Autoradiographic localization of aromatic hydrocarbon receptor (AHR) in rhesus monkey ovary

Abstract

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic congener of a large class of manmade pollutants that persist in the environment. TCDD exerts its toxic effects, in part, by binding to its receptor known as the aromatic hydrocarbon receptor (AHR). TCDD is estrogen modulatory and in some systems its receptor associates directly with estrogen receptors via co-activator molecules. TCDD inhibits steroid synthesis in human ovarian granulosa cells and AHR is found in these cells. We have previously shown that AHR is found in whole rhesus monkey ovary, but have yet to establish its location. In the present study, we set out to show that radiolabeled TCDD binds to monkey ovarian follicles and that this binding is receptor mediated. Ovaries from Macaca mulatta were sectioned on a cryostat at 10 micro m; and sections were incubated with either control vehicle, (3)H-TCDD, or (3)H-TCDD plus alpha-naphthoflavone (ANF), a known receptor-blocking agent. Here, we show for the first time specific binding of TCDD to the granulosa cells of antral follicles and other regions of the rhesus monkey ovary. Our data indicate a 60-fold increase in binding with (3)H-TCDD over that of control, and that this binding is reduced to the levels seen in controls with the addition of the competitive antagonist ANF. These findings support the hypothesis that TCDD directly affects primate ovarian function via the AHR.

Very low-dose (femtomolar) 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) disrupts steroidogenic enzyme mRNAs and steroid secretion by human luteinizing granulosa cells

“…Recently we demonstrated that radiolabeled TCDD binds to AHR in rhesus monkey ovarian follicles at specific locations (GC>oocyte>theca); further supporting the notion that TCDD directly affects primate ovarian function through the AHR [20]. Similarly Wojtowicz et al .…”

Expression of aryl hydrocarbon receptor 1 (AHR1), AHR1 nuclear translocator 1 (ARNT1) and CYP1 family monooxygenase mRNAs and their activity in chicken ovarian follicles following in vitro exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

“…AHR-knockout mice display a number of defects suggesting that in addition to transducing xenobiotic signals, AHR is involved in the regulation of fundamental physiological processes (Benedict et al, 2003;Nebert et al, 2000). In mammals, the AHR physiological role is supported by the presence of AHR in several tissues, including the reproductive system (Baldridge and Hutz, 2007;Bussmann and Bara nao, 2006;Gregoraszczuk et al, 2001;Gregoraszczuk and Ptak, 2013;Jablonska et al, 2011;Pocar et al, 2004;Schlecht et al, 2004;Wojtowicz et al, 2005). Lee et al (2009) have revealed that both AHRs are expressed in chicken tissues, although only AHR1 mediates TCDD action.…”

Attenuation of cell cycle progression by 2,3,7,8-tetrachlorodibenzo-p-dioxin eliciting ovulatory blockade in gonadotropin-primed immature rats

“…It is generally accepted that TCDD action is mediated by the aryl hydrocarbon receptor (AhR)-signaling cascade, a transcription factor whose natural ligand remains unknown [11,12]. Since the presence of AhR has been reported in the ovary [13][14][15], TCDD could directly act at the ovary to disrupt critical cellular signals via AhR-mediated alterations in gene transcription, thereby contributing to the observed impairment of follicular maturation and ovulation. TCDD administration to immature rats primed with gonadotropins inhibits ovarian Ptgs2 expression [16], a requisite gene for ovulation [17].…”