Reactive Oxygen Species Precede Protein Kinase C-δ Activation Independent of Adenosine Triphosphate-sensitive Mitochondrial Channel Opening in Sevoflurane-induced Cardioprotection

Background: In the current study, the authors investigated the distinct role and relative order of protein kinase C (PKC)-δ adenosine triphosphate-sensitive mitochondrial K + (mito K + ATP) channels, and reactive oxygen species (ROS) in the signal transduction of sevoflurane-induced cardioprotection and specifically addressed their mechanistic link. Methods: Isolated rat trabeculae were preconditioned with 3.8% sevoflurane and subsequently subjected to an ischemic protocol by superfusion of trabeculae with hypoxic, glucose-free buffer (40 min) followed by 60 min of reperfusion. In addition, the acute affect of sevoflurane on PKC-δ and PKC-δ translocation and nitrotyrosine formation was established with use of immunofluorescent analysis. The inhibitors chelerythrine (6 μM), rottlerin (1 μM), 5-hydroxydecanoic acid sodium (100 μM), and n-(2-mercaptopropionyl)-glycine (300 μM) were used to study the particular role of PKC, PKC-δ, mito K + ATP, and ROS in sevoflurane-related intracellular signaling. Results: Preconditioning of trabeculae with sevoflurane preserved contractile function after ischemia. This contractile preservation was dependent on PKC-δ activation, mito K + ATP channel opening, and ROS production. In addition, on acute stimulation by sevoflurane, PKC-δ but not PKC-ε translocated to the sarcolemmal membrane. This translocation was inhibited by PKC inhibitors and ROS scavenging but not by inhibition of mito K + ATP channels. Furthermore, sevoflurane directly induced nitrosylation of sarcolemmal proteins, suggesting the formation of peroxynitrite. Conclusions: In sevoflurane-induced cardioprotection, ROS release but not mito K + ATP channel opening precedes PKC-δ activation. Sevoflurane induces sarcolemmal nitrotyrosine formation, which might be involved in the recruitment of PKC-δ to the cell membrane

Cardioprotection via activation of protein kinase C-δ depends on modulation of the reverse mode of the Na+/Ca2+ exchanger

BACKGROUND - Pretreatment with the volatile anesthetic sevoflurane protects cardiomyocytes against subsequent ischemic episodes caused by a protein kinase C (PKC)-δ mediated preconditioning effect. Sevoflurane directly modulates cardiac Ca handling, and because Ca also serves as a mediator in other cardioprotective signaling pathways, possible involvement of the Na/Ca exchanger (NCX) in relation with PKC-δ in sevoflurane-induced cardioprotection was investigated. METHODS AND RESULTS - Isolated right ventricular rat trabeculae were subjected to simulated ischemia and reperfusion (SI/R), consisting of superfusion with hypoxic glucose-free buffer for 40 minutes after rigor development, followed by reperfusion with normoxic glucose containing buffer. Preconditioning with sevoflurane before SI/R improved isometric force development during contractile recovery at 60 minutes after the end of hypoxic superfusion (83±7% [sevo] versus 57±2% [SI/R];n=8; P<0.01). Inhibition of the reverse mode of the NCX by KB-R7943 (10 μmol/L) or SEA0400 (1 μmol/L) during preconditioning attenuated the protective effect of sevoflurane. KB-R7943 and SEA0400 did not have intrinsic effects on the contractile recovery. Furthermore, inhibition of the NCX in trabeculae exposed to sevoflurane reduced sevoflurane-induced PKC-δ translocation toward the sarcolemma, as demonstrated by digital imaging fluorescent microscopy. The degree of PKC-δ phosphorylation at serine as determined by western blot analysis was not affected by sevoflurane. CONCLUSIONS - Sevoflurane-induced cardioprotection depends on the NCX preceding PKC-δ translocation presumably via increased NCX-mediated Ca influx. This may suggest that increased myocardial Ca load triggers the cardioprotective signaling cascade elicited by volatile anesthetic agents similar to other modes of preconditioning