mrs-1191 and Disease-Models--Animal

We reported previously that hypertonic saline (HS) treatment can prevent or upregulate the function of polymorphonuclear neutrophils (PMNs) via A2a-type adenosine receptors or A3-type adenosine receptors (A3R), respectively. A3R translocate to the cell surface upon PMN stimulation, and thus, HS promotes PMN responses under conditions of delayed HS treatment. Here we investigated if inhibition of A3R improves the protective effects of HS resuscitation in a mouse sepsis model. We found that HS nearly triples extracellular adenosine concentrations in whole blood and that inhibition of A3R with the selective antagonist MRS-1191 dose dependently improves the inhibitory effect of HS. MRS-1191 at a concentration of 1 nM enhanced the inhibitory effect of HS and reduced stimulatory effects of delayed HS treatment. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found that MRS-1191 reduces acute lung injury and PMN accumulation in lung tissue. Whereas delayed HS treatment (4 mL/kg of 7.5% NaCl) of mice 1 h after CLP aggravated PMN accumulation, lung tissue damage, and mortality 24 h after CLP, infusion of MRS-1191 (2 ng/kg body weight) combined with HS reduced these detrimental effects of delayed HS treatment. Our data thus show that A3 receptor antagonists can strengthen the beneficial effects of HS resuscitation by avoiding stimulatory adverse effects that result from delayed HS administration.

Topics: Adenosine A3 Receptor Antagonists; Animals; Cell Membrane; Dihydropyridines; Disease Models, Animal; Dose-Response Relationship, Drug; Humans; Lung; Male; Mice; Neutrophil Infiltration; Neutrophils; Receptor, Adenosine A3; Resuscitation; Saline Solution, Hypertonic; Sepsis; Time Factors

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.

Topics: Adenosine; Animals; Dihydropyridines; Disease Models, Animal; Hindlimb; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Skeletal; Phenethylamines; Phospholipase C beta; Pyrazoles; Pyrimidines; Receptor, Adenosine A1; Receptor, Adenosine A2A; Receptor, Adenosine A3; Reperfusion Injury; Signal Transduction; Xanthines