Toxicity of cannabidiol and its metabolites in TM3 mouse Leydig cells: a comparison with primary human Leydig cells.

Cannabidiol (CBD), one of the major components extracted from the plant Cannabis sativa L., has been used as a prescription drug to treat seizures in many countries. CBD-induced male reproductive toxicity has been reported in animal models; however, the underlying mechanisms remain unclear. We previously reported that CBD induced apoptosis in primary human Leydig cells, which constitute the primary steroidogenic cell population in the testicular interstitium. In this study, we investigated the effects of CBD and its metabolites on TM3 mouse Leydig cells. CBD, at concentrations below 30 µM, reduced cell viability, induced G1 cell cycle arrest, and inhibited DNA synthesis. CBD induced apoptosis after exposure to high concentrations (≥ 50 µM) for 24 h or a low concentration (20 µM) for 6 days. 7-Hydroxy-CBD and 7-carboxy-CBD, the main CBD metabolites of CBD, exhibited the similar toxic effects as CBD. In addition, we conducted a time-course mRNA-sequencing analysis in both primary human Leydig cells and TM3 mouse Leydig cells to understand and compare the mechanisms underlying CBD-induced cytotoxicity. mRNA-sequencing analysis of CBD-treated human and mouse Leydig cells over a 5-day time-course indicated similar responses in both cell types. Mitochondria and lysosome dysfunction, oxidative stress, and autophagy were the major enriched pathways in both cell types. Taken together, these findings demonstrate comparable toxic effects and underlying mechanisms in CBD-treated mouse and primary human Leydig cells.

[Effect of reactive oxygen species in cadmium chloride induced apoptosis of mouse Leydig cells].

OBJECTIVE: To study the effect of reactive oxygen species(ROS) in cadmium chloride-induced apoptosis of mouse Leydig cells(TM3 cells) and explore the underlying molecular mechanisms. METHODS: TM3 cells were used as an in vitro model for studying reproductive toxicity induced by cadmium exposure. The cells were treated with different concentrations of CdCl_2(0, 5 and 10 µmol/L) for 24 h. CCK-8 assay was used to detect the effect of CdCl_2 on TM3 cell activity. Hoechst33342 staining was performed to explore the formation of apoptotic bodies. DCFH-DA probe was used to detect the level of ROS in the cells. TM3 cells were pretreated with 1 mmol/L NAC for 1 h and then treated with 10 µmol/L CdCl_2 for 24 h. The protein expression levels of pro-apoptotic proteins Caspase-9 and cleaved Caspase-3 were detected by Western blot; RT-qPCR was used to measure the expression of anti-apoptotic gene Bcl-2 and pro-apoptotic genes Caspase-9 and Caspase-3. RESULTS: After exposure to CdCl_2 for 24 h, viability of TM3 cells decreased and the number of apoptotic bodies increased. Western blot result showed that the protein level of Caspase-9 in the 10 µmol/L CdCl_2 treatment group was increased to 0.86±0.10(P<0.05) compared with the control group(0.56±0.07). Compared with the control group(0.37±0.11), the protein level of cleaved Caspase-3 in the 5 and 10 µmol/L CdCl_2 treatment groups were increased to 0.65±0.03 and 1.05±0.13(P<0.05). Compared with the control group(46.80±1.24), the intracellular ROS content in the 5 and 10 µmol/L treatment groups increased to 60.47±1.39 and 80.63±1.34(P<0.05). Compared with the cadmium-treated group, NAC inhibited Caspase-9(CdCl_2 group: 0.89±0.07; CdCl_2+NAC group: 0.28±0.02)and cleaved Caspase-3(CdCl_2 group: 1.53±0.21; CdCl_2+NAC group: 0.66 ±0.07), the difference was statistically significant(P<0.05). At the same time, NAC decreased the ROS level(62.64±0.93) in the CdCl_2 exposure group(80.13±0.94)(P<0.05). In addition, RT-qPCR result showed that the Caspase-9 mRNA levels in the 5 and 10 µmol/L CdCl_2 treatment groups were 1.40±0.14 and 1.90±0.12(P<0.05), compared with the control group(0.97±0.10). Compared with the control group(0.88±0.08), the cleaved Caspase-3 mRNA levels in the 5 and 10 µmol/L CdCl_2 treatment groups were increased to 1.42±0.11 and 1.59±0.12(P<0.05). While in the 5 and 10 µmol/L CdCl_2-treated group, compared with the control group(0.94±0.02), the Bcl-2 mRNA level were decreased to 0.60±0.02 and 0.50±0.09(P<0.05). Compared with the cadmium treatment group(0.57±0.06), NAC could significantly improve the cadmium-induced Bcl-2 mRNA expression level(0.92±0.03), and Caspase-9(CdCl_2 group: 1.96±0.07; CdCl_2+NAC group: 1.04±0.02) and Caspase-3(CdCl_2 group: 1.65±0.02; CdCl_2+NAC group: 0.66±0.04) were decreased(P<0.05). CONCLUSION: The Caspase cascade in mouse Leydig cells can be activated by excessive ROS induced by CdCl_2, and inhibition of ROS production can significantly reduce the CdCl_2-induced apoptosis of TM3 cells.

Effects of T-2 toxin on the regulation of steroidogenesis in mouse Leydig cells.

T-2 toxin is one of the mycotoxins, a group of type A trichothecenes produced by several fungal genera including Fusarium species, which may lead to the decrease of testosterone secretion in primary Leydig cells derived from mouse testis. The previous study demonstrated T-2 toxin decrease the testosterone biosynthesis in the primary Leydig cells derived from the mouse testis directly. In this study, we further examined the direct biological effects of T-2 toxin on the process of steroidogenesis, primarily in Leydig cells of mice. Leydig cells of mature mouse were purified by Percoll gradient centrifugation and the cell purity was determined by 3ß-hydroxysteroid dehydrogenase (3ß-HSD) staining. To examine the decrease in T-2 toxin-induced testosterone secretion, we measured the transcription level of three key steroidogenic enzymes including 3ß-HSD-1, cytochrome P450 side-chain cleavage (P450scc) enzyme, and steroidogenic acute regulatory (StAR) protein in T-2 toxin/human chorionic gonadotropin (hCG) co-treated cells. Our previous study showed that T-2 toxin (10(-7), 10(-8), and 10(-9) M) significantly suppressed hCG (10 ng/ml)-induced testosterone secretion. The studies demonstrated that the suppressive effect is correlated with a decrease in the level of transcription of 3ß-HSD-1, P450scc, and StAR (p < 0.05).

Analysis of apoptosis induced by perfluorooctane sulfonates (PFOS) in mouse Leydig cells in vitro.

To explore the possible mechanism of perfluorooctane sulfonates (PFOS's) reproductive toxicity, mouse Leydig cells cultured in vitro were exposed to a serial concentration of PFOS for four more days of culture. Apoptosis during the process was checked. After 24 h, apoptosis occurred to all of the groups ≥ 50 µg/mL PFOS. After 72 h, 37.5 µg/mL dose also showed apoptosis, and the most apoptosis signals, averagely 18 per well, were observed in 62.5 µg/mL dose group. An increase in ROS (p < 0.05) and a decrease of mitochondrial membrane potential (p < 0.01) was confirmed in those groups with ≥ 12.5 µg/mL dose. ROS levels peaked in 50 µg/mL and 62.5 µg/mL groups, nearly two-folds higher than control. PFOS was also observed to down-regulate the protein expression of Bcl-2 and to up-regulate that of Bax. The apoptosis induced by PFOS in mouse Leydig cells was shown to be related to mitochondrially mediated pathways and to involve oxidative stress.

Effects of boric acid on cell death and oxidative stress of mouse TM3 Leydig cells in vitro.

BACKGROUND: Boron (B) is an abundant element on earth and presents at physiological pH in the form of boric acid (BA). It has both positive and negative effects on biological systems. BA and sodium borates have been considered as being toxic to the reproduction system in animal experiments. Unfortunately, the molecular mechanism underlying the toxic effects of BA is not fully understood. METHODS: Here, we demonstrate the influence of BA on mouse TM3 Leydig cells which are male reproductive system cells targeted by BA exposure. The cytotoxicity was evaluated by MTT and NRU assays. Annexin V-FITC/PI double staining kit, mitochondria membrane potential (ΔΨm) assay kit with JC-1 and caspase-3 colorimetric assay kit were used to indicate the cell death pathway. To estimate the role of oxidative stress in BA induced toxicity, glutathione (GSH) level, catalase (CAT) and superoxide dismutase (SOD) activities were measured manually. RESULTS: The cell viability assays showed that BA was not cytotoxic within the tested concentrations up to 1000 µM. Sub-toxic concentrations were used for detecting oxidative stress status. BA exposure was significantly reduced GSH level at 1000 µM and CAT activity in a concentration-dependent manner. However, SOD activity was increased at the tested concentrations (100-1000 µM). Moreover, ΔΨm was significantly decreased at 500 and 1000 µM of BA, while caspase-3 activity was not changed apparently. CONCLUSION: These findings demonstrated that BA is not cytotoxic and apoptotic but may slightly induces oxidative stress in TM3 Leydig cells at higher concentrations.

Protective effects of l-arginine against testosterone synthesis decreased by T-2 toxin in mouse Leydig cells.

The testosterone levels decreased by T-2 toxin in mouse Leydig cells were reported previously. It is not known, however, whether l-arginine improves the situation and what's the mechanism. Leydig cells were isolated and cultured with control, 10 nM T-2 toxin, 0.25, 0.5 or 1.0 mM l-arginine, and 10 nM T-2 toxin supplemented with 0.25, 0.5 or 1.0 mM l-arginine for 24 h. Cells and supernatants were collected to detect the mRNA expression and activities of P450scc (cholesterol side-chain cleavage enzyme), 3ß-HSD-1 (3ß-hydroxysteroid dehydrogenase/isomerase-1) and StAR (steroidogenic acute regulatory protein). Results revealed that l-arginine increased the testosterone levels declined by T-2 toxin and up-regulated the activities and mRNA expression of P450scc, 3ß-HSD-1 and StAR down-regulated by T-2 toxin in Leydig cells. Therefore, we concluded that l-arginine ameliorated the testosterone levels decreased by T-2 Toxin via regulating the mRNA expression and activities of P450scc, 3ß-HSD-1 and StAR in mouse Leydig cells.

Mycotoxin zearalenone induces apoptosis in mouse Leydig cells via an endoplasmic reticulum stress-dependent signalling pathway.

Zearalenone (ZEN) is a Fusarium mycotoxin that causes several reproductive disorders and genotoxic effects. This study demonstrated the involvement of endoplasmic reticulum (ER) stress in ZEN-induced mouse Leydig cell death. Our study showed that ZEN reduced cell proliferation in a murine Leydig tumour cell line in a dose-dependent manner. The involvement of apoptosis as a major cause of ZEN-induced cell death was further confirmed by the results of a caspase-3 activity assay, which showed a ZEN dose-dependent increase in cell death. Treatment of MLTC-1 and primary mouse Leydig cells with ZEN upregulated the expression of the ER stress-typical markers GRP78, CHOP and caspase-12 protein. Further, pre-treating the cells with 4-phenylbutyrate or knocking down GRP78 using lentivirus-encoded shRNA significantly diminished ZEN-induced apoptosis and inhibited the expression of CHOP and caspase-12. In summary, these results suggest that the activation of an ER stress pathway plays a key role in ZEN-induced apoptosis in the mouse Leydig cells.

T-2 toxin inhibits gene expression and activity of key steroidogenesis enzymes in mouse Leydig cells.

T-2 toxin is one of the mycotoxins, a group of type A trichothecenes produced by several fungal genera including Fusarium species, which may lead to the decrease of the testosterone secretion in the primary Leydig cells derived from the mouse testis. The previous study demonstrated the effects of T-2 toxin through direct decrease of the testosterone biosynthesis in the primary Leydig cells derived from the mouse testis. In this study, we further examined the direct biological effects of T-2 toxin on steroidogenesis production, primarily in Leydig cells of mice. Mature mouse Leydig cells were purified by Percoll gradient centrifugation and the cell purity was determined by 3ß-hydroxysteroid dehydrogenase (3ß-HSD) staining. To examine T-2 toxin-induced testosterone secretion decrease, we measured the transcription levels of 3 key steroidogenic enzymes and 5 enzyme activities including 3ß-HSD-1, P450scc, StAR, CYP17A1, and 17ß-HSD in T-2 toxin/human chorionicgonadotropin (hCG) co-treated cells. Our previous study showed that T-2 toxin (10(-7) M, 10(-8) M and 10(-9) M) significantly suppressed hCG (10 ng/ml)-induced testosterone secretion. The studies demonstrated that the suppressive effect is correlated with the decreases in the levels of transcription of 3ß-HSD-1, P450scc, and StAR (P<0.05) and also in enzyme activities of 3ß-HSD-1, P450scc, StAR, CYP17A1, and 17ß-HSD (P<0.05).

Endocrine disruptors differentially target ATP-binding cassette transporters in the blood-testis barrier and affect Leydig cell testosterone secretion in vitro.

Endocrine-disrupting chemicals (EDCs) are considered to cause testicular toxicity primarily via interference with steroid hormone function. Alternatively, EDCs could possibly exert their effects by interaction with ATP-binding cassette (ABC) transporters that are expressed in the blood-testis barrier. In this study, we investigated the effects of bisphenol A (BPA), tetrabromobisphenol A (TBBPA), bis(2-ethylhexyl) phthalate, mono(2-ethylhexyl) phthalate, perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS) on breast cancer resistance protein (BCRP), multidrug resistance proteins 1 and 4 (MRP1 and MRP4), and P-glycoprotein (P-gp) using membrane vesicles overexpressing these transporters. BPA solely inhibited BCRP activity, whereas TBBPA, PFOA, and PFOS inhibited all transporters tested. No effect was observed for the phthalates. Using transporter-overexpressing Madin-Darby canine kidney cells, we show that BPA and PFOA, but not TBBPA, are transported by BCRP, whereas none of the compounds were transported by P-gp. To investigate the toxicological implications of these findings, testosterone secretion and expression of steroidogenic genes were determined in murine Leydig (MA-10) cells upon exposure to the selected EDCs. Only BPA and TBBPA concentration dependently increased testosterone secretion by MA-10 cells to 6- and 46-fold of control levels, respectively. Inhibition of the Mrp's by MK-571 completely blocked testosterone secretion elicited by TBBPA, which could not be explained by coinciding changes in expression of steroidogenic genes. Therefore, we hypothesize that transporter-mediated efflux of testosterone precursors out of MA-10 cells is inhibited by TBBPA resulting in higher availability for testosterone production. Our data show the toxicological and clinical relevance of ABC transporters in EDC risk assessment related to testicular toxicity.