Hypoxia Mediates Mutual Repression between microRNA-27a and PPAR gamma in the Pulmonary Vasculature

Pulmonary hypertension (PH) is a serious disorder that causes significant morbidity and mortality. The pathogenesis of PH involves complex derangements in multiple pathways including reductions in peroxisome proliferator-activated receptor gamma (PPARc). Hypoxia, a common PH stimulus, reduces PPARc in experimental models. In contrast, activating PPARc attenuates hypoxia-induced PH and endothelin 1 (ET-1) expression. To further explore mechanisms of hypoxia-induced PH and reductions in PPARc, we examined the effects of hypoxia on selected microRNA (miRNA or miR) levels that might reduce PPARc expression leading to increased ET-1 expression and PH. Our results demonstrate that exposure to hypoxia (10% O2) for 3-weeks increased levels of miR-27a and ET-1 in the lungs of C57BL/6 mice and reduced PPARc levels. Hypoxiainduced increases in miR-27a were attenuated in mice treated with the PPARc ligand, rosiglitazone (RSG, 10 mg/kg/d) by gavage for the final 10 d of exposure. In parallel studies, human pulmonary artery endothelial cells (HPAECs) were exposed to control (21% O2) or hypoxic (1% O2) conditions for 72 h. Hypoxia increased HPAEC proliferation, miR-27a and ET-1 expression, and reduced PPARc expression. These alterations were attenuated by treatment with RSG (10 mM) during the last 24 h of hypoxia exposure. Overexpression of miR-27a or PPARc knockdown increased HPAEC proliferation and ET-1 expression and decreased PPARc levels, whereas these effects were reversed by miR-27a inhibition. Further, compared to lungs from littermate control mice, miR-27a levels were upregulated in lungs from endothelial-targeted PPARc knockout (ePPARc KO) mice. Knockdown of either SP1 or EGR1 was sufficient to significantly attenuate miR-27a expression in HPAECs. Collectively, these studies provide novel evidence that miR-27a and PPARc mediate mutually repressive actions in hypoxic pulmonary vasculature and that targeting PPARc may represent a novel therapeutic approach in PH to attenuate proliferative mediators that stimulate proliferation of pulmonary vascular cells. Citation: Kang B-Y, Park KK, Green DE, Bijli KM, Searles CD, et al. (2013) Hypoxia Mediates Mutual Repression between microRNA-27a and PPARc in the Pulmonary Vasculature. PLoS ONE 8(11): e79503. doi:10.1371/journal.pone. 0079503 Editor: James West, Vanderbilt University Medical Center, United States of America Received June 14, 2013; Accepted September 22, 2013; Published November 14, 2013 This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Funding: This study was supported by funding from a Veterans Affairs Merit Review Award (1I01BX001910 to CMH), from NIH grants DK 074518 and HL102167 (to CMH and RLS), and from an American Heart Association National Scientist Development Grant (13SDG14150004 to BYK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: michael.hart3@va.gov