Alternative Therapeutic Modalities in Treatment of Ischemic Heart Disease: Experimental studies on retinoic acid signaling in myocardial remodelling and remote gene therapy using heme oxygenase-1

Background: All-trans retinoic acid (atRA), an active derivative of vitamin A, regulates cell differentiation, proliferation and cardiac morphogenesis via transcriptional activation of retinoic acid receptors (RARs) acting on retinoic acid response elements (RARE). We hypothesized that the retinoic acid (RA) signalling pathway is activated in myocardial ischemia and postischemic remodelling. Methods and Findings: Myocardial infarction was induced through ligating the left coronary artery in mice. In vivo cardiac activation of the RARs was measured by imaging RARE-luciferase reporter mice, and analysing expression of RAR target genes and proteins by real time RT-PCR and western blot. Endogenous retinoids in postinfarcted hearts were analysed by triple-stage liquid chromatography/tandem mass spectrometry. Cardiomyocytes (CM) and cardiofibroblasts (CF) were isolated from infarcted and sham operated RARE luciferase reporter hearts and monitored for RAR activity and expression of target genes. The effect of atRA on CF proliferation was evaluated by EdU incorporation. Myocardial infarction increased thoracic RAR activity in vivo (p,0.001), which was ascribed to the heart through ex vivo imaging (p = 0.002) with the largest signal 1 week postinfarct. This was accompanied by increased cardiac gene and protein expression of the RAR target genes retinol binding protein 1 (p = 0.01 for RNA, p = 0,006 for protein) and aldehyde dehydrogenase 1A2 (p = 0.04 for RNA, p = 0,014 for protein), while gene expression of cytochrome P450 26B1 was downregulated (p = 0.007). Concomitantly, retinol accumulated in the infarcted zone (p = 0.02). CM and CF isolated from infarcted hearts had higher luminescence than those from sham operated hearts (p = 0.02 and p= 0.008). AtRA inhibited CF proliferation in vitro (p = 0.02). Conclusion: The RA signalling pathway is activated in postischemic hearts and may play a role in regulation of damage and repair during remodelling. Citation: Bilbija D, Haugen F, Sagave J, Baysa A, Bastani N, et al. (2012) Retinoic Acid Signalling Is Activated in the Postischemic Heart and May Influence Remodelling. PLoS ONE 7(9): e44740. doi:10.1371/journal.pone. 0044740 Editor: Yao Liang Tang, University of Cincinnati, United States of America Received May 9, 2012; Accepted August 7, 2012; Published September 28, 2012 Copyright: 2012 Bilbija et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The study was supported by grants from the Norwegian Health Association, Throne Holst Foundation, The Novo Nordisk Foundation, Freia Chocolate Factory’s Medical Fund, the Center for Heart Failure Research, and the University of Oslo. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: This study was partly funded by Freia Chocolate Factory’s Medical Fund. There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors. * E-mail: dusan.bilbija@medisin.uio. no