In vitro time-dependent vancomycin-resistant Staphylococcus aureus-induced free radical generation and status of antioxidant enzymes in murine peritoneal macrophage

Abstract

Staphylococcus aureus is most frequently isolated pathogen causing bloodstream infections, skin and soft tissue infections, and pneumonia. The immune cells use reactive oxygen species (ROS) for carrying out their normal functions, while an excess amount of ROS can attack cellular components that lead to cell damage. The aim of the present study was to evaluate the free radical generation and status of the antioxidant enzymes in murine peritoneal macrophage during in vitro vancomycin-resistant S. aureus (VRSA) treatment with different time intervals. Peritoneal macrophages were treated with 5 × 106 colony-forming units (CFU)/mL VRSA cell suspension in vitro for different time intervals (1, 2, 3, 6, 12, and 24 h), and superoxide anion generation, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, myeloperoxidase (MPO) activity, nitric oxide (NO) generation, antioxidant enzyme status, and components of glutathione cycle were analyzed. Superoxide anion generation, NADPH oxidase activity, MPO activity, and NO generation got peak at 3 h indicates maximum free radical generation through activation of NADPH oxidase in murine peritoneal macrophages during VRSA infection. Reduced glutathione level, glutathione peroxidase, glutathione reductase, and glutathione S-transferase activity were decreased significantly (P < 0.05) with increasing time of VRSA infection. But the oxidized glutathione level was time-dependently increased significantly (P < 0.05) in murine peritoneal macrophages. All the changes in peritoneal macrophages after 3 h in vitro VRSA treatment had no significant difference. From this study, it may be summarized that in vitro VRSA infection not only generates excess free radical but also affects the antioxidant status and glutathione cycle in murine peritoneal macrophages.