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

The acute phase response is beneficial to the animal in restoring homeostasis, and measuring the circulating acute phase proteins, cytokines, and enzymes can be used to evaluate the innate immune system's responses to invader agents such as bacterial lipopolysaccharide. Measurement of these parameters has shown to be useful as diagnostic and prognostic markers in animal endotoxemia.

The aim of the present experimental study was expression of the acute phase response following the induction of endotoxemia by Escherichia coli serotype O55:B5 in sheep and the relationships among the acute phase response parameters during endotoxemia and their changing patterns.

Five clinically healthy 1-year-old Iranian fattailed ewes (25±1.5 kg, bodyweight) were randomly selected and lipopolysaccharide from Escherichia coli serotype O55:B5 was infused at 20 μg/kg intravenously to each animal. Fluid therapy was performed in all ewes over 120 minutes after lipopolysaccharide injection and continued for 180 minutes. Blood samples were collected from all ewes prior and 1, 2, 3, 4, 5, 6, and 24 hours after lipopolysaccharide injection and sera were separated. Serum concentrations of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma, superoxide dismutase, and glutathione peroxidase were assayed.

The rapid and significant elevation of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, and interferon-gamma were seen after endotoxemia induction. Serum concentrations of superoxide dismutase and glutathione peroxidase were significantly decreased after intravenous lipopolysaccharide infusion. The results of the present experimental study showed that haptoglobin, serum amyloid A, tumor necrosis factor-alpha, and interferon-gamma at all hours studied after endotoxemia induction were positively correlated together. These parameters were negatively correlated with superoxide dismutase and glutathione peroxidase at all hours after lipopolysaccharide infusion.

The results of the present experiment can provide evidence for associations among acute phase proteins, cytokines, and enzymes and their changes during endotoxemia in sheep.