Camellia euphlebia protects against corticosterone-induced apoptosis in differentiated PC12 cells by regulating the mitochondrial apoptotic pathway and PKA/CREB/BDNF signaling pathway.

Camellia euphlebia is a Chinese folk medicine, known for its multiple pharmacological properties. Our previous studies have demonstrated its antidepressant activity by several animal models of depression. The possible underlying mechanism was further explored by investigating the neuroprotective effect of Camellia euphlebia extract (CEE) on corticosterone-induced apoptosis in neuronally differentiated PC12 cells. The results of methyl-thiazolyl-tetrazolium assay, lactate dehydrogenase release assay, Hoechst 33342 staining, propidium iodide staining, AV-FITC/PI double staining and DNA fragmentation analysis consistently indicated that pretreatment of PC12 cells with CEE at 20-80 μg/mL significantly reversed 300 μmol/L corticosterone-induced apoptosis in a dose dependent manner. Furthermore, intracellular mitochondrial membrane potential, reactive oxygen species accumulation, calcium level, Bcl-2/Bax ratio, caspase activity were assessed, and the results indicated that CEE exhibited its anti-apoptotic effect through the regulation of mitochondrial apoptosis pathway. Additionally, CEE increased the cyclic adenosine monophosphate-dependent protein kinase (PKA) level, which phosphorylated cAMP response element binding protein (CREB), and finally elevated the mRNA expression of brain-derived neurotrophic factor (BDNF) gene. It is speculated that the antidepressant effect of CEE in vivo may be associated with the cytoprotection of neuron damaged by corticosterone, and the cellular mechanism involves the mitochondrial-mediated apoptosis and PKA-CREB-BDNF signaling pathway.