Follicle-stimulating hormone responsiveness in antral follicles from aryl hydrocarbon receptor knockout mice

Abstract

BackgroundPrevious studies have demonstrated that pre-pubertal aryl hydrocarbon receptor knockout (AHRKO) mice have slow antral follicle growth and reduced capacity to produce estradiol compared to wild-type (WT) mice. Although previous studies have suggested that this is likely due to a reduced ability of the AHRKO follicles to respond to follicle-stimulating hormone (FSH), this possibility was not directly tested. Thus, the goal of these studies was to test the hypothesis that low FSH responsiveness is responsible for the slow growth and reduced estradiol production observed in pre-pubertal AHRKO versus WT antral follicles.MethodsAntral follicles from WT and AHRKO mice were cultured with varying amounts of FSH (0–15 IU/mL) for up to 7 days, and subjected to measurements of growth, FSH receptor and steroidogenic regulator expression, sex steroid hormone levels, and inhibin beta-A expression. General linear models (GLM) for repeated measures were used to compare follicle diameters over time among treatments. If the global tests from GLM were significant, Tukey’s tests were used for pairwise comparisons. Remaining comparisons among groups were performed using one-way analysis of variance followed by Tukey’s post hoc test.ResultsThe results indicate that FSH stimulated growth in both WT and AHRKO follicles, but that high levels of FSH (10–15 IU/mL) were required for AHRKO follicles to reach maximal growth, whereas lower levels of FSH (5 IU/mL) were required for WT follicles to reach maximal growth. Further, FSH stimulated expression of FSH receptor, steroidogenic factors, and inhibin beta-A as well as production of steroid hormones in both WT and AHRKO follicles, but the degree of stimulation differed betw een WT and AHRKO follicles. Interestingly, FSH treatment increased expression of FSH receptor, some steroidogenic regulators, inhibin beta-A, and steroid hormone production more in AHRKO follicles compared to WT follicles.ConclusionsCollectively, these data suggest that the slow growth, but not reduced steroidogenesis in AHRKO follicles, is due to their reduced ability to respond to FSH compared to WT follicles. These data also suggest that the AHR may contribute to the ability of FSH to stimulate proper follicle growth, but it may not contribute to FSH-induced steroidogenesis.

Estrogen receptor-α and aryl hydrocarbon receptor involvement in the actions of botanical estrogens in target cells

“…Because cell context and tissue type can affect gene response to ligands, we next assessed BE actions in primary hepatocytes from mouse liver, a cell in which AhR carries out major functions including gene regulation (Hernandez-Ochoa et al, 2013; Schmidt et al, 1996). When we treated primary hepatocytes isolated from wild type or AhR knockout mice with BEs, TCDD, or E2, we observed a nearly complete loss of the activation of CYP1A1, CYP1B1, and leptin by BEs and TCDD in hepatocytes from AhR knockout mice compared to what was seen in the hepatocytes of WT mice (Fig.…”

“…Isolation of mouse primary hepatocytes from AhR knockout female mice and their wildtype female littermates was modified from the procedure described (Hernandez-Ochoa et al, 2013; Schmidt et al, 1996). Six week-old female mice were sacrificed by CO 2 inhalation, perfused transcardially first with 20 ml of Perfusion Buffer I [Hank’s Balanced Salt Solution (HBSS) without Ca 2+ and Mg 2+ (Invitrogen, Ca# 14174) supplemented with 10 mM HEPES, 0.075% sodium bicarbonate, and 1.2 mM EDTA (pH 8.0)] and then with 20 ml of Perfusion Buffer II [HBSS with Ca 2+ and Mg 2+ (Invitrogen, Cat# 14025) supplemented with 25 mM HEPES and 3 unit/ml collagenase II (Worthington)] through the hepatic portal vein.…”

In vitro re-expression of the aryl hydrocarbon receptor (Ahr) in cultured Ahr-deficient mouse antral follicles partially restores the phenotype to that of cultured wild-type mouse follicles

“…While the mechanism by which Ahr re-expression affects follicle growth is unknown, previous studies indicate that the impaired Ahr KO follicle growth is partially due to reduced gonadotropin responsiveness of Ahr KO ovaries compared to WT ovaries (Barnett et al, 2007). Further, previous studies show that the AHR can bind to the promoter region of the follicle stimulating hormone receptor ( Fshr ) as a transcription factor (Hernandez-Ochoa et al, 2010, Hernandez-Ochoa et al, 2013). Therefore, re-expression of the Ahr into Ahr KO follicles may have recovered some of the binding ability of FSH and this may have helped restore follicle growth to WT levels.…”