Chlorogenic acid enhances autophagy by upregulating lysosomal function to protect against SH-SY5Y cell injury induced by H2O2

Autophagy serves an important role in amyloid-beta (A beta) metabolism and tau processing and clearance in Alzheimer's disease. The progression of A beta plaque accumulation and hyperphosphorylation of tau proteins are enhanced by oxidative stress. A hydrogen peroxide (H2O2) injury cell model was established using SH-SY5Y cells. Cells were randomly divided into normal, H2O2 and chlorogenic acid (5-caffeoylquinic acid; CGA) groups. The influence of CGA on cell viability was evaluated using a Cell Counting Kit-8 assay and cell death was assessed using Hoechst 33342 nuclear staining. Autophagy induction and fusion of autophagic vacuoles assays were performed using monodansylcadaverine staining. Additionally, SH-SY5Y cells expressing Ad-mCherry-green fluorescent protein-LC3B were established to detect autophagic flow. LysoTracker Red staining was used to evaluate lysosome function and LysoSensor (TM) Green staining assays were used to assess lysosomal acidification. The results demonstrated that CGA decreased the apoptosis rate, increased cell viability and improved cell morphology in H2O2-treated SH-SY5Y cells. Furthermore, CGA alleviated the accumulation of autophagic vacuoles, reduced the LC3BII/I ratio and decreased P62 levels, resulting in increased autophagic flux. Additionally, CGA upregulated lysosome acidity and increased the expression levels of cathepsin D. Importantly, these effects of CGA on H2O2-treated SH-SY5Y cells were mediated via the mTOR-transcription factor EB signaling pathway. These results indicated that CGA protected cells against H2O2-induced oxidative damage via the upregulation of autophagosomes, which promoted autophagocytic degradation and increased autophagic flux.