Abstract 13912: 17-Beta-Estradiol Directly Regulates Microtubule Dynamics: New Insights Into Sex-Differences in Right Ventricular Function in Pulmonary Hypertension

Introduction: Female sex is associated with better right ventricular (RV) function in pulmonary hypertension (PH). The female sex hormone 17-beta-estradiol is postulated to mediate these differences, but the molecular mechanisms underlying these observations are incompletely defined. Interestingly, 17-beta-estradiol induces microtubule depolymerization in cell culture, which may be relevant to RV dysfunction because microtubule remodeling promotes RV dysfunction via dysregulation of junctophilin-2 (MT-JPH2 pathway). We speculate that 17-beta-estradiol modulates the MT-JPH2 pathway and preserves RV function in PH. Methods: Pressure-volume assessments quantified RV function in monocrotaline (MCT) and pulmonary artery-banded (PAB) rats. Immunoblots quantified the tubulin and junctophilin-2 protein content in RV extracts. Echocardiography quantified RV function by RV fractional area change for 379 human PH patients. Sedimentation experiments, fluorescence-based polymerization assessments, and total internal reflection fluorescence (TIRF) microscopy examined the effects of 17-beta-estradiol on microtubules. Results: Female sex results in better RV function and less dysregulation of the MT-JPH2 pathway in both MCT and PAB rats. Moreover, in human PH, female sex was associated with better RV function, which persisted after adjusting for afterload. 17-beta-estradiol inhibited microtubule polymerization in vitro and TIRF microscopy showed 17-beta-estradiol localized to microtubule tips and prevented further microtubule polymerization. Conclusions: Preclinical and human studies show that females are better able to tolerate RV pressure overload. There are blunted microtubule-mediated t-tubule remodeling and preserved RV function in female MCT and PAB rats. In human PH, females have better RV function. These findings may be due to 17-beta-estradiol directly regulating microtubule dynamics as shown by sedimentation and polymerization assays and TIRF microscopy. These results provide additional insights into sex-differences in RV function in PH.