Cardiolipin and phosphatidylethanolamine role in dibucaine interaction with the mitochondrial membrane

Mitochondrial membranes are pointed out as the site of cardiotoxic action of local anaesthetics. Its three main phospholipids components are phosphatidylcholine, phosphatidylethanolamine and cardiolipin. Cardiolipins, in eukaryotes, are only found in mitochondria and are essential for the maintenance of its integrity and dynamics. Fluorescence and nuclear magnetic resonance spectroscopy were used to study the interactions of a local anaesthetics, Dibucaine (DBC), with different mitochondrial membrane models constituted by combinations of its three main lipid components in which cardiolipin was a natural extract (CL_mix). Both CL_mix presence/absence and its percentage in the model membranes were evaluated. Fluorescence spectroscopy showed that DBC lowered the transition temperature of all membrane models understudy. DBC partition showed to be dependent of CL_mix presence and phosphatidylethanolamine:CL ratio. Furthermore, the maximum emission wavelength (λ_max) exhibited a notorious decreased with increasing phospholipid to DBC ratio, in all the membrane models containing CL_mix. Nevertheless, it remained approximately the same in the membrane without CL_mix. This indicates a differential membrane localization of the anaesthetics, dependent on the membrane models used. NMR results showed that DBC interaction and location in the membrane models is mainly influenced by CL_mix presence, and DBC can significant alter lipid systems properties e.g. percentage and type of lipid phase present. Taken all together it was shown that DBC interaction and location are largely dependent on the membrane model system. Furthermore, DBC is able to produce significant changes in the lipidic systems which might help to explain its high toxicity.