ABSTRACT Interleukin-18 is an acute phase pro-inflammatory molecule crucial for mediating viral clearance by activating Th1 CD4 + , cytotoxic CD8 + T, and NK cells. Here, we show that mature IL-18 is generated in the thymus following numerous distinct forms of tissue damage, all of which cause caspase-1-mediated immunogenic cell death. We report that IL-18 stimulated cytotoxic NK cells limit endogenous thymic regeneration, a critical process that ensures restoration of immune competence after acute insults like stress, infection, chemotherapy, and radiation. NK cells suppressed thymus recovery by aberrantly targeting thymic epithelial cells (TECs), which act as the master regulators of organ function and regeneration. Together these studies reveal a novel pathway regulating tissue regeneration in the thymus and offer IL-18 as a potential therapeutic target to boost thymic function. Moreover, given the enthusiasm for IL-18 as a cancer immunotherapy for its capacity to elicit a type-1 immune response, these findings also offer insight into potential off-target effects.

Stress-induced hair loss is a prevalent health concern, with mechanisms that remain unclear, and effective treatment options are not yet available. In this study, we investigated whether stress-induced hair loss was related to an imbalanced immune microenvironment. Screening the skin-infiltrated immune cells in a stressed mouse model, we discovered a significant increase in macrophages upon stress induction. Clearance of macrophages rescues mice from stress-induced hair shedding and depletion of hair follicle stem cells (HFSCs) in the skin, demonstrating the role of macrophages in triggering hair loss in response to stress. Further flow cytometry analysis revealed a significant increase in M1 phenotype macrophages in mice under stressed conditions. In searching for humoral factors mediating stress-induced macrophage polarization, we found that the hormone Norepinephrine (NE) was elevated in the blood of stressed mice. In addition, in-vivo and in-vitro studies confirm that NE can induce macrophage polarization toward M1 through the β-adrenergic receptor, Adrb2. Transcriptome, enzyme-linked immunosorbent assay (ELISA), and western blot analyses reveal that the NLRP3/caspase-1 inflammasome signaling and its downstream effector interleukin 18 (IL-18) and interleukin 1 beta (IL-1β) were significantly upregulated in the NE-treated macrophages. However, inhibition of the NE receptor Adrb2 with ICI118551 reversed the upregulation of NLRP3/caspase-1, IL-18, and IL-1β. Indeed, IL-18 and IL-1β treatments lead to apoptosis of HFSCs. More importantly, blocking IL-18 and IL-1β signals reversed HFSCs depletion in skin organoid models and attenuated stress-induced hair shedding in mice. Taken together, this study demonstrates the role of the neural (stress)-endocrine (NE)-immune (M1 macrophages) axis in stress-induced hair shedding and suggestes that IL-18 or IL-1β may be promising therapeutic targets.
© 2024 Wiley Periodicals LLC.

Fibroblasts are a major cell type within breast microenvironment which play key roles in tissue remodeling during the processes of normal development, injury, and malignancy. During wound healing and tumorigenesis, fibroblasts facilitate production and degradation of the extracellular matrix and produce inflammatory mediators which act as immune regulators. Domain Discoidin Receptor 1 (DDR1) is a cell surface tyrosine kinase receptor expressed by epithelial and stromal cells which is activated by collagen. In the breast, DDR1 expression and activity has been implicated in the development of fibrosis as well as chemotherapy resistance. We set out to examine whether selective inhibition of DDR1 would modulate fibroblast immunomodulatory function to generate an immune-permissive breast microenvironment and reduce stromal desmoplasia. In vivo, DDR1 inhibition resulted in mammary fibroblast tissue remodeling, reduced collagen deposition, and changes in immunomodulatory cytokine expression. Furthermore, DDR1 inhibition was associated with increased CD45.2+ immune cell infiltration and reduced Ly6G+/Ly6C− neutrophil infiltration. Mechanistically, we developed an ex-vivo 3D collagen hydrogel model of desmoplasia to study the effects of DDR1 inhibition on the expression of immune modulating factors and fibroblast functions and features. We found that DDR1 regulates the expression and secretion of key immunomodulatory cytokines (IL-6, IL-8, and MCP-1). Collectively these findings suggest that breast fibroblast-specific DDR1 mediates collagen deposition and immunomodulatory function within the mammary gland and warrants further investigation as a potential target for fibroblast-modulating therapy in benign and neoplastic breast disorders.

Despite remarkable clinical efficacy of immune checkpoint blockade (ICB) in cancer treatment, ICB benefits for triple-negative breast cancer (TNBC) remain limited. Through pooled in vivo CRISPR knockout (KO) screens in syngeneic TNBC mouse models, we found that deletion of the E3 ubiquitin ligase Cop1 in cancer cells decreases secretion of macrophage-associated chemokines, reduces tumor macrophage infiltration, enhances anti-tumor immunity, and strengthens ICB response. Transcriptomics, epigenomics, and proteomics analyses revealed that Cop1 functions through proteasomal degradation of the C/ebpδ protein. The Cop1 substrate Trib2 functions as a scaffold linking Cop1 and C/ebpδ, which leads to polyubiquitination of C/ebpδ. In addition, deletion of the E3 ubiquitin ligase Cop1 in cancer cells stabilizes C/ebpδ to suppress expression of macrophage chemoattractant genes. Our integrated approach implicates Cop1 as a target for improving cancer immunotherapy efficacy in TNBC by regulating chemokine secretion and macrophage infiltration in the tumor microenvironment.
Copyright © 2021 Elsevier Inc. All rights reserved.

Severe thrombocytopenia is a significant challenge in patients undergoing myelosuppressive chemotherapy for malignancies. Understanding the biology of platelet-producing megakaryocytes development in the bone marrow microenvironment may facilitate the development of novel therapies to stimulate platelet production and prevent thrombocytopenia. We report here that osteoblasts supported megakaryopoiesis by secreting interleukin-9 (IL-9), which stimulated IL-9 receptor (IL-9R)/Stat3 signaling in promoting megakaryopoiesis. IL-9 production in osteoblasts was negatively regulated by the mechanistic target of rapamycin complex 1 (mTORC1) signaling in a NF-κB-dependent manner. Constitutive activation of mTORC1 inhibited IL-9 production in osteoblasts and suppressed megakaryocytic cells expansion, whereas mTORC1 inactivation increased IL-9 production and enhanced megakaryocyte and platelet numbers in mice. In mouse models, we showed that IL-9 administration stimulated megakaryopoiesis, whereas neutralizing endogenous IL-9 or IL-9R depletion inhibited the process. Importantly, we found that low doses of IL-9 efficiently prevented chemotherapy-induced thrombocytopenia (CIT) and accelerated platelet recovery after CIT. These data indicate that IL-9 is an essential regulator of megakaryopoiesis and a promising therapeutic agent for treatment of thrombocytopenia such as CIT.
© 2017 by The American Society of Hematology.