THYMIC PEPTIDE MODULATES GLUTATHIONE REDOX CYCLE AND ANTIOXIDANT ENZYMES IN MACROPHAGES

The effect of a 6-kDa thymic peptide (TP) on the oxidative burst of th e murine macrophage cell line J774 was determined. TP was incubated wi th J774 cells at 37 degrees C and 5% CO2 for 18 h, oxidative burst was triggered by zymosan, and chemiluminescence was amplified by luminol and measured in an automated luminometer. TP exhibited a concentration -dependent suppression of oxidative burst. To study the mechanisms inv olved in TP's suppression of oxidative burst, its effect on the glutat hione redox cycle and antioxidant enzymes was investigated. J774 cells were incubated with varying concentrations of TP for 18 h, washed, re suspended in phosphate-buffered saline, and sonicated to obtain cell l ysate. Biochemical assays were performed with the lysate. TP was shown to increase the level of glutathione, and activities of glutathione-p eroxidase and glutathione-reductase, indicating its ability to modulat e the glutathione redox cycle. The activity of antioxidant enzyme supe roxide dismutase was enhanced significantly by TP treatment while cata lase activity remained unaffected. These results suggest that TP posse sses an antioxidant property and therefore may be involved in the regu lation of free radical mediated reactions.