N-acetylcysteine protects against microcystin-LR-induced endoplasmic reticulum stress and germ cell apoptosis in zebrafish testes

The gut microbe-derived metabolite trimethylamine-N-oxide induces aortic valve fibrosis via PERK/ATF-4 and IRE-1α/XBP-1s signaling in vitro and in vivo

BACKGROUND AND AIMS

The gut microbe-derived metabolite trimethylamine-N-oxide (TMAO) has been implicated in the development of cardiovascular fibrosis. Endoplasmic reticulum (ER) stress occurs after the dysfunction of ER and its structure. The three signals PERK/ATF-4, IRE-1α/XBP-1s and ATF6 are activated upon ER stress. Recent reports have suggested that the activation of PERK/ATF-4 and IRE-1α/XBP-1s signaling contributes to cardiovascular fibrosis. However, whether TMAO mediates aortic valve fibrosis by activating PERK/ATF-4 and IRE-1α/XBP-1s signaling remains unclear.

METHODS

Human aortic valve interstitial cells (AVICs) were isolated from aortic valve leaflets. PERK IRE-1α, ATF-4, XBP-1s and CHOP expression, and production of collagen Ⅰ and TGF-β1 were analyzed following treatment with TMAO. The role of PERK/ATF-4 and IRE-1α/XBP-1s signaling pathways in TMAO-induced fibrotic formation was determined using inhibitors and small interfering RNA.

RESULTS

Diseased valves produced greater levels of ATF-4, XBP-1, collagen Ⅰ and TGF-β1. Interestingly, diseased cells exhibited augmented PERK/ATF-4 and IRE-1α/XBP-1s activation after TMAO stimulation. Inhibition and silencing of PERK/ATF-4 and IRE-1α/XBP-1s each resulted in enhanced suppression of TMAO-induced fibrogenic activity in diseased cells. Mice treated with dietary choline supplementation had substantially increased TMAO levels and aortic valve fibrosis, which were reduced by 3,3-dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) treatment. Moreover, a high-choline and high-fat diet remodeled the gut microbiota in mice.

CONCLUSIONS

TMAO promoted aortic valve fibrosis through activation of PERK/ATF-4 and IRE-1α/XBP-1s signaling pathways in vitro and in vivo. Modulation of diet, gut microbiota, TMAO, PERK/ATF-4 and IRE1-α/XBP-1s may be a promising approach to prevent aortic valve fibrosis.

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.

Long-Term Exposure to Microcystin-LR Induces Gastric Toxicity by Activating the Mitogen-Activated Protein Kinase Signaling Pathway

Previous studies have primarily concentrated on the hepatotoxicity of MC-LR, whereas its gastric toxicity effects and mechanisms of long-term exposure under low dosage remain unknown. Herein, the gastric tissue from C57BL/6 mice fed with drinking water contaminated by low-dose MC-LR (including 1, 60, and 120 μg/L) was investigated. The results obtained showed that exposure to different concentrations of MC-LR resulted in significant shedding and necrosis of gastric epithelial cells in mice, and a down-regulation of tight junction markers, including ZO-1, Claudin1, and Occludin in the stomach, which might lead to increased permeability of the gastric mucosa. Moreover, the protein expression levels of p-RAF/RAF, p-ERK1/2/ERK1/2, Pink1, Parkin, and LC3-II/LC-3-I were increased in the gastric tissue of mice exposed to 120 μg/L of MC-LR, while the protein expression level of P62 was significantly decreased. Furthermore, we found that pro-inflammatory factors, including IL-6 and TNF-ɑ, were dramatically increased, while the anti-inflammatory factor IL-10 was significantly decreased in the gastric tissue of MC-LR-exposed mice. The activation of the MAPK signaling pathway and mitophagy might contribute to the development of gastric damage by promoting inflammation. We first reported that long-term exposure to MC-LR induced gastric toxicity by activating the MAPK signaling pathway, providing a new insight into the gastric toxic mechanisms caused by MC-LR.

Mechanisms underlying the role of endoplasmic reticulum stress in the placental injury and fetal growth restriction in an ovine gestation model

BACKGROUND

Exposure to bisphenol A (BPA), an environmental pollutant known for its endocrine-disrupting properties, during gestation has been reported to increase the risk of fetal growth restriction (FGR) in an ovine model of pregnancy. We hypothesized that the FGR results from the BPA-induced insufficiency and barrier dysfunction of the placenta, oxidative stress, inflammatory responses, autophagy and endoplasmic reticulum stress (ERS). However, precise mechanisms underlying the BPA-induced placental dysfunction, and subsequently, FGR, as well as the potential involvement of placental ERS in these complications, remain to be investigated.

METHODS

In vivo experiment, 16 twin-pregnant (from d 40 to 130 of gestation) Hu ewes were randomly distributed into two groups (8 ewes each). One group served as a control and received corn oil once a day, whereas the other group received BPA (5 mg/kg/d as a subcutaneous injection). In vitro study, ovine trophoblast cells (OTCs) were exposed to 4 treatments, 6 replicates each. The OTCs were treated with 400 μmol/L BPA, 400 μmol/L BPA + 0.5 μg/mL tunicamycin (Tm; ERS activator), 400 μmol/L BPA + 1 μmol/L 4-phenyl butyric acid (4-PBA; ERS antagonist) and DMEM/F12 complete medium (control), for 24 h.

RESULTS

In vivo experiments, pregnant Hu ewes receiving the BPA from 40 to 130 days of pregnancy experienced a decrease in placental efficiency, progesterone (P4) level and fetal weight, and an increase in placental estrogen (E2) level, together with barrier dysfunctions, OS, inflammatory responses, autophagy and ERS in type A cotyledons. In vitro experiment, the OTCs exposed to BPA for 24 h showed an increase in the E2 level and related protein and gene expressions of autophagy, ERS, pro-apoptosis and inflammatory response, and a decrease in the P4 level and the related protein and gene expressions of antioxidant, anti-apoptosis and barrier function. Moreover, treating the OTCs with Tm aggravated BPA-induced dysfunction of barrier and endocrine (the increased E2 level and decreased P4 level), OS, inflammatory responses, autophagy, and ERS. However, treating the OTCs with 4-PBA reversed the counteracted effects of Tm mentioned above.

CONCLUSIONS

In general, the results reveal that BPA exposure can cause ERS in the ovine placenta and OTCs, and ERS induction might aggravate BPA-induced dysfunction of the placental barrier and endocrine, OS, inflammatory responses, and autophagy. These data offer novel mechanistic insights into whether ERS is involved in BPA-mediated placental dysfunction and fetal development.

Cyanotoxins Increase Cytotoxicity and Promote Nonalcoholic Fatty Liver Disease Progression by Enhancing Cell Steatosis

Freshwater prokaryotic cyanobacteria within harmful algal blooms produce cyanotoxins which are considered major pollutants in the aquatic system. Direct exposure to cyanotoxins through inhalation, skin contact, or ingestion of contaminated drinking water can target the liver and may cause hepatotoxicity. In the current study, we investigated the effect of low concentrations of cyanotoxins on cytotoxicity, inflammation, modulation of unfolded protein response (UPR), steatosis, and fibrosis signaling in human hepatocytes and liver cell models. Exposure to low concentrations of microcystin-LR (MC-LR), microcystin-RR (MC-RR), nodularin (NOD), and cylindrospermopsin (CYN) in human bipotent progenitor cell line HepaRG and hepatocellular carcinoma (HCC) cell lines HepG2 and SK-Hep1 resulted in increased cell toxicity. MC-LR, NOD, and CYN differentially regulated inflammatory signaling, activated UPR signaling and lipogenic gene expression, and induced cellular steatosis and fibrotic signaling in HCC cells. MC-LR, NOD, and CYN also regulated AKT/mTOR signaling and inhibited autophagy. Chronic exposure to MC-LR, NOD, and CYN upregulated the expression of lipogenic and fibrosis biomarkers. Moreover, RNA sequencing (RNA seq) data suggested that exposure of human hepatocytes, HepaRG, and HCC HepG2 cells to MC-LR and CYN modulated expression levels of several genes that regulate non-alcoholic fatty liver disease (NAFLD). Our data suggest that low concentrations of cyanotoxins can cause hepatotoxicity and cell steatosis and promote NAFLD progression.

Adverse effects of microcystins on sperm: A systematic review

Eutrophication of water bodies can lead to cyanobacterial blooms, with the resultant release of microcystins (MCs), posing a threat to the ecosystem and human health. MCs are environmental toxins with male reproductive toxicity. However, there is a dearth of reviews focusing on sperm or spermatogenesis. In this paper, studies on sperm toxicity caused by MCs in recent 20 years were collected and summarized, aiming at revealing the toxic effects and potential mechanisms of MCs on sperm. Based on the previous findings, MCs can decline sperm quality and count, and cause malformation in vertebrates and invertebrates. The reason might be that MCs cause indirect damage to sperm through impairing the structure and function of the testis. The mechanisms of MCs-induced sperm toxicity mainly result from alterations in genetic material, abnormalities in the structure and function of sperm. The epigenetic modifications such as miRNA and piRNA were also involved in MC-LR-induced sperm damage. In conclusion, MCs exposure is harmful to sperm, but its direct effects and mechanisms on sperm are still not known, which remains a significant research direction. Our review will provide a basis for the protection of male reproductive health damage caused by microcystins.

Microcystin leucine arginine induces human sperm damage: Involvement of the Ca2+/CaMKKβ/AMPK pathway

As a common pollutant in the water environment, microcystin leucine arginine (MC-LR) can enter semen and damage the sperm in animals. However, the mechanism by which MC-LR damages human sperm is unclear. Therefore, human sperm samples were obtained from the Henan Provincial Sperm Bank and exposed to different concentrations (0, 1, 10, and 100 μg/L) of MC-LR for 1, 2, 4, and 6 h, to invegest the effects and potential mechanism of MC-LR on sperm. The results showed that MC-LR mainly accumulated in the neck and flagellum of human sperm. Compared to the control group, the sperm capacitation rate and motility were significantly decreased in the 100 μg/L group. After exposure of 100 μg/L of MC-LR, the central microtubule and microtubule doublet of sperm flagellum were blurred, asymmetrical, or even lost. Furthermore, the expression levels of flagellin DNAH17, SPEF2, SPAG16, SPAG6, and CFAP44 in human sperm were reduced. Also, the phosphorylation levels of CaMKKβ and AMPK can be inhibited by MC-LR. These findings revealed that MC-LR can induce functional and structural damage in human sperm, and the Ca²⁺/CaMKKβ/AMPK pathway may be involved in this process. This study will provide a basis for prevention and treatment of male fertility declines caused by MC-LR.

Pubertal lead exposure affects ovary development, folliculogenesis and steroidogenesis by activation of IRE1α-JNK signaling pathway in rat

Epidemic studies showed that lead exposures are associated with various female reproductive dysfunctions, including infertility, miscarriage, preterm delivery, and early menopause. However, the mechanism involved is still unclear. In the current study, SD rats were exposed to lead at doses of 0, 5, 25, 50 or 250 mg/L through drinking water from postnatal day 21-56. Lead exposures did not affect the body weight or ovary weight. However, the puberty initiation (ages by which vagina opens and estrous cycle occurs) was significantly delayed by as many as 5.8 and 6.8 days respectively (P < 0.05). Also, lead exposures disrupted the estrous cycles, reduced the numbers of primordial and primary follicles and increased the number of atretic follicles by adult. Furthermore, for the highest does group, serum levels of progesterone and testosterone decreased by 80.2% (P < 0.01) and 49.9% (P < 0.05) respectively, while estradiol level increased by 69.8% (P < 0.01). Western blot analyses indicated that lead exposures specifically down-regulated the expressions of steroidogenic protein STAR, CYP17A1, and HSD3B1, while up-regulated FSHR and CYP19A1. Also, the exposure stimulated the endoplasmic reticulum stress (ERS)-related IRE1α-JNK signaling pathway members. Such activation may also result in apoptosis since the death-signaling molecules CHOP and cleaved-CASP3 were up-regulated while BCL2 was down-regulated. In conclusion, lead exposure during juvenile and puberty significantly affected ovary development and functions. The effects may relate to ERS response since the 6 members related to the pathway were all consistently activated.

Microcystin-LR induced transgenerational effects of thyroid disruption in zebrafish offspring by endoplasmic reticulum stress-mediated thyroglobulin accumulation and apoptosis

MC-LR can interfere with thyroid function in fish, but the underlying mechanism is still unclear. Current study focuses to study the intergenerational inheritance of MC-LR-induced thyroid toxicity in zebrafish and in rat thyroid cells. In vivo experiments, adult female zebrafish (F0) were exposed to MC-LR (0, 5, and 25 μg/L) for 90 days and mated with male zebrafish without MC-LR exposure to generate F1 generation. F1 embryos were allowed to develop normally to 7 days post-fertilization (dpf) in clear water. In the F0 generation, MC-LR induced disturbance of the hypothalamic-pituitary-thyroid (HPT) axis, leading to a decrease in the production of thyroid hormones. Maternal MC-LR exposure also induced growth inhibition by altering thyroid hormones (THs) homeostasis and interfering with thyroid metabolism and development in F1 offspring. Mechanistically, MC-LR caused excessive accumulation of ROS and induced ER stress that further lead to activation of UPR in the F0 and F1 offspring of zebrafish. Interestingly, our findings suggested that MC-LR exposure hampered thyroglobulin turnover by triggering IRE1 and PERK pathway in zebrafish and FRTL-5 thyroid cells, thus disturbing the thyroid endocrine system and contributing to the thyroid toxicity from maternal to its F1 offspring of zebrafish. Particularly, inhibition of the IRE1 pathway by siRNA could alleviate thyroid development injury induced by MC-LR in FRTL-5 cells. In addition, MC-LR induced thyroid cell apoptosis by triggering ER stress. Taken together, our results demonstrated that maternal MC-LR exposure causes thyroid endocrine disruption by ER stress contributing to transgenerational effects in zebrafish offspring.

Microcystin-LR accelerates follicular atresia in mice via JNK-mediated adherent junction damage of ovarian granulosa cells

Microcystin-LR (MC-LR), one of aquatic environmental contaminants with reproductive toxicity produced by cyanobacterial blooms, but its toxic effects and mechanisms on the ovary are not fully understood. Here, proteomic techniques and molecular biology experiments were performed to study the potential mechanism of MC-LR-caused ovarian toxicity. Results showed that protein expression profile of ovarian granulosa cells (KK-1) was changed by 17 μg/mL MC-LR exposure. Comparing with the control group, 118 upregulated proteins as well as 97 downregulated proteins were identified in MC-LR group. Function of differentially expressed proteins was found to be enriched in pathways related to adherent junction, such as cadherin binding, cell-cell junction, cell adhesion and focal adherens. Furthermore, in vitro experiments, MC-LR significantly downregulated the expression levels of proteins associated with adherent junction (β-catenin, N-cadherin, and α-catenin) as well as caused cytoskeletal disruption in KK-1 cells (P < 0.05), indicating that the adherent junction was damaged. Results of in vivo experiments have shown that after 14 days of acute MC-LR exposure (40 μg/kg), damaged adherent junction and an increased number of atretic follicles were observed in mouse ovaries. Moreover, MC-LR activated JNK, an upstream regulator of adherent junction proteins, in KK-1 cells and mouse ovarian tissues. In contrast, JNK inhibition alleviated MC-LR-induced adherent junction damage in vivo and in vitro, as well as the number of atretic follicles. Taken together, findings from the present study indicated that JNK is involved in MC-LR-induced granulosa cell adherent junction damage, which accelerated follicular atresia. Our study clarified a novel mechanism of MC-LR-caused ovarian toxicity, providing a theoretical foundation for protecting female reproductive health from environmental pollutants.

Microcystin-leucine-arginine affects brain gene expression programs and behaviors of offspring through paternal epigenetic information

Microcystin-leucine-arginine (MC-LR) adversely affects male reproduction and interferes with the development of the offspring. Here, we establish a zebrafish (Danio rerio) model to understand the cross-generational effects of MC-LR in a male-lineage transmission pattern. F0 embryos were reared in water containing MC-LR (0, 5, and 25 μg/L) for 90 days and the developmental indices of F1 and F2 embryos were then measured with no MC-LR treatment. The results show that paternal MC-LR exposure reduced the hatching rate, heart rate and body weight in F1 and F2 generations. Global DNA methylation significantly increased in sperm and testes with the elevation expressions of DNA methyltransferases. Meanwhile, DNA methylation of brain-derived neurotrophic factor (bdnf) promoter was increased in sperm after paternal MC-LR exposure. Subsequently, increased DNA methylation of bdnf promoter and decreased gene expression of bdnf in the brain of F1 male zebrafish were detected. F1 offspring born to F0 males exhibit the depression of BDNF/AKT/CREB pathway and recapitulate these paternal neurodevelopment phenotypes in F2 offspring. In addition, the DNA methylations of dio3b and gad1b promoters were decreased and gene expressions of gad1b and dio3b were increased, accompanied with neurotransmitter disturbances in the brain of F1 male zebrafish after paternal MC-LR exposure. These data revealed that MC-LR displays a potential epigenetic impact on the germ line, reprogramming the epigenetic and transcriptional regulation of brain development, and contributing to aberrant expression of neurodevelopment-related genes and behavior disorders.

A new identity of microcystins: Environmental endocrine disruptors? An evidence-based review

Microcystins (MCs) are widely distributed cyanobacterial toxins in eutrophic waters. At present, the endocrine-disrupting effects of MCs have been extensively studied, but whether MCs can be classified as environmental endocrine disruptors (EDCs) is still unclear. This review is aimed to evaluate the rationality for MCs as to be classified as EDCs based on the available evidence. It has been identified that MCs meet eight of ten key characteristics of chemicals that can be classified as EDCs. MCs interfere with the six processes, including synthesis, release, circulation, metabolism, binding and action of natural hormones in the body. Also, they are fit two other characteristics of EDC: altering the fate of producing/responding cells and epigenetic modification. Further evidence indicates that the endocrine-disrupting effect of MCs may be an important cause of adverse health outcomes such as metabolic disorders, reproductive disorders and effects on the growth and development of offspring. Generally, MCs have endocrine-disrupting properties, suggesting that it is reasonable for them to be considered EDCs. This is of great importance in understanding and evaluating the harm done by MCs on humans.

Liver dysfunction and energy storage mobilization in traíra, Hoplias malabaricus (Teleostei, Erythrinidae) induced by subchronic exposure to toxic cyanobacterial crude extract

Microcystins (MC) are hepatotoxic for organisms. Liver MC accumulation and structural change are intensely studied, but the functional hepatic enzymes and energy metabolism have received little attention. This study investigated the liver and hepatocyte structures and the activity of key hepatic functional enzymes with emphasis on energetic metabolism changes after subchronic fish exposure to cyanobacterial crude extract (CE) containing MC. The Neotropical erythrinid fish, Hoplias malabaricus, were exposed intraperitoneally to CE containing 100 μg MC-LR eq kg^-1 for 30 days and, thereafter, the plasma, liver, and white muscle was sampled for analyses. Liver tissue lost cellular structure organization showing round hepatocytes, hyperemia, and biliary duct obstruction. At the ultrastructural level, the mitochondria and the endoplasmic reticulum exhibited disorganization. Direct and total bilirubin increased in plasma. In the liver, the activity of acid phosphatase (ACP) increased, and the aspartate aminotransferase (AST) decreased; AST increased in plasma. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were unchanged in the liver, muscle, and plasma. Glycogen stores and the energetic metabolites as glucose, lactate, and pyruvate decrease in the liver; pyruvate decreased in plasma and lactate decreased in muscle. Ammonia levels increased and protein concentration decreased in plasma. CE alters liver morphology by causing hepatocyte intracellular disorder, obstructive cholestasis, and dysfunction in the activity of key liver enzymes. The increasing energy demand implies glucose mobilization and metabolic adjustments maintaining protein preservation and lipid recruitment to supply the needs for detoxification allowing fish survival.

Environmental exposure to microcystin-LR increases the risks of urinary bladder proliferation and carcinogenesis: Evidence from case control, animal, and in vitro studies

To date, no reported studies have explored the impacts of microcystin-LR (MC-LR) on bladder tissues, and even the occurrence of bladder cancer. The current study explores the role of MC-LR in the development of bladder cancer through human observation and experimental research. In the population study, the odds ratio of bladder cancer for MC-LR was 6.073 (95 % CI, 2.117-17.422) after adjusting interference confounders. MC-LR is mainly located in the nucleus of epithelial cells in bladder cancer tissues instead of normal tissues. A positive association was observed between MC-LR and advanced tumor stage in serum and tissues. The animal study confirmed that prolonged MC-LR treatment promoted the bladder cancer phenotype accompanied by urinary bladder proliferation. In vitro, we indicated that MC-LR activated the PI3K/AKT/GSK3β/Cyclin D1 and JAK2/STAT3/Bcl2 signaling pathways to induce the growth of SV-HUC-1 cells. Moreover, MC-LR promoted the angiogenesis of SV-HUC-1 cells through PI3K/AKT/mTOR/HIF-1α/VEGF pathway. Our study provided the first evidence that prolonged MC-LR treatment increases the incidence of bladder cancer from human investigations, mice models, and in vitro studies, implying the profound importance of the investigation of MC-LR for public health.

Subchronic Toxicity of Microcystin-LR on Young Frogs (Xenopus laevis) and Their Gut Microbiota

Although toxic effects of microcystins (MCs) in mammals and fish have been extensively studied, the effects of MCs on the immune system and gut microbiota of amphibians have not received sufficient attention. As MCs cause general damage to the vertebrate liver and immune system and trigger an inflammatory response, and the gut microbiota is closely related to host metabolism and immunity, we speculated that MCs can cause changes in the immune system and gut microbiota of amphibians. To verify this, we examined the intestinal and liver injury of Xenopus laevis exposed to different microcystin-leucine-arginine (MC-LR) concentrations and the effects on the gut microbiota through high-throughput sequencing of 16S rDNA of the gut microbiota combined with histopathological analysis, enzyme activity determination, and qRT-PCR. Our results showed that MC-LR caused focal infiltration of inflammatory cells and increased the number of T cells and local congestion and vacuolization in X. laevis liver, but reduced the number, density, height, and regularity of villi. These liver and intestinal injuries became more obvious with an increase in MC-LR concentration. MC-LR significantly decreased the activities of malondialdehyde and alkaline phosphatase and the expression of TGF-β in the liver. Moreover, MC-LR significantly altered the gut microbiota of X. laevis. The relative abundance of Firmicutes and Bacteroidetes in high-concentration MC-LR groups was significantly reduced compared to that in low-concentration MC-LR groups, whereas Fusobacteria was significantly enriched. The metabolic gene composition of the gut microbiota in low-concentration MC-LR (≤5 μg/L) groups was significantly different from that in high-concentration MC-LR (≥20 μg/L) groups. These results deepen our understanding of the toxicity of MCs to aquatic organisms and assessment of the ecological risk of MCs in amphibians.

Ameliorative effect of N-acetylcysteine on the testicular tissue of adult male albino rats after glyphosate-based herbicide exposure

Glyphosate (GLP) is a broad-spectrum herbicide that is frequently used in crop production, but its residues remain in foodstuffs. This, in turn, has led to potential adverse effects on both human and animal health. Recent studies emphasized that GLP induces teratogenic effects and reproductive disorders, but its mechanism of toxicity is highly debated. N-acetylcysteine (NAC) is well known for its potent antioxidant capacity in addition to anti-inflammatory and cytoprotective properties. Therefore, our study aimed to investigate the reproductive toxicity of GLP in mature rats and evaluate the possible ameliorative effect of NAC against this toxicity. To this end, 30 adult male rats were assigned into three groups (10 rats per group) as follows: Group I, negative control; group II, GLP-exposed; 375 mg/kg GLP, orally; group III, NAC-cotreated, 160 mg/kg NAC 1 h before GLP, plus GLP, 375 mg/kg orally for 6 weeks. At the end of the experiment, the testicles were collected for semen analysis and biochemical, histopathological, and immunohistochemical studies. GLP-exposed rats exhibited disturbances in seminal parameters and a significant increase in malondialdehyde levels and expression of apoptotic markers. Several histopathological changes were observed, including strong immunoreactions for caspase-3 and proliferating cell nuclear antigen. Conversely, the administration of NAC before GLP was able to improve seminal parameters, attenuate the induced oxidative stress and apoptosis in addition to the regeneration of testicular damage. In conclusion, NAC can ameliorate the reproductive toxicity induced by GLP to an acceptable degree.

ATF6 deficiency damages the development of spermatogenesis in male Atf6 knockout mice

Activating transcription factor 6 (ATF6), also known as ACHM7, ATF6A, encodes a transcription factor that activates target genes for the unfolded protein response (UPR) during endoplasmic reticulum (ER) stress. It functions as nuclear transcription factor via a cis-acting ER stress response element (ERSE) that is presented in the promoters of genes encoding ER chaperones. Studies have shown that endoplasmic reticulum stress (ERS) can cause damage to spermatozoa and testes, leading to male sterility. And we find that the expression of ATF6 in spermatozoa of some infertile patients is significantly reduced. Then, we construct the Atf6 knockout mice model and interestingly find a decline in male fertility. The downstream gene testis-specific serine/threonine-protein kinase 4 (Tssk4) is screened based on transcriptome sequencing. We use Western blot and real-time PCR to confirm this result in both 293T cells and Atf6 knockout mice. TSSK4 is essential in male germ cell genesis and sperm maturation. Our results suggest that the expression of TSSK4 may be regulated by ATF6. The effect of Atf6 knockout on the reproductive development of male mice may be related to the low expression of TSSK4, which further verify that there may be some relationship between ERS and male reproduction.

Paternal exposure to microcystin-LR triggers developmental neurotoxicity in zebrafish offspring via an epigenetic mechanism involving MAPK pathway

Microcystin-LR (MCLR) induced impairment to male reproductive system and revealed the effects of transgenerational toxicity on offspring. But very little is known about the inheritance of these effects to offspring and the mechanisms involved. Here, we used methylated DNA immunoprecipitation sequencing (MeDIP-Seq) and microarray to characterize whole-genome DNA methylation and mRNA expression patterns in zebrafish testis after 6-week exposure to 5 and 20 μg/L MCLR. Accompanied with these analyses it revealed that MAPK pathway and ER pathway significantly enriched in zebrafish testes. Apoptosis and testicular damage were also observed in testis. Next, we test the transmission of effects to compare control-father and MCLR exposure-father progenies. DNA methylation analyses (via reduced representation bisulfite sequencing) reveal that the enrichment of differentially methylated regions on neurodevelopment after paternal MCLR exposure. Meanwhile, several genes associated with neurodevelopment were markedly downregulated in zebrafish larvae, and swimming speed was also reduced in the larvae. Interestingly, paternal MCLR exposure also triggered activation the phosphorylation of mitogen-activated protein kinase (MAPK) pathway which is also associated with neurodevelopmental disorders. These results demonstrated the significant effect that paternal MCLR exposure may have on gene-specific DNA methylation patterns in testis. Inherited epigenetic alterations through the germline may be the mechanism leading to developmental neurotoxicity in the offspring.

Inhibition of endoplasmic reticulum stress-related autophagy attenuates MCLR-induced apoptosis in zebrafish testis and mouse TM4 cells

Microcystin-leucine arginine (MCLR), a widespread environmental contaminant produced by cyanobacteria, poses a severe threat to the male reproductive system. However, the mechanisms of MCLR-induced testis injury accompanied by autophagy are still obscure. This study aimed to investigate the effects of MCLR on autophagy and apoptosis on the male reproductive system and its mechanism both in vitro and in vivo. MCLR caused damage to the testis of zebrafish, resulting in decreased hatching and growth retardation in the offspring. It also remarkably enhanced autophagic flux by elevating the expression of LC3BII, ATG5, and ATG12 proteins. The autophagic flux was also confirmed through the formation of autophagosomes in the ultrastructure of the zebrafish testis and the accumulation of LC3-positive puncta in zebrafish testis and mouse TM4 cells. Further evaluations revealed that inhibition of autophagy by 3-methyladenine (3-MA) significantly attenuated MCLR-induced apoptosis. This finding indicated that autophagy plays an essential role in cell death in the male reproductive system. Besides, inhibiting endoplasmic reticulum (ER) stress using 4-phenylbutyrate (4-PBA) remarkably blocked autophagy and partially suppressed apoptosis in TM4 cells induced by MCLR. This phenomenon suggested that ER stress-related autophagy was involved in MCLR-induced apoptosis. This study reveals crosstalk between ER stress and autophagy via the PERK/eIF2α/ATF4 signaling pathway. It further suggests that ER stress-related autophagy contributes to MCLR-induced apoptosis and injury in the male reproductive system. These findings provide a novel insight into MCLR-induced impairments of the testis.

Di-(2-ethylhexyl) phthalate induces testicular endoplasmic reticulum stress and germ cell apoptosis in adolescent mice

Di-(2-ethylhexyl) phthalate (DEHP) is a male reproductive toxicant. This research is aimed at investigating the effect of pubertal DEHP exposure on testicular endoplasmic reticulum (ER) stress and germ cell apoptosis. Five-week-old male mice were orally administered with DEHP (0, 0.5, 50, or 500 mg/kg/day) for 35 days. Testis weight and sperm count were reduced in mice exposed to 500 mg/kg/day DEHP. The number of seminiferous tubules in stages VII-VIII, mature seminiferous tubules, was reduced and the number of seminiferous tubules in stages IX-XII, immature seminiferous tubules, was elevated in mice treated with 500 mg/kg/day DEHP. Numerous apoptotic germ cells were observed in mouse seminiferous tubules exposed to 50 and 500 mg/kg/day DEHP. Moreover, cleaved caspase-3 was elevated in mouse testes exposed to 500 mg/kg/day DEHP. In addition, Bcl-2 was reduced and Bax/Bcl-2 was elevated in mouse testes exposed to 500 mg/kg/day DEHP. Additional experiment showed that GRP78, an ER molecular chaperone, was downregulated in mouse testes exposed to 500 mg/kg/day DEHP. Testicular p-IRE-1α, p-JNK, and CHOP, three markers of ER stress, were upregulated in mice exposed to 500 mg/kg/day DEHP. These results suggest that pubertal exposure to high doses of DEHP induces germ cell apoptosis partially through initiating ER stress in testes.

Increasing Nrf2 Activity as a Treatment Approach in Neuropsychiatry

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor encoded by NFE2L2. Under oxidative stress, Nrf2 does not undergo its normal cytoplasmic degradation but instead travels to the nucleus, where it binds to a DNA promoter and initiates transcription of anti-oxidative genes. Nrf2 upregulation is associated with increased cellular levels of glutathione disulfide, glutathione peroxidase, glutathione transferases, thioredoxin and thioredoxin reductase. Given its key role in governing the cellular antioxidant response, upregulation of Nrf2 has been suggested as a common therapeutic target in neuropsychiatric illnesses such as major depressive disorder, bipolar disorder and schizophrenia, which are associated with chronic oxidative and nitrosative stress, characterised by elevated levels of reactive oxygen species, nitric oxide and peroxynitrite. These processes lead to extensive lipid peroxidation, protein oxidation and carbonylation, and oxidative damage to nuclear and mitochondrial DNA. Intake of N-acetylcysteine, coenzyme Q₁₀ and melatonin is accompanied by increased Nrf2 activity. N-acetylcysteine intake is associated with improved cerebral mitochondrial function, decreased central oxidative and nitrosative stress, reduced neuroinflammation, alleviation of endoplasmic reticular stress and suppression of the unfolded protein response. Coenzyme Q₁₀, which acts as a superoxide scavenger in neuroglial mitochondria, instigates mitohormesis, ameliorates lipid peroxidation in the inner mitochondrial membrane, activates uncoupling proteins, promotes mitochondrial biogenesis and has positive effects on the plasma membrane redox system. Melatonin, which scavenges mitochondrial free radicals, inhibits mitochondrial nitric oxide synthase, restores mitochondrial calcium homeostasis, deacetylates and activates mitochondrial SIRT3, ameliorates increased permeability of the blood-brain barrier and intestine and counters neuroinflammation and glutamate excitotoxicity.

The latest advances in the reproductive toxicity of microcystin-LR

Microcystin-LR (MC-LR) is an emerging environmental pollutant produced by cyanobacteria that poses a threat to wild life and human health. In recent years, the reproductive toxicity of MC-LR has gained widespread attention, a large number of toxicological studies have filled the gaps in past research and more molecular mechanisms have been elucidated. Hence, this paper reviews the latest research advances on MC-LR-induced reproductive toxicity. MC-LR can damage the structure and function of the testis, ovary, prostate, placenta and other organs of animals and then reduce their fertility. Meanwhile, MC-LR can also be transmitted through the placenta to the offspring causing trans-generational and developmental toxicity including death, malformation, growth retardation, and organ dysfunction in embryos and juveniles. The mechanisms of MC-LR-induced reproductive toxicity mainly include the inhibition of protein phosphatase 1/2 A (PP1/2 A) activity and the induction of oxidative stress. On the one hand, MC-LR triggers the hyperphosphorylation of certain proteins by inhibiting intracellular PP1/2 A activity, thereby activating multiple signaling pathways that cause inflammation and blood-testis barrier destruction, etc. On the other hand, MC-LR-induced oxidative stress can result in cell programmed death via the mitochondrial and endoplasmic reticulum pathways. It is worth noting that epigenetic modifications are also involved in reproductive cell apoptosis, which may be an important direction for future research. Furthermore, this paper proposes for the first time that MC-LR can produce estrogenic effects in animals as an environmental estrogen. New findings and suggestions in this review could be areas of interest for future research.

MCLR induces dysregulation of calcium homeostasis and endoplasmic reticulum stress resulting in apoptosis in Sertoli cells

Microcystins-LR (MCLR) is a potent reproductive system toxin. We have previously shown that MCLR induced endoplasmic reticulum (ER) stress and apoptosis in testis. ER is the main calcium storage site in cells, and its calcium homeostasis plays an important role in the regulation of apoptosis. Hence, in the present study, we have investigated the role of calcium (Ca²⁺) in inducing apoptosis and how it affect the mitochondria and endoplasmic reticulum in TM4 cells. Our study found that MCLR induced an increase in Ca²⁺ concentration in TM4 cells. Compared to the controls, MCLR induced phosphorylation of calmodulin-dependent protein kinase II (CaMKII) which was involved in MAPKs activation, resulting in the induction of mitochondrial apoptosis pathways. Ca²⁺ chelator Bapta-AM partially reversed MCLR-induced apoptosis, confirming the possible involvement of calcium homeostasis disruption after MCLR exposure. Meanwhile, MCLR activated unfolded protein response and activated the ER apoptotic pathway by activating caspase-12. In addition, exposure to MCLR causes mitochondrial defects and increased apoptosis by up-regulating caspase 3 and cytosol cytochrome c expression. Collectively, these results demonstrated that MCLR disturbed calcium homeostasis, which caused ER-mitochondria dysfunction, ultimately promoted cell apoptosis in Sertoli cells.

Antioxidant effects of N-acetylcysteine on the male reproductive system: A systematic review

This study aimed to evaluate the effect of N-acetyl cysteine on the male reproductive system and consensus and classification of data found from previous studies. It is undeniable that N-acetyl cysteine as a powerful antioxidant compound can medicate many diseases such as cardiovascular, kidney, liver and reproductive system disorders. With the increasing environmental pollution that has a direct adverse effect on male fertility, the use of this compound is able to positively function on human fertility health. In this study, we have been collected the main data of scientific articles (1994-2020) about N-acetyl cysteine effects. By searching in the scientific databases of PubMed, Google Scholar, Science Direct, Wiley and Web of Science, related articles were extracted. As a result, all observations have confirmed that N-acetyl cysteine can improve and normalise the spermatogenesis in the male reproduction system.

Ameliorative effects of jamun seed and orange peel extracts on microcystin LR induced alterations in calcitonin cells and parathyroid gland of rats

This study investigated changes in calcitonin cells (C-cells) and parathyroid glands (PTG) induced by microcystin LR (MCLR) exposure to rats and evaluated ameliorative effects of jamun (Syzygium cumini) seed (JSE) and orange (Citrus sinensis) peel (OPE) extracts. Wistar rats were treated as-Group A (control), Group B (MCLR), Group C (MCLR + JSE), Group D (MCLT + OPE), Group E (OPE) and Group F (JSE). Microcystin dose was (10 μg/kg body wt/day whereas OPE and JSE dose was 200 mg/kg body wt/day. Thyroid and PTG were fixed on 15 and 30 days following the treatment. C-cells of treated rats for 15 days with MCLR; MCLR + JSE and MCLR + OPE exhibit degranulation, mitochondrial swelling and prominent RER. In MCLR treated rats few cells completely lack secretory granules. After 30 days MCLR treatment accumulation of secretory granules and degeneration were noticed in C-cells. C-cell nuclear volume (NV) of MCLR, MCLR + JSE and MCLT + OPE treated rats show an increase. In MCLR, MCLR + JSE and MCLR + OPE treated rats PTG exhibit hyperchromatic nuclei, nuclear elongation and increased NV after 15 days. After 30 days MCLR treatment nuclei of PTG become more hyperchromatic, more elongated, show degeneration of nuclei and increase in NV. NV is increased in Group C and Group D. PTG remain unaltered 30 days following treatment with OPE and JSE. Microcystin LR provoke physiological effects on the blood calcium and alterations in C cells and PTG, which cause serious threat to organism. These changes can be protected by JSE and OPE.

Endoplasmic reticulum stress serves an important role in cardiac ischemia/reperfusion injury (Review)

Although acute myocardial infarction is one of the most common fatal diseases worldwide, the understanding of its underlying pathogenesis continues to develop. Myocardial ischemia/reperfusion (I/R) can restore myocardial oxygen and nutrient supply. However, a large number of studies have demonstrated that recovery of blood perfusion after acute ischemia causes reperfusion injury to the heart. With progress made in the understanding of the underlying mechanisms of myocardial I/R and oxidative stress, a novel area of research that merits greater study has been identified, that of I/R-induced endoplasmic reticulum (ER) stress (ERS). Cardiac I/R can alter the function of the ER, leading to the accumulation of unfolded/misfolded proteins. The resulting ERS then induces the activation of signal transduction pathways, which in turn contribute to the development of I/R injury. The mechanism of I/R injury, and the causal relationship between I/R and ERS are reviewed in the present article.

Microcystin-LR exposure decreased the fetal weight of mice by disturbance of placental development and ROS-mediated endoplasmic reticulum stress in the placenta

The placenta is essential for sustaining the growth of the fetus. The aim of this study was to investigate the role of the placenta in MCLR-induced significant reduction in fetal weight, especially the changes in placental structure and function. Pregnant mice were intraperitoneally injected with MCLR (5 or 20 μg/kg) from gestational day (GD) 13 to GD17. The results showed MCLR reduced fetal weight and placenta weight. The histological specimens of the placentas were taken for light and electron microscopy studies. The internal space of blood vessels decreased obviously in the placental labyrinth layer of mice treated with MCLR. After the ultrastructural examination, the edema and intracytoplasmic vacuolization, dilation of the endoplasmic reticulum and corrugation of the nucleus were observed. In addition, maternal MCLR exposure caused a reduction of 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) expression in placentae, a critical regulator of fetal development. Several genes of placental growth factors, such as Vegfα and Pgf and several genes of nutrient transport pumps, such as Glut1 and Pcft were depressed in placentas of MCLR-treated mice, however nutrient transporters Fatp1 and Snat4 were promoted. Moreover, significant increases in malondialdehyde (MDA) revealed the occurrence of oxidative stress caused by MCLR, which was also verified by remarkable decrease in the glutathione levels, total antioxidant capacity (T-AOC) as well as the activity of antioxidant enzymes. Real-time PCR and western blot analysis revealed that GRP78, CHOP, XBP-1, peIF2α and pIRE1 were remarkable increased in placentas of MCLR-treated mice, indicating that endoplasmic reticulum (ER) stress pathway was activated by MCLR. Furthermore, oxidative stress and ER stress consequently triggered apoptosis which contributed to the impairment of placental development. Collectively, these results suggest maternal MCLR exposure results in reduced fetal body weight, which might be associated with ROS-mediated endoplasmic reticulum stress and impairment in placental structure and function.

Plasmon-Enhanced Oxidase-Like Activity and Cellular Effect of Pd-Coated Gold Nanorods

Local surface plasmon resonance (LSPR)-enhanced catalysis has attracted much attention recently. Palladium nanoparticles have been reported to have various nanozyme activities and exhibit promising potentials for biomedical applications. However, as Pd is a poor plasmonic metal, little attention has been paid to its LSPR-regulated nanozyme activity. Herein, by using Au nanorods (AuNRs) as a strong plasmonic core, we coated a thin layer Pd to form a rod-shaped core-shell structure. The obtained Au@PdNRs showed tunable LSPR bands in the near-infrared (NIR) spectral range inheriting from the Au core and yet an exposed Pd surface for catalysis. The oxidase-like activity was investigated in the dark and upon SPR excitation. The plasmon-enhanced activity was observed and was mainly ascribed to the local photothermal effect. Finally, to enhance biocompatibility, mesoporous silica-coated nanorods were used to detect the oxidase-like activity in cells. After being endocytosed by cells, upon plasmon excitation, the oxidase activity of Au@PdNRs could be manifested and lead to higher cytotoxicity and depolarization of mitochondrial membrane potential. Our studies highlight the feasibility of regulating the nanozyme activity of plasmonic nanostructures using their unique NIR plasmonic features with spatiotemporal control.

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.

Molecular characterization of caspase-8-like and its expression induced by microcystin-LR in grass carp (Ctenopharygodon idella)

Caspase-8, an initiator caspase, plays a vital role in apoptosis. In this study, caspase-8-like (named as Cicaspase-8-like), a homologue of caspase-8, was identified in grass carp (Ctenopharygodon idella). The full-length cDNA sequence of CiCaspase-8-like was 1409 bp and contained a 162 bp 5'-UTR, a 239 bp 3'-UTR and a 1008 bp coding sequence. The putative amino acids sequence was 335 residues long, including a large subunit (P20) and a small subunit (P10), but lacking conserved death effector domains. A histidine active site DHSQMDAFVCCVLSHG and a cysteine active-site motif KPKLFFIQACQG were found in P20. Phylogenetic analysis showed that Cicaspase-8-like clustered with the caspase-8 and caspase-8-like of other fish and grouped closely with Carassius auratus caspase-8-like. Quantitative real-time PCR revealed that the Cicaspase-8-like mRNA were expressed constitutively in all tested tissues from healthy grass carp, with high expression level in the blood, spleen, liver and gill, indicating its role in immune reaction. The expression of Cicaspase-8-like mRNA was decreased significantly in the liver because of the stress caused by microcystin-LR (MC-LR) (75 and 100 μg MC-LR/kg BW) at 24 h and 96 h post injection (P < 0.05), but it was increased significantly in grass carp treated with 25 μg MC-LR/kg BW at 24 h (P < 0.05) post injection. Cleaved fragments of Cicaspase-8-like were observed using western blot analysis, and the expression of Cicaspase-8-like protein was increased after MC-LR treatments. Moreover, the expression of both caspase-9 and caspase-3 mRNA increased significantly after treatment with the three doses of MC-LR. TUNEL assay results showed remarkable changes in apoptosis after the MC-LR treatment. These results suggest that Cicaspase-8-like is an important caspase and plays an essential role in MC-LR-induced apoptosis.

Novel curcumin analogue hybrids: Synthesis and anticancer activity

In this study, twenty curcumin analogue hybrids as potential anticancer agents through regulation protein of TrxR were designed and synthesized. Results of anticancer activity showed that 5,7-dimethoxy-3-(3-(2-((1E, 4E)-3-oxo-5-(pyridin-2-yl)penta-1,4-dien-1- yl)phenoxy)propoxy)-2-(3,4,5-trimethoxyphenyl)-4H-chromen-4-one (compound 7d) could induce gastric cancer cells apoptosis by arresting cell cycle, break mitochondria function and inhibit TrxR activity. Meanwhile, western blot revealed that this compound could dramatically up expression of Bax/Bcl-2 ratio and high expression of TrxR oxidation. These results preliminarily show that the important role of ROS mediated activation of ASK1/MAPK signaling pathways by this title compound.