Effect of adenosine A2A receptor agonist (CGS) on ischemia/reperfusion injury in isolated rat liver

Abstract

Ischemia/reperfusion injury during liver transplantation is a major cause of primary nonfunctioning graft for which there is no effective treatment other than retransplantation. Adenosine prevents ischemia-reperfusion-induced hepatic injury via its A2A receptors. The aim of this study was to investigate the role of A2A receptor agonist on apoptotic ischemia/reperfusion-induced hepatic injury in rats. Isolated rat livers within University of Wisconsin solution were randomly divided into four groups: (1) continuous perfusion of Krebs-Henseleit solution through the portal vein for 165 minutes (control); (2) 30-minute perfusion followed by 120 minutes of ischemia and 15 minutes of reperfusion; (3) like group 2, but with the administration of CGS 21680, an A2A receptor agonist, 30 microg/100 ml, for 1 minute before ischemia; (4) like group 3, but with administration of SCH 58261, an A2A receptor antagonist. Serum liver enzyme levels were measured by biochemical analysis, and intrahepatic caspase-3 activity was measured by fluorometric assay; apoptotic cells were identified by morphological criteria, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) fluorometric assay, and immunohistochemistry for caspase-3. Results showed that at 1 minute of reperfusion, there was a statistically significant reduction in liver enzyme levels in the animals pretreated with CGS (p < 0.05). On fluorometric assay, caspase-3 activity was significantly decreased in group 3 compared to group 2 (p < 0.0002). The reduction in postischemic apoptotic hepatic injury in the CGS-treated group was confirmed morphologically, by the significantly fewer apoptotic hepatocyte cells detected (p < 0.05); immunohistochemically, by the significantly weaker activation of caspase-3 compared to the ischemic group (p < 0.05); and by the TUNEL assay (p < 0.05). In conclusion, the administration of A2A receptor agonist before induction of ischemia can attenuate postischemic apoptotic hepatic injury and thereby minimize liver injury. Apoptotic hepatic injury seems to be mediated through caspase-3 activity.

Pharmacological postconditioning protects against hepatic ischemia/reperfusion injury

“…By using an in vitro experimental model mimicking hepatocyte reoxygenation injury after cold hypoxia, we can now report on the possibility of protecting against hepatocyte reoxygenation injury by the addition of the adenosine A2A receptor agonist CGS21680 at the beginning of reoxygenation. Previous studies have shown that adenosine A2A receptor stimulation induces hepatic preconditioning both in vitro and in vivo8, 21, 22, 34, 35 and prevents cell death by both necrosis and apoptosis 21, 36. Such protective effects are mediated by the capacity of the adenosine A2A receptor to activate cyclic adenosine monophosphate/protein kinase A, PI3K/Akt, protein kinase Cε (PKCε), and PKCδ, which in turn lead to the stimulation of a network of signals involving p38 mitogen‐activated protein kinase 8, 21, 37.…”

Mouse hepatocytes and LSEC proteome reveal novel mechanisms of ischemia/reperfusion damage and protection by A2aR stimulation

“…Ischemic preconditioning demonstrated its efficacy in several models [2][3][4][5][6][7] and different pharmacological preconditioning approaches have been developed to overcome limitations of surgical preconditioning [2][3][4][5][6][7]13]. Previous studies have shown that pretreatment with the A2aR agonist CGS21680 enhanced tolerance against hepatic IR damage [4,11]. This work describes, for the first time, the proteome alterations of mouse HP and LSEC isolated from livers exposed to IR in the presence or absence of A2aR stimulation, elucidating the liver cell contribution to IR damage and hepatoprotection by pharmacological preconditioning.…”

“…To this respect, pharmacological induction of liver preconditioning could represent a more efficient and reliable technique. In vitro and in vivo studies have established a key role of the adenosine A2a receptor (A2aR) stimulation as an approach for pharmacological induction of liver preconditioning [4,[10][11][12]. In fact, even short periods of hypoxia lead to the enhanced breakdown of adenine nucleotides to adenosine, because of the decreased production of ATP.…”

Regulation of Leukocyte Function by Adenosine Receptors

“…A 2A agonists have also been found to reduce injury following ischemia or trauma in liver (Alchera et al, 2008; Ben-Ari et al, 2005; Cao et al, 2009; Day et al, 2004, 2005b; Harada et al, 2000), kidney (Day et al, 2003, 2005a; Okusa et al, 1999, 2001), skin (Peirce et al, 2001), lung (Gazoni et al, 2008; Rivo et al, 2007; Sharma et al, 2010), heart (Patel et al, 2009; Rork et al, 2008; Xi et al, 2009; Yang et al, 2006b), intestine (Di Paola et al, 2010), and spinal cord (Cassada et al, 2002; Li et al, 2006; Reece et al, 2008). The cellular targets of A 2A Rs initially were not clear.…”