MiP2005: Session 4
Mitochondrial Physiology Network 10.9: 47 (2005) - download pdf
Comparison of the effects of nonesterified fatty acids and of their ethanolamine amides (N-acylethanolamines) on isolated mitochondria and on mitochondria within intact cells, including triggering of apoptosis.
Lech Wojtczak, M Wasilewski, D Dymkowska
Nencki Institute of Experimental Biology, Pasteura 3, PL-02-093 Warsaw, Poland. – firstname.lastname@example.org
Nonesterified long-chain fatty acids are excellent energy-providing respiratory substrates for numerous tissues but they are also well-known protonophores and uncouplers of oxidative phosphorylation for isolated mitochondria and mitochondria within intact cells . Elevated concentrations of fatty acids can elicit cell death, both necrotic and apoptotic . N-Acylethanolamines (NAEs) form a class of important fatty acid derivatives that have recently attracted attention because of their formation and accumulation in injured heart and brain . The main representative of these compounds, N-arachidonoylethanolamine (also called anandamide) may have signalling functions and also acts as ligand for cannabinoid receptors. The present work compares some effects of nonesterified fatty acids with those of NAEs.
In isolated rat heart mitochondria NAEs were much weaker protonophores than corresponding nonesterified fatty acids . In contrast, in the presence of micromolar concentrations of Ca2+, long-chain unsaturated NAEs, N-arachidonoylethanolamine and N-oleoylethanolamine, were potent openers of the mitochondrial permeability transition pore. They also acted as weak inhibitors of mitochondrial respiration, in particular of complex I of the respiratory chain. As weak uncouplers, NAEs decreased the rate of the formation of reactive oxygen species (ROS) by respiring mitochondria. However, N-arachidonoylethanolamine partly prevented the drastic decrease of ROS formation produced by chemical uncouplers. In this respect, it exerted a similar, though much weaker, effect as that by known inhibitors of complexes I and III, rotenone and antimycin A.
Acting on cells in culture, arachidonic acid and, to a lesser extent, oleic acid elicited apoptotic cell death in the following cell types: rat hepatoma AS-30D, mouse Ehrlich ascites carcinoma, human lymphoblastoid Jurkat cells and human leukemia HL-60 cells. However, mouse neuroblastoma N2a cells appeared resistant to arachidonic and oleic acids. Interestingly, this cell line was also more resistant to ultraviolet irradiation than the former cell lines. Apoptosis induced in susceptible cell lines by arachidonic and oleic acids proceeded along the mitochondrial pathway characterized by release of cytochrome c from mitochondria to the cytosol and activation of caspase-3.
Conflicting information exists in the literature on proapoptotic and antiproliferating activity of N-arachidonoylethanolamine. In the present study we were unable to induce apoptosis by NAEs in rat myoblasts H9c2, primary rat neonatal cardiomyocytes and mouse neuroblastoma N2a cells. Further studies in this line are, however, required.
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