Activation of the Aryl Hydrocarbon Receptor by the Calcium/Calmodulin-Dependent Protein Kinase Kinase Inhibitor 7-Oxo-7H-benzimidazo[2,1-a]benz[de]isoquinoline-3-carboxylic Acid (STO-609)

作者：Monteiro Patricia; Gilot David^*; Langouet Sophie; Fardel Olivier

来源：Drug Metabolism and Disposition, 2008, 36(12): 2556-2563.

DOI：10.1124/dmd.108.023333

This study was designed to analyze the effects of the Ca(2+)/calmodulin-dependent protein kinase kinase ( CaMKK) inhibitor STO-609 (7-oxo-7H-benzimidazo[2,1-a]benz[de]isoquinoline-3-carboxylic acid) toward the aryl hydrocarbon receptor (AhR) pathway because Ca(2+)/calmodulin-dependent protein kinase ( CaMK) I alpha, known as a downstream CaMKK effector, has been recently shown to contribute to the AhR cascade. STO-609 failed to alter up-regulation of the AhR target CYP1A1 in response to the potent AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin ( TCDD) in MCF-7 cells. STO-609, used at a 25 mu M concentration known to fully inhibit CaMKK activity, was surprisingly found to markedly induce CYP1A1 expression and activity by itself in MCF-7 cells; it similarly up-regulated various other AhR target genes in human macrophages. STO-609-related CYP1A1 induction was prevented by chemical inhibition or small interfering RNA-mediated knockdown expression of AhR. Moreover, STO-609 was demonstrated to physically interact with the ligand-binding domain of AhR, as assessed by TCDD binding competition assay, and to induce AhR translocation to the nucleus. As already reported for AhR agonists, STO-609 triggered the increase of [Ca(2+)](i) and activation of CaMKI alpha, whose inhibition through the use of the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid- acetoxymethyl ester or the CaMK inhibitor KN-93(2-[N-(2-hydroxyethyl)]-N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine), respectively, prevented STO-609-mediated CYP1A1 activity induction. Taken together, these results demonstrate that the CaMKK inhibitor STO-609 can act as an AhR ligand and, in this way, fully activates the Ca(2+)/CaMKI alpha/AhR cascade. Such data, therefore, make unlikely any contribution of CaMKK activity to the AhR pathway and, moreover, suggest that caution may be required when using STO-609 as a specific inhibitor of CaMKKs.

• 出版日期2008-12