4-Vinylcyclohexene diepoxide reduces fertility in female Siberian hamsters when treated during their reproductively active and quiescent states

Pueratin improves diminished ovarian reserve by inhibiting apoptosis

Pueratin (Pue) is an extract from Pueraria lobata, and exhibits therapeutic effects for the treatment of inflammation. However, the beneficial effects and mechanisms underlying Pue in the treatment of diminished ovarian reserve (DOR) remains to be fully elucidated. The aim of the present study was to investigate the effect of Pue on Bcl-2 and Bax protein expression in rats with DOR, associated with infertility within clinical practice, induced by 4-vinylcyclohexene diepoxide (VCD). A model of DOR was established in female Sprague Dawley rats by an intraperitoneal injection of 80 mg/kg VCD daily for 45 days. From day 1, the Sprague Dawley rats were orally administered with drugs daily for 45 days. They were divided into normal, model, Pue-low dose (L), Pue-medium dose (M) and Pue-high dose (H) groups (50, 100 and 300 mg/kg Pue, respectively). Follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E₂) levels were subsequently detected using ELISA. H&E staining and TUNEL staining were used to evaluate histopathological changes and apoptosis levels in the ovary, respectively. Bcl-2 and Bax protein expression levels in rat ovaries were evaluated using immunohistochemistry and western blotting. Compared with those in the model group, FSH and LH levels in the Pue-L, -M and -H groups were significantly decreased, whilst E₂ levels were significantly increased (P<0.05). After intragastric administration, the volume of the ovaries and uteri of rats in the Pue groups was increased compared with the model group, and the numbers of primordial follicles and primary follicles were also increased. The number of apoptotic cells and the expression of Bax were significantly reduced in a dose-dependent manner (P<0.05), compared with the model group. In addition, Bcl-2 protein expression and the Bcl-2/Bax ratio were found to be significantly increased in the Pue-treated groups in a dose-dependent manner (P<0.05), compared with the model group. In conclusion, Pue treatment improved ovarian function by regulating hormone balance in addition to Bcl-2 and Bax expression.

Rescue role of hesperidin in 4-vinylcyclohexene diepoxide-induced toxicity in the brain, ovary and uterus of wistar rats

Background The ovotoxicity of 4-vinylcyclohexene diepoxide (VCD) has been established in several experimental models. Hesperidin (HSD) is a bi-flavonoid found in citrus fruits and has been reported to be a potent antioxidant and anti-inflammatory agent. Here, we have evaluated the rescue role of hesperidin on VCD-induced toxicity in the brain, ovary, and uterus of rats. Methods Six groups of rats containing ten rats in each group were orally given corn oil (control), hesperidin (100 mg/kg), hesperidin (200 mg/kg), VCD (250 mg/kg), VCD [(250 mg/kg)+hesperidin (100 mg/kg)] and VCD [(250 mg/kg)+hesperidin (200 mg/kg)] once a day for 30 days, respectively. Thereafter, we determined the selected biomarkers of oxidative damage, inflammation, endocrine balance, and histology of the reproductive organs. Results The data showed that hesperidin rescued VCD-induced increase in oxidative stress (hydrogen peroxide and malondialdehyde) and inflammatory (nitric oxide) biomarkers. In addition, hesperidin restored the reduction in antioxidant enzymes (catalase, glutathione S-transferase, glutathione peroxidase) activities and glutathione level in the brain, ovary, and uterus of rats (p<0.05). Lastly, hesperidin preserved the histological structure of the ovary and uterus of rats exposed to VCD. Conclusions Overall, the rescue role of hesperidin on VCD-induced toxicity in the brain and reproductive organs of female rats may be due to its antioxidative and anti-inflammatory properties.

Simultaneous exposure to vinylcyclohexene and methylmercury in Drosophila melanogaster: biochemical and molecular analyses

Background

Exposure to vinylcyclohexene (VCH) and methylmercury (MeHg⁺) can induce oxidative stress and gene modulation. Several studies have been evaluating the effects of VCH and MeHg⁺, but little is known about interactive effects between them. This work aimed to assess the exposure and co-exposure effects of MeHg⁺ and VCH on oxidative stress and gene modulation in Drosophila melanogaster.

Methods

Reactive species production, glutathione S-transferase (GST) and acetylcholinesterase (AChE) activities were evaluated after exposure and co-exposure to VCH (1 mM) and MeHg⁺ (0.2 mM) for one or three days in the head and body (thorax and abdomen) of flies. The expression of genes related to redox state and inflammatory response was evaluated after exposure and co-exposure to VCH and MeHg⁺ for three days.

Results

Survival decreased only in flies co-exposed to VCH and MeHg⁺ for three days. All treatments increased total reactive species production after one day of exposure. However, no significant changes were observed in the head after three days of exposure. One day of exposure to VCH caused an increase in the head GST activity, whereas MeHg⁺ induced an increase after three days of exposure. Regarding the body, all treatments increased GST activity after one day of exposure, but only the flies exposed to MeHg⁺ presented an increase in GST activity after three days of exposure. Treatments did not alter AChE activity in the head. As for gene expression, there was a significant increase in the Relish transcription factor gene in the flies’ body, but Nrf2, Keap1, Jafrac1, TrxR1, and NF-κβ were not altered.

Conclusion

The results suggest that exposure to VCH and MeHg⁺ induce oxidative stress and activation of an inflammatory response in fruit flies.

4-Vinylcyclohexene diepoxide disrupts sperm characteristics, endocrine balance and redox status in testes and epididymis of rats

OBJECTIVES

Exposure to 4-vinylcyclohexene diepoxide (VCD) was reported to induce testicular germ cell toxicity in rodents. However, there is paucity of information on the precise biochemical and molecular mechanisms of VCD-induced male reproductive toxicity.

METHODOLOGY

This study investigated the influence of VCD on testicular and epidydimal functions following oral exposure of Wistar rats to VCD at 0, 100, 250 and 500 mg/kg for 28 consecutive days.

RESULTS

Administration of VCD significantly decreased the body weight gain and organo-somatic indices of the testes and epididymis. When compared with the control, VCD significantly decreased superoxide dismutase and catalase activities in the testes whereas it significantly decreased superoxide dismutase activity but increased catalase activity in the epididymis. Moreover, while glutathione peroxidase activity and glutathione level remain unaffected, exposure of rats to VCD significantly increased glutathione S-transferase activity as well as hydrogen peroxide and malondialdehyde levels in testes and epididymis of the treated rats. The spermiogram of VCD-treated rats showed significant decrease in epididymal sperm count, sperm progressive motility, testicular sperm number and daily sperm production when compared with the control. Administration of VCD significantly decreased circulatory concentrations of follicle-stimulating hormone, luteinizing hormone and testosterone along with testicular and epididymal degeneration in the treated rats. Immunohistochemical analysis showed significantly increased cyclooxygenase-2, inducible nitric oxide synthase, caspase-9 and caspase-3 protein expressions in the testes of VCD-treated rats.

CONCLUSION

Exposure to VCD induces testicular and epidydimal dysfunctions via endocrine suppression, disruption of antioxidant enzymes activities, increase in biomarkers of oxidative stress, inflammation and apoptosis in rats.

Mate preference for dominant vs. subordinate males in young female Syrian hamsters (Mesocricetus auratus) following chemically-accelerated ovarian follicle depletion

Life history theory predicts that selectivity for mates generally declines as females age. We previously demonstrated this phenomenon in Syrian hamsters (Mesocricetus auratus), in that older females showed reduced preference for dominant over subordinate males. To test the hypothesis that decreased reproductive quality due to aging reduces mate preference, we decoupled reproductive and chronological age by treating young female hamsters with 4-vinylcyclohexene diepoxide (VCD), which destroys ovarian follicles and functionally accelerates ovarian follicle depletion without compromising the general health of rodents. In this study, VCD effectively reduced follicle numbers in young Syrian hamsters. VCD-treated and control females were allowed to choose between a dominant and a subordinate male in a Y-maze on the day of proestrus. Both VCD-treated and control females demonstrated preference for the dominant male by leaving a greater proportion of vaginal scent marks near him, which is a behavior that females display when soliciting prospective mates. However, there was no effect of treatment on the proportion of vaginal scent marks left for the dominant male. Furthermore, ovarian follicle numbers were not significantly correlated with any behaviors in either group. We conclude that accelerated ovarian follicle depletion does not reduce mate preference in young female hamsters.

An assessment of anti-Müllerian hormone in predicting mating outcomes in female hamsters that have undergone natural and chemically-accelerated reproductive aging

In mammals, female fertility declines with age due in part to a progressive loss of ovarian follicles. The rate of follicle decline varies among individuals making it difficult to predict the age of onset of reproductive senescence. Serum anti-Müllerian hormone (AMH) concentrations correlate with the numbers of ovarian follicles, and therefore, AMH could be a useful predictor of female fertility. In women and some production animals, AMH is used to identify which individuals will respond best to ovarian stimulation for assisted reproductive technologies. However, few studies have evaluated AMH's predictive value in unassisted reproduction, and they have yielded conflicting results. To assess the predictive value of AMH in the context of reproductive aging, we prospectively measured serum AMH in 9-month-old Siberian hamsters shortly before breeding them. Female Siberian hamsters experience substantial declines in fertility and fecundity by 9months of age. We also measured serum AMH in 5-month-old females treated with 4-vinylcyclohexene diepoxide (VCD), which selectively destroys ovarian follicles and functionally accelerates ovarian aging. Vehicle-treated 5-month-old females served as controls. AMH concentrations were significantly reduced in VCD-treated females yet many females with low AMH reproduced successfully. On average, both young and old hamsters that littered had higher AMH concentrations than females that did not. However, some females with relatively high AMH concentrations failed to litter, whereas several with low AMH succeeded. Our results suggest that mean AMH concentration can predict mating outcomes on a population or group level, but on an individual basis, a single AMH determination is less informative.