Clinically used anti-tubuline drugs restrict AHR-CYP1A2 signalling pathway via C-JUN-N-Terminal kinase: A study in primary cultures of human hepatocytes

Perturbation of microtubular network has been shown to cause suppression of inducibility of major cytochromes P450 (CYP) through several nuclear receptors. Here we tested the effects of clinically used microtubules-interfering agents (MIAs), such as colchicine, vincristine, vinblastine and taxol on aryl hydrocarbon receptor (AhR) signaling pathway in primary cultures of human hepatocytes. We show that tested MIAs decreased induction of CYP1A2 mRNA by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and restrict TCDD-dependent nuclear translocation of AhR. On the other hand, these MIAs increased the content of AhR protein and AhR mRNA by transcriptional mechanism. We show that the MIAs activate c-jun-N-terminal kinase (JNK), partly p38 but not extracellular-regulated protein kinase (ERK). Consistently, sorbitol, a model activator of JNK, inhibited TCDD-mediated induction of CYP1A2 mRNA. We conclude that the effects of tested MIAs on AhR-CYP1A2 signaling pathway are dual, i.e. they inhibit transcriptional activity and nuclear translocation of AhR but in parallel increase AhR protein and mRNA level. Microtubules destabilizers have the same effects as stabilizer taxol. This implies that AhR functions depend on microtubules dynamics but not integrity. Perturbation of AhR-CYP1A2 signaling by MIAs comprises AhR-JNK/p38 interactions. We also demonstrate that the effects of MIAs in human hepatocytes do not proceed via arresting cell cycle as confirmed by flow cytometry (FACS) analyses.

This work was supported by the grant from the Ministry of Education, Youth and Sports of the Czech Republic MSM 6198959216 (to J.U.), by the grant from Grant Agency of the Czech Republic GACR 303/07/0128 (to Z.D.) and by EMBO Short Term Fellowship ASTF 275-2006 (to Z. D.).