Letter by Rose and Dunn Regarding Article, “Expression of Heat Shock Protein 27 in Human Atherosclerotic Plaques and Increased Plasma Level of Heat Shock Protein 27 in Patients With Acute Coronary Syndrome”
To the Editor:
We read with interest the paper by Park et al1 that examined the proteome of carotid endarterectomy specimens from 10 patients, using 2-dimensional gel analysis and mass spectrometry. They performed separate analysis of the plaque core and nearby “normal” areas. Their results demonstrated decreased expression of 13 proteins in the plaques, including heat shock protein 27 (Hsp27) and cytoskeletal proteins. In particular, there was very little phosphorylated Hsp27 in the plaques compared with adjacent areas. Their results are similar to those reported by Martin-Ventura et al2; these authors performed proteomic analysis of proteins secreted by cultured plaques and healthy areas of endarterectomy specimens, and they also found a significant decrease in Hsp27 from cultured plaques. Park et al1 imply, correctly in our opinion, that their study is better designed than that of Martin-Ventura et al,2 because one can argue that analysis of secreted proteins may be influenced by culture conditions. However, it is difficult to interpret the significance of a reduced set of particular proteins in plaques because they lack cellularity, and, secondly, as pointed put by Wick,3 a decrease in proteins such as Hsp27 in plaques probably reflects the presence of high levels of proteases, such as plasmin in the plaque, known to degrade Hsp27.4
Our recent study5 supports the hypothesis that induction of phosphorylated Hsp27 protects against atherosclerosis, without analysis of plaques. We examined cardiac biopsies from heart transplant recipients with and without angiographically detectable coronary artery disease. These biopsies seem to be “normal” by histology. Two-dimensional gel analysis and mass spectrometry revealed 20-fold upregulation of phosphorylated Hsp27 in biopsies from patients without disease compared with those who had developed atherosclerosis. This was confirmed by immunocytochemistry, which showed that the differences were attributable to vascular expression of Hsp27.
Park et al1 have made an interesting contribution to the field, using a set of patients who were different from our own. Their results provide additional support for a role of Hsp27 in protecting against intimal proliferation and atherosclerosis.
Park HK, Park EC, Bae SW, Park MY, Kim SW, Yoo HS, Tudev M, Ko YH, Choi YH, Kim S, Kim DI, Kim YW, Lee BB, Yoon JB, Park JE. Expression of heat shock protein 27 in human atherosclerotic plaques and increased plasma level of heat shock protein 27 in patients with acute coronary syndrome. Circulation. 2006; 114: 886–893.
Martin-Ventura JL, Duran MC, Blanco-Colio LM, Meilhac O, Leclercq A, Michel JB, Jensen ON, Hernandez-Merida S, Tunon J, Vivanco F, Egido J. Identification by a differential proteomic approach of heat shock protein 27 as a potential marker of atherosclerosis. Circulation. 2004; 110: 2216–2219.
Wick G. The heat is on: heat-shock proteins and atherosclerosis. Circulation. 2006; 114: 870–872.
Martin-Ventura JL, Nicolas V, Houard X, Blanco-Colio LM, Leclercq A, Egido J, Vranckx R, Michel JB, Meilhac O. Biological significance of decreased Hsp27 in human atherosclerosis. Arterioscler Thromb Vasc Biol. 2006; 26: 1337–1343.
De Souza AI, Wait R, Mitchell AG, Banner NR, Dunn MJ, Rose ML. Heat shock protein 27 is associated with freedom from graft vasculopathy after human cardiac transplantation. Circ Res. 2005; 97: 192–198.