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Platelet-activating factor (PAF) is a potent bioactive
phospholipid mediator involved in inflammation, platelet activation,
vascular permeability, leukocyte recruitment, bronchoconstriction and immune
signalling. PAF acts primarily through the platelet-activating factor receptor
(PTAFR / PAFR), a G-protein-coupled receptor. Excessive
PAF signalling can contribute to inflammatory and vascular injury and has also
been implicated in tumour-cell proliferation, migration, angiogenesis and
metastasis in some cancers. In the nervous system, excessive PAF signalling can
promote neuroinflammation, oxidative stress and excitotoxic neuronal injury,
although physiological PAF also participates in synaptic signalling. Therefore,
pathological PAF activity is generally considered up in
inflammatory disease contexts, while the desired modulation is typically
down or PAF-receptor antagonism. Ginkgolides, particularly
ginkgolide B, are well-characterized antagonists of the PAF
receptor and contribute to the pharmacological activity of standardized
Ginkgo biloba extracts such as EGb 761.
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