Pyrroloquinoline quinone protects mouse brain endothelial cells from high glucose-induced damage in vitro

Aim： To investigate the effects of pyrroloquinoline quinone （PQQ）, an oxidoreductase cofactor, on high glucose-induced mouse endothelial cell damage in vitro. Methods： Mouse brain microvascular endothelial bEND.3 cells were exposed to different glucose concentrations （5.56, 25 and 40 mmol/L） for 24 or 48 h. The cell viability was examined using MTT assay. Flow cytometry was used to analyze the apoptosis and ROS levels in the cells. MitoTracker Green staining was used to examine the mitochondria numbers in the cells. Western blot analysis was used to analyze the expression of HIF-1α and the proteins in JNK pathway. Results： Treatment of bEND.3 cells with high glucose significantly decreased the cell viability, while addition of PQQ （1 and 10 μmol/L） reversed the high glucose-induced cell damage in a concentration-dependent manner. Furthermore, PQQ （100 pmol/L） significantly suppressed the high glucose-induced apoptosis and ROS production in the cells. PQQ significantly reversed the high glucose- induced reduction in both the mitochondrial membrane potential and mitochondria number in the cells. The high glucose treatment significantly increased the expression of HIF-la and JNK phosphorylation in the cells, and addition of PQQ led to a further increase of HIF-la level and a decrease of JNK phosphorylation. Addition of JNK inhibitor SP600125 （10 μmol/L） also significantly suppressed high glucose-induced apoptosis and JNK phosphorylation in bEND.3 cells. Conclusion： PQQ protects mouse brain endothelial cells from high glucose damage in vitro by suppressing intracellular ROS and apoptosis via inhibiting JNK signaling pathway.