Critical role of extracellular heat shock cognate protein 70 in the myocardial inflammatory response and cardiac dysfunction after global ischemia-reperfusion

Abstract

Critical role of extracellular heat shock cognate protein 70 in the myocardial inflammatory response and cardiac dysfunction after global ischemia-reperfusion. Am J Physiol Heart Circ Physiol 294: H2805-H2813, 2008. First published April 25, 2008 doi:10.1152/ajpheart.00299.2008.-Previous studies showed that Toll-like receptor 4 (TLR4) modulates the myocardial inflammatory response to ischemia-reperfusion injury, and we recently found that cytokines link TLR4 to postischemic cardiac dysfunction. Although TLR4 can be activated in cultured cells by endogenous agents including heat shock protein 70, how it is activated during myocardial ischemia-reperfusion is unknown. In the present study, we examined 1) whether heat shock cognate protein 70 (HSC70), which is constitutively expressed in the myocardium, is released during ischemia-reperfusion; 2) whether extracellular HSC70 induces the myocardial inflammatory response and modulates cardiac function; and 3) whether HSC70 exerts these effects via TLR4. We subjected isolated mouse hearts to global ischemia-reperfusion via the Langendorff technique. Immunoblotting and immunostaining detected the release of HSC70 from the myocardium during reperfusion. Treatment with an antibody specific to HSC70 suppressed myocardial cytokine expression and improved cardiac functional recovery after ischemia-reperfusion. Recombinant HSC70 induced NF-B activation and cytokine expression and depressed myocardial contractility in a TLR4-dependent manner. These effects required the substratebinding domain of HSC70. Fluorescence resonance energy transfer analysis of isolated macrophages demonstrated that extracellular HSC70 interacts with TLR4. Therefore, this study demonstrates for the first time that 1) the myocardium releases HSC70 during ischemiareperfusion, 2) extracellular HSC70 contributes to the postischemic myocardial inflammatory response and to cardiac dysfunction, 3) HSC70 exerts these effects through a TLR4-dependent mechanism, and 4) the substrate-binding domain of HSC70 is required to induce these effects. Thus extracellular HSC70 plays a critical role in regulating the myocardial innate immune response and cardiac function after ischemia-reperfusion.Toll-like receptor 4; cytokines; nuclear factor-B; messenger ribonucleic acid CARDIAC SURGERY OFTEN INVOLVES obligatory global myocardial ischemia-reperfusion, which causes a myocardial inflammatory response characterized by cytokine production (16, 18). Several proinflammatory cytokines, including TNF-␣, IL-1␤, and IL-6, contribute to myocardial injury after ischemia-reperfusion (12, 31). Preserving cardiac function after global ischemia-reperfusion therefore requires regulation of the myocardial inflammatory response. However, the signaling mechanisms underlying the myocardial inflammatory response to global ischemia-reperfusion are unclear.Previous studies implicated Toll-like receptor 4 (TLR4) signaling in the inflammatory response associated with myocardial ischemia-reperfusion injury. In mice treated with the TLR4 antagonis...

Extracellular Heat Shock Protein 70 Induces Cardiomyocyte Inflammation and Contractile Dysfunction via TLR2

“…45 One report using global ischemia-reperfusion in an isolated heart model suggested that heat shock cognate protein 70 (90% homologous to HSP70) is acutely induced by ischemia in cardiomyocytes and is secreted and rapidly detected in coronary effluent. 46 Inhibitory antibody to heat shock cognate protein 70 was able to attenuate ischemia-induced cardiac dysfunction. 46 Our results add to these observations by demonstrating that extracellular HSP70 directly decreased cardiomyocyte contractility and increased cell death; an effect that depended on the signalling pathway defined by TLR2, MyD88, and NFκB.…”

“…46 Inhibitory antibody to heat shock cognate protein 70 was able to attenuate ischemia-induced cardiac dysfunction. 46 Our results add to these observations by demonstrating that extracellular HSP70 directly decreased cardiomyocyte contractility and increased cell death; an effect that depended on the signalling pathway defined by TLR2, MyD88, and NFκB.…”

Isolated hearts treated with skeletal muscle homogenates exhibit altered function

“…However, heat stress results in many cellular alterations which may also be involved. For example, when HSC70, the constitutively expressed member of the HSP70 family, was added to the buffer of an isolated heart system, myocardial TLR4 was activated and cardiac contractility, reduced (Zou et al 2008). Thus, other HSPs or perhaps other DAMP molecules such as uric acid, which is known to be increased following heat stress, could also play a role (Shi et al 2003).…”

Transgenic Expression of Hsc70 in Pancreatic Islets Enhances Autoimmune Diabetes in Response to β Cell Damage

“…More recently, extracellular inducible hsp70 has been reported to increase activation of hepatocytes following ischemia-reperfusion injury (40) and to induce airway inflammatory responses (41). Importantly, extracellular hsc70 was shown to play a critical role in myocardial inflammation following injury (42). In addition to release during cellular necrosis, there are now recognized to be active, stress-induced secretion mechanisms for hsp, including hsc70 (43,44).…”