Relative morphological abnormalities of sperm in the caudal epididymis of high- and low-dose-rate gamma-irradiated ICR mice

Thiopurines exert harmful effects on spermatogenesis in Nudt15R138C knock-in mice

BACKGROUND

The association between thiopurine use and testicular reproductive functions remains unclear. In this study, we investigated whether thiopurines affect testicular functions based on the NUDT15 genotypes using Nudt15R138C knock-in mice.

METHODS

The male Nudt15R138C knock-in mice (9-12 weeks) were treated with mercaptopurine (MP: 0.5 mg/kg/day) for 4 or 12 weeks. To examine reversibility, some mice were maintained for a further 12 weeks under MP-free condition.

RESULTS

After MP treatment for 4 weeks, Nudt15R138C/R138C mice exhibited a significant reduction of testis weight compared to Nudt15+/+ mice and Nudt15+/R138C mice. The epithelial height and diameter of seminiferous tubules were significantly reduced in Nudt15R138C/R138C mice compared to Nudt15+/+ and Nudt15+/R138C mice. Apoptotic cells were significantly increased in Nudt15R138C/R138C mice, and most of apoptotic cells were spermatogonia. There were no significant changes in sperm counts and sperm morphology in MP-treated Nudt15R138C/R138C mice after 4-week MP treatment. On the other hand, after MP treatment for 12 weeks, the Nudt15+/R138C mice, but not Nudt15+/+ mice, exhibited a significant reduction in the testis weight and atrophic changes of seminiferous tubules, but these changes disappeared after 12-week rearing under MP-free condition. Despite a significant increase in abnormal sperm rate, there were no changes in the ability to conceive. No differences in serum levels of follicle-stimulating hormone or testosterone were observed between MP-treated Nudt15+/R138C and Nudt15+/+ mice after 12-week MP treatment.

CONCLUSIONS

Thiopurines exert harmful effects on testicular reproductive function according to host NUDT15 genotypes.

Evaluation of Global DNA Methylation and Gene Expression of Izumo1 and Izumo1r in Gonads after High- and Low-Dose Radiation in Neonatal Mice

The intergenerational effects from chronic low-dose exposure are matters of concern. It is thus important to elucidate the radiation-induced effects of germ cell maturation, fertilization and embryonic development. It is well known that DNA methylation levels in CpG sites in gametes are reprogrammed in stages during their maturity. Furthermore, the binding of Izumo on the surface of sperm and Juno on the surface of oocytes is essential for fertilization. Thus, there is a possibility that these genes are useful indicators to evaluate fertility in mice after irradiation exposure. Therefore, in this study, we analyzed global DNA methylation patterns in the testes and gene expression of Izumo1 and Izumo1r (Juno) in the gonads of mice after neonatal acute high-dose ionizing radiation (HDR) and chronic low-dose ionizing radiation (LDR). One-week-old male and female mice were irradiated with a total dose of 4 Gy, with acute HDR at 7 days at a dose rate of 30 Gy/h and LDR continuously at a dose rate of 6 mGy/h from 7 to 35 days. Their gonads were subsequently analyzed. The results of global DNA methylation patterns in the testes showed that methylation level increased with age in the control group, the LDR group maintained its DNA methylation level, and the HDR group showed decreased DNA methylation levels with age. In the control group, the gene expression level of Izumo1 in the testis did not show age-related changes, although there was high expression at 100 days of age. However, in the LDR group, the expression level recovered after the end of irradiation, while it remained low regardless of age in the HDR group. Conversely, gene expression of Izumo1r (Izumo1 receptor) in the ovary decreased with age in the control group. Although the gene expression of Izumo1r decreased with age in the LDR group, it remained low in the HDR group. Our results indicate that LDR can induce different DNA methylation patterns, and both high- and low-dose radiation before sexual maturity might affect gametogenesis and fertility.

Differential Effects of Low and High Radiation Dose Rates on Mouse Spermatogenesis

The adverse effects of radiation are proportional to the total dose and dose rate. We aimed to investigate the effects of radiation dose rate on different organs in mice. The mice were subjected to low dose rate (LDR, ~3.4 mGy/h) and high dose rate (HDR, ~51 Gy/h) radiation. LDR radiation caused severe tissue toxicity, as observed in the histological analysis of testis. It adversely influenced sperm production, including sperm count and motility, and induced greater sperm abnormalities. The expression of markers of early stage spermatogonial stem cells, such as Plzf, c-Kit, and Oct4, decreased significantly after LDR irradiation, compared to that following exposure of HDR radiation, in qPCR analysis. The compositional ratios of all stages of spermatogonia and meiotic cells, except round spermatid, were considerably reduced by LDR in FACS analysis. Therefore, LDR radiation caused more adverse testicular damage than that by HDR radiation, contrary to the response observed in other organs. Therefore, the dose rate of radiation may have differential effects, depending on the organ; it is necessary to evaluate the effect of radiation in terms of radiation dose, dose rate, organ type, and other conditions.

Red-Fleshed Apple Anthocyanin Extracts Attenuate Male Reproductive System Dysfunction Caused by Busulfan in Mice

In this research, we analyzed the effect of an intragastrical oral administration of red-fleshed apple anthocyanin extract (RAAE) on busulfan-treated mice. First, we showed that the most abundant component in RAAE was cyanidin 3-O-galactoside. To determine the effect of the RAAE, the mice were divided into control and four other different concentrations of RAAE feeding treatment groups (BA0, no RAAE; BA.1, 0.1 mg/kg; BA1, 1 mg/kg; and BA5, 5 mg/kg) following busulfan injection. We observed that RAAE treatments displayed ameliorative effects on male reproductive system dysfunction caused by busulfan, such as recovering the irregular arrangements of seminiferous tubules, increasing the number of spermatogonia and spermatocytes, improving sperm concentration by 3-fold in BA.1, and improving sperm motility by 2-fold in BA1. The liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis showed significant up- or downregulation of certain metabolites, such as lysophosphatidylcholine (LysoPC), L-arginine, glycine, anandamide, and L-carnitine, which could contribute to the positive effects of RAAE, especially in PBA1 (plasma of BA1) and PBA5 (plasma of BA5). Taken together, the results indicate that 1 mg/kg of RAAE is a suitable concentration for rescuing spermatogenesis in mice. The research suggests that RAAE could be a potential nutraceutical for protecting spermatogenesis after busulfan therapy in cancer.

Low doses of carbendazim and chlorothalonil synergized to impair mouse spermatogenesis through epigenetic pathways

Pesticides have been extensively produced and used to help the agricultural production which leads to the contamination of the environment, soil, groundwater sources, and even foodstuffs. Fungicides carbendazim (CBZ) and chlorothalonil (Chl) are widely applied in agriculture and other aspects. CBZ or Chl have been reported to disrupt spermatogenesis and decrease semen quality. However, it is not understood the effects of pubertal exposure to low doses of CBZ and Chl together, and the underlying mechanisms. Therefore, the aim of current investigation was to explore the negative impacts of pubertal exposure to low doses of CBZ and Chl together on spermatogenesis and the role of epigenetic modifications in the process. We demonstrated that CBZ and Chl together synergize to decrease sperm motility in vitro (CBZ 1.0 + Chl 0.1, CBZ 10.0 + CHl 1.0, CBZ 100.0 + Chl 10 μM in incubation medium for 24 h) and sperm concentration and motility in vivo with ICR mice (CBZ 0.1 + Chl 0.1, CBZ 1.0 + CHl 1.0, CBZ 10.0 + Chl 10 mg/kg body weight; oral gavage for five weeks). CBZ + Chl significantly increase reactive oxygen species (ROS) and apoptosis by the increase in the protein level of caspase 8 in vitro. Moreover, CBZ + Chl synergized to disrupt mouse spermatogenesis with the disturbance in sperm production proteins and sperm proteins (VASA, A-Myb, STK31, AR, Acrosin). CBZ + Chl synergized to decrease the protein level of estrogen receptor alpha and the protein level of DNA methylation marker 5 mC in Leydig cells, and to increase the protein levels of histone methylation marker H3K9 and the methylation enzyme G9a in germ cells. Therefore, greater attention should be paid to the use of CBZ and Chl as pesticides to minimise their adverse impacts on spermatogenesis.

Estrogen Receptor-Related DNA and Histone Methylation May Be Involved in the Transgenerational Disruption in Spermatogenesis by Selective Toxic Chemicals

Air pollution is a global threat to human health especially spermatogenesis. Animal and epidemiological studies suggest that epigenetic factors can transmit the pathologies transgenerationally. Paternal epigenetic effects can greatly impact offspring health. In this study and together with our previous report, we found that H₂S donor Na₂S and/or NH₃ donor NH₄Cl diminished mouse fertility, decreased spermatozoa concentration and motility, and impaired spermatogenesis in three consequent generations (F0, F1, and F2). In the current study, we found that DNA methylation, histone methylation, and estrogen receptor alpha (ERα) were impaired by NH₄Cl and/or Na₂S in F0, F1, and F2 mouse testes. Moreover, NH₄Cl and/or Na₂S might act as environmental endocrine-disrupting chemicals to decrease estrogen and testosterone in mouse blood. It has been reported that ERα signaling is intertwined together with DNA methylation and histone methylation, which plays very important roles in spermatogenesis. These data together indicate that the transgenerational disruption in spermatogenesis by NH₄Cl and/or Na₂S may be through ERα-related DNA methylation and histone methylation pathways. Therefore, we strongly recommend that greater attention should be paid to NH₃ and/or H₂S contamination to minimize their impact on human health especially spermatogenesis.

Low dose chlorothalonil impairs mouse spermatogenesis through the intertwining of Estrogen Receptor Pathways with histone and DNA methylation

Recently, environment contaminants including pesticides, fungicides, mycotoxin and others chemicals have been suggested to be responsible for the decline in the human spermatozoa quality especially motility and the increase in infertility rate. Chlorothalonil is used widely for protection of vegetables and crops because it is a broad spectrum fungicide. It has been reported that chronic occupational exposure to fungicides was associated with poor spermatozoa morphology in young men. The pubertal period is very important for the male reproductive system development due to spermatogonial cell proliferation, the expansion of meiotic and haploid germ cells. Although some investigations have studied the male reproductive toxicity of chlorothalonil, almost no studies focused on spermatogenesis. The aim of our current investigation was to explore the impacts of chlorothalonil on spermatogenesis and the underlying mechanisms. It demonstrates: i) chlorothalonil decreased boar spermatozoa motility in vitro and increased the cell apoptosis; ii) chlorothalonil inhibited mouse spermatogenesis in vivo; iii) chlorothalonil disturbed spermatogenesis through the disruption of estrogen receptor signalling; iv) chlorothalonil disrupted histone methylation and DNA methylation which might be through estrogen signalling pathways. Due to the over use or incorrect use, chlorothalonil might cause serious problems to human health, especially spermatogenesis. Therefore we strongly recommend that greater attention should be paid to this fungicide to minimise its impact on human health especially spermatogenesis.

Decrease in male mouse fertility by hydrogen sulfide and/or ammonia can Be inheritable

Numerous epidemiological studies suggest that air pollutants cause a decline in the quality of human spermatozoa and thus a reduction in fertility. However, the exact cause of infertility remains unknown. Air pollution gases, such as NH₃ and H₂S are either free or bound to airborne particular materials (PM) and are abundant and reactive. The aim of this current investigation was to explore the impacts of NH₃ and/or H₂S on male fertility and the underlying mechanisms. Male mouse exposed to H₂S and/or NH₃ and after two generations were used to evaluate the impacts on fertility. The fertility, and spermatozoa quality parameters and proteins involved in spermatogenesis were investigated. Our current investigation demonstrates: i) H₂S and/or NH₃ decrease male fertility by 20-30%, reduce the spermatozoa concentration about 20-40%, decrease 10-20%, increase around 30%; ii) the reduction in male fertility by H₂S and/or NH₃ can be inheritable; iii) H₂S and/or NH₃ can diminish male fertility through the disruption of spermatogenesis without affecting other body parameters such as body weight and organ index. One component of air pollutants, for example NH₃, does not have a severe impact; however, two or more pollutants such as H₂S and NH₃ combined can cause serious health problems, especially with regard to male fertility. We suggest that greater attention should be paid to these air pollutants to improve human health and fertility.

The Effect of Aluminum Exposure on Reproductive Ability in the Bank Vole (Myodes glareolus)

Human impact on the environment is steadily increasing the amounts of aluminum in the ecosystems. This element accumulates in plants and water, potentially exposing herbivores to its harmful effect. In heavily polluted sites, a decrease in the density of small rodent populations has been observed. This decline may be caused by many factors, including decreased fertility. The aim of the presented research was to determine how aluminum, administered at concentrations similar to those recorded in industrial districts (Al I = 3 mg/l, Al II = 200 mg/l), affects the reproductive abilities of small rodents. As the indicators of reproductive abilities, body weight, weight of the testes and accessory sex glands of males, and uterus weight of females were estimated. In females, the number of matured follicles (types 6, 7, and 8) was analyzed, while in males, the quantity and quality (matured, viable, swollen, motile, head abnormalities) of epididymal sperm cells were assessed. Moreover, the development of testes, measured by spermatogenic index, was determined. The model species was the bank vole. Our results have proven that aluminum impairs adult individuals' reproductive abilities by decreasing the quality and quantity of sperm cells and by causing morphologically abnormal development of the gonads. However, no difference in male organometric parameters was found, and only in females treated with 3 mg/l Al, the uterus weight was higher than control. No differences were found in the total number of matured follicles. These results suggest that the decline in rodent numbers in industrial districts is due, at least in part, to poorer males' reproductive abilities, resulting from exposure to aluminum contamination.

Hydrogen Sulfide and/or Ammonia Reduces Spermatozoa Motility through AMPK/AKT Related Pathways

A number of emerging studies suggest that air pollutants such as hydrogen sulfide (H₂S) and ammonia (NH₃) may cause a decline in spermatozoa motility. The impact and underlying mechanisms are currently unknown. Boar spermatozoa (in vitro) and peripubertal male mice (in vivo) were exposed to H₂S and/or NH₃ to evaluate the impact on spermatozoa motility. Na₂S and/or NH₄Cl reduced the motility of boar spermatozoa in vitro. Na₂S and/or NH₄Cl disrupted multiple signaling pathways including decreasing Na⁺/K⁺ ATPase activity and protein kinase B (AKT) levels, activating Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and phosphatase and tensin homolog deleted on chromosome ten (PTEN), and increasing reactive oxygen species (ROS) to diminish boar spermatozoa motility. The increase in ROS might have activated PTEN, which in turn diminished AKT activation. The ATP deficiency (indicated by reduction in Na⁺/K⁺ ATPase activity), transforming growth factor (TGF_β) activated kinase-1 (TAK1) activation, and AKT deactivation stimulated AMPK, which caused a decline in boar spermatozoa motility. Simultaneously, the deactivation of AKT might play some role in the reduction of boar spermatozoa motility. Furthermore, Na₂S and/or NH₄Cl declined the motility of mouse spermatozoa without affecting mouse body weight gain in vivo. Findings of the present study suggest that H₂S and/or NH₃ are adversely associated with spermatozoa motility.

Effects of environmental radiation on testes and spermatogenesis in wild large Japanese field mice (Apodemus speciosus) from Fukushima

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that occurred after the Great East Japan Earthquake in March 2011 released large quantities of radionuclides to the environment. The long-term effects of radioactive cesium (Cs) on biota are of particular concern. We investigated the accumulation of radioactive Cs derived from the FDNPP accident, and chronic effects of environmental radionuclides on male reproduction, in the large Japanese field mouse (Apodemus speciosus). In 2013 and 2014, wild mice were captured at 2 sites in Fukushima Prefecture and at 2 control sites that were distant from Fukushima. Although the median concentrations of (134)Cs and (137)Cs in the mice from Fukushima exceeded 4,000 Bq/kg, there were no significant differences in the apoptotic cell frequencies or the frequencies of morphologically abnormal sperm among the capture sites. Thus, we conclude that radiation did not cause substantial male subfertility in Fukushima during 2013 and 2014, and radionuclide pollution levels in the study sites would not be detrimental to spermatogenesis of the wild mice in Fukushima.

Radioprotective potential of melatonin against ⁶⁰Co γ-ray-induced testicular injury in male C57BL/6 mice

Background

Melatonin, the chief secretary product of pineal gland, is a strong free radical scavenger and antioxidant molecule. The radioprotective efficacy and underlying mechanisms refer to its antioxidant role in somatic cells. The purpose of this study, therefore, was to investigate the prophylactic implications of melatonin against γ-ray-induced injury in germinal cells (testes). C57BL/6 male mice were administered melatonin (100 mg/kg) intra-peritoneally 30 min prior to a single dose of whole-body γ-irradiation (5 Gy, 1 Gy/minute) using ⁶⁰Co teletherapy unit. Animals were sacrificed at 2h, 4h and 8h post-irradiation and their testes along with its spermatozoa taken out and used for total antioxidant capacity (TAC), lipid peroxidation, comet assay, western blotting and sperm motility and viability. In another set of experiment, animals were similarly treated were sacrificed on 1^st, 3^rd, 7^th, 15^th and 30^th day post-irradiation and evaluated for sperm abnormalities and histopathological analysis.

Results

Whole-body γ-radiation exposure (5 Gy) drastically depleted the populations of spermatogenic cells in seminiferous tubules on day three, which were significantly protected by melatonin. In addition, radiation-induced sperm abnormalities, motility and viability in cauda-epididymes were significantly reduced by melatonin. Melatonin pre-treatment significantly inhibited radiation-induced DNA strands breaks and lipid peroxidation. At this time, radiation-induces activation of ATM-dependent p53 apoptotic proteins-ATM, p53, p21, Bax, cytochrome C, active caspase-3 and caspases-9 expression, which were significantly reversed in melatonin pre-treated mice. This reduced apoptotic proteins by melatonin pre-treatment was associated with the increase of anti-apoptotic-Bcl-x and DNA repair-PCNA proteins in irradiated mice. Further, radiation-induced decline in the TAC was significantly reversed in melatonin pre-treated mice.

Conclusions

The present results indicated that melatonin as prophylactic agent protected male reproductive system against radiation-induced injury in mice. The detailed study will benefit in understanding the role of melatonin in modulation of radiation-induced ATM-dependent p53-mediated pro-vs.-anti apoptotic proteins in testicular injury. These results can be further exploited for use of melatonin for protection of male reproductive system in radiotherapy applications involving hemibody abdominal exposures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0156-9) contains supplementary material, which is available to authorized users.

Low-dose-rate radiation exposure leads to testicular damage with decreases in DNMT1 and HDAC1 in the murine testis

This study examined the effects of continuous low-dose-rate radiation exposure (3.49 mGy/h) of gamma rays on mice testicles. C57BL/6 mice were divided into sham and radiation groups (n = 8 each), and were exposed to either sham irradiation or 2 Gy for 21 days, 0.2 Gy for 2 days, or 0.02 Gy for 6 h of low-dose-rate irradiation. Testicular weight, seminiferous tubular diameter, and seminiferous epithelial depth were significantly decreased in the mice irradiated with 2 Gy at 1 and 9 days after exposure. Moreover, the low-dose-rate radiation exposure induced an increase in malondialdehyde levels, and a decrease in superoxide dismutase activity in the testis of mice irradiated with 2 Gy at 1 and 9 days after exposure. The sperm count and motility in the epididymis also decreased in mice irradiated with 2 Gy at 1 and 9 days after exposure, whereas there was no significant effect on the proportion of abnormal sperm. The expressions of DNA methlytransferases-1 and histone deacetylases 1 in testes irradiated with 2 Gy were significantly decreased compared with the sham group. In conclusion, the damage exerted on the testes and epididymis largely depended on the total dose of low-dose-rate radiation.

Sperm abnormalities in high- and low-dose-rate Gamma-irradiated Korean dark-striped field mice, Apodemus agrarius coreae

To evaluate the in vivo effects of low-dose-rate (0.7 mGy h(-1)) gamma radiation, abnormal shapes of sperm in the caudal epidydimus of Apodemus agrarius coreae (A. a. coreae) were used. The six categories of abnormal forms (amorphous heads, blunt hooks, excessive hooks, two heads and tails, folded tails and short tails) of sperm were observed eight days after gamma irradiation (0, 0.5, 1 and 2 Gy) with a high dose rate (0.8 Gy min(-1)) and a low dose rate. The frequency of total abnormal sperm gradually increased starting from 0.5 Gy after high-dose-rate radiation. Blunt hooks and short tails shaped sperm, in particular, were gradually increasing in the high-dose-rate irradiated mice. Dose rate reduction effects for the frequency of abnormal sperms in low-dose-rate irradiated mice to high-dose-rate irradiated mice were 1 at 0.5 Gy, 0.7 at 1 Gy and 0.5 at 2 Gy. Our results indicate that low-dose-rate radiation is not detrimental to spermatogenic cells.