Decreased Activity of Inducible Nitric Oxide Synthase Type 2 and Modulation of the Expression of Glutathione S-Transferase a, bcl-2, and Metaflothioneins during the Differentiation of CaCo-2 Cells1 Fran#{231}oise Vecchini,2 Eric Pringault,

Reactive oxygen species modulate the cell growth of a wide variety of mammalian cells. To determine whether oxidative metabolism is altered during the differentiation process, we studied the expression of proand antioxidant proteins in proliferating and differentiated CaCo-2 cells, a human colon adenocarcinoma cell line. Nitric oxide synthase type 2 (INOS) produces nitric oxide (NO). Depending on its rate of synthesis, NO may either promote cellular and DNA damage or reduce the ability of other free radicals to induce cell injury. Using Western and Northern blot analysis and arginine conversion assay, we demonstrate that the expression of iNOS decreases when cells undergo differentiation. This biological event entails a diminished produc on of NO metabolites and correlates with the loss of activation of soluble guanylate cyclase activity. In differentiated cells, a 2-fold downregulation of the nuclear factor scB activity was observed, suggesting that nuclear factor scB could be one of the 1NOS gene regulatory factors in the CaCo-2 model. In parallel, we studied the expression of other antioxidant proteins including glutathione S-transferase a (GSTa), bcl-2, and the metallOthiOneinS (MTs). We show that the protein levels of GSTa and MT increase du#{241}ng the differentiation of CaCo-2 cells, whereas bcl-2 levels decrease. Our investigation indicates that the expression of iNOS, GSTa, bcl-2, and MT is associated with the enterocytic differentiation. The shift in the expression of specific antioxidant genes du#{241}ngCaCo-2 cell differentiation may occur to avoid alterations in the cell redox potential