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

Therapeutic potential of flavopiridol in diabetic retinopathy: Targeting DDX58

Diabetic retinopathy (DR), a common complication of diabetes, is characterized by inflammation and neovascularization, and is intricately regulated by the ubiquitin-proteasome system (UPS). Despite advancements, identifying ubiquitin-related genes and drugs specifically targeting DR remains a significant challenge. In this study, bioinformatics analyses and the Connectivity Map (CMAP) database were utilized to explore the therapeutic potential of genes and drugs for DR. Through these methodologies, flavopiridol was identified as a promising therapeutic candidate. To evaluate flavopiridol's therapeutic potential in DR, an in vitro model using Human Umbilical Vein Endothelial Cells (HUVECs) induced by high glucose (HG) conditions was established. Additionally, in vivo models using mice with streptozotocin (STZ)-induced DR and oxygen-induced retinopathy (OIR) were employed. The current study reveals that flavopiridol possesses robust anti-inflammatory and anti-neovascularization properties. To further elucidate the molecular mechanisms of flavopiridol, experimental validation and molecular docking techniques were employed. These efforts identified DDX58 as a predictive target for flavopiridol. Notably, our research demonstrated that flavopiridol modulates the DDX58/NLRP3 signaling pathway, thereby exerting its therapeutic effects in suppressing inflammation and neovascularization in DR. This study unveils groundbreaking therapeutic agents and innovative targets for DR, and establishes a progressive theoretical framework for the application of ubiquitin-related therapies in DR.

Microvascular destabilization and intricated network of the cytokines in diabetic retinopathy: from the perspective of cellular and molecular components

Microvascular destabilization is the primary cause of the inner blood-retinal barrier (iBRB) breakdown and increased vascular leakage in diabetic retinopathy (DR). Microvascular destabilization results from the combinational effects of increased levels of growth factors and cytokines, involvement of inflammation, and the changed cell-to-cell interactions, especially the loss of endothelial cells and pericytes, due to hyperglycemia and hypoxia. As the manifestation of microvascular destabilization, the fluid transports via paracellular and transcellular routes increase due to the disruption of endothelial intercellular junctional complexes and/or the altered caveolar transcellular transport across the retinal vascular endothelium. With diabetes progression, the functional and the structural changes of the iBRB components, including the cellular and noncellular components, further facilitate and aggravate microvascular destabilization, resulting in macular edema, the neuroretinal damage and the dysfunction of retinal inner neurovascular unit (iNVU). Although there have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying the microvascular destabilization, some still remain to be fully elucidated. Recent data indicate that targeting the intricate signaling pathways may allow to against the microvascular destabilization. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in the microvascular destabilization in DR. In this review, we discuss: (1) the brief introduction of DR and microvascular destabilization; (2) the cellular and molecular components of iBRB and iNVU, and the breakdown of iBRB; (3) the matrix and cell-to-cell contacts to maintain microvascular stabilization, including the endothelial glycocalyx, basement membrane, and various cell-cell interactions; (4) the molecular mechanisms mediated cell-cell contacts and vascular cell death; (5) the altered cytokines and signaling pathways as well as the intricate network of the cytokines involved in microvascular destabilization. This comprehensive review aimed to provide the insights for microvascular destabilization by targeting the key molecules or specific iBRB cells, thus restoring the function and structure of iBRB and iNVU, to treat DR.

The emerging role of the semaphorin family in cartilage and osteoarthritis

In the pathogenesis of osteoarthritis, various signaling pathways may influence the bone joint through a common terminal pathway, thereby contributing to the pathological remodeling of the joint. Semaphorins (SEMAs) are cell-surface proteins actively involved in and primarily responsible for regulating chondrocyte function in the pathophysiological process of osteoarthritis (OA). The significance of the SEMA family in OA is increasingly acknowledged as pivotal. This review aims to summarize the mechanisms through which different members of the SEMA family impact various structures within joints. The findings indicate that SEMA3A and SEMA4D are particularly relevant to OA, as they participate in cartilage injury, subchondral bone remodeling, or synovitis. Additionally, other elements such as SEMA4A and SEMA5A may also contribute to the onset and progression of OA by affecting different components of the bone and joint. The mentioned mechanisms demonstrate the indispensable role of SEMA family members in OA, although the detailed mechanisms still require further exploration.

Sema4D Knockout Attenuates Choroidal Neovascularization by Inhibiting M2 Macrophage Polarization Via Regulation of the RhoA/ROCK Pathway

Purpose

The aim of this study was to elucidate the role of Sema4D in the pathogenesis of senescence-associated choroidal neovascularization (CNV) and to explore its underlying mechanisms.

Methods

In this study, we utilized a model of laser-induced CNV in both young (3 months old) and old (18 months old) mice, including those with or without Sema4D knockout. The expression and localization of Sema4D in CNV were assessed using PCR, Western blot, and immunostaining. Subsequently, the morphological and imaging examinations were used to evaluate the size of CNV and vascular leakage. Finally, the expression of M2 markers, senescence-related markers, and molecules involved in the RhoA/ROCK pathway was detected.

Results

We found that Sema4D was predominantly expressed in macrophages within CNV lesions, and both the mRNA and protein levels of Sema4D progressively increased following laser photocoagulation, a trend more pronounced in old mice. Moreover, Sema4D knockout markedly inhibited M2 polarization in senescent macrophages and reduced the size and leakage of CNV, particularly in aged mice. Mechanistically, aging was found to upregulate RhoA/ROCK signaling, and knockout of Sema4D effectively suppressed the activation of this pathway, with more significant effects observed in aged mice.

Conclusions

Our findings revealed that the deletion of Sema4D markedly inhibited M2 macrophage polarization through the suppression of the RhoA/ROCK pathway, ultimately leading to the attenuation of senescence-associated CNV. These data indicate that targeting Sema4D could offer a promising approach for gene editing therapy in patients with neovascular age-related macular degeneration.

Mammalian Diaphanous1 signalling in neurovascular complications of diabetes

Over the past few decades, diabetes gradually has become one of the top non-communicable disorders, affecting 476.0 million in 2017 and is predicted to reach 570.9 million people in 2025. It is estimated that 70 to 100% of all diabetic patients will develop some if not all, diabetic complications over the course of the disease. Despite different symptoms, mechanisms underlying the development of diabetic complications are similar, likely stemming from deficits in both neuronal and vascular components supplying hyperglycaemia-susceptible tissues and organs. Diaph1, protein diaphanous homolog 1, although mainly known for its regulatory role in structural modification of actin and related cytoskeleton proteins, in recent years attracted research attention as a cytoplasmic partner of the receptor of advanced glycation end-products (RAGE) a signal transduction receptor, whose activation triggers an increase in proinflammatory molecules, oxidative stressors and cytokines in diabetes and its related complications. Both Diaph1 and RAGE are also a part of the RhoA signalling cascade, playing a significant role in the development of neurovascular disturbances underlying diabetes-related complications. In this review, based on the existing knowledge as well as compelling findings from our past and present studies, we address the role of Diaph1 signalling in metabolic stress and neurovascular degeneration in diabetic complications. In light of the most recent developments in biochemical, genomic and transcriptomic research, we describe current theories on the aetiology of diabetes complications, highlighting the function of the Diaph1 signalling system and its role in diabetes pathophysiology.

Role of microglia/macrophage polarisation in intraocular diseases (Review)

Macrophages form a crucial component of the innate immune system, and their activation is indispensable for various aspects of immune and inflammatory processes, tissue repair, and maintenance of the balance of the body's state. Macrophages are found in all ocular tissues, spanning from the front surface, including the cornea, to the posterior pole, represented by the choroid/sclera. The neural retina is also populated by specialised resident macrophages called microglia. The plasticity of microglia/macrophages allows them to adopt different activation states in response to changes in the tissue microenvironment. When exposed to various factors, microglia/macrophages polarise into distinct phenotypes, each exhibiting unique characteristics and roles. Furthermore, extensive research has indicated a close association between microglia/macrophage polarisation and the development and reversal of various intraocular diseases. The present article provides a review of the recent findings on the association between microglia/macrophage polarisation and ocular pathological processes (including autoimmune uveitis, optic neuritis, sympathetic ophthalmia, retinitis pigmentosa, glaucoma, proliferative vitreoretinopathy, subretinal fibrosis, uveal melanoma, ischaemic optic neuropathy, retinopathy of prematurity and choroidal neovascularization). The paradoxical role of microglia/macrophage polarisation in retinopathy of prematurity is also discussed. Several studies have shown that microglia/macrophages are involved in the pathology of ocular diseases. However, it is required to further explore the relevant mechanisms and regulatory processes. The relationship between the functional diversity displayed by microglia/macrophage polarisation and intraocular diseases may provide a new direction for the treatment of intraocular diseases.

The potential of therapeutic strategies targeting mitochondrial biogenesis for the treatment of insulin resistance and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a persistent metabolic disorder marked by deficiencies in insulin secretion and/or function, affecting various tissues and organs and leading to numerous complications. Mitochondrial biogenesis, the process by which cells generate new mitochondria utilizing existing ones plays a crucial role in energy homeostasis, glucose metabolism, and lipid handling. Recent evidence suggests that promoting mitochondrial biogenesis can alleviate insulin resistance in the liver, adipose tissue, and skeletal muscle while improving pancreatic β-cell function. Moreover, enhanced mitochondrial biogenesis has been shown to ameliorate T2DM symptoms and may contribute to therapeutic effects for the treatment of diabetic nephropathy, cardiomyopathy, retinopathy, and neuropathy. This review summarizes the intricate connection between mitochondrial biogenesis and T2DM, highlighting the potential of novel therapeutic strategies targeting mitochondrial biogenesis for T2DM treatment and its associated complications. It also discusses several natural products that exhibit beneficial effects on T2DM by promoting mitochondrial biogenesis.

Role of MST2/YAP1 signaling pathway in retinal cells apoptosis and diabetic retinopathy

Diabetic retinopathy (DR) is a main factor affecting vision of patients, and its pathogenesis is not completely clear. The purpose of our study was to investigate correlations between MST2 and DR progression, and to study the possible mechanism of MST2 and its down pathway in high glucose (HG)-mediated RGC-5 apoptosis. The diabetic rat model was established by intraperitoneal injection of streptozotocin (STZ) 60 mg/kg. HE and TUNEL staining were used to evaluate the pathological changes and apoptosis of retinal cells in rats. Western blot, qRT-PCR and immunohistochemistry showed that levels of MST2 were increased in diabetic group (DM) than control. In addition, the differential expression of MST2 is related to HG-induced apoptosis of RGC-5 cells. CCK-8 and Hoechst 33,342 apoptosis experiments showed that MST2 was required in HG-induced apoptosis of RGC-5 cells. Further research revealed that MST2 regulated the protein expression of YAP1 at the level of phosphorylation in HG-induced apoptosis. Simultaneously, we found that Xmu-mp-1 acts as a MST2 inhibitor to alleviate HG-induced apoptosis. In summary, our study indicates that the MST2/YAP1 signaling pathway plays an important role in DR pathogenesis and RGC-5 apoptosis. This discovery provides new opportunities for future drug development targeting this pathway to prevent DR.

Pipecolic acid mitigates ferroptosis in diabetic retinopathy by regulating GPX4-YAP signaling

Diabetic retinopathy (DR) is currently recognized as the leading cause of end-stage eye disease. Pipecolic acid, a metabolite, has a significant regulatory effect on several pathological processes. However, the exact mechanism by which it causes damage in diabetic retinopathy is unknown. Between September 2021 and December 2022, 40 patients were retrospectively examined and divided into two groups: the healthy group (n = 20) and the DR group (n = 20). Metabolomic analysis found that pipecolic acid plays an important role in this process. Streptozotocin-induced diabetic mice and high-glucose cultured human retinal capillary endothelial cells (HRCECs) were then treated with pipecolic acid. Several oxidative stress measurements and RNA sequencing of retinal cells were tested. A gene interaction study was conducted using bioinformatics. Comparison of serological metabolites between healthy volunteers and DR patients showed that pipecolic acid was significantly lower in DR patients, and there was a negative correlation between the level of pipecolic acid with blood glucose and glycated hemoglobin. Yes-associated protein (YAP) mRNA, Malondialdehyde (MDA), and reactive oxygen species (ROS) levels were significantly higher in diabetic mice, but glutathione peroxidase (GSH-Px) levels were significantly lower. Pipecolic acid significantly alleviated oxidative stress and YAP expression. The number of vascular tubes was significantly higher in the DR group, and pipecolic acid treatment significantly reduced tube formation. RNA-Sequencing analysis revealed that YAP and glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4) expression was reduced, and functional enrichment analysis revealed that ferroptosis and Hippo signaling pathways play an important role in this process. Additionally, pipecolic acid's ability to improve DR is diminished after YAP and GPX4 ablation. This study found that pipecolic acid, as a metabolite, may impede the progression of DR by inhibiting the YAP-GPX4 signaling pathway.

Diabetes mellitus: Classification, mediators, and complications; A gate to identify potential targets for the development of new effective treatments

Nowadays, diabetes mellitus has emerged as a significant global public health concern with a remarkable increase in its prevalence. This review article focuses on the definition of diabetes mellitus and its classification into different types, including type 1 diabetes (idiopathic and fulminant), type 2 diabetes, gestational diabetes, hybrid forms, slowly evolving immune-mediated diabetes, ketosis-prone type 2 diabetes, and other special types. Diagnostic criteria for diabetes mellitus are also discussed. The role of inflammation in both type 1 and type 2 diabetes is explored, along with the mediators and potential anti-inflammatory treatments. Furthermore, the involvement of various organs in diabetes mellitus is highlighted, such as the role of adipose tissue and obesity, gut microbiota, and pancreatic β-cells. The manifestation of pancreatic Langerhans β-cell islet inflammation, oxidative stress, and impaired insulin production and secretion are addressed. Additionally, the impact of diabetes mellitus on liver cirrhosis, acute kidney injury, immune system complications, and other diabetic complications like retinopathy and neuropathy is examined. Therefore, further research is required to enhance diagnosis, prevent chronic complications, and identify potential therapeutic targets for the management of diabetes mellitus and its associated dysfunctions.

Potential Retinal Biomarkers in Alzheimer's Disease

Alzheimer's disease (AD) represents a major diagnostic challenge, as early detection is crucial for effective intervention. This review examines the diagnostic challenges facing current AD evaluations and explores the emerging field of retinal alterations as early indicators. Recognizing the potential of the retina as a noninvasive window to the brain, we emphasize the importance of identifying retinal biomarkers in the early stages of AD. However, the examination of AD is not without its challenges, as the similarities shared with other retinal diseases introduce complexity in the search for AD-specific markers. In this review, we address the relevance of using the retina for the early diagnosis of AD and the complex challenges associated with the search for AD-specific retinal biomarkers. We provide a comprehensive overview of the current landscape and highlight avenues for progress in AD diagnosis by retinal examination.

Assessment of Inner Blood-Retinal Barrier: Animal Models and Methods

Proper functioning of the neural retina relies on the unique retinal environment regulated by the blood-retinal barrier (BRB), which restricts the passage of solutes, fluids, and toxic substances. BRB impairment occurs in many retinal vascular diseases and the breakdown of BRB significantly contributes to disease pathology. Understanding the different molecular constituents and signaling pathways involved in BRB development and maintenance is therefore crucial in developing treatment modalities. This review summarizes the major molecular signaling pathways involved in inner BRB (iBRB) formation and maintenance, and representative animal models of eye diseases with retinal vascular leakage. Studies on Wnt/β-catenin signaling are highlighted, which is critical for retinal and brain vascular angiogenesis and barriergenesis. Moreover, multiple in vivo and in vitro methods for the detection and analysis of vascular leakage are described, along with their advantages and limitations. These pre-clinical animal models and methods for assessing iBRB provide valuable experimental tools in delineating the molecular mechanisms of retinal vascular diseases and evaluating therapeutic drugs.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Knockout of Sema4D alleviates liver fibrosis by suppressing AOX1 expression

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

Signaling pathways and intervention for therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents one of the fastest growing epidemic metabolic disorders worldwide and is a strong contributor for a broad range of comorbidities, including vascular, visual, neurological, kidney, and liver diseases. Moreover, recent data suggest a mutual interplay between T2DM and Corona Virus Disease 2019 (COVID-19). T2DM is characterized by insulin resistance (IR) and pancreatic β cell dysfunction. Pioneering discoveries throughout the past few decades have established notable links between signaling pathways and T2DM pathogenesis and therapy. Importantly, a number of signaling pathways substantially control the advancement of core pathological changes in T2DM, including IR and β cell dysfunction, as well as additional pathogenic disturbances. Accordingly, an improved understanding of these signaling pathways sheds light on tractable targets and strategies for developing and repurposing critical therapies to treat T2DM and its complications. In this review, we provide a brief overview of the history of T2DM and signaling pathways, and offer a systematic update on the role and mechanism of key signaling pathways underlying the onset, development, and progression of T2DM. In this content, we also summarize current therapeutic drugs/agents associated with signaling pathways for the treatment of T2DM and its complications, and discuss some implications and directions to the future of this field.

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

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Nanobody inhibitors of Plexin-B1 identify allostery in plexin-semaphorin interactions and signalling

Plexin-B1 is a receptor for the cell surface semaphorin, Sema4D. This signalling system has been implicated in a variety of human diseases, including cancer, multiple sclerosis and osteoporosis. Whilst inhibitors of the Plexin-B1:Sema4D interaction have been previously reported, understanding their mechanism has been hindered by an incomplete structural view of Plexin-B1. In this study, we have raised and characterised a pair of nanobodies that are specific for mouse Plexin-B1, and which inhibit the binding of Sema4D to mouse Plexin-B1 and its biological activity. Structural studies of these nanobodies reveal that they inhibit the binding of Sema4D in an allosteric manner, binding to epitopes not previously reported. In addition, we report the first unbound structure of human Plexin-B1, which reveals that Plexin-B1 undergoes a conformational change on Sema4D binding. These changes mirror those seen upon binding of allosteric peptide modulators, which suggests a new model for understanding Plexin-B1 signalling, and provides a potential innovative route for therapeutic modulation of Plexin-B1.

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

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

Clinical values of serum Semaphorin 4D (Sema4D) in medication‑related osteonecrosis of the jaw

BACKGROUND

Bisphosphonates (BPs) are widely used in clinical practice to prevent and treat bone metabolism-related diseases. Medication-related osteonecrosis of the jaw (MRONJ) is one of the major sequelae of BPs use. Early prediction and intervention of MRONJ are of great significance.

METHODS

Ninety-seven patients currently on treatment with BPs or with a history of BPs usage and 45 healthy volunteers undergoing dentoalveolar surgery were included in this study. Participants' serum Semaphorin 4D (Sema4D) levels were measured and analyzed before participants underwent surgery (T0) and after a 12-month follow-up (T1). Kruskal-Wallis test and ROC analysis were used to examine the predictive effect of Sema4D on MRONJ.

RESULTS

Sema4D levels in serum of patients corresponding to confirmed MRONJ were significantly lower at both T0 and T1 time points compared to non-MRONJ and healthy controls. Sema4D has a statistically predictive effect on the occurrence and diagnosis of MRONJ. Serum Sema4D levels were significantly reduced in MRONJ class 3 patients. MRONJ patients who received intravenous BPs had significantly lower Sema4D levels than those who received oral BPs.

CONCLUSION

Serum Sema4D level has predictive value for the onset of MRONJ in BPs users within 12 weeks after dentoalveolar surgery.

Comparative transcriptomic analysis and genome-wide characterization of the Semaphorin family reveal the potential mechanism of angiogenesis around embryo in ovoviviparous black rockfish (Sebastes schlegelii)

To guarantee the quality and survival rate of their offspring, ovoviviparous teleost evolved special characteristics of in vivo fertilization and embryo development. Maternal black rockfish, having over 50 thousand embryos developing within the ovary simultaneously, provided around 40% nutrition throughout oocyte development, while the capillaries around each embryo contributed the rest 60% during pregnancy. Since fertilization, capillaries started to proliferate and developed into a placenta-like structure that covered over half of each embryo. Aimed to characterize the potential mechanism behind, comparative transcriptome analysis of samples collected according to the process of pregnancy. Three important time point in the process, including mature oocyte stage, fertilization and sarcomere period, were chosen for the transcriptome sequencing. Our study identified key pathways and genes involved in the cell cycle as well as DNA replication and repair, cell migration and adhesion, immune, and metabolic functions. Notably, several of the semaphoring gene family members were differently expressed. To confirm the accuracy of these genes, total of 32 sema genes were identified from the whole genome and distinct expression pattern of sema genes was observed in different pregnant stages. Our results revealed a novel insight for further investigating the functions of sema genes in reproduction physiology and embryo processes in ovoviviparous teleost.

Retinopathy of prematurity: A review of pathophysiology and signaling pathways

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina and a leading cause of visual impairment and childhood blindness worldwide. The disease is characterized by an early stage of retinal microvascular degeneration, followed by neovascularization that can lead to subsequent retinal detachment and permanent visual loss. Several factors play a key role during the different pathological stages of the disease. Oxidative and nitrosative stress and inflammatory processes are important contributors to the early stage of ROP. Nitric oxide synthase and arginase play important roles in ischemia/reperfusion-induced neurovascular degeneration. Destructive neovascularization is driven by mediators of the hypoxia-inducible factor pathway, such as vascular endothelial growth factor and metabolic factors (succinate). The extracellular matrix is involved in hypoxia-induced retinal neovascularization. Vasorepulsive molecules (semaphorin 3A) intervene preventing the revascularization of the avascular zone. This review focuses on current concepts about signaling pathways and their mediators, involved in the pathogenesis of ROP, highlighting new potentially preventive and therapeutic modalities. A better understanding of the intricate molecular mechanisms underlying the pathogenesis of ROP should allow the development of more effective and targeted therapeutic agents to reduce aberrant vasoproliferation and facilitate physiological retinal vascular development.

Inhibition of the Semaphorin 4D-Plexin-B1 axis prevents calcification in vascular smooth muscle cells

Vascular calcification is common in cardiovascular diseases including atherosclerosis, and is associated with an increased risk of pathological events and mortality. Some semaphorin family members play an important role in atherosclerosis. In the present study, we show that Semaphorin 4D/Sema4D and its Plexin-B1 receptor were significantly upregulated in calcified aorta of a rat chronic kidney disease model. Significantly higher Sema4D and Plexin-B1 expression was also observed during inorganic phosphate-induced calcification of vascular smooth muscle cells. Knockdown of Sema4D or Plexin-B1 genes attenuated both the phosphate-induced osteogenic phenotype of vascular smooth muscle cells, through regulation of SMAD1/5 signaling, as well as apoptosis of vascular smooth muscle cells, through modulation of the Gas6/Axl/Akt survival pathway. Taken together, our results offer new insights on the role of Sema4D and Plexin-B1 as potential therapeutic targets against vascular calcification. [BMB Reports 2023; 56(3): 160-165].

The value of serum Sema4D level in reflecting the inflammatory state of acute ST-segment elevation myocardial infarction

Background

This study sought to investigate the expression of soluble semaphorin 4D (sSema4D) in acute ST-segment elevation myocardial infarction (STEMI) and to explore its value in evaluating the inflammatory status of acute myocardial infarction (AMI).

Methods

From October 2020 to June 2021, 100 patients with STEMI diagnosed at the Department of Cardiology of our hospital were selected as the STEMI group, 83 patients with unstable angina (UA) were selected as the UA group, and 78 patients with negative coronary angiography (CAG) were selected as the control group. The baseline data of the 3 groups of patients were recorded, the sSema4D levels were determined, the expression of sSema4D levels in AMI was analyzed, and the value of sSema4D levels in reflecting inflammatory state of AMI was explored.

Results

Compared with UA group and control group, the expression of sSema4D in peripheral blood of STEMI group was significantly increased (P<0.001), which could better reflect the inflammatory status of patients with STEMI than traditional inflammatory indicators [hypersensitive c-reactive protein (hs-CRP)] (P<0.05). The receiver operating characteristic (ROC) curve showed that sSema4D (AUC =0.780, cut-off =19.62, 95% CI: 0.629, 0.837, P<0.001) was more specific than hs-CRP (AUC =0.697, cut-off =3.39, 95% CI: 0.629, 0.765, P<0.001) in reflecting the inflammatory status of STEMI patients.

Conclusions

sSema4D levels have certain value in reflecting the inflammatory state of STEMI.

Ophthalmic Solution of Smart Supramolecular Peptides to Capture Semaphorin 4D against Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss in working age population. Intravitreal injection of anti-VEGF antibody is widely used in clinical practice. However, about 27% of patients show poor response to anti-VEGF therapy and about 50% of these patients continue to have macular thickening. Frequent intravitreal injections of antibody may increase the chance of endophthalmitis and cause visual loss or even blindness once happened. Therefore, there is a greatly urgent need for novel noninvasive target to treat DR clinically. Here, the formulation of a smart supramolecular peptide (SSP) eye drop for DR treatment that is effective via specifically identifying and capturing soluble semaphorin 4D (sSema4D), a strongly pro-angiogenesis and exudates factor, is reported. The SSP nanostructures encapsulate sSema4D so that all biological effects mediated by three receptors of sSema4D are inhibited, thereby significantly alleviating pathological retinal angiogenesis and exudates in DR. Moreover, it is found that combination of SSPs eye drop and anti-VEGF injection shows better therapeutic effect over anti-VEGF treatment alone. Overall, SSP eye drop provide an alternative and effective method for noninvasive treatment for DR.

The Role of Interferon Regulatory Factor 1 in Regulating Microglial Activation and Retinal Inflammation

Microglia are resident immune cells in the central nervous system (CNS). Microglial activation plays a prominent role in neuroinflammation and CNS diseases. However, the underlying mechanisms of microglial activation are not well understood. Here, we report that the transcription factor interferon regulatory factor 1 (IRF1) plays critical roles in microglial activation and retinal inflammation by regulating pro- and anti-inflammatory gene expression. IRF1 expression was upregulated in activated retinal microglia compared to those at the steady state. IRF1 knockout (KO) in BV2 microglia cells (BV2ΔIRF1) created by CRISPR/Cas9 genome-editing technique causes decreased microglia proliferation, migration, and phagocytosis. IRF1-KO decreased pro-inflammatory M1 marker gene expression induced by lipopolysaccharides (LPS), such as IL-6, COX-2, and CCL5, but increased anti-inflammatory M2 marker gene expression by IL-4/13, such as Arg-1, CD206, and TGF-β. Compared to the wild-type cells, microglial-conditioned media (MCM) of activated BV2ΔIRF1 cell cultures reduced toxicity or death to several retinal cells, including mouse cone photoreceptor-like 661 W cells, rat retinal neuron precursor R28 cells, and human ARPE-19 cells. IRF1 knockdown by siRNA alleviated microglial activation and retinal inflammation induced by LPS in mice. Together, the findings suggest that IRF1 plays a vital role in regulating microglial activation and retinal inflammation and, therefore, may be targeted for treating inflammatory and degenerative retinal diseases.

Diabetic retinopathy: Involved cells, biomarkers, and treatments

Diabetic retinopathy (DR), a leading cause of vision loss and blindness worldwide, is caused by retinal neurovascular unit dysfunction, and its cellular pathology involves at least nine kinds of retinal cells, including photoreceptors, horizontal and bipolar cells, amacrine cells, retinal ganglion cells, glial cells (Müller cells, astrocytes, and microglia), endothelial cells, pericytes, and retinal pigment epithelial cells. Its mechanism is complicated and involves loss of cells, inflammatory factor production, neovascularization, and BRB impairment. However, the mechanism has not been completely elucidated. Drug treatment for DR has been gradually advancing recently. Research on potential drug targets relies upon clear information on pathogenesis and effective biomarkers. Therefore, we reviewed the recent literature on the cellular pathology and the diagnostic and prognostic biomarkers of DR in terms of blood, protein, and clinical and preclinical drug therapy (including synthesized molecules and natural molecules). This review may provide a theoretical basis for further DR research.

An antagonistic monoclonal anti-Plexin-B1 antibody exerts therapeutic effects in mouse models of postmenopausal osteoporosis and multiple sclerosis

Osteoporosis and multiple sclerosis are highly prevalent diseases with limited treatment options. In light of these unmet medical needs, novel therapeutic approaches are urgently sought. Previously, the activation of the transmembrane receptor Plexin-B1 by its ligand semaphorin 4D (Sema4D) has been shown to suppress bone formation and promote neuroinflammation in mice. However, it is unclear whether inhibition of this receptor–ligand interaction by an anti–Plexin-B1 antibody could represent a viable strategy against diseases related to these processes. Here, we raised and systematically characterized a monoclonal antibody directed against the extracellular domain of human Plexin-B1, which specifically blocks the binding of Sema4D to Plexin-B1. In vitro, we show that this antibody inhibits the suppressive effects of Sema4D on human osteoblast differentiation and mineralization. To test the therapeutic potential of the antibody in vivo, we generated a humanized mouse line, which expresses transgenic human Plexin-B1 instead of endogenous murine Plexin-B1. Employing these mice, we demonstrate that the anti–Plexin-B1 antibody exhibits beneficial effects in mouse models of postmenopausal osteoporosis and multiple sclerosis in vivo. In summary, our data identify an anti–Plexin-B1 antibody as a potential therapeutic agent for the treatment of osteoporosis and multiple sclerosis.

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.

Inhibition of CD146 attenuates retinal neovascularization via vascular endothelial growth factor receptor 2 signalling pathway in proliferative diabetic retinopathy

PURPOSE

To investigate the expression of CD146 and its role in proliferative diabetic retinopathy (PDR).

METHODS

Enzyme linked immunosorbent assay was performed to analyse the expression and relationship of sCD146, vascular endothelial growth factor (VEGF), sVEGFR1 and sVEGFR2 in vitreous specimens from PDR and idiopathic epiretinal membranes (IERM) or idiopathic macular hole patients. The location of CD146 in ERMs was detected by immunofluorescence. The oxygen-induced retinopathy (OIR) mice model was established and the adeno-associated virus expressing a shRNA of CD146 (AAV1-shCD146-GFP) was administered via intravitreal injection. The effect of AAV1-shCD146-GFP was explored by immunofluorescence, Western blot and quantitative real-time PCR.

RESULTS

The levels of sCD146 in vitreous specimens from PDR patients and CD146 in retinas from OIR mice were significantly increased. Immunofluorescence showed that CD146 was co-located with CD31, VEGF, VEGFR1 and VEGFR2, respectively. Intravitreal injection of AAV1-shCD146-GFP could dramatically reduce the formation of neovascularization and non-perfusion area by inhibiting VEGFR2 phosphorylation.

CONCLUSION

Our results indicated that CD146 was involved in the development of retinal neovascularization via VEGFR2 pathway. Anti-CD146 may be an innovative or adjuvant therapy, which provides a new direction for the treatment of PDR and other ocular neovascular diseases.

Axon guidance molecules in immunometabolic diseases

The global prevalence of metabolic diseases, such as obesity, diabetes, and atherosclerosis, is rapidly increasing and has now reached epidemic proportions. Chronic tissue inflammation is a characteristic of these metabolic diseases, indicating that immune responses are closely involved in the pathogenesis of metabolic disorders. However, the regulatory mechanisms underlying immunometabolic crosstalk in these diseases are not completely understood. Recent studies have revealed the multifaceted functions of semaphorins, originally identified as axon guidance molecules, in regulating tissue inflammation and metabolic disorders, thereby highlighting the functional coupling between semaphorin signaling and immunometabolism. In this review, we explore how semaphorin signaling transcends beyond merely guiding axons to controlling immune responses and metabolic diseases.

Cell Heterogeneity Uncovered by Single-Cell RNA Sequencing Offers Potential Therapeutic Targets for Ischemic Stroke

Ischemic stroke is a detrimental neurological disease characterized by an irreversible infarct core surrounded by an ischemic penumbra, a salvageable region of brain tissue. Unique roles of distinct brain cell subpopulations within the neurovascular unit and peripheral immune cells during ischemic stroke remain elusive due to the heterogeneity of cells in the brain. Single-cell RNA sequencing (scRNA-seq) allows for an unbiased determination of cellular heterogeneity at high-resolution and identification of cell markers, thereby unveiling the principal brain clusters within the cell-type-specific gene expression patterns as well as cell-specific subclusters and their functions in different pathways underlying ischemic stroke. In this review, we have summarized the changes in differentiation trajectories of distinct cell types and highlighted the specific pathways and genes in brain cells that are impacted by stroke. This review is expected to inspire new research and provide directions for investigating the potential pathological mechanisms and novel treatment strategies for ischemic stroke at the level of a single cell.

Cyanidin-3-o-glucoside (C3G) inhibits vascular leakage regulated by microglial activation in early diabetic retinopathy and neovascularization in advanced diabetic retinopathy

Cyanidin-3-O-glucoside (C3G) is a kind of anthocyanin which shows strong anti-inflammation, anti-tumor and anti-oxidant properties. This paper was designed to explore the potential effects of C3G on diabetic retinopathy (DR). C57BL/6 mice were administrated with streptozotocin (STZ) or vehicle control for the establishment of diabetic models. To simulate hyperglycemia and hypoxia, D-glucose (30 mM) and CoCl₂ (200 μm/l) were utilized to treat HRECs, respectively. The migration, invasion, inflammation and tube formation abilities of cells were evaluated with the adoption of wound healing, transwell, ELISA and tube formation assays, respectively. Besides, immunofluorescence staining was utilized to detect proliferation and retinal vessels. Evans blue permeation assay were performed to evaluate the vascular leakage in DR mice. Moreover, western blot and qPCR were used to quantify the mRNA and protein expressions of ionized calcium-binding adapter molecule (Iba)-1 and tight junction proteins. Results showed that C3G alleviated the inflammation, microglial activation and angiogenesis in DR mice. Moreover, the proliferation and inflammation of BV2 cells induced by high glucose (HG) were suppressed by C3G. Evans blue permeation assay demonstrated the potency of C3G in attenuating vascular leakage. In addition, C3G suppressed the migration, invasion and angiogenesis of human retinal endothelial cells (HRECs) DR model in vitro.By confirming the role of C3G in inhibiting vascular leakage regulated by microglia activation in early DR and angiogenesis in advanced DR, this study pointed out the potential of C3G as a therapeutic drug for DR management.

Pyroptosis in the Retinal Neurovascular Unit: New Insights Into Diabetic Retinopathy

Diabetic retinopathy (DR) is prevalent among people with long-term diabetes mellitus (DM) and remains the leading cause of visual impairment in working-aged people. DR is related to chronic low-level inflammatory reactions. Pyroptosis is an emerging type of inflammatory cell death mediated by gasdermin D (GSDMD), NOD-like receptors and inflammatory caspases that promote interleukin-1β (IL-1β) and IL-18 release. In addition, the retinal neurovascular unit (NVU) is the functional basis of the retina. Recent studies have shown that pyroptosis may participate in the destruction of retinal NVU cells in simulated hyperglycemic DR environments. In this review, we will clarify the importance of pyroptosis in the retinal NVU during the development of DR.

Emerging Targets in Type 2 Diabetes and Diabetic Complications

Type 2 diabetes is a metabolic, chronic disorder characterized by insulin resistance and elevated blood glucose levels. Although a large drug portfolio exists to keep the blood glucose levels under control, these medications are not without side effects. More importantly, once diagnosed diabetes is rarely reversible. Dysfunctions in the kidney, retina, cardiovascular system, neurons, and liver represent the common complications of diabetes, which again lack effective therapies that can reverse organ injury. Overall, the molecular mechanisms of how type 2 diabetes develops and leads to irreparable organ damage remain elusive. This review particularly focuses on novel targets that may play role in pathogenesis of type 2 diabetes. Further research on these targets may eventually pave the way to novel therapies for the treatment-or even the prevention-of type 2 diabetes along with its complications.

Synergistic inflammatory signaling by cGAS may be involved in the development of atherosclerosis

Inappropriate activation or overactivation of cyclic GMP-AMP synthase (cGAS) by double-stranded deoxyribonucleic acid (dsDNA) initiates a regulatory signaling cascade triggering a variety of inflammatory responses, which are a great threat to human health. This study focused on identifying the role of cGAS in atherosclerosis and its potential mechanisms. The relationship between cGAS and atherosclerosis was identified in an ApoE ^-/- mouse model. Meanwhile, RNA sequencing (RNA-seq) analysis of the underlying mechanisms of atherosclerosis in RAW264.7 macrophages treated with cGAS inhibition was conducted. Results showed that cGAS was positively correlated with atherosclerotic plaque area, and was mainly distributed in macrophages. RNA-seq analysis revealed that inflammatory response, immune response and cytokine–cytokine receptor interaction may play important roles in the development of atherosclerosis. Real-time quantitative polymerase chain reaction (RT-qPCR) results showed that the expression of the pro-inflammatory factors, signal transducer and activator of transcription (Stat), interferon regulatory factor (Irf), toll-like receptors (Tlrs), and type I interferons (Ifns) were synergistically reduced when cGAS was inhibited. Furthermore, cGAS inhibition significantly inhibited RAW264.7 macrophage M1 polarization. These results demonstrate that cGAS may contribute to the development of atherosclerosis through synergistic inflammatory signaling of TLRs, STAT/IRF as well as IFNs, leading to macrophage M1 polarization.

Circular RNA-ZNF532 regulates diabetes-induced retinal pericyte degeneration and vascular dysfunction

Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults. Vascular pericyte degeneration is the predominant clinical manifestation of DR, yet the mechanism governing pericyte degeneration is poorly understood. Circular RNAs (circRNAs) play important roles in multiple biological processes and disease progression. Here, we investigated the role of circRNA in pericyte biology and diabetes-induced retinal vascular dysfunction. cZNF532 expression was upregulated in pericytes under diabetic stress, in the retinal vessels of a diabetic murine model, and in the vitreous humor of diabetic patients. cZNF532 silencing reduced the viability, proliferation, and differentiation of pericytes and suppressed the recruitment of pericytes toward endothelial cells in vitro. cZNF532 regulated pericyte biology by acting as a miR-29a-3p sponge and inducing increased expression of NG2, LOXL2, and CDK2. Knockdown of cZNF532 or overexpression of miR-29a-3p aggravated streptozotocin-induced retinal pericyte degeneration and vascular dysfunction. By contrast, overexpression of cZNF532 or inhibition of miR-29a-3p ameliorated human diabetic vitreous-induced retinal pericyte degeneration and vascular dysfunction. Collectively, these data identify a circRNA-mediated mechanism that coordinates pericyte biology and vascular homeostasis in DR. Induction of cZNF532 or antagonism of miR-29a-3p is an exploitable therapeutic approach for the treatment of DR.

The neuroscience of diabetic retinopathy

Diabetic retinopathy remains a leading cause of blindness despite recent advance in therapies. Traditionally, this complication of diabetes was viewed predominantly as a microvascular disease but research has pointed to alterations in ganglion cells, glia, microglia, and photoreceptors as well, often occurring without obvious vascular damage. In neural tissue, the microvasculature and neural tissue form an intimate relationship with the neural tissue providing signaling cues for the vessels to form a distinct barrier that helps to maintain the proper neuronal environment for synaptic signaling. This relationship has been termed the neurovascular unit (NVU). Research is now focused on understanding the cellular and molecular basis of the neurovascular unit and how diabetes alters the normal cellular communications and disrupts the cellular environment contributing to loss of vision in diabetes.

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

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

The Role of Semaphorins in Metabolic Disorders

Semaphorins are a family originally identified as axonal guidance molecules. They are also involved in tumor growth, angiogenesis, immune regulation, as well as other biological and pathological processes. Recent studies have shown that semaphorins play a role in metabolic diseases including obesity, adipose inflammation, and diabetic complications, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, diabetic wound healing, and diabetic osteoporosis. Evidence provides mechanistic insights regarding the role of semaphorins in metabolic diseases by regulating adipogenesis, hypothalamic melanocortin circuit, immune responses, and angiogenesis. In this review, we summarize recent progress regarding the role of semaphorins in obesity, adipose inflammation, and diabetic complications.

The role of semaphorins in small vessels of the eye and brain

Small vessel diseases, such as ischemic retinopathy and cerebral small vessel disease (CSVD), are increasingly recognized in patients with diabetes, dementia and cerebrovascular disease. The mechanisms of small vessel diseases are poorly understood, but the latest studies suggest a role for semaphorins. Initially identified as axon guidance cues, semaphorins are mainly studied in neuronal morphogenesis, neural circuit assembly, and synapse assembly and refinement. In recent years, semaphorins have been found to play important roles in regulating vascular growth and development and in many pathophysiological processes, including atherosclerosis, angiogenesis after stroke and retinopathy. Growing evidence indicates that semaphorins affect the occurrence, perfusion and regression of both the macrovasculature and microvasculature by regulating the proliferation, apoptosis, migration, barrier function and inflammatory response of endothelial cells, vascular smooth muscle cells (VSMCs) and pericytes. In this review, we concentrate on the regulatory effects of semaphorins on the cell components of the vessel wall and their potential roles in microvascular diseases, especially in the retina and cerebral small vessel. Finally, we discuss potential molecular approaches in targeting semaphorins as therapies for microvascular disorders in the eye and brain.

Cho S, Britton W, S. Kern T, Antonetti DA, Hellström A, E.H. Smith L. Targeting Neurovascular Interaction in Retinal Disorders

The tightly structured neural retina has a unique vascular network comprised of three interconnected plexuses in the inner retina (and choroid for outer retina), which provide oxygen and nutrients to neurons to maintain normal function. Clinical and experimental evidence suggests that neuronal metabolic needs control both normal retinal vascular development and pathological aberrant vascular growth. Particularly, photoreceptors, with the highest density of mitochondria in the body, regulate retinal vascular development by modulating angiogenic and inflammatory factors. Photoreceptor metabolic dysfunction, oxidative stress, and inflammation may cause adaptive but ultimately pathological retinal vascular responses, leading to blindness. Here we focus on the factors involved in neurovascular interactions, which are potential therapeutic targets to decrease energy demand and/or to increase energy production for neovascular retinal disorders.

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

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