Macrophage NLRP3-dependent IL-1β production contributes to aortic fibrosis in heart failure with preserved ejection fraction

Abstract

Fibrosis is the main pathological feature of aortic stiffness, which is a common extracardiac comorbidity of heart failure with preserved ejection fraction (HFpEF) and a contributor to left ventricular (LV) diastolic dysfunction. Systemic low-grade inflammation plays a crucial role in the pathogenesis of HFpEF and the development of vascular fibrosis. In this study, we investigate the inflammatory mechanism of aortic fibrosis in HFpEF using a novel mouse model. LV diastolic dysfunction with preserved ejection fraction and aortic fibrosis induced by a high-fat diet (HFD) combined with subcutaneous aldosterone infusion are utilized. The constructed model exhibits augmented macrophage recruitment and NLR family pyrin domain containing 3 (NLRP3)-dependent interleukin (IL)-1β production in fibrotic aortas. In addition, a bone marrow transplant is employed to induce macrophage-specific NLRP3 deficiency in the HFpEF mouse model. These mice show almost completely suppressed cleaved-caspase-1 and mature IL-1β protein expression in the aortas, indicating that macrophage NLRP3 inflammasome activation enhances the IL-1β overproduction in fibrotic aortas. Furthermore, we show that macrophage NLRP3 inflammasome inhibition improves aortic fibrosis and LV diastolic dysfunction. In conclusion, this study demonstrates the pivotal effect of macrophage NLRP3-dependent IL-1β production on aortic fibrosis and cardiac function in HFpEF, suggesting a potential target for HFpEF therapy.

1. Introduction

Heart failure with preserved ejection fraction (HFpEF) accounts for approximately half of all cases of heart failure. In recent years, the prevalence of HFpEF has been increasing, attracting considerable attention worldwide [1,2]. In addition to cardiac phenotypes such as left ventricular (LV) diastolic dysfunction, HFpEF is characterized by multiple extracardiac comorbidities, such as non-alcoholic fatty liver disease and vascular diseases. Among vascular diseases, vascular stiffness, especially aortic stiffness, deserves particular attention, as patients with HFpEF are more likely to develop large artery stiffness. Aortic stiffness, which is usually caused by excessive fibrosis manifesting as degradation of elastic fibers and increased collagen deposition, can lead to adverse ventricular-arterial interaction and subsequently diastolic dysfunction [3–6]. A correlation between aortic stiffness and LV diastolic dysfunction has been demonstrated in patients with HFpEF [7]. Nevertheless, only a handful of studies on aortic fibrosis and its underlying mechanisms have been conducted in HFpEF mouse models.

Systemic low-grade inflammation plays a pivotal role in the pathogenesis of HFpEF and is associated with deleterious vascular changes [8,9]. Inflammatory biomarkers are also associated with vascular fibrosis [10,11]. Immune cell infiltration, especially macrophages, is the main manifestation of vascular inflammation. Macrophages and macrophage-derived inflammatory cytokines increase matrix metalloproteinase (MMP) expression, leading to matrix collagen deposition and driving myofibroblast activation [12,13]. Interleukin (IL)-1β is one of the most abundant inflammatory cytokines secreted by macrophages [14]. NLR family pyrin domain containing 3 (NLRP3) inflammasome activation induces IL-1β production [15]. Previous research has demonstrated that increased macrophage IL-1β in the heart promotes cardiac dysfunction during the development of HFpEF [16]. Moreover, NLRP3 inflammasome activation in the arterial smooth muscle layer is associated with vascular calcification in diabetic mice [17]. However, whether macrophages and NLRP3-dependent IL-1β production contribute to aortic fibrosis in HFpEF remains unknown.

In this study, we developed a mouse model of HFpEF induced by a high-fat diet (HFD) combined with subcutaneous aldosterone (ALD) infusion. Subsequently, pathological fibrosis in the aortas and the underlying mechanism were explored. We found that inhibiting NLRP3-dependent IL-1β overproduction in macrophages mitigates aortic fibrosis and LV diastolic dysfunction in HFpEF.