title: Response of Acanthamoeba castellanii mitochondria to oxidative stress.
abstract: The purpose of this study was to examine the effects of oxidative stress caused by hydroperoxide (H(2)O(2)) in the presence of iron ions (Fe(2+)) on mitochondria of the amoeba Acanthamoeba castellanii. We used isolated mitochondria of A. castellanii and exposed them to four levels of H(2)O(2) concentration: 0.5, 5, 15, and 25 mM. We measured basic energetics of mitochondria: oxygen consumption in phosphorylation state (state 3) and resting state (state 4), respiratory coefficient rates (RC), ADP/O ratios, membrane potential (DeltaPsi(m)), ability to accumulate Ca(2+) , and cytochrome c release. Our results show that the increasing concentrations of H(2)O(2) stimulates respiration in states 3 and 4. The highest concentration of H(2)O(2) caused a 3-fold increase in respiration in state 3 compared to the control. Respiratory coefficients and ADP/O ratios decreased with increasing stress conditions. Membrane potential significantly collapsed with increasing hydroperoxide concentration. The ability to accumulate Ca(2+) also decreased with the increasing stress treatment. The lowest stress treatment (0.5 mM H(2)O(2)) significantly decreased oxygen consumption in state 3 and 4, RC, and membrane potential. The ADP/O ratio decreased significantly under 5 mM H(2)O(2) treatment, while Ca(2+) accumulation rate decreased significantly at 15 mM H(2)O(2). We also observed cytochrome c release under increasing stress conditions. However, this release was not linear. These results indicate that as low as 0.5 mM H(2)O(2) with Fe(2+) damage the basic energetics of mitochondria of the unicellular eukaryotic organism Acanthamoeba castellanii.
authors: Institute of Dendrology, Polish Academy of Sciences, Kórnik, Poland. lidiatrocha@gazeta.pl
authors: Lidia K
authors: LK
authors: Trocha
authors: Olgierd
authors: O
authors: Stobienia
mesh_terms: D048248:Acanthamoeba castellanii / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D045304:Cytochromes c / Q000378:metabolism; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism* / Q000502:physiology; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D000244:Adenosine Diphosphate; D045304:Cytochromes c; D010100:Oxygen