Expression of cyclooxygenase-1 and cyclooxygenase-2 in the normal human heart and in myocardial infarction.
BACKGROUND
Cyclooxygenase is a key enzyme in prostanoid synthesis. It exists in two isoforms: cyclooxygenase-1 (COX-1), which is constitutively expressed in cells and tissues maintaining normal homeostasis, and cyclooxygenase-2 (COX-2), which is normally not present in most cells, but can be induced by various stimuli. Little is known about the significance of COX isoforms in the normal human heart and in myocardial infarction (MI). Thus, we aimed to investigate the immunohistochemical expression of COX-1 and COX-2 in the normal human heart and in MI.


METHODS
Our study included autopsy samples of heart tissue from 15 healthy individuals who died in accidents, and from 40 patients with MI who died few hours to a month after the onset of symptoms. Immunohistochemistry was performed by a sensitive peroxidase-streptavidin method on formalin fixed, paraffin-embedded tissue, using monoclonal antibodies against COX-1 and COX-2.


RESULTS
In normal hearts, COX-1 was found in endothelial and smooth muscle cells of blood vessels and in endothelial cells of the endocardium. In MI, it was expressed in inflammatory cells, as well as in myofibroblasts and capillaries of granulation and fibrous tissue. COX-2 was either not present or it was present in occasional myocytes in the normal hearts. In MI, its expression was induced in cardiomyocytes as well as in interstitial inflammatory cells, and in capillaries and myofibroblasts in granulation tissue.


CONCLUSIONS
Our results suggest that COX-1 is associated with normal homeostasis in the heart, whereas COX-2 probably mediates inflammatory reaction in MI. It appears that both COX-1 and COX-2 are associated with the healing processes and scar formation after MI.
Zidar
Nina
N
Institute of Pathology, Medical Faculty, University of Ljubljana, Korytkova 2, 1000, Ljubljana, Slovenia. nina.zidar@mf.uni-lj.si
Dolenc-Strazar
Zvezdana
Z
Jeruc
Jera
J
Jerse
Maja
M
Balazic
Joze
J
Gartner
Urska
U
Jermol
Urska
U
Zupanc
Tomaz
T
Stajer
Dusan
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001344:Autopsy; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D051545:Cyclooxygenase 1 / Q000032:analysis*; D051546:Cyclooxygenase 2 / Q000032:analysis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007249:Inflammation / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000201:enzymology* / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology
D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human