Pathophysiological and therapeutic implications of urocortin-2 in heart failure with preserved ejection fraction

Introduction

Although initially believed to be less severe than heart failure with reduced ejection fraction (HFrEF), heart failure with preserved ejection fraction (HFpEF) prevalence has increased and accounts for as much as 50% of heart failure cases [1,2]. Treatment options remain limited and aim primarily for symptom relief and improvement of quality of life [2]. Urocortin-2 (Ucn-2) belongs to the corticotrophin-releasing hormone (CRH) family and has been found to have significant beneficial hemodynamic, hormonal and renoprotective effects both in both animal models and humans with HFrEF [3,4].

Objectives

In this work we studied the role of the Ucn-2/CRHR2 system in the pathophysiology of HFpEF and evaluated the efficacy of Ucn-2 as a novel therapeutic strategy in this clinical syndrome.

Methods

18-week-old male ZSF1-Lean (n=26) and ZSF1-Obese (n=28) rats randomly received either Ucn-2 (15 μg/kg/day, subcutaneously) or vehicle (0.9% NaCl), for 12 weeks, resulting in 4 experimental groups: ZSF1-Lean + Ucn-2; ZSF1-Lean + vehicle; ZSF1-Obese + Ucn-2; ZSF1-Obese + vehicle. During the treatment period, evolution of cardiac (dys)function was assessed by echocardiography and exercise tolerance test. After treatment, invasive hemodynamic analysis was performed, with subsequent sample collection. Histological analysis of the left ventricle (LV) was performed as well as quantitative western blotting and RT-PCR analysis for relevant molecular markers (Figure 1).

Results

mRNA expression of Ucn-2 and CRHR2, as well as protein levels of CRHR2, were decreased in the LV of ZSF1-Obese rats compared to ZSF1-Lean and correlated with LV structure and diastolic function. ZSF1-Obese rats showed systemic hypertension, decreased endurance capacity and impaired LV relaxation, with preserved ejection fraction and cardiac index. Chronic Ucn-2 treatment attenuated hypertension and modestly enhanced effort tolerance. In both morphometric and echocardiographic analysis we found that ZSF1-Obese rats presented significantly higher cardiac and LV weight, compared to Lean counterparts. Cardiomyocyte cross-sectional area and fibrosis were found to be increased in Obese rats, corroborating morphometric and echocardiographic measurements. Chronic Ucn-2 treatment attenuated both cardiac hypertrophy and fibrosis. Furthermore, ZSF1-Obese rats displayed increased BNP and TNF-α LV mRNA expression, both of which were decreased with Ucn-2 treatment. Interestingly, Col3A1 LV mRNA expression was found to be decreased in ZSF1-Obese rats compared to ZSF1-Lean, and Ucn-2 therapy resulted in a faint further decrease of Col3A1 expression, compared to non-treated animals.

Conclusion

This work suggests that Ucn-2/CRHR2 system is altered in experimental HFpEF and that chronic administration of Ucn-2 attenuates LV dysfunction and remodeling, in particular the hypertrophic changes of the cardiac muscle.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Portuguese Foundation for Science and Technology (FCT), under the auspices of the Cardiovas-cular R&D Center–UnIC [UIDB/00051/2020 and UIDP/00051/2020] and project IMPAcT [PTDC/MED-FSL/31719/2017; POCI-01–0145-FEDER-031719].

Pharmacological Targeting of Senescence with ABT-263 in Experimental Heart Failure with Preserved Ejection Fraction

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Fundação Ciência e Tecnlogia

HFpEF is the most common form of heart disease in the elderly and is associated with high morbidity and mortality. Our understanding of HFpEF pathophysiology is limited and development of efficient therapies that alter the clinical course of the disease has proved greatly challenging. Although aging is a risk factor of HFpEF1, the involvement of aging hallmarks such as cell senescent and immunosenescence is unclear. Recently, a link between endothelial senescence and HFpEF development was demonstrated in mice with accelerated aging [1], endorsing anti-aging pharmacologic as potential new therapeutic alternatives for HFpEF. In fact, the senolytic (drugs that selectively promote apoptosis of senescent cells) ABT-263 has already proven efficacy in the context of cardiovascular diseases. Further studies are needed to clarify the relevance of aging and of anti-aging therapies in the context of HFpEF.

Using ZSF1 obese rats (ZSF1-Ob) as model of HFpEF we showed from 18 weeks signs of immunosenescence compared to ZSF1-Ln, namely an increased frequency of circulating myeloid cells and decreased frequency of T and B cells. Concomitantly, expression of pro-inflammatory factors (IL-6, IL-1, TGF-β, TNF-α) was upregulated in peripheral blood mononuclear cells (PBMCs) of ZSF1-Ob which also displayed characteristic features of cell senescence (p21 expression, lysosomal endogenous Beta-galactosidase (SA-B-Gal) senescence-associated secretory phenotype (SASP) and up-regulation of BCL-XL. Importantly, no signs of cellular senescence (SA-B-gal, pH2AX and senescence associated pathways) were found in the main hematopoietic organs (spleen and bone marrow). Alongside, these systemic alterations, an upsurge of cellular senescence was observed in myocardium of ZSF1-Ob rats, particularly in endothelial and hematopoietic cells. Serum of ZSF1-Ob rat was able to induce activation and cellular senescence of cardiac microvascular endothelial cells, indicating that systemic circulating factors may be the upstream mechanism of cellular senescence and dysfunction in HFpEF. Analysis of HFpEF patients and a control cohort adjusted to main co-morbidities further demonstrated accumulation of senescent monocytes in HFpEF patients. In these patients, the senescence marker SA-B-Gal correlated with plasmatic brain natriuretic peptide (BNP) levels and pulmonary artery systolic pressure. Targeting aging hallmarks through the treatment of ZSF1-Ob rat with ABT-263 resulted in a reduction in circulating senescent cells, decreased systemic and local inflammation, re-established immune proportions, restore the levels of circulating BNP and attenuated myocardial remodeling, particularly endothelial dysfunction and fibrosis.

Collectively these findings support that premature cellular senescence contributes to the establishment of a deleterious pro-inflammatory environment in HFpEF and that senolytic agents hold promise for the treatment of this syndrome.