Study On The Oxidative Damage And Reprodutive Toxicity Molecular Mechanism Of Di-(2-ethylhexyl) Phthalate In Mice

Phthalates is widely used as a plasticizer in industry and life. Because phthalates increases the flexibility and tenacity of plastic, used wider and wider in plastic industry, its biological responses has been gained much interest by environment and medicine operators increasingly. The phthalate ester di- (2-ethylhexyl)-phthalate (DEHP), a kind of phthalates, is the most commercially important plasticizer for PVC plastics. Di-(2-ethylhexyl)-phthalate has been listed as prioritily monitoring enviromental pollutants for its refractory, extentive pollution sources, extentive toxicity, high level pollution. This reseach is to explore oxidative damage, genotoxicity and reprodutive toxicity molecular mechanism of di- (2-ethylhexyl)-phthalate in mice, which is of great significance to understand the toxicity of di-(2-ethylhexyl)-phthalate comprehensively. This reseach also can provide scientific basis to some extent to further evaluate a safe standard of enviromental and occupational di-(2-ethylhexyl)-phthalate concentration. In this study is to explore oxidative damage by examining changes of the activity of superoxide dismutase (SOD) and the content of MDA in internal orgins of mice, explore genotoxicity by using single cell gel electrophoresis (SCGE) and explore the possible reprodutive toxicity molecular mechanism of di-(2-ethylhexyl)-phthalate via PT-PCR.The result:1. Oxidative damage induced by di-(2-ethyIhexyl)-phthaIate in internal orgians of miceSPF-class KunMing male mice were exposed to di-(2-ethylhexyl)-phthalate at different concentrations by being injected in the abdomen of the mice and measure superoxide dismutase actvity and the content of MDA in liver, testis, brain and pulmonary to evaluate oxidative damage in internal organs of mice. The result showed low contentration of di-(2-ethylhexyl)-phthalate (125mg/kg) can make superoxide dismutase activity incease and the content of MDA decrease in liver, testis, brain, and induce oxidative stress in mice. High contentration of di- (2-ethylhexyl)-phthalate (375mg/kg) can induce uperoxide dismutase activity deease and the content of MDA increase in liver, testis, brain, lipid peroxidation incease. But in pulmonary of mice, low contentration of di-(2-ethylhexyl) -phthalate (125mg/kg) can make superoxide dismutase activity decease and the content of MDA increase, induce oxidative damage. As di-(2-ethylhexyl) -phthalate contentration increased, lipid peroxidation inceased, the damage was more severrity. Lipid peroxidation occurred in four important internal organs(liver, testis, brain and pulmonary), but four organs had different peroxide sensitivity, with most sensitive of toxicity of DEHP in pulmonary, with more sensitive of toxicity of DEHP in liver and testicle, slow in brain.2.DEHP induced DNA damage in brain cellIn this stduy single cell gel electrophoresis (SCGE) was applied to examine genotoxicity in male mice which were injected in the abdomen of the mice with different di-(2-ethylhexyl)-phthalate concentrations. The result showed 125 mg/kg and 375mg/kg di-(2-ethylhexyl)-phthalate concentration, compared with control group, Tail Moment and Tail DNA% were significantly elevated (p < 0.01). This indicated that DEHP can cause DNA damage in the brain, As di-(2-ethylhexyl) -phthalate contentration increased, Tail Moment and Tail DNA% would rise with the increase of the doses, DNA damage was more severity, indicating the apparent dose- dependent effect of the damage in the brain tissue caused by DEHP. But di-(2-ethylhexyl)-phthalate concentration was 500mg/kg, Tail Moment and Tail DNA% was declined significantly compared with 375 mg/kg DEHP exposure group (p<0.01). It is possible that high DEHP concentration induce crosslink (DNA-DNA crosslink and/or DNA -protein crosslink) in brain.3. DEHP induced reprodutive toxicity molecular mechanismMany studies on reprodutive toxicity of di-(2-ethylhexyl)-phthalate, but reprodutive toxicity melecuar mechanism of di-(2-ethylhexyl)-phthalate is not clear. So the reprodutive toxicity melecuar mechanism of di-(2-ethylhexyI)-phthalate are important to be revealed for its significance to the field of scientific research and the society. Synthesis of androgen dependent on the hypothalamus - pituitary - testicular axis and the balance adjustment within the testis, Cholesterol side-chain lyase P450scc and steroids acute regulatory synthesis protein StAR is two key substances of the testosterone synthesis, affecting the level of testosterone synthesis. This stduy indicated that Different concentrations of DEHP (125mg/kg, 250 mg / kg, 375 mg / kg) of testicular tissue in mice, cholesterol side-chain lyase P450sccmRNA and steroids acute regulatory synthesis protein StARmRNA expression levels compared with the control group, significantly deceased (p<0.01).As di-(2-ethylhexyl)-phthalate contentration increased, cholesterol side- chain lyase P450sccmRNA and steroids acute regulatory synthesis protein StARmRNA expression levels deceased with the increase of the doses, indicating the apparent dose- dependent effect, which indicated that DEHP may be inhibit P450sccmRNA and StARmRNA expression levels, thereby inhibit the synthesis of testosterone, induce reprodutive toxicity.