Osteopontin Promotes Protective Antigenic Tolerance against Experimental Allergic Airway Disease

In the context of inflammation, osteopontin (Opn) is known to promote effector responses, facilitating a proinflammatory environment; however, its role during antigenic tolerance induction is unknown. Using a mouse model of asthma, we investigated the role of Opn during antigenic tolerance induction and its effects on associated regulatory cellular populations prior to disease initiation. Our experiments demonstrate that Opn drives protective antigenic tolerance by inducing accumulation of IFN-β–producing plasmacytoid dendritic cells, as well as regulatory T cells, in mediastinal lymph nodes. We also show that, in the absence of TLR triggers, recombinant Opn, and particularly its SLAYGLR motif, directly induces IFN-β expression in Ag-primed plasmacytoid dendritic cells, which renders them extra protective against induction of allergic airway disease upon transfer into recipient mice. Lastly, we show that blockade of type I IFNR prevents antigenic tolerance induction against experimental allergic asthma. Overall, we unveil a new role for Opn in setting up a tolerogenic milieu boosting antigenic tolerance induction, thus leading to prevention of allergic airway inflammation. Our results provide insight for the future design of immunotherapies against allergic asthma

Immunological synapse formation between T regulatory cells and cancer-associated fibroblasts promotes tumour development

Cancer-associated fibroblasts (CAFs) have emerged as a dominant non-hematopoietic cell population in the tumour microenvironment, serving diverse functions in tumour progression. However, the mechanisms via which CAFs influence the anti-tumour immunity remain poorly understood. Here, using multiple tumour models and biopsies from cancer patients, we report that α-SMA+ CAFs can form immunological synapses with Foxp3+ regulatory T cells (Tregs) in tumours. Notably, α-SMA+ CAFs can phagocytose and process tumour antigens and exhibit a tolerogenic phenotype which instructs movement arrest, activation and proliferation in Tregs in an antigen-specific manner. Moreover, α-SMA+ CAFs display double-membrane structures resembling autophagosomes in their cytoplasm. Single-cell transcriptomic data showed an enrichment in autophagy and antigen processing/presentation pathways in α-SMA-expressing CAF clusters. Conditional knockout of Atg5 in α-SMA+ CAFs promoted inflammatory re-programming in CAFs, reduced Treg cell infiltration and attenuated tumour development. Overall, our findings reveal an immunosuppressive mechanism entailing the formation of synapses between α-SMA+ CAFs and Tregs in an autophagy-dependent manner

Activin-A induces regulatory T cells that suppress T helper cell immune responses and protect from allergic airway disease

Activin-A is a pleiotropic cytokine that participates in developmental, inflammatory, and tissue repair processes. Still, its effects on T helper (Th) cell–mediated immunity, critical for allergic and autoimmune diseases, are elusive. We provide evidence that endogenously produced activin-A suppresses antigen-specific Th2 responses and protects against airway hyperresponsiveness and allergic airway disease in mice. Importantly, we reveal that activin-A exerts suppressive function through induction of antigen-specific regulatory T cells that suppress Th2 responses in vitro and upon transfer in vivo. In fact, activin-A also suppresses Th1-driven responses, pointing to a broader immunoregulatory function. Blockade of interleukin 10 and transforming growth factor β1 reverses activin-A–induced suppression. Remarkably, transfer of activin-A–induced antigen-specific regulatory T cells confers protection against allergic airway disease. This beneficial effect is associated with dramatically decreased maturation of draining lymph node dendritic cells. Therapeutic administration of recombinant activin-A during pulmonary allergen challenge suppresses Th2 responses and protects from allergic disease. Finally, we demonstrate that immune cells infiltrating the lungs from individuals with active allergic asthma, and thus nonregulated inflammatory response, exhibit significantly decreased expression of activin-A's responsive elements. Our results uncover activin-A as a novel suppressive factor for Th immunity and a critical controller of allergic airway disease

Διερεύνηση του ρόλου της κυτταροκίνης οστεοποντίνης σε εδραιωμένες ανοσοαπαντήσεις τύπου-2

Osteopontin (Opn) is important for T helper type 1 (TH1) immunity and autoimmunity. However, the role of this cytokine in TH2-mediated allergic disease, as well as its effects on primary versus secondary antigenic encounters and its role in antigenic peripheral tolerance, remain unclear. Here we demonstrate that OPN is expressed in the lungs of asthmatic individuals and Opn-s, the secreted form of Opn, exerts opposing effects on mouse TH2 effector responses and subsequent allergic airway disease: pro-inflammatory at primary systemic sensitization, and anti-inflammatory during secondary pulmonary antigenic challenge. These opposing effects of Opn-s are mainly mediated by regulation of TH2-suppressing plasmacytoid dendritic cells (DCs) during primary sensitization and TH2-promoting conventional DCs during secondary antigenic challenge. Therapeutic administration of recombinant Opn during pulmonary secondary antigenic challenge decreased established TH2 responses and protected from allergic disease. Our data demonstrated the anti-inflammatory role of Opn in TH2-type allergic airway responses. Furthermore Opn is also highly expressed in activated Foxp3+ Tregs. Thus, we also investigated whether Opn had an impact on peripheral tolerance. Opn-deficient mice were impaired in mounting antigenic tolerance against a TH2-driven asthma model disease, while administration of rOpn had the opposite effect. rOpn promoted tolerance by expansion of suppressive plasmacytoid dendritic cells (pDCs) and expansion of Foxp3+ Tregs. In fact, rOpn was a pDC survival factor that instructed these cells to generate Treg cells, and also promoted the expansion of Foxp3+ Tregs. Overall, these novel effects on TH2 allergic responses and peripheral tolerance, place Opn as an important therapeutic target and a key cytokine controlling peripheral tolerance, and thus provide new insight into its role in immunit

Διερεύνηση του ρόλου της κυτταροκίνης οστεοποντίνης σε εδραιωμένες ανοσοαπαντήσεις τύπου-2

Osteopontin (Opn) is important for T helper type 1 (TH1) immunity and autoimmunity. However, the role of this cytokine in TH2-mediated allergic disease, as well as its effects on primary versus secondary antigenic encounters and its role in antigenic peripheral tolerance, remain unclear. Here we demonstrate that OPN is expressed in the lungs of asthmatic individuals and Opn-s, the secreted form of Opn, exerts opposing effects on mouse TH2 effector responses and subsequent allergic airway disease: pro-inflammatory at primary systemic sensitization, and anti-inflammatory during secondary pulmonary antigenic challenge. These opposing effects of Opn-s are mainly mediated by regulation of TH2-suppressing plasmacytoid dendritic cells (DCs) during primary sensitization and TH2-promoting conventional DCs during secondary antigenic challenge. Therapeutic administration of recombinant Opn during pulmonary secondary antigenic challenge decreased established TH2 responses and protected from allergic disease.Our data demonstrated the anti-inflammatory role of Opn in TH2-type allergic airway responses. Furthermore Opn is also highly expressed in activated Foxp3+ Tregs. Thus, we also investigated whether Opn had an impact on peripheral tolerance. Opn-deficient mice were impaired in mounting antigenic tolerance against a TH2-driven asthma model disease, while administration of rOpn had the opposite effect. rOpn promoted tolerance by expansion of suppressive plasmacytoid dendritic cells (pDCs) and expansion of Foxp3+ Tregs. In fact, rOpn was a pDC survival factor that instructed these cells to generate Treg cells, and also promoted the expansion of Foxp3+ Tregs. Overall, these novel effects on TH2 allergic responses and peripheral tolerance, place Opn as an important therapeutic target and a key cytokine controlling peripheral tolerance, and thus provide new insight into its role in immunity

Study of the role of corticotropin releasing hormone (CHR) and its related pertides on the expression of toll like receptor (TLR-4)

Όταν η coticotropin releasing hormone (CRH) εκφράζετι σε περιφερικούς ιστούς, έχει προ-φλεγμονώδη δράση. Στο παρελθόν έχουμε δείξει ότι η CRH αυξάνει την επαγόμενη από το LPS έκκριση προφλεγμονώδων κυτοκινών. Ως γνωστόν το LPS σηματοδοτεί μέσω του υποδοχέα TLR-4 για να προκαλέσει τις προφλεγμονώδεις δράσεις του και έχει επίσης διαπιστωθεί, ότι η έκφραση του υποδοχέα TLR-4, είναι αυξημένη κατά την διάρκεια της φλεγμονής. Με βάση τα παραπάνω δεδομένα ο σκοπός της παρούσας μελέτης, ήταν ο προσδιορισμός της επίδρασης των νευροπεπιδίων της οικογένειας CRH, στην έκφραση του υποδοχέα TLR-4 στα μακροφάγα κύτταρα. Για την επίτευξη του σκοπού αυτού σαν μοντέλα μακροφάγων επιλέξαμε την κυτταρική σειρά μεκροφάγων ποντικού Raw264.7 και την κυτταρική σειρά μονοκυττάρων ανθρώπου THP-1. Παρατηρήσαμε ότι με επίδραση των κυττάρων Raw264.7 με τα νευροπεπτίδια CRH, UCN και UCN2, προκλήθηκε αύξηση των επιπέδων του mRNA του TLR-4. Το αποτέλεσμα της επίδρασης των νευροπεπτιδίων πραγματοποιείται στο μεταγραφικό επίπεδο μέσω της ενεργοποίησης του ελάχιστου υποκινητή. Ο υποκινητής του υποδοχέα TLR-4 περιέχει αρκετά σημεία πρόσδεσης για τον μεταγραφικό παράγοντα PU.1, ο οποίος καθοδηγεί την έκφρασή του. Επίδραση των κυττάρων Raw264.7 με οποιοδήποτε από τα τρία νευροπεπτίδια, είχε σαν αποτέλεσμα την αυξημένη πρόσδεση του PU.1. Η επαγωγή της πρόσδεσης του PU.1 γίνεται μέσω του υποδοχέα CRHR2, αφού η δράση αυτή αναστέλλεται από την anti-sauvagine30. Επίδραση των κυττάρων με τα νευροπεπτίδια παρουσία LPS μειώνει την ανασταλτική επίδραση του LPS στην έκφραση του υποδοχέα TLR-4, γεγονός που υποδεικνύει έναν πιθανό μηχανισμό μέσω του οποίου η CRH αυξάνει την LPS-επαγόμενη έκκριση προφλεγμονώδων κυτταροκινών. Τα δεδομένα μας προτείνουν ότι το σήμα του CRHR2 επιδρά στην ενεργοποίηση των μακροφάγων από το LPS αυξάνοντας την έκφραση του υποδοχέα TLR-4 μέσω της ενεργοποίησης του μεταγραφικού παράγοντα PU.1We have previously shown that CRH augments lipopolysaccharide (LPS) -induced pro-inflammatory cytokine secretion. LPS signals via Toll like receptor-4 to mediate its pro-inflammatory actions. Expression of TLR4 is found increased during inflammation. Aim of the present study was to determine the role of CRH and its related peptides Urocortin 1 (UCN1) and Urocortin 2 (UCN2) on TLR4 expression in macrophages. Treatment of Raw264.7 macrophages with CRH, UCN1 or UCN2 upregulated TLR4 mRNA levels. The effect of CRH and Urocortins occured at the transcriptional level by activating the minimal TLR4 promoter. TLR4 promoter contains several PU.1 binding sites that drive its expression. Treatment of RAW264.7 macrophages with any of the three peptides resulted in increased PU.1 DNA binding. Induction of PU.1 binding occured via CRH2 since it was inhibited by anti-sauvagine-30. Treatment of cells with CRH, UCN or UCNII in the presence of LPS blocked the inhibitory effect of LPS to TLR4 expression indicating a possible mechanism through which CRH augments LPS-induced pro-inflammatory cytokine secretion. Our data suggest that CRH2 signals affect macrophage activation by LPS partly by upregulating TLR4 expression via activation of the transcription factor PU.1

Rebooting Regulatory T Cell and Dendritic Cell Function in Immune-Mediated Inflammatory Diseases: Biomarker and Therapy Discovery under a Multi-Omics Lens

Immune-mediated inflammatory diseases (IMIDs) are a group of autoimmune and chronic inflammatory disorders with constantly increasing prevalence in the modern world. The vast majority of IMIDs develop as a consequence of complex mechanisms dependent on genetic, epigenetic, molecular, cellular, and environmental elements, that lead to defects in immune regulatory guardians of tolerance, such as dendritic (DCs) and regulatory T (Tregs) cells. As a result of this dysfunction, immune tolerance collapses and pathogenesis emerges. Deeper understanding of such disease driving mechanisms remains a major challenge for the prevention of inflammatory disorders. The recent renaissance in high throughput technologies has enabled the increase in the amount of data collected through multiple omics layers, while additionally narrowing the resolution down to the single cell level. In light of the aforementioned, this review focuses on DCs and Tregs and discusses how multi-omics approaches can be harnessed to create robust cell-based IMID biomarkers in hope of leading to more efficient and patient-tailored therapeutic interventions

Osteopontin expression by CD103−dendritic cells drives intestinal inflammation

Intestinal CD103− dendritic cells (DCs) are pathogenic for colitis. Unveiling molecular mechanisms that render these cells proinflammatory is important for the design of specific immunotherapies. In this report, we demonstrated that mesenteric lymph node CD103− DCs express, among other proinflammatory cytokines, high levels of osteopontin (Opn) during experimental colitis. Opn expression by CD103− DCs was crucial for their immune profile and pathogenicity, including induction of T helper (Th) 1 and Th17 cell responses. Adoptive transfer of Opn-deficient CD103− DCs resulted in attenuated colitis in comparison to transfer of WT CD103− DCs, whereas transgenic CD103− DCs that overexpress Opn were highly pathogenic in vivo. Neutralization of secreted Opn expressed exclusively by CD103− DCs restrained disease severity. Also, Opn deficiency resulted in milder disease, whereas systemic neutralization of secreted Opn was therapeutic. We determined a specific domain of the Opn protein responsible for its CD103− DC-mediated proinflammatory effect. We demonstrated that disrupting the interaction of this Opn domain with integrin α9, overexpressed on colitic CD103− DCs, suppressed the inflammatory potential of these cells in vitro and in vivo. These results add unique insight into the biology of CD103− DCs and their function during inflammatory bowel disease