p,p'-Dichlorodiphenoxydichloroethylene induced apoptosis of Sertoli cells through oxidative stress-mediated p38 MAPK and mitochondrial pathway.

p,p'-DDE, the major metabolite of dichlorodiphenoxytrichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. However, the mechanism underlying its male reproductive toxicity remains limited. Our previous studies have demonstrated that p,p'-DDE could induce mitochondria-mediated apoptosis of cultured rat Sertoli cells. In the present study, we investigated mitogen-activated protein kinase pathways as well as other mitochondria-related molecules including Bax family members and cytochrome c. Results showed that p,p'-DDE could induce oxidative stress-mediated p38 and JNK phosphorylation. In addition, elevated mRNA levels of cytochrome c and ratios of bax/bcl-w and bak/bcl-w were induced by p,p'-DDE treatment, which could be inhibited by RNA synthesis inhibitor (actinomycin D). p,p'-DDE-induced apoptosis was blocked by NAC (N-acetyl-L-cystein) preincubation and attenuated by pretreatment with p38 inhibitor (SB202190) or actinomycin D, but not with JNK inhibitor (SP600125). All of the findings suggested that oxidative stress-mediated p38 MAPK pathway and the balance between pro- and anti-apoptotic bax-gene family might play critical roles in p,p'-DDE-induced apoptosis.

ß-Benzene hexachloride induces apoptosis of rat Sertoli cells through generation of reactive oxygen species and activation of JNKs and FasL.

ß-benzene hexachloride (ß-BHC), the major metabolite of benzene-hexachloride (BHC), is a weak estrogen-like chemical. It is a known persistent organic pollutant and male reproductive toxicant. However, the mechanism by which ß-BHC exposure causes male reproductive toxicity remains unknown. In the present study, rat Sertoli cells were used to investigate the molecular mechanism involved in ß-BHC-induced toxicity in male reproductive system. The results indicated that ß-BHC exposure at over 30 µM showed the induction of apoptotic cell death. ß-BHC could induce elevation in reactive oxygen species (ROS) generation, increase in the leakage rate of LDH and MDA level, and decrease in SOD activity. In addition, there was an increase in the cellular levels of phospho-JNKs and FasL in the ß-BHC-induced apoptosis; and a significant reduction of procaspase-3 and -8 was observed over 30-µM ß-BHC treatment. The translocation of NF-κB enhanced with the increase of concentration of ß-BHC. Furthermore, NAC administration, a scavenger of ROS, reversed ß-BHC-induced apoptosis effects via inhibition of JNKs activation, FasL expression, and NF-κB translocation. These results lead us to speculate that ROS generation may play a critical role in the initiation of ß-BHC-induced apoptosis by activation of the JNKs, translocation of NF-κB, expression of FasL, and further activation of caspase cascade.

p,p'-DDE induces mitochondria-mediated apoptosis of cultured rat Sertoli cells.

p,p'-Dichlorodiphenoxydichloroethylene (p,p'-DDE), the major metabolite of dichlorodiphenoxytrichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. However, the mechanism underlying male reproductive toxicity of p,p'-DDE remains limited. In the present study, Sertoli cells were used to investigate the molecular mechanism involved in p,p'-DDE's male reproductive toxicity. Results showed that p,p'-DDE exposure at over 30 microM showed induction of apoptotic cell death. p,p'-DDE could induce mitochondria-mediated apoptotic changes including elevation in reactive oxygen species (ROS) generation, decrease in mitochondrial membrane potential (DeltaPsi(m)), and release of cytochrome c into the cytosol, which could be blocked by antioxidant agent N-acetyl-l-cysteine (NAC). In addition, elevated ratios of Bax/Bcl-w and Bak/Bcl-w and cleavages of procaspase-3 and -9 were induced by p,p'-DDE treatment. All of the results suggested that ROS generation may play a critical role in the initiation of p,p'-DDE-induced apoptosis by mediation of the disruption of DeltaPsi(m), the release of cytochrome c into the cytosol and further the activation of caspase cascade.

[Action mechanism of p,p'-DDE and/or beta-BHC on JNK and MAPK signal transduction pathways in rat Sertoli cells].

OBJECTIVE: To study the action mechanism of p,p'-DDE and/or beta-BHC on JNK and MAPK signal transduction pathways in rat Sertoli cells in vitro. METHODS: We cultured the Sertoli cells isolated from rat testicular tissues for 2 days in vitro, divided them into a control group incubated with DMSO and 3 case groups exposed to p,p'-DDE and / or beta-BHC at the final concentration of 10, 30, 50 micromol/L for 24 hours, and then detected the expression levels of JNK and c-jun mRNA by two-step RT-PCR. RESULTS: Twenty-four hours after p,p'-DDE treatment, the grayscale values of JNK mRNA were 0.068 +/- 0.001, 0.164 +/- 0.002, 0.207 +/- 0.006 and 0.499 +/- 0.017, and those of c-jun mRNA were 0.122 +/- 0.002, 0.157 +/- 0.006, 0.218 +/- 0.007 and 0.289 +/- 0.004 respectively in the DMSO control and the 10, 30 and 50 micromol/L groups. The expressions of JNK and c-jun mRNA were elevated with increased concentration of p,p'-DDE, with significant differences between the control and the case groups (P < 0.05), and they were also significantly upregulated in the beta-BHC and p,p'-DDE + beta-BHC groups in a dose-dependent manner. The grayscale values of JNK mRNA in the p,p'-DDE, beta-BHC and p,p'-DDE + beta-BHC groups at the concentration of 10 micromol/L were 0.164 +/- 0.002, 0.149 +/- 0.003 and 0.178 +/- 0.004, and those of c-jun mRNA were 0.157 +/- 0.006, 0.131 +/- 0.004 and 0.172 +/- 0.002, respectively, both significantly higher in the combination group than in the former two (P < 0.05). And the same was the case with the 30 and 50 micromol/L concentrations. CONCLUSION: Both p,p'-DDE and beta-BHC can enhance the expressions of JNK and c-jun in Sertoli cells, and their combination can produce even more obvious effect.

[Effects of p,p'-DDE and beta-BHC on the apoptosis of Sertoli cells in vitro].

OBJECTIVE: To explore the effects of p,p'-DDE and beta-BHC on the apoptosis of Sertoli cells in vitro via activation of Caspase. METHODS: Sertoli cells were treated in vitro for 24 hours with a serial concentrations of p,p'-DDE (10, 30 and 50 micromol/L), beta-BHC (10, 30 and 50 micromol/L) and p,p'-DDE + beta-BHC (10, 30 and 50 micromol/L). The inhibitory group was first treated with 100 micromol/L Caspase-3 inhibitor Ac-DEVD-CHO treating for 2 hours before 50 micromol/L p, p'-DDE + 50 micromol/L beta-BHC 24 hours-treatment. The vitality of Sertoli cells was determined by MTT and the apoptosis rate was measured by AO/EB double fluorescence staining. The expressions of Caspase-3, Caspase-8 and Caspase-9 were determined by RT-PCR. RESULTS: Average optical density (A) values were 0.498 +/- 0.039, 0.481 +/- 0.065, 0.397 +/- 0.032 and 0.286 +/- 0.049 in p,p'-DDE groups (10, 30, 50 and 70 micromol/L), and 0.518 +/- 0.103, 0.490 +/- 0.060, 0.454 +/- 0.054 and 0.302 +/- 0.030 in beta-BHC groups (10, 30, 50 and 70 micromol/L). In the mixture-treated groups (10, 30 and 50 micromol/L), the average A values were 0.483 +/- 0.048, 0.473 +/- 0.058 and 0.337 +/- 0.052. Compared with the solvent control group (0.527 +/- 0.022) , 50 micromol/L group of p, p'-DDE, beta-BHC or their mixture caused a significant decrease of Sertoli cell viability (t values were 4.599, 2.716, 6.537 respectively, P < 0.05). AO/EB double fluorescence staining analysis showed that apoptosis rates of Sertoli cells were significantly increased with all treated groups. The expressions of Caspase-3, Caspase-8 and Caspase-9 were upregulated as the concentrations of p,p'-DDE, beta-BHC and their mixture were increased. CONCLUSION: p,p'-DDE, beta-BHC and their mixture could induce the apoptosis of Sertoli cells in vitro which was associated with activation of Caspase-3 mediated by cleavage of Caspase-8 and Caspase-9.

[Mechanisms of mitogen-activated protein kinase pathway in male reproductive toxicity induced organochlorine pesticides].

Mitogen-activated protein kinase pathway may closely associated with cell growth, differentiation and apoptosis, it may play an important role in cell death. With growing evidences from in vitro test, recently it demonstrated that the MAPK play a key role in the reproductive toxicity induced organochlorine pesticides and also showed that the products of Reactive Oxygen Species (ROS) induced organochlorine pesticides in these process. The relationship between MAPK and their activation results in apoptosis induced organochlorine pesticides, for further clarification of the mechanism of male reproductive toxicity induced organochlorine pesticides.