Artikel
The roles of IL-32 and the IL-33/ST2 axis in granulomatosis with polyangiitis (GPA)
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Veröffentlicht: | 12. September 2014 |
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Gliederung
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Background: Apart from its autoimmune reaction, GPA is characterized by granulomatous inflammation primarily involving the respiratory tract and resulting in destruction of tissues, cartilage/bone and other granulomatous manifestations. Interleukin(IL)-32 as well as IL-33 and its receptor ST2 have been implicated in mediating inflammatory and/or destructive mechanisms in rheumatic diseases. Their assumed reciprocal behavior regarding bone remodeling prompted us to examine their expression and function(s) in GPA.
Methods: Herein, we examined IL-32, IL-33 and IL-33 receptor (ST2) mRNA expression and protein in peripheral blood mononuclear and polymorphonuclear cells (PBMC, PMN) as well as in respiratory tract tissue in GPA in comparison to controls, using real-time PCR, western blot and immunohistochemistry.
Results: There were no differences regarding the mRNA expression of IL-32, IL-33 and ST2 in both, PBMC and PMN between GPA and healthy controls. However, PMN from GPA patients seemed to generate different cleavage products of IL-33. In the granulomatous inflammation, higher numbers of vimentin+/IL-32+ fibroblast-like cells and CD68+/IL32+ macrophages/multinucleated giant cells were observed in comparison to chronic rhinosinusitis, On the other side, whereas the number of IL-33+ cells (e.g. osteoblasts) appeared to be down-regulated in comparison to IL-32+ cells, a strong ST2 expression was detected in the GPA tissues.
Conclusion: Our findings indicate that an imbalance between IL-32 and the IL-33/ST2 axis might add to the tissue and bone destruction in GPA in situ. In addition, the GPA autoantigen proteinase 3 could play a role in generating IL-32 and IL-33 fragments with increased proinflammatory activities in an autocrine manner.