RESUMEN
Ubiquitous reduction of the gap junction protein Connexin43 (Cx43) in mice provides beneficial effects on progression and composition of atherosclerotic lesions. Cx43 is expressed in multiple atheroma-associated cells but its function in each cell type is not known. To examine specifically the role of Cx43 in immune cells, we have lethally irradiated low-density lipoprotein receptor-deficient mice and reconstituted with Cx43+/+, Cx43+/- or Cx43-/- haematopoietic fetal liver cells. Progression of atherosclerosis was significantly lower in aortic roots of Cx43+/- chimeras compared with Cx43+/+ and Cx43-/- chimeras, and their plaques contained significantly less neutrophils. The relative proportion of circulating leukocytes was similar between the three groups. Interestingly, the chemoattraction of neutrophils, which did not express Cx43, was reduced in response to supernatant secreted by Cx43+/- macrophages in comparison with the ones of Cx43+/+ and Cx43-/- macrophages. Cx43+/- macrophages did not differ from Cx43+/+ and Cx43-/- macrophages in terms of M1/M2 polarisation but show modified gene expression for a variety chemokines and complement components. In conclusion, titration of Cx43 expression in bone marrow-derived macrophages reduces atherosclerotic plaque formation and chemoattraction of neutrophils to the lesions.
Asunto(s)
Aorta/metabolismo , Enfermedades de la Aorta/prevención & control , Aterosclerosis/prevención & control , Conexina 43/metabolismo , Trasplante de Células Madre Hematopoyéticas , Células Madre Hematopoyéticas/metabolismo , Animales , Aorta/patología , Enfermedades de la Aorta/genética , Enfermedades de la Aorta/inmunología , Enfermedades de la Aorta/metabolismo , Enfermedades de la Aorta/patología , Aterosclerosis/genética , Aterosclerosis/inmunología , Aterosclerosis/metabolismo , Aterosclerosis/patología , Células Cultivadas , Quimiotaxis de Leucocito , Técnicas de Cocultivo , Conexina 43/deficiencia , Conexina 43/genética , Modelos Animales de Enfermedad , Macrófagos/inmunología , Macrófagos/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , Infiltración Neutrófila , Fenotipo , Placa Aterosclerótica , Interferencia de ARN , Receptores de LDL/deficiencia , Receptores de LDL/genética , Transfección , Irradiación Corporal TotalRESUMEN
BACKGROUND: Endothelial dysfunction is the initiating event of atherosclerosis. The expression of connexin40 (Cx40), an endothelial gap junction protein, is decreased during atherogenesis. In the present report, we sought to determine whether Cx40 contributes to the development of the disease. METHODS AND RESULTS: Mice with ubiquitous deletion of Cx40 are hypertensive, a risk factor for atherosclerosis. Consequently, we generated atherosclerosis-susceptible mice with endothelial-specific deletion of Cx40 (Cx40del mice). Cx40del mice were indeed not hypertensive. The progression of atherosclerosis was increased in Cx40del mice after 5 and 10 weeks of a high-cholesterol diet, and spontaneous lesions were observed in the aortic sinuses of young mice without such a diet. These lesions showed monocyte infiltration into the intima, increased expression of vascular cell adhesion molecule-1, and decreased expression of the ecto-enzyme CD73 in the endothelium. The proinflammatory phenotype of Cx40del mice was confirmed in another model of induced leukocyte recruitment from the lung microcirculation. Endothelial CD73 is known to induce antiadhesion signaling via the production of adenosine. We found that reducing Cx40 expression in vitro with small interfering RNA or antisense decreased CD73 expression and activity and increased leukocyte adhesion to mouse endothelial cells. These effects were reversed by an adenosine receptor agonist. CONCLUSIONS: Cx40-mediated gap junctional communication contributes to a quiescent nonactivated endothelium by propagating adenosine-evoked antiinflammatory signals between endothelial cells. Alteration in this mechanism by targeting Cx40 promotes leukocyte adhesion to the endothelium, thus accelerating atherosclerosis.