Abstract 13529: Protective Role of 5-azacytidine on Myocardial Infarction is Associated With Modulation of Macrophage Phenotype and Inhibition of Fibrosis
Background: Macrophages undergo classical activation (M1) or alternative activation (M2) in response to various signals. In the tissue injury, M2 phenotype of macrophage is involved in tissue regeneration. This study was designed to access the functional effect of 5-azacytidine (5AZ) on phenotypic change of macrophages in myocardial infarction (MI).
Methods: A mouse macrophage cell line RAW264.7 was stimulated with peptidoglycan (PGN), with or without 5-azacytidine (5AZ). Nitric oxide (NO) production was quantified by Griess method. Inducible nitric oxide synthase (iNOS) was measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot. In animal study, MI was induced in rats, and divided into two groups; saline-injection group and 5AZ-injection group. Cardiac function evaluation and immunohistochemical analysis were performed 2 weeks after MI. iNOS and arginase-1 (Arg1) were used as phenotype markers of M1 or M2, respectively.
Results: 5AZ treatment significantly reduced PGN-induced NO production to 77.87%. Both mRNA and protein levels of iNOS were induced by PGN, which were blocked by 5AZ treatment. Consistently, iNOS promoter activity was increased by PGN and attenuated by 5AZ. Next, the effect of 5AZ on injured cardiac niche was examined. In MI model, cardiac function was significantly preserved by 5AZ administration. Ejection fraction improved to 59.00±8.03% from 42.52±2.58% and cardiac contractility (LV dP/dt-max, LV dP/dt-min) was greater in 5AZ administration group (8929.71±1257.17, -4788.59±306.05 mmHg vs. 6610.4±282.4, -4219.5±162.9 mmHg, p<0.05). Interestingly, Arg1-expressing macrophages in infarcted myocardium were more abundant in 5AZ administration group.
In cardiac fibroblasts, pro-fibrotic mediators, such as collagen type 1 and connective tissue growth factor, and cell proliferation were increased by AngII, which were attenuated by 5AZ treatment.
Conclusion: 5AZ exerts its cardiac protective role through modulation of macrophage and inhibition of fibrosis, and could be therapeutic intervention in the cardiac injury.
- © 2013 by American Heart Association, Inc.