Adenosine A ₁ Receptor Activation Induces Delayed Preconditioning in Rats Mediated by Manganese Superoxide Dismutase

Abstract

Background-We have previously described a second window of protection against infarction in rabbits 24 to 72 hours after adenosine A 1 receptor (A 1 R) activation. In this study, we examined the potential role of the mitochondrial antioxidant manganese superoxide dismutase (Mn-SOD) as a potential end effector in mediating this protection. Methods and Results-Rats were treated with an intravenous bolus of the A 1 R agonist 2-chloro-N 6 -cyclopentyladenosine (CCPA, 75 g/kg) or saline vehicle. They were also given a 5 mg/kg IV infusion of a 22-mer phosphorothioate oligodeoxynucleotide (ODN) with sequence antisense to the initiation site of rat Mn-SOD mRNA. Sense ODN and scrambled ODN were used as controls. Twenty-four hours later, hearts were isolated and perfused with buffer at constant pressure and subjected to 35 minutes of regional ischemia and 2 hours of reperfusion. Treatment with CCPA compared with saline vehicle (control) significantly reduced infarct size, expressed as percentage of myocardium at risk (22.3Ϯ3.3% versus 42.1Ϯ3.8%, respectively; Pϭ0.001). This protection was completely abolished by prior treatment with antisense ODN, which had no effect on its own. Neither sense ODN nor scrambled ODN had an effect on the CCPA-induced delayed cardioprotection. In separate animals, 24 hours after the same treatment, hearts were assayed for Mn-SOD content and activity. CCPA treatment induced a significant increase in myocardial Mn-SOD content and activity compared with the control condition; this increase was abolished by pretreatment with antisense ODN. Conclusions-This is the first study to show that transient A 1 R activation induces delayed cardioprotection in the rat. These results strongly suggest an important role for mitochondrial Mn-SOD as a potential end effector of this protection.

Sulindac confers high level ischemic protection to the heart through late preconditioning mechanisms

“…Several studies have demonstrated a cardio-protective function for Hsp27, either through its exogenous overexpression from a transgene, or through its activation in preconditioning (25)(26)(27). In addition, this chaperone is known to contribute to preconditioning induced by a range of stimuli including opioids, isoproterinol, and ischemia (28)(29)(30). The protective effect of Hsp27 may include an anti-apoptotic role, which has been implicated in studies reporting an interaction of Hsp27 with cytochrome c and inhibition of apoptosome function (31).…”

Insulin-induced myocardial protection in isolated ischemic rat hearts requires p38 MAPK phosphorylation of Hsp27

“…Ser15 and Ser85 phosphorylation of Hsp27 by MAPKAPK-2 is the key mechanism in reduction of apoptosis and facilitation of F-actin remodeling that protects cells from doxorubicin toxicity (69). Further evidence for phosphorylation of Hsp27 having a role in myocardial protection is provided by studies on activation of the p44/42 MAPK (ERK1/2) and p38 MAPK pathways by atorvastatin (20) and on activation of the adenosine A 1 receptor and p38 MAPK (14).…”

Gene expression profile of mouse myocardium with transgenic overexpression of A1adenosine receptors

“…We hypothesized that transgenic cardiac-specific overexpression of A 1 ARs would likely produce demonstrable changes in gene expression related to cardioprotective mechanisms based upon two lines of evidence: 1) delayed cardioprotection by preconditioning or A 1 AR activation relies upon de novo protein synthesis (3,16), which in turn is often dependent upon altered gene transcription; and 2) adenosine receptor activation has been shown to alter gene expression of atrial natriuretic peptide (ANP) (17), Na ϩ -I Ϫ symporter (6), MIP-1␣ (21), and IL-6 (19). In the current study, we have also demonstrated a decrease in the transcript level for MIP-1␣ and an increase in gene expression of preproANP with increased levels of adenosine receptors.…”

“…For example, in the late phase of ischemic preconditioning new protein synthesis is required for cardioprotection (16). Furthermore, it has been demonstrated that adenosine-mediated delayed protection is dependent upon de novo protein synthesis (3). These changes in protein translation also result from changes in gene transcription.…”