Rapid clearance of circulating haptoglobin from plasma during acute pulmonary embolism in rats results in HMOX1 up-regulation in peripheral blood leukocytes.
BACKGROUND
Acute pulmonary embolism (PE) causes pulmonary hypertension (PH) via several mechanisms including pulmonary vasospasm. We hypothesize that PE with associated PH leads to alterations in plasma protein concentrations indicative of disease severity and prognosis.


OBJECTIVE
To identify plasma proteins altered in abundance by PE in rats.


METHODS
Plasma samples were obtained from rats at 2, 6 and 18 h after experimental PE produced with intrajugular injection of polystyrene beads at three different levels of severity (mild, moderate and severe). Total plasma protein was separated using two-dimensional sodium dodecylsulfate-polyacrylamide gel electrophoresis (2D SDS-PAGE) and candidate protein spots altered in expression by PE were identified by mass spectroscopy. Haptoglobin identity and amount was verified by western blot analysis.


RESULTS
The PE model produced a dose-dependent increase in right ventricular systolic pressure (RVSP) (mmHg) at 2 h: mild 39+/-1.7, moderate 40+/-1.8 and severe 51+/-1.3 mmHg, coincident with significant increases in free plasma (hemoglobin). Combined 2D SDS-PAGE and Western blot analysis indicated time- and dose-dependant loss of plasma haptoglobin levels in response to acute PE. Haptoglobin (HP) was essentially absent from plasma within 2 h of severe PE. Clearance of HP from plasma was accompanied by increased expression of heme oxygenase-1 (hmox1) in peripheral blood leukocytes and in HMOX1 enzyme activity in the liver.


CONCLUSIONS
PE that causes pulmonary hypertension is associated with haptoglobin depletion and up-regulation of HMOX1 enzyme.
Zagorski
J
J
Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC 28203, USA.
Marchick
M R
MR
Kline
J A
JA
D000208:Acute Disease; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D006242:Haptoglobins / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000097:blood*; D006461:Hemolysis; D006976:Hypertension, Pulmonary / Q000097:blood / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology; D007963:Leukocytes, Mononuclear / Q000201:enzymology*; D008099:Liver / Q000201:enzymology; D008297:Male; D013058:Mass Spectrometry; D040901:Proteomics / Q000379:methods; D011655:Pulmonary Embolism / Q000097:blood* / Q000150:complications / Q000201:enzymology* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012720:Severity of Illness Index; D013997:Time Factors; D015854:Up-Regulation; D014655:Vascular Resistance; D016278:Ventricular Function, Right; D017725:Ventricular Pressure
D006242:Haptoglobins; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat