Effect of a platelet activating factor antagonist, WEB 2086, on allergen induced asthmatic responses.

BACKGROUND--Platelet activating factor (PAF) has been implicated in the pathogenesis of airway hyperresponsiveness in asthma. The purpose of this study was to evaluate the effects of a selective PAF antagonist (WEB 2086), given in doses known to antagonise the effects of inhaled PAF in human subjects, on allergen induced early and late asthmatic responses and on airway hyperresponsiveness. METHODS--Eight atopic, mildly asthmatic subjects were studied during a screening period and two treatment periods. During the screening period subjects inhaled an allergen to which they were known to be sensitised and the response was measured as the fall in the forced expired volume in one second (FEV1) to show the presence of early (0-1 h) and late (3-7 h) asthmatic responses. On another day the subjects inhaled allergen diluent. During the treatment periods subjects inhaled allergen after one week's pretreatment with WEB 2086 (100 mg three times a day) or placebo administered in a randomised, double blind, crossover fashion. Histamine airway responsiveness was measured 24 hours before and 24 hours after allergen and the results were expressed as the provocative concentration causing a 20% fall in FEV1 (PC20). RESULTS--The maximal early asthmatic response after allergen with placebo treatment was 18.4% (SE 4.4%) and with WEB 2086 18.9% (4.4%). The maximal late response with placebo treatment was 21.7% (5.3%) and with WEB 2086 21.2% (3.0%). The log difference (before and after allergen) in histamine PC20 was 0.35 (0.06) after placebo treatment and 0.30 (0.1) after WEB 2086. CONCLUSIONS--These results indicate that one week of treatment with an orally administered PAF antagonist (WEB 2086) does not attenuate allergen induced early or late responses or airway hyperresponsiveness.     

The platelet activating factor receptor antagonist WEB 2170 improves glomerular hemodynamics and morphology in a proliferative model of mesangial cell injury.

Rats were treated with the platelet activating factor receptor antagonist WEB 2170 (15 mg/kg/day) in three different protocols to evaluate a possible role of platelet activating factor in an experimental proliferative model of glomerular disease. The glomerular immune injury was initiated by the i.v. administration of a rabbit anti-rat thymocyte antiserum. Anti-rat thymocyte antiserum induces a proliferative glomerulonephritis with reduction of glomerular filtration rate (614 +/- 94) compared with controls (1,120 +/- 192 microL/min/100 g body wt) when studied at day 7. Treatment of rats with WEB 2170 over 8 days (starting at day -1; protocol 1) ameliorated the loss in glomerular filtration rate (936 +/- 82 microL/min/100 g body wt) in nephritic rats at day 7; however, it had no effect on controls (1,142 +/- 104 microL/min/100 g body wt). Interventional treatment with WEB 2170 (starting at day 4 after anti-rat thymocyte antiserum; protocol 2) also improved glomerular function when glomerular filtration rate was already reduced (410 +/- 41 microL/min/100 g body wt) at day 4. The platelet activating factor receptor antagonist given at day 7 after induction of disease (protocol 3) did not improve impaired glomerular filtration rate. Preinterventional and interventional treatment with WEB 2170 reduced the infiltration of polymorphonuclear granulocytes in glomeruli. Interventional treatment with WEB 2170 also reduced glomerular morphologic damage in nephritic glomeruli. The data demonstrate a beneficial effect of the platelet activating factor receptor antagonist in this animal model of proliferative glomerulonephritis which suggests that platelet activating factor might play an important role in the mediation of this disease.     

血小板活化因子及受体拮抗剂对肝星状细胞增殖的影响

目的 观察血小板活化因子(PAF)及受体拮抗剂对体外培养的肝星状细胞(HSC)增殖的影响.方法 采用LX-2肝星状细胞系作为活化的HSC的研究模型.采用噻唑蓝比色法检测HSC的增殖.流式细胞PI染色及BrdU掺入法检测HSC的细胞周期.结果 PAF(1×10~(-8)～1×10~(-3)mol/L)各浓度组OD_(492)显著高于对照组(P<0.05);PAF(1×10~(-6))加PAF受体拮抗剂(1×10~(-7)～1×10~(-4)mol/L)组OD_(492)明显少于PAF(1×10~(-6)mol/L)组(P<0.05).PAF组HSC的S%和Prl明显增高.结论 PAF能够剂量依赖性地促进HSC增殖,而PAF受体拮抗剂能够抑制其作用.     

Effects of the endothelin receptor antagonist bosentan on cardiac performance during porcine endotoxin shock

BACKGROUND: Cardiac dysfunction during septic shock is well described but the underlying mechanisms still remain to be resolved. This study was conducted to elucidate the involvement of endothelin in cardiac function during endotoxin shock by the use of endothelin receptor antagonism. METHODS: Anaesthetised and haemodynamically stable landrace pigs received the nonpeptide mixed endothelin receptor antagonist bosentan, two hours after onset of endotoxaemia (n=7). Cardiopulmonary vascular changes, including cardiac index, stroke work index, coronary artery blood flow, rate of change of left ventricular pressure (dp/dt), and arterial and coronary sinus plasma levels of endothelin-1-like immunoreactivity were compared to a control group only receiving endotoxin (n=7). RESULTS: Plasma endothelin-1-like immunoreactivity increased threefold in the control group. Bosentan effectively counteracted the endotoxin induced decrease in cardiac index. This was accompanied by a significant reduction of both right and left ventricular afterload. In addition, coronary artery blood flow increased and coronary vascular resistance decreased compared to controls. Dp/dt remained unaffected by endothelin receptor antagonism. A further increase in plasma endothelin-1-like immunoreactivity was seen in response to bosentan. CONCLUSION: These results indicate that the increased endothelin production during endotoxaemia contributes to a depressed cardiac performance and that endothelin receptor antagonism may counteract this development. Possible mechanisms for the improved cardiac performance include both a reduction of afterload and enhanced coronary blood flow.     

A platelet activating factor receptor antagonist inhibits cytokine production in human whole blood by bacterial toxins and live bacteria

We previously reported that a platelet-activating factor receptor (PAFR) antagonist (TCV-309) suppressed lipopolysaccharide (LPS)-induced mortality and tumor necrosis factor (TNF) production in mice. However, the effect of TCV-309 on cytokine production induced by Staphylococcus enterotoxin B (SEB) or live bacteria has not been reported. In this study we investigated the effect of TCV-309 on cytokine production in human whole blood induced by LPS, SEB, and both Gram-positive and -negative bacteria. Human whole blood diluted 5:1 (980 microL) was placed in the wells of a 24-well plate. Ten microliters of LPS, SEB, Escherichia coli O18 K(+), or Staphylococcus aureus were added to each well. After incubation at 37 degrees C for 6 h, TNF, interleukin (IL)-6, and IL-8 in the culture medium were measured. TCV-309 did not affect the growth of either E. coli or S. aureus bacteria in the culture medium for the 6 h incubation. LPS, SEB, and both E. coli and S. aureus induced TNF, IL-6, and IL-8 in human whole blood. TCV-309 significantly inhibited the production of TNF, IL-6, and IL-8 induced by LPS, SEB, and bacteria. A PAFR antagonist suppressed cytokine production induced by LPS, SEB, and both Gram-positive and -negative bacteria in human whole blood. A PAFR plays an important role of producing proinflammatory cytokines induced by both toxins and live bacteria. IMPLICATIONS: The platelet-activating factor receptor plays an important role in producing proinflammatory cytokines induced by bacterial toxins, such as lipopolysaccharide,Staphylococcus enterotoxin B, and live Gram-positive and Gram-negative bacteria.     

Protective effect of a platelet-activating factor antagonist (WEB-2086) in postischemic renal failure

The purpose of this study was to evaluate the renoprotective effect of a specific platelet-activating factor antagonist (WEB-2086) in an experimental model of normothermic renal ischemia. Twenty New Zealand white rabbits were studied for 2 days before and 24 hours after a 60-minute period of renal ischemia induced by bilateral clamping of the renal arteries. The animals were divided into two groups: a control group (group A; n=10) and a treated group (group B; n=10). In group A the urinary flow rate decreased significantly (from 0.098±0.008 ml/min to 0.029±0.005 ml/min) (p<0.001) and there was a significant reduction in creatinine clearance (from 11.4±1.2 ml/min to 3.4±1.1 ml/min) (p<0.001). In group B no significant changes were observed, although the urinary flow rate increased even in the postischemic period (from 0.09±0.008 ml/min to 0.11±0.02 ml/min). Microcirculatory cortical flow showed a postischemic reduction in both groups, although it was most significant in the control group (group A=43.7%, group B=71.5%;p<0.001). Histologic study showed mild damage with patchy tubular necrosis in both groups, although this injury was less severe in the treated group. The results suggest that the preoperative administration of WEB-2086 produces a potent diuretic effect with significant attenuation of postischemic acute renal failure.Presented at the Seventeenth World Congress of the International Union of Angiology, London, England, April 3–7, 1995 (IUA Prize).Supported by a grant from the National Institutes of Health (INS) (FIS 95/0837), Madrid, Spain.     

An experimental study on shock after temporary hepatic inflow occlusion and platelet activating factor (PAF)

The potential effect of CV6209, a platelet activating factor (PAF) antagonist, on shock after temporary hepatic inflow occlusion was investigated. Five groups of rats were given following chemicals i.v. (Group A: both 3 mg/kg of CV6209 and 100 U/kg of heparin, Group B: 3 mg/kg of CV6209, Group C: 100 U/kg of heparin, Group D: 4 ml/kg of normal saline, Group E: 4 ml/kg of normal saline under splanchnic decompression with port-jugular bypass) and were subjected to 45 minutes of hepatic inflow occlusion. The survival rates 24 hours after the occlusion were 80%, 60% 45%, 30% and 80% in groups A, B, C, D and E, respectively. All rats except for those in group E developed hypotension during the occlusion period. The blood pressure was reversed to pre-occlusion level after declamping in groups A and B, although hypotension continued in groups C and D. Blood chemistry also revealed diminished elevation of serum mitochondrial GOT after the occlusion in PAF antagonist group. These results suggest that portal congestion is the most responsible for shock and death after temporary hepatic inflow occlusion and PAF is a mediator of the injury.     

Endotoxin-induced myocardial depression in rats: effect of ibuprofen and SDZ 64-688, a platelet activating factor receptor antagonist

We tested the hypothesis that lipopolysaccharide (LPS)-induced myocardial dysfunction is mediated by cyclooxygenase-derived metabolites of arachidonic acid or platelet activating factor (PAF). Ether-anesthetized rats were injected iv with normal saline (NS; 2.5 ml/kg), ibuprofen (cyclooxygenase inhibitor; 15 mg/kg), or SDZ 64-688 (PAF receptor antagonist; 5 mg/kg). Thirty minutes later, the rats were injected iv with NS (5 ml/kg) or Escherichia coli 0111:B4 LPS (20 mg/kg). Two hours later, atria were harvested, connected to an isometric force transducer-amplifier-recorder apparatus, and maintained in vitro in oxygenated 37.5 degrees C Krebs--Henseleit buffer. Force of contraction indexed to body weight (FOCI; g/kg) was significantly (P less than 0.05) lower in the NS/LPS group (N = 7) than in the NS/NS group (N = 7). Pretreatment with ibuprofen (ibuprofen/LPS group; N = 8) did not affect the adverse effect of LPS on atrial FOCI. In contrast, pretreatment with SDZ 64-688 (64-688/LPS group; N = 8) ameliorated (P less than 0.05) the deleterious effect of LPS on contractility. The PAF antagonist did not manifest intrinsic positive inotropic activity (64-688/NS group; N = 8). These results support the notion that LPS-induced myocardial dysfunction in the rat is mediated, at least in part, by PAF.     

血小板活化因子（PAF）受体mRNA在人睾丸组织和精子的表达

本文应用ＲＴ－ＰＣＲ和序列测定研究了人睾丸组织和精子内血小板因子受体（ＰＡＦ－Ｒ）ｍＲＮＡ的表达。结果证实（１）人睾丸组织和精子表达ＰＡＦ－ＲｍＲＮＡ,（２）ＰＡＦ－ＲｃＤＮＡ序列与人其它组织ＰＡＦ－ＲｃＤＮＡ序列完全一致。结果揭示,人睾丸组织和精子有ＰＡＦ－Ｒ的ｍＲＮＡ表达。     

Platelet activating factor receptor antagonist improves survival and attenuates eicosanoid release in severe endotoxemia.

Exogenous platelet activating factor (PAF) causes hypotension, plasma extravasation, metabolic acidosis, and death. These effects are similar to those of endotoxin as well as the eicosanoids. A specific PAF receptor antagonist, BN52021, was used to determine its effects on the hemodynamic events, the eicosanoid production, and on survival in severe rat endotoxemia. Endotoxin alone significantly produced hypotension, prostaglandins (TxB2, PGE2) release, and death. In contrast pretreatment with BN52021, a specific PAF receptor antagonist, significantly altered the hypotension, significantly attenuated the eicosanoid release, and improved the survival rate (p less than 0.01). These findings suggest that PAF receptor activation is an early event in endotoxemia. Eicosanoid release in endotoxemia could be related to PAF synthesis and PAF receptor activation. These findings support the hypothesis that there may be an intimate relationship between PAF and the eicosanoids and that in endotoxemia some of the effects of PAF may be mediated via the cyclo-oxygenase pathway.     

Effect of platelet activating factor (PAF) on the migration of human lymphocytes.

BACKGROUND--There is growing evidence to suggest the importance of the lymphocyte in the pathogenesis of asthma, particularly in the late phase reactions and ongoing bronchial hyperreactivity. Platelet activating factor (PAF) has also been identified as a potentially important mediator in asthma. METHODS--The migration of human peripheral blood lymphocytes obtained from normal volunteers in response to PAF and the effect of PAF antagonists was studied in a well standardised in vitro assay using nitrocellulose micropore filters in a microchemotaxis chamber. RESULTS--PAF is a potent stimulus to in vitro human lymphocyte migration; at an optimal concentration of 1 nM it augmented lymphocyte chemokinesis to 310% (SE 33%) of control values. The response to PAF appears to be specific since lyso-PAF and other related membrane phospholipids had no effect. PAF-induced migration could be abrogated by specific PAF receptor antagonists such as WEB 2086 (100 nM), and was partially blocked by the cyclooxygenase inhibitor flurbiprofen at a concentration of 1 microM. CONCLUSIONS--PAF stimulates the in vitro migration of human lymphocytes through a specific PAF receptor. Part of the response may be due to the generation of cyclooxygenase products. PAF may play a part in the recruitment of lymphocytes to asthmatic airways.     

Metabolism of platelet activating factor (PAF) and lyso-PAF in polymorphonuclear granulocytes from severely burned patients

We studied the metabolism of 3H-platelet activating factor (PAF) and lyso-PAF in human polymorphonuclear granulocytes (PMN) from severely burned patients (n = 6) on days 1, 5, 9, 15, and 25 post-trauma. All patients suffered from a severe burn trauma of more than 30% total body surface area. Stimulation of PMN in healthy donors (n = 10) with the Ca-ionophore resulted in the conversion of 3H-lyso-PAF into PAF (18 +/- 2% of total radioactivity) and alkyl-acyl-glycero-phosphorylcholine (alkyl-acyl-GPC, 50 +/- 6%). In burned patients a significantly reduced formation of 3H-PAF was observed between days 1 and 15 post-trauma (day 9: 1 +/- 1%, p less than 0.0001). This pattern was normalized again in patients (n = 5) who survived the trauma after septic periods and was observed during the second week post-trauma. In one patient who succumbed to his injuries a sustained inhibition of PAF formation was observed up to his death. The decreased formation of PAF correlated weakly with the appearance of immature granulocytes within the analyzed cell fraction (ratio of immature cells versus PAF-formation, r = -0.55, p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of ONO 3708, a new thromboxane receptor antagonist, on cardiovascular response during the early phases of endotoxin shock in anesthetized dogs

The effects of ONO 3708, a new thromboxane A2 receptor antagonist, on cardiovascular and airway responses, at an early phase during endotoxin shock were investigated in anesthetized dogs. The i.v. infusion (1mg.kg-1) of E.coli endotoxin caused an increase in mean pulmonary artery pressure (MPAP) from 9.9 +/- 1.0 to 19.1 +/- 2.3 mmHg at 5 min, and at 15 min after infusion, elevated MPAP returned toward the control level. Pretreatment with ONO 3708 abolished these effects of endotoxin on pulmonary artery pressure at an early phase. The change in airway pressure reached a maximum of 14.4 +/- 1.7 cmH2O from 10.0 +/- 1.9 at 5 min, followed by a gradual decline toward a baseline value at 30 min in the control group. ONO 3708 significantly attenuated increase in airway pressure induced by E. coli endotoxin. But pretreatment with ONO 3708 could not prevent decrease in systemic arterial pressure and cardiac output induced by endotoxin. These results suggest that role of thromboxane A2 on the cardiovascular response during endotoxin shock is played only on pulmonary vascular changes, and ONO 3708 has a beneficial effect at least during the early phase of endotoxin shock.     

The effect of platelet activating factor antagonist BN 52021 on bacterial translocation and ICAM-I expression in experimental obstructive jaundice.

Expression of intracellular adhesion molecule-1 (ICAM-1) in an obstructive jaundice model and the potential protective role of platelet activating factor antagonist over small intestine and liver together with its effects on bacterial translocation are examined in this study. Forty-eight male Wistar albino rats were assigned into four equal groups of 12. In groups I and II, animals were sham operated. In groups III and IV, common bile duct ligation and division were performed. In group I and group III, 0.5 ml/day normal saline was applied intraperitoneally daily from day 2 to 6 of the study; in group II and group IV, 1 mg/kg/day BN 52021 was applied intraperitoneally daily from day 2 to 6 of the study. All animals were sacrificed on postoperative day 7. ICAM-1 expression (CD54 positivity) was analyzed in the liver and ileum tissue by immunohistochemical method. Samples from blood, liver mesenteric lymph nodes, and spleen were cultured under aerobic conditions. It is revealed that ICAM-1 expression was statistically higher in group III, with highest bacterial translocation and liver and spleen injury when compared to other groups. Serum alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), gamma-glutamyltranspeptidase (GGT), bilirubin, tumor necrosis factor alpha (TNFalpha), and interleukin 1beta(IL-1beta) values were at the highest level in group III, and there was a statistical decrease in group IV compared to group III. The administration of BN52021 in experimental obstructive jaundice is a useful way to reduce liver and intestinal mucosal villi damage by inhibiting bacterial translocation and systemic inflammatory response.