Protective roles of adenosine A₁, A_2A, and A₃receptors in skeletal muscle ischemia and reperfusion injury

Abstract

Although adenosine exerts cardio-and vasculoprotective effects, the roles and signaling mechanisms of different adenosine receptors in mediating skeletal muscle protection are not well understood. We used a mouse hindlimb ischemia-reperfusion model to delineate the function of three adenosine receptor subtypes. Adenosine A(3) receptor-selective agonist 2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (Cl-IBMECA; 0.07 mg/kg ip) reduced skeletal muscle injury with a significant decrease in both Evans blue dye staining (5.4 +/- 2.6%, n = 8 mice vs. vehicle-treated 28 +/- 6%, n = 7 mice, P < 0.05) and serum creatine kinase level (1,840 +/- 910 U/l, n = 13 vs. vehicle-treated 12,600 +/- 3,300 U/l, n = 14, P < 0.05), an effect that was selectively blocked by an A(3) receptor antagonist 3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenylethynyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191; 0.05 mg/kg). The adenosine A(1) receptor agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA; 0.05 mg/kg) also exerted a cytoprotective effect, which was selectively blocked by the A(1) antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.2 mg/kg). The adenosine A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680; 0.07 mg/kg)-induced decrease in skeletal muscle injury was selectively blocked by the A(2A) antagonist 2-(2-furanyl)-7-[3-(4-methoxyphenyl)propyl]-7H-pyrazolo[4,3-e] [1,2,4]triazolo[1,5-C]pyrimidin-5-amine (SCH-442416; 0.017 mg/kg). The protection induced by the A(3) receptor was abrogated in phospholipase C-beta2/beta3 null mice, but the protection mediated by the A(1) or A(2A) receptor remained unaffected in these animals. The adenosine A(3) receptor is a novel cytoprotective receptor that signals selectively via phospholipase C-beta and represents a new target for ameliorating skeletal muscle injury.

The A3Adenosine Receptor: History and Perspectives

“…In transfected CHO cells, the ability of both recombinant hA 3 ARs to inhibit cAMP accumulation and endogenous A 3 ARs in RBL-2H3 to stimulate PLC is abolished by pretreatment with pertussis toxin, suggesting a functional coupling of this G i protein receptor (Ali et al, 1990;Zhou et al, 1992;Varani et al, 2000). Furthermore, A 3 ARs signaling could increase phosphatidylinositol-specific PLC activity (Ali et al, 1990;Ramkumar et al, 1993;Abbracchio et al, 1995;Zheng et al, 2007) and cause the release of Ca 2+ from intracellular stores in different cellular models Merighi et al, 2001;Englert et al, 2002;Fossetta et al, 2003;Shneyvays et al, 2004Shneyvays et al, , 2005Kim et al, 2012). In a broad study of site-directed mutagenesis of the A 3 AR, the mutation of the highly conserved tryptophan (W6.48) in the transmembrane domain 6 of GPCRs was first characterized .…”

“…Interestingly, the A 3 AR agonist is a prime candidate for pharmacologic intervention in the first few hours postinjury based on several working hypotheses concerning its mechanism of protection. The pathway involves PLC b2/b3, which in turn activates PKC via diacylglycerol (Zheng et al, 2007). PKC has been shown to activate K ATP channels and cause protection.…”

Adenosine A1 Receptor Activation Attenuates Lung Ischemia-Reperfusion Injury

“…There is evidence for an anti-inflammatory role for A 1 R in lung 5 , liver 15 , kidney 16 , heart 17 , intestine 18 and skeletal muscle. 19 However, other studies have suggested that A 1 R antagonism has beneficial effects in lung and heart IR models. 10,20 In the current study, we used an in vivo hilar clamp model in WT and A 1 R−/− mice to clarify a protective role of exogenous activation of A 1 R in lung IR injury.…”

Does Squatting Worsen Lower Limb Ischemia in Patients with Peripheral Arterial Disease?

“…Once the patient is back to the normal position, there is a possibility of ischemia reperfusion (IR) injury. This IR injury is well known and is mediated by superoxide and adenosine [6]. This cycle of events may result in further damage to the already compromised tissues and accelerate the disease with each and every episode of squatting.…”