Portal de Periódicos da CAPES

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

2008; American Society for Pharmacology and Experimental Therapeutics; Volume: 36; Issue: 12 Linguagem: Inglês

10.1124/dmd.108.023333

1521-009X

Patricia Monteiro, David Gilot, Sophie Langouët, Olivier Fardel,

Drug Transport and Resistance Mechanisms

This study was designed to analyze the effects of the Ca 2+ /calmodulin-dependent protein kinase kinase (CaMKK) inhibitor STO-609 (7-oxo-7 H -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) Iα, 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 μM 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 CaMKIα, 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+ /CaMKIα/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.