Transgelin as a therapeutic target to prevent hypoxic pulmonary hypertension

We previously observed that transgelin was preferentially expressed in human pulmonary arterial smooth muscle cells (PAMSCs) under hypoxia and that the upregulation of transgelin was independent of hypoxia-inducible factor 1α (HIF-1α). Reduced transgelin expression was accompanied by significantly impaired migration ability in vitro. However, the regulation mechanism of transgelin and its function in preventing hypoxic pulmonary hypertension (HPH) was unclear. In the present study, RNA interference with hypoxia-inducible factor 2α (HIF-2α) was employed in human PASMCs. Transgelin expression was diminished in HIF-2α-siRNA-treated cells at both the mRNA and protein levels under hypoxia. However, HIF-2α did not transactivate the transgelin promoter directly. TGF-β1 concentration in human PASMCs culture medium was higher under hypoxia, and the accumulated TGF-β1 under hypoxia was regulated by HIF-2α. Furthermore, luciferase and chromatin immunoprecipitation assays indicated that TGF-β1/Smad3 could bind to the transgelin promoter, resulting in increased transgelin expression. In addition to nonintact cellular migration, inhibition of transgelin expression resulted in impaired proliferation in vitro under hypoxia. A lentiviral vector used to inhibit transgelin expression was constructed and intratracheally instilled in rats 3 wk prior to hypoxia treatment. Our final results indicated that inhibition of transgelin expression locally could attenuate increased right ventricular systolic pressure and its associated cardiac and pulmonary vessel remodeling under hypoxia. Our findings indicate that HIF-2α upregulates transgelin indirectly and that accumulated TGF-β1 is a mediator in the upregulation of transgelin by HIF-2α under hypoxia. Inhibition of transgelin expression locally could prevent HPH and pulmonary vascular remodeling in vivo.