsenic species and blood TC and LDL-C in US adults. Methods: Urinary arsenic, arsenic acid (AA), dimethylarsinic (DMA), monomethylarsonic (MMA), TC, LDL-C, and other key covariates were obtained from the available National Health and Nutrition Examination Survey (NHANES) data from 2003 to 2020. Multiple linear regression analysis and generalized linear model are used to analyze linear and nonlinear relationships, respectively. Results: In total, 6633 adults aged 20 years were enrolled into the analysis. The median total urinary arsenic level was 7.86 µg/L. A positive association of urinary arsenic concentration quartiles was observed with TC (β: 2.42 95% CI 1.48, 3.36). The OR for TC of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.34 (95% CI 1.13, 1.59). The OR for LDL-C of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.36 (95% CI 1.15, 1.62). For speciated arsenics analysis, the OR for arsenic acid and TC was 1.35 (95% CI 1.02, 1.79), whereas the OR for DMA and LDL-L was 1.20 (95% CI 1.03, 1.41), and the OR for MMA and LDL-L was 1.30 (95% CI 1.11, 1.52). Conclusions: Urinary arsenic and arsenic species were positively associated with increased LDL-C concentration. Prevention of exposure to arsenic and arsenic species maybe helpful for the control of TC and LDL-C level in adults.

PIN1-mediated ROS production is involved in antagonism of N-acetyl-L-cysteine against arsenic-induced hepatotoxicity

Arsenic, a widely existing environmental contaminant, is recognized to be toxic to multiple organs. Exposure to arsenic results in liver damage via excessive production of reactive oxidative species (ROS). PIN1 regulates the levels of ROS. N-acetyl-L-cysteine (NAC) is an ROS scavenger that protects the hepatic functions. Whether PIN1 plays a regulatory role in NAC-mediated antagonism against arsenic hepatotoxicity remains largely unknown. In our study, the protective effects of NAC against arsenic (NaAsO2)-induced hepatotoxicity were evaluated in vitro and in vivo. Arsenic exposure induced cytotoxicity by increasing the intracellular ROS production, impairing mitochondrial function and inducing apoptosis in L02 hepatocytes. Overexpression of PIN1 markedly protected against arsenic cytotoxicity, decreased ROS levels, and mitigated mitochondrial dysfunction and apoptosis in L02 cells. However, loss of PIN1 further aggravated arsenic-induced cytotoxicity and abolished the protective effects of NAC in L02 cells. An in vivo study showed that pretreatment with NAC rescued arsenic-induced liver injury by restoring liver function and suppressing hepatic oxidative stress. Overexpression of PIN1 in mice transfected with AAV-Pin1 relieved arsenic-induced liver dysfunction and hepatic oxidative stress. Taken together, our study identified PIN1 as a novel intervention target for antagonizing arsenic-induced hepatotoxicity, highlighting a new pharmacological mechanism of NAC targeting PIN1 in antagonism against arsenic toxicity.

Arsenic trioxide-induced autophagy affected the antioxidant capacity and apoptosis rate of chicken hepatocytes

Arsenic has recently received widespread attention due to its high toxicological effects on multiple animals; however, the mechanism underlying this toxicity is unclear. We investigated the damaging effects of arsenic trioxide (ATO) on hepatocytes and the effects of regulating autophagy on the hepatocyte damage induced by ATO exposure. First, we investigated the effects of ATO exposure (0, 0.6, 1.2, 2.4, and 4.8 μM) on the biochemical function and autophagy of chicken hepatocytes. The findings showed that as the concentration of ATO increased, the lactate dehydrogenase (LDH) concentration increased, more autophagosomes were observed via transmission electron microscopy (TEM), and the gene and protein expression levels of P62, LC3Ⅱ, and Beclin1 increased. Adding N-acetyl-l-cystine (NAC, 1 mM) attenuated autophagy and the hepatocyte damage induced by ATO. Then, we used rapamycin (Rapa) and 3-methylpurine (3-MA) to regulate the autophagy induced by exposure to 4.8 μM ATO and observed changes in the antioxidant capacity and apoptosis rate of chicken hepatocytes. Induction of autophagy reduced ATO-induced hepatocyte apoptosis but caused no significant effect on oxidative stress in chicken hepatocytes. Inhibition of autophagy exacerbated ATO-induced hepatocyte oxidative stress and apoptosis. These findings demonstrate that autophagy plays an important role in ATO-induced cell damage.

Effects of Long-Term Exposure to Copper on the Keap1/Nrf2 Signaling Pathway and Msr-Related Redox Status in the Kidneys of Rats

The objective of the present study was to examine the effects of long-term exposure on oxidative damage, Keap1/Nrf2 signaling pathway, and Msr-related redox status in the kidneys of rats. Therefore, in this experimental study, a total of 32 CD-1 rats were randomized into 4 groups and treated with 30-, 60-, and 120-mg/kg Cu for 24 weeks. Different serum biomarkers suggestive of renal functions, pathological changes, and oxidative stress were analyzed in kidney tissues. Moreover, the levels of the Keap1/Nrf2 signaling pathway and redox status-related gene mRNA and proteins were also detected. The results indicated that Cu exposure dramatically increased the contents of creatinine and carbamide. Furthermore, histopathological alterations and mitochondrial damage in kidneys of rats of different Cu-treated groups were obviously observed. In addition, Cu exposure markedly changed the levels of glutathione, catalase, and total antioxidant capacity, and upregulated the contents of protein carbonyl, nitric oxide, and malondialdehyde. Moreover, higher levels of Cu treatments significantly increased the expression of Keap1/Nrf2 signaling pathway and redox status-related genes (NQO1, SOD-1, TRX, MsrA, MsrB1, MsrB2, MsrB3). Simultaneously, the mRNA expression levels of Nrf2, HO-1, and CAT were upregulated in rats exposed to 30- and 60-mg/kg Cu, but downregulated in the 120-mg/kg Cu group compared with the control group. Moreover, the Keap1/Nrf2 signaling pathway and redox status-related protein expression levels (HO-1, SOD-1, TRX, MsrA, MsrB1, MsrB2) were significantly increased in treated rats. In summary, it is suggested that the Keap1/Nrf2 signaling pathway and activation of Msr prevent Cu-induced nephrotoxicity and attenuate oxidative damage.

Evaluation of toxic effects induced by arsenic trioxide or/and antimony on autophagy and apoptosis in testis of adult mice

Arsenic trioxide (ATO) and antimony (Sb) are well-known ubiquitous environmental contaminants and cause unpromising male reproductive effects in target and non-target exposed organisms. The main objective of this study was to investigate the effects of ATO or/and Sb on process of autophagy, apoptosis, and reproductive organ in adult mice. For this reason, a total of 32 adult mice were randomly divided into different groups like control group, ATO-treated group, Sb-treated group, and combined group. The duration of current experimental trial was 2 months. Various adverse effects of ATO or/and Sb on sperm parameters, oxidative stress, autophagy, and apoptosis were determined in testis of mice. Results indicated that parameters of sperm quality for organ coefficient, sperm count, ratio of sperm survival, testosterone level, and germ cells were significantly decreased, while malformation rate and vacuolization significantly increased in mice exposed to different treatments. Furthermore, the status of antioxidant index of T-AOC, SOD, and MsrB1 levels was reduced, while MDA increased significantly in ATO + Sb group. Results on TEM investigation determined that the autophagosomes, autolysosome, nuclear pyknosis, and chromatin condensation were prominent ailments, and the levels of autophagy and pro-apoptosis indictors including Beclin1, Atg-5, LC3B/LC3A, caspase-8, cytc, cleaved caspase-3, p53, and Bax were up-regulated in treated group, while the content of an anti-apoptosis maker (Bcl-2) was down-regulated. In conclusion, the results of our experiment suggested that abnormal process of autophagy and apoptosis was triggered by arsenic and antimony, and intensity of toxic effects increased in combined treatments of ATO and Sb.

Arsenic exposure induces intestinal barrier damage and consequent activation of gut-liver axis leading to inflammation and pyroptosis of liver in ducks

Arsenic is an important hazardous metalloid commonly found in polluted soil, rivers and groundwater. However, few studies exist regarding the effect of arsenic trioxide (ATO) on the gut-liver axis and consequent hepatotoxicity in waterfowl. Here, we investigated the influence of ATO on duck intestines and livers, and explored the role of the gut-liver axis in ATO-induced hepatotoxicity and intestinal toxicity. Our results demonstrated that ATO-exposure induced intestinal damage, liver inflammatory cell infiltration and vesicle steatosis. Additionally, the intestinal microbiota community in ATO-exposed ducks displayed significantly decreased α-diversity and an altered bacterial composition. Moreover, ATO-exposure markedly reduced the expression of intestinal barrier-related proteins (Claudin-1, MUC2, ZO-1 and Occludin), resulting in increased intestinal permeability and elevated lipopolysaccharide levels. Simultaneously, ATO-exposure also upregulated pyroptosis-related index levels in the liver and jejunum, and increased pro-inflammatory cytokine production (IFN-γ, TNF-α, IL-18, and IL-1β). Our further mechanistic studies showed that ATO-induced liver and jejunum inflammation were provoked by the activation of the LPS/TLR4/NF-κB signaling pathway and NLRP3 inflammasome. In summary, these results manifested that ATO exposure can cause liver and jejunal inflammation and pyroptosis, and the indirect gut-liver axis pathway may play an essential role in the potential mechanism of ATO-induced hepatotoxicity.

Arsenic and antimony co-induced nephrotoxicity via autophagy and pyroptosis through ROS-mediated pathway in vivo and in vitro

Arsenic (As) and antimony (Sb) are commonly accumulated environmental pollutants that often coexist in nature and cause serious widespread biological toxicity. To investigate the nephrotoxicity induced by As and Sb in detail, we explored the mechanism by which As and Sb cotreatment induced autophagy and pyroptosis in vivo and in vitro. In this study, mice were treated with 4 mg/kg arsenic trioxide (ATO) or/and 15 mg/kg antimony trichloride (SbCl₃) by intragastric intubation for 60 days. TCMK-1 cells were treated with ATO (12.5 μM), SbCl₃ (25 μM) or a combination of As and Sb for 24 h. The results of the in vivo experiment demonstrated that As or/and Sb exposure could induce histopathological changes in the kidneys, and increase the levels of biochemical indicators of nephrotoxicity. In addition, As and Sb can co-induce oxidative stress, which further activate autophagy and pyroptosis. In an in vitro experiment, As and/or Sb coexposure increased ROS generation and decreased MMP. Moreover, the results of related molecular experiments further confirmed that As and Sb coactivated autophagy and pyroptosis. In conclusion, our results indicated that As and Sb co-exposure could cause autophagy and pyroptosis via the ROS pathway, and these two metals might have a synergistic effect on nephrotoxicity.

Fate of arsenic in living systems: Implications for sustainable and safe food chains

Arsenic, a group 1 carcinogen for humans, is abundant as compared to other trace elements in the environment and is present mainly in the Earth's crust and soil. The arsenic distributions in different geographical regions are dependent on their geological histories. Anthropogenic activities also contribute significantly to arsenic release into the environment. Arsenic presents several complications to humans, animals, and plants. The physiology of plants and their growth and development are affected by arsenic. Arsenic is known to cause cancer and several types of organ toxicity, such as cardiotoxicity, nephrotoxicity, and hepatotoxicity. In the environment, arsenic exists in variable forms both as inorganic and organic species. From arsenic containing compartments, plants can absorb and accumulate arsenic. Crops grown on these contaminated soils pose several-fold higher toxicity to humans compared with drinking water if arsenic enters the food chain. Information regarding arsenic transfer at different trophic levels in food chains has not been summarized until now. The present review focuses on the food chain perspective of arsenic, which affects all components of the food chain during its course. The circumstances that facilitate arsenic accumulation in flora and fauna, as components of the food chain, are outlined in this review.

Arsenic or/and antimony induced mitophagy and apoptosis associated with metabolic abnormalities and oxidative stress in the liver of mice

Arsenic and antimony are coexisting cumulative environmental pollutants that cause severe and extensive biological toxicity. However, their interactions and toxic mechanisms in the liver remain to be fully elucidated. In this study, a total of sixty 4-week-old mice were divided into four groups and treated with 4 mg/kg arsenic trioxide (ATO) or/and 15 mg/kg antimony (Sb) for 60 days. The results demonstrated that biochemical indicators of hepatotoxicity (ALT, AST, ALP) were upregulated in all treated groups. Additionally, the oxidative burden of the liver was increased in the cotreated groups compared with the individual toxicant-treated groups. Meanwhile, mitochondrial injury, autophagosomes, hepatic-congestion and karyopyknosis were obviously observed in cotreated groups. Additionally, coupled with serum biochemical index (TG, TC), histopathology examination and metabolomics results, we found that cotreatment with ATO and Sb resulted in lipid metabolism disorder and steatosis of liver tissues. Our further investigation found that the levels of pro-apoptotic (Caspase-3, Caspase-9, Bax, P53, Cytc) and mitophagy (LC3-B, P62, PINK1, Parkin) indexes in the cotreated groups were markedly increased, whereas the levels of anti-apoptosis index (Bcl-2) were decreased. Collectively, these results show that co-exposure to ATO and Sb can cause abnormal liver energy metabolism and oxidative stress. Moreover, mitophagy and apoptosis play important roles in the mechanisms of arsenic/antimony cytotoxicity to mouse livers.

Roles of SET7/9 and LSD1 in the Pathogenesis of Arsenic-induced Hepatocyte Apoptosis

BACKGROUND AND AIMS

Multiple regulatory mechanisms play an important role in arsenic-induced liver injury. To investigate whether histone H3 lysine 4 (H3K4) methyltransferase (SET7/9) and histone H3K4 demethyltransferase (LSD1/KDM1A) can regulate endoplasmic reticulum stress (ERS)-related apoptosis by modulating the changes of H3K4 methylations in liver cells treated with arsenic_.

METHODS

Apoptosis, proliferation and cell cycles were quantified by flow cytometry and real-time cell analyzer. The expression of ERS- and epigenetic-related proteins was detected by Western blot analysis. The antisense SET7/9 expression vector and the overexpressed LSD1 plasmid were used for transient transfection of LO2 cells. The effects of NaAsO₂ on the methylation of H3 in the promoter regions of 78 kDa glucose-regulated protein, activating transcription factor 4 and C/EBP-homologous protein were evaluated by chromatin immunoprecipitation assay.

RESULTS

The protein expression of LSD1 (1.25±0.08 vs. 1.77±0.08, p=0.02) was markedly decreased by treatment with 100 µM NaAsO₂, whereas the SET7/9 (0.68±0.05 vs. 1.10±0.13, p=0.002) expression level was notably increased, which resulted in increased H3K4me1/2 (0.93±0.64, 1.19±0.22 vs. 0.71±0.13, 0.84±0.13, p=0.03 and p=0.003). After silencing SET7/9 and overexpressing LSD1 by transfection, apoptosis rate (in percentage: 3.26±0.34 vs. 7.04±0.42, 4.80±0.32 vs. 7.52±0.38, p=0.004 and p=0.02) was significantly decreased and proliferation rate was notably increased, which is reversed after inhibiting LSD1 (in percentage: 9.31±0.40 vs. 7.52±0.38, p=0.03). Furthermore, the methylation levels of H3 in the promoter regions of GRP78 (20.80±2.40 vs. 11.75±2.47, 20.46±2.23 vs. 14.37±0.91, p=0.03 and p=0.01) and CHOP (48.67±4.04 vs. 16.67±7.02, 59.33±4.51 vs. 20.67±3.06, p=0.004 and p=0.001) were significantly increased in LO₂ cells exposed to 100 µM NaAsO₂ for 24 h.

CONCLUSIONS

Histone methyltransferase SET7/9 and histone demethyltransferase LSD1 jointly regulate the changes of H3K4me1/me2 levels in arsenic-induced apoptosis. NaAsO₂ induces apoptosis in LO2 cells by activating the ERS-mediated apoptotic signaling pathway, at least partially by enhancing the methylation of H3 on the promoter regions of ERS-associated genes, including GRP78 and CHOP.

Combined effect of arsenic and fluoride at environmentally relevant concentrations in zebrafish (Danio rerio) brain: Alterations in stress marker and apoptotic gene expression

Arsenic and fluoride are two naturally occurring toxicants to which various organisms including a major part of the human populations are co-exposed to. However, interactions between them inside body are quite complicated and needs proper evaluation. Inconclusive reports regarding their combined effects on brain prompted us to conduct this study where we investigated their individual as well as combined effects on female zebrafish brain at environmentally relevant concentrations (50 μgL^-1 arsenic trioxide and 15 mgL^-1 sodium fluoride) after different time intervals (15, 30 and 60 days). Persistent near-basal level of GSH, least increased MDA content and catalase activity portrayed arsenic and fluoride co-exposure as less toxic which was corroborated with far less damage caused in the histoarchitecture of optic tectum region in midbrain. Stress-responsive genes viz., Nrf2 and Hsp70 were overexpressed after individual as well as combined exposures, indicating a common cellular response to combat the formed oxidative stresses. Biphasic response of AChE upon individual exposure confirmed their neurotoxic effects too. Expression profile of p53 (unaltered), Bax (lower or near-basal) and Bcl2 (comparatively higher), along with absence of DNA fragmentation indicated no induction of apoptosis in the co-exposed group. Tissue accumulation of arsenic and fluoride was significantly less in the brain of co-exposed zebrafish when compared to their individual exposures. This preliminary study indicates an antagonistic effect of these two toxicants in zebrafish brain and needs further studies involving oxidative stress independent markers to understand the detailed molecular mechanism.

The protective role of autophagy against arsenic trioxide-induced cytotoxicity and ROS-dependent pyroptosis in NCTC-1469 cells

Arsenic trioxide (As2O3) is widely used in traditional Chinese medicine to treat tumors. This study investigated the effect of As(III) on pyroptosis in murine hepatocytes in vitro and how this relates to autophagy. NCTC1469-cells were treated with As(III) alone (6, 12 and 18 μM) or in combination with N-acetylcysteine (NAC,1 mM), 3-methyladenine (3-MA, 5 mM) or rapamycin (Rapa,100 nM) for 24 h. The results showed that As(III)-treatment reduced cell viability in a dose-dependent manner, but induced lactic dehydrogenase (LDH) activity. As(III)-treatment also resulted in increased intracellular reactive oxygen species (ROS) levels and decreased mitochondrial membrane potential (MMP), therefore promoting pyroptosis. Moreover, As(III)-treatment upregulated the expression of autophagy and pyroptosis-related genes (LC3-A, LC3-B, P62, Beclin-1, Atg5, Caspase-1, Gasdermin D, IL-18, IL-1β) and downregulated the expression of m-TOR, NLRP3, ASC genes. Meanwhile the accumulation of light chain 3-B/A (LC3B/LC3A), autophagy-related gene 5 (Atg-5), Bcl-2-interacting protein (Beclin-1), Caspase-1, Gasdermin D, interleukin-1β (IL-1β), IL-18 and poptosis-associated speck-like protein (ASC) proteins were upregulated while nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) was downregulated in all As(III)-treatment groups. Furthermore, the inhibition of autophagy by 3-MA aggravated AsIII-induced pyroptosis and cytotoxicity. However, NAC or Rapa markedly alleviated the abovementioned phenomenon under As(III) stress. In addition, we speculate that the protective mechanism of NAC on As(III)-induced pyroptosis in hepatocytes mainly include the elimination of ROS because of the chelation of As(III) in the culture medium. In conclusion, these results provide new insight into the mechanisms underlying AsIII-induced cytotoxicity and pyroptosis in hepatocytes in vitro.

Arsenic-induced autophagy regulates apoptosis in AML-12 cells

Arsenic (As), a potent toxicant, is known to be a hepatotoxicant. Although As induced liver apoptosis and autophagy, the relationship between apoptosis and autophagy of hepatocytes caused by As remains largely unknown. 3-methyladenine (3-MA) and rapamycin can inhibit and promote autophagy of AML-12 cells, respectively. Hence, in this study, AML-12 cells were treated with different concentrations (0, 2, 4, 6, 8, 10 and 12 μmol/L) of As₂O₃, and 5 mmol/L 3-MA or 100 nmol/L rapamycin were applied to distinguish the effect of autophagy on apoptosis in AML-12. Results showed that exposure to As induced cell apoptosis and autophagy, which were mediated by the significantly altered expression levels of autophagy markers (mTOR, LC3, PI3K and P62), and apoptosis markers (Bcl-2 and caspase-3). Further analysis indicated that a certain dosage of 3-MA and rapamycin decreased apoptosis and the caspase-3 expression, which suggested that As-induced autophagy regulated AML-12 cells apoptosis through the expressions of PI3K, mTOR, P62 and Bcl-2.

Arsenic (III) and/or copper (II) induces oxidative stress in chicken brain and subsequent effects on mitochondrial homeostasis and autophagy

As two quite complicated substances, arsenic (As) and copper (Cu) have polluted to the environment. As is highly toxic and could cause nerve damage. Cu is involved in the occurrence of oxidative stress. The brain is one of the main target organs of heavy metal toxicity, but the damage mechanism activated by As and/or Cu in the chicken brain has not been precisely researched. This study is designed to analyze the nervous system damage induced by As and/or Cu exposure from both structural and molecular levels. Under the As and/or Cu stress, local hemorrhage, inflammatory infiltration and mitochondrial damage were observed. Enzymes and non-enzyme antioxidants clearly show that the redox balance is deviated gradually. The results of real-time quantitative PCR and Western blotting revealed that there may be a cascading effect between oxidative stress and disruption of mitochondrial dynamics, the key protein of mitochondrial fusion has decreased and the fission protein has increased. The superposition of these two types of damage may activate the celluar autophagy pathway, the up-regulation of autophagy related genes (ATGs) levels could be observed. All data indicated that excessive As and/or Cu in the environment may pose a threat to the nervous system of poultry. These findings have neurophysiological meaning for exploring cross-contamination of As and Cu in the environment, and offering precautions to economic losses and negative effects on the health of animals and humans. In addition, it provides a reference for feed preparation and environmental protection in agricultural production.

Toxic effects of arsenic trioxide on spermatogonia are associated with oxidative stress, mitochondrial dysfunction, autophagy and metabolomic alterations

Arsenic is a toxic metalloid that can cause male reproductive malfunctions and is widely distributed in the environment. The aim of this study was to investigate the cytotoxicity of arsenic trioxide (ATO) induced GC-1 spermatogonial (spg) cells. Our results found that ATO increased the levels of catalase (CAT) and malonaldehyde (MDA) and reactive oxygen species (ROS), while decreasing glutathione (GSH) and the total antioxidant capacity (T-AOC). Therefore, ATO triggered oxidative stress in GC-1 spg cells. In addition, ATO also caused severe mitochondrial dysfunction that included an increase in residual oxygen consumption (ROX), and decreased the routine respiration, maximal and ATP-linked respiration (ATP-L-R), as well as spare respiratory capacity (SRC), and respiratory control rate (RCR); ATO also damaged the mitochondrial structure, including mitochondrial cristae disordered and dissolved, mitochondrial vacuolar degeneration. Moreover, degradation of p62, LC3 conversion, increasing the number of acidic vesicle organelles (AVOs) and autophagosomes and autolysosomes are demonstrated that the cytotoxicity of ATO may be associated with autophagy. Meanwhile, the metabolomics analysis results showed that 20 metabolites (10 increased and 10 decreased) were significantly altered with the ATO exposure, suggesting that maybe there are the perturbations in amino acid metabolism, lipid metabolism, glycan biosynthesis and metabolism, metabolism of cofactors and vitamins. We concluded that ATO was toxic to GC-1 spg cells via inducing oxidative stress, mitochondrial dysfunction and autophagy as well as the disruption of normal metabolism. This study will aid our understanding of the mechanisms behind ATO-induced spermatogenic toxicity.