title: Characterization of a platelet-activating factor receptor antagonist isolated from haifenteng (Piper futokadsura): specific inhibition of in vitro and in vivo platelet-activating factor-induced effects.
abstract: Platelet-activating factor (PAF) is a potent lipid mediator of inflammation and asthma. Using a receptor preparation of rabbit platelet membranes, we identified a novel antagonist of PAF in the methylene chloride extract of a Chinese herbal plant, haifenteng (Piper futokadsura). The active antagonist, kadsurenone, was isolated and characterized in several in vitro and in vivo assays. It is a specific and competitive inhibitor of PAF binding to its receptor with a Ki of 5.8 X 10(-8) M vs. a Ki of 6.3 X 10(-9) M for PAF itself. It inhibits PAF-induced aggregation of rabbit platelets and human neutrophils at 2.4-24 microM, without showing any PAF agonistic activity. It potently inhibits PAF-induced degranulation of human neutrophils at 2.5-50 microM, also without any agonist activity. Kadsurenone is active orally at 25-50 mg/kg of body weight in blocking PAF-induced cutaneous permeability in the guinea pig. It also inhibits PAF-induced increases of hematocrit and circulating N-acetylglucosaminidase in the rat at greater than 10 mg/kg i.p. in a dose-dependent manner. Kadsurenone does not interfere with the function of several pharmacological mediators and receptors tested. Its structural specificity is evidenced by the poor PAF-antagonistic activities of three related structures isolated from the same haifenteng extract.
authors.forename: T Y
authors.initials: TY
authors.lastname: Shen
authors.forename: S B
authors.initials: SB
authors.lastname: Hwang
authors.forename: M N
authors.initials: MN
authors.lastname: Chang
authors.forename: T W
authors.initials: TW
authors.lastname: Doebber
authors.forename: M H
authors.initials: MH
authors.lastname: Lam
authors.forename: M S
authors.initials: MS
authors.lastname: Wu
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: G Q
authors.initials: GQ
authors.lastname: Han
authors.forename: R Z
authors.initials: RZ
authors.lastname: Li
mesh_terms: D000818:Animals; D001572:Benzofurans; D001578:Benzopyrans / Q000494:pharmacology*; D002199:Capillary Permeability / Q000187:drug effects; D006168:Guinea Pigs; D006801:Humans; D017705:Lignans; D019684:Magnoliopsida / Q000032:analysis*; D008433:Mathematics; D009504:Neutrophils / Q000187:drug effects; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled
chemical_list: D001572:Benzofurans; D001578:Benzopyrans; D017705:Lignans; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; C044540:kadsurenone