Protocatechuic acid promotes cell proliferation and reduces basal apoptosis in cultured neural stem cells.

Protocatechuic acid (PCA), a phenolic compound isolated from the kernels of Alpinia oxyphylla, showed anti-oxidant neuroprotective property in our previous study. However, it is still unknown whether PCA have effects on the cultured neural stem cells (NSCs). In this study, we investigated the roles of PCA in the survival and apoptosis of rat NSCs under normal conditions. NSCs obtained from 13.5-day-old rat embryos were propagated as neurospheres and cultured under normal conditions with or without PCA for 4 and 7 days. The cell viability was determined by the cell counting kit-8 (CCK-8) test, while cell proliferation was assayed by bromodeoxyuridine (BrdU) labeling. PCA increased the cellular viability of NSCs and stimulated cell proliferation in a dose- and time-dependent manner. Apoptotic cells were detected after 4 days by observing the nuclear morphological changes and flow cytometric analysis. Compared with the control on both culture days, treatment with PCA effectively reduced the levels of apoptosis of NSCs. At the same time, the reactive oxygen species (ROS) level in NSCs was depressed. In addition, PCA also significantly decreased the activity of elevated caspase-3, indicating that PCA may inhibit apoptosis of NSCs via suppression of the caspase cascade. These results suggest that PCA may be a potential growth inducer and apoptosis inhibitor for NSCs.