Oxidative Stress and Neutrophil Function Following Oral Supplementation of a Silibinin-Phosphatidylcholine Complex in Cats
The purpose of this study was to determine the effect of oral supplementation of a silibinin-phosphatidylcholine complex SPC on parameters of oxidative stress and neutrophil function in healthy cats.
Blood samples were collected from 10 purpose-bred cats prior to and immediately after five days of oral supplementation of SPC (10 mg/kg; supplied by Nutramax Laboratories). Leukocytes were isolated from heparinized peripheral blood and incubated with monochlorobimane (mBCl). Monochlorobimane conjugates with reduced glutathione (GSH) resulting in a fluorescent signal that can be detected with flow cytometry. Leukocytes were also incubated with dihydrorhodamine 123 (DHR) and then mixed with E. coli conjugated to the fluorescent marker Alexa 488. DHR fluoresces in the presence of free radicals such that this combination of markers allows the measurement of E. coli phagocytosis and the subsequent oxidative burst by flow cytometry. The antioxidant enzymes superoxide dismutase and glutathione peroxidase, along with the reduced-to-oxidized glutathione ratio (GSH:GSSG) and a measure of lipid peroxidation (malondialdehyde) were measured using spectrophotometry in erythrocytes and whole blood.
A significant increase in intracellular GSH content was found in neutrophils of cats supplemented with SPC, with fluorescence intensity increasing from 515.3 ± 191.5 to 592.7 ± 178.1 (P = .026). A significant increase in phagocytic function was also noted, with the percent of neutrophils exhibiting maximal phagocytosis and oxidative burst increasing from 37% ± 11.8 to 45% ± 17.5 (P = .049) following 5 days of SPC supplementation. Other measures of oxidative stress did not change significantly.
Silibinin is a flavonoid with antioxidant properties used in treating a variety of human diseases including liver disease, diabetes mellitus, and cancer. One of silibinin's proposed mechanisms of action is to increase intracellular glutathione content. Oral supplementation of SPC in cats appears to increase neutrophil GSH content and phagocytic function, both of which would be potentially beneficial in cats suffering from diseases associated with oxidative stress.