A new isoxazolic compound acts as alpha7 nicotinic receptor agonist in human umbilical vein endothelial cells.

Recent evidence suggests that the alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) participate in the development of angiogenesis and could be a new endothelial target for revascularization in therapeutic angiogenesis. It has been shown that in human umbilical vein endothelial cells (HUVECs) alpha7 nAChR agonists increase the intracellular calcium concentration ([Ca2+]i), thus inducing proliferation and vessel formation which are important stages of angiogenesis. In the present study we evaluated the effect of new isoxazole compounds on the cytosolic Ca2+ signal in HUVECs using the fluorescent Ca2+ indicator Fluo-3AM and probing the involvement of alpha7 nAChR by means of pharmacological tools. HUVECs expressed mainly alpha7 nAChR, since there was no significant difference in the increase in [Ca2+]i induced by nicotine, a non-selective nicotinic agonist, in relation to choline, a selective alpha7 nAChR agonist. The increase in [Ca2+]i induced by 1 mM choline was inhibited significantly (p = 0.014) in cells which had been pre-incubated for 15 min with methyllycaconitine (MLA), a selective alpha7 nAChR antagonist. The studied compounds 1, 2, and 3 induced an increase in [Ca2+]i in a dose-dependent manner. Compound 1 at 10 microM induced a greater increase in [Ca2+]i than compounds 2 and 3. The increase in [Ca2+]i induced by compound 1 was significantly inhibited by MLA (p = 0.013) and completely inhibited by mecamylamine, a non-selective nAChR antagonist, indicating that the isoxazolic compound 1 acts as an alpha7 nAChR agonist.