Potent Inhibitors of Pro-Inflammatory Cytokine Production Produced by a Marine-Derived Bacterium

Cytokines produced through the antigen presenting cell (APC)−T-cell interaction play a key role in the activation of the allergic asthmatic response. Evaluating small molecules that inhibit the production of these pro-inflammatory proteins is therefore important for the discovery of novel chemical structures with potential antiasthma activity. We adapted a mouse splenocyte cytokine assay to screen a library of 2,500 marine microbial extracts for their ability to inhibit TH2 cytokine release and identified potent activity in a marine-derived strain CNQ431, identified as a Streptomyces species. Bioactivity guided fractionation of the organic extract of this strain led to the isolation of ten new 9-membered bis-lactones, splenocins A−J (1−10). The new compounds display potent biological activities, comparable to that of the corticosteroid dexamethasone, with IC50 values from 2 to 50 nM in the splenocyte cytokine assay. This study provides the foundation for the optimization of these potent anti-inflammatory compounds for development in the treatment of asthma.