Toward Harnessing Sex Steroid Signaling as a Therapeutic Target in Pulmonary Arterial Hypertension

Sex and Gender Differences in Lung Disease

Sex differences in the anatomy and physiology of the respiratory system have been widely reported. These intrinsic sex differences have also been shown to modulate the pathophysiology, incidence, morbidity, and mortality of several lung diseases across the life span. In this chapter, we describe the epidemiology of sex differences in respiratory diseases including neonatal lung disease (respiratory distress syndrome, bronchopulmonary dysplasia) and pediatric and adult disease (including asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, lung cancer, lymphangioleiomyomatosis, obstructive sleep apnea, pulmonary arterial hypertension, and respiratory viral infections such as respiratory syncytial virus, influenza, and SARS-CoV-2). We also discuss the current state of research on the mechanisms underlying the observed sex differences in lung disease susceptibility and severity and the importance of considering both sex and gender variables in research studies' design and analysis.

17β-Estradiol and estrogen receptor α protect right ventricular function in pulmonary hypertension via BMPR2 and apelin

Women with pulmonary arterial hypertension (PAH) exhibit better right ventricular (RV) function and survival than men; however, the underlying mechanisms are unknown. We hypothesized that 17β-estradiol (E2), through estrogen receptor α (ER-α), attenuates PAH-induced RV failure (RVF) by upregulating the procontractile and prosurvival peptide apelin via a BMPR2-dependent mechanism. We found that ER-α and apelin expression were decreased in RV homogenates from patients with RVF and from rats with maladaptive (but not adaptive) RV remodeling. RV cardiomyocyte apelin abundance increased in vivo or in vitro after treatment with E2 or ER-α agonist. Studies employing ER-α-null or ER-β-null mice, ER-α loss-of-function mutant rats, or siRNA demonstrated that ER-α is necessary for E2 to upregulate RV apelin. E2 and ER-α increased BMPR2 in pulmonary hypertension RVs and in isolated RV cardiomyocytes, associated with ER-α binding to the Bmpr2 promoter. BMPR2 is required for E2-mediated increases in apelin abundance, and both BMPR2 and apelin are necessary for E2 to exert RV-protective effects. E2 or ER-α agonist rescued monocrotaline pulmonary hypertension and restored RV apelin and BMPR2. We identified what we believe to be a novel cardioprotective E2/ER-α/BMPR2/apelin axis in the RV. Harnessing this axis may lead to novel RV-targeted therapies for PAH patients of either sex.

Association of premature menopause with incident pulmonary hypertension: A cohort study

Background

Several forms of pulmonary hypertension (PH) disproportionately affect women. Animal and human studies suggest that estradiol exerts mixed effects on the pulmonary vasculature. Whether premature menopause represents a risk factor for PH is unknown.

Methods and findings

In this cohort study, women in the UK Biobank aged 40–69 years who were postmenopausal and had complete data available on reproductive history were included. Premature menopause, defined as menopause occurring before age 40 years. Postmenopausal women without premature menopause served as the reference group. The primary outcome was incident PH, ascertained by appearance of a qualifying ICD code in the participant’s UK Biobank study record. Of 136,715 postmenopausal women included, 5,201 (3.8%) had premature menopause. Participants were followed up for a median of 11.1 (interquartile range 10.5–11.8) years. The primary outcome occurred in 38 women (0.73%) with premature menopause and 409 (0.31%) without. After adjustment for age, race, ever-smoking, body-mass index, systolic blood pressure, antihypertensive medication use, non-high-density lipoprotein cholesterol, cholesterol-lowering medication use, C-reactive protein, prevalent type 2 diabetes, obstructive sleep apnea, heart failure, mitral regurgitation, aortic stenosis, venous thromboembolism, forced vital capacity (FVC), the forced expiratory volume in 1 second-to-FVC ratio, use of menopausal hormone therapy, and hysterectomy status, premature menopause was independently associated with PH (hazard ratio 2.13, 95% CI 1.31–3.23, P<0.001). In analyses of alternate menopausal age thresholds, risk of PH appeared to increase progressively with younger age at menopause (P_trend <0.001), with 4.8-fold risk in women with menopause before age 30 years (95% CI 1.82–12.74, P = 0.002). Use of menopausal hormone therapy did not modify the association of premature menopause with PH.

Conclusions

Premature menopause may represent an independent risk factor for PH in women. Further investigation of the role of sex hormones in PH is needed in animal and human studies to elucidate pathobiology and identify novel therapeutic targets.

Molecular mechanisms of right ventricular dysfunction in pulmonary arterial hypertension: focus on the coronary vasculature, sex hormones, and glucose/lipid metabolism

Pulmonary arterial hypertension (PAH) is a rare, life-threatening condition characterized by dysregulated metabolism, pulmonary vascular remodeling, and loss of pulmonary vascular cross-sectional area due to a variety of etiologies. Right ventricular (RV) dysfunction in PAH is a critical mediator of both long-term morbidity and mortality. While combinatory oral pharmacotherapy and/or intravenous prostacyclin aimed at decreasing pulmonary vascular resistance (PVR) have improved clinical outcomes, there are currently no treatments that directly address RV failure in PAH. This is, in part, due to the incomplete understanding of the pathogenesis of RV dysfunction in PAH. The purpose of this review is to discuss the current understanding of key molecular mechanisms that cause, contribute and/or sustain RV dysfunction, with a special focus on pathways that either have led to or have the potential to lead to clinical therapeutic intervention. Specifically, this review discusses the mechanisms by which vessel loss and dysfunctional angiogenesis, sex hormones, and metabolic derangements in PAH directly contribute to RV dysfunction. Finally, this review discusses limitations and future areas of investigation that may lead to novel understanding and therapeutic interventions for RV dysfunction in PAH.