Background-5ЈAMP-activated protein kinase (AMPK), a well-known regulator of cellular energy status, is also implicated in ischemic preconditioning leading to cardioprotection. We hypothesized that AMPK is involved in anesthetic-induced cardioprotection and that this activation is mediated by reactive oxygen species (ROS). Methods and Results-Isolated Langendorff-perfused rat hearts were subjected to 35 minutes of global ischemia (I) followed by 120 minutes of reperfusion (I/R). Hearts were assigned to a control group (Con) or a sevoflurane (Sevo) group receiving 3 times 5-minute episodes of sevoflurane (2.5vol%) before I/R. Phosphorylation of both AMPK and endothelial nitric oxide synthase (eNOS) were determined by Western blot analysis. Cardioprotection was assessed after I/R from recovery of left ventricular pressure and from infarct size (triphenyltetrazolium chloride staining). In the control group, ischemia resulted in a 2-fold increase in phosphorylation levels of AMPK (Con 0.13Ϯ0.01 versus Con-I 0.28Ϯ0.05, PϽ0.05), which was sustained after 120 minutes of reperfusion (Con-I/R 0.26Ϯ0.02, PϽ0.05). Sevoflurane preconditioning had no affect on AMPK phosphorylation before ischemia (Sevo 0.12Ϯ0.03, PϾ0.05), but almost doubled the increase in AMPK phosphorylation relative to control after ischemia (Sevo-I 0.48Ϯ0.09, PϽ0.05), an effect that was sustained after reperfusion (Sevo-I/R 0.49Ϯ0.12, PϽ0.05). The AMPK-inhibitor compound C (10 mol/L) reduced the sevoflurane-mediated increase in phosphorylation of AMPK and its target eNOS and abolished cardioprotection. The ROS-scavenger n-(2-mercaptopropionyl)-glycine (1 mmol/L) blunted the sevoflurane-mediated increase in AMPK and eNOS phosphorylation and prevented cardioprotection. Conclusions-Sevoflurane-induced AMPK activation protects the heart against ischemia and reperfusion injury and relies on upstream production of ROS. (Circulation. 2009;120[suppl 1]:S10-S15.)

Background and Goal of Study: Recent investigations showed that sevoflurane can induce pharmacological preconditioning in myocardium. However, the effects of sevoflurane on myocardial ischemia and reperfusion injury have not been well studied. This study was designed to investigate the incidence and severity of ventricular arrhythmias observed during ischemia and reperfusion in an in vivo rabbit model. A second goal of this investigation was to assess whether sevoflurane can influence ischemia and reperfusion-induced arrhythmias and reduce the intensity of myocardial infarct size following ischemia and reperfusion. Materials and Methods: Rabbits received regional ischemia by 30 min of the LAD occlusion followed by 3 hrs of reperfusion under ketamine/xylazine (k/x) or sevoflurane anaesthesia. Before this, rabbits were randomized into five groups (n=6, respectively). In the control group and sevoflurane group, rabbits were subjected to 30 min of LAD occlusion and 3 hrs of reperfusion under k/x or sevoflurane anaesthesia, respectively (C,S). The ischemia-preconditioned (IP) rabbits underwent 5 min LAD occlusion followed by 10 min of reperfusion (C-IP,S-IP). In the C-SP (sevoflurane-preconditioned) group, 30 min of sevoflurane exposure at a 1.5% end-tidal concentration was followed by 15 min of washout by 3 hrs of reperfusion under k/x anaesthesia. At the end of the 3-hrs reperfusion period, area at risk (R) was delineated by Evan's blue and infarct size (I) determined by tetrazolium staining. Results and Discussion: The hemodynamics and rate pressure product did not alter significantly at any point among all the groups. R revealed no significant difference among all groups. I/Rvalues of each group were 59.2±4.8% in Group C, 30.9±3.695% in Group S, 59.2±3.3% in Group C-IP, 16.8±4.l % in Group S-IP and 45.2±3.0% in Group C-SP. Compared with group C, myocardial protective effect was observed in groups of S, C-IP, S-IP and C-SP. The incidence of arrhythmias during myocardial ischemia were 50% in C, 16% in S, 83% in C-IP, 0% in S-IP, 50% in C-SP. As for the incidence of arrhythmias during reperfusion was 67% in C, 0% in S, 67% in C-IP, 0% in S-IP, 67% in C-SP. These results suggest that sevoflurane exposure reduces arrhythmias during not only ischemia but reperfision in rabbit heart. Conclusion(s): It was suggested that sevoflurane protects the ischemic rabbit myocardium from infarction as well as ventricular arrhythmias. References:

The myocardium possesses intrinsic protective mechanisms against ischemia and reperfusion injury (I/R). 5′AMP-activated protein kinase (AMPK) is known as regulator of cellular energy status and is reduced during diabetes mellitus. Recently, AMPK is also implicated in ischemic preconditioning leading to cardioprotection against I/R. We hypothesize that AMPK is involved in anesthetic-induced cardioprotection and that this AMPK activation is evoked by production of reactive oxygen species (ROS). Isolated Langendorff-perfused rat hearts were subjected to 35 minutes of global ischemia followed by 120 minutes of reperfusion. Hearts were divided into 2 groups: a Control group and a Sevo group receiving three times 5-minute episodes of 2.5 vol% sevoflurane before I/R. AMPK phosphorylation was determined with Western Blot analysis. Cardioprotection was assessed as recovery of left ventricular pressure after I/R and as infarct size using triphenyltetrazolium chloride staining. In the Control group, I/R resulted in a twofold increase in phosphorylation levels of AMPK (Control 1.0 ± 0.1 vs. Control-I/R: 2.3 ± 0.1 a.u., n = 4, p < 0.05). Sevoflurane preconditioning did not immediately, prior to ischemia, affect the AMPK phosphorylation (Sevo 0.9 ± 0.2 vs. Control 1.0 ± 0.2, n = 6), but doubled the increase in AMPK phosphorylation to control after ischemia (Sevo-I: 2.0 ± 0.5 (vs. Control-I), n = 6, p < 0.05), as well as after I/R (Sevo-I/R: 2.1 ± 0.3 vs. (Control-I/R), n = 6, p < 0.05). The AMPK-inhibitor compound C (1 and 10 μM) reduced the increase in AMPK phosphorylation and abolished the cardioprotection derived from functional recovery and infarct size. In addition, the ROS-scavenger n-(2-mercaptopropionyl)-glycine (MPG, 1mM) also reduced the sevoflurane-mediated increase in AMPK phosphorylation and completely prevented cardioprotection. These results demonstrate for the first time a direct link between AMPK activation and the production of ROS in cardioprotection. We conclude that anesthetic-induced AMPK activation protects the heart against I/R and relies on production of ROS, which might be especially important in the context of impaired cardioprotection in the diabetic myocardium.