To clarify the molecular mechanism of ethylene glycol monomethyl ether (EGME)-induced testicular toxicity, the potential for EGME-related changes in transcript levels of genes including spermatocyte-specific genes was evaluated in the testis of rats given single dosing of EGME at 200, 600, or 2000 mg/kg. Furthermore, the contribution of decreased testicular testosterone on EGME-induced spermatocyte toxicity was investigated by comparing to transcriptional profile due to a testosterone synthesis inhibitor, ketoconazole (KET), at 30 or 300 mg/kg. EGME at 600 mg/kg or more dose-dependently caused testicular toxicity characterized by degeneration and necrosis of spermatocytes at stage VII–XIV seminiferous tubules. The spermatocyte injury was well correlated with decreased spermatocyte-specific gene expression. Analysis of upstream regulators by the Ingenuity Pathways Analysis system suggested that up-regulation of oxidative stress, protein kinase activation, and histone acetylation was involved in EGME-induced spermatocyte toxicity. Interestingly, KET decreased testicular testosterone to a similar extent compared to the EGME treatment, but KET at up to 300 mg/kg did not show any histopathological abnormality or change in the expression of spermatocyte-specific genes. These results suggested that the decreased testicular testosterone have little impact on EGME-induced spermatocyte injury. In contrast, KET showed trends toward increases in Hsd3b2 and Hsd17b2 mRNAs, presumably resulting from inhibition of androgen synthesis. Transcriptome analysis clearly demonstrated the differential effects of EGME and KET on androgen synthesis. In conclusion, EGME caused spermatocyte toxicity correlated with decreased expression of spermatocyte-specific genes. Furthermore, oxidative stress, protein kinase activation, and histone acetylation were suggested to be involved in EGME-induced testicular toxicity.
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