A Short-Term Exposure to Tributyltin Blocks Leydig Cell Regeneration in the Adult Rat Testis

Structure-activity relationship and mechanistic study of organotins as inhibitors of human, pig, and rat gonadal 3β-hydroxysteroid dehydrogenases

Organotins have been widely used in various industrial applications. This study investigated the structure-activity relationship as inhibitors of human, pig, and rat gonadal 3β-hydroxysteroid dehydrogenases (3β-HSD). Human KGN cell, pig, and rat testis microsomes were utilized to assess the inhibitory effects of 18 organotins on the conversion of pregnenolone to progesterone. Among them, diphenyltin, triethyltin, and triphenyltin exhibited significant inhibitory activity against human 3β-HSD2 with IC50 values of 114.79, 106.98, and 5.40 μM, respectively. For pig 3β-HSD, dipropyltin, diphenyltin, triethyltin, tributyltin, and triphenyltin demonstrated inhibitory effects with IC50 values of 172.00, 100.19, 87.00, 5.75, and 1.65 μM, respectively. Similarly, for rat 3β-HSD1, dipropyltin, diphenyltin, triethyltin, tributyltin, and triphenyltin displayed inhibitory activity with IC50 values of 81.35, 43.56, 55.55, 4.09, and 0.035 μM, respectively. They were mixed inhibitors of pig and rat 3β-HSD, while triphenyltin was identified as a competitive inhibitor of human 3β-HSD2. The mechanism underlying the inhibition of organotins on 3β-HSD was explored, revealing that they may disrupt the enzyme activity by binding to cysteine residues in the catalytic sites. This proposition was supported by the observation that the addition of dithiothreitol reversed the inhibition caused by all organotins except for triethyltin, which was partially reversed. In conclusion, this study provides valuable insights into the structure-activity relationship of organotins as inhibitors of human, pig, and rat gonadal 3β-HSD. The mechanistic investigation suggests that these compounds likely exert their inhibitory effects through binding to cysteine residues in the catalytic sites.

Evaluating the histomorphological and biochemical changes induced by Tributyltin Chloride on pituitary-testicular axis of adult albino rats and the possible ameliorative role of hesperidin

This study was performed to explore in detail the toxic effects of Tributyltin Chloride (TBT) on the pituitary-testicular axis and the possible amelioration with Hesperidin. Seventy-two adult male albino rats were divided into four groups: Control group (I), TBT-treated group (II), TBT+Hesperidin group (III), and Recovery group (IV). Body and testicular weights were measured. Blood samples were taken to estimate serum levels of testosterone, FSH and LH hormones by enzyme-linked immunosorbent assay (ELISA). Malondialdehyde (MDA) level was measured in testes homogenates. Tissue samples from the pituitary glands and testes were processed for light, electron microscope examination, and immunohistochemical detection of anti-FSH, and Ki67 proteins. Results showed a statistically significant decrease in testicular weight, serum testosterone, FSH and LH levels and a significant increase in tissue MDA in the TBT group when compared to the control group. TBT treatment caused severe histopathological changes with decreased area percent of PAS-stained basophils, and anti FSH immuno-stained gonadotrophs in the pituitary gland. The testes of group II also showed marked tissue damage, cell loss with decreased epithelial height and decreased number of proliferating spermatogenic cells. Hesperidin supplementation with TBT proved significant amelioration of the previously mentioned parameters in both glands which could improve male fertility. In conclusion: The flavonoid Hesperidin has the potential to protect against the reproductive damage induced by TBT in susceptible individuals.

Tributyltin chloride (TBTCL) induces cell injury via dysregulation of endoplasmic reticulum stress and autophagy in Leydig cells

Tributyltin chloride (TBTCL), a commonly used antiseptic substance, is commonly found in the environment. Human exposure to TBTCL through the consumption of contaminated seafood, fish, or drinking water has aroused concern. It is well-characterized that TBTCL has multiple detrimental effects on the male reproductive system. However, the potential cellular mechanisms are not fully elucidated. Here, we characterized molecular mechanisms of TBTCL-induced cell injury in Leydig cells, a critical supporter for spermatogenesis. We showed that TBTCL induces apoptosis and cell cycle arrest in TM3 mouse Leydig cells. RNA sequencing analyses revealed that endoplasmic reticulum (ER) stress and autophagy were potentially involved in TBTCL-induced cytotoxicity. We further showed that TBTCL causes ER stress and inhibited autophagy flux. Notably, the inhibition of ER stress attenuates not only TBTCL-induces autophagy flux inhibition but also apoptosis and cell cycle arrest. Meanwhile, the activation of autophagy alleviates, and inhibition of autophagy exaggerates TBTCL-induced apoptosis and cell cycle arrest flux. These results suggest that TBTCL-induced ER stress and autophagy flux inhibition contributed to apoptosis and cell cycle arrest in Leydig cells, providing novel understanding into the mechanisms of TBTCL-induced testis toxicity.

Multiomics analysis of male infertility

Infertility affects 8-12% of couples globally, and the male factor is a primary cause in approximately 50% of couples. Male infertility is a multifactorial reproductive disorder, which can be caused by paracrine and autocrine factors, hormones, genes, and epigenetic changes. Recent studies in rodents and most notably in humans using multiomics approach have yielded important insights into understanding the biology of spermatogenesis. Nonetheless, the etiology and pathogenesis of male infertility are still largely unknown. In this review, we summarized and critically evaluated findings based on the use of advanced technologies to compare normal and obstructive azoospermia (OA) versus non-obstructive azoospermia (NOA) men, including whole-genome bisulfite sequencing (WGBS), single cell RNA-seq (scRNA-seq), whole exome sequencing (WES), and ATAC-seq. It is obvious that the multiomics approach is the method of choice for basic research and clinical studies including clinical diagnosis of male infertility.

Cypermethrin inhibits Leydig cell development and function in pubertal rats

Cypermethrin is a broad-spectrum pyrethroid insecticide that is widely used. It may induce adverse endocrine-disrupting effects on the male reproductive system. Whether cypermethrin can disrupt Leydig cell development and function in the late puberty remains elusive. The objective of this study was to explore the effect of cypermethrin exposure to male rats on the development and function of Leydig cells in late puberty and explore the underlying mechanism. Thirty-six male Sprague-Dawley rats (age of 35 days) were gavaged with cypermethrin (0, 12.5, 25, and 50 mg/kg/day) from postnatal day 35-49. Cypermethrin significantly lowered serum testosterone level while elevating serum luteinizing hormone level at a dose of 50 mg/kg, without altering serum follicle-stimulating hormone level. Cypermethrin markedly decreased CYP11A1-positive Leydig cell number at 50 mg/kg without affecting SOX9-positive Sertoli cell number. It significantly down-regulated the expression of Leydig cell genes, Lhcgr, Star, Cyp11a1, and Cyp17a1 and their proteins, while up-regulating the expression of Sertoli cell genes, Dhh and Amh, and their proteins, at doses of 12.5-50 mg/kg. In addition, cypermethrin significantly increased malondialdehyde level while lowering the expression of Sod1 and Sod2 and their proteins at 50 mg/kg. Cypermethrin markedly induced reactive oxidative species at a concentration of 200 μM and reduced mitochondrial membrane potential at 25 μM and higher concentrations after 24 h of treatment to primary Leydig cells in vitro. In conclusion, cypermethrin inhibits the development and function of Leydig cells in male rats in late puberty.

Insights into the Regulation on Proliferation and Differentiation of Stem Leydig Cells

Male hypogonadism is a clinical syndrome caused by testosterone deficiency. Hypogonadism can be caused by testicular disease (primary hypogonadism) or hypothalamic-pituitary dysfunction (secondary hypogonadism). The present strategy for treating hypogonadism is the administration of exogenous testosterone. But exogenous testosterone is reported to have negative side effects including adverse cardiovascular events and disruption of physiological spermatogenesis probably due to its inability to mimic the physiological circadian rhythm of testosterone secretion in vivo. In recent years, a growing number of articles demonstrated that stem Leydig cells (SLCs) can not only differentiate into functional Leydig cells (LCs) in vivo to replace chemically disrupted LCs, but also secrete testosterone in a physiological pattern. The proliferation and differentiation of SLCs are regulated by various factors. However, the mechanisms involved in regulating the development of SLCs remain to be summarized. Factors involved in the regulation of SLCs can be divided into environmental pollutants, growth factors, cytokine and hormones. Environmental pollutants such as Perfluorooctanoic acid (PFOA) and Triphenyltin (TPT) could suppress SLCs proliferation or differentiation. Growth factors including FGF1, FGF16, NGF and activin A are essential for the maintenance of SLCs self-renewal and differentiation. Interleukin 6 family could inhibit differentiation of SLCs. Among hormones, dexamethasone suppresses SLCs differentiation, while aldosterone suppresses their proliferation. The present review focuses on new progress about factors regulating SLC's proliferation and differentiation which will undoubtedly deepen our insights into SLCs and help make better clinical use of them. Different factors affect on the proliferation and differentiation of stem Leydig cells. Firstly, each rat was intraperitoneally injected EDS so as to deplete Leydig cells from the adult testis. Secondly, the CD51+ or CD90+ cells from the testis of rats are SLCs, and the p75+ cells from human adult testes are human SLCs. These SLCs in the testis start to proliferate and some of them differentiate into LCs. Thirdly, during the SLCs regeneration period, researchers could explore different function of those factors (pollutants, growth factors, cytokines and hormones) towards SLCs.

Long-term exposure to environmental levels of phenanthrene disrupts spermatogenesis in male mice

Phenanthrene (Phe) is a tricyclic polycyclic aromatic hydrocarbon with high bioavailability under natural exposure. However, there are few studies on the reproductive toxicity of Phe in mammals. In this study, male Kunming mice were gavaged once every two days with Phe (5, 50, and 500 ng/kg) for 28 weeks. The accumulation levels of Phe in the testis were dose-dependently increased. Histopathological staining showed that Phe exposure reduced the number of spermatogonia, sperm and Sertoli cells. The percentage of testicular apoptotic cells was significantly increased, which was further verified by the upregulated BAX protein. The expression of the GDNF/PI3K/AKT signaling pathway was downregulated, which might suppress the self-renewal and differentiation of spermatogonial stem cells. Meanwhile, Phe exposure inhibited the expression of Sertoli cell markers (Fshr, WT1, Sox9) and the Leydig cell marker Cyp11a1, indicating damage to the function of Sertoli cells and Leydig cells. Serum estrogen and testicular estrogen receptor alpha were significantly upregulated, while androgen receptor expression was downregulated. These alterations might be responsible for impaired spermatogenesis. This study provides new insights for evaluating the reproductive toxicity and potential mechanisms of Phe in mammals.

Maternal exposure to tributyltin during early gestation increases adverse pregnancy outcomes by impairing placental development

Tributyltin (TBT) is a persistent organotin pollutant widely used as agricultural and wood biocides, exhibiting well-documented toxicity to reproductive functions in aquatic organisms. However, the effect of TBT on early pregnancy and placental development has been rarely studied in mice. Pregnant mice were fed with 0, 0.2, and 2 mg/kg/day TBT from gravid day 1 to day 8 or 13. TBT exposure led to an increase in the number of resorbed embryo and a reduction in the weight of fetus at gestational days 13. Further study showed that TBT significantly decreased placental weight and area, lowered laminin immunoreactivity and the expressions of placental development-related molecules including Fra1, Eomes, Hand1, and Ascl2. Moreover, TBT treatment markedly inhibited the placental proliferation and induced up-regulation of p53 and cleaved caspase-3 proteins, and down-regulation of Bcl-2 protein. In addition, TBT administration increased levels of malondialdehyde and H₂ O₂ and decreased activities of catalase and superoxide dismutase. Collectively, these results suggested TBT-induced adverse pregnancy outcomes during early pregnancy might be involved in developmental disorders of the placenta via dysregulation of key molecules, proliferation, apoptosis, and oxidative stress.

Common markers of testicular Sertoli cells

INTRODUCTION

Sertoli cells play central roles in the development of testis formation in fetuses and the initiation and maintenance of spermatogenesis in puberty and adulthood, and disorders of Sertoli cell proliferation and/or functional maturation can cause male reproductive disorders at various life stages. It's well documented that various genes are either overexpressed or absent in Sertoli cells during the conversion of an immature, proliferating Sertoli cell to a mature, non-proliferating Sertoli cell, which are considered as Sertoli cell stage-specific markers. Thus, it is paramount to choose an appropriate Sertoli cell marker that will be used not only to identify the developmental, proliferative, and maturation of Sertoli cell status in the testis during the fetal period, prepuberty, puberty, or in the adult, but also to diagnose the mechanisms underlying spermatogenic dysfunction.

AREAS COVERED

In this review, we principally enumerated 5 categories of testicular Sertoli cell markers - including immature Sertoli cell markers, mature Sertoli cell markers, immature/mature Sertoli cell markers, Sertoli cell functional markers, and others.

EXPERT OPINION

By delineating the characteristics and applications of more than 20 Sertoli cell markers, this review provided novel Sertoli cell markers for the more accurate diagnosis and mechanistic evaluation of male reproductive disorders.

Counteracting effects of heavy metals and antioxidants on male fertility

Infertility is regarded as a global health problem affecting 8-12% of couples. Male factors are regarded as the main cause of infertility in 40% of infertile couples and contribute to this condition in combination with female factors in another 20% of cases. Abnormal sperm parameters such as oligospermia, asthenospermia, and teratozoospermia result in male factor infertility. Several studies have shown the deteriorative impact of heavy metals on sperm parameters and fertility in human subjects or animal models. Other studies have pointed to the role of antioxidants in counteracting the detrimental effects of heavy metals. In the currents study, we summarize the main outcomes of studies that assessed the counteracting impacts of heavy metal and antioxidants on male fertility. Based on the provided data from animal studies, it seems rational to administrate appropriate antioxidants in persons who suffer from abnormal sperm parameters and infertility due to exposure to toxic elements. Yet, further human studies are needed to approve the beneficial effects of these antioxidants.

Gut microbiota-mediated tributyltin-induced metabolic disorder in rats

Tributyltin (TBT), an environmental pollutant widely used in antifouling coatings, can cause multiple-organ toxicity and gut microbiome dysbiosis in organisms, and can even cause changes in the host metabolomic profiles. However, little is known about the underlying effects and links of TBT-induced metabolic changes and gut microbiome dysbiosis. In this study, rats were exposed to TBT at a dose of 100 μg kg^-1 body weight (BW) for 38 days, followed by multi-omics analysis, including microbiome, metabolomics, and metallomics. Results showed that TBT exposure reduced rat weight gain and decreased the serum triglyceride (TG) level. Metabolic analysis revealed that TBT fluctuated linoleic acid metabolism and glycerophospholipid metabolism in the liver; the tricarboxylic acid cycle (TCA cycle), nicotinate and nicotinamide metabolism, and arachidonic acid metabolism in serum; glycine, serine, and threonine metabolism, the one carbon pool by folate, nicotinate, and nicotinamide metabolism; and tryptophan metabolism in feces. Furthermore, TBT treatment dictated liver inflammation due to enhancing COX-2 expression by activating protein kinase R-like ER kinase (PERK) and C/EBP homologous protein (CHOP) to induce endoplasmic reticulum (ER) stress instead of stimulating arachidonic acid metabolism. Meanwhile, alteration of the intestinal flora [Acetivibrio]_ethanolgignens_group, Acetatifactor, Eisenbergiella, Lachnospiraceae_UCG-010, Enterococcus, Anaerovorax, and Bilophila under TBT exposure were found to be involved in further mediating liver inflammation, causing lipid metabolism abnormalities, such as TG, linoleic acid, and glycerophospholipids, and interfering with the energy supply process. Among these, [Acetivibrio]_ethanolgignens_group, Enterococcus, and Bilophila could be considered as potential biomarkers for TBT exposure based on receiver operator characteristic (ROC) curve analysis.

Effects of gestational Perfluorooctane Sulfonate exposure on the developments of fetal and adult Leydig cells in F1 males

Studies have showed that some of the most common male reproductive disorders present in adult life might have a fetal origin. Perfluorooctane sulfonic (PFOS) is one of the major environmental pollutants that may affect the development of male reproductive system if exposed during fetal or pubertal periods. However, whether PFOS exposure during fetal period affects testicular functions in the adult is still unclear. Herein, we investigated the effects of a brief gestational exposure to PFOS on the development of adult Leydig- and Sertoli-cells in the male offspring. Eighteen pregnant Sprague-Dawley rats were randomly divided into three groups and each received 0, 1 or 5 mg/kg/day PFOS from gestational day 5-20. The testicular functions of F1 males were evaluated on day 1, 35 and 90 after birth. PFOS treatment significantly decreased serum testosterone levels of animals by all three ages examined. The expression level of multiple mRNAs and proteins of Leydig (Scarb1, Cyp11a1, Cyp17a1 and Hsd17b3) and Sertoli (Dhh and Sox9) cells were also down-regulated by day 1 and 90. PFOS exposure might also inhibit Leydig cell proliferation since the number of PCNA-positive Leydig cells were significantly reduced by postnatal day 35. Accompanied by changes in Leydig cell proliferation and differentiation, PFOS also significantly reduced phosphorylation of glycogen synthase kinase-3β while increased phosphorylation of β-catenin. In conclusion, gestational PFOS exposure may have significant long-term effects on adult testicular functions of the F1 offspring. Changes in Wnt signaling may play a role in the process.

miR-205 Expression Elevated With EDS Treatment and Induced Leydig Cell Apoptosis by Targeting RAP2B via the PI3K/AKT Signaling Pathway

The adult Leydig cells (ALCs), originated from stem Leydig cells (SLCs), can secrete testosterone which is essential for germ cell development and sexual behavior maintenance. As a synthetic compound, ethane dimethane sulfonate (EDS), a well-known alkylating agent, has been reported to specifically ablate ALCs. In this study, EDS was verified to ablate differentiated pig LCs by experiments. Subsequently, the primary isolated pig LCs (containing SLCs and differentiated LCs) and EDS-treated LCs (almost exclusively SLCs) were collected for RNA-seq 4,904 genes and 15 miRNAs were differently expressed between the two groups. Down-regulated genes in the EDS-treated group were mainly related to steroid hormone biosynthesis. The highest up-regulation miRNAs was miR-205 after EDS treatment. Additionally, miR-205 was expressed more highly in pig SLCs clones compared with differentiated LCs. Through qRT-PCR, western blot (WB), TUNEL, EDU and flow cytometry, miR-205 was found to induce cell apoptosis, but did not affect proliferation or differentiation in both TM3 and GC-1spg mouse cell lines. Through luciferase reporter assays and WB, RAP2B was identified as a target gene of miR-205. Besides, overexpression of miR-205 inhibited the expressions of PI3K, Akt and p-AKT. All these findings were helpful for elucidating the regulation mechanism in pig LCs.

Triphenyltin chloride reduces the development of rat adrenal cortex during puberty

Triphenyltin has been classified as an endocrine disruptor. However, whether triphenyltin interferes with the adrenal glands during puberty remains unknown. Here, we reported the effects of triphenyltin on the adrenal glands in rats. Male Sprague Dawley rats (age of 35 days) were orally administered with 0, 0.5, 1, or 2 mg/kg/day triphenyltin for 18 days. Triphenyltin significantly lowered corticosterone levels at 1 and 2 mg/kg and adrenocorticotropic hormone at 2 mg/kg. The RNA-Seq analysis detected multiple differentially expressed genes. Four down-regulated genes were transcription factor genes (Nr4a1, Nr4a2, Nr4a3, and Ppard), which might be associated with the suppression of the adrenal cortex function. RNA-seq and qPCR showed that triphenyltin dose-dependently down-regulated the expression of the genes for cholesterol transport and biosynthesis, including Scarb1, Ldlr, Hmgcs1, Hmgcr, and Hsd17b7. Further Western blotting revealed that it lowered NR4A1, PPRAD, LDLR, and HMGCS1 protein levels. We treated H295R adrenal cells with 1-100 nM triphenyltin for 72 h. Triphenyltin induced significant higher ROS production at 100 nM and did not induce apoptosis at 10 and 100 nM. In conclusion, triphenyltin inhibits production of corticosterone via blocking the expression of cholesterol uptake transporters and cholesterol biosynthesis.

Environmental contaminants and male infertility: Effects and mechanisms

The escalating prevalence of male infertility and decreasing trend in sperm quality have been correlated with rapid industrialisation and the associated discharge of an excess of synthetic substances into the environment. Humans are inevitably exposed to these ubiquitously distributed environmental contaminants, which possess the ability to intervene with the growth and function of male reproductive organs. Several epidemiological reports have correlated the blood and seminal levels of environmental contaminants with poor sperm quality. Numerous in vivo and in vitro studies have been conducted to investigate the effect of various environmental contaminants on spermatogenesis, steroidogenesis, Sertoli cells, blood-testis barrier, epididymis and sperm functions. The reported reprotoxic effects include alterations in the spermatogenic cycle, increased germ cell apoptosis, inhibition of steroidogenesis, decreased Leydig cell viability, impairment of Sertoli cell structure and function, altered expression of steroid receptors, increased permeability of blood-testis barrier, induction of peroxidative and epigenetic alterations in spermatozoa resulting in poor sperm quality and function. In light of recent scientific reports, this review discusses the effects of environmental contaminants on the male reproductive function and the possible mechanisms of action.

Acute heat-treatment disrupts inhibin-related protein production and gene expression in the adult rat testis

Heat reversibly disrupts spermatogenesis, but the effects on Sertoli cell (SC) function and inhibin/activin-related proteins are less well-defined. Adult rat testis weights decreased by 40% within 2 weeks after heat-treatment (43 °C, 15 min), due to loss of pachytene spermatocytes and round spermatids. Coincident effects were reduced SC nuclear volume at one week and >50% reduction in expression of several critical SC genes (Inha, Cld11, Gja1, Tjp1, Cldn3) by 2 weeks. Leydig cell steroidogenic enzymes, Cyp11a1, Hsd3b1, were also reduced. Activin gene expression was unaffected at this time, but expression of the activin-binding protein, follistatin (Fst), increased >2-fold. At 4-8 weeks, coincident with the recovery of spermatocytes and early spermatids, but progressive loss of elongated spermatids, most SC genes had recovered; however, testicular activin A was reduced and activin B increased. At 8 weeks, serum inhibin was decreased and, consequently, serum FSH increased. Crucially, germ cell damage was not associated with a significant inflammatory response. At 14 weeks, most testicular parameters had returned to normal, but testis weights remained slightly reduced. These data indicate that, following acute heat-treatment, expression of several key Sertoli and Leydig cell genes declined in parallel with the initial loss of meiotic germ cells, whereas activins were responsive to the subsequent loss of mature spermatids, leading to an increase in testicular activin B production relative to activin A.

Aflatoxin B1 impairs leydig cells through inhibiting AMPK/mTOR-mediated autophagy flux pathway

Aflatoxin B1 (AFB1), a potential endocrine disrupter, has been shown to induce hepatotoxicity in animal models, but the effects of AFB1 on Leydig cell function are unclear. In this study, in vivo exposure to AFB1 at 15 and 150 μg/kg/day lowered serum testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels, reduced Leydig cell number, and down-regulated the expression of testosterone biosynthesis-related genes. In vitro study showed that AFB1 (10 μM) significantly increased ROS levels, and decreased T production in Leydig cells by suppressing certain T-biosynthesis gene expressions. Moreover, AFB1 induced Leydig cell apoptosis through lowering pAMPK/AMPK ratio and increasing pmTOR/mTOR ratio, and then further up-regulating autophagy and apoptosis proteins, LC3, BECLIN 1, and BAX, as well as down-regulating autophagy flux protein P62 and anti-apoptosis protein BCL-2. AFB1-induced toxicity in Leydig cells was characterized by inhibiting T-biosynthesis gene expression, reducing Leydig cell number, promoting ROS production, and inducing cell apoptosis via suppressing AMPK/mTOR-mediated autophagy flux pathway.

Trimethyltin (TMT) Reduces Testosterone Production in Adult Leydig Cells in Rats

Trimethyltin (TMT) is widely used as a plastic heat stabilizer and can cause severe toxicity. Here, the effects of TMT on testosterone production by adult Leydig cells and the related mechanisms of action were investigated. Eighteen adult male Sprague Dawley rats (56 days old) were randomly divided into 3 groups and given intraperitoneal injection of TMT for 21 consecutive days at the doses of 0 (vehicle control), 5, or 10 mg/kg/d. After treatment, trunk blood was collected for hormonal analysis. In addition, related gene and protein expression in testes was detected. At 10 mg/kg, TMT significantly reduced serum testosterone levels but increased serum luteinizing and follicle-stimulating hormone levels. The messenger RNA and protein levels of luteinizing hormone/chorionic gonadotropin receptor, steroidogenic acute regulatory protein, cytochrome P450 17-hydroxylase/17,20-lyase, follicle-stimulating hormone receptor, and SRY box 9 were significantly lower in the TMT-treated testes than in controls. Immunohistochemical study showed that TMT decreased adult Leydig cell number. In conclusion, these findings indicate that TMT reduced adult Leydig cell testosterone production in vivo by directly downregulating the expression of steroidogenic enzymes and decreasing adult Leydig cell number in the testis.

DNA fragmentation factor 40 expression in T cells confers sensibility to tributyltin-induced apoptosis

DNA fragmentation factor 40 (DFF40), an endonuclease, mediates the final and irreversible step of apoptosis by conducting oligonucleosomal DNA fragmentation. New emerging studies have proposed a role of DFF40 in genomic stability, besides its nuclease activity. Overexpression of DFF40 in tumoral cells increases their sensitivity to chemotherapeutic drugs. In this study, we sought to determine if DFF40 expression influences the toxicity of tributyltin (TBT), a well-known immunotoxic and apoptosis-inducing compound. The strategy used was to knockout DFF40 expression by CRISPR-cas9 method in Jurkat T cells and to determine the toxicity of TBT in DFF40 KO cells and DFF40 WT Jurkat cells. DFF40 KO Jurkat cells show an increase of cell viability following a 24-h TBT exposure (p < 0.05). There is a resistance to TBT-induced apoptosis determined by annexin V/PI am labeling (p < 0.05). Interestingly, the basal level of ROS rises in DFF40 KO Jurkat cells, but ROS production levels after TBT exposure remains at the same basal level. Other apoptosis or DNA damage makers (procaspase-3, caspase-6, and PARP cleavage) are significantly delayed and decreased. DFF40 deficient cells do not present histone H2AX phosphorylation, whereas wild-type cells present a phosphorylation following a 6-h exposure to TBT (p < 0.001). The re-expression of DFF40 in DFF40 KO cells restores the cytotoxic effects of TBT. Overall, these data suggest a role of DFF40 in cells sensitivity to TBT and possibly in DNA stability.

Endocrine disruptors of inhibiting testicular 3β-hydroxysteroid dehydrogenase

Testicular 3β-hydroxysteroid dehydrogenase (HSD3B) is a steroidogenic enzyme, catalyzing the conversion of 3β-hydroxysteroids into 3-keto-steroids. Two distinct isoforms in the human are cloned, HSD3B1 and HSD3B2, and HSD3B2 is located in the testis. HSD3B2 is a two-substrate enzyme, which binds to cofactor NAD⁺ and a 3β-steroid. Many endocrine disruptors, including industrial compounds (phthalates, bisphenols, and perfluoroalkyl substances), insecticides and biocides (organochlorine insecticides and organotins), food additives (butylated hydroxyanisole, resveratrol, gossypol, flavones, and isoflavones), and drugs (etomidate, troglitazone, medroxyprogesterone acetate, and ketoconazole) inhibit testicular HSD3B, possibly interfering with androgen synthesis. In this review, we discuss the distinct testicular isoform of HSD3B, its gene, chemistry, subcellular location, and the endocrine disruptors that directly inhibit testicular HSD3B and their inhibitory modes.

Dibutyltin Dichloride Retards Leydig Cell Developmental Regeneration in Adult Rat Testis

Dibutyltin dichloride (DBTCl), widely used as plastic stabilizer, can cause comprehensive toxicity. The present study aims to investigate the effects of DBTCl on rat Leydig cell developmental regeneration and characterize the related mechanism. Adult male Sprague Dawley rats were randomly divided into four groups and gavaged with saline (control) or 5, 10, or 20 mg/kg/day of DBTCl consecutively for 10 days. At the end of the DBTCl treatment, all rats received a single intraperitoneal injection (i.p.,) of 75 mg/kg ethane dimethane sulfonate (EDS) to eliminate all the adult Leydig cells and to induce Leydig cell developmental regeneration. Leydig cell developmental regeneration was evaluated by measuring the levels of serum testosterone, luteinizing hormone, and follicle-stimulating hormone on days 7, 35, and 56 post-EDS. Leydig cell gene and protein expression levels, as well as cell morphology and cell counts were also carried out on day 56 post-EDS. The present study found that DBTCl significantly reduced serum testosterone levels on days 35 and 56 post-EDS, but increased serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels on day 56 at ≥ 5 mg/kg/day. The mRNA and protein levels of Leydig (Lhcgr, Scarb1, Star, Cyp11a1, Hsd17b3, and Hsd11b1) and Sertoli cells (Fshr, Amh, and Sox9) were significantly downregulated in the DBTCl-treated testes compared to the control. Immunohistochemical staining showed that DBTCl-treatment caused fewer regenerated Leydig cells and impaired Sertoli cell development and function in the testis on day 56 post-EDS. In conclusion, the present study demonstrates that DBTCl retards rat Leydig cell developmental regeneration by downregulating steroidogenesis-related enzymes at the gene and protein levels, inhibiting Leydig cell proliferation and impairing Sertoli cell function and development.

4-Bromodiphenyl ether delays pubertal Leydig cell development in rats

Polybrominated diphenyl ethers are a class of brominated flame retardants that are potential endocrine disruptors. 4-Bromodiphenyl ether (BDE-3) is the most abundant photodegradation product of higher polybrominated diphenyl ethers. However, whether BDE-3 affects Leydig cell development during puberty is still unknown. The objective of this study was to explore effects of BDE-3 on the pubertal development of rat Leydig cells. Male Sprague Dawley rats (35 days of age) were gavaged daily with BDE-3 (0, 50, 100, and 200 mg/kg body weight/day) for 21 days. BDE-3 decreased serum testosterone levels (1.099 ± 0.412 ng/ml at a dose of 200 mg/kg BDE-3 when compared to the control level (2.402 ± 0.184 ng/ml, mean ± S.E.). BDE-3 decreased Leydig cell size and cytoplasmic size at a dose of 200 mg/kg, decreased Lhcgr, Star, Dhh, and Sox9 mRNA levels at ≥ 100 mg/kg and Scarb1, Cyp11a1, Hsd17b3, and Fshr at 200 mg/kg. BED-3 also decreased the phosphorylation of AKT1, AKT2, ERK1/2, and AMPK at 100 or 200 mg/kg. BDE-3 in vitro induced ROS generation, inhibited androgen production, down-regulated Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Srd5a1, and Akr1c14 expression in immature Leydig cells after 24-h treatment. In conclusion, the current study indicates that BDE-3 disrupts Leydig cell development via suppressing AKT, ERK1/2, and AMPK phosphorylation and inducing ROS generation.

Lambda-cyhalothrin delays pubertal Leydig cell development in rats

Lambda-cyhalothrin (LCT) is a widely used broad-spectrum pyrethroid insecticide and is expected to cause deleterious effects on the male reproductive system. However, the effects of LCT on Leydig cell development during puberty are unclear. The current study addressed these effects. Twenty-eight-day-old male Sprague Dawley rats orally received LCT (0, 0.25, 0.5 or 1 mg/kg body weight/day) for 30 days. The levels of serum testosterone, luteinizing hormone, and follicle-stimulating hormone, Leydig cell number, and its specific gene and protein expression were determined. LCT exposure lowered serum testosterone levels at doses of 0.5 and 1 mg/kg and luteinizing hormone levels at a dose of 1 mg/kg, but increased follicle-stimulating hormone levels at doses of 0.5 and 1 mg/kg. LCT lowered Star and Hsd3b1 mRNA or their protein levels at a dose of 1 mg/kg. Immature Leydig cells were purified from pubertal rats and treated with different concentrations of LCT for 24 h and medium androgen levels, Leydig cell mRNA and protein levels, the mitochondrial membrane potential (△Ψm), and the apoptotic rate of immature Leydig cells were investigated. LCT inhibited androgen production at 5 μM and downregulated Scarb1 at 0.05 μM, Hsd3b1 and Hsd11b1 at 0.5 μM, and Cyp11a1 at 5 μM. LCT also decreased △Ψm at 0.5 and 50 μM. In conclusion, LCT can influence the function of Leydig cells.