Evaluating the Role of LOXL2 in Post-menopausal Arterial Stiffening

Abstract

Introduction: Cardiovascular disease (CVD) is the number one cause of death for both men and women. Even though pre-menopausal women are relatively protected from CVD, a disproportionate increase in CVD risk and incidence occurs after menopause. Aortic stiffening, as occurs in aging, is predictive of major adverse cardiovascular events, independent from the traditional CVD risk factors. Epidemiological studies have shown that older, post-menopausal women exhibit an accelerated pace of aortic stiffening, eventually surpassing age-matched men, with exacerbated isolated systolic hypertension, diastolic dysfunction, and left ventricular remodeling. The hormonal shift, particularly loss of estrogen, present in post-menopausal women has also been widely studied; however, it is increasingly clear that estrogen loss alone is not responsible for the elevated CVD risk. More recently, a shift to androgen signaling has emerged as a key facet in post-menopausal women's health. Thus, mechanistic differences and manifestations of arterial stiffness in men and women require further investigation to help identify and develop novel risk assessment tools and therapeutic targets. Here we propose LOXL2, a key matrix remodeling enzyme, as a potential therapeutic target. In this study, we determined if post-menopausal females present accelerated arterial stiffening, and an abrupt and larger increase in LOXL2. We also studied the effect of sex hormones in LOXL2 activation. Methods and results: Male and female C57Bl/6J mice were used. Female mice underwent ovariectomy (OVX) or sham surgery at 10 weeks old. Three groups were compared: 1) OVX, 2) sham control females, and 3) age-matched males. Body weight, pulse wave velocity (PWV, the gold-standard index of in vivo arterial stiffening), and blood pressure (BP) were measured non-invasively from 12 to 53 weeks old. Results showed a significant increase in both body weight and PWV in the OVX females compared to sham females and males. BP remained similar for all groups, with a slight increase in OVX females. Mice were dissected, and aorta and heart were extracted and prepared for Western blotting measurements. OVX mice showed a low heart to body weight ratio. Western blotting (pilot data) revealed an increasing trend in LOXL2, ERα, and ERβ in the aorta and heart of OVX females. To test LOXL2 activation by sex hormones in vitro, human aortic smooth muscle cells (HASMC) and human aortic endothelial cells (HAEC) were exposed to dihydrotestosterone (DHT) and estradiol (E2) concentrations that mimic the hormonal levels of menstruating women, post-menopausal women, and men (post-puberty) for 16h. Western blotting showed highest levels of LOXL2 when mimicking the post-menopausal women hormonal levels in HASMCs but not in HAECs. Conclusion: Vascular stiffness is exacerbated in OVX females compared to sham females and males. OVX mice present a higher LOXL2 protein abundance in the aorta and heart, as well as increased ERα and ERβ. LOXL2 is modulated by sex hormones, showing significant increase when mimicking post-menopausal women’ hormonal levels. Future studies will continue to: 1) determine the molecular mechanisms underlaying increased arterial stiffness in females after menopause, 2) identify and test novel targets to stop and/or reverse this increase in vascular stiffening, and 3) study the role of hormonal shift in old females in arterial aging. NHLBI grant R01HL148112 01 (L.S.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.