Destruction of redox and mitochondrial dynamics co-contributes to programmed cell death in chicken kidney under arsenite or/and copper (II) exposure

Systemic toxicity of biodegradable polyglycolic acid microplastics on the gut-liver-brain axis in zebrafish

Polyglycolic acid (PGA), a novel type of hazardous biodegradable plastic, is gradually being widely used in the biomedical and food packaging industries. However, the long-term ecological effects of PGA degradation to microplastics (MPs) in aquatic organisms remain unknown. The gut-liver-brain axis regulates the exchange of information between the gut, liver, and brain, and is a key target for tissue damage caused by pollutants. Adult zebrafish were exposed to 1 or 100 mg/L PGA MP suspension for 28 d. PGA affects the intestinal vascular barrier through gene expression downstream of the Wnt/β-catenin pathway, increasing intestinal permeability and disrupting the environment of intestinal microbial diversity. This, in turn, promoted the accumulation of lipopolysaccharide (LPS). Disturbance of the intestinal microbiota balance and its metabolites are transferred to the liver and brain through the gut-liver-brain axis, causing disorders in hepatic lipid metabolism and synthesis. Behavioural experiments showed that long-term exposure to PGA MP caused anxiety-like behaviour and cognitive impairment, which may be related to the disruption of the gut-liver-brain axis, thus inducing inflammation and disrupting the normal functioning of the body. In summary, this study evaluated the safety of the new degradable plastic, PGA, but its ecological risks still require attention.

Copper dyshomeostasis and its relationship to AMPK activation, mitochondrial dynamics, and biogenesis of mitochondria: A systematic review of in vivo studies

INTRODUCTION

Copper dyshomeostasis can be related to an increase in copper levels, resulting in toxicity, or to a decrease in tissues levels, impairing cuproenzyme activities. Inside cells, copper can be found in the cytoplasm and inside organelles, and the main organelle that compartmentalizes copper is the mitochondrion. This organelle can form networks and may fuse or fission from this, determining the mitochondrial fusion and fission processes, respectively. Together with mitophagy (autophagy of mitochondria) and mitochondrial biogenesis, mitochondrial fusion and fission (denominated mitochondrial dynamics) determine the number of mitochondria in a cell. A master regulator of mitochondrial dynamics and biogenesis of new mitochondria is AMPK. Considering that both a decrease and an increase in copper levels can influence mitochondrial turnover, especially in diseases related to copper dyshomeostasis, the objective of this systematic review was to verify the current knowledge on the influence of copper homeostasis on AMPK activation, mitochondrial dynamics, and biogenesis of new mitochondria in vivo.

METHODS

PubMed (MEDLINE), Embase, and Web of Science databases were used to search for articles in the literature. Data about the effects of a decrease or an increase in copper levels on the expression of proteins involved in mitochondrial dynamics or biogenesis, and data about AMPK and p-AMPK levels were extracted.

RESULTS

Meta-analysis has demonstrated that high copper levels increase mitochondrial fission and inhibit mitochondrial fusion. Additionally, an increase in copper levels results in AMPK activation. Few studies have analyzed the effects of high copper levels on proteins related to mitochondrial biogenesis, as well as the impact of a decrease in this metal on mitochondrial dynamics and biogenesis, and on AMPK activation.

CONCLUSIONS

Despite the results gathered in this review, other studies are necessary to completely understand the role of copper in regulating AMPK activation, mitochondrial dynamics, and the biogenesis of new mitochondria, since the cell response to a copper dyshomeostasis could be different depending on the species and tissues analyzed.

Arsenic exposure induced renal fibrosis via regulation of mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling pathway

Environmental arsenic exposure is one of the major global public health problems. Studies have shown that arsenic exposure can cause renal fibrosis, but the underlying mechanism is still unclear. Integrating the in vivo and in vitro models, this study investigated the potential molecular pathways for arsenic-induced renal fibrosis. In this study, SD rats were treated with 0, 5, 25, 50, and 100 mg/L NaAsO2 for 8 weeks via drinking water, and HK2 cells were treated with different doses of NaAsO2 for 48 h. The in vivo results showed that arsenic content in the rats' kidneys increased as the dose increased. Body weight decreased and kidney coefficient increased at 100 mg/L. As a response to the elevated NaAsO2 dose, inflammatory cell infiltration, renal tubular injury, glomerular atrophy, tubulointerstitial hemorrhage, and fibrosis became more obvious indicated by HE and Masson staining. The kidney transcriptome profiles further supported the protein-protein interactions involved in NaAsO2-induced renal fibrosis. The in vivo results, in together with the in vitro experiments, have revealed that exposure to NaAsO2 disturbed mitochondrial dynamics, promoted mitophagy, activated inflammation and the TGF-β1/SMAD signaling pathway, and finally resulted in fibrosis. In summary, arsenic exposure contributed to renal fibrosis via regulating the mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling axis. This study presented an adverse outcome pathway for the development of renal fibrosis due to arsenic exposure through drinking water.

Liver Injury Induced by Exposure to Polystyrene Microplastics Alone or in Combination with Cadmium in Mice Is Mediated by Oxidative Stress and Apoptosis

Microplastics (MPs) have been considered an emerging environmental pollutant which, when combined with toxic metals, enter the circulatory system of mammals and eventually cause damage. Therefore, it is important to study the toxicity of the mixture of MPs and heavy metals for evaluating risk assessment of mammals. In the present study, the toxicological effects of different concentrations of polystyrene (PS)-MPs alone or in combination with cadmium chloride (CdCl2) during chronic exposure (8 weeks) were evaluated using intragastric administration in mice. Using comparative analysis, it was revealed that PS-MPs alone or in combination with Cd could destroy the normal structural morphology of liver tissue and increase the levels of two biochemical indicators of liver damage, thereby inducing changes in antioxidant and hyperoxide capacities. In addition, PS-MPs and/or Cd activated the antioxidant signaling pathway Nrf2-Keap1 and affected the endogenous apoptosis signaling pathway p53-Bcl-2/Bax, thus promoting apoptosis. These findings suggested that exposure to MPs alone or in combination with Cd led to adverse effects on the liver. Furthermore, it was revealed that co-exposure to MPs and Cd reduced Cd toxicity, thereby highlighting the possibility MPs may act as carriers of other toxic substances and coordinate with them. Therefore, evaluating the synergistic or anti-agonistic effects of MPs on the toxicity and bioavailability of xenobiotics is in the future critical in environmental toxicological studies.

Study on the mechanism of arsenic-induced renal injury based on SWATH proteomics technology

BACKGROUND

Arsenic (As) poisoning is a worldwide endemic disease affecting thousands of people. As is excreted mainly through the renal system, and arsenic has toxic effects on the kidneys, but the mechanism has not been elucidated. In this study, the molecular basis of arsenic's nephrotoxicity was studied by using a high-throughput proteomics technique.

METHODS

Eight SD (Sprague-Dawley) rats, half male and half female, were fed an As diet containing 50 mg/kg NaAsO2. Age- and sex-matched rats fed with regular chow were used as controls. At the end of the experiment (90 days), kidney tissue samples were collected and assessed for pathological changes using hematoxylin-eosin staining. Proteomic methods were used to identify alterations in protein expression levels in kidney tissues, and bioinformatic analyses of differentially expressed proteins between arsenic-treated and control groups were performed. The expression of some representative proteins was validated by Western blot analysis.

RESULTS

NaAsO2 could induce renal injury. Compared with the control group, 112 proteins were up-regulated, and 46 proteins were down-regulated in the arsenic-treated group. These proteins were associated with the electron transport chain, oxidative phosphorylation, mitochondrial membrane, apoptosis, and proximal tubules, suggesting that the mechanisms associated with them were related to arsenic-induced kidney injury and nephrotoxicity. The expressions of Atp6v1f, Cycs and Ndufs1 were verified, consistent with the results of omics.

CONCLUSION

These results provide important evidence for arsenic-induced kidney injury and provide new insights into the molecular mechanism of arsenic-induced kidney injury.

A regulatory module comprising G3BP1-FBXL5-IRP2 axis determines sodium arsenite-induced ferroptosis

Arsenic contamination is extremely threatening to the global public health. It was reported that sodium arsenite exposure induces serious kidney injury. However, the underlying mechanism is unclear. Ferroptosis is a newly characterized form of iron-dependent programmed cell death, which is implicated in the pathogenesis of various human diseases, including kidney injury. The lethal accumulation of iron-catalyzed lipid peroxidation is the fundamental biochemical characteristic of ferroptosis. Herein we report that sodium arsenite exposure initiates ferroptosis in mammalian HEK293, MEF and HT1080 cells, and induces ferroptosis-associated acute kidney injury in mice. RNA-binding protein G3BP1, the switch component of stress granules, is indispensable for sodium arsenite-induced ferroptosis in a stress granule-independent manner. Mechanistically, G3BP1 stabilizes IRP2, the master regulator of cellular iron homeostasis, through binding to and suppressing the translation of FBXL5 mRNA, which encodes the E3 ligase component to mediate IRP2 ubiquitination and proteasomal degradation. Sodium arsenite intoxication expedites this G3BP1-FBXL5-IRP2 axis and elevates cellular labile free iron, which is responsible for sodium arsenite exposure-induced lipid peroxidation and ferroptotic cell death. In summary, this study highlights a regulatory module comprising G3BP1-FBXL5-IRP2 axis in determining sodium arsenite-induced ferroptosis and ferroptosis-associated acute kidney injury in mice.

Effects of Delaying Post-hatch Feeding on the Plasma Metabolites of Broiler Chickens Revealed by Targeted and Untargeted Metabolomics

Exogenous nutrients are essential for body and skeletal muscle growth in newly hatched chicks, and delaying post-hatch feeding negatively affects body growth, meat yield, and meat quality. The aim of this study was to investigate the effects of delayed post-hatch feeding on the metabolic profiles of broiler chickens using a combination of targeted and untargeted metabolomics. Newly hatched chicks had either immediate free access to feed (freely fed chicks) or no access to feed from 0 to 2 days of age (delayed-fed chicks); both groups were subsequently provided feed ad libitum until 13 days of age. Untargeted metabolomic analysis was performed using gas chromatography-mass spectrometry, whereas targeted metabolomic analysis of amino acids was performed using high-performance liquid chromatography with ortho-phthalaldehyde derivatization. Delayed feeding increased the plasma levels of sucrose, maltose, serotonin, lactitol, gentiobiose, xylitol, threonic acid, and asparagine, and decreased the plasma levels of creatinine, aspartic acid, and glutamic acid. In addition, the digestibility of the nitrogen-free extract (starch and sugar) and the cecal butyric acid concentration increased in chicks subjected to delayed feeding. In contrast, delayed feeding did not affect muscle protein degradation or digestibility in chicks. Taken together, our results indicate that delaying feeding until 48 h post-hatch alters multiple metabolic pathways, which are accompanied by changes in intestinal carbohydrate digestion and cecal butyric acid content in broiler chickens.

Disruption of intestinal structure, tight junction complex, immune response and microbiota after chronic exposure to copper in swamp eel (Monopterus albus)

As an essential micronutrient, copper is crucial in aquatic organisms' growth and development. Numerous studies have consistently reported that excessive intake of copper can have harmful effects on organisms. However, there are limited studies on the impact of copper on the intestine of the swamp eel (Monopterus albus). This study aimed to investigate the changes of intestinal histopathology, tight junction complex, immune response, and microbiota in swamp eel treated with 0 mg/L Cu2+, 0.05 mg/L Cu2+, and 0.10 mg/L Cu2+ for 56 d. Intestinal histopathology showed major changes such as the increased number of erythrocytes and goblet cells in the lamina propria, and separation of the lamina propria. The expression of genes involved in tight junction complex (ZO-1, Claudin-3, Claudin-12 and Claudin-15) was significantly changed. In addition, copper exposure significantly increased the mRNA levels of TLR3, TLR7, TLR8, NF-κB, I-κB, TNF-α and IL-8, especially in 0.10 mg/L Cu2+ group. In contrast, the relative expression level of anti-inflammatory cytokine TGF-β was significantly decreased after exposure to copper. Analysis of the intestinal microbiome showed the intestinal microbiota of swamp eels in the control and copper exposure groups were dominated by Firmicutes and Proteobacteria at the phylum level. Notably, copper exposure changed the diversity of the intestinal microbiota and decreased the relative abundance of Firmicutes and Proteobacteria in the intestine of swamp eel. Collectively, this study demonstrates that chronic copper exposure induces intestinal pathologic changes and inflammatory response, disrupts the intestinal microbial diversity and microbiota composition, and decreases intestinal barrier function in swamp eel, which enhances our understanding of copper-induced intestinal toxicity in fish.

Mitochondria-mediated apoptosis and endoplasmic reticulum stress are involved in the toxicity induced by copper in the porcine spleen

Copper (Cu) is one of the common heavy metal pollutants in the environment, and its toxic mechanisms have been extensively studied. However, the immunotoxicity induced by Cu remains rarely reported, and the effects of Cu on endoplasmic reticulum stress and mitochondria-mediated apoptosis have been little studied in the spleen. In this study, pigs were fed with different contents of Cu (10, 125, and 250 mg/kg Cu) for 80 days to establish a toxicity model. The results showed the Cu exposure triggered endoplasmic reticulum stress in the spleen, as evidenced by increased mRNA and protein levels of GRP94, GRP78, CHOP, XBP1, ATF6, and JNK; the positive rate of GRP78 increased by immunofluorescence analysis. Additionally, mitochondrial fission and fusion homeostasis were disrupted, the expression levels of mitochondrial dynamics-related genes Mfn1, Mfn2, and OPA1 decreased, DRP1 increased, and the positive rate of Mfn1 decreased by immunofluorescence analysis. Furthermore, Cu exposure could induce apoptosis, as demonstrated by the increased expression level of related proteins and genes Bak, Bax, Caspase-3, P53, and Cytc. In conclusion, these results suggest chronic Cu exposure can lead to endoplasmic reticulum stress and imbalance in mitochondrial dynamics and induced apoptosis of pig spleen, and these results provided new insights into the underlying mechanism of Cu exposure caused splenic toxicity, which has public health implications where humans and animals are exposed to copper contamination.

Copper in cancer: From pathogenesis to therapy

One of the basic trace elements for the structure and metabolism of human tissue is copper. However, as a heavy metal, excessive intake or abnormal accumulation of copper in the body can cause inevitable damage to the organism because copper can result in direct injury to various cell components or disruption of the redox balance, eventually leading to cell death. Interestingly, a growing body of research reports that diverse cancers have raised serum and tumor copper levels. Tumor cells depend on more copper for their metabolism than normal cells, and a decrease in copper or copper overload can have a detrimental effect on tumor cells. New modalities for identifying and characterizing copper-dependent signals offer translational opportunities for tumor therapy, but their mechanisms remain unclear. Therefore, this article summarizes what we currently know about the correlation between copper and cancer and describes the characteristics of copper metabolism in tumor cells and the prospective application of copper-derived therapeutics.

Melatonin ameliorates chronic copper-induced lung injury

Copper (Cu) is an important trace element required for several biological processes. The use of copper is increasing gradually in several applications. Previous studies suggest that excess levels of copper are attributed to induce oxidative stress and inflammation, mediating tissue damage. Inline, melatonin the hormone of darkness has been reported to exhibit various therapeutic effects including strong free radical scavenging properties and anti-inflammatory effects. However, its effects against pulmonary injury promoted by copper are not explored and remain unclear so far. Therefore, the present study was aimed to investigate the protective effect of melatonin against copper-induced lung damage. Female Sprague Dawley (SD) rats were exposed to 250 ppm of copper in drinking water for 16 weeks and treated with melatonin (i.p.) 5 and 10 mg/kg from the week (13-16th). The extent of tissue damage was assessed by tissue oxidative stress parameters, metal estimation and histological analysis. Copper-challenged rats showed altered oxidative stress variables. In addition, metal analysis revealed increased copper accumulation in the lungs and histological staining results further indicated severe tissue injury and inflammatory cell infiltration in copper-exposed rats. To this side, treatment with melatonin showed antioxidant and anti-inflammatory activities evidenced by reduced oxidative stress, tissue inflammation and collagen deposition as compared to copper-exposed animals. Moreover, spectral findings suggested melatonin treatment modulated the frequency sift, as compared to copper-challenged animals. Altogether, the present results suggest that melatonin might play a potential role in preventing copper-induced lung aberrations via inhibiting the ROS-mediated oxidative stress and inflammation.

A review: Systematic research approach on toxicity model of liver and kidney in laboratory animals

Therapeutic experiments are commonly performed on laboratory animals to investigate the possible mechanism(s) of action of toxic agents as well as drugs or substances under consideration. The use of toxins in laboratory animal models, including rats, is intended to cause toxicity. This study aimed to investigate different models of hepatotoxicity and nephrotoxicity in laboratory animals to help researchers advance their research goals. The current narrative review used databases such as Medline, Web of Science, Scopus, and Embase and appropriate keywords until June 2021. Nephrotoxicity and hepatotoxicity models derived from some toxic agents such as cisplatin, acetaminophen, doxorubicin, some anticancer drugs, and other materials through various signaling pathways are investigated. To understand the models of renal or hepatotoxicity in laboratory animals, we have provided a list of toxic agents and their toxicity procedures in this review.

Zinc Alleviates Arsenic-Induced Inflammation and Apoptosis in the Head Kidney of Common Carp by Inhibiting Oxidative Stress and Endoplasmic Reticulum Stress

Arsenic (As) pollution is ubiquitous in water, which shows immunotoxicity to aquatic organisms. As an indispensable regulator of gene transcription and enzymatic modification, zinc (Zn) may play a preventive and therapeutic effect on As toxicity. The purpose of this study was to investigate the interactions of As and Zn on the head kidney of common carp Cyprinus carpio. Herein the carp were treated alone or in combination with waterborne As³⁺ (2.83 mg/L) and/or Zn²⁺ (1 mg/L). Results suggested a head kidney-toxic effect of As exposure, which was manifested by the histopathological damage of the head kidney, elevation of nuclear translocation of pro-inflammatory nuclear factor-kappa light chain enhancer of B cells (NF-κB), and blockage of the anti-oxidative nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. The global activation of three endoplasmic reticulum (ER) stress pathways led to the execution of programmed cell death, including ER apoptosis mediated by C/EBP-homologous protein (CHOP), death receptor-mediated exogenous cell apoptosis, and the endogenous apoptosis executed by Caspases9. The combined application of Zn can significantly improve the histopathological damage of the head kidney, the imbalance of the antioxidant system, and the apoptosis outcomes due to ER stress. In conclusion, this study indicates that Zn has an antagonistic effect on the head kidney injury of common carp induced by sub-chronic As exposure. The results of this study provide basic data for the risk assessment of As accumulation in an aquatic environment and a reference for the use of Zn preparation in aquaculture.

Activation of endoplasmic reticulum-mitochondria coupling drives copper-induced autophagy in duck renal tubular epithelial cells

Copper (Cu) as a transition metal can be toxic to public and ecosystem health at high level, but the specific mechanism of Cu-evoked nephrotoxicity remains elusive. Here, we first revealed the crosstalk between mitofusin2 (Mfn2)-dependent mitochondria-associated endoplasmic reticulum membrane (MAM) dynamics and autophagy in duck renal tubular epithelial cells under Cu exposure. Primary duck renal tubular epithelial cells were treated with 100 and 200 μM Cu sulfate for 12 h and exposed to lentivirus to deliver mitofusin2 (Mfn2). We found that excessive Cu disrupted MAM integrity, decreased the mitochondrial calcium level, co-localization of IP3R and VDAC1, the mRNA levels of PACS2, Mfn2, IP3R and MCU, and Mfn2 and VDAC1 protein levels, causing MAM dysfunction. Furthermore, Mfn2 overexpression ameliorated Cu-induced MAM dysfunction, and increased Cu-evoked autophagy in duck renal tubular epithelial cells accompanied with the elevation of autophagosomes number, ROS level, LC3 puncta, Atg5 and LC3B mRNA levels, and Beclin1, Atg14, LC3BII/LC3BI protein levels. Accordingly, our data proved that excessive Cu could trigger MAM dysfunction and autophagy in duck renal tubular epithelial cells, and Cu-induced autophagy could be activated through Mfn2-dependent MAM, providing evidence on the toxicological exploration mechanisms of Cu.

Long-term exposure to copper induces mitochondria-mediated apoptosis in mouse hearts

Copper is a trace element necessary for the normal functioning of organisms, but excessive copper contents may be toxic to the heart. The goal of this study was to investigate the role of excessive copper accumulation in mitochondrial damage and cell apoptosis inhibition. In vivo, the heart copper concentration and cardiac troponin I (c-TnI) and N-terminal forebrain natriuretic peptide (NT-pro-BNP) levels increased in the copper-laden model group compared to those of the control group. Histopathological and ultrastructural observations revealed that the myocardial collagen volume fraction (CVF), perivascular collagen area (PVCA) and cardiomyocyte cross-sectional area (CSA) were markedly elevated in the copper-laden model group compared with the control group. Furthermore, transmission electron microscopy (TEM) showed that the mitochondrial double-layer membrane was incomplete in the copper-laden model groups. Furthermore, cytochrome C (Cyt-C) expression was downregulated in mitochondria but upregulated in the cytoplasm in response to copper accumulation. In addition, Bcl-2 expression decreased, while Bax and cleaved caspase-3 levels increased. These results indicate that copper accumulation in cardiomyocyte mitochondria induces mitochondrial injury, and Cyt-C exposure and induces apoptosis, further resulting in heart damage.

Association of Metals and Metalloids With Urinary Albumin/Creatinine Ratio: Evidence From a Cross-Sectional Study Among Elderly in Beijing

Background

Environmental exposure to toxic elements contributes to the pathogenesis of chronic kidney disease (CKD). Few studies focus on the association of urinary metals and metalloids concentrations with the urinary albumin/creatinine ratio (UACR) among elderly, especially in areas and seasons with severe air pollution.

Objective

We aimed to evaluate the associations of urinary metals and metalloids concentration with UACR, which is an early and sensitive indicator of CKD.

Method

We conducted a cross-sectional study among 275 elderly people in Beijing from November to December 2016, which has experienced the most severe air pollution in China. We measured 15 urinary metals and metalloids concentration and estimated their association with UACR using a generalized linear model (GLM). Bayesian kernel machine regression (BKMR) and quantile g-computation (qgcomp) models were also conducted to evaluate the combined effect of metal and metalloid mixtures concentration.

Results

Of the 275 elderly people included in the analysis, we found that higher urinary Cu concentration was positively associated with UACR using GLM (β = 0.36, 95% CI: 0.25, 0.46). Using the BKMR model, we found that the change in UACR was positively associated with a change in urinary Cu concentration from its 25th to 75th percentile value with all other metals and metalloids concentration fixed at their 25th, 50th, or 75th percentile levels. Urinary Cu concentration had the most significant positive contribution (59.15%) in the qgcomp model. Our finding was largely robust in three mixture modeling approaches: GLM, qgcomp, and BKMR.

Conclusion

This finding suggests that urinary Cu concentration was strongly positively associated with UACR. Further analyses in cohort studies are required to corroborate this finding.

Curcumin alleviates arsenic-induced injury in duck skeletal muscle via regulating the PINK1/Parkin pathway and protecting mitochondrial function

Arsenic is a well-known environmental pollutant due to its toxicity, which can do harm to animals and human. Curcumin is a polyphenolic compound derived from turmeric, commonly accepted to have antioxidant properties. However, whether curcumin can ameliorate the damage caused by arsenic trioxide (ATO) in duck skeletal muscle remains largely unknown. Therefore, the present study aims to investigate the potential molecular mechanism of curcumin against ATO-induced skeletal muscle injury. The results showed that treating with curcumin could attenuate body weight loss induced by ATO and reduced arsenic content accumulation in the skeletal muscle of duck. Curcumin was also able to alleviated the oxidative stress triggered by ATO, which was manifested by the increase of T-AOC and SOD, and MDA decrease. Moreover, we observed that curcumin could ease mitochondrial damage and vacuolate degeneration of nucleus. Our further investigation found that ATO disrupted normal mitochondrial fission/fusion (Drp1, OPA1, Mfn1/2) and restrained mitochondrial biogenesis (PGC-1α, Nrf1/2, TFAM), while curcumin could promote mitochondrial fusion and activated PGC-1α pathway. Furthermore, curcumin was found that it could not only reduce the mRNA and protein levels of mitophagy (PINK1, Parkin, LC3, p62) and pro-apoptotic genes (p53, Bax, Caspase-3, Cytc), but also increased the levels of anti-apoptotic genes (Bcl-2). In conclusion, curcumin was able to alleviate ATO-induced skeletal muscle damage by improving mitophagy and preserving mitochondrial function, which can serve as a novel strategy to take precautions against ATO toxicity.

Selenium alleviates mercury chloride-induced liver injury by regulating mitochondrial dynamics to inhibit the crosstalk between energy metabolism disorder and NF-κB/NLRP3 inflammasome-mediated inflammation

Mercury (Hg) is a persistent heavy metal contaminant with definite hepatotoxicity. Selenium (Se) has been shown to alleviate liver damage induced by heavy metals. Therefore, the present study aimed to explore the mechanism of the antagonistic effect of Se on mercury chloride (HgCl2)-induced hepatotoxicity in chickens. Firstly, we confirmed that Se alleviated HgCl2-induced liver injury through histopathological observation and liver function analyzation. The results also showed that Se prevented HgCl2-induced liver lipid accumulation and dyslipidemia by regulating the gene expression related to lipid as well as glucose metabolism. Moreover, Se blocked the nuclear factor kappa B (NF-κB)/NLR family pyrin domain containing 3 (NLRP3) inflammasome signaling pathway, which was the key to alleviate the inflammation caused by HgCl2. Mechanically, Se inhibited immoderate mitochondrial division, fusion, and biogenesis caused by HgCl2, and also improved mitochondrial respiration, which were essential for preventing energy metabolism disorder and inflammation. In conclusion, our results suggested that Se inhibited energy metabolism disorder and inflammation by regulating mitochondrial dynamics, thereby alleviating HgCl2-induced liver injury in chickens. These results are expected to provide potential intervention and therapeutic targets for diseases caused by inorganic mercury poisoning.

In situ monitoring of the effect of Cu2+ on the membrane permeability of a single living cell with a dual-electrode tip of a scanning electrochemical microscope

Here, an Au-Cu dual-electrode tip was designed to monitor the effect of Cu²⁺ on the membrane permeability of a single living cell in situ using scanning electrochemical microscopy. The probe approach curves (PACs) were obtained using potassium ferricyanide as a redox mediator. Meanwhile, according to the simulation, theoretical PACs could be acquired. Thus, the cell membrane permeability coefficient (P_m) values were obtained by overlapping the experimental PACs with the theoretical values. Cu²⁺ was directly generated by electrolyzing the Cu electrode of the dual-electrode tip to investigate its effect on the cell membrane permeability in situ. This work has potential value to improve the understanding of the mechanism of acute heavy metal damage on the cell membrane and will also help clarify the role of heavy metal ions in physiological or pathological processes.

Metabolomics analysis reveals the effects of copper on mitochondria-mediated apoptosis in kidney of broiler chicken (Gallus gallus)

Copper (Cu) is one of the ubiquitous environmental pollutants which have raised wide concerns about the potential toxic effects and public health threat. For deeply investigating the nephrotoxicity induced by Cu, the effects of Cu on mitochondria-mediated apoptosis in kidney were first to analyze by combining metabolomics and molecular biology techniques. In this study, broiler chicks were fed with different contents of Cu (11, 110, 220, and 330 mg/kg Cu) for 49 d. The results of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining and transmission electron microscope showed that Cu could induce apoptosis in kidney, characterized by the increasing of TUNEL-positive cells and mitochondrial vacuolation. Additionally, a total of 62 differential metabolites were detected by liquid chromatography-mass spectrometry (LC-MS), and mainly enriched in the metabolic pathways including riboflavin metabolism, glutathione metabolism, sphingolipid metabolism, and glycerophospholipid metabolism, which were closely to mitochondrial metabolism. Meanwhile, the decreased mitochondrial membrane potential (MMP), increased mitochondrial membrane permeability and the change of mRNA and protein expression levels associated with mitochondria-mediated apoptosis and mitochondrial dynamics confirmed that Cu could induce mitochondria-mediated apoptosis. Therefore, our results demonstrated that Cu induced mitochondria-mediated apoptosis in kidney. Moreover, this study highlighted the metabolic characteristics of Cu to kidney, which suggested that mitochondrial metabolism could be considered as an important factor influencing toxicity.

New insights into crosstalk between apoptosis and necroptosis co-induced by chlorothalonil and imidacloprid in Ctenopharyngodon idellus kidney cells

Overuse and co-exposure of pesticides have become a public health problem and threat seriously water health and environmental organisms and even humans. Chlorothalonil (CT) and imidacloprid (IMI) are high-selling pesticides worldwide, which can persist in the environment, and present a series of severely toxic effects on non-target animals. However, the effect of co-application on aquatic organisms is unknown. Based on the concept of the toxic unit (TU), toxic interaction of CT and IMI was evaluated and showed the additive and synergistic toxicity on Ctenopharyngodon idellus (grass carp) kidney cell line (CIK cells). Cell death analysis found an obvious increase of the apoptosis and necrosis rates exposed to CT and IMI, and aggravation when applied together. Moreover, CT and IMI co-exposure accelerated the inhibition of CYP450s/ROS/HIF-1α signal, the decline of energy metabolism, mitochondrial dynamics disorder, activation of Bcl2/Bax/Cyt C/Casp3/Casp9 pathway and RIP1/RIP3/MLKL pathway. Bioinformatics analysis showed autophagy, cell response, NOD-like receptor signaling pathway might be affected by co-exposure. In summary, the above results indicate that co-exposure to CT and IMI has synergistic toxicity and aggravates cell death via inhibition of the CYP450s/ROS/HIF-1α signal. These data provide new insights for evaluating the stacking interaction and revealing the toxicological effects of pesticide mixture.

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.

Copper-induced sublethal effects in Bufo gargarizans tadpoles: growth, intestinal histology and microbial alternations

Copper (Cu) is one of the environmental contaminations which can pose significant risks for organisms. The current study explores the effects of Cu exposure on the growth, intestinal histology and microbial ecology in Bufo gargarizans. The results revealed that 0.5-1 μM Cu exposure induced growth retardation (including reduction of total body length and wet weight) and intestinal histological injury (including disordered enterocyte, changes in the villi and vacuoles) of tadpoles. Also, high-throughput sequencing analysis showed that Cu exposure caused changes in richness, diversity and structure of intestinal microbiota. Moreover, the composition of intestinal microbiota was altered in tadpoles exposed to different concentrations of Cu. At the phylum level, we observed the abundance of proteobacteria was increased, while the abundance of fusobacteria was decreased in the intestinal microbiota of tadpoles exposed to 1 μM Cu. At the genus level, a reduced abundance of kluyvera and aeromonas was observed in the intestinal microbiota of tadpoles under the exposure of 0-0.5 μM Cu. Finally, functional predictions revealed that tadpoles exposed to copper may be at a higher risk of developing metabolic disorders or diseases. Above all, our results will develop a comprehensive view of the Cu exposure in amphibians and will yield a new consideration for sublethal effects of Cu on aquatic organisms.

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.

Transition metals and metal complexes in autophagy and diseases

Transition metals refer to the elements in the d and ds blocks of the periodic table. Since the success of cisplatin and auranofin, transition metal-based compounds have become a prospective source for drug development, particularly in cancer treatment. In recent years, extensive studies have shown that numerous transition metal-based compounds could modulate autophagy, promising a new therapeutic strategy for metal-related diseases and the design of metal-based agents. Copper, zinc, and manganese, which are common components in physiological pathways, play important roles in the progression of cancer, neurodegenerative diseases, and cardiovascular diseases. Furthermore, enrichment of copper, zinc, or manganese can regulate autophagy. Thus, we summarized the current advances in elucidating the mechanisms of some metals/metal-based compounds and their functions in autophagy regulation, which is conducive to explore the intricate roles of autophagy and exploit novel therapeutic drugs for human diseases.

Endoplasmic reticulum stress aggravates copper-induced apoptosis via the PERK/ATF4/CHOP signaling pathway in duck renal tubular epithelial cells

Copper (Cu) is a vital micronutrient required for numerous fundamental biological processes, but excessive Cu poses potential detrimental effects on public and ecosystem health. However, the molecular details linking endoplasmic reticulum (ER) stress and apoptosis in duck renal tubular epithelial cells have not been fully elucidated. In this study, duck renal tubular epithelial cells exposed to Cu sulfate (CuSO₄) (0, 100 and 200 μM) and a PERK inhibitor (GSK2606414, GSK, 1 μM) for 12 h were used to investigate the crosstalk between ER stress and apoptosis under Cu exposure. Cell and ER morphological and functional characteristics, intracellular calcium (Ca²⁺) levels, apoptotic rates, ER stress and apoptosis-related mRNA and protein levels were examined. The results showed that excessive Cu could cause ER expansion and swelling, increase the expression levels of ER stress-associated genes (PERK, eIF2α, ATF4 and CHOP) and proteins (p-PERK and CHOP), induce intracellular Ca²⁺ overload, upregulate the expression levels of apoptosis-associated genes (Bax, Bak1, Caspase9 and Caspase3) and the cleaved-Caspase3 protein, downregulate Bcl-xl and Bcl2 mRNA levels and trigger apoptosis. PERK inhibitor treatment could ameliorate the above changed factors caused by Cu. In conclusion, these findings indicate that excessive Cu could trigger ER stress via activation of the PERK/ATF4/CHOP signaling pathway and that ER stress might aggravate Cu-induced apoptosis in duck renal tubular epithelial cells.

Activation of the ROS/HO-1/NQO1 signaling pathway contributes to the copper-induced oxidative stress and autophagy in duck renal tubular epithelial cells

The aim of this study was to investigate the crosstalk between oxidative stress and autophagy through the ROS/HO-1/NQO1 pathway caused by copper (Cu). Duck renal tubular epithelial cells were treated in Cu sulfate (CuSO₄) (0, 100 and 200 μM) for 12 h, and in the combination of CuSO₄ (200 μM) and reactive oxygen species (ROS) scavenger (butyl hydroxyanisole, BHA, 100 μM), or HO-1 inhibitor (zinc protoporphyrin, ZnPP, 10 μM) for 12 h. Results revealed that Cu could significantly elevate the levels of intracellular ROS, superoxide dismutase, hydrogen peroxide, malondialdehyde, glutathione, simultaneously reduce catalase and glutathione peroxidase levels, and upregulate HO-1, SOD-1, CAT, NQO1, GCLM mRNA levels and HO-1, SOD-1 protein levels. Additionally, Cu could observably increase the number of autophagosomes, acidic vesicle organelles (AVOs) and LC3 puncta; upregulate mRNA levels of mTOR, Beclin-1, ATG7, ATG5, ATG3, LC3II and protein levels of Beclin-1, LC3II/LC3I, downregulate LC3I mRNA level. Both treatments with BHA and ZnPP could significantly alleviate the changes of antioxidant indexes levels and ROS accumulation, reduce the increase of the number of autophagosomes, AVOs and LC3 puncta, and mitigate the above changed oxidative stress and autophagy related mRNA and protein levels induced by Cu. In summary, our findings indicated that excessive Cu could induce oxidative stress and autophagy by activating the ROS/HO-1/NQO1 pathway, and inhibition of HO-1 might attenuate Cu-induced oxidative stress and autophagy in duck renal tubular epithelial cells.

Molecular Mechanisms Underlying Protective Role of Quercetin on Copper Sulfate-Induced Nephrotoxicity in Mice

Copper overload is an established cause of nephrotoxicity, but the precise molecular mechanism remains unknown. Our study aimed to investigate the molecular mechanism of copper sulfate (CuSO₄)-induced nephrotoxicity and the protective effect of the natural compound quercetin using a mouse model. Mice were orally administered CuSO₄ only (200 mg/kg per day), or co-administered CuSO₄ (200 mg/kg per day) plus quercetin (25, 50, or 100 mg/kg per day), or quercetin only (100 mg/kg per day), or vehicle for 28 days. The blood and kidneys were collected for the examination of serum biomarkers, oxidative stress biomarkers, changes in histopathology and gene and protein expression. Our results show that quercetin supplementation attenuates CuSO₄-induced renal dysfunction and tubular necrosis in a dose-dependent manner. Quercetin supplementation at 50 and 100 mg/kg significantly attenuated CuSO₄-induced oxidative damage. Quercetin supplementation also inhibited the activities of caspases-9 and-3, and the expression of p53 and Bax mRNAs. Furthermore, quercetin supplementation markedly activated the expression of Nrf2 and HO-1 mRNAs, but inhibited the expression of NF-κB, IL-1β, IL-6, and TNF-α mRNAs. In conclusion, our results revealed that quercetin supplementation could inhibit CuSO₄-induced nephrotoxicity in mice via the inhibition of mitochondrial apoptotic and NF-κB pathways and the activation of Nrf2/HO-1 pathway. Our study highlights quercetin as a potential candidate in treating copper overload-induced nephrotoxicity.

Copper induces energy metabolic dysfunction and AMPK-mTOR pathway-mediated autophagy in kidney of broiler chickens

To explore the effects of copper (Cu) on energy metabolism and AMPK-mTOR pathway-mediated autophagy in kidney, a total of 240 one-day-old broiler chickens were randomized into four equal groups and fed on the diets with different levels of Cu (11, 110, 220, and 330 mg/kg) for 49 d. Results showed that excess Cu could induce vacuolar degeneration and increase the number of autophagosomes in kidney, and the adenosine triphosphate (ATP) level and mRNA levels of energy metabolism-related genes were decreased with the increasing dietary Cu level. Moreover, immunohistochemistry and immunofluorescence showed that the positive expressions of Beclin1 and LC3-II were mainly located in cytoplasm of renal tubular epithelial cells and increased significantly with the increasing levels of Cu. The mRNA levels of Beclin1, Atg5, LC3-I, LC3-II, Dynein and the protein levels of Beclin1, Atg5, LC3-II/LC3-I and p-AMPKα1/AMPKα1 were markedly elevated in treated groups compared with control group (11 mg/kg Cu). However, the mRNA and protein levels of p62 and p-mTOR/mTOR were significantly decreased with the increasing levels of Cu. These results suggest that impaired energy metabolism induced by Cu may lead to autophagy via AMPK-mTOR pathway in kidney of broiler chickens.

Oxidative stress and mitochondrial dysfunction involved in ammonia-induced nephrocyte necroptosis in chickens

Ammonia (NH₃), an environmental pollutant, poses a serious threat to human and avian health. Although previous studies have showed that NH₃ caused kidney injury, the molecular mechanisms of nephrotoxicity induced by NH₃ remain unclear. To explore the mechanisms of NH₃ nephrotoxicity, a total of 36 broiler chicks at one day of age were exposed to NH₃. After 42 days of exposure, blood samples were collected to determine creatinine and uric acid; and kidney samples were weighted and then collected to detect ultrastructural changes, oxidative stress parameters, ATPases, necroptosis- and mitochondrial dynamics-related genes. The results showed that chickens exposed to NH₃ showed lower relative kidney weight and an increase concentration in serum creatinine and uric acid. NH₃ exposure caused nephrocyte necrosis and increased the expression of necroptosis-related genes (TNF-α, RIPK1, RIPK3, MLKL, and JNK). Besides, the activities of antioxidant systems (SOD, CAT, GSH-Px, and T-AOC) were reduced, whereas the concentrations of H₂O₂ and MDA were elevated. Lower activities of ATPases were obtained in NH₃ treatment groups. Furthermore, the mitochondrial fission-related genes drp1 and mff were activated, and mitochondrial fusion-related genes opa1, mfn1 and mfn2 were suppressed after NH₃ exposure. Based on the above results, we conclude that NH₃ caused-oxidative stress and mitochondrial dysfunction mediated nephrocyte necroptosis in chickens. This study may provide new insight into NH₃ nephrotoxicity.

As3+ or/and Cu2+ exposure triggers oxidative stress imbalance, induces inflammatory response and apoptosis in chicken brain

Arsenic (As) and copper (Cu) are common environmental pollutants in nature. When they are excessively present in living organisms, they can cause heavy metal poisoning. There were relatively few studies of the toxicological concentrations of As and Cu in the brain using chicken as a model. Therefore, in this study, arsenic trioxide or/and copper sulfate were added to chicken diets for a 12-week toxicity test. The test results showed that excessive intake of As or/and Cu led to a significant reduction in the total antioxidant capacity (T-AOC), catalase (CAT) and hydroxyl radicals. And significant increase in nitric oxide synthase (NOS) indicates an imbalanced oxidation reaction. In addition, the increase in heat shock protein (HSPs), the increase of NF-κB pathway-related pro-inflammatory mediators, the change of apoptosis factors on the death receptor and mitochondrial apoptosis pathway show that, As or/and Cu exposure induced chicken brain has heat shock response (HSP), tissue inflammation and apoptosis. This damage is inseparable from the oxidative imbalance. It is worth noting that these injury changes are time-dependent, and the combined effect of these two metals is more severe than that of a single group of injuries. Our findings can inform the regulation of animal feed additives and avoid agricultural economic losses or biological health damage.

Chronic copper poisoning in beef cattle in the state of Mato Grosso, Brazil

ABSTRACT: Copper is an essential micromineral in animal feed; however, when consumed in excess, it can cause liver necrosis, hemolytic crisis, hemoglobinuric nephrosis and death in cattle. Although uncommon in this species, copper poisoning occurs as a result of exacerbated supplementation, deficiency of antagonist microminerals, or previous liver lesions. An outbreak of chronic copper poisoning is reported in semi-confined cattle after supplementation with 50 mg/Kg of dry matter copper. The cattle showed clinical signs characterized by anorexia, motor incoordination, loss of balance, jaundice, brownish or black urine, diarrhea and death, or were found dead, 10 to 302 days after consumption. Of the 35 cattle that died, 20 underwent necropsy, whose frequent findings were jaundice, enlarged liver with evident lobular pattern, black kidneys, and urinary bladder with brownish to blackish content. Microscopically, the liver showed vacuolar degeneration and/or zonal hepatocellular centrilobular or paracentral coagulative necrosis, in addition to cholestasis, mild periacinal fibrosis, apoptotic bodies, and mild to moderate mononuclear inflammation. Degeneration and necrosis of the tubular epithelium and intratubular hemoglobin cylinders were observed in the kidneys. Copper levels in the liver and kidneys ranged from 5,901.24 to 28,373.14 μmol/kg and from 303.72 to 14,021 μmol/kg, respectively. In conclusion, copper poisoning due to excessive nutritional supplementation is an important cause of jaundice, hemoglobinuria, and death in semi-confined cattle.

Copper induces oxidative stress with triggered NF-κB pathway leading to inflammatory responses in immune organs of chicken

Copper (Cu) is a necessary trace mineral due to its biological activity. Excessive Cu can induce inflammatory response in humans and animals, but the underlying mechanism is still unknown. Here, 240 broilers were used to study the effects of excessive Cu on oxidative stress and NF-κB-mediated inflammatory responses in immune organs. Chickens were fed with diet containing different concentrations of Cu (11, 110, 220, and 330 mg of Cu/kg dry matter). The experiment lasted for 49 days. Spleen, thymus, and bursa of Fabricius (BF) on day 49 were collected for histopathological observation and assessment of oxidative stress status. Additionally, the mRNA and protein levels of NF-κB and inflammatory cytokines were also analyzed. The results indicated that excess Cu could increase the number and area of splenic corpuscle as well as the ratio of cortex and medulla in thymus and BF. Furthermore, excessive Cu intake could decrease activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px); but increase contents of malondialdehyde (MDA), TNF-α, IL-1, IL-1β; up-regulate mRNA levels of TNF-α, IFN-γ, IL-1, IL-1β, IL-2, iNOS, COX-2, NF-κB and protein levels of TNF-α, IFN-γ, NF-κB, p-NF-κB in immune organs. In conclusion, excessive Cu could cause pathologic changes and induce oxidative stress with triggered NF-κB pathway, and might further regulate the inflammatory response in immune organs of chicken.

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.

Molecular Insights of Copper Sulfate Exposure-Induced Nephrotoxicity: Involvement of Oxidative and Endoplasmic Reticulum Stress Pathways

The precise pathogenic mechanism in Cu exposure-cause nephrotoxicity remains unclear. This study investigated the underlying molecular mechanism of copper sulfate (CuSO₄)-induced nephrotoxicity. Mice were treated with CuSO₄ at 50, 100, 200 mg/kg/day or co-treated with CuSO₄ (200 mg/kg/day) and 4-phenylbutyric acid (4-PBA, 100 mg/kg/day) for 28 consecutive days. HEK293 cells were treated with CuSO₄ (400 μM) with or without superoxide dismutase, catalase or 4-PBA for 24 h. Results showed that CuSO₄ exposure can cause renal dysfunction and tubular necrosis in the kidney tissues of mice. CuSO₄ exposure up-regulated the activities and mRNA expression of caspases-9 and -3 as well as the expression of glucose-regulated protein 78 (GRP78), GRP94, DNA damage-inducible gene 153 (GADD153/CHOP), caspase-12 mRNAs in the kidney tissues. Furthermore, superoxide dismutase and catalase pre-treatments partly inhibited CuSO₄-induced cytotoxicity by decreasing reactive oxygen species (ROS) production, activities of caspases-9 and -3 and DNA fragmentations in HEK293 cells. 4-PBA co-treatment significantly improved CuSO₄-induced cytotoxicity in HEK293 cells and inhibited CuSO₄ exposure-induced renal dysfunction and pathology damage in the kidney tissues. In conclusion, our results reveal that oxidative stress and endoplasmic reticulum stress contribute to CuSO₄-induced nephrotoxicity. Our study highlights that targeting endoplasmic reticulum and oxidative stress may offer an approach for Cu overload-caused nephrotoxicity.

The Activation of Heat-Shock Protein After Copper(II) and/or Arsenic(III)-Induced Imbalance of Homeostasis, Inflammatory Response in Chicken Rectum

Arsenic and copper, two toxic pollutants, are powerful inducers of oxidative stress. Exposure to copper and arsenic can cause intestinal injury in cockerel. This study was carried out to investigate the effects of these two pollutants on the gastrointestinal tract of cockerels. Experimental results showed that the activity of antioxidant enzymes (catalase and glutathione peroxidase) was inhibited and the ionic balance was destroyed after exposure to copper sulfate (300 mg/kg) and/or arsenic trioxide (30 mg/kg). However, the expression of pro-inflammatory cytokines (nuclear factor kappa-B, cyclooxygenase-2, tumor necrosis factor-α, and prostaglandin E2 synthases) increased markedly. Damages to the biofilm structure and inflammatory cell infiltration were simultaneously observed during histological examination. Heat-shock proteins were also expressed in large quantities after exposure to the poisons. Collectively, exposure to arsenite and/or Cu²⁺ can cause rectal damage in cockerels, inducing inflammation and an imbalance in immune system responses. Sometimes, exposure to both pollutants can produce even more toxic effects. Heat-shock proteins can protect the tissue from the exotoxins but the specific mechanisms require exploration. After oral ingestion of toxins, the rectum can still be damaged, necessitating attention to the safety of poultry breeding, human food safety, and environmental protection.

Long-term exposure to copper induces autophagy and apoptosis through oxidative stress in rat kidneys

Copper (Cu) is an essential trace element for most organisms. However, excessive Cu can be highly toxic. The purpose of this study was to elucidate the mechanism underlying Cu toxicity in the kidneys of rats after treatment with CuCl₂ (15 [control], 30, 60, or 120 mg/kg in the diet) for 180 days. Histological and ultrastructural changes, antioxidant enzyme activity, and the mRNA and protein levels of apoptosis and autophagy-related genes were measured. The results showed that Cu exposure led to significant accumulation of copper in kidneys and disorganized kidney morphology. The activities of total anti-oxidation capacity (T-AOC) and superoxide dismutase (SOD) in the kidneys decreased significantly, while the malondialdehyde (MDA) content increased. Furthermore, excessive Cu markedly upregulated the expression of autophagy and apoptosis-related genes (LC3A, LC3B, ATG-5, Beclin-1, Caspase3, CytC, P53, Bax), but downregulated the expression of P62, mTOR and BCL-2. Moreover, the LC3B/LC3A, ATG-5, Beclin-1, P53, Caspase3 proteins were up-regulated while P62 was down-regulated in the kidney tissues of the treatment groups. Overall, these findings provide strong evidence that excess Cu can trigger autophagy and apoptosis via the mitochondrial pathway by inducing oxidative stress in rat kidneys.

Oxidative damage under As3+ and/or Cu2+ stress leads to apoptosis and autophagy and may be cross-talking with mitochondrial disorders in bursa of Fabricius

Arsenic (As) exists in many forms in the whole natural environment, with As³⁺ the highest toxicity. Herein our study demonstrated that arsenic trioxide (As₂O₃) at a dose of 30 mg/kg caused serious oxidative damage to chickens' bursa of Fabricius (BF) in a time-dependent manner. Copper (Cu) is a necessary micronutrient and a key catalytic cofactor of many enzymes. We found excessive Cu (in the form of 300 mg/kg copper sulfate (CuSO₄)) also induced severe oxidative stress (OxS), and its co-exposure with As³⁺ had a greater destructive power against oxidative system. Under electron microscope, swollen mitochondria, disappeared cristae and agglutinated chromatin were observed, accompanied by myeloid structure and autophagosome. The results showed apoptosis and autophagy occurred under the action of As³⁺ and Cu²⁺, and the situation was more serious in combined exposure group, which was further explained by terminal deoxynucleotidyl transferase (TdT)-mediated 2'-Deoxyuridine 5'-Triphosphate (dUTP) Nick-End Labeling (TUNEL). By quantitative real time polymerase chain reaction (RT-qPCR) and western blot, we found that mitochondrial dynamics were disordered under OxS, and the abnormal changes of B-cell lymphoma (Bcl)-2, p53, Bcl-2-interacting protein (Beclin)-1 and autophagy-related gene (ATG) 4B indicated the crosstalk between apoptosis and autophagy. In conclusion, apoptosis and autophagy of BF induced by As³⁺ and Cu²⁺ and mitochondrial disorder are closely related to the collapse of antioxidant system, and their connections are inseparable. Our results provide a reference for environmental risk prevention and selection of poultry feed additives and pesticides to avoid the health risks caused by As³⁺ and Cu²⁺ exposure.

Excessive Cu2+ deteriorates arsenite-induced apoptosis in chicken brain and resulting in immunosuppression, not in homeostasis

Trace elements such as copper (Cu) and arsenic (As) are two of the major contaminants and well-known inducers of cognitive deficits and neurobehavioral changes. This study evaluated the immunotoxicity of their individual or combined exposure on different brain regions in chickens. Consequently, nuclear damage and organelle lesions, especially mitochondria were observed under Cu or/and As stress, in which positive regulation of key proteins, dynamin-related protein 1 (Drp1), Cytochrome C (Cyt c), BCL2-associated X (Bax), Caspases 3 and P53 was detected by qRCR and Western blot analyses, indicating disturbed mitochondrial dynamic equilibrium and apoptosis execution. In addition, qRCR analysis confirmed the involvement of cytokines secreted by different populations of helper T cells, indicative of cellular immunity. Gene expression studies showed marked up regulation of Th1/Th17 cytokines along with heat shock protein (HSP) 70, a synergism was noted in co-administration group. Interesting, lower apoptosis index was noted in brainstem compared to cerebrum and cerebellum. An intense immunosuppression and heat shock response against Cu or/and As was also seen in cerebrum and cerebellum but not in brainstem. In conclusion, our study suggests a synergistic neurotoxicity in chickens under Cu and As exposure. These findings provide a basic understanding of mitochondrial abnormality-initiated neuropathology in response to environmental pollutant mixtures, suggesting an adaptive response to the frangibility of the central nerve system.

Arsenic trioxide or/and copper sulfate co-exposure induce glandular stomach of chicken injury via destruction of the mitochondrial dynamics and activation of apoptosis as well as autophagy

Arsenic and copper are naturally occurring element. Contamination from natural processes and anthropogenic activities can be discovered all over the world and their unique interactions with the environment lead to widespread toxicity. When the content was excessive, the organism would be hurt seriously. The glandular stomach is an important organ of the poultry gastrointestinal tract. This study was aimed to investigate the toxicity of arsenic trioxide or/and copper sulfate (As or/and Cu) on chicken glandular stomach. Seventy-two 1-day-old Hy-Line chickens were randomly divided into control (C) group, arsenic trioxide (As) group, copper sulfate (Cu) group and arsenic trioxide and copper sulfate (AsCu) group, and exposed to 30 mg/kg arsenic trioxide or/and 300 mg/kg copper sulphates for 12 weeks. The indicators of mitochondrial dynamics, apoptosis and autophagy were tested in the glandular stomach. The results showed that exposure to As or/and Cu caused mitochondrial dynamic imbalance. Additionally, the levels of pro-apoptosis and autophagy indicators were increased and the levels of anti-apoptosis indicators were decreased in the treatment groups. Beyond that, in the treatment groups, we could clearly see karyopyknosis and chromatin condensation were associated with increased apoptosis rate, as well as the disappearance of the nuclear membrane, the swelling of mitochondria and the accumulation of autophagosomes were involved in the death of cells. It was worth noting that the glandular stomach lesions were time-dependent, and the combination of As and Cu were worse than the As and Cu alone. Collectively, our results suggest that As or/and Cu aggravate mitochondrial dysfunction, apoptosis and autophagy in a time-dependent manner, and the combined toxicity of As and Cu was higher.