Corticotropin-releasing factor and the urocortins induce the expression of TLR4 in macrophages via activation of the transcription factors PU.1 and AP-1.

Corticotropin-releasing factor (CRF) augments LPS-induced proinflammatory cytokine production from macrophages. The aim of the present study was to determine the mechanism by which CRF and its related peptides urocortins (UCN) 1 and 2 affect LPS-induced cytokine production. We examined their role on TLR4 expression, the signal-transducing receptor of LPS. For this purpose, the murine macrophage cell line RAW 264.7 and primary murine peritoneal macrophages were used. Exposure of peritoneal macrophages and RAW 264.7 cells to CRF, UCN1, or UCN2 up-regulated TLR4 mRNA and protein levels. To study whether that effect occurred at the transcriptional level, RAW 264.7 cells were transfected with a construct containing the proximal region of the TLR4 promoter linked to the luciferase gene. CRF peptides induced activation of the TLR4 promoter, an effect abolished upon mutation of a proximal PU.1-binding consensus or upon mutation of an AP-1-binding element. Indeed, all three peptides promoted PU.1 binding to the proximal PU.1 site and increased DNA-binding activity to the AP-1 site. The effects of CRF peptides were inhibited by the CRF2 antagonist anti-sauvagine-30, but not by the CRF1 antagonist antalarmin, suggesting that CRF peptides mediated the up-regulation of TLR4 via the CRF2 receptor. Finally, CRF peptides blocked the inhibitory effect of LPS on TLR4 expression. In conclusion, our data suggest that CRF peptides play an important role on macrophage function. They augment the effect of LPS by inducing Tlr4 gene expression, through CRF2, via activation of the transcription factors PU.1 and AP-1

Tregs restrain dendritic cell autophagy to ameliorate autoimmunity

Design of efficacious Treg-based therapies and establishment of clinical tolerance in autoimmune diseases have proven to be challenging. The clinical implementation of Treg immunotherapy has been hampered by various impediments related to the stability and isolation procedures of Tregs as well as the specific in vivo targets of Treg modalities. Herein, we have demonstrated that Foxp3+ Tregs potently suppress autoimmune responses in vivo through inhibition of the autophagic machinery in DCs in a cytotoxic T-lymphocyte-associated protein 4-dependent (CTLA4-dependent) manner. Autophagydeficient DCs exhibited reduced immunogenic potential and failed to prime autoantigen-specific CD4+ T cells to mediate autoimmunity. Mechanistically, CTLA4 binding promoted activation of the PI3K/Akt/mTOR axis and FoxO1 nuclear exclusion in DCs, leading to decreased transcription of the autophagy component microtubule-associated protein 1 light chain 3β (Lc3b). Human DCs treated with CTLA4-Ig, a fusion protein composed of the Fc region of IgG1 and the extracellular domain of CTLA4 (also known as abatacept, marketed as Orencia), demonstrated reduced levels of autophagosome formation, while DCs from CTLA4-Ig-treated rheumatoid arthritis patients displayed diminished LC3B transcripts. Collectively, our data identify the canonical autophagy pathway in DCs as a molecular target of Foxp3+ Treg-mediated suppression that leads to amelioration of autoimmune responses. These findings may pave the way for the development of therapeutic protocols that exploit Tregs for the treatment of autoimmunity as well as diseases in which disturbed tolerance is a common denominator

Osteopontin has a crucial role in allergic airway disease through regulation of dendritic cell subsets

Osteopontin (Opn) is important for T helper type 1 (TH1) immunity and autoimmunity. However, the role of this cytokine in T H2-mediated allergic disease as well as its effects on primary versus secondary antigenic encounters remain unclear. Here we demonstrate that OPN is expressed in the lungs of asthmatic individuals and that 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 effects of Opn-s are mainly mediated by the 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 mice from allergic disease. These effects on T H2 allergic responses suggest that Opn-s is an important therapeutic target and provide new insight into its role in immunity. © 2007 Nature Publishing Group

Neurohormonal activity and vascular properties late after aortic coarctation repair

Background: Coarctation of aorta (CoA) patients present cardiovascular complications late after repair the causes of which are not fully understood. Our study investigates the neurohormonal and immune activation and the elastic properties of the aorta and peripheral vessels in adult patients with coarctation of aorta (CoA), late after repair. Methods: Nineteen adult patients with repaired CoA and 29 matched healthy controls underwent aortic distensibility, stiffness index, a study of the elastic properties of peripheral vessels proximal to the coarctation site and measurement of plasma cytokine and neurohormone levels. Results: Distensibility index was reduced (p = 0.02) and stiffness index was increased (p = 0.005) in CoA patients compared to control. Augmentation index (p = 0.0007) and augmented pressure (p = 0.001) were higher in CoA patients and Forearm Blood Flow (FBF) index was reduced (p = 0.009). Plasma levels of sICAM-1 (p = 0.01), sVCAM-1 (p = 0.05), E-selectin (p = 0.01), sFas-ligand (p = 0.02) and IL-10 (p = 0.01) were also elevated in CoA patients vs control. TNF-a, IL-6, Endothelin-1 and NT-pro-BNP levels were not. Conclusions: Adults with repaired CoA seem to develop a late inflammatory reaction, which reflects a functional problem in all vessels, regardless of the initial lesion. This may explain the late complications of the disease despite early repair and improved surgical procedures. © 2011 Elsevier Ireland Ltd. All rights reserved

Autophagy orchestrates the regulatory program of tumor-associated myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) densely accumulate into tumors and potently suppress antitumor immune responses, promoting tumor development. Targeting MDSCs in tumor immunotherapy has been hampered by lack of understanding of the molecular pathways that govern MDSC differentiation and function. Herein, we identify autophagy as a crucial pathway for MDSC-mediated suppression of antitumor immunity. Specifically, MDSCs in patients with melanoma and mouse melanoma exhibited increased levels of functional autophagy. Ablation of autophagy in myeloid cells markedly delayed tumor growth and endowed antitumor immune responses. Notably, tumor-infiltrating autophagy-deficient monocytic MDSCs (M-MDSCs) demonstrated impaired suppressive activity in vitro and in vivo, whereas transcriptome analysis revealed substantial differences in genes related to lysosomal function. Accordingly, autophagy-deficient M-MDSCs exhibited impaired lysosomal degradation, thereby enhancing surface expression of MHC class II molecules, resulting in efficient activation of tumor-specific CD4+ T cells. Finally, targeting of the membrane-associated RING-CH1 (MARCH1) E3 ubiquitin ligase that mediates the lysosomal degradation of MHC II in M-MDSCs attenuated their suppressive function, and resulted in markedly decreased tumor volume followed by development of a robust antitumor immunity. Collectively, these findings depict autophagy as a molecular target of MDSC-mediated suppression of antitumor immunity. © 2018 American Society for Clinical Investigation. All rights reserved

Mitochondrial Oxidative Damage Underlies Regulatory T Cell Defects in Autoimmunity

Regulatory T cells (Tregs) are vital for the maintenance of immune homeostasis, while their dysfunction constitutes a cardinal feature of autoimmunity. Under steady-state conditions, mitochondrial metabolism is critical for Treg function; however, the metabolic adaptations of Tregs during autoimmunity are ill-defined. Herein, we report that elevated mitochondrial oxidative stress and a robust DNA damage response (DDR) associated with cell death occur in Tregs in individuals with autoimmunity. In an experimental autoimmune encephalitis (EAE) mouse model of autoimmunity, we found a Treg dysfunction recapitulating the features of autoimmune Tregs with a prominent mtROS signature. Scavenging of mtROS in Tregs of EAE mice reversed the DDR and prevented Treg death, while attenuating the Th1 and Th17 autoimmune responses. These findings highlight an unrecognized role of mitochondrial oxidative stress in defining Treg fate during autoimmunity, which may facilitate the design of novel immunotherapies for diseases with disturbed immune tolerance. Herein, Alissafi et al. reveal that in Tregs during autoimmunity there is elevated mitochondrial oxidative stress, which induces a DNA damage response and cell death. Using a mouse model, they show that mitochondrial ROS scavenging in Tregs ameliorates autoimmune responses. These findings define new Treg checkpoints in autoimmune diseases. © 2020 Elsevier Inc

Patrolling human SLE haematopoietic progenitors demonstrate enhanced extramedullary colonisation; implications for peripheral tissue injury

Systemic lupus erythematosus (SLE) is an autoimmune disease where bone-marrow-derived haematopoietic cells have a key role in its pathogenesis with accumulating evidence suggesting an aberrant function of haematopoietic stem/progenitor cells (HSPCs). We examined whether patrolling HSPCs differ from bone-marrow HSPCs both in SLE and healthy individuals, and how they participate in peripheral tissue injury. By employing next-generation RNA sequencing, the transcriptomes of CD34(+) HSPCs deriving from the bone marrow and those patrolling the bloodstream of both healthy and individuals with SLE were compared. Patrolling SLE and Healthy human HSPC kinetics were examined through their inoculation into humanised mice. Patrolling and bone-marrow HSPCs have distinct molecular signatures, while patrolling SLE HSPCs showed an enhanced extramedullary gene expression profile. Non-mobilised, SLE-derived circulating HSPCs demonstrated altered homing capacities. Xenotransplantation of circulating HSPCs in humanised mice showed that human peripheral blood HSPCs possess the ability for extramedullary organ colonisation to the kidneys. Circulating and bone marrow-derived HSPCs are distinct in steady and diseased states. Patrolling SLE CD34(+) HSPCs are able to home at extramedullary sites such as the spleen and kidneys, potentially participating in peripheral tissue injury