Abstract Body (Do not enter title and authors here): Background: Inflammatory response is a key player in heart failure with preserved ejection fraction, however the underlying mechanisms remain unclear. Recent evidence indicates that macrophage inflammation driven by the transcriptional coregulatory protein NCOR1 could play a pivotal role in disease states.
Hypothesis: NCOR1 orchestrates macrophage inflammation and cardiac dysfunction in HFpEF.
Methods: HFpEF was induced in mice using a validated model combining high-fat diet and L-NAME for 15 weeks. Cardiac function was assessed using high-resolution ultrasound imaging and LV samples were used to study macrophage polarization and inflammation by FACS. We generated myeloid-specific NCOR1-KO mice to investigate the in vivo effects of macrophage NCOR1 depletion on HFpEF. In vitro experiments included RAW 264.7 cells polarization and the assessment of macrophage phenotype switching in the presence or the absence of NCOR1. To study the crosstalk of macrophages with the surrounding cardiac cells, cardiomyocytes (H9c2) and endothelial cells (HAECS) were exposed to conditioned media from cultured RAW.
Results: The expression of macrophage markers in human LV specimens showed an increase in pro-inflammatory macrophages (M1) and a decrease in regulatory macrophages (M2) as compared to age-matched control mice. HFpEF mice showed increased expression of vascular adhesion molecules (ICAM1, ICAM2, E-selectin) and a significant recruitment of M1 macrophages as proved by qPCR, WB, and flow cytometry analysis. Of interest, diastolic dysfunction - assessed by E/A ratio and isovolumic relaxation time (IVRT) – and lung congestion were significantly reduced in mice with macrophage NCOR1 deletion as compared to WT littermates, while exercise tolerance was significantly improved. These findings were associated with a reduction of myocardial inflammation (TNF-a, IL6, IL-1b) in Ncor1-KO mice. In vitro assays showed that stimulation of macrophages with PA induced M1 type switch and increased NCOR1, TNF-a, IL-6, and IL-1b levels, whereas NCOR1 depletion prevented detrimental changes of macrophage conditional medium (Fig.1).
Conclusion: Targeting macrophage NCOR1 could represent a promising approach to blunt myocardial inflammation in HFpEF.