Toll-like Receptor 9 Can be Activated by Endogenous Mitochondrial DNA to Induce Podocyte Apoptosis.
Toll-like Receptor 9 Can be Activated by Endogenous Mitochondrial DNA to Induce Podocyte Apoptosis.
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Toll样受体9可被内源线粒体DNA激活诱导足细胞凋亡
DOI：
10.1038/srep22579
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发表时间：
2016-03-03
影响因子：
4.6
通讯作者：
Shi S
中科院分区：
文献类型：
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作者：
Bao W;Xia H;Liang Y;Ye Y;Lu Y;Xu X;Duan A;He J;Chen Z;Wu Y;Wang X;Zheng C;Liu Z;Shi S
toll样受体9 （TLR9）感知细菌DNA未甲基化CpG基序特征，诱导先天免疫反应。TLR9在一些肾小球疾病患者的足细胞中有新的表达，但其在足细胞损伤中的作用尚未确定。由于TLR9激活介导足细胞凋亡的p38 MAPK和NFkB，我们假设TLR9在肾小球疾病中诱导足细胞凋亡。我们用嘌呤霉素氨基核苷（PAN）处理永生化足细胞，观察到足细胞凋亡并伴有TLR9上调。通过siRNA阻止TLR9上调可显著降低NFκB p65或p38活性和细胞凋亡，表明TLR9介导足细胞凋亡。接下来，我们发现内源性线粒体DNA (mtDNA)，其CpG基序也未甲基化，是TLR9的配体，因为PAN诱导mtDNA在TLR9定位的内溶酶体中积累，内溶酶体DNase 2的过表达减弱了PAN诱导的p38或p65活性和足细胞凋亡，DNase 2沉默足以激活p38或p65并诱导细胞凋亡。pan处理大鼠足细胞中TLR9表达上调，凋亡标志物增加。因此，新表达的TLR9可能利用内源性mtDNA作为配体促进足细胞凋亡，这是肾小球疾病中足细胞损伤的新机制。
Toll-like receptor 9 (TLR9) senses bacterial DNA characteristic of unmethylated CpG motifs to induce innate immune response. TLR9 isde novoexpressed in podocytes of some patients with glomerular diseases, but its role in podocyte injury remains undetermined. Since TLR9 activates p38 MAPK and NFkB that are known to mediate podocyte apoptosis, we hypothesized that TLR9 induces podocyte apoptosis in glomerular diseases. We treated immortalized podocytes with puromycin aminonucleosides (PAN) and observed podocyte apoptosis, accompanied by TLR9 upregulation. Prevention of TLR9 upregulation by siRNA significantly attenuated NFκB p65 or p38 activity and apoptosis, demonstrating that TLR9 mediates podocyte apoptosis. We next showed that endogenous mitochondrial DNA (mtDNA), whose CpG motifs are also unmethylated, is the ligand for TLR9, because PAN induced mtDNA accumulation in endolysosomes where TLR9 is localized, overexpression of endolysosomal DNase 2 attenuated PAN-induced p38 or p65 activity and podocyte apoptosis and DNase 2 silencing was sufficient to activate p38 or p65 and induce apoptosis. In PAN-treated rats, TLR9 was upregulated in the podocytes, accompanied by increase of apoptosis markers. Thus,de novoexpressed TLR9 may utilize endogenous mtDNA as the ligand to facilitate podocyte apoptosis, a novel mechanism underlying podocyte injury in glomerular diseases.