男性不妊精子の酸化的DNA障害とその病理学的意義

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In 1997, we investigated whether a high level of oxidative DNA damage in spermatozoa occurs in infertile male patients, and examined the influence of antioxidant treatments on the levels of this damage. The levels of oxidative DNA damage in spermatozoa of infertile male (n= 19) and control patients (n= 17) were compared. In addition, 14 infertile males were given antioxidants for 2 months. The levels of 8-hydroxy-2'-deoxyguanosine, a form of oxidative damage, in the spermatozoa were determined using high performance liquid chromatography with electrochemical detection. The levels of 8-hydroxy-2'-deoxyguanosine in the sperm DNA were significantlyhigher in mate infertile patients than control (1.5*0.2 versus 1.0*0.1/10^5 deoxyguanosine), and were correlated with sperm concentrations in ejaculates. Antioxidant treatment resulted in significant positive effects on sperm concentrations, with a significant reduction in sperm 8-hydroxy-2'-deoxyguanosine levels (from 1.5*0.2 to 1.1*0.14/10^5 d … More eoxyguanosine).In 1998, we investigated the role of radical oxygen species in the testicular germ cell apoptosis induced by heat stress. Testicular cells isolated from immature rats were cultured with or without elevated temperature, and occurrence of apoptosis in these cells was defined by the appearance of DNA fragmentation Following agarose gel electrophoresis, and by the flow cytometric quantification of apoptotic cells. At 32.5ﾟC, < 1% of cells showed signs of apoptosis throughout the culture period, whereas, under heat stress, the proportion of apoptotic cells increased to 14 % after I h exposure at 43ﾟC followed by 23 h culture at 32.5 ﾟC.Similar to the effect of heat stress, exogenously supplied oxygen free radicals also induced apoptosis. In contrast, treatment with catalase significantly attenuated heat stress-induced apoptosis. Furthermore, heat stress of testicular cells was associated with an increased intracellular peroxide level.Our studies demonstrate an association between the level of oxidative DNA damage in spermatozoa and male infertility, and indicate the involvement of radical oxygen species during testicular germ cell apoptosis induced by heat stress. Less