Suppression of fibroblast cell cycle progression in G1 phase by N-acetylcysteine

Toxicol Appl Pharmacol. 1998 Apr;149(2):210-6. doi: 10.1006/taap.1997.8361.


The antioxidant N-acetyl-L-cysteine (NAC) has been increasingly used as an experimental tool to assess involvement of reactive oxygen species in cell signaling and is being evaluated as a preventive and therapeutic agent for cancer and pulmonary diseases related to inflammation and oxidative stress. However, a detailed characterization of the effect of NAC on cell cycle progression has not been reported. In the present study, modulation of cell cycle progression by NAC was analyzed in mouse fibroblast NIH3T3 cells grown in 10% fetal bovine serum. Complete inhibition of NIH3T3 cell proliferation was obtained with 20 mM NAC. Inhibition of cell proliferation by NAC (at or below 20 mM) was not due to cell death, and the antiproliferative effect of NAC was reversible. Flow cytometric analysis of cell cycle phase distribution indicated that NAC blocked the cell cycle in the G1 phase. Consistent with this observation, NAC inhibited DNA synthesis. After releasing the G1-block by NAC, S phase re-entry occurred between 8 and 12 h, suggesting that NAC blocked the cell cycle in early to mid-G1 phase. NAC prevented activation of mitogen-activated protein (MAP) kinases p42MAPK and p44MAPK and inhibited expression of cyclin D1, but had no effect on the levels of proliferating cell nuclear antigen. Incubation of cells with PD98059, a specific inhibitor of MAP kinase kinase 1, partially arrested the cell cycle in the G1 phase. These results indicate that the antiproliferative effect of NAC is linked in part to inhibition of the MAP kinase pathway.

Publication types

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

MeSH terms

  • 3T3 Cells
  • Acetylcysteine / pharmacology*
  • Animals
  • Antioxidants / pharmacology*
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Cycle / drug effects*
  • Cell Death / drug effects
  • Cell Division / drug effects
  • Cyclin D1 / antagonists & inhibitors
  • Cyclin D1 / biosynthesis
  • DNA / biosynthesis
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Flavonoids / pharmacology
  • Flow Cytometry
  • Free Radical Scavengers / pharmacology*
  • G1 Phase / drug effects
  • MAP Kinase Kinase 1
  • Mice
  • Mitogen-Activated Protein Kinase Kinases*
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / antagonists & inhibitors


  • Antioxidants
  • Enzyme Inhibitors
  • Flavonoids
  • Free Radical Scavengers
  • Proliferating Cell Nuclear Antigen
  • Cyclin D1
  • DNA
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • MAP Kinase Kinase 1
  • Map2k1 protein, mouse
  • Mitogen-Activated Protein Kinase Kinases
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
  • Acetylcysteine