Mechanism of neuropeptide Y mediated potentiation of P2X1 receptordependent vasoconstriction in human and mouse small arteries

Resumen

Background and Purpose: Neuropeptide Y (NPY) is co-released with ATP and norepinephrine by sympathetic nerves that innervate arteries. Here, we explore the mechanism by which NPY can augment vasoconstriction mediated by activation of the P2X1 receptor for ATP. Experimental Approach: Patients Small arteries (500–200 μm) from subcutaneous abdominal adipose tissue samples were obtained from normotensive female volunteers. Animals Mesenteric arteries (<200 μm) from male C57BL/6 mice were used. Isometric contractility measurements were made on arterial rings by wire myography. Neurogenic responses were elicited by electrical field stimulation. Data are expressed as mean ± SEM, and n representsthe number of animals. Analysis was performed using ANOVA orKruskal–Wallis test followed by a Student–Newman–Keuls t test, posthoc Tukey honestly significant difference test, or Mann–Whitney U test where appropriate. Comparison between segments from the same samples was assessed by a paired t test or a Wilcoxon signedrank test.Key Results: Human arteries Purinergic agonist α,β-methylene ATP (α,β-meATP; 300 nM) evoked contractions that were potentiated by NPY (10 nM) in arteries (potentiation = 198%; P < .01; N = 9). In addition, NPY (1 nM– 100 μM) evoked concentration-dependent contractions on basal tone with functional and non-functional endothelium (EC50 = 1.25 × 10−8 ± 4.09 × 10−9 M; P < .05; N = 6; and EC50 = 1.69 × 10−8 ± 4.24 × 10−9 M; P < .05; N = 5, respectively). α,β-meATP-evoked responses were sensitive to suramin (IC50 = 1.28 × 10−6 ± 2.82 × 10−7 M; P < .05; N = 3), and a selective P2X1 receptor antagonist (NF449); [100 nM] was sufficient to completely block of α,β-meATP-induced contractions (inhibition = 85%;P < .005; N = 5). NPY-induced potentiation on α,β-meATP-evoked contractions was not reduced by selective NPY1R antagonism (BIBO3304 [10 nM]; n.s.; N = 5) or NPY2R antagonism (BIIE0246 [100 nM]; n.s.; N = 5). However, NPY-induced potentiation was abolished when both antagonists were applied together (inhibition = 58%; P = .059; N = 3). Mouse arteries Previous results showed that nifedipine (100 nM) does not block α,β-meATP (100 nM) peaks; however, nifedipine inhibits NPY potentiation of α,β-meATP contractions (inhibition = 49%, P < .05; N = 10). In addition, purinergic and adrenergic contractile responses induced by EFS were blocked by TTx (1 μM; inhibition ~75% to 64 Hz, P < .01; N = 7) and guanethidine (10 μM; inhibition ~60% to 64 Hz; P < .05; N = 10), respectively, and also of the partial inhibition of the selective P2X1R (NF449 [3 μM]; inhibition ~40% to 64 Hz; P < .05; N = 6). Conclusion and Implications: Data suggest that NPY exerts a positive modulatory effect on α,β-meATP-evoked contractions by combined activation of NPY1R and NPY2R in human and mice vascular tissue and requires L-type Ca2+ channel activity.