Date: 15 Nov 2008

The effect of clonidine on VEGF expression in human retinal pigment epithelial cells (ARPE-19)

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The purpose of this study was to investigate the effect of clonidine, an alpha2-adrenergic receptor (α2-ADR) agonist, on vascular endothelial growth factor (VEGF) expression and secretion in the human retinal pigment epithelial cell line (ARPE-19) stimulated with interleukin-1β (IL-1β).


Alpha2-ADRs (α2A, α2B, and α2C) mRNA expression in ARPE-19 cells was examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Clonidine and inhibitors against protein kinases that are involved in the regulation of the intracellular signal transduction were added to serum-free medium before stimulation of IL-1β. The α2-ADR antagonist, Yohimbine, was loaded 30 min before the addition of clonidine. The expression of VEGF mRNA and protein was measured by real-time PCR and enzyme-linked immunosorbent assay.


Alpha2A-ADR, α2B-ADR, and α2C-ADR mRNA was expressed in RPE cells. Clonidine, an inhibitor of p38MAPK and MEK1/2, inhibited the expression of VEGF protein and mRNA in the RPE cells stimulated with IL-1β. The inhibitory effect of clonidine on the secretion of VEGF protein stimulated with IL-1β was blocked by α2-ADR antagonists.


The effect of clonidine on the expression of VEGF may be via suppression of the p38MAPK and MEK1/2 signal transduction pathways activated with IL-1β.

The authors have no financial relationship with any organization.
The authors have full control of all primary data, and agree to allow Graefe’s Archive for Clinic and Experimental Ophthalmology to review the data upon request.