Despite the severity and common occurrence of equine endotoxaemia, the available anti-endotoxic treatments do not effectively target key inflammatory mechanisms such as leucocyte activation and cytokine production. In this study, four compounds with potential anti-endotoxic effects, namely rolipram, azithromycin, ethyl pyruvate and metformin, were investigated in vitro using equine whole blood stimulated with bacterial lipopolysaccharide. TNF-α and IL-1β production were measured in plasma. Rolipram was the most potent inhibitor of cytokine production (IC50 0.84 and 4.68 μm for TNF-α and IL-1β, respectively) with almost complete inhibition of TNF-α, but inhibited IL-1β by only 39.46%. Azithromycin produced almost complete inhibition of both cytokines, but tended to be less potent than rolipram (IC50 10.66 and 17.4 μm for TNF-α and IL-1β, respectively). Metformin inhibited TNF-α production with similar potency to rolipram and azithromycin (IC50 3.35 μm) but showed significantly lower efficacy (45.93%; P < 0.05), and had no inhibitory effect on IL-1β. Ethyl pyruvate was the least potent (IC50 68.35 μm and >10 mm for TNF-α and IL-1β production, respectively). Further work is required to investigate whether these or related compounds may have potential use in the treatment of equine endotoxaemia in vivo.
© 2014 John Wiley & Sons Ltd.