Differences among cell types in NAD(+) compartmentalization: a comparison of neurons, astrocytes, and cardiac myocytes

J Neurosci Res. 2007 Nov 15;85(15):3378-85. doi: 10.1002/jnr.21479.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Astrocytes / chemistry*
  • Astrocytes / drug effects
  • Astrocytes / metabolism
  • Blotting, Western
  • Cell Death / physiology
  • Cells, Cultured
  • Cyclosporine / pharmacology
  • Cytosol / chemistry
  • Enzyme Activation / physiology
  • Male
  • Methylnitronitrosoguanidine / pharmacology
  • Mice
  • Myocytes, Cardiac / chemistry*
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / metabolism
  • NAD / drug effects
  • NAD / metabolism*
  • Neurons / chemistry*
  • Neurons / drug effects
  • Neurons / metabolism
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases / metabolism
  • Rats
  • Rats, Sprague-Dawley

Substances

  • NAD
  • Methylnitronitrosoguanidine
  • Cyclosporine
  • Parp1 protein, rat
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases