Effects of NAD at purine receptors in isolated blood vessels

Abstract

Nicotinamide adenine dinucleotide (NAD) belongs to the family of naturally occurring adenine dinucleotides, best known for their various intracellular roles. However, there is evidence that they can also be released from cells to act as novel extracellular signalling molecules. Relatively little is known about the extracellular actions of NAD, especially in the cardiovascular system. The present study investigated the actions of NAD in the rat thoracic aorta, porcine coronary artery and porcine mesenteric arteries, mounted in organ baths for isometric tension recording. In the rat thoracic aorta and porcine coronary artery, NAD caused endothelium-independent concentration-dependent vasorelaxations which were unaffected by palmitoylCoA, a P2Y1 receptor antagonist, but which were blocked by CGS15943, a non-selective adenosine receptor antagonist. In the porcine coronary artery, NAD-evoked relaxations were abolished by SCH58261, a selective A2A receptor antagonist. In the rat thoracic aorta, NAD-evoked relaxations were attenuated by A2A receptor antagonism with SCH58261 but were unaffected by an A2B receptor antagonist, MRS1754. In contrast, in the porcine mesenteric artery, NAD-evoked endothelium-independent contractions, which were unaffected by a P2 receptor antagonist, suramin, or by NF449, a P2X1 receptor antagonist, but were attenuated following P2X receptor desensitisation with αβ-meATP. In conclusion, the present results show that NAD can alter vascular tone through actions at purine receptors in three different arteries from two species; its molecular targets differ according to the type of blood vessel.

Fig. 1

Chemical structure of nicotinamide adenine dinucleotide

Fig. 2

The effect of nicotinamide adenine dinucleotide (NAD) in segments from: a rat thoracic aorta (RTA), b porcine mesenteric artery (PMA) and c porcine coronary artery (PCA). Arteries were precontracted with methoxamine a and U46619 (b, c). Responses were evaluated in endothelium intact vessels (Control) and in those in which the endothelium had been removed (Denuded) in each of the RTA, PMA and PCA (n = 7–10, n = 6–11, n = 5–6, respectively). Results are mean ± SEM

Fig. 3

Relaxatory responses in the rat thoracic aorta to nicotinamide adenine dinucleotide (NAD) in the presence of a PaCoA, b CGS15943, c SCH58261 and d MRS1754. Dimethyl sulfoxide (DMSO) is the vehicle control for CGS15943 and SCH58261. Vessels were precontracted with methoxamine. Results are shown as mean ± SEM (n = 5–6, n = 4–5, n = 12–15 and n = 4–8, respectively). *P < 0.05; **P < 0.01; ***P < 0.001

Fig. 4

A representative trace for the relaxatory responses to cumulative addition of increasing concentrations of nicotinamide adenine dinucleotide (NAD) in the rat thoracic aorta in the absence (Control, upper trace) and the presence of SCH58261 (SCH58261, lower trace). Vessels were precontracted with methoxamine

Fig. 5

The contractile response of porcine mesenteric artery to nicotinamide adenine dinucleotide (NAD) in the absence and presence of a suramin and b αβ-meATP. The arteries had been precontracted with U46619. Results are shown as mean ± SEM (n = 4 and n = 7–8, respectively). **P < 0.01; ***P < 0.001

Fig. 6

A representative trace for the contractile response to nicotinamide adenine dinucleotide (NAD) of porcine mesenteric artery in the absence (Control, upper trace) and presence of αβ-meATP (αβ-meATP, lower trace). The arteries had been precontracted with U46619

Fig. 7

The porcine mesenteric artery contractile response to nicotinamide adenine dinucleotide (NAD) in the presence of a PaCoA, b CGS15943 and c SCH58261 (n = 7, n = 8 and n = 4, respectively). The arteries had been precontracted with U46619. Results are shown as mean ± SEM

Fig. 8

The porcine coronary artery relaxation to nicotinamide adenine dinucleotide (NAD) in the presence of a PaCoA, b CGS15943 and c SCH58261. Preparations were precontracted with U46619. Results are shown as mean ± SEM (n = 5, n = 6 and n = 6 respectively). *P < 0.05; **P < 0.01; ***P < 0.001

Fig. 9

A representative trace for the porcine coronary artery relaxation to nicotinamide adenine dinucleotide (NAD) in the absence (Control, upper trace) and presence of SCH58261 (SCH58261, lower trace). Vessels were precontracted with U46619