IL-17A-producing CD8+ T cells promote PDAC via induction of inflammatory cancer-associated fibroblasts.

OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) is characterised by an abundant desmoplastic stroma composed of cancer-associated fibroblasts (CAF) and interspersed immune cells. A non-canonical CD8+ T-cell subpopulation producing IL-17A (Tc17) promotes autoimmunity and has been identified in tumours. Here, we evaluated the Tc17 role in PDAC. DESIGN: Infiltration of Tc17 cells in PDAC tissue was correlated with patient overall survival and tumour stage. Wild-type (WT) or Il17ra-/- quiescent pancreatic stellate cells (qPSC) were exposed to conditional media obtained from Tc17 cells (Tc17-CM); moreover, co-culture of Tc17-CM-induced inflammatory (i)CAF (Tc17-iCAF) with tumour cells was performed. IL-17A/F-, IL-17RA-, RAG1-deficient and Foxn1nu/nu mice were used to study the Tc17 role in subcutaneous and orthotopic PDAC mouse models. RESULTS: Increased abundance of Tc17 cells highly correlated with reduced survival and advanced tumour stage in PDAC. Tc17-CM induced iCAF differentiation as assessed by the expression of iCAF-associated genes via synergism of IL-17A and TNF. Accordingly, IL-17RA controlled the responsiveness of qPSC to Tc17-CM. Pancreatic tumour cells co-cultured with Tc17-iCAF displayed enhanced proliferation and increased expression of genes implicated in proliferation, metabolism and protection from apoptosis. Tc17-iCAF accelerated growth of mouse and human tumours in Rag1-/- and Foxn1nu/nu mice, respectively. Finally, Il17ra-expressed by fibroblasts was required for Tc17-driven tumour growth in vivo. CONCLUSIONS: We identified Tc17 as a novel protumourigenic CD8+ T-cell subtype in PDAC, which accelerated tumour growth via IL-17RA-dependent stroma modification. We described a crosstalk between three cell types, Tc17, fibroblasts and tumour cells, promoting PDAC progression, which resulted in poor prognosis for patients.

Dimethyl fumarate alters intracellular Ca2+ handling in immune cells by redox-mediated pleiotropic effects.

Dimethyl fumarate (DMF) is widely used to treat the human autoimmune diseases multiple sclerosis (MS) and psoriasis. DMF causes short-term oxidative stress and activates the antioxidant response via the transcription factor Nrf2 but its immunosuppressive effect is not well understood. Immune cell activation depends on calcium signaling which itself is influenced by the cellular redox state. We therefore measured calcium, reactive oxygen species levels and glutathione content in lymphocytes from immunized mice before onset of experimental autoimmune encephalomyelitis, in peripheral blood mononuclear cells from MS patients treated with DMF, and in mouse splenocytes treated ex vivo with DMF. This demonstrated altered redox states and increased lymphocytic calcium levels in all model systems. DMF caused an immediate influx of calcium from the extracellular space, long-term increased cytosolic calcium levels and reduced calcium stored in intracellular stores. The DMF-elicited current had the electrophysiological characteristics of a transient receptor potential channel and the intracellular calcium levels were normalized by antagonists of TRPA1. Interestingly, the sarco/endoplasmic reticulum Ca2+-ATPase SERCA2b was downregulated but more active due to glutathionylation of the redox-sensitive cysteine 674. DMF therefore causes pleiotropic changes in cellular calcium homeostasis which are likely caused by redox-sensitive post-translational modifications. These changes probably contribute to its immunosuppressive effects.

Lugdunin amplifies innate immune responses in the skin in synergy with host- and microbiota-derived factors.

Recently our groups discovered lugdunin, a new cyclic peptide antibiotic that inhibits Staphylococcus aureus epithelial colonization in humans and rodents. In this work, we analyzed its immuno-modulatory and antimicrobial potential as a single agent or in combination with other microbiota- or host-derived factors. We show that pretreatment of primary human keratinocytes or mouse skin with lugdunin in combination with microbiota-derived factors results in a significant reduction of S. aureus colonization. Moreover, lugdunin increases expression and release of LL-37 and CXCL8/MIP-2 in human keratinocytes and mouse skin, and results in the recruitment of monocytes and neutrophils in vivo, both by a TLR/MyD88-dependent mechanism. Interestingly, S. aureus elimination by lugdunin is additionally achieved by synergistic antimicrobial activity with LL-37 and dermcidin-derived peptides. In summary, our results indicate that lugdunin provides multi-level protection against S. aureus and may thus become a promising treatment option for S. aureus skin infections in the future.

Imiquimod-Induced Psoriasis in Mice Depends on the IL-17 Signaling of Keratinocytes.

The pathology of psoriasis strongly depends on IL-17A. Monoclonal antibodies blocking either the cytokine or its receptor are among the most efficient treatments for psoriatic patients. Keratinocytes can be activated upon exposure to IL-17A and tumor necrosis factor-α and secrete secondary cytokines and chemokines in the inflamed skin. In psoriasis and its imiquimod-induced mouse model, a strong skin infiltration of neutrophils and inflammatory monocytes can be observed. However, to date, it is not clear how exactly those cellular populations are attracted to the skin and how they contribute to the pathogenesis of the disease. To define the crucial cell type responding to IL-17 and initiating the downstream pathology in psoriasis-like dermatitis, we used mice specifically lacking the IL-17 receptor (IL-17RA) in different cell types. Deletion of IL-17RA in T cells or myeloid had no impact on disease development. Only deletion of this receptor in keratinocytes reflected the full-body deletion of IL-17RA, resulting in strongly reduced dermatitis development. Imiquimod treatment of those IL-17 signaling-deficient mice maintained high monocytic infiltration but failed to attract neutrophils into the skin. We conclude that keratinocytes are a critical cellular target for IL-17A-mediated neutrophil attraction and psoriasis development.