The NOS (nitric oxide synthase) inhibitor ADMA (asymmetric dimethylarginine) contributes to the pathogenesis of pulmonary hypertension. Reduced levels of the enzymes metabolizing ADMA, dimethylarginine dimethylaminohydrolases (DDAH1 and DDAH2) and increased levels of miR-21 are linked to disease pathology, but the mechanisms are not understood. In the present study we assessed the potential role of miR-21 in the regulation of hypoxia-induced changes in ADMA metabolism in vitro and in vivo. Hypoxia inhibited DDAH1 and DDAH2 expression and increased ADMA levels in cultured human pulmonary endothelial cells. In contrast, in human pulmonary smooth muscle cells, only DDAH2 was reduced whereas ADMA levels remained unchanged. Endothelium-specific down-regulation of DDAH1 by miR-21 in hypoxia induced endothelial dysfunction and was prevented by overexpression of DDAH1 and miR-21 blockade. DDAH1, but not DDAH2, mRNA levels were reduced, whereas miR-21 levels were elevated in lung tissues from patients with pulmonary arterial hypertension and mice with pulmonary hypertension exposed to 2 weeks of hypoxia. Hypoxic mice treated with miR-21 inhibitors and DDAH1 transgenic mice showed elevated lung DDAH1, increased cGMP levels and attenuated pulmonary hypertension. Regulation of DDAH1 by miR-21 plays a role in the development of hypoxia-induced pulmonary hypertension and may be of broader significance in pulmonary hypertension.
- asymmetric dimethylarginine (ADMA)
- dimethyl-arginine dimethylaminohydrolase (DDAH)
- pulmonary hypertension
- smooth muscle
Abbreviations: ADMA, asymmetric dimethylarginine; BrdU, bromodeoxyuridine; D7-ADMA, [2,3,3,4,4,5,5-2H]asymmetric dimethylarginine; DDAH, dimethylarginine dimethylaminohydrolase; DDAH1tg, DDAH1 transgenic; HPAEC, human pulmonary arterial endothelial cell; HPASMC, human pulmonary artery smooth muscle cell; IPAH, idiopathic pulmonary arterial hypertension; LNA, locked nucleic acid anti-miRNA; MOI, multiplicity of infection; L-NMMA, NG-monomethyl-L-arginine; NOS, nitric oxide synthase; PAH, pulmonary arterial hypertension; PASMC, pulmonary arterial smooth muscle cell; PCNA, proliferating cell nuclear antigen; PKG, protein kinase G; RVH, right ventricular hypertrophy; RVSP, right ventricular systolic pressure; SDMA, symmetric dimethylarginine; t½, half-life; VEGF, vascular endothelial growth factor
- © The Authors Journal compilation © 2014 Biochemical Society