Anti-neuroinflammatory effects of geranium oil in microglial cells

Microglial cells are major immune cells in the brain, and their activation is involved in neurodegenerative diseases such as Alzheimer's disease. Activated microglial cells secrete proinflammatory factors including nitric oxide (NO), which is an important mediator of neuroinflammation and neuronal cell death. In the present study, we demonstrated that geranium oil inhibited NO production, as well as the expression of the proinflammatory enzymes cyclooxygenase-2 (COX-2) and induced nitric oxide synthase (iNOS) in primary cultures of activated microglial cells. When tested at their natural relative concentrations in the oil, none of the major constituents of the oil could inhibit NO production. However, at higher concentrations, citronellol exhibited an inhibitory activity. The results suggest a possible synergistic interaction between these components. Thus, geranium oil might be beneficial in the prevention/treatment of neurodegenerative diseases where neuroinflammation is part of the pathophysiology. (c) 2009 Elsevier Ltd. All rights reserved.