799: Does cholesterol exposure of myometrial cells affect oxytocin receptor gene expression and downstream signaling?

Abstract

Obesity increases the risk of dysfunctional labor and cesarean delivery. The etiology still remains unclear. Obesity has a positive correlation to elevated blood cholesterol levels. In animal models and in vitro studies, high cholesterol levels decreases uterine contractility. The objective of this study is to investigate the effect of cholesterol on oxytocin receptor expression and downstream signaling using a human myometrial cell line. Immortalized human myometrial, PHM1-41 cells were exposed to either 0 (vehicle) or 50 μg/ml of cholesterol for 24 hours; cytotoxicity assays confirmed this dose was non-cytotoxic. Vehicle and cholesterol exposed cells were then treated with 1μM/ml of oxytocin (OXT) for 2 hours. The expression of mRNAs encoding oxytocin receptor (OXTR) and select downstream signaling contractility genes - Protein kinase C (PRKCA), Map kinase (MAP2k2), gap junction gene Debrin-1 (DBN1) and select key relaxation genes - Adenylate cyclase 1 (ADCY1v1) and Adrenergic receptor B2 (ADRB2) were analyzed by quantitative RT-PCR. Differences in mRNA levels between different groups (control, cholesterol only, oxytocin only, cholesterol + oxytocin) were evaluated. The mRNA expression of OXTR, key downstream contractility genes - PRKCA, gap junction gene - DBN1 and key relaxation genes - ADCY1v1 and ADRB2 were identified in control, cholesterol exposed, OXT-exposed and OXT + cholesterol groups, whereas the mRNA expression for Map kinase-2 (MAP2k2) receptor was only identified in OXT-exposed cells. Cholesterol treatment (±OXT) had no effect on the expression of mRNAs for OXTR, downstream contractility genes, gap junction genes and relaxation genes by PHM1-41 cells. Our results suggest that cholesterol exposure of PHM1-41 myometrial cells alone doesn’t affect the mRNA expression of OXTR oxytocin receptor expression or downstream contractility and relaxation signaling genes.