A New Isoxazolic Compound Acts as <i>α</i>7 Nicotinic Receptor Agonist in Human Umbilical Vein Endothelial Cells

Recent evidence suggests that the α7 nicotinic acetylcholine receptors (α7 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) α7 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 α7 nAChR by means of pharmacological tools. HUVECs expressed mainly α7 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 α7 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 α7 nAChR antagonist. The studied compounds 1, 2, and 3 induced an increase in [Ca²⁺]_i in a dose-dependent manner. Compound 1 at 10 μm 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 α7 nAChR agonist.