PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose

Abstract

Background Oxidative stress mediated by hyperglycemia damages cell-reparative processes such as mitophagy. Down-regulation of mitophagy is considered to be a susceptible factor for diabetes mellitus (DM) and its complications. However, the role of mitophagy in DM-associated periodontitis has not been fully elucidated. Apoptosis of human gingival epithelial cells (hGECs) is one of the representative events of DM-associated periodontitis. Thus, this study aimed to investigate PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy activated in the process of high glucose (HG)-induced hGECs apoptosis. Methods For dose–response studies, hGECs were incubated in different concentrations of glucose (5.5, 15, 25, and 50 mmol/L) for 48 h. Then, hGECs were challenged with 25 mmol/L glucose for 12 h and 48 h, respectively. Apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL), caspase 9 and mitochondrial membrane potential (MMP). Subsequently, autophagy was evaluated by estimating P62, LC3 II mRNA levels, LC3 fluorescent puncta and LC3-II/I ratio. Meanwhile, the involvement of PINK1-mediated mitophagy was assessed by qRT-PCR, western blotting and immunofluorescence. Finally, hGECs were transfected with shPINK1 and analyzed by MMP, caspase 9 and annexin V-FITC apoptosis. Results The number of TUNEL-positive cells and caspase 9 protein were significantly increased in cells challenged with HG (25 mmol/L) for 48 h (HG 48 h). MMP was impaired both at HG 12 h and HG 48 h, but the degree of depolarization was more serious at HG 48 h. The autophagy improved as the amount of LC3 II increased and p62 decreased in HG 12 h. During this process, HG 12 h treatment induced PINK1-mediated mitophagy. PINK1 silencing with HG 12 h resulted in MMP depolarization and cell apoptosis. Conclusions These results suggested that loss of the PINK1 gene may cause mitochondrial dysfunction and increase sensitivity to HG-induced apoptosis of hGECs at the early stage. PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose.

The role of mitochondrial dysfunction in periodontitis: From mechanisms to therapeutic strategy

“…A recent study shows that PINK1 inhibits oxidative stress-induced apoptosis by adjusting the expression of apoptosis related-genes Bax and Bcl-2 after the pretreatment of PDLSCs with antioxidants. 55 Zhu et al 56 Results revealed that the increased expression of pro-inflammatory factors and mtROS depended on the decreased expression levels of PINK1, parkin and LC3. Therefore, mitophagy may be a therapeutic target to mitigate cell death and inflammatory damage.…”

“…A recent study shows that PINK1 inhibits oxidative stress‐induced apoptosis by adjusting the expression of apoptosis related‐genes Bax and Bcl‐2 after the pretreatment of PDLSCs with antioxidants 55 . Zhu et al 56 constructed a high glucose‐induced apoptosis model of human gingival epithelial cells. The rescue experiment verified that PINK1 regulated the expression level of apoptotic signal caspase 9, suggesting that PINK1/parkin‐mediated mitophagy protects diabetic periodontitis cells from apoptosis.…”