Human myocardium releases heat shock protein 27 (HSP27) after global ischemia: the proinflammatory effect of extracellular HSP27 through toll-like receptor (TLR)-2 and TLR4.

Chunhua Jin,Joseph C Cleveland,Lihua Ao,Qingchun Zeng,David A Fullerton,Xianzhong Meng,Jilin Li

doi:10.2119/molmed.2014.00058

Abstract

The myocardial inflammatory response contributes to cardiac functional injury associated with heart surgery obligating global ischemia/reperfusion (I/R). Toll-like receptors (TLRs) play an important role in the mechanism underlying myocardial I/R injury. The aim of this study was to examine the release of small constitutive heat shock proteins (HSPs) from human and mouse myocardium after global ischemia and examine the role of extracellular small HSP in myocardial injury. HSP27 release was assessed by enzyme-linked immunosorbent assay. Anti-HSP27 was applied to evaluate the role of extracellular HSP27 in the postischemic inflammatory response and functional injury in mouse hearts. Isolated hearts and cultured coronary vascular endothelial cells were exposed to recombinant HSP27 to determine its effect on proinflammatory signaling and production of proinflammatory mediators. HSP27 levels were markedly elevated in coronary sinus blood of patients and in coronary effluent of mouse hearts after global ischemia. Neutralizing extracellular HSP27 suppressed myocardial nuclear factor (NF)-κB activation and interleukin (IL)-6 production and improved cardiac function in mouse hearts. Perfusion of HSP27 to mouse hearts induced NF-κB activation and IL-6 production and depressed contractility. Further, recombinant HSP27 induced NF-κB phosphorylation and upregulated monocyte chemoattractant protein (MCP)-1 and intercellular adhesion molecule (ICAM)-1 production in both human and mouse coronary vascular endothelial cells. TLR2 knockout (KO) or TLR4 mutation abolished NF-κB phosphorylation and reduced MCP-1 and ICAM-1 production induced by extracellular HSP27 in endothelial cells. In conclusion, these results show that the myocardium releases HSP27 after global ischemia and that extracellular HSP27 is proinflammatory and contributes to the inflammatory mechanism of myocardial functional injury. Both TLR2 and TLR4 are involved in mediating the proinflammatory effect of extracellular HSP27.

Highlights

Global myocardial ischemia/reperfusion (I/R) associated with cardiac surgery induces the cardiac inflammatory response with overexpression of proinflammatory genes [1]
In TLR2 KO cells and TLR4-defective cells (Figure 5). These results show that both TLR2 and TLR4 play an important role in mediating the inflammatory responses of cardiac vascular endothelial cells to extracellular HSP27
The results of this study demonstrate (a) human and mouse myocardium releases HSP27 after global ischemia, (b) extracellular HSP27 is involved in the mechanism of postischemic myocardial inflammatory responses and cardiac functional injury, (c) extracellular HSP27 induces the production of proinflammatory mediators in mouse hearts and in human and mouse coronary vascular endothelial cells, (d) both TLR2 and TLR4 are involved in mediating the proinflammatory effect of extracellular HSP27 and (e) nuclear factor (NF)-κB appears to play a major role in the inflammatory responses to extracellular HSP27

Summary

Introduction

Global myocardial ischemia/reperfusion (I/R) associated with cardiac surgery induces the cardiac inflammatory response with overexpression of proinflammatory genes [1]. Cardial inflammatory response contributes to cardiac dysfunction [6,7]. Modulation of TLR signaling has been shown to improve cardiac function after myocardial I/R [6,16,17]. These innate immunoreceptors have been proposed to be potential targets in cardiac dysfunction caused by I/R [18]. Investigation of the mechanism by which TLRs are activated in the myocardium will be helpful for the development of novel therapeutic strategies for myocardial

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