VEGF, by stimulating endothelial cells to migrate, proliferate and differentiate, plays a major role in angiogenesis. Increase in intracellular cAMP is known to inhibit basal as well as VEGF-induced endothelial cell proliferation. Cyclic nucleotide phosphodiesterases (PDEs) play a key role in signal transduction by hydrolyzing specifically cyclic nucleotides.
Our team has previously reported that PDE2 and PDE4 up-regulations (activity, protein and mRNA) in human umbilical vein endothelial cells (HUVECs) are implicated in VEGF-induced angiogenesis and that inhibition of PDE2 and PDE4 isozyme activities prevents the development of angiogenesis by increasing cAMP level, by inhibiting cell proliferation, cell migration and cell cycle progression (Favot et al., Thromb Haemost 2003, 90: 334 and 2004, 92: 634). On another hand, we have shown that polyphenols inhibit PDEs (Orallo et al., Naunyn Schmiedebergs Arch Pharmacol 2004, 370: 452; Planta Med 2005, 71: 99; Alvarez et al., Br J Pharmacol. 2006, 147: 269).
The polyphenol curcumin, isolated from the plant Curcuma longa, is present in curry powder, and is known to have anti-infl ammatory, anti-oxidant and anti-cancer properties. The anti-carcinogenic properties of curcumin have been demonstrated in animals by its ability to inhibit tumor initiation and tumor progression. Therefore, this study was aimed to investigate the participation of PDEs in anti-angiogenic properties of curcumin.
The effect of curcumin on PDE activities was assessed by the determination of IC50 values on the five isozymes PDE1-PDE5 purified from vascular tissues. Curcumin was able to inhibit PDE1, PDE2, PDE3 and PDE4 with IC50 values in the range of 10 to20μm, and PDE5 with an IC50 value of35μm.
Curcumin at a concentration of 10μm inhibited both basal and VEGF-stimulated HUVEC proliferation (58 %and 54 %respectively, P=0.003). Furthermore, 10μm curcumin inhibited significantly (52 %, P=0.001) VEGF-induced HUVEC migration similarly to the selective PDE2 inhibitor (0.1μm BAY-60-7550, 69 %, P=0.003) and the selective PDE4 inhibitor (10μm rolipram, 41 %, P=0.006)).
These results, showing for the first time that curcumin inhibits PDE activities, suggest that curcumin present in food might inhibit angiogenesis at endothelial cell level by inhibiting PDE activities.Le texte complet de cet article est disponible en PDF.