| Vasculitis is a clinicopathologic process that involves inflammation and necrosis of blood vessels, resulting in a wide range of clinical diseases, including glomerulonephritis and systemic lupus erythemotosus. Lesions in kidneys, brain, and heart can be life-threatening. However, the pathogenesis of vasculitis is poorly understood. The treatment of vasculitis is still very limited and far from ideal. A growing body of evidence indicates that endothelial cell injury is a fundamental step in the development of all types of vasculitis. Among the proposed mechanisms of endothelial injury, the most important and best-studied mechanism is immune complex-mediated injury that is caused by leukocytes as mediated by IgG receptors (Fc?Rs) and complement activation. Fc?Rs are a group of receptors that specifically bind Fc portion of IgG and its immune complexes. They play quite important roles in coordinating between cellular and humoral immune responses. There are three types of Fc?Rs, Fc?RI/CD64,Fc?RII/CD32 and Fc?RIII/CD16,mainly expressed on hematopoietic cells. Three types of Fc?Rs can be subdivided into thirteen isoforms. According to reports, there were immune complex deposits on blood vessels of vasculitic patients, and circulating immune complex in the blood. However, how immune complexes are localized to specific regions of blood vessels is unclear. Because there was no evidence to show that Fc?Rs were expressed on normal endothelial cells. Fc?Rs expressed on some endothelial cells with specialized function or on the injury endothelial cells. According to reports, the concentrations of inflammatory cytokines TNF-?, IFN-?, IL-1, and GM-CSF had significantly increased in blood of vasculitic patients. These cytokines can regulate endothelial cell gene expression and Fc?Rs expression. However, there is not any report about Fc?Rs expression on cytokine stimulated endothelial cells up now. In order to elucidate a possible mechanism of immune complex localization to vessels in the pathogenesis of vasculitis, human aortic endothelial cells (HAEC), human umbilical vein endothelial cells (HUVEC), human breast skin microvascular endothelial cells (HMVEC), and canine aortic endothelial cells (CAEC) were stimulated withinflammatory cytokines and the expression of Fc?Rs was measured by using an enzyme-linked immunosorbent assay (ELISA). We also localized Fc?Rs and observed the function of Fc?Rs through immunofluorescent microscope and confocal microscope. And further analyzed the changes of Fc?Rs transcripts and identified the isoform of Fc?Rs by RT-PCR.The results show that unstimulated HAEC, HUVEC and HMVEC express low levels of Fc?RII and Fc?RIII,but not Fc?RI. Recombinant human tumor necrosis factor-? (TNF-?,200 U/ml) and interferon-? (IFN-?, 100 U/ml) significantly increased the expression of Fc? receptor type II (Fc?RII) by 4-6 fold (P<0.0001),and Fc?RIII by 1.5-2 fold after 72-hour stimulation. IL-1 also increased Fc?RII expression, but not GM-CSF. The enhanced Fc?RII was expressed on the cell surface as shown under a fluorescent microscope. The Fc?RII showed receptor capping after crosslinked by antibodies and incubation at 37℃ as observed under a confocal microscope. Fluorescence condensed in one or two areas. The enhanced Fc?RII expression was also demonstrated with an adhesion assay using opsonized sheep red blood cells and an immunocytochemical staining. The effect of both cytokines on endothelial cell Fc?RII expression was time, dose, and cytokine- maintenance dependent. TNF-? dramatically enhanced Fc?RII expression at the concentration as low as 1 U/ml (P<0.001), and 15 U/ml IFN-??also significantly increased Fc?RII expression level (P<0.05). The expression level of Fc?RII increased as the doses of two cytokines increased, respectively. Enhanced Fc?RII expression was observed as early as 24 hours following stimulation with TNF-??(P<0.01) and 48 hours with IFN-?(P<0.02), and reached a peak at 72 hours (P<0.0001). The expression level of Fc?RII returned to the original level aft...
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