Long-chain acylcarnitines determine ischaemia/reperfusion-induced damage in heart mitochondria

Abstract

The accumulation of long-chain fatty acids (FAs) and their CoA and carnitine esters is observed in the ischaemic myocardium after acute ischaemia/reperfusion. The aim of the present study was to identify harmful FA intermediates and their detrimental mechanisms of action in mitochondria and the ischaemic myocardium. In the present study, we found that the long-chain acyl-CoA and acylcarnitine content is increased in mitochondria isolated from an ischaemic area of the myocardium. In analysing the FA derivative content, we discovered that long-chain acylcarnitines, but not acyl-CoAs, accumulate at concentrations that are harmful to mitochondria. Acylcarnitine accumulation in the mitochondrial intermembrane space is a result of increased carnitine palmitoyltransferase 1 (CPT1) and decreased carnitine palmitoyltransferase 2 (CPT2) activity in ischaemic myocardium and it leads to inhibition of oxidative phosphorylation, which in turn induces mitochondrial membrane hyperpolarization and stimulates the production of reactive oxygen species (ROS) in cardiac mitochondria. Thanks to protection mediated by acyl-CoA-binding protein (ACBP), the heart is much better guarded against the damaging effects of acyl-CoAs than against acylcarnitines. Supplementation of perfusion buffer with palmitoylcarnitine (PC) before occlusion resulted in a 2-fold increase in the acylcarnitine content of the heart and increased the infarct size (IS) by 33%. A pharmacologically induced decrease in the mitochondrial acylcarnitine content reduced the IS by 44%. Long-chain acylcarnitines are harmful FA intermediates, accumulating in ischaemic heart mitochondria and inducing inhibition of oxidative phosphorylation. Therefore, decreasing the acylcarnitine content via cardioprotective drugs may represent a novel treatment strategy.

Novel Molecular Interactions of Acylcarnitines and Fatty Acids with Myoglobin

“…4). Overall, we find that the headgroup of fatty acids tend to show a higher percentage of hydrogen bonding with Lys 45 or Lys 63 than their respective acylcarnitines (Fig. 4).…”

“…In MD simulations, the carboxyl headgroup in LCFA and long-chain acylcarnitines (i.e. C12 or longer) exhibited hydrogen-bonding interactions with Lys 45 or Lys 63 . The results showed that these headgroups switched between Lys 45 and Lys 63 during the 100-ns simulation, with an average dwelling time on the order of 25 ns.…”

“…The results showed that these headgroups switched between Lys 45 and Lys 63 during the 100-ns simulation, with an average dwelling time on the order of 25 ns. During the 100-ns simulations, the majority of the H-bonding is associated with Lys 45 , with some exceptions (Fig. 4).…”

“…1, B and D). Specifically, the carboxyl headgroup of the fatty acid or acylcarnitine interacts with the side chain amino group of Lys 45 and Lys 63 , whereas the lipid tail region exhibits hydrophobic contacts. Estimated binding energies predicted by Autodock (see Table 1) were lower for the short-and medium-chain fatty acids and their respective acylcarnitines (i.e.…”

“…In addition, we also performed simulations using arachidonate or arachidonoylcarnitine (C20:4) to understand the effects of polyunsaturation on binding dynamics, due to the presence of four double bonds. In all cases, the starting structure has the carboxyl group of the lipid interacting with Lys 45 and Lys 63 of Mb enabling hydrogen bonding. Analysis of the trajectories for short-and medium-chain acylcarnitines revealed that the ligand starts to move out of the binding site within the first 10-ns simulation time and is thereafter exposed to the hydrophilic environment (Fig.…”