Ascorbic acid protects against cadmium-induced endoplasmic reticulum stress and germ cell apoptosis in testes

Toxicity of Polystyrene Microplastics with Cadmium on the Digestive System of Rana zhenhaiensis Tadpoles

Microplastics pollution in freshwater systems is attracting increasing attention. However, our knowledge of its combined toxicity with heavy metals is scarce. In this study, Rana zhenhaiensis was used as the model animal to study the combined poisoning mechanism of cadmium or microplastics on the digestive systems of tadpoles in freshwater. Results showed that the exposure to cadmium and polystyrene increased the mortality and metamorphosis rate of R. zhenhaiensis tadpoles, and delayed their growth and development. Cadmium was detected in the livers and intestines, while polystyrene mainly accumulated in the gills and intestines of tadpoles. The individual exposure of cadmium or polystyrene can cause pathological damage to liver tissue, induce oxidative stress in liver, and change gene expression. Cadmium co-exposure with polystyrene can reduce the cadmium accumulation in the liver. While polystyrene can slightly increase cadmium accumulation in the intestine. Exposure to cadmium and polystyrene altered the abundance and community structure of intestinal microbiota, and polystyrene increased the dysregulation of the gut microbiome. In this study, the combined exposure of microplastics and cadmium had a negative impact on R. zhenhaiensis tadpoles, but the introduction of microplastics on the toxicity of cadmium on the tadpoles needs further investigation, due to the different characteristics of microplastics.

Reproductive toxicity of cadmium stress in male animals

Cadmium (Cd) is a common heavy metal pollutant in the environment, and the widespread use of products containing Cd compounds in industry has led to excessive levels in the environment, which enter the animal body through the food chain, thus seriously affecting the reproductive development of animals. Related studies have reported that Cd severely affects spermatogonia development and spermatogenesis in animals. In contrast, the reproductive toxicity of Cd in males and its mechanism of action have not been clarified. Therefore, this paper reviewed the toxic effects of Cd on germ cells, spermatogonia somatic cells and hypothalamic-pituitary-gonadal axis (HPG axis) of male animals and its toxic action mechanisms of oxidative stress, apoptosis and autophagy from the perspectives of cytology, genetics and neuroendocrinology. The effects of Cd stress on epigenetic modification of reproductive development in male animals were also analyzed. We hope to provide a reference for the in-depth study of the toxicity of Cd on male animal reproduction.

Perfluorooctanoic acid induces Leydig cell injury via inhibition of autophagosomes formation and activation of endoplasmic reticulum stress

Perfluorooctanoic acid (PFOA) is a man-made chemical broadly distributed in various ecological environment and human bodies, which poses potential health risks. Its toxicity, especially the male reproduction toxicity has drawn increasing attention due to declining birth rates in recent years. However, how PFOA induces male reproductive toxicity remains unclear. Here, we characterize PFOA-induced cell injury and reveal the underlying mechanism in mouse Leydig cells, which are critical to spermatogenesis in the testes. We show that PFOA induces cell injury as evidenced by reduced cell viability, cell morphology changes and apoptosis induction. RNA-sequencing analysis reveals that PFOA-induced cell injury is correlated with compromised autophagy and activated endoplasmic reticulum (ER) stress, two conserved biological processes required for regulating cellular homeostasis. Mechanistic analysis shows that PFOA inhibits autophagosomes formation, and activation of autophagy rescues PFOA-induced apoptosis. Additionally, PFOA activates ER stress, and pharmacological inhibition of ER stress attenuates PFOA-induced cell injury. Taken together, these results demonstrate that PFOA induces cell injury through inhibition of autophagosomes formation and induction of ER stress in Leydig cells. Thus, our study sheds light on the cellular mechanisms of PFOA-induced Leydig cell injury, which may be suggestive to human male reproductive health risk assessment and prevention from PFOA exposure-induced reproductive toxicity.

Contribution of Oxidative Stress, Apoptosis, Endoplasmic Reticulum Stress and Autophagy Pathways to the Ameliorative Effects of Hesperidin in NaF-Induced Testicular Toxicity

The ameliorative effects of hesperidin (HES) on the toxicities created by sodium fluoride (NaF) in the testes tissue of rats were studied via oxidative stress, apoptosis and endoplasmic reticulum (ER) stress pathways. The animals were divided into five distinct groups (7 rats in each group). Group 1 was control group, group 2 received NaF-only (600 ppm), group 3 received HES-only (200 mg/kg bw); group 4 received NaF (600 ppm)+HES (100 mg/kg bw) and group 5 received NaF (600 ppm)+HES (200 mg/kg bw) for 14 days. NaF-induced testes tissue damage by reducing activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and levels of glutathione (GSH), and increasing lipid peroxidation levels. NaF treatment significantly downregulated the mRNA levels of SOD1, CAT and GPx. NaF supplementation caused apoptosis in the testes by upregulating p53, NFkB, caspase-3, caspase-6, caspase-9, and Bax and downregulating Bcl-2. Furthermore, NaF caused ER stress via increasing mRNA transcript levels of PERK, IRE1, ATF-6 and GRP78. NaF treatment led to autophagy via upregulation of Beclin1, LC3A, LC3B and AKT2. In testes tissue, however, co-treatment with HES at doses of 100 and 200 mg/kg significantly reduced oxidative stress, apoptosis, autophagy and ER stress. Overall, the findings of this study suggest that HES may help to reduce testes damage caused by NaF toxicity.

Vitamin C protects against hypoxia, inflammation, and ER stress in primary human preadipocytes and adipocytes

Dysregulation of adipose tissue involves increased cellular hypoxia, ER stress, and inflammation and altered adipokine production, contributing to the aetiology of obesity-related diseases including type 2 diabetes and cardiovascular disease. This study aimed to investigate the effects of Vitamin C supplementation on these processes in primary human preadipocytes and adipocytes. Treatment of preadipocytes and adipocytes with the proinflammatory cytokine TNFα and palmitic acid (PA), to mimic the obesogenic milieu, significantly increased markers of hypoxia, ER stress and inflammation and reduced secretion of high molecular weight (HMW) adiponectin. Importantly, Vitamin C abolished TNFα+PA induced hypoxia and significantly reduced the increases in ER stress and inflammation in both cell types. Vitamin C also significantly increased the secretion of HMW adiponectin from adipocytes. These findings indicate that Vitamin C can reduce obesity-associated cellular stress and thus provide a rationale for future investigations.

Roles of stress response-related signaling and its contribution to the toxicity of zearalenone in mammals

Zearalenone (ZEA) is a mycotoxin frequently found in cereal crops and cereal-derived foodstuffs worldwide. It affects plant productivity, and is also a serious hazard to humans and animals if being exposed to food/feed contaminated by ZEA. Studies over the last decade have shown that the toxicity of ZEA in animals is mainly mediated by the various stress responses, such as endoplasmic reticulum (ER) stress, oxidative stress, and others. Accumulating evidence shows that oxidative stress and ER stress signaling are actively implicated in and contributes to the pathophysiology of various diseases. Biochemically, the deleterious effects of ZEA are associated with apoptosis, DNA damage, and lipid peroxidation by regulating the expression of genes implicated in these biological processes. Despite these findings, the underlying mechanisms responsible for these alterations remain unclear. This review summarized the characteristics, metabolism, toxicity and the deleterious effects of ZEA exposure in various tissues of animals. Stress response signaling implicated in the toxicity as well as potential therapeutic options with the ability to reduce the deleterious effects of ZEA in animals were highlighted and discussed.

Zingerone attenuates zearalenone-induced steroidogenesis impairment and apoptosis in TM3 Leydig cell line

Zingerone¹ (Zing) is one of the bioactive compounds of ginger rhizome (Zingiber officinale), whose beneficial effects have been reported previously on reproductive organ complications. The current study purposed to survey probable protective impacts of Zing against Zearalenone (ZEA)-induced changes in the TM3 Leydig cell line. Exposure of TM3 cells to ZEA (25 μM) attenuates the levels of testosterone and steroidogenesis-related genes, which was reversed by 25 μM of Zing. ZEA also induced ROS generation and apoptosis in TM3 cells. Zing treatment improved the stress oxidative and apoptosis-related changes induced by ZEA in TM3 cells by modulating autophagy-related proteins and activating PI3K-AKT-mTOR and Nrf2 pathways. The findings of this study represented a theoretical basis for Zing's protective actions against ZEA toxic effects on TM3 cells.

Protection of apigenin against acrylonitrile-induced sperm and testis injury in rats: involvement of activation of ASK1-JNK/p38 signaling pathway

This study aims to clarify if apigenin (AP) could play a pivotal role in attenuating acrylonitrile (ACN)-induced sperm and testis injury by inhibiting ASK1-JNK/p38 signaling pathway. Male Sprague-Dawley rats were randomly divided into five groups: a control group (corn oil), an ACN group (ACN 46 mg kg^-1), an ACN + AP1 group (ACN + AP 117 mg kg^-1), an ACN + AP2 group (ACN + AP 234 mg kg^-1) and an ACN + AP3 group (ACN + AP 351 mg kg^-1). The ACN + AP groups were given ACN by gavage after a pretreatment with different dosages of AP for 30 min, whereas the rats in the control group received an equivalent volume of corn oil. The gavage was conducted for 6 days per week in 4 weeks. The results showed that AP reduced sperm deformity rate and DNA fragment index and attenuated the testicular injury induced by ACN. AP could also alleviate oxidative stress, downregulate ASK1-JNK/p38 signaling pathway and eventually inhibit mitochondria-mediated testicular apoptosis. In brief, AP could dampen oxidative stress thereby inhibiting testicular apoptosis mediated by ASK1-JNK/p38 signaling pathway, alleviating ACN-induced sperm and testis injury and exerting a protective effect on male reproductive system.

Evaluating endoplasmic reticulum stress and unfolded protein response through the lens of ecology and evolution

Considerable progress has been made in understanding the physiological basis for variation in the life-history patterns of animals, particularly with regard to the roles of oxidative stress and hormonal regulation. However, an underappreciated and understudied area that could play a role in mediating inter- and intraspecific variation of life history is endoplasmic reticulum (ER) stress, and the resulting unfolded protein response (UPR^ER ). ER stress response and the UPR^ER maintain proteostasis in cells by reducing the intracellular load of secretory proteins and enhancing protein folding capacity or initiating apoptosis in cells that cannot recover. Proper modulation of the ER stress response and execution of the UPR^ER allow animals to respond to intracellular and extracellular stressors and adapt to constantly changing environments. ER stress responses are heritable and there is considerable individual variation in UPR^ER phenotype in animals, suggesting that ER stress and UPR^ER phenotype can be subjected to natural selection. The variation in UPR^ER phenotype presumably reflects the way animals respond to ER stress and environmental challenges. Most of what we know about ER stress and the UPR^ER in animals has either come from biomedical studies using cell culture or from experiments involving conventional laboratory or agriculturally important models that exhibit limited genetic diversity. Furthermore, these studies involve the assessment of experimentally induced qualitative changes in gene expression as opposed to the quantitative variations that occur in naturally existing populations. Almost all of these studies were conducted in controlled settings that are often quite different from the conditions animals experience in nature. Herein, we review studies that investigated ER stress and the UPR^ER in relation to key life-history traits including growth and development, reproduction, bioenergetics and physical performance, and ageing and senescence. We then ask if these studies can inform us about the role of ER stress and the UPR^ER in mediating the aforementioned life-history traits in free-living animals. We propose that there is a need to conduct experiments pertaining to ER stress and the UPR^ER in ecologically relevant settings, to characterize variation in ER stress and the UPR^ER in free-living animals, and to relate the observed variation to key life-history traits. We urge others to integrate multiple physiological systems and investigate how interactions between ER stress and oxidative stress shape life-history trade-offs in free-living animals.

Protective effect of Polygonatum sibiricum against cadmium-induced testicular injury in mice through inhibiting oxidative stress and mitochondria-mediated apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonatum sibiricum (PS), the dried rhizome of the liliaceous plant including P. sibiricum Red., P. cyrtonema Hua. and P. kingianum Coll. et Hemsl., is a widely used Chinese herbal medicines. It was first published in "Special Records of Famous Doctors", in which is described to replenished Qi and nourish Yin, strengthening the spleen and nourishing the lungs and kidney. Based on the principle of kidney controlling the reproduction, kidney-tonifying therapy has traditionally been seen as most applicable to the treatment of infertility. The current investigation has focused on the protective effect of PS against cadmium-induced testicular injury in mice.

AIM OF THE STUDY

To investigate the protective effect of PS against cadmium-induced testicular injury in mice via the TXNIP-NLRP3-Caspase-1 and CytC-Caspase-9-Caspase-3 pathways.

MATERIALS AND METHODS

PS was processed into Polygonatum sibiricum aqueous extract (PSAE). A mouse testicular injury model was established by a single intraperitoneal (i.p.) injection of cadmium chloride (CdCl₂) (2.5 mg/kg b.w.), and the mice were treated intragastrically with PSAE (10 g/kg b.w.) once daily for 35 consecutive days. At the end of the experiment blood and testicular tissue samples were collected to analyze sperm survival rate and sperm deformity rate, serum testosterone T content, testicular oxidation related indicators levels (SOD, MDA, GSH, CAT) in testicular tissue, and histopathological changes of testicular tissues. The testicular cell cycle and reactive oxygen species (ROS) levels were measured by flow cytometry, the expression levels of thioredoxin-interacting protein (TXNIP), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), Caspase-1, interleukin (IL)-1β, Cyctochrome C (CytC), Caspase-3, and Caspase-9 mRNA in testicular tissue were detected by qRT-PCR and the protein expression levels of TXNIP, NLRP3, Caspase-1, CytC, Caspase-3, and Caspase-9 were detected by Western blot and immunohistochemical method.

RESULTS

The results indicated that compared with the model group, PSAE brought testicular weight to a near-normal range, improved sperm survival rate and reduced sperm abnormality rate, elevated the level of testosterone, made the damaged testis tissue recover to near normal, reduced the level of ROS, and inhibited testicular cell apoptosis. Further study showed that PSAE significantly decreased the levels of relative genes and proteins in testicular cells, such as TXNIP, NLRP3, Caspase-1, IL-1β, CytC, Caspase-3, and Caspase-9, which suggested that PSAE could regulate oxidative stress through the TXNIP-NLRP3-Caspase-1 signaling pathway, and inhibit apoptosis in the mitochondrial pathway via CytC-Caspase-9-Caspase-3 pathway. In summary, we have confirmed that PSAE exerted a powerful protective effect on CdCl₂-induced testicular injury in mice through inhibiting oxidative stress and mitochondria-mediated apoptosis.

Selenium Protects against Zearalenone-Induced Oxidative Stress and Apoptosis in the Mouse Kidney by Inhibiting Endoplasmic Reticulum Stress

This study assessed the molecular mechanism of selenium (Se) protecting against kidney injury induced by zearalenone (ZEA) in mice. The experimental mice were divided into 4 groups including the control group, the Se group, the ZEA group, and the Se+ZEA group; ZEA and Se were administered orally for 28 days. The changes in renal biochemical index (BUN, UA, and CRE), biochemical change of kidney damage such as BUN, UA, and CRE, and oxidative damage such as MDA, T-SOD, and GSH-Px were investigated. Pathological sections and TUNEL staining were used to analyze renal pathological changes and cell apoptosis. qRT-PCR and Western blot were employed to detect the expression of genes and proteins which were related with endoplasmic reticulum stress. The results showed that ZEA increased the concentration of BUN, UA, and CRE and the content of MDA and decreased the activities of T-SOD and GSH-Px in the mouse kidneys. However, Se reversed above changes of the biochemical and antioxidant indexes of renal injury. Moreover, the results also showed that ZEA can increase the expression of Bax, caspase-12, caspase-3, Bip, CHOP, JNK protein, and mRNA and decrease the expression of Bcl-2 protein and mRNA. But Se reversed these proteins and genes related to endoplasmic reticulum stress and apoptosis. It can be concluded that Se protected against the kidney damage induced by ZEA. Se may protect the kidney from ZEA-induced apoptosis and oxidative stress by inhibiting ERS.

Effects of Myo-inositol Alone and in Combination with Seleno-Lmethionine on Cadmium-Induced Testicular Damage in Mice

BACKGROUND

Cadmium (Cd) impairs gametogenesis and damages the blood-testis barrier.

OBJECTIVE

As the primary mechanism of Cd-induced damage is oxidative stress, the effects of two natural antioxidants, myo-inositol (MI) and seleno-L-methionine (Se), were evaluated in mice testes.

METHODS

Eighty-four male C57 BL/6J mice were divided into twelve groups: 0.9% NaCl (vehicle; 1 ml/kg/day i.p.); Se (0.2 mg/kg/day per os); Se (0.4 mg/kg/day per os); MI (360 mg/kg/day per os); MI plus Se (0.2 mg/kg/day); MI plus Se (0.4 mg/kg/day); CdCl2 (2 mg/kg/day i.p.) plus vehicle; CdCl2 plus MI; CdCl2 plus Se (0.2 mg/kg/day); CdCl2 plus Se (0.4 mg/kg/day); CdCl2 plus MI plus Se (0.2 mg/kg/day); and CdCl2 plus MI plus Se (0.4 mg/kg/day). After 14 days, testes were processed for biochemical, structural and immunohistochemical analyses.

RESULTS

CdCl2 increased iNOS and TNF-α expression and Malondialdehyde (MDA) levels, lowered glutathione (GSH) and testosterone, induced testicular lesions, and almost eliminated claudin-11 immunoreactivity. Se administration at 0.2 or 0.4 mg/kg significantly reduced iNOS and TNF-α expression, maintained GSH, MDA and testosterone levels, structural changes and low claudin-11 immunoreactivity. MI alone or associated with Se at 0.2 or 0.4 mg/kg significantly reduced iNOS and TNF-α expression and MDA levels, increased GSH and testosterone levels, ameliorated structural organization and increased claudin-11 patches number.

CONCLUSION

We demonstrated a protective effect of MI, a minor role of Se and an evident positive role of the association between MI and Se on Cd-induced damages of the testis. MI alone or associated with Se might protect testes in subjects exposed to toxicants, at least to those with behavior similar to Cd.

Endoplasmic Reticulum Stress Induced by Toxic Elements-a Review of Recent Developments

Endoplasmic reticulum of all eukaryotic cells is a membrane-bound organelle. Under electron microscope it appears as parallel arrays of "rough membranes" and a maze of "smooth vesicles" respectively. It performs various functions in cell, i.e., synthesis of proteins to degradation of xenobiotics. Bioaccumulation of drugs/chemicals/xenobiotics in the cytosol can trigger ER stress. It is recognized by the accumulation of unfolded or misfolded proteins in the lumen of ER. Present review summarizes the present status of knowledge on ER stress caused by toxic elements, viz arsenic, cadmium, lead, mercury, copper, chromium, and nickel. While inorganic arsenic may induce various glucose-related proteins, i.e., GRP78, GRP94 and CHOP, XBP1, and calpains, cadmium upregulates GRP78. Antioxidants like ascorbic acid, NAC, and Se inhibit the expression of UPR. Exposure to lead also changes ER stress related genes, i.e., GRP 78, GRP 94, ATF4, and ATF6. Mercury too upregulates these genes. Nickel, a carcinogenic element upregulates the expression of Bak, cytochrome C, caspase-3, caspase-9, caspase-12, and GADD 153. Much is not known on ER stress caused by nanoparticles. The review describes inter-organelle association between mitochondria and ER. It also discusses the interdependence between oxidative stress and ER stress. A cross talk amongst different cellular components appears essential to disturb pathways leading to cell death. However, these molecular switches within the signaling network used by toxic elements need to be identified. Nevertheless, ER stress especially caused by toxic elements still remains to be an engaging issue.

The protective effect of recombinant globular adiponectin on testis by modulating autophagy, endoplasmic reticulum stress and oxidative stress in streptozotocin-induced diabetic mice

This study was to investigate whether recombinant globular adiponectin produced its protective effect on the testis of diabetic mice by modulating autophagy, endoplasmic reticulum stress and oxidative stress. Male mice were randomly divided into control, diabetic, diabetic treated with low and high dose of adiponectin. Mice were killed at the termination after 4 weeks and 8 weeks of adiponectin treatment. Serum levels of glucose, lipids, testosterone, insulin, LH and FSH were measured. The protein expression of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), Caspase12, Beclin1, microtubule-associated protein light chain 3 (LC3) and p62 was determined by western blotting. The mRNA expression of adiponectin receptor 1 (AdipoR1), p22phox, p47phox, nuclear factor erythroid2-related factor 2 (Nrf2), NAD(P)H-quinone oxidoreductase 1(NQO1), heme oxygenase-1 (HO-1) and superoxide dismutase (SOD) were determined by real-time fluorescence quantitative PCR. The testicular weight, the sperm number and motility, and the serum levels of testosterone and insulin were significantly decreased in diabetic mice (P < 0.05). The expression of Beclin1, LC3, Nrf2, NQO1, HO-1, SOD and AdipoR1 were significantly decreased (P < 0.05), while the expression of GRP78, CHOP, Caspase12, p62, p22phox and p47phox were notably increased in the testes of diabetic mice (P < 0.05). Adiponectin treatment significantly reversed the above-mentioned changes in the testes of diabetic mice, some of which were dose- and time-dependent (P < 0.05). These data suggested that recombinant globular adiponectin may produce the protective effect on the testes of diabetic mice by inducing autophagy and inhibiting ER stress and oxidative stress.

The Role of Endoplasmic Reticulum Stress Response in Male Reproductive Physiology and Pathology: A Review

Endoplasmic reticulum (ER) stress, defined as prolonged disturbances in protein folding and accumulation of unfolded proteins in the ER. Perturbation of the ER, such as distribution of oxidative stress, iron imbalance, Ca²⁺ leakage, protein overload, and hypoxia, can cause ER stress. The cell reacts to ER stress by activating protective pathways, called the unfolded protein response (UPR), which is comprised of cellular mechanisms aimed for maintaining cellular homeostasis or, in case of excessively severe stress, at the initiation of cellular apoptosis. The three UPR signaling pathways from the ER stress sensors are initiated by activating transcription factor 6, inositol requiring enzyme 1, and protein kinase RNA-activated-like ER kinase. A number of physiological and pathological conditions, environmental toxicants and variety of pharmacological agents showed disruption of proper ER functions and thereby cause ER stress in male reproductive organ in rat model. The present review summarizes the existing data concerning the molecular and biological mechanism of ER stress in male reproduction and male infertility. ER stress initiated cell death pathway has been related to several diseases, including hypoxia, heath disease, diabetes, and Parkinson's disease. Although there is not enough evidence to prove the relationship between ER stress and male infertility in human, most studies in this review found that ER stress was correlated with male reproduction and infertility in animal models. The ER stress could be novel signaling pathway of regulating male reproductive cellular apoptosis. Infertility might be a result of disturbing the ER stress response during the process of male reproduction.

Drug screening for Pelizaeus-Merzbacher disease by quantifying the total levels and membrane localization of PLP1

Background

Pelizaeus-Merzbacher disease (PMD) is caused by point mutations or copy number changes in the proteolipid protein 1 gene (PLP1). PLP1 is exclusively localized in the myelin sheath of oligodendrocytes. Amino acid-substituted PLP1 protein is unable to fold properly and is subsequently degraded and/or restrictedly translated, resulting in a decrease in the PLP1 protein level and a failure to localize to the membrane. Furthermore, misfolded proteins increase the burden on the intracellular quality control system and trafficking, finally resulting in cell apoptosis. The objective of this study was to identify therapeutic chemicals for PMD by quantifying the total levels and membrane localization of PLP1.

Method

We established a cell line stably expressing PLP1^A243V fused with green fluorescent protein in oligodendrocyte-derived MO3.13 cells. We screened a chemical library composed of drugs approved for central nervous system disorders that increased both the total intensity of PLP1^A243V in the whole cell and the cell membrane localization. We analyzed the change in the endoplasmic reticulum (ER) stress and the gene expression of candidate chemicals using a micro-array analysis. Finally, we tested the in vivo effectiveness using myelin synthesis deficient (msd) mice with Plp^A243V.

Results and conclusion

Piracetam significantly increased the PLP1^A243V intensity and membrane localization and decreased the ER stress. It was also shown to reverse the gene expression changes induced by PLP1^A243V in a micro-array analysis. However, in vivo treatment of piracetam did not improve the survival of msd mice (Plp1^A243V).

Estimation of cadmium content in Egyptian foodstuffs: health risk assessment, biological responses of human HepG2 cells to food-relevant concentrations of cadmium, and protection trials using rosmarinic and ascorbic acids

Cadmium (Cd) is an environmental pollutant that can get entry into human body via ingestion of contaminated foods causing multiple organ damage. This study aimed at monitoring Cd residues in 20 foodstuffs of animal origin that are commonly consumed in Egypt. Health risk assessment was conducted via calculation of Cd dietary intakes and non-carcinogenic target hazard quotient. An in vitro approach was performed to investigate the constitutive effects of Cd on human hepatoma (HepG2) cells under food-relevant concentrations. Trials to reduce Cd-induced adverse effects on HepG2 cells were done using rosmarinic (RMA) and ascorbic acids (ASA). The achieved results indicated contamination of the tested foodstuffs with Cd at high levels with potential human health hazards. Cd at food-relevant concentrations caused significant cytotoxicity to HepG2 cells. This may be attributed to induction of oxidative stress and inflammation, as indicated by the overexpression of stress and inflammatory markers. At the same time, Cd downregulated xenobiotic transporters and upregulated the proliferation factors. Co-exposure of HepG2 cells to Cd and micronutrients such as RMA and ASA led to recovery of cells from the oxidative damage, and subsequently cell viability was strongly improved. RMA and ASA ameliorated the biological responses of HepG2 cells to Cd exposure.

Arctigenin ameliorates renal impairment and inhibits endoplasmic reticulum stress in diabetic db/db mice

AIMS

Diabetic nephropathy (DN) is the most common complication of diabetes mellitus. Endoplasmic reticulum (ER) plays an important role in the development and progression of DN. Arctigenin (ATG), a lignan extract from Fructus Arctii, exhibits anti-inflammatory, anticarcinogenic, anti-oxidative stress and immunomodulatory properties. The present research aimed to investigate whether ATG could protect against diabetes-related renal injury and inhibit ER stress in db/db mice.

MAIN METHODS

Male db/db mice were randomly divided into two groups: DN group and ATG treatment group (DN + ATG). db/m mice were defined as the normal control group (NC). ATG was dissolved in 0.5% carboxymethyl cellulose sodium salt solution and administered orally at a dose of 80 mg/kg to mice in the DN + ATG group once daily for 8 consecutive weeks. HK2 cells were used to determine the effects of ATG on ER stress and cell apoptosis in vitro.

KEY FINDINGS

ATG administration significantly reduced blood glucose, urine albumin excretion, and urine albumin to creatinine ratio, and attenuated renal pathological injury when compared with untreated db/db mice. These changes were accompanied by decreased expression of both ER stress-related markers and caspase 12 level in the kidneys of db/db mice. In vitro, high glucose activated ER stress signal transduction pathway and induced cell apoptosis in HK2 cells, which were blocked by ATG.

SIGNIFICANCE

Our results suggest that ATG exerts renoprotective effects on diabetes-related renal injury in db/db mice and cytoprotective effects on high glucose induced cell apoptosis and inhibits ER stress.

Proanthocyanidins Protect Epithelial Cells from Zearalenone-Induced Apoptosis via Inhibition of Endoplasmic Reticulum Stress-Induced Apoptosis Pathways in Mouse Small Intestines

This study evaluated the protective effect of proanthocyanidins (PCs) on reducing apoptosis in the mouse intestinal epithelial cell model MODE-K exposed to zearalenone (ZEA) through inhibition of the endoplasmic reticulum stress (ERS)-induced apoptosis pathway. Our results showed that PCs could reduce the rate of apoptosis in MODE-K cells exposed to ZEA (p < 0.01). PCs significantly increased the ZEA-induced antioxidant protective effects on the enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and on the content of GSH. PCs also significantly decreased the ZEA-induced increase in the content of malondialdehyde (MDA). The analysis indicated that ZEA increased both mRNA and protein expression levels of C/EBP homologous protein (CHOP), GRP78, c-Jun N-terminal kinase (JNK), and cysteinyl aspartate specific proteinase 12 (caspase-12) (p < 0.05), which are related to the ERS-induced apoptosis pathway. ZEA decreased levels of the pro-apoptotic related protein Bcl-2 (p < 0.05) and increased the anti-apoptotic related protein Bax (p < 0.05). Co-treatment with PCs was also shown to significantly reverse the expression levels of these proteins in MODE-K cells. The results demonstrated that PCs could protect MODE-K cells from oxidative stress and apoptosis induced by ZEA. The underlying mechanism may be that PCs can alleviate apoptosis in mouse intestinal epithelial cells by inhibition of the ERS-induced apoptosis pathway.

Beneficial Effects of Small Molecule Oligopeptides Isolated from Panax ginseng Meyer on Pancreatic Beta-Cell Dysfunction and Death in Diabetic Rats

To determine whether treatment with ginseng oligopeptides (GOPs) could modulate hyperglycemia related to type 2 diabetes mellitus (T2DM) in rats induced by high-fat diet and low doses of alloxan, type 2 diabetes was induced in male Sprague-Dawley (SD) rats by injecting them once with 105 mg/kg alloxan and feeding them high-carbohydrate/high-fat diet with or without GOP administration (0.125, 0.5, and 2.0 g/kg Body Weight) for 7, 24, and 52 weeks. Oral glucose test tolerance (OGTT), plasma glucose, serum insulin, level of antioxidant, and beta cell function were measured. Morphological observation and immunohistochemistry study of insulin of islets was performed by light microscopy. The insulin level and the expression of NF-κB and Bcl-2 family in pancreatic islets were also detected by Western blot analysis. In addition, survival time and survival rate were observed. After the treatment, the abnormal OGTT were partially reversed by GOPs treatment in diabetic rats. The efficacy of GOPs was manifested in the amelioration of pancreatic damage, as determined by microscopy analysis. Moreover, GOPs treatment increased the normal insulin content and decreased the expression of the NF-κB-signaling pathway. Compared with those in the control model, the survival time and rate were significantly longer. It is suggested that GOPs exhibit auxiliary therapeutic potential for diabetes.

Isobaric tags for relative and absolute quantification-based proteomic analysis of testis biopsies in rhesus monkeys treated with transient scrotal hyperthermia

This study aimed to examine the cellular and molecular events that occur in rhesus monkey testes after scrotal hyperthermia. Eight male adult rhesus monkeys were subjected to scrotal hyperthermia at 43°C for 30 min daily for 6 consecutive days. Sperm concentration, reproductive hormones, and testis histology were examined before hyperthermia (day 0), and at 8, 15, 30, 45, 60, 75, and 90 days after the initiation of hyperthermia. iTRAQ-based proteomic analysis was conducted on testicular tissues collected on days 0, 8, and 60 to identify differentially expressed proteins at the early and recovery stages of testicular damage. The sperm concentration was significantly decreased at days 30 and 45 after treatment (p < 0.01) and recovered to baseline at day 60. When compared with day 0, 101 and 24 differentially expressed proteins were identified at days 8 and 60 after heat treatment, respectively. The molecular functions of the differentially expressed proteins at day 8 were mainly nucleic acid binding, unfolded protein binding, nucleotide binding, and nucleoside phosphate binding. Spliceosome was enriched as the most significant pathway at day 8. CIRBP, PSIP1, Sam68, and Decorin were validated and found to be consistent with the proteomic data, indicating the reliability of the proteomic profiles identified in this study. In summary, we suggest that the proteins identified in this study may play important roles in heat-induced spermatogenic impairment. Some of these proteins, such as CIRBP, PSIP1, Sam68, and Decorin, may be early molecular targets responsible for spermatogenesis suppression induced by heat treatment.

Cell damage and apoptosis in the hepatopancreas of Eriocheir sinensis induced by cadmium

Cadmium (Cd) is one of the most common pollutants in the environment and it is known to cause a range of tissue damages and apoptosis in invertebrates. In this study, we investigated the effect of Cd on the hepatopancreas of the crab Eriocheir sinensis, a commercially and ecologically important species of crustacean. The crabs were first exposed to water containing different concentrations of Cd²⁺ (0, 0.63, 1.26, 2.52, 5.04 and 10.07mg/L) for 6days. Typical morphological characteristics and physiological changes of apoptosis were then observed using various methods, including AO/EB double fluorescence staining, transmission electron microscopy and DNA fragmentation analysis. The results showed that Cd²⁺ induced cell damage and apoptosis in a concentration-dependent manner. Transmission electron microscopy revealed the presence of cellular swelling and necrosis with reduced number of microvilli on the cell surface and damages to individual organelles. The mitochondria became swollen and vacuolated. The rough endoplasmic reticulum (Rer) was expanded, with membrane rupture and many different sizes of vesicles, suggesting the destruction of protein-synthesizing structures in the hepatopancreatic cells. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidases (GPx) initially increased and subsequently decreased with increasing Cd²⁺ concentrations. This was accompanied by increases in malondialdehyde (MDA) and H₂O₂ contents, which led to membrane lipid peroxidation. Crabs exposed to Cd²⁺ also displayed significant increases in caspase-3, -8, and -9 activities compared to control crabs. Cadmium induced the production and accumulation of ROS in the hepatopancreas, which resulted in oxidative damage and abnormal metabolism. Taken together, the results indicated that Cd²⁺ could induce oxidative damage as well caspase-dependent apoptosis in E. sinensis hepatopancreas.

Vitamin C modulates the metabolic and cytokine profiles, alleviates hepatic endoplasmic reticulum stress, and increases the life span of Gulo-/- mice

Suboptimal intake of dietary vitamin C (ascorbate) increases the risk of several chronic diseases but the exact metabolic pathways affected are still unknown. In this study, we examined the metabolic profile of mice lacking the enzyme gulonolactone oxidase (Gulo) required for the biosynthesis of ascorbate. Gulo^−/− mice were supplemented with 0%, 0.01%, and 0.4% ascorbate (w/v) in drinking water and serum was collected for metabolite measurements by targeted mass spectrometry. We also quantified 42 serum cytokines and examined the levels of different stress markers in liver. The metabolic profiles of Gulo^−/− mice treated with ascorbate were different from untreated Gulo^−/− and normal wild type mice. The cytokine profiles of Gulo^−/− mice, in return, overlapped the profile of wild type animals upon 0.01% or 0.4% vitamin C supplementation. The life span of Gulo^−/− mice increased with the amount of ascorbate in drinking water. It also correlated significantly with the ratios of serum arginine/lysine, tyrosine/phenylalanine, and the ratio of specific species of saturated/unsaturated phosphatidylcholines. Finally, levels of hepatic phosphorylated endoplasmic reticulum associated stress markers IRE1α and eIF2α correlated inversely with serum ascorbate and life span suggesting that vitamin C modulates endoplasmic reticulum stress response and longevity in Gulo^−/− mice.

Association of maternal serum cadmium level during pregnancy with risk of preterm birth in a Chinese population

Cadmium (Cd) was a developmental toxicant that induces fetal malformation and growth restriction in mice. However, epidemiological studies about the association of maternal serum Cd level with risk of preterm birth were limited. This study was to investigate whether maternal serum Cd level during pregnancy is associated with risk of preterm birth in a Chinese population. Total 3254 eligible mother-and-singleton-offspring pairs were recruited. Maternal serum Cd level was measured by GFAAS. Based on tertiles, maternal serum Cd concentration was classified as low (LCd, <0.65 μg/L), medium (MCd, 0.65-0.94 μg/L) and high (HCd, ≥0.95 μg/L). Odds ratio (OR) for preterm birth was estimated using multiple logistic regression models. Results showed the rate of preterm birth among LCd, M-Cd and HCd was 3.5%, 3.8%, and 9.4%, respectively. Subjects with HCd had a significantly higher risk for preterm birth (OR: 2.86; 95%CI: 1.95, 4.19; P < 0.001) than did those with LCd. Adjusted OR for preterm birth was 3.02 (95%CI: 2.02, 4.50; P < 0.001) among subjects with HCd compared to subjects with LCd. Taken together, the above results suggest that maternal serum Cd level during pregnancy is positively associated with risk of preterm birth.

Cadmium induced oxidative damage and apoptosis in the hepatopancreas of Meretrix meretrix

Even trace amounts of cadmium (Cd), a non-essential metal, are known to be toxic to aquatic organisms. Here we investigated the relationship between cadmium ion (Cd(2+)) exposure and oxidative damage and apoptosis in the hepatopancreas of the clam Meretrix meretrix. Clams were exposed to different concentrations of Cd(2+) (0, 1.5, 3, 6 and 12 mg L(-1)) for 5 days. We monitored both antioxidant enzyme activity, including that of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), and levels of malondialdehyde (MDA), glutathione (GSH) and glutathione disulfide (GSSG). Apoptosis of hepatopancreatic cells was detected by DNA laddering and AO/EB double fluorescent staining. The results show that the rate of apoptotis, MDA levels, and caspase-3 activity, increased with Cd(2+) concentration, whereas GPx activity and the ratio of GSH/GSSG, decreased. SOD and CAT enzyme activity first increased, then decreased, with increasing Cd(2+) concentration; peak activity of these enzymes was recorded in the 3 mg L(-1) Cd(2+)-treatment group. These results show that Cd-induced oxidative damage can both induce, and aggravate, apoptosis in the hepatopancreatic cells of clams, even at Cd(2+) concentrations far below the semi-lethal dose for adult clams. The observed changes in caspase-3 activity enhanced significantly at lower Cd(2+) concentrations, indicating that caspase-3 is a suitable biomarker for heavy metal pollution, especially cadmium pollution, in marine organisms.

Maternal serum cadmium level during pregnancy and its association with small for gestational age infants: a population-based birth cohort study

The association between maternal cadmium (Cd) exposure during pregnancy and the increased risk of fetal growth restriction (FGR) remains controversial. The present study evaluated the association between maternal serum Cd level and risk of small for gestational age (SGA) infants in a Chinese population. The present study analyzed a subsample of the C-ABCS cohort that recruited 3254 eligible mother-and-singleton-offspring pairs. Maternal serum Cd level during pregnancy was measured by graphite furnace atomic absorption spectrometry. The rate and odds ratio (OR) for SGA infant were calculated. The rate for SGA infant was 10.6% among subjects with H-Cd (≥1.06 μg/L), significantly higher than 7.5% among subjects with L-Cd (<1.06 μg/L). OR was 1.45 (95% CI: 1.11, 1.90; P = 0.007) among subjects with H-Cd. Adjusted OR for SGA infants was 1.43 (95% CI: 1.09, 1.88; P = 0.007) among subjects with H-Cd. Taken together, we observe the fact that maternal Cd exposure at middle gestational stage, elevates the risk of SGA in contrast to early gestational stage. The present results might be interesting and worth more discussing, and guarantee to further studies.

Different fixative methods influence histological morphology and TUNEL staining in mouse testes

Society of Toxicologic Pathology has recommended mDF to fix testes since 2002. However, subsequent studies showed that false TUNEL-positive cells were observed in mDF-fixed testes. This study compared the effects of different fixation methods on histology and TUNEL staining in mouse testes. Results showed that fixation for 24 or 36h in mDF provided better morphologic details in untreated testes, but markedly enhanced false TUNEL-positive staining. To optimize the fixation, testes were fixed using mDF for 6h and then PFA for 18h. Interestingly, fixation using mDF/PFA manifested better morphologic details, and rarely caused false TUNEL-positive cells in testes. Finally, we examined germ cell apoptosis in testes using mDF/PFA fixation in cadmium-treated mice. As expected, cadmium triggered germ cell apoptosis which was well visualized in the mDF/PFA fixed testes. Taken together, mDF plus PFA fixation not only minimizes false TUNEL-positive cells, but also provides integrated morphologic details in testes.

Cadmium Protection Strategies--A Hidden Trade-Off?

Cadmium (Cd) is a non-essential transition metal which is introduced into the biosphere by various anthropogenic activities. Environmental pollution with Cd poses a major health risk and Cd toxicity has been extensively researched over the past decades. This review aims at changing the perspective by discussing protection mechanisms available to counteract a Cd insult. Antioxidants, induction of antioxidant enzymes, and complexation of Cd to glutathione (GSH) and metallothionein (MT) are the most potent protective measures to cope with Cd-induced oxidative stress. Furthermore, protection mechanisms include prevention of endoplasmic reticulum (ER) stress, mitophagy and metabolic stress, as well as expression of chaperones. Pre-exposure to Cd itself, or co-exposure to other metals or trace elements can improve viability under Cd exposure and cells have means to reduce Cd uptake and improve Cd removal. Finally, environmental factors have negative or positive effects on Cd toxicity. Most protection mechanisms aim at preventing cellular damage. However, this might not be possible without trade-offs like an increased risk of carcinogenesis.

Curcumin ameliorates testicular damage in diabetic rats by suppressing cellular stress-mediated mitochondria and endoplasmic reticulum-dependent apoptotic death

In the present study, we sought to explore whether curcumin plays any beneficial role against STZ induced testicular abnormalities in diabetic rats, and if so, what possible mechanism it utilizes to provide protection. Exposure to STZ (50mg/kg body weight, i.p., once) reduced testis-to-body weight ratio, enhanced blood glucose level and intracellular ROS, altered testicular markers, diminished serum testosterone and impaired cellular redox balance. Administration of curcumin at a dose of 100mg/kg body weight for 8 weeks effectively normalized all the alterations. Curcumin also showed inhibitory effect on the elevation of pro-inflammatory cytokines and translocation of NFκB into the nucleus and promoted the activation of the transcription factor Nrf-2 to provide protection against oxidants. To protect cells from STZ-induced stress-mediated damage, curcumin acted on the key mediators of the apoptotic cell death such as JNK and p38. In addition, this active molecule upregulated Bcl-2 expression, blocked the expression of pro-apoptotic proteins (Bax, Bad and Bid), decreased intracellular Ca(2+) level, inhibited active caspase cascade and attenuated PARP cleavage. These results suggest that curcumin provides protection against cellular stress-mediated mitochondrial and endoplasmic reticulum-dependent apoptotic death of the testicular cells under diabetic condition and suggests the possibility of using this molecule as a potential therapeutic in the treatment of stress-mediated diabetic testicular dysfunction.

Redox reactions in mammalian spermatogenesis and the potential targets of reactive oxygen species under oxidative stress

Reduction-oxidation (Redox) reactions are ubiquitous mechanisms for vital activities in all organisms, and they play pivotal roles in the regulation of spermatogenesis as well. Here we focus on 3 redox-involved processes that have drawn much recent attention: the regulation of signal transduction by reactive oxygen species (ROS) such as hydrogen peroxide, oxidative protein folding in the endoplasmic reticulum (ER), and sulfoxidation of protamines during sperm chromatin condensation. The first 2 of these processes are emerging topics in cell biology and are applicable to most living cells, which includes spermatogenic cells. The roles of ROS in signal transduction have been elucidated in the last 2 decades and have received broad attention, most notably from the viewpoint of the proper control of mitotic signals. Redox processes in the ER are important because this is the organelle where secretory and membrane proteins are synthesized and proceed toward their functional structure, so that malfunction of the ER affects not only the involved cells but also the accepting cells of the secreted proteins in multicellular organisms. Sulfoxidation is the third of these processes, and the sulfoxidation of chromatin is a unique process in sperm maturation. During recent sulfoxidase research, GPX4 has emerged as a promising enzyme that plays essential roles in the production of fertile sperm, but the involvement of other redox proteins is also becoming evident. Because the molecules involved in the redox reactions are prone to oxidation, they can be sensitive to oxidative damage, which makes them potential targets for antioxidant therapy.

Cadmium and cellular signaling cascades: interactions between cell death and survival pathways

Cellular stress elicited by the toxic metal Cd(2+) does not coerce the cell into committing to die from the onset. Rather, detoxification and adaptive processes are triggered concurrently, allowing survival until normal function is restored. With high Cd(2+), death pathways predominate. However, if sublethal stress levels affect cells for prolonged periods, as in chronic low Cd(2+) exposure, adaptive and survival mechanisms may deregulate, such that tumorigenesis ensues. Hence, death and malignancy are the two ends of a continuum of cellular responses to Cd(2+), determined by magnitude and duration of Cd(2+) stress. Signaling cascades are the key factors affecting cellular reactions to Cd(2+). This review critically surveys recent literature to outline major features of death and survival signaling pathways as well as their activation, interactions and cross talk in cells exposed to Cd(2+). Under physiological conditions, receptor activation generates 2nd messengers, which are short-lived and act specifically on effectors through their spatial and temporal dynamics to transiently alter effector activity. Cd(2+) recruits physiological 2nd messenger systems, in particular Ca(2+) and reactive oxygen species (ROS), which control key Ca(2+)- and redox-sensitive molecular switches dictating cell function and fate. Severe ROS/Ca(2+) signals activate cell death effectors (ceramides, ASK1-JNK/p38, calpains, caspases) and/or cause irreversible damage to vital organelles, such as mitochondria and endoplasmic reticulum (ER), whereas low localized ROS/Ca(2+) levels act as 2nd messengers promoting cellular adaptation and survival through signal transduction (ERK1/2, PI3K/Akt-PKB) and transcriptional regulators (Ref1-Nrf2, NF-κB, Wnt, AP-1, bestrophin-3). Other cellular proteins and processes targeted by ROS/Ca(2+) (metallothioneins, Bcl-2 proteins, ubiquitin-proteasome system, ER stress-associated unfolded protein response, autophagy, cell cycle) can evoke death or survival. Hence, temporary or permanent disruptions of ROS/Ca(2+) induced by Cd(2+) play a crucial role in eliciting, modulating and linking downstream cell death and adaptive and survival signaling cascades.

Grape seed proanthocyanidins ameliorate pancreatic beta-cell dysfunction and death in low-dose streptozotocin- and high-carbohydrate/high-fat diet-induced diabetic rats partially by regulating endoplasmic reticulum stress

Background

It is increasingly being realized that failure of pancreatic beta cells to secrete enough insulin to adequately compensate for obesity and insulin resistance is the primary defects of type 2 diabetes mellitus (T2DM). Pancreatic beta cells possess a highly developed and active endoplasmic reticulum (ER), reflecting their role in folding, export and processing of newly synthesized insulin. ER stress-induced pancreatic beta-cell failure is a novel event in the pathogenesis of T2DM. Some studies with antioxidants indicated a beneficial impact on ER stress. Our previous study found that strong antioxidants, grape seed proanthocyanidins (GSPs), ameliorated ER stress to protect skeletal muscle from cell death in type 2 diabetic rats. The present study continued to investigate the effect of GSPs on beta-cell failure and ER stress in diabetic pancreas.

Methods

Male Sprague–Dawley rats made type 2 diabetic with 2 injections of 25 mg/kg streptozotocin and 8 weeks of the high-carbohydrate/high-fat diet were fed a basal diet with or without GSPs administration for 16 weeks. Oral glucose tolerance, plasma glucose, serum insulin and the score of beta-cell function were measured. Morphological observation was performed by light and electron microscopic analyses. Islet cell apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling staining. Additionally, the level of insulin and the expression of ER stress markers in pancreatic islets were also studied using immunohistochemical staining.

Results

After 16 weeks treatment, the score of beta-cell function and the abnormal oral glucose tolerance of diabetic rats were partially reversed by GSPs treatment. The efficacious effect of GSPs was also manifested in the amelioration of pancreatic damage and ER dilatation by microscopic analyses. Moreover, GSPs treatment increased normal insulin content and decreased the number of apoptotic cells in diabetic islets. Importantly, GSPs treatment partially alleviated ER stress by decreasing some ER stress markers.

Conclusion

These findings suggest that GSPs might have auxiliary therapeutic potential for pancreatic beta-cell dysfunction and death in T2DM.

N-acetylcysteine protects against cadmium-induced germ cell apoptosis by inhibiting endoplasmic reticulum stress in testes

Cadmium (Cd) is a reproductive toxicant that induces germ cell apoptosis in the testes. Previous studies have demonstrated that endoplasmic reticulum (ER) stress is involved in Cd-induced germ cell apoptosis. The aim of the present study was to investigate the effects of N-acetylcysteine (NAC), an antioxidant, on Cd-induced ER stress and germ cell apoptosis in the testes. Male CD-1 mice were intraperitoneally injected with CdCl2 (2.0 mg kg(-1)). As expected, acute Cd exposure induced germ cell apoptosis in the testes, as determined by terminal dUTP nick-end labelling (TUNEL). However, the administration of NAC alleviated Cd-induced germ cell apoptosis in the testes. Further analysis showed that NAC attenuated the Cd-induced upregulation of testicular glucose-regulated protein 78 (GRP78), an important ER molecular chaperone. Moreover, NAC inhibited the Cd-induced phosphorylation of testicular eukaryotic translation initiation factor 2α (eIF2α), a downstream target of the double-stranded RNA-activated kinase-like ER kinase (PERK) pathway. In addition, NAC blocked the Cd-induced activation of testicular X binding protein (XBP)-1, indicating that NAC attenuates the Cd-induced ER stress and the unfolded protein response (UPR). Interestingly, NAC almost completely prevented the Cd-induced elevation of C/EBP homologous protein (CHOP) and phosphorylation of c-Jun N-terminal kinase (JNK), two components of the ER stress-mediated apoptotic pathway. In conclusion, NAC protects against Cd-induced germ cell apoptosis by inhibiting endoplasmic reticulum stress in the testes.

Grape seed proanthocyanidin extracts alleviate oxidative stress and ER stress in skeletal muscle of low-dose streptozotocin- and high-carbohydrate/high-fat diet-induced diabetic rats

Although ER stress in pancreas, liver, and adipose tissue was reported to be a novel event linked to the pathogenesis of type 2 diabetes mellitus, there is much less information on this event in skeletal muscle. Some studies indicated that treatment with antioxidants had beneficial effects on ER stress and diabetes. This study focuses on the effects of a strong antioxidant, grape seed proanthocyanidin extracts (GSPE), on skeletal muscle in diabetic rats induced with low dose streptozotocin- and a high-carbohydrate/high-fat diet. After 16 wk of GSPE treatment, diabetic rats showed decreased plasma glucose levels and insulin resistance. The efficacious effect of GSPE was manifested by the amelioration of muscular damage and dysfunction, as observed by histological examination and periodic acid Schiff staining. Concurrently, calcium overload and the abnormal activities of antioxidant enzymes and ATPases in diabetic muscles were partially reversed by GSPE treatment. GSPE also increased the activity of protein kinase B (a mediator of insulin's metabolic action) and partially alleviated severe ER stress. These findings suggest that GSPE may have auxiliary therapeutic potential for type 2 diabetes mellitus by decreasing oxidative stress and ER stress in skeletal muscle.