Study On Mechanisms And Protective Effects Of Selenium On Cadmium-induced Reproductive Toxicity In Male Mice

Cadmium (Cd) is a ubiquitous environmental pollution. The general populationexposure to cadmium predominantly results from food chains and consumption ofcadmium contaminated water. Cadmium essentially makes it an accumulative toxinmostly in the kidneys, testes, bones and other systems. As a confirmationenvironment endocrine disrupting chemical, cadmium is more sensitive toreproductive system, including testis, epididymis, the seminal vesicle, seminiferousduct and prostate glands. Testicular, two of the main physiological functions arespermatogenesis and steroidogenesis. Studies show that the environment endocrinedisruptors can lead to disrupt in the role of the biological sex hormones secretion andits energy down, germ cell apoptosis, the decrease in the number of sperm,reproductive organs anomalies, and the impact on various biological sex, reproductivefunction, etc. Oxidative stress has been considered a primary initiating mechanismduring cadmium-induced testicular damage. The present study found that someharmful factors, such as the hormone deprivation, oxidative stress and endocrine disruptors can aggravate testicular germ cell apoptosis, and too much germ cellapoptosis can interfere with the normal testicular development and spermatogenesis.However, the mechanisms of cadmium on inhibition of testicular testosteronesynthesis and germ cell apoptosis are still not clear.Selenium (Se), a human body essential trace element, in addition to participate innormal human physiological outside, still as an antioxidant effective oxygen freeradical scavenging, protect the organs and tissues from oxidative damage andimprove the body’s immune system. Reports show that selenium is essential fornormal testicular development, spermatogenesis, spermatozoa motility and functions.This research aimed to explore the productive toxicity of cadmium and its relativeprotective mechanisms of selenium against testicular germ cell apoptosis andinhibition of testosterone synthesis in cadmium-induced mice by in vivo study.Hopefully, it will help to providing important theoretical basis, new clues and waysfor the prevention and control of human male reproductive toxicity exposure tocadmium.PartⅠ Study on protective effects of selenium oncadmium-induced reproductive toxicity in mice1. Protective effects of selenium on cadmium-induced testicular andepididymis toxicity in miceObjective: To explore the effects of selenium on cadmium-induced testicular andepididymis toxicity in mice. Methods: Total90ICR mice were randomly divided intofive groups of18animals in each group. GroupⅠ: normal mice orally received only the vehicle. Group Ⅱ: mice orally received cadmium (as CdCl2) at a dose of5mg/kg BW. Group Ⅲ: mice orally received selenium (as Na2SeO3) at a dose of0.1mg/kg BW plus cadmium5mg/kg BW. Group Ⅳ: mice orally received selenium0.2mg/kg BW plus cadmium5mg/kg BW. Group Ⅴ: mice orally received selenium0.4mg/kg BW plus cadmium5mg/kg BW. Mice were given daily gavages administrationwith selenium for1h prior to the addition of cadmium. Mice were euthanized bycervical dislocation at the15th,25thand35thday after gavage (n=6per group and perperiod). Epididymal caput and cauda and testicular structures were observed by lightmicroscopy. Ultrastructural changes in testicular seminiferous tubules were observedby transmission electron microscope. FCM DNA contents analysis of testicular germcells and epididymal sperm cells. Results: At15th,25thand35thday, cadmium to thedamage of epididymis and testicular structure in the spermatogenic cycle and itspresent typical injury, compensatory and decompensation injury of the process, andselenium (0.1，0.2,0.4mg/kg) can reduce the toxic injury of epididymis and testicularstructure induced by cadmium. At35thday, prior administration of selenium (0.1,0.2,0.4mg/kg) significantly increased the percentages of1C DNA cells（33.72±1.40、32.85±1.47、34.49±0.38）%of testicular germ cells in comparison to thecadmium-treated groups (P<0.01) and control groups (P<0.05). Similarly, prioradministration of selenium (0.1,0.2,0.4mg/kg) significantly increase the percentagesof HC DNA cell（s36.47±2.86、35.84±2.85、35.63±1.39）%of epididymal sperm cellsin comparison to control groups (P<0.01). Conclusion: Selenium has certainprotective effects on epididymis and testicular toxicity induced by cadmium. Thesedata also indicate the protective effects of selenium on inhibition of spermatogenesisin mice exposed to cadmium. 2. Protective effects of selenium on cadmium-induced sperm toxicityin miceObjective: To explore the effects of selenium on cadmium-induced sperm toxicity inmice. Methods: Epididymal sperm smears were stained with1%eosin Y and spermcount was used a hemocytometer. Sperm motility was analyzed by acomputer-assisted semen analysis (CASA) system. Results: At25thand35thday,prior administration of selenium (0.1，0.2,0.4mg/kg) significantly decreased thesperm abnormality level and sperm concentration profile in comparison to thecadmium-treated groups (P<0.05). At15th,25thand35thday, prior administration ofselenium (0.2,0.4mg/kg) significantly increased motile compared withcadmium-treated groups. Sperm motility parameters of progressive and VAP weresignificantly higher in animals received cadmium and treated with selenium (0.1，0.2,0.4mg/kg) in comparison to selenium non-treated groups (P<0.05). Conclusion:Selenium has protective effects on sperm toxicity induced by cadmium. PartⅡ Mechanisms study on protective effects of selenium oncadmium-induced reproductive toxicity in mice1. Effects of selenium on cadmium-induced oxidative stress andtesticular germ cell apoptosis in miceObjective: To study the effects of cadmium on oxidative stress and spermatogeniccell apoptosis of mice testis and the protective effects of selenium against it.Methods: The activity of superoxide dismutase (SOD)，glutathione Peroxidase(GSH-Px) and the contents of malondialdehyde (MDA) were measured by colormethod. Testicular germ cell apoptosis was observed by TdT-mediated dUTP-biotinnick end labeling (TUNEL). The levels of Caspase-3, Bcl-2and Bax proteins weredetected by western blot. Results: At35thday, prior administration of selenium (0.1,0.2,0.4mg/kg) significantly increased the activity of SOD and decreased thecontent of MDA in comparison to the cadmium-treated groups (P<0.05). Seleniumcould prevent testicular germ cell apoptosis induced by cadmium. Prioradministration of selenium (0.4mg/kg) significantly increased the expressions ofBcl-2protein and down-regulated the expression of Caspase-3and Bax proteins incomparison to the cadmium-treated groups (P<0.05). Conclusion: These dataindicated the protective effects of selenium against cadmium-induced oxidativestress and testicular germ cell apoptosis, which could be directly useful forspermatogenesis. 2. Effects of selenium on cadmium-induced inhibition of testosteronesynthesis in miceObjective: To explore the effects of selenium on inhibition of testosterone synthesisin mice exposed to cadmium. Methods: Testosterone in serum was measuredusing125I-based RIA kits following the manufacturer’s protocols. The protein levelsof StAR, P450scc and17β-HSD were detected by western blot. Results: The levelsof serum testosterone were significantly higher in animals received selenium (0.4mg/kg) and treated with cadmium (at15thand35thday) compared to cadmium-treatedgroups (P<0.05). At35thday, prior administration of selenium (0.1,0.2,0.4mg/kg)significantly increased the level of StAR protein expression in comparison to thecadmium-treated groups (P<0.05). Selenium (0.1mg/kg) significantly increased thelevel of P450scc protein expression in comparison to the cadmium-treated groups(P<0.05). Selenium (0.4mg/kg) significantly increased the level of17β-HSD proteinexpression in comparison to the cadmium-treated groups (P<0.05). Conclusion: Thepresent study suggest that the protective potential of selenium againstcadmium-induced inhibition of testosterone synthesis, which could be partially useful...