Calcium homeostasis and reactive oxygen species production in cells transformed by mitochondria from individuals with sporadic Alzheimer's disease.
Alzheimer's disease (AD) is associated with defects in mitochondrial function. Mitochondrial-based disturbances in calcium homeostasis, reactive oxygen species (ROS) generation, and amyloid metabolism have been implicated in the pathophysiology of sporadic AD. The cellular consequences of mitochondrial dysfunction, however, are not known. To examine these consequences, mitochondrially transformed cells (cybrids) were created from AD patients or disease-free controls. Mitochondria from platelets were fused to rho0 cells created by depleting the human neuroblastoma line SH-SY5Y of its mitochondrial DNA (mtDNA). AD cybrids demonstrated a 52% decrease in electron transport chain (ETC) complex IV activity but no difference in complex I activity compared with control cybrids or SH-SY5Y cells. This mitochondrial dysfunction suggests a transferable mtDNA defect associated with AD. ROS generation was elevated in the AD cybrids. AD cybrids also displayed an increased basal cytosolic calcium concentration and enhanced sensitivity to inositol-1,4, 5-triphosphate (InsP3)-mediated release. Furthermore, they recovered more slowly from an elevation in cytosolic calcium induced by the InsP3 agonist carbachol. Mitochondrial calcium buffering plays a major role after this type of perturbation. beta-amyloid (25-35) peptide delayed the initiation of calcium recovery to a carbachol challenge and slowed the recovery rate. Nerve growth factor reduced the carbachol-induced maximum and moderated the recovery kinetics. Succinate increased ETC activity and partially restored the AD cybrid recovery rate. These subtle alterations in calcium homeostasis and ROS generation might lead to increased susceptibility to cell death under circumstances not ordinarily toxic.
Sheehan
J P
JP
Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908, USA.
Swerdlow
R H
RH
Miller
S W
SW
Davis
R E
RE
Parks
J K
JK
Parker
W D
WD
Tuttle
J B
JB
D000227:Adenine Nucleotides / Q000378:metabolism; D000368:Aged; D000544:Alzheimer Disease / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics; D004579:Electron Transport; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D006706:Homeostasis; D006801:Humans; D007700:Kinetics; D008297:Male; D008561:Membrane Fusion; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism* / Q000637:transplantation*; D009097:Multienzyme Complexes / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D009447:Neuroblastoma; D010088:Oxidoreductases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012016:Reference Values; D013385:Succinate Dehydrogenase / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000227:Adenine Nucleotides; D004272:DNA, Mitochondrial; D009097:Multienzyme Complexes; D017382:Reactive Oxygen Species; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase; D016660:NAD(P)H Dehydrogenase (Quinone); D003576:Electron Transport Complex IV; D002118:Calcium