title: Regulation of normal cell cycle progression by flavin-containing oxidases.
abstract: Mechanisms underlying the role of reactive oxygen species (ROS) generated by flavin-containing oxidases in regulating cell cycle progression were examined in human and rodent fibroblasts. Incubation of confluent cell cultures with nontoxic/nonclastogenic concentrations of the flavoprotein inhibitor, diphenyleneiodonium (DPI), reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase activity and basal ROS levels, but increased proteolysis of cyclin D1, p21(Waf1) and phospho-p38(MAPK). When these cells were allowed to proliferate by subculture in DPI-free medium, an extensive G(1) delay was observed with concomitant activation of p53/p21(Waf1) signaling and reduced phosphorylation of mitogen-activated kinases. Compensation for decreased oxidant generation by simultaneous exposure to DPI and nontoxic doses of the ROS generators, gamma-radiation or t-butyl-hydroperoxide, attenuated the G(1) delay. Whereas the DPI-induced G(1) checkpoint was completely dependent on PHOX91, ATM and WAF1, it was only partially dependent on P53. Interestingly, G(1) to S progression was not affected when another flavin-containing enzyme, nitric oxide synthase, was inhibited nor was it associated with changes in mitochondrial membrane potential. Proliferating cells treated with DPI also experienced a significant but attenuated delay in G(2). We propose that ATM performs a critical function in mediating normal cellular proliferation that is regulated by nonphagocytic NAD(P)H oxidase enzymes activity, which may serve as a novel target for arresting cancer cells in G(1).
authors.affiliation: Department of Radiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA.
authors.forename: P
authors.initials: P
authors.lastname: Venkatachalam
authors.forename: S M
authors.initials: SM
authors.lastname: de Toledo
authors.forename: B N
authors.initials: BN
authors.lastname: Pandey
authors.forename: L A
authors.initials: LA
authors.lastname: Tephly
authors.forename: A B
authors.initials: AB
authors.lastname: Carter
authors.forename: J B
authors.initials: JB
authors.lastname: Little
authors.forename: D R
authors.initials: DR
authors.lastname: Spitz
authors.forename: E I
authors.initials: EI
authors.lastname: Azzam
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D005415:Flavins / Q000378:metabolism* / Q000502:physiology; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009861:Onium Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D005415:Flavins; D006131:Growth Inhibitors; D024101:Mitochondrial Proteins; D009861:Onium Compounds; C007517:diphenyleneiodonium; D019255:NADPH Oxidases