Potential mechanisms of rheumatoid arthritis therapy: Focus on macrophage polarization

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that affects multiple organs and systems in the human body, often leading to disability. Its pathogenesis is complex, and the long-term use of traditional anti-rheumatic drugs frequently results in severe toxic side effects. Therefore, the search for a safer and more effective antirheumatic drug is extremely important for the treatment of RA. As important immune cells in the body, macrophages are polarized. Under pathological conditions, macrophages undergo proliferation and are recruited to diseased tissues upon stimulation. In the local microenvironment, they polarize into different types of macrophages in response to specific factors and perform unique functions and roles. Previous studies have shown that there is a link between macrophage polarization and RA, indicating that certain active ingredients can ameliorate RA symptoms through macrophage polarization. Notably, Traditional Chinese medicine (TCM) monomer component and compounds demonstrate a particular advantage in this process. Building upon this insight, we reviewed and analyzed recent studies to offer valuable and meaningful insights and directions for the development and application of anti-rheumatic drugs.

Adipose tissue-selective ablation of ADAM10 results in divergent metabolic phenotypes following long-term dietary manipulation

A Disintegrin And Metalloproteinase domain-containing protein 10 (ADAM10), is involved in several metabolic and inflammatory pathways. We speculated that ADAM10 plays a modulatory role in adipose tissue inflammation and metabolism. To this end, we studied adipose tissue-specific ADAM10 knock-out mice (aKO). While young, regular chow diet-fed aKO mice showed increased insulin sensitivity, following prolonged (33 weeks) high-fat diet (HFD) exposure, aKO mice developed obesity and insulin resistance. Compared to controls, aKO mice showed less inflammatory adipokine profile despite the significant increase in adiposity. In brown adipose tissue, aKO mice on HFD had changes in CD8+ T cell populations indicating a lesser inflammatory pattern. Following HFD, both aKO and control littermates demonstrated decreased adipose tissue pro-inflammatory macrophages, and increased anti-inflammatory accumulation, without differences between the genotypes. Collectively, our observations indicate that selective deletion of ADAM10 in adipocytes results in a mitigated inflammatory response, leading to increased insulin sensitivity in young mice fed with regular diet. This state of insulin sensitivity, following prolonged HFD, facilitates energy storage resulting in increased fat accumulation which ultimately leads to the development of a phenotype of obesity and insulin resistance. In conclusion, the data indicate that ADAM10 has a modulatory effect of inflammation and whole-body energy metabolism.

Notch signaling regulates pulmonary fibrosis

Pulmonary fibrosis is a progressive interstitial lung disease associated with aging. The pathogenesis of pulmonary fibrosis remains unclear, however, alveolar epithelial cell injury, myofibroblast activation, and extracellular matrix (ECM) accumulation are recognized as key contributors. Moreover, recent studies have implicated cellular senescence, endothelial-mesenchymal transition (EndMT), and epigenetic modifications in the pathogenesis of fibrotic diseases. Various signaling pathways regulate pulmonary fibrosis, including the TGF-β, Notch, Wnt, Hedgehog, and mTOR pathways. Among these, the TGF-β pathway is extensively studied, while the Notch pathway has emerged as a recent research focus. The Notch pathway influences the fibrotic process by modulating immune cell differentiation (e.g., macrophages, lymphocytes), inhibiting autophagy, and promoting interstitial transformation. Consequently, inhibiting Notch signaling represents a promising approach to mitigating pulmonary fibrosis. In this review, we discuss the role of Notch signaling pathway in pulmonary fibrosis, aiming to offer insights for future therapeutic investigations.

Photobiomodulation Increases M2-Type Polarization of Macrophages by Inhibiting Versican Production After Spinal Cord Injury

Spinal cord injury (SCI) is a catastrophic accidence with little effective treatment, and inflammation played an important role in that. Previous studies showed photobiomodulation (PBM) could effectively downregulate the process of inflammation with modification of macrophage polarization after SCI; however, the potential mechanism behind that is still unclear. In the presented study, we aimed to investigate the effect of PBM on the expression level of versican, a matrix molecular believed to be associated with inflammation, and tried to find the mechanism on how that could regulate the inflammation process. Using immunofluorescence technique and western blot, we found the expression level of versican is increased after injury and markedly downregulated by irradiation treatment. Using virus intrathecal injection, we found the knock-down of versican could produce the effect similar to that of PBM and might have an effect on inflammation and macrophage polarization after SCI. To further verify the deduction, we peptide the supernatant of astrocytes to induce M0, M1, and M2 macrophages. We found that the versican produced by astrocytes might have a role on the promotion of M2 macrophages to inflammatory polarization. Finally, we investigated the potential pathway in the regulation of M2 polarization with the induction of versican. This study tried to give an interpretation on the mechanism of inflammation inhibition for PBM in the perspective of matrix regulation. Our results might provide light on the inflammation regulation after SCI.

The Role of Pericytes in Lipopolysaccharide-Induced Murine Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a heterogeneous clinical syndrome that is most commonly triggered by infection-related inflammation. Lung pericytes can respond to infection and act as immune and proangiogenic cells; moreover, these cells can differentiate into myofibroblasts in nonresolving ARDS and contribute to the development of pulmonary fibrosis. Here, we aimed to characterize the role of lung cells, which present characteristics of pericytes, such as peri-endothelial location and expression of a panel of specific markers. A murine model of lipopolysaccharide (LPS)-induced resolving ARDS was used to study their role in ARDS. The development of ARDS was confirmed after LPS instillation, which was resolved 14 days after onset. Immunofluorescence and flow cytometry showed early expansion of neural-glial antigen 2+ β-type platelet-derived growth factor receptor+ pericytes in murine lungs with loss of CD31+ β-type platelet-derived growth factor receptor+ endothelial cells. These changes were accompanied by specific changes in lung structure and loss of vascular integrity. On day 14 after ARDS onset, the composition of pericytes and endothelial cells returned to baseline values. LPS-induced ARDS activated NOTCH signaling in lung pericytes, the inhibition of which during LPS stimulation reduced the expression of its downstream target genes, pericyte markers, and angiogenic factors. Together, these data indicate that lung pericytes in response to inflammatory injury activate NOTCH signaling that supports their maintenance and in turn can contribute to recovery of the microvascular endothelium.

Aflatoxin B1 exposure deteriorates immune abnormalities in a BTBR T+ Itpr3tf/J mouse model of autism by increasing inflammatory mediators' production in CD19-expressing cells

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficiencies in communication, repetitive and stereotyped behavioral patterns, and difficulties in reciprocal social engagement. The presence of immunological dysfunction in ASD has been well established. Aflatoxin B1 (AFB1) is a prevalent mycotoxin found in food and feed, causing immune toxicity and hepatotoxicity. AFB1 is significantly elevated in several regions around the globe. Existing research indicates that prolonged exposure to AFB1 results in neurological problems. The BTBR T+ Itpr3tf/J (BTBR) mice, which were used as an autism model, exhibit the primary behavioral traits that define ASD, such as repeated, stereotyped behaviors and impaired social interactions. The main objective of this work was to assess the toxic impact of AFB1 in BTBR mice. This work aimed to examine the effects of AFB1 on the expression of Notch-1, IL-6, MCP-1, iNOS, GM-CSF, and NF-κB p65 by CD19+ B cells in the spleen of the BTBR using flow cytometry. We also verified the impact of AFB1 exposure on the mRNA expression levels of Notch-1, IL-6, MCP-1, iNOS, GM-CSF, and NF-κB p65 in the brain of BTBR mice using real-time PCR. The findings of our study showed that the mice treated with AFB1 in the BTBR group exhibited a substantial increase in the presence of CD19+Notch-1+, CD19+IL-6+, CD19+MCP-1+, CD19+iNOS+, CD19+GM-CSF+, and CD19+NF-κB p65+ compared to the mice in the BTBR group that were treated with saline. Our findings also confirmed that administering AFB1 to BTBR mice leads to elevated mRNA expression levels of Notch-1, IL-6, MCP-1, iNOS, GM-CSF, and NF-κB p65 in the brain, in comparison to BTBR mice treated with saline. The data highlight that exposure to AFB1 worsens immunological abnormalities by increasing the expression of inflammatory mediators in BTBR mice.

The Role of Macrophages in Lung Fibrosis and the Signaling Pathway

Lung fibrosis is a dysregulated repair process caused by excessive deposition of extracellular matrix that can severely affect respiratory function. Macrophages are a group of immune cells that have multiple functions and can perform a variety of roles. Lung fibrosis develops with the involvement of pro-inflammatory and pro-fibrotic factors secreted by macrophages. The balance between M1 and M2 macrophages has been proposed to play a role in determining the trend and severity of lung fibrosis. New avenues and concepts for preventing and treating lung fibrosis have emerged in recent years through research on mitochondria, Gab proteins, and exosomes. The main topic of this essay is the impact that mitochondria, Gab proteins, and exosomes have on macrophage polarization. In addition, the potential of these factors as targets to enhance lung fibrosis is also explored. We have also collated the functions and mechanisms of signaling pathways associated with the regulation of macrophage polarization such as Notch, TGF-β/Smad, JAK-STAT and cGAS-STING. The goal of this article is to explain the potential benefits of focusing on macrophage polarization as a way to relieve lung fibrosis. We aspire to provide valuable insights that could lead to enhancements in the treatment of this condition.

Jagged2 targeting in lung cancer activates anti-tumor immunity via Notch-induced functional reprogramming of tumor-associated macrophages

Signaling through Notch receptors intrinsically regulates tumor cell development and growth. Here, we studied the role of the Notch ligand Jagged2 on immune evasion in non-small cell lung cancer (NSCLC). Higher expression of JAG2 in NSCLC negatively correlated with survival. In NSCLC pre-clinical models, deletion of Jag2, but not Jag1, in cancer cells attenuated tumor growth and activated protective anti-tumor T cell responses. Jag2-/- lung tumors exhibited higher frequencies of macrophages that expressed immunostimulatory mediators and triggered T cell-dependent anti-tumor immunity. Mechanistically, Jag2 ablation promoted Nr4a-mediated induction of Notch ligands DLL1/4 on cancer cells. DLL1/4-initiated Notch1/2 signaling in macrophages induced the expression of transcription factor IRF4 and macrophage immunostimulatory functionality. IRF4 expression was required for the anti-tumor effects of Jag2 deletion in lung tumors. Antibody targeting of Jagged2 inhibited tumor growth and activated IRF4-driven macrophage-mediated anti-tumor immunity. Thus, Jagged2 orchestrates immunosuppressive systems in NSCLC that can be overcome to incite macrophage-mediated anti-tumor immunity.

Notch ligands are biomarkers of anti-TNF response in RA patients

Notch and its ligands play a critical role in rheumatoid arthritis (RA) pathogenesis. Hence, studies were conducted to delineate the functional significance of the Notch pathway in RA synovial tissue (ST) cells and the influence of RA therapies on their expression. Morphological studies reveal that JAG1, DLL4, and Notch1 are highly enriched in RA ST lining and sublining CD68+CD14+ MΦs. JAG1 and DLL4 transcription is jointly upregulated in RA MΦs reprogrammed by TLR4/5 ligation and TNF, whereas Syntenin-1 exposure expands JAG1, DLL4, and Notch1 expression levels in these cells. Single-cell RNA-seq data exhibit that JAG1 and Notch3 are overexpressed on all fibroblast-like synoviocyte (FLS) subpopulations, in parallel, JAG2, DLL1, and Notch1 expression levels are modest on RA FLS and are predominately potentiated by TLR4 ligation. Intriguingly, JAG1, DLL1/4, and Notch1/3 are presented on RA endothelial cells, and their expression is mutually reconfigured by TLR4/5 ligation in the endothelium. Synovial JAG1/JAG2/DLL1 or Notch1/3 transcriptomes were unchanged in patients who received disease-modifying anti-rheumatic drugs (DMARDs) or IL-6R Ab therapy regardless of disease activity score. Uniquely, RA MΦs and endothelial cells rewired by IL-6 displayed DLL4 transcriptional upregulation, and IL-6R antibody treatment disrupted RA ST DLL4 transcription in good responders compared to non-responders or moderate responders. Nevertheless, the JAG1/JAG2/DLL1/DLL4 transcriptome was diminished in anti-TNF good responders with myeloid pathotype and was unaltered in the fibroid pathotype except for DLL4. Taken together, our findings suggest that RA myeloid Notch ligands can serve as markers for anti-TNF responsiveness and trans-activate Notch receptors expressed on RA FLS and/or endothelial cells.

Notch signaling in adipose tissue macrophages prevents diet-induced inflammation and metabolic dysregulation

The importance of macrophages in adipose tissue (AT) homeostasis and inflammation is well established. However, the potential cues that regulate their function remain incompletely understood. To bridge this important gap, we sought to characterize novel pathways involved using a mouse model of diet-induced obesity. By performing transcriptomics analysis of AT macrophages (ATMs), we found that late-stage ATMs from high-fat diet mice presented with perturbed Notch signaling accompanied by robust proinflammatory and metabolic changes. To explore the hypothesis that the deregulated Notch pathway contributes to the development of AT inflammation and diet-induced obesity, we employed a genetic approach to abrogate myeloid Notch1 and Notch2 receptors. Our results revealed that the combined loss of Notch1 and Notch2 worsened obesity-related metabolic dysregulation. Body and AT weight gain was higher, blood glucose levels increased and metabolic parameters were substantially worsened in deficient mice fed high-fat diet. Moreover, serum insulin and leptin were elevated as were triglycerides. Molecular analysis of ATMs showed that deletion of Notch receptors escalated inflammation through the induction of an M1-like pro-inflammatory phenotype. Our findings thus support a protective role of myeloid Notch signaling in adipose tissue inflammation and metabolic dysregulation.

RND3 Potentiates Proinflammatory Activation through NOTCH Signaling in Activated Macrophages

Macrophage activation is a complex process with multiple control elements that ensures an adequate response to the aggressor pathogens and, on the other hand, avoids an excess of inflammatory activity that could cause tissue damage. In this study, we have identified RND3, a small GTP-binding protein, as a new element in the complex signaling process that leads to macrophage activation. We show that RND3 expression is transiently induced in macrophages activated through Toll receptors and potentiated by IFN-γ. We also demonstrate that RND3 increases NOTCH signaling in macrophages by favoring NOTCH1 expression and its nuclear activity; however, Rnd3 expression seems to be inhibited by NOTCH signaling, setting up a negative regulatory feedback loop. Moreover, increased RND3 protein levels seem to potentiate NFκB and STAT1 transcriptional activity resulting in increased expression of proinflammatory genes, such as Tnf-α, Irf-1, or Cxcl-10. Altogether, our results indicate that RND3 seems to be a new regulatory element which could control the activation of macrophages, able to fine tune the inflammatory response through NOTCH.

Paralemmin-3 augments lipopolysaccharide-induced acute lung injury with M1 macrophage polarization via the notch signaling pathway

BACKGROUND

Acute lung injury (ALI) involves severe lung damage and respiratory failure, which are accompanied by alveolar macrophage (AM) activation. The aim of this article is to verify the influence of paralemmin-3 (PALM3) on alveolar macrophage (AM) polarization in ALI and the underlying mechanism of action.

METHODS

An ALI rat model was established by successive lipopolysaccharide (LPS) inhalations. The influence of PALM3 on the survival rate, severity of lung injury, and macrophage polarization was analyzed. Furthermore, we explored the underlying mechanism of PALM3 in regulating macrophage polarization.

RESULTS

PALM3 overexpression increased mortality of ALI rats, augmented lung pathological damage, and promoted AM polarization toward M1 cells. Conversely, PALM3 knockdown had the opposite effects. Mechanistically, PALM3 might promote M1 polarization by acting as an adaptor to facilitate transduction of Notch signaling.

CONCLUSION

PALM3 aggravates lung injury and induces macrophage polarization toward M1 cells by activating the Notch signaling pathway in LPS-induced ALI, which may shed light on ALI/ARDS treatments.

The role of the Notch signalling pathway in the pathogenesis of ulcerative colitis: from the perspective of intestinal mucosal barrier

Ulcerative colitis is a common digestive disorder worldwide, with increasing incidence in recent years. It is an urgent problem to be solved, as it seriously affects and threatens the health and life of the global population. Studies have shown that dysfunction of the intestinal mucosal barrier is a critical pathogenic factor and molecular basis of ulcerative colitis, and some scholars have described it as a "barrier organ disease." While the Notch signalling pathway affects a series of cellular processes, including proliferation, differentiation, development, migration, and apoptosis. Therefore, it can regulate intestinal stem cells, CD4+ T cells, innate lymphoid cells, macrophages, and intestinal microbiota and intervene in the chemical, physical, immune, and biological mucosal barriers in cases of ulcerative colitis. The Notch signalling pathway associated with the pathogenesis of ulcerative colitis has distinct characteristics, with good regulatory effects on the mucosal barrier. However, research on ulcerative colitis has mainly focused on immune regulation, anti-inflammatory activity, and antioxidant stress; therefore, the study of the Notch signalling pathway suggests the possibility of understanding the pathogenesis of ulcerative colitis from another perspective. In this article we explore the role and mechanism of the Notch signalling pathway in the pathogenesis of ulcerative colitis from the perspective of the intestinal mucosal barrier to provide new targets and theoretical support for further research on the pathogenesis and clinical treatment of ulcerative colitis.

Exploring the Multiple Roles of Notch1 in Biological Development: An Analysis and Study Based on Phylogenetics and Transcriptomics

At present, there is a research gap concerning the specific functions and mechanisms of the Notch gene family and its signaling pathway in jawless vertebrates. In this study, we identified a Notch1 homologue (Lr. Notch1) in the Lethenteron reissneri database. Through bioinformatics analysis, we identified Lr. Notch1 as the likely common ancestor gene of the Notch gene family in higher vertebrates, indicating a high degree of conservation in the Notch gene family and its signaling pathways. To validate the biological function of Lr. Notch1, we conducted targeted silencing of Lr. Notch1 in L. reissneri and analyzed the resultant gene expression profile before and after silencing using transcriptome analysis. Our findings revealed that the silencing of Lr. Notch1 resulted in differential expression of pathways and genes associated with signal transduction, immune regulation, and metabolic regulation, mirroring the biological function of the Notch signaling pathway in higher vertebrates. This article systematically elucidated the origin and evolution of the Notch gene family while also validating the biological function of Lr. Notch1. These insights offer valuable clues for understanding the evolution of the Notch signaling pathway and establish a foundation for future research on the origin of the Notch signaling pathway, as well as its implications in human diseases and immunomodulation.

Roles of Macrophages and Their Interactions with Schwann Cells After Peripheral Nerve Injury

The adult peripheral nervous system has a significant ability for regeneration compared to the central nervous system. This is related to the unique neuroimmunomodulation after peripheral nerve injury (PNI). Unlike the repair of other tissues after injury, Schwann cells (SCs) respond immediately to the trauma and send out signals to precisely recruit macrophages to the injured site. Then, macrophages promote the degradation of the damaged myelin sheath by phagocytosis of local debris. At the same time, macrophages and SCs jointly secrete various cytokines to reconstruct a microenvironment suitable for nerve regeneration. This unique pathophysiological process associated with macrophages provides important targets for the repair and treatment of PNI, as well as an important reference for guiding the repair of other nerve injuries. To understand these processes more systematically, this paper describes the characteristics of macrophage activation and metabolism in PNI, discusses the underlying molecular mechanism of interaction between macrophages and SCs, and reviews the latest research progress of crosstalk regulation between macrophages and SCs. These concepts and therapeutic strategies are summarized to provide a reference for the more effective use of macrophages in the repair of PNI.

NOTCH4 potentiates the IL-13 induced genetic program in M2 alternative macrophages through the AP1 and IRF4-JMJD3 axis

IL-13 signaling polarizes macrophages to an M2 alternatively activated phenotype, which regulates tissue repair and anti-inflammatory responses. However, an excessive activation of this pathway leads to severe pathologies, such as allergic airway inflammation and asthma. In this work, we identified NOTCH4 receptor as an important modulator of M2 macrophage activation. We show that the expression of NOTCH4 is induced by IL-13, mediated by Janus kinases and AP1 activity, probably mediated by the IL-13Rα1 and IL-13Rα2 signaling pathway. Furthermore, we demonstrate an important role for NOTCH4 signaling in the IL-13 induced gene expression program in macrophages, including various genes that contribute to pathogenesis of the airways in asthma, such as ARG1, YM1, CCL24, IL-10, or CD-163. We also demonstrate that NOTCH4 signaling modulates IL-13-induced gene expression by increasing IRF4 activity, mediated, at least in part, by the expression of the histone H3K27me3 demethylase JMJD3, and by increasing AP1-dependent transcription. In summary, our results provide evidence for an important role of NOTCH4 signaling in alternative activation of macrophages by IL-13 and suggest that NOTCH4 may contribute to the increased severity of lesions in M2 inflammatory responses, such as allergic asthma, which points to NOTCH4 as a potential new target for the treatment of these pathologies.

GOAT: Gene-level biomarker discovery from multi-Omics data using graph ATtention neural network for eosinophilic asthma subtype

MOTIVATION

Asthma is a heterogeneous disease where various subtypes are established and molecular biomarkers of the subtypes are yet to be discovered. Recent availability of multi-omics data paved a way to discover molecular biomarkers for the subtypes. However, multi-omics biomarker discovery is challenging because of the complex interplay between different omics layers.

RESULTS

We propose a deep attention model named Gene-level biomarker discovery from multi-Omics data using graph ATtention neural network (GOAT) for identifying molecular biomarkers for eosinophilic asthma subtypes with multi-omics data. GOAT identifies genes that discriminate subtypes using a graph neural network by modeling complex interactions among genes as the attention mechanism in the deep learning model. In experiments with multi-omics profiles of the COREA (Cohort for Reality and Evolution of Adult Asthma in Korea) asthma cohort of 300 patients, GOAT outperforms existing models and suggests interpretable biological mechanisms underlying asthma subtypes. Importantly, GOAT identified genes that are distinct only in terms of relationship with other genes through attention. To better understand the role of biomarkers, we further investigated two transcription factors, CTNNB1 and JUN, captured by GOAT. We were successful in showing the role of the transcription factors in eosinophilic asthma pathophysiology in a network propagation and transcriptional network analysis, which were not distinct in terms of gene expression level differences.

AVAILABILITY AND IMPLEMENTATION

Source code is available https://github.com/DabinJeong/Multi-omics_biomarker. The preprocessed data underlying this article is accessible in data folder of the github repository. Raw data are available in Multi-Omics Platform at http://203.252.206.90:5566/, and it can be accessible when requested.

Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis

Ehrlichia chaffeensis has evolved multiple strategies to evade innate defenses of the mononuclear phagocyte. Recently, we reported the E. chaffeensis tandem repeat protein (TRP)120 effector functions as a Notch ligand mimetic and a ubiquitin ligase that degrades the nuclear tumor suppressor, F-box and WD repeat domain-containing 7, a negative regulator of Notch. The Notch intracellular domain (NICD) is known to inhibit apoptosis primarily by interacting with X-linked inhibitor of apoptosis protein (XIAP) to prevent degradation. In this study, we determined that E. chaffeensis activation of Notch signaling increases XIAP levels, thereby inhibiting apoptosis through both the intrinsic and executioner pathways. Increased NICD and XIAP levels were detected during E. chaffeensis infection and after TRP120 Notch ligand mimetic peptide treatment. Conversely, XIAP levels were reduced in the presence of Notch inhibitor DAPT. Cytoplasmic and nuclear colocalization of NICD and XIAP was observed during infection and a direct interaction was confirmed by co-immunoprecipitation. Procaspase levels increased temporally during infection, consistent with increased XIAP levels; however, knockdown (KD) of XIAP during infection significantly increased apoptosis and Caspase-3, -7, and -9 levels. Furthermore, treatment with SM-164, a second mitochondrial activator of caspases (Smac/DIABLO) antagonist, resulted in decreased procaspase levels and increased caspase activation, induced apoptosis, and significantly decreased infection. In addition, RNAi KD of XIAP also decreased infection and significantly increased apoptosis. Moreover, ectopic expression of TRP120 HECT Ub ligase catalytically defective mutant in HeLa cells decreased NICD and XIAP levels and increased caspase activation compared to HeLa cells with functional HECT Ub ligase catalytic activity (TRP120-WT). This investigation reveals a mechanism whereby E. chaffeensis modulates Notch signaling to stabilize XIAP and inhibit apoptosis.

γ-Secretase fanning the fire of innate immunity

Innate immunity is the first line of defense against pathogens, alerting the individual cell and surrounding area to respond to this potential invasion. γ-secretase is a transmembrane protease complex that plays an intricate role in nearly every stage of this innate immune response. Through regulation of pattern recognition receptors (PRR) such as TREM2 and RAGE γ-secretase can modulate pathogen recognition. γ-secretase can act on cytokine receptors such as IFNαR2 and CSF1R to dampen their signaling capacity. While γ-secretase-mediated regulated intramembrane proteolysis (RIP) can further moderate innate immune responses through downstream signaling pathways. Furthermore, γ-secretase has also been shown to be regulated by the innate immune system through cytokine signaling and γ-secretase modulatory proteins such as IFITM3 and Hif-1α. This review article gives an overview of how γ-secretase is implicated in innate immunity and the maintenance of its responses through potentially positive and negative feedback loops.

MCT-Dependent Cryptosporidium parvum-Induced Bovine Monocyte Extracellular Traps (METs) under Physioxia

The apicomplexan protozoan parasite Cryptosporidium parvum is responsible for cryptosporidiosis, which is a zoonotic intestinal illness that affects newborn cattle, wild animals, and people all over the world. Mammalian monocytes are bone marrow-derived myeloid leukocytes with important defense effector functions in early host innate immunity due to their ATP purinergic-, CD14- and CD16-receptors, adhesion, migration and phagocytosis capacities, inflammatory, and anti-parasitic properties. The formation of monocyte extracellular traps (METs) has recently been reported as an additional effector mechanism against apicomplexan parasites. Nonetheless, nothing is known in the literature on METs extrusion neither towards C. parvum-oocysts nor sporozoites. Herein, ATP purinergic receptor P2X1, glycolysis, Notch signaling, and lactate monocarboxylate transporters (MCT) were investigated in C. parvum-exposed bovine monocytes under intestinal physioxia (5% O₂) and hyperoxia (21% O₂; most commonly used hyperoxic laboratory conditions). C. parvum-triggered suicidal METs were confirmed by complete rupture of exposed monocytes, co-localization of extracellular DNA with myeloperoxidase (MPO) and histones (H1-H4) via immunofluorescence- and confocal microscopy analyses. C. parvum-induced suicidal METs resulted not only in oocyst entrapment but also in hindered sporozoite mobility from oocysts according to scanning electron microscopy (SEM) analyses. Early parasite-induced bovine monocyte activation, accompanied by membrane protrusions toward C. parvum-oocysts/sporozoites, was unveiled using live cell 3D-holotomographic microscopy analysis. The administration of NF449, an inhibitor of the ATP purinergic receptor P2X1, to monocytes subjected to varying oxygen concentrations did not yield a noteworthy decrease in C. parvum-induced METosis. This suggests that the cell death process is not dependent on P2X1. Additionally, blockage of glycolysis in monocyte through 2-deoxy glucose (2-DG) inhibition reduced C. parvum-induced METosis but not significantly. According to monocyte energetic state measurements, C. parvum-exposed cells neither increased extracellular acidification rates (ECAR) nor oxygen consumption rates (OCR). Lactate monocarboxylate transporters (MCT) inhibitor (i.e., AR-C 141990) treatments significantly diminished C. parvum-mediated METs extrusion under physioxic (5% O₂) condition. Similarly, treatment with either DAPT or compound E, two selective Notch inhibitors, exhibited no significant suppressive effects on bovine MET production. Overall, for the first time, we demonstrate C. parvum-mediated METosis as P2X1-independent but as an MCT-dependent defense mechanism under intestinal physioxia (5% CO₂) conditions. METs findings suggest anti-cryptosporidial effects through parasite entrapment and inhibition of sporozoite excystation.

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.

NOTCH signaling inhibition after DAPT treatment exacerbates alveolar echinococcosis hepatic fibrosis by blocking M1 and enhancing M2 polarization

Alveolar echinococcosis (AE) is a lethal helminthic liver disease caused by persistent infection with Echinococcus multilocularis (E. multilocularis). Although more and more attention has been paid to the macrophages in E. multilocularis infection, the mechanism of macrophage polarization, a critical player in liver immunity, is seldom studied. NOTCH signaling is involved in cell survival and macrophage-mediated inflammation, but the role of NOTCH signaling in AE has been equally elusive. In this study, liver tissue samples from AE patients were collected and an E. multilocularis infected mouse model with or without blocking NOTCH signaling was established to analyze the NOTCH signaling, fibrotic and inflammatory response of the liver after E. multilocularis infection. Changes in polarization and origin of hepatic macrophages were analyzed by flow cytometry. In vitro qRT-PCR and Western blot assays were performed to analyze key receptors and ligands in NOTCH signaling. Our data demonstrated that hepatic fibrosis develops after AE, and the overall blockade of NOTCH signaling caused by DAPT treatment exacerbates the levels of hepatic fibrosis and alters the polarization and origin of hepatic macrophages. Blocking NOTCH signaling in macrophages after E. multilocularis infection downregulates M1 and upregulates M2 expression. The downregulation of NTCH3 and DLL-3 in the NOTCH signaling pathway is significant. Therefore, NOTCH3/DLL3 may be the key pathway in NOTCH signaling regulating macrophage polarization affecting fibrosis caused by AE.

Monocyte-derived Dll4 is a novel contributor to persistent systemic inflammation in HIV patients

Background

In people living with HIV (PLWH) on combination antiretroviral therapy (cART), persistent systemic inflammation is a driving force for the progression of comorbidities, such as cardiovascular and cerebrovascular diseases. In this context, monocyte- and macrophage-related inflammation rather than T cell activation is a major cause of chronic inflammation. However, the underlying mechanism of how monocytes cause persistent systemic inflammation in PLWH is elusive.

Methods and Results

In vitro, we demonstrated that lipopolysaccharides (LPS) or tumor necrosis factor alpha (TNFα), induced a robust increase of Delta-like ligand 4 (Dll4) mRNA and protein expression in human monocytes and Dll4 secretion (extracellular Dll4, exDll4) from monocytes. Enhanced membrane-bound Dll4 (mDll4) expression in monocytes triggered Notch1 activation to promote pro-inflammatory factors expression. Dll4 silencing and inhibition of Nocth1 activation diminished the LPS or TNFα -induced inflammation. exDll4 releases in response to cytokines occurred in monocytes but not endothelial cells or T cells. In clinical specimens, we found that PLWH, both male and female, on cART, showed a significant increase in mDll4 expression, activation of Dll4-Notch1 signaling, and inflammatory markers in monocytes. Although there was no sex effect on mDII4 in PLWH, plasma exDll4 was significantly elevated in males but not females compared to HIV uninfected individuals. Furthermore, exDll4 plasma levels paralleled with monocytes mDll4 in male PLWH. Circulating exDll4 was also positively associated with pro-inflammatory monocytes phenotype and negatively associated with classic monocytes phenotype in male PLWH.

Conclusion

Pro-inflammatory stimuli increase Dll4 expression and Dll4-Notch1 signaling activation in monocytes and enhance monocyte proinflammatory phenotype, contributing to persistent systemic inflammation in male and female PLWH. Therefore, monocyte mDll4 could be a potential biomarker and therapeutic target of systemic inflammation. Plasma exDll4 may also play an additional role in systemic inflammation but primarily in men.

Notch signaling is activated in knee-innervating dorsal root ganglia in experimental models of osteoarthritis joint pain

BACKGROUND

We aimed to explore activation of the Notch signaling pathway in knee-innervating lumbar dorsal root ganglia (DRG) in the course of experimental osteoarthritis (OA) in mice, and its role in knee hyperalgesia.

METHODS

Cultured DRG cells were stimulated with the TLR4 agonist, lipopolysaccharide (LPS). Notch signaling in the cells was either inhibited with the γ-secretase inhibitor, DAPT, or with soluble Jagged1, or activated through immobilized Jagged1. CCL2 production was analyzed at mRNA and protein levels. In in vivo experiments, knee hyperalgesia was induced in naïve mice through intra-articular (IA) injection of LPS. The effect of inhibiting Notch signaling was examined by pre-injecting DAPT one hour before LPS. OA was induced through surgical destabilization of the medial meniscus (DMM) in male C57BL/6 mice. Gene expression in DRG was analyzed by qRT-PCR and RNAscope in situ hybridization. Activated Notch protein (NICD) expression in DRG was evaluated by ELISA and immunofluorescence staining. DAPT was injected IA 12 weeks post DMM to inhibit Notch signaling, followed by assessing knee hyperalgesia and CCL2 expression in the DRG.

RESULTS

In DRG cell cultures, LPS increased NICD in neuronal cells. Inhibition of Notch signaling with either DAPT or soluble Jagged1 attenuated LPS-induced increases of Ccl2 mRNA and CCL2 protein. Conversely, activating Notch signaling with immobilized Jagged1 enhanced these LPS effects. In vivo, IA injection of LPS increased expression of Notch genes and NICD in the DRG. Pre-injection of DAPT prior to LPS alleviated LPS-induced knee hyperalgesia, and decreased LPS-induced CCL2 expression in the DRG. Notch signaling genes were differentially expressed in the DRG from late-stage experimental OA. Notch1, Hes1, and NICD were increased in the neuronal cell bodies in DRG after DMM surgery. IA administration of DAPT alleviated knee hyperalgesia post DMM, and decreased CCL2 expression in the DRG.

CONCLUSIONS

These findings suggest a synergistic effect of Notch signaling with TLR4 in promoting CCL2 production and mediating knee hyperalgesia. Notch signaling is activated in knee-innervating lumbar DRG in mice with experimental OA, and is involved in mediating knee hyperalgesia. The pathway may therefore be explored as a target for alleviating OA pain.

A multiscale hybrid model for exploring the effect of Resolvin D1 on macrophage polarization during acute inflammation

Dysregulated inflammation underlies various diseases. Specialized pro-resolving mediators (SPMs) like Resolvin D1 (RvD1) have been shown to resolve inflammation and halt disease progression. Macrophages, key immune cells that drive inflammation, respond to the presence of RvD1 by polarizing to an anti-inflammatory type (M₂). However, RvD1's mechanisms, roles, and utility are not fully understood. This paper introduces a gene-regulatory network (GRN) model that contains pathways for RvD1 and other SPMs and proinflammatory molecules like lipopolysaccharides. We couple this GRN model to a partial differential equation - agent-based hybrid model using a multiscale framework to simulate an acute inflammatory response with and without the presence of RvD1. We calibrate and validate the model using experimental data from two animal models. The model reproduces the dynamics of key immune components and the effects of RvD1 during acute inflammation. Our results suggest RvD1 can drive macrophage polarization through the G protein-coupled receptor 32 (GRP32) pathway. The presence of RvD1 leads to an earlier and increased M₂ polarization, reduced neutrophil recruitment, and faster apoptotic neutrophil clearance. These results support a body of literature that suggests that RvD1 is a promising candidate for promoting the resolution of acute inflammation. We conclude that once calibrated and validated on human data, the model can identify critical sources of uncertainty, which could be further elucidated in biological experiments and assessed for clinical use.

The Effect of Poria cocos Polysaccharide PCP-1C on M1 Macrophage Polarization via the Notch Signaling Pathway

The homogeneous galactoglucan PCP-1C extracted from Poria cocos sclerotium has multiple biological activities. The present study demonstrated the effect of PCP-1C on the polarization of RAW 264.7 macrophages and the underlying molecular mechanism. Scanning electron microscopy showed that PCP-1C is a detrital-shaped polysaccharide with fish-scale patterns on the surface, with a high sugar content. The ELISA assay, qRT-PCR assay, and flow cytometry assay showed that the presence of PCP-1C could induce higher expression of M1 markers, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-12 (IL-12), when compared with the control and the LPS group, and it caused a decrease in the level of interleukin-10 (IL-10), which is the marker for M2 macrophages. At the same time, PCP-1C induces an increase in the CD86 (an M1 marker)/CD206 (an M2 marker) ratio. The results of the Western blot assay showed that PCP-1C induced activation of the Notch signaling pathway in macrophages. Notch1, ligand Jagged1, and Hes1 were all up-regulated with the incubation of PCP-1C. These results indicate that the homogeneous Poria cocos polysaccharide PCP-1C improves M1 macrophage polarization through the Notch signaling pathway.

Notch Signaling in Acute Inflammation and Sepsis

Notch signaling, a highly conserved pathway in mammals, is crucial for differentiation and homeostasis of immune cells. Besides, this pathway is also directly involved in the transmission of immune signals. Notch signaling per se does not have a clear pro- or anti-inflammatory effect, but rather its impact is highly dependent on the immune cell type and the cellular environment, modulating several inflammatory conditions including sepsis, and therefore significantly impacts the course of disease. In this review, we will discuss the contribution of Notch signaling on the clinical picture of systemic inflammatory diseases, especially sepsis. Specifically, we will review its role during immune cell development and its contribution to the modulation of organ-specific immune responses. Finally, we will evaluate to what extent manipulation of the Notch signaling pathway could be a future therapeutic strategy.

Targeting Notch1-YAP Circuit Reprograms Macrophage Polarization and Alleviates Acute Liver Injury in Mice

BACKGROUND & AIMS

Hepatic immune system disorder plays a critical role in the pathogenesis of acute liver injury. The intrinsic signaling mechanisms responsible for dampening excessive activation of liver macrophages are not completely understood. The Notch and Hippo-YAP signaling pathways have been implicated in immune homeostasis. In this study, we investigated the interactive cell signaling networks of Notch1/YAP pathway during acute liver injury.

METHODS

Myeloid-specific Notch1 knockout (Notch1^M-KO) mice and the floxed Notch1 (Notch1^FL/FL) mice were subjected to lipopolysaccharide/D-galactosamine toxicity. Some mice were injected via the tail vein with bone marrow-derived macrophages transfected with lentivirus-expressing YAP. Some mice were injected with YAP siRNA using an in vivo mannose-mediated delivery system.

RESULTS

We found that the activated Notch1 and YAP signaling in liver macrophages were closely related to lipopolysaccharide/D-galactosamine-induced acute liver injury. Macrophage/neutrophil infiltration, proinflammatory mediators, and hepatocellular apoptosis were markedly ameliorated in Notch1^M-KO mice. Importantly, myeloid Notch1 deficiency depressed YAP signaling and facilitated M2 macrophage polarization in the injured liver. Furthermore, YAP overexpression in Notch1^M-KO livers exacerbated liver damage and shifted macrophage polarization toward the M1 phenotype. Mechanistically, macrophage Notch1 signaling could transcriptionally activate YAP gene expression. Reciprocally, YAP transcriptionally upregulated the Notch ligand Jagged1 gene expression and was essential for Notch1-mediated macrophage polarization. Finally, dual inhibition of Notch1 and YAP in macrophages further promoted M2 polarization and alleviated liver damage.

CONCLUSIONS

Our findings underscore a novel molecular insight into the Notch1-YAP circuit for controlling macrophage polarization in acute liver injury, raising the possibility of targeting macrophage Notch1-YAP circuit as an effective strategy for liver inflammation-related diseases.

Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis

Ehrlichia chaffeensis has evolved multiple strategies to evade innate defenses of the mononuclear phagocyte. Recently, we reported the E. chaffeensis TRP120 effector functions as a Notch ligand mimetic and a ubiquitin ligase that degrades the nuclear tumor suppressor, F-box and WD repeat domain-containing 7 (FBW7), a negative regulator of Notch. The Notch receptor intracellular domain (NICD) is known to inhibit apoptosis primarily by interacting with X-linked inhibitor of apoptosis protein (XIAP) to prevent degradation. In this study, we determined E. chaffeensis activation of Notch signaling increases XIAP levels, thereby inhibiting intrinsic apoptosis. Increased NICD and XIAP levels were detected during E. chaffeensis infection and after TRP120 Notch ligand mimetic peptide treatment. Conversely, XIAP levels were reduced in the presence of Notch inhibitor DAPT. Cytoplasmic colocalization of NICD and XIAP was observed during infection and a direct interaction was confirmed by co-immunoprecipitation. Procaspase levels increased temporally during infection, consistent with increased XIAP levels; however, knockdown of XIAP during infection significantly increased apoptosis and Caspase-3, -7 and -9 levels. Further, treatment with SM-164, a second mitochondrial activator of caspases (Smac/DIABLO) antagonist, resulted in decreased procaspase levels and increased caspase activation, induced apoptosis, and significantly decreased infection. In addition, iRNA knockdown of XIAP also decreased infection and significantly increased apoptosis. Moreover, ectopic expression of TRP120 HECT Ub ligase catalytically defective mutant in HeLa cells decreased NICD and XIAP levels and increased caspase activation compared to WT. This investigation reveals a mechanism whereby E. chaffeensis repurposes Notch signaling to stabilize XIAP and inhibit apoptosis.

Author Summary

Ehrlichia chaffeensis is a tick-borne, obligately intracellular bacterium that exhibits tropism for mononuclear phagocytes. E. chaffeensis survives by mobilizing various molecular strategies to promote cell survival, including modulation of apoptosis. This investigation reveals an E. chaffeensis initiated, Notch signaling regulated, antiapoptotic mechanism involving inhibitor of apoptosis proteins (IAPs). Herein, we demonstrate that E. chaffeensis induced Notch activation results in Notch intracellular domain stabilization of X-linked inhibitor of apoptosis protein (XIAP) to inhibit intrinsic apoptosis. This study highlights a novel mechanistic strategy whereby intracellular pathogens repurpose evolutionarily conserved eukaryotic signaling pathways to engage an antiapoptotic program for intracellular survival.

Roles of transducin-like enhancer of split (TLE) family proteins in tumorigenesis and immune regulation

Mammalian transducin-like enhancer of split family proteins (TLEs) are homologous to Drosophila Groucho (Gro) and are essential transcriptional repressors. Seven TLE family members, TLE1-7, have been identified to date. These proteins do not bind DNA directly; instead, they bind a set of transcription factors and thereby inhibit target gene expression. Loss of TLEs in mice usually leads to defective early development; however, TLE functions in developmentally mature cells are unclear. Recent studies have revealed that TLEs are dysregulated in certain human cancer types and may function as oncogenes or tumor suppressors in different contexts. TLE levels also affect the efficacy of cancer treatments and the development of drug resistance. In addition, TLEs play critical roles in the development and function of immune cells, including macrophages and lymphocytes. In this review, we provide updates on the expression, function, and mechanism of TLEs; discuss the roles played by TLEs in tumorigenesis and the inflammatory response; and elaborate on several TLE-associated signaling pathways, including the Notch, Wnt, and MAPK pathways. Finally, we discuss potential strategies for targeting TLEs in cancer therapy.

Bacillus subtilis programs the differentiation of intestinal secretory lineages to inhibit Salmonella infection

The role of intestinal microbiota on fate determination of intestinal epithelial cells has not been extensively examined. In this study, we explore the effect of Bacillus subtilis on programmed intestinal epithelial differentiation. We find that B. subtilis stimulates the differentiation of intestinal secretory cells. Moreover, B. subtilis inhibits the Notch pathway to reduce the expression of hairy and enhancer of split 1, thereby shifting intestinal stem cell differentiation toward a secretory cell fate. Moreover, we demonstrate that the programming effect of B. subtilis on intestinal differentiation is Toll-like receptor 2 pathway dependent. B. subtilis is associated with increased numbers of Paneth and goblet cells in the intestine. This results in the production of antimicrobial peptides to protect the intestinal mucosal barrier against Salmonella typhimurium. This study demonstrates that B. subtilis contributes to the differentiation of secretory cells by affecting Notch pathway signaling to maintain the intestinal barrier.

Nrf2-mediated anti-inflammatory polarization of macrophages as therapeutic targets for osteoarthritis

Macrophages are the most abundant immune cells within the synovial joints, and also the main innate immune effector cells triggering the initial inflammatory responses in the pathological process of osteoarthritis (OA). The transition of synovial macrophages between pro-inflammatory and anti-inflammatory phenotypes can play a key role in building the intra-articular microenvironment. The pro-inflammatory cascade induced by TNF-α, IL-1β, and IL-6 is closely related to M1 macrophages, resulting in the production of pro-chondrolytic mediators. However, IL-10, IL1RA, CCL-18, IGF, and TGF are closely related to M2 macrophages, leading to the protection of cartilage and the promoted regeneration. The inhibition of NF-κB signaling pathway is central in OA treatment via controlling inflammatory responses in macrophages, while the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway appears not to attract widespread attention in the field. Nrf2 is a transcription factor encoding a large number of antioxidant enzymes. The activation of Nrf2 can have antioxidant and anti-inflammatory effects, which can also have complex crosstalk with NF-κB signaling pathway. The activation of Nrf2 can inhibit the M1 polarization and promote the M2 polarization through potential signaling transductions including TGF-β/SMAD, TLR/NF-κB, and JAK/STAT signaling pathways, with the regulation or cooperation of Notch, NLRP3, PI3K/Akt, and MAPK signaling. And the expression of heme oxygenase-1 (HO-1) and the negative regulation of Nrf2 for NF-κB can be the main mechanisms for promotion. Furthermore, the candidates of OA treatment by activating Nrf2 to promote M2 phenotype macrophages in OA are also reviewed in this work, such as itaconate and fumarate derivatives, curcumin, quercetin, melatonin, mesenchymal stem cells, and low-intensity pulsed ultrasound.

Effects of the interaction of Notch and TLR4 pathways on inflammation and heart function in septic heart

We investigated the role of the interaction between the Notch and Toll-like receptor 4 (TLR4) pathways in septic myocardial injury. The sepsis model was induced in rats with lipopolysaccharide (LPS). Rats were divided into control, LPS, LPS + TAK242 ((6R)-6-[N-(2-chloro-4-fluorophenyl)sulfamoyl]cyclohex-1-ene-1-carboxylate) and LPS + DAPT (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-s-phenylglycinetbutylester) groups. Heart function was evaluated with a Cardiac Doppler ultrasound. Myocardial morphological changes were detected by hematoxylin-eosin staining (H&E). Apoptosis was assessed by a TUNEL assay. The mRNA and protein levels were detected with real-time PCR, Western blot, and immunohistochemistry analysis. We found that heart function in the LPS + TAK242 group was significantly improved, but not in the LPS + DAPT group. LPS + TAK242 had a lower level of degeneration and necrosis of cardiomyocytes and inflammatory cell infiltration, as well as lower apoptosis and caspase-3 expression than the LPS group. Compared with the LPS group, the inflammatory cell infiltration was reduced in the LPS + DAPT group, while the degeneration and necrosis of cardiomyocytes were not obviously improved. Additionally, the expression levels of tumor necrosis factor-α and Interleukin-6, the protein contents of Notch intracellular domain and Hes1, and the P65 nuclear factor kappa-B (NF-κB) to P-P65 NF-κB ratio in LPS + TAK242 group and LPS + DAPT group were significantly lower than those in LPS group. Conclusively, the interaction between TLR4 and Notch signaling pathways enhances the inflammatory response in the septic heart by activating NF-κB. Blocking the TLR4 pathway with TAK242 can improve heart dysfunction and myocardial damage in sepsis, while blocking the Notch pathway with DAPT cannot effectively prevent heart dysfunction and myocardial damage in sepsis.

Inhibition of Notch Signaling Stimulates Osteoclastogenesis From the Common Trilineage Progenitor Under Inflammatory Conditions

Osteoclasts, macrophages and dendritic cells (DCs) can be derived from a common trilineage myeloid progenitor of hematopoietic origin. Progenitor commitment is susceptible to regulation through Notch signaling. Our aim was to determine the effects of Notch modulation on trilineage progenitor commitment and functional properties of differentiated cells under inflammatory conditions. We used the conditional inducible CX3CR1CreERT2 mouse strain to achieve overexpression of the Notch 1 intracellular domain (NICD1) or to inhibit Notch signaling via deletion of the transcription factor RBP-J in a bone marrow population, used as a source of the trilineage progenitor (CD45+Ly6G−CD3−B220−NK1.1−CD11b–/loCD115+). Cre-recombinase, under the control of the CX3CR1 promoter, expressed in the monocyte/macrophage lineage, was induced in vitro by 4-hydroxytamoxifen. Differentiation of osteoclasts was induced by M-CSF/RANKL; macrophages by M-CSF; DCs by IL-4/GM-CSF, and inflammation by LPS. Functionally, DCs were tested for the ability to process and present antigen, macrophages to phagocytose E. coli particles, and osteoclasts to resorb bone and express tartrate-resistant acid phosphatase (TRAP). We found that Notch 1 signal activation suppressed osteoclast formation, whereas disruption of the Notch canonical pathway enhanced osteoclastogenesis, resulting in a higher number and size of osteoclasts. RANK protein and Ctsk gene expression were upregulated in osteoclastogenic cultures from RBP-J+ mice, with the opposing results in NICD1+ mice. Notch modulation did not affect the number of in vitro differentiated macrophages and DCs. However, RBP-J deletion stimulated Il12b and Cd86 expression in macrophages and DCs, respectively. Functional assays under inflammatory conditions confirmed that Notch silencing amplifies TRAP expression by osteoclasts, whereas the enhanced phagocytosis by macrophages was observed in both NICD1+ and RBP-J+ strains. Finally, antigen presentation by LPS-stimulated DCs was significantly downregulated with NICD1 overexpression. This experimental setting allowed us to define a cell-autonomous response to Notch signaling at the trilineage progenitor stage. Although Notch signaling modulation affected the activity of all three lineages, the major effect was observed in osteoclasts, resulting in enhanced differentiation and function with inhibition of canonical Notch signaling. Our results indicate that Notch signaling participates as the negative regulator of osteoclast activity during inflammation, which may be relevant in immune and bone diseases.

Notch/NICD/RBP-J signaling axis regulates M1 polarization of macrophages mediated by advanced glycation end products

Advanced glycation end products (AGEs) aggregation and macrophages polarization are identified as the main factors contributing to bone diseases caused by aging or diabetes, such as senile or diabetic osteoporosis. Here, we aimed to elucidate the involvement and potential mechanism of AGEs in macrophages polarization and osteoclastogenesis. Firstly, AGEs-treated RAW264.7 macrophages were observed to up-regulate the release of nitric oxide (NO), the expression of M1-associated genes and the surface antigen marker CD86. The detection of osteoclast-related markers and TRAP staining revealed that the osteoclastogenic ability of M1 macrophages was markedly enhanced by AGEs. Further, AGEs were found to effectively activate the transduction of Notch signaling pathway and promote the nuclear translocation of NICD1. In addition, with the signals transduction of Notch pathway blocked by γ-secretase inhibitor DAPT and siRNA targeting silencing RBP-J, AGEs-induced M1 polarization was significantly mitigated. Collectively, we defined a critical role for AGEs in inducing M1 polarization and osteoclastogenesis of macrophages, and further identified Notch/NICD/RBP-J signaling axis as an essential mechanism regulating AGEs-mediated M1 polarization.

Zizhu Ointment Accelerates Wound-Healing of Diabetic Ulcers through Promoting M2 Macrophage Polarization via Downregulating the Notch4 Signaling Pathway

Objective

The long-term clinical practice shows that Zizhu ointment (ZZO) is an empirical formula for the treatment of diabetic ulcers (DUs). In this study, we investigated the underlying mechanism of ZZO in the treatment of DU mice.

Methods

Through streptozotocin induction and high-fat diet, a DU mouse model was established and ZZO was given for treatment. The activation of Notch4 signaling was examined by immunofluorescence staining, RT-PCR, as well as Western blotting. Flow cytometry was performed to detect the counts of F4/80+ cells, M1 and M2 macrophages, as well as the expression of CD11c, CD206, etc. The role of Notch4 in wound healing in diabetic mice was verified by Notch4 inhibitors and agonists.

Results

Accelerated wound healing and decreased expression levels of Notch4 and its target genes and ligands were observed in diabetic mice treated with ZZO. ZZO promoted M2 macrophage polarization, downregulated the expression of proinflammatory factors, and upregulated the levels of anti-inflammatory factors. The same tendency was observed in diabetic mice after treatment with Notch4 inhibitors. Knockout of Notch4 accelerated the wound healing rate as well.

Conclusions

ZZO accelerates wound healing of diabetic mice through inhibiting the activation of Notch4 signaling, promoting M2 macrophage polarization, and alleviating inflammation.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

Photobiomodulation Attenuates Neurotoxic Polarization of Macrophages by Inhibiting the Notch1-HIF-1α/NF-κB Signalling Pathway in Mice With Spinal Cord Injury

Spinal cord injury (SCI) is a catastrophic disease with a complex pathogenesis that includes inflammation, oxidative stress, and glial scar formation. Macrophages are the main mediators of the inflammatory response and are distributed in the epicentre of the SCI. Macrophages have neurotoxic and neuroprotective phenotypes (also known as classically and alternatively activated macrophages or M1 and M2 macrophages) that are associated with pro- or anti- inflammatory gene expression. Our previous study demonstrated that photobiomodulation (PBM) alters the polarization state of macrophages in the SCI region towards the M2 phenotype and promotes the recovery of motor function in rats with SCI. However, the mechanism by which PBM promotes SCI repair remains largely undefined. This study is based on the replacement of conventional percutaneous irradiation with implantable biofibre optic in vivo irradiation. The aim was to further investigate the effects of PBM on SCI in mice under new irradiation patterns and its potential mechanisms of action. PBM was administered to male mice with clamped SCI for four consecutive weeks and significantly promoted the recovery of motor function in mice. Analysis of the macrophage phenotypes in the epicentre of the SCI in mice showed that PBM mainly inhibited the neurotoxic activation of macrophages in the SCI area and reduced the secretion of inflammatory factors such as IL-1α and IL-6; PBM had no effect on M2 macrophages. Immediately afterwards, we constructed in vitro models of the inflammatory polarization of macrophages and PBM intervention. We found that PBM attenuated the neurotoxicity of M1 macrophages on VSC 4.1 motor neurons and dorsal root ganglion (DRG) neurons. The effects of PBM on neurotoxic macrophages and the possible mechanisms of action were analysed using RNA sequencing (RNA-seq), which confirmed that the main role of PBM was to modulate the inflammatory response and immune system processes. Analysis of the differentially expressed genes (DEGs) associated with the inflammatory response showed that PBM had the most significant regulatory effects on genes such as interleukin (IL)-1α, IL-6, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) and had obvious inhibitory effects on inflammation-related Notch1 and hypoxia-inducible factor-1α (HIF-1α) pathway genes. RNA-seq analysis of the effect of PBM on gene expression in resting-state macrophages and M2 macrophages did not show significant differences (data not shown). In conclusion, PBM promoted better motor recovery after SCI in mice by inhibiting the neurotoxic polarization of macrophages and the release of inflammatory mediators by acting on the Notch1-HIF-1α/NF-κB Signalling Pathway.

Velásquez Z, Borggrefe T, Gärtner U, Kamena F, Taubert A, Hermosilla C. ATP Purinergic Receptor P2X1-Dependent Suicidal NETosis Induced by Cryptosporidium parvum under Physioxia Conditions

Cryptosporidiosis is a zoonotic intestinal disease that affects humans, wildlife, and neonatal cattle, caused by Cryptosporidium parvum. Neutrophil extracellular traps (NETs), also known as suicidal NETosis, are a powerful and ancient innate effector mechanism by which polymorphonuclear neutrophils (PMN) battle parasitic organisms like protozoa and helminths. Here, C. parvum oocysts and live sporozoites were utilized to examine suicidal NETosis in exposed bovine PMN under both 5% O₂ (physiological conditions within small intestinal tract) and 21% O₂ (normal hyperoxic conditions in research facilities). Both sporozoites and oocysts induced suicidal NETosis in exposed PMN under physioxia (5% O₂) and hyperoxia (21% O₂). Besides, C. parvum-induced suicidal NETosis was affirmed by total break of PMN, co-localization of extracellular DNA decorated with pan-histones (H1A, H2A/H2B, H3, H4) and neutrophil elastase (NE) by means of confocal- and immunofluorescence microscopy investigations. C. parvum-triggered NETs entrapped sporozoites and impeded sporozoite egress from oocysts covered by released NETs, according to scanning electron microscopy (SEM) examination. Live cell 3D-holotomographic microscopy analysis visualized early parasite-induced PMN morphological changes, such as the formation of membrane protrusions towards C. parvum while undergoing NETosis. Significant reduction of C. parvum-induced suicidal NETosis was measured after PMN treatments with purinergic receptor P2X1 inhibitor NF449, under both oxygen circumstances, this receptor was found to play a critical role in the induction of NETs, indicating its importance. Similarly, inhibition of PMN glycolysis via 2-deoxy glucose treatments resulted in a reduction of C. parvum-triggered suicidal NETosis but not significantly. Extracellular acidification rates (ECAR) and oxygen consumption rates (OCR) were not increased in C. parvum-exposed cells, according to measurements of PMN energetic state. Treatments with inhibitors of plasma membrane monocarboxylate transporters (MCTs) of lactate failed to significantly reduce C. parvum-mediated NET extrusion. Concerning Notch signaling, no significant reduction was detected after PMN treatments with two specific Notch inhibitors, i.e., DAPT and compound E. Overall, we here describe for the first time the pivotal role of ATP purinergic receptor P2X1 in C. parvum-mediated suicidal NETosis under physioxia (5% O₂) and its anti-cryptosporidial properties.

Molecular mechanisms of developmental pathways in neurological disorders: a pharmacological and therapeutic review

Developmental signalling pathways such as Wnt/β-catenin, Notch and Sonic hedgehog play a central role in nearly all the stages of neuronal development. The term 'embryonic' might appear to be a misnomer to several people because these pathways are functional during the early stages of embryonic development and adulthood, albeit to a certain degree. Therefore, any aberration in these pathways or their associated components may contribute towards a detrimental outcome in the form of neurological disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and stroke. In the last decade, researchers have extensively studied these pathways to decipher disease-related interactions, which can be used as therapeutic targets to improve outcomes in patients with neurological abnormalities. However, a lot remains to be understood in this domain. Nevertheless, there is strong evidence supporting the fact that embryonic signalling is indeed a crucial mechanism as is manifested by its role in driving memory loss, motor impairments and many other processes after brain trauma. In this review, we explore the key roles of three embryonic pathways in modulating a range of homeostatic processes such as maintaining blood-brain barrier integrity, mitochondrial dynamics and neuroinflammation. In addition, we extensively investigated the effect of these pathways in driving the pathophysiology of a range of disorders such as Alzheimer's, Parkinson's and diabetic neuropathy. The concluding section of the review is dedicated to neurotherapeutics, wherein we identify and list a range of biological molecules and compounds that have shown enormous potential in improving prognosis in patients with these disorders.

Combined Therapeutics for Atherosclerosis Treatment Using Polymeric Nanovectors

Atherosclerosis is an underlying risk factor in cardiovascular diseases (CVDs). The combination of drugs with microRNAs (miRNA) inside a single nanocarrier has emerged as a promising anti-atherosclerosis strategy to achieve the exploitation of their complementary mechanisms of action to achieve synergistic therapeutic effects while avoiding some of the drawbacks associated with current systemic statin therapies. We report the development of nanometer-sized polymeric PLGA nanoparticles (NPs) capable of simultaneously encapsulating and delivering miRNA-124a and the statin atorvastatin (ATOR). The polymeric NPs were functionalized with an antibody able to bind to the vascular adhesion molecule-1 (VCAM1) overexpressed in the inflamed arterial endothelium. The dual-loaded NPs were non-toxic to cells in a large range of concentrations, successfully attached overexpressed VCAM receptors and released the cargoes in a sustainable manner inside cells. The combination of both ATOR and miRNA drastically reduced the levels of proinflammatory cytokines such as IL-6 and TNF-α and of reactive oxygen species (ROS) in LPS-activated macrophages and vessel endothelial cells. In addition, dual-loaded NPs precluded the accumulation of low-density lipoproteins (LdL) inside macrophages as well as morphology changes to a greater extent than in single-loaded NPs. The reported findings validate the present NPs as suitable delivery vectors capable of simultaneously targeting inflamed cells in atherosclerosis and providing an efficient approach to combination nanomedicines.

NOTCH4 Exhibits Anti-Inflammatory Activity in Activated Macrophages by Interfering With Interferon-γ and TLR4 Signaling

NOTCH4 is a member of the NOTCH family of receptors whose expression is intensively induced in macrophages after their activation by Toll-like receptors (TLR) and/or interferon-γ (IFN-γ). In this work, we show that this receptor acts as a negative regulator of macrophage activation by diminishing the expression of proinflammatory cytokines, such as IL-6 and IL-12, and costimulatory proteins, such as CD80 and CD86. We have observed that NOTCH4 inhibits IFN-γ signaling by interfering with STAT1-dependent transcription. Our results show that NOTCH4 reprograms the macrophage response to IFN-γ by favoring STAT3 versus STAT1 phosphorylation without affecting their expression levels. This lower activation of STAT1 results in diminished transcriptional activity and expression of STAT1-dependent genes, including IRF1, SOCS1 and CXCL10. In macrophages, NOTCH4 inhibits the canonical NOTCH signaling pathway induced by LPS; however, it can reverse the inhibition exerted by IFN-γ on NOTCH signaling, favoring the expression of NOTCH-target genes, such as Hes1. Indeed, HES1 seems to mediate, at least in part, the enhancement of STAT3 activation by NOTCH4. NOTCH4 also affects TLR signaling by interfering with NF-κB transcriptional activity. This effect could be mediated by the diminished activation of STAT1. These results provide new insights into the mechanisms by which NOTCH, TLR and IFN-γ signal pathways are integrated to modulate macrophage-specific effector functions and reveal NOTCH4 acting as a new regulatory element in the control of macrophage activation that could be used as a target for the treatment of pathologies caused by an excess of inflammation.

Hidradenitis Suppurativa: Host-Microbe and Immune Pathogenesis Underlie Important Future Directions

Hidradenitis suppurativa (HS) is an inflammatory disease of the skin with a chronic, relapsing-remitting course. The pathogenesis of the disease is poorly understood and involves multiple factors, including genetics, environment, host-microbe interactions, and immune dysregulation. In particular, the composition of the cutaneous microbiome shifts as the disease progresses, although it is unclear whether this is a primary or secondary process. Trials with immunomodulatory therapy elucidate the role of specific immune pathways and cytokine signaling in disease mechanism, such as TNF-α, IL-1β, IL-12, IL-17, IL-23, and complement. Future studies should continue examining the causes of and contributing factors to microbial changes and immune dysregulation in HS pathogenesis.

Three-Dimensional Culture Systems for Dissecting Notch Signalling in Health and Disease

Three-dimensional (3D) culture systems opened up new horizons in studying the biology of tissues and organs, modelling various diseases, and screening drugs. Producing accurate in vitro models increases the possibilities for studying molecular control of cell–cell and cell–microenvironment interactions in detail. The Notch signalling is linked to cell fate determination, tissue definition, and maintenance in both physiological and pathological conditions. Hence, 3D cultures provide new accessible platforms for studying activation and modulation of the Notch pathway. In this review, we provide an overview of the recent advances in different 3D culture systems, including spheroids, organoids, and “organ-on-a-chip” models, and their use in analysing the crucial role of Notch signalling in the maintenance of tissue homeostasis, pathology, and regeneration.

Cross-regulation of notch/AKT and serum/glucocorticoid regulated kinase 1 (SGK1) in IL-4-stimulated human macrophages

Notch signaling regulates the responses of macrophages to different stimuli in a context-dependent manner. The roles of Notch signaling in proinflammatory macrophages are well characterized, whereas its involvement, if any, in IL-4-stimulated macrophages (M(IL-4)) is still unclear. We observed that Notch signaling is functional in human M(IL-4). We performed transcriptome analysis of the Notch1 intracellular domain (NIC1)-overexpressing human monocytic cell line THP-1 with or without IL-4 stimulation to understand the global impact of Notch signaling in M(IL-4). The results revealed that NIC1-overexpressing THP-1 upregulated proinflammatory-associated genes and target genes of IL-4 signaling. We identified serum/glucocorticoid regulated kinase 1 (SGK1) as one of the genes increased by NIC1 overexpression in M(IL-4). To dissect the signaling pathway leading to SGK1 upregulation, we pretreated THP-1-derived macrophages with specific inhibitors of Notch (DAPT), AKT (LY294002) or ERK (U0126). Among these inhibitors, only LY294002 decreased the SGK1 mRNA levels in M(IL-4), indicating that the AKT pathway plays a key role in SGK1 transcription in M(IL-4). Furthermore, treatment of THP-1-derived macrophages with the SGK1 inhibitor (GSK650394) suppressed AKT phosphorylation, but not STAT6, in response to IL-4, indicating that SGK1 positively regulates AKT pathway in M(IL-4). Finally, GSK650394 treatment of human M(IL-4) increased the levels of PPARG mRNA and its protein, indicating a negative role of SGK1 in M(IL-4) function. Overall, we report that the Notch signaling and AKT pathways cooperatively regulate SGK1 expression in M(IL-4) where SGK1, in turn, plays an important role in suppressing IL-4-induced PPAR_γ expression.

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.

Treponema denticola dentilisin triggered TLR2/MyD88 activation upregulates a tissue destructive program involving MMPs via Sp1 in human oral cells

Periodontal disease is driven by dysbiosis in the oral microbiome, resulting in over-representation of species that induce the release of pro-inflammatory cytokines, chemokines, and tissue-remodeling matrix metalloproteinases (MMPs) in the periodontium. These chronic tissue-destructive inflammatory responses result in gradual loss of tooth-supporting alveolar bone. The oral spirochete Treponema denticola, is consistently found at significantly elevated levels in periodontal lesions. Host-expressed Toll-Like Receptor 2 (TLR2) senses a variety of bacterial ligands, including acylated lipopolysaccharides and lipoproteins. T. denticola dentilisin, a surface-expressed protease complex comprised of three lipoproteins has been implicated as a virulence factor in periodontal disease, primarily due to its proteolytic activity. While the role of acylated bacterial components in induction of inflammation is well-studied, little attention has been given to the potential role of the acylated nature of dentilisin. The purpose of this study was to test the hypothesis that T. denticola dentilisin activates a TLR2-dependent mechanism, leading to upregulation of tissue-destructive genes in periodontal tissue. RNA-sequencing of periodontal ligament cells challenged with T. denticola bacteria revealed significant upregulation of genes associated with extracellular matrix organization and degradation including potentially tissue-specific inducible MMPs that may play novel roles in modulating host immune responses that have yet to be characterized within the context of oral disease. The Gram-negative oral commensal, Veillonella parvula, failed to upregulate these same MMPs. Dentilisin-induced upregulation of MMPs was mediated via TLR2 and MyD88 activation, since knockdown of expression of either abrogated these effects. Challenge with purified dentilisin upregulated the same MMPs while a dentilisin-deficient T. denticola mutant had no effect. Finally, T. denticola-mediated activation of TLR2/MyD88 lead to the nuclear translocation of the transcription factor Sp1, which was shown to be a critical regulator of all T. denticola-dependent MMP expression. Taken together, these data suggest that T. denticola dentilisin stimulates tissue-destructive cellular processes in a TLR2/MyD88/Sp1-dependent fashion.

Inhibition of gamma-secretase activity without interfering in Notch signalling decreases inflammatory response in patients with cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) patients present an exacerbated inflammatory response associated with tissue damage and ulcer development. Increasing numbers of patients have exhibited treatment failure, which remains not well understood. We hypothesized that adjuvant anti-inflammatory therapy would benefit CL patients. The aim of the present study was to investigate the contribution of Notch signalling and gamma-secretase activity to the inflammatory response observed in CL patients. Notch signalling is a molecular signalling pathway conserved among animal species. Gamma-secretase forms a complex of proteins that, among other pathways, modulates Notch signalling and immune response. We found that Notch 1 cell receptor signalling protects against the pathologic inflammatory response, and JLK6, a gamma-secretase inhibitor that does not interfere with Notch signalling, was shown to decrease the in-vitro inflammatory response in CL. Our data suggest that JLK6 may serve as an adjuvant treatment for CL patients.