EFFECTS OF 2-CHLORODEOXYADENOSINE AND GOLD SODIUM THIOMALATE ON HUMANBCL-2 GENE-EXPRESSION

Aberrant expression of apoptosis-related genes, including the ''cell d eath suppressor gene'' bcl-2, may play an important pathogenetic role in cancer and autoimmune diseases. In vivo upregulation of bcl-2 mRNA in synovial lining cells of patients with rheumatoid arthritis but not in patients with osteoarthritis has been recently found. In the prese nt study we investigated whether agents exerting beneficial effects in patients with rheumatoid arthritis, namely the long used Gold Sodium Thiomalate (GST) and the novel immunosuppressive, purine analogue 2-ch lorodeoxyadenosine (2-CdA), a lymphocyte apoptosis-inducing agent inte rfere directly with induction of bcl-2 mRNA expression. The phytohemag glutinin (PHA)-induced in vitro proliferation of normal human peripher al blood lymphocytes was significantly inhibited by non-toxic concentr ations of 2-CdA and GST which are whithin the range of in vivo plasma concentrations in patients receiving the respective treatment. Using R NA dot-blot analysis and hybridization with an IL-2-specific probe we found that GST, similarly to dexamethasone that served as control, sup pressed the PHA-induced IL-2 mRNA accumulation dose-dependently. In co ntrast, 2-CdA (0.1 mu g/ml) at concentrations that inhibit by 80-90% t he PHA-induced proliferative responses of lymphocytes did not affect I L-2 mRNA accumulation. Hybridization with a bcl-2-specific probe showe d that the activation-induced accumulation and kinetics of bcl-2 mRNA were not changed in the presence of a wide range of concentrations of either GST or 2-CdA. Similarly, the mRNA accumulation of the ''house-k eeping'' control gene beta-actin remained unchanged by both agents. Th ese findings indicate that biosynthesis of bcl-2 is not specifically a ffected by GST and CdA, suggesting that the immunomodulating effects o f these agents, including their efficacy in suppressing chronic arthri tis, are not related with a bcl-2-dependent mechanism.