Hyaluronic Acid binding protein 2 is a novel regulator of vascular integrity.
OBJECTIVE
The disruption of the endothelial cell barrier is a critical feature of inflammation and an important contributing factor to acute lung injury (ALI), an inflammatory condition that is a major cause of morbidity and mortality in critically ill patients. We evaluated the role of the extracellular serine protease, hyaluronic acid binding protein 2 (HABP2), in vascular barrier regulation.


RESULTS
By using immunoblot and immunohistochemical analysis, we observed that lipopolysaccharide (LPS) induces HABP2 expression in murine lung endothelium in vivo and in human pulmonary microvascular endothelial cells (ECs) in vitro. High-molecular-weight hyaluronan (HMW-HA, approximately 1x10(6) Da) decreased HABP2 protein expression in human pulmonary microvascular ECs and decreased purified HABP2 enzymatic activity, whereas low-molecular-weight HA (LMW-HA, approximately 2500 Da) increased these activities. The effects of LMW-HA, but not HMW-HA, on HABP2 activity were inhibited with a peptide of the polyanion-binding domain of HABP2. Silencing (small interfering RNA) HABP2 expression augmented HMW-HA-induced EC barrier enhancement and inhibited LPS and LMW-HA-mediated EC barrier disruption, results that were reversed with overexpression of HABP2. Silencing protease-activated receptor 1 and 3, RhoA, or Rho kinase expression attenuated LPS-, LMW-HA-, and HABP2-mediated EC barrier disruption. By using murine models of acute lung injury, we observed that LPS- and ventilator-induced pulmonary vascular hyperpermeability was significantly reduced with vascular silencing (small interfering RNA) of HABP2.


CONCLUSIONS
HABP2 negatively regulates vascular integrity via activation of protease-activated receptor/RhoA/Rho kinase signaling and represents a potentially useful therapeutic target for syndromes of increased vascular permeability.
Mambetsariev
Nurbek
N
Department of Medicine, University of Chicago, CIS Bldg W403E, Chicago, IL 60637, USA.
Mirzapoiazova
Tamara
T
Mambetsariev
Bolot
B
Sammani
Saad
S
Lennon
Frances E
FE
Garcia
Joe G N
JG
Singleton
Patrick A
PA
D055371:Acute Lung Injury / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000009:adverse effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D044462:Receptors, Proteinase-Activated / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D012122:Ventilators, Mechanical / Q000009:adverse effects; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D008070:Lipopolysaccharides; D044462:Receptors, Proteinase-Activated; D006820:Hyaluronic Acid; D054460:rho-Associated Kinases; C433550:HABP2 protein, human; C499020:Habp2 protein, mouse; D012697:Serine Endopeptidases; D020742:rhoA GTP-Binding Protein