Background-We intended to identify proteins that are differentially expressed in human atherosclerotic plaques. Methods and Results-Comparative 2-dimensional electrophoretic analysis on carotid atherosclerotic endarterectomy specimens (nϭ10) revealed that heat shock protein 27 (Hsp27) expression was significantly increased in the nearby normal-appearing area compared with the plaque core area from the same vessel specimen, which was further confirmed by Western blot analysis. The Hsp27 expression in the adjacent normal-appearing vessel areas was much higher than that in nonatherosclerotic reference arteries. The phosphorylation of Hsp27 showed a gradation in the degree of phosphorylation: greatest in the reference arteries, intermediate in the adjacent normal-appearing area, and lowest in plaque core area. Immunohistochemical analysis showed that the phosphorylation of Hsp27 of smooth muscle cells in the carotid endarterectomy specimens was decreased compared with that in the reference artery specimen. The mean plasma level of Hsp27 was significantly higher in patients with acute coronary syndrome (ACS) (nϭ27; 106.1Ϯ74.1 ng/mL) than in the normal reference subjects (nϭ29; 45.8Ϯ29.5 ng/mL; PϽ0.005). The plasma levels of Hsp27 were significantly correlated with those of heat shock protein 70 (Hsp70) (rϭ0.422, PϽ0.0005), with adjustment for ACS/reference status. Conclusions-In the atherosclerotic lesion, Hsp27 expression is increased in the normal-appearing vessel adjacent to atherosclerotic plaque, whereas levels in the plaque itself are significantly decreased. Both plaque and adjacent artery show decreased Hsp27 phosphorylation compared with reference vessel. In ACS, plasma Hsp27 and Hsp70 are increased, and levels of Hsp27 correlate with Hsp70, C-reactive protein, and CD40L levels.

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