Hypoxia mediates mutual repression between microRNA-27a and PPARγ 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 (PPARγ). Hypoxia, a common PH stimulus, reduces PPARγ in experimental models. In contrast, activating PPARγ attenuates hypoxia-induced PH and endothelin 1 (ET-1) expression. To further explore mechanisms of hypoxia-induced PH and reductions in PPARγ, we examined the effects of hypoxia on selected microRNA (miRNA or miR) levels that might reduce PPARγ 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 PPARγ levels. Hypoxia-induced increases in miR-27a were attenuated in mice treated with the PPARγ 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 PPARγ expression. These alterations were attenuated by treatment with RSG (10 µM) during the last 24 h of hypoxia exposure. Overexpression of miR-27a or PPARγ knockdown increased HPAEC proliferation and ET-1 expression and decreased PPARγ 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 PPARγ knockout (ePPARγ 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 PPARγ mediate mutually repressive actions in hypoxic pulmonary vasculature and that targeting PPARγ may represent a novel therapeutic approach in PH to attenuate proliferative mediators that stimulate proliferation of pulmonary vascular cells.
Departments of Medicine, Atlanta Veterans Affairs Medical Centers and Emory University, Atlanta, Georgia, United States of America.
Bum-Yong
BY
Kang
Kathy K
KK
Park
David E
DE
Green
Kaiser M
KM
Bijli
Charles D
CD
Searles
Roy L
RL
Sutliff
C Michael
CM
Hart
D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D049109:Cell Proliferation; D004195:Disease Models, Animal; D051766:Early Growth Response Protein 1 / Q000235:genetics; D042783:Endothelial Cells / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006801:Humans; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D008168:Lung / Q000098:blood supply* / Q000378:metabolism*; D051379:Mice; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D047495:PPAR gamma / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism; D034622:RNA Interference; D016329:Sp1 Transcription Factor / Q000235:genetics
D051766:Early Growth Response Protein 1; D019332:Endothelin-1; D035683:MicroRNAs; C540674:Mirn27 microRNA, mouse; D047495:PPAR gamma; D016329:Sp1 Transcription Factor