Induction and characterization of endotoxin tolerance in equine peripheral blood mononuclear cells in vitro

Abstract

Endotoxemia is responsible for severe illness in horses. Individuals can become unresponsive to the endotoxin molecule after an initial exposure; this phenomenon has been called developing a state of 'endotoxin tolerance' (ET). ET has been induced in horses in vivo; however, cytokine expression associated with ET has not been investigated. The purpose of this study was to develop and validate a method for inducing ET in equine peripheral blood mononuclear cells (PBMCs) in vitro, and to describe the cytokine profile which is associated with the ET.Blood was collected from 6 healthy horses and PBMCs were isolated. ET was induced by culturing cells with three concentrations of endotoxin given to induce ET, and evaluated after a second dose of endotoxin given to challenge the cells. The relative mRNA expression of IL-10 and IL-12 was measured by use of quantitative PCR.ET was induced in all cells (n=6) exposed to the 2-step endotoxin challenge. In PBMCs treated with 1.0 ng/ml of endotoxin followed by challenge with 10 ng/ml of endotoxin, the relative mRNA expression of IL-10 in tolerized cells was not different from positive control cells. In contrast, the relative mRNA expression of IL-12 in tolerized cells was decreased by 15-fold after the second endotoxin challenge compared with positive control cells.This experiment demonstrated a reliable method for the ex vivo induction of ET in equine PBMCs. A marked suppression of IL-12 production is associated with ET. The production of IL-10 was not altered in ET in our model.

Plasma Procalcitonin Concentration in Healthy Horses and Horses Affected by Systemic Inflammatory Response Syndrome

“…PCT levels in horses in this study were generally lower than levels reported in humans with SIRS . This dissimilarity might be related to the different species studied, less severe inflammation in the studied horses, or possibly endotoxin tolerance . Moreover, Yilmaz and colleagues (2008) evaluated the changes in PCT concentrations in dogs after administration of endotoxin, which resulted lower than our results.…”

In vitro evaluation of defined oligosaccharide fractions in an equine model of inflammation

“…In this solution, the measured endotoxin concentration was the highest (approximately 10–19 ng/ml) and we cannot exclude that endotoxin tolerance was induced during the PBMC pre-incubation period, suppressing the response after the actual challenge [26]. On the other hand, the 1% solution of GOS/FOS/AOS (approximately 5–10 ng/ml endotoxin) already caused a significant reduction of the LPS response in comparison with the 0.5% GOS/FOS/AOS solution, whilst the 2% GOS/FOS solution (approximately 6–11 ng/ml endotoxin) induced a significant increase of the LPS response compared with the 1% GOS/FOS solution.…”

Mitochondrial DAMPs Induce Endotoxin Tolerance in Human Monocytes: An Observation in Patients with Myocardial Infarction

“…In-depth studies of ET development in gene-deficient mice analyzed the participation of intracellular molecules in this process and established the roles of SHIP-1, A20 and IRAK-M. This pseudokinase could be considered a “master regulator” of ET because it is consistently induced into ET [8], [9] and is implicated in human pathologies in which ET is manifest, such as sepsis [10], cancer [11], ACS [3] and asthma [12]. In a human in vitro ET model, rapid IRAK-M up-regulation was described and is expressed in freshly isolated sepsis monocytes [10].…”