Patterns of Nogo mRNA and protein expression in the developing and adult rat and after CNS lesions

Nogo-A neutralization in the central nervous system with a blood-brain barrier-penetrating antibody

The poor penetration of monoclonal antibodies (mAb) across the blood-brain barrier (BBB) impedes the development of regenerative therapies for neurological diseases. For example, Nogo-A is a myelin-associated protein highly expressed in the central nervous system (CNS) whose inhibitory effects on neuronal plasticity can be neutralized with direct administration of 11C7 mAb in CNS tissues/fluids, but not with peripheral administrations such as intravenous injections. Therefore, in the present study, we engineered a CNS-penetrating antibody against Nogo-A by combining 11C7 mAb and the single-chain variable fragment (scFv) of 8D3, a rat antibody binding transferrin receptor 1 (TfR) and mediating BBB transcytosis (11C7-scFv8D3). The binding of 11C7-scFv8D3 to Nogo-A and to TfR/CD71 was validated by capture ELISA and Biolayer Interferometry. After intravenous injection in mice, capture ELISA measurements revealed fast plasma clearance of 11C7-scFv8D3 concomitantly with brain and spinal cord accumulation at levels up to 19 fold as high as those of original 11C7 mAb. 11C7-scFv8D3 detection in the parenchyma indicated effective blood-to-CNS transfer. A single dose of 11C7-scFv8D3 induced stronger activation of the growth-promoting AkT/mTOR/S6 signaling pathway than 11C7 mAb or control antibody. Taken together, our results show that BBB-crossing 11C7-scFv8D3 engages Nogo-A in the mouse CNS and stimulates neuronal growth mechanisms.

How does Nogo receptor influence demyelination and remyelination in the context of multiple sclerosis?

Multiple sclerosis (MS) can progress with neurodegeneration as a consequence of chronic inflammatory mechanisms that drive neural cell loss and/or neuroaxonal dystrophy in the central nervous system. Immune-mediated mechanisms can accumulate myelin debris in the disease extracellular milieu during chronic-active demyelination that can limit neurorepair/plasticity and experimental evidence suggests that potentiated removal of myelin debris can promote neurorepair in models of MS. The myelin-associated inhibitory factors (MAIFs) are integral contributors to neurodegenerative processes in models of trauma and experimental MS-like disease that can be targeted to promote neurorepair. This review highlights the molecular and cellular mechanisms that drive neurodegeneration as a consequence of chronic-active inflammation and outlines plausible therapeutic approaches to antagonize the MAIFs during the evolution of neuroinflammatory lesions. Moreover, investigative lines for translation of targeted therapies against these myelin inhibitors are defined with an emphasis on the chief MAIF, Nogo-A, that may demonstrate clinical efficacy of neurorepair during progressive MS.

Downregulation of Nogo-B ameliorates cerebral ischemia/reperfusion injury in mice through regulating microglia polarization via TLR4/NF-kappaB pathway

Many studies have shown a close association between Nogo-B and inflammation-related diseases. However, uncertainty does exist, regarding Nogo-B function in the pathological progression of cerebral ischemia/reperfusion (I/R) injury. Middle cerebral artery occlusion/reperfusion (MCAO/R) model was utilized in C57BL/6L mice to mimic ischemic stroke in vivo. Using oxygen-glucose deprivation and reoxygenation (ODG/R) model in microglia cells (BV-2) to establish cerebral I/R injury in vitro. Various methods, including Nogo-B siRNA transfection, mNSS and the rotarod test, TTC, HE and Nissl staining, immunofluorescence staining, immunohistochemistry, Western blot, ELISA, TUNEL and qRT-PCR were employed to probe into the effect of Nogo-B downregulation on cerebral I/R injury and the potential mechanisms. A small amount of Nogo-B expression (protein and mRNA) was observed in cortex and hippocampus before ischemia, then Nogo-B expression increased significantly on day 1, reaching the maximum on day 3, remaining stable on day 14 after I/R, and decreasing gradually after 21 days, but it still rose significantly compared with that observed preischemia. Nogo-B down-regulation could markedly reduce the neurological score and infarct volume, improve the histopathological changes and neuronal apoptosis, lower the number of CD86⁺/Iba1⁺ cells and the levels of IL-1β, IL-6, and TNF-α, and raise the density of NeuN fluorescence, the number of CD206⁺/Iba1⁺ cells, and the level of IL-4, IL-10 and TGF-β in brain of MCAO/R mice. Treatment with Nogo-B siRNA or TAK-242 in BV-2 cells could obviously decrease the CD86 fluorescence density and the mRNA expression of IL-1β, IL-6 and TNF-α, increase CD206 fluorescence density and the mRNA expression of IL-10 after OGD/R injury. In addition, the expression of TLR4, p-IκBα and p-p65 proteins significantly increased in the brain after MCAO/R and BV-2 cells exposed to OGD/R. Treatment with Nogo-B siRNA or TAK-242 prominently reduced the expression of TLR4, p-IκBα and p-p65. Our findings suggest that the down-regulation of Nogo-B exerts protective effect on cerebral I/R injury by modulating the microglia polarization through inhibiting TLR4/NF-κB signaling pathway. Nogo-B may be a potential therapeutic target for ischemic stroke.

Nogo-A reduces ceramide de novo biosynthesis to protect from heart failure

AIMS

Growing evidence correlate the accrual of the sphingolipid ceramide in plasma and cardiac tissue with heart failure (HF). Regulation of sphingolipid metabolism in the heart and the pathological impact of its derangement remain poorly understood. Recently, we discovered that Nogo-B, a membrane protein of endoplasmic reticulum, abundant in the vascular wall, down-regulates the sphingolipid de novo biosynthesis via serine palmitoyltransferase (SPT), first and rate liming enzyme, to impact vascular functions and blood pressure. Nogo-A, a splice isoform of Nogo, is transiently expressed in cardiomyocyte (CM) following pressure overload. Cardiac Nogo is up-regulated in dilated and ischaemic cardiomyopathies in animals and humans. However, its biological function in the heart remains unknown.

METHODS AND RESULTS

We discovered that Nogo-A is a negative regulator of SPT activity and refrains ceramide de novo biosynthesis in CM exposed to haemodynamic stress, hence limiting ceramide accrual. At 7 days following transverse aortic constriction (TAC), SPT activity was significantly up-regulated in CM lacking Nogo-A and correlated with ceramide accrual, particularly very long-chain ceramides, which are the most abundant in CM, resulting in the suppression of 'beneficial' autophagy. At 3 months post-TAC, mice lacking Nogo-A in CM showed worse pathological cardiac hypertrophy and dysfunction, with ca. 50% mortality rate.

CONCLUSION

Mechanistically, Nogo-A refrains ceramides from accrual, therefore preserves the 'beneficial' autophagy, mitochondrial function, and metabolic gene expression, limiting the progression to HF under sustained stress.

Nogo-A and LINGO-1: Two Important Targets for Remyelination and Regeneration

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) that causes progressive neurological disability in most patients due to neurodegeneration. Activated immune cells infiltrate the CNS, triggering an inflammatory cascade that leads to demyelination and axonal injury. Non-inflammatory mechanisms are also involved in axonal degeneration, although they are not fully elucidated yet. Current therapies focus on immunosuppression; however, no therapies to promote regeneration, myelin repair, or maintenance are currently available. Two different negative regulators of myelination have been proposed as promising targets to induce remyelination and regeneration, namely the Nogo-A and LINGO-1 proteins. Although Nogo-A was first discovered as a potent neurite outgrowth inhibitor in the CNS, it has emerged as a multifunctional protein. It is involved in numerous developmental processes and is necessary for shaping and later maintaining CNS structure and functionality. However, the growth-restricting properties of Nogo-A have negative effects on CNS injury or disease. LINGO-1 is also an inhibitor of neurite outgrowth, axonal regeneration, oligodendrocyte differentiation, and myelin production. Inhibiting the actions of Nogo-A or LINGO-1 promotes remyelination both in vitro and in vivo, while Nogo-A or LINGO-1 antagonists have been suggested as promising therapeutic approaches for demyelinating diseases. In this review, we focus on these two negative regulators of myelination while also providing an overview of the available data on the effects of Nogo-A and LINGO-1 inhibition on oligodendrocyte differentiation and remyelination.

Intranasal delivery of full-length anti-Nogo-A antibody: A potential alternative route for therapeutic antibodies to central nervous system targets

Antibody delivery to the CNS remains a huge hurdle for the clinical application of antibodies targeting a CNS antigen. The blood-brain barrier and blood-CSF barrier restrict access of therapeutic antibodies to their CNS targets in a major way. The very high amounts of therapeutic antibodies that are administered systemically in recent clinical trials to reach CNS targets are barely viable cost-wise for broad, routine applications. Though global CNS delivery of antibodies can be achieved by intrathecal application, these procedures are invasive. A non-invasive method to bring antibodies into the CNS reliably and reproducibly remains an important unmet need in neurology. In the present study, we show that intranasal application of a mouse monoclonal antibody against the neurite growth-inhibiting and plasticity-restricting membrane protein Nogo-A leads to a rapid transfer of significant amounts of antibody to the brain and spinal cord in intact adult rats. Daily intranasal application for 2 wk of anti-Nogo-A antibody enhanced growth and compensatory sprouting of corticofugal projections and functional recovery in rats after large unilateral cortical strokes. These findings are a starting point for clinical translation for a less invasive route of application of therapeutic antibodies to CNS targets for many neurological indications.

Dynamic induction of the myelin-associated growth inhibitor Nogo-A in perilesional plasticity regions after human spinal cord injury

The myelin-associated inhibitor Nogo-A (Reticulon 4, RTN4) restricts axonal outgrowth, plasticity, and neural circuitry formation in experimental models of spinal cord injury (SCI) and is targeted in clinical interventions starting treatment within 4 weeks post-SCI. Specifically, Nogo-A expressed by oligodendroglia restricts compensatory neurite sprouting. To interrogate the hypothesis of an inducible, lesion reactive Nogo-A expression over time, we analyzed the spatiotemporal Nogo-A expression at the spinal lesion core (region of tissue necrosis and axonal damage/pruning) and perilesional rim (region of plasticity formation). Spinal cord specimens of SCI subjects (n = 22) were compared to neuropathologically unaltered controls (n = 9). Nogo-A expression was investigated ranging from acute (0-3 days), early subacute (4-21 days), late subacute (22-90 days) to early chronic-chronic (91 days to 1.5 years after SCI) stages after SCI. Nogo-A expression in controls is confined to motoneurons in the anterior horn and to oligodendrocytes in gray and white matter. After SCI, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes (i) inclined at the organizing perilesional rim specifically, (ii) increased further over time, and (iii) peaked at chronic stages after SCI. By contrast, at the lesion core, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes did not increase. Increasing numbers of Nogo-A+ oligodendrocytes coincided with oligodendrogenesis corroborated by Nogo-A coexpression of Ki67+ , TPPP/p25+ proliferating oligodendrocytes. Nogo-A oligodendrocyte expression emerges at perilesional (plasticity) regions over time and suggests an extended therapeutical window for anti-Nogo-A pathway targeting interventions beyond 4 weeks in patients after SCI.

Evolution of factors shaping the endoplasmic reticulum

Endomembrane system compartments are significant elements in virtually all eukaryotic cells, supporting functions including protein synthesis, post-translational modifications and protein/lipid targeting. In terms of membrane area the endoplasmic reticulum (ER) is the largest intracellular organelle, but the origins of proteins defining the organelle and the nature of lineage-specific modifications remain poorly studied. To understand the evolution of factors mediating ER morphology and function we report a comparative genomics analysis of experimentally characterized ER-associated proteins involved in maintaining ER structure. We find that reticulons, REEPs, atlastins, Ufe1p, Use1p, Dsl1p, TBC1D20, Yip3p and VAPs are highly conserved, suggesting an origin at least as early as the last eukaryotic common ancestor (LECA), although many of these proteins possess additional non-ER functions in modern eukaryotes. Secondary losses are common in individual species and in certain lineages, for example lunapark is missing from the Stramenopiles and the Alveolata. Lineage-specific innovations include protrudin, Caspr1, Arl6IP1, p180, NogoR, kinectin and CLIMP-63, which are restricted to the Opisthokonta. Hence, much of the machinery required to build and maintain the ER predates the LECA, but alternative strategies for the maintenance and elaboration of ER shape and function are present in modern eukaryotes. Moreover, experimental investigations for ER maintenance factors in diverse eukaryotes are expected to uncover novel mechanisms.

miR-182-5p Regulates Nogo-A Expression and Promotes Neurite Outgrowth of Hippocampal Neurons In Vitro

Nogo-A protein is a key myelin-associated inhibitor of axonal growth, regeneration, and plasticity in the central nervous system (CNS). Regulation of the Nogo-A/NgR1 pathway facilitates functional recovery and neural repair after spinal cord trauma and ischemic stroke. MicroRNAs are described as effective tools for the regulation of important processes in the CNS, such as neuronal differentiation, neuritogenesis, and plasticity. Our results show that miR-182-5p mimic specifically downregulates the expression of the luciferase reporter gene fused to the mouse Nogo-A 3′UTR, and Nogo-A protein expression in Neuro-2a and C6 cells. Finally, we observed that when rat primary hippocampal neurons are co-cultured with C6 cells transfected with miR-182-5p mimic, there is a promotion of the outgrowth of neuronal neurites in length. From all these data, we suggest that miR-182-5p may be a potential therapeutic tool for the promotion of axonal regeneration in different diseases of the CNS.

Synaptic or Non-synaptic? Different Intercellular Interactions with Retinal Ganglion Cells in Optic Nerve Regeneration

Axons of adult neurons in the mammalian central nervous system generally fail to regenerate by themselves, and few if any therapeutic options exist to reverse this situation. Due to a weak intrinsic potential for axon growth and the presence of strong extrinsic inhibitors, retinal ganglion cells (RGCs) cannot regenerate their axons spontaneously after optic nerve injury and eventually undergo apoptosis, resulting in permanent visual dysfunction. Regarding the extracellular environment, research to date has generally focused on glial cells and inflammatory cells, while few studies have discussed the potentially significant role of interneurons that make direct connections with RGCs as part of the complex retinal circuitry. In this study, we provide a novel angle to summarize these extracellular influences following optic nerve injury as "intercellular interactions" with RGCs and classify these interactions as synaptic and non-synaptic. By discussing current knowledge of non-synaptic (glial cells and inflammatory cells) and synaptic (mostly amacrine cells and bipolar cells) interactions, we hope to accentuate the previously neglected but significant effects of pre-synaptic interneurons and bring unique insights into future pursuit of optic nerve regeneration and visual function recovery.

Genome-wide methylation analyses identifies Non-coding RNA genes dysregulated in breast tumours that metastasise to the brain

Brain metastases comprise 40% of all metastatic tumours and breast tumours are among the tumours that most commonly metastasise to the brain, the role that epigenetic gene dysregulation plays in this process is not well understood. We carried out 450 K methylation array analysis to investigate epigenetically dysregulated genes in breast to brain metastases (BBM) compared to normal breast tissues (BN) and primary breast tumours (BP). For this, we referenced 450 K methylation data for BBM tumours prepared in our laboratory with BN and BP from The Cancer Genome Atlas. Experimental validation on our initially identified genes, in an independent cohort of BP and in BBM and their originating primary breast tumours using Combined Bisulphite and Restriction Analysis (CoBRA) and Methylation Specific PCR identified three genes (RP11-713P17.4, MIR124-2, NUS1P3) that are hypermethylated and three genes (MIR3193, CTD-2023M8.1 and MTND6P4) that are hypomethylated in breast to brain metastases. In addition, methylation differences in candidate genes between BBM tumours and originating primary tumours shows dysregulation of DNA methylation occurs either at an early stage of tumour evolution (in the primary tumour) or at a later evolutionary stage (where the epigenetic change is only observed in the brain metastasis). Epigentic changes identified could also be found when analysing tumour free circulating DNA (tfcDNA) in patient’s serum taken during BBM biopsies. Epigenetic dysregulation of RP11-713P17.4, MIR3193, MTND6P4 are early events suggesting a potential use for these genes as prognostic markers.

Sphingolipid Metabolism and Signaling in Endothelial Cell Functions

The endothelium, inner layer of blood vessels, constitutes a metabolically active paracrine, endocrine, and autocrine organ, able to sense the neighboring environment and exert a variety of biological functions important to preserve the health of vasculature, tissues, and organs. Sphingolipids are both fundamental structural components of the eukaryotic membranes and signaling molecules regulating a variety of biological functions. Ceramide and sphingosine-1-phosphate (S1P), bioactive sphingolipids, have emerged as important regulators of cardiovascular functions in health and disease. In this review we discuss recent insights into the role of ceramide and S1P biosynthesis and signaling in regulating endothelial cell functions, in health and diseases. We also highlight advances into the mechanisms regulating serine palmitoyltransferase, the first and rate-limiting enzyme of de novo sphingolipid biosynthesis, with an emphasis on its inhibitors, ORMDL and NOGO-B. Understanding the molecular mechanisms regulating the sphingolipid de novo biosynthesis may provide the foundation for therapeutic modulation of this pathway in a variety of conditions, including cardiovascular diseases, associated with derangement of this pathway.

Silencing Nogo-B improves the integrity of blood-retinal barrier in diabetic retinopathy via regulating Src, PI3K/Akt and ERK pathways

OBJECTIVE

To examine the mechanisms of Nogo-B (RTN4B) in the protection of blood-retinal barrier in experimental diabetic retinopathy.

METHODS

The level of Nogo-B in vitreous and plasma samples was detected with ELISA. Diabetes was induced in Sprague-Dawley rats with intraperitoneal injection of streptozotocin. The rats were injected intravitreally with adeno-associated virus (AAV) for knockdown the expression of Nogo-B in retina or/and as AAV negative control. The permeability of blood-retinal barrier was detected with Rhodamine-B-dextran leakage assay. The expressions of Nogo-B, junctional proteins, inflammatory factors and signaling pathways were examined with Western blot and quantitative real-time PCR.

RESULTS

Nogo-B expression was significantly upregulated in clinical samples and experimental diabetic rat models. Under normal condition, Nogo-B knockdown resulted in the increased permeability of retinal blood vessels. In diabetic rat retinas, the vascular leakage was increased significantly, which was partially decreased by Nogo-B knockdown through increasing p/t-Src (Tyr529) and p/t-Akt (Ser473), and decreasing p/t-ERK1/2.

CONCLUSION

Nogo-B was increased in diabetic retinopathy and silencing Nogo-B is a promising therapy for diabetic retinopathy.

NEP1‑40 promotes myelin regeneration via upregulation of GAP‑43 and MAP‑2 expression after focal cerebral ischemia in rats

Axon regeneration after lesions to the central nervous system (CNS) is largely limited by the presence of growth inhibitory molecules expressed in myelin. Nogo‑A is a principal inhibitor of neurite outgrowth, and blocking the activity of Nogo‑A can induce axonal sprouting and functional recovery. However, there are limited data on the expression of Nogo‑A after CNS lesions, and the mechanism underlying its influences on myelin growth remains unknown. The aim of the present study was to observe the time course of Nogo‑A after cerebral ischemia/reperfusion in rats using immunohistochemistry and western blot techniques, and to test the effect of its inhibitor Nogo extracellular peptide 1‑40 (NEP1‑40) on neural plasticity proteins, growth‑associated binding protein 43 (GAP‑43) and microtubule associated protein 2 (MAP‑2), as a possible mechanism underlying myelin suppression. A classic model of middle cerebral artery occlusion (MCAO) was established in Sprague‑Dawley rats, which were divided into three groups: i) MCAO model group; ii) MCAO + saline group; and iii) MCAO + NEP1‑40 group. Rats of each group were divided into five subgroups by time points as follows: days 1, 3, 7, 14 and 28. Animals that only received sham operation were used as controls. The Nogo‑A immunoreactivity was located primarily in the cytoplasm of oligodendrocytes. The number of Nogo‑A immunoreactive cells significantly increased from day 1 to day 3 after MCAO, nearly returning to the control level at day 7, increased again at day 14 and decreased at day 28. Myelin basic protein (MBP) immunoreactivity in the ipsilateral striatum gradually decreased from day 1 to day 28 after ischemia, indicating myelin loss appeared at early time points and continuously advanced during ischemia. Then, intracerebroventricular infusion of NEP1‑40, which is a Nogo‑66 receptor antagonist peptide, was administered at days 1, 3 and 14 after MCAO. It was observed that GAP‑43 considerably increased from day 1 to day 7 and then decreased to a baseline level at day 28 compared with the control. MAP‑2 expression across days 1‑28 significantly decreased after MCAO. Administration of NEP1‑40 attenuated the reduction of MBP, and upregulated GAP‑43 and MAP‑2 expression at the corresponding time points after MCAO compared with the MCAO + saline group. The present results indicated that NEP1‑40 ameliorated myelin damage and promoted regeneration by upregulating the expression of GAP‑43 and MAP‑2 related to neuronal and axonal plasticity, which may aid with the identification of a novel molecular mechanism of restriction in CNS regeneration mediated by Nogo‑A after ischemia in rats.

Kidney disease in diabetes: From mechanisms to clinical presentation and treatment strategies

Metabolic and haemodynamic perturbations and their interaction drive the development of diabetic kidney disease (DKD) and its progression towards end stage renal disease (ESRD). Increased mitochondrial oxidative stress has been proposed as the central mechanism in the pathophysiology of DKD, but other mechanisms have been implicated. In parallel to increased oxidative stress, inflammation, cell apoptosis and tissue fibrosis drive the relentless progressive loss of kidney function affecting both the glomerular filtration barrier and the renal tubulointerstitium. Alteration of glomerular capillary autoregulation is at the basis of glomerular hypertension, an important pathogenetic mechanism for DKD. Clinical presentation of DKD can vary. Its classical presentation, often seen in patients with type 1 diabetes (T1DM), features hyperfiltration and albuminuria followed by progressive fall in renal function. Patients can often also present with atypical features characterised by progressive reduction in renal function without albuminuria, others in conjunction with non-diabetes related pathologies making the diagnosis, at times, challenging. Metabolic, lipid and blood pressure control with lifestyle interventions are crucial in reducing the progressive renal function decline seen in DKD. The prevention and management of DKD (and parallel cardiovascular disease) is a huge global challenge and therapies that target haemodynamic perturbations, such as inhibitors of the renin-angiotensin-aldosterone system (RAAS) and SGLT2 inhibitors, have been most successful.

The influence of inhibiting renal neural regeneration on the efficacy of renal denervation to chronic heart failure

Aims

Some studies support the occurrence of nerve regeneration in renal arteries after renal denervation (RDN). But it is unclear whether inhibiting reinnervation after RDN is beneficial to enhancing the effect of RDN on chronic heart failure (CHF).

Methods and results

Chronic heart failure Sprague Dawley rats induced by transverse aortic constriction were administered with the analogue of Nogo‐B (Nogo group) or its antagonist (NEP group) respectively after RDN. Echocardiography, messenger RNA, and protein expression of calcitonin gene‐related peptide (CGRP) in renal artery and nerves surrounding renal artery were detected. Relative protein expression of CGRP was significantly decreased in the Nog group compared with the RDN group (0.64 ± 0.51 vs. 1.68 ± 1.07, P = 0.048). The number of nerves surrounding renal artery was higher in the NEP group than in the Nog group. Left ventricular end‐systolic volume and diameter (LVVs and LVDs) were greatly decreased, and left ventricular ejection fraction (LVEF) and fractional shortening (FS) increased significantly in the RDN, Nog and NEP groups when compared with the HF group (all P < 0.05). No significant differences were observed in left ventricular end‐diastolic volume and diameter; LVDs; LVVs; FS; LVEF; and the levels of plasma renin, noradrenaline, and N‐terminal pro‐B‐type natriuretic peptide among three groups: the RDN, Nog, and NEP groups.

Conclusions

Reinnervation of renal artery occurred in CHF rats after RDN, which had no effect on therapeutic role of RDN in CHF, and inhibiting this neural regeneration had no clinical significance and did not affect the efficacy of RDN to CHF.

Plasticity-Enhancing Effects of Levodopa Treatment after Stroke

Dopaminergic treatment in combination with rehabilitative training enhances long-term recovery after stroke. However, the underlying mechanisms on structural plasticity are unknown. Here, we show an increased dopaminergic innervation of the ischemic territory during the first week after stroke induced in Wistar rats subjected to transient occlusion of the middle cerebral artery (tMCAO) for 120 min. This response was also found in rats subjected to permanent focal ischemia induced by photothrombosis (PT) and mice subjected to PT or tMCAO. Dopaminergic branches were detected in the infarct core of mice and rats in both stroke models. In addition, the Nogo A pathway was significantly downregulated in rats treated with levodopa (LD) compared to vehicle-treated animals subjected to tMCAO. Specifically, the number of Nogo A positive oligodendrocytes as well as the levels of Nogo A and the Nogo A receptor were significantly downregulated in the peri-infarct area of LD-treated animals, while the number of Oligodendrocyte transcription factor 2 positive cells increased in this region after treatment. In addition, we observed lower protein levels of Growth Associated Protein 43 in the peri-infarct area compared to sham-operated animals without treatment effect. The results provide the first evidence of the plasticity-promoting actions of dopaminergic treatment following stroke.

Nogo-A Modulates the Synaptic Excitation of Hippocampal Neurons in a Ca2+-Dependent Manner

A tight regulation of the balance between inhibitory and excitatory synaptic transmission is a prerequisite for synaptic plasticity in neuronal networks. In this context, the neurite growth inhibitor membrane protein Nogo-A modulates synaptic plasticity, strength, and neurotransmitter receptor dynamics. However, the molecular mechanisms underlying these actions are unknown. We show that Nogo-A loss-of-function in primary mouse hippocampal cultures by application of a function-blocking antibody leads to higher excitation following a decrease in GABA_ARs at inhibitory and an increase in the GluA1, but not GluA2 AMPAR subunit at excitatory synapses. This unbalanced regulation of AMPAR subunits results in the incorporation of Ca²⁺-permeable GluA2-lacking AMPARs and increased intracellular Ca²⁺ levels due to a higher Ca²⁺ influx without affecting its release from the internal stores. Increased neuronal activation upon Nogo-A loss-of-function prompts the phosphorylation of the transcription factor CREB and the expression of c-Fos. These results contribute to the understanding of the molecular mechanisms underlying the regulation of the excitation/inhibition balance and thereby of plasticity in the brain.

Role of serum Nogo-B as a biomarker for diagnosis of chronic liver diseases and its severity

Background

Nogo-B is one of the members of the reticulon family. Nogo-B influences the proliferation of the hepatic stellate cells inducing liver fibrotic changes. We aimed at measuring the serum levels of Nogo-B in patients with chronic liver disease (CLD) with different etiologies. Ninety subjects were included, 18 of them were normal healthy individuals and 72 had liver disease (fibrosis/cirrhosis) with different etiologies: post-hepatitis C infection, post-hepatitis B infection, NASH, and autoimmune hepatitis. Serum Nogo-B was assessed using ELISA. Patients were subdivided according to the Child-Pugh score into 3 groups: group 1—Child A (24 patients); group 2—Child B (24 patients); and group 3—Child C (24 patients).

Results

Serum Nogo-B levels were found to be significantly higher in patients (1477.92 ± 1113.50) when compared with healthy control (301.28 ± 180.87) (p < 0.001). There was a statistically significant difference in serum Nogo-B level between the three sub-groups of patients (p < 0.001). A positive correlation was found between serum Nogo-B and MELD score (r = 0.46, p-value < 0.001). However, there was no correlation found between Nogo-B and FIB-4 index or APRI score. There was a significant positive correlation between serum Nogo-B level and coagulation profile and serum bilirubin. An inverse correlation was found between serum Nogo-B with serum albumin. A ROC curve was done to examine the validity of Nogo-B in the diagnosis of liver cirrhosis, and the area under the curve was found to be 0.979, a cutoff value of 600 with a sensitivity of 97.2% and a specificity of 94.4% (p-value < 0.001).

Conclusion

Nogo-B had a high value in the identification of patients with any severity of CLD. There is a highly significant correlation between Nogo-B and the synthetic function of the liver; it could be used as a measure of hepatic functional reserve.

The Regulatory Role of Reticulons in Neurodegeneration: Insights Underpinning Therapeutic Potential for Neurodegenerative Diseases

In the last few decades, cytoplasmic organellar dysfunction, such as that of the endoplasmic reticulum (ER), has created a new area of research interest towards the development of serious health maladies including neurodegenerative diseases. In this context, the extensively dispersed family of ER-localized proteins, i.e. reticulons (RTNs), is gaining interest because of its regulative control over neural regeneration. As most neurodegenerative diseases are pathologically manifested with the accretion of misfolded proteins with subsequent induction of ER stress, the regulatory role of RTNs in neural dysfunction cannot be ignored. With the limited information available in the literature, delineation of the functional connection between rising consequences of neurodegenerative diseases and RTNs need to be elucidated. In this review, we provide a broad overview on the recently revealed regulatory roles of reticulons in the pathophysiology of several health maladies, with special emphasis on neurodegeneration. Additionally, we have also recapitulated the decisive role of RTN4 in neurite regeneration and highlighted how neurodegeneration and proteinopathies are mechanistically linked with each other through specific RTN paralogues. With the recent findings advocating zebrafish Rtn4b (a mammalian Nogo-A homologue) downregulation following central nervous system (CNS) lesion, RTNs provides new insight into the CNS regeneration. However, there are controversies with respect to the role of Rtn4b in zebrafish CNS regeneration. Given these controversies, the connection between the unique regenerative capabilities of zebrafish CNS by distinct compensatory mechanisms and Rtn4b signalling pathway could shed light on the development of new therapeutic strategies against serious neurodegenerative diseases.

Effects of Nogo-A and its receptor on the repair of sciatic nerve injury in rats

Regeneration of injured peripheral nerves is an extremely complex process. Nogo-A (neurite outgrowth inhibitor-A) inhibits axonal regeneration by interacting with Nogo receptor in the myelin sheath of the central nervous system (CNS). The aim of this study was to investigate the effects of Nogo-A and its receptor on the repair of sciatic nerve injury in rats. Sprague-Dawley rats (n=96) were randomly divided into 4 groups: control group (control), sciatic nerve transection group (model), immediate repair group (immediate repair), and delayed repair group (delayed repair). The rats were euthanized 1 week and 6 weeks after operation. The injured end tissues of the spinal cord and sciatic nerve were obtained. The protein expressions of Nogo-A and Nogo-66 receptor (NgR) were detected by immunohistochemistry. The protein expressions of Nogo-A, NgR, and Ras homolog family member A (RhoA) were detected by western blot. At 1 week after operation, the pathological changes in the immediate repaired group were less, and the protein expressions of Nogo-A, NgR, and RhoA in the spinal cord and sciatic nerve tissues were decreased (P<0.05) compared with the model group. After 6 weeks, the pathological changes in the immediate repair group and the delayed repair group were alleviated and the protein expressions decreased (P<0.05). The situation of the immediate repair group was better than that of the delayed repair group. Our data suggest that the expression of Nogo-A and its receptor increased after sciatic nerve injury, indicating that Nogo-A and its receptor play an inhibitory role in the repair process of sciatic nerve injury in rats.

Exercise-induced Nogo-A influences rodent motor learning in a time-dependent manner

The adult, mature central nervous system (CNS) has limited plasticity. Physical exercising can counteract this limitation by inducing plasticity and fostering processes such as learning, memory consolidation and formation. Little is known about the molecular factors that govern these mechanisms, and how they are connected with exercise. In this study, we used immunohistochemical and behavioral analyses to investigate how running wheel exercise affects expression of the neuronal plasticity-inhibiting protein Nogo-A in the rat cortex, and how it influences motor learning in vivo. Following one week of exercise, rats exhibited a decrease in Nogo-A levels, selectively in motor cortex layer 2/3, but not in layer 5. Nogo-A protein levels returned to baseline after two weeks of running wheel exercise. In a skilled motor task (forelimb-reaching), administration of Nogo-A function-blocking antibodies over the course of the first training week led to improved motor learning. By contrast, Nogo-A antibody application over two weeks of training resulted in impaired learning. Our findings imply a bimodal, time-dependent function of Nogo-A in exercise-induced neuronal plasticity: While an activity-induced suppression of the plasticity-inhibiting protein Nogo-A appears initially beneficial for enhanced motor learning, presumably by allowing greater plasticity in establishing novel synaptic connections, this process is not sustained throughout continued exercise. Instead, upregulation of Nogo-A over the course of the second week of running wheel exercise in rats implies that Nogo-A is required for consolidation of acquired motor skills during the delayed memory consolidation process, possibly by inhibiting ongoing neuronal morphological reorganization to stabilize established synaptic pathways. Our findings suggest that Nogo-A downregulation allows leaning to occur, i.e. opens a ‘learning window’, while its later upregulation stabilizes the learnt engrams. These findings underline the importance of appropriately timing of application of Nogo-A antibodies in future clinical trials that aim to foster memory performance while avoiding adverse effects.

The Implication of Reticulons (RTNs) in Neurodegenerative Diseases: From Molecular Mechanisms to Potential Diagnostic and Therapeutic Approaches

Reticulons (RTNs) are crucial regulatory factors in the central nervous system (CNS) as well as immune system and play pleiotropic functions. In CNS, RTNs are transmembrane proteins mediating neuroanatomical plasticity and functional recovery after central nervous system injury or diseases. Moreover, RTNs, particularly RTN4 and RTN3, are involved in neurodegeneration and neuroinflammation processes. The crucial role of RTNs in the development of several neurodegenerative diseases, including Alzheimer's disease (AD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or other neurological conditions such as brain injury or spinal cord injury, has attracted scientific interest. Reticulons, particularly RTN-4A (Nogo-A), could provide both an understanding of early pathogenesis of neurodegenerative disorders and be potential therapeutic targets which may offer effective treatment or inhibit disease progression. This review focuses on the molecular mechanisms and functions of RTNs and their potential usefulness in clinical practice as a diagnostic tool or therapeutic strategy.

Nogo-A Is Critical for Pro-Inflammatory Gene Regulation in Myocytes and Macrophages

Nogo-A (Rtn 4A), a member of the reticulon 4 (Rtn4) protein family, is a neurite outgrowth inhibitor protein that is primarily expressed in the central nervous system (CNS). However, previous studies revealed that Nogo-A was upregulated in skeletal muscles of Amyotrophic lateral sclerosis (ALS) patients. Additionally, experiments showed that endoplasmic reticulum (ER) stress marker, C/EBP homologous protein (CHOP), was upregulated in gastrocnemius muscle of a murine model of ALS. We therefore hypothesized that Nogo-A might relate to skeletal muscle diseases. According to our knocking down and overexpression results in muscle cell line (C2C12), we have found that upregulation of Nogo-A resulted in upregulation of CHOP, pro-inflammatory cytokines such as interleukin (IL)-6 and tumor necrosis factor (TNF)-α, while downregulation of Nogo-A led to downregulation of CHOP, IL-6 and TNF-α. Immunofluorescence results showed that Nogo-A and CHOP were expressed by myofibers as well as tissue macrophages. Since resident macrophages share similar functions as bone marrow-derived macrophages (BMDM), we therefore, isolated macrophages from bone marrow to study the role of Nogo-A in activation of these cells. Lipopolysaccharide (LPS)-stimulated BMDM in Nogo-KO mice showed low mRNA expression of CHOP, IL-6 and TNF-α compared to BMDM in wild type (WT) mice. Interestingly, Nogo knockout (KO) BMDM exhibited lower migratory activity and phagocytic ability compared with WT BMDM after LPS treatment. In addition, mice experiments data revealed that upregulation of Nogo-A in notexin- and tunicamycin-treated muscles was associated with upregulation of CHOP, IL-6 and TNF-α in WT group, while in Nogo-KO group resulted in low expression level of CHOP, IL-6 and TNF-α. Furthermore, upregulation of Nogo-A in dystrophin-deficient (mdx) murine model, myopathy and Duchenne muscle dystrophy (DMD) clinical biopsies was associated with upregulation of CHOP, IL-6 and TNF-α. To the best of our knowledge, this is the first study to demonstrate Nogo-A as a regulator of inflammation in diseased muscle and bone marrow macrophages and that deletion of Nogo-A alleviates muscle inflammation and it can be utilized as a therapeutic target for improving muscle diseases.

Neurite Outgrowth Inhibitor (NogoA) Is Upregulated in White Matter Lesions of Complex Cortical Malformations

Complex cortical malformations (CCMs), such as hemimegalencephaly and polymicrogyria, are associated with drug-resistant epilepsy and developmental impairment. They share certain neuropathological characteristics including mammalian target of rapamycin (mTOR) activation and an atypical number of white matter neurons. To get a better understanding of the pathobiology of the lesion architecture, we investigated the role of neurite outgrowth inhibitor A (NogoA), a known regulator of neuronal migration. Epilepsy surgery specimens from 16 CCM patients were analyzed and compared with sections of focal cortical dysplasia IIB (FCD IIB, n = 22), tuberous sclerosis complex (TSC, n = 8) as well as healthy controls (n = 15). Immunohistochemistry was used to characterize NogoA, myelination, and mTOR signaling. Digital slides were evaluated automatically with ImageJ. NogoA staining showed a significantly higher expression within the white matter of CCM and FCD IIB, whereas cortical tubers presented levels similar to controls. Further analysis of possible associations of NogoA with other factors revealed a positive correlation with mTOR and seizure frequency. To identify the main expressing NogoA cell type, double staining revealed dysmorphic neuronal white matter cells. Increased NogoA expression is associated with profound inhibition of neuritic sprouting and therefore contributes to a decrease in neuronal network complexity in CCM patients.

Astrocytes as a target for Nogo-A and implications for synapse formation in vitro and in a model of acute demyelination

Central nervous system (CNS) function depends on precise synaptogenesis, which is shaped by environmental cues and cellular interactions. Astrocytes are outstanding regulators of synapse development and plasticity through contact-dependent signals and through the release of pro- and antisynaptogenic factors. Conversely, myelin and its associated proteins, including Nogo-A, affect synapses in a inhibitory fashion and contribute to neural circuitry stabilization. However, the roles of Nogo-A-astrocyte interactions and their implications in synapse development and plasticity have not been characterized. Therefore, we aimed to investigate whether Nogo-A affects the capacity of astrocytes to induce synaptogenesis. Additionally, we assessed whether downregulation of Nogo-A signaling in an in vivo demyelination model impacts the synaptogenic potential of astrocytes. Our in vitro data show that cortical astrocytes respond to Nogo-A through RhoA pathway activation, exhibiting stress fiber formation and decreased ramified morphology. This phenotype was associated with reduced levels of GLAST protein and aspartate uptake, decreased mRNA levels of the synaptogenesis-associated genes Hevin, glypican-4, TGF-β1 and BDNF, and decreased and increased protein levels of Hevin and SPARC, respectively. Corroborating these findings, conditioned medium from Nogo-A-treated astrocytes suppressed the formation of structurally and functionally mature synapses in cortical neuronal cultures. After cuprizone-induced acute demyelination, we observed reduced immunostaining for Nogo-A in the visual cortex accompanied by higher levels of Hevin expression in astrocytes and an increase in excitatory synapse density. Hence, we suggest that interactions between Nogo-A and astrocytes might represent an important pathway of plasticity regulation and could be a target for therapeutic intervention in demyelinating diseases in the future.

Fast Regulation of GABAAR Diffusion Dynamics by Nogo-A Signaling

Precisely controlling the excitatory and inhibitory balance is crucial for the stability and information-processing ability of neuronal networks. However, the molecular mechanisms maintaining this balance during ongoing sensory experiences are largely unclear. We show that Nogo-A signaling reciprocally regulates excitatory and inhibitory transmission. Loss of function for Nogo-A signaling through S1PR2 rapidly increases GABA_AR diffusion, thereby decreasing their number at synaptic sites and the amplitude of GABAergic mIPSCs at CA3 hippocampal neurons. This increase in GABA_AR diffusion rate is correlated with an increase in Ca²⁺ influx and requires the calcineurin-mediated dephosphorylation of the γ2 subunit at serine 327. These results suggest that Nogo-A signaling rapidly strengthens inhibitory GABAergic transmission by restricting the diffusion dynamics of GABA_ARs. Together with the observation that Nogo-A signaling regulates excitatory transmission in an opposite manner, these results suggest a crucial role for Nogo-A signaling in modulating the excitation and inhibition balance to restrict synaptic plasticity.

NOGO-A immunolabeling is present in glial cells and some neurons of the recovering lumbar spinal cord in lizards

The transected lumbar spinal cord of lizards was studied for its ability to recover after paralysis. At 34 days post-lesion about 50% of lizards were capable of walking with a limited coordination, likely due to the regeneration of few connecting axons crossing the transection site of the spinal cord. This region, indicated as "bridge", contains glial cells among which oligodendrocytes and their elongation that are immunolabeled for NOGO-A. A main reactive protein band occurs at 100-110 kDa but a weaker band is also observed around 240 kDa, suggesting fragmentation of the native protein due to extraction or to physiological processing of the original protein. Most of the cytoplasmic immunolabeling observed in oligodendrocytes is associated with vesicles of the endoplasmic reticulum. Also, the nucleus is labeled in some oligodendrocytes that are myelinating sparse axons observed within the bridge at 22-34 days post-transection. This suggests that axonal regeneration is present within the bridge region. Immunolabeling for NOGO-A shows that the protein is also present in numerous reactive neurons, in particular motor-neurons localized in the proximal stump of the transected spinal cord. Ultrastructural immunolocalization suggests that NOGO is synthesized in the ribosomes of these neurons and becomes associated with the cisternae of the endoplasmic reticulum, probably following a secretory pathway addressed toward the axon. The present observations suggest that, like for the regenerating spinal cord of fish and amphibians, also in lizard NOGO-A is present in reactive neurons and appears associated to axonal regeneration and myelination.

Application of Antibodies to Neuronally Expressed Nogo-A Increases Neuronal Survival and Neurite Outgrowth

Nogo-A, a glycoprotein expressed in oligodendrocytes and central nervous system myelin, inhibits regeneration after injury. Antibodies against Nogo-A neutralize this inhibitory activity, improve locomotor recovery in spinal cord-injured adult mammals, and promote regrowth/sprouting/saving of damaged axons beyond the lesion site. Nogo-A is also expressed by neurons. Complete ablation of Nogo-A in all cell types expressing it has been found to lead to recovery in some studies but not in others. Neuronal ablation of Nogo-A reduces axonal regrowth after injury. In view of these findings, we hypothesized that, in addition to neutralizing Nogo-A in oligodendrocytes and myelin, Nogo-A antibodies may act directly on neuronal Nogo-A to trigger neurite outgrowth and neuronal survival. Here, we show that polyclonal and monoclonal antibodies against Nogo-A enhance neurite growth and survival of cultured cerebellar granule neurons and increase expression of the neurite outgrowth-promoting L1 cell adhesion molecule and polysialic acid. Application of inhibitors of signal transducing molecules, such as c-src, c-fyn, protein kinase A, and casein kinase II reduce antibody-triggered neurite outgrowth. These observations indicate that the recovery-promoting functions of antibodies against Nogo-A may not only be due to neutralizing Nogo-A in oligodendrocytes and myelin, but also to their interactions with Nogo-A on neurons.

Identification of a new functional domain of Nogo-A that promotes inflammatory pain and inhibits neurite growth through binding to NgR1

Nogo-A is a key inhibitory molecule to axon regeneration, and plays diverse roles in other pathological conditions, such as stroke, schizophrenia, and neurodegenerative diseases. Nogo-66 and Nogo-Δ20 fragments are two known functional domains of Nogo-A, which act through the Nogo-66 receptor (NgR1) and sphingosine-1-phosphate receptor 2 (S1PR2), respectively. Here, we reported a new functional domain of Nogo-A, Nogo-A aa 846-861, was identified in the Nogo-A-specific segment that promotes complete Freund's adjuvant (CFA)-induced inflammatory pain. Intrathecal injection of its antagonist peptide 846-861PE or the specific antibody attenuated the CFA-induced inflammatory heat hyperalgesia. The 846-861 PE reduced the content of transient receptor potential vanilloid subfamily member 1 (TRPV1) in dorsal root ganglia (DRG) and decreased the response of DRG neurons to capsaicin. These effects were accompanied by a reduction in LIMK/cofilin phosphorylation and actin polymerization. GST pull-down and fluorescence resonance energy transfer (FRET) assays both showed that Nogo-A aa 846-861 bound to NgR1. Moreover, we demonstrated that Nogo-A aa 846-861 inhibited neurite outgrowth from cortical neurons and DRG explants. We concluded that Nogo-A aa 846-861 is a novel ligand of NgR1, which activates the downstream signaling pathways that inhibit axon growth and promote inflammatory pain.

Cholinergic System and NGF Receptors: Insights from the Brain of the Short-Lived Fish Nothobranchius furzeri

Nerve growth factor (NGF) receptors are evolutionary conserved molecules, and in mammals are considered necessary for ensuring the survival of cholinergic neurons. The age-dependent regulation of NTRK1/NTRKA and p75/NGFR in mammalian brain results in a reduced response of the cholinergic neurons to neurotrophic factors and is thought to play a role in the pathogenesis of neurodegenerative diseases. Here, we study the age-dependent expression of NGF receptors (NTRK1/NTRKA and p75/NGFR) in the brain of the short-lived teleost fish Nothobranchius furzeri. We observed that NTRK1/NTRKA is more expressed than p75/NGFR in young and old animals, although both receptors do not show a significant age-dependent change. We then study the neuroanatomical organization of the cholinergic system, observing that cholinergic fibers project over the entire neuroaxis while cholinergic neurons appear restricted to few nuclei situated in the equivalent of mammalian subpallium, preoptic area and rostral reticular formation. Finally, our experiments do not confirm that NTRK1/NTRKA and p75/NGFR are expressed in cholinergic neuronal populations in the adult brain of N. furzeri. To our knowledge, this is the first study where NGF receptors have been analyzed in relation to the cholinergic system in a fish species along with their age-dependent modulation. We observed differences between mammals and fish, which make the African turquoise killifish an attractive model to further investigate the fish specific NGF receptors regulation.

Expression of Nogo-A in dorsal root ganglion in rats with cauda equina injury

OBJECTIVE

To investigate the expression of Nogo-A in dorsal root ganglion (DRG) in rats with cauda equina injury and the therapeutic effects of blocking Nogo-A and its receptor.

METHODS AND MATERIALS

Fifty-eight male Sprague-Dawley rats were divided randomly into either the sham operation group (n = 24) or the cauda equina compression (CEC) control group (n = 34). Behavioral, histological, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses were conducted to assess the establishment of the model. The dynamic expression change of Nogo-A was evaluated using real time-qPCR. Immunofluorescence was used to evaluate the expression of Nogo-A in the DRG and cauda equina. Furthermore, 20 male Sprague-Dawley rats were equally divided into 4 groups, including the sham group, the CEC group, the NEP1-40 (the NgR antagonist peptide) treatment group, and the JTE-013 (the S1PR2 antagonist) treatment group. Behavioral assessments and western blotting were used to evaluate the therapeutic effect of cauda equina injury via blocking Nogo-A and its receptor.

RESULTS

Tactile allodynia and heat hyperalgesia in the CEC model developed as soon as 1 day after surgery and recovered to normal at 7 days, which was followed by the downregulation of Nogo-A in DRG neurons. However, the locomotor function impairment in the CEC model showed a different prognosis from the sensory function, which was consistent with the expression change of Nogo-A in the spinal cord. Immunofluorescence results also demonstrated that Nogo A-positive/NF200-negative neurons and axons increased in the DRG and cauda equina 7 days after surgery. Surprisingly, Schwann cells, which myelinate axons in the PNS, also expressed considerable amounts of Nogo-A. Then, after blocking the Nogo-A/NgR signaling pathway by NEP1-40, significant improvement of mechanical allodynia was identified in the first 2 days after the surgery. Western blotting suggested the NEP1-40 treatment group had lower expression of cleaved caspase-3 than the CEC and JTE-013 treatment group.

CONCLUSION

Neuronal Nogo-A in the DRG may be involved in regeneration and play a protective role in the CEC model. Whereas Nogo-A, released from the injured axons or expressed by Schwann cells, may act as an inhibiting factor in the process of CEC repairment. Thus, blocking the Nogo-A/NgR signaling pathway can alleviate mechanical allodynia by apoptosis inhibition.

Nogo receptor antagonist LOTUS exerts suppression on axonal growth-inhibiting receptor PIR-B

Damaged axons in the adult mammalian central nervous system have a restricted regenerative capacity mainly because of Nogo protein, which is a major myelin-associated axonal growth inhibitor with binding to both receptors of Nogo receptor-1 (NgR1) and paired immunoglobulin-like receptor (PIR)-B. Lateral olfactory tract usher substance (LOTUS) exerts complete suppression of NgR1-mediated axonal growth inhibition by antagonizing NgR1. However, the regulation of PIR-B functions in neurons remains unknown. In this study, protein-protein interactions analyses found that LOTUS binds to PIR-B and abolishes Nogo-binding to PIR-B completely. Reverse transcription-polymerase chain reaction and immunocytochemistry revealed that PIR-B is expressed in dorsal root ganglions (DRGs) from wild-type and Ngr1-deficient mice (male and female). In these DRG neurons, Nogo induced growth cone collapse and neurite outgrowth inhibition, but treatment with the soluble form of LOTUS completely suppressed them. Moreover, Nogo-induced growth cone collapse and neurite outgrowth inhibition in Ngr1-deficient DRG neurons were neutralized by PIR-B function-blocking antibodies, indicating that these Nogo-induced phenomena were mediated by PIR-B. Our data show that LOTUS negatively regulates a PIR-B function. LOTUS thus exerts an antagonistic action on both receptors of NgR1 and PIR-B. This may lead to an improvement in the defective regeneration of axons following injury.

Experimental pediatric stroke shows age-specific recovery of cognition and role of hippocampal Nogo-A receptor signaling

Ischemic stroke is a leading cause of death worldwide and clinical data suggest that children may recover from stroke better than adults; however, supporting experimental data are lacking. We used our novel mouse model of experimental juvenile ischemic stroke (MCAO) to characterize age-specific cognitive dysfunction following ischemia. Juvenile and adult mice subjected to 45-min MCAO, and extracellular field recordings of CA1 neurons were performed to assess hippocampal synaptic plasticity changes after MCAO, and contextual fear conditioning was performed to evaluate memory and biochemistry used to analyze Nogo-A expression. Juvenile mice showed impaired synaptic plasticity seven days after MCAO, followed by full recovery by 30 days. Memory behavior was consistent with synaptic impairments and recovery after juvenile MCAO. Nogo-A expression increased in ipsilateral hippocampus seven days after MCAO compared to contralateral and sham hippocampus. Further, inhibition of Nogo-A receptors reversed MCAO-induced synaptic impairment in slices obtained seven days after juvenile MCAO. Adult MCAO-induced impairment of LTP was not associated with increased Nogo-A. This study demonstrates that stroke causes functional impairment in the hippocampus and recovery of behavioral and synaptic function is more robust in the young brain. Nogo-A receptor activity may account for the impairments seen following juvenile ischemic injury.

Blockade of Nogo-A/Nogo-66 receptor 1 (NgR1) Inhibits Autophagic Activation and Prevents Secondary Neuronal Damage in the Thalamus after Focal Cerebral Infarction in Hypertensive Rats

Focal cerebral infarction leads to autophagic activation, which contributes to secondary neuronal damage in the ipsilateral thalamus. Although Nogo-A deactivation enhances neuronal plasticity, its role in autophagic activation in the thalamus after ischemic stroke remains unclear. This study aimed to investigate the potential roles of Nogo-A/Nogo-66 receptor 1 (NgR1) in autophagic activation in the ipsilateral thalamus after cerebral infarction. Focal neocortical infarction was established using the middle cerebral artery occlusion (MCAO) method. Secondary damage in the ipsilateral thalamus was assessed by Nissl staining and immunostaining. The expression of Nogo-A, NgR1, Rho-A and Rho-associated coiled-coil containing protein kinase 1 (ROCK1) as well as autophagic flux were evaluated by immunofluorescence and immunoblotting. The roles of Nogo-A-NgR1 signaling in autophagic activation were determined by intraventricular delivery of an NgR1 antagonist peptide, NEP1-40, at 24 h after MCAO. The results showed that Nogo-A and NgR1 overexpression temporally coincided with marked increases in the levels of Beclin1, LC3-II and sequestosome 1 (SQSTM1)/p62 in the ipsilateral thalamus at seven and fourteen days after MCAO. In contrast, NEP1-40 treatment significantly reduced the expression of Rho-A and ROCK1 which was accompanied by marked reductions of LC3-II conversion as well as the levels of Beclin1 and SQSTM1/p62. Furthermore, NEP1-40 treatment significantly reduced neuronal loss and gliosis in the ipsilateral thalamus, and accelerated somatosensory recovery at the observed time-points after MCAO. These results suggest that blockade of Nogo-A-NgR1 signaling inhibits autophagic activation, attenuates secondary neuronal damage in the ipsilateral thalamus, and promotes functional recovery after focal cerebral cortical infarction.

A proteolytic C-terminal fragment of Nogo-A (reticulon-4A) is released in exosomes and potently inhibits axon regeneration

Glial signals are known to inhibit axonal regeneration and functional recovery after mammalian central nervous system trauma, including spinal cord injury. Such signals include membrane-associated proteins of the oligodendrocyte plasma membrane and astrocyte-derived, matrix-associated proteins. Here, using cell lines and primary cortical neuron cultures, recombinant protein expression, immunoprecipitation and immunoblot assays, transmission EM of exosomes, and axon regeneration assays, we explored the secretion and activity of the myelin-associated neurite outgrowth inhibitor Nogo-A and observed exosomal release of a 24-kDa C-terminal Nogo-A fragment from cultured cells. We found that the cleavage site in this 1192-amino-acid-long fragment is located between amino acids 961-971. We also detected a Nogo-66 receptor (NgR1)-interacting Nogo-66 domain on the exosome surface. Enzyme inhibitor treatment and siRNA knockdown revealed that β-secretase 1 (BACE1) is the protease responsible for Nogo-A cleavage. Functionally, exosomes with the Nogo-66 domain on their surface potently inhibited axonal regeneration of mechanically injured cerebral cortex neurons from mice. Production of this fragment was observed in the exosomal fraction from neuronal tissue lysates after spinal cord crush injury of mice. We also noted that, relative to the exosomal marker Alix, a Nogo-immunoreactive, 24-kDa protein is enriched in exosomes 2-fold after injury. We conclude that membrane-associated Nogo-A produced in oligodendrocytes is processed proteolytically by BACE1, is released via exosomes, and is a potent diffusible inhibitor of regenerative growth in NgR1-expressing axons.

Protein Tyrosine Phosphatase σ Inhibitory Peptide Promotes Recovery of Diaphragm Function and Sprouting of Bulbospinal Respiratory Axons after Cervical Spinal Cord Injury

Damage to respiratory neural circuitry and consequent loss of diaphragm function is a major cause of morbidity and mortality after cervical spinal cord injury (SCI). Upon SCI, inspiratory signals originating in the medullary rostral ventral respiratory group (rVRG) become disrupted from their phrenic motor neuron (PhMN) targets, resulting in diaphragm paralysis. Limited growth of both damaged and spared axon populations occurs after central nervous system trauma attributed, in part, to expression of various growth inhibitory molecules, some that act through direct interaction with the protein tyrosine phosphatase sigma (PTPσ) receptor located on axons. In the rat model of C2 hemisection SCI, we aimed to block PTPσ signaling to investigate potential mechanisms of axon plasticity and respiratory recovery using a small molecule peptide mimetic that inhibits PTPσ. The peptide was soaked into a biocompatible gelfoam and placed directly over the injury site immediately after hemisection and replaced with a freshly soaked piece 1 week post-SCI. At 8 weeks post-hemisection, PTPσ peptide significantly improved ipsilateral hemidiaphragm function, as assessed in vivo with electromyography recordings. PTPσ peptide did not promote regeneration of axotomized rVRG fibers originating in ipsilateral medulla, as assessed by tracing after adeno-associated virus serotype 2/mCherry injection into the rVRG. Conversely, PTPσ peptide stimulated robust sprouting of contralateral-originating rVRG fibers and serotonergic axons within the PhMN pool ipsilateral to hemisection. Further, relesion through the hemisection did not compromise diaphragm recovery, suggesting that PTPσ peptide-induced restoration of function was attributed to plasticity of spared axon pathways descending in contralateral spinal cord. These data demonstrate that inhibition of PTPσ signaling can promote significant recovery of diaphragm function after SCI by stimulating plasticity of critical axon populations spared by the injury and consequently enhancing descending excitatory input to PhMNs.

Oligodendrocyte- and Neuron-Specific Nogo-A Restrict Dendritic Branching and Spine Density in the Adult Mouse Motor Cortex

Nogo-A has been well described as a myelin-associated inhibitor of neurite outgrowth and functional neuroregeneration after central nervous system (CNS) injury. Recently, a new role of Nogo-A has been identified as a negative regulator of synaptic plasticity in the uninjured adult CNS. Nogo-A is present in neurons and oligodendrocytes. However, it is yet unclear which of these two pools regulate synaptic plasticity. To address this question we used newly generated mouse lines in which Nogo-A is specifically knocked out in (1) oligodendrocytes (oligoNogo-A KO) or (2) neurons (neuroNogo-A KO). We show that both oligodendrocyte- and neuron-specific Nogo-A KO mice have enhanced dendritic branching and spine densities in layer 2/3 cortical pyramidal neurons. These effects are compartmentalized: neuronal Nogo-A affects proximal dendrites whereas oligodendrocytic Nogo-A affects distal regions. Finally, we used two-photon laser scanning microscopy to measure the spine turnover rate of adult mouse motor cortex layer 5 cells and find that both Nogo-A KO mouse lines show enhanced spine remodeling after 4 days. Our results suggest relevant control functions of glial as well as neuronal Nogo-A for synaptic plasticity and open new possibilities for more selective and targeted plasticity enhancing strategies.

Recent advances in nanotherapeutic strategies for spinal cord injury repair

Spinal cord injury (SCI) is a devastating and complicated condition with no cure available. The initial mechanical trauma is followed by a secondary injury characterized by inflammatory cell infiltration and inhibitory glial scar formation. Due to the limitations posed by the blood-spinal cord barrier, systemic delivery of therapeutics is challenging. Recent development of various nanoscale strategies provides exciting and promising new means of treating SCI by crossing the blood-spinal cord barrier and delivering therapeutics. As such, we discuss different nanomaterial fabrication methods and provide an overview of recent studies where nanomaterials were developed to modulate inflammatory signals, target inhibitory factors in the lesion, and promote axonal regeneration after SCI. We also review emerging areas of research such as optogenetics, immunotherapy and CRISPR-mediated genome editing where nanomaterials can provide synergistic effects in developing novel SCI therapy regimens, as well as current efforts and barriers to clinical translation of nanomaterials.

Modifying PTEN recruitment promotes neuron survival, regeneration, and functional recovery after CNS injury

Phosphatase and tensin homolog (PTEN) regulates apoptosis and axonal growth in the developing and adult central nervous system (CNS). Here, we show that human PTEN C-terminal PDZ interactions play a critical role in neuronal apoptosis and axon regeneration after traumatic CNS injury and stroke, highlighted by the findings that antagonizing the PDZ-motif interactions of PTEN has therapeutic applicability for these indications. Interestingly, the death-inducing function of PTEN following ischemic insult depends on a PDZ-domain interaction with MAGI-2 and MAST205, PDZ proteins that are known to recruit PTEN to the plasma membrane and stabilize its interaction with PIP3. Treatments with a human peptide that prevents PTEN association with MAGI-2 or MAST205 increased neuronal survival in multiple stroke models, in vitro. A pro-survival effect was also observed in models of retinal ischemia, optic nerve transection, and after middle cerebral artery occlusion (MCAO) in adult rats. The human PTEN peptide also improved axonal regeneration in the crushed optic nerve. Furthermore, human PTEN peptide therapy promoted functional improvement after MCAO or retinal ischemia induced via ophthalmic artery ligation. These findings show that the human peptide-based targeting of C-terminal PTEN PDZ interactions has therapeutic potential for insults of the CNS, including trauma and stroke.

Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis

BACKGROUND

Clinically significant portal hypertension (CSPH) and severe portal hypertension (SPH) increase the risk for decompensation and life-threatening complications in liver cirrhosis. Pathologic angiogenesis might contribute to the formation of these conditions. Placental growth factor (PlGF) and Nogo-A protein are biomarkers of pathological angiogenesis, but data on their role in liver cirrhosis and portal hypertension is scarce.

AIM

To determine plasma levels of PlGF and Nogo-A in patients with liver cirrhosis, CSPH, SPH and potential to predict portal hypertension.

METHODS

A cohort of 122 patients with hepatitis C virus and/or alcohol-induced liver cirrhosis with characterized hepatic venous pressure gradient (HVPG) were included in the study. Demographic data, medical history, Child-Turcotte-Pugh and Model of End Stage liver disease score, clinical chemistry, liver stiffness values were recorded on the day of the procedure prior HVPG measurement. The degree of portal hypertension was determined by the invasive HVPG measurement. Nogo-A and PlGF plasma levels were evaluated using enzyme linked immunosorbent assay. The control group consisted of 30 healthy age- and sex- matched individuals.

RESULTS

Peripheral PlGF levels were higher and Nogo-A levels were lower in patients with liver cirrhosis (23.20 vs 9.85; P < 0.0001 and 2.19 vs 3.12; P = 0.004 respectively). There was a positive linear correlation between peripheral levels of PlGF and HVPG (r = 0.338, P = 0.001) and negative linear correlation between the peripheral Nogo-A levels and HVPG (r = -0.267, P = 0.007). PlGF levels were higher in CSPH and SPH (P = 0.006; P < 0.0001) whereas Nogo-A levels were lower (P = 0.01; P < 0.033). Area under the curve for the diagnosis of CSPH for PlGF was 0.68 (P = 0.003) and for Nogo-A - 0.67 (P = 0.01); for SPH 0.714 (P < 0.0001) and 0.65 (P = 0.014) respectively. PlGF levels were higher and Nogo-A levels were lower in patients with esophageal varices (P < 0.05). PlGF cut-off value of 25 pg/mL distinguished patients with CSPH at 55.7% sensitivity and 76.7% specificity; whereas Nogo-A cut-off value of 1.12 ng/mL was highly specific (93.1%) for the diagnosis of CSPH.

CONCLUSION

Plasma PlGF levels were higher while Nogo-A levels were lower in patients with liver cirrhosis and portal hypertension. Biomarkers showed moderate predictive value in determining CSPH and SPH.

Constraint-induced movement therapy enhances angiogenesis and neurogenesis after cerebral ischemia/reperfusion

Constraint-induced movement therapy after cerebral ischemia stimulates axonal growth by decreasing expression levels of Nogo-A, RhoA, and Rho-associated kinase (ROCK) in the ischemic boundary zone. However, it remains unclear if there are any associations between the Nogo-A/RhoA/ROCK pathway and angiogenesis in adult rat brains in pathological processes such as ischemic stroke. In addition, it has not yet been reported whether constraint-induced movement therapy can promote angiogenesis in stroke in adult rats by overcoming Nogo-A/RhoA/ROCK signaling. Here, a stroke model was established by middle cerebral artery occlusion and reperfusion. Seven days after stroke, the following treatments were initiated and continued for 3 weeks: forced limb use in constraint-induced movement therapy rats (constraint-induced movement therapy group), intraperitoneal infusion of fasudil (a ROCK inhibitor) in fasudil rats (fasudil group), or lateral ventricular injection of NEP1–40 (a specific antagonist of the Nogo-66 receptor) in NEP1–40 rats (NEP1–40 group). Immunohistochemistry and western blot assay results showed that, at 2 weeks after middle cerebral artery occlusion, expression levels of RhoA and ROCK were lower in the ischemic boundary zone in rats treated with NEP1–40 compared with rats treated with ischemia/reperfusion or constraint-induced movement therapy alone. However, at 4 weeks after middle cerebral artery occlusion, expression levels of RhoA and ROCK in the ischemic boundary zone were markedly decreased in the NEP1–40 and constraint-induced movement therapy groups, but there was no difference between these two groups. Compared with the ischemia/reperfusion group, modified neurological severity scores and foot fault scores were lower and time taken to locate the platform was shorter in the constraint-induced movement therapy and fasudil groups at 4 weeks after middle cerebral artery occlusion, especially in the constraint-induced movement therapy group. Immunofluorescent staining demonstrated that fasudil promoted an immune response of nerve-regeneration-related markers (BrdU in combination with CD31 (platelet endothelial cell adhesion molecule), Nestin, doublecortin, NeuN, and glial fibrillary acidic protein) in the subventricular zone and ischemic boundary zone ipsilateral to the infarct. After 3 weeks of constraint-induced movement therapy, the number of regenerated nerve cells was noticeably increased, and was accompanied by an increased immune response of tight junctions (claudin-5), a pericyte marker (α-smooth muscle actin), and vascular endothelial growth factor receptor 2. Taken together, the results demonstrate that, compared with fasudil, constraint-induced movement therapy led to stronger angiogenesis and nerve regeneration ability and better nerve functional recovery at 4 weeks after cerebral ischemia/reperfusion. In addition, constraint-induced movement therapy has the same degree of inhibition of RhoA and ROCK as NEP1–40. Therefore, constraint-induced movement therapy promotes angiogenesis and neurogenesis after cerebral ischemia/reperfusion injury, at least in part by overcoming the Nogo-A/RhoA/ROCK signaling pathway. All protocols were approved by the Institutional Animal Care and Use Committee of China Medical University, China on December 9, 2015 (approval No. 2015PS326K).

Effects of remote ischemic preconditioning on astrocyte proliferation and glial scars after cerebral infarction

The aim of this study was to investigate whether remote ischemic preconditioning (RIPC) can promote neurological function recovery after middle cerebral artery occlusion (MCAO) in rats and its possible mechanism. A total of 32 Sprague Dawley (SD) rats were randomly divided into RIPC group (n = 16) and MCAO group (n = 16). In the RIPC group, 1 h before induction of MCAO, the rats received bilateral femoral artery ischemic preconditioning (10 min/time), followed by 10 min of relaxation, and a total of three cycles were carried out. Then, the MCAO-2h model was established. In the MCAO group, the MCAO-2h model was established at 1 h after the separation of bilateral femoral arteries. The modified neurological severity score (mNSS) was assessed. At postmodeling day 7, triphenyltetrazolium chloride (TTC) staining and immunohistochemistry were conducted, and neurological function recovery, infarct size, and the expression levels of glial fibrillary acidic protein (GFAP), synaptophysin (SYN), and neurite outgrowth inhibitor A (Nogo-A) were observed. At postmodeling day 7, the difference in mNSS was statistically significant ( P < 0.05). Infarct size was significantly smaller in the RIPC group than in the MCAO group ( P < 0.05). The number of GFAP+ cells was significantly lesser in the RIPC group than in the MCAO group ( P < 0.05). The difference in thickness of the glial scar was not statistically significant ( P = 0.091). At postmodeling day 7, the expression level of SYN integrated optical density (IOD) was significantly higher in the RIPC group than in the MCAO group ( P < 0.05). The number of Nogo-A+ cells was significantly lesser in the RIPC group than in the MCAO group ( P < 0.05). At day 7 after MCAO, RIPC can promote neurological function recovery in rats and reduce infarct size. The mechanism may be that after 7 days, RIPC reduces GFAP expression, inhibits the trend of glial scar formation and Nogo-A expression, and increases SYN expression.

A Network Pharmacology Analysis to Explore the Effect of Astragali Radix-Radix Angelica Sinensis on Traumatic Brain Injury

Traumatic brain injury (TBI) is a critical public health and socioeconomic problem worldwide. The herb pair Astragali Radix (AR)-Radix Angelica Sinensis (RAS) is a common prescribed herbal formula or is added to other Chinese medicine prescriptions for traumatic brain injury (TBI) treatment. However, the underlying mechanisms are unclear. In this study, we aimed to explore the active ingredients and action targets of AR-RAS based on the combined methods of network pharmacology prediction and experimental verification. Furthermore, the corresponding potential mechanisms of “multicomponents, multitargets, and multipathways” were disclosed. Methods. A network pharmacology approach including ADME (absorption, distribution, metabolism, and excretion) filter analysis, target prediction, known therapeutic targets collection, Gene Ontology (GO), pathway enrichment analysis, and network construction was used in this study. Further verification experiments were performed to reveal the therapeutic effects of AR-RAS in a rat model of TBI. Results. The comprehensive systematic approach was to successfully identify 14 bioactive ingredients in AR-RAS, while 33 potential targets hit by these ingredients related to TBI. Based on GO annotation analysis, multiple biological processes were significantly regulated by AR-RAS. In addition, 89 novel signaling pathways (P<0.05) underlying the effects of AR-RAS for TBI treatment were identified by DAVID. The neurotrophin signaling pathway was suggested as the major related pathway targeted by AR-RAS to improve axonal growth. The animal experiment confirmed that AR-RAS significantly induced tissue recovery and improved neurological deficits on the 14th day (P<0.01). Treatment with AR-RAS markedly reduced the protein and mRNA expression level of NogoA in the hippocampus of TBI rats. Conclusion. Our work illuminates the “multicompounds, multitargets, and multipathways” curative action of AR-RAS in the treatment of TBI by network pharmacology. The animal experiment verifies the effects of AR-RAS on neurological function improvement and axonal outgrowth via downregulation of NogoA expression, providing a theoretical basis for further research on treatment of TBI.

Oligodendrocytic but not neuronal Nogo restricts corticospinal axon sprouting after CNS injury

Recovery from injury to the central nervous system (CNS) is limited in the mammalian adult. Nonetheless, some degree of spontaneous recovery occurs after partial CNS injury. Compensatory axonal growth from uninjured neurons, termed sprouting, contributes to this naturally occurring recovery process and can be modulated by molecular intervention. Extensive studies have depicted a long-held hypothesis that oligodendrocyte-derived Nogo restricts axonal sprouting and functional recovery after CNS injury. However, cell type-specific function of Nogo in compensatory sprouting, spinal axon repair or functional recovery after CNS injury has not been reported. Here we present data showing that inducible, cell type-specific deletion of Nogo from oligodendrocytes led to a ~50% increase in the compensatory sprouting of corticospinal tract (CST) axons in the cervical spinal cord after unilateral pyramidotomy in mice. In contrast to a previously proposed growth-promoting role of neuronal Nogo in the optic nerve, deleting neuronal Nogo did not significantly affect CST axon sprouting in the spinal cord. Sprouting axons were associated with the expression of synaptic marker VGLUT1 in both the oligodendrocytic Nogo deletion and control mice. However, we did not detect any functional improvement in fine motor control associated with the increased sprouting in oligodendrocytic Nogo deletion mice. These data show for the first time with genetic evidence that Nogo specifically expressed by oligodendrocytes restricts compensatory sprouting after CNS injury, supporting a longstanding but heretofore untested hypothesis. While implicating a focus on sprouting as a repair mechanism in the translational potential of targeting the myelin inhibitory pathway, our study illustrates the challenge to harness enhanced structural plasticity for functional improvement.

Nogo-B receptor increases the resistance to tamoxifen in estrogen receptor-positive breast cancer cells

BACKGROUNDS

Tamoxifen is typically used to treat patients with estrogen receptor alpha (ERα)-positive breast cancer. However, 30% of these patients gain acquired resistance to tamoxifen during or after tamoxifen treatment. As a Ras modulator, Nogo-B receptor (NgBR) is required for tumorigenesis through the signaling crosstalk with epidermal growth factor (EGF) receptor (EGFR)-mediated pathways. NgBR is highly expressed in many types of cancer cells and regulates the sensitivity of hepatocellular carcinoma to chemotherapy. In this study, we found the expression of NgBR is increased in tamoxifen-resistant ERα-positive breast cancer cells.

METHODS

Tamoxifen-resistant ERα-positive MCF-7 and T47D breast cancer cell lines were established by culturing with gradually increased concentration of 4-hydroxytamoxifen (4-OHT). The effects of NgBR on tamoxifen resistance was determined by depleting NgBR in these cell lines using previously validated small interfering RNA (siRNA). The effects of 4-OHT on cell viability and apoptosis were determined using well-accepted methods such as clonogenic survival assay and Annexin V/propidium iodide staining. The alteration of EGF-stimulated signaling and gene expression was determined by western blot analysis and real-time PCR, respectively.

RESULTS

NgBR knockdown with siRNA attenuates EGF-induced phosphorylation of ERα and restores the sensitivity to tamoxifen in ERα-positive breast cancer cells. Mechanistically, our data demonstrated that NgBR knockdown increases the protein levels of p53 and decreases survivin, which is an apoptosis inhibitor.

CONCLUSIONS

These results suggested that NgBR is a potential therapeutic target for increasing the sensitivity of ERα-positive breast cancer to tamoxifen.

Nogo-A inhibits vascular regeneration in ischemic retinopathy

Nogo-A is a potent glial-derived inhibitor of axon growth in the injured CNS and acts as a negative regulator of developmental angiogenesis by inhibiting vascular endothelial cell migration. However, its function in pathological angiogenesis has never been studied after ischemic injury in the CNS. Using the mouse model of oxygen-induced retinopathy (OIR) which yields defined zones of retinal ischemia, our goal was to investigate the role of Nogo-A in vascular regeneration. We demonstrate a marked upregulation of the Nogo-A receptor sphingosine 1-phosphate receptor 2 in blood vessels following OIR, while Nogo-A is abundantly expressed in surrounding glial cells. Acute inhibition of Nogo-A with function-blocking antibody 11C7 significantly improved vascular regeneration and consequently prevented pathological pre-retinal angiogenesis. Ultimately, inhibition of Nogo-A led to restoration of retinal function as determined by electrophysiological response of retinal cells to light stimulation. Our data suggest that anti-Nogo-A antibody may protect neuronal cells from ischemic damage by accelerating blood vessel repair in the CNS. Targeting Nogo-A by immunotherapy may improve CNS perfusion after vascular injuries.

Loss of Nogo-A, encoded by the schizophrenia risk gene Rtn4, reduces mGlu3 expression and causes hyperexcitability in hippocampal CA3 circuits

Recent investigations of Nogo-A, a well characterized protein inhibitor of neurite outgrowth in the brain, have revealed additional functions including a role in neuropsychiatric disorders such as schizophrenia. Here we examined Nogo-A functions in mouse CA3 hippocampal circuitry. Patch clamp recordings showed that the absence of Nogo-A results in a hyperactive network. In addition, mGlu3 metabotropic glutamate receptors, which exhibit mutations in certain forms of schizophrenia, were downregulated specifically in the CA3 area. Furthermore, Nogo-A^-/- mice showed disordered theta oscillations with decreased incidence and frequency, similar to those observed in mGlu3^-/- mice. As disruptions in theta rhythmicity are associated with impaired spatial navigation, we tested mice using modified Morris water maze tasks. Mice lacking Nogo-A exhibited altered search strategies, displaying greater dependence on global as opposed to local reference frames. This link between Nogo-A and mGlu3 receptors may provide new insights into mechanisms underlying schizophrenia.

Nogo-A promotes inflammatory heat hyperalgesia by maintaining TRPV-1 function in the rat dorsal root ganglion neuron

Nogo-A is a key inhibitory molecule of axon regeneration in oligodendrocytes. However, little is known about its role in adult neurons. In this study, we showed an important function of Nogo-A on regulation of inflammatory pain in dorsal root ganglion (DRG) neurons. In adult rats with complete Freund's adjuvant (CFA) hind paw inflammation, DRG neurons showed a significant increase in Nogo-A expression. Disruption of Nogo-A signaling with Nogo-66 receptor antagonist peptide, Nogo-A blocking antibody, Nogo-A short hairpin RNA, or Nogo-A gene knockout attenuated CFA-induced inflammatory heat hyperalgesia. Moreover, disruption of Nogo-A signaling suppressed the function and expression in DRG neurons of the transient receptor potential vanilloid subfamily member (TRPV)-1 channel, which is known to be the endogenous transducer of noxious heat during inflammation. These effects were accompanied with a reduction in LIM domain kinase (LIMK)/cofilin phosphorylation and actin polymerization. Similar disruption of actin filament architecture by direct action of Latrunculin A reduced the TRPV-1 activity and up-regulation of TRPV-1 protein caused by CFA. We conclude that Nogo-A plays an essential role in the development of inflammatory heat hyperalgesia, partly through maintaining TRPV-1 function via activation of the LIMK/cofilin pathway, which regulates actin filament dynamics. These findings support a therapeutic potential of modulating Nogo-A signaling in pain management.-Hu, F., Liu, H.-C., Su, D.-Q., Chen, H.-J., Chan, S.-O., Wang, Y., Wang, J. Nogo-A promotes inflammatory heat hyperalgesia by maintaining TRPV-1 function in the rat dorsal root ganglion neuron.

Exploring the Crosstalk Between LMNA and Splicing Machinery Gene Mutations in Dilated Cardiomyopathy

Mutations in the LMNA gene, which encodes for the nuclear lamina proteins lamins A and C, are responsible for a diverse group of diseases known as laminopathies. One type of laminopathy is Dilated Cardiomyopathy (DCM), a heart muscle disease characterized by dilation of the left ventricle and impaired systolic function, often leading to heart failure and sudden cardiac death. LMNA is the second most commonly mutated gene in DCM. In addition to LMNA, mutations in more than 60 genes have been associated with DCM. The DCM-associated genes encode a variety of proteins including transcription factors, cytoskeletal, Ca2+-regulating, ion-channel, desmosomal, sarcomeric, and nuclear-membrane proteins. Another important category among DCM-causing genes emerged upon the identification of DCM-causing mutations in RNA binding motif protein 20 (RBM20), an alternative splicing factor that is chiefly expressed in the heart. In addition to RBM20, several essential splicing factors were validated, by employing mouse knock out models, to be embryonically lethal due to aberrant cardiogenesis. Furthermore, heart-specific deletion of some of these splicing factors was found to result in aberrant splicing of their targets and DCM development. In addition to splicing alterations, advances in next generation sequencing highlighted the association between splice-site mutations in several genes and DCM. This review summarizes LMNA mutations and splicing alterations in DCM and discusses how the interaction between LMNA and splicing regulators could possibly explain DCM disease mechanisms.