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Differences among cell types in NAD + compartmentalization: A comparison of neurons, astrocytes, and cardiac myocytes
Author(s) -
Alano Conrad C.,
Tran Alexandra,
Tao Rong,
Ying Weihai,
Karliner Joel S.,
Swanson Raymond A.
Publication year - 2007
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.21479
Subject(s) - nad+ kinase , mitochondrial permeability transition pore , mitochondrion , myocyte , poly adp ribose polymerase , cytosol , biology , programmed cell death , biochemistry , microbiology and biotechnology , chemistry , enzyme , apoptosis , polymerase
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. © 2007 Wiley‐Liss, Inc.