Altered balance of interleukin-13/interferon-gamma contributes to lacrimal gland destruction and secretory dysfunction in CD25 knockout model of Sjögren’s syndrome

Abstract

IntroductionThe lacrimal gland (LG) of the CD25-/- model of Sjögren’s syndrome (SS) has high interleukin (IL)-17, IL-13 and interferon-gamma (IFN-γ) cytokines. The specific contribution of these cytokines to the onset and severity of dacryoadenitis in the CD25-/- mice has not been evaluated.MethodsCD25−/−IL-17A−/−, CD25−/−IL-17−/−IFN-γ−/− and CD25−/−IFN-γ−/− were used at 4, 8, 12, 16 weeks (W). Total lymphocytic infiltration was evaluated by histology and characterized by flow cytometry. Epidermal growth factor (EGF) concentration was measured in tears. Immunofluorescent staining evaluated expression of IFN-γ receptor (IFN-γR) and apoptosis. Real-time PCR evaluated inflammatory and T cell-related cytokines expression in LG. Caspase-3, -8, -9 activities was assayed in LG lysates. T helper cytokines were measured in serum by Luminex assay.ResultsThe greatest total LG infiltration at 8 W was seen in CD25−/−IL-17A−/− (95%), followed by CD25−/− (71%) and IL-17−/− (12%). Tear EGF concentration was in normal range in CD25−/− at 4 W and in very low levels in both CD25−/− and CD25−/−IL-17A−/−. CD25−/− had high levels of inflammatory cytokines transcripts in LG compared to IL-17−/− mice; however, CD25−/−IL-17A−/− had even higher IL-1β, IFN-γR, caspase-3, -8, -9 mRNA levels, greater immunoreactivity to IFN-γR in LG acini, greater number of apoptotic+ cells and greater caspases activities in the LG at 8 W. CD25−/−IL-17A−/− had lower IL-13 concentration and lower IL-13/IFN-γ ratio compared to CD25−/− in serum. CD25−/−IFN-γ−/− had lower number of apoptotic+ cells and decreased caspase-3 expression in LG. CD25−/−IL-17−/−IFN-γ−/− had lower total lymphocytic cell infiltration at 8 W (48%), CD4+T cell infiltration and expression of IFN-γR and apoptotic+ cells in the LG and increased tear EGF concentration in tears.ConclusionsIFN-γ is critical for LG destruction and secretory dysfunction in the CD25−/− model of SS. Altered balance between IFN-γ and IL-13 in the CD25−/−IL-17A−/− mice accelerates LG destruction by increasing glandular apoptosis and facilitating apoptosis through increased expression of IFN-γR by glandular epithelium and activation of caspases. Targeting both IFN-γ and IL-17 may be beneficial for treating the LG inflammation in SS.

Sexual dimorphic function of IL-17 in salivary gland dysfunction of the C57BL/6.NOD-Aec1Aec2 model of Sjögren’s syndrome

“…Although we did not examine the lacrimal glands in this study, ablating Il-17 in the CD25KO model of dry eye SjS created the opposite effect in the lacrimal glands in which at 16 weeks of age, deletion of Il-17 accelerated lacrimal gland infiltration and acinar apoptosis. Deletion of Ifn-γ decreased caspase activity levels and TUNEL + cells, whereas ablation of both Il-17 and Ifn-γ ameliorated dacryoadenitis and improves glandular function59. Therefore, in this particular KO model, IFN-γ is more pathogenic than IL-17 in dacryoadenitis.…”

TFOS DEWS II Tear Film Report

“…Fifteen interleukins or interleukin-associated molecules were for the most part increased in ADDE but two decreased and one increased in MGD [415,417,423,425,427,429]. There was disagreement over whether interferon gamma (IFNG) is increased or decreased in ADDE (although it is clearly increased in animal dry eye models) [423,427,429,474,475]. MMP-9 was increased in ADDE, post-LASIK dry eye, blepharitis, and conjunctivochalasis [415,421,433].…”

The Pathophysiology of Dry Eye Disease

“…152–155 IFN-γ produced by the infiltrating cells increases caspase expression and causes acinar apoptosis. 150, 151, 156–158 Altered nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) signaling has been implicated in SS 159–161 and increased NFκB signaling in epithelial cells was found to promote lacrimal gland acinar apoptosis that preceded lymphocytic infiltration in a mouse SS model. 161 Infiltration with autoreactive T cells and oxidative stress have also been observed in the aged lacrimal gland, indicating that aging is associated with inflammation and is not simply a degenerative process.…”