Ablation of small conductance calcium-activated potassium type-2 channel (SK₂) delays occurrence of bupivacaine-induced cardiotoxicity in isolated mouse hearts

Abstract

Bupivacaine is frequently used for conducting regional anesthesia. When accidentally injected or excessively absorbed into circulation, bupivacaine can induce severe arrhythmia and potentially lead to cardiac arrest. The specific mechanisms underlying this cardiotoxicity, however, remain to be clarified. We transfected HEK-293 cells to express the small conductance calcium-activated potassium type-2 channel (SK2), and used a whole-cell patch clamp method in order to explore how bupivacaine affected these channels. We subsequently used SK2 knockout mice to explore the relevance of SK2 channels in bupivacaine-induced cardiotoxicity in isolating mouse hearts, mounting them on a Langendorff apparatus, and perfusing them with bupivacaine. Using this system, arrhythmia, asystole, and cardiac functions were monitored. We observed dose-dependent inhibition of SK2 channels by bupivacaine: half-maximal inhibitory concentration (IC50) value = 18.6 μM (95% CI 10.8–32.1). When SK2 knockout (SK2 −/−) or wild-type (WT) mice were perfused with Krebs-Henseleit buffer (KHB), we did not observe any instances of arrhythmia. When SK2 −/− mice or WT were perfused with KHB containing bupivacaine (40 μM), the time to arrhythmia (Tarrhythmia) and time to asystole (Tasystole) were both significantly longer in SK2 −/− mice relative to WT mice ( P < 0.001). Similarly, SK2 −/− mice exhibited a significantly longer time to 25%, 50%, and 75% reductions in heart rate (HR) and rate-pressure product (RPP) relative to WT mice following bupivacaine perfusion ( P < 0.001). These results reveal that bupivacaine was able to mediate a dose-dependent inhibition of SK2 channels in HEK-293 cells, and deletion of SK2 channels can delay bupivacaine-induced cardiotoxicity in isolated mouse hearts.

SK2 channel deletion reduces susceptibility to bupivacaine-induced cardiotoxicity in mouse

“…10,11 Previous study has shown that bupivacaine could inhibit the SK2 current in a concentration-dependent manner in HEK293 cells. 15 After knocking out the SK2 channel gene, the toxicity of bupivacaine in an isolated mouse heart was significantly delayed. To verify the results, an in vivo mouse model was used in this study.…”

“…It was also found that the knockout of the SK2 channel gene could suppress the cardiotoxicity of bupivacaine in the isolated mouse heart. 15 However, this effect was not verified in vivo.…”