title: Critical role of extracellular heat shock cognate protein 70 in the myocardial inflammatory response and cardiac dysfunction after global ischemia-reperfusion.
abstract: 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-kappaB activation and cytokine expression and depressed myocardial contractility in a TLR4-dependent manner. These effects required the substrate-binding 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 ischemia-reperfusion, 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.
authors.affiliation: Department of Surgery, University of Colorado Denver, Denver, Colorado, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Zou
authors.forename: Lihua
authors.initials: L
authors.lastname: Ao
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Cleveland
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Yang
authors.forename: Xin
authors.initials: X
authors.lastname: Su
authors.forename: Guang-Yun
authors.initials: GY
authors.lastname: Cai
authors.forename: Anirban
authors.initials: A
authors.lastname: Banerjee
authors.forename: David A
authors.initials: DA
authors.lastname: Fullerton
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Meng
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005110:Extracellular Space / Q000378:metabolism; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism*; D007113:Immunity, Innate; D066298:In Vitro Techniques; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D009200:Myocardial Contraction; D015428:Myocardial Reperfusion Injury / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D009205:Myocarditis / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D009206:Myocardium / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010477:Perfusion; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D018487:Ventricular Dysfunction, Left / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D017725:Ventricular Pressure
chemical_list: D016207:Cytokines; D050883:HSC70 Heat-Shock Proteins; C494373:Hspa8 protein, rat; D016328:NF-kappa B; D011994:Recombinant Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4