Comparison of Cardio-protective Effects Induced by Different Modalities of Sevoflurane Conditioning in Isolated Rat Hearts Subjected to Ischemia-Reperfusion Injury

Objective It remains undetermined whether the combination of anesthetic preconditioning and anesthetic postconditioning could provide greater protection against myocardial ischemia-reperfusion injury than either anesthetic preconditioning or anesthetic postconditioning alone. The objectives of the current study were to compare the cardioprotective effects of sevoflurane preconditioning,sevoflurane postconditioning and sevoflurane preconditioning plus postconditioning,and to examine some possible underlying mechanisms which might explain the relative efficacy of the three different modalities of sevoflurane conditioning. Methods After 10 min of equilibration,isolated rat hearts were randomly assigned into one of the four groups: CTRL group(30 min of ischemia followed by 120 min of reperfusion alone) served as non-treated control; SpreC group(3% sevoflurane preconditioning was administered for 15 min followed by 10 min of washout before ischemia); SpostC group(3% sevoflurane postconditioning was administered during the first 15 min of reperfusion after ischemia); SpreC+SpostC group(the protocols of SpreC and SpostC groups were combined). Hemodynamics was compared within and between groups. Infarct size was determined at the end of 120 min of reperfusion using triphenyltetrazolium chloride(TTC) staining. Lactate dehydrogenase(LDH) and creatine kinase-MB(CK-MB) released from necroticmyocardium,were compared among groups. Time course of the two key pro-survival kinases,namely protein kinase B(PKB/Akt) and extracellular signal-regulated kinase 1/2(ERK 1/2) activation in four groups,were determined by Western blotting analysis. Mitochondrial permeability transition pore(mPTP) status was compared by assaying myocardium nicotinamide adenine dinucleotide(NAD+) content. Results When compared with unprotected CTRL ones,hearts in sevoflurane-treated groups(SpreC,SpostC and SpreC+SpostC) showed significantly better functional recovery(improved LVDP,+dp/dt,–dp/dt,CF,HR and reduced LVEDP),reduced myocardial infarct size,decreased LDH and CK-MB release(P0.05). Comparison of the above-mentioned varibles among three sevoflurane-treated groups showed that,maximal cardioprotection was obtained in SpreC+SpostC group(P0.05),and no difference was found between SpreC and SpostC groups(P0.05). Western blotting analysis revealed that CTRL hearts showed increased PKB/Akt and ERK-1/2 phosphorylation after ischemia-reperfusion when compared to the baseline values. Both SpreC and SpreC+SpostC induced a biphasic response in PKB/Akt and ERK-1/2 phosphorylation during the preconditioning and reperfusion phases following ischemia. SpostC induced only one phase of enhanced PKB/Akt and ERK-1/2 phosphorylation,which occurred after sevoflurane postconditioning. And the effects on phosphorylation of both PKB/Akt and ERK-1/2 induced by SpreC and SpostC was found to be additive at 15 min and 120 min of reperfusion. The CTRL hearts have the lowest myocardial NAD+ content among all groups(P0.05). While SpreC+SpostC hearts retained higher contents of NAD+ than either SpreC or SpostC ones(P0.05),suggesting that the combination of sevoflurane preconditioning and postconditioning had also additive effects on inhibiting mPTP opening induced by ischemia-reperfusion. Conclusions SpreC and SpostC were equally effective in protecting against MIRI,as manifested by functional recovery,infarct size and biomarkers reduction,kinase activation and mPTP inhibition. The combination of SpreC and SpostC offered additive protection in all these above aspects