Assessing Autophagy in the Leydig Cells

Triclosan inhibits testosterone biosynthesis in adult rats via inducing m6A methylation-mediated autophagy

Triclosan is a potent antibacterial compound widely used in everyday products. Whether triclosan affects Leydig cell function in adult male rats remains unknown. In this study, 0, 50, 100, or 200 mg/kg/day triclosan was gavaged to Sprague-Dawley male rats from 56 to 63 days postpartum. Triclosan significantly reduced serum testosterone levels at ≥ 50 mg/kg/day via downregulating the expression of Leydig cell gene Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3 and regulatory transcription factor Nr3c2 at 100-200 mg/kg. Further analysis showed that triclosan markedly increased autophagy as shown by increasing LC3II and BECN1 and decreasing SQSTM1. The mRNA m6A modification analysis revealed that triclosan significantly downregulated Fto expression at 200 mg/kg while upregulating Ythdf1 expression at 100 and 200 mg/kg, leading to methylation of Becn1 mRNA as shown by MeRIP assay. Triclosan significantly inhibited testosterone output in rat R2C Leydig cells at ≥ 5 μM via downregulating Fto and upregulating Ythdf1. SiRNA Ythdf1 knockdown can reverse triclosan-mediated mitophagy in R2C cells, thereby reversing the reduction of testosterone output. In summary, triclosan caused Becn1 m6A methylation by downregulating Fto and upregulating Ythdf1, which accelerated Becn1 translation, thus leading to the occurrence of autophagy and the decrease of testosterone biosynthesis.

VD3/VDR attenuates bisphenol A-induced impairment in mouse Leydig cells via regulation of autophagy

Bisphenol A (BPA) is an endocrine disruptor with reproductive toxicity. Further, 1,25-dihydroxyvitamin D3 (VD3) plays an important role in male reproduction by binding vitamin D receptor (VDR) and mediating the pleiotropic biological actions that include spermatogenesis. However, whether VD3/VDR regulates the effect of BPA on Leydig cells (LCs) injury remains unknown. This study aimed to explore the effects of VD on BPA-induced cytotoxicity in mouse LCs. Hereby, LCs treated with BPA, VD3, or both were subjected to the assays of cell apoptosis, proliferation, autophagy, and levels of target proteins. This study unveiled that cell viability was dose-dependently reduced after exposure to BPA. BPA treatment significantly inhibited LC proliferation, induced apoptosis, and also downregulated VDR expression. By jointly analyzing transcriptome data and Comparative Toxicogenomics Database (CTD) data, autophagy signaling pathways related to testicular development and male reproduction were screened out. Therefore, the autophagy phenomenon of cells was further detected. The results showed that BPA treatment could activate cell autophagy, Vdr-/- inhibits cell autophagy, and active VD3 does not have a significant effect on the autophagy of normal LCs. After VD3 and BPA were used in combination, the autophagy of cells was further enhanced, and VD3 could alleviate BPA-induced damage of LCs. In conclusion, this study found that supplementing VD3 could eliminate the inhibition of BPA on VDR expression, further enhance LCs autophagy effect, and alleviate the inhibition of LCs proliferation and induction of apoptosis by BPA, playing a protective role in cells. The research results will provide valuable strategies to alleviate BPA-induced reproductive toxicity.

Expression of the umami taste receptor T1R1/T1R3 in porcine testis of: Function in regulating testosterone synthesis and autophagy in Leydig cells

Testosterone is a vital male hormone responsible for male sexual characteristics. The taste receptor family 1 subunit 3 (T1R3) regulates testosterone synthesis and autophagy in non-taste cells, and the links with the taste receptor family 1 subunit 1 (T1R1) for umami perception. However, little is known about these mechanisms. Thus, we aimed to determine the relationship between the umami taste receptor (T1R1/T1R3) and testosterone synthesis or autophagy in testicular Leydig cells of the Xiang pig. There was a certain proportion of spermatogenic tubular dysplasia in the Xiang pig at puberty, in which autophagy was enhanced, and the testosterone level was increased with a weak expression of T1R3. Silenced T1R3 decreased testosterone level and intracellular cyclic adenosine monophosphate (cAMP) content and inhibited the messenger RNA (mRNA) expression levels of testosterone synthesis enzyme genes [steroidogenic acute regulatory protein (StAR), hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1 (3β-HSD1), cytochrome P450 family 17 subfamily A member 1 (CYP17A1) and hydroxysteroid 17-beta dehydrogenase 3 (17β-HSD3)]. In addition, T1R3 increased the number of acidic autophagy bubbles and upregulated the expression levels of autophagy markers [Microtubule-associated protein 1 A/1B-light chain 3 (LC3) and Beclin-1] in testicular Leydig cells of the Xiang pig. Using an umami tasting agonist (10 mM L-glutamate for 6 h), the activation of T1R1/T1R3 enhanced the testosterone synthesis ability by increasing the intracellular cAMP level and upregulated the expression levels of StAR, 3β-HSD1, CYP17A1 and 17β-HSD3 in Leydig cells. Furthermore, the number of acidic autophagy bubbles decreased in the T1R1/T1R3-activated group with the downregulation of the expression levels of the autophagy markers, including LC3 and Beclin-1. These data suggest that the function of T1R1/T1R3 expressed in testicular Leydig cells of the Xiang pig is related to testosterone synthesis and autophagy.

Knockdown of ZnT4 Induced Apoptosis, Inhibited Proliferation and testosterone synthesis of TM3 cells

Zinc deficiency has a huge impact on male reproduction. The zinc transporter (ZnT) family is involved in the maintenance of zinc homeostasis and testosterone synthesis. However, the underlying mechanisms remain to be investigated. Therefore, in this study, we aimed to determine the effect of zinc transporter 4 (ZnT4) on testosterone synthesis in male Kunming mice and mouse Leydig cells. The results of this study showed that compared with the zinc normal diet group (Con group), the zinc-deficient diet group (ZnD group) had decreased zinc content and increased ZnT4 expression in testicular tissues, and decreased serum testosterone levels, suggesting that ZnT4 may be involved in Leydig cell injury resulting from a zinc-deficient diet. Subsequently, mouse Leydig cell line TM3 cells were used to analyze the effect of ZnT4 downregulation on TM3 cell proliferation and apoptosis, on testosterone synthesis, and its underlying mechanisms. Here, we show that knockdown of ZnT4 can induce the accumulation of zinc, inhibit the viability, and induce apoptosis in TM3 cells. In addition, knockdown of ZnT4 downregulated testosterone concentration and expression of testosterone synthesis-related proteins steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase/D5-D4 isomerase (3β-HSD) in TM3 cells, while hCG could rescue their levels. We show that it is ZnT4 that plays a role in testosterone production through a mediated PI3K/Akt/mTOR autophagy pathway, whereas mTORC1 complex inhibitor (Rapa) blocks the decrease in testosterone levels caused by ZnT4 downregulation. In conclusion, the above results indicate that ZnT4 plays an important role in regulating testosterone synthesis.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

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.

Activation of Autophagy by Low-Dose Silica Nanoparticles Enhances Testosterone Secretion in Leydig Cells

Silica nanoparticles (SNPs) can cause abnormal spermatogenesis in male reproductive toxicity. However, the toxicity and toxicological mechanisms of SNPs in testosterone synthesis and secretion in Leydig cells are not well known. Therefore, this study aimed to determine the effect and molecular mechanism of low doses of SNPs in testosterone production in Leydig cells. For this, mouse primary Leydig cells (PLCs) were exposed to 100 nm Stöber nonporous spherical SNPs. We observed significant accumulation of SNPs in the cytoplasm of PLCs via transmission electron microscopy (TEM). CCK-8 and flow cytometry assays confirmed that low doses (50 and 100 μg/mL) of SNPs had no significant effect on cell viability and apoptosis, whereas high doses (more than 200 μg/mL) decreased cell viability and increased cell apoptosis in PLCs. Monodansylcadaverine (MDC) staining showed that SNPs caused the significant accumulation of autophagosomes in the cytoplasm of PLCs. SNPs activated autophagy by upregulating microtubule-associated protein light chain 3 (LC3-II) and BCL-2-interacting protein (BECLIN-1) levels, in addition to downregulating sequestosome 1 (SQSTM1/P62) level at low doses. In addition, low doses of SNPs enhanced testosterone secretion and increased steroidogenic acute regulatory protein (StAR) expression. SNPs combined with rapamycin (RAP), an autophagy activator, enhanced testosterone production and increased StAR expression, whereas SNPs combined with 3-methyladenine (3-MA) and chloroquine (CQ), autophagy inhibitors, had an opposite effect. Furthermore, BECLIN-1 depletion inhibited testosterone production and StAR expression. Altogether, our results demonstrate that low doses of SNPs enhanced testosterone secretion via the activation of autophagy in PLCs.

Evaluation of BPA effects on autophagy in Neuro-2a cells

Bisphenol A (BPA), which is used for the industrial production of polycarbonate plastics and epoxy resins, is found in many commercially available products. Plasticizer BPA produces chemical substances worldwide, and knowledge of its effects on humans and animals is increasing. In the present work, the morphology of cells was observed by optical microscopy and phalloidin staining to evaluate the toxic effect of BPA on Neuro-2a cells. Autophagy has an important role in the regulation of cell metabolism. To study the effect of BPA on the autophagy in Neuro-2a cells, the expression distribution of LC3 was detected by immunofluorescence, and the expression levels of p62 and Beclin1 were determined using western blot and quantitative real-time PCR (qRT-PCR), respectively. Optical microscopy and phalloidin staining revealed that the cells became rounded and small and that the dendritic spine of the cells were reduced at high BPA doses. Immunofluorescence analysis demonstrated that the expression of LC3 fluorescence intensity was weak at increasing BPA concentrations. Western blot results showed that the relative expression of protein p62 increased significantly and that the relative expression levels of the Beclin1 and the LC3 proteins significantly decreased with increasing BPA concentration. qRT-PCR results showed that the relative expression level of autophagy-related p62 mRNA increased significantly and that the relative expression level of Beclin1 mRNA decreased significantly with increasing BPA concentration. The above results indicated that BPA treatment exerted dose-dependent toxic effects on Neuro-2a cells, and BPA inhibited the autophagy level of Neuro-2a cells, thereby providing a new perspective in studying the toxic effect of BPA on Neuro-2a cells.

Macroautophagy involved in testosterone synthesis in Leydig cells of male dairy goat (Capra hircus)

Testosterone is an important steroid hormone that is indispensable for male sexual development and the reproductive system. Leydig cells (LCs), where autophagy is extremely active, reside in the testicular interstitium and are the major sites of testosterone production. However, the ultrastructural characteristics and the functional role of autophagy in LCs of livestock remain unknown. In this study, the LCs of the dairy goats were investigated to identify the steroidogenic activity and autophagy levels at different ages of development by light microscopy, immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy (TEM). Morphological results showed that the steroidogenic activity (3β-HSD staining) and ultrastructural characteristics of the LCs were changed with increasing age. TEM results demonstrated that the organelles involved in testosterone synthesis, e.g., smooth endoplasmic reticulum, mitochondria, and lipid droplets, were abundantly distributed within the cytoplasm of LCs in pubertal and adult testes. Moreover, autophagy activity was enhanced in the testes at pubertal and adult stages compared with that at the juvenile stage. Several different autophagic vacuoles, including pre-autophagosomes, autophagosomes, and autolysosomes, were observed within the cytoplasm of LCs from pubertal and adult testes. However, immunofluorescent staining and TEM results showed that no typical lipophagic or mitophagic vacuoles were observed in the cytoplasm of LCs. Furthermore, primary LCs from dairy goats were used to study the effect of autophagy on testosterone production. After treatment with 3-methyladenine (3-MA, an autophagy inhibitor), the primary LCs decreased testosterone production. In contrast, treatment with rapamycin (an autophagy activator), enhanced steroidogenesis in LCs. Collectively, these in vivo and in vitro results suggested that autophagy activity is related to steroidogenesis in LCs of dairy goats, which may ultimately influence the spermatogenesis and fertility of these animals.

Evaluation of Sertoli cell autophagy associated with laminin, fibronectin, and caspase-3 proteins' alteration, following testicular torsion rat

Autophagy is a vital process that maintains cellular homeostasis by joining lysosomes and providing energy production substrates. In testicular tissue, Sertoli cells play functional roles in spermatogenesis and steroidogenesis. It is well known that autophagy physiologically occurs in the Sertoli cells. Under pathological conditions, such as testicular torsion, autophagy can be activated under high-stress stimuli. It is worth noting that Sertoli cells receive autophagy-induced signals through some extracellular matrix proteins, e.g. laminin and fibronectin. The present study aims to evaluate Sertoli cells' autophagy-associated extracellular matrix proteins' alteration following testicular torsion in rat model. The animals were divided into two groups as sham and testicular torsion/detorsion groups. In the testicular torsion/detorsion group, testicular torsion was maintained for 6 hr, followed by detorsion for 14 days. The obtained results revealed that testicular torsion-induced oxidative stress leads to increased autophagy in Sertoli cells as well as the whole testicular tissue. Moreover, extracellular matrix proteins including laminin and fibronectin act as autophagy-regulating proteins, in which their expression levels are reduced and increased respectively. In addition, the level of caspase-3, as an autophagy inhibitory protein, did not increase significantly in the cytoplasm of Sertoli cells as opposed to whole testicular tissue, indicating that autophagy is active after testicular torsion in these cells.

Gestational exposure to tebuconazole affects the development of rat fetal Leydig cells

Tebuconazole is a triazole fungicide, used in agriculture to treat phytopathogenic fungi, and as a biocide, has been reported to be related to reproductive and developmental toxicity. The purpose of this study was to investigate the effect of tebuconazole exposure on rat fetal Leydig cells and fetal testis during pregnancy. Pregnant Sprague-Dawley rats were randomly divided into 4 groups, daily gavaged with corn oil (as a control), 25, 50, and 100 mg/kg body weight tebuconazole for 10 days (from the 12th day of pregnancy). Tebuconazole increased fetal serum testosterone and progesterone levels at a dose of 100 mg/kg. Exposure to 100 mg/kg tebuconazole significantly caused an increase in the number of fetal Leydig cells per testis without inducing cell aggregation. Tebuconazole up-regulated the expression of Star, Cyp11a1, Hsd17b3, and Fshr and their proteins. Further investigation found that tebuconazole caused increased phosphorylation of AKT1, ERK1/2, and mTOR, the level of BCL2, as well as the decrease of Beclin1, LC3B, and BAX, which may contribute to the fetal Leydig cell autophagy and proliferation. In conclusion, in utero exposure of tebuconazole causes the proliferation of fetal Leydig cells.

Cytoarchitectural improvement in Leydig cells of diabetic rats after treatment with aqueous and ethanol extracts of Dracaena arborea (Dracaenaceae)

BACKGROUND AND AIM

Recent studies have demonstrated the androgenic effects of Dracaena arborea in castrated and diabetic rats, but the cytoarchitectural mechanism at the level of Leydig cells (LCs) justifying this improvement in androgens production in diabetic rats has never been examined. We investigated the effects of aqueous and ethanol extracts of D. arborea on diabetes-induced cytoarchitectural impairments of LCs in rats.

EXPERIMENTAL PROCEDURE

Besides a normal group, 4 groups of diabetic rats were treated orally with Millipore water (10 ml/kg, diabetic), sildenafil citrate (1.44 mg/kg), aqueous (500 mg/kg) and ethanol (100 mg/kg) extracts of D. arborea for 21 days. On day 22, rats were sacrificed and the testes were removed and prepared for electron microscopic analyses of LCs ultrastructure.

RESULTS AND CONCLUSION

The ultrastructure of LCs in control rats was normal, while that in diabetic rats exhibited large heterochromatization in the nuclei, reduced amount of smooth endoplasmic reticulum with no lipid droplets in the cytoplasm, many autophagosomes and degenerated mitochondria containing lots of electron dense granules in the matrix. Interestingly, treatment with D. arborea especially its aqueous extract (500 mg/kg) alleviated these impairments, characterized by a rarification of heterochromatization in the nuclei coupled to an increase and the presence in the cytoplasm of prominent smooth endoplasmic reticulum and a reduction of electron dense granules in the matrix of mitochondria. These alleviating properties of D. arborea on LCs ultrastructure of diabetic rats could explain its androgenic potential. These results are useful for the management of patients suffering from diabetes-induced hypogonadism.

Gestational vinclozolin exposure suppresses fetal testis development in rats

Vinclozolin is a common dicarboximide fungicide used to protect crops from diseases. It is also an endocrine disruptor and is thought to be related to abnormalities of the reproductive tract. However, its mechanism of inducing abnormalities of the male reproductive tract is still unclear. The purpose of this study was to study the effect of gestational vinclozolin exposure on the development of rat fetal Leydig cells. Female pregnant Sprague-Dawley rats were exposed to vinclozolin (0, 25, 50, and 100 mg/kg body weight/day) by gavage from gestational day 14-21. Vinclozolin dose-dependently reduced serum testosterone levels at doses of 50 and 100 mg/kg and the anogenital distance at 100 mg/kg. RNA-seq, qPCR, and Western blotting showed that vinclozolin down-regulated the expression of Nr5a1, Sox9, Lhcgr, Cyp11a1, Hsd3b1, Hsd17b3, Amh, Pdgfa, and Dhh and their encoded proteins. Vinclozolin reduced the number of NR2F2-positive stem Leydig cells at a dose of 100 mg/kg and enhanced autophagy in the testes. In conclusion, vinclozolin disrupts reproductive tract development and testis development in male fetal rats via several pathways.

Adrenomedullin alleviates the pyroptosis of Leydig cells by promoting autophagy via the ROS-AMPK-mTOR axis

Adrenomedullin (ADM) exerts anti-oxidant, anti-inflammatory and anti-apoptotic effects in Leydig cells. However, the role and mechanism of ADM in the pyroptosis of Leydig cells are poorly understood. This study first showed the protective effects of ADM on the pyroptosis and biological functions of Leydig cells exposed to lipopolysaccharide (LPS) by promoting autophagy. Primary rat Leydig cells were treated with various concentrations of LPS and ADM, together with or without N-acetyl-L-cysteine (NAC) or 3-methyladenine (3-MA). Cell proliferation was detected through CCK-8 and BrdU incorporation assays, and ROS level was measured with the DCFDA assay. Real-time PCR, western blot, immunofluorescence, transmission electron microscopy, TUNEL and flow cytometry were performed to examine ADM's effect on the pyroptosis, autophagy and steroidogenic enzymes of Leydig cells and AMPK/mTOR signalling. Like NAC, ADM dose-dependently reduced LPS-induced cytotoxicity and ROS overproduction. ADM also dose-dependently ameliorated LPS-induced pyroptosis by reversing the increased expression of NLRP3, ASC, caspase-1, IL-1β, IL-18, GSDMD, caspase-3, caspase-7, TUNEL-positive and PI and active caspase-1 double-stained positive rate, DNA fragmentation and LDH concentration, which could be rescued via co-incubation with 3-MA. ADM dose-dependently increased autophagy in LPS-induced Leydig cells, as confirmed by the increased expression of LC3-I/II, Beclin-1 and ATG-5; decreased expression of p62 and autophagosomes formation; and increased LC3-II/LC3-I ratio. However, co-treatment with 3-MA evidently decreased autophagy. Furthermore, ADM dose-dependently rescued the expression of steroidogenic enzymes, including StAR, P450scc, 3β-HSD and CYP17, and testosterone production in LPS-induced Leydig cells. Like rapamycin, ADM dose-dependently enhanced AMPK phosphorylation but reduced mTOR phosphorylation in LPS-induced Leydig cells, which could be rescued via co-incubation with 3-MA. In addition, pyroptosis was further decreased, and autophagy was further promoted in LPS-induced Leydig cells upon co-treatment with ADM and rapamycin. ADM may protect the steroidogenic functions of Leydig cells against pyroptosis by activating autophagy via the ROS-AMPK-mTOR axis.