Sevoflurane induces cardioprotection through reactive oxygen species-mediated upregulation of autophagy in isolated guinea pig hearts.

PURPOSE: Sevoflurane increases reactive oxygen species (ROS), which mediate cardioprotection against myocardial ischemia-reperfusion injury. Emerging evidence suggests that autophagy is involved in cardioprotection. We examined whether reactive oxygen species mediate sevoflurane preconditioning through autophagy. METHODS: Isolated guinea pigs hearts were subjected to 30 min ischemia followed by 120 min reperfusion (control). Anesthetic preconditioning was elicited with 2 % sevoflurane for 10 min before ischemia (SEVO). The ROS-scavenger, N-(2-mercaptopropionyl) glycine (MPG, 1 mmol/l), was administered starting 30 min before ischemia to sevoflurane-treated (SEVO + MPG) or non-sevoflurane-treated (MPG) hearts. Infarct size was determined by triphenyltetrazolium chloride stain. Tissue samples were obtained after reperfusion to determine autophagy-related protein (microtubule-associated protein light chain I and II: LC3-I, -II) and 5' AMP-activated protein kinase (AMPK) expression using Western blot analysis. Electron microscopy was used to detect autophagosomes. RESULTS: Infarct size was significantly reduced and there were more abundant autophagosomes in SEVO compared with control. Western blot analysis revealed that the ratio of LC3-II/I and phosphorylation of AMPK were significantly increased in SEVO. These effects were abolished by MPG. CONCLUSIONS: Sevoflurane induces cardioprotection through ROS-mediated upregulation of autophagy.

Sevoflurane confers additive cardioprotection to ethanol preconditioning associated with enhanced phosphorylation of glycogen synthase kinase-3ß and inhibition of mitochondrial permeability transition pore opening.

OBJECTIVE: The purposes of this study were to investigate whether sevoflurane (SEVO) enhances moderate-dose ethanol (EtOH) preconditioning and whether this additional cardioprotection is associated with glycogen synthase kinase-3ß (GSK-3ß), protein kinase B (Akt), mammalian target of rapamycin (mTOR), 70-kDa ribosomal s6 kinase-1 (p70s6K), and/or mitochondrial permeability transition pore (MPTP) opening. DESIGN: In vitro study using an isolated heart Langendorff preparation. SETTING: University research laboratory. PARTICIPANTS: Male guinea pigs (n = 170). INTERVENTIONS: Isolated perfused guinea pig hearts underwent 30-minute ischemia and 120-minute reperfusion (control). The EtOH group received 5% EtOH in the drinking water for 8 weeks. Anesthetic preconditioning was elicited by a 10-minute exposure to 2% SEVO in EtOH (EtOH + SEVO group) or non-EtOH (SEVO group) hearts. The inhibition of GSK-3ß phosphorylation and mTOR was achieved with LY294002 and rapamycin, respectively. GSK-3ß, Akt, mTOR, and p70s6K expressions were determined by western blot. Calcium-induced MPTP opening was assessed in isolated calcein-loaded mitochondria. MEASUREMENTS AND MAIN RESULTS: After ischemia-reperfusion, the EtOH, SEVO, and EtOH + SEVO groups had higher left ventricular developed pressure recovery and lower end-diastolic pressure versus the control group. Infarct size was smaller in the EtOH and SEVO groups versus control and even smaller in the EtOH + SEVO group. Phosphorylation of GSK-3ß and Akt, but not mTOR and p70s6K, was increased in the EtOH and SEVO groups. Phosphorylation of GSK-3ß, but not mTOR and p70s6K, was further increased in the EtOH + SEVO group. The EtOH and SEVO groups exhibited a smaller calcium-induced MPTP opening, and the EtOH + SEVO presented an even smaller MPTP opening. CONCLUSIONS: SEVO and chronic EtOH preconditioning offer additive cardioprotection. This effect is associated with an increased GSK-3ß phosphorylation and an inhibition of MPTP opening.

Aprotinin abolishes sevoflurane postconditioning by inhibiting nitric oxide production and phosphorylation of protein kinase C-delta and glycogen synthase kinase 3beta.

BACKGROUND: It remains controversial whether aprotinin use during cardiac surgery is cardioprotective or detrimental. In contrast, volatile anesthetics may offer cardioprotection perioperatively. Increased nitric oxide, protein kinase C activation, and glycogen synthase kinase 3beta inhibition play a role in sevoflurane-induced cardioprotection. The authors investigated whether aprotinin affects sevoflurane postconditioning. METHODS: Isolated guinea pig hearts underwent 30 min of global ischemia and 120 min of reperfusion (control [CTL]). Postconditioning was elicited with sevoflurane (2%) for 2 min at reperfusion onset (POST). Aprotinin (250 kallikrein inhibitor units/ml) was administered for 5 min at reperfusion onset (POST + APRO and CTL + APRO). In additional experiments, both sevoflurane and aprotinin were given before ischemia and throughout the reperfusion period (SEVO + APRO (throughout)) to mimic clinical conditions. Left ventricular developed and end-diastolic pressures and infarct size were measured. Western blot analysis determined phosphorylated protein kinase C-delta, protein kinase C-delta, Akt, and glycogen synthase kinase 3beta expression. Nitric oxide production during reperfusion was measured by nitric oxide sensor. RESULTS: After ischemia-reperfusion, POST had significantly higher left ventricular developed (56 +/- 11 vs. 26 +/- 8 mmHg [mean +/- SD]) and lower end-diastolic pressures (20 +/- 9 vs. 47 +/- 15 mmHg) and reduced infarct size (15 +/- 3% vs. 41 +/- 10%) versus CTL. Aprotinin abolished these improvements. Expressions of phospho-Akt (activated), phospho-protein kinase C-delta (activated), and phospho-glycogen synthase kinase 3beta (inhibited) were significantly increased in POST. Aprotinin attenuated these increased expressions. Nitric oxide production after reperfusion was higher in POST than in CTL, but not in POST + APRO. CONCLUSIONS: Aprotinin abolishes sevoflurane postconditioning, associated with inhibited phosphorylation of Akt, protein kinase C-delta, and glycogen synthase kinase 3beta and reduced nitric oxide production.

Acute memory phase of sevoflurane preconditioning is associated with sustained translocation of protein kinase C-alpha and epsilon, but not delta, in isolated guinea pig hearts.

BACKGROUND AND OBJECTIVE: Anaesthetic preconditioning (APC) exerts cardioprotective effects by reducing infarct size and improving recovery of contractile function after ischaemia-reperfusion. The interval between brief exposure to volatile anaesthetic and sustained ischaemia, the acute memory phase, is dependent on intracellular signalling mediating this cardioprotection. Intramyocyte translocation of protein kinase C (PKC) is known to be a key mediator in APC. We examined the relationship between the time frame of the acute memory phase of sevoflurane preconditioning and intramyocyte translocation of PKC-alpha, delta and epsilon to the particulate fraction. METHODS: Isolated perfused guinea pig hearts were subjected to 30 min ischaemia and 120 min reperfusion. APC was elicited with one minimum alveolar concentration sevoflurane for 10 min. Washout times of 10, 30, 60 and 90 min were studied. Contractile recovery was assessed by monitoring left ventricular developed pressures. Infarct size was determined by triphenyltetrazolium chloride staining. Translocation of PKC was examined by western blot analysis. RESULTS: After ischaemia-reperfusion, left ventricular developed pressure recovered to a greater degree with APC compared with control for washout times of 10 and 30 min, but not 60 and 90 min. Similarly, infarct size was reduced for washout times of 10 and 30 min, but not 60 and 90 min. Sustained translocation of PKC-alpha and epsilon, but not delta, was associated with the time frame of the acute memory phase. CONCLUSION: The acute memory phase of sevoflurane preconditioning is limited to less than 60 min. Sustained translocation of PKC-alpha and epsilon, but not delta, correlates with this acute memory phase of sevoflurane preconditioning.

Induction of autophagy restores the loss of sevoflurane cardiac preconditioning seen with prolonged ischemic insult.

Sevoflurane preconditioning against myocardial ischemia-reperfusion injury is lost if the ischemic insult is too long. Emerging evidence suggests that induction of autophagy may also confer cardioprotection against ischemia-reperfusion injury. We examined whether induction of autophagy prolongs sevoflurane preconditioning protection during a longer ischemic insult. Isolated guinea pigs hearts were subjected to 30 or 45 min ischemia, followed by 120 min reperfusion (control). Anesthetic preconditioning was elicited with 2% sevoflurane for 10 min prior to ischemia (SEVO-30, SEVO-45). Chloramphenicol (autophagy upregulator, 300 µM) was administered starting 20 min before ischemia and throughout reperfusion in SEVO-45 (SEVO-45+CAP). To inhibit autophagy, 3-methyladenine (10 µM) was administered during sevoflurane administration in SEVO-45+CAP. Infarct size was determined by triphenyltetrazolium chloride stain. Tissue samples were obtained before ischemia to determine autophagy-related protein (microtubule-associated protein light chain I and II: LC3-I, II), Akt and glycogen synthase kinase 3ß (GSK3ß) expression using Western blot analysis. The effect of autophagy on calcium-induced mitochondrial permeability transition pore (MPTP) opening in isolated calcein-loaded mitochondria was assessed. Electron microscopy was used to detect autophagosomes. Infarct size was significantly reduced in SEVO-30, but not in SEVO-45. Chloramphenicol restored sevoflurane preconditioning lost by 45 min ischemia. There were more abundant autophagozomes and LC3-II expression was significantly increased in SEVO-45+CAP. Induction of autophagy before ischemia enhanced GSK3ß phosphorylation and inhibition of calcium-induced MPTP opening. These effects were abolished by 3-methyladenine. Pre-ischemic induction of autophagy restores sevoflurane preconditioning lost by longer ischemic insult. This effect is associated with enhanced inhibition of MPTP by autophagy.

Direct evidence for inhibition of mitochondrial permeability transition pore opening by sevoflurane preconditioning in cardiomyocytes: comparison with cyclosporine A.

To assess whether sevoflurane preconditioning is associated with inhibition of mitochondrial permeability transition pore (MPTP), the effects of sevoflurane were compared with those of cyclosporine A, a known inhibitor of MPTP opening. Isolated perfused guinea pig hearts underwent 30 min global ischemia and 120 min reperfusion (control). Sevoflurane preconditioning was elicited by administration of 2% sevoflurane for 10 min with 10 min washout before ischemia (sevoflurane). A preconditioning-like cardioprotection was also induced by administering cyclosporine A (0.2 µM) for 15 min, starting 5 min before ischemia and for 10 min after the onset of reperfusion (cyclosporine A). Left ventricular developed and end-diastolic pressures, coronary flow and infarct size were measured. Expressions of Akt and glycogen synthase kinase 3ß (GSK3ß), known mediators of inhibition of MPTP opening, were determined by Western blot analysis. GSK3ß inhibition was achieved with LY294002. The effects of sevoflurane and cyclosporine A on calcium-induced MPTP opening in isolated calcein-loaded mitochondria were assessed. After ischemia-reperfusion, sevoflurane and cyclosporine A had higher left ventricular developed pressure. Infarct size was significantly reduced in sevoflurane and cyclosporine A vs. control. This was abolished by LY294002 in sevoflurane, but not in cyclosporine A. Akt and GSK3ß phosphorylation after reperfusion were significantly increased in sevoflurane and cyclosporine A. Ca²âº-induced reduction in calcein fluorescence was significantly attenuated in sevoflurane and cyclosporine A. Preconditioning agents, sevoflurane and cyclosporine A increase the threshold of calcium-induced MPTP opening to a similar extent. This effect by sevoflurane, but not cyclosporine A is at least partially mediated by GSK3ß inactivation.