DBP-induced endoplasmic reticulum stress in male germ cells causes autophagy, which has a cytoprotective role against apoptosis in vitro and in vivo

Lead Causes Lipid Droplet Accumulation by Impairing Lysosomal Function and Autophagic Flux in Testicular Sertoli Cells

Lead (Pb) is one of the most common environmental pollutants that negatively impacts male reproductive health. Thus far, the underlying molecular mechanisms of Pb-induced reproductive toxicity are still not well understood. In this study, 64 male ICR mice were given drinking water with Pb (0, 100, 200, and 300 mg/L) for 90 days. We found that exposure to 300 mg/L Pb resulted in reduced sperm quality and elevated autophagy-related protein levels in the mouse testes. Our findings indicate that the Pb hindered the autophagic clearance by impairing the lysosomes' function and then obstructing the fusion of lysosomes and autophagosomes. The autophagy cycle obstruction prevented the lipid droplets from breakdown and led to their accumulation in the Sertoli cells. In turn, the ccytotoxic effects that resulted from the interruption of the autophagy maturation stage, instead of the elongation phase, could be alleviated by either Chloroquine or Bafilomycin A1. Furthermore, exposure to 400 μM Pb initiated the TFE3 nuclear translocation and caused the increased expression of its target genes. Then, the knockdown of TFE3 reduced the formation of the autophagosome. In addition, the use of the antioxidant NAC notably enhanced the autophagic activity and reduced the occurrence of lipid droplets in the Sertoli cells. This study demonstrated that Pb disrupted the autophagic flow, which caused lipid droplet accumulation in the TM4 cells. Consequently, focusing on the maturation stage of autophagy might offer a potential therapeutic approach to alleviate male reproductive toxicity caused by Pb exposure.

Phthalates toxicity in vivo to rats, mice, birds, and fish: A thematic scoping review

Background

Phthalates, a large group of endocrine disruptors, are ubiquitous in the environment and detrimental to human health. This scoping review aimed to summarize the effects of phthalates on laboratory animals relevant to humans, assess toxicity, and analyze mechanisms of toxicity for public health concerns.

Methods

Articles were retrieved from Google Scholar, PubMed, ScienceDirect, and Web of Science search engines. The search used the term "toxicity of phthalates in vivo, animals or birds or fish." Original research articles published between 2010 and 2024 describing in vivo toxicity in rat, mouse, bird, and fish models, were included. Conversely, articles that did not meet the above criteria were excluded from this scoping review. Two authors independently extracted data using data extraction tools based on themes, while a third arbitrated if consensus was not met. A senior researcher developed the themes, which were further refined through discussions. Data analysis involved quantitative (percentage of studies) and qualitative (content analysis) methods.

Results

Of the 8180 articles screened, 153 met the inclusion criteria. Most of them were published after 2015 (74.50 %). The scoping review showed that DEHP (56.20 %) and DBP (21.57 %) were the most studied phthalates followed by BBP, DiBP, DMP, DEP, BBOP, and DiNP. Scarce data were available on DnOP, DPHP, DPeP, DUDP, DTDP, DMiP, and DiOP. Interestingly, studies of combinations of two or more phthalates were also present. The main laboratory animals employed were rats (48.37 %) and mice (39.87 %), while the least studied were birds (5.22 %) and fish (6.53 %). Most studies related to testicular toxicity (37.60 %), hepatotoxicity (23.53 %), and ovarian toxicity (18.30 %) investigations, while the rest consisted of neurotoxicity (6.88 %), renal toxicity (6.53 %), and thyroid toxicity studies (4.57 %). Studies focused on oxidative stress (34.64 %), apoptosis (22.22 %), steroid hormone deprivation (20.26 %), lipid metabolism disorder (11.76 %), and immunotoxicity (5.88 %) as mechanisms of toxicity. The most commonly used techniques were H&E, RT-qPCR, ROS assay, WB, IHC, ELISA, RIA, TUNEL, TEM, IFM, FCM, and RNA-seq.

Conclusions

DEHP and DBP are the most toxic and studied phthalates, while BBP, DiNP, DiBP, DiDP, BBOP, DMP, and DiOP and their combinations require more accurate studies to confirm their toxic effects on human health and mechanisms of action. These will assist policymakers in adopting strategies to minimize public exposure and adverse effects.

Mixtures of phthalates disrupt expression of genes related to lipid metabolism and peroxisome proliferator-activated receptor signaling in mouse granulosa cells

Phthalates are a class of known endocrine-disrupting chemicals that are found in common everyday products. Several studies associate phthalate exposure with detrimental effects on ovarian function, including growth and development of the follicle and production of steroid hormones. We hypothesized that dysregulation of the ovary by phthalates may be mediated by phthalate toxicity towards granulosa cells, a major cell type in ovarian follicles responsible for key steps of hormone production and nourishing the developing oocyte. To test the hypothesis that phthalates target granulosa cells, we harvested granulosa cells from adult CD-1 mouse ovaries and cultured them for 96 h in vehicle control, a phthalate mixture, or a phthalate metabolite mixture (0.1 to 100 μg/ml). After culture, we measured metabolism of the phthalate mixture into monoester metabolites by the granulosa cells, finding that granulosa cells do not significantly contribute to ovarian metabolism of phthalates. Immunohistochemistry of phthalate metabolizing enzymes in whole ovaries confirmed that these enzymes are not strongly expressed in granulosa cells of antral follicles and that ovarian metabolism of phthalates likely occurs primarily in the stroma. RNA sequencing of treated granulosa cells identified 407 differentially expressed genes, with overrepresentation of genes from lipid metabolic processes, cholesterol metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Expression of significantly differentially expressed genes related to these pathways was confirmed using qPCR. Our results agree with previous findings that phthalates and phthalate metabolites have different effects on the ovary, but both interfere with PPAR signaling in granulosa cells.

Effect of endocrine-disrupting chemicals on the expression of a calcium ion channel receptor (ryanodine receptor) in the mud crab (Macrophthalmus japonicus)

Endocrine-disrupting chemicals (EDCs) are toxic pollutants generated by artificial activities. Moreover, their hormone-like structure induces disturbances, such as mimicking or blocking metabolic activity. Previous studies on EDCs have focused on the adverse effect of the endocrine system in vertebrates, with limited investigations conducted on ion channels in invertebrates. Thus, in this study, we investigated the potential adverse effects of exposure to bisphenol-A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) at the molecular level on the ryanodine receptor (RyR), a calcium ion channel receptor in Macrophthalmus japonicus. In the phylogenetic analysis, the RyR amino acid sequences in M. japonicus clustered with those in the Crustacean and formed separated branches for RyR in insects and mammals. When exposed to 1 μg L-1 BPA, a significant increase in RyR mRNA expression was observed in the gills on day 1, although a similar level to the control group was observed from day 4 to day 7. However, the RyR expression due to DEHP exposure decreased on days 1 and 4, although it increased on day 7 following exposure to 10 μg L-1. The RyR expression pattern in the hepatopancreas increased for up to 4 days, depending on the BPA concentration. However, there was a tendency for the expression to decrease gradually after the statistical significance increased during the early stage of DEHP exposure (D1). Hence, the transcriptional alterations in the M. japonicus RyR gene observed in the study suggest that exposure toxicities to EDCs, such as BPA and DEHP, have the potential to disrupt calcium ion channel signaling in the gills and hepatopancreas of M. japonicus crabs.

Mitigation of benzyl butyl phthalate toxicity in male germ cells with combined treatment of parthenolide, N-acetylcysteine, and 3-methyladenine

Benzyl butyl phthalate (BBP) is a widely used plasticizer that poses various potential health hazards. Although BBP has been extensively studied, the direct mechanism underlying its toxicity in male germ cells remains unclear. Therefore, we investigated BBP-mediated male germ cell toxicity in GC-1 spermatogonia (spg), a differentiated mouse male germ cell line. This study investigated the impact of BBP on reactive oxygen species (ROS) generation, apoptosis, and autophagy regulation, as well as potential protective measures against BBP-induced toxicity. A marked dose-dependent decrease in GC-1 spg cell proliferation was observed following treatment with BBP at 12.5 μM. Exposure to 50 μM BBP, approximating the IC50 of 53.9 μM, markedly increased cellular ROS generation and instigated apoptosis, as evidenced by augmented protein levels of both intrinsic and extrinsic apoptosis-related markers. An amount of 50 μM BBP induced marked upregulation of autophagy regulator proteins, p38 MAPK, and extracellular signal-regulated kinase and substantially downregulated the phosphorylation of key kinases involved in regulating cell proliferation, including phosphoinositide 3-kinase, protein kinase B, mammalian target of rapamycin (mTOR), c-Jun N-terminal kinase. The triple combination of N-acetylcysteine, parthenolide, and 3-methyladenine markedly restored cell proliferation, decreased BBP-induced apoptosis and autophagy, and restored mTOR phosphorylation. This study provides new insights into BBP-induced male germ cell toxicity and highlights the therapeutic potential of the triple inhibitors in mitigating BBP toxicity.

Elucidating the mechanisms and mitigation strategies for six-phthalate-induced toxicity in male germ cells

Phthalate esters (PAEs) are primary plasticizers and endocrine-disrupting chemicals (EDCs) that are extensively used in numerous everyday consumer products. Although the adverse effects of single PAEs have been studied, our understanding of the effect of multiple phthalate exposure on male germ cell vitality remains limited. Therefore, this study aimed to investigate the collective effects of a mixture of PAEs (MP) comprising diethyl-, bis (2-ethylhexyl)-, dibutyl-, diisononyl-, diisobutyl-, and benzyl butyl-phthalates in the proportions of 35, 21, 15, 15, 8, and 5%, respectively, on differentiated male germ cells using GC-1 spermatogonia (spg) cells. As a mixture, MP substantially hindered GC-1 spg cell proliferation at 3.13 μg/mL, with a half-maximal inhibitory concentration of 16.9 μg/mL. Treatment with 25 μg/mL MP significantly induced reactive oxygen species generation and promoted apoptosis. Furthermore, MP activated autophagy and suppressed phosphorylation of phosphoinositide 3-kinase, protein kinase B, and mammalian target of rapamycin (mTOR). The triple inhibitor combination treatment comprising parthenolide, N-acetylcysteine, and 3-methyladenine effectively reversed MP-induced GC-1 spg cell proliferation inhibition, mitigated apoptosis and autophagy, and restored mTOR phosphorylation. This study is the first to elucidate the mechanism underlying MP-induced male germ cell toxicity and the restoration of male germ cell proliferation mediated by chemical inhibitors. Therefore, it provides valuable insights into the existing literature by proposing a combinatorial toxicity mitigation strategy to counteract male germ cell toxicity induced by various EDCs exposure.

Mixtures of phthalates disrupt expression of genes related to lipid metabolism and peroxisome proliferator-activated receptor signaling in mouse granulosa cells

Phthalates are a class of known endocrine disrupting chemicals that are found in common everyday products. Several studies associate phthalate exposure with detrimental effects on ovarian functions, including growth and development of the follicle and production of steroid hormones. We hypothesized that dysregulation of the ovary by phthalates may be mediated by phthalate toxicity towards granulosa cells, a major cell type in ovarian follicles responsible for key steps of hormone production and nourishing the developing oocyte. To test the hypothesis that phthalates target granulosa cells, we harvested granulosa cells from adult CD-1 mouse ovaries and cultured them for 96 hours in vehicle control, a phthalate mixture, or a phthalate metabolite mixture (0.1-100 μg/mL). After culture, we measured metabolism of the phthalate mixture into monoester metabolites by the granulosa cells, finding that granulosa cells do not significantly contribute to ovarian metabolism of phthalates. Immunohistochemistry of phthalate metabolizing enzymes in whole ovaries confirmed that these enzymes are not strongly expressed in granulosa cells of antral follicles and that ovarian metabolism of phthalates likely occurs primarily in the stroma. RNA sequencing of treated granulosa cells identified 407 differentially expressed genes, with overrepresentation of genes from lipid metabolic processes, cholesterol metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Expression of significantly differentially expressed genes related to these pathways were confirmed using qPCR. Our results agree with previous findings that phthalates and phthalate metabolites have different effects on the ovary and interfere with PPAR signaling in granulosa cells.

Melatonin alleviates di-butyl phthalate (DBP)-induced ferroptosis of mouse leydig cells via inhibiting Sp2/VDAC2 signals

As one of the endocrine-disrupting chemicals (EDCs), dibutyl phthalate (DBP) has been extensively used in industry. DBP has been shown to cause damage to Leydig cells, yet its underlying mechanism remains elusive. In this study, we show that DBP induces ferroptosis of mouse Leydig cells via upregulating the expression of Sp2, a transcription factor. Also, Sp2 is identified to promote the transcription of Vdac2 gene by binding to its promoter and subsequently involved in DBP-induced ferroptosis of Leydig cells. In addition, DBP is proved to induce ferroptosis via inducing oxidative stress, while inhibition of oxidative stress by melatonin alleviates DBP-induced ferroptosis and upregulation of Sp2 and VDAC2. Taken together, our findings demonstrate that melatonin can alleviate DBP-induced ferroptosis of mouse Leydig cells via inhibiting oxidative stress-triggered Sp2/VDAC2 signals.

Curcumin attenuates diphenyl phosphate-induced apoptosis in GC-2spd(ts) cells through activated autophagy via the Nrf2/P53 pathway

Diphenyl phosphate (DPhP) is one of the frequently used derivatives of aryl phosphate esters and is used as a plasticizer in industrial production. Like other plasticizers, DPhP is not chemically bound and can easily escape into the environment, thereby affecting human health. DPhP has been associated with developmental toxicity, reproductive toxicity, neurodevelopmental toxicity, and interference with thyroid homeostasis. However, understanding of the underlying mechanism of DPhP on the reproductive toxicity of GC-2spd(ts) cells remains limited. For the first time, we investigated the effect of DPhP on GC-2spd(ts) cell apoptosis. By decreasing nuclear factor erythroid-derived 2-related factor (Nrf2)/p53 signaling, DPhP inhibited autophagy and promoted apoptosis. DPhP reduced total antioxidant capacity and nuclear Nrf2 and its downstream target gene expression. In addition, we investigated the protective effects of Curcumin (Cur) against DPhP toxicity. Cur attenuated the DPhP-induced rise in p53 expression while increasing Nrf2 expression. Cur inhibited DPhP-induced apoptosis in GC-2spd(ts) cells by activating autophagy via Nrf2/p53 signaling. In conclusion, our study provides new insights into the reproductive toxicity hazards of DPhP and demonstrates that Cur is an important therapeutic agent for alleviating DPhP-induced reproductive toxicity by regulating Nrf2/p53 signaling.

Diisobutyl phthalate (DiBP)-induced male germ cell toxicity and its alleviation approach

Diisobutyl phthalate (DiBP) is a commonly used plasticizer in manufacturing consumer and industrial products to improve flexibility and durability. Despite of the numerous studies, however, the direct mechanism underlying the male reproductive damage of DiBP is poorly understood. In this study, we investigated the male germ cell toxicity of DiBP using GC-1 spermatogonia (spg) cells. Our results indicated that DiBP exposure causes oxidative stress and apoptosis in GC-1 spg cells. In addition, DiBP-derived autophagy activation and down-regulation of phosphoinositide 3-kinase (PI3K)-AKT and extracellular signal-regulated kinase (ERK) pathways further inhibited GC-1 spg cell proliferation, indicating that DiBP can instigate male germ cell toxicity by targeting several pathways. Importantly, a combined treatment of parthenolide, N-acetylcysteine, and 3-methyladenine significantly reduced DiBP-induced male germ cell toxicity and restored proliferation. Taken together, the results of this study can provide valuable information to the existing literature by enhancing the understanding of single phthalate DiBP-derived male germ cell toxicity and the therapeutic interventions that can mitigate DiBP damage.

Cypermethrin induces endoplasmic reticulum stress and autophagy, leads to testicular dysfunction

Cypermethrin is a pyrethroid insecticide that is used to control insects and protect crops. However, pesticide residues and their possible toxicity to non-target animals such as mammals are concerning. Although cypermethrin reduces testosterone levels, the molecular mechanisms involved, particularly those regarding endoplasmic reticulum (ER) stress and autophagy regulation, have not yet been fully elucidated. In this study, we demonstrated testicular toxicity of cypermethrin in mouse Leydig (TM3) and Sertoli (TM4) cells. Cypermethrin suppresses TM3 and TM4 cell proliferation and induces apoptosis. Moreover, it interrupted calcium homeostasis in intracellular organelles and dissipated mitochondrial membrane polarization in mouse testicular cells. Moreover, we verified the accumulation of Sqstm1/p62 protein in the mitochondria of cypermethrin-treated TM3 and TM4 cells. Furthermore, we confirmed that cypermethrin activated autophagy and the ER stress pathway in a time-dependent manner in both cell types. Finally, we determined that cypermethrin downregulated testicular function-related genes, steroidogenesis, and spermatogenesis in mouse testis cells. Therefore, we conclude that cypermethrin regulates autophagy and ER stress, leading to testicular dysfunction.

Adverse cardiovascular effects of long-term exposure to diethyl phthalate in the rat aorta

Phthalates are classified as priority environmental pollutants, since they are ubiquitous in the environment, have endocrine disrupting properties and can contribute to impaired health. Used primarily in personal care products and excipients for pharmaceuticals, diethyl phthalate (DEP) is a short-chain alkyl phthalate that has been linked to decreased blood pressure, glucose tolerance, and increased gestational weight gain in humans, while in animals it has been associated with atherosclerosis and metabolic syndrome. Although all these findings are related to risk factors or cardiovascular diseases, DEP's vascular impacts still need to be clarified. Thus, performing ex vivo and in vitro experiments, we aimed to understand the vascular DEP effects in rat. To evaluate the vascular contractility of rat aorta exposed to different doses of DEP (0.001-1000 μM), an organs bath was used; and resorting to a cell line of the rat aorta vascular smooth muscle, electrophysiology experiments were performed to analyse the effects of a rapid (within minutes with no genomic effects) and a long-term (24 h with genomic effects) exposure of DEP on the L-type Ca2+ current (ICa,L), and the expression of several genes related with the vascular function. For the first time, vascular electrophysiological properties of an EDC were analysed after a long-term genomic exposure. The results show a hormetic response of DEP, inducing a Ca2+ current inhibition of the rat aorta, which may be responsible for impaired cardiovascular electrical health. Thus, these findings contribute to a greater scientific knowledge about DEP's effects in the cardiovascular system, specifically its implications in the development of electrical disturbances like arrhythmias and its possible mechanisms.

Polystyrene nanoplastics aggravated dibutyl phthalate-induced blood-testis barrier dysfunction via suppressing autophagy in male mice

Nanoplastics (NPs) frequently cause adverse health effects by transporting organic pollutants such as dibutyl phthalate (DBP) into organisms by utilizing their large specific surface area, large surface charge, and increased hydrophobicity. However, the effects of NPs combined with DBP on the reproductive systems of mammals are still unclear. The present investigation involved the administration of polystyrene NPs (PS-NPs) to BALB/c mice via gavage, with a size of 100 nm and at doses of 5 mg/kg/day or 50 mg/kg/day, along with DBP at a dose of 0.5 mg/kg/day, or a combination of PS-NPs and DBP, for 30 days, to assess their potential for reproductive toxicity. The co-exposure of mice to PS-NPs and DBP resulted in a significant increase in reproductive toxicities compared to exposure to PS-NPs or DBP alone. This was demonstrated by a marked decrease in sperm quality, significant impairment of spermatogenesis, and increased disruption of the blood-testis barrier (BTB). Furthermore, a combination of in vivo and in vitro investigations were conducted to determine that the co-exposure of DBP and PS-NPs resulted in a noteworthy reduction in the expressions of tight junction proteins (ZO-1 and occludin). Moreover, the in vitro findings revealed that monobutyl phthalate (MBP, the active metabolite of DBP, 0.5 μg/mL) and PS-NPs (30 μg/mL or 300 μg/mL) inhibited autophagy in Sertoli cells, thereby increasing the expression of matrix metalloproteinases (MMPs). The study found that PS-NPs and DBP co-exposure caused harmful effects in male reproductive organs by disrupting BTB, which may be alleviated by reactivating autophagy. The paper's conclusions provided innovative perspectives on the collective toxicities of PS-NPs and other emerging pollutants.

Ferroptosis: a novel regulated cell death participating in cellular stress response, radiotherapy, and immunotherapy

BACKGROUND

Ferroptosis is a regulated cell death mode triggered by iron-dependent toxic membrane lipid peroxidation. As a novel cell death modality that is morphologically and mechanistically different from other forms of cell death, such as apoptosis and necrosis, ferroptosis has attracted extensive attention due to its association with various diseases. Evidence on ferroptosis as a potential therapeutic strategy has accumulated with the rapid growth of research on targeting ferroptosis for tumor suppression in recent years.

METHODS

We summarize the currently known characteristics and major regulatory mechanisms of ferroptosis and present the role of ferroptosis in cellular stress responses, including ER stress and autophagy. Furthermore, we elucidate the potential applications of ferroptosis in radiotherapy and immunotherapy, which will be beneficial in exploring new strategies for clinical tumor treatment.

RESULT AND CONCLUSION

Based on specific biomarkers and precise patient-specific assessment, targeting ferroptosis has great potential to be translated into practical new approaches for clinical cancer therapy, significantly contributing to the prevention, diagnosis, prognosis, and treatment of cancer.

DBP induced autophagy and necrotic apoptosis in HepG2 cells via the mitochondrial damage pathway

Phthalate esters (PAEs) are widely present in human tissues and pose significant health risks. In this study, HepG2 cells were treated with 0.0625, 0.125, 0.25, 0.5 and 1 mM Dibutyl phthalate (DBP) for 48 h to investigate mitochondrial toxicity. The results showed that DBP caused mitochondrial damage, autophagy, apoptosis and necroptosis; Transcriptomics analysis identified that MAPK and PI3K were significant factors in the cytotoxic changes induced by DBP; N-Acetyl-L-cysteine (NAC), SIRT1 activator, ERK inhibitor, p38 inhibitor and ERK siRNA treatments counteracted the changes of SIRT1/PGC-1α and Nrf2 pathway-related proteins, autophagy and necroptotic apoptosis proteins induced by DBP. While PI3K and Nrf2 inhibitors exacerbated the changes in SIRT1/PGC-1α, Nrf2-associated proteins and autophagy and necroptosis proteins induced by DBP. In addition, the autophagy inhibitor 3-MA alleviated the increase in DBP-induced necroptosis proteins. These results suggested that DBP-induced oxidative stress activated the MAPK pathway, inhibited the PI3K pathway, which in turn inhibited the SIRT1/PGC-1α pathway and Nrf2 pathway, thereby causing cell autophagy and necroptosis.

Effects of single or combined exposure to bisphenol A and mono(2-ethylhexyl)phthalate on oxidant/antioxidant status, endoplasmic reticulum stress, and apoptosis in HepG2 cell line

Endocrine disrupting chemicals (EDCs) may affect many biological processes like growth and stress response. Bisphenol A (BPA) is a plasticizer that is used to harden plastics and polycarbonates. Phthalates are used to add flexibility to polyvinyl chloride containing plastics. The main metabolite of di(2-ethylhexyl) phthalate (DEHP) is mono(2-ethylhexyl) phthalate (MEHP) and it is even more toxic than the parent compound. Humans are usually exposed to these chemicals in mixtures by different routes starting from fetal period. However, there are not many studies in literature that investigate the combined effects of these chemicals. The aim of this study is to investigate toxic effects of BPA and/or MEHP on HepG2 cell line. We have evaluated cytotoxicity, cytomorphological, apoptotic changes, oxidative stress, oxidant/antioxidant status alterations, and endoplasmic reticulum (ER) stress. Combined exposure to BPA and MEHP caused alterations in oxidant/antioxidant status and ER stress marker proteins in both cytoplasmic and nuclear cellular fractions. We can suggest that combined exposure to EDCs may cause serious toxicological outcomes and more mechanistic studies are needed to determine the combined toxic effects.

Autophagy: A Double-Edged Sword in Male Reproduction

Autophagy, an evolutionarily conserved cell reprogramming mechanism, exists in all eukaryotic organisms. It is a fundamental and vital degradation/recycling pathway that removes undesirable components, such as cytoplasmic organelles, misfolded proteins, viruses, and intracellular bacteria, to provide energy and essential materials for organisms. The success of male reproduction depends on healthy testes, which are mainly composed of seminiferous tubules and mesenchyme. Seminiferous tubules are composed of Sertoli cells (SCs) and various germ cells, and the main functional part of mesenchyme are Leydig cells (LCs). In recent years, a large amount of evidence has confirmed that autophagy is active in many cellular events associated with the testes. Autophagy is not only important for testicular spermatogenesis, but is also an essential regulatory mechanism for the ectoplasmic specialization (ES) integrity of SCs, as well as for the normal function of the blood-testes barrier (BTB). At the same time, it is active in LCs and is crucial for steroid production and for maintaining testosterone levels. In this review, we expanded upon the narration regarding the composition of the testes; summarized the regulation and molecular mechanism of autophagy in SCs, germ cells, and LCs; and concluded the roles of autophagy in the process of spermatogenesis and testicular endocrinology. Through integrating the latest summaries and advances, we discuss how the role of autophagy is a double-edged sword in the testes and may provide insight for future studies and explorations on autophagy in male reproduction.

Interaction between apoptosis and autophagy in testicular function

Several processes including oxidative stress, apoptosis, inflammation and autophagy are related to testicular function. Recent studies indicate that a crosstalk between apoptosis and autophagy is essential in regulating testicular function. Autophagy and apoptosis communicate with each other in a complex way, allowing them to work for or against each other in testicular cell survival and death. Several xenobiotics especially endocrine-disrupting chemicals (EDCs) have caused reproductive toxicity because of their potential to modify the rate of autophagy and trigger apoptosis. Therefore, the purpose of the present review was to shed light on how autophagy and apoptosis interact together in the testis.

Dibutyl phthalate-induced oxidative stress and apoptosis in swine testis cells and therapy of naringenin via PTEN/PI3K/AKT signaling pathway

Dibutyl phthalate (DBP) is a phthalic acid ester (PAE) that has posed a health hazard to the organisms. Naringenin (NRG) is a flavanone compound that has shown protection against several environmental chemicals through suppression of oxidative stress and activation of phosphatidylinositol 3-kinase/threonine kinase (PI3K/AKT) signaling pathway. Herein, swine testis (ST) cells were treated with 1.8 μM of DBP or/and 25.39 nM of NRG for 24 h, we described the discovery path of NRG inhibition on apoptosis in DBP-exposed ST cells through targeting phosphatase and tensin homologue deleted on chromosome 10 (PTEN). We first found that the anti-apoptosis effect of NRG is dependent on mitochondrial pathway through flow cytometry and related gene/protein expression, and then we detected PI3K/AKT pathway-related gene/protein expression, and established a computational docking assay between NRG and PTEN. We found that NRG specifically binds to three basic residues (His93, Lys125, Lys128) of P loop in PTEN, as well as phosphatase domains (Asp92, His93, Cys124, Lys125, Ala126, Lys128, and Arg130) in active dephosphorylation pockets, thereby reducing PTEN level and activating PI3K/AKT signaling pathway, and further inhibiting oxidative stress and mitochondrial pathway apoptosis. Taken together, our results push forward that NRG deserves further attention as a potential antagonistic therapy against DBP through targeting PTEN to inhibit oxidative stress and activate PI3K/AKT signaling pathway.

BTC as a Novel Biomarker Contributing to EMT via the PI3K-AKT Pathway in OSCC

Purpose: Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumors of the head and neck, while metastasis is the main cause of OSCC-related death. There is an urgent need to explore novel prognostic biomarkers and identify biological targets related to metastasis in OSCC treatment.

Methods: Analysis of differential expression was performed using datasets in The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Immunohistochemistry (IHC) was conducted to assess the expression of betacellulin (BTC) in OSCC. SCC4 and CAL27 cells were used for in vitro experiments, in which CCK-8, transwell assays, and wounding healing assays were performed to verify the biological functions of BTC. The role of BTC in EMT was analyzed by EMT score and Western blot.

Results: Through the analysis of the mRNA expression profile data from TCGA database in OSCC, we found that only low expression of BTC was significantly correlated with a poor prognosis in OSCC patients. The results of IHC assays and TCGA databases showed that the expression level of BTC was related to the tumor stage, histological grade, and metastasis status. In vitro analysis showed that overexpression of BTC significantly suppressed the proliferation and migration of OSCC cells. Furthermore, we confirmed that BTC could affect EMT through the PI3K-AKT signaling pathway.

Conclusion: The overexpression of BTC suppresses the proliferation, migration, and EMT of OSCC cells via the PI3K-AKT pathways, leading to a better prognosis in OSCC. BTC may be used as a novel molecular marker to assess the prognosis of OSCC patients.

Endocrine-Disrupting Chemicals and Their Adverse Effects on the Endoplasmic Reticulum

There is growing concern regarding the health and safety issues of endocrine-disrupting chemicals (EDCs). Long-term exposure to EDCs has serious adverse health effects through both hormone-direct and hormone-indirect ways. Accordingly, some EDCs can be a pathogen and an inducer to the susceptibility of disease, even if they have a very low affinity on the estrogen receptor, or no estrogenic effect. Endoplasmic reticulum (ER) stress recently attracted attention in this research area. Because ER and ER stress could be key regulators of the EDC’s adverse effects, such as the malfunction of the organ, as well as the death, apoptosis, and proliferation of a cell. In this review, we focused on finding evidence which shows that EDCs could be a trigger for ER stress and provide specific examples of EDCs, which are known to cause ER stress currently.

Busulfan Suppresses Autophagy in Mouse Spermatogonial Progenitor Cells via mTOR of AKT and p53 Signaling Pathways

In testis, a rare undifferentiated germ cell population with the capacity to regenerate robustly and support spermatogenesis, is defined as spermatogonial progenitor cells (SPCs) population. As a widely used drug for tumor therapy or bone marrow transplantation, busulfan has a severe side effect on SPCs population and causes a consequent infertility. Recently, accumulating evidence revealed the protective role of autophagy in stem cell maintenance under exogenous stress. To better understand the role of autophagy in SPCs fates, we investigated the potential function of autophagy in SPCs under busulfan stress, and found that treatment of busulfan induced the formation of autophagic vesicles and autophagosomes in mouse SPCs. Subsequently, a connection of autophagy and SPCs maintenance and survival was demonstrated in a dose-dependent manner. Moreover, mTOR was identified as an essential factor for autophagy in SPCs with a complicated mechanism: (1) mTOR is phosphorylated by AKT to activate its target genes, p70s6 kinase, resulting in the inhibition of autophagy during short-term busulfan treatment. (2) mTOR mediates autophagy with p53 together, to regulate the fate of SPCs. Collectively, observations from this study indicate that moderate autophagy effectively protects SPCs from the stress of chemotherapy, which may provide an important hint for fertility protection in clinic.

USP15 participates in DBP-induced testicular oxidative stress injury through regulating the Keap1/Nrf2 signaling pathway

Di-n-butylphthalate (DBP) has been listed as an environmental priority pollutant in China due to its distinct biotoxicity. Epidemiological studies have shown that exposure to DBP is closely related to a series of congenital and acquired defects in the male reproductive system. The oxidative stress injury caused by DBP plays an important role in these defects. Previous studies have demonstrated that the Keap1/Nrf2 antioxidative pathway plays a protective role in DBP-induced oxidative stress injury. However, the further molecular regulation mechanism of the activation of Nrf2 pathway remains unclear. Here, we demonstrate that DBP caused testicular oxidative stress injury and Nrf2 pathway was activated in response to the injury in vivo and in vitro. Moreover, we validated that reduced level of USP15 attenuates DBP-induced oxidative stress injury through restraining the ubiquitylation and degradation of Nrf2. Notably, USP15 is confirmed as a target of miR-135b-5p and miR-135b-5p mediated inhibition of USP15 is involved in the DBP-induced oxidative stress injury. Collectively, these findings indicated that decreased level of USP15 functions a significant protective effect on the oxidative stress injury of testis caused by DBP via regulating the Keap1/Nrf2 signaling pathway.

Binding and detoxification ability of lactobacillus acidophilus towards di-n-butyl phthalate: Change of MAPK pathway in Caco-2 cell model

Di-n-butyl phthalate (DBP), a common compound of phthalates, can pose a risk to humans as a contaminant in the food industry. At present, the molecular mechanism of gene and protein toxicity caused by DBP in human cells is unclear. This in vitro study investigated the potential of inactivated Lactobacillus acidophilus NCFM in alleviating the damage caused by DBP in Caco-2 cells. According to the results from transcriptome and proteome analyses, the Caco-2 cells treated by DBP was resulted finally endoplasmic reticulum stress and mitochondrial oxidative damage. The most important differentially expressed genes and proteins involved in Caco-2 cells treated with NCFM to relieve DBP's cytotoxicity were TNF, NF-κB, CREB, P21, GADD45, FOS and CASP3. The molecular mechanism of DBP toxicity alleviated by strain NCFM was involved the MAPK pathway, via DBP bind to strain NCFM and avoid the activation of TNF receptor by DBP, so down-regulated the NF-κB, CREB, P21, GADD45, and CASP3, relieving the apoptosis of Caco-2 cells. Overall, our data provide new insights into detoxification of phthalate by using Lactobacillus. SIGNIFICANCE: Here we sequenced and assembled the transcriptome from Caco-2 cells which were treated with 4 groups: Control, DBP, strain NCFM, and strain NCFM+DBP groups, and combined it with proteome to characterize DBP detoxification genes/proteins through multiomics analysis. The cell viability in DBP treated groups were significantly increased by NCFM strain, indicating NCFM strain has the ability to alleviate the cytotoxicity of DBP via their binding ability with toxins. Furthermore, the results of transcriptome and proteome analysis showed that the signaling pathway of strain NCFM can alleviate DBP toxicity through MAPK pathway, and the potential biomarkers were identified too. This research may provided new information for developing new detoxification strategies for DBP.

Toxicity assessment of dimethyl carbonate following 28 days repeated inhalation exposure

Dimethyl carbonate (DMC) has been used as a reagent in methylation reactions, can be used as paints, coatings, and adhesives, and is a chemical that is being used increasing, which poses a health hazard to workers who handle it. So, the toxic reactions of F344 rats with inhalation exposure to 600, 1600, and 5000 ppm concentrations for 6 hours, 5 days a week, 4 weeks was evaluated. During the exposure period, general signs were observed, body weight and food consumption were measured, and hematologic and blood biochemical tests, organ weight measurements, necropsy, and histopathological examination were performed after the end of exposure. During the exposure period, dimethyl carbonate was exposed to an average of 599.26±31.40, 1614.64±80.79 and 5106.83±297.13 ppm in the chambers of the T1, T2 and T3 test groups, respectively. During the test period, general signs, weight change, food consumption, organ weight measurement, necropsy, and histopathological examination did not show any effects related to exposure to the test substance. However, as a result of blood and blood biochemical tests, an increase in AST, ALP, APTT, and PT levels was observed. From these results, it is judged that liver is the target organ when repeated inhalation exposure of dimethyl carbonate, the test substance, for 4 weeks, and the exposure-related effects of the test substance were observed at PT and ALP levels up to 600 ppm exposure concentration, but NOEC (No Observed Effect Concentration) was determined to be less than 600 ppm because it was not judged as an adverse effect.

Contextualizing Autophagy during Gametogenesis and Preimplantation Embryonic Development

Mammals face environmental stressors throughout their lifespan, which may jeopardize cellular homeostasis. Hence, these organisms have acquired mechanisms to cope with stressors by sensing, repairing the damage, and reallocating resources to increase the odds of long-term survival. Autophagy is a pro-survival lysosome-mediated cytoplasm degradation pathway for organelle and macromolecule recycling. Furthermore, autophagy efflux increases, and this pathway becomes idiosyncratic depending upon developmental and environmental contexts. Mammalian germ cells and preimplantation embryos are attractive models for dissecting autophagy due to their metastable phenotypes during differentiation and exposure to varying environmental cues. The aim of this review is to explore autophagy during mammalian gametogenesis, fertilization and preimplantation embryonic development by contemplating its physiological role during development, under key stressors, and within the scope of assisted reproduction technologies.

Pentoxifylline improves the survival of spermatogenic cells via oxidative stress suppression and upregulation of PI3K/AKT pathway in mouse model of testicular torsion-detorsion

Testicular torsion-detorsion results in enhanced formation of free radicals which contribute to the pathophysiology of testicular tissue damage. Recent reports have identified protective role of pentoxifylline (PTX) against free radicals. Thus, we determined the protective effect of pentoxifylline against testicular damage in mouse model of testicular torsion-detorsion.

Twenty (6 weeks old) male mice were divided into 4 groups of 5 animals each namely: Control (sham operated group), T1 (Torsion-detosion + single dose 100 mg/kg PTX, T2 (torsion-detorsion + 20 mg/kg PTX for 2 weeks and T/D (torsion-detorsion only). Animals in T1, T2 and T/D groups underwent 2 h of testicular torsion with the left testes rotated 720° (clockwisely) followed by 30 min of detorsion. After detorsion, drug administration was done intraperitoneally. The left testes of all the animals were excised on the 35th day after torsion-detortion for histopathological and biochemical assay. Histomorphological analysis of the seminiferous tubules showed that there were significant increase (P < 0.01 or 0.05) in the mean seminiferous tubule diameter, Johnson score and germ cells of animals in Control and T1 compared to T2 and T/D with no significant difference (P > 0.05) in testes weight, sertoli, leydig and myoid cells in all groups. IHC results showed significant increase (P < 0.01 or 0.05) in id4 and scp3 protein markers in Control, T1 and T2 compared to T/D. Oxidative stress analysis revealed that Pentoxifylline significantly increased (P < 0.01 or 0.05) the level of SOD, catalase, mRNA expression of akt and pi3k genes but significantly suppress (P < 0.01 or 0.05) MDA and Caspase-3 level in Control, T1 and T2 compared to T/D. Pentoxifylline could be used as an adjunct therapy to surgery in the treatment of torsion-detorsion related testicular injury, However, Further studies are needed to evaluate the effects of pentoxifylline on testicular torsion.

Dibutyl phthalate rapidly alters calcium homeostasis in the gills of Danio rerio

This study investigates the impacts of exposure to an environment Ca²⁺ challenge and the mechanism of action of dibutyl phthalate (DBP) on Ca²⁺ influx in the gills of Danio rerio. In vitro profile of ⁴⁵Ca²⁺ influx in gills was verified through the basal time-course. Fish were exposed to low, normal and high Ca²⁺ concentrations (0.02, 0.7 and 2 mM) for 12 h. So, gills were morphologically analysed and ex vivo⁴⁵Ca²⁺ influx at 30 and 60 min was determined. For the in vitro studies, gills were treated for 60 min with DBP (1 pM, 1 nM and 1 μM) with/without blockers/activators of ionic channels, Ca²⁺ chelator, inhibitors of ATPases, ionic exchangers and protein kinase C to study the mechanism of DBP-induced ⁴⁵Ca²⁺ influx. Exposure to high environmental Ca²⁺ augmented ⁴⁵Ca²⁺ influx when compared to fish exposed to normal and low Ca²⁺ concentrations. Additionally, histopathological changes were observed in the gills of fish maintained for 12 h in low and high Ca²⁺. In vitro exposure of gills to DBP (1 pM) disturbed Ca²⁺ homeostasis. DBP stimulated ⁴⁵Ca²⁺ influx in gills through the transitory receptor potential vanilloid 1 (TRPV1), and reverse-mode Na⁺/Ca²⁺ exchanger (NCX) activation, protein kinase C and K⁺ channels and sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA). These data suggest that in vivo short-term exposure of gills to low and high Ca²⁺ leads to ⁴⁵Ca²⁺ influx and histopathological changes. Additionally, the DBP-induced rapid ⁴⁵Ca²⁺ influx is mediated by TRPV1, NCX activation with the involvement of PKC, K⁺-channels and SERCA, thereby altering Ca²⁺ homeostasis.

A multi-omics approach reveals molecular mechanisms by which phthalates induce cardiac defects in zebrafish (Danio rerio)

The potential risks of phthalates affecting human and animal health as well as the environment are emerging as serious concerns worldwide. However, the mechanism by which phthalates induce developmental effects is under debate. Herein, we found that embryonic exposure of zebrafish to di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) increased the rate of heart defects including abnormal heart rate and pericardial edema. Changes in the transcriptional profile demonstrated that genes involved in the development of the heart, such as tbx5b, nppa, ctnt, my17, cmlc1, were significantly altered by DEHP and DBP at 50 μg/L, which agreed with the abnormal cardiac outcomes. Methylated DNA immunoprecipitation sequencing (MeDIP-Seq) further showed that significant hypomethylation of nppa and ctnt was identified after DEHP and DBP exposure, which was consistent with the up-regulation of these genes. Notably, hypermethylation on the promoter region (<1 kb) of tbx5b was found after DEHP and DBP exposure, which might be responsible for its decrease in transcription. In conclusion, phthalates have the potential to induce cardiac birth defects, which might be associated with the transcriptional regulation of the involved developmental factors such as tbx5b. These findings would contribute to understand the molecular pathways that mediated the cardiac defects caused by phthalates.

Inhibiting the PI3K/Akt, NF-κB signalling pathways with syringic acid for attenuating the development of oral squamous cell carcinoma cells SCC131

OBJECTIVES

To evaluate the anti-inflammatory and antiproliferative effect of syringic acid (SRA) on oral squamous cell carcinoma (OSCC) SCC131 cells via suppression of NF-κB-induced PI3K/Akt signalling pathway.

METHODS

The present study assesses the anticancer effects of SRA alongside human oral cancer (HOC) SCC131 cells through the fabrication of reactive oxygen species (ROS) and activated apoptosis. DAPI and Rh-123 staining were used to assess the apoptotic nuclear characteristic, mitochondrial membrane potential, cell adhesion and migration by fluorescence microscope with SRA treatment.

KEY FINDINGS

Syringic acid inhibits cell viability (IC₅₀ values of 25 µm), adhesion, migration and induced apoptosis. MTT assay demonstrated SRA-induced apoptotic events, inhibition of invasion and angiogenic signalling in SCC131 cell line. Furthermore, SRA treated with SCC131 cells suppresses the protein expression of inflammatory, angiogenesis and PI3K/Akt signalling pathways. It is suggested that SRA prevents the translocation of NF-κB and PI3K/Akt activated products to the nucleus, thereby suppressing angiogenesis via downregulation of vascular endothelial growth factor.

CONCLUSIONS

Therefore, addition of SRA to SCC131 cells may provide a promising natural therapeutic strategy against squamous cell carcinomas with potential application in clinical analysis.

In utero di-n-butyl phthalate exposure induced abnormal autophagy in renal tubular cells via hedgehog signaling in newborn rats

Di-n-butyl phthalate (DBP) is a pollutant that is widely present in the environment. We have previously demonstrated that maternal exposure to DBP resulted in renal fibrosis in offspring, but the underlying mechanism was not well elucidated. Therefore, the current study aims to understand the underlying molecular mechanisms in these sex-specific developmental alterations. Here, we used RNA-seq analysis to explore the underlying molecular mechanisms of DBP-associated renal fibrosis. Pregnant rats received DBP orally at a dose of 850 mg/kg BW/day during gestational days 14-18. Upregulated autophagy in renal tubules in offspring was confirmed in the DBP-treated group via accessing LC3Ⅱ/Ⅰ protein expression. Increased expression of the HhIP gene was found in the DBP-treated group via RNA-seq analysis. Immunohistochemistry (IHC) staining and Western blot analysis confirmed increased expression of HhIP protein and inhibited hedgehog signaling. Increased HhIP expression further leaded to impaired activation of hedgehog signaling, which is critical for normal embryonic development. Additional in vitro experiments on renal tubular cells suggest that inactivation of hedgehog signaling induced autophagy in renal tubular cells. Taken together, our findings show that maternal exposure to DBP induced autophagy through regulation of hedgehog signaling via overexpression of HhIP in foetal renal tubular cells, which may be essential for renal fibrosis development.

Acute exposure to bis(2-ethylhexyl)phthalate disrupts calcium homeostasis, energy metabolism and induces oxidative stress in the testis of Danio rerio

Bis(2-ethylhexyl)phthalate (BEHP) negatively affects testicular functions in different animal species, disturbing reproductive physiology and male fertility. The present study investigated the in vitro acute effect of BEHP on the mechanism of action of ionic calcium (Ca²⁺) homeostasis and energy metabolism. In addition, the effect of BEHP on oxidative stress was studied in vitro and in vivo in the testis of Danio rerio (D. rerio). Testes were treated in vitro for 30 min with 1 μM BEHP for ⁴⁵Ca²⁺ influx measurements. Testes were also incubated with 1 μM BEHP for 1 h (in vitro) or 12 h (in vivo) for the measurements of lactate content, ¹⁴C-deoxy-d-glucose uptake, lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT) activity, total reactive oxygen species (ROS) production and lipid peroxidation. In addition, the effect of BEHP (1 μM) on GGT, glutamic oxaloacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activity in the liver was evaluated after in vivo treatment for 12 h. BEHP disturbs the Ca²⁺ balance in the testis when given acutely in vitro. BEHP stimulated Ca²⁺ influx occurs through L-type voltage-dependent Ca²⁺ channels (L-VDCC), transitory receptor potential vaniloid (TRPV1) channels, reverse-mode Na⁺/Ca²⁺ exchanger (NCX) activation and inhibition of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA). BEHP affected energy metabolism in the testis by decreasing the lactate content and LDH activity. In vitro and in vivo acute effects of BEHP promoted oxidative stress by increasing ROS production, lipid peroxidation and GGT activity in the testis. Additionally, BEHP caused liver damage by increasing GPT activity.

Zinc Deficiency Promotes Testicular Cell Apoptosis in Mice

Zinc (Zn) plays an important role in spermatogenesis, and carbon tetrachloride (CCl₄) induces testicular oxidative damage and cell death. The objective of the present study was to define the effects of Zn deficiency in combination with CCl₄ treatment on testicular apoptosis and the associated mechanisms. Mice were fed the following diets with three different Zn levels for 6 weeks: normal zinc (ZN) diet (30 mg Zn/kg), zinc-deficient (ZD) diet (2 mg Zn/kg), and adequate zinc (ZA) diet (100 mg Zn/kg). Beginning in the third week, CCl₄ was intraperitoneally injected into half of the mice in each diet group six times over 3 weeks. We found that Zn was distributed in various tissues and organs in normal mice and that the zinc content in the testis of normal mice was high. The Zn-deficient diet reduced the zinc concentration in the testis tissue, and the testicular/body weight ratio significantly decreased. Moreover, the TUNEL results proved that CCl₄ stimulation of mice fed with a zinc-deficient diet caused marked apoptosis of testicular cells. Furthermore, the ROS levels in the testes obviously increased after Zn-deficient mice were stimulated with CCl₄, whereas reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) showed reduced activities. In addition, proteins associated with the apoptosis signaling pathway were detected with ELISA kits. P-p53, cleaved caspase-3, cleaved PRAP, p-Bad, p-JNK, p-ERK, and p-NF-κB p65 increased by varying degrees under zinc deficiency or CCl₄ stimulation. All the data indicated that Zn deficiency significantly enhanced the harm to the testis induced by oxidative stress and damage, while CCl₄ stimulation exacerbated the oxidative damage in testicular cells, leading to apoptosis through the activation of p53, MAPK, and NF-κB.

Silica nanoparticles induce spermatocyte cell autophagy through microRNA-494 targeting AKT in GC-2spd cells

Researches had shown that silica nanoparticles (SiNPs) could reduce the quantity and quality of sperms. However, chronic effects of SiNPs have not been well addressed. In this study, mice spermatocyte cells (GC-2spd cells) were continuously exposed to SiNPs (5 μg/mL) for 30 passages and then the changes of microRNA (miRNA) profile and mRNA profile were detected. The function of miRNAs was verified by inhibitors to explore the regulation role of miRNAs in reproductive toxicity induced by SiNPs. The results showed that SiNPs induced cytotoxicity, and activated autophagy in GC-2spd cells. SiNPs led to a total of 1604 mRNAs (697 up-regulated and 907 down-regulated) and 15 miRNAs (6 up-regulated such as miRNA-138 and miRNA-494 and 9 down-regulated) with different expression in GC-2spd cells. The combined miRNA profile and mRNA profile showed that 415 mRNAs with different expression in 5 μg/mL SiNPs group were regulated by miRNA. Furthermore, our study demonstrated that SiNPs decreased the expressions of AKT mRNAs. Moreover, SiNPs had an activation effect on the AMPK/TSC/mTOR pathway. However, inhibitor of miRNA-494 could attenuate the expression levels of AMPK, TSC, LC3Ⅱ and alleviate the decreased of AKT, mTOR, p-mTOR induced by SiNPs. The above results suggested that the low-dose SiNPs exposure could promote autophagy by miRNA-494 targeting AKT, thereby activating AMPK/TSC/mTOR pathway in GC-2spd cells. MiRNA-494 is an important regulator of autophagy by targeting AKT, which provides new evidence for the male reproductive toxicity mechanism of SiNPs.

Increasing ERK phosphorylation by inhibition of p38 activity protects against cadmium-induced apoptotic cell death through ERK/Drp1/p38 signaling axis in spermatocyte-derived GC-2spd cells

Many studies report that cadmium chloride (CdCl₂)-induces oxidative stress is associated with male reproductive damage in the testes. CdCl₂ also induces mitochondrial fission by increasing dynamin-related protein 1 (Drp1) expression as well as the mitochondria-dependent apoptosis pathway by extracellular signal-regulated kinase (ERK) activation. However, it remains unclear whether mechanisms linked to the mitochondrial damage signal via CdCl₂-induced mitogen-activated protein kinases (MAPK) cause damage to spermatocytes. In this study, increased intracellular and mitochondrial reactive oxygen species (ROS) levels, mitochondrial membrane potential (∆Ψm) depolarization, and mitochondrial fragmentation and swelling were observed at 5 μM of CdCl₂ exposure, resulting in increased apoptotic cell death. Moreover, CdCl₂-induced cell death is closely associated with the ERK/Drp1/p38 signaling axis. Interestingly, SB203580, a p38 inhibitor, effectively prevented CdCl₂-induced apoptotic cell death by reducing ∆Ψm depolarization and intracellular and mitochondrial ROS levels. Knockdown of Drp1 expression diminished CdCl₂-induced mitochondrial deformation and ROS generation and protected GC-2spd cells from apoptotic cell death. In addition, electron microscopy showed that p38 inhibition reduced CdCl2-induced mitochondrial interior damage more effectively than N-acetyl-L-cysteine (NAC), an ROS scavenger; ERK inhibition; or Drp1 knockdown. Therefore, these results demonstrate that inhibition of p38 activity prevents CdCl₂-induced apoptotic GC-2spd cell death by reducing depolarization of mitochondrial membrane potential and mitochondrial ROS levels via ERK phosphorylation in a signal pathway different from the CdCl₂-induced ERK/Drp1/p38 axis and suggest a therapeutic strategy for CdCl₂-induced male infertility.

Inhibition of endoplasmic reticulum stress-induced autophagy promotes the killing effect of X-rays on sarcoma in mice

Endoplasmic reticulum (ER) stress is a conserved cellular process for cells to clear unfolded or misfolded proteins and maintain cell homeostasis under stress conditions. Autophagy may act as a pro-survival strategy to cope with multiple stress conditions in tumor progression and distant metastasis. Although many studies have demonstrated that there is a close correlation between radiation-induced ER stress and autophagy, the molecular mechanisms currently remain unclear. In the present study, we performed an in vivo study concerning the effect of autophagy induced by ER stress on the radiosensitivity of mouse sarcoma using X-rays. Our results documented that X-rays could induce ER stress in sarcoma and then autophagy was activated by unfolded protein response (UPR) through the IRE1-JNK-pBcl2-Beclin1 signaling axis. The induction of autophagy caused a decline in cell apoptosis while inhibiting the autophagy resulted in increased apoptosis and inhibition of tumor progression. Combined treatment of X-ray exposure and chloroquine increased ER stress-related apoptosis and enhanced the radiosensitivity of mouse sarcoma that was not sensitive to X-ray irradiation alone. Thus, our study indicates that inhibition of ER stress-induced autophagy might be a novel strategy to improve the efficacy of radiotherapy against radioresistant sarcoma.

The role of ANXA5 in DBP-induced oxidative stress through ERK/Nrf2 pathway

Di-N-butylphthalate (DBP) have given rise to more and more attention due to its unique endocrine toxicity to male reproductive system. Our previous studies have demonstrated antioxidative Nrf2 (nuclear factor erythroid related factor 2) pathway play a vital role in DBP induced oxidative stress injury. ANXA5 (annexin A5), which is highly expressed in testicular Leydig and Sertoli cells, was found upregulated after DBP stimulation. Mouse Leydig and Sertoli cells were exposed to different concentration of DBP for 24 h to examine the ROS (Reactive oxygen species), MDA (Malondialdehyde), SOD (superoxide dismutase) level and ANXA5, Nrf2, NQO1 (NAD(P)H-quinone oxidoreductase 1), HO-1 (heme oxygenase 1) and ERK/P-ERK protein expression by DHE (Dihydroethidium) staining, ELISA (enzyme-linked immunosorbent assay) and Western blot respectively. Firstly, the oxidative stress injury induced by DBP was re-validated. Then, we confirmed the change of Nrf2 pathway and ANXA5 level after DBP exposure to testicular cells. Additionally, overexpressed ANXA5 could activate Nrf2/HO-1/NQO1 antioxidant pathway and significantly attenuate DBP-induced oxidative stress. Ultimately, we demonstrated ANXA5 could increase ERK phosphorylated level and the activated role of ANXA5 on ERK/Nrf2 pathway could be reversed by ERK inhibitor. Overall, this study illuminated that ANXA5 could defend testicle Leydig and Sertoli cells against DBP-induced oxidative stress injury through ERK/Nrf2 pathway.

Di-n-butyl phthalate, butylbenzyl phthalate, and their metabolites exhibit different apoptotic potential in human peripheral blood mononuclear cells

Human peripheral blood mononuclear cells (PBMCs) are one of the main cell models used in studies concerning the exposure of humans (in vitro) to various chemical substances. Changes in PBMCs may reflect the general reaction of the organism regarding the effect of xenobiotics. The aim of this work was to evaluate the effect of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP) and their metabolites: mono-n-butylphthalate (MBP), mono-benzylphthalate (MBzP) upon the induction of apoptosis in human peripheral blood mononuclear cells in vitro. PBMCs were incubated with the studied compounds at concentrations from 1 to 100 μg/mL for 12 h and/or 24 h. In order to clarify the mechanism of phthalates-induced programmed cell death, the changes in the calcium ions (Ca²⁺) level, alterations in the transmembrane mitochondrial potential (ΔѰm) and caspase-8, -9, -3 activity as well as externalization of phosphatidylserine have been determined. An increased Ca²⁺ level and a reduction of the ΔѰm were observed in PBMCs incubated with all of the studied compounds, and particularly with DBP and BBP. Phthalates caused an increase of caspases activity. The most pronounced increase was observed for caspase -9. The most pronounced pro-apoptotic changes were caused by DBP followed by BBP and then by their metabolites.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

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.

Autophagy in male reproduction

Autophagy is a fundamental process that exists in all eukaryotic organisms, with a primary function of catabolizing undesirable components to provide energy and essential materials. Increasing evidence illustrates that autophagy is invovled in a broad range of cellular events within the male reproductive system. In the process of spermatogenesis, autophagy is crucial for the formation of specific structures that guarantee successful spermatogenesis, as well as for the degradation of certain constituents. The underlying connections between autophagy and androgen binding protein, lipid metabolism and testosterone biosynthesis would increase our understanding of male testicular endocrinology. Moreover, cumulative studies reveal that autophagy is a double-edged sword when the organism suffers from endocrine disrupting chemicals. This review contains a collection of the current literature concerning the above aspects of autophagy, which may provide insights for future study and exploration. Abbreviations: 3-MA: 3-methyladenine; ABP: androgen-binding protein; AKT: protein kinase B; AMPK: adenosine monophosphate-activated protein kinase; ART: assisted reproductive technologies; Atg: autophagy-related gene; CE: cholesteryl ester; CL: corpus luteum; CQ: chloroquine; CYP11A1: cholesterol side chain cleavage enzyme; CytC: cytochrome C; DEHP: di-2-ethylhexyl phthalate; DFCP1: double FYVE-containing protein 1; EDCs: endocrine-disrupting chemicals; ERK1/2: extracellular signal-regulated kinase 1/2; ES: ectoplasmic specialization; FC: free cholesterol; FIP2000: focal adhesion kinase family interacting protein of 200kDa; FSH: follicle stimulating hormone; HDL: high-density lipoprotein; IVF: in vitro fertilization; LC3: microtubule-associated protein light chain 3; LD: lipid droplet; LH: luteinising hormone; MC-LR: microcystin-LR; MEFs: mouse embryonic fibroblast cells; MT: microtubule; mtDNA: mitochondrial DNA; mTOR: mammalian target of rapamycin; NHERF2: Na⁺/H⁺ exchanger regulatory factor 2; NMR: naked mole-rat; PCD: programmed cell death; PDLIM1: PDZ and LIM domain 1; PGCs: primordial germ cells; PGF_2α: prostaglandin F_2α; PI3K: phosphatidylinositol-3-kinase; PI3P: phosphatidylinositol-3-phosphate; ROS: reactive oxygen species; SCG10: superior cervical ganglia protein 10; SR-BI: scavenger receptor class B, type I; StAR protein: steroidogenic acute regulatory protein; TC: total cholesterol; TEM: transmission electron microscopy; TUNEL: terminal deoxynucleotidyl transferase mediated dUTP nick end labeling; ULK1: mammalian uncoordinated-51-like kinase 1; WIPI: WD-repeat domain phosphoinositide-interacting.

Di-n-butyl phthalate epigenetically induces reproductive toxicity via the PTEN/AKT pathway

Di-n-butyl phthalate (DBP) is a kind of ubiquitous chemical linked to hormonal disruptions that affects male reproductive system. However, the mechanism of DBP-induced germ cells toxicity remains unclear. Here, we demonstrate that DBP induces reduction of proliferation, increase of apoptosis and DNA damage dependent on the PTEN/AKT pathway. Mechanistically, DBP decreases PTEN promoter methylation and increases its transcriptional activity, leading to increased PTEN expression. Notably, DNMT3b is confirmed as a target of miR-29b and miR-29b-mediated status of PTEN methylation is involved in the effects of DBP treatment. Meanwhile, DBP decreases AKT pathway expression via increasing PTEN expression. In addition, the fact that DBP decreases the sperm number and the percentage of motile and progressive sperm is associated with downregulated AKT pathway and sperm flagellum-related genes. Collectively, these findings indicate that DBP induces aberrant PTEN demethylation, leading to inhibition of the AKT pathway, which contributes to the reproductive toxicity.

HC diet inhibited testosterone synthesis by activating endoplasmic reticulum stress in testicular Leydig cells

Emerging epidemiological studies indicate that hypercholesterolaemia is a risk factor for testosterone deficiency. However, the underlying mechanism is unclear. Testicular Leydig cells are the primary source of testosterone in males. To identify the effect and mechanism of cholesterol overload on Leydig cell function, rats were fed with a HC (HC) diet to induce hypercholesterolaemia. During the 16‐week feeding period, serum testosterone levels were reduced in a time‐dependent manner in rats fed the HC diet. Accordingly, these steroidogenic enzymes within the Leydig cells, including steroidogenic acute regulatory protein (StAR), cholesterol side‐chain cleavage cytochrome P450 (P450scc) and 3β‐hydroxysteroid dehydrogenase (3β‐HSD), were down‐regulated. Notably, the HC‐fed rats showed evident endoplasmic reticulum (ER) stress in the testis, including a dilated ER as an evident pathological change in the Leydig cell ultrastructure, up‐regulated ER stress biomarker (binding immunoglobulin protein) levels and activation of the activating transcription factor 6 (ATF6)‐related unfolded protein response pathway. Further analysis showed that when 4‐phenyl butyric acid (4‐PBA) was used to block ER stress in HC‐fed rats for 8 weeks, the testosterone deficiency was significantly alleviated. Our findings suggested that high dietary cholesterol intake affected serum testosterone levels by down‐regulating steroidogenic enzymes and that activated ER stress might serve as the underlying mechanism.

Effects of 60Co γ Irradiation on the Reproductive Function of Caenorhabditis elegans

The effects of ionizing radiation on the reproductive system have always been a matter of great interest. Both artificial and naturally occurring ionizing radiation can directly or indirectly affect the reproductive system via the introduction of DNA single-strand and double-strand breaks, the excitation of water molecules, and the generation of free radicals. In order to quantitatively investigate the effects of ionizing radiation on reproductive function, ⁶⁰Co γ irradiation was applied on a model organism, Caenorhabditis elegans (C. elegans). The egg-laying and embryo-hatching activities were observed for the parent (F0) and the first 2 progeny (F1 and F2) generations. The incidence rate of ovipositor malformation was also recorded. Acridine orange was used to detect the number of apoptotic germ cells. With the above metrics, the effects of ⁶⁰Co γ irradiation on the reproductive function of C. elegans were systematically evaluated. The results showed that the postirradiation egg-laying and embryo-hatching activities of the F0 generation were increasingly suppressed by increasing doses of ⁶⁰Co γ irradiation. Those of the F1 generation showed a trend toward recovery although also suppressed by the radiation to the F0 generation compared with the control. Those activities were restored to normal or near-normal levels for the F2 generation. The incidence rate of ovipositor malformation was greatly increased by ⁶⁰Co γ irradiation according to radiation doses. Gamma irradiation by ⁶⁰Co also substantially induced germ cell apoptosis, and the apoptosis rate increased with increasing radiation doses. Therefore, ⁶⁰Co γ irradiation affects the reproductive function of C. elegans. The suppression on its reproductive function increases with increasing radiation doses. The reproductive functions of progeny generations are also affected and weakened.

ZnSO4 rescued vimentin from collapse in DBP-exposed Sertoli cells by attenuating ER stress and apoptosis

Sertoli cells (SCs) provide physical and nutritional support for spermatogenesis. Dibutyl phthalate (DBP) is a plasticizer that has male reproductive toxicity. The collapse of vimentin in DBP-exposed SCs is thought to induce the sloughing of spermatocytes from seminiferous tubules. In this study, we explored methods to rescue vimentin from collapse in DBP-exposed SCs. DBP not only induced the hyperphosphorylation of vimentin but also triggered endoplasmic reticulum (ER) stress and apoptosis in SCs. Treatment with BAPTA-AM, an antagonist of Ca²⁺, significantly decreased the level of phosphorylated vimentin, while LY294002, an inhibitor of Akt1, did not. ER stress and apoptosis remained at high levels, and the distribution of vimentin was not improved. ZnSO₄ treatment did not decrease the level of phosphorylated vimentin. However, after treatment, ER stress and apoptosis were obviously inhibited, and the distribution of vimentin was reconverted. These results indicated that ZnSO₄ could alleviate the collapse of vimentin by attenuating ER stress and apoptosis. This study suggested that an appropriate zinc supply might be a choice to alleviate DBP-induced adverse reproductive effects.

Developmental toxicity of dibutyl phthalate and citrate ester plasticizers in Xenopus laevis embryos

Citrate esters have been considered as alternatives to phthalate plasticizers. Being considered to have low toxicity in mammals, their toxicological information for aquatic animals remains poorly understood. We examined the developmental toxicity of citrate esters including tributyl O-acetylcitrate (ATBC), triethyl 2-acetylcitrate (ATEC), and trihexyl O-acetylcitrate (ATHC) together with dibutyl phthalate (DBP) based on the frog embryo teratogenesis assay-Xenopus (FETAX). ATBC has the lowest 96 h LC₅₀ and 96 h EC₅₀ values. In RT-qPCR, the ratio of bax and bcl-2 mRNA was significantly increased by DBP, but not by ATBC, ATEC and ATHC. DNA fragmentation was obvious in DBP-treated tadpoles, but not in those treated with ATBC and ATEC, whereas ATHC caused necrotic DNA degradation. Lipid hydroperoxide levels in tadpoles were significantly increased by DBP and ATHC, but not by ATBC and ATEC, suggesting that induction of oxidative stress by DBP and ATHC in embryos. In tadpoles with head abnormalities, basihyal bone, ceratohyal bone and Meckel's cartilage were frequently missed together with reduction in branchial gill bones. Col2a1 mRNA in the head of tadpoles was significantly decreased by low concentration of DBP, ATHC, and high concentration of ATEC. In stage 25 embryos FoxN3 mRNA, a master regulator for differentiation of neural crest cells to chondrocytes in head, was significantly decreased by DBP and ATHC, but not by ATBC and ATEC. In conclusion, ATEC was recommended as the alternative to phthalate plasticizer having the lowest developmental toxicity in amphibian embryos.

Maternal exposure to di-n-butyl phthalate (DBP) promotes epithelial-mesenchymal transition via regulation of autophagy in uroepithelial cell

Maternal exposure to di-n-butyl phthalate (DBP) induces hypospadias, but the underlying mechanisms remain elusive. Here we hypothesize that aberrant activation of autophagy and epithelial-mesenchymal transition (EMT) are the leading cause of DBP-related hypospadias. Pregnant rats received DBP orally at a dose of 750 mg/kg/day during gestational days 14-18. In DBP-induced hypospadiac male offspring, immunohistochemistry (IHC) staining and Western blot showed increased expression of autophagy and EMT markers in genital tubercle (GT) tissue compared to the control. In addition, lower testosterone levels and androgen receptor (AR) expression in GT tissue were detected. In vitro studies revealed that impaired AR signaling was involved in DBP-induced autophagy and autophagy activation furthermore promoted EMT in urethral epithelial cells. DBP combined with chloroquine, an autophagy inhibitor, reduced the expression of EMT markers compared with DBP treatment alone, while DBP combined with the autophagy inducer rapamycin elevated the expression of EMT markers. The autophagy-lysosomal pathway inhibitor CQ but not proteasome inhibitor MG-132 rescued the decrease of E-cadherin after DBP treatment, which indicated autophagy-induced E-cadherin degradation contributes to DBP-related EMT. Taken together, our findings show that prenatal exposure to DBP induces abnormal autophagy and EMT that may play important roles in hypospadias development.