RESUMEN
Neutrophils are important effector cells of tissue injury in several pathological conditions, among them, immune complexes (IC)-induced inflammation and tissue injury. There is evidence that endothelins modulate IC-induced tissue injury in experimental models in vivo. In the present study we investigated the effect of endothelins on neutrophil activation by IC in vitro. To this purpose, pre-formed insoluble immune complexes were used to stimulate human neutrophils and production of leukotriene B(4) (LTB(4)) and hydrogen peroxyde (H(2)O(2)) were measured as indicative of phospholipase A(2) and oxidative burst activation and myeloperoxidase (MPO) release as indicative of cell degranulation. The effect of endothelins (ETs) in these events induced by IC was then examined. We found that IC stimulated all three events in human neutrophils. Addition of ET-1 but not ET-2 or ET-3 to the IC-stimulated neutrophils potentiated LTB(4) but not H(2)O(2) production. The endothelins added to resting neutrophils did not induce LTB(4) production but they were effective to stimulate H(2)O(2) production. The increased MPO activity induced by IC was not affected by endothelins nor did they stimulate the release of this enzyme in resting cells. These results show that endothelins are able to activate some neutrophil functions and to upregulate the IC-induced production of the pro-inflammatory molecule LTB(4). These data indicate that products of endothelial cells, such as endothelins, can be involved in the potentiation of neutrophil-dependent tissue injury.
Asunto(s)
Complejo Antígeno-Anticuerpo/farmacología , Endotelina-1/farmacología , Endotelina-2/farmacología , Endotelina-3/farmacología , Neutrófilos/efectos de los fármacos , Anticuerpos/inmunología , Degranulación de la Célula/efectos de los fármacos , Humanos , Peróxido de Hidrógeno/metabolismo , Peróxido de Hidrógeno/farmacología , Leucotrieno B4/biosíntesis , Activación Neutrófila , Neutrófilos/metabolismo , Neutrófilos/fisiología , Peroxidasa/metabolismo , Estallido Respiratorio/efectos de los fármacos , Albúmina Sérica Bovina/inmunologíaRESUMEN
Myocardial stretch elicits a biphasic increase in developed force with a first rapid force response and a second slow force response (SFR). The rapid phase is due to an increase in myofilament Ca(2+) responsiveness; the SFR, analyzed here, is ascribed to a progressive increase in Ca(2+) transients. Experiments were performed in cat papillary muscles to further elucidate the signaling pathway underlying the SFR. Although the SFR was diminished by BQ-123, a similar endothelin (ET)-1-induced increase in force was not affected: 23 +/- 2 vs. 23 +/- 3% (not significant). Instead, BQ-123 suppressed the contractile effects of ET-2 or ET-3 (21 +/- 2 and 25 +/- 3% vs. -1 +/- 1 and -7 +/- 3% respectively, P < 0.05), suggesting that ET-2 or ET-3, but not ET-1, was involved in the SFR. Each isoform activated the Na(+)/H(+) exchanger (NHE-1), increasing intracellular Na(+) concentration by 2.0 +/- 0.1, 2.3 +/- 0.1, and 2.1 +/- 0.4 mmol/l for ET-1, ET-2, and ET-3, respectively (P < 0.05). The NHE-1 inhibitor HOE-642 prevented the increases in force and intracellular Na(+) concentration induced by all the ET isoforms, but only ET-2 and ET-3 effects were sensitive to BQ-123. Real-time RT-PCR measurements of prepro-ET-1, -ET-2, and -ET-3 were performed before and 5, 15, and 30 min after stretch. No changes in ET-1 or ET-2, but an increase of approximately 60% in ET-3, mRNA after 15 min of stretch were detected. Stretch-induced ET-3 mRNA upregulation and its mechanical counterpart were suppressed by AT(1) receptor blockade with losartan. These data suggest a role for AT(1)-mediated ET-3 released in the early activation of NHE-1 that follows myocardial stretch.