NEW FINDINGS

What is the central question of this study? In this study, we investigated whether MD1 interacted with the sympathetic nerves in ventricular arrhythmia (VA) during heart failure with preserved ejection fraction (HFpEF). What is the main finding and its importance? Mice with HFpEF showed increased susceptibility to VA, adverse electrical remodelling, impaired heart rate variability, enhanced sympathetic hyperactivity, activation of the NLRP3 inflammasome and increased interleukin-1β release. These changes induced by HFpEF were exacerbated by MD1 deficiency.

ABSTRACT

Sympathetic hyperactivity can promote malignant ventricular arrhythmia (VA), and myeloid differentiation 1 (MD1) has been reported to play an important role in obesity-induced VA. However, it is not known whether an interaction of MD1 with sympathetic hyperactivity contributes to the VA induced by heart failure with preserved ejection fraction (HFpEF). The aim of this study was to investigate the potential interaction between MD1 and sympathetic hyperactivity in HFpEF-induced VA and the underlying mechanism. Eight-week-old MD1-knockout (MD1-KO) and wild-type (WT) mice were subjected to a model of HFpEF induced by uninephrectomy, a continuous saline or d-aldosterone infusion and provision of drinking water containing 1.0% sodium chloride for 4 weeks. Echocardiography and haemodynamics were used to verify the model of HFpEF. An isolated electrophysiological study was performed to assess the susceptibility to VA. Four weeks later, the mice with HFpEF showed an increased heart weight to tibia length ratio, decreased left ventricular minimum rates of pressure rise (dP/dt ), increased τ, lung weight to tibia length ratio and preserved left ventricular ejection fraction compared with WT mice. The mice with HFpEF exhibited increased susceptibility to VA, as shown by the shortened effective refractory period, prolonged action potential duration (APD), increased APD alternans threshold and higher incidence of VA. Moreover, we also found that mice with HFpEF showed impaired heart rate variability, sympathetic hyperactivity, activation of the NLRP3 inflammasome and increased interleukin-1β release. These changes induced by HFpEF were exacerbated by MD1 deficiency. We conclude that MD1-KO contributes to sympathetic hyperactivity and facilitates VA in HFpEF via activation of the NLRP3 inflammasome. Treatment targeting MD1 and NLRP3 might decrease the risk of HFpEF-induced VA.