Acta Pharmacologica Sinica (2009) 30: 537-544; doi: 10.1038/aps.2009.28; published online 6th April 2009

Aim: Catecholamine-induced vascular smooth muscle cell (VSMC) proliferation is one of the major events in the pathogenesis of atherosclerosis and vascular remodeling. The calcineurin-NFAT pathway plays a role in regulating growth and differentiation in various cell types. We investigated whether the calcineurin-NFAT pathway was involved in the regulation of phenylephrine-induced VSMC proliferation.

Methods: Proliferation of VSMC was measured using an MTT assay and cell counts. Localization of NFATc1 was detected by immunofluorescence staining. NFATc1-DNA binding was determined by EMSA and luciferase activity analyses. NFATc1 and calcineurin levels were assayed by immunoprecipitation.

Results: Phenylephrine (PE, an α₁-adrenoceptor agonist) increased VSMC proliferation and cell number.  Prazosin (an α₁-adrenoceptor antagonist), cyclosporin A (CsA, an inhibitor of calcineurin) and chelerythrine (an inhibitor of PKC) decreased PE-induced proliferation and cell number.  Additional treatment of VSMC with CsA or chelerythrine further inhibited proliferation and cell number in the chelerythrine-pretreatment group and the CsA-pretreatment group.  CsA and chelerythrine alone had no effect on either absorbance or cell number.  CsA decreased PE-induced calcineurin levels and activity. NFATc1 was translocated from the cytoplasm to the nucleus upon treatment with PE.  This translocation was reversed by CsA. CsA decreased the PE-induced NFATc1 level in the nucleus. PE increased NFAT’s DNA binding activity and NFAT-dependent reporter gene expression. CsA blocked these effects.
                                                                                                                                                                                     
Conclusion: CsA partially suppresses PE-induced VSMC proliferation by inhibiting calcineurin activity and NFATc1 nuclear translocation. The calcineurin-NFATc1 pathway is involved in the hyperplastic growth of VSMC induced by phenylephrine.

Keywords: phenylephrine; calcineurin; nuclear factor of activated T cells; proliferation; vascular smooth muscle cells