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Tarnjit K. Khera, Madeleine L. Stimpson, Haley Peckham, Gemma L. Beers, David A. Copland, Yordan Sbirkov, Lindsay B. Nicholson, Sarah J. George, Andrew D. Dick; Canonical Wnt Signalling Is Active During The Peak Of Uveitis And Can Regulate Macrophage Activation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5273.
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Examination of CD45+ cells in experimental autoimmune uveoretinitis (EAU) demonstrates that myeloid cell phenotype alters during disease. GSK-3 is a constitutively active protein kinase important for the regulation of both innate and adaptive immune responses, including LPS-mediated TLR signalling and IFNγ-induced STAT3 signalling. GSK-3 is in part regulated by wnt signalling that will determine the extent to which β-catenin is activated and thus translocate to the nucleus. Therefore the balance of regulating GSK-3 activity via wnt signals and ultimately β-catenin is important for determining macrophage responses during inflammation. The purpose of this study was to determine if wnt signalling during EAU is operative and whether macrophage activation is regulated by GSK-3 and β-catenin.
Clinical disease in B10.RIII and C57BL/6 mice was monitored by fundus imaging. Within the retinas co-expression of β-catenin and CD45 by immunofluorescence, and wnt gene expression was quantified by qPCR. Macrophages were stimulated with IFNγ and gene expression of wnt signalling molecules quantified. Also, macrophages from WT or TNFR1-/- mice were stimulated alone or in the presence of β-catenin or GSK-3 inhibitors, prior to nitric oxide (NO) quantification. Macrophages from β-galactosidase wnt reporter mice were stimulated and β-galactosidase production quantified.
Gene expression of the wnt signalling molecules were increased at peak disease, which correlated with high expression of active β-catenin in CD45+ and CD45- cells within the retina. IFNγ induced fzd1, wnt3a and wnt5a gene expression; LPS and TNF also induced canonical wnt signalling in macrophages from wnt reporter mice. Furthermore, inhibiting β-catenin increased IFNγ-induced NO by macrophages in a TNFR1-dependent manner, whereas inhibition of GSK-3α and GSK-3β suppressed it. However, inhibition of GSK-3β alone also increased IFNγ-induced but decreased LPS-induced NO production.
Macrophages can be regulated reciprocally by β-catenin and GSK-3. In EAU there is an increase in β-catenin activity and wnt gene expression at the peak of disease. Manipulation of wnt signalling could offer a new therapeutic approach by altering macrophage phenotype to suppress disease and restore tissue homeostasis.
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