RESUMEN
OBJECTIVE: Black individuals are at an increased risk of myocardial infarction and stroke, 2 vascular diseases with strong thrombotic components. Platelet activation is a key step in platelet clot formation leading to myocardial infarction and stroke, and recent work supports a racial difference in platelet aggregation through the thrombin protease-activated receptors (PARs). The underlying mechanism for this racial difference, however, has not been established. Determining where in the signaling cascade these racial differences emerge will aid in understanding why individuals of differing racial ancestry may possess an inherent difference in their responsiveness to antiplatelet therapies. APPROACH AND RESULTS: Washed human platelets from black volunteers were hyperaggregable in response to PAR4-mediated platelet stimulation compared with whites. Interestingly, the racial difference in PAR4-mediated platelet aggregation persisted in platelets treated ex vivo with aspirin and 2MeSAMP (2-methylthioadenosine 5'-monophosphate triethylammonium salt hydrate), suggesting that the racial difference is independent of secondary feedback. Furthermore, stimulation of platelets from black donors with PAR4-activating peptide showed a potentiated level of activation through the Gq pathway compared with platelets from white donors. Differences in signaling included increased Ca(2+) mobilization, Rap1 (Ras-related protein 1) activation, and integrin αIIbß3 activation with no observed difference in platelet protein expression between the groups tested. CONCLUSIONS: Our study is the first to demonstrate that the Gq pathway is differentially regulated by race after PAR4 stimulation in human platelets. Furthermore, the racial difference in PAR4-mediated platelet aggregation persisted in the presence of cyclooxygenase and P2Y12 receptor dual inhibition, suggesting that current antiplatelet therapy may provide less protection to blacks than whites.
Asunto(s)
Población Negra , Subunidades alfa de la Proteína de Unión al GTP Gq-G11/sangre , Activación Plaquetaria/fisiología , Receptores de Trombina/sangre , Población Blanca , Adulto , Señalización del Calcio , Inhibidores de la Ciclooxigenasa/farmacología , Femenino , Humanos , Masculino , Activación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/fisiología , Complejo GPIIb-IIIa de Glicoproteína Plaquetaria/metabolismo , Prostaglandina-Endoperóxido Sintasas/sangre , Proteína Quinasa C/sangre , Antagonistas del Receptor Purinérgico P2Y/farmacología , Receptores Purinérgicos P2Y12/sangre , Complejo Shelterina , Transducción de Señal , Proteínas de Unión a Telómeros/sangreRESUMEN
OBJECTIVE: To investigate the regulation of whole-blood cyclooxygenase-1 and -2 (COX-2 and COX-1) activities by methotrexate (MTX) in rheumatoid arthritis (RA) patients. METHODS: Whole blood was withdrawn from nine healthy volunteers, 12 RA patients treated with MTX (RA/MTX) and six RA patients treated with chloroquine (RA/CQ). COX-1 activity was quantified as platelet thromboxane B(2) production in unstimulated blood and COX-2 activity was measured as prostaglandin E(2) (PGE(2)) production in whole blood stimulated with LPS. Thromboxane B(2) and PGE(2) were measured by radioimmunoassay. We studied the drug effect in vitro by direct incubation of MTX with blood obtained from normal donors. Ex vivo assays were performed with blood collected from RA/MTX and RA/CQ patients. The influence of serum factors on enzyme activities was analysed in blood collected from normal donors and incubated with RA/MTX, autologous or heterologous serum. RESULTS: In vitro assays showed no direct action of MTX on the activity of either enzyme. Assays performed with blood from RA/MTX patients showed preferential inhibition of COX-2 activity (PGE(2) = 10.11 +/- 2.42 ng/ml) when compared with blood of normal donors (PGE(2) = 37.7 +/- 4.36 ng/ml; P = 0.001). Inhibition of COX-2 activity was also observed when blood of normal donors was co-incubated with RA/MTX serum. CONCLUSION: Our results clearly show that the anti-inflammatory action of low-dose MTX is partly mediated by a serum factor induced by MTX or a MTX metabolite that preferentially inhibits the activity of COX-2.
Asunto(s)
Artritis Reumatoide/sangre , Isoenzimas/antagonistas & inhibidores , Metotrexato/farmacología , Artritis Reumatoide/tratamiento farmacológico , Artritis Reumatoide/enzimología , Ciclooxigenasa 1 , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa/farmacología , Inhibidores de la Ciclooxigenasa/uso terapéutico , Femenino , Humanos , Isoenzimas/sangre , Masculino , Proteínas de la Membrana , Metotrexato/uso terapéutico , Persona de Mediana Edad , Prostaglandina-Endoperóxido Sintasas/sangreRESUMEN
INTRODUCTION: beta-trace protein or D2 prostaglandin synthase is a dual functional protein. Its role and clinical value in cerebrospinal fluid is under study. MATERIAL AND METHODS: Seventy four pediatric patients suffering from viral meningoencephalitis and 7 with bacterial meningoencephalitis were studied. Sera and cerebrospinal fluid samples were taken. Albumin and beta-trace protein were quantified by immunodiffusion and nephelometry respectively. RESULTS: Increased cerebrospinal fluid beta-trace protein levels in comparison with normal value were observed. Nevertheless such expected increment was no possible seen in bacterial meningoencephalitis. CONCLUSIONS: beta-trace protein may contribute with the etiological diagnosis in meningoencephalitis.