Wu Bangwei, Ni Huanchun, Li Jian, Zhuang Xinyu, Zhang Jinjin, Qi Zhiyong, Chen Qiying, Wen Zhichao, Shi Haiming, Luo Xinping, Jin Bo
Cell Physiol Biochem. 2017;42(2):713-728. doi: 10.1159/000477889. Epub 2017 Jun 15.
BACKGROUND/AIMS: Mitochondrial DNA (mtDNA), acting as a newly found 'danger-associated molecular patterns' (DAMPs), is released into circulation upon tissue injury and performs as a considerable activator of inflammation and immune response. However, the role of circulating mtDNA in experimental autoimmune myocarditis (EAM) as well as Toll like receptor4 (TLR4) mediated cardiac inflammation and injury remains unknown.
A model of EAM was established in BALB/c mice by immunization with porcine cardiac myosin. Lipopolysaccharide (LPS) was used to stimulate TLR4 activation in EAM mice and H9C2 cells.
LPS stimulation significantly aggravated cardiac inflammation and tissue injury in EAM, as demonstrated by increased myocardium inflammatory cell infiltration, and up-regulated inflammatory cytokines and troponin I(TnI) level in serum. Circulating mtDNA level was increased in EAM and TLR4 activation led to a greater elevation, which may be related to Reactive oxygen species (ROS) stress involved mtDNA damage characterized by reduced mtDNA copy number in myocardium tissue. In addition, the expression of Toll like receptor9 (TLR9), a ligand of mtDNA, was significantly up-regulated in the myocardium of EAM and EAM LPS group; meanwhile, TLR9 inhibition by ODN 2088 caused an inhibited apoptosis in LPS treated H9C2 cells. Moreover, in EAM and EAM LPS group, simultaneously giving ODN 2088 treatment significantly ameliorated cardiac inflammation and tissue injury compared with untreated group.
Increased circulating mtDNA combined with upregulated TLR9 expression may corporately play a role in EAM as well as TLR4 activation mediated cardiac inflammation and injury.
背景/目的：线粒体DNA（mtDNA）作为一种新发现的“危险相关分子模式”（DAMPs），在组织损伤时释放到循环中，是炎症和免疫反应的重要激活剂。然而，循环mtDNA在实验性自身免疫性心肌炎（EAM）以及Toll样受体4（TLR4）介导的心脏炎症和损伤中的作用尚不清楚。
通过用猪心肌肌凝蛋白免疫BALB/c小鼠建立EAM模型。脂多糖（LPS）用于刺激EAM小鼠和H9C2细胞中的TLR4激活。
LPS刺激显著加重了EAM中的心脏炎症和组织损伤，表现为心肌炎症细胞浸润增加，血清中炎症细胞因子和肌钙蛋白I（TnI）水平上调。EAM中循环mtDNA水平升高，TLR4激活导致其进一步升高，这可能与活性氧（ROS）应激导致的mtDNA损伤有关，其特征是心肌组织中mtDNA拷贝数减少。此外，mtDNA的配体Toll样受体9（TLR9）在EAM和EAM LPS组心肌中的表达显著上调；同时，ODN 2088抑制TLR9可导致LPS处理的H9C2细胞凋亡受到抑制。此外，在EAM和EAM LPS组中，与未治疗组相比，同时给予ODN 2088治疗可显著改善心脏炎症和组织损伤。
循环mtDNA增加与TLR9表达上调可能共同在EAM以及TLR4激活介导的心脏炎症和损伤中发挥作用。
