Murine Glial Cells Regenerate NAD, After Peroxide-Induced Depletion, Using Either Nicotinic Acid, Nicotinamide, or Quinolinic Acid as Substrates

Abstract: The potential for regeneration of intracellular pyridine nucleotide levels from different precursors, after peroxide-induced NAD depletion, in cultured glial cells was investigated. Cultured murine glial cells showed a decrease in intracellular NAD levels of >40% after treatment with H₂O₂ (100 µ M ). Removal of the H₂O₂ followed by a 2-h incubation did not result in NAD recovery in the absence of precursors. However, NAD levels increased significantly in these cells after the following substrate additions, at minimum effective concentrations of 1 m M for quinolinic acid (QUIN), 500 µ M for nicotinamide, and 2 µ M for nicotinic acid. The regeneration of significant amounts of NAD from nicotinic acid at doses 250 and 500 times lower than either nicotinamide or QUIN indicates a preferred route for NAD biosynthesis in glial cells in vitro, probably via nicotinic acid phosphoribosylation.