CD72-semaphorin3A axis: A new regulatory pathway in systemic lupus erythematosus.

CD72 is a regulatory co-receptor on B cells, with a role in the pathogenesis of systemic lupus erythematosus (SLE) in both human and animal models. Semaphorin3A (sema3A) is a secreted member of the semaphorin family that can reconstruct B cells' regulatory functions by upregulating IL-10 expression and inhibiting the pro-inflammatory activity of B and T cells in autoimmune diseases. The aim of our present study was to identify a new ligand for CD72, namely sema3A, and exploring the signal transduction pathways following its ligation in B cells. We established that CD72 functions as sema3A binding and signal-transducing receptor. These functions of CD72 are independent of neuropilin-1 (NRP-1) (the known sema3A receptor). We discovered that sema3A induces the phosphorylation of CD72 on tyrosine residues and the association of CD72 with SHP-1 and SHP-2. In addition, the binding of sema3A to CD72 on B cells inhibits the phosphorylation of STAT-4 and HDAC-1 and induces the phosphorylation of p38-MAPK and PKC-theta in B-cells derived B-lymphoblastoid (BLCL) cells, and in primary B-cells isolated from either healthy donors or SLE patients. We concluded that sema3A is a functional regulatory ligand for CD72 on B cells. The sema3A-CD72 axis is a crucial regulatory pathway in the pathogenesis of autoimmune and inflammatory diseases namely SLE, and modulation of this pathway may have a potential therapeutic value for autoimmune diseases.

Local treatment with Sema3a could promote the osseointegration of hydroxyapatite coated titanium rod in diabetic rats.

Recently, semaphorin 3A (Sema3A) has been identified as a critical gene for osteogenic differentiation of mesenchymal stem cells and increases osteoblastic bone formation. However, in current research studies, there is a lack of focus on whether Sema3a can affect the osseointegration of titanium rods in diabetes and through what biological mechanisms. Therefore, the present work was aimed to evaluate the effect of local administration with Sema3A on hydroxyapatite coated titanium rod osseointegration in diabetic rat model and preliminary exploration of possible mechanisms. The MC3T3-E1 cells were co-cultured with Sema3A and high glucose and induced to osteogenesis, and the cell viability, osteogenic activity was observed by Cell Counting Kit-8(CCK-8), Alkaline Phosphatase staining, Alizarin Red Staining, and Western Blot. In vitro experiments, CCK-8, ALP, and ARS staining results show that the mineralization and osteogenic activity of MC3T3-E1increased significantly after intervention by Sema3A, as well as a higher levels of protein expressions including Runt-Related Transcription Factor 2, silent mating type information regulation 2 homolog-1(SIRT1), catalase (CAT), superoxide dismutase 1 (SOD1), and superoxide dismutase 2 (SOD2). In vivo experiment, a better stability and osseointegration of the titanium rod were observed after treatment with Sema3A, as well as a higher SOD1, SOD2, CAT, and SIRT1 gene expression. The present study indicates that local treatment with Sema3A was associated with increased osseointegration of titanium rod by reducing the oxidative stress of osteoblasts and enhancing the function of osteoblasts in a diabetic rat.

Sema3a inhibits the differentiation of Raw264.7 cells to osteoclasts under 2Gy radiation by reducing inflammation.

Astronauts and cancer patients receive different types of radiation, and radiation decreases bone strength and leads to radiation-induced osteoporosis. This effect is attributed to the activation of osteoclasts. Our aim was to study the effect of Sema3a on the differentiation of the murine macrophage cell line Raw264.7 into osteoclasts upon irradiation. Raw264.7 cells were divided into four groups: A, receiving no radiation; B, receiving no radiation + 50ngng/ml Sema3a; C, receiving 2Gy radiation; and D, receiving 2Gy radiation +50ngng/ml Sema3a. After treatment, cells were subjected to a proliferation assay, migration assay, live and apoptosis assay, and an ROS assay, along with analyses of bone resorption activity, TRAP staining and RT-PCR to assess the effect of Sema3a on Raw264.7 cells under 2Gy radiation. Sema3a inhibited the proliferation of Raw264.7 cells and showed statistical significance at a concentration of 100ngng/ml (P<0.05). Under 2Gy radiation, cell migration was reduced (P<0.05). In addition, 2Gy radiation resulted in more apoptotic cells, a higher level of ROS, larger bone resorption lacunae and more Trap-positive cells (p<0.05), and radiation increased CSTK, NFAT, TRAP-5b, Rankl/OPG, IL-1, IL-6, TNFa and P53 gene expression (P<0.05). Sema3a had an inhibitory effect on the differentiation of Raw264.7 cells and the migration and activity of osteoclasts upon irradiation but did not affect ROS. Sema3a also decreased the expression of CSTK, NFAT, TRAP-5b, Rankl/OPG, IL-1, IL-6 and TNFa on the 3rd and 7th days after irradiation (p<0.05), whereas P53 expression was increased (P<0.05). Sema3a reduced the inflammation induced by radiation and negatively regulated osteoclast differentiation. Sema3a promoted Raw264.7 cell apoptosis after irradiation, indicating that Sema3a could be a potential therapeutic target for radiation-induced osteoporosis.

Semaphorin3A: A Potential Therapeutic Tool for Lupus Nephritis.

Background: The immune regulatory properties of semaphorin3A (sema3A) (both innate and adaptive) are well established in many in vitro studies. The injection of sema3A into a mice model of rheumatoid arthritis was proven to be highly beneficial, both in attenuating clinical symptoms and in decreasing inflammatory mechanisms. Objectives: This study was designed in order to assess the possible therapeutic benefits of sema3A following its injection into female NZB/W mice. Methods: Forty-eight NZB/W mice were recruited for this study. Thirty mice were treated as a "prevention group" and 18 were used as a "treatment group." Eight-week-old mice were acclimated and then divided into the two abovementioned groups. Results: The injection of sema3A into young mice (at week 12) before the onset of disease (the prevention group) delayed the appearance of proteinuria. Here, the median time to severe proteinuria was 110 days, 95% CI: 88-131. However, in mice in which the empty vector was injected, the median time to severe proteinuria was 63 days, 95% CI: 0-139. sema3A treatment, significantly reduced renal damage, namely, it prevented the deposition of immune complexes in the glomeruli. When sema3A was injected at the onset of proteinuria (the treatment group), aiming to treat rather than to prevent disease in these mice, survival was increased and the deterioration of proteinuria was delayed. Conclusion: Semaphorin3A is highly beneficial in reducing lupus nephritis in NZB/W mice. It delays the appearance and deterioration of proteinuria, and increases the survival rates in these mice. The regulatory mechanisms of sema3A involve both innate and adaptive immune responses. Further studies will establish the idea of applying sema3A in the treatment of lupus nephritis.

Semaphorin 3a transfection into the left stellate ganglion reduces susceptibility to ventricular arrhythmias after myocardial infarction in rats.

AIMS: Myocardial infarction (MI) induces neural remodelling of the left stellate ganglion (LSG), which may contribute to ischaemia-induced arrhythmias. The neural chemorepellent Semaphorin 3a (Sema3a) has been identified as a negative regulator of sympathetic innervation in the LSG and heart. We previously reported that overexpression of Sema3a in the border zone could reduce the arrhythmogenic effects of cardiac sympathetic hyperinnervation post-MI. This study investigated whether Sema3a overexpression within the LSG confers an antiarrhythmic effect after MI through decreasing extra- and intra-cardiac neural remodelling. METHODS AND RESULTS: Sprague-Dawley rats were subjected to MI, and randomly allocated to intra-LSG microinjection of either phosphate-buffered saline (PBS), adenovirus encoding green fluorescent protein (AdGFP), or adenovirus encoding Sema3a (AdSema3a). Sham-operated rats served as controls. Two weeks after infarction, MI-induced nerve sprouting and sympathetic hyperinnervation in the LSG and myocardium were significantly attenuated by intra-LSG injection with AdSema3a, as assessed by immunohistochemistry and western blot analysis of growth-associated protein 43 and tyrosine hydroxylase. This was also confirmed by sympathetic nerve function changes assessed by cardiac norepinephrine content. Additionally, intra-LSG injection with AdSema3a alleviated MI-induced accumulation of dephosphorylated connexin 43 in the infarct border zone. Furthermore, Sema3a overexpression in the LSG reduced the incidence of inducible ventricular tachyarrhythmia by programmed electrical stimulation post-MI, and arrhythmia scores were significantly lower in the AdSema3a group than in the PBS and AdGFP groups. CONCLUSION: Semaphorin 3a overexpression in the LSG ameliorates the inducibility of ventricular arrhythmias after MI, mainly through attenuation of neural remodelling within the cardiac-neuraxis.

Inhibition of pathological retinal neovascularization by semaphorin 3A.

OBJECTIVE: Pathological retinal angiogenesis is a major cause of vision loss. Semaphorin 3A (Sema3A), a chemorepellent guidance protein, plays crucial roles in neural and vascular patterning. To identify its role in retinal neovascularization, we investigated its antiangiogenic effects. METHODS: Human umbilical vein endothelial cells (HUVECs) were used for the in vitro study, and an oxygen-induced retinopathy (OIR) mouse model was used for the in vivo study. The HUVECs were incubated with Sema3A, and cell proliferation, migration, apoptosis, cell cycle, tube formation, and c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (p38 MAPK) signaling pathways were measured using Cell Counting Kit-8, Transwell, flow cytometry, Matrigel assays, and western blot. C57BL/6J mouse pups were exposed to 75% oxygen for 5 days and then brought to room air and injected with Sema3A intravitreously. At postnatal day 18, the retinal nonperfused areas were measured. The in vitro and in vivo vascular endothelial growth factor-165 (VEGF165) secretion was measured using enzyme-linked immunosorbent assay. RESULTS: Sema3A not only inhibited VEGF165-induced proliferation, but also induced cell cycle arrest in a dose-dependent manner. Furthermore, Sema3A inhibited migration and tube formation, both in general and in VEGF165-containing culture medium. Using an enzyme-linked immunosorbent assay, we showed that Sema3A did not affect VEGF165 secretion, but it did impede VEGF165 function. Additionally, Sema3A significantly inhibited the phosphorylation of the JNK and p38MAPK signaling pathways. When administered intravitreously, Sema3A reduced the pathological vascular changes seen in the retinal neovascularization OIR model. CONCLUSIONS: These results suggest that the administration of Sema3A could be a useful therapeutic strategy for preventing hypoxia/ischemic-induced retinal neovascularization.

Intranasal administration of semaphorin-3A alleviates sneezing and nasal rubbing in a murine model of allergic rhinitis.

Sneezing and persistent itching of the nasal mucosa are distressing symptoms of allergic rhinitis (AR). Recent studies have revealed that hyperinnervation of sensory neurons in the nasal turbinate is one of the underlying causes of sneezing and itching. Since Semaphorin-3A (Sema3A) has been previously shown to restrict innervation of sensory neurons, it is presumed that reduced Sema3A expression in the nasal mucosa might contribute to the hypersensitivity. Analysis of the mouse model of ovalbumin-sensitized AR demonstrated a decreased expression of Sema3A in the nasal epithelium, which was accompanied by an increased nerve fiber density in the lamina propria of the turbinate. In rescue experiments, intranasal administration of recombinant Sema3A in the AR model mice alleviated sneezing and nasal rubbing symptoms. In addition, histological examinations also revealed that nerve fiber density was decreased in the lamina propria of the Sema3A-treated nasal turbinate. These results suggest that the nasal hypersensitivity of AR may be attributed to reduction of Sema3A expression and intranasal administration of Sema3A may provide a novel approach to alleviate the allergic symptoms for AR treatment.

Semaphorin 3A attenuates electrical remodeling at infarct border zones in rats after myocardial infarction.

Electrical remodeling at infarct border zone has been shown to contribute to the occurrence of ventricular arrhythmias after myocardial infarction (MI). Electrical remodeling is causally associated with sympathetic neural remodeling in MI. Semaphorin 3A (Sema3A), a potent neural chemorepellent for sympathetic axons, has been demonstrated to suppress sympathetic neural remodeling after MI. In the present study, we investigated whether treatment with Sema3A can ameliorate electrical remodeling at infarct border zones using a rat model of MI. Wistar rats underwent sham operation (n = 20), the ligation of left coronary artery (MI group, n = 30), MI with control adenovirus (Ad group, n = 30), and MI with Sema3A adenovirus (Sema3A group, n = 30). Eight weeks after treatment, electrophysiological properties including heart rate variability (HRV), monophasic action potential duration (MAPD) and effective refractory period (ERP) and the expression of arrhythmia-related ion channel proteins including Kv4.2, KChIP2 and Kir2.1 at the infarcted border of the left ventricle were examined. These channel proteins may be required for maintaining normal heart rhythm. Compared with the Ad group, Sema3A significantly increased HRV and shortened MAPD and ERP (all p < 0.05). The expression levels of Kv4.2, KChIP2 and Kir2.1 proteins were significantly decreased in MI group and Ad group, compared to sham control. In contrast, the expression levels of these proteins were restored in Sema3A group, which may represent the molecular basis of the Sema3A-mediated inhibition of electrical remodeling. In conclusion, Sema3A can ameliorate electrical remodeling at infarct border zones after MI.