title: Differences among cell types in NAD(+) compartmentalization: a comparison of neurons, astrocytes, and cardiac myocytes.
abstract: Activation of the nuclear enzyme poly(ADP-ribose)-1 leads to the death of neurons and other types of cells by a mechanism involving NAD(+) depletion and mitochondrial permeability transition. It has been proposed that the mitochondrial permeability transition (MPT) is required for NAD(+) to be released from mitochondria and subsequently consumed by PARP-1. In the present study we used the MPT inhibitor cyclosporine-A (CsA) to preserve mitochondrial NAD(+) pools during PARP-1 activation and thereby provide an estimate of mitochondrial NAD(+) pool size in different cell types. Rat cardiac myocytes, mouse cardiac myocytes, mouse cortical neurons, and mouse cortical astrocytes were incubated with the genotoxin N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in order to activate PARP-1. In all four cell types MNNG caused a reduction in total NAD(+) content that was blocked by the PARP inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone. Inhibition of the mitochondrial permeability transition with cyclosporine-A (CsA) prevented PARP-1-induced NAD(+) depletion to a varying degree in the four cell types tested. CsA preserved 83.5% +/- 5.2% of total cellular NAD(+) in rat cardiac myocytes, 85.7% +/- 8.9% in mouse cardiac myocytes, 55.9% +/- 12.9% in mouse neurons, and 22.4% +/- 7.3% in mouse astrocytes. CsA preserved nearly 100% of NAD(+) content in mitochondria isolated from these cells. These results confirm that it is the cytosolic NAD(+) pool that is consumed by PARP-1 and that the mitochondrial NAD(+) pool is consumed only after MPT permits mitochondrial NAD(+) to exit into the cytosol. These results also suggest large differences in the mitochondrial and cytosolic compartmentalization of NAD(+) in these cell types.
authors.affiliation: Neurology Service, Veterans Affairs Medical Center, 127 Neurology, San Francisco, CA 94121, USA. conrad.alano@ucsf.edu
authors.forename: Conrad C
authors.initials: CC
authors.lastname: Alano
authors.forename: Alexandra
authors.initials: A
authors.lastname: Tran
authors.forename: Rong
authors.initials: R
authors.lastname: Tao
authors.forename: Weihai
authors.initials: W
authors.lastname: Ying
authors.forename: Joel S
authors.initials: JS
authors.lastname: Karliner
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Swanson
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D015153:Blotting, Western; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D003600:Cytosol / Q000737:chemistry; D004789:Enzyme Activation / Q000502:physiology; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D009243:NAD / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009243:NAD; D008769:Methylnitronitrosoguanidine; D016572:Cyclosporine; C499322:Parp1 protein, rat; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases