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 A3 adenosine receptors (A3AR) induced vascular effects and its relation to ROS and Nox1, 2 and 4 using aortic tissues from wild type (WT) and A3AR knockout (A3KO) mice. The selective A3AR agonist Cl-IBMECA (10-10- 10-5 M) induced contraction of the aorta from WT but not from A3KO 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 PEG (SOD+Catalase) (100 U/ml each). Cl-IBMECA-induced contraction was not affected by mast cell degranulator compound 48/80 (100 μg/ml) or 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 A3KO aorta and this increase was inhibited by apocynin (10-5 M), DPI (10-5 M) and the A3AR antagonist MRS1523 (10-5 M). Furthermore, Cl-IBMECA selectively increased the protein expression of Nox2 subunit by 150±15% in WT but not in A3KO 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 A3KO aortas. In conclusion, A3AR enhances ROS generation, possibly through activating Nox2, with subsequent contraction of the mouse aorta.
- Received February 18, 2011.
- Revision received May 4, 2011.
- Accepted May 20, 2011.
- The American Society for Pharmacology and Experimental Therapeutics