Anti-neuroinflammatory effects of Ginkgo biloba extract EGb761 in LPS-activated primary microglial cells

Abstract

Background: Neuroinflammation is a key factor of Alzheimer's disease (AD) and other neurodegenerative conditions. Microglia are the resident mononuclear immune cells of the central nervous system (CNS). They play an essential role in the maintenance of homeostasis and responses to neuroinflammation. Ginkgo biloba extract EGb 761 is one of the most commonly used natural medicines owing to its established efficacy and remarkable biological activities especially in respect to CNS diseases. However, only few studies have addressed the effects and mechanisms of Ginkgo biloba extract in microglia activation.

Methods: We measured the production of pro-inflammatory mediators and cytokines by ELISA and analyzed gene expressions by qRT-PCR and Western Blot in LPS treated cultured primary rat microglia.

Results: The Ginkgo biloba extract EGb 761 significantly inhibited the release of prostaglandin E₂ (PGE₂) and differentially regulated the levels of pro-inflammatory cytokines. The inhibition of LPS-induced PGE₂ release in primary microglia was partially dependent on reduced protein synthesis of mPGES-1 and the reduction in the activation of cytosolic phospholipase A2 (cPLA2) without altering COX-2 enzymatic activity, inhibitor of kappa B alpha (IkappaBalpha) degradation, and the activation of multiple mitogen activated protein kinases (MAPKs). Altogether, we showed that EGb 761 reduces neuro-inflammatory activation in primary microglial cells by targeting PGE₂ release and cytokines.

Conclusion: Ginkgo biloba extract EGb 761 displayed anti-neuroinflammatory activity in LPS-activated primary microglia cells. EGb 761 was able to reduce neuroinflammatory activation by targeting the COX/PGE₂ pathway. This effect might contribute to the established clinical cognitive efficacy in Alzheimer's disease, vascular and mixed dementia.

Keywords: Alzheimer's disease; Cyclooxygenase; Cytokines; Neurodegeneration; Neuroinflammation; Prostaglandin E(2).