Testis

Methoxyacetic Acid Disregulation of Androgen Receptor and Androgen-Binding Protein Expression in Adult Rat Testis

Abstract

Chemical agents can disrupt the balance between survival and apoptosis during spermatogenesis and thus give rise to reduced counts of spermatozoa, or oligospermia. One such agent that renders significant germ cell apoptosis at specific stages of the cycle of the seminiferous epithelium is methoxy acetic acid (MAA), the active metabolite of a commonly used solvent, methoxyethanol. Although MAA gives rise to apoptosis of pachytene spermatocytes, it is not known whether MAA exerts solely a direct effect on germ cells, or whether it also affects other testicular cell types such as the Sertoli cells. In the present investigation, we test the hypothesis that MAA has direct effects on Sertoli cells in vivo. We report that AR immunohistochemistry in MAA treated rats revealed that the stage specific expression of AR protein in Sertoli cells was significantly altered. In MAA-treated animals high AR expression was found in Sertoli cells coincident with the MAA-induced apoptosis of late-stage pachytene spermatocytes. The altered expression of AR in MAA-treated animals was also seen using seminiferous tubules harvested by Laser Capture Microdissection (LCM). In addition to effects on AR expression, androgen-binding protein (ABP) mRNA levels were also altered in a stage-specific manner. Using a different system, mouse Sertoli cell lines TM4 and MSC-1, positive for either AR or ABP, respectively, we demonstrate a direct effect of MAA on ABP protein and mRNA expression in the MSC-1 cell, but did not detect any effect on AR protein or mRNA expression in TM4 cells. Finally, using mouse fibroblasts that express endogenous AR and were stably transfected with two AR promoter/ reporter systems, MMTV-CAT and probasin-luciferase, respectively, we examined the ability of MAA to potentiate DHT activation of AR. Results demonstrate that although MAA did not activate AR directly, it did potentiate DHT activation of the AR two- to four-fold. Our results demonstrate that MAA alters the expression level of AR and ABP in vivo and increases AR transcriptional activity in tissue culture cells. We suggest that the abnormal spermatogenesis generated by MAA is at least partly due to direct effects on Sertoli cells. Whether MAA elicits a pro-apoptotic signal from Sertoli cells, or diminishes a pro-survival signal required by germ cells, downstream to altering AR and ABP expression, in a stage-specific fashion, however, remains to be determined.