Biology and function of neuroimmune semaphorins 4A and 4D

Inhibition of Sema4D attenuates pressure overload-induced pathological myocardial hypertrophy via the MAPK/NF-κB/NLRP3 pathways

Sema4D (CD100) is closely related to pathological and physiological processes, including tumor growth, angiogenesis and cardiac development. Nevertheless, the role and mechanism of Sema4D in cardiac hypertrophy are still unclear to date. To assess the impact of Sema4D on pathological cardiac hypertrophy, TAC surgery was performed on C57BL/6 mice which were transfected with AAV9-mSema4D-shRNA or AAV9-mSema4D adeno-associated virus by tail vein injection. Our results indicated that Sema4D knockdown mitigated cardiac hypertrophy, fibrosis and dysfunction when exposed to pressure overload, and Sema4D downregulation markedly inhibited cardiomyocyte hypertrophy induced by angiotensin II. Meanwhile, Sema4D overexpression had the opposite effect in vitro and in vivo. Furthermore, analysis of signaling pathways showed that Sema4D activated the MAPK pathway during cardiac hypertrophy induced by pressure overload, and the pharmacological mitogen-activated protein kinase kinase 1/2 inhibitor U0126 almost completely reversed Sema4D overexpression-induced deteriorated phenotype, resulting in improved cardiac function. Further research indicated that myocardial hypertrophy induced by Sema4D was closely related to the expression of the pyroptosis-related proteins PP65, NLRP3, caspase-1, ASC, GSDMD, IL-18 and IL-1β. In conclusion, our study demonstrated that Sema4D regulated the process of pathological myocardial hypertrophy through modulating MAPK/NF-κB/NLRP3 pathway, and Sema4D may be the promising interventional target of cardiac hypertrophy and heart failure.

Plexin B1 controls Treg numbers, limits allergic airway inflammation, and regulates mucins

We investigated the effect of global Plexin B1 deficiency on allergic airway responses to house dust mite (HDM) or ovalbumin (OVA). In the HDM model, there were higher Th2 cytokine levels in the BALF of Plexin B1 knock-out (KO) mice compared to wild type (WT), and tissue inflammation and mucus production were modestly enhanced. In the OVA model, Plexin B1 deficiency led to increases in lung inflammation, mucus production, and lung Th2 cytokines accompanied by dysregulated mucin gene expression without affecting anti-OVA IgE/IgG1 levels. Spleen cells from Plexin B1 KO mice proliferated more robustly than WT cells in vitro to a variety of stimuli. Plexin B1 KO CD4+ T cells from spleens expressed higher levels of Ki-67 and CD69 compared to WT cells. Spleen cells from naïve Plexin B1 KO mice secreted increased amounts of IL-4 and IL-6 when pulsed in vitro with OVA whereas in vivo OVA-primed spleen cells produced IL-4/IL-5 when subjected to in vitro OVA restimulation. The upregulated allergic inflammatory response in Plexin B1 KO mice was associated with a lower number of Tregs in the lung tissues. Moreover, these mice displayed lower numbers of Treg cells in the lymphoid tissues at the baseline. These results demonstrate a previously unrecognized link between Plexin B1, Treg cells, and mucus in allergic lung inflammation.

Sema4D is diminished in leukocyte platelet-rich fibrin and impairs pre-osteoblastic MC3T3-E1 cells' functionality

OBJECTIVE

Semaphorin 4D (Sema4D) is a coupling factor expressed on osteoclasts that may hinder osteoblast differentiation. Since the leukocyte platelet-rich fibrin (L-PRF) membrane promotes growth factor concentration, this study aims to quantify the amount of Sema4D in L-PRF membranes, and analyze the impact of Sema4D on osteoblast cell function in vitro.

DESIGN

Enzyme-linked immunosorbent assay (ELISA) was used to quantify the levels of Sema4D in both L-PRF and whole blood (serum). To analyze the impairment of Sema4D on osteoblasts, MC3T3-E1 cells were induced to osteogenic differentiation and exposed to Sema4D ranging from 10 to 500 ng/ml concentrations. The following parameters were assayed: 1) cell viability by MTT assay after 24, 48, and 72 h; 2) matrix mineralization by Alizarin Red staining after 14 days, 3) Runt-related transcription factor 2 (RUNX-2), osteocalcin (OCN), osteonectin (ONC), bone sialoprotein (BSP) and alkaline phosphatase (ALP) gene expression by qPCR. For all data, the significance level was set at 5%.

RESULTS

The amount of Sema4D in the whole blood (serum) was higher than in L-PRF. Osteoblasts exposed to Sema4D at all tested concentrations exhibited a decrease in matrix mineralization formation as well in RUNX-2, OCN, ONC, BSP, and ALP gene expression (p < 0.05).

CONCLUSION

The presence of Sema4D, a molecule known for suppressing osteoblast activity, diminishes within L-PRF, enhancing its ability to facilitate bone regeneration.

SEMA4A promotes prostate cancer invasion: involvement of tumor microenvironment

Semaphorin 4A (SEMA4A) belonged to a family of membrane-bound proteins that were initially recognized as a kind of axon guidance factors in nervous system. It was preferentially expressed on immune cells and has been proven to play a prominent role in immune function and angiogenesis. In this study, we found that SEMA4A was highly expressed in prostate cancer (PCa) tissues and correlated with Gleason scores and distant metastasis. SEMA4A could induce Epithelial-mesenchymal transition (EMT) of PCa cells and consequently promote invasion by establishing a positive loop with IL-10 in stromal cells. In vivo experiments showed more dissemination in mice injected with SEMA4A-overexpressing cells in mouse models and both the number and size of lung metastases were significantly increased in SEMA4A-overexpressing tumors. SEMA4A depletion by genetic means prevents lung metastasis in PCa xenograft models. Our data suggest a crucial role of SEMA4A in PCa and blocking SEMA4A-IL-10 axis represents an attractive approach to improving therapeutic outcomes.

Semaphorin 4D Induces Vasculogenic Differentiation of Dental Pulp Stem Cells

This work aimed to evaluate the effect of Semaphorin 4D (SEMA4D) signaling through Plexin B1 on the vasculogenic differentiation of dental pulp stem cells. We assessed the protein expression of SEMA4D and Plexin B1 in dental pulp stem cells (DPSC) from permanent human teeth and stem cells from human exfoliated deciduous (SHED) teeth using Western blots. Their expression in human dental pulp tissues and DPSC-engineered dental pulps was determined using immunofluorescence. We then exposed dental pulp stem cells to recombinant human SEMA4D (rhSEMA4D), evaluated the expression of endothelial cell differentiation markers, and assessed the vasculogenic potential of rhSEMA4D using an in vitro sprouting assay. Lastly, Plexin B1 was silenced to ascertain its role in SEMA4D-mediated vasculogenic differentiation. We found that SEMA4D and Plexin B1 are expressed in DPSC, SHED, and human dental pulp tissues. rhSEMA4D (25-100 ng/mL) induced the expression of endothelial markers, i.e., vascular endothelial growth factor receptor (VEGFR)-2, cluster of differentiation (CD)-31, and tyrosine kinase with immunoglobulin-like and EGF-like domains (Tie)-2, in dental pulp stem cells and promoted capillary-like sprouting in vitro (p < 0.05). Furthermore, Plexin B1 silencing abrogated the vasculogenic differentiation of dental pulp stem cells and significantly inhibited capillary sprouting upon exposure to rhSEMA4D. Collectively, these data provide evidence that SEMA4D induces vasculogenic differentiation of dental pulp stem cells through Plexin B1 signaling.

Do Semaphorins Play a Role in Development of Fibrosis in Patients with Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is associated with systemic changes in immune response linked with chronic low-grade inflammation and disease progression. Semaphorins, a large family of biological response modifiers, were recently recognized as one of the key regulators of immune responses, possibly also associated with chronic liver diseases. The aim of this study was to identify semaphorins associated with NAFLD and their relationship with steatosis and fibrosis stages. In this prospective, case-control study, serum semaphorin concentrations (SEMA3A, -3C, -4A, -4D, -5A and -7A) were measured in 95 NAFLD patients and 35 healthy controls. Significantly higher concentrations of SEMA3A, -3C and -4D and lower concentrations of SEAMA5A and -7A were found in NAFLD. While there was no difference according to steatosis grades, SEMA3C and SEMA4D significantly increased and SEMA3A significantly decreased with fibrosis stages and had better accuracy in predicting fibrosis compared to the FIB-4 score. Immunohistochemistry confirmed higher expression of SEMA4D in hepatocytes, endothelial cells and lymphocytes in NAFLD livers. The SEMA5A rs1319222 TT genotype was more frequent in the NAFLD group and was associated with higher liver stiffness measurements. In conclusion, we provide the first evidence of the association of semaphorins with fibrosis in patients with NAFLD.

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.

Unbiased cell surface proteomics identifies SEMA4A as an effective immunotherapy target for myeloma

The accessibility of cell surface proteins makes them tractable for targeting by cancer immunotherapy, but identifying suitable targets remains challenging. Here we describe plasma membrane profiling of primary human myeloma cells to identify an unprecedented number of cell surface proteins of a primary cancer. We used a novel approach to prioritize immunotherapy targets and identified a cell surface protein not previously implicated in myeloma, semaphorin-4A (SEMA4A). Using knock-down by short-hairpin RNA and CRISPR/nuclease-dead Cas9 (dCas9), we show that expression of SEMA4A is essential for normal myeloma cell growth in vitro, indicating that myeloma cells cannot downregulate the protein to avoid detection. We further show that SEMA4A would not be identified as a myeloma therapeutic target by standard CRISPR/Cas9 knockout screens because of exon skipping. Finally, we potently and selectively targeted SEMA4A with a novel antibody-drug conjugate in vitro and in vivo.

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.

Identifying Function Determining Residues in Neuroimmune Semaphorin 4A

Semaphorin 4A (Sema4A) exerts a stabilizing effect on human Treg cells in PBMC and CD4+ T cell cultures by engaging Plexin B1. Sema4A deficient mice display enhanced allergic airway inflammation accompanied by fewer Treg cells, while Sema4D deficient mice displayed reduced inflammation and increased Treg cell numbers even though both Sema4 subfamily members engage Plexin B1. The main objectives of this study were: 1. To compare the in vitro effects of Sema4A and Sema4D proteins on human Treg cells; and 2. To identify function-determining residues in Sema4A critical for binding to Plexin B1 based on Sema4D homology modeling. We report here that Sema4A and Sema4D display opposite effects on human Treg cells in in vitro PBMC cultures; Sema4D inhibited the CD4+CD25+Foxp3+ cell numbers and CD25/Foxp3 expression. Sema4A and Sema4D competitively bind to Plexin B1 in vitro and hence may be doing so in vivo as well. Bayesian Partitioning with Pattern Selection (BPPS) partitioned 4505 Sema domains from diverse organisms into subgroups based on distinguishing sequence patterns that are likely responsible for functional differences. BPPS groups Sema3 and Sema4 into one family and further separates Sema4A and Sema4D into distinct subfamilies. Residues distinctive of the Sema3,4 family and of Sema4A (and by homology of Sema4D) tend to cluster around the Plexin B1 binding site. This suggests that the residues both common to and distinctive of Sema4A and Sema4D may mediate binding to Plexin B1, with subfamily residues mediating functional specificity. We mutated the Sema4A-specific residues M198 and F223 to alanine; notably, F223 in Sema4A corresponds to alanine in Sema4D. Mutant proteins were assayed for Plexin B1-binding and Treg stimulation activities. The F223A mutant was unable to stimulate Treg stability in in vitro PBMC cultures despite binding Plexin B1 with an affinity similar to the WT protein. This research is a first step in generating potent mutant Sema4A molecules with stimulatory function for Treg cells with a view to designing immunotherapeutics for asthma.

Semaphorins as Potential Immune Therapeutic Targets for Cancer

Semaphorins are a large class of secreted or membrane-bound molecules. It has been reported that semaphorins play important roles in regulating several hallmarks of cancer, including angiogenesis, metastasis, and immune evasion. Semaphorins and their receptors are widely expressed on tumor cells and immune cells. However, the biological role of semaphorins in tumor immune microenvironment is intricate. The dysregulation of semaphorins influences the recruitment and infiltration of immune cells, leading to abnormal anti-tumor effect. Although the underlying mechanisms of semaphorins on regulating tumor-infiltrating immune cell activation and functions are not fully understood, semaphorins can notably be promising immunotherapy targets for cancer.

Downregulation of miR-125a-5p and miR-218-5p in Peripheral Blood Mononuclear Cells of Patients with Relapsing-Remitting Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the brain and spinal cord. Evidences have demonstrated that microRNAs (miRNAs) are involved in the pathological process of MS that may confer a valuable diagnostic biomarker for disease diagnosis, prognosis, and treatment. Hence, we assessed the expression pattern of miR-125a-5p and miR-218-5p in the peripheral blood mononuclear cells (PBMCs) of subjects with relapsing-remitting multiple sclerosis (RRMS). We recruited 50 RRMS patients and 50 age- and sex-matched healthy control subjects. PBMCs were isolated from the peripheral blood samples, RNA content was extracted, cDNA was synthesized, and finally expression level of miRNAs was determined using quantitative real-time PCR. Our data indicate significant downregulation of both miR-125a-5p and miR-218-5p in RRMS patients compared to healthy controls (P< .0001). The levels of both miRNAs were significantly downregulated in an age-dependent manner compared with consistent healthy control groups (30-40 years old P< .0001). Expression level of miR-218-5p was significantly changed in only female patients (Female group P< .0001; Male group P= .12). Receiver operating characteristic (ROC) curve data indicated that the expression levels of both miRNAs were able to discriminate RRMS patients from healthy subjects (P< .05). Moreover, bioinformatic enrichment analysis revealed that the target genes of these miRNAs had cardinal roles in the regulation of key biological pathways involved in the clinical course and pathogenesis of MS. Collectively, our results suggested that miR-125a-5p and miR-218-5p play a role in RRMS pathogenesis and have an age- and sex-dependent expression pattern in these patients.

Signaling from membrane semaphorin 4D in T lymphocytes

Semaphorin 4D (Sema4D) is widely represented in the immune system in both membrane and soluble form, and controls immune processes through the specific receptors - these are generally accepted views. Here, an alternative way of Sema4D-dependent immunoregulation is presented, suggesting its functioning as a receptor. We have shown that activation of membrane Sema4D induces phosphorylation of Lck/ZAP-70 in intact T lymphocytes and enhances it in stimulated T cells. Since Sema4D is constitutively presented on the membrane of T lymphocytes, and classical Sema4D receptors are highly expressed by antigen-presenting cells, the membrane Sema4D can serve as an obligate costimulatory molecule in T lymphocyte priming or T-dependent B cell activation.

Semaphorins in health and disease

Cell-cell communication is pivotal to guide embryo development, as well as to maintain adult tissues homeostasis and control immune response. Among extracellular factors responsible for this function, are the Semaphorins, a broad family of around 20 different molecular cues conserved in evolution and widely expressed in all tissues. The signaling cascades initiated by semaphorins depend on a family of conserved receptors, called Plexins, and on several additional molecules found in the receptor complexes. Moreover, multiple intracellular pathways have been described to act downstream of semaphorins, highlighting significant diversity in the signaling cascades controlled by this family. Notably, semaphorin expression is altered in many human diseases, such as immunopathologies, neurodegenerative diseases and cancer. This underscores the importance of semaphorins as regulatory factors in the tissue microenvironment and has prompted growing interest for assessing their potential relevance in medicine. This review article surveys the main contexts in which semaphorins have been found to regulate developing and healthy adult tissues, and the signaling cascades implicated in these functions. Vis a vis, we will highlight the main pathological processes in which semaphorins are thought to have a role thereof.

Semaphorin 4A, 4C, and 4D: Function comparison in the autoimmunity, allergy, and cancer

Semaphorins are a group of proteins that are divided into eight subclasses and identified by a conserved Sema domain on their carboxyl terminus. Sema4A, 4C, and 4D are the members of the fourth class of semaphorin family, which are known as membrane semaphorins; however, these molecules can be altered to soluble semaphorins by proteolytic cleavage. Semaphorins have various roles in the immune, nervous, and metabolic systems. In the immune system, these molecules contribute to the formation of cellular, humoral, and innate immune responses, such as inflammation, leukocyte migration, immunological synapse formation, and germinal center events. Given the diverse roles of semaphorins in the immune system, in this review, we have tried to give a comprehensive look at the role of these molecules in autoimmunity, allergy, and cancer. Sema4D and 4A seem to play a critical role in the pathogenesis of some autoimmune diseases, such as multiple sclerosis. In contrast, it has been shown that Sema4A and 4C have beneficial effects on allergies, and their absence can exacerbate the severity of the disease. In the case of cancer, an increase in all three of these molecules has been reported. Sema4D and 4C can contribute to tumor progression in human patients or experimental models, while the role of Sema4A has not yet been fully understood. In conclusion, semaphorins seem to be a favorable therapeutic target for autoimmune diseases and allergies. However, in cancer, studies have not yet been able to identify the exact role of semaphorins, and further studies are needed.

Hypoglycaemia leads to a delayed increase in platelet and coagulation activation markers in people with type 2 diabetes treated with metformin only: Results from a stepwise hypoglycaemic clamp study

AIMS

To investigate the effect of hypoglycaemia on platelet and coagulation activation in people with type 2 diabetes.

MATERIALS AND METHODS

This monocentric, open, single-arm, mechanistic trial included 14 people with established type 2 diabetes (four women, 10 men, age 55 ± 7 years, glycated haemoglobin concentration 51 ± 7 mmol/mol) receiving metformin monotherapy. A stepwise hyperinsulinaemic-hypoglycaemic clamp experiment (3.5 and 2.5 mmol/L, for 30 minutes respectively) was performed, aiming to investigate platelet and coagulation activity during predefined plateaus of hypoglycaemia, as well as 1 day and 7 days later.

RESULTS

While platelet activation assessed by light transmittance aggregometry did not significantly increase after the hypoglycaemic clamp procedure, the more sensitive flow cytometry-based measurement of platelet surface activation markers showed hypoglycaemia-induced activation 24 hours (PAC1^pos CD62P^pos , PAC1^pos CD63P^pos and PAC1^pos CD62P^pos CD63^pos ; P < .01) and 7 days after the hypoglycaemic clamp (P < .001 for PAC1^pos CD63^pos ; P < .01 for PAC1^pos CD62P^pos and PAC1^pos CD62P^pos CD63^pos ) in comparison to baseline. Coagulation markers, such as fibrinogen, D-dimer, plasminogen activator inhibitor-1, von Willebrand factor activity and factor VIII, were also significantly increased, an effect that was most pronounced 24 hours after the hypoglycaemic clamp.

CONCLUSION

A single event of insulin-induced hypoglycaemia led to an increase in markers of platelet activation and coagulation in people with early stages of type 2 diabetes on metformin therapy. However, the activation occurred with a delay and was evident 24 hours and 7 days after the actual hypoglycaemic episode.

Reciprocal changes in CD11c+CD11b+ and CD11c+CD8α+ dendritic cell subsets determine protective or permissive immune response in murine experimental VL

CD11c⁺CD8α⁺ and CD11c⁺CD11b⁺ dendritic cells are two major subsets of murine splenic CD11c⁺ DCs which play a crucial role in T cell priming and shaping Th1/Th2 responses, but their role in the context of experimental visceral leishmaniasis (VL) is poorly understood. Herein, we showed that L. donovani infection in Balb/c mice preferentially decreased the population abundance of CD11c⁺CD11b⁺ DCs and increased relative abundance of splenic CD11c⁺CD8α ⁺DCs. During infection, splenic CD11c⁺CD11b⁺ DCs induced Th1 differentiation whereas CD11c⁺CD8α⁺ DCs promoted Th2 differentiation. Additionally, treatment of infected mice with miltefosine as experimental control exhibited host defense allowing the restoration of CD11c⁺CD11b⁺ population and decrease in CD11c⁺CD8α⁺ subset. Furthermore, reciprocal regulation of immune accessory surface molecules, Sema4A and OX40L critically determined Th1/Th2 response induced by these DC subsets during VL. L. donovani infection significantly induced OX40L expression and slightly downregulated SEMA 4A expression in CD11c⁺CD8α⁺ DCs whereas miltefosine treatment significantly downregulated OX40L expression along with pronounced upregulation of SEMA 4A expression in CD11c⁺CD11b⁺ DCs. SiRNA mediated knockdown of SEMA 4A markedly reduced CD11c⁺CD11b⁺ driven IFN-γ, TNF-α and IL-12 synthesis in miltefosine treated mice whereas functional blocking of OX40L decreased CD11c⁺CD8α⁺ induced IL-10, IL-4 and TGF-β synthesis in L. donovani infected group. Vaccination of Balb/c mice with antigen-pulsed + CpG-ODN-activated DC subsets revealed that only antigen-pulsed CD11c⁺CD11b⁺ DCs eliminated parasite load in visceral organ and restored protective Th1 cytokine response. Collectively, our results suggest that differential regulation of splenic CD11c⁺ subsets by L. donovani is essential for disease progression and specific subtypes may be exploited as prophylactic measures against visceral leishmaniasis.

Induction of Inflammation and Fibrosis by Semaphorin 4A in Systemic Sclerosis

OBJECTIVE

To analyze the potential role of semaphorin 4A (Sema4A) in inflammatory and fibrotic processes involved in the pathology of systemic sclerosis (SSc).

METHODS

Sema4A levels in the plasma of healthy controls (n = 11) and SSc patients (n = 20) were determined by enzyme-linked immunosorbent assay (ELISA). The expression of Sema4A and its receptors in monocytes and CD4+ T cells from healthy controls and SSc patients (n = 6-7 per group) was determined by ELISA and flow cytometry. Th17 cytokine production by CD4+ T cells (n = 5-7) was analyzed by ELISA and flow cytometry. The production of inflammatory mediators and extracellular matrix (ECM) components by dermal fibroblast cells (n = 6) was analyzed by quantitative polymerase chain reaction, ELISA, Western blotting, confocal microscopy, and ECM deposition assay.

RESULTS

Plasma levels of Sema4A, and Sema4A expression by circulating monocytes and CD4+ T cells, were significantly higher in SSc patients than in healthy controls (P < 0.05). Inflammatory mediators significantly up-regulated the secretion of Sema4A by monocytes and CD4+ T cells from SSc patients (P < 0.05 versus unstimulated SSc cells). Functional assays showed that Sema4A significantly enhanced the expression of Th17 cytokines induced by CD3/CD28 in total CD4+ T cells as well in different CD4+ T cell subsets (P < 0.05 versus unstimulated SSc cells). Finally, Sema4A induced a profibrotic phenotype in dermal fibroblasts from both healthy controls and SSc patients, which was abrogated by blocking or silencing the expression of Sema4A receptors.

CONCLUSION

Our findings indicate that Sema4A plays direct and dual roles in promoting inflammation and fibrosis, 2 main features of SSc, suggesting that Sema4A might be a novel therapeutic target in SSc.

Semaphorin4A causes loss of mature oligodendrocytes and demyelination in vivo

Background

Inappropriate contact between the immune system and the central nervous system is thought to be a cause of demyelination. We previously reported the ability of the class IV semaphorin, Semaphorin4A (Sema4A), to induce apoptosis in human oligodendrocytes; however, these results have yet to be translated to an in vivo setting. Importantly, HIV-associated neurocognitive disorder remains a significant complication for patients on combined anti-retroviral therapy, with white matter damage seen on MRI.

Methods

Human cerebrospinal fluid and serum was assayed for Sema4A using a Sema4A-specific ELISA. Wild-type mice were injected with Sema4A via stereotaxic infusion. Data was assessed for significance using unpaired t tests, comparing the corpus callosum of PBS-injected mice versus Sema4A-injected mice.

Results

Here, we demonstrate elevated levels of Sema4A in the cerebrospinal fluid and serum of people with HIV infection. Furthermore, we demonstrate that direct injection of Sema4A into the corpus callosum of mice results in loss of myelin architecture and decreased myelin, concomitant with apoptosis of mature myelinating oligodendrocytes. Sema4A injection also causes increased activation of microglia.

Conclusions

Taken together, our data further establish Sema4A as a potentially significant mediator of demyelinating diseases and a direct connection between the immune system and oligodendrocytes.

Overexpression of Semaphorin-3A and Semaphorin-4D in the Peripheral Blood from Newly Diagnosed Patients with Chronic Lymphocytic Leukemia

Background: Semaphorins play prominent roles in physiological and pathological processes such as vascular development, tumor growth and immune responses. Semaphorins have different roles in various kinds of cancers, but there is no study concerning their expression in the chronic lymphocytic leukemia (CLL). This study aimed to assess the SEMA3A, SEMA4A and SEMA4D expression in patients with CLL. Materials and Methods: Peripheral blood specimens were collected from 30 newly-diagnosed untreated patients with CLL and 30 healthy subjects as a control group. The SEMA3A, SEMA4A and SEMA4D expression was determined by real-time PCR method. Results: The fold change expression of SEMA3A and SEMA4D was 7.58 ± 2.66 and 3.20 ± 0.99 in patients with CLL, and was 1.01 ± 0.31 and 1.00 ± 0.27 in healthy subjects, respectively. The CLL patients expressed higher amounts of SEMA3A and SEMA4D in comparison with healthy subjects (P<0.02 and P<0.03, respectively). The fold change expression of SEMA3A in patients with stage II (11.12 ± 5.35) was also higher than patients with stage I (4.49 ± 1.61, P<0.05). No significant difference was also observed in the expression of SEMA4A and SEMA4D between patients with stage I and stage II CLL. In both CLL and control groups, the fold change expression of SEMA3A was higher in men than in women (P<0.03 and P<0.02, respectively). Conclusion: The results of the study indicated elevated expression of the SEMA3A and SEMA4D in patients with CLL. The SEMA3A expression was influenced by tumor stage and gender of participants.

Neuroimmune Semaphorin 4A in Cancer Angiogenesis and Inflammation: A Promoter or a Suppressor?

Neuroimmune semaphorin 4A (Sema4A), a member of semaphorin family of transmembrane and secreted proteins, is an important regulator of neuronal and immune functions. In the nervous system, Sema4A primarily regulates the functional activity of neurons serving as an axon guidance molecule. In the immune system, Sema4A regulates immune cell activation and function, instructing a fine tuning of the immune response. Recent studies have shown a dysregulation of Sema4A expression in several types of cancer such as hepatocellular carcinoma, colorectal, and breast cancers. Cancers have been associated with abnormal angiogenesis. The function of Sema4A in angiogenesis and cancer is not defined. Recent studies have demonstrated Sema4A expression and function in endothelial cells. However, the results of these studies are controversial as they report either pro- or anti-angiogenic Sema4A effects depending on the experimental settings. In this mini-review, we discuss these findings as well as our data on Sema4A regulation of inflammation and angiogenesis, which both are important pathologic processes underlining tumorigenesis and tumor metastasis. Understanding the role of Sema4A in those processes may guide the development of improved therapeutic treatments for cancer.

Class 4 Semaphorins and Plexin-B receptors regulate GABAergic and glutamatergic synapse development in the mammalian hippocampus

To understand how proper circuit formation and function is established in the mammalian brain, it is necessary to define the genes and signaling pathways that instruct excitatory and inhibitory synapse development. We previously demonstrated that the ligand-receptor pair, Sema4D and Plexin-B1, regulates inhibitory synapse development on an unprecedentedly fast time-scale while having no effect on excitatory synapse development. Here, we report previously undescribed synaptogenic roles for Sema4A and Plexin-B2 and provide new insight into Sema4D and Plexin-B1 regulation of synapse development in rodent hippocampus. First, we show that Sema4a, Sema4d, Plxnb1, and Plxnb2 have distinct and overlapping expression patterns in neurons and glia in the developing hippocampus. Second, we describe a requirement for Plexin-B1 in both the presynaptic axon of inhibitory interneurons as well as the postsynaptic dendrites of excitatory neurons for Sema4D-dependent inhibitory synapse development. Third, we define a new synaptogenic activity for Sema4A in mediating inhibitory and excitatory synapse development. Specifically, we demonstrate that Sema4A signals through the same pathway as Sema4D, via the postsynaptic Plexin-B1 receptor, to promote inhibitory synapse development. However, Sema4A also signals through the Plexin-B2 receptor to promote excitatory synapse development. Our results shed new light on the molecular cues that promote the development of either inhibitory or excitatory synapses in the mammalian hippocampus.

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.

CD100/Sema4D Increases Macrophage Infection by Leishmania (Leishmania) amazonensis in a CD72 Dependent Manner

Leishmaniasis is caused by trypanosomatid protozoa of the genus Leishmania, which infect preferentially macrophages. The disease affects 12 million people worldwide, who may present cutaneous, mucocutaneous or visceral forms. Several factors influence the form and severity of the disease, and the main ones are the Leishmania species and the host immune response. CD100 is a membrane bound protein that can also be shed. It was first identified in T lymphocytes and latter shown to be induced in macrophages by inflammatory stimuli. The soluble CD100 (sCD100) reduces migration and expression of inflammatory cytokines in human monocytes and dendritic cells, as well as the intake of oxidized low-density lipoprotein (oxLDL) by human macrophages. Considering the importance of macrophages in Leishmania infection and the potential role of sCD100 in the modulation of macrophage phagocytosis and activation, we analyzed the expression and distribution of CD100 in murine macrophages and the effects of sCD100 on macrophage infection by Leishmania (Leishmania) amazonensis. Here we show that CD100 expression in murine macrophages increases after infection with Leishmania. sCD100 augments infection and phagocytosis of Leishmania (L.) amazonensis promastigotes by macrophages, an effect dependent on macrophage CD72 receptor. Besides, sCD100 enhances phagocytosis of zymosan particles and infection by Trypanosoma cruzi.

Human Semaphorin-4A drives Th2 responses by binding to receptor ILT-4

Semaphorin-4A (Sema4A) has been implicated in the co-stimulation of T cells and drives Th1 immune responses by binding to the receptor T-cell immunoglobulin and mucin domain protein 2 (Tim-2) in mice. Here we show that human, but not murine, Sema4A is preferentially expressed on antigen-presenting cells, and co-stimulates CD4⁺ T-cell proliferation and drives Th2 responses. By employing two independent cloning strategies, we demonstrate that Immunoglobulin-like transcript 4 (ILT-4) is a receptor for human SEMA4A (hSEMA4A) on activated CD4⁺ T cells. We also find hSEMA4A to be highly expressed in human asthmatic lung tissue, implying its potential function in disease pathogenesis. Our study defines a different biological function of hSEMA4A from its murine homolog through its binding to the receptor of ILT-4 to co-stimulate CD4⁺T cells and regulate Th2 cells differentiation.

View Point: Semaphorin-3E: An Emerging Modulator of Natural Killer Cell Functions?

Semaphorin-3E (Sema-3E) is a member of a large family of proteins originally identified as axon guidance cues in neural development. It is expressed in different cell types, such as immune cells, cancer cells, neural cells, and epithelial cells. Subsequently, dys-regulation of Sema-3E expression has been reported in various biological processes that range from cancers to autoimmune and allergic diseases. Recent work in our laboratories revealed a critical immunoregulatory role of Sema-3E in experimental allergic asthma. We further speculate possible immune modulatory function(s) of Sema-3E on natural killer (NK) cells.

Low levels of the immunoregulator Semaphorin 4D (CD100) in sera of HIV patients

INTRODUCTION

Semaphorin-4D (CD100), generated by CD4/CD8 T-cells and its receptor on B cells - CD72, play a role in immune regulation. Both have soluble forms - sCD100/sCD72.

METHODS

sCD100 and sCD72 levels were determined by ELISA (MyBioSource, USA).

RESULTS

28 chronic HIV patients and 50 matched healthy volunteers participated in our study. Before treatment, CD4 T-cells counts were 267 ± 216 cells/mcl and viral load (VL) was 586,675 ± 1897,431 copies/ml. Two years following HAART, CD4 T-cells counts rose to 475 ± 264 cells/mcl and VL dropped to 2050 ± 10,539 copies/ml. CD8 T-cells counts were stable. sCD72 levels prior (4.13 ± 2.03 ng/ml) and following HAART (3.53 ± 2.01 ng/ml) were similar to control levels (4.51 ± 2.66 ng/ml). sCD100 levels before (40.47 ± 31.4 ng/ml) and following HAART (37.68 ± 29.44 ng/ml) were significantly lower compared to controls (99.67 ± 36.72 ng/ml) despite the significant increase in CD4 T-cells counts.

CONCLUSIONS

The permanent low levels of the immunoregulator sCD100 suggest a role for CD100 in the immune dysfunction and T cells exhaustion of HIV.

Whole transcriptome profiling of taste bud cells

Analysis of single-cell RNA-Seq data can provide insights into the specific functions of individual cell types that compose complex tissues. Here, we examined gene expression in two distinct subpopulations of mouse taste cells: Tas1r3-expressing type II cells and physiologically identified type III cells. Our RNA-Seq libraries met high quality control standards and accurately captured differential expression of marker genes for type II (e.g. the Tas1r genes, Plcb2, Trpm5) and type III (e.g. Pkd2l1, Ncam, Snap25) taste cells. Bioinformatics analysis showed that genes regulating responses to stimuli were up-regulated in type II cells, while pathways related to neuronal function were up-regulated in type III cells. We also identified highly expressed genes and pathways associated with chemotaxis and axon guidance, providing new insights into the mechanisms underlying integration of new taste cells into the taste bud. We validated our results by immunohistochemically confirming expression of selected genes encoding synaptic (Cplx2 and Pclo) and semaphorin signalling pathway (Crmp2, PlexinB1, Fes and Sema4a) components. The approach described here could provide a comprehensive map of gene expression for all taste cell subpopulations and will be particularly relevant for cell types in taste buds and other tissues that can be identified only by physiological methods.

Semaphorin 4C: A Novel Component of B-Cell Polarization in Th2-Driven Immune Responses

Background

Semaphorins are important molecules in embryonic development and multiple semaphorins have been identified as having key roles in immune regulation. To date, there is little known about Semaphorin 4C (Sema4C) in immune biology. We report for the first time that Sema4C is inducible in human and murine B-cells and may be important for normal B-cell development.

Methods

Human tonsillar B-cells were studied following activation via anti-CD40 antibodies in the presence or absence of representative Th1, Th2, and regulatory cytokines. Murine B-cells from WT and Sema4C^−/− mice were similarly stimulated. B-cell phenotyping in WT and Sema4C mutant mice was performed by flow cytometry and lymphoid architecture was studied by immunohistochemistry. Sema4C expression and synapse formation were analyzed by confocal microscopy.

Results

Gene array studies performed on human tonsillar B-cells stimulated to produce IgE revealed that Sema4C was among the top genes expressed at 24 h, and the only semaphorin to be increased under Th2 conditions. Validation studies demonstrated that human and murine B-cells expressed Sema4C under similar conditions. Sema4C^−/− mice had impaired maturation of B-cell follicles in spleens and associated decreases in follicular and marginal zone B-cells as well as impaired IgG and IgA production. In keeping with a potential role in maturation of B-cells, Sema4C was expressed predominantly on CD27⁺ human B-cells. Within 72 h of B-cell activation, Sema4C was localized to one pole in a synapse-like structure, in association with F-actin, B-cell receptor, and Plexin-B2. Cell polarization was impaired in Sema4C^−/− mice.

Conclusion

We have identified a novel immune semaphorin induced in human and murine B-cells under Th2 conditions. Sema4C appears to be a marker for human memory B-cells. It may be important for B-cell polarization and for the formation of normal splenic follicles.

Chemorepellent Semaphorin 3E Negatively Regulates Neutrophil Migration In Vitro and In Vivo

Neutrophil migration is an essential step in leukocyte trafficking during inflammatory responses. Semaphorins, originally discovered as axon guidance cues in neural development, have been shown to regulate cell migration beyond the nervous system. However, the potential contribution of semaphorins in the regulation of neutrophil migration is not well understood. This study examines the possible role of a secreted chemorepellent, Semaphorin 3E (Sema3E), in neutrophil migration. In this study, we demonstrated that human neutrophils constitutively express Sema3E high-affinity receptor, PlexinD1. Sema3E displayed a potent ability to inhibit CXCL8/IL-8-induced neutrophil migration as determined using a microfluidic device coupled to real-time microscopy and a transwell system in vitro. The antimigratory effect of Sema3E on human neutrophil migration was associated with suppression of CXCL8/IL-8-mediated Ras-related C3 botulinum toxin substrate 1 GTPase activity and actin polymerization. We further addressed the regulatory role of Sema3E in the regulation of neutrophil migration in vivo. Allergen airway exposure induced higher neutrophil recruitment into the lungs of Sema3e^-/- mice compared with wild-type controls. Administration of exogenous recombinant Sema3E markedly reduced allergen-induced neutrophil recruitment into the lungs, which was associated with alleviation of allergic airway inflammation and improvement of lung function. Our data suggest that Sema3E could be considered an essential regulatory mediator involved in modulation of neutrophil migration throughout the course of neutrophilic inflammation.

Semaphorins 4A and 4D in chronic inflammatory diseases

Long-term inflammatory processes directed at a particular endogenous or exogenous antigen, or sometimes of unknown etiology, form the pathogenetic basis for many debilitating conditions, such as cardiovascular, pulmonary, autoimmune, neurologic diseases, and cancer. Recent discoveries of neuroimmune semaphorins 4A and 4D (Sema4A and Sema4D, respectively) expression and function in the immune system and their key regulatory roles in fine tuning of inflammatory processes made them the molecules of interest for a potential immunotherapy. In this short review, we discuss the current knowledge in the Sema4A and Sema4D actions in chronic inflammation underlying the outlined above diseases.

The role of Sema4D/CD100 as a therapeutic target for tumor microenvironments and for autoimmune, neuroimmune and bone diseases

INTRODUCTION

Semaphorin 4D (Sema4D), also known as CD100, has been implicated in physiologic roles in the immune and nervous systems. However, the interaction of Sema4D with its high affinity receptor, Plexin-B1, reveals a novel role for Sema4D produced by the tumor microenvironment in tumor angiogenesis and metastasis.

AREAS COVERED

The ligation of Sema4D/CD100 with CD72 on immune and inflammatory cells is known to stimulate immune responses and regulation. Because CD100 and CD72 are expressed on lung immune and nonimmune cells, as well as on mast cells, the CD100/CD72 interaction plays another important role in allergic airway inflammation and mast cell functions. A better understanding of Sema4D-mediated cell signaling in physiological and pathological processes may be crucial for crafting new Sema4D-based therapeutics for human disease and tumor microenvironments. Strategies to achieve effective management through treatment with Sema4D include special siRNAs, neutralizing antibodies and knockdown.

EXPERT OPINION

This review focuses on the links between Sema4D and human diseases such as cancer, bone metabolism, immune responses and organ development. The current knowledge regarding the expression of Sema4D and its receptors and its functional roles is systemically reviewed to explore Sema4D as both a target and a therapeutic in human diseases.

Tax and Semaphorin 4D Released from Lymphocytes Infected with Human Lymphotropic Virus Type 1 and Their Effect on Neurite Growth

Human lymphotropic virus type 1 (HTLV-1) is a retrovirus causing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a neurodegenerative central nervous system (CNS) axonopathy. This virus mainly infects CD4(+) T lymphocytes without evidence of neuronal infection. Viral Tax, secreted from infected lymphocytes infiltrated in the CNS, is proposed to alter intracellular pathways related to axonal cytoskeleton dynamics, producing neurological damage. Previous reports showed a higher proteolytic release of soluble Semaphorin 4D (sSEMA-4D) from CD4(+) T cells infected with HTLV-1. Soluble SEMA-4D binds to its receptor Plexin-B1, activating axonal growth collapse pathways in the CNS. In the current study, an increase was found in both SEMA-4D in CD4(+) T cells and sSEMA-4D released to the culture medium of peripheral blood mononuclear cells (PBMCs) from HAM/TSP patients compared to asymptomatic carriers and healthy donors. After a 16-h culture, infected PBMCs showed significantly higher levels of CRMP-2 phosphorylated at Ser(522). The effect was blocked either with anti-Tax or anti-SEMA-4D antibodies. The interaction of Tax and sSEMA-4D was found in secreted medium of PBMCs in patients, which might be associated with a leading role of Tax with the SEMA-4D-Plexin-B1 signaling pathway. In infected PBMCs, the migratory response after transwell assay showed that sSEMA-4D responding cells were CD4(+)Tax(+) T cells with a high CRMP-2 pSer(522) content. In the present study, the participation of Tax-sSEMA-4D in the reduction in neurite growth in PC12 cells produced by MT2 (HTLV-1-infected cell line) culture medium was observed. These results lead to the participation of plexins in the reported effects of infected lymphocytes on neuronal cells.

Saturation monitoring of VX15/2503, a novel semaphorin 4D-specific antibody, in clinical trials

Background

Receptor occupancy, or saturation, assays are often utilized in preclinical and clinical development programs to evaluate the binding of a biologic to a cellular target. These assays provide critical information regarding the dose of drug required to “saturate” the target as well as important pharmacodymamic (PD) data. A flow cytometric method was developed to measure the degree of Semaphorin 4D (SEMA4D; CD100) saturation by VX15/2303, an investigational monoclonal antibody specific for SEMA4D.

Methods

The assay detects VX15/2503, a human IgG₄ specific for SEMA4D, with an IgG₄‐specific monoclonal antibody.

Results

Data generated allowed assessment of two related SEMA4D‐specific pharmacodynamic (PD) markers: (1) The measurement of cellular SEMA4D (cSEMA4D) saturation by VX15/2503, and (2) the cell membrane expression levels of cSEMA4D.

Conclusions

This assay specifically and reproducibly measured cSEMA4D saturation and expression levels. Evaluation of the SEMA4D‐specific PD markers were critical in determining the clinical saturation threshold of cSEMA4D by VX15/2503. © 2015 he Authors Cytometry Part B: Clinical Cytometry Published by Wiley Periodicals, Inc.

Semaphorin 4A as novel regulator and promising therapeutic target in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease manifesting in joint destruction. The recognized hallmark of RA pathogenesis is the involvement of immune cells which produce many mediators potentiating an inflammatory environment. RA synovial fibroblasts (RASFs) contribute significantly to disease progression by initiating and regulating many pathways of joint destruction. Detailed molecular insights into RASF biology may lead to identification of important therapeutic targets. The discovery of common molecular targets for joint resident and inflammatory cells may help to develop the most effective therapeutic strategy. One such pathway includes semaphorin 4A as reported in a recent article in Arthritis Research & Therapy.

Generation and preclinical characterization of an antibody specific for SEMA4D

Semaphorin 4D (SEMA4D or CD100) is a member of the semaphorin family of proteins and an important mediator of the movement and differentiation of multiple cell types, including those of the immune, vascular, and nervous systems. Blocking the binding of SEMA4D to its receptors can result in physiologic changes that may have implications in cancer, autoimmune, and neurological disease. To study the effects of blocking SEMA4D, we generated, in SEMA4D-deficient mice, a panel of SEMA4D-specific hybridomas that react with murine, primate, and human SEMA4D. Utilizing the complementarity-determining regions from one of these hybridomas (mAb 67-2), we generated VX15/2503, a humanized IgG4 monoclonal antibody that is currently in clinical development for the potential treatment of various malignancies and neurodegenerative disorders, including multiple sclerosis and Huntington's disease. This work describes the generation and characterization of VX15/2503, including in vitro functional testing, epitope mapping, and an in vivo demonstration of efficacy in an animal model of rheumatoid arthritis.

A live-cell, high-content imaging survey of 206 endogenous factors across five stress conditions reveals context-dependent survival effects in mouse primary beta cells

AIMS/HYPOTHESIS

Beta cell death is a hallmark of diabetes. It is not known whether specific cellular stresses associated with type 1 or type 2 diabetes require specific factors to protect pancreatic beta cells. No systematic comparison of endogenous soluble factors in the context of multiple pro-apoptotic conditions has been published.

METHODS

Primary mouse islet cells were cultured in conditions mimicking five type 1 or type 2 diabetes-related stresses: basal 5 mmol/l glucose, cytokine cocktail (25 ng/ml TNF-α, 10 ng/ml IL-1β, 10 ng/ml IFN-γ), 1 μmol/l thapsigargin, 1.5 mmol/l palmitate and 20 mmol/l glucose (all in the absence of serum). We surveyed the effects of a library of 206 endogenous factors (selected based on islet expression of their receptors) on islet cell survival through multi-parameter, live-cell imaging.

RESULTS

Our survey pointed to survival factors exhibiting generalised protective effects across conditions meant to model different types of diabetes and stages of the diseases. For example, our survey and follow-up experiments suggested that OLFM1 is a novel protective factor for mouse and human beta cells across multiple conditions. Most strikingly, we also found specific protective survival factors for each model stress condition. For example, semaphorin4A (SEMA4A) was toxic to islet cells in the serum-free baseline and serum-free 20 mmol/l glucose conditions, but protective in the context of lipotoxicity. Rank product testing supported the consistency of our observations.

CONCLUSIONS/INTERPRETATION

Collectively, our survey reveals previously unidentified islet cell survival factors and suggest their potential utility in individualised medicine.

The Involvement of Immune Semaphorins in the Pathogenesis of Inflammatory Bowel Diseases (IBDs)

Background and Aims

Immune semaphorins are a large family of proteins involved in the pathogenesis of inflammatory diseases through the regulation of immune homeostasis and tissue inflammation. We aim to assess the possible involvement of semaphorin3A (sema3A) and 4A (sema4A) in peripheral immune responses and bowel tissue inflammation of patients suffering from Crohn’s disease (CD) and ulcerative colitis (UC).

Patients and Methods

Twenty-seven CD patients and 10 UC patients were studied and compared to 10 patients followed for acute diverticulitis (disease control) and 12 healthy individuals. All were evaluated for sema3A expression on T regulatory cells (Tregs), serum levels of sema3A and sema4A, and tissue expression of sema3A and sema4A in bowel biopsies.

Results

The percentage (%) of T regulatory cells (Tregs) expressing sema3A in patients with active CD (64.5% ±14.49%) and active UC (49.8% ±16.45%) was significantly lower when compared to that of healthy controls (88.7% ±3.6%, p< 0.001 and p< 0.0001, respectively). This expression was seen to be in negative correlation with CD activity. Serum levels of Sema4A were significantly lower in patients with CD and UC when compared to that of controls (5.69±1.48ng\ml for CD, 5.26±1.23 ng/ml for UC patients vs 9.74±2.73ng/ml for normal controls, P<0.001). Sema4A was highly expressed in lymphocytes of the lamina propria of CD and UC patients but absent in patients with diverticulitis or in normal individuals.

Conclusions

Altered % of Tregs expressing sema3A in patients with inflammatory bowel diseases (IBD) is partially responsible for their failure in preventing CD4+ effector T cell induced inflammation in IBD in peripheral blood. The increased expression of sema4A in bowel biopsies from CD and UC patients is suggestive of its central role in regulating local tissue inflammation in the bowel.

Familial 1q22 microduplication associated with psychiatric disorders, intellectual disability and late-onset autoimmune inflammatory response

Background

Despite the extensive use of chromosomal microarray technologies in patients with neurodevelopmental disorders has permitted the identification of an increasing number of causative submicroscopic rearrangements throughout the genome, constitutional duplications involving chromosome 1q22 have seldom been described in those patients.

Results

We report on a pedigree with seven affected members showing varying degrees of behavioural and emotional disturbances including general anxiety disorder, mood disorders, and intellectual disability. Two adult female patients also showed late onset autoimmune inflammatory responses characterized by alopecia, skin ulcers secondary to inflammatory vasculitis, interstitial lung disease, and Raynaud’s phenomenon. Array-CGH analysis identified in the affected individuals a 290 Kb microduplication in the chromosome 1q22. The rearrangement involves eleven known genes and is not present in the databases of polymorphic copy number variants.

Conclusions

The rearrangement segregates with the neurological clinical features observed in our patients, suggesting that dosage imbalance of one or more genes in this genomic region may lead to the observed phenotype. The association between the microduplication and the inflammatory disease is much less evident. Additional reported patients carrying similar microduplications are needed to clarify this aspect.

Neuroimmune semaphorin 4D is necessary for optimal lung allergic inflammation

Neuroimmune semaphorin 4D (Sema4D) was found to be expressed and function in the nervous and immune systems. In the immune system, Sema4D is constitutively expressed on T cells and regulates T cell priming. In addition, it displays a stimulatory function on macrophages, DC, NK cells, and neutrophils. As all these cells are deeply involved in asthma pathology, we hypothesized that Sema4D plays a critical non-redundant regulatory role in allergic airway response. To test our hypothesis, we exposed Sema4D(-/-) and WT mice to OVA injections and challenges in the well-defined mouse model of OVA-induced experimental asthma. We observed a significant decrease in eosinophilic airway infiltration in allergen-treated Sema4D(-/-) mice relative to WT mice. This reduced allergic inflammatory response was associated with decreased BAL IL-5, IL-13, TGFβ1, IL-6, and IL-17A levels. In addition, T cell proliferation in OVA₃₂₃₋₃₃₉-restimulated Sema4D(-/-) cell cultures was downregulated. We also found increased Treg numbers in spleens of Sema4D(-/-) mice. However, airway hyperreactivity (AHR) to methacholine challenges was not affected by Sema4D deficiency in either acute or chronic experimental disease setting. Surprisingly, lung DC number and activation were not affected by Sema4D deficiency. These data provide a new insight into Sema4D biology and define Sema4D as an important regulator of Th2-driven lung pathophysiology and as a potential target for a combinatory disease immunotherapy.

Immune plexins and semaphorins: old proteins, new immune functions

Plexins and semaphorins are a large family of proteins that are involved in cell movement and response. The importance of plexins and semaphorins has been emphasized by their discovery in many organ systems including the nervous (Nkyimbeng-Takwi and Chapoval, 2011; McCormick and Leipzig, 2012; Yaron and Sprinzak, 2012), epithelial (Miao et al., 1999; Fujii et al., 2002), and immune systems (Takamatsu and Kumanogoh, 2012) as well as diverse cell processes including angiogenesis (Serini et al., 2009; Sakurai et al., 2012), embryogenesis (Perala et al., 2012), and cancer (Potiron et al., 2009; Micucci et al., 2010). Plexins and semaphorins are transmembrane proteins that share a conserved extracellular semaphorin domain (Hota and Buck, 2012). The plexins and semaphorins are divided into four and eight subfamilies respectively based on their structural homology. Semaphorins are relatively small proteins containing the extracellular semaphorin domain and short intracellular tails. Plexins contain the semaphorin domain and long intracellular tails (Hota and Buck, 2012). The majority of plexin and semaphorin research has focused on the nervous system, particularly the developing nervous system, where these proteins are found to mediate many common neuronal cell processes including cell movement, cytoskeletal rearrangement, and signal transduction (Choi et al., 2008; Takamatsu et al., 2010). Their roles in the immune system are the focus of this review.

Neuroimmune semaphorin 4A downregulates the severity of allergic response

To define the role of semaphorin 4A (Sema4A) in allergic response, we employed Sema4A⁻/⁻ and wild-type (WT) mice in the experimental model of ovalbumin (OVA)-induced allergic airway inflammation. We observed a selective increase in eosinophilic airway infiltration accompanied by bronchial epithelial cell hyperplasia in allergen-treated Sema4A⁻/⁻ mice relative to WT mice. This enhanced inflammatory response was associated with a selective increase in bronchoalveolar lavage (BAL) interleukin 13 (IL-13) content, augmented airway hyperreactivity, and lower regulatory T cell (Treg) numbers. In vivo allergen-primed Sema4A⁻/⁻ CD4+ T cells were more effective in transferring T helper type 2 (Th2) response to naive mice as compared with WT CD4+ T cells. T-cell proliferation and IL-13 productions in OVA₃₂₃₋₃₃₉-restimulated Sema4A⁻/⁻ cell cultures were upregulated. Generated bone marrow chimeras showed an equal importance of both lung-resident cell and inflammatory cell Sema4A expression in optimal disease regulation. These data provide a new insight into Sema4A biology and define Sema4A as an important regulator of Th2-driven lung pathophysiology.

Placental expression of CD100, CD72 and CD45 is dysregulated in human miscarriage

Context and Objective

The etiology of miscarriage is often multifactorial. One major cause, immunological rejection of the fetus, has not been clearly elucidated. Our aim was to establish whether the semaphorin CD100, its natural receptor CD72, and the glycoprotein CD45, implicated in immune mechanisms, are involved in pregnancy loss by examining their placental expression with real-time PCR, immunohistochemistry and western blotting techniques.

Patients

Placenta tissue from 72 Caucasian women undergoing surgical uterine evacuation due to early spontaneous pregnancy loss between the 8^th and 12^th week of gestation was divided into four groups based on miscarriage number. Gestational age-matched placentas from 18 healthy women without a history of miscarriage undergoing voluntary pregnancy termination were the control group. Placenta from 6 Caesarean deliveries performed at 38–40 weeks of gestation was also studied.

Results

CD100, CD72 and CD45 were expressed in placenta and exhibited different mRNA and protein levels in normal pregnancy and miscarriage. In particular, protein levels were highly dysregulated around 10 weeks of gestation in first and second miscarriage placentas. The CD100 soluble form was produced and immediately shed from placental tissue in all samples.

Conclusions

Fetal CD100, CD72 and CD45 seem to play a role in miscarriage. The present data support the involvement of the fetal immune system in pregnancy maintenance as well as failure.

Gene-class analysis of expression patterns induced by psychoactive pharmaceutical exposure in fathead minnow (Pimephales promelas) indicates induction of neuronal systems

Psychoactive pharmaceuticals are among the most frequently prescribed drugs, contributing to persistent measurable concentrations in aquatic systems. Typically, it is assumed that such contaminants have no human health implications because they exist in extremely low concentrations. We exposed juvenile fathead minnows (Pimephales promelas) to three pharmaceuticals, fluoxetine, venlafaxine and carbamazepine, individually and in a mixture, and measured their effect on the induction of gene expression in fish brains using microarray analysis. Gene expression changes were accompanied by behavioral changes and validated by qPCR analysis. Gene Set Enrichment Analysis was used to perform gene-class analysis of gene expression, testing for enrichment of gene sets known to be involved in human neuronal development, regulation and growth. We found significant enrichment of gene sets for each of the treatments, with the largest induction of expression by the mixture treatment. These results suggest that the psychoactive pharmaceuticals are able to alter expression of fish genes associated with development, regulation and differentiation of synapses, neurons and neurotransmitters. The results provide a new perspective for the consideration of potential consequence for human health due to environmental exposure to unmetabolized psychoactive pharmaceuticals.