ADENOSINE AND A RELATED CARBOCYCLIC NUCLEOSIDE ANALOG SELECTIVELY INHIBIT TUMOR-NECROSIS-FACTOR-ALPHA PRODUCTION AND PROTECT MICE AGAINST ENDOTOXIN CHALLENGE

Adenosine (ADO) and its structurally related analogues are known to re gulate the activities of immune and inflammatory cells, including a nu mber of key functions of mononuclear phagocytes. In this study ADO and the synthetic ADO analogue MDL201112 inhibited TNF-alpha, but not IL- 1, production by activated mouse peritoneal macrophages and the macrop hage-like cell lines J774 and RAW-264. Northern blot analysis indicate d that MDL201112 selectively inhibited the expression of steady-state TNF-alpha RNA in LPS + IFN-gamma-activated J774 and RAW-264 cells. Thi s effect could not be attributed to changes in TNF-alpha RNA stability . In contrast, ADO had no effect on RNA levels for TNF-alpha and IL-1, suggesting that ADO acts at a post-transcriptional biosynthetic step. To determine whether either compound inhibited TNF-alpha-mediated inf lammatory responses, mice were treated with ADO or MDL201112 and chall enged with a lethal dose of endotoxic LPS and D-galactosamine, an hepa totoxin that sensitizes mice to lethal LPS challenge. A single i.p. in jection of MDL201112 (100 mg/kg) protected over 90% of the mice, wheth er injected 1 h before or at the time of LPS challenge. MDL201112 also inhibited the appearance of TNF-alpha in the serum of LPS-challenged animals. The compound did not block D-galactosamine sensitization nor did it prevent lethality caused by the injection of rTNF-alpha. ADO fa iled to protect animals against endotoxin lethality, most likely due t o the rapid metabolism of the nucleoside in vivo. These results establ ish ADO and MDL201112 as potent inhibitors of TNF-alpha biosynthesis a nd suggest that MDL201112 or similar analogues warrant further study a s potential agents for the treatment of endotoxin shock and other dise ases in which TNF-alpha plays an important pathogenic role.