Duration of in vivo endotoxin tolerance in horses

作者：Holcombe Susan J; Jacobs Carrie C; Cook Vanessa L; Gandy Jeffery C; Hauptman Joseph G; Sordillo Lorraine M

来源：Veterinary Immunology and Immunopathology, 2016, 173: 10-16.

DOI：10.1016/j.vetimm.2016.03.016

• Horse
• Endotoxin tolerance
• TNF alpha
• IL-6
• IL-8
• Lipopolysaccharide (LPS)

Endotoxemia models are used to study mechanisms and treatments of early sepsis. Repeated endotoxin exposures induce periods of endotoxin tolerance, characterized by diminished proinflammatory responses to lipopolysaccharide (LPS) and modulated production of proinflammatory cytokines. Repeated measure designs using equine endotoxemia models are rarely performed, despite the advantages associated with reduced variability, because the altered responsiveness would confound study results and because the duration of equine endotoxin tolerance is unknown. We determined the interval of endotoxin tolerance, in vivo, in horses based on physical, clinicopathologic, and proinflammatory gene expression responses to repeated endotoxin exposures. Six horses received 30 ng/kg LPS in saline infused over 30 min. Behavior pain scores, physical examination parameters, and blood for complete blood count and proinflammatory gene expression were obtained at predetermined intervals for 24 h. Horses received a total of 3 endotoxin exposures. The first exposure was LPS I, followed 7 days later by LPS 7 or 14-21 days later by LPS 14-21. Lipopolysaccharide exposures were allocated in a randomized, crossover design. Lipopolysaccharide produced clinical and clinicopathologic signs of endotoxemia and increased expression of tumor necrosis factor alpha (TNF alpha), interleukin (IL)-6 and IL-8, P < 0.001. Horses exhibited evidence of endotoxin tolerance following LPS 7 but not following LPS 14-21. Horses had significantly lower pain scores, heart rates, respiratory rates and duration of fever, after LPS 7 compared to LPS I and LPS 14-21, P < 0.001, and expression of TNF alpha was lower in the whole blood of horses after LPS 7, P = 0.05. Clinical parameters and TNF alpha gene expression were similar or slightly increased in horses following LPS 14-21 compared to measurements made in horses following LPS 1, suggesting that endotoxin tolerance had subsided. A minimum of 3 weeks between experiments is warranted if repeated measures designs are used to assess in vivo response to endotoxin in horses.

• 出版日期2016-5