The relationships among acute phase response proteins, cytokines, and enzymes during ovine experimental endotoxemia

BACKGROUND: The acute phase response is beneficial to theanimal in restoring homeostasis, and measuring the circulatingacute phase proteins, cytokines, and enzymes can be used toevaluate the innate immune system's responses to invader agentssuch as bacterial lipopolysaccharide. Measurement of theseparameters has shown to be useful as diagnostic and prognosticmarkers in animal endotoxemia. OBJECTIVES: The aim of thepresent experimental study was expression of the acute phaseresponse following the induction of endotoxemia by Escherichiacoli serotype O55:B5 in sheep and the relationships among the acutephase response parameters during endotoxemia and their changingpatterns. METHODS: Five clinically healthy 1-year-old Iranian fattailedewes (25±1.5 kg, bodyweight) were randomly selected andlipopolysaccharide from Escherichia coli serotype O55:B5 wasinfused at 20 μg/kg intravenously to each animal. Fluid therapy wasperformed in all ewes over 120 minutes after lipopolysaccharideinjection and continued for 180 minutes. Blood samples werecollected from all ewes prior and 1, 2, 3, 4, 5, 6, and 24 hours afterlipopolysaccharide injection and sera were separated. Serumconcentrations of haptoglobin, serum amyloid A, tumor necrosisfactor-alpha, interferon-gamma, superoxide dismutase, andglutathione peroxidase were assayed. RESULTS: The rapid andsignificant elevation of haptoglobin, serum amyloid A, tumornecrosis factor-alpha, and interferon-gamma were seen afterendotoxemia induction. Serum concentrations of superoxidedismutase and glutathione peroxidase were significantly decreasedafter intravenous lipopolysaccharide infusion. The results of thepresent experimental study showed that haptoglobin, serumamyloid A, tumor necrosis factor-alpha, and interferon-gamma atall hours studied after endotoxemia induction were positivelycorrelated together. These parameters were negatively correlatedwith superoxide dismutase and glutathione peroxidase at all hoursafter lipopolysaccharide infusion. CONCLUSIONS: The results ofthe present experiment can provide evidence for associationsamong acute phase proteins, cytokines, and enzymes and theirchanges during endotoxemia in sheep.