Involvement of NF-κB and AP-1 activation in icariin promoted cardiac differentiation of mouse embryonic stem cells

Icariin has been reported to facilitate the differentiation of mouse embryonic stem (ES) cells into cardiomyocytes; however, the mechanism on cardiomyogenic cell lineage differentiation has not been fully elucidated yet. In the present studies, an underlying signaling network including p38, extracellular signal-regulated kinase 1, 2 (ERK1, 2), nuclear factor-kappa B (NF-kappa B), activator protein-1 (AP-1) transcription factors c-jun and c-fos was assumed in icariin induced cardiomyogenesis. Icariin rapidly activated p38 and ERK1, 2 in embryoid bodies, treatment with p38 antagonist 4-(4-Fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole (SB203580) or ERK1, 2 inhibitor 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene (U0126) significantly abolished icariin induced cardiac commitment MEF2C gene expression and nuclear translocation, as well as cardiac-specific protein a-actinin expression, indicating that p38 and ERK1, 2 are specifically involved in icariin stimulated cardiomyogenic cell lineage differentiation of ES cells. Further, I kappa B alpha phosphorylation and NF-kappa B p65 translocation to the nucleus appeared rapidly when embryoid bodies exposed to icariin, and the expression of I kappa B alpha or NF-kappa B p65 in cytoplasm was decreased concomitantly. Moreover, icariin increased c-jun and c-fos mRNA and protein expression. Either SB203580 or U0126 displayed inhibitory effect on icanin induced NF-kappa B and AP-1 activation. It could be concluded that p38 and ERK1, 2 are activated in a coordinated manner, which in turn contribute to NF-kappa B and AP-1 activation in icariin induced cardiomyogenic cell lineage differentiation of mouse ES cells. (C) 2008 Elsevier B.V. All rights reserved.