Plexin-A4-semaphorin 3A signaling is required for Toll-like receptor- and sepsis-induced cytokine storm

Prophylactic and Therapeutic Efficacy of Boric Acid on Lipopolysaccharide-Induced Liver and Kidney Inflammation in Rats

In our study, we aimed to examine possible prophylactic (P) or therapeutic (T) effects of boric acid (BA) on lipopolysaccharide (LPS) induced liver and kidney damages. Thirty-two rats were divided into four groups as control, LPS, BAP+LPS, and LPS+BAT. BA was given orally to the rats one hour before the intraperitoneal LPS administration in the BAP+LPS group and one hour after the LPS administration in the LPS+BAT group. Malondialdehyde (MDA), myeloperoxidase (MPO), interleukin-6 (IL-6), IL-10, reduced glutathione (GSH), total oxidant and antioxidant status (TOS and TAS), semaphorin-3A (SEMA3A), cytochrome c (CYCS), and caspase-3 (CASP3) parameters were determined by ELISA method to monitor inflammation, oxidative stress, and apoptosis in the liver and kidney tissues of rats. In addition, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine (CREA), C-reactive protein (CRP), gamma glutamyl transferase (GGT), glucose (GLU), sodium (Na), potassium (K), and chlorine (Cl) biochemical parameters were measured in rat serums to monitor liver and kidney functions. Liver and kidney tissues were also examined histopathologically and immunohistochemically. All data were statistically analyzed. Our histological, biochemical, inflammatory, oxidative stress, and apoptotic findings showed that LPS causes serious damage to liver and kidney tissues. Boric acid application brought about significant improvements on the parameters. However, this improvement was seen in the BAP+LPS group, and the results of the LPS+BAT group were insufficient to improve. Our results showed that boric acid administration is effective on severe liver and kidney damage caused by LPS. It has been concluded that prophylactic application is more effective, while therapeutic application is insufficient.

Multiscale 3D genome organization underlies duck fatty liver with no adipose inflammation or serious injury

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease. Little is known about how gene expression and chromatin structure are regulated in NAFLD due to lack of suitable model. Ducks naturally develop fatty liver similar to serious human non-alcoholic fatty liver (NAFL) without adipose inflammation and liver fibrosis, thus serves as a good model for investigating molecular mechanisms of adipose metabolism and anti-inflammation. Here, we constructed a NAFLD model without adipose inflammation and liver fibrosis in ducks. By performing dynamic pathological and transcriptomic analyses, we identified critical genes involving in regulation of the NF-κB and MHCII signaling, which usually lead to adipose inflammation and liver fibrosis. We further generated dynamic three-dimensional chromatin maps during liver fatty formation and recovery. This showed that ducks enlarged hepatocyte cell nuclei to reduce inter-chromosomal interaction, decompress chromatin structure, and alter strength of intra-TAD and loop interactions during fatty liver formation. These changes partially contributed to the tight control the NF-κB and the MHCII signaling. Our analysis uncovers duck chromatin reorganization might be advantageous to maintain liver regenerative capacity and reduce adipose inflammation. These findings shed light on new strategies for NAFLD control.

Novel tripeptide RKH derived from Akkermansia muciniphila protects against lethal sepsis

OBJECTIVE

The pathogenesis of sepsis is complex, and the sepsis-induced systemic proinflammatory phase is one of the key drivers of organ failure and consequent mortality. Akkermansia muciniphila (AKK) is recognised as a functional probiotic strain that exerts beneficial effects on the progression of many diseases; however, whether AKK participates in sepsis pathogenesis is still unclear. Here, we evaluated the potential contribution of AKK to lethal sepsis development.

DESIGN

Relative abundance of gut microbial AKK in septic patients was evaluated. Cecal ligation and puncture (CLP) surgery and lipopolysaccharide (LPS) injection were employed to establish sepsis in mice. Non-targeted and targeted metabolomics analysis were used for metabolites analysis.

RESULTS

We first found that the relative abundance of gut microbial AKK in septic patients was significantly reduced compared with that in non-septic controls. Live AKK supplementation, as well as supplementation with its culture supernatant, remarkably reduced sepsis-induced mortality in sepsis models. Metabolomics analysis and germ-free mouse validation experiments revealed that live AKK was able to generate a novel tripeptide Arg-Lys-His (RKH). RKH exerted protective effects against sepsis-induced death and organ damage. Furthermore, RKH markedly reduced sepsis-induced inflammatory cell activation and proinflammatory factor overproduction. A mechanistic study revealed that RKH could directly bind to Toll-like receptor 4 (TLR4) and block TLR4 signal transduction in immune cells. Finally, we validated the preventive effects of RKH against sepsis-induced systemic inflammation and organ damage in a piglet model.

CONCLUSION

We revealed that a novel tripeptide, RKH, derived from live AKK, may act as a novel endogenous antagonist for TLR4. RKH may serve as a novel potential therapeutic approach to combat lethal sepsis after successfully translating its efficacy into clinical practice.

Association of Immune Semaphorins with COVID-19 Severity and Outcomes

Semaphorins have recently been recognized as crucial modulators of immune responses. In the pathogenesis of COVID-19, the activation of immune responses is the key factor in the development of severe disease. This study aimed to determine the association of serum semaphorin concentrations with COVID-19 severity and outcomes. Serum semaphorin concentrations (SEMA3A, -3C, -3F, -4D, -7A) were measured in 80 hospitalized adult patients with COVID-19 (moderate (n = 24), severe (n = 32), critical, (n = 24)) and 40 healthy controls. While SEMA3C, SEMA3F and SEMA7A serum concentrations were significantly higher in patients with COVID-19, SEMA3A was significantly lower. Furthermore, SEMA3A and SEMA3C decreased with COVID-19 severity, while SEMA3F and SEMA7A increased. SEMA4D showed no correlation with disease severity. Serum semaphorin levels show better predictive values than CRP, IL-6 and LDH for differentiating critical from moderate/severe COVID-19. SEMA3F and SEMA7A serum concentrations were associated with the time to recovery, requirement of invasive mechanical ventilation, development of pulmonary thrombosis and nosocomial infections, as well as with in-hospital mortality. In conclusion, we provide the first evidence that SEMA3A, SEMA3C, SEMA3F and SEMA7A can be considered as new biomarkers of COVID-19 severity.

Semaphorins in immune cell function, inflammatory and infectious diseases

The Semaphorin family is a group of proteins studied broadly for their functions in nervous systems. They consist of eight subfamilies ubiquitously expressed in vertebrates, invertebrates, and viruses and exist in membrane-bound or secreted forms. Emerging evidence indicates the relevance of semaphorins outside the nervous system, including angiogenesis, cardiogenesis, osteoclastogenesis, tumour progression, and, more recently, the immune system. This review provides a broad overview of current knowledge on the role of semaphorins in the immune system, particularly its involvement in inflammatory and infectious diseases, including chlamydial infections.

Protective effects of blocking PD-1 pathway on retinal ganglion cells in a mouse model of chronic ocular hypertension

Purpose

In this study, we aimed to investigate whether Programmed cell death 1 ligand 1/programmed cell death 1 ligand 2 (PD-L1/PD-L2) double knockout (dKO) has a protective effect on RGCs in a mouse model of chronic ocular hypertension (COHT).

Methods

We used superparamagnetic iron oxide to induce COHT in mice. Apoptosis of retinal ganglion cells (RGCs) and activation of microglia were evaluated using western blotting (WB) and immunofluorescence staining of the mouse retina. In addition, we also conducted transcriptome sequencing and further gene expression analyses using the gene ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) database.

Results

In the mouse model of COHT, PD-L1/PD-L2 prevented the apoptosis of RGCs to some extent. Blocking the programmed cell death 1 (PD-1) pathway also increased the number of anti-inflammatory M2-activated microglia and enhanced the phosphorylation of its related pathway signal transducer and activator of transcription (STAT)6. Sequencing results showed that this protective effect may have been achieved by regulating the NF-B, tumour necrosis factor (TNF), PI3K/Akt and toll-like receptor signaling pathway etc.

Conclusion

Blocking the PD-1 pathway has a protective effect on RGCs in the mouse model of COHT induced by superparamagnetic iron oxide.

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

An increase in Semaphorin 3A biases the axonal direction and induces an aberrant dendritic arborization in an in vitro model of human neural progenitor differentiation

Background

Semaphorins (Sema) belong to a large family of repellent guidance cues instrumental in guiding axons during development. In particular, Class 3 Sema (Sema 3) is among the best characterized Sema family members and the only produced as secreted proteins in mammals, thereby exerting both autocrine and paracrine functions. Intriguingly, an increasing number of studies supports the crucial role of the Sema 3A in hippocampal and cortical neurodevelopment. This means that alterations in Sema 3A signaling might compromise hippocampal and cortical circuits and predispose to disorders such as autism and schizophrenia. Consistently, increased Sema 3A levels have been detected in brain of patients with schizophrenia and many polymorphisms in Sema 3A or in the Sema 3A receptors, Neuropilins (Npn 1 and 2) and Plexin As (Plxn As), have been associated to autism.

Results

Here we present data indicating that when overexpressed, Sema 3A causes human neural progenitors (NP) axonal retraction and an aberrant dendritic arborization. Similarly, Sema 3A, when overexpressed in human microglia, triggers proinflammatory processes that are highly detrimental to themselves as well as NP. Indeed, NP incubated in microglia overexpressing Sema 3A media retract axons within an hour and then start suffering and finally die. Sema 3A mediated retraction appears to be related to its binding to Npn 1 and Plxn A2 receptors, thus activating the downstream Fyn tyrosine kinase pathway that promotes the threonine-serine kinase cyclin-dependent kinase 5, CDK5, phosphorylation at the Tyr15 residue and the CDK5 processing to generate the active fragment p35.

Conclusions

All together this study identifies Sema 3A as a critical regulator of human NP differentiation. This may imply that an insult due to Sema 3A overexpression during the early phases of neuronal development might compromise neuronal organization and connectivity and make neurons perhaps more vulnerable to other insults across their lifespan.

SUSD2 suppresses CD8+ T cell antitumor immunity by targeting IL-2 receptor signaling

Dysfunctional CD8+ T cells, which have defective production of antitumor effectors, represent a major mediator of immunosuppression in the tumor microenvironment. Here, we show that SUSD2 is a negative regulator of CD8+ T cell antitumor function. Susd2-/- effector CD8+ T cells showed enhanced production of antitumor molecules, which consequently blunted tumor growth in multiple syngeneic mouse tumor models. Through a quantitative mass spectrometry assay, we found that SUSD2 interacted with interleukin (IL)-2 receptor α through sushi domain-dependent protein interactions and that this interaction suppressed the binding of IL-2, an essential cytokine for the effector functions of CD8+ T cells, to IL-2 receptor α. SUSD2 was not expressed on regulatory CD4+ T cells and did not affect the inhibitory function of these cells. Adoptive transfer of Susd2-/- chimeric antigen receptor T cells induced a robust antitumor response in mice, highlighting the potential of SUSD2 as an immunotherapy target for cancer.

Semaphorin 3A in the Immune System: Twenty Years of Study

Semaphorin 3A is a secreted glycoprotein, which was originally identified as axon guidance factor in the neuronal system, but it also possesses immunoregulatory properties. Here, the effect of semaphorin 3A on T-lymphocytes, myeloid dendritic cells and macrophages is systematically analyzed on the bases of all publications available in the literature for 20 years. Expression of semaphorin 3A receptors – neuropilin-1 and plexins A – in these cells is described in details. The data obtained on human and murine cells is described comparatively. A comprehensive overview of the interaction of semaphorin 3A with mononuclear phagocyte system is presented for the first time. Semaphorin 3A signaling mostly results in changes of the cytoskeletal machinery and cellular morphology that regulate pathways involved in migration, adhesion, and cell–cell cooperation of immune cells. Accumulating evidence indicates that this factor is crucially involved in various phases of immune responses, including initiation phase, antigen presentation, effector T cell function, inflammation phase, macrophage activation, and polarization. In recent years, interest in this field has increased significantly because semaphorin 3A is associated with many human diseases and therefore can be used as a target for their treatment. Its involvement in the immune responses is important to study, because semaphorin 3A and its receptors turn to be a promising new therapeutic tools to be applied in many autoimmune, allergic, and oncology diseases.

Prediction of Adrenocortical Carcinoma Relapse and Prognosis with a Set of Novel Multigene Panels

Effective assessment of adrenocortical carcinoma (ACC) prognosis is critical in patient management. We report four novel and robust prognostic multigene panels. Sig27var25, SigIQvar8, SigCmbnvar5, and SigCmbn_B predict ACC relapse at area under the curve (AUC) of 0.89, 0.79, 0.78, and 0.80, respectively, and fatality at AUC of 0.91, 0.88, 0.85, and 0.87, respectively. Among their 33 component genes, 31 are novel. They could be differentially expressed in ACCs from normal tissues, tumors with different severity (stages and lymph node metastasis), ACCs with TP53 mutations, and tumors with differentially expressed immune checkpoints (CTLA4, PD1, TGFBR1, and others). All panels correlate with reductions of ACC-associated CD8+ and/or NK cells. Furthermore, we provide the first evidence for the association of mesenchymal stem cells (MSCs) with ACC relapse (p = 2 × 10−6) and prognosis (p = 2 × 10−8). Sig27var25, SigIQvar8, SigCmbnvar5, and SigCmbn_B correlate with MSC (spearman r ≥ 0.53, p ≤ 1.38 × 10−5). Sig27var25 and SigIQvar8 were derived from a prostate cancer (PC) and clear cell renal cell carcinoma (ccRCC) multigene signature, respectively; SigCmbnvar5 and SigCmbn_B are combinations of both panels, revealing close relationships of ACC with PC and ccRCC. The origin of these four panels from PC and ccRCC favors their prognostic potential towards ACC.

Plexin-A4 Mediates Cytotoxic T-cell Trafficking and Exclusion in Cancer

Cytotoxic T cell (CTL) infiltration of the tumor carries the potential to limit cancer progression, but their exclusion by the immunosuppressive tumor microenvironment hampers the efficiency of immunotherapy. Here, we show that expression of the axon guidance molecule Plexin-A4 (Plxna4) in CTLs, especially in effector/memory CD8⁺ T cells, is induced upon T-cell activation, sustained in the circulation, but reduced when entering the tumor bed. Therefore, we deleted Plxna4 and observed that Plxna4-deficient CTLs acquired improved homing capacity to the lymph nodes and to the tumor, as well as increased proliferation, both achieved through enhanced Rac1 activation. Mice with stromal or hematopoietic Plxna4 deletion exhibited enhanced CTL infiltration and impaired tumor growth. In a melanoma model, adoptive transfer of CTLs lacking Plxna4 prolonged survival and improved therapeutic outcome, which was even stronger when combined with anti-programmed cell death protein 1 (PD-1) treatment. PLXNA4 abundance in circulating CTLs was augmented in melanoma patients versus healthy volunteers but decreased after the first cycle of anti-PD-1, alone or in combination with anti-cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4), in those patients showing complete or partial response to the treatment. Altogether, our data suggest that Plxna4 acts as a "checkpoint," negatively regulating CTL migration and proliferation through cell-autonomous mechanisms independent of the interaction with host-derived Plxna4 ligands, semaphorins. These findings pave the way toward Plxna4-centric immunotherapies and propose Plxna4 detection in circulating CTLs as a potential way to monitor the response to immune checkpoint blockade in patients with metastatic melanoma.

Neural guidance factors as hubs of immunometabolic crosstalk

Semaphorins were originally identified as axon-guidance molecules essential for neural development. In addition to their functions in the neural system, members of the semaphorin family have critical functions in many pathophysiological processes, including immune responses, bone homeostasis, cancer and metabolic disorders. In particular, several lines of evidence indicate that mammalian/mechanistic target of rapamycin (mTOR), a central regulator of cell metabolism, regulates the functions of semaphorins in various types of cells, revealing a novel link between semaphorins and cell metabolism. In this review, we discuss recent advances in the immunometabolic functions of semaphorins, with a particular focus on mTOR signaling.

Recurrent Urinary Tract Infection: A Mystery in Search of Better Model Systems

Urinary tract infections (UTIs) are among the most common infectious diseases worldwide but are significantly understudied. Uropathogenic E. coli (UPEC) accounts for a significant proportion of UTI, but a large number of other species can infect the urinary tract, each of which will have unique host-pathogen interactions with the bladder environment. Given the substantial economic burden of UTI and its increasing antibiotic resistance, there is an urgent need to better understand UTI pathophysiology - especially its tendency to relapse and recur. Most models developed to date use murine infection; few human-relevant models exist. Of these, the majority of in vitro UTI models have utilized cells in static culture, but UTI needs to be studied in the context of the unique aspects of the bladder's biophysical environment (e.g., tissue architecture, urine, fluid flow, and stretch). In this review, we summarize the complexities of recurrent UTI, critically assess current infection models and discuss potential improvements. More advanced human cell-based in vitro models have the potential to enable a better understanding of the etiology of UTI disease and to provide a complementary platform alongside animals for drug screening and the search for better treatments.

Semaphorin3A increases M1-like microglia and retinal ganglion cell apoptosis after optic nerve injury

Background

The mechanisms leading to retinal ganglion cell (RGC) death after optic nerve injury have not been fully elucidated. Current evidence indicates that microglial activation and M1- and M2-like dynamics may be an important factor in RGC apoptosis after optic nerve crush (ONC). Semaphorin3A (Sema3A) is a classic axonal guidance protein,which has been found to have a role in neuroinflammation processes. In this study, we investigated the contribution of microglial-derived Sema3A to progressive RGC apoptosis through regulating paradigm of M1- and M2-like microglia after ONC.

Method

A mouse ONC model and a primary microglial-RGC co-culture system were used in the present study. The expression of M1- and M2-like microglial activation markers were assessed by real-time polymerase chain reaction (RT-qPCR). Histological and Western blot (WB) analyses were used to investigate the polarization patterns of microglia transitions and the levels of Sema3A. RGC apoptosis was investigated by TUNEL staining and caspase-3 detection.

Results

Levels of Sema3A in the mouse retina increased after ONC. Treatment of mice with the stimulating factor 1 receptor antagonist PLX3397 resulted in a decrease of retinal microglia. The levels of CD16/32 (M1) were up-regulated at days 3 and 7 post-ONC. However, CD206 (M2) declined on day 7 after ONC. Exposure to anti-Sema3A antibodies (anti-Sema3A) resulted in a decrease in the number of M1-like microglia, an increase in the number of M2-like microglia, and the amelioration of RGC apoptosis.

Conclusions

An increase in microglia-derived Sema3A in the retina after ONC partially leads to a continuous increase of M1-like microglia and plays an important role in RGC apoptosis. Inhibition of Sema3A activity may be a novel approach to the prevention of RGC apoptosis after optic nerve injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00603-7.

Plexin-A4 mediates amyloid-β-induced tau pathology in Alzheimer's disease animal model

Amyloid-β (Aβ) and tau are major pathological hallmarks of Alzheimer's disease (AD). Several studies have revealed that Aβ accelerates pathological tau transition and spreading during the disease progression, and that reducing tau can mitigate pathological features of AD. However, molecular links between Aβ and tau pathologies remain elusive. Here, we suggest a novel role for the plexin-A4 as an Aβ receptor that induces aggregated tau pathology. Plexin-A4, previously known as proteins involved in regulating axon guidance and synaptic plasticity, can bound to Aβ with co-receptor, neuropilin-2. Genetic downregulation of plexin-A4 in neurons was sufficient to prevent Aβ-induced activation of CDK5 and reduce tau hyperphosphorylation and aggregation, even in the presence of Aβ. In an AD mouse model that manifests both Aβ and tau pathologies, genetic downregulation of plexin-A4 in the hippocampus reduced tau pathology and ameliorated spatial memory impairment. Collectively, these results indicate that the plexin-A4 is capable of mediating Aβ-induced tau pathology in AD pathogenesis.

Downregulation of Endothelial Plexin A4 Under Inflammatory Conditions Impairs Vascular Integrity

Objective: Besides hyperlipidemia, inflammation is an important determinant in the initiation and the progression of atherosclerosis. As Neuroimmune Guidance Cues (NGCs) are emerging as regulators of atherosclerosis, we set out to investigate the expression and function of inflammation-regulated NGCs. Methods and results: NGC expression in human monocytes and endothelial cells was assessed using a publicly available RNA dataset. Next, the mRNA levels of expressed NGCs were analyzed in primary human monocytes and endothelial cells after stimulation with IL1β or TNFα. Upon stimulation a total of 14 and 19 NGCs in monocytes and endothelial cells, respectively, were differentially expressed. Since plexin A4 (PLXNA4) was strongly downregulated in endothelial cells under inflammatory conditions, the role of PLXNA4 in endothelial function was investigated. Knockdown of PLXNA4 in endothelial cells markedly impaired the integrity of the monolayer leading to more elongated cells with an inflammatory phenotype. In addition, these cells showed an increase in actin stress fibers and decreased cell-cell junctions. Functional assays revealed decreased barrier function and capillary network formation of the endothelial cells, while vascular leakage and trans-endothelial migration of monocytes was increased. Conclusion: The current study demonstrates that pro-inflammatory conditions result in differential expression of NGCs in endothelial cells and monocytes, both culprit cell types in atherosclerosis. Specifically, endothelial PLXNA4 is reduced upon inflammation, while PLXNA4 maintains endothelial barrier function thereby preventing vascular leakage of fluids as well as cells. Taken together, PLXNA4 may well have a causal role in atherogenesis that deserves further investigation.

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 3A contributes to sepsis‑induced immunosuppression by impairing CD4+ T cell anergy

Semaphorin 3A (Sema3A), a member of the Sema family of proteins, appears to serve an important role in sepsis and sepsis‑induced immunosuppression and has been regarded as a crucial regulator involved in cellular immune response. However, the role of Sema3A in CD4+ T cell anergy during sepsis remains to be elucidated. In the present study, the cecal ligation and perforation model and lipopolysaccharide (LPS) were used to simulate sepsis and the role of Sema3A in sepsis‑induced CD4+ T cell anergy was investigated in vivo and in vitro. In vivo, the serum concentration of Sema3A was enhanced and exacerbated sepsis‑induced T cell immunosuppression and multiple organ dysfunction syndromes (MODS). Administration of (‑)‑epigallocatechin‑3‑gallate, an inhibitor of Sema3A, markedly improved sepsis‑induced T cell immunosuppression and MODS. In vitro, both lymphoid and myeloid lineages secreted high concentration of Sema3A in LPS‑induced sepsis, especially in the lymphoid lineage. Inhibition of Sema3A alleviated T cell anergy. The NF‑κB signaling pathway was involved in Sema3A‑mediated autocrine loop aggravating T cell immune dysfunction during LPS‑induced sepsis. Inhibiting Sema3A exerted significant improvement of sepsis‑induced immunosuppression and MODS, which was associated with improvement of CD4+ T cells anergy via regulation of the NF‑κB signaling pathway.

Single-cell transcriptomes of mouse bladder urothelium uncover novel cell type markers and urothelial differentiation characteristics

Objectives

Much of the information to date in terms of subtypes and function of bladder urothelial cells were derived from anatomical location or by the expression of a small number of marker genes. To have a comprehensive map of the cellular anatomy of bladder urothelial cells, we performed single‐cell RNA sequencing to thoroughly characterize mouse bladder urothelium.

Materials and methods

A total of 18,917 single cells from mouse bladder urothelium were analysed by unbiased single‐cell RNA sequencing. The expression of the novel cell marker was confirmed by immunofluorescence using urinary tract infection models.

Results

Unsupervised clustering analysis identified 8 transcriptionally distinct cell subpopulations from mouse bladder urothelial cells. We discovered a novel type of bladder urothelial cells marked by Plxna4 that may be involved with host response and wound healing. We also found a group of basal‐like cells labelled by ASPM that could be the progenitor cells of adult bladder urothelium. ASPM⁺ urothelial cells are significantly increased after injury by UPEC. In addition, specific transcription factors were found to be associated with urothelial cell differentiation. At the last, a number of interstitial cystitis/bladder pain syndrome–regulating genes were found differentially expressed among different urothelial cell subpopulations.

Conclusions

Our study provides a comprehensive characterization of bladder urothelial cells, which is fundamental to understanding the biology of bladder urothelium and associated bladder disease.

Effective Prediction of Prostate Cancer Recurrence through the IQGAP1 Network

IQGAP1 expression was analyzed in: (1) primary prostate cancer, (2) xenografts produced from LNCaP, DU145, and PC3 cells, 3) tumor of PTEN-/- and TRAMP mice, and (3) castration resistant PC (CRPC) produced by LNCaP xenografts and PTEN-/- mice. IQGAP1 downregulations occurred in CRPC and advanced PCs. The downregulations were associated with rapid PC recurrence in the TCGA PanCancer (n = 492, p = 0.01) and MSKCC (n = 140, p = 4 × 10-6) cohorts. Differentially expressed genes (n = 598) relative to IQGAP1 downregulation were identified with enrichment in chemotaxis, cytokine signaling, and others along with reductions in immune responses. A novel 27-gene signature (Sig27gene) was constructed from these DEGs through random division of the TCGA cohort into a Training and Testing population. The panel was validated using an independent MSKCC cohort. Sig27gene robustly predicts PC recurrence at (hazard ratio) HR 2.72 and p < 2 × 10-16 in two independent PC cohorts. The prediction remains significant after adjusting for multiple clinical features. The novel and robust nature of Sig27gene underlie its great translational potential as a prognostic biomarker to predict PC relapse risk in patients with primary PC.

MiR-223-3p in Cardiovascular Diseases: A Biomarker and Potential Therapeutic Target

Cardiovascular diseases, involving vasculopathy, cardiac dysfunction, or circulatory disturbance, have become the major cause of death globally and brought heavy social burdens. The complexity and diversity of the pathogenic factors add difficulties to diagnosis and treatment, as well as lead to poor prognosis of these diseases. MicroRNAs are short non-coding RNAs to modulate gene expression through directly binding to the 3′-untranslated regions of mRNAs of target genes and thereby to downregulate the protein levels post-transcriptionally. The multiple regulatory effects of microRNAs have been investigated extensively in cardiovascular diseases. MiR-223-3p, expressed in multiple cells such as macrophages, platelets, hepatocytes, and cardiomyocytes to modulate their cellular activities through targeting a variety of genes, is involved in the pathological progression of many cardiovascular diseases. It participates in regulation of several crucial signaling pathways such as phosphatidylinositol 3-kinase/protein kinase B, insulin-like growth factor 1, nuclear factor kappa B, mitogen-activated protein kinase, NOD-like receptor family pyrin domain containing 3 inflammasome, and ribosomal protein S6 kinase B1/hypoxia inducible factor 1 α pathways to affect cell proliferation, migration, apoptosis, hypertrophy, and polarization, as well as electrophysiology, resulting in dysfunction of cardiovascular system. Here, in this review, we will discuss the role of miR-223-3p in cardiovascular diseases, involving its verified targets, influenced signaling pathways, and regulation of cell function. In addition, the potential of miR-223-3p as therapeutic target and biomarker for diagnosis and prediction of cardiovascular diseases will be further discussed, providing clues for clinicians.

Potential application of mesenchymal stem cells and their exosomes in lung injury: an emerging therapeutic option for COVID-19 patients

The COVID-19 pandemic has negatively impacted the global public health and the international economy; therefore, there is an urgent need for an effective therapy to treat COVID-19 patients. Mesenchymal stem cells (MSCs) have been proposed as an emerging therapeutic option for the SARS-CoV-2 infection. Recently, numerous clinical trials have been registered to examine the safety and efficacy of different types of MSCs and their exosomes for treating COVID-19 patients, with less published data on the mechanism of action. Although there is no approved effective therapy for COVID-19 as of yet, MSC therapies showed an improvement in the treatment of some COVID-19 patients. MSC’s therapeutic effect is displayed in their ability to reduce the cytokine storm, enhance alveolar fluid clearance, and promote epithelial and endothelial recovery; however, the safest and most effective route of MSC delivery remains unclear. The use of poorly characterized MSC products remains one of the most significant drawbacks of MSC-based therapy, which could theoretically promote the risk for thromboembolism. Optimizing the clinical-grade production of MSCs and establishing a consensus on registered clinical trials based on cell-product characterization and mode of delivery would aid in laying the foundation for a safe and effective therapy in COVID-19. In this review, we shed light on the mechanistic view of MSC therapeutic role based on preclinical and clinical studies on acute lung injury and ARDS; therefore, offering a unique correlation and applicability in COVID-19 patients. We further highlight the challenges and opportunities in the use of MSC-based therapy.

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.

Semaphorin3A-Inhibitor Ameliorates Doxorubicin-Induced Podocyte Injury

Podocyte injury is an independent risk factor for the progression of renal diseases. Semaphorin3A (SEMA3A), expressed in podocytes and tubular cells in the mammalian adult kidneys, has been reported to regulate diverse biological functions and be associated with renal diseases. Here, we investigated pathological roles of SEMA3A signaling on podocyte injury using a doxorubicin (Dox)-induced mouse model and examined the therapeutic effect of SEMA3A-inhibitor (SEMA3A-I). We demonstrated that Dox caused massive albuminuria and podocyte apoptosis as well as an increase of SEMA3A expression in podocytes, all of which were ameliorated with SEMA3A-I treatment. In addition, c-Jun N-terminal kinase (JNK), known as a downstream of SEMA3A signaling, was activated in Dox-injected mouse podocytes while SEMA3A-I treatment partially blocked the activation. In vitro, SEMA3A-I protected against Dox-induced podocyte apoptosis and recombinant SEMA3A caused podocyte apoptosis with activation of JNK signaling. JNK inhibitor, SP600125, attenuated SEMA3A-induced podocyte apoptosis, indicating that the JNK pathway would be involved in SEMA3A-induced podocyte apoptosis. Furthermore, the analysis of human data revealed a positive correlation between levels of urinary SEMA3A and protein, suggesting that SEMA3A is associated with podocyte injury. In conclusion, SEMA3A has essential roles in podocyte injury and it would be the therapeutic target for protecting from podocyte injury.

Immunoregulatory properties of mesenchymal stem cells: Micro-RNAs

Mesenchymal stem cells (MSCs) are multipotent cells that are excellent candidates for different cellular therapies due to their physiological properties such as immunoregulatory function. whetheare currently utilized for regenerative medication and treatment of a number of inflammatory illnesses given their ability to considerably impact tissue microenvironments via extracellular vesicles or toll-like receptor pathway modulation. MicroRNAs (miRNAs) are small noncoding RNAs that target the messenger RNA and play a critical role in different biological procedures, such as the development and reaction of the immune system. Moreover, miRNAs have recently been revealed to have serious functions in MSCs to regulate immunomodulatory properties. In this review, we study how the miRNAs pathway can modulate the immunoregulatory activity of MSCs by counting their interactions with immune cells and also discuss the possibility of using miRNA-based implications for MSC-based therapies.

Semaphorin 3E Regulates the Response of Macrophages to Lipopolysaccharide-Induced Systemic Inflammation

Semaphorin 3E (Sema3E) is a secreted protein that was initially discovered as a neuronal guidance cue. Recent evidence showed that Sema3E plays an essential role in regulating the activities of various immune cells. However, the exact role of Sema3E in macrophage function, particularly during inflammation, is not fully understood. We studied the impact of Sema3E gene deletion on macrophage function during the LPS-induced acute inflammatory response. We found that Sema3E-deficient (Sema3e^-/- ) mice were better protected from LPS-induced acute inflammation as exemplified by their superior clinical score and effective temperature control compared with their wild-type littermates. This superior control of inflammatory response in Sema3e^-/- mice was associated with significantly lower phosphorylation of ERK1/2, AKT, STAT3, and NF-κB, and a concomitant reduction in inducible NO synthase expression and production of TNF and IL-6 compared with their Sema3e^+/+ littermates. Sema3e^-/- mice also contained significantly higher numbers of activated macrophages compared with their Sema3e^+/+ littermates at both baselines and after LPS challenge. In vivo-specific deletion of the Sema3E high-affinity receptor, plexinD1, on macrophages led to the improvement in clinical disease following exposure to a lethal dose of LPS. Collectively, our data show that Sema3E plays an essential role in dampening the early inflammatory response to LPS by regulating macrophage function, suggesting an essential role of this pathway in macrophage inflammatory response.

DNA methylation profiles are associated with complex regional pain syndrome after traumatic injury

Factors contributing to development of complex regional pain syndrome (CRPS) are not fully understood. This study examined possible epigenetic mechanisms that may contribute to CRPS after traumatic injury. DNA methylation profiles were compared between individuals developing CRPS (n = 9) and those developing non-CRPS neuropathic pain (n = 38) after undergoing amputation following military trauma. Linear Models for Microarray (LIMMA) analyses revealed 48 differentially methylated cytosine-phosphate-guanine dinucleotide (CpG) sites between groups (unadjusted P's < 0.005), with the top gene COL11A1 meeting Bonferroni-adjusted P < 0.05. The second largest differential methylation was observed for the HLA-DRB6 gene, an immune-related gene linked previously to CRPS in a small gene expression study. For all but 7 of the significant CpG sites, the CRPS group was hypomethylated. Numerous functional Gene Ontology-Biological Process categories were significantly enriched (false discovery rate-adjusted q value <0.15), including multiple immune-related categories (eg, activation of immune response, immune system development, regulation of immune system processes, and antigen processing and presentation). Differentially methylated genes were more highly connected in human protein-protein networks than expected by chance (P < 0.05), supporting the biological relevance of the findings. Results were validated in an independent sample linking a DNA biobank with electronic health records (n = 126 CRPS phenotype, n = 19,768 non-CRPS chronic pain phenotype). Analyses using PrediXcan methodology indicated differences in the genetically determined component of gene expression in 7 of 48 genes identified in methylation analyses (P's < 0.02). Results suggest that immune- and inflammatory-related factors might confer risk of developing CRPS after traumatic injury. Validation findings demonstrate the potential of using electronic health records linked to DNA for genomic studies of CRPS.

Derivation of Macrophages from Mouse Bone Marrow

Macrophages are cellular components of the immune system that are essential for responding to pathogens, initiating inflammation and maintaining tissue homeostasis. Isolation, culture, and functional characterization of bone marrow-derived macrophages from mice are exceptionally powerful in vitro techniques used to examine aspects of macrophage biology, including effector functions, such as phagocytosis, cytokine secretion, oxidative burst, migration, and antigen processing and presentation. These studies can be carried out using wild-type, gene-ablated, and/or transgenic mice. The quantity, purity, and ease of culture of these cells enhance their utility for primary cell cultures to understand macrophage biology. Mouse macrophages have become a cognate animal model for the study of human macrophage biology and disease. This chapter outlines protocols used to generate, polarize, quantitate, and functionally evaluate macrophages derived from bone marrow precursor cells.

O-GlcNAc Transferase Suppresses Inflammation and Necroptosis by Targeting Receptor-Interacting Serine/Threonine-Protein Kinase 3

Elevated glucose metabolism in immune cells represents a hallmark feature of many inflammatory diseases, such as sepsis. However, the role of individual glucose metabolic pathways during immune cell activation and inflammation remains incompletely understood. Here, we demonstrate a previously unrecognized anti-inflammatory function of the O-linked β-N-acetylglucosamine (O-GlcNAc) signaling associated with the hexosamine biosynthesis pathway (HBP). Despite elevated activities of glycolysis and the pentose phosphate pathway, activation of macrophages with lipopolysaccharide (LPS) resulted in attenuated HBP activity and protein O-GlcNAcylation. Deletion of O-GlcNAc transferase (OGT), a key enzyme for protein O-GlcNAcylation, led to enhanced innate immune activation and exacerbated septic inflammation. Mechanistically, OGT-mediated O-GlcNAcylation of the serine-threonine kinase RIPK3 on threonine 467 (T467) prevented RIPK3-RIPK1 hetero- and RIPK3-RIPK3 homo-interaction and inhibited downstream innate immunity and necroptosis signaling. Thus, our study identifies an immuno-metabolic crosstalk essential for fine-tuning innate immune cell activation and highlights the importance of glucose metabolism in septic inflammation.

Class-3 Semaphorins and Their Receptors: Potent Multifunctional Modulators of Tumor Progression

Semaphorins are the products of a large gene family containing 28 genes of which 21 are found in vertebrates. Class-3 semaphorins constitute a subfamily of seven vertebrate semaphorins which differ from the other vertebrate semaphorins in that they are the only secreted semaphorins and are distinguished from other semaphorins by the presence of a basic domain at their C termini. Class-3 semaphorins were initially characterized as axon guidance factors, but have subsequently been found to regulate immune responses, angiogenesis, lymphangiogenesis, and a variety of additional physiological and developmental functions. Most class-3 semaphorins transduce their signals by binding to receptors belonging to the neuropilin family which subsequently associate with receptors of the plexin family to form functional class-3 semaphorin receptors. Recent evidence suggests that class-3 semaphorins also fulfill important regulatory roles in multiple forms of cancer. Several class-3 semaphorins function as endogenous inhibitors of tumor angiogenesis. Others were found to inhibit tumor metastasis by inhibition of tumor lymphangiogenesis, by direct effects on the behavior of tumor cells, or by modulation of immune responses. Notably, some semaphorins such as sema3C and sema3E have also been found to potentiate tumor progression using various mechanisms. This review focuses on the roles of the different class-3 semaphorins in tumor progression.

Semaphorin Signaling in Cancer-Associated Inflammation

The inflammatory and immune response elicited by the growth of cancer cells is a major element conditioning the tumor microenvironment, impinging on disease progression and patients’ prognosis. Semaphorin receptors are widely expressed in inflammatory cells, and their ligands are provided by tumor cells, featuring an intense signaling cross-talk at local and systemic levels. Moreover, diverse semaphorins control both cells of the innate and the antigen-specific immunity. Notably, semaphorin signals acting as inhibitors of anti-cancer immune response are often dysregulated in human tumors, and may represent potential therapeutic targets. In this mini-review, we provide a survey of the best known semaphorin regulators of inflammatory and immune cells, and discuss their functional impact in the tumor microenvironment.

Generation and Culture of Mouse Embryonic Fibroblasts

In addition to leukocytes, a variety of cells also participate in the innate immune response, including endothelial cells, epithelial cells, and fibroblasts. Thus, the study of these cells is highly relevant in broadening our understanding of mechanisms that modulate innate immunity. With the rise of genetically engineered animals, it is now common to confirm in vitro data acquired using immortalized cell lines with more physiologically relevant primary cells from these animals ex vivo. Indeed, many studies exploring innate immune system function employ mouse embryonic fibroblasts (MEFs). These cells are relatively simple to generate and are a powerful tool to explore regulatory networks, examine biochemical profiling of protein complexes, and investigate novel signaling pathways associated with innate immune system signaling. Here, we provide a robust protocol to isolate, maintain, and store primary MEFs. This protocol is designed for users with minimal experience using mouse models. We have also added precautions and common pitfalls associated with these procedures.

The association of semaphorins 3C, 5A and 6D with liver fibrosis stage in chronic hepatitis C

Semaphorins are a diverse family of immunoregulators recently recognized to play a major role in various phases of immune responses. Their role in chronic viral hepatitis C (CHC) and contribution to the progression of liver disease is unknown. The aim of this study was to analyse the association of secreted semaphorins with the severity of liver disease in patients with CHC. Serum concentrations of semaphorins were measured in 114 treatment-naive CHC patients and 36 healthy controls. Serum concentrations of SEMA3A, SEMA3C, SEMA5A, SEMA6B and SEMA6D were significantly increased in patients with CHC compared to controls. While serum concentrations of SEMA3C and SEMA6D significantly increased with fibrosis stage in both HCV-g1 and HCV-g3 infections, the concentration of SEMA5A inversely correlated with fibrosis stage in both HCV genotypes. ROC analysis showed that serum concentrations of SEMA3C (>4.0ng/mL, AUC 0.88) and SEMA6D (>4.5, AUC 0.82) had higher AUC than widely used APRI (AUC 0.71) and FIB-4 (AUC 0.74) scores. Serum concentrations of SEMA3C and SEMA6D significantly decreased after DAA and PEG IFN-α/ribavirin therapy, while the serum concentration of SEMA5A significantly increased after DAAs therapy. Immunohistochemistry confirmed the expression of SEMA3C and SEMA5A in hepatocytes, endothelial cells and lymphocytes of cirrhotic livers from CHC patients but not in controls. In conclusion, we provide the first evidence that SEMA3C, SEMA5A and SEMA6D can be considered as markers of liver injury in CHC.

Concise Review: TLR Pathway-miRNA Interplay in Mesenchymal Stromal Cells: Regulatory Roles and Therapeutic Directions

Mesenchymal stromal cells (MSCs) deploy Toll-like receptors (TLRs) to respond to exogenous and endogenous signals. Activation of TLR pathways in MSCs alters their inflammatory profile and immunomodulatory effects on cells from both the innate and adaptive immune systems. Micro-RNAs (miRNAs), whose expression is modulated by TLR activation, can regulate inflammatory responses by targeting components of the TLR signaling pathways either in MSCs or in the cells with which they interact. Here, we review how the miRNA-TLR pathway axis can regulate the immunomodulatory functions of MSCs, including their interactions with monocytes/macrophages and natural killer cells, and discuss the therapeutic implications for MSC-based therapies. Stem Cells 2018;36:1655-1662.

Inhibition of semaphorin-3a suppresses lipopolysaccharide-induced acute kidney injury

Semaphorin-3a (Sema3A), a soluble axon guidance cue, appears to play an important role in the development of acute kidney injury (AKI) and has been regarded as an early diagnostic marker to evaluate the progression of AKI. However, the role of Sema3A in sepsis-associated AKI remains unknown. In this study, lipopolysaccharide (LPS) was used to simulate sepsis-associated AKI and the role of Sema3A in LPS-induced AKI was investigated in vivo and in vitro. In our in vivo study, Sema3A was found in tubular epithelial cells (TECs), which presented a higher level after LPS treatment. Meanwhile, the results of our in vitro experiment showed that Sema3A was also elevated in NRK-52E cells treated by LPS. Notably, inhibition of Sema3A by (-)-epigallocatechin-3-gallate (EGCG) could significantly reduce kidney inflammation and apoptosis in mice. Likewise, EGCG intervention also ameliorated the inflammation and apoptosis of cells in vitro. Furthermore, our research also found that the Rac1/NF-κB p65 and JNK pathways were possibly involved in the Sema3A-mediated inflammation and apoptosis of TECs, respectively. Our findings suggest that Sema3A play a pathogenic role by promoting inflammation and apoptosis of TECs in LPS-induced AKI. It might serve as a useful treatment target in ameliorating sepsis-associated AKI. KEY MESSAGES: Sema3A is upregulated in LPS-induced AKI. Inhibition of Sema3A attenuates inflammation and apoptosis of TECs in LPS-induced AKI. Sema3A enhances the LPS-induced inflammation of TECs through the Rac1/NF-κB p65 pathway. Sema3A exacerbates the LPS-induced apoptosis of TECs through the JNK pathway.

Semaphorin 6D reverse signaling controls macrophage lipid metabolism and anti-inflammatory polarization

Polarization of macrophages into pro-inflammatory or anti-inflammatory states has distinct metabolic requirements, with mechanistic target of rapamycin (mTOR) kinase signaling playing a critical role. However, it remains unclear how mTOR regulates metabolic status to promote polarization of these cells. Here we show that an mTOR-Semaphorin 6D (Sema6D)-Peroxisome proliferator receptor γ (PPARγ) axis plays critical roles in macrophage polarization. Inhibition of mTOR or loss of Sema6D blocked anti-inflammatory macrophage polarization, concomitant with severe impairments in PPARγ expression, uptake of fatty acids, and lipid metabolic reprogramming. Macrophage expression of the receptor Plexin-A4 is responsible for Sema6D-mediated anti-inflammatory polarization. We found that a tyrosine kinase, c-Abl, which associates with the cytoplasmic region of Sema6D, is required for PPARγ expression. Furthermore, Sema6D is important for generation of intestinal resident CX3CR1^hi macrophages and prevents development of colitis. Collectively, these findings highlight crucial roles for Sema6D reverse signaling in macrophage polarization, coupling immunity, and metabolism via PPARγ.

Gpr97 Exacerbates AKI by Mediating Sema3A Signaling

Background G protein-coupled receptors (GPCRs) participate in a variety of physiologic functions, and several GPCRs have critical physiologic and pathophysiologic roles in the regulation of renal function. We investigated the role of Gpr97, a newly identified member of the adhesion GPCR family, in AKI.Methods AKI was induced by ischemia-reperfusion or cisplatin treatment in Gpr97-deficient mice. We assessed renal injury in these models and in patients with acute tubular necrosis by histologic examination, and we conducted microarray analysis and in vitro assays to determine the molecular mechanisms of Gpr97 function.Results Gpr97 was upregulated in the kidneys from mice with AKI and patients with biopsy-proven acute tubular necrosis compared with healthy controls. In AKI models, Gpr97-deficient mice had significantly less renal injury and inflammation than wild-type mice. Gpr97 deficiency also attenuated the AKI-induced expression of semaphorin 3A (Sema3A), a potential early diagnostic biomarker of renal injury. In NRK-52E cells subjected to oxygen-glucose deprivation, siRNA-mediated knockdown of Gpr97 further increased the expression of survivin and phosphorylated STAT3 and reduced toll-like receptor 4 expression. Cotreatment with recombinant murine Sema3A protein counteracted these effects. Finally, additional in vivo and in vitro studies, including electrophoretic mobility shift assays and luciferase reporter assays, showed that Gpr97 deficiency attenuates ischemia-reperfusion-induced expression of the RNA-binding protein human antigen R, which post-transcriptionally regulates Sema3A expression.Conclusions Gpr97 is an important mediator of AKI, and pharmacologic targeting of Gpr97-mediated Sema3A signaling at multiple levels may provide a novel approach for the treatment of AKI.

Immunomodulatory Functions of Neuronal Guidance Proteins

Neuronal guidance proteins (NGPs) were originally identified for their role during the embryonic development of the nervous system. Recent years have seen the discovery of NGP functions during immune responses. In this context, NGPs were demonstrated to control leukocyte migration and the release of cytokines during conditions of acute inflammation, such as lung injury or sepsis. However, NGPs also display potent actions in the resolution of inflammation, chronic inflammatory conditions, the development of atherosclerosis, and during ischemia followed by reperfusion. Here, we provide an overview of the current state of knowledge about the role of NGPs in the immune system and describe their immunomodulatory function.

A novel role for myeloid cell-specific neuropilin 1 in mitigating sepsis

Sepsis-typically caused by an uncontrolled and amplified host systemic inflammatory response to microbial infection-is a life-threatening complex clinical disorder and remains a major cause of infection-related deaths in the intensive care unit. Emerging evidence suggests that neuropilin 1 (Nrp1), an originally defined coreceptor for class 3 semaphorins and VEGF, plays important roles in the immune system; however, the function and regulation of macrophage Nrp1 in host immune defense against bacterial infection remain unknown. To address this problem, we generated myeloid cell-specific Nrp1-knockout (Nrp1^myel-KO) mice and applied 2 stringent animal models of sepsis: cecal ligation and puncture as well as intraperitoneal injection of LPS. Here, we reported that myeloid cell-specific Nrp1-deficient mice exhibited enhanced susceptibility to cecal ligation and puncture- and LPS-induced sepsis, which correlated with significantly decreased survival rates and heightened levels of proinflammatory cytokines in both peritoneal lavage and serum. Mechanistically, LPS specifically attenuated the expression of Nrp1 in macrophages, which was mediated by TLR4-NF-κB p50 and -65 pathways. By using isolated primary macrophages, loss of Nrp1 consistently resulted in increased production of proinflammatory cytokines, including iNOS, TNF-α, and IL-6. Together, these findings demonstrate a novel role of macrophage Nrp1 in sepsis.-Dai, X. Okon, I., Liu, Z., Wu, Y., Zhu, H., Song, P., Zou, M.-H. A novel role for myeloid cell-specific neuropilin 1 in mitigating sepsis.

The role of the semaphorins in cancer

The semaphorins were initially characterized as axon guidance factors, but have subsequently been implicated also in the regulation of immune responses, angiogenesis, organ formation, and a variety of additional physiological and developmental functions. The semaphorin family contains more then 20 genes divided into 7 subfamilies, all of which contain the signature sema domain. The semaphorins transduce signals by binding to receptors belonging to the neuropilin or plexin families. Additional receptors which form complexes with these primary semaphorin receptors are also frequently involved in semaphorin signaling. Recent evidence suggests that semaphorins also fulfill important roles in the etiology of multiple forms of cancer. Some semaphorins have been found to function as bona-fide tumor suppressors and to inhibit tumor progression by various mechanisms while other semaphorins function as inducers and promoters of tumor progression.

Structure of the Plexin Ectodomain Bound by Semaphorin-Mimicking Antibodies

Semaphorin family proteins act on cells to mediate both repulsive and attractive guidance via binding to plexin family receptors, thereby playing fundamental roles in the morphogenesis and homeostasis of various tissues. Although semaphorin-plexin signaling is implicated in various diseases and is thus a target of intensive research, our mechanistic understanding of how semaphorins activate plexins on the cell surface is limited. Here, we describe unique anti-plexin-A1 antibodies that can induce a collapsed morphology in mouse dendritic cells as efficiently as the semaphorin 3A (Sema3A) ligand. Precise epitope analysis indicates that these “semaphorin-mimicking” antibodies dimerize cell-surface plexin-A1 by binding to the N-terminal sema domain of the plexin at sites away from the interface used by the Sema3A ligand. Structural analysis of plexin-A1 fragments using negative stain electron microscopy further revealed that this agonistic capacity is closely linked to the location and orientation of antibody binding. In addition, the full-length plexin-A1 ectodomain exhibited a highly curved “C” shape, reinforcing the very unusual dimeric receptor conformation of this protein at the cell surface when engaged with Sema3A or agonistic antibodies.

A novel podocyte gene, semaphorin 3G, protects glomerular podocyte from lipopolysaccharide-induced inflammation

Kidney diseases including diabetic nephropathy have become huge medical problems, although its precise mechanisms are still far from understood. In order to increase our knowledge about the patho-physiology of kidney, we have previously identified >300 kidney glomerulus-enriched transcripts through large-scale sequencing and microarray profiling of the mouse glomerular transcriptome. One of the glomerulus-specific transcripts identified was semaphorin 3G (Sema3G) which belongs to the semaphorin family. The aim of this study was to analyze both the in vivo and in vitro functions of Sema3G in the kidney. Sema3G was expressed in glomerular podocytes. Although Sema3G knockout mice did not show obvious glomerular defects, ultrastructural analyses revealed partially aberrant podocyte foot processes structures. When these mice were injected with lipopolysaccharide to induce acute inflammation or streptozotocin to induce diabetes, the lack of Sema3G resulted in increased albuminuria. The lack of Sema3G in podocytes also enhanced the expression of inflammatory cytokines including chemokine ligand 2 and interleukin 6. On the other hand, the presence of Sema3G attenuated their expression through the inhibition of lipopolysaccharide-induced Toll like receptor 4 signaling. Taken together, our results surmise that the Sema3G protein is secreted by podocytes and protects podocytes from inflammatory kidney diseases and diabetic nephropathy.

Semaphorins and Plexins in Kidney Disease

Semaphorins are soluble or membrane-bound cues, which control multiple aspects of cell-cell communication, differentiation, morphology and function. Most of their effects are mediated by a family of transmembrane receptors called plexins. Semaphorins and plexins have emerged as central regulators of diverse physiological and pathophysiological processes in various organs. This review summarizes the role of semaphorins and plexins in renal pathophysiology and their potential use as biomarkers of kidney disease.

Exosomal miR-223 Contributes to Mesenchymal Stem Cell-Elicited Cardioprotection in Polymicrobial Sepsis

Mesenchymal stem cells (MSCs) have been shown to elicit cardio-protective effects in sepsis. However, the underlying mechanism remains obscure. While recent studies have indicated that miR-223 is highly enriched in MSC-derived exosomes, whether exosomal miR-223 contributes to MSC-mediated cardio-protection in sepsis is unknown. In this study, loss-of-function approach was utilized, and sepsis was induced by cecal ligation and puncture (CLP). We observed that injection of miR-223-KO MSCs at 1 h post-CLP did not confer protection against CLP-triggered cardiac dysfunction, apoptosis and inflammatory response. However, WT-MSCs were able to provide protection which was associated with exosome release. Next, treatment of CLP mice with exosomes released from miR-223-KO MSCs significantly exaggerated sepsis-induced injury. Conversely, WT-MSC-derived-exosomes displayed protective effects. Mechanistically, we identified that miR-223-KO exosomes contained higher levels of Sema3A and Stat3, two known targets of miR-223 (5p &3p), than WT-exosomes. Accordingly, these exosomal proteins were transferred to cardiomyocytes, leading to increased inflammation and cell death. By contrast, WT-exosomes encased higher levels of miR-223, which could be delivered to cardiomyocytes, resulting in down-regulation of Sema3A and Stat3. These data for the first time indicate that exosomal miR-223 plays an essential role for MSC-induced cardio-protection in sepsis.