Published online before print August 25, 2008, doi: 10.1161/CIRCULATIONAHA.107.761916
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(Circulation. 2008;118:1183-1194.)
© 2008 American Heart Association, Inc.
Vascular Medicine |
Fhl-1, a New Key Protein in Pulmonary Hypertension
From the University of Giessen Lung Center, Giessen, Germany (G.K., L.M.M., R.T., J.W., K.H., B.E., A.Z., H.A.G., R.T.S., R.M.B., F.G., W.S., O.E., L.F., N.W.); Department of Biochemistry, University of Giessen, Giessen, Germany (M.W., S.S.); and Max-Planck Institute for Heart and Lung Research, Bad Nauheim, Germany (R.T.S.).
Correspondence to Grazyna Kwapiszewska, PhD, Med Klinik II, Klinik Strasse 36, 35392 Giessen, Germany. E-mail Grazyna.Kwapiszewska{at}uglc.de
Received December 26, 2007; accepted July 10, 2008.
Background— Pulmonary hypertension (PH) is a severe disease with a poor prognosis. Different forms of PH are characterized by pronounced vascular remodeling, resulting in increased vascular resistance and subsequent right heart failure. The molecular pathways triggering the remodeling process are poorly understood. We hypothesized that underlying key factors can be identified at the onset of the disease. Thus, we screened for alterations to protein expression in lung tissue at the onset of PH in a mouse model of hypoxia-induced PH.
Methods and Results— Using 2-dimensional polyacrylamide gel electrophoresis in combination with matrix-assisted laser desorption/ionization time-of-flight analysis, we identified 36 proteins that exhibited significantly altered expression after short-term hypoxic exposure. Among these, Fhl-1, which is known to be involved in muscle development, was one of the most prominently upregulated proteins. Further analysis by immunohistochemistry, Western blot, and laser-assisted microdissection followed by quantitative polymerase chain reaction confirmed the upregulation of Fhl-1, particularly in the pulmonary vasculature. Comparable upregulation was confirmed (1) after full establishment of hypoxia-induced PH, (2) in 2 rat models of PH (monocrotaline-treated and hypoxic rats treated with the vascular endothelial growth factor receptor antagonist SU5416), and (3) in lungs from patients with idiopathic pulmonary arterial hypertension. Furthermore, we demonstrated that regulation of Fhl-1 was hypoxia-inducible transcription factor dependent. Abrogation of Fhl-1 expression in primary human pulmonary artery smooth muscle cells by small-interfering RNA suppressed, whereas Fhl-1 overexpression increased, migration and proliferation. Coimmunoprecipitation experiments identified Talin1 as a new interacting partner of Fhl-1.
Conclusions— Protein screening identified Fhl-1 as a novel protein regulated in various forms of PH, including idiopathic pulmonary arterial hypertension.
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