Soluble SEMA4D/CD100: A novel immunoregulator in infectious and inflammatory diseases

Asiaticoside alleviates lipopolysaccharide-induced acute lung injury by blocking Sema4D/CD72 and inhibiting mitochondrial dysfunction in RAW264.7 cell and mice

Acute lung injury (ALI) is a common disease with complex pathogenesis. However, the treatment is mainly symptomatic with limited clinical options. Asiaticoside (AS), a Chinese herbal extract, has protective effects against LPS-induced ALI in mice and inhibits nitric oxide and prostaglandin E2 synthesis; however, the specific mechanism of AS in the prevention and treatment of LPS-induced ALI needs further study. Sema4D/CD72 pathway, mitochondrial dysfunction, and miRNA-21 are closely associated with inflammation. Therefore, the present study aimed to explore whether AS exerts its therapeutic effect on ALI by influencing Sema4D/CD72 pathway and mitochondrial dysfunction, restoring the balance of inflammatory factors, and influencing miRNA-21 expression. Cell and animal experiments were performed to investigate the effect of AS on ALI. Lipopolysaccharide (LPS) was used to establish the ALI model. CCK8 and flow cytometry were used to detect the cell viability and apoptosis rate. HE staining and wet-to-dry weight ratio (W/D) of lung tissue were determined. The expressions of Sema4D, CD72, NF-κB p65, Bax, Bcl2, and caspase 3 in RAW264.7 cells and lung tissues were detected by western blot, and the levels of IL-10 and IL-1β induced by LPS in supernatant of RAW264.7 cells and BALF were measured by ELISA. And the expression of miRNA-21 in cells and lung tissues was detected by fluorescence quantitative PCR. The result shows that AS treatment suppressed LPS-induced cell damage and lung injury in mice. AS treatment could alleviate the pathological changes such as inflammatory infiltration and histopathological changes in the lungs caused by LPS, and reduce the ratio of W/D. AS significantly alleviated the decrease of mitochondrial membrane potential induced by LPS, inhibited the increase of ROS production, and reduced the expression of mitochondrial fission proteins Drp1 and Fis1. The high-dose AS group significantly downregulated the expression of Sema4D, CD72, phosphorylated NF-κB p65, and apoptosis-related proteins, decreased the pro-inflammatory factor IL-1β, and enhanced the level of anti-inflammatory factor IL-10. In addition, AS promoted miRNA-21 expression. These effects inhibited apoptosis and restored the balance between anti- and pro-inflammatory factors. This represents the inaugural report elucidating the mechanism by which AS inhibits the Sema4D/CD72 signaling pathway. These findings offer novel insights into the potential application of AS in both preventing and treating ALI.

Associations of SEMA7A, SEMA4D, ADAMTS10, and ADAM8 with KRAS, NRAS, BRAF, PIK3CA, and AKT Gene Mutations, Microsatellite Instability Status, and Cytokine Expression in Colorectal Cancer Tissue

Semaphorins (SEMAs), ADAM, and ADAMTS family members are implicated in various cancer progression events within the tumor microenvironment across different cancers. In this study, we aimed to evaluate the expression of SEMA7A, SEMA4D, ADAM8, and ADAMTS10 in colorectal cancer (CRC) in relation to the mutational landscape of KRAS, NRAS, BRAF, PIK3CA, and AKT genes, microsatellite instability (MSI) status, and clinicopathological features. We also examined the associations between the expression of these proteins and selected cytokines, chemokines, and growth factors, assessed using a multiplex assay. Protein concentrations were quantified using ELISA in CRC tumors and tumor-free surgical margin tissue homogenates. Gene mutations were evaluated via RT-PCR, and MSI status was determined using immunohistochemistry (IHC). GSEA and statistical analyses were performed using R Studio. We observed a significantly elevated expression of SEMA7A in BRAF-mutant CRC tumors and an overexpression of ADAM8 in KRAS 12/13-mutant tumors. The expression of ADAMTS10 was decreased in PIK3CA-mutant CRC tumors. No significant differences in the expression of the examined proteins were observed based on MSI status. The SEMA7A and SEMA4D expressions were correlated with the expression of numerous cytokines associated with various immune processes. The potential immunomodulatory functions of these molecules and their suitability as therapeutic targets require further investigation.

ATAXIN-2 intermediate-length polyglutamine expansions elicit ALS-associated metabolic and immune phenotypes

Intermediate-length repeat expansions in ATAXIN-2 (ATXN2) are the strongest genetic risk factor for amyotrophic lateral sclerosis (ALS). At the molecular level, ATXN2 intermediate expansions enhance TDP-43 toxicity and pathology. However, whether this triggers ALS pathogenesis at the cellular and functional level remains unknown. Here, we combine patient-derived and mouse models to dissect the effects of ATXN2 intermediate expansions in an ALS background. iPSC-derived motor neurons from ATXN2-ALS patients show altered stress granules, neurite damage and abnormal electrophysiological properties compared to healthy control and other familial ALS mutations. In TDP-43Tg-ALS mice, ATXN2-Q33 causes reduced motor function, NMJ alterations, neuron degeneration and altered in vitro stress granule dynamics. Furthermore, gene expression changes related to mitochondrial function and inflammatory response are detected and confirmed at the cellular level in mice and human neuron and organoid models. Together, these results define pathogenic defects underlying ATXN2-ALS and provide a framework for future research into ATXN2-dependent pathogenesis and therapy.

Fibroblasts with high matrix metalloproteinase 2 expression regulate CD8+ T-cell residency and inflammation via CD100 in psoriasis

BACKGROUND

Psoriasis is a T cell-mediated chronic inflammatory skin condition characterized by the interaction of T cells with various cell types, forming an inflammatory microenvironment that sustains psoriatic inflammation. Homeostasis of these tissue-resident T cells is supported by fibroblasts, the primary structural cells in the dermis. In psoriasis, there is increased expression of matrix metalloproteinase 2 (MMP2), mediating structural alterations in skin tissues and modulating inflammation. Additionally, the CD100-plexin-B2 (PLXNB2) axis is known to enhance psoriasis inflammation via keratinocytes, and CD103 levels are associated with the severity of psoriasis upon relapse.

OBJECTIVES

To elucidate the role of fibroblasts and the MMP2-CD100 axis in modulating psoriasis inflammation.

METHODS

CD100 expression and function in psoriasis were assessed using immunofluorescence, enzyme-linked immunosorbent assay, single-cell transcriptome sequencing, cellular interaction analyses and quantitative reverse transcriptase polymerase chain reaction. CD8+ T cells from people with psoriasis were isolated using magnetic beads, to investigate the regulatory effect of MMP2 on CD100 expression on their membranes. Single-cell transcriptome sequencing, spatial transcriptome sequencing, mimetic timing analysis, immunofluorescence and flow cytometry were used to determine the origin of MMP2 and its impact on CD103+ CD8+ T cells. The hypotheses were further validated in vivo using MMP2 and CD100 inhibitors.

RESULTS

Soluble CD100 (sCD100) was significantly upregulated in both psoriatic lesions and peripheral blood, amplifying psoriasis inflammation by promoting the production of inflammatory cytokines by keratinocytes, fibroblasts and endothelial cells via the sCD100-PLXNB2 axis. Fibroblasts that highly expressed MMP2 (MMP2hi) exacerbated psoriasis symptoms by facilitating CD100 shedding from CD8+ T-cell membranes. Additionally, it was shown that fibroblasts enhance the upregulation of the CD8+ T-cell residency factor CD103 in co-cultures with CD8+ T cells. Inhibitors targeting MMP2 and CD100 were effective in reducing inflammation in an imiquimod-induced psoriasis model.

CONCLUSIONS

Our findings underscore the pivotal role of MMP2hi fibroblasts in the amplification and recurrence of inflammatory responses in psoriasis. These fibroblasts augment psoriasis inflammation through the CD100-PLXNB2 axis by facilitating CD100 shedding on CD8+ T-cell membranes and by upregulating CD103, thereby enhancing CD8+ T-cell residency.

YY1 Lactylation Aggravates Autoimmune Uveitis by Enhancing Microglial Functions via Inflammatory Genes

Activated microglia in the retina are essential for the development of autoimmune uveitis. Yin-Yang 1 (YY1) is an important transcription factor that participates in multiple inflammatory and immune-mediated diseases. Here, an increased YY1 lactylation in retinal microglia within in the experimental autoimmune uveitis (EAU) group is observed. YY1 lactylation contributed to boosting microglial activation and promoting their proliferation and migration abilities. Inhibition of lactylation suppressed microglial activation and attenuated inflammation in EAU. Mechanistically, cleavage under targets & tagmentation （CUT&Tag） analysis revealed that YY1 lactylation promoted microglial activation by regulating the transcription of a set of inflammatory genes, including STAT3, CCL5, IRF1, IDO1, and SEMA4D. In addition, p300 is identified as the writer of YY1 lactylation. Inhibition of p300 decreased YY1 lactylation and suppressed microglial inflammation in vivo and in vitro. Collectively, the results showed that YY1 lactylation promoted microglial dysfunction in autoimmune uveitis by upregulating inflammatory cytokine secretion and boosting cell migration and proliferation. Therapeutic effects can be achieved by targeting the lactate/p300/YY1 lactylation/inflammatory genes axis.

Cholangiocytes Modulate CD100 Expression in the Liver and Facilitate Pathogenic T-Helper 17 Cell Differentiation

BACKGROUND & AIMS

Chronic inflammation surrounding bile ducts contributes to the disease pathogenesis of most cholangiopathies. Poor efficacy of immunosuppression in these conditions suggests biliary-specific pathologic principles. Here we performed biliary niche specific functional interpretation of a causal mutation (CD100 K849T) of primary sclerosing cholangitis (PSC) to understand related pathogenic mechanisms.

METHODS

Biopsy specimens of explanted livers and endoscopy-guided sampling were used to assess the CD100 expression by spatial transcriptomics, immune imaging, and high-dimensional flow cytometry. To model pathogenic cholangiocyte-immune cell interaction, splenocytes from mutation-specific mice were cocultured with cholangiocytes. Pathogenic pathways were pinpointed by RNA sequencing analysis of cocultured cells and cross-validated in patient materials.

RESULTS

CD100 is mainly expressed by immune cells in the liver and shows a unique pattern around PSC bile ducts with RNA-level colocalization but poor detection at the protein level. This appears to be due to CD100 cleavage as soluble CD100 is increased. Immunophenotyping suggests biliary-infiltrating T cells as the major source of soluble CD100, which is further supported by reduced surface CD100 on T cells and increased metalloproteinases in cholangiocytes after coculturing. Pathogenic T cells that adhered to cholangiocytes up-regulated genes in the T-helper 17 cell differentiation pathway, and the CD100 mutation boosted this process. Consistently, T-helper 17 cells dominate biliary-resident CD4 T cells in patients.

CONCLUSIONS

CD100 exerts its functional impact through cholangiocyte-immune cell cross talk and underscores an active, proinflammatory role of cholangiocytes that can be relevant to novel treatment approaches.

Soluble Semaphorin 4D Serum Concentrations Are Elevated in Critically Ill Patients with Liver Cirrhosis and Correlate with Aminotransferases

Semaphorin 4D (Sema4D), also known as CD100, is a multifunctional transmembrane protein with immunoregulatory functions. Upon the activation of immune cells, soluble Semaphorin 4D (sSema4D) is proteolytically cleaved from the membrane by metalloproteinases. sSema4D levels are elevated in various (auto-)inflammatory diseases. Our aim was to investigate sSema4D levels in association with sepsis and critical illnesses and to evaluate sSema4D's potential as a prognostic biomarker. We measured sSema4D levels in 192 patients upon admission to our medical intensive care unit. We found similar levels of sSema4D in 125 patients with sepsis compared to 67 non-septic patients. sSema4D levels correlated with leukocytes but not with other markers of systemic inflammation such as C-reactive protein or procalcitonin. Most interestingly, in a subgroup of patients suffering from pre-existing liver cirrhosis, we observed significantly higher levels of sSema4D. Consistently, sSema4D was also positively correlated with markers of hepatic and cholestatic injury. Our study suggests that sSema4D is not regulated in sepsis compared to other causes of critical illness. However, sSema4D seems to be associated with hepatic injury and inflammation.

Genome-wide Analysis Identified SEMA4D, Novel Candidate Gene for Temperature Sensitivity in Patients With Non-Small Cell Lung Cancer

BACKGROUND

In the era of precision medicine, individual temperature sensitivity has been highlighted. This trait has traditionally been used for cold-heat pattern identification to understand the inherent physical characteristics, which are influenced by genetic factors, of an individual. However, genome-wide association studies (GWASs) on this trait are limited.

METHODS

Using genotype data from 90 patients with advanced non-small cell lung cancer (NSCLC) and epidermal growth factor receptor mutations, we performed a GWAS to assess the association between single nucleotide polymorphisms (SNPs) and temperature sensitivity, such as cold and heat scores. The score of each participant was evaluated using self-administered questionnaires on common symptoms and a 15-item symptom-based cold-heat pattern identification questionnaire.

RESULTS

The GWAS was adjusted for confounding factors, including age and sex, and significant associations were identified for cold and heat scores: SNP rs145814326, located on the intron of SORCS2 at chromosome 4p16.1, had a P-value of 1.86 × 10-7; and SNP rs79297667, located upstream from SEMA4D at chromosome 9q22.2, had a P-value of 8.97 × 10-8. We also found that the genetic variant regulates the expression level of SEMA4D in the main tissues, including the lungs and white blood cells, in NSCLC.

CONCLUSIONS

SEMA4D was found to be significantly associated with temperature sensitivity in patients with NSCLC, suggesting an increased expression of SEMA4D in patients with higher heat scores. The potential role of temperature sensitivity as a prognostic or predictive marker of immune response in NSCLC should be further studied.

Suppressed transcript diversity and immune response in COVID-19 ICU patients: a longitudinal study

Understanding the dynamic changes in gene expression during Acute Respiratory Distress Syndrome (ARDS) progression in post-acute infection patients is crucial for unraveling the underlying mechanisms. Study investigates the longitudinal changes in gene/transcript expression patterns in hospital-admitted severe COVID-19 patients with ARDS post-acute SARS-CoV-2 infection. Blood samples were collected at three time points and patients were stratified into severe and mild ARDS, based on their oxygenation saturation (SpO2/FiO2) kinetics over 7 d. Decline in transcript diversity was observed over time, particularly in patients with higher severity, indicating dysregulated transcriptional landscape. Comparing gene/transcript-level analyses highlighted a rather limited overlap. With disease progression, a transition towards an inflammatory state was evident. Strong association was found between antibody response and disease severity, characterized by decreased antibody response and activated B cell population in severe cases. Bayesian network analysis identified various factors associated with disease progression and severity, viz. humoral response, TLR signaling, inflammatory response, interferon response, and effector T cell abundance. The findings highlight dynamic gene/transcript expression changes during ARDS progression, impact on tissue oxygenation and elucidate disease pathogenesis.

SEMA4D/VEGF surface enhances endothelialization by diminished-glycolysis-mediated M2-like macrophage polarization

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammatory responses after percutaneous coronary intervention led to neoathrosclerosis and in-stent restenosis and thus increase the risk of adverse clinical outcomes. In this work, a metabolism reshaped surface is engineered, which combines the decreased glycolysis promoting, M2-like macrophage polarization, and rapid endothelialization property. Anionic heparin plays as a linker and mediates cationic SEMA4D and VEGF to graft electronically onto PLL surfaces. The system composed by anticoagulant heparin, immunoregulatory SEMA4D and angiogenic VEGF endows the scaffold with significant inhibition of platelets, fibrinogen and anti-thrombogenic properties, also noteworthy immunometabolism reprogram, anti-inflammation M2-like polarization and finally leading to rapid endothelializaiton performances. Our research indicates that the immunometabolism method can accurately reflect the immune state of modified surfaces. It is envisioned immunometabolism study will open an avenue to the surface engineering of vascular implants for better clinical outcomes.

Denosumab and Zoledronic Acid Differently Affect Circulating Immune Subsets: A Possible Role in the Onset of MRONJ

This work investigated whether the anti-resorptive drugs (ARDs) zoledronic acid (Zol) and denosumab (Dmab) affect differently the levels of circulating immune cell subsets, possibly predicting the risk of developing medication-related ONJ (MRONJ) during the first 18 months of treatment. Blood samples were collected from 10 bone metastatic breast cancer patients receiving cyclin inhibitors at 0, 6, 12, and 18 months from the beginning of Dmab or Zol treatment. Eight breast cancer patients already diagnosed with MRONJ and treated with cyclin inhibitors and ARDs were in the control group. PBMCs were isolated; the trend of circulating immune subsets during the ARD treatment was monitored, and 12 pro-inflammatory cytokines were analyzed in sera using flow cytometry. In Dmab-treated patients, activated T cells were stable or increased, as were the levels of IL-12, TNF-α, GM-CSF, IL-5, and IL-10, sustaining them. In Zol-treated patients, CD8+T cells decreased, and the level of IFN-γ was undetectable. γδT cells were not altered in Dmab-treated patients, while they dramatically decreased in Zol-treated patients. In the MRONJ control group, Zol-ONJ patients showed a reduction in activated T cells and γδT cells compared to Dmab-ONJ patients. Dmab was less immunosuppressive than Zol, not affecting γδT cells and increasing activated T cells.

Potential clinical biomarkers in monitoring the severity of Hantaan virus infection

Hantavirus, which causes hemorrhagic fever with renal syndrome (HFRS) is almost prevalent worldwide. While Hantaan virus (HTNV) causes the most severe form of HFRS with typical clinical manifestations of thrombocytopenia, increased vascular permeability, and acute kidney injury. Although the knowledge of the pathogenesis of HFRS is still limited, immune dysfunction and pathological damage caused by disorders of immune regulation are proposed to play a vital role in the development of the disorder, and the endothelium is considered to be the primary target of hantaviruses. Here, we reviewed the production and function of multiple molecules, mainly focusing on their role in immune response, endothelium, vascular permeability regulation, and platelet and coagulation activation which are closely related to the pathogenesis of HTNV infection. meanwhile, the relationship between these molecules and characteristics of HTNV infection including the hospital duration, immune dysfunction, thrombocytopenia, leukocytosis, and acute kidney injury are also presented, to provide a novel insight into the potential role of these molecules as monitoring markers for HTNV infection.

Protection of Barrier Function in Cultured Human Corneal Epithelial Cells by Semaphorin 4D

PURPOSE

Corneal epithelial barrier function is important to maintain corneal homeostasis and is impaired by inflammation. We aimed to investigate the localization of semaphorin 4D (Sema4D) in the cornea, and its effects on the barrier function of cultured corneal epithelial cells.

METHODS

The expressions of semaphorin4 D and its receptor in the murine cornea were examined by immunoblot, immunofluorescent staining and confocal microscopy observations. Human corneal epithelial (HCE) cells stimulated by TNF-α or IL-1β were cultured with or without Sema4D. Cell viability was examined by CCK8, cell migration was evaluated by scratch wound assay, and barrier function was assessed by transepithelial electrical resistance (TEER) and Dextran-FITC permeability assay. The expression of tight junction proteins in HCE cells was examined by immunoblot, immunofluorescent staining and qRT-PCR.

RESULTS

We demonstrated that the protein of Sema4D and its receptor, plexin-B1, was expressed in murine cornea. Sema4D induced an increase in the TEER and a decrease in the permeability of HCE cells. It also induced the expression of tight junction protein ZO-1, occludin and claudin-1 in HCE cells. Furthermore, under stimulation of TNF-α or IL-1β, Sema4D treatment could inhibit the decreased TEER and the elevated permeability of HCE cells.

CONCLUSIONS

Sema4D is located distinctly in corneal epithelial cells and promoted their barrier function by increasing the expression of tight junction proteins. Sema4D may act as a preventive for maintaining corneal epithelial barrier function during ocular inflammation.

Knockout of Sema4D alleviates liver fibrosis by suppressing AOX1 expression

Liver fibrosis can occur in many chronic liver diseases, and no effective treatments are available due to the poorly characterized molecular pathogenesis. Semaphorin 4D (Sema4D) has immune functions and serves important roles in T cell priming. Here, we found that Sema4D was highly expressed in fibrotic liver, and the expression of Sema4D increased with hepatic stellate cells (HSCs) activation. Knockout of Sema4D alleviated liver fibrosis. Mechanistically, knockout of Sema4D alleviated liver fibrosis by suppressing the expression of AOX1 in retinol metabolism. Further investigation demonstrated that retinoic acid receptor α (RARA), an important nuclear receptor of retinoic acid, was reduced by Sema4D knockout during liver fibrogenesis. Sema4D knockout-mediated suppression of liver fibrosis was partly mediated by regulating the balance of Th1, Th2, Th17, and T-bet+Treg cells via inhibiting AOX1/RARA. Thus, targeting Sema4D may hold promise as a potential therapeutic approach for treating liver fibrosis.

Platelet formation and activation are influenced by neuronal guidance proteins

Platelets are anucleate blood cells derived from megakaryocytes. They link the fundamental functions of hemostasis, inflammation and host defense. They undergo intracellular calcium flux, negatively charged phospholipid translocation, granule release and shape change to adhere to collagen, fibrin and each other, forming aggregates, which are key to several of their functions. In all these dynamic processes, the cytoskeleton plays a crucial role. Neuronal guidance proteins (NGPs) form attractive and repulsive signals to drive neuronal axon navigation and thus refine neuronal circuits. By binding to their target receptors, NGPs rearrange the cytoskeleton to mediate neuron motility. In recent decades, evidence has indicated that NGPs perform important immunomodulatory functions and influence platelet function. In this review, we highlight the roles of NGPs in platelet formation and activation.

The value of serum Sema4D level in predicting the prognosis of patients with acute ST-segment elevation myocardial infarction and with high thrombus burden

BACKGROUND

Acute ST-segment elevation myocardial infarction (STEMI) is a serious cardiovascular disease. High thrombus burden is an independent risk factor for poor prognosis of acute myocardial infarction. However, there is no study on the correlation between soluble semaphorin 4D (sSema4D) level and high thrombus burden in patients with STEMI.

PURPOSE

This study aimed to investigate the relationship between sSema4D level and the thrombus burden of STEMI and further explore its effect on the main predictive value of the occurrence of major adverse cardiovascular events (MACE).

METHODS

From October 2020 to June 2021, 100 patients with STEMI diagnosed in our hospital's cardiology department were selected. According to the thrombolysis in myocardial infarction(TIMI)score, STEMI patients were divided into high thrombus burden groups (55 cases) and non-high thrombus burden groups (45 cases) 0.74 patients with stable coronary heart disease (CHD) were selected as stable CHD group, and 75 patients with negative coronary angiography (CAG) were selected as control group. Serum sSema4D levels were measured in 4 groups. The correlation between serum sSema4D and high-sensitivity C-reactive protein (hs-CRP) in patients with STEMI was analyzed. The relationship of serum sSema4D levels between the high and non-high thrombus burden group was evaluated. The effect of sSema4D levels on the occurrence of MACE was explored in one year after percutaneous coronary intervention.

RESULTS

Serum sSema4D level was positively correlated with hs-CRP level in STEMI patients (P < 0.05) with a correlation coefficient of 0.493. The sSema4D level was significantly higher in the high versus non-high thrombus burden group (22.54(20.82,24.17), P < 0.05). Moreover, MACE occurred in 19 cases in high thrombus burden group and 3 cases in non-high thrombus burden group. The results of Cox regression analysis showed that sSema4D was an independent predictor of MACE (OR = 1.497,95% CI: 1.213-1.847, P < 0.001).

CONCLUSION

The sSema4D level is associated with coronary thrombus burden and is an independent risk factor for MACE.

Low expression of SEMA4D as a potential predictive molecular marker of poor survival in patients with melanoma combined with liver cancer

This study explored the correlation between semaphorin 4D (SEMA4D) and the prognosis and survival time of patients with melanoma combined with liver cancer. A total of 272 patients were recruited, and clinical and follow-up data were recorded. The expression levels of SEMA4D and SEMA3B were determined. Pearson's χ² test and Spearman's rank correlation coefficient were used to analyze the relationship between prognosis and the assessed parameters of melanoma patients. Univariate and multivariate Logistic regression and Cox proportional risk regression analyses were used for further analysis. Additionally, receiver operating characteristic curve and survival curves of subjects were plotted. The Pearson's χ² test showed that the prognosis of melanoma patients was significantly correlated with age, tumor grade, and decreased SEMA4D expression. Additionally, Spearman's correlation coefficient analysis showed that age, tumor grade, and SEMA4D expression were significantly correlated with prognosis. Univariate logistic regression analysis showed that age and tumor grade, and SEMA4D expression, were significantly correlated with prognosis. Older patients, a higher tumor grade, and lower SEMA4D expression were associated with a poorer prognosis. Multivariate logistic regression analysis showed that older patients had a poorer prognosis, and patients with lower SEMA4D expression levels had a significantly worse prognosis than patients with higher SEMA4D expression levels. Kaplan-Meier analysis showed that the survival time of older patients was lower than that of the younger patients. The survival times of patients with lower SEMA4D expression levels were significantly lower than that of patients with higher SEMA4D expression levels. Multivariate Cox regression analysis showed that the survival time of older patients was lower than that of younger patients. The survival time of melanoma patients with low SEMA4D expression was significantly lower than that of patients with higher SEMA4D expression. SEMA4D was significantly associated with melanoma, and lower SEMA4D expression was associated with a poorer survival prognosis in melanoma patients.

The Potential Immunomodulatory Roles of Semaphorin 4D in Human Periapical Lesions

INTRODUCTION

Semaphorin 4D (SEMA4D) is an important immunoregulator in the development of inflammatory diseases. Currently, the role of SEMA4D in human apical periodontitis remains unclear. This study aims to investigate the expression of SEMA4D and its potential immunomodulatory roles in apical periodontitis.

METHODS

A total of 31 periapical tissues and 6 healthy gingival tissues were used in this experiment. Hematoxylin-eosin staining, immunohistochemical staining, and multiplex immunofluorescence staining were performed for histologic examination and immunochemical analysis. For data processing, the number of SEMA4D⁺, CD4⁺, CD8⁺, and CD20⁺ cells was analyzed by QuPath. In addition, the colocalization of SEMA4D with CD4, CD8, and CD20 was detected.

RESULTS

Radicular cysts (RCs) (n = 18) and periapical granulomas (PGs) (n = 13) were identified by histologic evaluation. The number of SEMA4D⁺ cells in PGs was significantly greater than that in RCs (P < .05). T-cell and B-cell infiltration did not differ significantly between RCs and PGs. An increased number of CD20⁺ cells was observed in both types of apical periodontitis compared to CD8⁺ cells and CD4+ cells. Additionally, the presence of SEMA4D/CD4 and SEMA4D/CD20 double-positive cells was also markedly higher in PGs than in RCs.

CONCLUSION

The expression of SEMA4D and related immune cells showed different characteristics between RCs and PGs. The disparate expression patterns indicated the possible different pathologic states of the 2 types of periapical lesions. This study provides a new perspective on the description of the comprehensive microenvironment of periapical lesions.

Sema4D-plexin-B1 signaling in recruiting dental stem cells for vascular stabilization on a microfluidic platform

The recruitment of mural cells is critical for stabilization of nascent vessels. Stem cells from human exfoliated deciduous teeth (SHED) are considered to have mural cell-like properties. However, the signaling mechanisms that regulate the cross-talk between endothelial cells and SHED in recruiting them as mural cells is much less well understood. Herein, using a 3D biomimetic microfluidic device, for the first time, we unraveled the role of semaphorin 4D (Sema4D)-plexin-B1 signaling in the recruitment of SHED as mural cells during angiogenic sprouting and vasculature formation by endothelial cells (ECs) in a 3D fibrin matrix. The specific compartmentalized design of the microfluidic chip facilitated recreation of the multi-step dynamic process of angiogenesis in a time and space dependent manner. Enabled by the chip design, different morphogenic steps of angiogenesis including endothelial proliferation, migration & invasion, vascular sprout formation and recruitment of mural cells as well as functional aspects including perfusion and permeability were examined under various pharmacological and genetic manipulations. The results showed that Sema4D facilitates the interaction between endothelial cells and SHED and promotes the recruitment of SHED as mural cells in vascular stabilization. Our results further demonstrated that Sema4D exerts these effects by acting on endothelial-plexin-B1 by inducing expression of platelet-derived growth factor (PDGF)-BB, which is a major mural cell recruitment factor.

SEMA4D/PlexinB1 promotes AML progression via activation of PI3K/Akt signaling

Background

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. SEMA4D is a 150 kDa transmembrane protein that belongs to the IV class of the subfamily of semaphorin family. Previous studies have reported that SEMA4D is a multifunctional target in many solid tumors, involving multiple physiological systems, and there are emerging therapies to target these pathways. The role of SEMA4D in AML has not yet been explored.

Methods

The SEMA4D expression prolile, clinical data and potential prognostic analysis were acquired via the cBioPortal and GEPIA databases. SEMA4D expression was measured using real-time quantitative PCR and western blot. Cell counting kit-8 (CCK8) and flow cytometry were used to evaluate the malignant biological characteristics.

Results

We observed that SEMA4D was increased in AML patients and correlated with risk stratification and prognosis. Moreover, SEMA4D promotes the proliferation and inhibits apoptosis of AML cells by binding to its receptor, PlexinB1, and reduces the sensitivity of AML cells to daunorubicin. In addition, SEMA4D/PlexinB1 promotes the proliferation and survival of AML cells by activating the PI3K/Akt signaling pathway. VX15/2503, an anti-SEMA4D antibody, can inhibit the proliferation of AML cells in xenograft mouse models, thereby inhibiting the development of AML.

Conclusion

SEMA4D will serve as a unique predictive biomarker and a possible therapeutic target in AML.

Locally Secreted Semaphorin 4D Is Engaged in Both Pathogenic Bone Resorption and Retarded Bone Regeneration in a Ligature-Induced Mouse Model of Periodontitis

It is well known that Semaphorin 4D (Sema4D) inhibits IGF-1-mediated osteogenesis by binding with PlexinB1 expressed on osteoblasts. However, its elevated level in the gingival crevice fluid of periodontitis patients and the broader scope of its activities in the context of potential upregulation of osteoclast-mediated periodontal bone-resorption suggest the need for further investigation of this multifaceted molecule. In short, the pathophysiological role of Sema4D in periodontitis requires further study. Accordingly, attachment of the ligature to the maxillary molar of mice for 7 days induced alveolar bone-resorption accompanied by locally elevated, soluble Sema4D (sSema4D), TNF-α and RANKL. Removal of the ligature induced spontaneous bone regeneration during the following 14 days, which was significantly promoted by anti-Sema4D-mAb administration. Anti-Sema4D-mAb was also suppressed in vitro osteoclastogenesis and pit formation by RANKL-stimulated BMMCs. While anti-Sema4D-mAb downmodulated the bone-resorption induced in mouse periodontitis, it neither affected local production of TNF-α and RANKL nor systemic skeletal bone remodeling. RANKL-induced osteoclastogenesis and resorptive activity were also suppressed by blocking of CD72, but not Plexin B2, suggesting that sSema4D released by osteoclasts promotes osteoclastogenesis via ligation to CD72 receptor. Overall, our data indicated that ssSema4D released by osteoclasts may play a dual function by decreasing bone formation, while upregulating bone-resorption.

Soluble Sema4D Level Is Positively Correlated with Sema4D Expression in PBMCs and Peripheral Blast Number in Acute Leukemia

Semaphorin 4D (Sema4D) is highly expressed in various cancers and leukemia. It is involved in the development of acute leukemia. A high level of soluble Sema4D is also present in the plasma of acute leukemia patients. However, it remains unknown whether Sema4D is associated with the clinical characteristics of acute leukemia. In this study, Sema4D expression was examined in peripheral blood mononuclear cells (PBMCs) and bone marrow mononuclear cells (BMMCs) of patients with acute leukemia, and it was highly expressed in the PBMCs of B-acute lymphoblastic leukemia (ALL), T-ALL, and acute myeloid leukemia (AML) patients and in the BMMCs of B-ALL and AML patients but not in the BMMCs of T-ALL patients. Sema4D expression was higher in the PBMCs of T-ALL patients than in the PBMCs of B-ALL or AML patients. In addition, Sema4D expression in BMMCs was reduced in B-ALL patients during the chemotherapy process. It was lower in remission patients than in newly diagnosed and patients without remission. In acute leukemia, soluble Sema4D level in serum is positively correlated with Sema4D expression in PBMCs, leukocyte number, and peripheral blast number. Those results suggest that the levels of Sema4D and its soluble form are associated with acute leukemia development and may be regarded as a potential biomarker in pediatric acute leukemia.

γδ T cell costimulatory ligands in antitumor immunity

Antitumor immunity relies on the ability of T cells to recognize and kill tumor targets. γδ T cells are a specialized subset of T cells that predominantly localizes to non-lymphoid tissue such as the skin, gut, and lung where they are actively involved in tumor immunosurveillance. γδ T cells respond to self-stress ligands that are increased on many tumor cells, and these interactions provide costimulatory signals that promote their activation and cytotoxicity. This review will cover costimulatory molecules that are known to be critical for the function of γδ T cells with a specific focus on mouse dendritic epidermal T cells (DETC). DETC are a prototypic tissue-resident γδ T cell population with known roles in antitumor immunity and are therefore useful for identifying mechanisms that may control activation of other γδ T cell subsets within non-lymphoid tissues. This review concludes with a brief discussion on how γδ T cell costimulatory molecules can be targeted for improved cancer immunotherapy.

Tenofovir Modulates Semaphorin 4D Signaling and Regulates Bone Homeostasis, Which Can Be Counteracted by Dipyridamole and Adenosine A2A Receptor

Semaphorin 4D (Sema4D) is a neurotrophin that is secreted by osteoclasts and binds to its receptor PlexinB1 on osteoblasts to inhibit their differentiation and function. Adenosine A2A activation inhibits osteoclast Sema4D-mediated secretion, diminishes inflammatory osteolysis and prevents bone loss following tenofovir (one of the most used antivirals in HIV). Therefore, tenofovir might activate Sema4D signaling to alter bone turnover. Female C57Bl/6/A2AKO mice were ovariectomized and treated with saline (control), tenofovir 75 mg/Kg/day, dipyridamole 25 mg/Kg/day or a combination for 5 weeks and long bones were prepared for histology. Primary murine-induced osteoclast/osteoblast were challenged with tenofovir/dipyridamole 1 μM each, and the expression of Sema4D/PlexinB1, RhoA/ROCK/IGF1R was studied by RT-PCR, Western blot and immunostaining. In vivo tenofovir showed an increased expression of Sema4D when compared to control mice, and dipyridamole reverted the expression in an A2A-dependent manner. In vitro, tenofovir increases Sema4D expression and secretion in osteoclast precursors, and pre-treatment with dipyridamole reverted this effect. pRhoA and ROCK1 activation were increased and IRS1/IGF1R expression was diminished by tenofovir in the Vav3/ARHGAP18 mechanism in osteoblast precursors and reverted by dipyridamole in an A2A-dependent manner. This suggests that tenofovir increases bone loss by activation of Sema4D/PlexinB1 signaling, which inhibits osteoblast differentiation. Agents that increase local adenosine concentrations, such as dipyridamole, might prevent bone loss following the inhibition of this pathway.

The emerging roles of semaphorin4D/CD100 in immunological diseases

In vertebrates, the semaphorin family of proteins is composed of 21 members that are divided into five subfamilies, i.e. classes 3 to 7. Semaphorins play crucial roles in regulating multiple biological processes, such as neural remodeling, tissue regeneration, cancer progression, and, especially, in immunological regulation. Semaphorin 4D (SEMA4D), also known as CD100, is an important member of the semaphorin family and was first characterized as a lymphocyte-specific marker. SEMA4D has diverse effects on immunologic processes, including immune cell proliferation, differentiation, activation, and migration, through binding to its specific membrane receptors CD72, PLXNB1, and PLXNB2. Furthermore, SEMA4D and its underlying signaling have been increasingly linked with several immunological diseases. This review focuses on the significant immunoregulatory role of SEMA4D and the associated underlying mechanisms, as well as the potential application of SEMA4D as a diagnostic marker and therapeutic target for the treatment of immunological diseases.

A heterozygous germline CD100 mutation in a family with primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease without clear etiology or effective treatment. Genetic factors contribute to PSC pathogenesis, but so far, no causative mutation has been found. We performed whole-exome sequencing in a family with autosomal dominant inheritance of PSC and identified a heterozygous germline missense mutation in SEMA4D, encoding a K849T variant of CD100. The mutation was located in an evolutionarily conserved, unstructured cytosolic region of CD100 affecting downstream signaling. It was found to alter the function of CD100-expressing cells with a bias toward the T cell compartment that caused increased proliferation and impaired interferon-γ (IFN-γ) production after stimulation. Homologous mutation knock-in mice developed similar IFN-γ impairment in T cells and were more prone to develop severe cholangitis when exposed to 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet. Transfer of wild-type T cells to knock-in mice before and during DDC exposure attenuated cholangitis. Taken together, we identified an inherited mutation in the disordered cytosolic region of CD100 resulting in T cell functional defects. Our findings suggest a protective role for T cells in PSC that might be used therapeutically.

The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical Diseases of Acute Inflammation

Semaphorins are a group of proteins that have been studied extensively for their critical function in neuronal development. They have been shown to regulate airway development, tumorigenesis, autoimmune diseases, and the adaptive immune response. Notably, emerging literature describes the role of immunoregulatory semaphorins and their receptors, plexins and neuropilins, as modulators of innate immunity and diseases defined by acute injury to the kidneys, abdomen, heart and lungs. In this review we discuss the pathogenic functions of semaphorins in clinical conditions of acute inflammation, including sepsis and acute lung injury, with a focus on regulation of the innate immune response as well as potential future therapeutic targeting.

Semaphorin 4D is a potential biomarker in pediatric leukemia and promotes leukemogenesis by activating PI3K/AKT and ERK signaling pathways

Semaphorin 4D (Sema4D) is highly expressed in a variety of tumors and is associated with high invasion, poor prognosis and poor therapeutic response. However, the expression and role of Sema4D in leukemia remains unclear. The present study investigated the expression of Sema4D in pediatric leukemia and its effects in leukemia cells. The results demonstrated that Sema4D protein was highly expressed in peripheral blood mononuclear cells of patients with pediatric leukemia, and high levels of soluble Sema4D were also observed in the plasma of these patients. Sema4D knockdown induced cell cycle arrest in G₀/G₁ phase, inhibited proliferation and promoted apoptosis in BALL‑1 cells, while Sema4D overexpression exhibited the opposite effect. In Jurkat cells, Sema4D knockdown inhibited proliferation and promoted apoptosis, while Sema4D overexpression decreased the abundance of the cells in the G₀/G₁ phase of the cell cycle and promoted proliferation. Sema4D overexpression also increased the migratory capacity of Jurkat cells and the invasive capacity of BALL‑1 cells. The phosphorylation level of PI3K was decreased in both Sema4D knocked‑down Jurkat and BALL‑1 cells, and the phosphorylation level of ERK was decreased in Sema4D knocked‑down BALL‑1 cells. The phosphorylation levels of PI3K, ERK and AKT were elevated in patients with pediatric leukemia, and were correlated to the increased Sema4D expression. Sema4D overexpression was associated with a shorter overall survival in patients with acute myeloid leukemia. Overall, the results of the present study indicated that Sema4D serves an important role in leukemia development by activating PI3K/AKT and ERK signaling, and it may be used as a potential target for the diagnosis and treatment of leukemia.

Semaphorin 4D is a potential biomarker in pediatric leukemia and promotes leukemogenesis by activating PI3K/AKT and ERK signaling pathways

Semaphorin 4D (Sema4D) is highly expressed in a variety of tumors and is associated with high invasion, poor prognosis and poor therapeutic response. However, the expression and role of Sema4D in leukemia remains unclear. The present study investigated the expression of Sema4D in pediatric leukemia and its effects in leukemia cells. The results demonstrated that Sema4D protein was highly expressed in peripheral blood mononuclear cells of patients with pediatric leukemia, and high levels of soluble Sema4D were also observed in the plasma of these patients. Sema4D knockdown induced cell cycle arrest in G₀/G₁ phase, inhibited proliferation and promoted apoptosis in BALL-1 cells, while Sema4D overexpression exhibited the opposite effect. In Jurkat cells, Sema4D knockdown inhibited proliferation and promoted apoptosis, while Sema4D overexpression decreased the abundance of the cells in the G₀/G₁ phase of the cell cycle and promoted proliferation. Sema4D overexpression also increased the migratory capacity of Jurkat cells and the invasive capacity of BALL-1 cells. The phosphorylation level of PI3K was decreased in both Sema4D knocked-down Jurkat and BALL-1 cells, and the phosphorylation level of ERK was decreased in Sema4D knocked-down BALL-1 cells. The phosphorylation levels of PI3K, ERK and AKT were elevated in patients with pediatric leukemia, and were correlated to the increased Sema4D expression. Sema4D overexpression was associated with a shorter overall survival in patients with acute myeloid leukemia. Overall, the results of the present study indicated that Sema4D serves an important role in leukemia development by activating PI3K/AKT and ERK signaling, and it may be used as a potential target for the diagnosis and treatment of leukemia.

Imbalance Between Soluble and Membrane-Bound CD100 Regulates Monocytes Activity in Hepatitis B Virus-Associated Acute-on-Chronic Liver Failure

CD100 is an important immune semaphorin that is a secreted and membrane bound protein involved in infectious diseases. However, CD100 expression profile and the regulation to innate immune system in hepatitis B virus (HBV)-associated acute-on-chronic liver failure (ACLF) was not previously reported. The aim of this study was to investigate CD100 level and modulatory function of CD100 to CD14⁺ monocytes in HBV-ACLF patients. Plasma-soluble CD100 (sCD100) level and membrane-bound CD100 (mCD100) expression on peripheral CD14⁺ monocytes was analyzed in HBV-ACLF patients. CD14⁺ monocytes-induced cytotoxicity and CD14⁺ monocytes-mediated T cell activation in response to CD100 stimulation was also assessed in direct and indirect contact coculture culture systems. HBV-ACLF patients had lower plasma sCD100 and higher mCD100 level on CD14⁺ monocytes compared with asymptomatic HBV carriers, chronic hepatitis B patients, and controls. CD14⁺ monocytes from HBV-ACLF patients induced limited target Huh7.5 cell death and secreted less interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and granzyme B in both direct and indirect contact coculture systems compared with controls. Recombinant sCD100 not only enhanced CD14⁺ monocytes-mediated Huh7.5 cell death and granzyme B secretion, but it also elevated CD14⁺ monocytes-induced IFN-γ/interleukin-17 production by CD4⁺ T cells as well as IFN-γ/TNF-α secretion by CD8⁺ T cells in HBV-ACLF patients. The current data indicated that severe inflammation induced sCD100/mCD100 imbalance to inactivate CD14⁺ monocytes response, which might be beneficial for the survival of HBV-ACLF patients.

CD100 modulates cytotoxicity of CD8+ T cells in patients with acute myocardial infarction

BACKGROUND

CD100 is an immune semaphorin family member that highly expressed on T cells, which take part in the development of acute myocardial infarction (AMI). Matrix metalloproteinases (MMPs) are important mediators for membrane-bound CD100 (mCD100) shedding from T cells to generate soluble CD100 (sCD100), which has immunoregulatory effect on T cells. The aim of this study was to investigate modulatory role of CD100 on CD8⁺ T cell activity in AMI patients.

METHODS

Peripheral sCD100 and MMP-2 level, as well as mCD100 level on T cells was assessed in patients with stable angina pectoris (SAP), unstable angina pectoris (UAP), and AMI. The regulatory function of MMP-2 on mCD100 shedding, sCD100 formation, and cytotoxicity of CD8⁺ T cells was analyzed in direct and indirect contact co-culture system.

RESULTS

AMI patients had higher peripheral sCD100 and lower mCD100 expression on CD8⁺ T cells in comparison with SAP, UAP, and controls. CD8⁺ T cells in AMI patients showed elevated direct cytotoxicity, enhanced cytokine production, and increased perforin/granzyme B secretion. Recombinant sCD100 stimulation promoted cytolytic function of CD8⁺ T cells in controls and AMI patients. Furthermore, AMI patients also had elevated circulating MMP-2 level. Recombinant MMP-2 stimulation induced mCD100 shedding from CD8⁺ T cells and sCD100 generation, resulting in enhancement of CD8⁺ T cell cytotoxicity in AMI patients.

CONCLUSION

Up-regulation of MMP-2 might contribute to elevation of mCD100 shedding and sCD100 formation, leading to increased cytotoxicity CD8⁺ T cells in AMI patients.

Neutrophil-Derived Semaphorin 4D Induces Inflammatory Cytokine Production of Endothelial Cells via Different Plexin Receptors in Kawasaki Disease

Inflammation of endothelial cells (ECs) plays an important role in the pathogenesis of coronary artery lesions (CALs) in Kawasaki disease (KD). Semaphorin 4D (Sema4D) is the first semaphorin shown to have immunoregulatory functions by interacting with its receptors—plexin Bs. Recently, Sema4D has been reported to exert a proinflammatory effect on the endothelium and to be involved in cardiovascular disease. However, the role of Sema4D in KD remains unknown. This study was aimed at revealing the change of soluble Sema4D (sSema4D) in the serum of patients with KD and the effect of the sSema4D-plexin axis on the production of proinflammatory cytokines from human coronary endothelial cells (HCAECs) stimulated with sera from KD patients. Our results showed that serum sSema4D levels were specifically elevated in KD patients, especially in those with CALs, and correlated positively with disease severity and serum concentrations of interleukin- (IL-) 1β, IL-6, and IL-8. The disintegrin and metalloproteinase domain 17- (AMAM17-) mediated Sema4D shedding from neutrophils contributed to the elevation of sSema4D in the serum of KD patients. Furthermore, we found that Sema4D induced IL-1β production of HCAECs via plexin B2, whereas it promoted IL-6 and IL-8 production via plexin B1. Moreover, the expression of both plexin B1 and plexin B2 was upregulated in HCAECs treated with KD sera, and silencing of the two plexin receptors suppressed the overexpression of IL-1β, IL-6, and IL-8 in KD serum-treated HCAECs. Thus, our findings indicated that sSema4D released from neutrophils participates in the pathogenesis of KD-CALs by promoting inflammatory cytokine production of ECs via both plexin B1 and plexin B2, and Sema4D may be a novel predictor for KD-CALs and a candidate therapeutic target for anti-inflammatory strategies of KD.

Semaphorin 4D Induces an Imbalance of Th17/Treg Cells by Activating the Aryl Hydrocarbon Receptor in Ankylosing Spondylitis

Objectives

Semaphorin 4D (Sema4D) is constitutively expressed on T cells and osteoclasts, and regulates T cell proliferation and bone remodeling. In addition, several studies have shown that Sema4D is involved in the pathogenesis of autoimmunity. We undertook this study to investigate the mechanism by which Sema4D affects the pathogenic progress of ankylosing spondylitis (AS).

Methods

Soluble Sema4D (sSema4D) levels in serum were analyzed by enzyme-linked immunosorbent assay. The cell surface levels and transcripts of Sema4D were evaluated in CD4 + and CD19 + cells from the AS patients and healthy individuals. The mRNA expression levels were assessed by quantitative polymerase chain reaction (qPCR). The proportions of Treg cells and IL-17-producing T-cells (Th17 cells) differentiated from CD4 + T cells were analyzed by flow cytometric analysis. The aryl hydrocarbon receptor (AhR) agonistic effect of Sema4D was detected by analyzing the activation of downstream signaling pathways and target genes using Luciferase and EROD assay.

Results

Levels of sSema4D were elevated in both serum from AS patients, and clinical features markers were correlated with serum sSema4D levels. Sema4D facilitated CD4 + T cells proliferation and Th17 cells differentiation and inhibited Treg cells differentiation by enhancing RORγt expression and reducing Foxp3 expression, with increasing expression and secretion of IL-17 and IL-22. It induced the expression and activity of AhR target gene CYP1A1 and XRE reporter activity via interaction with CD72.

Conclusion

These findings indicate that Sema4D as a potent activator of T cells in the immune response contributes to the inflammation of AS by inducing imbalance in Th17 and Treg cell populations in an AhR-dependent manner, suggesting it is a crucial participant in AS pathogenesis.

Sema4D Aggravated LPS-Induced Injury via Activation of the MAPK Signaling Pathway in ATDC5 Chondrocytes

Osteoarthritis (OA) is the most common chronic degenerative joint disease, and it remains the main cause of chronic disability in elderly individuals. Sema4D (semaphorin 4D) is involved in the immune system and related to bone injury, osteoporosis, osteoblast differentiation, and rheumatoid arthritis. However, the role of Sema4D in OA remains unclear. Hence, the LPS-stimulated chondrocyte cell injury model was constructed in this study to investigate the role of Sema4D in OA development. The results showed that Sema4D was increased in LPS-treated ATDC5 cells, and the knockdown of Sema4D suppressed the decline of cell viability, the increase of cell apoptosis, and the increase of IL-6, IL-1β, and TNF-α secretion in ATDC5 cells induced by LPS. Meanwhile, Sema4D overexpression aggravated the cell injury triggered by LPS, and inhibiting Plexin B1 partly abolished the effect of Sema4D overexpression on LPS-induced chondrocyte injury. Furthermore, silencing of Sema4D blocked the activation of the MAPK pathway in LPS-stimulated ATDC5 cells. Enhanced Sema4D promoted the activation of the MAPK pathway in LPS-stimulated ATDC5 cells. What is more, inhibiting the MAPK signaling pathway abolished the promoting effect of Sema4D overexpression on LPS-induced chondrocyte injury. Therefore, our study suggested that the knockdown of Sema4D protects ATDC5 cells against LPS-induced injury through inactivation of the MAPK signaling pathway via interacting with Plexin B1.

Insufficient CD100 shedding contributes to suppression of CD8+ T-cell activity in non-small cell lung cancer

CD100 is an immune semaphorin constitutively expressed on T-cells. Matrix metalloproteinase (MMP) is an important mediator of membrane-bound CD100 (mCD100) cleavage to generate soluble CD100 (sCD100), which has immunoregulatory activity in immune cell responses. The aim of the study was to investigate the level and role of sCD100 and mCD100 in modulating CD8⁺ T-cell function in non-small cell lung cancer (NSCLC). sCD100 and MMP-14 levels in the serum and bronchoalveolar lavage fluid (BALF), and mCD100 expression on peripheral and lung-resident CD8⁺ T-cells were analysed in NSCLC patients. The ability to induce sCD100 and the effect of MMP-14 on mCD100 shedding for the regulation of non-cytolytic and cytolytic functions of CD8⁺ T-cells were also analysed in direct and indirect contact co-culture systems. NSCLC patients had lower serum sCD100 and higher mCD100 levels on CD8⁺ T-cells compared with healthy controls. BALF from the tumour site also had decreased sCD100 and increased mCD100 on CD8⁺ T-cells compared with the non-tumour site. Recombinant CD100 stimulation enhanced non-cytolytic and cytolytic functions of CD8⁺ T-cells from NSCLC patients, whereas blockade of CD100 receptor CD72 attenuated CD8⁺ T-cell activity. NSCLC patients had lower MMP-14 in the serum and in BALF from the tumour site. Recombinant MMP-14 mediated mCD100 shedding from CD8⁺ T-cell membrane, and led to promotion of CD8⁺ T-cell response in NSCLC patients. Overall, decreased MMP-14 resulted in insufficient CD100 shedding, leading to suppression of peripheral and lung-resident CD8⁺ T-cell activity in NSCLC.

Negative regulation of dendritic cell activation in psoriasis mediated via CD100-plexin-B2

Psoriasis is a chronic inflammatory skin disease in which dendritic cells (DCs) play a pivotal role by inducing Th1/Th17 immune responses; however, the regulation of DC activation in psoriasis remains largely unknown. Previously we found that the level of soluble CD100 was increased in sera of psoriasis patients, and CD100 promoted the activation of inflammasome in keratinocytes. In the present study, CD100 knockout mice were utilized for generation of imiquimod (IMQ)-induced psoriatic dermatitis, with the result that skin inflammation in the early, but not late, phase of the psoriatic dermatitis was significantly exacerbated compared to that in wild-type controls. This was attributed mainly to the deficiency of CD100 in hematopoietic cells. Bone marrow-derived DCs, but not T cells or keratinocytes, from CD100 knockout mice produced significantly increased levels of IL-1β, IL-36, and IL-23 upon stimulation with IMQ in a plexin-B2-dependent manner. Moreover, the surface level of plexin-B2 on DCs of psoriasis patients was lower than that of healthy individuals, and CD100 attenuated IMQ-induced production of IL-1β and IL-36 from monocyte-derived DCs of psoriasis patients. Our results uncovered a negative regulatory mechanism for DCs activation in psoriasis, which was mediated via CD100-plexin-B2 in a cell type- and receptor-specific manner. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Inhibition of Sema4D/PlexinB1 signaling alleviates vascular dysfunction in diabetic retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and leads to blindness. Anti‐VEGF is a primary treatment for DR. Its therapeutic effect is limited in non‐ or poor responders despite frequent injections. By performing a comprehensive analysis of the semaphorins family, we identified the increased expression of Sema4D during oxygen‐induced retinopathy (OIR) and streptozotocin (STZ)‐induced retinopathy. The levels of soluble Sema4D (sSema4D) were significantly increased in the aqueous fluid of DR patients and correlated negatively with the success of anti‐VEGF therapy during clinical follow‐up. We found that Sema4D/PlexinB1 induced endothelial cell dysfunction via mDIA1, which was mediated through Src‐dependent VE‐cadherin dysfunction. Furthermore, genetic disruption of Sema4D/PlexinB1 or intravitreal injection of anti‐Sema4D antibody reduced pericyte loss and vascular leakage in STZ model as well as alleviated neovascularization in OIR model. Moreover, anti‐Sema4D had a therapeutic advantage over anti‐VEGF on pericyte dysfunction. Anti‐Sema4D and anti‐VEGF also conferred a synergistic therapeutic effect in two DR models. Thus, this study indicates an alternative therapeutic strategy with anti‐Sema4D to complement or improve the current treatment of DR.

MMP2/MMP9-mediated CD100 shedding is crucial for inducing intrahepatic anti-HBV CD8 T cell responses and HBV clearance

BACKGROUND & AIMS

CD100 is constitutively expressed on T cells and can be cleaved from the cell surface by matrix metalloproteases (MMPs) to become soluble CD100 (sCD100). Both membrane-bound CD100 (mCD100) and sCD100 have important immune regulatory functions that promote immune cell activation and responses. This study investigated the expression and role of mCD100 and sCD100 in regulating antiviral immune responses during HBV infection.

METHODS

mCD100 expression on T cells, sCD100 levels in the serum, and MMP expression in the liver and serum were analysed in patients with chronic HBV (CHB) and in HBV-replicating mice. The ability of sCD100 to mediate antigen-presenting cell maturation, HBV-specific T cell activation, and HBV clearance were analysed in HBV-replicating mice and patients with CHB.

RESULTS

Patients with CHB had higher mCD100 expression on T cells and lower serum sCD100 levels compared with healthy controls. Therapeutic sCD100 treatment resulted in the activation of DCs and liver sinusoidal endothelial cells, enhanced HBV-specific CD8 T cell responses, and accelerated HBV clearance, whereas blockade of its receptor CD72 attenuated the intrahepatic anti-HBV CD8 T cell response. Together with MMP9, MMP2 mediated mCD100 shedding from the T cell surface. Patients with CHB had significantly lower serum MMP2 levels, which positively correlated with serum sCD100 levels, compared with healthy controls. Inhibition of MMP2/9 activity resulted in an attenuated anti-HBV T cell response and delayed HBV clearance in mice.

CONCLUSIONS

MMP2/9-mediated sCD100 release has an important role in regulating intrahepatic anti-HBV CD8 T cell responses, thus mediating subsequent viral clearance during HBV infection.

LAY SUMMARY

Chronic hepatitis B virus (HBV) infection is a major public health problem worldwide. The clearance of HBV relies largely on an effective T cell immune response, which usually becomes dysregulated in chronic HBV infection. Our study provides a new mechanism to elucidate HBV persistence and a new target for developing immunotherapy strategies in patients chronically infected with HBV.

CD100 Effects in Macrophages and Its Roles in Atherosclerosis

CD100 or Sema4D is a protein from the semaphorin family with important roles in the vascular, nervous and immune systems. It may be found as a membrane bound dimer or as a soluble molecule originated by proteolytic cleavage. Produced by the majority of hematopoietic cells including B and T lymphocytes, natural killer and myeloid cells, as well as endothelial cells, CD100 exerts its actions by binding to different receptors depending on the cell type and on the organism. Cell-to-cell adhesion, angiogenesis, phagocytosis, T cell priming, and antibody production are examples of the many functions of this molecule. Of note, high CD100 serum levels has been found in inflammatory as well as in infectious diseases, but the roles of the protein in the pathogenesis of these diseases has still to be clarified. Macrophages are highly heterogeneous cells present in almost all tissues, which may change their functions in response to microenvironmental conditions. They are key players in the innate and adaptive immune responses and have decisive roles in sterile conditions but also in several diseases such as atherosclerosis, autoimmunity, tumorigenesis, and antitumor responses, among others. Although it is known that macrophages express CD100 and its receptors, few studies have focused on the role of this semaphorin in this cell type or in macrophage-associated diseases. The aim of this review is to critically revise the available data about CD100 and atherosclerosis, with special emphasis on its roles in macrophages and monocytes. We will also describe the few available data on treatments with anti-CD100 antibodies in different diseases. We hope that this review stimulates future studies on the effects of such an important molecule in a cell type with decisive roles in inflammatory diseases such as atherosclerosis.

CD72/CD100 and PD-1/PD-L1 markers are increased on T and B cells in HIV-1+ viremic individuals, and CD72/CD100 axis is correlated with T-cell exhaustion

In our work, we analyzed the role of the CD100/CD72 and PD-1/PD-L1 axes in immune response dysfunction in human immunodeficiency virus (HIV)-1 infection in which high expressions of PD-1 and PD-L1 were associated with an immunosuppressive state via limitation of the HIV-1-specific T-cell responses. CD100 was demonstrated to play a relevant role in immune responses in various pathological processes and may be responsible for immune dysregulation during HIV-1 infection. We investigated the function of CD72/CD100, and PD-1/PDL-1 axes on T and B cells in HIV-infected individuals and in healthy individuals. We analyzed the frequencies and fluorescence intensities of these four markers on CD4+, CD8+ T and B cells. Marker expressions were increased during active HIV-1 infection. CD100 frequency on T cells was positively associated with the expression of PD-1 and PD-L1 on T cells from HIV-infected treatment-naïve individuals. In addition, the frequency of CD72-expressing T cells was associated with interferon gamma (IFN-γ) production in HIV-infected treatment-naïve individuals. Our data suggest that the CD72/CD100 and PD-1/PD-L1 axes may jointly participate in dysregulation of immunity during HIV-1 infection and could partially explain the immune systems' hyper-activation and exhaustion.

Semaphorin 4D levels in heart failure patients: a potential novel biomarker of acute heart failure?

AIMS

Semaphorin 4D (Sema4D) is expressed on platelets and T-cells and known to be involved in inflammation. The aims of this study include comparing Sema4D and N terminal pro brain natriuretic peptide (NT-proBNP) serum levels in heart failure (HF) patients to a control group, evaluating the correlation between Sema4D and NT-proBNP levels, and assessing Sema4D serum levels in HF patients during acute exacerbation and remission.

METHODS AND RESULTS

Forty-five patients diagnosed with HF (based on echocardiographic findings, positive NT-proBNP levels, and normal C-reactive protein) and 11 healthy controls (declaring no chronic diseases or medications) comprised the study population. Demographic, clinical, laboratory, and echocardiographic data were used to create the study database. NT-proBNP and Sema4D serum samples were taken on admission and discharge. NT-proBNP levels were significantly higher in the HF group than in controls (P < 0.001). Sema4D levels were significantly higher in HF patients than in healthy controls (2143.04 ± 1253 vs. 762.18 ± 581.6 ng/mL, P < 0.001, respectively). Using linear regression, a higher creatinine level was found to predict both higher levels of NT-proBNP and Sema4D (P = 0.05 and P < 0.014, respectively), while a reduced ejection fraction was found to predict higher NT-proBNP levels only (P < 0.001 and P = 0.87, respectively). Average Sema4D levels reduced significantly at remission (3534.94 ± 1650.55 vs. 2455.67 ± 1424, P = 0.03), while mean NT-proBNP levels did not change significantly.

CONCLUSIONS

Sema4D levels in HF patients' serum are significantly higher than in healthy controls. Clinical improvement caused rapid reduction in Sema4D levels, possibly reflecting the inflammatory aspect of HF. These findings might suggest that Sema4D can be used as a diagnostic biomarker of acute HF. Further studies of Sema4D and HF are warranted.

SEMA4D-heparin Complexes Immobilized on Titanium Surfaces Have Anticoagulant, Cell-Migration-Promoting, and Immunoregulatory Effects

Soluble semaphorin 4D (SEMA4D) is a 120 kDa transmembrane protein, which belongs to the semaphorin family of axon guidance molecules that act primarily axonal repellents. SEMA4D elicits its migration-promoting and immunomodulatory effects through activation of PLXNB1 and CD72, respectively. In this study, SEMA4D combined with heparin were adsorbed onto cationic surfaces. The biocompatibility evaluation results indicated that the SEMA4D-heparin-modified surfaces displayed less platelet adhesion and activation, prolonged activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) and reduced fibrinogen gamma chain (FGG) exposure and fibrinogen adhesion. Additionally, endothelial cells (ECs) showed improved adhesion density and proliferation activity on the SEMA4D-heparin-modified surfaces. Chemotactic and haptotaxis assays indicated a highly guided migration for ECs on the modified surfaces. The immunological tests revealed that the SEMA4D-heparin complexes had a positive immunomodulatory effect on macrophages and promoted macrophages polarization into M2 phenotypes. Overall, the results suggested that the SEMA4D-heparin complexes can be a potential therapeutic agent to promote tissue healing and accelerate in situ endothelialization with minimal side effects and positive immunomodulatory effect.

Activation of stimulator of interferon genes (STING) induces ADAM17-mediated shedding of the immune semaphorin SEMA4D

Stimulator of interferon genes (STING) is an endoplasmic reticulum-resident membrane protein that mediates cytosolic pathogen DNA-induced innate immunity and inflammatory responses in host defenses. STING is activated by cyclic di-nucleotides and is then translocated to the Golgi apparatus, an event that triggers STING assembly with the downstream enzyme TANK-binding kinase 1 (TBK1). This assembly leads to the phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3), which in turn induces expression of type-I interferon (IFN) and chemokine genes. STING also mediates inflammatory responses independently of IRF3, but these molecular pathways are largely unexplored. Here, we analyzed the RAW264.7 macrophage secretome to comprehensively identify proinflammatory factors released into the extracellular medium upon STING activation. In total, we identified 1299 proteins in macrophage culture supernatants, of which 23 were significantly increased after STING activation. These proteins included IRF3-dependent cytokines, as well as previously unknown targets of STING, such as the immune semaphorin SEMA4D/CD100, which possesses proinflammatory cytokine-like activities. Unlike for canonical cytokines, the expression of the SEMA4D gene was not up-regulated. Instead, upon STING activation, membrane-bound SEMA4D was cleaved into a soluble form, suggesting the presence of a post-translational shedding machinery. Importantly, the SEMA4D shedding was blocked by TMI-1, an inhibitor of the sheddase ADAM metallopeptidase domain 17 (ADAM17) but not by the TBK1 inhibitor BX795. These results suggest that STING activates ADAM17 and that this activation produces soluble proinflammatory SEMA4D independently of the TBK1/IRF3-mediated transcriptional pathway.

Endogenous Regulators of the Immune System (sCD100, Malonic Dialdehyde, and Arginase)

Tissue damage in various diseases, hypoxic conditions, and some pathologies are associated with production of endogenous factors such as the soluble form of the surface receptor CD100, malonic dialdehyde, and arginase and their release into circulation. These factors modulate functional state of lymphocytes in the immune system: potentiate activation of B lymphocytes, activate synthesis and secretion of IL-25 and IL-17 cytokines, and suppress proliferative activity of T lymphocytes, thus modulating immunological reactivity of the organism. Reactions of innate and adaptive immunity develop against the background of changed immunological reactivity, which should be taken into account in the development of pathogenetically substantiated therapy.

Semaphorin 4D from CD15+ Granulocytes via ADAM10-Induced Cleavage Contributes to Antibody Production in Bullous Pemphigoid

Autoreactive B-cell activation and antibody production are critical events for the development of bullous pemphigoid (BP). However, the mechanism that is involved in the modulation of B-cell activation and autoantibody generation has not been fully understood. Semaphorin 4D (Sema4D, or CD100) plays important roles in immune regulation related to B cells, but its implications in BP remain obscure. The aim of our study was to characterize Sema4D and the underlying mechanism contributing to the autoimmune features of BP. We found that soluble Sema4D (sSema4D) levels were elevated and correlated with disease severity and activity in serum and blister fluids from patients with BP. Additionally, Sema4D-expressing cells accumulated in subepidermal blisters of BP lesions. In patient-derived peripheral blood mononuclear cells, by promoting the differentiation of B cells into plasmablasts, sSema4D boosted anti-BP180/anti-BP230 antibody production in a time- and dose-dependent manner, which may be attributed to CD72-mediated activation of Akt/NF-κB phosphorylated (p-)65/ERK cascades in B cells. We determined that a disintegrin and metalloproteinase 10 is a proteolytic enzyme for the cleavage of sSema4D from CD15+ granulocytes instead of T cells, which is probably responsible for the high concentration of sSema4D in BP blister fluid and serum. These findings suggest that Sema4D is a crucial participant in BP pathogenesis.

Semaphorin 4D in human head and neck cancer tissue and peripheral blood: A dense fibrotic peri-tumoral stromal phenotype

The search for stromal biomarkers in carcinoma patients is a challenge in the field. Semaphorin 4D (Sema4D), known for its various developmental, physiological and pathological effects, plays a role in pro and anti-inflammatory responses. It is expressed in many epithelial tumors including head and neck squamous cell carcinoma (HNSCC). Recently, we found that HNSCC-associated Sema4D modulates an immune-suppressive, tumor-permissible environment by inducing the expansion of myeloid derived suppressor cells. The purpose of this study was to determine the value of Sema4D as a biomarker for the peri-tumoral stromal phenotype in human HNSCC. Our data showed Sema4D^+ve/high tumor cells in 34% of the studied cohort with positive correlation to Stage III (p=0.0001). Sema4D^+ve/high tumor cells correlated directly with dense fibrotic peri-tumoral stroma (p=0.0001) and inversely with infiltrate of Sema4D^+ve/high tumor-associated inflammatory cells (TAIs) (p=0.01). Most of the Sema4D^+ve/high TAIs were co-positive for the macrophage biomarker CD163. Knockdown of Sema4D in WSU-HN6 cells inhibited collagen production by fibroblasts, and decreased activated TGF-β1 levels in culture medium of HNSCC cell lines. In a stratification model of HNSCC using combined Sema4D and the programmed death ligand 1 (PDL-1), Sema4D^+ve/high tumor cells represented a phenotype distinct from the PDL-1 positive tumors. Finally,Sema4D was detected in plasma of HNC patients at significantly higher levels (115.44, ± 39.37) compared to healthy donors (38.60± 12.73) (p <0.0001). In conclusion, we present a novel HNSCC tumor stratification model, based on the expression of the biomarker Sema4D. This model opens new avenues to novel targeted therapeutic strategies.