P323	HIF 1α, 2α and target gene expression in vulnerable human atherosclerotic plaques.
1J.C.Sluimer, 2J.M.Gasc, 3D.Black, 1P.Aarts, 4L.H.Van den Akker, 2P.Corvol, 1M.J.Daemen, 1A.P.Bijnens
1Department of Pathology, CARIM, University of Maastricht,, Maastricht, NL; 2Collège-de-France, INSERM U36, Paris, FR; 3Organon Research Scotland, Newhouse, GB; 4Department of Surgery, Maasland Hospital, Sittard, NL.

Hypoxia, which induces hypoxia-inducible factors (HIF) 1α and 2α, has been detected in rabbit atherosclerotic plaques in macrophage-rich regions. In addition, hypoxia is observed in other inflammatory responses, inducing HIF 1α, 2α and HIF target genes. Moreover, several HIF targets have a known function in atherosclerosis. Based on these observations, we hypothesize that HIF pathways are involved in atherosclerosis. Therefore, we investigated the expression of HIF1α, 2α and HIF responsive genes involved in carbohydrate metabolism, i.e. Glucose Transporter (GLUT) 1 and 3, Carbonic Anhydrase (CA) IX, Hexokinase (HK) 1 and 2 in human non-diseased veins and arteries and carotid arteries with early, stable or thrombus-containing atherosclerotic lesions. Microarray analysis (n=4) showed a 1.4 fold upregulation of HIF1α and a 1.2 fold downregulation of GLUT3 mRNA in stable versus early lesions. In thrombus-containing versus stable lesions, we found a 2.5 fold upregulation and 1.6 fold down regulation of HK2 and GLUT3, respectively. Expression of HIF2α, GLUT1, HK1 and CA IX mRNA was not differential at any stage. In situ hybridization (n=6) was used to determine the cell types expressing HIF1α and 2α RNA in human atherosclerosis. RNA was strongly expressed in intimal macrophages and smooth muscle cells (SMC), but little expression was detected in the media or in intimal endothelial cells (EC). Since the HIF1α and 2α pathway is regulated through protein stabilization, we validated RNA expression using immunohistochemistry (n=62). HIF1α and 2α protein were strongly expressed in macrophage foam cells and modestly in intimal SMC and EC. Expression was stronger in advanced lesions compared to early lesions and absent in non-diseased vessels. Moreover, the protein expression of GLUT1, -3, HK1 and 2 in human atherosclerosis was similarly distributed. In conclusion, HIF pathway expression increased with progression from early to advanced human atherosclerotic lesions and was mostly detected in macrophage regions. Since these inflammatory regions are associated with plaque vulnerability, we postulate that expression of HIF1α, 2α and their responsive genes induce a vulnerable plaque phenotype.

Copyright © 2005 S. Karger AG, Basel. Any further use of this abstract requires written permission from the publisher.