Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
J Biol Chem. 2011 Sep 9;286(36):31308-19. doi: 10.1074/jbc.M111.246124. Epub 2011 Jul 20.
Innate immune response after transient ischemia is the most common cause of myocardial inflammation and may contribute to injury, yet the detailed signaling mechanisms leading to such a response are not well understood. Herein we tested the hypothesis that myocardial ischemia activates interleukin receptor-associated kinase-1 (IRAK-1), a kinase critical for the innate immune signaling such as that of Toll-like receptors (TLRs), via a mechanism that involves heat shock proteins (HSPs) and TLRs. Coronary artery occlusion induced a rapid myocardial IRAK-1 activation within 30 min in wild-type (WT), TLR2(-/-), or Trif(-/-) mice, but not in TLR4(def) or MyD88(-/-) mice. HSP60 protein was markedly increased in serum or in perfusate of isolated heart following ischemia/reperfusion (I/R). In vitro, recombinant HSP60 induced IRAK-1 activation in cells derived from WT, TLR2(-/-), or Trif(-/-) mice, but not from TLR4(def) or MyD88(-/-) mice. Both myocardial ischemia- and HSP60-induced IRAK-1 activation was abolished by anti-HSP60 antibody. Moreover, HSP60 treatment of cardiomyocytes (CMs) led to marked activation of caspase-8 and -3, but not -9. Expression of dominant-negative mutant of Fas-associated death domain protein or a caspase-8 inhibitor completely blocked HSP60-induced caspase-8 activation, suggesting that HSP60 likely activates an apoptotic program via the death-receptor pathway. In vivo, I/R-induced myocardial apoptosis and cytokine expression were significantly attenuated in TLR4(def) mice or in WT mice treated with anti-HSP60 antibody compared with WT controls. Taken together, the current study demonstrates that myocardial ischemia activates an innate immune signaling via HSP60 and TLR4, which plays an important role in mediating apoptosis and inflammation during I/R.
短暂性缺血后的固有免疫反应是心肌炎症的最常见原因，并可能导致损伤，但导致这种反应的详细信号机制尚不清楚。在此，我们通过涉及热休克蛋白（HSPs）和 TLRs 的机制，检验了心肌缺血通过激活白细胞介素受体相关激酶-1（IRAK-1），即固有免疫信号传导（如 Toll 样受体（TLRs））所必需的激酶的假说。在野生型（WT）、TLR2（-/-）或 Trif（-/-）小鼠中，冠状动脉闭塞导致 IRAK-1在 30 分钟内迅速激活，但在 TLR4（def）或 MyD88（-/-）小鼠中则不然。缺血/再灌注（I/R）后，血清或分离心脏灌流液中的 HSP60 蛋白明显增加。在体外，重组 HSP60 诱导来自 WT、TLR2（-/-）或 Trif（-/-）小鼠的细胞中的 IRAK-1 激活，但不诱导来自 TLR4（def）或 MyD88（-/-）小鼠的细胞中的 IRAK-1 激活。抗 HSP60 抗体可消除心肌缺血和 HSP60 诱导的 IRAK-1 激活。此外，HSP60 处理心肌细胞（CMs）导致 caspase-8 和 -3 的显著激活，但不导致 caspase-9 的激活。Fas 相关死亡结构域蛋白的显性负突变体或 caspase-8 抑制剂的表达完全阻断 HSP60 诱导的 caspase-8 激活，表明 HSP60 可能通过死亡受体途径激活凋亡程序。在体内，与 WT 对照相比，TLR4（def）小鼠或用抗 HSP60 抗体处理的 WT 小鼠中，I/R 诱导的心肌细胞凋亡和细胞因子表达明显减弱。总之，本研究表明，心肌缺血通过 HSP60 和 TLR4 激活固有免疫信号，在介导 I/R 期间的凋亡和炎症中发挥重要作用。
