Involvement of COX-1 in A₃ adenosine receptor-mediated contraction through endothelium in mice aorta

Abstract

We investigated whether A(3) adenosine receptor (A(3)AR) is involved in endothelium-mediated contraction through cyclooxygenases (COXs) with the use of wild-type (WT) and A(3) knockout (A(3)KO) mice aorta. A(3)AR-selective agonist, Cl-IBMECA, produced a concentration-dependent contraction (EC(50): 2.9 +/- 0.2 x 10(-9) M) in WT mouse aorta with intact endothelium (+E) and negligible effects in A(3)KO +E aorta. At 10(-7) M, contractions produced by Cl-IBMECA were 29% in WT +E, while being insignificant in A(3)KO +E aorta. Cl-IBMECA-induced responses were abolished in endothelium-denuded tissues (-E), in both WT and A(3)KO aorta. A(3)AR gene and protein expression were reduced by 74 and 72% (P < 0.05), respectively, in WT -E compared with WT +E aorta, while being undetected in A(3)KO +E/-E aorta. Indomethacin (nonspecific COXs blocker, 10(-5) M), SC-560 (specific COX-1 blocker, 10(-8) M), SQ 29549 (thromboxane prostanoid receptor antagonist, 10(-6) M), and furegrelate (thromboxane synthase inhibitor, 10(-5) M) inhibited Cl-IBMECA-induced contraction significantly. Cl-IBMECA-induced thromboxane B(2) production was also attenuated significantly by indomethacin, SC-560, and furegrelate in WT +E aorta, while having negligible effects in A(3)KO +E aorta. NS-398 (specific COX-2 blocker) produced negligible inhibition of Cl-IBMECA-induced contraction in both WT +E and A(3)KO +E aorta. Cl-IBMECA-induced increase in COX-1 and thromboxane prostanoid receptor expression were significantly inhibited by MRS1523, a specific A(3)AR antagonist in WT +E aorta. Expression of both A(3)AR and COX-1 was located mostly on endothelium of WT and A(3)KO +E aorta. These results demonstrate for the first time the involvement of COX-1 pathway in A(3)AR-mediated contraction via endothelium.

NADPH Oxidase Pathway Is Involved in Aortic Contraction Induced by A3 Adenosine Receptor in Mice

“…The role of A 3 AR in the control of vascular tone has also been demonstrated by our laboratory (Ansari et al, 2007b). In another study, infusion of adenosine in A 3 KO mice has been shown to cause a significant decrease in blood pressure compared with that in WT mice (Zhao et al, 2000).…”

“…We have shown previously that COX-1 plays a role in this A 3 AR response (Ansari et al, 2007b); therefore, it is likely that there may be a relationship between Nox and COX-1. Nox activity has been shown to be activated through the arachidonic acid pathway in cardiac fibroblasts (Colston et al, 2005).…”

“…All experiments were performed in endothelium-intact aortic rings, because we previously showed that activation of A 3 AR leads to endothelium-dependent aortic contraction because of the higher expression of A 3 AR in endothelium compared with that in aortic smooth muscle in mouse (Ansari et al, 2007b). The cumulative concentration-response curves for the selective A 3 AR agonist Cl-IBMECA (10 Ϫ10 -10 Ϫ5 M) were run in parallel in aortic rings from both WT and A 3 KO mice.…”

“…However, the physiological role of A 3 AR in vascular responses is not fully characterized, although its role in myocardial ischemia and reperfusion injury has been demonstrated (Maddock et al, 2003;Zatta et al, 2006). We previously demonstrated that activation of A 3 AR leads to endothelium-dependent aortic contraction through cyclooxygenase-1 (COX-1) using A 3 AR knockout (A 3 KO) mice (Ansari et al, 2007b). A 3 AR has also been shown to inhibit or negatively modulate coronary flow in isolated mouse heart (Talukder et al, 2002), to cause vasoconstriction in hamster arterioles (Shepherd et al, 1996), and to reverse vascular hyporeactivity after hemorrhagic shock in rats (Zhou et al, 2010).…”

Mechanisms involved in the adenosine-induced vasorelaxation to the pig prostatic small arteries

“…Although all four adenosine receptors subtypes are found in vascular smooth muscle cells, only A 2A and A 2B have been shown to be present on endothelial cells [5][6][7]. A 3 purinoceptors have also been localized on endothelial cells in mouse aorta producing smooth muscle contraction, via cyclooxygenase-1 [8].…”