Identification of R146225 as a novel, orally active inhibitor of interleukin-5 biosynthesis.

Interleukin (IL)-5 regulates the growth, differentiation, and activation of eosinophils. When activated, eosinophils release an array of proinflammatory and cytotoxic products and act as prominent effector cells in the process of allergic inflammation. Depriving eosinophils of IL-5 may therefore represent a viable approach to treat allergic disorders. This study describes the identification of R146225, a novel six-substituted azauracil derivative, as a potent, orally active inhibitor of IL-5 biosynthesis, capable of reducing pulmonary eosinophilia in mice. In vitro, R146225 inhibited IL-5 protein formation by activated human whole blood (IC(50) = 34 nM), human peripheral blood mononuclear cells (IC(50) = 24 nM), and murine spleen cells (IC(50) = 6 nM). In contrast, the compound enhanced generation of interferon-gamma and had little or no inhibitory effect on the production of IL-2 and IL-4. Reverse transcription-polymerase chain reaction analysis of stimulated whole blood cells indicated R146225's ability to down-regulate IL-5 mRNA expression. In vivo p.o. administration of R146225 (2.5 mg/kg) to mice before an i.v. anti-CD3 antibody challenge reduced IL-5 but enhanced interferon-gamma serum levels, without affecting IL-2 and IL-4 production. Analogous to the in vitro results, R146225 suppressed splenic IL-5 mRNA expression, while message levels of the other cytokines remained unchanged. Moreover, p.o. dosing of R146225 (0.6-2.5 mg/kg) dose dependently reduced the pulmonary accumulation of eosinophils induced in mice by an intranasal instillation of Cryptococcus neoformans. Based on these data, R146225 may be useful in the therapy of eosinophil-driven allergic conditions.

The inhibitory effect of pentamidine on the production of chemotactic cytokines by in vitro stimulated human blood cells.

Pentamidine is an antiprotozoal drug with additional antiinflammatory activities that are not well understood. We now report that pentamidine inhibited the human whole blood production of the chemotactic cytokines (chemokines) interleukin (IL)-8, growth related gene alpha (GRO alpha) and monocyte chemotactic protein-1 (MCP-1). The title compound dose-dependently suppressed the lipopolysaccharide (LPS)- and phytohemagglutinin (PHA)-stimulated whole blood generation of these chemokines with IC50-values of 2.1 and 2.2 microM (IL-8), 2.4 and 1.8 microM (GRO alpha) and 2.8 and 2.4 microM (MCP-1). The inhibition was specific: when tested at 10 microM, pentamidine had no significant inhibitory effect on the PHA-induced generation of the non-chemotactic cytokines tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-2, IL-4, IL-5, IL-10 and interferon-gamma (IFN-gamma), except for a partial inhibition on IL-6. Time course experiments indicated that pentamidine (10 microM) retained its ability to inhibit PHA-stimulated IL-8 production even when its addition was delayed for up to 24h after mitogen stimulation. Furthermore, reverse transcription PCR studies showed that pentamidine had no effect on IL-8 mRNA expression. These findings indicate that pentamidine is a post-transcription acting inhibitor of human chemokine production. This activity may contribute to the anti-inflammatory action ascribed to the title compound.