RESUMEN
Thrombin, a key player in coagulation, is widely held to induce and promote inflammation. As of now, the features, kinetics and control of thrombin's proinflammatory effects on the skin remain to be characterized in detail. We, therefore, injected thrombin into the ear skin of mice and observed strong, dose-dependent and transient ear swelling responses as well as mast cell (MC) degranulation. Unexpectedly, thrombin induced even stronger, not reduced, ear swelling in MC-deficient KitW-sh/W-sh mice. Prior local reconstitution of KitW-sh/W-sh mice with MCs inhibited this effect, indicating that MCs may contribute to the control of thrombin-induced skin inflammation. In line with previous studies, we found that MCs express the thrombin receptors PAR1, PAR3 and PAR4, thrombin induces direct and dose-dependent MC degranulation, and that degranulated MCs inactivate thrombin. Further findings suggested that MC-mediated protection from thrombin-induced inflammation is likely to rely on the effects of MC proteases. We show for the first time that MC-deficient mice and MC protease 4-deficient mice with normal numbers of MCs show markedly increased ear swelling in response to thrombin as compared to wild-type mice. Taken together, these results suggest that thrombin-induced skin inflammation is controlled, in part, by MC protease 4 released from activated MCs. For MC-driven diseases such as chronic spontaneous urticaria, which has been linked to increased thrombin generation, this might mean that MCs may contribute to the resolution of skin inflammatory responses.
Asunto(s)
Inflamación/metabolismo , Mastocitos/citología , Trombina/farmacología , Animales , Oído , Ratones , Ratones Endogámicos C57BL , Proteínas Proto-Oncogénicas c-kit/metabolismo , Serina Endopeptidasas/metabolismo , Piel/metabolismo , Urticaria/metabolismoRESUMEN
The maintenance and modulation of cutaneous mast cell (MC) numbers is held to be important for skin immune responses to allergens and pathogens. The increase in MC numbers in the skin is achieved by proliferation and the differentiation of precursor to mature MCs. Fibroblast-derived SCF is thought to be the major skin MC growth factor and it potently induces MC proliferation. The mechanisms of fibroblast-induced skin MC differentiation, including the role of SCF, however, remain insufficiently characterized and understood. Using cocultures of immature murine MCs and fibroblasts, we found that the adhesion of immature MCs to fibroblasts via VCAM-1 and α4 ß7 integrin is very important for subsequent differentiation, which is driven by fibroblast membrane-bound SCF and additional fibroblast-derived membrane-bound signals. Thus, our results show that fibroblast-induced MC differentiation is induced by direct cell-cell contact and involves both Kit-dependent and Kit-independent pathways. Our findings add to the understanding of how immature mast cells mature in murine skin and encourage further analyses of the underlying mechanisms, which may result in novel targets for the modulation of skin mast cell driven diseases.
Asunto(s)
Comunicación Celular , Mastocitos/fisiología , Proteínas Proto-Oncogénicas c-kit/genética , Proteínas Proto-Oncogénicas c-kit/metabolismo , Factor de Células Madre/metabolismo , Molécula 1 de Adhesión Celular Vascular/metabolismo , Animales , Adhesión Celular , Diferenciación Celular , Membrana Celular , Técnicas de Cocultivo , Femenino , Fibroblastos/metabolismo , Expresión Génica , Histidina Descarboxilasa/genética , Ratones , Ratones Endogámicos C57BL , Serina Endopeptidasas/genética , Transducción de Señal , Fenómenos Fisiológicos de la Piel , Regulación hacia ArribaRESUMEN
Mast cell numbers are markedly increased at sites of chronic inflammation. However, the underlying mechanisms of mast cell accumulation including mast cell progenitor trafficking remain to be identified in detail. Thus, the aim of this study was to identify the adhesion molecules involved in rolling, firm adhesion and transendothelial diapedesis of murine bone marrow-derived cultured mast cells (BMCMC) as a model for immature mast cells. We could show that BMCMCs exhibit in vivo rolling on skin vessel walls and strong adhesion to skin endothelial cells (ECs) in vitro under static and flow conditions. Interestingly, interaction of BMCMC with the EC adhesion molecules E- and P-selectin, vascular cell adhesion molecule-1 (VCAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1) is required to mediate rolling and firm adhesion to ECs. The adhesion of BMCMCs to skin ECs is further enhanced by TNF, IL-4, IL-15 and vascular endothelial cell growth factor. Furthermore, BMCMCs exhibit directed and dose-dependent transmigration across an endothelial barrier, mediated by a PECAM-1-dependent mechanism. Our results demonstrate that BMCMCs can undergo a tightly regulated extravasation cascade consisting of rolling on and adhesion to endothelium and followed by directed diapedesis and reveal selectins, VCAM-1 and PECAM-1 as required adhesion molecules. These processes may contribute to mast cell accumulation in chronic inflammatory skin diseases and reveal opportunities to modulate peripheral tissue numbers of mast cells.