Biological Significance of Decreased HSP27 in Human Atherosclerosis

Abstract

Objective-Because culprit atherosclerotic plaques contain proteases, we hypothesized that the diminished heat shock protein 27 (HSP27) released by atherosclerotic plaques could be due to proteolysis. We assessed the role of HSP27 in human vascular smooth muscle cells (VSMCs) under proteolytic injury. Methods and Results-Active plasmin is present in culprit atherosclerotic plaques. Recombinant HSP27 was cleaved by plasmin and this effect was prevented by different inhibitors. Fragments and aggregated forms of HSP27 appeared after incubation of mammary control endarteries with plasmin. Coincubation of atherosclerotic plaques with recombinant HSP27 or mammary endarteries led to HSP27 proteolysis. After incubation of VSMCs with plasmin, HSP27 was overexpressed, phosphorylated, aggregated, and redistributed from the cytoskeleton to the cytosol, nucleus, and cell membrane. Plasmin-induced VSMC apoptosis was significantly higher in VSMCs treated by HSP27 siRNA. Immunohistochemical analysis of atherosclerotic plaques showed that plasmin(ogen) and apoptotic cells are localized in the core/shoulder whereas HSP27 and VSMCs are mainly expressed in the cap/media. Conclusions-Extracellular HSP27 can be degraded by enzymes released from atherosclerotic plaques and may reflect a proteolytic imbalance. Intracellular HSP27 downregulation decreases VSMCs resistance to proteolytically-induced apoptosis. HSP27 might play a pivotal role in the prevention of plaque instability and rupture.

Plasma Concentration of Heat Shock Protein 27 and Risk of Cardiovascular Disease: A Prospective, Nested Case-Control Study

“…Also, expression of a specific diphosphorylated form of HSP27 was present in healthy blood vessels as opposed to vessels with cardiac allograft vasculopathy in patients who had undergone cardiac transplantation (28 ). Recently, it was re- ported that intracellular HSP27 allowed protection against plasmin-induced anoikis in human vascular smooth muscle cells and was inversely localized with apoptotic cells within culprit atherosclerotic carotid plaques (29 ). The role of HSP27 in the extracellular compartment remains unclear; exogenously added HSP27 was shown to prevent neutrophil apoptosis (30 ) but did not have any effect on plasmin-induced apoptosis in vascular smooth muscle cells (29 ).…”

“…Recently, it was re- ported that intracellular HSP27 allowed protection against plasmin-induced anoikis in human vascular smooth muscle cells and was inversely localized with apoptotic cells within culprit atherosclerotic carotid plaques (29 ). The role of HSP27 in the extracellular compartment remains unclear; exogenously added HSP27 was shown to prevent neutrophil apoptosis (30 ) but did not have any effect on plasmin-induced apoptosis in vascular smooth muscle cells (29 ). To our knowledge, 2 clinical studies of HSP27 and atherosclerosis have been reported.…”

Proteomic Analysis Permits the Identification of New Biomarkers of Arterial Wall Remodeling in Hypertension

“…As previously described, incubation of vascular tissue ex vivo for 24 h in serum-free culture medium is compatible with proteomic analysis and provides valuable information on the vessel wall secretome by comparing various experimental conditions (18)(19)(20).…”

Vascular proteomics

“…To confirm our hypothesis that plasma content can reflect arterial wall secretion, we showed that circulating concentrations of HSP27 were decreased in subjects with atherosclerosis, indicating that this protein could be a novel biomarker of atherosclerosis in relation to healthy subjects. The biological significance of decreased HSP27 plasma levels in human atherosclerosis has been recently described [35]. Based on observations showing that culprit atherosclerotic plaques contain proteases [36,37], we hypothesized that the decreased HSP27 released by atherosclerotic plaques could be caused by proteolysis of the protein.…”

“…Based on observations showing that culprit atherosclerotic plaques contain proteases [36,37], we hypothesized that the decreased HSP27 released by atherosclerotic plaques could be caused by proteolysis of the protein. This extracellular degradation of HSP27 in atherosclerotic plaques could reflect a pathological vascular remodeling process, in which the final balance between proteases and antiproteases favors the degradative process of the ECM [35]. Controlled clinical trials in well-defined clinical populations will be necessary to evaluate the predictive value of all these candidate proteins as there is currently limited evidence of their usefulness in clinical practice.…”