Tumor-stroma interactions contribute to tumorigenesis. Tumor cells can educate the stroma at primary and distant sites to facilitate the recruitment of heterogeneous populations of immature myeloid ...cells, known as myeloid-derived suppressor cells (MDSCs). MDSCs suppress T cell responses and promote tumor proliferation. One outstanding question is how the local and distant stroma modulate MDSCs during tumor progression. Down-regulation of β-catenin is critical for MDSC accumulation and immune suppressive functions in mice and humans. Here, we demonstrate that stroma-derived Dickkopf-1 (Dkk1) targets β-catenin in MDSCs, thus exerting immune suppressive effects during tumor progression. Mice bearing extraskeletal tumors show significantly elevated levels of Dkk1 in bone microenvironment relative to tumor site. Strikingly, Dkk1 neutralization decreases tumor growth and MDSC numbers by rescuing β-catenin in these cells and restores T cell recruitment at the tumor site. Recombinant Dkk1 suppresses β-catenin target genes in MDSCs from mice and humans and anti-Dkk1 loses its antitumor effects in mice lacking β-catenin in myeloid cells or after depletion of MDSCs, demonstrating that Dkk1 directly targets MDSCs. Furthermore, we find a correlation between CD15(+) myeloid cells and Dkk1 in pancreatic cancer patients. We establish a novel immunomodulatory role for Dkk1 in regulating tumor-induced immune suppression via targeting β-catenin in MDSCs.
The nuclear receptor (NR) superfamily of transcription factors regulates various key aspects of physiological processes; however, their role(s) in immune cells’ function are just beginning to ...unravel. Although few NRs have been shown to be critical for dendritic cell (DC) function, a lack of knowledge about their complete representation in DCs has limited the ability to harness their full potential. Here, we performed a comprehensive NR expression profiling and identified the key members of NR superfamily being expressed in immature, immunogenic, and tolerogenic DCs. Comparative analysis revealed discrete changes in the expression of various NRs among the studied DC subtypes, indicating a likely role in the modulation of DC functionality. Next, we characterized Nr4a2, a member of orphan NR family, and found that it suppresses the activation of bone marrow derived dendritic cells triggered by LPS. Overexpression and knockdown of Nr4a2 demonstrated that Nr4a2 orchestrates the expression of immunoregulatory genes, hence inducing a tolerogenic phenotype in bone marrow derived dendritic cells. Furthermore, we also found that Nr4a2 provides protection from EAE by promoting an increase in Treg cells, while limiting effector T cells. Our findings suggest a previously unidentified role for Nr4a2 as a regulator of DC tolerogenicity and demonstrate its potential as therapeutic target in DC‐associated pathophysiologies.
This study identifies 39 nuclear receptors being expressed in bone marrow derived dendritic cells. Of these, Nr4a2 limits the immunogenicity while endowing DCs with tolerogenic potential (I). In vivo administration of such bone marrow derived dendritic cells, which have ectopically expressing Nr4a2, attenuates EAE (II).
Abstract Neutrophils are increasingly implicated in chronic inflammation and metabolic disorders. Here, we show that visceral adipose tissue (VAT) from individuals with obesity contains more ...neutrophils than in those without obesity and is associated with a distinct bacterial community. Exploring the mechanism, we gavaged microbiome-depleted mice with stool from patients with and without obesity during high-fat or normal diet administration. Only mice receiving high-fat diet and stool from subjects with obesity show enrichment of VAT neutrophils, suggesting donor microbiome and recipient diet determine VAT neutrophilia. A rise in pro-inflammatory CD4+ Th1 cells and a drop in immunoregulatory T cells in VAT only follows if there is a transient spike in neutrophils. Human VAT neutrophils exhibit a distinct gene expression pattern that is found in different human tissues, including tumors. VAT neutrophils and bacteria may be a novel therapeutic target for treating inflammatory-driven complications of obesity, including insulin resistance and colon cancer.
Introduction: Since 1980s, endovascular therapy has evolved as an important therapeutic strategy for Coarctation of the Aorta (CoA). Aim: This study sought to present a comprehensive contemporary ...data on the efficacy and safety of endovascular therapy in all age groups with both native and recurrent CoA in patients presenting to a tertiary care centre in Southern India. Materials and Methods: This single centre retrospective study included 91 consecutive patients who underwent Balloon Angioplasty (BA) or stenting for CoA between November 2002 and October 2017. Clinical, angiographic and procedural data was collected and outcomes including procedural success, complications, incidence of re-stenosis and hypertension at follow-up were evaluated. The effect of pre-specified variables on the procedural result was also evaluated using chi-square or two sample t-test, as appropriate. Results: Of the 91 patients, 63 were males; median age was 20 years {interquartile range (IQR):11-29}. The median followup duration was 17 months (IQR -7.5 to 36 months). Eighty four (92%) cases were with native coarctation. Fifty five (60%) had discrete coarctation and 36 (40%) had associated tubular hypoplasia of isthmus. Seventy two (79%) patients underwent stent implantation and 19 (21%) underwent BA. Immediate procedural success was achieved in 68 (94%) patients in the stent implantation group and 13 (68%) patients in BA group. Sixty percent of the failures were from BA group. Twelve (18%) patients had re-obstruction on follow-up. Seven (11%) patients underwent re-intervention. Conclusion: Endovascular therapy is a relatively safe and effective treatment modality in CoA when done carefully at experienced centres and in appropriately selected patients.
Stem bromelain (SBM) is a therapeutic protein that has been studied for alkaline denaturation in the intestines, the principal site of its absorption. In this study, we investigated fluorinated ...alcohol 2,2,2-trifluoroethanol (TFE)-induced conformational changes in the specific/pre-molten globule (SMG) state of SBM observed at pH 10 by spectroscopic methods. Far-UV circular dichroism (CD) spectra showed that the protein retained its native-like secondary structure at TFE concentrations of up to 30% with a pronounced minimum at 222nm, characteristic of a helix. However, addition of slightly higher TFE concentrations (≥40%) resulted in an ∼2.5-fold induction of this helical feature and a time-dependent increase in non-amyloidic turbidity as evidenced by turbidometric, Congo red-binding, and Thioflavin T (ThT)-binding studies. Near-UV CD spectra suggested a gradual but significant loss of tertiary structure at 10–30% TFE. Tryptophan studies showed blue-shifted fluorescence, although the number of accessible tryptophans remained the same up to 30% TFE. The SMG showed enhanced binding of the fluorescent probe 1-anilino-8-naphthalene sulfonic acid (ANS) up to 30% TFE, beyond which binding plateaued. Thermal and guanidine hydrochloride (GdnHCl) transition studies in the near-UV range indicated a single cooperative transition for the SMG state in the presence of 30% TFE, similar to that observed for native SBM at pH 7.0 (although with different Tms), unlike the SMG state. TFE (30%) appeared to induce native-like stability to the original SMG. These observations suggest a transformation of the SMG to a characteristic molten globule (MG) conformation at 30% TFE, possibly due to TFE-induced rearrangement of hydrophobic interactions at the protein's isoelectric point.
Dysregulation of monocyte and macrophage responses are often observed in children with systemic juvenile idiopathic arthritis (sJIA) and cytokine storm syndrome (CSS), a potentially fatal ...complication of chronic rheumatic diseases. Both conditions are associated with activation of TLR signaling in monocyte and macrophage lineage cells, leading to overwhelming inflammatory responses. Despite the importance of TLR engagement in activating proinflammatory macrophages, relatively little is known about activation of intrinsic negative regulatory pathways to attenuate excessive inflammatory responses. In this study, we demonstrate that loss of diacylglycerol (DAG) kinase (Dgk) ζ, an enzyme which converts DAG into phosphatidic acid, limits inflammatory cytokine production in an arthritic mouse model dependent on TLR2 signaling and in a CSS mouse model dependent on TLR9 signaling. In vitro,
deficiency results in reduced production of TNF-α, IL-6, and IL-1β and in limited M1 macrophage polarization. Mechanistically,
deficiency decreases STAT1 and STAT3 phosphorylation. Moreover, Dgkζ levels are increased in macrophages derived from mice with CSS or exposed to plasma from sJIA patients with active disease. Our data suggest that
induction in arthritic conditions perpetuates systemic inflammatory responses mediated by macrophages and highlight a potential role of
-DAG/phosphatidic acid axis as a modulator of inflammatory cytokine production in sJIA and CSS.
The orphan nuclear receptor Nr4a2 is known to modulate both inflammatory and metabolic processes, but the mechanism by which it regulates innate inflammatory homeostasis has not been adequately ...addressed. This study shows that exposure to ligands for Toll-like receptors (TLRs) robustly induces Nr4a2 and that this induction is tightly regulated by the PI3K-Akt signaling axis. Interestingly, exogenous expression of Nr4a2 in macrophages leads to their alternative phenotype with induction of genes that are prototypical M2 markers. Moreover, Nr4a2 transcriptionally activates arginase 1 expression by directly binding to its promoter. Adoptive transfer experiments revealed that increased survival of animals in endotoxin-induced sepsis is Nr4a2-dependent. Thus our data identify a previously unknown role for Nr4a2 in the regulation of macrophage polarization.
An understanding of the role of Nr4a2 in inflammation is needed.
Nr4a2 is a transcription factor that induces expression of M2 characteristic genes, and adoptive transfer of macrophages overexpressing Nr4a2 gives protection against septic mortality.
Our data impart a new role for Nr4a2 in skewing macrophage plasticity to M2 type.
Therapeutic intervention of Nr4a2 may provide a cure for inflammatory diseases.
Phospholipases Cγ (PLCγ) 1 and 2 are a class of highly homologous enzymes modulating a variety of cellular pathways through production of inositol 1,4,5-trisphosphate and diacylglycerol (DAG). Our ...previous studies demonstrated the importance of PLCγ2 in osteoclast (OC) differentiation by modulating inositol 1,4,5-trisphosphate-mediated calcium oscillations and the up-regulation of the transcription factor NFATc1. Surprisingly, despite being expressed throughout osteoclastogenesis, PLCγ1 did not compensate for PLCγ2 deficiency. Because both isoforms are activated during osteoclastogenesis, it is plausible that PLCγ1 modulates OC development independently of PLCγ2. Here, we utilized PLCγ1-specific shRNAs to delete PLCγ1 in OC precursors derived from wild type (WT) mice. Differently from PLCγ2, we found that PLCγ1 shRNA significantly suppresses OC differentiation by limiting colony-stimulating factor 1 (CSF-1)-dependent proliferation and β-catenin/cyclinD1 levels. Confirming the specificity toward CSF-1 signaling, PLCγ1 is recruited to the CSF-1 receptor following exposure to the cytokine. To understand how PLCγ1 controls cell proliferation, we turned to its downstream effector, DAG. By utilizing cells lacking the DAG kinase ζ, which have increased DAG levels, we demonstrate that DAG modulates CSF-1-dependent proliferation and β-catenin/cyclinD1 levels in OC precursors. Most importantly, the proliferation and osteoclastogenesis defects observed in the absence of PLCγ1 are normalized in PLCγ1/DAG kinase ζ double null cells. Taken together, our study shows that PLCγ1 controls OC numbers via a CSF-1-dependent DAG/β-catenin/cyclinD1 pathway.
Abstract
Cytokine storm syndromes (CSS) are life-threatening conditions characterized by excessive activation of T cells, accumulation of well-differentiated macrophages in various organs and ...exuberant release of inflammatory cytokines. CSS are associated with a wide variety of infectious and noninfectious diseases, often occurring in patients with familial hemophagocytic lymphohistiocytosis and systemic juvenile idiopathic arthritis (sJIA). Although increased number of macrophages is observed in CSS, their role in disease initiation has never been investigated. Here we report that depletion of macrophages at disease onset decreases lethality and limits CSS in two clinically relevant animal models. Mechanistic studies reveal that phospholipase C gamma 2 (Plcʏ2) is critical for macrophage responses during CSS. To dissect how Plcʏ2 induces macrophage activation during CSS, we evaluated two Plcʏ2 downstream pathways, namely calcium and diacylglycerol (DAG). Calcium and DAG levels are tightly controlled by expression of Tmem178, a Plcʏ2-dependent protein and negative regulator of calcium fluxes, and Dgkζ, an enzyme converting DAG into phosphatidic acid, respectively. Intriguingly, by using Tmem178−/− or Dgkζ−/− mouse models, we discovered that calcium and DAG exert opposite effects, with increased calcium augmenting macrophage activation and CSS severity while accumulation of DAG limiting these excessive inflammatory responses. Importantly, macrophages exposed to plasma from sJIA patients that are at risk of developing CSS show skewing toward increased calcium and reduced DAG, via modulation of Tmem178 and Dgkζ expression. In conclusion our data indicate a potential role for macrophage-based therapies for CSS.