Abstract
Regulation of genes targeted by the ligand-activated aryl hydrocarbon receptor (AhR) has been shown to be controlled by calcium (Ca2+) changes induced by AhR agonists such as the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The present study was designed to characterize this link between Ca2+ and the AhR pathway. We report that fast elevation of intracellular Ca2+ in TCDD-exposed mammary MCF-7 cells was associated with transient enhanced activity of the Ca2+/calmodulin (CaM)-dependent protein kinase (CaMK) pathway. Chemical inhibition of this pathway using the CaM antagonist W7 or the CaMK inhibitor KN-93 strongly reduced TCDD-mediated induction of the AhR target gene CYP1A1. Small interfering RNA (siRNA)-mediated knockdown expression of CaMKIα, one of the CaMK isoforms, similarly prevented CYP1A1 up-regulation. Both KN-93 and siRNA targeting CaMKIα were found to abolish TCDD-mediated activation of CYP1A1 promoter and TCDD-triggered nuclear import of AhR, a crucial step of the AhR signaling pathway. TCDD-mediated inductions of various AhR targets, such as the drug metabolizing CYP1B1, the cytokine interleukin-1β, the chemokines interleukin-8 and CCL1, the adhesion molecule β7 integrin, and the AhR repressor, were also prevented by KN-93 in human macrophages. Taken together, these data identified the Ca2+/CaM/CaMKIα pathway as an important contributing factor to AhR-mediated genomic response.
Footnotes
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This work was supported by grants from the Ligue Nationale contre le Cancer, the University of Rennes I, and the Agence Francaise de Sécurité Sanitaire de l'Environnement et du Travail (AFSSET).
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P.M. received a fellowship from the Ligue Nationale contre le Cancer
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ABBREVIATIONS: AhR, aryl hydrocarbon receptor; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; XAP2, X-associated protein 2; XRE, enobiotic responsive elements; PAH, polycyclic aromatic hydrocarbon; CaM, calmodulin; CaMK, Ca2+/CaM-dependent protein kinase; 2-APB, 2-Aminoethoxydiphenylborate; BAPTA-AM, 1,2-bis(O-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetra(acetoxymethyl) ester; KN-93, 2-[N-(2-hydroxyethyl)]-N-(4-methoxybenzenesulfonyl)amino-N-(4-chlorocinnamyl)-N-methylbenzylamine; KN-92, 2-[N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine; W7, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide; AM, acetoxymethyl ester; Ab, antibody; EROD, ethoxyresorufin O-deethylase; RT-qPCR, reverse transcription-quantitative polymerase chain reaction; siRNA, small interfering RNA.
- Received November 5, 2007.
- Accepted December 17, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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