Transcription factor Egr-1 in calcific aortic valve disease.
OBJECTIVE
Previous immunohistochemistry studies have shown that the transcription factor, Egr-1, is increased in human atherosclerotic lesions but is absent from the normal adjacent aortic wall. The hypothesis was investigated that Egr-1 is also increased in calcified heart valve cusps because of the unique presence in these tissues of proteins known to be regulated by Egr-1, such as tenascin C (TN-C).


METHODS
Non-calcified and calcified human aortic valves were obtained at autopsy or from cardiac surgery. Egr-1 immunohistochemical studies were performed. The effects of Egr-1 on cellular proliferation and on mechanisms of calcification were also investigated using sheep aortic valve interstitial cell (SAVIC) cultures. Signal transduction pathways involving Egr-1 were studied with specific inhibitors.


RESULTS
Immunohistochemical studies revealed that calcific aortic stenosis cusps contained a significantly higher level of Egr-1 in the spindle-shaped interstitial cells of calcified human aortic valves, but not white blood cells. By comparison, Egr-1 was detected at very low levels in the interstitial cells of non-calcified human aortic valve cusps. SAVIC cultivated on denatured versus native collagen substrates demonstrated a marked increase in Egr-1 levels (by Western blotting), and an absence of calcification in these cultures, compared to SAVIC grown on native collagen which calcified severely with little Egr-1 expression. Parallel increases in TN-C and osteopontin (OPN), both of which are proteins associated with heart valve calcification, were observed (by Western blotting) in SAVIC grown on denatured collagen. Furthermore, a protein kinase-C (PKC) inhibitor blocked the up-regulation of Egr-1 and TN-C, implicating PKC-dependent signaling control of Egr-1 and TN-C up-regulation.


CONCLUSIONS
Egr-1 is up-regulated in human calcific aortic stenosis cusps compared to non-calcified normal cusps. Egr-1 up-regulation involves a PKC-dependent signaling pathway. TN-C and OPN appear to be co-regulated with Egr-1. Furthermore, in SAVIC cultures on denatured collagen, Egr-1 up-regulation was associated with inhibition of calcification. Taken together, these results suggest that complex Egr-1 mechanisms may be operative in calcific aortic stenosis.
Ghazvini-Boroujerdi
Marjan
M
Cardiology Research Laboratory, Children's Hospital of Philadelphia, Philadelphia, PA 19104-4318, USA.
Clark
Jocelyn
J
Narula
Navneet
N
Palmatory
Elizabeth
E
Connolly
Jeanne M
JM
DeFelice
Suzanne
S
Xu
Jie
J
Jian
Bo
B
Hazelwood
Senator
S
Levy
Robert J
RJ
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001021:Aortic Valve / Q000378:metabolism / Q000503:physiopathology; D001024:Aortic Valve Stenosis / Q000378:metabolism* / Q000503:physiopathology; D002114:Calcinosis / Q000378:metabolism* / Q000503:physiopathology; D009202:Cardiomyopathies / Q000378:metabolism* / Q000503:physiopathology; D049109:Cell Proliferation; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000032:analysis / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012756:Sheep; D019063:Tenascin / Q000378:metabolism; D015854:Up-Regulation
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D004791:Enzyme Inhibitors; D019063:Tenascin; D003094:Collagen; D011493:Protein Kinase C