Original article PARP mediates structural alterations in diabetic cardiomyopathy Jane Chiu, Hana Farhangkhoee, Bing Ying Xu 1 , Shali Chen, Biju George, Subrata Chakrabarti ⁎ Department of Pathology, 4033 Dental Sciences Building, University of Western Ontario, London, Ontario, Canada abstract article info Article history: Received 28 April 2008 Received in revised form 16 June 2008 Accepted 24 June 2008 Available online 8 July 2008 Keywords: Diabetic cardiomyopathy Hyperhexosemia PARP p300 Diabetic cardiomyopathy is characterized by structural alterations such as cardiomyocyte hypertrophy, necrosis and focal fibrosis. Hyperglycemia-induced oxidative damage may play an important role in this pathogenetic process. Recent studies have shown that poly (ADP-ribose) polymerase (PARP) is activated in response to oxidative stress and cellular damage as well, plays a role in gene expression. This study investigated mechanisms of diabetes-induced, PARP-mediated development of structural alterations in the heart. Two models of diabetic complications were used to determine the role of PARP in oxidative stress, cardiac hypertrophy and fibrosis in the heart. PARP-1 knockout (PARP -/- ) mice and their respective controls were fed a 30% galactose diet while male Sprague–Dawley rats were injected with streptozotocin and subsequently treated with PARP inhibitor 3-aminobenzamide (ABA). The in vivo experiments were verified in in vitro models which utilized both neonatal cardiomyocytes and endothelial cells. Our results indicate that hyperhexosemia caused upregulation of extracellular matrix proteins in association with increased transcriptional co-activator p300 levels, cardiomyocyte hypertrophy and increased oxidative stress. These pathogenetic changes were not observed in the PARP -/- mice and diabetic rats treated with ABA. Furthermore, these changes appear to be influenced by histone deacetylases. Similar results were obtained in isolated cardiomyocytes and endothelial cells. This study has elucidated for the first time a PARP-dependent, p300-associated pathway mediating the development of structural alterations in the diabetic heart. © 2008 Elsevier Inc. All rights reserved. 1. Introduction Pathogenetic mechanisms leading to the development of diabetic cardiomyopathy may involve both endothelial cells and cardiomyo- cytes. Structurally, diabetic cardiomyopathy is characterized by capillary basement membrane thickening and focal fibrosis due to increased production of extracellular matrix (ECM) proteins and cardiomyocyte hypertrophy [1,2]. Increased oxidative stress from chronic hyperglycemia may play a significant role in this process. Oxidative stress leads to DNA breakage which renders the DNA unstable thereby activating nuclear enzyme poly (ADP-ribose) poly- merase (PARP) in an attempt to repair such damage. Activated PARP transfers ADP-ribose units from NAD + (nicotinamide adenine dinu- cleotide) to itself and other nuclear chromatin-associated proteins [3]. When PARP is overactivated, which is the case in diabetes, intracellular NAD + is depleted creating a redox imbalance further exacerbating the oxidative state in the cell. The beneficial effects of PARP inhibition has been illustrated by PARP-1 knockout (PARP -/- ) mice. These animals are protected against streptozotocin (STZ)- induced diabetes [4] and myocardial ischemia/reperfusion injury [5] among other diseases. Transcriptional co-activator and histone acetyltransferase (HAT) p300 mediates cell growth, proliferation and differentiation as well, it controls a large number of transcription factors, nuclear receptors and DNA repair enzymes including PARP [6,7]. PARP itself has been shown to facilitate p300-mediated gene transcription [8]. Previously, we have shown that diabetes upregulates the expression of p300 along with PARP activity and that inhibition of p300 prevents diabetes-induced upregulation of PARP mRNA and ECM protein fibronectin (FN). FN plays a variety of physiological roles including cell survival, migration and proliferation [9]. We have also shown that in diabetes, increased ECM protein production may be mediated through the activation of vasoactive factors such as endothelin-1 (ET-1) [10,11]. It is however not clear as to the role of PARP and its relationship with epigenetic mechanisms, such as p300 activation, in the pathogenesis of diabetic cardiomyopathy. The role of PARP activation has been demonstrated to alter the function of the heart in diabetes. However, PARP has not been studied with respect to structural changes in the diabetic heart. Hence, in this study we investigated the role of PARP in the development of structural alterations in the heart in diabetes. We determined whether these effects were mediated in association with p300 in PARP -/- animals fed a 30% galactose diet as well as chemically-induced diabetic animals. Galactose-fed animals are well studied as a model of chronic diabetic complications with both biochemical and structural changes of chronic diabetic complications having been shown in this model [12,13]. These animals also exhibit diabetes-like contractile Journal of Molecular and Cellular Cardiology 45 (2008) 385–393 ⁎ Corresponding author. Tel.: +1 519 685 8500x36350; fax: +1 519 661 3370. E-mail address: Subrata.Chakrabarti@schulich.uwo.ca (S. Chakrabarti). 1 Current address: Department of Forensic Science, Kunming Medical College, Kunming, Yunnan, P.R. China. 0022-2828/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.yjmcc.2008.06.009 Contents lists available at ScienceDirect Journal of Molecular and Cellular Cardiology journal homepage: www.elsevier.com/locate/yjmcc