Garlic (Allium sativum) Extract Inhibits Lipopolysaccharide-Induced Toll-Like Receptor 4 Dimerization

概要

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Garlic has long been used as a folk medicine. Numerous studies have demonstrated that a garlic extract and its sulfur-containing compounds inhibited nuclear factor kappa B (NF-κB) activation induced by various receptor agonists including lipopolysaccharide (LPS). Toll-like receptors (TLRs) play a key role in sensing diverse microbial products and inducing innate immune responses. The dimerization of TLR4 is required for the activation of downstream signaling pathways, including NF-κB. Therefore, TLR4 dimerization may be one of the first lines of regulation in activating LPS-induced signaling pathways. We report here biochemical evidence that the ethyl acetate fraction of garlic inhibited the LPS-induced dimerization of TLR4, resulting in the inhibition of NF-κB activation and the expression of cyclooxygenase 2 and inducible nitric oxide synthase. Our results demonstrate for the first time that a garlic extract can directly inhibit the TLRs-mediated signaling pathway at the receptor level. These results shed a new insight into understanding how garlic modulates the immune responses that could modify the risk of many chronic diseases.
社団法人日本農芸化学会の論文
2008-02-23