lignans and kadsurenone

Topics: Animals; Benzofurans; Cerebrovascular Circulation; Drugs, Chinese Herbal; Humans; Lignans; Neuroprotective Agents; Piper; Plant Stems; Plants, Medicinal; Platelet Activating Factor

This paper deals with the recent progress in the study of anti-PAF constituents of medicinal herbs. The structural modification, synthesis of analogs and pharmacophore model are also introduced in brief.

Topics: Animals; Asthma; Benzofurans; Diterpenes; Drugs, Chinese Herbal; Furans; Ginkgolides; Humans; Lactones; Lignans; Plant Extracts; Platelet Activating Factor

A rational method of search for natural neolignans of desired structures is outlined. This involves consultation of a collection of chemical profiles of plant families. The profiles are assembled considering the biosynthetic class (in the present case lignoids), subclass (neolignans), structural types (neolignan skeletal) and relative frequency of substitutional derivatives belonging to each type (known compounds). The method is of course applicable to any class of natural products. Its use in the case of neolignans is here selected as an example in view of the recently discovered antagonism towards PAF of kadsurenone, a representative of this subclass of phytochemicals. Application of the chemical profiles to phylogenetic studies is illustrated.

Topics: Benzofurans; Drug Design; Lignans; Lignin; Molecular Structure; Plants, Medicinal; Platelet Activating Factor

Topics: Animals; Benzofurans; Benzopyrans; Depression, Chemical; Guinea Pigs; Lignans; Phospholipid Ethers; Platelet Activating Factor; Platelet Aggregation; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Structure-Activity Relationship; Thiazoles

Six amides, piperbonamides A-F, three neolignans piperbonins A-C, and 11 known compounds were isolated from the aerial parts of Piper bonii (Piperaceae). The structures of piperbonamides A-F and piperbonins A-C were elucidated based on the analysis of 1D and 2D NMR and MS data. Piperbonin A, (+)-trans-acuminatin, (+)-cis-acuminatin, (+)-kadsurenone, and pipernonaline showed weak activity against platelet aggregation with IC50 values of 118.2, 108.5, 90.02, 107.3, and 116.3 μM, respectively, as compared with the positive control, tirofiban, with an IC50 value of 5.24 μM. Piperbonamides A-F were inactive against five tumor cell lines at concentrations up to 40 μM.

Topics: Alkaloids; Amides; Benzofurans; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Flavonoids; Glycosides; Humans; Inhibitory Concentration 50; Lignans; Molecular Structure; Piper; Piperidines; Plant Components, Aerial; Platelet Aggregation; Platelet Aggregation Inhibitors; Structure-Activity Relationship; Tirofiban; Tyrosine

A sensitive and rapid LC-MS/MS method was developed and validated for the determination of kadsurenone in rat plasma using lysionotin as the internal standard (IS). The analytes were extracted from rat plasma with acetonitrile and separated on a SB-C18 column (50 × 2.1 mm, i.d.; 1.8 µm) at 30 °C. Elution was achieved with a mobile phase consisting of methanol-water-formic acid (65:35:0.1, v/v/v) at a flow rate of 0.30 mL/min. Detection and quantification for analytes were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 357.1 → 178.1 for kadsurenone, and m/z 345.1 → 315.1 for IS. Calibration curves were linear over a concentration range of 4.88-1464 ng/mL with a lower limit of quantification of 4.88 ng/mL. The intra- and inter-day accuracies and precisions were <8.9%. The LC-MS/MS assay was successfully applied for oral pharmacokinetic evaluation of kadsurenone using the rat as an animal model.

Topics: Animals; Benzofurans; Chromatography, Liquid; Least-Squares Analysis; Lignans; Male; Rats; Rats, Wistar; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry

Kadsurenone is a neolignan with specific antagonistic activity of platelet-activating factor, and is derived from the stems of Piper kadsura. To investigate the mechanism of hepatobiliary excretion of kadsurenone and its association with P-glycoprotein (P-gp), and to explore whether the hepatobiliary excretion of kadsurenone was associated with P-gp, a microdialysis system coupled with HPLC was developed to measure free-form kadsurenone in rat blood and bile. This study design was parallel in the following groups: six rats received kadsurenone alone (20 and 30 mg/kg, i.v.) as control group and the treated-group rats were co-administered with kadsurenone and CsA; P-gp inhibitor. The microdialysis probes were respectively inserted into the jugular vein toward right atrium and bile duct of male Sprague-Dawley rats for blood and bile sampling. CsA (20mg/kg) was administered 10 min prior to kadsurenone administration through the femoral vein and the collected samples were analyzed by a HPLC system. The analytes were separated by a C18 column (150 x 4.6 mm I.D., 5 microm) with a mobile phase of acetonitrile-water (50:50, v/v) at a flow-rate of 1 mL/min. The UV detection wavelength was set 235 nm. The calibration curve was linear over the concentration range of 0.05-10 microg/mL with the coefficient of determination of 0.997. The inter- and intra-assay accuracy and precision of the method ranged from -9.53% to 6.75%. The limit of detection and the limit of quantification were 0.01 and 0.05 microg/mL, respectively. The hepatobiliary excretion ratio of kadsurenone was defined by dividing the values of the area under the drug concentration curve (AUC) for bile and blood (AUC(bile)/AUC(blood)). The results indicated that the hepatobiliary excretion ratio of kadsurenone on the CsA treated-group was 1.2+/-0.1, which was not significantly different from the group of kadsurenone alone (1.3+/-0.2). This fact indicates that kadsurenone went through hepatobiliary excretion but might not be regulated by P-gp.

Topics: Animals; Area Under Curve; ATP Binding Cassette Transporter, Subfamily B, Member 1; Benzofurans; Bile; Chromatography, High Pressure Liquid; Cyclosporine; Data Interpretation, Statistical; Drugs, Chinese Herbal; Lignans; Male; Microdialysis; Piper; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Sensitivity and Specificity

A convergent synthesis of diversely substituted benzofuran neolignans (8) is described employing a single p-sulfinyl group on the phenols (3) as an ambident functional group for two types of carbon-carbon bond-forming reactions: (i) the direct synthesis of the dihydrobenzofuran skeletons through an aromatic Pummerer-type reaction and (ii) the ipso-substitution of the sulfur functional group by carbon substituents through a ligand exchange reaction.

Topics: Benzofurans; Ligands; Lignans; Lithium; Phenols; Sulfinic Acids

In a continuing search for PAF antagonists, five benzofuran neolignans have been isolated from the aerial part of Piper kadsura (Choisy) Ohwi, a Chinese traditional drug used for the treatment of inflammation and rheumatic conditions. The structure determination was based upon spectroscopic analysis. Two of the neolignans were found to have new structures and were named as (-)-denudatin B (the enantiomer of denudatin B, II) and kadsurenin M (7S,8S-3,4,3'-trimethoxy-7'-oxo-nor-8',9'-7.O. 4',8,5'-neolignan, V). The known compounds kadsurenon (I), (-)-acuminatin(III) and (+)-licarin A(IV) were also obtained from the same source. (-)-Denudatin B (II) showed potent PAF antagonistic activity in 3H-PAF receptor binding assay.

Topics: Benzofurans; Bridged Bicyclo Compounds; Drugs, Chinese Herbal; Humans; Lignans; Molecular Structure; Platelet Activating Factor; Stereoisomerism

Trimucytin is a potent platelet aggregation inducer isolated from Trimeresurus mucrosquamatus snake venom. Similar to collagen, trimucytin has a run of (Gly-Pro-X) repeats at the N-terminal amino acids sequence. It induced platelet aggregation, ATP release and thromboxane formation in rabbit platelets in a concentration-dependent manner. The aggregation was not due to released ADP since it was not suppressed by creatine phosphate/creatine phosphokinase. It was not either due to thromboxane A2 formation because indomethacin and BW755C did not have any effect on the aggregation even thromboxane B2 formation was completely abolished by indomethacin. Platelet-activating factor (PAF) was not involved in the aggregation since a PAF antagonist, kadsurenone, did not affect. However, RGD-containing peptide triflavin inhibited the aggregation, but not the release of ATP, of platelets induced by trimucytin. Indomethacin, mepacrine, prostaglandin E1 and tetracaine inhibited the thromboxane B2 formation of platelets caused by collagen and trimucytin. Forskolin and sodium nitroprusside inhibited both platelet aggregation and ATP release, but not the shape change induced by trimucytin. In quin-2 loaded platelets, the rise of intracellular calcium concentration caused by trimucytin was decreased by 12-O-tetradecanoyl phorbol-13 acetate, imipramine, TMB-8 and indomethacin. In the absence of extracellular calcium, both collagen and trimucytin caused no thromboxane B2 formation, but still induced ATP release which was completely blocked by R 59022. Inositol phosphate formation in platelets was markedly enhanced by trimucytin and collagen. MAB1988, an antibody against platelet membrane glycoprotein Ia, inhibited trimucytin- and collagen-induced platelet aggregation and ATP release.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Amino Acid Sequence; Animals; Antibodies, Monoclonal; Antigen-Antibody Reactions; Benzofurans; Calcium; Collagen; Crotalid Venoms; Lignans; Molecular Sequence Data; Peptides; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Proteoglycans; Rabbits; Sequence Homology, Amino Acid; Thromboxane A2

Denudatin B, an isomer of kadsurenone, was isolated from Magnolia fargesii. It inhibited the aggregation and ATP release of washed rabbit platelets caused by platelet-activating factor (PAF) in a concentration-dependent manner. The IC50 on PAF (2 ng/ml)-induced aggregation was about 10 micrograms/ml. High concentration of denudatin B (greater than 50 micrograms/ml) also inhibited the aggregation and ATP release of platelets caused by ADP, collagen, arachidonic acid and thrombin. However, shape change of platelets still existed. Prolongation of the incubation time with platelets could not cause further inhibition, and the aggregability of platelets could be restored after denudatin B was washed out from platelets. Thrombin-induced thromboxane B2 formation was almost completely suppressed. In the absence of extracellular calcium (EGTA 1 mM), ATP release caused by thrombin was inhibited. Thrombin-induced rise of the intracellular calcium concentration was suppressed by denudatin B, but not by BN52021 or kadsurenone. The generation of inositol phosphate in washed platelets caused by collagen, PAF and thrombin was also suppressed. The data indicate that PAF antagonist denudatin B has nonspecific antiplatelet action at high concentration by inhibiting phosphoinositides breakdown induced by collagen and thrombin.

Topics: Animals; Benzofurans; Blood Platelets; Calcium; Collagen; In Vitro Techniques; Lignans; Molecular Structure; Phosphatidylinositols; Platelet Activating Factor; Platelet Aggregation; Rabbits; Stereoisomerism; Thrombin; Thromboxane B2

Topics: Benzofurans; Cell Membrane; Drugs, Chinese Herbal; Humans; Kinetics; Lignans; Lignin; Molecular Structure; Platelet Activating Factor; Platelet Aggregation; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Structure-Activity Relationship

Denudatin B is an antiplatelet agent isolated from the flower buds of Magnolia fargesii. We studied the effects of denudatin B on the vasoconstriction of rat thoracic aorta induced by high potassium (K+) solution, norepinephrine (NE) and caffeine, and to elucidate its mode of action. The contraction of rat aorta caused by high K+ (60 mM) and cumulative concentrations of CaCl2 (0.03-3 mM) was inhibited concentration dependently by denudatin B with an IC50 of 21.2 micrograms/ml. NE (3 microM)-induced phasic and tonic contractions of rat aorta were inhibited by pretreatment with denudatin B (10-100 micrograms/ml). The relaxing action of denudatin B persisted in denuded aorta, in Ca2(+)-free and EGTA (2 mM)-containing medium. The vasorelaxing effects were not affected by indomethacin (20 microM), hemoglobin (10 microM) or methylene blue (50 microM) and were not accompanied by PGI2 formation. In quin-2/AM-loaded cultured rat vascular smooth muscle cells, denudatin B (100 micrograms/ml) inhibited the increase of intracellular calcium caused by NE (3 microM) in the presence or absence of extracellular calcium. Denudatin B did not affect the caffeine (10 mM)-induced contraction and the increase in intracellular calcium. Denudatin B (100 micrograms/ml) increased the cGMP, but not the cAMP level in intact and denuded aorta. The 45Ca2+ influx induced in rat aorta by high K+ (60 mM) or NE (3 microM) was markedly inhibited by denudatin B in a concentration-dependent manner. These results indicate that denudatin B relaxed vascular smooth muscle by inhibiting the Ca2+ influx through voltage-gated and receptor-operated Ca2+ channels; its effect to increase cGMP may enhance the vasorelaxation.

Topics: Animals; Aorta, Thoracic; Benzofurans; Caffeine; Calcium; Calcium Radioisotopes; Cells, Cultured; Cyclic AMP; Cyclic GMP; Drugs, Chinese Herbal; Epoprostenol; In Vitro Techniques; Lignans; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Norepinephrine; Potassium; Rats; Rats, Inbred Strains

This paper proposes a new tool that allows us to see the following in the same frame: (1) 3D geometrical features of a molecule, and (2) pseudo-3D representation of the lipophilicity molecular potential. It thus becomes very easy to compare the lipophilicity molecular potential gradient of different molecules having the same pharmacological properties. An example of two structurally dissimilar anti-PAF molecules is given.

Topics: Benzofurans; Computer Graphics; Diterpenes; Fats; Ginkgolides; Lactones; Lignans; Mathematics; Models, Molecular; Solubility

1. The effects of the platelet activating factor (Paf) antagonists alprazolam, BN 52021, kadsurenone, L 652,731 and SRI 63119 have been studied on Paf-induced chemiluminescence (CL) of guinea-pig, C. parvum-activated peritoneal macrophages in vitro. 2. All antagonists produced a shift to the right in the dose-response curve to Paf (0.001-10 mumol l-1). Schild plots for BN 52021, L 652,731, kadsurenone and SRI 63119 were linear, but only for BN 52021 and kadsurenone did the mean slope not differ significantly from unity. Mean pA2 values for BN 52021 and kadsurenone were 6.60 +/- 0.05 and 6.41 +/- 0.14 (mean + s.e.mean) respectively. Calculation of IC50 values for all antagonists (at 0.1 mumol l-1 Paf) gave an order of potency: L 652731 greater than kadsurenone greater than or equal to BN 52021 greater than alprazolam greater than SRI 63119. 3. When individual pA2 values for BN 52021 and kadsurenone were plotted against the maximal CL response to Paf of cell suspensions in the absence of antagonist (reflecting the degree of activation of the macrophages by the C. parvum), it was found that the affinity of both antagonists for macrophage Paf receptors remained relatively constant irrespective of the activation state of the cells. 4. We conclude that activation of guinea-pig peritoneal macrophages does not account for the increased affinity for macrophage Paf receptors previously observed for kadsurenone. Kadsurenone and BN 52021 presumably bind to a site on Paf receptors which is not affected by the activation process, while alprazolam and SRI 63119 are non-specific antagonists. The reason for the difference between the competitive nature of kadsurenone and its structural analogue L 652,731 is unclear.

Topics: Alprazolam; Animals; Benzofurans; Diterpenes; Furans; Ginkgolides; Guinea Pigs; In Vitro Techniques; Lactones; Lignans; Luminescent Measurements; Macrophage Activation; Macrophages; Male; Platelet Activating Factor; Thiazoles

Platelet-activating factor (PAF) has recently been described as a mediator of inflammatory processes. In this study, we quantitated the dose-response effects of topically applied PAF on microvascular permselectivity and investigated the biochemical pathways of this compound. Permselectivity alterations were assessed by measuring the clearance of macromolecules with fluorescein isothiocyanate dextran 150 (FITC-dx 150) as a tracer. The microvascular bed of the hamster cheek pouch served as a model. PAF was found to induce leakage of macromolecules from postcapillary venules. Control FITC-dx 150 plasma clearance (+/- SEM) was 72 +/- 10 nl/90 min. Clearances of 61 +/- 10 474 +/- 145, 622 +/- 57, 301 +/- 86, and 142 +/- 3 nl/90 min were obtained at PAF concentrations of 10(-9), 10(-8), 10(-7), 10(-6), and 10(-5) M, respectively. A one-way analysis of variance showed that the population means were not equal. Multiple comparison by the Student-Newman-Keuls test demonstrated that the clearances obtained with 10(-8), 10(-7), and 10(-6) M were significantly greater than controls. Significant differences existed between 10(-7) M PAF and 10(-9), 10(-6), and 10(-5) M PAF. In an effort to elucidate the biochemical pathways of PAF activity, several inhibitors of the arachidonic acid cascade and receptor blockers were used. Dexamethasone and kadsurenone attenuated the clearance response to PAF in a statistically significant manner, while indomethacin, OKY-046, and chlorpheniramine were without effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzofurans; Blood Pressure; Capillary Permeability; Cheek; Cricetinae; Dexamethasone; Dextrans; Dose-Response Relationship, Drug; Fluorescein-5-isothiocyanate; Fluoresceins; Hematocrit; Indomethacin; Lignans; Macromolecular Substances; Male; Mesocricetus; Methacrylates; Microcirculation; Platelet Activating Factor

During inflammation polymorphonuclear cells (PMNs) are exposed to agonistic stimuli including activated complement, kallikrein, arachidonic acid metabolites, monokines, and platelet-activating factor (PAF). We report that PAF not only directly activates PMNs but in miniscule quantities (10(-12) mol/L) "primes" them as well, that is, permits PMNs to respond to subsequent stimuli that would be otherwise ineffectual. PAF priming of responses including superoxide generation, elastase release, and aggregation is time dependent and is maximal within five minutes. PAF need not be present during the subsequent exhibition of PMN agonists, but priming is inhibited by cold and is also inhibited by the PAF receptor antagonists BN 52021, L-652, and kadsurenone. An intact PAF molecule is required because lyso-PAF and methoxy-PAF do not prime PMN responses. PAF priming is associated with both enhanced expression of the adhesive glycoprotein identified by OKM-1 antibody and an enhanced rise in intracellular calcium levels in response to the subsequent addition of agonists such as FMLP. PMNs primed with PAF and stimulated with either F-Met-Leu-Phe or phorbol esters are more effective in lysing and detaching cultured human endothelial cells--damage that can also be inhibited by the PAF antagonists. Because PAF is synthesized and exhibited on surfaces of endothelial cells perturbed by coagulation, we suggest that this lipid may potentiate otherwise trivial activators of marginated PMNs so that they become damaging to the PAF-synthesizing endothelium itself. If so, our studies suggest a possible therapeutic role for PAF inhibitors in excessive inflammatory states.

Topics: Benzofurans; Cell Aggregation; Cell Survival; Diterpenes; Endothelium, Vascular; Fetal Hemoglobin; Furans; Ginkgolides; Hemoglobins, Abnormal; Humans; Inflammation; Lactones; Lignans; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Pancreatic Elastase; Platelet Activating Factor; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Superoxides

Platelet-activating factor (PAF) has been implicated as a potential mediator of inflammatory processes. In this study, we quantified the effects of PAF on vessel diameter in a microvascular bed and investigated the biochemical pathways of this compound. The hamster cheek pouch microcirculation was observed with intravital microscopy. Experiments were video-recorded and analyzed with an image shearing device. Vasoconstriction was the predominant vasomotor response to PAF. PAF (10(-10) -10(-5) M) was applied topically to the pouch for 3 minutes. Arterioles ranging in size from 8 to 15 micron were the most sensitive, and they constricted completely in response to PAF 10(-7) and 10(-5) M. Arterioles 21-40 micron in diameter constricted to 12-17% of control after PAF at 10(-7) and 10(-5) M, respectively; they reopened to about 70% of their control value after a few minutes and remained near that size throughout the experiment. Arterioles 41-60 micron in diameter constricted to about 20% control size in response to 10(-7) and 10(-5) M PAF, and by the end of the experiment, these vessels had returned to about 90% control size. To determine the pathways of PAF actions, inhibitors of the arachidonic acid cascade and receptor blockers were used. Dexamethasone, indomethacin, OKY-046 (a thromboxane A2 synthetase inhibitor), and kadsurenone (a PAF-receptor blocker) blocked the vasoconstrictor response to PAF. Our experiments demonstrate that PAF-produced arteriolar constriction in a microvascular bed is 1) dose-related, 2) dependent upon vessel size, 3) largely due to thromboxane A2 activity, and 4) mediated by PAF-receptor interactions.

Topics: Animals; Arterioles; Benzofurans; Blood Pressure; Cheek; Cricetinae; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Hematocrit; Lignans; Male; Mesocricetus; Microcirculation; Platelet Activating Factor; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Thromboxane A2; Vasoconstriction

Unilateral ureteral obstruction (UUO) results in increased renal resistance as well as in exaggerated prostaglandin (PG) release from the obstructed hydronephrotic kidney (HNK). We have reported previously that platelet-activating factor (PAF) dose-dependently stimulates the release of PGs from both the HNK and unobstructed contralateral kidney (CLK), with CLK release being 10% that of the HNK. In the present report, we studied the interaction of PAF with its receptor by examining the effects of PAF-receptor antagonists on the release of PGs from the isolated perfused rabbit HNK and CLK stimulated by PAF; angiotensin II (AII), and bradykinin (BK) were also used as agonists. In the HNK, kadsurenone (3 microM) inhibited PAF-stimulated PGE2 and thromboxane B2 (TxB2) release by 28.2 and 62.5% respectively. CV-3988 (20 microM) and triazolam (5 microM) also preferentially diminished PAF-stimulated TxB2 release. In addition, all three drugs significantly diminished BK- and AII-stimulated TxB2 release, while CV-3988 was the only antagonist to affect peptide-stimulated PGE2 release. While effective against agonist-stimulated PG synthesis, these drugs had no direct effect on arachidonic acid metabolism to PGs. Furthermore, in the CLK, CV-3988 had no effect on BK- or AII-stimulated PGE2 release, whereas it totally inhibited PAF-stimulated release of PGE2. These results show that PAF-receptor antagonists in the HNK preferentially inhibit TxB2 release whether stimulated by PAF, AII or BK; in the CLK only PAF-stimulated PG release is affected. This biochemical difference may be of physiological significance and explain some of the functional differences between the HNK and CLK. Therefore, PAF may be an important mediator of some of the biochemical and functional changes associated with UUO.

Topics: Angiotensin II; Animals; Benzofurans; Dinoprostone; Kidney; Lignans; Male; Peptides; Platelet Activating Factor; Platelet Membrane Glycoproteins; Prostaglandins; Prostaglandins E; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Thromboxane B2; Triazolam; Ureteral Obstruction

The capacity of platelet-activating factor (PAF) to enhance human monocyte cytotoxicity for WEHI 164 cells was examined. Spontaneous monocyte cytotoxicity was 24 +/- 2% (mean +/- SEM, n = 9). Preincubation of monocytes with 1 pM-1 nM PAF for 18 hr significantly enhanced cytotoxicity in a dose-related manner, whereas less enhancement was observed at PAF concentrations above 1 nM. Maximal PAF-induced cytotoxicity was 68 +/- 6%, which was similar to that induced by optimal concentrations of tumour necrosis factor (TNF) and interferon-gamma. The specific PAF antagonist kadsurenone inhibited PAF-induced cytotoxicity but not TNF-induced cytotoxicity. The inactive PAF analogues lysoPAF and enantioPAF did not increase monocyte cytotoxicity. Two observations suggest that TNF mediates PAF-induced cytotoxicity: specific anti-TNF antibodies inhibited PAF-induced cytotoxicity toward WEHI 164 cells, and PAF did not enhance cytotoxicity to TNF-resistant cells. PAF represents a distinct class of phospholipid monocyte activators that increase monocyte cytotoxicity by TNF-dependent mechanisms.

Topics: Benzofurans; Cells, Cultured; Cytotoxicity, Immunologic; Dose-Response Relationship, Immunologic; Humans; Isomerism; Lignans; Monocytes; Platelet Activating Factor; Tumor Necrosis Factor-alpha

We treated four anesthetized dogs (Canis familiaris) with the platelet activating factor (PAF) receptor antagonist kadsurenone prior to 60 min of multifocal ischemia induced by air embolism, and measured neuronal recovery, blood flow and autologous 111In-labeled platelet accumulation for 4 h after ischemia. Four anesthetized animals with identical ischemia served as controls. Kadsurenone (3 mg/kg) administered 5 min prior to ischemia and continuously (1 mg/kg/hr) throughout ischemia and recovery significantly enhanced recovery of cortical somatosensory evoked response (CSER) amplitude (% of baseline) when compared to controls (27-36% vs 9-14%, p less than 0.05). We estimated platelet accumulation as 111In activity (cmp/g tissue) in the injured hemisphere minus that in the non-injured hemisphere. Kadsurenone treated animals did not exhibit significantly altered 111In-labeled platelet accumulation when compared to controls (6158 +/- 2386 vs 9979 +/- 3852, mean +/- SEM). Beneficial effects of PAF receptor blockade other than those on platelet accumulation may be involved.

Topics: Animals; Benzofurans; Brain Ischemia; Cerebral Cortex; Cerebrovascular Circulation; Dogs; Evoked Potentials, Somatosensory; Lignans; Male; Platelet Activating Factor; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled

Kadsurenone, a specific receptor antagonist of platelet-activating factor (PAF), and its analogues were prepared from derivatives of cinnamyl alcohol and (allyloxy)phenol. Racemic kadsurenone, resolvable by a Chiralpak column at low temperatures, has an IC50 value of 2 X 10(-7) M, which is about 50% of the activity of the natural product (IC50 = 1 X 10(-7) M). The structural specificity of kadsurenone was further demonstrated by the low PAF-receptor-blocking activities of denudatin B, mirandin A, desallylkadsurenone, and the 2-epimer of kadsurenone.

Topics: Animals; Benzofurans; Blood Platelets; Cell Membrane; Circular Dichroism; Indicators and Reagents; Kinetics; Lignans; Magnetic Resonance Spectroscopy; Platelet Activating Factor; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Structure-Activity Relationship

Topics: 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; Anaphylaxis; Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzofurans; Blood Pressure; Diphenhydramine; Guinea Pigs; In Vitro Techniques; Lignans; Lung; Male; Platelet Activating Factor; Platelet Count; Pyrazoles

Platelet activating factor (PAF; 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a lipid mediator of inflammation produced by inflammatory cells and also by renal glomerular mesangial cells. PAF may play a role in glomerular function and disease. Previously the authors reported that glomerular mesangial cells respond to PAF by increasing prostaglandin E2 (PGE2) synthesis and by cell contraction. This paper examines the specificity of BN52021, SRI 63-072 and kadsurenone on the effects of PAF on cultured rat glomerular mesangial cells. Both BN52021 and SRI 63-072 specifically decreased PAF (1 X 10(-6) M)-stimulated PGE2 production in a dose-dependent fashion (10(-7)-10(-5) M) without affecting the stimulation by angiotensin II (AII) or the calcium ionophore A23187. Kadsurenone also decreased PAF-stimulated PGE2 production, but in a less specific manner, as it also decreased AII- and A23187-stimulated PGE2 production. In order to examine the site of antagonism of PAF-induced PGE2 synthesis by BN52021 and SRI 63-072, the authors prelabeled cells with [14C]arachidonic acid. Both agents diminished the release of [14C]arachidonate from these prelabeled cells in response to PAF in a dose-dependent fashion, though not decreasing release in response to AII or A23187, indicating that they blocked the effect of PAF on phospholipase activation, consistent with receptor blocking activity. BN52021 and SRI 63-072 also inhibited PAF-induced contraction of cultured mesangial cells without an effect on basal tone of the cells or the contractile response to AII.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Benzofurans; Calcimycin; Cells, Cultured; Dinoprostone; Diterpenes; Dose-Response Relationship, Drug; Ginkgolides; Glomerular Mesangium; Lactones; Lignans; Male; Plant Extracts; Platelet Activating Factor; Prostaglandins E; Rats; Thiazoles

This paper describes a testing model for the detection and evaluation of PAF antagonists, based on the inhibition of PAF-elicited elastase release by human neutrophils. Incubations are performed in microtiter plates in the presence of a specific fluorogenic elastase substrate allowing direct measurement of the exocytosis response by means of a 96-well fluorescence reader. Determinations of the IC50 values for five established PAF antagonists, Ro 19-3704, BN 52021, CV-3988, 48740 RP and kadsurenone, showed that the new model is comparable in sensitivity and discriminative capacity to other in vitro assays. From the effect of antagonists on the PAF concentration-response curve pA2 values could be calculated and information on the type of antagonism obtained. BN 52021 was found to behave as a competitive antagonist while Ro 19-3704 showed a more complex type of inhibition. As a one-plate system, the test is simple to handle and highly reproducible, and appears therefore particularly useful for large drug screening programs.

Topics: Benzofurans; Diterpenes; Exocytosis; Fluorescence; Ginkgolides; Humans; Lactones; Lignans; Methods; Neutrophils; Pancreatic Elastase; Phospholipid Ethers; Plant Extracts; Platelet Activating Factor; Pyridines; Thiazoles

Specific binding of 3H-labeled platelet-activating factor (PAF) to rabbit platelet membranes was found to be regulated by monovalent and divalent cations and GTP. At 0 degrees C, inhibition of [3H]PAF binding by sodium is specific, with an ED50 of 6 mM, while Li+ is 25-fold less effective. On the contrary, K+, Cs+, and Rb+ enhance the binding. The divalent cations, Mg2+, Ca2+, and Mn2+ enhance the specific binding 8-10-fold. From both Scatchard and Klotz analyses, the inhibitory effect of Na+ is apparently due to an increase in the equilibrium dissociation constant (KD) of PAF binding to its receptors. However, the Mg2+-induced enhancement of the PAF specific binding may be attributed to an increased affinity of the receptor and an increased availability of the receptor sites. In the presence of Na+, PAF receptor affinity decreased with increasing temperature with a 100-fold sharp discontinuous decrease in receptor affinity at 24 degrees C. In contrast, the Mg2+-induced increase is independent of temperature suggesting that the Mg2+ regulatory site is different from Na+ regulatory site. [3H]PAF binding is also specifically inhibited by GTP; other nucleotides have little effect. PAF also stimulates hydrolysis of [gamma-32P]GTP with an ED50 of 0.7 nM, whereas 3-O-hexadecyl-2-O-acetyl-sn-glyceryl-1-phosphorylcholine showed no activity even at 10 microM. Moreover, such stimulatory effect of PAF is dependent on Na+ and can be abolished by the PAF-specific receptor antagonist, kadsurenone, but not by an inactive analog, kadsurin B. These results suggest that the PAF receptor may be coupled with the adenylate cyclase system via an inhibitory guanine nucleotide regulatory protein.

Topics: Animals; Benzofurans; Benzopyrans; Calcium; Cell Membrane; Enzyme Activation; GTP Phosphohydrolases; Guanosine Triphosphate; Kinetics; Lignans; Magnesium; Manganese; Platelet Activating Factor; Platelet Membrane Glycoproteins; Potassium; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Sodium; Temperature

The effects of the antagonist kadsurenone on the platelet activating factor (Paf)-induced chemiluminescence of guinea-pig peritoneal macrophages and on pig peripheral blood leucocyte aggregation were compared. Linearity and slopes of unity of the Schild plots confirmed the competitive nature of the antagonism by kadsurenone. pA2 values indicated a 91 fold lower affinity of kadsurenone for leucocyte Paf receptors than for those in macrophages. It is concluded that these two types of Paf receptors are not identical and are provisionally designated Paf1 and Paf2 receptors, respectively.

Topics: Animals; Benzofurans; Benzopyrans; Cell Aggregation; Guinea Pigs; Lignans; Luminescent Measurements; Macrophages; Male; Neutrophils; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Swine

The role of platelet activating factor (PAF) and its inhibition by specific receptor antagonists was studied in hypersensitivity reactions in guinea pig lung parenchymal strips and in guinea pigs in vivo. Immunological challenge of isolated lung parenchymal strips with ovalbumin resulted in a contractile response of 184 +/- 16 mg (n = 38). Pretreatment of the strips with a combination of the antihistamine diphenhydramine, the dual lipoxygenase and cyclooxygenase product synthesis inhibitor BW-755C, and the PAF receptor antagonist kadsurenone totally inhibited the increase in tension. The bronchoconstrictor effects induced by immunological challenge were also totally inhibited when the leukotriene receptor antagonist FPL-55,712 was used to replace BW-755C or another PAF receptor antagonist, alprazolam was used to replace kadsurenone. Ovalbumin challenge in sensitized guinea pigs in vivo resulted in airway constriction, circulatory failure and an abrupt fall in continuously measured platelet count by 75 +/- 12%, followed by death of all animals within 5-8 min. Pretreatment with diphenhydramine, BW-755C and kadsurenone (or alprazolam) improved survival to 64% (i.e., 7 of 11 animals) compared to a survival rate of 0% (i.e., 0 of 8 vehicle treated controls). Despite the improved survival, the severe thrombocytopenia was unaltered with the combined therapy. PAF, histamine and peptide leukotrienes appear to act in concert in mediating the anaphylaxis-induced airway constriction and circulatory failure in guinea pigs, but are not apparently responsible for the accompanying thrombocytopenia.

Topics: Alprazolam; Anaphylaxis; Animals; Benzodiazepines; Benzofurans; Benzopyrans; Diphenhydramine; Guinea Pigs; Histamine; Lignans; Male; Muscle Contraction; Platelet Activating Factor; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; SRS-A

The myotropic activities of PAF-acether, leukotriene B4, leukotriene D4 and histamine were compared on superfused guinea-pig lung parenchymal strip and were shown to have the following order of potency: PAF-acether greater than LTD4 greater than LTB4 greater than histamine. The contractile response of the lung parenchyma to PAF-acether was inhibited by aspirin, imidazole and OKY-046, which suggested that thromboxane A2 might play a mediator role in PAF-induced contractions. Neither an antagonist of leukotriene D4, FPL-55712, nor an antihistamine, mepyramine, had any effect on PAF contractions. The activity of a novel antagonist of PAF-acether, BN 52021, was also studied on superfused lung parenchyma contracted by histamine, leukotriene B4, leukotriene D4 and PAF-acether. This compound was without effect on the histamine response but it slightly reduced the contractions elicited by leukotriene D4 and potentiated those by leukotriene B4. BN 52021 (7.1 X 10(-6) M) inhibited by 63% the contraction induced by 5.7 X 10(-13) M PAF-acether and by 52% that induced by 5.7 X 10(-10) M PAF-acether and kadsurenone (8.4 X 10(-6) M), another PAF-acether antagonist, inhibited the same PAF-induced contractions by 75% and 20% respectively.

Topics: Animals; Aspirin; Benzofurans; Chromones; Diterpenes; Ginkgolides; Guinea Pigs; Histamine; Imidazoles; Lactones; Leukotriene B4; Lignans; Lung; Male; Methacrylates; Muscle Contraction; Muscle, Smooth; Plant Extracts; Platelet Activating Factor; Prostaglandin Antagonists; Pyrilamine; SRS-A

Relative potencies of platelet activating factor (PAF) and PAF analogs and several PAF receptor antagonists when inhibiting the [3H]PAF specific binding to human and rabbit platelet membranes and membrane fragments of human lung tissues were compared. In rabbit platelets, L-652,731 was found to be most potent in the list of PAF receptor antagonists with an equilibrium inhibition constant (Ki) of 9.83 (+/- 2.92) X 10(-9) M followed by L-653,150 greater than kadsurenone congruent to Ono-6240 greater than ginkgolide B greater than CV-3988 greater than L-651,142, whereas in human platelets the relative potencies of these PAF receptor antagonists were as follows: Ono-6240 greater than L-653,150 congruent to L-652,731 congruent to kadsurenone greater than ginkgolide B greater than CV-3988 greater than L-651,142. Ono-6240 was the most potent one with a Ki of 4.86 (+/- 1.44) X 10(-8) M which was roughly two times more potent than that in rabbit platelets, whereas the affinity of L-652,731 was about ten times less in human platelets (Ki = 1.03 (+/- 0.15) X 10(-7) M) compared to that in rabbit platelets (Ki = 9.83 (+/- 2.92) X 10(-9) M). These variations between species among PAF antagonists strongly suggest that there exists a species difference at or near the binding site of the receptor of platelet activating factor. The relative potency of these PAF receptor antagonists in human lung membranes differed very little from that in human platelets and was found to be Ono-6240 greater than L-653,150 congruent to kadsurenone congruent to L-652,731 greater than ginkgolide B greater than CV-3988 greater than L-651,142. Even though C16-PAF showed slightly higher potency in human lung, and CV-3988 and Ono-6240 showed slightly lower, the difference was too small to suggest that there is a difference in the PAF receptors between human platelets and human lung tissues.

Topics: Animals; Benzofurans; Blood Platelets; Cell Membrane; Diterpenes; Furans; Ginkgolides; Humans; Lactones; Lignans; Lung; Phospholipid Ethers; Plant Extracts; Platelet Activating Factor; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Species Specificity; Thiazoles; Thiophenes

The ECG and haemodynamic alterations caused by the i.v. infusion of platelet-activating factor (PAF) in the rabbit were studied after pretreatment with Kadsurenone, a specific PAF-receptor antagonist. Infusion of PAF at 0.8 microgram/kg in the rabbit caused important ECG changes, such as ST-segment depression and conduction arrhythmias, concomitantly with a marked reduction in left ventricular systolic pressure, mean arterial pressure and cardiac output, with a rise in total peripheral resistances and mean right atrial pressure. These physiological parameters became maximal at 75-120 seconds after PAF challenge, and returned to near prechallenge values within 25-60 minutes. Pretreatment with Kadsurenone, administered either intravenously (0.014 M, 1 ml/kg) or intraperitoneally (0.14 M, 1 ml/kg), exerted a quite complete protective effect in regard to the ECG changes and caused a significant reduction in the magnitude of all the haemodynamic alterations observed after intravenous infusion of PAF (0.8 microgram/kg). These results suggest that Kadsurenone is an effective inhibitor of PAF-induced cardiovascular changes in the rabbit, probably due to its competitive antagonism against PAF binding to specific receptors.

Topics: Animals; Benzofurans; Cardiovascular Physiological Phenomena; Cardiovascular System; Electrocardiography; Female; Hemodynamics; Lignans; Male; Platelet Activating Factor; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled

BN 52021 is a chemically defined substance extracted from Ginkgo biloba leaves. Its inhibitory potency was tested on washed human platelets prepared so as to render them specifically sensitivity either to adenosine 5'-diphosphate (ADP), arachidonic acid (AA) or PAF-acether. Its activity and specificity were compared with those of two other reported inhibitors of PAF-acether effects: Kadsurenone and CV 3988. PAF-acether-induced aggregation of washed human platelets was concentration dependently inhibited by BN 52021 (IC50: 2.22 +/- 0.79 microM against 7.5 nM PAF-acether (n = 3)). Under the same experimental conditions the aggregation triggered by ADP was not modified and that induced by AA was marginally affected. The PAF-acether EC50 in platelet-rich plasma was increased 5- and 46-fold with 1 microM and 5 microM of BN 52021 respectively. This strongly suggested that the mechanism of action of BN 52021 is of the competitive type. Analysis of [3H]PAF-acether binding showed that BN 52021 as well as unlabelled PAF-acether prevented [3H]PAF-acether binding to intact washed platelets. In washed human platelets Kadsurenone affected only PAF-acether-induced aggregation (IC50: 0.8 +/- 0.4 microM (n = 3)), whereas CV 3988 inhibited the aggregation induced by ADP, AA and PAF-acether (IC50 were 10.2 +/- 2.3 microM; 2.2 +/- 0.1 microM; 1.0 +/- 0.1 microM respectively (n = 3). In contrast, up to 30 microM, CV 3988 was a specific antagonist of PAF-acether-induced platelet aggregation in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Arachidonic Acid; Arachidonic Acids; Benzofurans; Benzopyrans; Blood Platelets; Diterpenes; Ginkgolides; Humans; In Vitro Techniques; Lactones; Lignans; Phospholipid Ethers; Plant Extracts; Platelet Activating Factor; Platelet Aggregation; Thiazoles

Leukotrienes (LT's) are produced in a number of hypersensitivity and in inflammatory conditions in the gastro-intestinal (GI) tract and may contribute to the pathogenesis of GI mucosal injury in their states. LT's do not appear to be produced by the GI mucosa in appreciable quantities under basal "physiological" conditions. Another important leucocyte derived mediator, platelet activating factor (PAF), which is produced in large quantities in hypersensitivity and inflammatory conditions, when given i.v. induces hyperaemia, vascular status and accompanying lesions of the gastric mucosa in rats. This might be related to its hypotensive effects or other actions on the microvasculature of the stomach. Thus PAF may have particular significance in those conditions where there is a profound leucocyte response. It might be an important link between the leucocyte activation that occurs in burn injury and the GI ulceration and haemorrhage that is observed in such patients. There does not appear to be any involvement of PAF in non-inflammatory gastric ulceration induced by aspirin or ethanol+HCl, since the PAF antagonist kadsurenone fails to exert any protective effects when co-administered with either of these drugs.

Topics: Animals; Aspirin; Benzofurans; Ethanol; Gastric Mucosa; Intestinal Mucosa; Lignans; Male; Platelet Activating Factor; Rats; Rats, Inbred Strains; SRS-A; Stomach Ulcer

BN52021 (Ginkgolide B) monohydrate C20H24O10 X H2O crystallizes in the triclinic space group P1 with two independant molecules in the unit cell of which parameters are a = 7.627(2), b = 11.514(3), c = 12.941(3)A, alpha = 97.05(2), beta = 90.27(2) and gamma = 108.71(2)o, V = 1067.06A3. Calculated density Dx = 1.320g X cm-3. The crystal structure was solved by Patterson methods starting from dreiding model data. The final reliability index R = 0.099 for 3848 observed reflections collected with a four-circle diffractometer. Anti-PAF activities of Kadsurenone, Kadsurin-A, Kadsurin-B and Piperenone, molecular structure of MIRANDIN-A, related compounds and BN52021 suggest that a distance 0-0 of about 6.6A observed in Kadsurenone and in BN52021 could be favourable to anti-PAF activity.

Topics: Benzofurans; Chemical Phenomena; Chemistry, Physical; Crystallization; Diterpenes; Ginkgolides; Lactones; Lignans; Molecular Conformation; Plant Extracts; Platelet Activating Factor; Temperature

Topics: Alkaloids; Benzofurans; Chemical Phenomena; Chemistry; Lignans; Medicine, Chinese Traditional; Medicine, East Asian Traditional; Plant Extracts; Plants, Medicinal; Platelet Activating Factor

Platelet activating factor (PAF), a potent lipid-like vasoactive agent, induced rat foot edema when it was injected subplantarly. The edema reached its maximum 1 h after PAF challenge. Indomethacin did not inhibit the peak edematous response whereas both PAF antagonists, kadsurenone and L-652,731, inhibit the PAF-induced rat foot edema (PFE). Both PAF antagonists also partially block the first phase of the carrageenin-induced rat foot edema (CFE). Using the inhibition of [3H]PAF receptor binding to prepared rabbit platelet membranes, release of PAF or PAF-like materials in carrageenin-injected rat hindpaw was observed. These results suggest that the released PAF or PAF-like materials together with the released histamine and kinin evoke the first phase hindpaw edema in the rats. Indomethacin or PAF antagonist, administered alone, does not block the first phase or the second phase of CFE, respectively. However, PAF antagonist potentiated the inhibitory effects of indomethacin suggesting that the released PAF may also be involved in the biosynthesis of prostaglandins to initiate the second phase of rat CFE.

Topics: Animals; Anti-Inflammatory Agents; Benzofurans; Benzopyrans; Carrageenan; Edema; Lignans; Male; Platelet Activating Factor; Rats; Rats, Inbred Strains; Time Factors

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.

Topics: Animals; Benzofurans; Benzopyrans; Capillary Permeability; Guinea Pigs; Humans; Lignans; Magnoliopsida; Mathematics; Neutrophils; Platelet Activating Factor; Platelet Aggregation; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled

Evidence from three types of experiments indicates that platelet activating factor (PAF)1 is an important mediator of endotoxin-induced hypotension in rats. a) Endotoxin infusion stimulates the time-dependent appearance of PAF in the blood. b) PAF infusion results immediately (less than 30 sec) in hypotension while endotoxin-induced hypotension takes 3-5 min to occur, allowing time for PAF production. c) Infusion of the specific PAF-receptor antagonist kadsurenone (2.2 mumole/kg bolus, 0.9 mumoles/min/kg continuous infusion), which inhibits PAF-induced hypotension by 67%, causes a 67% reversal of endotoxin-elicited hypotension. An additional finding of this study is that rats respond hypotensively to each of a series of low-dose PAF infusions but only to the first low-dose endotoxin infusion. These endotoxin-refractory rats do respond to subsequent PAF infusions.

Topics: Animals; Benzofurans; Benzopyrans; Endotoxins; Escherichia coli; Female; Hypotension; Kinetics; Lignans; Platelet Activating Factor; Platelet Membrane Glycoproteins; Rats; Rats, Inbred Strains; Receptors, Cell Surface; Receptors, G-Protein-Coupled

A natural product, kadsurenone, was isolated from the Chinese herbal preparation haifenteng (Caulis piperis futokadsurae) and characterized as an orally-active specific antagonist of the platelet-activating factor (PAF). Kadsurenone inhibits the specific binding of 3H-PAF to a receptor preparation from rabbit platelet membrane in a competitive and reversible manner, its Ki being 3.88 X 10(-8) M. It inhibits the aggregation of rabbit platelets in plasma induced by PAF with a pA2 of 6.28, but not those induced by arachidonic acid, epinephrine, ADP or A-23187. It inhibits the aggregation of isolated human neutrophils with a pA2 of 6.32. It also inhibits PAF-induced degranulation and release of beta-D-glucuronidase at 2-24 microM in vitro. In the rat, kadsurenone at 8-40 mg/kg i.p. inhibits the increases of plasma lysosomal enzymes and haematocrit induced by intravenous PAF. In the guinea pig, kadsurenone at 25-50 mg/kg p.o. reduces the increase of cutaneous vascular permeability induced by PAF. These results indicate that kadsurenone is a specific and effective receptor antagonist of PAF in several in vitro and in vivo systems.

Topics: Animals; Benzofurans; Benzopyrans; Binding, Competitive; Capillary Permeability; Guinea Pigs; Humans; Lignans; Lysosomes; Neutrophils; Plants, Medicinal; Platelet Activating Factor; Platelet Aggregation; Platelet Membrane Glycoproteins; Rabbits; Rats; Receptors, Cell Surface; Receptors, G-Protein-Coupled

trans-2,5-Bis(3,4,5-trimethoxyphenyl)tetrahydrofuran (L-652,731) is found to be a potent and orally active platelet activating factor (PAF)-specific and competitive receptor antagonist. It potently inhibits [3H]PAF (1 nM) binding to receptor sites on rabbit platelet membranes with an ED50 of 2 X 10(-8) M under the assay condition without the addition of mono- or divalent cations. In a comparative study, it is more potent than CV-3988, kadsurenone, and ginkgolide B as a receptor antagonist. The equilibrium dissociation constants (KB) of L-652,731 obtained either from the inhibition of receptor binding or from the inhibition of PAF-induced aggregation of gel-filtered rabbit platelet are 2.7 X 10(-8) and 2.1 X 10(-8) M, respectively. The agreement of these KB determinations based on receptor and cellular function suggests that L-652,731 does not inhibit other steps following PAF-receptor binding. L-652,731 does not antagonize the binding of several radioligands to their respective receptor. It shows no inhibitory effect on platelet aggregation induced by other aggregating agents including thrombin, collagen, A-23187, arachidonic acid, epinephrine, and ADP. L-652,731 is orally active; it inhibits PAF-induced rat cutaneous vascular permeability with an ED50 of 30 mg/kg orally. Significant inhibitory results of L-652,731 suggest that PAF may be partially involved in cutaneous vascular permeability induced by histamine and bradykinin.

Topics: Animals; Benzofurans; Benzopyrans; Blood Platelets; Bradykinin; Capillary Permeability; Chemical Phenomena; Chemistry; Dose-Response Relationship, Drug; Furans; Histamine; Humans; Lignans; Magnesium; Mathematics; Phospholipid Ethers; Platelet Activating Factor; Platelet Aggregation; Platelet Membrane Glycoproteins; Rabbits; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Sodium; Thiazoles

Mechanisms of platelet-activating factor (PAF)-induced increases of cutaneous vascular permeability in guinea pigs and in rats were further explored. PAF so far is the most potent vasoactive mediator, being more than 1000-fold more potent than histamine and bradykinin in both species. In guinea pigs, there is a time delay of 5 to 10 minutes before PAF action, whereas, in the rat, the increased vasopermeability occurs immediately following the intradermal PAF injection. Relative vasoactive potencies of PAF and several structure-related analogues in both species correlate very well with their relative inhibition of the binding of 3H-PAF to specific receptor sites on isolated rabbit platelet plasma membranes and their aggregatory abilities of rabbit platelets. Furthermore, the PAF-induced cutaneous vascular permeability is inhibitable by a competitive specific PAF receptor antagonist, kadsurenone, suggesting that binding of PAF to its specific receptor site is the first step to initiate its action of increased cutaneous vascular permeability. Several pure cyclooxygenase inhibitors, including indomethacin, diflunisal, and flurbiprofen, and the dual cyclooxygenase/lipoxygenase inhibitor, BW755C, but not the histamine antagonists, inhibit the PAF-induced vasopermeability in guinea pigs. The inhibition by indomethacin or BW755C can be fully reversed by coinjection intradermally with PAF and prostaglandin E1 but not leukotriene B4. Also, prostaglandin E1 but not leukotriene B4 enhances the guinea pig in vivo response to PAF in this model. However, in rats, none of the cyclooxygenase inhibitors, histamine antagonists, or BW755C inhibit the PAF effect of cutaneous phenomena even though prostaglandin E1 also enhances the PAF potency of the increased cutaneous vascular permeability. Kadsurenone, a competitive specific receptor antagonist, inhibits both histamine- and bradykinin-induced rat cutaneous vascular permeability which suggests that PAF may be involved in the vasopermeability induced by histamine and bradykinin.

Topics: Animals; Benzofurans; Benzopyrans; Binding Sites; Bradykinin; Cell Membrane Permeability; Cyclooxygenase Inhibitors; Drug Interactions; Female; Guinea Pigs; Histamine; Indomethacin; Lignans; Platelet Activating Factor; Platelet Aggregation; Rabbits; Rats; Rats, Inbred Strains; Skin; Species Specificity; Tritium