Hypoxia-induced microRNA-26b inhibition contributes to hypoxic pulmonary hypertension via CTGF.

The objective of this study was to explore the role of miRNAs in the control of HPH as well as molecular mechanism underlying. Computational analysis and luciferase assay were carried out to search the target gene of miR-26b. Luciferase assay, RT-PCR and western-blot analysis was performed to test interaction among hypoxia, miR-26b, SRF and CTGF. MiR-26b was significantly downregulated; meanwhile, CTGF and SRF were significantly upregulated in HPH rat model. Using computational analysis, CTGF was found to be a virtual target gene of miR-26b, and only cell transfected with vectors containing wild-type CTGF 3'UTR and miR-26b showed a lower luciferase activity than scramble control. Hypoxia significantly inhibited miR-26b promoter, and promoted SRF promoter. Meanwhile, hypoxia had no effect on CTGF promoter. In addition, SRF promoted the promoter of CTGF. MiR-26b was significantly downregulated; meanwhile, CTGF and SRF were upregulated in PASMCs exposed to hypoxia. In addition, miR-26b and SRF siRNA, but not CTGF siRNA, significantly inhibited SRF expression. Meanwhile, miR-26b, SRF siRNA, and CTGF siRNA significantly inhibited CTGF expression in hypoxia-treated cell. PASMCs treated with hypoxia showed higher cell viability and higher percentage cells in S phase than the control, which could be reversed by miR-26b, SRF siRNA, and CTGF siRNA transfection. These findings suggested that hypoxia induced miR-26b inhibition and SRF and CTGF upregulation in HPH rat model. CTGF mediated hypoxia-induced regulation of miR-26b and SRF in proliferation of PASMCs, which indicated that hypoxia-induced miR-26b inhibition contributed to the pathogenesis of HPH via CTGF.