Cu2+ toxicity inhibition of mitochondrial dehydrogenases in vitro and in vivo.
Wilson's disease results from mutations in the P-type Cu(2+)-ATPase causing Cu(2+) toxicity. We previously demonstrated that exposure of mixed neuronal/glial cultures to 20 microM Cu(2+) induced ATP loss and death that were attenuated by mitochondrial substrates, activators, and cofactors. Here, we show differential cellular sensitivity to Cu(2+) that was equalized to 5 microM in the presence of the copper exchanger/ionophore, disulfiram. Because Cu(2+) facilitates formation of oxygen radicals (ROS) which inhibit pyruvate dehydrogenase (PDH) and alpha-ketoglutarate dehydrogenase (KGDH), we hypothesized that their inhibition contributed to Cu(2+)-induced death. Toxic CU(2+) exposure was accompanied by early inhibition of neuronal and hepatocellular PDH and KGDH activities, followed by reduced mitochondrial transmembrane potential, DeltaPsi(M). Thiamine (1-6 mM), and dihydrolipoic acid (LA, 50 microM), required cofactors for PDH and KGDH, attenuated this enzymatic inhibition and subsequent death in all cell types. Furthermore, liver PDH and KGDH activities were reduced in the Atp7b mouse model of Wilson's disease prior to liver damage, and were partially restored by oral thiamine supplementation. These data support our hypothesis that Cu(2+)-induced ROS may inhibit PDH and KGDH resulting in neuronal and hepatocellular death. Therefore, thiamine or lipoic acid may constitute potential therapeutic agents for Wilson's disease.
Sheline
Christian T
CT
Department of Neurology and Center for the Study of Nervous System Injury Washington University School of Medicine, St. Louis, MO 63110, USA. shelinec@neuro.wustl.edu
Choi
Dennis W
DW
D000251:Adenosine Triphosphatases / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D027682:Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003300:Copper / Q000633:toxicity*; D000073840:Copper-Transporting ATPases; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000633:toxicity; D005260:Female; D006527:Hepatolenticular Degeneration / Q000235:genetics / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology
D027682:Cation Transport Proteins; D004791:Enzyme Inhibitors; D003300:Copper; D007658:Ketone Oxidoreductases; C053164:pyruvate dehydrogenase (NADP+); D007655:Ketoglutarate Dehydrogenase Complex; D000251:Adenosine Triphosphatases; D000073840:Copper-Transporting ATPases; C029892:cupric chloride