Attenuating Effect Of Quercetin On The Toxicity Of Testicular Germ Cells Induced By Cadmium And Nitrophenol

A variety of endocrine disrupting chemicals (EDC) has been released to the environment in the industrial progress; which may exert adverse health effects in human and animals, especially in reproduction system. Oxidative stress may be playing a key role in the mechanism of these adverse effects. Antioxidants may prevent negative effects induced by these chemicals. Flavonoids comprise the most common group of plant polyphenols and widerly distributed in plant kingdom. Owing to their potent antioxidant, free-radical scavenging activities and metal chelating ability, flavonoids can inhibit the production of reactive oxygen species. However, the protective mechanism of flavonoids on reproductive system is not well defined. The present study evaluated the oxidative toxicity of cadmium and 3-methyle-4-nitrophenol (PNMC) on testis in male mice, the effect of cadmium on oogenesis in female mice and studied the protective effect of quercetin on the reproductive toxicity induced by cadmium and 3-methyle-4-nitrophenol on testis.1. Protective effect of quercetin on cadmium-induced oxidative toxicity in germ cellsCadmium is a toxic heavy metal that is widely distributed in the environment. As a critical process, oxidative toxicity mediates the morphological and functional damages in germ cells after cadmium exposure. In this study the protective effect of quercetin on cadmium-induced oxidative toxicity was investigated in mouse testicular germ cells. After oral administration of cadmium chloride at 4 mg/kg body weight for 2 weeks, damages in spermatocytes and spermatozoa occurred in the seminiferous epithelium. Cadmium treatment significantly decreased the testicular antioxidant system, including decreases in the glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. Moreover, exposure to cadmium resulted in an increase of hydrogen peroxide (H2O2) level and lipid peroxidation in testes. In addition, cadmium provoked germ cell apoptosis by upregulating expression of the pro-apoptotic protein Bax and caspase-3, and downregulating expression of the anti-apoptotic protein Bcl-XL. However, combined administration of a common flavonoid quercetin at 75 mg/kg body weight significantly attenuated cadmium-induced germ cell apoptosis by suppressing the H2O2 production and lipid peroxidation in testicular tissue. Simultaneous supplementation of quercetin markedly reduced the decrease in GSH level and SOD and GSH-Px activities elicited by cadmium treatment. Additionally, quercetin protected germ cells from cadmium-induced apoptosis by downregulating the expression of Bax and caspase-3 and upregulating Bcl-XL expression. These results indicate that quercetin, due to its antioxidative and antiapoptotic character may impose effective protective action against cadmium-induced oxidative toxicity in mouse testicular germ cells. Cadmium, at the dose of which induced germ cell damage in male mice, was given to female mice for 2 weeks. Morphological results showed that there were no remarkable changes of ovary in all treatment. However, cadmium induced dose-dependent increase of number of developing oocyte. TUNEL immunohistochemistry staining revealed that there were no apoptotic cells in all treatment. Cadmium is suspected of exerting hormonic activity in female mice.2. Protective effect of quercetin on cadmium-induced oxidative damage in spermatogonia in miceThe spermatogonial-somatic cell coculture system was established with 6-day-old male mice. The medium of DMEM supplemented with L-glutamide, insulin, transferrin and selenite could maintain spermatogonial survival and proliferation. Spermatogonial cell maintains round shape and attach to somatic cells. Cadmium (1,2, and 4μM) treatment exerts toxic effect on spermatogonial at a dose-dependent manner. Cadmium induced the decrease in testicular cell viability and spermatogonial cell number. Cadmium induced lipid peroxidation by an elevation of thiobarbituric acid reactive substances as well as decreasing GSH-Px activity and SOD activity. However, supplement with quercetin restored cell viability and cell number, and alleviated cadmium-induced oxidative damage with inhibition of production of MDA and increase of GSH level as well as SOD activity. These results indicate that quercetin can protect germ cells from oxidative stress not only in vivo but alse in vitro, owing to its antioxidative bioactivity.3. Alleviative effect of quercetin on mouse germ cells intoxicated by PNMCAs a component of diesel exhaust particles, PNMC is a metabolite of the insecticide fenitrothion. In the present study, we found that a single intraperitoneal injection of PNMC at 100 mg/kg body weight induced severe testicular damage in mice after 1 week treatment. Exposure to PNMC induced an increase of hydroxyl radical (·OH) and H2O2 production, and induced lipid peroxidation, as well as a decrease in GSH level, SOD and GSH-Px activity. Furthermore, treatment of PNMC resulted in increased expression of the pro-apoptotic protein Bax and decrease expression of the anti-apoptotic protein Bcl-XL in germ cells. The testicular caspase-3 activity was significantly up-regulated in the PNMC-treated mice. Germ cell apoptosis was detected by TUNEL assay and the apoptotic cell was significantly increased in the PNMC-treated mice. In contrast, combined administration of a common flavonoid quercetin at 75 mg/kg body weight significantly attenuated PNMC-induced toxicity. These results indicated that the antioxidant quercetin displays a protective effect on PNMC-induced oxidative damage in mouse testes and may represent an efficient supplement to attenuate reproductive toxicity by environmental toxicants to ensure healthy sperm production.In conclusion, cadmium and PNMC are proved harmful to the testes of male mice. Exposure to cadmium and PNMC resulted in an increase of reactive oxygen species and lipid peroxidation, decreased the testicular antioxidant abilities, including decreases in the GSH level, SOD and GSH-Px activities. Moreover, cadmium and PNMC provoked germ cell apoptosis by upregulating expression of the pro-apoptotic protein Bax and caspase-3, and downregulating expression of the anti-apoptotic protein Bcl-XL. In contrast, combined administration of a common flavonoid quercetin at 75 mg/kg body weight significantly attenuated cadmium and PNMC-induced toxicity. These results indicated that the antioxidant quercetin displays a protective effect on PNMC-induced oxidative damage in mouse testes and may represent an efficient supplement to attenuate reproductive toxicity by environmental toxicants to ensure healthy sperm production.