In vitro evaluation of the effect of trans-10, cis-12 conjugated linoleic acid on phagocytosis by canine peripheral blood polymorphonuclear neutrophilic leukocytes exposed to methylprednisolone sodium succinate

Abstract

Objective - To examine whether in vitro treatment with trans-10, cis-12 conjugated linoleic acid (t10c12-CLA) restores the phagocytic capacity and oxidative burst activity (OBA) of canine polymorphonuclear neutrophilic leukocytes (PMNs) exposed to methylprednisolone sodium succinate (MPSS). Sample Population - Peripheral blood PMNs obtained from 12 healthy Beagles. Procedures - The experimental design involved administration of a high dose of MPSS, which is the recommended protocol for dogs with acute spinal cord injury. To evaluate PMN function, blood samples were collected from dogs before IV injections of doses of MPSS or saline (0.9% NaCl) solution (time 0) and 2, 12, and 24 hours after injections ceased. Polymorphonuclear neutrophilic leukocytes were isolated from blood samples and incubated with t10c12-CLA alone or t10c12-CLA in combination with N-acetylcysteine (an antioxidant agent). Phagocytic capacity and OBA were measured simultaneously by use of flow cytometry. Results - The phagocytic capacity and OBA of PMNs were suppressed by IV injection of MPSS and restored 12 hours after injection ceased. In vitro treatment with t10c12-CLA enhanced the phagocytic capacity and OBA of PMNs, regardless of whether dogs had been treated with MPSS. Effects of t10c12-CLA on OBA were detected only when phagocytosis was stimulated by microspheres. Use of N-acetylcysteine attenuated the stimulatory effects of t10c12-CLA. Conclusions and Clinical Relevance - Exposure to t10c12-CLA enhanced the phagocytic capacity and OBA of canine PMNs, and this effect may have involved t10c12-CLA-induced generation of reactive oxygen species.