Background:
Although the clinical importance of heart failure with preserved ejection fraction (HFpEF) has been extensively explored, most therapeutic regimens, including nitric oxide (NO) donors, lack therapeutic benefit. Although the clinical characteristics of HFpEF are somewhat heterogeneous, diastolic dysfunction (DD) is one of the most important features. Here we report that neuronal nitric oxide synthase (nNOS) induces DD by S-nitrosylation of histone deacetylase 2 (HDAC2).
Methods:
Two animal models of DD—SAUNA (SAlty drinking water/Unilateral Nephrectomy/Aldosterone) and mild transverse aortic constriction (mTAC) mice— as well as human heart samples from left ventricular hypertrophy (LVH) patients were used. Genetically modified mice that were either nNOS-ablated or HDAC2 S-nitrosylation-resistant were also challenged. N(ω)-propyl-L-arginine (NPLA), an nNOS selective inhibitor, and dimethyl fumarate (DMF), an NRF2 inducer, were used. Molecular events were further checked in human left ventricle specimens.
Results:
SAUNA or mTAC stress impaired diastolic function and exercise tolerance without overt systolic failure. Among the post-translational modifications tested, S-nitrosylation was most dramatically increased in both models. Utilizing heart samples from both mice and humans, we observed increases in nNOS expression and NO production. NPLA alleviated the development of DD
in vivo
. Similarly, nNOS knock out mice were resistant to SAUNA stress. nNOS-induced S-nitrosylation of HDAC2 was relayed by transnitrosylation of GAPDH. HDAC2 S-nitrosylation was confirmed in both DD mouse and human LVH. S-Nitrosylation of HDAC2 took place at C262 and C274. When DD was induced, HDAC2 S-nitrosylation was detected in wild type mouse, but not in HDAC2 knock-in mouse heart that expressed HDAC2 C262A/C274A. In addition, HDAC2 C262A/C274A mice maintained normal diastolic function under DD stimuli. Gene delivery with AAV9-NRF2, a putative denitrosylase of HDAC2, or pharmacologic intervention by DMF successfully induced HDAC2 denitrosylation and mitigated DD
in vivo
.
Conclusions:
Our observations are the first to demonstrate a new mechanism underlying DD pathophysiology. Our results provide theoretical and experimental evidence to explain the ineffectiveness of conventional NO-enhancement trials for improving DD with heart failure symptoms. More importantly, our results suggest that reduction of NO or denitrosylation of HDAC2 may provide a new therapeutic platform for the treatment of refractory HFpEF.
Cardiomyocyte Overexpression of Neuronal Nitric Oxide Synthase Delays Transition Toward Heart Failure in Response to Pressure Overload by Preserving Calcium Cycling