M1 Macrophages Activate Notch Signalling in Epithelial Cells: Relevance in Crohn's Disease

A Narrative Review: Immunometabolic Interactions of Host-Gut Microbiota and Botanical Active Ingredients in Gastrointestinal Cancers

The gastrointestinal tract is where the majority of gut microbiota settles; therefore, the composition of the gut microbiota and the changes in metabolites, as well as their modulatory effects on the immune system, have a very important impact on the development of gastrointestinal diseases. The purpose of this article was to review the role of the gut microbiota in the host environment and immunometabolic system and to summarize the beneficial effects of botanical active ingredients on gastrointestinal cancer, so as to provide prospective insights for the prevention and treatment of gastrointestinal diseases. A literature search was performed on the PubMed database with the keywords "gastrointestinal cancer", "gut microbiota", "immunometabolism", "SCFAs", "bile acids", "polyamines", "tryptophan", "bacteriocins", "immune cells", "energy metabolism", "polyphenols", "polysaccharides", "alkaloids", and "triterpenes". The changes in the composition of the gut microbiota influenced gastrointestinal disorders, whereas their metabolites, such as SCFAs, bacteriocins, and botanical metabolites, could impede gastrointestinal cancers and polyamine-, tryptophan-, and bile acid-induced carcinogenic mechanisms. GPRCs, HDACs, FXRs, and AHRs were important receptor signals for the gut microbial metabolites in influencing the development of gastrointestinal cancer. Botanical active ingredients exerted positive effects on gastrointestinal cancer by influencing the composition of gut microbes and modulating immune metabolism. Gastrointestinal cancer could be ameliorated by altering the gut microbial environment, administering botanical active ingredients for treatment, and stimulating or blocking the immune metabolism signaling molecules. Despite extensive and growing research on the microbiota, it appeared to represent more of an indicator of the gut health status associated with adequate fiber intake than an autonomous causative factor in the prevention of gastrointestinal diseases. This study detailed the pathogenesis of gastrointestinal cancers and the botanical active ingredients used for their treatment in the hope of providing inspiration for research into simpler, safer, and more effective treatment pathways or therapeutic agents in the field.

Identification of LPCAT1 as a key biomarker for Crohn's disease based on bioinformatics and machine learnings and experimental verification

Epithelial-mesenchymal transition (EMT) plays a crucial role in regulating inflammatory responses and fibrosis formation. This study aims to explore the molecular mechanisms of EMT-related genes in Crohn's disease (CD) through bioinformatics methods and identify potential key biomarkers. In our research, we identified differentially expressed genes (DEGs) related to EMT based on the GSE52746 dataset and the gene set in the GeneCards database. Key genes were identified through Lasso-cox and Random Forest and validated using the external dataset GSE10616. Immune infiltration analysis showed that Lysophosphatidylcholine acyltransferase 1 (LPCAT1) was positively correlated with Neutrophils and Macrophages M1. The Gene Set Enrichment Analysis (GSEA) results for LPCAT1 showed associations with celladhesionmolecules and ECM receptor interaction. Additionally, a lncRNA-miRNA-mRNA ceRNA network was constructed. Finally, we validated that knocking down LPCAT1 could inhibit the release of inflammatory factors, EMT, and the elevation of fibrosis indices as well as the activation of NF-κB signaling pathway in LPS-induced HT-29 cells. LPCAT1 plays an important role in the occurrence and development of CD and may become a new biomarker.

M1 and M2 Macrophages Differentially Regulate Colonic Crypt Renewal

BACKGROUND

The colonic epithelium is the most rapidly renewing tissue in the body and is organized into a single cell layer of invaginations called crypts. Crypt renewal occurs through Lgr5 + gut stem cells situated at the crypt base, which divide, produce daughter cells that proliferate, migrate, differentiate into all the cells required for normal gut function, and are finally shed into the crypt lumen. In health, this rapid renewal helps maintain barrier function next to the hostile gut microbial luminal environment. Inflammation results in an influx of immune cells including inflammatory M1 macrophages into the gut mucosa next to the crypt epithelium, but the direct effect of macrophages on crypt regeneration and renewal are poorly understood.

METHODS

Using an in vitro macrophage-crypt coculture model, we show that homeostatic M2 macrophages and inflammatory M1 macrophages confer different effects on the crypt epithelium.

RESULTS

Both M1 and M2 increase crypt cell proliferation, with M2 macrophages requiring physical contact with the crypt epithelium, whereas M1 macrophages exert their effect through a secreted factor. Only M1 macrophages reduce goblet and Tuft cell numbers and increase Lgr5 + crypt stem cell numbers, all dependent on physical contact with the crypt epithelium. Further studies showed that M1 macrophages increase the Wnt signaling pathways cyclin D1 and LEF1 through physical contact rather than a secreted factor.

CONCLUSIONS

These findings highlight the importance of understanding distinct cellular interactions and direct dialogue between cells and increase our understanding of the contribution of different immune cell subtypes on crypt cell biology during inflammation.

Palmitic acid in type 2 diabetes mellitus promotes atherosclerotic plaque vulnerability via macrophage Dll4 signaling

Patients with Type 2 Diabetes Mellitus are increasingly susceptible to atherosclerotic plaque vulnerability, leading to severe cardiovascular events. In this study, we demonstrate that elevated serum levels of palmitic acid, a type of saturated fatty acid, are significantly linked to this enhanced vulnerability in patients with Type 2 Diabetes Mellitus. Through a combination of human cohort studies and animal models, our research identifies a key mechanistic pathway: palmitic acid induces macrophage Delta-like ligand 4 signaling, which in turn triggers senescence in vascular smooth muscle cells. This process is critical for plaque instability due to reduced collagen synthesis and deposition. Importantly, our findings reveal that macrophage-specific knockout of Delta-like ligand 4 in atherosclerotic mice leads to reduced plaque burden and improved stability, highlighting the potential of targeting this pathway. These insights offer a promising direction for developing therapeutic strategies to mitigate cardiovascular risks in patients with Type 2 Diabetes Mellitus.

CTRP6 promotes the macrophage inflammatory response, and its deficiency attenuates LPS-induced inflammation

Macrophages play critical roles in inflammation and tissue homeostasis, and their functions are regulated by various autocrine, paracrine, and endocrine factors. We have previously shown that CTRP6, a secreted protein of the C1q family, targets both adipocytes and macrophages to promote obesity-linked inflammation. However, the gene programs and signaling pathways directly regulated by CTRP6 in macrophages remain unknown. Here, we combine transcriptomic and phosphoproteomic analyses to show that CTRP6 activates inflammatory gene programs and signaling pathways in mouse bone marrow-derived macrophages (BMDMs). Treatment of BMDMs with CTRP6 upregulated proinflammatory, and suppressed the antiinflammatory, gene expression. We also showed that CTRP6 activates p44/42-MAPK, p38-MAPK, and NF-κB signaling pathways to promote inflammatory cytokine secretion from BMDMs, and that pharmacologic inhibition of these signaling pathways markedly attenuated the effects of CTRP6. Pretreatment of BMDMs with CTRP6 also sensitized and potentiated the BMDMs response to lipopolysaccharide (LPS)-induced inflammatory signaling and cytokine secretion. Consistent with the metabolic phenotype of proinflammatory macrophages, CTRP6 treatment induced a shift toward aerobic glycolysis and lactate production, reduced oxidative metabolism, and elevated mitochondrial reactive oxygen species production in BMDMs. Importantly, in accordance with our in vitro findings, BMDMs from CTRP6-deficient mice were less inflammatory at baseline and showed a marked suppression of LPS-induced inflammatory gene expression and cytokine secretion. Finally, loss of CTRP6 in mice also dampened LPS-induced inflammation and hypothermia. Collectively, our findings suggest that CTRP6 regulates and primes the macrophage response to inflammatory stimuli and thus may have a role in modulating tissue inflammatory tone in different physiological and disease contexts.

Delta- like ligand 4- expressing macrophages and human diseases: Insights into pathophysiology and therapeutic opportunities

Macrophages are key players in the immune response and have been implicated in various human diseases, including atherosclerosis, cancer, and chronic inflammatory disorders. While numerous studies have delved into the nuances of macrophage behavior in these conditions, there remains a gap in understanding the specific role of Delta-like ligand 4 (Dll4)-expressing macrophages and their overarching implications across these diseases. Among the plethora of factors expressed by macrophages, Dll4 has emerged as a molecule of particular interest. Recent studies have highlighted its unique role in modulating macrophage functions and its potential implications in various diseases. This review seeks to consolidate existing knowledge, address this gap, and present a comprehensive overview of Dll4-expressing macrophages in the context of these disorders and highlight their potential as therapeutic targets. We examined the involvement of Dll4-expressing macrophages in multiple human diseases such as atherosclerosis, cancer and chronic inflammatory diseases, emphasizing their influence on disease progression. We also discussed the challenges, limitations, and emerging research areas in targeting Dll4-expressing macrophages and provide an outlook on potential therapeutic strategies for the treatment of these diseases. By addressing the previously existing research gap, we've provided a roadmap that brings together fragmented insights, paving the way for more holistic research and potentially more effective therapeutic strategies centered on Dll4-expressing macrophages.

Overexpression of sirtuin 1 attenuates calcium oxalate-induced kidney injury by promoting macrophage polarization

Sirtuin 1 (SIRT1) protein is involved in macrophage differentiation, while NOTCH signaling affects inflammation and macrophage polarization. Inflammation and macrophage infiltration are typical processes that accompany kidney stone formation. However, the role and mechanism of SIRT1 in renal tubular epithelial cell injury caused by calcium oxalate (CaOx) deposition and the relationship between SIRT1 and the NOTCH signaling pathway in this urological disorder are unclear. This study investigated whether SIRT1 promotes macrophage polarization to inhibit CaOx crystal deposition and reduce renal tubular epithelial cell injury. Public single-cell sequencing data, RT-qPCR, immunostaining approaches, and Western blotting showed decreased SIRT1 expression in macrophages treated with CaOx or exposed to kidney stones. Macrophages overexpressing SIRT1 differentiated towards the anti-inflammatory M2 phenotype, significantly inhibiting apoptosis and alleviating injury in the kidneys of mice with hyperoxaluria. Conversely, decreased SIRT1 expression in CaOx-treated macrophages triggered Notch signaling pathway activation, promoting macrophage polarization towards the pro-inflammatory M1 phenotype. Our results suggest that SIRT1 promotes macrophage polarization towards the M2 phenotype by repressing the NOTCH signaling pathway, which reduces CaOx crystal deposition, apoptosis, and damage in the kidney. Therefore, we propose SIRT1 as a potential target for preventing disease progression in patients with kidney stones.

Inflammatory macrophages prevent colonic goblet and enteroendocrine cell differentiation through Notch signaling

Inflammatory macrophages in the intestine are a key pathogenic factor driving inflammatory bowel disease (IBD). Here, we report the role of inflammatory macrophage-mediated notch signaling on secretory lineage differentiation in the intestinal epithelium. Utilizing IL-10-deficient (Il10-/-) mice, a model of spontaneous colitis, we found an increase in Notch activity in the colonic epithelium as well as an increase in intestinal macrophages expressing Notch ligands, which are increased in macrophages upon inflammatory stimuli. Furthermore, a co-culture system of inflammatory macrophages and intestinal stem and proliferative cells during differentiation reduced goblet and enteroendocrine cells. This was recapitulated when utilizing a Notch agonist on human colonic organoids (colonoids). In summary, our findings indicate that inflammatory macrophages upregulate notch ligands that activate notch signaling in ISC via cell-cell interactions, which in turn inhibits secretory lineage differentiation in the gastrointestinal (GI) tract.

Eriocalyxin B ameliorated Crohn's disease-like colitis by restricting M1 macrophage polarization through JAK2/STAT1 signalling

BACKGROUND AND AIMS

M1 polarization of macrophages in the intestine is an important maintenance factor of the inflammatory response in Crohn's disease (CD). Eriocalyxin B (EriB) is a natural medicine that antagonizes inflammation. Our study aimed to determine the effects of EriB on CD-like colitis in mice, as well as the possible mechanism.

METHODS

2,4,6-trinitrobenzene sulfonic acid (TNBS) mice and Il-10^-/- mice were used as CD animal models, and the therapeutic effect of EriB on CD-like colitis in mice was addressed by the disease activity index (DAI) score, weight change, histological analysis and flow cytometry assay. To assess the direct role of EriB in regulating macrophage polarization, bone marrow-derived macrophages (BMDMs) were induced to M1 or M2 polarization separately. Molecular docking simulations and blocking experiments were performed to explore the potential mechanisms by which EriB regulates the macrophage polarization.

RESULTS

EriB treatment reduced body weight loss, DAI score and histological score, demonstrating the improvement of colitis symptoms in mice. In vivo and in vitro experiments both showed that EriB decreased the M1 polarization of macrophages, and suppressed the release of proinflammatory cytokines (IL-1β, TNF-α and IL-6) in mouse colons and BMDMs. The activation of Janus kinase 2/signal transducer and activator of transcription 1 (JAK2/STAT1) signals could be inhibited by EriB, which may be related to the regulation of EriB on M1 polarization.

CONCLUSIONS

EriB inhibits the M1 polarization of macrophages by attenuating the JAK2/STAT1 pathway, which partially explains the potential mechanism by which EriB ameliorates colitis in mice, and provides a new regimen for the clinical treatment of CD.

Sotetsuflavone ameliorates Crohn's disease-like colitis by inhibiting M1 macrophage-induced intestinal barrier damage via JNK and MAPK signalling

OBJECTIVES

Intestinal inflammation and intestinal barrier dysfunction are two important pathological changes in Crohn's disease (CD). Sotetsuflavone (SF) is a natural monomeric herbal compound with anti-inflammatory and cytoprotective effects that is mostly nontoxic. The effect of SF on CD-like spontaneous colitis was investigated in this study.

METHODS

Il-10^-/- mice were used as a CD model and were administered different doses of SF. Lipopolysaccharide (LPS) plus IFN-γ-induced macrophages (RAW264.7) and a coculture system (RAW264.7 and organoids) were used in vitro. The protective effects of SF against CD-like colitis and macrophage differentiation and the mechanisms were evaluated.

RESULTS

SF treatment markedly improved spontaneous colitis in the CD model, as shown by the following evidence: reductions in the DAI, macroscopic scores (3.63 ± 1.30), colonic tissue inflammatory scores (2 ± 0.76) and proinflammatory factor levels and the attenuation of colon shortening (8 ± 0.93 cm) and weight loss (1.75 ± 1.83 g). Decreased intestinal permeability and intestinal bacterial translocation rates provided evidence of the protective effect of SF on intestinal barrier function. We also found that SF suppressed M1 macrophage-induced inflammatory responses. In the coculture system of mouse colonic organoids and RAW264.7 cells, SF significantly ameliorated M1 macrophage-induced intestinal epithelial damage. In addition, SF inhibited JNK and MAPK (p38) signalling in both Il-10^-/- mice and LPS plus IFN-γ-induced macrophages (RAW264.7).

CONCLUSIONS

The protective effects of SF against CD-like colitis may be achieved partially by inhibiting M1 macrophage-induced intestinal barrier damage via JNK and p38 signalling. SF may have therapeutic potential for treating CD, especially considering its safety.

Emerging role of hypoxia-inducible factor-1α in inflammatory autoimmune diseases: A comprehensive review

Hypoxia-inducible factor-1α (HIF-1α) is a primary metabolic sensor, and is expressed in different immune cells, such as macrophage, dendritic cell, neutrophil, T cell, and non-immune cells, for instance, synovial fibroblast, and islet β cell. HIF-1α signaling regulates cellular metabolism, triggering the release of inflammatory cytokines and inflammatory cells proliferation. It is known that microenvironment hypoxia, vascular proliferation, and impaired immunological balance are present in autoimmune diseases. To date, HIF-1α is recognized to be overexpressed in several inflammatory autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and function of HIF-1α is dysregulated in these diseases. In this review, we narrate the signaling pathway of HIF-1α and the possible immunopathological roles of HIF-1α in autoimmune diseases. The collected information will provide a theoretical basis for the familiarization and development of new clinical trials and treatment based on HIF-1α and inflammatory autoimmune disorders in the future.

Vascular Endothelial Growth Factor Receptor 1 Facilitates the Effect of Macrophages on Human Umbilical Vein Endothelial Cells Migration by Regulating the M1 Polarization

Purpose: To explore the impact of VEGF pathway on the M1 polarization and function of macrophages. Methods: VEGFR-knockdown macrophages were established by transfected with a shRNA. M1 macrophages were stimulated by LPS and IFN-γ, which was identified using the flow cytometry. Subsequently, M1 macrophages were treated with VEGF A, VEGF B, and PIGF, respectively. The expression level of iNOS, TNF-α, and IL-6 was detected utilizing RT-PCR. CD86 and iNOS level were checked by Western blot. The migration of HUVEC was evaluated by wound healing assay. Results: The percentage of F4/80+CD86+ macrophages was significantly elevated by the transfection of shRNA, accompanied by a significantly upregulated expression of CD86 and iNOS. After the stimulation of LPS and IFN-γ, CD86 and iNOS was dramatically upregulated in both the Lv-NC group and Lv-shVEGFR1 group. IL-6 and iNOS levels were greatly declined in macrophages co-treated with LPS, IFN-γ, and PIGF. No marked alterations on the healing degree were noticed in HUVEC stimulated by the supernatant of LPS/IFN-γ treated macrophages, which was dramatically declined by the knockdown of VEGFR1. Conclusion: VEGFR1 facilitated the effect of macrophages on HUVEC migration by regulating the M1 polarization.

Is the Macrophage Phenotype Determinant for Fibrosis Development?

Fibrosis is a pathophysiological process of wound repair that leads to the deposit of connective tissue in the extracellular matrix. This complication is mainly associated with different pathologies affecting several organs such as lung, liver, heart, kidney, and intestine. In this fibrotic process, macrophages play an important role since they can modulate fibrosis due to their high plasticity, being able to adopt different phenotypes depending on the microenvironment in which they are found. In this review, we will try to discuss whether the macrophage phenotype exerts a pivotal role in the fibrosis development in the most important fibrotic scenarios.

Bromodomain-containing protein 9 is a prognostic biomarker associated with immune infiltrates and promotes tumor malignancy through activating notch signaling pathway in negative HIF-2α clear cell renal cell carcinoma

HIF-2α selective inhibitor showed successful efficacy in sensitive clear cell renal cell carcinoma (ccRCC) presenting higher levels of HIF-2α compared to resistant tumors with low level of HIF-2α (negative HIF-2α ccRCC). Currently, negative HIF-2α ccRCC lacks truly effective therapeutic agents to improve the outcomes. Bromodomain-containing protein 9 (BRD9) plays a critical role in human hepatocellular carcinoma, squamous cell lung cancer, acute myeloid leukemia, and so on. However, expression and biological role of BRD9 in negative HIF-2α ccRCC is poorly understood. Clinically, we demonstrated that expression of BRD9 in negative HIF-2α ccRCC tissues was higher than that in positive HIF-2α ccRCC. Moreover, high BRD9 expression was correlated with unfavorable clinicopathological features and predicted the poor overall survival of negative HIF-2α ccRCC patients. Functionally, BRD9 knockout resulted in reduced proliferation, migration and invasion of negative HIF-2α ccRCC cells (Caki-2). In addition, BRD9 was related to the TIIC infiltration level in negative HIF-2α ccRCC tissues. Mechanistically, Gene set enrichment analysis (GSEA) showed that BRD9 was closely related to Notch signaling pathway. BRD9 knockout resulted in reduced mRNA level of Hes1 and Notch1 in negative HIF-2α ccRCC in vitro. The overexpression of NICD (Notch intracellular domain) enhanced malignant behaviors of Caki-2 cells with BRD9 knockout. And Notch inhibition led to attenuation of cell growth and reduced migration and invasion in Caki-2 cells. Overall, our results identified that BRD9 promotes the proliferation, migration and invasion of negative HIF-2α ccRCC cells by targeting Notch signaling pathway and serve as a promising biomarker for negative HIF-2α ccRCC.

Notch Signaling Pathway Is Activated by Sulfate Reducing Bacteria

Sulfate Reducing Bacteria (SRB), usually rare residents of the gut, are often found in increased numbers (called a SRB bloom) in inflammatory conditions such as Inflammatory Bowel Disease (IBD), pouchitis, and periodontitis. However, the underlying mechanisms of this association remain largely unknown. Notch signaling, a conserved cell-cell communication pathway, is usually involved in tissue development and differentiation. Dysregulated Notch signaling is observed in inflammatory conditions such as IBD. Lipolysaccharide and pathogens also activate Notch pathway in macrophages. In this study, we tested whether Desulfovibrio, the most dominant SRB genus in the gut, may activate Notch signaling. RAW 264.7 macrophages were infected with Desulfovibrio vulgaris (DSV) and analyzed for the expression of Notch signaling pathway-related proteins. We found that DSV induced protein expression of Notch1 receptor, Notch intracellular domain (NICD) and p21, a downstream Notch target, in a dose-and time-dependent manner. DSV also induced the expression of pro-IL1β, a precursor of IL-1β, and SOCS3, a regulator of cytokine signaling. The gamma secretase inhibitor DAPT or Notch siRNA dampened DSV-induced Notch-related protein expression as well the expression of pro-IL1β and SOCS3. Induction of Notch-related proteins by DSV was not affected by TLR4 -IN -C34(C34), a TLR4 receptor antagonist. Additionally, cell-free supernatant of DSV-infected macrophages induced NICD expression in uninfected macrophages. DSV also activated Notch pathway in the human epithelial cell line HCT116 and in mouse small intestine. Thus, our study uncovers a novel mechanism by which SRB interact with host cells by activating Notch signaling pathway. Our study lays a framework for examining whether the Notch pathway induced by SRB contributes to inflammation in conditions associated with SRB bloom and whether it can be targeted as a therapeutic approach to treat these conditions.

Notch Signaling Ligand Jagged1 Enhances Macrophage-Mediated Response to Helicobacter pylori

Helicobacter pylori (H. pylori) is one of the gram-negative bacteria that mainly colonize the stomach mucosa and cause many gastrointestinal diseases, such as gastritis, peptic ulcer, and gastric cancer. Macrophages play a key role in eradicating H. pylori. Recent data have shown that Notch signaling could modulate the activation and bactericidal activities of macrophages. However, the role of Notch signaling in macrophages against H. pylori remains unclear. In the present study, in the co-culture model of macrophages with H. pylori, the inhibition of Notch signaling using γ-secretase decreased the expression of inducible nitric oxide synthase (iNOS) and its product, nitric oxide (NO), and downregulated the secretion of pro-inflammatory cytokine and attenuated phagocytosis and bactericidal activities of macrophages to H. pylori. Furthermore, we identified that Jagged1, one of Notch signaling ligands, was both upregulated in mRNA and protein level in activated macrophages induced by H. pylori. Clinical specimens showed that the number of Jagged1⁺ macrophages in the stomach mucosa from H. pylori-infected patients was significantly higher than that in healthy control. The overexpression of Jagged1 promoted bactericidal activities of macrophages against H. pylori and siRNA-Jagged1 presented the opposite effect. Besides, the addition of exogenous rJagged1 facilitated the pro-inflammatory mediators of macrophages against H. pylori, but the treatment of anti-Jagged1 neutralizing antibody attenuated it. Taken together, these results suggest that Jagged1 is a promoting molecule for macrophages against H. pylori, which will provide insight for exploring Jagged1 as a novel therapeutic target for the control of H. pylori infection.

A mutation in NOTCH2 gene first associated with Hajdu-Cheney syndrome in a Greek family: diversity in phenotype and response to treatment

INTRODUCTION

Hajdu-Cheney Syndrome (HCS) is a rare genetic autosomal dominant disorder, characterized by distinctive facial features, acroosteolysis, and severe osteoporosis. Very rarely HCS is associated with polycystic kidney disease, splenomegaly or Crohn's disease (CD). It is caused by gain-of-function mutations in NOTCH2 gene. Treatment with bisphosphonates or denosumab is reported to result in BMD increase.

OBJECTIVE

We report a mutation in exon 34 of NOTCH2 gene, in a Greek pedigree, with diverse phenotypes among members.

DESCRIPTION OF THE PEDIGREE

The 48-year-old mother had a history of a T12 vertebral fracture, postpartum at the age of 21 and two subsequent uneventful full-term pregnancies and never received treatment. Her 29-year-old son, presented with severe osteoporosis and multiple morphological vertebral fractures. Her 21-year-old daughter had recurrent vertebral fractures starting at 10 years of age. At 17 years, she developed severe CD, resistant to treatment with biologic agents, and functional hypothalamic hypogonadism. One male pedigree died of cystic fibrosis. All subjects bore the typical facial characteristics and acroosteolysis, while none had splenomegaly or renal defects. Zoledronate infusion led to BMD increase.

GENETIC TESTING

Mutation in c.6758 G > A (NM_008163.1), leading to a Trp2253Ter replacement. This mutation has been reported as possibly pathogenic (SCV000620308), but not in association with HCS.

CONCLUSIONS

Bone involvement can present with diverse severity in the same pedigree, ranging from low BMD to multiple fragility fractures. Antiresorptive therapy improves BMD, but its anti-fracture efficacy remains to be shown. The presence of CD might indicate the significant role of NOTCH2 signaling in different tissues.

Pathogenic effects of inhibition of mTORC1/STAT3 axis facilitates Staphylococcus aureus-induced pyroptosis in human macrophages

BACKGROUND

Pyroptosis is a recently identified pathway of caspase-mediated cell death in response to microbes, lipopolysaccharide, or chemotherapy in certain types of cells. However, the mechanism of how pyroptosis is regulated is not well-established.

METHODS

Herein, the intracellular bacteria were detected by staining and laser confocal microscopy and TEM. Live/dead cell imaging assay was used to examine macrophage death. Western blot and immunohistochemical staining were used to examine the protein changes. IFA was used to identify typical budding vesicles of pyroptosis and the STAT3 nuclear localization. SEM was used to observe the morphological characteristics of pyroptosis. ELISA was used to detect the level of inflammatory cytokines. Pyroptosis was filmed in macrophages by LSCM.

RESULTS

S. aureus was internalized by human macrophages. Intracellular S. aureus induced macrophage death. S. aureus invasion increased the expression of NLRP3, Caspase1 (Casp-1 p20) and the accumulation of GSDMD-NT, GSDMD-NT pore structures, and the release of IL-1β and IL-18 in macrophages. Macrophages pyroptosis induced by S. aureus can be abrogated by blockage of S. aureus phagocytosis. The pyroptosic effect by S. aureus infection was promoted by either rapamycin or Stattic, a specific inhibitor for mTORC1 or STAT3. Inhibition of mTORC1 or STAT3 induced pyroptosis. mTORC1 regulated the pyroptosic gene expression through governing the nuclear localization of STAT3. mTORC1/STAT3 axis may play a regulatory role in pyroptosis within macrophages.

CONCLUSIONS

S. aureus infection induces human macrophage pyroptosis, inhibition of mTORC1/STAT3 axis facilitates S. aureus-induced pyroptosis. mTORC1 and STAT3 are associated with pyroptosis. Our findings demonstrate a regulatory function of the mTORC1/STAT3 axis in macrophage pyroptosis, constituting a novel mechanism by which pyroptosis is regulated in macrophages. Video Abstract Macrophages were infected with S. aureus for 3 h (MOI 25:1), and pyroptosis was filmed in macrophages by laser confocal microscopy. A representative field was recorded. Arrow indicates lysing dead cell.

Caveolin-1 in oncogenic metabolic symbiosis

Metabolic phenotypes of cancer cells are heterogeneous and flexible as a tumor mass is a hurriedly evolving system capable of constant adaptation to oxygen and nutrient availability. The exact type of cancer metabolism arises from the combined effects of factors intrinsic to the cancer cells and factors proposed by the tumor microenvironment. As a result, a condition termed oncogenic metabolic symbiosis in which components of the tumor microenvironment (TME) promote tumor growth often occurs. Understanding how oncogenic metabolic symbiosis emerges and evolves is crucial for perceiving tumorigenesis. The process by which tumor cells reprogram their TME involves many mechanisms, including changes in intercellular communication, alterations in metabolic phenotypes of TME cells, and rearrangement of the extracellular matrix. It is possible that one molecule with a pleiotropic effect such as Caveolin-1 may affect many of these pathways. Here, we discuss the significance of Caveolin-1 in establishing metabolic symbiosis in TME.

Gegen Qinlian decoction maintains colonic mucosal homeostasis in acute/chronic ulcerative colitis via bidirectionally modulating dysregulated Notch signaling

BACKGROUND

Gegen Qinlian decoction (GQ) is a well-known traditional Chinese medicine that has been clinically proven to be effective in treating ulcerative colitis (UC). However, its therapeutic mechanism has not been fully elucidated. Notch signaling plays an essential role in the regeneration of the intestinal epithelium.

PURPOSE

This study was designed to ascertain the mechanism by which GQ participates in the recovery of the colonic mucosa by regulating Notch signaling in acute and chronic UC models.

METHODS

Acute and chronic UC mice (C57BL/6) were established with 3 and 2% dextran sulfate sodium (DSS), respectively, and treated with oral administration of GQ. The expression of the Notch target gene Hes1 and the Notch-related proteins RBP-J, MAML and Math1 was analyzed by western blotting. PTEN mRNA levels were detected by qRT-PCR. Mucin production that is characteristic of goblet cells was determined by Alcian blue/periodic acid-Schiff staining and verified by examining MUC2 mRNA levels by qRT-PCR. Cell proliferation was assayed by immunohistochemistry analysis of Ki67. HT-29 and FHC cells and Toll-like receptor 4 knockout (TLR4^-/-) acute UC mice were also used in this study.

RESULTS

GQ restored the injured colonic mucosa in both acute and chronic UC models. We found that Notch signaling was hyperactive in acute UC mice and hypoactive in chronic UC mice. GQ downregulated Hes1, RBP-J and MAML proteins and augmented goblet cells in the acute UC models, whereas GQ upregulated Hes1, RBP-J and MAML proteins in chronic UC mice, reducing goblet cell differentiation and promoting crypt base columnar (CBC) stem cell proliferation. Hes1 mRNA was suppressed in TLR4^-/- UC mice, and GQ treatment reversed this effect. In vitro, GQ reduced Hes1 protein in Notch-activated HT29 and FHC cells but increased Hes1 protein in Notch-inhibited cells.

CONCLUSIONS

GQ restored the colonic epithelium by maintaining mucosal homeostasis via bidirectional regulation of Notch signaling in acute/chronic UC models.

WNT2b Activates Epithelial-mesenchymal Transition Through FZD4: Relevance in Penetrating Crohn´s Disease

BACKGROUND AND AIMS

Epithelial-mesenchymal transition [EMT] has been related to fibrosis and fistula formation, common complications associated with Crohn´s disease [CD]. The WNT signalling pathway mediates EMT, and specific WNT/FZD interactions have been related to the activation of this process in several diseases. We aim to analyse the relevance of EMT and WNT ligands and receptors in the penetrating behaviour of CD.

METHODS

Intestinal surgical resections were obtained from control and CD patients with a stenotic or penetrating behaviour. Fibrosis was determined by the histological analysis of collagen deposition and EMT by confocal microscopy. The expression of WNT ligands, inhibitors, and FZD receptors was analysed by RT-PCR, WB, IH, and IF studies. The effects of WNT2b and the role of FZD4 in EMT were analysed in HT29 epithelial cells.

RESULTS

Fibrosis and expression of EMT markers were detected in samples from CD patients irrespective of the clinical behaviour. However, an increased colocalisation of E-CADHERIN and VIMENTIN, an increased number of cells expressing WNT2b, and a higher expression of FZD4 and WNT2b/FZD4 interaction, were detected in intestinal tissue from the penetrating compared with the stenotic CD behaviour. WNT2b induced EMT in HT29 cells through FZD4 activation.

CONCLUSIONS

An increased EMT, associated with increased WNT2b/FZD4 interaction, was detected in intestinal tissue from CD patients with a penetrating behaviour. WNT2b, through FZD4 activation, induces EMT in vitro which points to a novel pharmacological target to prevent intestinal penetrating complications of CD.

The Role of Notch Signaling in Macrophages during Inflammation and Infection: Implication in Rheumatoid Arthritis?

Notch signaling coordinates numerous cellular processes and has been implicated in many pathological conditions, including rheumatoid arthritis (RA). Although the role of Notch signaling in development, maturation, differentiation, and activation of lymphocytes has been comprehensively reported, less is known about its role in myeloid cells. Certainly, limited data are available about the role of Notch signaling in macrophages during inflammation and infection. In this review, we discuss the recent advances pertaining to the role of Notch signaling in differentiation, activation, and metabolism of macrophages during inflammation and infection. We also highlight the reciprocal interplay between Notch signaling and other signaling pathways in macrophages under different inflammatory and infectious conditions including pathogenesis of RA. Finally, we discuss approaches that could consider Notch signaling as a potential therapeutic target against infection- and inflammation-driven diseases.

Macrophages as an Emerging Source of Wnt Ligands: Relevance in Mucosal Integrity

The Wnt signaling pathway is a conserved pathway involved in important cellular processes such as the control of embryonic development, cellular polarity, cellular migration, and cell proliferation. In addition to playing a central role during embryogenesis, this pathway is also an essential part of adult homeostasis. Indeed, it controls the proliferation of epithelial cells in different organs such as intestine, lung, and kidney, and guarantees the maintenance of the mucosa in physiological conditions. The origin of this molecular pathway is the binding between Wnt ligands (belonging to a family of 19 different homologous secreted glycoproteins) and their specific membrane receptors, from the Frizzled receptor family. This specific interaction triggers the activation of the signaling cascade, which in turn activates or suppresses the expression of different genes in order to change the behavior of the cell. On the other hand, alterations of this pathway have been described in pathological conditions such as inflammation, fibrosis, and cancer. In recent years, macrophages-among other cell types-have emerged as a potential source of Wnt ligands. Due to their high plasticity, macrophages, which are central to the innate immune response, are capable of adopting different phenotypes depending on their microenvironment. In the past, two different phenotypes were described: a proinflammatory phenotype-M1 macrophages-and an anti-inflammatory phenotype-M2 macrophages-and a selective expression of Wnt ligands has been associated with said phenotypes. However, nowadays it is assumed that macrophages in vivo move through a continual spectrum of functional phenotypes. In both physiological and pathological (inflammation, fibrosis and cancer) conditions, the accumulation and polarization of macrophages conditions the future of the tissue, facilitating various scenarios, such as resolution of inflammation, activation of fibrosis, and cancer development due to the modulation of the Wnt signaling pathway, in autocrine and paracrine manner. In this work, we provide an overview of studies that have explored the role of macrophages and how they act as a source of Wnt ligands and as mediators of mucosal integrity.

Targeting Notch-activated M1 macrophages attenuate lung tissue damage in a rat model of ventilator induced lung injury

Ventilator induced lung injury (VILI) may be involved in the activation of alveolar macrophages. The purpose of this study was to investigate the relationship between the Notch signaling pathway and macrophage polarization in VILI. The VILI model was established using rats. Hematoxylineosin staining was used to test the lung tissue morphology. Bicinchoninic acid assay and ELISA were performed to detect protein and tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10 levels in bronchoalveolar lavage fluids (BALF), respectively. The ratio of alveolar M1 and M2 macrophages was detected by flow cytometry. The mRNA and protein expression levels of Notch pathway-related proteins were determined using reverse transcription-quantitative PCR and western blotting. The present study found that high-frequency mechanical ventilation could cause pulmonary edema and increase the levels of protein, TNF-α and IL-6 in BALF while decreasing the level of IL-10 in BALF. High-frequency mechanical ventilation also induced polarization of alveolar macrophages to M1. The results also showed a significant increase in the levels of Notch pathway-related proteins including notch intracellular domain, Hes1, Hes5 and Hey1. Injection of N-[N-(3,5-difluorophenylacetyl)-1-alanyl] phenylglycine t-butyl ester could inhibit the Notch pathway and such an inhibition protected lung tissue and reduced lung inflammation caused by mechanical ventilation. After the Notch pathway was inhibited, the level of M1 polarization of macrophages caused by high-frequency mechanical ventilation was reduced. VILI caused pulmonary inflammation and macrophages to polarize to M1 and upregulated the expression levels of Notch pathway-related proteins. The inhibition of Notch pathway also reduced the proportion of M1 macrophages and inflammatory responses.

Ubiquitin D is Upregulated by Synergy of Notch Signalling and TNF-α in the Inflamed Intestinal Epithelia of IBD Patients

BACKGROUND AND AIMS

The intestinal epithelium of inflammatory bowel disease [IBD] patients is exposed to various pro-inflammatory cytokines, most notably tumour necrosis factor alpha [TNF-α]. We have previously shown that the Notch signalling pathway is also upregulated in such an epithelium, contributing to intestinal epithelial cell [IEC] proliferation and regeneration. We aimed to reproduce such environment in vitro and explore the gene regulation involved.

METHODS

Human IEC cell lines or patient-derived organoids were used to analyse Notch- and TNF-α-dependent gene expression. Immunohistochemistry was performed to analyse expression of ubiquitin D [UBD] in various patient-derived intestinal tissues.

RESULTS

In human IEC cell lines, we found that Notch signalling and TNF-α-induced NFκB signalling are reciprocally regulated to promote expression of a specific gene subset. Global gene expression analysis identified UBD to be one of the most highly upregulated genes, due to synergy of Notch and TNF-α. The synergistic expression of UBD was regulated at the transcriptional level, whereas the UBD protein had an extremely short half-life due to post-translational, proteasomal degradation. In uninflamed intestinal tissues from IBD patients, UBD expression was limited to IECs residing at the crypt bottom. In contrast, UBD-expressing IECs were seen throughout the crypt in inflamed tissues, indicating substantial induction by the local inflammatory environment. Analysis using patient-derived organoids consistently confirmed conserved Notch- and TNF-α-dependent expression of UBD. Notably, post-infliximab [IFX] downregulation of UBD reflected favourable outcome in IBD patients.

CONCLUSION

We propose that UBD is a novel inflammatory-phase protein expressed in IECs, with a highly rapid responsiveness to anti-TNF-α treatment.

Current clinical issue of skin lesions in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) is associated with a number of extraintestinal complications, including skin lesions. Most reports have shown that skin lesions are found in 10-15% of IBD cases, although this depends on the definition of skin lesions. The representative skin lesions in patients with IBD are erythema nodosum, pyoderma gangrenosum, Sweet's syndrome, and so on. These lesions are often associated with IBD progression, and intestinal lesions in particular require appropriate treatment. Recently, another clinical issue regarding skin lesions in patients with IBD, a so-called paradoxical reaction, during the treatment with anti-tumor necrosis factor (TNF)-α agents has emerged. These reactions are termed paradoxical reactions because the skin lesions sometimes resemble psoriasis, although the anti-TNF-α agents have been historically used to treat psoriasis. Paradoxical reactions are reportedly found in approximately 5-10% of patients using anti-TNF-α agents and are no longer rare. Now that the use of biologics is at its culmination, reports regarding paradoxical reactions are predicted to increase in number; thus, we must recognize skin lesions with IBD patients including this type of adverse events and manage them appropriately while consulting with dermatologists.

M1-Polarized Macrophages Promote Self-Renewing Phenotype of Hepatic Progenitor Cells with Jagged1-Notch Signalling Involved: Relevance in Primary Sclerosing Cholangitis

The immunologic interaction between parenchyma cells and encircling inflammatory cells is thought to be the most important mechanism of biliary damage and repair in primary sclerosing cholangitis (PSC). Monocytes/macrophages as master regulators of hepatic inflammation have been demonstrated to contribute to PSC pathogenesis. Macrophages coordinate with liver regeneration, and multiple phenotypes have been identified with diverse expressions of surface proteins and cytokine productions. We analyzed the expression of Notch ligand Jagged1 in polarized macrophages and investigated the relevance of Notch signalling activation in liver regeneration. M1 or M2 macrophages were generated from mouse bone marrow-derived macrophages (BMDMs) by classical or alternative activation, respectively. Then, the expression levels of Jagged1 (Jag1) of each phenotype were measured. The effects of polarized BMDMs on the expression of hepatic progenitor cell- (HPC-) specific markers and hairy and enhancer of split-1 (HES1) in HPCs in coculture were also analyzed. Monocyte-macrophage and Notch signalling-associated gene signatures were evaluated in the GEO database (access ID: GSE61260) by gene set enrichment analysis (GSEA). M1 macrophages were found associated with elevated Jag1 expression, which increased the fraction of HPC with self-renewing phenotypes (CD326⁺CD44⁺ or CD324⁺CD44⁺) and HES1 expression level in cocultured HPC. Blocking Jagged1 by siRNA or antibody in the coculture system attenuates HPC self-renewing phenotypes as well as HES1 expression in HPC. GSEA data show that macrophage activation and Notch signalling-associated gene signatures are enriched in PSC patients. These findings suggest that M1 macrophages promote an HPC self-renewing phenotype which is associated with Notch signalling activation within HPC. In the liver of PSC patients, the prevalence of activated macrophages, with M1 polarized accounting for the main part, is associated with increment of Notch signalling and enhancement of HPC self-renewal.

Adhesive Interactions between Mononuclear Phagocytes and Intestinal Epithelium Perturb Normal Epithelial Differentiation and Serve as a Therapeutic Target in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Disturbance of intestinal homeostasis is associated with the development of inflammatory bowel disease [IBD], and TGF-β signalling impairment in mononuclear phagocytes [MPs] causes murine colitis with goblet cell depletion. Here, we examined an organoid-MP co-culture system to study the role of MPs in intestinal epithelial differentiation and homeostasis.

METHODS

Intestinal organoids were co-cultured with lamina propria leukocytes and bone marrow-derived dendritic cells [BMDCs] from CD11c-cre Tgfbr2fl/fl mice. Organoid-MP adhesive interactions were evaluated by microscopy, RT-PCR, and flow cytometry. Murine colitis models (dextran sodium sulphate [DSS], CD11c-cre Tgfbr2fl/fl, T-cell-transfer) were used for histological and immunohistochemical analysis. Anti-E-cadherin antibody treatment or CD11c+-cell-specific CDH1 gene deletion were performed for E-cadherin neutralization or knockout. Colonic biopsies from patients with ulcerative colitis were analysed by flow cytometry.

RESULTS

Intestinal organoids co-cultured with CD11c+ lamina propria leukocytes or BMDCs from CD11c-cre Tgfbr2fl/fl mice showed morphological changes and goblet cell depletion with Notch signal activation, analogous to CD11c-cre Tgfbr2fl/fl colitis. E-cadherin was upregulated in CD11c+ MPs, especially CX3CR1+CCR2+ monocytes, of CD11c-cre Tgfbr2fl/fl mice. E-cadherin-mediated BMDC adhesion promoted Notch activation and cystic changes in organoids. Anti-E-cadherin antibody treatment attenuated colitis in CD11c-cre Tgfbr2fl/fl and T-cell-transferred mice. In addition, E-cadherin deletion in CD11c+ cells attenuated colitis in both CD11c-cre Tgfbr2fl/fl and DSS-treated mice. In patients with ulcerative colitis, E-cadherin expressed by intestinal CD11c+ leukocytes was enhanced compared with that in healthy controls.

CONCLUSIONS

E-cadherin-mediated MP-epithelium adhesion is associated with the development of colitis, and blocking these adhesions may have therapeutic potential for IBD.

A dietary flavone confers communicable protection against colitis through NLRP6 signaling independently of inflammasome activation

Flavones represent a class of polyphenols that are found in many plant-derived food sources. Herein, we provide evidence that the anti-inflammatory and antiproliferative effect of the flavone apigenin relies on the regulation of the gut microbiota by the NOD-like receptor family pyrin domain containing 6 (Nlrp6). When challenged by dextran sulfate sodium (DSS) in drinking water, mice were protected against colitis upon cohousing with apigenin-treated animals. In contrast, the protective effect was lost in the absence of Nlrp6. Sequencing of the 16S ribosomal RNA gene revealed a shift in the composition of the gut microbiota in apigenin-treated mice that was not observed in the absence of Nlrp6. Equally important, we find that the antiproliferative effect of apigenin was dominantly transmitted after cohousing, while being compromised in Nlrp6-deficient mice. In contrast, the symptoms of colitis were alleviated upon apigenin administration even in the absence of either caspase-1/11 or Asc. Collectively, these data indicate that apigenin modulated an inflammasome-independent mechanism by which Nlrp6 reprograms the gut microbiota for protecting mice against colitis. Our study highlights a modulation of the Nlrp6 signaling pathway by a prominent constituent of the human diet that may point toward improved ways to treat inflammatory bowel diseases.

CD16+ Macrophages Mediate Fibrosis in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Fibrosis is a common complication of Crohn's disease [CD], and is related to dysregulated tissular repair following inflammation, in which macrophages play a central role. We have previously observed that STAT6-/- mice present delayed mucosal recovery after 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis due to a deficiency in reparatory interleukin-4 [IL4]/STAT6-dependent M2 macrophages, which can be reverted by the exogenous transfer of this cell type. In the present study, we analyse the role of STAT6-dependent macrophages in intestinal fibrosis.

METHODS

Colitis was induced by weekly intra-rectal administration of TNBS [6 weeks] to STAT6-/- mice and wild-type [WT] animals. Colonic surgical resections were obtained from CD patients and from colon cancer patients.

RESULTS

Chronic colitis provoked a fibrogenic response in STAT6-/- mice, but not in WT animals. An accumulation of M2 macrophages, defined as CD206+ cells, was observed in WT mice, but not in STAT6-/- animals. Instead, the latter group showed an increase in CD16+ macrophages that correlated with the expression of fibrogenic markers. CD16+ macrophages were also increased in the damaged mucosa of Crohn's disease patients with stenotic or penetrating complications. Finally, administration of IL4-treated WT macrophages to STAT6-/- mice reduced TNBS-induced fibrosis.

CONCLUSIONS

Our study demonstrates that STAT6 deficiency dysregulates the macrophage response to inflammatory outbursts by increasing the presence of a population of CD16+ macrophages that seems to contribute to intestinal fibrosis.

A novel neuregulin - jagged1 paracrine loop in breast cancer transendothelial migration

Background

The interaction of breast cancer cells with other cells in the tumor microenvironment plays an important role in metastasis. Invasion and intravasation, two critical steps in the metastatic process, are influenced by these interactions. Macrophages are of particular interest when it comes to studying tumor cell invasiveness. Previous studies have shown that there is paracrine loop signaling between breast cancer cells and macrophages involving colony stimulating factor 1 (CSF-1) produced by tumor cells and epidermal growth factor (EGF) production by macrophages. In this paper, we identify a novel paracrine loop between tumor cells and macrophages involving neuregulin (NRG1) and notch signaling.

Methods

The aim of this study was to determine the role of NRG1, a ligand of the ErbB3 receptor, in macrophage stimulation of tumor cell transendothelial migration and intravasation. We used fluorescence-activated cell sorting (FACS) and western blot to determine ErbB3 and NRG1 expression, respectively. An in vitro transendothelial migration (iTEM) assay was used to examine the effects of short hairpin (sh)RNA targeting NRG1 in tumor cells and clustered regularly interspaced short palindromic repeats (CRISPR) knockout of jagged 1 (JAG1) in macrophages. Orthotopic xenograft injections in mice were used to confirm results in vivo.

Results

In our system, macrophages were the primary cells showing expression of ErbB3, and a blocking antibody against ErbB3 resulted in a significant decrease in macrophage-induced transendothelial migration of breast cancer cells. Stimulation of macrophages with NRG1 upregulated mRNA and protein expression of JAG1, a ligand of the Notch receptor, and JAG1 production by macrophages was important for transendothelial migration of tumor cells.

Conclusions

This study demonstrates that stimulation of macrophages by tumor cell NRG1 can enhance transendothelial migration and intravasation. We also demonstrate that this effect is due to induction of macrophage JAG1, an important ligand of the Notch signaling pathway.