Liver mitochondrial dysfunction and electron transport chain defect induced by high dietary copper in broilers

The protective role of quercetin against copper-induced female reproductive toxicity: Insights from transcriptome analysis

Quercetin has been shown to mitigate the cytotoxic effects of heavy metals. While copper is an essential trace element for bodily functions, excessive intake has been linked to impaired female reproductive function. Transcriptome analysis was employed to identify genes that are differentially expressed in response to high copper and were validated through qRT-PCR and western blotting. ATP content and Tunel were used to identify the damage of mitochondrial and cell apoptosis. PPI analysis revealed that MKI67, TOPII, ASPM, CASP3, PLK1, and TTK are central proteins within the network. Additionally, exposure to elevated levels of copper resulted in the dysregulation of 86 genes associated with mitochondria. Conversely, treatment with quercetin (QUE) in combination with high copper led to the normalization of 42 mitochondria-related genes previously affected by high copper levels. Furthermore, CuSO4 decreases ATP content and induces cell apoptosis, which can be reversed by QUE. Results suggest that elevated copper levels could lead to oxidative stress and apoptosis by inducing mitochondrial damage, while QUE has the potential to mitigate these effects, ultimately safeguarding granulosa cells and halting the progression of cell death. This study provides novel insights into the molecular pathways involved in female reproductive toxicity caused by excessive copper exposure.

MitomiR-1736-3p regulates copper-induced mitochondrial pathway apoptosis by inhibiting AATF in chicken hepatocytes

Copper (Cu) is a toxic heavy metal pollutant. The hepatic toxicity of Cu has attracted widespread attention from researchers. However, its underlying mechanism remains elusive. Mitochondrial microRNAs (mitomiRs) are considered important factors in regulating mitochondrial and cellular functions, and their roles have been implicated in the mechanisms of metal toxicity. Therefore, this research revealed the changes in the mitomiRs expression profile of chicken liver after Cu exposure. It was ultimately determined that mitomiR-1736-3p can be involved in Cu-induced chicken liver damage by targeting AATF. In particular, our investigations have uncovered that exposure to Cu can trigger heightened levels of apoptosis in the hepatic tissue of chickens and primary chicken embryo hepatocytes (CEHs). It is noteworthy that we found upregulation of miR-1736-3p expression can exacerbate Cu-induced cell apoptosis, while inhibition of miR-1736-3p can effectively reduce apoptosis occurrence. Subsequently, we found that Cu-induced cell apoptosis could be restored by overexpressing AATF, while silencing AATF exacerbated the level of apoptosis. Fascinatingly, this change in apoptotic level is directly influenced by AATF on Bax and Bak1, rather than on p53 and Bcl-2. Overall, these findings suggest that the mitomiR-1736-3p/AATF axis mediates the mitochondrial pathway of cell apoptosis potentially involved in Cu-induced chicken liver toxicity.

Effect of Copper Exposure on the Cholesterol Metabolism in Broiler Liver

Copper (Cu) is a kind of widely used dietary supplement in poultry production, and a common environmental pollutant at the same time. Excess Cu exposure has been reported to accumulate in the liver and induce cytotoxicity, but the effect of Cu toxicity on hepatic cholesterol metabolism is still uncertain. Herein, we aimed to reveal the effect of excess Cu on the liver and primary hepatocytes of broilers at various concentrations. We found that 110 mg/kg Cu supplement remarkably increased blood cholesterol levels by detecting serum TC, LDL-C, and HDL-C in the broilers, while there was no significant difference in 220 and 330 mg/kg Cu supplements. In addition, high Cu exposure resulted in severe hepatic steatosis and hepatic cord derangement in the broilers. Oil red O staining of primary hepatocytes showed that Cu treatment caused intracellular neutral lipid accumulation. However, the hepatic TC content indicated a downward trend in both liver tissues and hepatocytes after Cu exposure. Furthermore, the expression of cholesterol metabolism-related indicators (SREBP2, HMGCR, LDLR, and CYP7A1) was notably decreased in the Cu-treated groups. While the expression of the key enzyme of cholesterol esterification (ACAT2) did not change significantly. Taken together, our findings preliminarily revealed excess Cu-induced hepatic cholesterol metabolism dysfunction, providing a deeper understanding of the molecular mechanisms of Cu-induced hepatotoxicity.

SIRT3 regulates mitophagy in liver fibrosis through deacetylation of PINK1/NIPSNAP1

Damaged mitochondria, a key factor in liver fibrosis, can be removed by the mitophagy pathway to maintain homeostasis of the intracellular environment to alleviate the development of fibrosis. PINK1 (PTEN-induced kinase 1) and NIPSNAP1 (nonneuronal SNAP25-like protein 1), which cooperatively regulate mitophagy, have been predicted to include the sites of lysine acetylation related to SIRT3 (mitochondrial deacetylase sirtuin 3). Our study aimed to discuss whether SIRT3 deacetylates PINK1 and NIPSNAP1 to regulate mitophagy in liver fibrosis. Carbon tetrachloride (CCl4 )-induced liver fibrosis as an in vivo model and LX-2 cells as activated cells were used to simulate liver fibrosis. SIRT3 expression was significantly decreased in mice in response to CCl4 , and SIRT3 knockout in vivo significantly deepened the severity of liver fibrosis, as indicated by increased α-SMA and Col1a1 levels both in vivo and in vitro. SIRT3 overexpression decreased α-SMA and Col1a1 levels. Furthermore, SIRT3 significantly regulated mitophagy in liver fibrosis, as demonstrated by LC3-Ⅱ/Ⅰ and p62 expression and colocalization between TOM20 and LAMP1. Importantly, PINK1 and NIPSNAP1 expression was also decreased in liver fibrosis, and PINK1 and NIPSNAP1 overexpression significantly improved mitophagy and attenuated ECM production. Furthermore, after simultaneously interfering with PINK1 or NIPSNAP1 and overexpressing SIRT3, the effect of SIRT3 on improving mitophagy and alleviating liver fibrosis was disrupted. Mechanistically, we show that SIRT3, as a mitochondrial deacetylase, specifically regulates the acetylation of PINK1 and NIPSNAP1 to mediate the mitophagy pathway in liver fibrosis. SIRT3-mediated PINK1 and NIPSNAP1 deacetylation is a novel molecular mechanism in liver fibrosis.

Cuproptosis is involved in copper-induced hepatotoxicity in chickens

Copper (Cu) is an essential trace element, but it is also a ubiquitous environmental pollutant that threatens public health. Cuproptosis is a recently discovered cell death mode that unlike other programmed cell death, characterized by proteotoxic stress due to lipoylated protein aggregation and iron-sulfur cluster protein loss. Chickens as a high-trophic-level non-mammalian vertebrate that easily absorb and accumulate copper from the environment and food, but it is unclear whether the underlying molecular mechanisms that cause their hepatotoxicity under natural copper stress are related to cuproptosis. Therefore, we established animal models of chickens with different concentrations of copper exposure to dissect the role and mechanism of cuproptosis in chicken hepatotoxicity under natural copper stress. Our histopathological and biochemical results demonstrated that the liver structure with copper-treated exhibited dose-dependent damage. Meanwhile, copper treatment also dramatically increased serum and liver copper content and activated the expression of the membrane-associated copper transporter ATP7B. Furthermore, we found that Cu-exposure significantly increased the MDA content, and reduced the levels of T-AOC and SOD in serum and liver. Additionally, we found that the mRNA and protein levels of FDX1 were significantly upregulated in the 220 and 330 mg/kg Cu-treated groups. In our further studies, we found that copper did not alter protein levels of DLAT and DLST in chicken liver, but significantly increased Lipoylated-DLAT levels and oligomerization of Lipoylated-DLAT in the 330 mg/kg Cu-treatment group. Overall, we identified that FDX1-mediated protein lipoylation and proteotoxic stress indeed participate in copper-induced hepatotoxicity in chickens. Our results present novel insight into the pathogenesis of copper-induced hepatotoxicity in chickens and provide data to support filling in the role of cuproptosis in birds.

Exposure to copper activates mitophagy and endoplasmic reticulum stress-mediated apoptosis in chicken (Gallus gallus) cerebrum

A large amount of copper (Cu) used in production activities can lead to the enrichment of Cu in the environment, which can cause toxicity to animals. However, the toxicity mechanism of Cu on the cerebrum is still uncertain. Hence, a total of 240 chickens were separated into four groups in this study to reveal the potential connection between mitophagy and endoplasmic reticulum (ER) stress-mediated apoptosis in the chicken cerebrum in the case of excess Cu exposure. The cu exposure situation was simulated by diets containing various levels of copper (11 mg/kg, control group; 110 mg/kg, group I; 220 mg/kg, group II and 330 mg/kg, group III) for 49 days. The results of histology showed that vacuolar degeneration was observed in the treated groups, and the mitochondria swell and autophagosomes formation were found under excess Cu treatment. Additionally, the expression of mitophagy (PINK1, Parkin, LC3I, LC3II and p62) and ER stress (GRP78, PERK, ATF6, IRE1α, XBP1, CHOP, and JNK) indexes were significantly upregulated under excess Cu exposure. Furthermore, the mRNA and protein expression of Bcl-2 were decreased, while Bak1, Bax, Caspase12, and Caspase3 were increased compared to the control group. In summary, this study demonstrated that an overdose of Cu could induce mitophagy and ER stress-mediated apoptosis in the chicken cerebrum. These findings revealed an important potential connection between Cu toxicity and cerebrum damage, which provided a new insight into Cu neurotoxicity.

Broiler responses to copper levels and sources: growth, tissue mineral content, antioxidant status and mRNA expression of genes involved in lipid and protein metabolism

BACKGROUND

Five hundred 8-d old male broilers Cobb500 were randomly allotted into 10 treatments in factorial arrangement with 5 Cu levels (0, 4, 8, 12, and 16 mg/kg), and 2 sources (Cu proteinate, CuPro and Cu sulphate, CuSO4.5H2O) for a 10-d-experiment.

RESULTS

Feed conversion ratio (FCR) was better (P < 0.05) in CuPro fed chicks compared with CuSO4.5H2O group. Average daily feed intake (ADFI) decreased linearly (P < 0.05) as dietary Cu increased. A quadratic response (P < 0.05) to Cu levels was found for FCR, being optimized at 9.87 and 8.84 mg Cu/kg in CuPro and CuSO4.5H2O diets, respectively. Copper supplementation linearly increased liver Cu content (P < 0.05) and tended to linearly increase (P = 0.07) phosphorus (P) and copper in tibia. Manganese and zinc were higher (P < 0.05) in tibia of CuPro fed birds. Broilers fed CuPro exhibited lower liver iron (P < 0.05) content, lower activities of Cu, Zn superoxide dismutase (CuZnSOD) in breast muscle and liver, and glutathione peroxidase in liver. Glutathione peroxidase reduced linearly (P < 0.05) with CuPro levels and increased linearly (P < 0.05) with CuSO4.5H2O levels and were lower (P < 0.05) in all CuPro levels in breast muscle. Breast muscle malondialdehyde concentration tended to be higher (P = 0.08) in broilers fed CuSO4.5H2O. Copper levels linearly increased (P < 0.05) metallothionein (MT) and malate dehydrogenase (MDH) expression in liver, and six-transmembrane epithelial antigen of the prostate-1 (STEAP-1) in the intestine. Copper elicited a quadratic response (P < 0.050) in AKT-1 and mammalian target of rapamycin (mTOR) in breast muscle, CuZnSOD in liver and antioxidant 1 copper chaperone (ATOX 1) in intestine. Broilers fed CuPro exhibited higher mRNA expression of mTOR in muscle breast and lower CuZnSOD in liver and ATOX 1 in intestine. Interaction (P < 0.05) between levels and sources was found in mRNA expression for GSK-3β, MT, and CuZnSOD in breast muscle, FAS and LPL in liver and MT and CTR1 in intestine.

CONCLUSIONS

CuPro showed beneficial effects on feed conversion and bone mineralization. Organic and inorganic Cu requirements are 9.87 and 8.84 mg Cu/kg, respectively.

Gut microbiota disturbance exaggerates battery wastewater-induced hepatotoxicity through a gut-liver axis

As the primary source of electricity for various devices, batteries are important contributors to the overall electronic waste generated; and are widely considered a source of highly ecotoxic pollutants. Material leakage in battery manufacturing has not been completely solved, and the elucidation of the toxic mechanisms of battery wastewater exposure is needed. We demonstrated that battery waste exposure disrupted the intestinal flora and aggravated hepatotoxicity via the gut-liver axis. Under battery waste exposure, colon epithelium suffered physiological damage, and gene and protein expression levels related to gut barrier function (ZO-1, claudin-1, and Occludin) were significantly downregulated. Meanwhile, battery waste reduced the richness and diversity of the flora, causing metabolites produced by intestinal microbes to enter the gut-liver axis. Gut microbial dysbiosis impaired mitochondrial respiratory function in liver tissue cells, and mitophagy, apoptosis, and the disorder of glycolipids and amino acid metabolism were induced in hosts exposed to battery toxins. Altogether, these results provided novel insights into the underlying mechanisms of battery wastewater-related hepatotoxicity induced by gut microbiota via the gut-liver axis, which has public health implications where humans and animals are exposed to industrial toxins generated by uncontained battery disposal.

Mitochondrial miR-1285 regulates copper-induced mitochondrial dysfunction and mitophagy by impairing IDH2 in pig jejunal epithelial cells

Copper (Cu), a hazardous heavy metal, can lead to toxic effects on host physiology. Recently, specific mitochondria-localized miRNAs (mitomiRs) were shown to modulate mitochondrial function, but the underlying mechanisms remain undefined. Here, we identified mitomiR-1285 as an important molecule regulating mitochondrial dysfunction and mitophagy in jejunal epithelial cells under Cu exposure. Mitochondrial dysfunction and mitophagy were the important mechanisms of Cu-induced pathological damage in jejunal epithelial cells, which were accompanied by significant increase of mitomiR-1285 in vivo and in vitro. Knockdown of mitomiR-1285 significantly attenuated Cu-induced mitochondrial respiratory dysfunction, ATP deficiency, mitochondrial membrane potential reduction, mitochondrial reactive oxygen species accumulation, and mitophagy. Subsequently, bioinformatics analysis and luciferase reporter assay demonstrated that IDH2 was a direct target of mitomiR-1285. RNA interference of IDH2 dramatically reversed the effect that mitomiR-1285 knockdown relieved mitochondrial dysfunction and mitophagy induced by Cu, and the opposite effect was shown by overexpression of IDH2. Therefore, our results suggested that mitomiR-1285 aggravated Cu-induced mitochondrial dysfunction and mitophagy via suppressing IDH2 expression. These findings identified the important mechanistic connection between mitomiRs and mitochondrial metabolism under Cu exposure, providing a new insight into Cu toxicology.

Long-term copper exposure promotes apoptosis and autophagy by inducing oxidative stress in pig testis

Copper (Cu) is a heavy metal which is being used widely in the industry and agriculture. However, the overuse of Cu makes it a common environmental pollutant. In order to investigate the testicular toxicity of Cu, the pigs were divided into three groups and were given Cu at 10 (control), 125, and 250 mg/kg body weight, respectively. The feeding period was 80 days. Serum hormone results showed that Cu exposure decreased the concentrations of follicular stimulating hormone (FSH) and luteinizing hormone (LH) and increased the concentration of thyroxine (T4). Meanwhile, Cu exposure upregulated the expression of Cu transporter mRNA (Slc31a1, ATP7A, and ATP7B) in the testis, leading to increase in testicular Cu and led to spermatogenesis disorder. The Cu exposure led to an increased expression of antioxidant-related mRNA (Gpx4, TRX, HO-1, SOD1, SOD2, SOD3, CAT), along with increase in the MDA concentration in the testis. In LG group, the ROS in the testis was significantly increased. Furthermore, the apoptotic-related mRNA (Caspase3, Caspase8, Caspase9, Bax, Cytc, Bak1, APAF1, p53) and protein (Active Caspase3) and the autophagy-related mRNA (Beclin1, ATG5, LC3, and LC3B) expression increased after Cu exposure. The mitochondrial membrane potential in the testicular tissue decreased, while the number of apoptotic cells increased, as a result of oxidative stress. Overall, our study indicated that the Cu exposure promotes testicular apoptosis and autophagy by mediating oxidative stress, which is considered as the key mechanism causing testicular degeneration as well as dysfunction.

In-feed organic and inorganic manganese supplementation on broiler performance and physiological responses

Objective

A trial was conducted to investigate the effects of supplemental levels of Mn provided by organic and inorganic trace mineral supplements on growth, tissue mineralization, mineral balance, and antioxidant status of growing broiler chicks.

Methods

A total of 500 male chicks (8-d-old) were used in 10-day feeding trial, with 10 treatments and 10 replicates of 5 chicks per treatment. A 2×5 factorial design was used where supplemental Mn levels (0, 25, 50, 75, and 100 mg Mn/kg diet) were provided as MnSO₄·H₂O or MnPro. When Mn was supplied as MnPro, supplements of zinc, copper, iron, and selenium were supplied as organic minerals, whereas in MnSO₄·H₂O supplemented diets, inorganic salts were used as sources of other trace minerals. Performance data were fitted to a linear-broken line regression model to estimate the optimal supplemental Mn levels.

Results

Manganese supplementation improved body weight, average daily gain (ADG) and feed conversion ratio (FCR) compared with chicks fed diets not supplemented with Mn. Manganese in liver, breast muscle, and tibia were greatest at 50, 75, and 100 mg supplemental Mn/kg diet, respectively. Higher activities of glutathione peroxidase and superoxide dismutase (total-SOD) were found in both liver and breast muscle of chicks fed diets supplemented with inorganic minerals. In chicks fed MnSO₄·H₂O, ADG, FCR, Mn balance, and concentration in liver were optimized at 59.8, 74.3, 20.6, and 43.1 mg supplemental Mn/kg diet, respectively. In MnPro fed chicks, ADG, FCR, Mn balance, and concentration in liver and breast were optimized at 20.6, 38.0, 16.6, 33.5, and 62.3 mg supplemental Mn/kg, respectively.

Conclusion

Lower levels of organic Mn were required by growing chicks for performance optimization compared to inorganic Mn. Based on the FCR, the ideal supplemental levels of organic and inorganic Mn in chick feeds were 38.0 and 74.3 mg Mn/kg diet, respectively.

Cinnamon Extract and Probiotic Supplementation Alleviate Copper-Induced Nephrotoxicity via Modulating Oxidative Stress, Inflammation, and Apoptosis in Broiler Chickens

The present study aimed to assess the potential protective effects of cinnamon (Cinnamomum zeylanicum, Cin) and probiotic against CuSO4-induced nephrotoxicity in broiler chickens. One-day-old Cobb chicks were assigned into seven groups (15 birds/group): control group, fed basal diet; Cin group, fed the basal diet mixed with Cin (200 mg/kg); PR group, receiving PR (1 g/4 L water); Cu group, fed the basal diets mixed with CuSO4 (300 mg/kg); Cu + Cin group; Cu + PR group; and Cu + Cin + PR group. All treatments were given daily for 6 weeks. Treatment of Cu-intoxicated chickens with Cin and/or PR reduced (p < 0.05) Cu contents in renal tissues and serum levels of urea, creatinine, and uric acid compared to the Cu group. Moreover, Cin and PR treatment decreased lipid peroxidation and increased antioxidant enzyme activities in chickens' kidney. Additionally, significant reduction (p < 0.05) in the mRNA expression of tumor necrosis factor alpha (TNF-α), interleukin (IL-2) and Bax, and in cyclooxygenase (COX-II) enzyme expression, and significant elevation (p < 0.05) in mRNA expression of IL-10 and Bcl-2 were observed in kidneys of Cu + Cin, Cu + PR, and Cu + Cin + PR groups compared to Cu group. Conclusively, Cin and/or PR afford considerable renal protection against Cu-induced nephrotoxicity in chickens.

Exposure to copper induces mitochondria-mediated apoptosis by inhibiting mitophagy and the PINK1/parkin pathway in chicken (Gallus gallus) livers

Copper (Cu), a transition metal with essential cellular functions, exerts toxic effects when present in excess by inducing oxidative stress. However, the Cu-induced crosstalk between mitophagy and apoptosis and the underlying mechanisms are unknown. Here, the mechanism of Cu-induced hepatotoxicity mediated by mitophagy and apoptosis was explored in vivo and in vitro. In in vivo experiments, chickens were fed a diet with various levels of Cu (11, 110, 220, and 330 mg/kg) for 7 weeks, which led to ultrastructural damage, mitophagy, and apoptosis in liver tissue. In vitro experiments on primary chicken hepatocytes showed that Cu treatment for 24 h increased the numbers of mitophagosomes and upregulated PINK1, parkin, and p62 mRNA levels and parkin and p62 protein levels, inducing mitophagy. Moreover, treatment with 3- methyladenine (3-MA) aggravated Cu-induced S-phase arrest in cell cycle; increased the apoptotic rate; increased p53, Bak1, Bax, Cyt C, and Caspase3/cleaved-caspase3 mRNA and protein levels; and decreased Bcl2 mRNA and protein levels. However, rapamycin (Rapa) had the opposite effects on the above factors. In general, the results reveal that Cu exposure can cause mitophagy through the PINK1/Parkin pathway in chicken livers, and that mitophagy might attenuate Cu-induced mitochondrial apoptosis.

Inhibition of autophagy aggravates molybdenum-induced mitochondrial dysfunction by aggravating oxidative stress in duck renal tubular epithelial cells

Excessive molybdenum (Mo) has adverse effects on animals. To elucidate the effects of autophagy on Mo-induced nephrotoxicity, the duck renal tubular epithelial cells were cultured in medium in absence and presence of (NH₄)₆Mo₇O₂₄.4H₂O (0, 480, 720, 960 μM Mo), 3-Methyladenine (3-MA) (2.5 μM), and the combination of Mo and 3-MA for 12 h. After 12 h exposure, the MDC staining, morphologic observation, LC3 puncta, cell viability, autophagy-related genes mRNA and proteins levels, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) level, antioxidant indices, mitochondrial membrane potential (MMP), mitochondrial mass, mitochondrial respiratory control ratio (RCR) and oxidative phosphorylation rate (OPR) were determined. The results showed that excessive Mo exposure significantly elevated the number of autophagosome and LC3 puncta, upregulated Beclin-1, Atg5, LC3A and LC3B mRNA levels, and LC3II/LC3I and Beclin-1 protein levels, decreased mTOR, p62 and Dynein mRNA levels and p62 protein level. Besides, co-treatment with Mo and 3-MA dramatically increased LDH release, ROS level, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents as well as cell dam age, reduced cell viability, the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), MMP, mitochondrial mass, mitochondrial RCR and OPR compared to treatment with Mo alone. Taken together, these results suggest that excessive Mo exposure can induce autophagy in duck renal tubular epithelial cells, inhibition of autophagy aggravates Mo-induced mitochondrial dysfunction by regulating oxidative stress.

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.

Copper Induces Apoptosis Through Endoplasmic Reticulum Stress in Skeletal Muscle of Broilers

The purpose of this research was to investigate whether copper (Cu) exposure could induce apoptosis via endoplasmic reticulum stress (ERS) in skeletal muscle of broilers. A total of 240 one-day-old chickens were randomly divided into four groups by free access; the diets are as follows: control diet (Cu 11 mg/kg, control group) and high level of Cu diets (Cu 110 mg/kg, group I; Cu 220 mg/kg, group II; Cu 330 mg/kg, group III). The skeletal muscle tissues were collected on day 49 for further examination. The content of Cu, histopathology, and the expression levels of the genes and proteins related to ERS and apoptosis were detected. Results showed that the Cu levels in skeletal muscle were increased in a dose-dependent manner. Meanwhile, the spaces between the muscle fibers were wider with the increase of Cu content, and the myolysis was observed in group III. Besides, the mRNA expression levels of GRP78, GRP94, eIF2α, ATF6, XBP1, CHOP, Caspase-12, and Caspase3 were markedly increased in treated groups compared with control group, and the protein expression levels of GRP78, Caspase3, Active-Caspase3 and JNK were significantly elevated with the increase of dietary Cu. In summary, these findings suggested that Cu could induce apoptosis through ERS in skeletal muscle of broilers.

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.

Effects of copper on oxidative stress and autophagy in hypothalamus of broilers

The purpose of this research was to discuss the effects of copper (Cu)-induced toxicity on oxidative stress and autophagy in hypothalamus of broilers. In this study, 240 one-day-old broilers were randomly divided into 4 groups and the contents of dietary Cu in 4 groups were 11 mg/kg (control group), 110 mg/kg (group I), 220 mg/kg (group II), and 330 mg/kg (group III). The experiment lasted for 49 days and the hypothalamus tissues were collected for histological observation and detection of Cu content. Additionally, the indicators related to oxidative stress in hypothalamus were determined. Moreover, the mRNA expression levels of autophagy-related genes and the protein expression levels of Beclin1, LC3-II/LC3-I, and p62 in hypothalamus were measured. Results showed that the treated groups were observed vacuolar degeneration in hypothalamus compared to control group, and the Cu content in hypothalamus was increased with the increase of dietary Cu. Furthermore, the activities of SOD, CAT, T-AOC were increased in group I and group II and then decreased in group III, and the content of MDA and the mRNA levels of Nrf2, HO-1, SOD-1, CAT, GCLC, GCLM, and GST in treated groups were elevated compared to control group. Moreover, the mRNA expression levels of Beclin1, Atg5, LC3-I, LC3-II and the protein expression levels of Beclin1 and LC3-II/LC3-I up-regulated significantly with the increasing levels of Cu. However, the mRNA expression levels of p62 and mTOR and the protein expression level of p62 down-regulated remarkably. Taken together, our present study evidenced that excessive intake of Cu could induce oxidative stress and autophagy in hypothalamus of broilers.

Autophagy attenuates copper-induced mitochondrial dysfunction by regulating oxidative stress in chicken hepatocytes

Copper (Cu) is an essential trace element that is required for the catalysis of several cellular enzymes. Excessive Cu could induce hepatotoxicity in humans and multiple animals. The purpose of this study was to investigate the effects of autophagy machinery on Cu-induced hepatotoxicity. Chicken hepatocytes were cultured in medium in the absence and presence of Cu sulfate (CuSO₄) (0, 10, 50, and 100 μM) for 0, 6, 12, and 24 h, and in the combination of CuSO₄ and N-acetyl-l-cysteine (NAC) (1 mM), rapamycin (10 nM), and 3-methyladenine (3-MA) (5 mM) for 24 h. Results showed that Cu could markedly increase the number of autophagosomes and LC3 puncta, induce autophagy-related genes (Beclin1, ATG5, LC3Ⅰ, LC3Ⅱ, mTOR, and Dynein) mRNA expression and proteins (BECN1, LC3Ⅱ/LC3Ⅰ) expression. NAC could relieve Cu-induced the changes of above genes and proteins. Additionally, rapamycin attenuated Cu-induced the increased lactic dehydrogenase (LDH), aspartate amino transferase (AST), and alanine aminotransferase (ALT) activities, and SOD-1 mRNA expression as well as the decreased cell viability, reactive oxygen species (ROS), hydrogen peroxide, total superoxide dismutase (T-SOD), malonaldehyde (MDA), catalase (CAT), HO-1 mRNA expression, adenosine triphosphate (ATP) levels, mitochondrial mass, and mitochondria membrane potential (MMP). But 3-MA had the opposite effects on above factors. Collectively, these findings provide strong evidence that Cu could induce autophagy by generating excessive ROS in hepatocytes, and autophagy might attenuate Cu-induced mitochondrial dysfunction by regulating oxidative stress.