Objectives;
As atherosclerosis progresses smooth muscle cells (SMC) disappear in the medial layer of arterial wall, especially in the area where macrophage infiltration and inflammation is severe. We postulated that Heat Shock Protein 27 (Hsp27) expression may prevent the distruction of extracellular matrix (ECM) induced by oxidative stress in the progression of atherosclerosis. We tried to investigate the possible mechanism by which HSP27 modulate oxidized LDL-induced enzymatic breakdown of ECM components in SMCs.
Results;
RT-PCR analysis of smooth muscle cell lysates for the expression of collagen type Ⅰ, Ⅲ, Ⅳ and Ⅴ α was done with over-expression and silencing of HSP27. Smooth muscle cells were treated with 100 μg/ml of oxidized LDL. When the HSP27 was over expressed with adenoviral vector containing wild type HSP27 (Ad-HSP27) infection, collagen type Ⅰ and Ⅳ α expression were up-regulated (17.7 % and 26 % induction, respectively) compared to that of vector control (Ad-ADR) infection. Furthermore, Ad-HSP27 infected HASMC suppressed the production of IL-8 by more than 3-fold. When HSP27 was silenced with siHSP27 transfection, collagen type Ⅰ, Ⅲ, Ⅳ and Ⅴ α expression were reduced (17.5 %, 9.8 %, 7 % and 15.3 % reduction, respectively) compared to control (scrambled) transfection. Moreover, matrix metalloproteinase activity 2 was induced by siHSP27 transfection. We also tested whether HSP27 could prevent apoptosis. As expected, only wild type HSP27 could fully prevent oxidized LDL induced apoptosis by up-regulating bcl-2 expression, while mutant HSP27 did not affect bcl-2 expression but rather induced bax expression.
Conclusions;
HSP27 was involved in the regulation of breakdown of ECM components in SMC and SMC survival by regulating the collagen contents, inhibiting the inflammatory cytokines secretion, as well as protease production and up-regulating bcl-2 expression when exposed to oxidative stress. We suggest that HSP27 plays an important role for the smooth muscle cell survival and death in the progression of atherosclerosis.
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