Platelet-activating factor (PAF) is a unique and novel signaling phospholipid that has pleiotropic biologic properties in addition to platelet activation. Recent studies show that this novel compound plays a significant role in male reproduction and sperm function. PAF binds surface special receptors inducing the formation of inositol triphosphate (IP3) and diacylglycerol (DAG) and increasing intracellular calcium. The concentrations of sperm-derived PAF may help predict sperm motility and fertilization potential, which may serve as a valuable marker for assessing male fertility. Exogenous PAF can improve sperm motility, acrosome reaction and pregnancy rates in human intrauterine inseminations.
Fertilization in Vitro ; Humans ; Male ; Platelet Activating Factor ; pharmacology ; physiology ; Sperm Motility ; Spermatozoa ; drug effects ; physiology

OBJECTIVETo explore the inhibitory effect and mechanism of rutin against platelet activating factor (PAF) induced platelet aggregation, 5-HT release and intra-platelet free calcium concentration.

METHODSThe rate of washed rabbit platelet (WRP) aggregation was measured by turbidimetry and O-phthaldialdehyde (OPT) fluoro-spectrophotometry (FSPM) was used to determine 5-HT content. The intraplatelet free calcium concentration was measured with Fura-2/AM FSPM assay.

RESULTSRutin in vitro was concentration-dependently inhibiting PAF (9.55 x 10(-9) mol/L) induced WRP aggregation, the IC50 of 5-HT release was 0.73, 1.13 mmol/L respectively and the intraplatelet free calcium concentration elevation evoked by PAF (4.78 x 10(-10) mol/L) were inhibited by 68.3, 136, 274, 545 mumol/L of rutin dose-dependently.

CONCLUSIONRutin could inhibit PAF induced platelet aggregation, 5-HT release and the increase of intraplatelet free calcium.

Animals ; Biological Transport, Active ; Blood Platelets ; metabolism ; Calcium ; metabolism ; Male ; Platelet Activating Factor ; antagonists & inhibitors ; Platelet Activation ; drug effects ; Platelet Aggregation Inhibitors ; pharmacology ; Rabbits ; Rutin ; pharmacology ; Serotonin ; metabolism

AIMTo observe the levels of interleukin-12 (IL-12) and platelet activating factor (PAF) in severe acute pancreatitis (SAP) in rats and the efficacy of Ginkgolide B (BN52021) in treating SAP.

METHODSWistar rats were randomly divided into 3 groups: model group (SAP), treatment group (BN) and negative control group (NC). SAP was induced by retrograde infusion of 5% sodium taurocholate into the pancreatic duct in Wistar rats. NC rats only receive abdominal incision. In groups of SAP and NC rats received the femoral vein injection of isotonic Na chloride 15 minutes after induction of SAP; in BN group,rats received BN52021 instead. After operation rats were sacrificed at 1, 6 and 12 hour for plasma IL-12 and PAF determined with ELISA.

RESULTSAn increase of IL-12 in group BN was observed VS group SAP or group NC at 1 h stage (p = 0.011, P < 0.01). At 6 h or 12 h stage,an increase of IL-12 in group SAP was observed VS group NC (P < 0.01, P < 0.05). The plasma level of PAF in group SAP or group BN was increased significantly at 1 h time stage VS group NC (P < 0.001). At 6 h or 12 h stage, a decrease of PAF in group BN or group NC was observed VS group SAP (P < 0.05, P < 0.01).

CONCLUSIONIt confirmed that the plasma level of cytokine IL-12 in SAP group was decreased significantly in early stage and it witnessed a remarkable increase of cytokine PAF. The plasma level of IL-12 was increased in early stage but PAF was decreased in rats treatment by BN52021 which inhibited the development of SAP.

Acute Disease ; Animals ; Ginkgolides ; pharmacology ; Interleukin-12 ; blood ; Lactones ; pharmacology ; Male ; Pancreatitis ; blood ; Platelet Activating Factor ; metabolism ; Rats ; Rats, Wistar

Animals ; Cells, Cultured ; Female ; Granulosa Cells ; metabolism ; Pituitary Adenylate Cyclase-Activating Polypeptide ; genetics ; metabolism ; Platelet Activating Factor ; pharmacology ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley

AIMTo study the antagonistic effect of myricetin on platelet activing factor (PAF).

METHODSThe specific binding of [3H] PAF to rabbit platelet receptor was investigated using radio ligand binding assay (RLBA). Platelet adhesion induced by PAF was measured with spectrophotometry. The elevation of inner free calcium concentration in rabbit polymorphonuclear leukocytes (PMNs) induced by PAF was assayed by Fura-2 fluorescent technique.

RESULTSThe specific binding inhibition potency of Myr was found to be concentration-dependent. The IC50 of Myr in [3H] PAF 1, 2 and 4 nmol.L-1 were 34.8, 85.7 and 118.6 mumol.L-1, respectively. The PAF induced reactions of rabbit platelet adhesion and PMNs inner free calcium concentration increase were inhibited by Myr in a dose-dependent manner. The IC50 of Myr to inhibit platelet adhesion was 13.1 mumol.L-1.

CONCLUSIONThe specific receptor binding of PAF can be antagonized by myricetin.

Animals ; Calcium ; metabolism ; Flavonoids ; pharmacology ; Male ; Neutrophils ; metabolism ; Platelet Activating Factor ; antagonists & inhibitors ; metabolism ; Platelet Activation ; drug effects ; Platelet Adhesiveness ; drug effects ; Platelet Aggregation Inhibitors ; pharmacology ; Platelet Membrane Glycoproteins ; metabolism ; Rabbits ; Receptors, G-Protein-Coupled ; metabolism

The present study was carried out to examine the mechanisms of the synergistic interaction of PAF and A23187 mediated platelet aggregation. We found that platelet aggregation mediated by subthreshold concentrations of PAF (5 nM) and A23187 (1 micrometer) was inhibited by PAF receptor blocker (WEB 2086, IC50=0.65 micrometer) and calcium channel blockers, diltiazem (IC50=13 micrometer) and verapamil (IC50=18 micrometer). Pretreatment of platelets with PAF and A23187 induced rise in intracellular calcium and this effect was also blocked by verapamil. While examining the role of the down stream signaling pathways, we found that platelet aggregation induced by the co-addition of PAF and A23187 was also inhibited by low concentrations of phospholipase C (PLC) inhibitor (U73122; IC50 = 10 micrometer), a cyclooxygenase inhibitor (indomethacin; IC50=0.2 micrometer) and inhibitor of TLCK, herbimycin A with IC50 value of 5 micrometer. The effect was also inhibited by a specific TXA2 receptor antagonist, SQ 29548 with very low IC50 value of 0.05 micrometer. However, the inhibitors of MAP kinase, PD98059 and protein kinase C, chelerythrine had no effect on PAF and A23187-induced platelet aggregation. These data suggest that the synergism between PAF and A23187 in platelet aggregation involves activation of thromboxane and tyrosine kinase pathways.
Blood Platelets/*drug effects ; Calcimycin/*pharmacology ; Humans ; Indomethacin/pharmacology ; Ionophores/pharmacology ; Platelet Activating Factor/metabolism/*pharmacology ; Platelet Aggregation/*physiology ; Protein-Tyrosine Kinase/antagonists & inhibitors/*physiology ; Quinones/pharmacology ; Research Support, Non-U.S. Gov't ; Thromboxane A2/*physiology ; Verapamil/pharmacology

OBJECTIVEGastrointestinal dysfunction is closely correlated with the destruction of intestinal barrier function induced by serious infection. Platelet activating factor (PAF) may induce intestinal injuries. This study aimed to investigate the effect of PAF on the injury of intestinal mucosal immuno-barrier function in young rats.

METHODSEighteen-day-old Wistar rats were randomized to lipopolysaccharide (LPS) (5 mg/kg), LPS plus PAF receptor antagonist and normal saline injection (Control). PAF receptor antagonist BN52021 5 mg/kg was administered before or 30 minutes after LPS injection (pretreatment or treatment). The ileum specimens (n=8) were harvested at 1.5, 3, 6, 24, 48 and 72 hrs after LPS injection. Double antibody-PEG radioimmunoassay was used to determine the secretory IgA (sIgA) content in intestinal mucosa. Hematoxylin and erosin staining was used for histological evaluation. The ratio of wet and dry weight (W/D) of ileum tissues was calculated.

RESULTSIntestinal villi edema, capillary congestion, extension of the subepithelial lympho channel, and polymorphonuclear infiltration in enteric cavity were noted in the LPS group at 1.5, 3, 6 and 24 hrs after LPS injection. In the PAF receptor antagonist group only villi edema was found. The W/D ratio in the LPS group was significantly higher than that in the Control group at all time points, but it was slightly reduced by the PAF receptor antagonist pretreatment or treatment. The sIgA content was obviously decreased after 1.5, 3, 6, 24 and 48 hrs of LPS challenge compared with that in the Control group (P < 0.01). It reached to a nadir at 6 hrs (0.15 +/- 0.04 microg/mL). The level of sIgA in the PAF receptor antagonist group was higher than that in the LPS group at each time point. There was no statistical difference in the sIgA level between the PAF receptor pretreatment and treatment groups.

CONCLUSIONSPAF plays roles in the injury of intestinal immuno-barrier function. Preventive and remedial use of PAF receptor antagonist BN52021 may relieve intestinal injury.

Animals ; Diterpenes ; pharmacology ; Ginkgolides ; Immunoglobulin A, Secretory ; analysis ; Intestines ; immunology ; pathology ; Lactones ; pharmacology ; Lipopolysaccharides ; toxicity ; Platelet Activating Factor ; physiology ; Rats ; Rats, Wistar

AIMTo explore the effect of platelet-activating factor on long-term potentiation in the CA1 region of rat hippocampal slices.

METHODSWe recorded the excitatory postsynaptic potentials (EPSPs) and investigated effect of long-term potentiation by PAF in rat hippocampus in vitro.

RESULTSLow doses (1 micromol/L ) of PAF could induce LTP, while higher doses (10-50 micromol/L) of PAF could inhibit induction of LTP. But it couldn't inhibit the LTP induced by subsequent high frequency stimulation and the EPSP of basal. GB of PAF receptor antagonists could prevent the LTP induced by low doses of PAF, and could't inhibit the LTP induced by HFS.

CONCLUSIONHigher doses of PAF is an HIV-1-induced neurotoxin, it may contribute to the HAD pathogenesis by inhibition of LTP.

Animals ; Electric Stimulation ; Hippocampus ; drug effects ; physiology ; Long-Term Potentiation ; Male ; Organ Culture Techniques ; Platelet Activating Factor ; administration & dosage ; pharmacology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo observe the platelet activating factor (PAF) antagonistic effect of kaempferol.

METHODThe specific binding of [3H] PAF to rabbit platelet receptor was investigatedwith radio ligand binding assay (RLBA). Platelet adhesion induced by PAF was measured with spectrophotometry. The elevation of inner free calcium concentration in rabbit polymorphonuclear leukocytes (PMNs) induced by PAF was determined with Fura-2 fluorescent technique.

RESULTThe 1, 2 or 4 nmol x L(-1) [3H]PAF specific binding to rabbit platelet receptor was inhibited by Kae dosage dependently and the IC50 were 30.8, 74.6 and 92.0 micro mol x L(-1), respectively. The PAF induced reactions of rabbit platelet adhesion and PMNs inner free calcium concentration elevation were inhibited by Kae in a dose-dependent manner. The IC50 of Kae to inhibit platelet adhesion was 65 micromol x L(-1).

CONCLUSIONKae is effective in inhibiting the action of PAF and it is a new PAF receptor antagonist.

Animals ; Blood Platelets ; drug effects ; physiology ; Calcium ; metabolism ; Kaempferols ; pharmacology ; Male ; Neutrophils ; metabolism ; Platelet Activating Factor ; metabolism ; Platelet Adhesiveness ; drug effects ; Platelet Membrane Glycoproteins ; antagonists & inhibitors ; metabolism ; Rabbits ; Radioligand Assay ; Receptors, G-Protein-Coupled ; antagonists & inhibitors ; metabolism

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.
Diltiazem/pharmacology ; Dose-Response Relationship, Drug ; Drug Synergism ; Estrenes/pharmacology ; Flavones/pharmacology ; Human ; In Vitro ; Indomethacin/pharmacology ; Kinetics ; Mitogen-Activated Protein Kinases/metabolism ; Phosphorylation/drug effects ; Platelet Activating Factor/*pharmacology ; Platelet Activation/drug effects ; Platelet Aggregation/*drug effects/physiology ; Pyrrolidinones/pharmacology ; Serotonin/*pharmacology ; Thromboxane A2/biosynthesis ; Verapamil/pharmacology