Anti‐inflammatory effects of four potential anti‐endotoxaemic drugs assessed in vitro using equine whole blood assays

Abstract

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.

Effects of polymyxin‐B on TNF‐α production in equine whole blood stimulated with three different bacterial toxins

“…Ten minutes after addition of polymyxin‐B, all samples (except the negative control) were stimulated by the addition of LPS ( E. coli O55:B5), LTA ( Enterococcus hirae ) or PGN ( Staphylococcus aureus ), achieving a final toxin concentration of 1 μg/ml. This toxin concentration was used to ensure a reliably measurable TNF‐α response based on preliminary (Bauquier & Bailey, ) studies performed to identify optimal toxin concentrations for the assays used in our laboratory and previous studies performed in our laboratory (Bauquier, Tudor, & Bailey, ). For each toxin for each horse, two samples comprised negative (no toxin and no polymyxin‐B) and positive (1 μg/ml of toxin but no polymyxin‐B) controls.…”

Evaluation of digital cryotherapy using a commercially available sleeve style ice boot in healthy horses and horses receiving i.v. endotoxin

“…The objectives of this study were to evaluate skin and lamellar cooling achieved using the sleeve style ice boot in healthy horses, and in the same horses using an endotoxaemia model. Intravenous administration of endotoxin was chosen for the endotoxaemia model because it causes consistent, predictable and reversible clinical signs with a low risk of permanent complications . By evaluating cooling in healthy horses, and endotoxaemic horses, we hoped to gain information applicable to clinical cases.…”