Excessive activation of microglia due to pathogenic bacterial infection or injury releases proinflammatory mediators such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, reactive oxygen species (ROS), nitric oxide (NO), inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 [5]. Here, NOS2 is linked to bacterial infectious disease.