RESUMEN
Previously we have shown that S-oxalins (monothiolesters of oxalic acid) are ubiquitous mammalian metabolites whose concentrations decrease when lymphocytes are stimulated to proliferate. The present study was undertaken to further examine the role of S-oxalins in the proliferation process. When added to lymphocytes stimulated with concanavalin A, the S-oxalin, S-oxalylglutathione (GS-Ox), inhibited DNA synthesis by 50% when present at ca. 0.15 mM and virtually 100% at 0.5 mM. The inhibition was reversible. The presence of GS-Ox blocked IL-2 production, but addition of IL-2 did not permit DNA synthesis to proceed. GS-Ox also inhibited proliferation of an IL-2-dependent cell line, BT2. In primary lymphocytes GS-Ox reduced IL-2 receptor expression, but not in an IL-2-dependent blast cell line. Overall RNA synthesis and protein synthesis were not significantly altered by GS-Ox. Levels of the positive transcription factor, NF-kappaB, were decreased after incubation of lymphocytes with GS-Ox, but the amount of a negative transcription factor, NREA, was largely unchanged. The results not only provide further evidence that S-oxalins are small-molecule cell proliferation inhibitors, they also clarify to some extent the specific steps in the activation response modulated by S-oxalins.