Ginkgolides protect PC12 cells against hypoxia-induced injury by p42/p44 MAPK pathway-dependent upregulation of HIF-1α a expression and HIF-1DNA-binding activity

We hypothesized that the neuroprotective role of the standardized Ginkgo biloba (Ginkgoaceae) extract EGb 761 under hypoxic conditions might be associated with its function to increase HIF-1 activity based on the fact that oxygen availability is crucial for cellular metabolism and viability and that HIF-1 plays an essential role in cellular oxygen homeostasis under hypoxic conditions. In this study, we therefore investigated the effects of ginkgolides, the main constituent of the non-flavone fraction of EGb 761, on the content and activity of HIF-1 alpha, a key factor to determine HIF-1 activity, in hypoxic PC12 cells induced by cobalt chloride. Our data demonstrated that ginkgolides have a significant protective role against hypoxia-induced injury in the PC12 cells. The findings also strongly support our hypothesis that the protective role of ginkgolides is due to the up-regulation of HIF-1 alpha a protein expression and modification through the ginkgolides-induced activation of the p42/p44 MAPK pathway. In addition, it was evident that ginkgolides could significantly increase the HIF-1 DNA binding activity, which might also be associated with the protective effects of ginkgolides by promoting the expression of target genes of HIF-1 under hypoxic conditions.