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The Journal of pharmacology and experimental therapeutics

NADPH oxidase pathway is involved in aortic contraction induced by A3 adenosine receptor in mice.


PMID 21606175

Abstract

The NADPH oxidase (Nox) subunits 1, 2 (gp91 phox), and 4 are the major sources for reactive oxygen species (ROS) in vascular tissues. In conditions such as ischemia-reperfusion and hypoxia, both ROS and adenosine are released, suggesting a possible interaction. Our aim in this study was to examine the A(3) adenosine receptor (A(3)AR)-induced vascular effects and its relation to ROS and Nox1, 2, and 4 using aortic tissues from wild-type (WT) and A(3)AR knockout (A(3)KO) mice. The selective A(3)AR agonist 2-chloro-N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (Cl-IBMECA) (10(-10)-10(-5) M) induced contraction of the aorta from WT but not from A(3)KO mice, and this contraction was inhibited by the Nox inhibitor apocynin (10(-5) M) and the ROS scavengers superoxide dismutase-polyethylene glycol and catalase-polyethylene glycol (100 U/ml each). Cl-IBMECA-induced contraction was not affected by the mast cell degranulator compound 48/80 (100 μg/ml) or the stabilizer cromolyn sodium (10(-4) M). In addition, Cl-IBMECA (10(-7) M) increased intracellular ROS generation by 35 ± 14% in WT but not in A(3)KO aorta, and this increase was inhibited by apocynin (10(-5) M), diphenyleneiodonium chloride (10(-5) M), and the A(3)AR antagonist 3-propyl-6-ethyl-5-[(ethylthio)carbonyl]-2 phenyl-4-propyl-3-pyridine carboxylate (MRS1523) (10(-5) M). Furthermore, Cl-IBMECA selectively increased the protein expression of the Nox2 subunit by 150 ± 15% in WT but not in A(3)KO mice without affecting either Nox1 or 4, and this increase was inhibited by apocynin. The mRNA of Nox2 was unchanged by Cl-IBMECA in either WT or A(3)KO aortas. In conclusion, A(3)AR enhances ROS generation, possibly through activation of Nox2, with subsequent contraction of the mouse aorta.