Abstract Body (Do not enter title and authors here): Background: The NLRP3 inflammasome is implicated in right ventricular (RV) dysfunction, particularly in low endogenous estrogen states found in males and postmenopausal females. We hypothesized that NLRP3 inhibition through estrogen receptor alpha (ERα) enhances RV contractility and improves RV-pulmonary artery (PA) coupling.
Methods: RVs from male and pre- or postmenopausal female PH patients with RV failure (RVF) were assessed for NLRP3 activation by analyzing proteomics data and staining for NLRP3 and ASC. Male or female human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were treated with endothelin-1 (ET1) ± 17beta-estradiol (E2). RV cardiomyocytes (RVCMs) were isolated from male and intact or ovariectomized female rats treated with monocrotaline (MCT) or pulmonary artery banding (PAB). Male or female ERα loss-of-function mutant (ERαmut) rats were employed to study the effects of ERα. RV-PA coupling was assessed by pressure-volume loops (PV-loops) in the WT and ERαmut MCT-treated rats. NLRP3 activation in RVCMs and iPSC-CMs was assessed by NLRP3-ASC colocalization and downstream targets. RVCM contractility and cytosolic calcium (c-Ca2+) were evaluated via IONOPTIX system. P<0.05 was considered significant.
Results: Proteomics and immunofluorescence studies revealed that upregulation of NLRP3 activity and signaling in human RVF are more pronounced in males and postmenopausal females (p<0.05). In ET-1-treated iPSC-CMs, NLRP3 was more activated in male than female iPSC-CMs (p<0.05). RVCMs from male, but not female, MCT- or PAB-rats demonstrated increased NLRP3-ASC colocalization (p<0.05). E2 treatment prevented MCT-induced impairment of RV-PA coupling and had beneficial effects on survival. E2 treatment of male and OVX female wildtype (WT) rat RVCMs reduced NLRP3-ASC co-localization and increased Ca2+-dependent contractility (p<0.05). Similarly, E2 treatment in male iPSC-CMs prevented ET-1-induced NLRP3 activation. E2’s inhibitory effects on NLRP3 activation, impairment of RV-PA coupling, improved survival, NLRP3-induced contractile dysfunction, and c-Ca2+ in male WT rat RVCMs were abrogated in ERαmut rat RVCMs (p<0.05).
Conclusion: NLRP3 activation impairs RV contractile function in a sexually dimorphic manner. The E2-ERα pathway protects against this dysfunction. E2 enhances RV function and survival in both male and postmenopausal models of RVF, suggesting its potential as a therapeutic target in low estrogen states.