Epigallocatechin-3-gallate (EGCG) Helps Maintain Mitochondrial Function in MPP+-induced PC12 Cells

Impairments to mitochondrial function and metabolism can make neurons vulnerable to stress and degeneration. Several studies have shown that aberrations in the electron transport chain (ETC) and the Krebs cycle are involved in the pathogenesis of Parkinson’s disease (PD). Therefore, targeting these pathways is becoming increasingly important in the discovery of new treatment for neurodegenerative diseases like PD. (−)-epigallocatechin-3-gallate (EGCG), the most common polyphenol found in Green tea, has been shown to exert neuroprotective effects and lower the risk of developing PD. However, the mechanism by which it accomplishes this remains to be elucidated. The purpose of this study was to shed light on these mechanisms by exploring the effects of EGCG against MPP+-induced mitochondrial dysfunction with PC12 cells being used as a PD pathological cell model. The cell viability differences between cells treated with varying combinations of MPP+ and EGCG were measured using a CCK-8 assay. The morphology changes induced by the different treatments were then identified with fluorescence microscopy. Next, a Seahorse assay was carried out to investigate mitochondrial function followed by GC-MS and LC-MS analysis to evaluate mitochondrial metabolism. 13C metabolic flux analysis was then used to trace the metabolic flux of the Krebs cycle. The results of the CCK-8 assay and fluorescence microscopy showed that EGCG helps attenuate the decreased viability of PC12 cells as well as the morphology changes induced by MPP+. The Seahorse and GC-MS assay found that the it also helps prevent impaired mitochondrial respiration caused by MPP+. The impaired mitochondrial respiration manifested as alterations to the Krebs cycle and glycolysis. In addition, 13C metabolic flux analysis revealed significant increases in Krebs cycle activity in MPP+-induced PC12 cells if treated with EGCG beforehand. Moreover, LC-MS showed a distinct metabolite profile for each group and identified 26 potent biomarkers. In conclusion, this study demonstrated that EGCG exerts a neuroprotective effect on PC12 cells and helps maintain mitochondrial metabolic balance in the presence of MPP+.