Siglec-H(-/-) Plasmacytoid Dendritic Cells Protect Against Acute Liver Injury by Suppressing IFN-γ/Th1 Response and Promoting IL-21(+) CD4 T Cells.

Siglec-H is a receptor specifically expressed in mouse plasmacytoid dendritic cells (pDCs), which functions as a negative regulator of interferon-α production and plays a critical role in pDC maturation to become antigen-presenting cells. The function of pDCs in autoimmune and inflammatory diseases has been reported. However, the effect of Siglec-H expression in pDCs in liver inflammation and diseases remains unclear. Using the model of concanavalin A-induced acute liver injury (ALI), we investigated the Siglec-H/pDCs axis during ALI in BDCA2 transgenic mice and Siglec-H-/- mice. Anti-BDCA2 antibody, anti-interleukin (IL)-21R antibody, and Stat3 inhibitor were used to specifically deplete pDCs, block IL21 receptor, and inhibit Stat3 signaling, respectively. Splenocytes and purified naive CD4 T cells and bone marrow FLT3L-derived pDCs were cocultured and stimulated with phorbol myristate acetate/ionomycin and CD3/CD28 beads, respectively. Data showed that specific depletion of pDCs aggravated concanavalin A-induced ALI. Remarkably, alanine aminotransferase, hyaluronic acid, and proinflammatory cytokines IL6 and tumor necrosis factor-α levels were lower in the blood and liver of Siglec-H knockout mice. This was associated with attenuation of both interferon-γ/Th1 response and Stat1 signaling in the liver of Siglec-H knockout mice while intrahepatic IL21 and Stat3 signaling pathways were upregulated. Blocking IL21R or Stat3 signaling in Siglec-H knockout mice restored concanavalin A-induced ALI. Finally, we observed that the Siglec-H-null pDCs exhibited immature and immunosuppressive phenotypes (CCR9LowCD40Low), resulting in reduction of CD4 T-cell activation and promotion of IL21+CD4 T cells in the liver. During T-cell-mediated ALI, Siglec-H-null pDCs enhance immune tolerance and promote IL21+CD4 T cells in the liver. Targeting Siglec-H/pDC axis may provide a novel approach to modulate liver inflammation and disease.

Ahodantin J ，Wu J ，Funaki M ，Flores J ，Wang X ，Zheng P ，Liu Y ，Su L ... -  《Cellular and Molecular Gastroenterology and Hepatology》

Mitoxantrone attenuates lipopolysaccharide-induced acute lung injury via inhibition of NEDD8 activating enzyme.

Lipopolysaccharide (LPS) triggers the activation of nuclear factor kappa B (NF-κB) by interacting with Toll-like receptor 4 (TLR4), leading to the production of various proinflammatory enzymes and cytokines that are crucial in the development of acute lung injury (ALI). Mitoxantrone (MTX) has been demonstrated to mitigate the inflammatory response caused by LPS; however, its precise function in the context of ALI is not fully comprehended. This study aimed to investigate the inhibitory effects and underlying mechanisms of MTX against LPS-induced ALI. ALI was induced in C57BL/6 mice via a single intratracheal administration of LPS (5 mg/kg), followed by an intraperitoneal injection of MTX to evaluate its therapeutic potential. The effects of MTX on lung injury and the progression of inflammation in ALI mice were assessed using a comprehensive range of techniques, including hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), myeloperoxidase activity measurement, cell enumeration in bronchoalveolar lavage fluid (BALF), Western blotting, and enzyme-linked immunosorbent assay (ELISA). Additionally, IHC, Western blotting, and co-immunoprecipitation were used to elucidate the specific signaling pathways and molecular mechanisms by which MTX exerted its anti-inflammatory effects in ALI mice. Surface plasmon resonance (SPR) and molecular docking were used to examine the target to which MTX binds directly to reduce inflammation. We also established a lung epithelial cell injury model using LPS-treated A549 cells. The polyubiquitination of IκBα and TRAF6 in LPS-induced A549 cells was detected through Western blotting following immunoprecipitation. In mice with LPS-induced ALI, MTX exhibits anti-inflammatory effects by ameliorating histopathological abnormalities caused by LPS, reducing inflammatory cell infiltration, and decreasing the production of proinflammatory enzymes and cytokines. It has been observed that MTX directly binds to the NEDD8 activating enzyme (NAE), thereby inhibiting the transfer of NEDD8 to the substrates UBC12, Cul1, and Cul5. Consequently, the polyubiquitination of IκBα and TRAF6 is disrupted, leading to the suppression of TAK1 activation by TRAF6. This suppression of TAK1 activity hindered the phosphorylation of IKK and MAPK. By stabilizing IκBα through dephosphorylation via IKK inhibition and preventing polyubiquitination, NF-κB activation is reduced. This cascade of events ultimately leads to a reduction in the production of proinflammatory enzymes and cytokines, effectively mitigating the inflammatory response in ALI. In A549 cells, MTX reduces the LPS-induced K48-linked polyubiquitination of IκBα and K63-linked polyubiquitination of TRAF6. This process can be reversed by the overexpression of NEDD8. Additionally, treatment with MG-132, a proteasome inhibitor, can restore the polyubiquitination of IκBα that was inhibited by MTX. These findings confirm the essential role of Cul1/5 neddylation in ALI and suggest that MTX could be a promising therapeutic agent for ALI.

Liu H ，Liu Y ，Lin X ，Fan J ，Huang Z ，Li A ... -  《-》

Human airway macrophages are metabolically reprogrammed by IFN-γ resulting in glycolysis-dependent functional plasticity.

Airway macrophages (AM) are the predominant immune cell in the lung and play a crucial role in preventing infection, making them a target for host directed therapy. Macrophage effector functions are associated with cellular metabolism. A knowledge gap remains in understanding metabolic reprogramming and functional plasticity of distinct human macrophage subpopulations, especially in lung resident AM. We examined tissue-resident AM and monocyte-derived macrophages (MDM; as a model of blood derived macrophages) in their resting state and after priming with IFN-γ or IL-4 to model the Th1/Th2 axis in the lung. Human macrophages, regardless of origin, had a strong induction of glycolysis in response to IFN-γ or upon stimulation. IFN-γ significantly enhanced cellular energetics in both AM and MDM by upregulating both glycolysis and oxidative phosphorylation. Upon stimulation, AM do not decrease oxidative phosphorylation unlike MDM which shift to 'Warburg'-like metabolism. IFN-γ priming promoted cytokine secretion in AM. Blocking glycolysis with 2-deoxyglucose significantly reduced IFN-γ driven cytokine production in AM, indicating that IFN-γ induces functional plasticity in human AM, which is mechanistically mediated by glycolysis. Directly comparing responses between macrophages, AM were more responsive to IFN-γ priming and dependent on glycolysis for cytokine secretion than MDM. Interestingly, TNF production was under the control of glycolysis in AM and not in MDM. MDM exhibited glycolysis-dependent upregulation of HLA-DR and CD40, whereas IFN-γ upregulated HLA-DR and CD40 on AM independently of glycolysis. These data indicate that human AM are functionally plastic and respond to IFN-γ in a manner distinct from MDM. These data provide evidence that human AM are a tractable target for inhalable immunomodulatory therapies for respiratory diseases.

Cox DJ ，Connolly SA ，Ó Maoldomhnaigh C ，Brugman AAI ，Sandby Thomas O ，Duffin E ，Gogan KM ，Ó Gallchobhair O ，Murphy DM ，O'Rourke SA ，O'Connell F ，Nadarajan P ，Phelan JJ ，Gleeson LE ，Basdeo SA ，Keane J ... -  《eLife》

The double-stranded RNA bluetongue virus induces type I interferon in plasmacytoid dendritic cells via a MYD88-dependent TLR7/8-independent signaling pathway.

Ruscanu S ，Pascale F ，Bourge M ，Hemati B ，Elhmouzi-Younes J ，Urien C ，Bonneau M ，Takamatsu H ，Hope J ，Mertens P ，Meyer G ，Stewart M ，Roy P ，Meurs EF ，Dabo S ，Zientara S ，Breard E ，Sailleau C ，Chauveau E ，Vitour D ，Charley B ，Schwartz-Cornil I ... -  《-》

Regulation of Th1 T Cell Differentiation by Iron via Upregulation of T Cell Immunoglobulin and Mucin Containing Protein-3 (TIM-3).

Iron plays an important role in host-pathogen interactions, in being an essential element for both pathogen and host metabolism, but also by impacting immune cell differentiation and anti-microbial effector pathways. Iron has been implicated to affect the differentiation of T lymphocytes during inflammation, however, so far the underlying mechanism remained elusive. In order to study the role of iron in T cell differentiation we here investigated how dietary iron supplementation affects T cell function and outcome in a model of chronic infection with the intracellular bacterium Salmonella enterica serovar typhimurium (S. Typhimurium). Iron loading prior to infection fostered bacterial burden and, unexpectedly, reduced differentiation of CD4+ T helper cells type 1 (Th1) and expression of interferon-gamma (IFNγ), a key cytokine to control infections with intracellular pathogens. This effect could be traced back to iron-mediated induction of the negative immune checkpoint regulator T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), expressed on the surface of this T cell subset. In vitro experiments demonstrated that iron supplementation specifically upregulated mRNA and protein expression of TIM-3 in naïve Th cells in a dose-depdendent manner and hindered priming of those T cells towards Th1 differentiation. Importantly, administration of TIM-3 blocking antibodies to iron-loaded mice infected with S. Typhimurium virtually restored Th1 cell differentiation and significantly improved bacterial control. Our data uncover a novel mechanism by which iron modulates CD4+ cell differentiation and functionality and hence impacts infection control with intracellular pathogens. Specifically, iron inhibits the differentiation of naive CD4+ T cells to protective IFNγ producing Th1 lymphocytes via stimulation of TIM-3 expression. Finally, TIM-3 may serve as a novel drug target for the treatment of chronic infections with intracellular pathogens, specifically in iron loading diseases.

Pfeifhofer-Obermair C ，Tymoszuk P ，Nairz M ，Schroll A ，Klais G ，Demetz E ，Engl S ，Brigo N ，Weiss G ... -  《Frontiers in Immunology》