Biphasic behavior of bupivacaine and cardiolipin-containing biomimetic membrane interaction

Intravenous administration of bupivacaine, a lipophilic long-acting local anesthetic can cause serious cardiotoxicity. However, the mechanisms underlying this response are uncertain. Cardiolipin (CL) is the predominant polyglycerophospholipid that exists in the mitochondrial membrane. In a recent study we reported that bupivacaine, but not lidocaine, disrupts cardiolipin-containing liposomes by increasing membrane permeability. This study further investigated the change in surface pressure of phospholipid monolayers after incorporation of local anesthetics. From this study, we found that relatively high concentrations of bupivacaine evoked a biphasic behavior when model membrane contained CL. At low bupivacaine concentration, such biphasic behavior was not observed even though surface pressure increased initially. In contrast, lidocaine had no significant effects on membrane surface pressure and integrity even in the presence of CL. These data are consistent with our previous findings using liposomes. We suggest that in vivo cardiotoxic effects of bupivacaine on cardiolipin-containing mitochondrial membranes can be related and predicted from in vitro biphasic behavior of bupivacaine interaction with biomimetic phospholipid monolayers.