Abstract
The aim of the present study was to evaluate the effect of two different antioxidants, α-tocopherol and ascorbic acid, on the chemotactic activity and susceptibility to Mannheimia haemolytica leukotoxin (Lkt) of white blood cells obtained from calves exposed to transport in vitro. Both antioxidants used were found to affect the chemotactic activity of white blood cells. Supplementation of α-tocopherol at a concentration of 0.2 mg/ml and 0.5 mg/ml induced significant (P ⪬ 0.05) increase of chemotactic activity in white blood cells compared to control. In case of ascorbic acid supplementation the highest chemotactic activity was observed at a concentration of 0.5 mg/ml. The results obtained in microtitration (MTT) assay also suggest that high concentrations of α-tocopherol (0.5 mg/ml) play a role in protecting bovine leukocytes against the cytotoxic effect of Lkt, the susceptibility of the leukocytes on M. haemolytica Lkt was lower in comparison to control about 6%. The antioxidants used in this study have been found to have a protective effect on cells participating in the immune response to M. haemolytica. This particularly applies to high concentrations of α-tocopherol. The clinical aspect of these results may lie in protection of leukocytes exposed to leukotoxin of M. haemolytica. It should be emphasized that the results provide only partial information on the effect of the antioxidants studied on cells participating in an organism’s defence mechanisms. For an evaluation that would enable proper prevention of bovine respiratory diseases, research should be continued and expanded to include analysis of cellular structures.
Highlights
Both antioxidants used were found to affect the chemotactic activity of white blood cells
The results obtained in microtitration (MTT) assay suggest that high concentrations of -tocopherol (0.5 mg/ml) play a role in protecting bovine leukocytes against the cytotoxic effect of Lkt, the susceptibility of the leukocytes on M. haemolytica Lkt was lower in comparison to control about 6%
Cultures of leukocytes isolated from calves subjected to transport stress grown in RPMI 1640 medium supplemented with -tocopherol or ascorbic acid showed increased chemotactic activity towards the chemotactic factor
Summary
Both antioxidants used were found to affect the chemotactic activity of white blood cells. Supplementation of -tocopherol at a concentration of 0.2 mg/ml and 0.5 mg/ml induced significant (P 0.05) increase of chemotactic activity in white blood cells compared to control. The antioxidants used in this study have been found to have a protective effect on cells participating in the immune response to M. haemolytica This applies to high concentrations of -tocopherol. Previous studies (Urban-Chmiel 2006; Urban-Chmiel et al 2006) have shown that transport stress has a major effect on the antioxidant and oxidative status in bovine leukocytes and increases their susceptibility to Mannheimia haemolytica leukotoxin (Lkt). These changes may play a negative role in M. haemolytica respiratory infection in calves. Administration of exogenous -tocopherol incorporated in liposomes protected against lung oedema in animal models of acute respiratory distress syndrome (ARDS) and against chemically induced lung injury by lipopolysaccharide (LPS) in a mouse model, which is correlated with antioxidant and oxidative status in cells
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