Institute of Cardiovascular Sciences, Department of Physiology, St. Boniface Research Centre, Faculty of Medicine, University of Manitoba, 351 Tache Avenue, Winnipeg, MB, Canada R2H 2A6.
Cytokine. 2013 Jan;61(1):304-14. doi: 10.1016/j.cyto.2012.10.013. Epub 2012 Nov 8.
Toll-like receptors (TLRs) are important in a variety of inflammatory diseases including acute cardiac disorders. TLR4 innate signaling regulates the synthesis of anti-inflammatory cytokine, interleukin-10 (IL-10) upon TLR4 agonists' re-stimulation. Anti-apoptotic action of IL-10 in cardiac dysfunction is generally accepted but its protective mechanism through TLR4 is not yet understood. We studied the effect of IL-10 in the activation of TLR4 downstream signals leading to cardiomyocytes survival. IL-10 caused a significant increase in the expression of CD14, MyD88 and TLR4. TLR4 activation led to the translocation of the interferon regulatory factor 3 (IRF3) into the nucleus. Phosphorylation of IRF3 enhanced mRNA synthesis for IL-1β but not TNF-α and was elevated even after removal of IL-10 stimulation. Furthermore, degradation of inhibitory kappa B (IκB) kinase (Ikk) suggested that IκBβ was the main activating kinase for IRF3-regulated NF-κB activation and phosphorylation of p65. Phosphorylated NF-κB p65 was translocated into the nucleus. Concomitantly, an increase in Bcl-xL activity inhibited Bax and the proteolytic activity of caspase 3 as well as a decrease in PARP cleavage. An inhibition of MyD88, modulated the above listed responses to IL-10 as there was a decrease in TLR4 and IRF3 and an increase in TNF-α mRNA. This was associated with a decrease in NF-κB p65, Bcl-xL mRNA and protein levels as well as there was an activation of Bax and PARP cleavage independent of caspase 3 activation. These data in cardiomyocytes suggest that IL-10 induced anti-apoptotic signaling involves upregulation of TLR4 through MyD88 activation.
Toll 样受体 (TLRs) 在多种炎症性疾病中起重要作用,包括急性心脏疾病。TLR4 先天信号调节抗炎细胞因子白细胞介素-10 (IL-10) 的合成,在 TLR4 激动剂再刺激时。IL-10 在心脏功能障碍中的抗凋亡作用已被普遍接受,但通过 TLR4 的保护机制尚不清楚。我们研究了 IL-10 在激活 TLR4 下游信号导致心肌细胞存活中的作用。IL-10 导致 CD14、MyD88 和 TLR4 的表达显著增加。TLR4 激活导致干扰素调节因子 3 (IRF3) 向核内易位。IRF3 的磷酸化增强了 IL-1β但不是 TNF-α的 mRNA 合成,即使在去除 IL-10 刺激后也会升高。此外,抑制性κB 激酶 (IκB kinase, IKK) 的降解表明 IκBβ是 IRF3 调节的 NF-κB 激活和 p65 磷酸化的主要激活激酶。磷酸化的 NF-κB p65 易位入核。同时,Bcl-xL 活性的增加抑制了 Bax 和半胱天冬酶 3 的蛋白水解活性,以及 PARP 切割的减少。MyD88 的抑制作用调节了上述对 IL-10 的反应,因为 TLR4 和 IRF3 减少,TNF-α mRNA 增加。这与 NF-κB p65、Bcl-xL mRNA 和蛋白水平的降低以及 Bax 和 PARP 切割的激活相关,而不依赖于半胱天冬酶 3 的激活。这些在心肌细胞中的数据表明,IL-10 诱导的抗凋亡信号涉及通过 MyD88 激活上调 TLR4。