Baicalein inhibits Raf-1-mediated phosphorylation of MEK-1 in C6 rat glioma cells.


Baicalein is a flavonoid derived from the Scutellaria root. In investigations of the inhibitors of prostaglandin synthesis in C6 rat glioma cells, we found that baicalein had a potent inhibitory activity on prostaglandin synthesis induced by either histamine or A23187, a Ca(2+) ionophore. Baicalein inhibited histamine- or A23187-induced phosphorylation of p42/p44 extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK), which causes the phosphorylation of cytosolic phospholipase A(2) (PLA(2)). Baicalein also inhibited the phosphorylation of MAPK kinase-1 (MEK-1) induced by histamine or A23187 in the cells. To examine the site of action of baicalein, MEK-1 and Raf-1 were prepared by immunoprecipitation with anti-MEK-1 and anti-Raf-1 antibodies, respectively. Baicalein inhibited the phosphorylation of exogenous MEK-1 by Raf-1 under cell-free conditions, while it did not change the phosphorylation of exogenous p42 MAPK by MEK-1. These results imply that baicalein inhibits the ERK/MAPK cascade, acting on the phosphorylation of MEK-1 by Raf-1.

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@article{Nakahata2003BaicaleinIR, title={Baicalein inhibits Raf-1-mediated phosphorylation of MEK-1 in C6 rat glioma cells.}, author={Norimichi Nakahata and Chikako Tsuchiya and Keigo Nakatani and Yasushi Ohizumi and Satoko Ohkubo}, journal={European journal of pharmacology}, year={2003}, volume={461 1}, pages={1-7} }