Inhibition of c-jun expression induces antioxidant enzymes under serum deprivation

We previously reported that antisense c-jun suppressed apoptosis induced by serum deprivation in F-MEL cells. To elucidate the molecular mechanisms re sponsible for this suppression of apoptosis we investigated the activities and protein expression of antioxidant materials in the cell under serum dep rivation, In the parental F-MEL cells enzyme activities of catalase, glutat hione S-transferase (GST), and glutathione peroxidase (GPx) increased to re ach the maximum at 24-72 h after removal of serum and then decreased to ini tial levels or a little less. Superoxide dismutase (SOD) maintained the ini tial level for 72 h and increased 1.5- to a-fold at 96 h. Glutathione (GSH) levels increased at 24 h and then dropped significantly to one-third the i nitial level. On the other hand, in c-junAS (+) cells, in which antisense c -jun was expressed and c-Jun protein expression was reduced to undetectable level. We found 1.9-, 2.7-, 4.8-, and 15.8-fold increase in the activities of catalase, GST, SOD, and GPx, respectively, at 96 h, GSH maintained almo st the same level as the initial. Enhancement of these enzyme activities in c-junAS (+) cells was induced under serum deprivation. Western blottings f or catalase, GST, and SOD also showed enhanced increase in protein expressi on, supporting the increase in enzyme activities. Cellular peroxide level u nder serum deprivation was monitored by how cytometry using DCFH-DA as a pr obe. We found that the peroxide level increased at 24 h and then decreased at 72 and 96 h in c-junAS (+) cells, and reduction of the peroxide level co incided with an increase in antioxidant enzyme activities. These results in dicate that antioxidant materials such as catalase, GST, SOD, GPx, and GSH are induced by serum deprivation when c-jun expression is inhibited in F-ME L cells. The link between inhibition of c-jun expression and enhancement of cellular antioxidant defense is discussed. (C) 2000 Academic Press.