Germ Cell Apoptosis In Rats Research Articles

Is losartan a promising agent for the treatment of type 1 diabetes-induced testicular germ cell apoptosis in rats?

Diabetes mellitus (DM) is common metabolic disease that poses a major risk to public health and fertility. Previous studies indicate that DM may cause male infertility by triggering oxidative stress and germ cell apoptosis in the testis. Due to the undesirable effects of known antidiabetic drugs, scientists have begun to investigate the use of alternative drugs to control infertility complications observed in men. In this context, present study aimed to investigate the possible antiapoptotic effect of losartan against DM-induced testicular germ cell apoptosis. Expreimental DM model was induced by intraperitoneal injection of streptozocin (STZ, 55mg/kg) to 28 rats, which were then randomly assigned to 4 groups; 1 mL saline solution was given to DM + saline group by oral gavage, 5mg/kg/day oral losartan was given to DM + low-dose losartan, 20mg/kg/day oral losartan was given to DM + mid-dose losartan and, 80mg/kg/day oral losartan was given to DM + high-dose losartan group for 4 weeks. Bax, Bcl-2 and cleaved-Caspase 3 immunoexpression, terminal-deoxynucleotidyl transferase dutp nick end labeling (TUNEL), Annexin-V and Real Time PCR analyses performed to evaluate antiapoptotic effects of losartan on diabetic rats' testis. In addition, biochemical analyzes carried out to evaluate change in oxidative stress. The results showed that losartan may have dose-related antiapoptotic effects on rats' testis via decreasing oxidative stress.

The protective effect of curcumin on testicular tissue in a cryptorchid rat model

Cryptorchidism is the most common abnormality of male sexual development. For the protection of testicular functions, antioxidants have emerged as novel options. This study aimed to investigate the protective effect of curcumin (Cur), a strong antioxidant, on the Flutamide-induced cryptorchidism testicular tissue. Pregnant rats were randomly allocated to 3 groups (n=10, each): a control, a model, and a Cur-treated group (100mg/kg/d). All offspring were delivered by days 21-22 of gestation and the male rats were sacrificed at postnatal birth days (PNDs) PND60. The testicles were separated and weighed, followed by TUNEL staining to detect germ cell apoptosis, an ELISA kit to measure SOD and MDA, and Western blot analysis to evaluate the expression of Bax, Bcl-2, and PCNA. Curcumin administration ameliorated the histological appearance of the testis and greatly reduced the level of apoptosis in cryptorchidism rats' testicular cells. After curcumin treatment, the expression of proliferating cell nuclear antigen (PCNA) was restored in the testis tissues of cryptorchidism rats. Curcumin therapy reduced Bax expression while increasing Bcl-2 expression, according to the molecular study. Curcumin therapy also reduced malondialdehyde (MDA) levels and enhanced superoxide dismutase (SOD) levels in cryptorchidism rats' testis tissue. It can be concluded that curcumin administration significantly reduced the germ cell apoptosis in rats with cryptorchidism, which provides new insight for antioxidant therapy in preserving testicular functions before or after surgery in cryptorchidism.

Antagonistic Effect of Cuscuta chinensis on a Rat Model with Unilateral Cryptorchidism.

BackgroundThe aim of this study was to investigate the effect of Cuscuta chinensis Lam. on germ cell apoptosis in a rat model of unilateral cryptorchidism.Material/MethodsThirty male SD rats were randomly and equally divided into a control group, a model group, and a Cuscuta group (5.0 g/kg/d) (n=10). The rat model of unilateral cryptorchidism in the model and Cuscuta groups was established by removal of the right gubernaculum, while rats in the control group received no treatment. After modeling, rats in the Cuscuta chinensis group were intragastrically administered Cuscuta chinensis extract (5.0 g/kg/d), while rats in the control group and model group were administered an equal volume of normal saline. After 90 days, all the rats were sacrificed and the testicles were separated and weighed, followed by TUNEL staining to detect germ cell apoptosis, flow cytometry to measure JC-1, ROS, and MDA, and Western blot analysis to evaluate the expression of Bax, Bcl-2, and cleaved caspase3.ResultsNinety days after the operation, Cuscuta chinensis Lam significantly minimized the damage caused by modeling by increasing weight of testis, reducing the germ cell apoptosis, and enhancing the mitochondrial membrane potential of testicles, as shown by levels of JC-1, ROS, and MDA, as well as elevating the level of Bcl-2/Bax and reducing the level of cleaved caspase3 (P<0.05).ConclusionsTreatment with Cuscuta chinensis Lam reduced the germ cell apoptosis in rats with unilateral cryptorchidism, which provides new insight for the development of cryptorchidism therapy in the future.

Resveratrol Ameliorates Microcystin-LR-Induced Testis Germ Cell Apoptosis in Rats via SIRT1 Signaling Pathway Activation.

Microcystin-leucine arginine (MC-LR), a cyclic heptapeptide produced by cyanobacteria, is a strong reproductive toxin. Studies performed in rat Sertoli cells and Chinese hamster ovary cells have demonstrated typical apoptosis after MC-LR exposure. However, little is known on how to protect against the reproductive toxicity induced by MC-LR. The present study aimed to explore the possible molecular mechanism underlying the anti-apoptosis and protective effects of resveratrol (RES) on the co-culture of Sertoli–germ cells and rat testes. The results demonstrated that MC-LR treatment inhibited the proliferation of Sertoli–germ cells and induced apoptosis. Furthermore, sirtuin 1 (SIRT1) and Bcl-2 were inhibited, while p53 and Ku70 acetylation, Bax expression, and cleaved caspase-3 were upregulated by MC-LR. However, RES pretreatment ameliorated MC-LR-induced apoptosis and SIRT1 inhibition, and downregulated the MC-LR-induced increase in p53 and Ku70 acetylation, Bax expression, and caspase-3 activation. In addition, RES reversed the MC-LR-mediated reduction in Ku70 binding to Bax. The present study indicated that the administration of RES could ameliorate MC-LR-induced Sertoli–germ cell apoptosis and protect against reproductive toxicity in rats by stimulating the SIRT1/p53 pathway, suppressing p53 and Ku70 acetylation and enhancing the binding of Ku70 to Bax.

Aerobic exercise blocks interleukin-6 levels and germ cell apoptosis in obese rats.

To investigate the effect of a high-fat diet and aerobic exercise intervention and its related mechanism on rat germ cell apoptosis. Forty male Sprague-Dawley rats were randomly divided into control group, high-fat diet group, control exercise group and high-fat exercise group. Rats were fed with high-fat diet or were given weight-free swimming. The levels of TG, TC, HDL, LDL and IL-6 in serum of rats were measured. The body weight, body length and inguinal fat weight were measured to calculate the Lee's index and lipid/body weight ratio. The expression of IL-6 mRNA in inguinal fat and IL-6R,Bcl-2 and Bax mRNA in testis was detected by RT-PCR. The morphological structure of testis was observed, and the Johnsen's ten-point score was calculated by HE staining, and the germ cell apoptosis was detected by TUNEL method. We got from the experimental results: a high-fat diet induces obesity and lipid metabolism disorder, alters testis morphological structure and increases germ cell apoptosis in rats. Aerobic exercise improves the lipid metabolism disorder and interferes with germ cell apoptosis by reducing interleukin-6 and interleukin-6 receptor expression.

The ameliorative effects of vinpocetine on apoptosis and HSP-70 expression in testicular torsion in rats

Vinpocetine is a potent antioxidant and free radical scavenger. We investigated the effects of vinpocetine on torsion/detorsion (T/D) induced testicular damage, HSP-70 expression and germ cell apoptosis in rats. Sixty Wistar albino adult male rats were divided into five groups of 12. The groups comprised a control group, a sham treated group, a T/D group, a vinpocetine treated group, and a T/D plus vinpocetine treated group. The left testis of each rat was subjected to unilateral torsion followed by detorsion after 2 h. Vinpocetine was administered intraperitoneally immediately and for 10 days following detorsion. At the end of the study, the rats were sacrificed and their testes removed and processed. HSP-70 expression, apoptosis and histopathological damage scores were determined for each group. Testicular T/D caused significant increases in apoptosis and HSP-70 expression, and a significant decrease in Johnsen’s testicular biopsy scores and mean seminiferous tubule diameter. Vinpocetine ameliorated testicular histopathology and HSP-70 expression in the T/D + vinpocetine group. Consequently, vinpocetine may prevent testicular injury following testicular torsion owing to its antioxidant effects.

Humanin protects against chemotherapy-induced stage-specific male germ cell apoptosis in rats.

Humanin (HN) has cytoprotective action on male germ cells after testicular stress induced by heat and hormonal deprivation. To examine whether HN has protective effects on chemotherapy-induced male germ cell apoptosis, we treated four groups of adult rats with (i) vehicle (control), (ii) HN, (iii) cyclophosphamide (CP); or (iv) HN+CP. To investigate whether the protective effects of HN on germ cells require the presence of Leydig cells, another four groups of rats were pre-treated with ethane dimethanesulfonate (EDS), a Leydig cell toxicant, to eliminate Leydig cells. After 3 days, when Leydig cells were depleted by EDS, we administered: (i) vehicle, (ii) HN, (iii) CP; or (iv) HN+CP to rats. All rats were killed 12 h after the injection of HN and/or CP. Germ cell apoptosis was detected by TUNEL assay and quantified by numerical count. Compared with control and HN (alone), CP significantly increased germ cell apoptosis; HN +CP significantly reduced CP-induced apoptosis at early (I-VI) and late stages (IX-XIV) but not at middle stages (VII-VIII) of the seminiferous epithelial cycle. Pre-treatment with EDS markedly suppressed serum and intratesticular testosterone (T) levels, and significantly increased germ cell apoptosis at the middle (VII-VIII) stages. CP did not further increase germ cell apoptosis in the EDS-pre-treated rats. HN significantly attenuated germ cell apoptosis at the middle stages in EDS pre-treated rats. To investigate whether HN has any direct effects on Leydig cell function, adult Leydig cells were isolated and treated with ketoconazole (KTZ) to block testosterone synthesis. HN was not effective in preventing the reduction of T production by KTZ in vitro. We conclude that HN decreases CP and/or EDS-induced germ cell apoptosis in a stage-specific fashion. HN acts directly on germ cells to protect against EDS-induced apoptosis in the absence of Leydig cells and intratesticular testosterone levels are very low.

N-acetyl-l-cysteine modulates multiple signaling pathways to rescue male germ cells from apoptosis induced by chronic hCG administration to rats

The present study was aimed to investigate the beneficial effects of N-acetyl-L: -cysteine (NAC, 150mg/kg bw twice/week) against testicular germ cell apoptosis in rats induced by chronic hCG administration (100IU/rat/day for 30days). NAC co-treatment improved serum testosterone, prevented rise in lipid peroxidation, intracellular H(2)O(2) and the activities of antioxidant enzymes in germ cells. Replenishment of intracellular GSH and total antioxidant capacity was seen. There was a marked reduction in TUNEL positive germ cells and expression of caspase-3 (p<0.01) and PARP cleavage. Pro-apoptotic markers Fas, FasL, caspase-8 were also significantly downregulated. While Bcl-2 was fully restored, rise in Bax, caspase-9, phospho-JNK/JNK and phospho-c-Jun/c-Jun expression was significantly arrested. Anti-apoptotic phospho-Akt/Akt and NF-κB were otherwise found upregulated. Taken together, the above findings demonstrate that NAC intervention rescued the testicular germ cells from demise following chronic hCG treatment through regulation of multiple signaling mechanisms of metazoan apoptosis.

Testicular Annexin A5 Expression Augmented by Experimental Cryptorchidism and Could Affect Germ Cell Apoptosis in Rats

To examine the expression of annexin A5, a recently emerged multifunctional protein, in the testis after experimental cryptorchidism. The hemilateral testes of rats were surgically relocated from the scrotum into the abdomen. The annexin A5 content was evaluated by Western blot analysis, and its distribution was determined by immunohistochemistry. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) was performed to detect the apoptotic cells. Although annexin A5 content was not changed in the scrotal testis, it was dramatically increased in the abdominal testis during the 4-week observation period. TUNEL-positive apoptotic spermatogonia appeared in some of the seminiferous tubules only 1 day after the surgery. The appearance of TUNEL-positive cells was accompanied by augmented expression of annexin A5. Spermatocytes disappeared by 1 week after cryptorchidism, and annexin A5 expression was significantly increased inside the seminiferous tubules. In the cryptorchid testis, annexin A5 of the interstitial cells disappeared, as did 3beta-hydroxy steroid dehydrogenase. Annexin A5 on endothelial cells was not changed by the cryptorchidism. These data demonstrate first that the expression of annexin A5 is increased in the seminiferous tubules of cryptorchid testes and suggest that it is related to the degenerative response of germ cells.

Mitogen-Activated Protein Kinase Signaling in Male Germ Cell Apoptosis in the Rat1

Programmed germ cell death is critical for functional spermatogenesis. Increased germ cell apoptosis can be triggered by various regulatory stimuli, including testicular hyperthermia or deprivation of gonadotropins and intratesticular testosterone. We have previously shown the involvement of the mitogen-activated protein kinase (MAPK) 14 in apoptotic signaling of male germ cells across species after hormone deprivation. This study investigates the role of MAPK14 in germ cell apoptosis in rats triggered by testicular hyperthermia. The contributions of the MAPK1/3 and the MAPK8 to male germ cell death were also examined after this intervention. We show that 1) testicular hyperthermia results in induction of both MAPK1/3 and MAPK14 but not MAPK8; 2) inhibition of MAPK1/3 has no effect on the incidence of heat-induced germ cell apoptosis, suggesting that MAPK1/3 signaling may be dispensable for heat-induced male germ cell apoptosis; and 3) activation of MAPK14 and BCL2 phosphorylation are critical for heat-induced male germ cell apoptosis in rats. Thus, unlike the hormone deprivation model, heat stress through activation of the MAPK14 signaling promotes germ cell apoptosis by provoking BCL2 phosphorylation, leading to its inactivation and the subsequent activation of the mitochondria-dependent death pathway. These novel findings point to a critical role of MAPK14 in stage- and cell-specific activation of male germ cell apoptosis triggered by hormone deprivation or heat stress.

Role of Caspase 2 in Apoptotic Signaling in Primate and Murine Germ Cells1

This study investigates the role of caspase 2 in apoptotic signaling of nonhuman primate male germ cells triggered by mild testicular hyperthermia, testosterone (T(e)) implants, or by combined interventions. Mean incidence of germ cell apoptosis increased significantly by Day 3 in the heat (H(e)) alone group and by Day 8 in the Te alone group but peaked at Day 3 in H(e) + T(e) group. We found activation of caspase 2 in both germ cells and Sertoli cells after induction of apoptosis. Most notably, active caspase 2 immunoreactivity was detected only in those germ cells susceptible to apoptosis compared with controls, where little or no such staining is detected. To further explore the role of caspase 2 in regulating male germ cell death, we next evaluated the efficacy of caspase 2 inhibition in preventing or attenuating heat-induced germ cell apoptosis in rats. Caspase 2 inhibition significantly (P < 0.05) prevented such heat-induced germ cell apoptosis. The protection offered by the caspase 2 inhibitor occurred upstream of mitochondria, involving suppression of mitogen-activated protein kinase (MAPK) 14 activation and inducible nitric oxide synthase (NOS2) induction and, in turn, suppression of cytochrome c-mediated death pathway. Together, our results show that caspase 2 is activated in male germ cells undergoing apoptosis in nonhuman primates after heat stress, hormonal deprivation, or after combined interventions. Blockade of caspase 2 activation prevents heat-induced germ cell apoptosis in rats by suppressing the MAPK14- and NO-mediated intrinsic pathway signaling.

Role of endogenous cannabinoids in ischemia/reperfusion injury following testicular torsion in rats

The role of endogenous cannabinoids in ischemia/reperfusion induced germ cell apoptosis in rats was investigated. Baseline group was for basal normal values. The Sham operated group served as a control group. The torsion/detorsion (T/D) group underwent torsion (1 h) and detorsion; AN1, AN2, and AN3 groups received anandamide (10 mg/kg) 30 min before torsion, 30 min after torsion, and just after detorsion, respectively. In the AM251 group, AM251 (0.5 mg/kg) was injected 45 min before torsion and in the AN/AM group, AM251 and anandamide were injected 45 and 30 min before torsion, respectively. Lipid peroxidation, antioxidant enzymes, and germ cell apoptosis was determined. Malondialdehyde (MDA) levels in the T/D group were significantly higher than the control group. Moreover, MDA values in the AN1, AN2, and AN3 groups were significantly lower than T/D. There were significant decreases in catalase and superoxide dismutase activities in the T/D group versus the control group. These values in the AN1, AN2, and AN3 groups were significantly higher than T/D. It was also shown that MDA levels in the AN/AM group were significantly higher than the AN1 group. In the AN/AM group, catalase and superoxide dismutase activities were significantly lower versus the AN1 group. The mean germ cell apoptosis scores in all animals with testicular T/D were significantly higher than the control group. There was no difference between the apoptotic indices in the AN1, AN2, AN3, and T/D groups. Apoptosis scores in AM251 and AN/AM were significantly higher compared with the T/D and AN1 groups. Although anandamide increased antioxidant markers, it failed to reduce germ cell apoptosis. AM251 worsened the antioxidant defense system, which is reflected as higher germ cell apoptosis.

TESTICULAR HYPERTHERMIA BUT NOT HORMONE DEPRIVATION RESULTS IN STAGE- AND CELL-SPECIFIC ACTIVATION OF ERK AND INACTIVATION OF BCL-2.

In earlier studies, we have shown that the mitochondria-dependent (intrinsic) pathway is the key pathway for male germ cell apoptosis across species. To characterize the upstream signaling pathways that activate this death pathway, here we investigated the contributions of ERK (extracellular signal-regulated kinase) and JNK (c-Jun NH2-terminal kinase) to male germ cell apoptosis in rats after hormone deprivation or heat stress. In the hormone deprivation model, rats were given a daily injection of vehicle for 14 days or GnRH-antagonist, acyline (1.6 mg/kg BW) for 2, 5, and 14 days. In the hyperthermia model, scrota of rats were exposed once to a temperature of 22°C (control) or 43°C for 15 minutes and killed at ½, 2, and 6 hours after heat treatment. Testicular hyperthermia but not hormone withdrawal led to sustained activation of ERK. Immunocytochemistry further revealed ERK activation only in the Sertoli cells involving exclusively heat-susceptible early (I-IV) and late (XII-XIV) stages within ½ hour of heating. By 6 hours, immunostaining for active ERK was, however, evident, mostly in germ cells. Co-staining for TUNEL and phospho-ERK confirmed activation of ERK only in those germ cells undergoing apoptosis. Heat-induced germ cell apoptosis was also preceded by JNK activation, as evidenced by an increase in phospho c-Jun in testis lysates within ½ hour of heating. Unlike ERK, phospho-c-Jun immunostaining was detected only in those heat-susceptible germ cells. Because activation of both ERK and JNK is known to induce BCL-2 phosphorylation leading to its inactivation, we next examined whether the increased germ cell apoptosis after heat stress is associated with BCL-2 phosphorylation. Compared with control, where no staining was detected, we found marked increase in serine-phosphorylated form of inactive BCL-2 only in heat-susceptible germ cells. Co-staining for TUNEL and phospho-BCL-2 confirmed phosphorylation of BCL-2 only in those germ cells undergoing apoptosis. The BCL-2 phosphorylation was not apparent during hormone deprivation-induced apoptosis. These results suggest that (1) ERK and JNK promote male germ cell apoptosis via inactivation of BCL-2 through serine phosphorylation, and (2) ERK signaling is decisively different between these two paradigms and may represent an important step in the signal transduction pathway by which heat stress induces male germ cell apoptosis.

Effect of cocaine on germ cell apoptosis in rats at different ages

To investigate the effect of cocaine on apoptosis and caspase-3 activity in germ cells in male rats at different ages. Cocaine hydrochloride was given (15 mg/kg body weight s.c.) to male Sprague-Dawley rats of 3 weeks (n = 8), 6 weeks (n = 8) and 12 weeks (n = 8) of age, daily for 28 Days. The serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), testosterone (T) and estrogen (E2) were assayed, and the DNA fragmentation of germ cells was determined by gel eletronphoresis. The cell cycle, apoptosis and caspase-3 activity of germ cells were tested by flow cytometry. After the 28-day cocaine treatment, testes weight of the 3-week-old rats, the testes and body weights of the 6-week-old rats were decreased significantly compared to those of their corresponding controls (P < 0.05). The serum level of T was decreased significantly in the 3-week-old and 6-week-old rats, and the serum level of PRL was also decreased significantly in 12-week-old rats compared to the controls (P < 0.05). In all the three cocaine-treated groups, the isolated DNA displayed a clear ladder pattern, especially in the 6-week old rats. The number of apoptosic germ cells increased significantly in 3- and 6-week-old rats treated with cocaine (P < 0.05). The caspase-3 activity in all three groups increased significantly compared to the controls (P < 0.05), especially in the 6-week-old rats. Cocaine exposure for 28 Days leads to significant damage to male gonad and apoptosis elevation in testes of rats of different ages, especially in those of 6 weeks of age. The increase in caspase-3 activity might be a key pathway related to the early stage of apoptosis as the mechanism of cocaine-induced germ cell loss.

Estradiol treatment induces testicular oxidative stress and germ cell apoptosis in rats

In order to understand the pathogenesis of estradiol induced effects in the seminiferous epithelium, studies were undertaken in adult rats with estradiol-3-benzoate administered for different durations. After 30 d of treatment, a significant rise in lipid peroxidation with concomitant fall in the activities of superoxide dismutase and catalase was observed. Both, serum and intra-testicular testosterone levels were found severely depleted. Seminiferous epithelium was devoid of elongated spermatids and spermatozoa by 30 d of treatment. Number of spermatocytes and round spermatids were significantly (p < 0.001) reduced. Flowcytometric analysis confirmed a drastic reduction of the haploid cell population (1c peak). Beginning from day 10 of treatment, there was a consistent rise in the number of pyknotic/apoptotic germ cells in the seminiferous epithelium. A gradual increase in Bax protein expression was observed with the duration of treatment. The shift in Bax immunostaining from the cytoplasm and nucleus of germ cells (at 10 d of treatment) to only nuclei of cells by 30 d of treatment was also noticed. By this time testicular tissue showed three-fold increase in caspase-8 enzyme activity. Viable testicular cells isolated in vitro decreased drastically subsequent to different periods of estradiol treatment. The above findings substantiate the fact that the testicular pathogenesis of estradiol benzoate treatment may be primarily because of altered reproductive hormone levels and high oxidative stress leading to germ cell apoptosis and subsequent germ cell loss in the seminiferous epithelium.

Adenoviral-mediated HGF expression inhibits germ cell apoptosis in rats with cryptorchidism.

Prior studies have shown that the hepatocyte growth factor (HGF), as known for its multiple biological effects, possibly regulates spermatogenesis or tubulogenesis in the testis. To clarify the effect of HGF on restoration of spermatogenesis, or testicular weight, we transferred the HGF gene into the testis of the rat experimental cryptorchid model. Replication-deficient recombinant adenoviral vectors containing the CAG promoter driving rat HGF (pAxCAHGF) and LacZ (pAxCALacZ) were constructed. Sprague-Dawley rats surgically induced with unilateral cryptorchidism and subsequent orchidopexy were divided into three groups: control (PBS), pAxCALacZ and pAxCAHGF by intratesticular injection. At 2 and 4 weeks after subsequent orchidopexy, testes were removed and weighed. These specimens were analyzed histopathologically, and examined for cell apoptosis. HGF expression in these specimens associated with c-Met receptor-mediated signal molecules was examined by reverse transcription-polymerase chain reaction (RT-PCR), Western blot or immunohistochemical study. Adenovirus-mediated HGF gene transfer induced overexpression of HGF in some seminiferous epithelial cells and interstitial cells, increased the phosphorylation of ERK and Akt, and decreased numbers of apoptotic cells of germ cells. HGF transduction also significantly increased the numbers of germ cells and testicular weight by 4 weeks compared with the other control groups. Adenoviral-mediated HGF gene transfer into the testis in the cryptorchidism rats inhibited germ cell apoptosis and restored spermatogenesis.

Deciphering the pathways of germ cell apoptosis in the testis

A growing body of evidence demonstrates that germ cell death both spontaneous (during normal spermatogenesis) and that induced by suppression of hormonal support or increased scrotal temperature occurs via apoptosis. The mechanisms by which these proapoptotic stimuli activate germ cell apoptosis are not well understood. In order to provide some insight, here we report the key molecular components of the effector pathways leading to caspase activation and increased germ cells apoptosis triggered by mildly increased scrotal temperature. Short-term exposure (43 °C for 15 min) of the testis to mild heat results, within 6 h, in stage- and cell-specific activation of germ cell apoptosis in rats. Initiation of apoptosis was preceded by a redistribution of Bax from a cytoplasmic to paranuclear localization in heat-susceptible germ cells. Such relocation of Bax is further accompanied by sequestration of mitochondria and endoplasmic reticulum (ER) into paranuclear areas, cytosolic translocation of cytochrome c and is associated with activation of the initiator caspase 9 and the executioner caspases 3, 6, and 7, and cleavage of PARP. Furthermore, Bax is co-localized with ER in the susceptible germ cells as assessed by combined two-photon and confocal microscopy and Western blot analyses of fractionated testicular lysates. In additional studies, using gld and lpr cg mice, which harbor loss-of-function mutations in Fas-ligand (FasL) and Fas, respectively, we demonstrated that heat-induced germ cell apoptosis is not blocked, thus providing further evidence that the Fas signaling system is dispensable for heat-induced germ cell apoptosis in the testis. Taken together, these results demonstrate that the mitochondria- and possibly also ER-dependent pathways are the key apoptotic pathways for heat induced germ cell death in the testis.

Role of mitochondrial cytochrome c in cocaine-induced apoptosis in rat testes

Objectives We have previously demonstrated that cocaine exposure leads to apoptosis in rat testes. To understand further the mechanism of cocaine-induced testicular damage, we studied the effect of cocaine on cytochrome c release from the mitochondria. We also determined the caspase 3, caspase 8, and caspase 9 activities in rat testes after chronic cocaine exposure. Methods Thirty-day-old male Sprague-Dawley rats received cocaine hydrochloride or equal volumes of normal saline subcutaneously daily for 90 days. The testes were removed at 15, 30, and 90 days of cocaine or saline administration. Mitochondria and cytosolic fractions from testes were isolated. Western blotting was performed in both fractions using anti-cytochrome c antibody. Caspase 3, caspase 8, and caspase 9 activities were determined by fluorometric assay. Results The expression of cytochrome c protein in the cytosolic fraction was increased on day 15 and persisted for up to 90 days after cocaine injection compared with controls. However, the expression of cytochrome c in testes was decreased in the mitochondria fraction on days 15, 30, and 90 after cocaine injections compared with the corresponding controls. The caspase activity study showed caspase 3 and caspase 9 activities increased in cocaine-treated testes at each point of the study compared with the corresponding controls. However, the caspase 8 activity in cocaine-treated testes did not change significantly at each point of the study compared with the corresponding controls. Conclusions Our results suggest that the release of cytochrome c from mitochondria and its subsequent activation of caspase 9 and caspase 3 in testes play a key role in cocaine-induced germ cell apoptosis. Our findings also indicate that cocaine-induced testicular germ cell apoptosis in rats is at least initiated through a mitochondria-associated pathway.

Zearalenone induces male germ cell apoptosis in rats

Zearalenone (ZEA), a nonsteroidal estrogenic mycotoxin, is known to cause toxicity of testis in male rats. To investigate whether apoptosis is involved in ZEA-induced testicular toxicity and to identify the stage and target germ cell type, 10-week-old Sprague–Dawley male rats were treated with a single intraperitoneal (i.p.) dose of ZEA (5 mg/kg) and euthanized at 3, 6, 12, 24, or 48 h subsequently. Histopathologically, germ cell degeneration was found at stages I–VI 12 h after dosing. Degenerating germ cells were shown to undergo apoptosis as revealed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cells increased in a stage-specific manner, the peak frequency gradually progressing at stages I–VI of seminiferous tubules with time after dosing, suggesting that the damaged germ cells, especially spermatogonia and spermatocytes, gradually underwent the processes leading to apoptosis. DNA laddering on gel electrophoresis was apparent 12 h after dosing. The results demonstrated that a single dose of ZEA induces testicular germ cell apoptosis in a time-dependent and stage-specific pattern. This study has established that apoptosis is the principal mechanism contributing to germ cell depletion and testicular atrophy following ZEA exposure.

Doxorubicin induces male germ cell apoptosis in rats.

To clarify whether apoptosis is involved in doxorubicin (DXR)-induced testicular toxicity and to identify the target germ cell type, adult Sprague-Dawley rats were treated with a single intravenous dose of DXR (8 or 12 mg/kg) and euthanized at 3, 6, 12, 24, and 48 h subsequently. Histologically, germ cell degeneration was first found 6 h after dosing in meiotically dividing spermatocytes and early round spermatids of seminiferous tubules at stage 1, and subsequently observed in spermatogonia at stages I-VI showing ultrastructural characteristics of apoptosis. Coincident with the appearance of morphological changes, degenerating germ cells were shown to be undergoing apoptosis as revealed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cells increased in a stage- and cell type-specific manner, the peak of frequency gradually progressing from stage I of seminiferous tubules to later stages with time after dosing, suggesting that the damaged germ cells, especially spermatogonia, gradually underwent the processes leading to apoptosis. DNA laddering on gel electrophoresis was apparent 24 and 48 h after dosing. The results demonstrate that apoptosis plays an important role in the induction of testicular toxicity caused by DXR with meiotically dividing spermatocytes and type A and intermediate spermatogonia as highly vulnerable target cells.