Effect of canine hyperimmune plasma on TNFα and inflammatory cell levels in a lipopolysaccharide-mediated rat air pouch model of inflammation

Introduction

Unregulated elevated levels of serum TNFα have been associated with proinflammatory cytokine cascades that are characteristic in diseases such as septic shock. Endotoxic shock, which has a poorer prognosis than found with other forms of septic shock, is mediated by lipopolysaccharide (LPS), a molecule that is released from the outer membrane of Gram-negative bacteria. LPS is a potent stimulator of TNFα secretion by serum monocytes and tissue macrophages. Whilst the use of monotherapeutic TNFα antagonists has been trailed, none have been registered for use in patients with sepsis.

Objective

The purpose of this study was to test the effect of canine hyperimmune frozen plasma (HFP), which is known to contain elevated levels of soluble TNFα receptor 1 (sTNFR1), on TNFα and inflammatory cell levels in a LPS-mediated rat air pouch model of inflammation.

Methods

A dorsal air pouch in 175 to 200 g Sprague-Dawley rats was formed by 20 ml subcutaneous infusions of sterile air. Prophylactic subcutaneous injections of canine HFP, canine fresh frozen plasma (FFP) or carprofen were administered daily for 3 days into the lateral flank of the right foreleg at doses recommended by the manufacturers (n = 10 for each treatment group). Pouch fluid was harvested by syringe at 1, 6, 12, 24 and 48 hours post LPS administration and subjected to histological and cytokine/cytokine receptor analysis. TNFα and sTNFR1 levels were determined by ELISA and an immunofluorescent dot blot assay.

Results

Pouch fluid analysis: maximal effects were detected at 6 hours post LPS administration. TNFα levels were significantly depressed in animals dosed with HFP, but not in animals treated with FFP or carprofen (P < 0.05). sTNFR1 levels were significantly elevated in HFP, but not in FFP or carprofen dosed animals (P < 0.05). Neutrophils numbers were significantly depressed in HFP dosed, but not in FFP or carprofen treated animals (P < 0.05).

Conclusion

There appears to be a correlation between elevated levels of sTNFR1 and depression of TNFα and neutrophil levels in the pouch fluid of HFP dosed rats (r = -0.73, P < 0.0001). The data suggest that canine HFP, which has been demonstrated to contain elevated levels of sTNFR1 compared with FFP, has a direct effect on depressing TNFα levels and neutrophil sequestration in the rat air pouch model of inflammation. These data suggest that HFP may be worthy of further investigation to determine whether such preparations have a therapeutic potential for treatment of acute inflammatory diseases in which TNFα is implicated.