Human monocyte chemoattractant protein‐1 (MCP‐1) in mice has two orthologs, MCP‐1 and MCP‐5. MCP‐1, which is highly expressed in osteoclasts rather than in osteoclast precursor cells, is an important ...factor in osteoclast differentiation. However, the roles of MCP‐5 in osteoclasts are completely unknown. In this study, contrary to MCP‐1, MCP‐5 was downregulated during receptor activator of nuclear factor kappa B ligand (RANKL)‐induced osteoclast differentiation and was considered an inhibitory factor in osteoclast differentiation. The inhibitory role of MCP‐5 in osteoclast differentiation was closely related to the increase in Ccr5 expression and the inhibition of IκB degradation by RANKL. Transgenic mice expressing MCP‐5 controlled by Mx‐1 promoter exhibited an increased bone mass because of a decrease in osteoclasts. This result strongly supported that MCP‐5 negatively regulated osteoclast differentiation. MCP‐5 also prevented severe bone loss caused by RANKL.
Increasing evidences suggest a correlation between gut and type 1 diabetes (T1D).
The objective of this study is to evaluate the gut inflammatory profile and microbiota in patients with T1D compared ...with healthy control (CTRL) subjects and patients with celiac disease (CD) as gut inflammatory disease controls.
The inflammatory status and microbiome composition were evaluated in biopsies of the duodenal mucosa of patients with T1D (n = 19), in patients with CD (n = 19), and CTRL subjects (n = 16) recruited at San Raffaele Scientific Institute, in Milan, Italy, between 2009 and 2015.
Inflammation was evaluated by gene expression study and immunohistochemistry. Microbiome composition was analyzed by 16S ribosomal RNA gene sequencing.
An increased expression of CCL13, CCL19, CCL22, CCR2, COX2, IL4R, CD68, PTX3, TNFα, and VEGFA was observed in patients with T1D compared with CTRL subjects and patients with CD. Immunohistochemical analysis confirmed T1D-specific inflammatory status compared with healthy and CD control tissues, mainly characterized by the increase of the monocyte/macrophage lineage infiltration. The T1D duodenal mucosal microbiome results were different from the other groups, with an increase in Firmicutes and Firmicutes/Bacteroidetes ratio and a reduction in Proteobacteria and Bacteroidetes. The expression of genes specific for T1D inflammation was associated with the abundance of specific bacteria in the duodenum.
This study shows that duodenal mucosa in T1D presents disease-specific abnormalities in the inflammatory profile and microbiota. Understanding the mechanisms underlying these features is critical to disentangle the complex pathogenesis of T1D and to gain new perspectives for future therapies targeting the intestine.
Acute kidney injury (AKI) is associated with significant morbidity and its chronic inflammation contributes to subsequent chronic kidney disease (CKD) development. Yes-associated protein (YAP), the ...major transcriptional coactivator of the Hippo pathway, has been shown associated with chronic inflammation, but its role and mechanism in AKI-CKD transition remain unclear. Here we aimed to investigate the role of YAP in AKI-induced chronic inflammation. Renal ischemia/reperfusion (I/R) was used to induce a mouse model of AKI-CKD transition. We used verteporfin (VP), a pharmacological inhibitor of YAP, to treat post-IRI mice for a period, and evaluated the influence of YAP inhibition on long-term outcomes of AKI. In our results, severe IRI led to maladaptive tubular repair, macrophages infiltration, and progressive fibrosis. Following AKI, the Hippo pathway was found significantly altered with YAP persistent activation. Besides, tubular YAP activation was associated with the maladaptive repair, also correlated with interstitial macrophage infiltration. Monocyte chemoattractant protein 1 (MCP-1) was found notably upregulated with YAP activation. Of note, pharmacological inhibition of YAP in vivo attenuated renal inflammation, including macrophage infiltration and MCP-1 overexpression. Consistently, in vitro oxygen-glucose deprivation and reoxygenation (OGD/R) induced YAP activation and MCP-1 overproduction whereas these could be inhibited by VP. In addition, we modulated YAP activity by RNA interference, which further confirmed YAP activation enhances MCP-1 expression. Together, we concluded tubular YAP activation with maladaptive repair exacerbates renal inflammation probably via promoting MCP-1 production, which contributes to AKI-CKD transition.
Monocyte recruitment to sites of inflammation is regulated by members of the chemokine family of chemotactic cytokines. However, the mechanisms that govern the migration of monocytes from bone marrow ...to blood and from blood to inflamed tissues are not well understood. Here we report that CC chemokine receptor 2 (CCR2) is highly expressed on a subpopulation of blood monocytes whose numbers are markedly decreased in CCR2(-/-) mice. In bone marrow, however, CCR2(-/-) mice had an increased number of monocytes, suggesting that CCR2 is critical for monocyte egress. Intravenous infusion of ex vivo-labeled WT or CCR2(-/-) bone marrow into WT recipient mice demonstrated that CCR2 is necessary for efficient monocyte recruitment from the blood to inflamed tissue. Analysis of mice lacking monocyte chemoattractant protein-1 (MCP-1), MCP-3, MCP-5, or MCP-2 plus MCP-5 revealed that MCP-3 and MCP-1 are the CCR2 agonists most critical for the maintenance of normal blood monocyte counts. These findings provide evidence that CCR2 and MCP-3/MCP-1 are critical for monocyte mobilization and suggest new roles for monocyte chemoattractants in leukocyte homeostasis.
Accumulating evidence suggests that fibrosis is a multicellular process with contributions from alveolar epithelial cells (AECs), recruited monocytes/macrophages, and fibroblasts. We have previously ...shown that AEC injury is sufficient to induce fibrosis, but the precise mechanism remains unclear. Several cell types, including AECs, can produce CCL2 and CCL12, which can promote fibrosis through CCR2 activation. CCR2 signaling is critical for the initiation and progression of pulmonary fibrosis, in part through recruitment of profibrotic bone marrow-derived monocytes. Attempts at inhibiting CCL2 in patients with fibrosis demonstrated a marked upregulation of CCL2 production and no therapeutic response. To better understand the mechanisms involved in CCL2/CCR2 signaling, we generated mice with conditional deletion of CCL12, a murine homolog of human CCL2. Surprisingly, we found that mice with complete deletion of CCL12 had markedly increased concentrations of other CCR2 ligands and were not protected from fibrosis after bleomycin injury. In contrast, mice with lung epithelial cell-specific deletion of CCL12 were protected from bleomycin-induced fibrosis and had expression of CCL2 and CCL7 similar to that of control mice treated with bleomycin. Deletion of CCL12 within AECs led to decreased recruitment of exudate macrophages. Finally, injury to murine and human primary AECs resulted in increased production of CCL2 and CCL12, in part through activation of the mTOR pathway. In conclusion, these data suggest that targeting CCL2 may be a viable antifibrotic strategy once the pathways involved in the production and function of CCL2 and other CCR2 ligands are better defined.
The tumor premetastatic niche initiated by primary tumors is constructed by multiple molecular factors and cellular components and provides permissive condition that allows circulating tumor cells to ...successfully metastasize. Myeloid‐derived suppressor cells (MDSCs), a population of immature cells in pathological conditions, play a critical role in the formation of the premetastatic niche. However, few researches are focused on the function of monocytic MDSCs (mo‐MDSCs), a subtype of MDSCs, in the construction of the niche. Here, we show that the number of mo‐MDSCs is significantly increased in the premetastatic lungs of tumor‐bearing mice, thus promoting tumor cell arrest and metastasis. Before the arrival of tumor cells, the lung‐recruited mo‐MDSCs produced IL‐1β, thereby increasing E‐selectin expression and promoting tumor cell arrest on endothelial cells. Depletion of mo‐MDSCs in the premetastatic lungs decreased IL‐1β production, resulting in reduced E‐selectin expression. In addition, compared with alveolar macrophages and interstitial macrophages, mo‐MDSCs were the major source of IL‐1β expression in the premetastatic lungs. Cytokine array analyses and transwell experiments revealed that CCL12 recruits mo‐MDSCs to premetastatic lungs. CCL12 knockdown in tumor‐bearing mice significantly decreased mo‐MDSC infiltration into the premetastatic lungs, leading to reduced E‐selectin expression. Overall, the permissive conditions produced by the infiltrated mo‐MDSCs correlated with increased tumor cell arrest and metastasis. These results reveal a novel role of mo‐MDSCs in constructing the premetastatic niche. Thus, inhibition of mo‐MDSCs infiltration may change the premetastatic niche to normal condition and attenuate tumor metastasis.
What's new?
During premetastasis, the tissue microenvironment of distant metastatic target organs is altered to permit habitation for circulating tumor cells. Premetastatic niche formation is influenced by granulocytic myeloid‐derived suppressor cells (G‐MDSCs), but according to this study, the other major MDSC subtype, monocytic MDSCs (mo‐MDSCs), hitherto unknown factors in premetastatic niche construction, are also critical. In tumor‐bearing mice, mo‐MDSCs were greatly increased in premetastatic lung tissue, where they produced IL‐1β, thereby promoting E‐selectin expression and subsequent tumor cell adhesion to the vascular endothelium. Lung infiltration by mo‐MDSCs was significantly decreased via knockdown of chemokine (C‐C motif) ligand 12 (CCL12).
Gal‐8 is proposed as an immune‐stimulator molecule that promotes an inflammatory cellular profile during elicitation of the adaptive immune response.
Galectin‐8 (Gal‐8) is a mammalian ...β‐galactoside‐binding lectin, endowed with proinflammatory properties. Given its capacity to enhance antigen‐specific immune responses in vivo, we investigated whether Gal‐8 was also able to promote APC activation to sustain T cell activation after priming. Both endogenous dendritic cells (DCs) and bone marrow‐derived DCs (BMDCs) treated with exogenous Gal‐8 exhibited a mature phenotype characterized by increased MHC class II (MHCII), CD80, and CD86 surface expression. Moreover, Gal‐8‐treated BMDCs (Gal‐8–BMDCs) stimulated antigen‐specific T cells more efficiently than immature BMDCs (iBMDCs). Proinflammatory cytokines IL‐3, IL‐2, IL‐6, TNF, MCP‐1, and MCP‐5, as well as growth factor G‐CSF, were augmented in Gal‐8–BMDC conditioned media, with IL‐6 as the most prominent. Remarkably, BMDCs from Gal‐8‐deficient mice (Lgals8−/− BMDC) displayed reduced CD86 and IL‐6 expression and an impaired ability to promote antigen‐specific CD4 T cell activation. To test if Gal‐8‐induced activation correlates with the elicitation of an effective immune response, soluble Gal‐8 was coadministrated with antigen during immunization of BALB/cJ mice in the experimental foot‐and‐mouth disease virus (FMDV) model. When a single dose of Gal‐8 was added to the antigen formulation, an increased specific and neutralizing humoral response was developed, sufficient to enhance animal protection upon viral challenge. IL‐6 and IFN‐γ, as well as lymphoproliferative responses, were also incremented in Gal‐8/antigen‐immunized animals only at 48 h after immunization, suggesting that Gal‐8 induces the elicitation of an inflammatory response at an early stage. Taking together, these findings argue in favor of the use of Gal‐8 as an immune‐stimulator molecule to enhance the adaptive immune response.
CCL13/MCP-4, is a CC family chemokine that is chemoattractant for eosinophils, basophils, monocytes, macrophages, immature dendritic cells, and T cells, and its capable of inducing crucial ...immuno-modulatory responses through its effects on epithelial, muscular and endothelial cells. Similar to other CC chemokines, CCL13 binds to several chemokine receptors (CCR1, CCR2 and CCR3), allowing it to elicit different effects on its target cells. A number of studies have shown that CCL13 is involved in many chronic inflammatory diseases, in which it functions as a pivotal molecule involved in the selective recruitment of cell lineages to the inflamed tissues and their subsequent activation. Based on these studies, we suggest that blocking the actions of CCL13 can serve as a novel strategy for the generation of agents with anti-inflammatory activity. The main goal of this review is to present the current information about CCL13, its gene and protein structure and the roles of this chemokine during innate/adaptive immune responses in inflammatory diseases.
ABSTRACT
CC chemokine ligand 2 (CCL2), a ligand of CC chemokine receptor 2 (CCR2), is essential to mount an adequate inflammatory response to repair acute skeletal muscle injury. We studied the ...mechanisms by which CCL2 regulates muscle inflammation and regeneration. Mobilization of monocytes/macrophages (MOs/MPs) but not lymphocytes or neutrophils was impaired from bone marrow to blood and from blood to injured muscles in Ccl2–/– mice. This was accompanied by poor phagocytosis, reduced up‐regulation of insulin‐like growth factor‐1 (IGF‐1), and impaired muscle regeneration. Bone marrow transfer from wild‐type mice to irradiated Ccr2–/– but not Ccl2–/– mice restored muscle inflammation. Intravenously injected CCL2‐deficient bone marrow monocytes could not enter wild‐type injured muscles as well as wild‐type bone marrow monocytes. Intravenously injected wild‐type bone marrow monocytes could not enter CCL2‐deficient injured muscles as well as wild‐type injured muscles. CCL2 stimulated IGF‐1 expression by wild‐type but not CCR2‐deficient intramuscular macrophages. A single intramuscular injection of IGF‐1, but not PBS, markedly improved muscle regeneration in Ccl2–/– mice. We conclude that CCL2 is a major ligand of CCR2 to recruit MOs/MPs into injured muscles to conduct phagocytosis and produce IGF‐1 for injury repair. CCL2 needs to be expressed by bone marrow cells, circulating monocytes, and injured muscle tissue cells to recruit MOs/MPs into injured muscles. CCL2/CCR2 signaling also up‐regulates IGF‐1 expression by intramuscular macrophages to promote acute skeletal muscle injury repair.—Lu, H., Huang, D., Ransohoff, R. M., Zhou, L. Acute skeletal muscle injury: CCL2 expression by both monocytes and injured muscle is required for repair. FASEB J. 25, 3344–3355 (2011). www.fasebj.org
Plexiform neurofibroma, a benign peripheral nerve tumor, is associated with the biallelic loss of function of the NF1 tumor suppressor in Schwann cells. Here, we show that FLLL32, a small molecule ...inhibitor of JAK2/STAT3 signaling, reduces neurofibroma growth in mice with conditional, biallelic deletion of Nf1 in the Schwann cell lineage. FLLL32 treatment or Stat3 deletion in tumor cells reduced inflammatory cytokine expression and tumor macrophage numbers in neurofibroma. Although STAT3 inhibition downregulated the chemokines CCL2 and CCL12, which can signal through CCR2 to recruit macrophages to peripheral nerves, deletion of Ccr2 did not improve survival or reduce macrophage numbers in neurofibroma-bearing mice. Interestingly, Iba1+; F4/80+;CD11b+ macrophages accounted for ~20-40% of proliferating cells in untreated tumors. FLLL32 suppressed macrophage proliferation, implicating STAT3-dependent, local proliferation in neurofibroma macrophage accumulation, and decreased Schwann cell proliferation and increased Schwann cell death. The functions of STAT3 signaling in neurofibroma Schwann cells and macrophages, and its relevance as a therapeutic target in neurofibroma, merit further investigation.
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