Fhl-1, a new key protein in pulmonary hypertension.
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.


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.
Kwapiszewska
Grazyna
G
Med Klinik II, University of Giessen Lung Center, Klinik Strasse 36, 35392 Giessen, Germany. Grazyna.Kwapiszewska@uglc.de
Wygrecka
Malgorzata
M
Marsh
Leigh M
LM
Schmitt
Sigrid
S
Trösser
Roger
R
Wilhelm
Jochen
J
Helmus
Katja
K
Eul
Bastian
B
Zakrzewicz
Anna
A
Ghofrani
Hossein A
HA
Schermuly
Ralph T
RT
Bohle
Rainer M
RM
Grimminger
Friedrich
F
Seeger
Werner
W
Eickelberg
Oliver
O
Fink
Ludger
L
Weissmann
Norbert
N
D000818:Animals; D002465:Cell Movement; D049109:Cell Proliferation; D004195:Disease Models, Animal; D006801:Humans; D006976:Hypertension, Pulmonary / Q000209:etiology* / Q000473:pathology; D000860:Hypoxia / Q000150:complications; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D060588:LIM Domain Proteins; D008168:Lung / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D009124:Muscle Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D009130:Muscle, Smooth; D040901:Proteomics / Q000379:methods; D011651:Pulmonary Artery; D034741:RNA, Small Interfering / Q000494:pharmacology; D015854:Up-Regulation
C101149:FHL1 protein, human; C486306:Fhl1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D009124:Muscle Proteins; D034741:RNA, Small Interfering