Tanshinone Ⅱ A, the major lipophilic component of Danshen, promotes neuronal differentiation through MAPK42/44 mediated pathways

Danshen has been used in stroke treatment for thousands of years in China. However, the underlying mechanism still remains elusive. Neuron loss is the cardinal feature of stroke. Stimulating endogenous neurogene- sis, especially neuronal differentiation, might potentially provide therapeutic effects to these diseases. To interpret Danshen＇ s disease-modifying effects, the effects of tanshinone 11 A （T 11 A）, the major lipophilic component of Danshen, on neuronal differentiation in rat PC12 pheochromocytoma cells and the rat embryonic cortical neural stem cells （NSCs） were observed. PC12 cells and NSCs were incubated with T II A for 7 days. To detect the neu- ronal differentiation, GAP-43 expression was detected by western blots assay and β-tubulin HI expression was de- tected by immunocytochemical staining. Results showed that T Ⅱ A dose-dependently promoted neuronal differentia- tion. T Ⅱ A activated mitogen-activated protein kinase 42/44 （MAPK42/44） and its downstream transcription fac- tor, cAMP response element-binding protein （CREB）. In addition , T Ⅱ A up-regulated the expressions of brain de- rived neurotrophic factor （BDNF） and nerve growth factor （NGF）. The MEK inhibitor and the antagonist to the re- ceptors of NGF and BDNF could partially attenuate the differentiation effects, indicating that MAPK42/44 mediated BDNF and NGF signals were involved in T Ⅱ A＇ s differentiation effects. Caveolin-1 （ CAV-1 ）, the major functional protein of membrane caveolae, plays critical roles in the endocytosis of exogenous materials. CAV1, which was ac-tivated by T Ⅱ A, might help T Ⅱ A transport across cell membrane to initiate its differentiation effects. It was prov- en by the evidences that suppressing the function of caveolin inhibited the differentiation effects of T Ⅱ A. There- fore, it was concluded that T Ⅱ A promoted neuronal differentiation partially through MAPK42/44 mediated B DNF and NEF signals in a caveolae-dependent manner.