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

Effects of an Anti-Fertility Product on Reproductive Structures of Common Vole Males and Residues of Compounds

Some rodent species cause significant damage to agriculture and forestry, and some can transmit pathogens to humans and livestock. The common vole (Microtus arvalis) is widespread in Europe, and its population outbreaks have resulted in massive crop loss. Bait-based fertility control could contribute to rodent pest management. Bait containing 4-vinylcyclohexene diepoxide (VCD) and triptolide (TP), registered as ContraPest®, was delivered to male common voles for 14 or 28 consecutive days. The effects on reproductive structures and residues in the liver and testes were assessed. There was no effect on testis weight, sperm viability, sperm motility and oxidative stress in sperm cells. Results regarding the mitochondrial membrane potential of sperm, DNA fragmentation and progressively motile sperm cells were inconclusive. However, there was an increase in morphological sperm defects in voles treated for 14/28 days and fewer normal sperm cells in voles treated for 28 days. There were no TP residues in the testes, few and low TP residues and no VCD residues in liver tissues, making considerable secondary exposure to non-target species unlikely. Treatments with VCD + TP seemed to have minor effects on the reproductive organs of males. Further studies should evaluate the effect of VCD + TP on females and on the reproductive success of common voles and other pest rodent species.

The status of fertility control for rodents-recent achievements and future directions

Management of overabundant rodents at a landscape scale is complex but often required to sustainably reduce rodent abundance below damage thresholds. Current conventional techniques such as poisoning are not species specific, with some approaches becoming increasingly unacceptable to the general public. Fertility control, first proposed for vertebrate pest management over 5 decades ago, has gained public acceptance because it is perceived as a potentially more species-specific and humane approach compared with many lethal methods. An ideal fertility control agent needs to induce infertility across one or more breeding seasons, be easily delivered to an appropriate proportion of the population, be species specific with minimal side-effects (behavioral or social structure changes), and be environmentally benign and cost effective. To date, effective fertility control of rodents has not been demonstrated at landscape scales and very few products have achieved registration. Reproductive targets for fertility control include disrupting the hormonal feedback associated with the hypothalamic-pituitary-gonadal axis, gonad function, fertilization, and/or early implantation. We review progress on the oral delivery of various agents for which laboratory studies have demonstrated efficacy in females and/or males and synthesize progress with the development and/or use of synthetic steroids, plant extracts, ovarian specific peptides, and immunocontraceptive vaccines. There are promising results for field application of synthetic steroids (levonorgestrel, quinestrol), chemosterilants (4-vinylcyclohexene diepoxide), and some plant extracts (triptolide). For most fertility control agents, more research is essential to enable their efficient and cost-effective delivery such that rodent impacts at a population level are mitigated and food security is improved.

Quercetin and vitamin E attenuate diabetes-induced testicular anomaly in Wistar rats via the mitochondrial-mediated apoptotic pathway

The role of quercetin and vitamin E treatment against streptozotocin (STZ)-induced testicular abnormalities in diabetic rats and the possible mechanism of action they use for protection were investigated. Diabetes was induced by STZ (45 mg/kg i.p. once) and blood glucose was determined. Plasmatic insulin, testosterone, luteinising hormone and follicle-stimulating hormone (FSH) were determined by ELISA. Levels of cytochrome c, caspase 3 and caspase 9 were evaluated by immunohistochemistry, while lesions were viewed by histology. Insulin played a role in testicular protection against male infertility through modulation of luteinising hormone (LH). This consequently increased Leydig and Sertoli cells and maturation of germ cells with the attached epididymis having abundant spermatozoa. The study showed a positive correlation in the levels of LH, FSH and testosterone; it was further established that all treatments normalised diabetes-induced alterations. Treatment with quercetin and vitamin E resulted in 34% decrease of apoptogenic cytochrome c release. This protected the testes against excessive apoptosis by decreasing caspase 3 and caspase 9 activation by up to 30 and 28% respectively (p < .05). Histology also showed that treatment prevented testicular cell death. The findings show that quercetin/vitamin E possess free radical scavenging properties that protected against testicular damage in diabetes. This suggests the possibility of pharmaco-therapeutic intervention.

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.

Assessing the toxicant effect of spontaneously volatilized 4-vinylcyclohexane exposure in nymphs of the lobster cockroach nauphoeta cinerea

Vinylcyclohexene (VCH) is an environmental contaminant well known for its ovotoxicant effects in several organisms. However, the mechanisms underlying the toxicity of VCH as well as its harmful effects toward other organs are until unclear. In this work, we assess some endpoint signals of toxicity induced by volatilized VCH exposure using nymphs of the lobster cockroach Nauphoeta cinerea. Nymphs were exposed to VCH via inhalation for 70 days. The levels of volatilized VCH were quantified by headspace gas chromatography and the concentration varied between 3.41 and 7.03 nmol/μl. VCH inhalation caused a reduction of 35% in the survival rate of the exposed animals. Nymphs exposed to volatilized VCH for 35 and 70 days had a reduction in the body weight gain of 1.8- and 2.6-fold, respectively with a reduction in dissected head, fat body, and maturing reproductive organs. The exposure did not change water consumption, excepting on the 20th day (with a 3-fold change) and decreased the food intake significantly. Regarding biochemical markers, we found that the activity of GST from the dissected organs was increased by volatilized VCH after both 35 and 70 days of exposure. The fat body presented the most prominent GST activity especially after 35 days of exposure with 1.6-fold higher than the control group. Exposure also caused an increase in RS levels in the fat body of 1.35-fold and 1.47-fold after 35 and 70 days, respectively and did not affect the activity of the AChE from the head. Our findings support the harmful impact of volatilized VCH inhalation, highlighting the cockroach N.cinerea as a valuable insect model to investigate environmental toxicants.