Involvement of the Mitochondrial Ca2+-Independent Phospholipase iPLA2 in the Induction of Mitochondrial Permeability Transition Pore by Long-Chain Acylcarnitines

It is known that activated derivatives of long-chain fatty acids acylcarnitines (LCAC) are considered the most toxic, which, along with calcium, can participate in the induction of the mitochondrial pore, involving various types of phospholipases. In this study, the effect of inhibitors of Ca²⁺-independent and Ca²⁺-dependent phospholipases, as well as an inhibitor of carnitine palmitoyltransferase on the induction of pores with D,L-palmitoylcarnitine (PC, C16:0) was investigated. In experiments on isolated rat liver mitochondria, the effect of PC on mitochondrial respiration rate, membrane potential (ΔΨm) and mitochondrial swelling during oxidation of glutamate and pyruvate or succinate was studied. It was shown that inhibitors of carnitine palmitoyltransferase-1 etomoxir 2, Ca²⁺-dependent phospholipase cPLA2 aristolochic acid or Ca²⁺-independent phospholipase iPLA2γ bromoenol lactone and PACOCF3 caused an increase in critical concentrations of D,L-palmitoylcarnitine (PC*), which were required to decrease the membrane potential and induce mitochondrial swelling. In the ADP activated state 3 (ADP + Mg²⁺ + hexokinase), Ethomoxir 2 and aristolochic acid promoted the inhibition of respiration and dissipation of membrane potential caused by excess of PC, while phospholipase inhibitors iPLA2γ PACOCF3 and bromoenol lactone provided a pronounced protective effect. Inhibition of iPLA2γ prevented the decrease of ΔΨm and inhibition of respiration caused by PC. Thus, the results obtained indicated the involvement of mitochondrial phospholipase iPLA2γ in the induction of the mitochondrial pore by long-chain acylcarnitines.