Regulation of reactive oxygen species on the mitophagy of human periodontal ligament cells through the PINK1/Parkin pathway under starvation.

This study aimed to explore the specific mechanism, mediated by the reactive oxygen species (ROS) and PINK1/Parkin pathway, of the mitochondrial autophagy of human periodontal ligament cells (hPDLCs) under starvation conditions.hPDLCs were isolated and cultured from normal periodontal tissues. Earle's balanced salt solution (EBSS) was used to simulated a starvation environment and thus stimulate hPDLCs mitochondrial autophagy. N-Acetyl-L-cysteine (NAC) was used to inhibit ROS production to explore the role of ROS in hPDLC mitochondrial autophagy. Cyclosporin A was used to inhibit the PINK1/Parkin pathway to study the role of ROS and the PINK1/Parkin pathway in hPDLCs activation under starvation. The mitochondrial membrane potential was detected by flow cytometry with a JC-1 mitochondrial membrane potential detection kit. The morphological structure of mitochondria and the formation of mitochondrial autophagosome were observed by transmission electron microscopy. Mito tracker red cmxros and lyso tracker green staining were used to observe the localization of mitochondria and lysosomes. The formation intensity of ROS was detected with a DCFH-DA ROS fluorescent probe. The expression levels of mitochondrial autophagy genes (Tomm20 and Timm23) and the PINK1/Parkin pathway were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The expression levels of mitochondrial autophagy proteins (Tomm20 and Timm23) and PINK1/Parkin protein were detected by Western blot.EBSS starvation for 30 min induced the strongest activation of hPDLCs mitochondrial autophagy, increased the expression of ROS, downregulated the expression of mitochondrial autophagy-related genes (Tomm20 and Timm23) (P<0.001), and upregulated the PINK1/Parkin pathway (P<0.001). After NACinhibited ROS production, mitochondrial autophagy was also inhibited. Meanwhile, the expression of Tomm20 and Timm23 was upregulated (P<0.001 and P<0.05), and the expression of the PINK1/parkin pathway (P<0.001 and P<0.05) was down regulated. When cyclosporin A inhibited the expression of the PINK1/Parkin pathway (P<0.05 and P<0.05), it reversed the mitochondrial autophagy of hPDLCs (P<0.001 and P<0.01) and also upregulated the expression of Tomm20 and Timm23 (P<0.001 and P<0.01).ROS enhanced the mitochondrial autophagy of hPDLCs primarily through the PINK1/Parkin pathway under starvation conditions.目的: 探究人牙周膜细胞（hPDLC）在饥饿条件下活性氧（ROS）与PINK1/Parkin通路介导hPDLC线粒体自噬的具体机制。方法: 分离培养正常牙周组织的hPDLSC，利用Earle’s平衡盐溶液（EBSS）模拟饥饿环境诱导hPDLC线粒体自噬，利用N-乙酰-L-半胱氨酸（NAC）抑制ROS生成以探讨ROS在hPDLC线粒体自噬的作用，利用环孢素A（CsA）抑制PINK1/Parkin通路以研究ROS与PINK1/Parkin通路在饥饿条件下激活hPDLC中的作用。采用流式细胞术及JC-1线粒体膜电位检测试剂盒，检测线粒体膜电位；采用透射电镜观察线粒体自噬体的生成及线粒体形态变化；采用线粒体红色荧光探针定位线粒体，溶酶体绿色荧光探针定位溶酶体；采用DCFH-DA ROS荧光探针检测ROS生成强度；采用实时荧光定量聚合酶链反应（RT-qPCR）检测细胞中线粒体自噬基因（Tomm20、Timm23）及PINK1/Parkin通路的表达水平，采用蛋白质印迹 （Western blot）检测细胞中线粒体自噬蛋白（Tomm20、Timm23）及PINK1/Parkin通路蛋白表达水平。结果: EBSS饥饿作用30 min后，诱导激活hPDLC线粒体自噬的作用最强，ROS表达增加，且线粒体自噬相关基因（Tomm20、Timm23）下调（P<0.001），PINK1/Parkin通路表达上调（P<0.001）。NAC抑制ROS的产生后，自噬被抑制，同时Tomm20、Timm23表达上调（P<0.001，P<0.05），PINK1/Parkin通路表达下调（P<0.001，P<0.05）。而当CsA抑制PINK1/Parkin通路表达时（P<0.05，P<0.05），自噬被逆转，同时Tomm20、Timm23表达上调（P<0.001，P<0.01）。结论: ROS在饥饿条件下主要通过PINK1/Parkin通路增强hPDLC线粒体自噬。.