Induction of mild intracellular redox imbalance inhibits proliferation of CaCo-2 cells

Intracellular redox status plays a critical role in cell function, such as proliferation. Oxidative stress, which elicits redox imbalance, also affect s cell growth. Therefore, it is often difficult to distinguish the effects of redox imbalance from those of oxidative stress. The objective of this st udy was to determine the role of redox imbalance independent of reactive ox ygen species (ROS) production, in proliferation of human colonic CaCo-2 cel ls. Low concentrations of diamide plus 1,3-bis(2 chloroethyl)-1-nitrosourea (BCNU) increased intracellular GSSG and decreased GSH and the GSH: GSSG ra tio. These changes occurred within 30 min, which preceded a decrease in thy midine incorporation at 6 and 24 h. ROS formation was not detected under th ese conditions. This suppression of cell proliferative activity was attenua ted by N-acetyl cysteine, in parallel with restoration of the intracellular GSH redox status. DL-buthionine-[S, R]-sulfoximine (BSO) decreased intrace llular GSH level, but did not change the GSH: GSSG ratio. BSO alone had no effect on cell proliferation, but its presence exaggerated the suppressive effect of diamide plus BCNU. Flow cytometric analysis showed that cells wer e arrested at G(1)-to-S transition and G(2)/M phase. Collectively, this stu dy shows that mild intracellular redox imbalance inhibited cell proliferati on independent of ROS generation. Moreover, cells with compromised cellular GSH were susceptible to redox imbalance-induced inhibition of proliferatio n.