Enhanced neurite outgrowth of human model (NT2) neurons by small-molecule inhibitors of Rho/ROCK signaling

Modulation of the Nogo signaling pathway to overcome amyloid-β-mediated neurite inhibition in human pluripotent stem cell-derived neurites

JOURNAL/nrgr/04.03/01300535-202509000-00026/figure1/v/2024-11-05T132919Z/r/image-tiff Neuronal cell death and the loss of connectivity are two of the primary pathological mechanisms underlying Alzheimer's disease. The accumulation of amyloid-β peptides, a key hallmark of Alzheimer's disease, is believed to induce neuritic abnormalities, including reduced growth, extension, and abnormal growth cone morphology, all of which contribute to decreased connectivity. However, the precise cellular and molecular mechanisms governing this response remain unknown. In this study, we used an innovative approach to demonstrate the effect of amyloid-β on neurite dynamics in both two-dimensional and three-dimensional culture systems, in order to provide more physiologically relevant culture geometry. We utilized various methodologies, including the addition of exogenous amyloid-β peptides to the culture medium, growth substrate coating, and the utilization of human-induced pluripotent stem cell technology, to investigate the effect of endogenous amyloid-β secretion on neurite outgrowth, thus paving the way for potential future applications in personalized medicine. Additionally, we also explore the involvement of the Nogo signaling cascade in amyloid-β-induced neurite inhibition. We demonstrate that inhibition of downstream ROCK and RhoA components of the Nogo signaling pathway, achieved through modulation with Y-27632 (a ROCK inhibitor) and Ibuprofen (a Rho A inhibitor), respectively, can restore and even enhance neuronal connectivity in the presence of amyloid-β. In summary, this study not only presents a novel culture approach that offers insights into the biological process of neurite growth and inhibition, but also proposes a specific mechanism for reduced neural connectivity in the presence of amyloid-β peptides, along with potential intervention points to restore neurite growth. Thereby, we aim to establish a culture system that has the potential to serve as an assay for measuring preclinical, predictive outcomes of drugs and their ability to promote neurite outgrowth, both generally and in a patient-specific manner.

The potential of baicalin to enhance neuroprotection and mitochondrial function in a human neuronal cell model

Baicalin is a flavone glycoside derived from flowering plants belonging to the Scutellaria genus. Previous studies have reported baicalin's anti-inflammatory and neuroprotective properties in rodent models, indicating the potential of baicalin in neuropsychiatric disorders where alterations in numerous processes are observed. However, the extent of baicalin's therapeutic effects remains undetermined in a human cell model, more specifically, neuronal cells to mimic the brain environment in vitro. As a proof of concept, we treated C8-B4 cells (murine cell model) with three different doses of baicalin (0.1, 1 and 5 μM) and vehicle control (DMSO) for 24 h after liposaccharide-induced inflammation and measured the levels of TNF-α in the medium by ELISA. NT2-N cells (human neuronal-like cell model) underwent identical baicalin treatment, followed by RNA extraction, genome-wide mRNA expression profiles and gene set enrichment analysis (GSEA). We also performed neurite outgrowth assays and mitochondrial flux bioanalysis (Seahorse) in NT2-N cells. We found that in C8-B4 cells, baicalin at ≥ 1 μM exhibited anti-inflammatory effects, lowering TNF-α levels in the cell culture media. In NT2-N cells, baicalin positively affected neurite outgrowth and transcriptionally up-regulated genes in the tricarboxylic acid cycle and the glycolysis pathway. Similarly, Seahorse analysis showed increased oxygen consumption rate in baicalin-treated NT2-N cells, an indicator of enhanced mitochondrial function. Together, our findings have confirmed the neuroprotective and mitochondria enhancing effects of baicalin in human-neuronal like cells. Given the increased prominence of mitochondrial mechanisms in diverse neuropsychiatric disorders and the paucity of mitochondrial therapeutics, this suggests the potential therapeutic application of baicalin in human neuropsychiatric disorders where these processes are altered.

Neurotoxicity and Developmental Neurotoxicity of Copper Sulfide Nanoparticles on a Human Neuronal In-Vitro Test System

Nanoparticles (NPs) are becoming increasingly important novel materials for many purposes, including basic research, medicine, agriculture, and engineering. Increasing human and environmental exposure to these promising compounds requires assessment of their potential health risks. While the general direct cytotoxicity of NPs is often routinely measured, more indirect possible long-term effects, such as reproductive or developmental neurotoxicity (DNT), have been studied only occasionally and, if so, mostly on non-human animal models, such as zebrafish embryos. In this present study, we employed a well-characterized human neuronal precursor cell line to test the concentration-dependent DNT of green-manufactured copper sulfide (CuS) nanoparticles on crucial early events in human brain development. CuS NPs turned out to be generally cytotoxic in the low ppm range. Using an established prediction model, we found a clear DNT potential of CuS NPs on neuronal precursor cell migration and neurite outgrowth, with IC50 values 10 times and 5 times, respectively, lower for the specific DNT endpoint than for general cytotoxicity. We conclude that, in addition to the opportunities of NPs, their risks to human health should be carefully considered.

Preparation of Viable Human Neurites for Neurobiological and Neurodegeneration Studies

Few models allow the study of neurite damage in the human central nervous system. We used here dopaminergic LUHMES neurons to establish a culture system that allows for (i) the observation of highly enriched neurites, (ii) the preparation of the neurite fraction for biochemical studies, and (iii) the measurement of neurite markers and metabolites after axotomy. LUHMES-based spheroids, plated in culture dishes, extended neurites of several thousand µm length, while all somata remained aggregated. These cultures allowed an easy microscopic observation of live or fixed neurites. Neurite-only cultures (NOC) were produced by cutting out the still-aggregated somata. The potential application of such cultures was exemplified by determinations of their protein and RNA contents. For instance, the mitochondrial TOM20 protein was highly abundant, while nuclear histone H3 was absent. Similarly, mitochondrial-encoded RNAs were found at relatively high levels, while the mRNA for a histone or the neuronal nuclear marker NeuN (RBFOX3) were relatively depleted in NOC. Another potential use of NOC is the study of neurite degeneration. For this purpose, an algorithm to quantify neurite integrity was developed. Using this tool, we found that the addition of nicotinamide drastically reduced neurite degeneration. Also, the chelation of Ca2+ in NOC delayed the degeneration, while inhibitors of calpains had no effect. Thus, NOC proved to be suitable for biochemical analysis and for studying degeneration processes after a defined cut injury.

Improved Cryopreservation of Human Induced Pluripotent Stem Cell (iPSC) and iPSC-derived Neurons Using Ice-Recrystallization Inhibitors

Human induced pluripotent stem cells (iPSCs) and iPSC-derived neurons (iPSC-Ns) represent a differentiated modality toward developing novel cell-based therapies for regenerative medicine. However, the successful application of iPSC-Ns in cell-replacement therapies relies on effective cryopreservation. In this study, we investigated the role of ice recrystallization inhibitors (IRIs) as novel cryoprotectants for iPSCs and terminally differentiated iPSC-Ns. We found that one class of IRIs, N-aryl-D-aldonamides (specifically 2FA), increased iPSC post-thaw viability and recovery with no adverse effect on iPSC pluripotency. While 2FA supplementation did not significantly improve iPSC-N cell post-thaw viability, we observed that 2FA cryopreserved iPSC-Ns re-established robust neuronal network activity and synaptic function much earlier compared to CS10 cryopreserved controls. The 2FA cryopreserved iPSC-Ns retained expression of key neuronal specific and terminally differentiated markers and displayed functional electrophysiological and neuropharmacological responses following treatment with neuroactive agonists and antagonists. We demonstrate how optimizing cryopreservation media formulations with IRIs represents a promising strategy to improve functional cryopreservation of iPSCs and post-mitotic iPSC-Ns, the latter of which have been challenging to achieve. Developing IRI enabling technologies to support an effective cryopreservation and an efficiently managed cryo-chain is fundamental to support the delivery of successful iPSC-derived therapies to the clinic.

Modeling Central Nervous System Injury In Vitro: Current Status and Promising Future Strategies

The central nervous system (CNS) injury, which occurs because of mechanical trauma or ischemia/hypoxia, is one of the main causes of mortality and morbidity in the modern society. Until know, despite the fact that numerous preclinical and clinical studies have been undertaken, no significant neuroprotective strategies have been discovered that could be used in the brain trauma or ischemia treatment. Although there are many potential explanations for the failure of those studies, it is clear that there are questions regarding the use of experimental models, both in vivo and in vitro, when studying CNS injury and searching new therapeutics. Due to some ethical issues with the use of live animals in biomedical research, implementation of experimental strategies that prioritize the use of cells and tissues in the in vitro environment has been encouraged. In this review, we examined some of the most commonly used in vitro models and the most frequently utilized cellular platforms in the research of traumatic brain injury and cerebral ischemia. We also proposed some future strategies that could improve the usefulness of these studies for better bench-to-bedside translational outcomes.

Antipsychotic-like effects of fasudil, a Rho-kinase inhibitor, in a pharmacologic animal model of schizophrenia

Current antipsychotics used to treat schizophrenia have associated problems, including serious side effects and treatment resistance. We recently identified a significant association of schizophrenia with exonic copy number variations in the Rho GTPase activating protein 10 (ARHGAP10) gene using genome-wide analysis. ARHGAP10 encodes a RhoGAP superfamily member that is involved in small GTPase signaling. In mice, Arhgap10 gene variations result in RhoA/Rho-kinase pathway activation. We evaluated the pharmacokinetics of fasudil and hydroxyfasudil using liquid chromatography-tandem mass spectrometry in mice. The antipsychotic effects of fasudil on hyperlocomotion, social interaction deficits, prepulse inhibition deficits, and novel object recognition deficits were also investigated in a MK-801-treated pharmacological mouse schizophrenia model. Fasudil and its major metabolite, hydroxyfasudil, were detected in the brain at concentrations above their respective K_i values for Rho-kinase after intraperitoneal injection of 10 mg kg^-1 fasudil. Fasudil improved the hyperlocomotion, social interaction deficits, prepulse inhibition deficits, and novel object recognition deficits in MK-801-treated mice in a dose-dependent manner. Following oral administration of fasudil, brain hydroxyfasudil was detected at concentration above the K_i value for Rho-kinase whilst fasudil was undetectable. MK-801-induced hyperlocomotion was also improved by oral fasudil administration. These results suggest that fasudil has antipsychotic-like effects on the MK-801-treated pharmacological mouse schizophrenia model. There are two isoforms in Rho-kinase, and further investigation is needed to clarify the isoforms involved in the antipsychotic-like effects of fasudil in the MK-801-treated mouse schizophrenia model.

Protection against Hypoxia-Reoxygenation Injury of Hippocampal Neurons by H2S via Promoting Phosphorylation of ROCK2 at Tyr722 in Rat Model

The RhoA-ROCK signaling pathway is associated with the protective effects of hydrogen sulfide (H₂S) against cerebral ischemia. H₂S protects rat hippocampal neurons (RHNs) against hypoxia-reoxygenation (H/R) injury by promoting phosphorylation of RhoA at Ser188. However, effect of H₂S on the phosphorylation of ROCK₂-related sites is unclear. The present study was designed to investigate whether H₂S can play a role in the phosphorylation of ROCK₂ at Tyr722, and explore whether this role mediates the protective effect of H/R injury in RHNs. Prokaryotic recombinant plasmids ROCK₂^wild-pGEX-6P-1 and ROCK₂^Y722F-pGEX-6P-1 were constructed and transfected into E. coli in vitro, and the expressed protein, GST-ROCK₂^wild and GST-ROCK₂^Y722F were used for phosphorylation assay in vitro. Eukaryotic recombinant plasmids ROCK₂^Y722-pEGFP-N1 and ROCK₂^Y722F-pEGFP-N1 as well as empty plasmid were transfected into the RHNs. Western blot assay and whole-cell patch-clamp technique were used to detect phosphorylation of ROCK₂ at Tyr722 and BK_Ca channel current in the RHNs, respectively. Cell viability, leakages of intracellular enzymes lactate dehydrogenase (LDH), and nerve-specific enolase (NSE) were measured. The H/R injury was indicated by decrease of cell viability and leakages of intracellular LDH and NSE. The results of Western blot have shown that NaHS, a H₂S donor, significantly promoted phosphorylation of GST-ROCK₂^wild at Tyr722, while no phosphorylation of GST-ROCK₂^Y722F was detected. The phosphorylation of ROCK₂^wild promoted by NaHS was also observed in RHNs. NaHS induced more potent effects on protection against H/R injury, phosphorylation of ROCK₂ at Tyr722, inhibition of ROCK₂ activity, as well as increase of the BK_Ca current in the ROCK₂^Y722-pEGFP-N1-transfected RHNs. Our results revealed that H₂S protects the RHNs from H/R injury through promoting phosphorylation of ROCK₂ at Tyr722 to inhibit ROCK₂ activity and potentially by opening channel currents.

Insulin and Its Key Role for Mitochondrial Function/Dysfunction and Quality Control: A Shared Link between Dysmetabolism and Neurodegeneration

Insulin was discovered and isolated from the beta cells of pancreatic islets of dogs and is associated with the regulation of peripheral glucose homeostasis. Insulin produced in the brain is related to synaptic plasticity and memory. Defective insulin signaling plays a role in brain dysfunction, such as neurodegenerative disease. Growing evidence suggests a link between metabolic disorders, such as diabetes and obesity, and neurodegenerative diseases, especially Alzheimer's disease (AD). This association is due to a common state of insulin resistance (IR) and mitochondrial dysfunction. This review takes a journey into the past to summarize what was known about the physiological and pathological role of insulin in peripheral tissues and the brain. Then, it will land in the present to analyze the insulin role on mitochondrial health and the effects on insulin resistance and neurodegenerative diseases that are IR-dependent. Specifically, we will focus our attention on the quality control of mitochondria (MQC), such as mitochondrial dynamics, mitochondrial biogenesis, and selective autophagy (mitophagy), in healthy and altered cases. Finally, this review will be projected toward the future by examining the most promising treatments that target the mitochondria to cure neurodegenerative diseases associated with metabolic disorders.

Hypomyelinating Leukodystrophy 8 (HLD8)-Associated Mutation of POLR3B Leads to Defective Oligodendroglial Morphological Differentiation Whose Effect Is Reversed by Ibuprofen

POLR3B and POLR3A are the major subunits of RNA polymerase III, which synthesizes non-coding RNAs such as tRNAs and rRNAs. Nucleotide mutations of the RNA polymerase 3 subunit b (polr3b) gene are responsible for hypomyelinating leukodystrophy 8 (HLD8), which is an autosomal recessive oligodendroglial cell disease. Despite the important association between POLR3B mutation and HLD8, it remains unclear how mutated POLR3B proteins cause oligodendroglial cell abnormalities. Herein, we show that a severe HLD8-associated nonsense mutation (Arg550-to-Ter (R550X)) primarily localizes POLR3B proteins as protein aggregates into lysosomes in the FBD-102b cell line as an oligodendroglial precursor cell model. Conversely, wild type POLR3B proteins were not localized in lysosomes. Additionally, the expression of proteins with the R550X mutation in cells decreased lysosome-related signaling through the mechanistic target of rapamycin (mTOR). Cells harboring the mutant constructs did not exhibit oligodendroglial cell differentiated phenotypes, which have widespread membranes that extend from their cell body. However, cells harboring the wild type constructs exhibited differentiated phenotypes. Ibuprofen, which is a non-steroidal anti-inflammatory drug (NSAID), improved the defects in their differentiation phenotypes and signaling through mTOR. These results indicate that the HLD8-associated POLR3B proteins with the R550X mutation are localized in lysosomes, decrease mTOR signaling, and inhibit oligodendroglial cell morphological differentiation, and ibuprofen improves these cellular pathological effects. These findings may reveal some of the molecular and cellular pathological mechanisms underlying HLD8 and their amelioration.

Looking at Developmental Neurotoxicity Testing from the Perspective of an Invertebrate Embryo

Developmental neurotoxicity (DNT) of chemical compounds disrupts the formation of a normal brain. There is impressive progress in the development of alternative testing methods for DNT potential in chemicals, some of which also incorporate invertebrate animals. This review briefly touches upon studies on the genetically tractable model organisms of Caenorhabditis elegans and Drosophila melanogaster about the action of specific developmental neurotoxicants. The formation of a functional nervous system requires precisely timed axonal pathfinding to the correct cellular targets. To address this complex key event, our lab developed an alternative assay using a serum-free culture of intact locust embryos. The first neural pathways in the leg of embryonic locusts are established by a pair of afferent pioneer neurons which use guidance cues from membrane-bound and diffusible semaphorin proteins. In a systematic approach according to recommendations for alternative testing, the embryo assay quantifies defects in pioneer navigation after exposure to a panel of recognized test compounds for DNT. The outcome indicates a high predictability for test-compound classification. Since the pyramidal neurons of the mammalian cortex also use a semaphorin gradient for neurite guidance, the assay is based on evolutionary conserved cellular mechanisms, supporting its relevance for cortical development.

Combined Treatment of Bone Marrow Mesenchymal Stem Cells and Fasudil Promotes Neurovascular Remodeling and Neurological Function Recovery in Ischemic Stroke

Stroke remains a highly deadly and disabling disease with limited treatment tragedies due to the limitations of available treatments; novel therapies for stroke are needed. In this article, the synergistic results of dual bone marrow mesenchymal stem cells (BMSC) and fasudil treatment in rat models of ischemic stroke still require further identification. Sprague-Dawley rats were used to construct the middle cerebral artery, occlusion models. BMSCs were incubated with fasudil, and MTT was performed to evaluate cell proliferation. The rats were treated with fasudil + BMSC, BMSC, fasudil, and saline. Blood samples were collected for complete blood count analysis and measurement of serum TNF-α levels. The neurological functions were evaluated. After the rats were sacrificed, immunohistochemical staining and TTC staining was performed. Fasudil promoted the proliferation of BMSCs and induced their differentiation into neuron-like cells. BMSCs increased the proportion of neutrophils; nevertheless, fasudil counteracted the neutrophil increase. The TUJ-1/MAP2/VIII factor expression in the fasudil + BMSC group was significantly higher than that in the other groups. The number of GFAP-positive cells decreased in the fasudil + BMSC and BMSC alone groups. The infarct volume in the fasudil + BMSC and BMSC alone groups was significantly lower than in the fasudil alone and control groups. Both BMSCs and fasudil exert neurorestorative effects in rat models of cerebral ischemia. Fasudil neutralizes the pro-inflammatory effects of BMSCs, while BMSCs and fasudil together had synergistic effects promoting neurovascular remodeling and neurological function recovery in stroke. A combination of BMSCs and fasudil provides a promising method for the treatment of ischemic stroke.

Delivery of Wnt inhibitor WIF1 via engineered polymeric microspheres promotes nerve regeneration after sciatic nerve crush

Injuries within the peripheral nervous system (PNS) lead to sensory and motor deficits, as well as neuropathic pain, which strongly impair the life quality of patients. Although most current PNS injury treatment approaches focus on using growth factors/small molecules to stimulate the regrowth of the injured nerves, these methods neglect another important factor that strongly hinders axon regeneration-the presence of axonal inhibitory molecules. Therefore, this work sought to explore the potential of pathway inhibition in promoting sciatic nerve regeneration. Additionally, the therapeutic window for using pathway inhibitors was uncovered so as to achieve the desired regeneration outcomes. Specifically, we explored the role of Wnt signaling inhibition on PNS regeneration by delivering Wnt inhibitors, sFRP2 and WIF1, after sciatic nerve transection and sciatic nerve crush injuries. Our results demonstrate that WIF1 promoted nerve regeneration (p < 0.05) after sciatic nerve crush injury. More importantly, we revealed the therapeutic window for the treatment of Wnt inhibitors, which is 1 week post sciatic nerve crush when the non-canonical receptor tyrosine kinase (Ryk) is significantly upregulated.

Impact of ibuprofen and peroxisome proliferator-activated receptor gamma on emotion-related neural activation: A randomized, placebo-controlled trial

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen have shown initial promise in producing antidepressant effects. This is perhaps due to these drugs being peroxisome proliferator-activated receptor gamma (PPARγ) agonists, in addition to their inhibition of cyclooxygenase enzymes. Some, albeit mixed, evidence suggests that PPARγ agonists have antidepressant effects in humans and animals. This double-blind, placebo-controlled, pharmacologic functional magnetic resonance imaging (ph-fMRI) study aimed to elucidate the impact of ibuprofen on emotion-related neural activity and determine whether observed effects were due to changes in PPARγ gene expression. Twenty healthy volunteers completed an emotional face matching task during three fMRI sessions, conducted one week apart. Placebo, 200 mg, or 600 mg ibuprofen was administered 1 h prior to each scan in a pseudo-randomized order. Peripheral blood mononuclear cells were collected at each session to isolate RNA for PPARγ gene expression. At the doses used, ibuprofen did not significantly change PPARγ gene expression. Ibuprofen dose was associated with decreased blood oxygen level-dependent (BOLD) activation in the dorsolateral prefrontal cortex and fusiform gyrus during emotional face processing (faces-shapes). Additionally, PPARγ gene expression was associated with increased BOLD activation in the insula and transverse and superior temporal gyri (faces-shapes). No interaction effects between ibuprofen dose and PPARγ gene expression on BOLD activation were observed. Thus, results suggest that ibuprofen and PPARγ may have independent effects on emotional neurocircuitry. Future studies are needed to further delineate the roles of ibuprofen and PPARγ in exerting antidepressant effects in healthy as well as clinical populations.

Ibuprofen does not inhibit RhoA-mediated growth cone collapse of embryonic chicken retinal axons by LPA

Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that causes neuronal growth cones to collapse and neurites to retract through a RhoA-ROCK mediated pathway. It has been reported that the NSAID ibuprofen improves regeneration after spinal cord injury through a mechanism of inhibiting RhoA. This leads to the hypothesis that ibuprofen should block LPA-mediated growth cone collapse. We tested this hypothesis by treating embryonic chick retinal neurons with ibuprofen followed by LPA. Retinal growth cones collapsed with LPA in the presence of ibuprofen similar to control; however, growth cone collapse was effectively blocked by a ROCK inhibitor. Thus, our results do not support the designation of ibuprofen as a direct RhoA inhibitor.

Developmental Neurotoxicity of Fipronil and Rotenone on a Human Neuronal In Vitro Test System

Pesticide exposure during in utero and early postnatal development can cause a wide range of neurological defects. However, relatively few insecticides have been recognized as developmental neurotoxicants, so far. Recently, discovery of the insecticide, fipronil, in chicken eggs has raised public concern. The status of fipronil as a potential developmental neurotoxicant is still under debate. Whereas several in vivo and in vitro studies suggest specific toxicity, other in vitro studies could not confirm this concern. Here, we tested fipronil and its main metabolic product, fipronil sulfone both at concentrations between 1.98 and 62.5 µM, alongside with the established developmental neurotoxicant, rotenone (0.004-10 µM) in vitro on the human neuronal precursor cell line NT2. We found that rotenone impaired all three tested DNT endpoints, neurite outgrowth, neuronal differentiation, and precursor cell migration in a dose-dependent manner and clearly separable from general cytotoxicity in the nanomolar range. Fipronil and fipronil sulfone specifically inhibited cell migration and neuronal differentiation, but not neurite outgrowth in the micromolar range. The rho-kinase inhibitor Y-27632 counteracted inhibition of migration for all three compounds (EC50 between 12 and 50 µM). The antioxidant, n-acetyl cysteine, could ameliorate the inhibitory effects of fipronil on all three tested endpoints (EC 50 between 84 and 164 µM), indicating the involvement of oxidative stress. Fipronil sulfone had a stronger effect than fipronil, confirming the importance to test metabolic products alongside original pesticides. We conclude that in vitro fipronil and fipronil sulfone display specific developmental neurotoxicity on developing human model neurons.

Mechanisms and repair strategies for white matter degeneration in CNS injury and diseases

White matter degeneration is an important pathophysiological event of the central nervous system that is collectively characterized by demyelination, oligodendrocyte loss, axonal degeneration and parenchymal changes that can result in sensory, motor, autonomic and cognitive impairments. White matter degeneration can occur due to a variety of causes including trauma, neurotoxic exposure, insufficient blood flow, neuroinflammation, and developmental and inherited neuropathies. Regardless of the etiology, the degeneration processes share similar pathologic features. In recent years, a plethora of cellular and molecular mechanisms have been identified for axon and oligodendrocyte degeneration including oxidative damage, calcium overload, neuroinflammatory events, activation of proteases, depletion of adenosine triphosphate and energy supply. Extensive efforts have been also made to develop neuroprotective and neuroregenerative approaches for white matter repair. However, less progress has been achieved in this area mainly due to the complexity and multifactorial nature of the degeneration processes. Here, we will provide a timely review on the current understanding of the cellular and molecular mechanisms of white matter degeneration and will also discuss recent pharmacological and cellular therapeutic approaches for white matter protection as well as axonal regeneration, oligodendrogenesis and remyelination.

Structural and Functional Plasticity in the Regenerating Olfactory System of the Migratory Locust

Regeneration after injury is accompanied by transient and lasting changes in the neuroarchitecture of the nervous system and, thus, a form of structural plasticity. In this review, we introduce the olfactory pathway of a particular insect as a convenient model to visualize neural regeneration at an anatomical level and study functional recovery at an electrophysiological level. The olfactory pathway of the locust (Locusta migratoria) is characterized by a multiglomerular innervation of the antennal lobe by olfactory receptor neurons. These olfactory afferents were axotomized by crushing the base of the antenna. The resulting degeneration and regeneration in the antennal lobe could be quantified by size measurements, dye labeling, and immunofluorescence staining of cell surface proteins implicated in axonal guidance during development. Within 3 days post lesion, the antennal lobe volume was reduced by 30% and from then onward regained size back to normal by 2 weeks post injury. The majority of regenerating olfactory receptor axons reinnervated the glomeruli of the antennal lobe. A few regenerating axons project erroneously into the mushroom body on a pathway that is normally chosen by second-order projection neurons. Based on intracellular responses of antennal lobe output neurons to odor stimulation, regenerated fibers establish functional synapses again. Following complete absence after nerve crush, responses to odor stimuli return to control level within 10–14 days. On average, regeneration of afferents, and re-established synaptic connections appear faster in younger fifth instar nymphs than in adults. The initial degeneration of olfactory receptor axons has a trans-synaptic effect on a second order brain center, leading to a transient size reduction of the mushroom body calyx. Odor-evoked oscillating field potentials, absent after nerve crush, were restored in the calyx, indicative of regenerative processes in the network architecture. We conclude that axonal regeneration in the locust olfactory system appears to be possible, precise, and fast, opening an avenue for future mechanistic studies. As a perspective of biomedical importance, the current evidence for nitric oxide/cGMP signaling as positive regulator of axon regeneration in connectives of the ventral nerve cord is considered in light of particular regeneration studies in vertebrate central nervous systems.

Y-27632 Induces Neurite Outgrowth by Activating the NOX1-Mediated AKT and PAK1 Phosphorylation Cascades in PC12 Cells

Y-27632 is known as a selective Rho-associated coiled coil-forming kinase (ROCK) inhibitor. Y-27632 has been shown to induce neurite outgrowth in several neuronal cells. However, the precise molecular mechanisms linking neurite outgrowth to Y-27632 are not completely understood. In this study, we examined the ability of Y-27632 to induce neurite outgrowth in PC12 cells and evaluated the signaling cascade. The effect of Y-27632 on the neurite outgrowth was inhibited by reactive oxygen species (ROS) scavengers such as N-acetyl cysteine (NAC) and trolox. Furthermore, Y-27632-induced neurite outgrowth was not triggered by NADPH oxidase 1 (NOX1) knockdown or diphenyleneiodonium (DPI), a NOX inhibitor. Suppression of the Rho-family GTPase Rac1, which is under the negative control of ROCK, with expression of the dominant negative Rac1 mutant (Rac1N17) prevented Y-27632-induced neurite outgrowth. Moreover, the Rac1 inhibitor NSC23766 prevented Y-27632-induced AKT and p21-activated kinase 1 (PAK1) activation. AKT inhibition with MK2206 suppressed Y-27632-induced PAK1 phosphorylation and neurite outgrowth. In conclusion, our results suggest that Rac1/NOX1-dependent ROS generation and subsequent activation of the AKT/PAK1 cascade contribute to Y-27632-induced neurite outgrowth in PC12 cells.

Asiaticoside but not its aglycone exhibits neuritogenicity through TrkA receptor signaling: a bridge between ERK1/2-CREB and Akt-GSK3β/RhoA

The neuritogenicity and the neuroregenerative potential of asiaticoside (AS) and its aglycone, asiatic acid (AA), has been generally reported. We recently identified the participation of extracellular signal-regulated protein kinases 1/2 (ERK1/2) and protein kinase B (Akt) in the neuritogenic mechanism of AS and AA. In this study, we further investigated the possible upstream target molecule and the associated downstream signaling of both triterpenoids in mouse neuroblastoma Neuro-2a cells. Our immunoblotting and immunofluorescence assays revealed that either AS or AA exerted neurite extension activity through inhibitory effect on glycogen synthase kinase 3β (GSK3β) and Ras homolog gene family member A (RhoA). AS appeared significantly more potent in promoting neurite elongation than AA, and concurrently expressed a higher degree of inhibition on GSK3β and RhoA activations. The mediation of GSK3β and RhoA activities in AS-treated cells involved Akt signaling. Moreover, when using GW441756, a specific tropomyosin receptor kinase A (TrkA) receptor signaling inhibitor, the ERK1/2 and Akt phosphorylation, the inhibitory effects on GSK3β and RhoA and the neurite outgrowth induced by AS, but not AA, were totally suppressed. In conclusion, our findings supported the different upstream regulators of AS and AA in promoting neuritogenicity in Neuro-2a cells. Although both AS and AA could enhance neurite elongation through the suppression of GSK3β and RhoA activities, only AS could modulate the effect through TrkA receptor signaling.

Tanshinone IIA Promotes Axonal Regeneration in Rats with Focal Cerebral Ischemia Through the Inhibition of Nogo-A/NgR1/RhoA/ROCKII/MLC Signaling

Purpose

The aim of this study was to evaluate the neuroprotective effect of tanshinone IIA (TSA) on focal cerebral ischemia in rats and to investigate whether it was associated with Nogo-A/NgR1/RhoA/Rho-associated protein kinase 2 (ROCKII)/myosin light chain (MLC) signaling.

Methods

In this study, focal cerebral ischemia animal model was used. Neurological deficit scores and infarction volume were investigated to evaluate the neuroprotection of TSA. Hematoxylin-eosin staining, Nissl staining, and immunofluorescence staining were conducted to detect ischemic changes in brain tissue and changes in neurofilament protein 200 (NF200) and growth-associated protein-43 (GAP-43) expression, respectively. Western blotting and qRT-PCR analyses were used to detect the expression levels of NF200, GAP-43 and Nogo-A/NgR1/RhoA/ROCKII/MLC pathway-related signaling molecules.

Results

TSA treatment can improve the survival rate of rats, reduce the neurological score and infarct volume, and reduce neuron damage. In addition, TSA also increased axon length and enhanced expression of NF200 and GAP-43. Importantly, TSA significantly attenuated the expression of Nogo-A, NgR1, RhoA, ROCKII, and p-MLC, and thus inhibiting the activation of this signaling pathway.

Conclusion

TSA promoted axonal regeneration by inhibiting the Nogo-A/NgR1/RhoA/ROCKII/MLC signaling pathway, thereby exerting neuroprotective effects in cerebral ischemia rats, which provided support for the clinical application of TSA in stroke treatment.

Ibuprofen enhances synaptic function and neural progenitors proliferation markers and improves neuropathology and motor coordination in Machado-Joseph disease models

Machado-Joseph disease or spinocerebellar ataxia type 3 is an inherited neurodegenerative disease associated with an abnormal glutamine over-repetition within the ataxin-3 protein. This mutant ataxin-3 protein affects several cellular pathways, leading to neuroinflammation and neuronal death in specific brain regions resulting in severe clinical manifestations. Presently, there is no therapy able to modify the disease progression. Nevertheless, anti-inflammatory pharmacological intervention has been associated with positive outcomes in other neurodegenerative diseases. Thus, the present work aimed at investigating whether ibuprofen treatment would alleviate Machado-Joseph disease. We found that ibuprofen-treated mouse models presented a significant reduction in the neuroinflammation markers, namely Il1b and TNFa mRNA and IKB-α protein phosphorylation levels. Moreover, these mice exhibited neuronal preservation, cerebellar atrophy reduction, smaller mutant ataxin-3 inclusions and motor performance improvement. Additionally, neural cultures of Machado-Joseph disease patients' induced pluripotent stem cells-derived neural stem cells incubated with ibuprofen showed increased levels of neural progenitors proliferation and synaptic markers such as MSI1, NOTCH1 and SYP. These findings were further confirmed in ibuprofen-treated mice that display increased neural progenitor numbers (Ki67 positive) in the subventricular zone. Furthermore, interestingly, ibuprofen treatment enhanced neurite total length and synaptic function of human neurons. Therefore, our results indicate that ibuprofen reduces neuroinflammation and induces neuroprotection, alleviating Machado-Joseph disease-associated neuropathology and motor impairments. Thus, our findings demonstrate that ibuprofen treatment has the potential to be used as a neuroprotective therapeutic approach in Machado-Joseph disease.

Protein kinases: master regulators of neuritogenesis and therapeutic targets for axon regeneration

Proper neurite formation is essential for appropriate neuronal morphology to develop and defects at this early foundational stage have serious implications for overall neuronal function. Neuritogenesis is tightly regulated by various signaling mechanisms that control the timing and placement of neurite initiation, as well as the various processes necessary for neurite elongation to occur. Kinases are integral components of these regulatory pathways that control the activation and inactivation of their targets. This review provides a comprehensive summary of the kinases that are notably involved in regulating neurite formation, which is a complex process that involves cytoskeletal rearrangements, addition of plasma membrane to increase neuronal surface area, coupling of cytoskeleton/plasma membrane, metabolic regulation, and regulation of neuronal differentiation. Since kinases are key regulators of these functions during neuromorphogenesis, they have high potential for use as therapeutic targets for axon regeneration after injury or disease where neurite formation is disrupted.

A method to rapidly analyze the simultaneous release of multiple pharmaceuticals from electrospun fibers

Electrospun fibers are a commonly used cell scaffold and have also been used as pharmaceutical delivery devices. In this study, we developed a method to analyze the release of multiple pharmaceuticals from a single electrospun fiber scaffold and determine how each pharmaceutical's loading concentration affects the release rate of each pharmaceutical. Our analysis methods were tested on electrospun fibers loaded with two pharmaceuticals: 6-aminonicotinamide (6AN) and ibuprofen. Pharmaceutical concentration in electrospun fibers ranged from 1.5% to 8.5% by weight. We found that 6AN release was dependent on the concentration of 6AN and ibuprofen loaded into the fibers, while ibuprofen release was only dependent on the loading concentration of ibuprofen but not 6AN. Unexpectedly, ibuprofen release became dependent on both 6AN and ibuprofen loading concentrations when fibers were aged for 1-month post-fabrication at room temperature in the laboratory followed by a 4-hour incubation inside the cell culture incubator at 37 °C and 5% CO₂. One additional discovery was an unknown signal that was attributed to the medical grade syringes used for electrospinning, which was easily removed using our method. These results demonstrate the utility of the methods developed here and indicate multiple agents can be released concomitantly from electrospun fibers to meet the demands of more complex tissue engineering approaches. Future work will focus on analysis of pharmaceutical release profiles to exploit the dependencies on pharmaceutical loading concentrations.

Drugs used in the treatment of bipolar disorder and their effects on cholesterol biosynthesis - A possible therapeutic mechanism

Objectives: To understand the therapeutic mechanisms of bipolar disorder (BD) drugs at molecular and cellular levels.Methods: Next generation sequencing was used to determine the transcriptional effects of a combination of four commonly prescribed BD drugs (lithium, valproate, lamotrigine and quetiapine) or vehicle (0.2% DMSO) in NT2-N (human neuronal) cells and rats. Differential expression of genes and pathway analysis were performed using edgeR in R and Gene Set Enrichment Analysis software respectively. Free cholesterol levels and neurite outgrowth were quantified in NT2-N cells following combination and individual BD drug treatments.Results: Pathway analysis showed up-regulation of many elements of the cholesterol biosynthesis pathway in NT2-N cells and oxidative phosphorylation in rat brains. Intracellular cholesterol transport genes were upregulated (NPC1, NPC2 and APOE), while the cholesterol efflux gene (ABCA1) was downregulated. BD drug combination tended to increase intracellular cholesterol levels and neurite outgrowth, but these effects were not seen for the drugs when used individually.Conclusions: These data suggest that BD drug combination is increasing cholesterol biosynthesis and the newly synthesised cholesterol is being utilised within the cells, possibly for synthesis of new membranes to facilitate neurite outgrowth. This mechanism possibly underpins clinical efficacy in individuals with BD treated with polypharmacy.

Insulin and Autophagy in Neurodegeneration

Crosstalk in the pathophysiological processes underpinning metabolic diseases and neurodegenerative disorders have been the subject of extensive investigation, in which insulin signaling and autophagy impairment demonstrate to be a common factor in both conditions. Although it is still somewhat conflicting, pharmacological and genetic strategies that regulate these pathways may be a promising approach for aggregate protein clearancing and consequently the delaying of onset or progression of the disease. However, as the response due to this modulation seems to be time-dependent, finding the right regulation of autophagy may be a potential target for drug development for neurodegenerative diseases. In this way, this review focuses on the role of insulin signaling/resistance and autophagy in some neurodegenerative diseases, discussing pharmacological and non-pharmacological interventions in these diseases.

The utility of stem cells for neural regeneration

The use of stem cells in biomedical research is an extremely active area of science. This is because they provide tools that can be used both in vivo and vitro to either replace cells lost in degenerative processes, or to model such diseases to elucidate their underlying mechanisms. This review aims to discuss the use of stem cells in terms of providing regeneration within the nervous system, which is particularly important as neurons of the central nervous system lack the ability to inherently regenerate and repair lost connections. As populations are ageing, incidence of neurodegenerative diseases are increasing, highlighting the need to better understand the regenerative capacity and many uses of stem cells in this field.

The effect of rho kinase inhibition on morphological and electrophysiological maturity in iPSC-derived neurons

Induced pluripotent stem cell (iPSC)-derived neurons permit the study of neurogenesis and neurological disease in a human setting. However, the electrophysiological properties of iPSC-derived neurons are consistent with those observed in immature cortical neurons, including a high membrane resistance depolarized resting membrane potential and immature firing properties, limiting their use in modeling neuronal activity in adult cells. Based on the proven association between inhibiting rho kinase (ROCK) and increased neurite complexity, we seek to determine if short-term ROCK inhibition during the first 1-2 weeks of differentiation would increase morphological complexity and electrophysiological maturity after several weeks of differentiation. While inhibiting ROCK resulted in increased neurite formation after 24 h, this effect did not persist at 3 and 6 weeks of age. Additionally, there was no effect of ROCK inhibition on electrophysiological properties at 2-3, 6, or 12 weeks of age, despite an increase in evoked and spontaneous firing and a more hyperpolarized resting membrane potential over time. These results indicate that while there is a clear effect of time on electrophysiological maturity, ROCK inhibition did not accelerate maturity.

Nonsteroidal anti-inflammatory drugs attenuate amyloid-β protein-induced actin cytoskeletal reorganization through Rho signaling modulation

Amyloid-β protein (Aβ) neurotoxicity occurs along with the reorganization of the actin-cytoskeleton through the activation of the Rho GTPase pathway. In addition to the classical mode of action of the non-steroidal anti-inflammatory drugs (NSAIDs), indomethacin, and ibuprofen have Rho-inhibiting effects. In order to evaluate the role of the Rho GTPase pathway on Aβ-induced neuronal death and on neuronal morphological modifications in the actin cytoskeleton, we explored the role of NSAIDS in human-differentiated neuroblastoma cells exposed to Aβ. We found that Aβ induced neurite retraction and promoted the formation of different actin-dependent structures such as stress fibers, filopodia, lamellipodia, and ruffles. In the presence of Aβ, both NSAIDs prevented neurite collapse and formation of stress fibers without affecting the formation of filopodia and lamellipodia. Similar results were obtained when the downstream effector, Rho kinase inhibitor Y27632, was applied in the presence of Aβ. These results demonstrate the potential benefits of the Rho-inhibiting NSAIDs in reducing Aβ-induced effects on neuronal structural alterations.

Effect of fasudil on cognitive function following status convulsion in rats

Fasudil has been demonstrated to possess a protective effect in neural injury; however, its protective effect on convulsive brain injury remains to be assessed. The aim of the present study was to investigate the latent mechanism and effect of fasudil on cognitive function following status convulsion (SC) in rats. Initially, to determine the effects of SC, the expression levels of Ras homolog gene family, member A (RhoA)/Rho-associated protein kinase (ROCK) signaling pathway-associated proteins were measured by western blot analysis in 16 rats. To investigate the effects of fasudil on cognitive function in SC rats, a further 40 rats were assigned to four groups: Group I (healthy untreated rats), group II (healthy rats treated with fasudil), group III (SC rats) and group IV (SC rats treated with fasudil). An object-in-place memory task and the Morris Water Maze test were subsequently performed. Histopathological alterations in brain tissue and SC latency were additionally analyzed. Following SC, protein expression levels of myelin-associated glycoprotein, myelin oligodendrocyte glycoprotein and leucine rich repeat and immunoglobulin-like domain-containing protein 1 were significantly increased (P<0.05) and levels of neurite outgrowth inhibitor protein A were significantly decreased (P<0.01). SC had no effect on RhoA level (P=0.921); however, it significantly increased the levels of phosphorylated RhoA (P<0.01). Cognitive function was significantly decreased following SC and significantly increased following fasudil intervention. Fasudil intervention improved CA1 structure, which was lost following SC. SC severely impaired cognitive function and affected the expression of neurite growth inhibitory factors. Fasudil treatment improved cognitive function and central nervous system (CNS) injury, and decreased SC susceptibility in rats. Fasudil and SC may regulate the CNS by affecting the expression of neurite growth inhibitory factors in the RhoA/ROCK signaling pathway.

Electrical brain stimulation induces dendritic stripping but improves survival of silent neurons after optic nerve damage

Repetitive transorbital alternating current stimulation (rtACS) improves vision in patients with chronic visual impairments and an acute treatment increased survival of retinal neurons after optic nerve crush (ONC) in rodent models of visual system injury. However, despite this protection no functional recovery could be detected in rats, which was interpreted as evidence of “silent survivor” cells. We now analysed the mechanisms underlying this “silent survival” effect. Using in vivo microscopy of the retina we investigated the survival and morphology of fluorescent neurons before and after ONC in animals receiving rtACS or sham treatment. One week after the crush, more neurons survived in the rtACS-treated group compared to sham-treated controls. In vivo imaging further revealed that in the initial post-ONC period, rtACS induced dendritic pruning in surviving neurons. In contrast, dendrites in untreated retinae degenerated slowly after the axonal trauma and neurons died. The complete loss of visual evoked potentials supports the hypothesis that cell signalling is abolished in the surviving neurons. Despite this evidence of “silencing”, intracellular free calcium imaging showed that the cells were still viable. We propose that early after trauma, complete dendritic stripping following rtACS protects neurons from excitotoxic cell death by silencing them.

Regulation of Microglial Phagocytosis by RhoA/ROCK-Inhibiting Drugs

Inflammation within the central nervous system (CNS) is a major component of many neurodegenerative diseases. The underlying mechanisms of neuronal loss are not fully understood, but the activation of CNS resident phagocytic microglia seems to be a significant element contributing to neurodegeneration. At the onset of inflammation, high levels of microglial phagocytosis may serve as an essential prerequisite for creating a favorable environment for neuronal regeneration. However, the excessive and long-lasting activation of microglia and the augmented engulfment of neurons have been suggested to eventually govern widespread neurodegeneration. Here, we investigated in a functional assay of acute inflammation how the small GTPase RhoA and its main target the Rho kinase (ROCK) influence microglial phagocytosis of neuronal debris. Using BV-2 microglia and human NT2 model neurons, we demonstrate that the pain reliever Ibuprofen decreases RhoA activation and microglial phagocytosis of neuronal cell fragments. Inhibition of the downstream effector ROCK with the small-molecule agents Y-27632 and Fasudil reduces the engulfment of neuronal debris and attenuates the production of the inflammatory mediator nitric oxide during stimulation with lipopolysaccharide. Our results support a therapeutic potential for RhoA/ROCK-inhibiting agents as an effective treatment of excessive inflammation and the resulting progression of microglia-mediated neurodegeneration in the CNS.

A robust and reproducible human pluripotent stem cell derived model of neurite outgrowth in a three-dimensional culture system and its application to study neurite inhibition

The inability of neurites to grow and restore neural connections is common to many neurological disorders, including trauma to the central nervous system and neurodegenerative diseases. Therefore, there is need for a robust and reproducible model of neurite outgrowth, to provide a tool to study the molecular mechanisms that underpin the process of neurite inhibition and to screen molecules that may be able to overcome such inhibition. In this study a novel in vitro pluripotent stem cell based model of human neuritogenesis was developed. This was achieved by incorporating additional technologies, notably a stable synthetic inducer of neural differentiation, and the application of three-dimensional (3D) cell culture techniques. We have evaluated the use of photostable, synthetic retinoid molecules to promote neural differentiation and found that 0.01 μM EC23 was the optimal concentration to promote differentiation and neurite outgrowth from human pluripotent stem cells within our model. We have also developed a methodology to enable quick and accurate quantification of neurite outgrowth derived from such a model. Furthermore, we have obtained significant neurite outgrowth within a 3D culture system enhancing the level of neuritogenesis observed and providing a more physiological microenvironment to investigate the molecular mechanisms that underpin neurite outgrowth and inhibition within the nervous system. We have demonstrated a potential application of our model in co-culture with glioma cells, to recapitulate aspects of the process of neurite inhibition that may also occur in the injured spinal cord. We propose that such a system that can be utilised to investigate the molecular mechanisms that underpin neurite inhibition mediated via glial and neuron interactions.

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Development of a robust, novel neurite outgrowth assay from human pluripotent stem cell derived neural cell aggregates.

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Synthetic retinoids induce neural differentiation of pluripotent stem cells to a greater extent than natural ATRA.

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Neurospheres cultured on a 3D scaffold provide a more physiologically relevant model of neurite outgrowth.

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Suppression of neurite outgrowth by glioma cells in 3D enables the study of neurite inhibitory mechanisms in the glial scar.

ROCK inhibition enhances neurite outgrowth in neural stem cells by upregulating YAP expression in vitro

Spontaneous axonal regeneration of neurons does not occur after spinal cord injury because of inhibition by myelin and other inhibitory factors. Studies have demonstrated that blocking the Rho/Rho-kinase (ROCK) pathway can promote neurite outgrowth in spinal cord injury models. In the present study, we investigated neurite outgrowth and neuronal differentiation in neural stem cells from the mouse subventricular zone after inhibition of ROCK in vitro. Inhibition of ROCK with Y-27632 increased neurite length, enhanced neuronal differentiation, and upregulated the expression of two major signaling pathway effectors, phospho-Akt and phospho-mitogen-activated protein kinase, and the Hippo pathway effector YAP. These results suggest that inhibition of ROCK mediates neurite outgrowth in neural stem cells by activating the Hippo signaling pathway.

SCISSOR-Spinal Cord Injury Study on Small molecule-derived Rho inhibition: a clinical study protocol

INTRODUCTION

The approved analgesic and anti-inflammatory drugs ibuprofen and indometacin block the small GTPase RhoA, a key enzyme that impedes axonal sprouting after axonal damage. Inhibition of the Rho pathway in a central nervous system-effective manner requires higher dosages compared with orthodox cyclooxygenase-blocking effects. Preclinical studies on spinal cord injury (SCI) imply improved motor recovery after ibuprofen/indometacin-mediated Rho inhibition. This has been reassessed by a meta-analysis of the underlying experimental evidence, which indicates an overall effect size of 20.2% regarding motor outcome achieved after ibuprofen/indometacin treatment compared with vehicle controls. In addition, ibuprofen/indometacin may also limit sickness behaviour, non-neurogenic systemic inflammatory response syndrome (SIRS), neuropathic pain and heterotopic ossifications after SCI. Consequently, 'small molecule'-mediated Rho inhibition after acute SCI warrants clinical investigation.

METHODS AND ANALYSIS

Protocol of an investigator-initiated clinical open-label pilot trial on high-dose ibuprofen treatment after acute traumatic, motor-complete SCI. A sample of n=12 patients will be enrolled in two cohorts treated with 2400 mg/day ibuprofen for 4 or 12 weeks, respectively. The primary safety end point is an occurrence of serious adverse events, primarily gastroduodenal bleedings. Secondary end points are pharmacokinetics, feasibility and preliminary effects on neurological recovery, neuropathic pain and heterotopic ossifications. The primary safety analysis is based on the incidence of severe gastrointestinal bleedings. Additional analyses will be mainly descriptive and casuistic.

ETHICS AND DISSEMINATION

The clinical trial protocol was approved by the responsible German state Ethics Board, and the Federal Institute for Drugs and Medical Devices. The study complies with the Declaration of Helsinki, the principles of Good Clinical Practice and all further applicable regulations. This safety and pharmacokinetics trial informs the planning of a subsequent randomised controlled trial. Regardless of the result of the primary and secondary outcome assessments, the clinical trial will be reported as a publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT02096913; Pre-results.

Exercise Training Inhibits the Nogo-A/NgR1/Rho-A Signals in the Cortical Peri-infarct Area in Hypertensive Stroke Rats

OBJECTIVE

The aim of this study was to test the hypothesis that exercise training promotes motor recovery after stroke by facilitating axonal remodeling via inhibition of the Nogo-A/NgR1 and Rho-A pathway.

DESIGN

A distal middle cerebral artery occlusion model was generated in stroke-prone renovascular hypertensive rats. Stroke-prone renovascular hypertensive rats were randomly divided into a control group, an exercise training group, and a sham group. Motor function was measured using the grip strength test. Axon and myelin remodeling markers, growth-associated protein 43, myelin basic protein, Tau, and amyloid precursor protein were detected by immunofluorescence. The expression of Nogo-A, NgR1, and Rho-A was demonstrated by immunofluorescence and Western blotting in the peri-infarction area at 7, 14, 28, and 52 days after distal middle cerebral artery occlusion.

RESULTS

Grip strength was higher in the exercise training group (P < 0.05). Exercise training increased the expression of growth-associated protein 43, myelin basic protein (at 7, 14, and 28 days), and Tau (at 7 and 14 days), and decreased the expression of axonal damage amyloid precursor protein (at 7 and 14 days), compared with the control group. The protein levels of Nogo-A (at 7 and 14 days), NgR1 (at 7, 14, and 28 days), and Rho-A (at 14 and 28 days) were reduced after exercise training.

CONCLUSIONS

Exercise training promotes axonal recovery, which is associated with functional improvement after cerebral infarction. Down-regulation of the Nogo-A/NgR1/Rho-A may mediate the axonal remodeling induced by exercise training.

In vitro models of axon regeneration

A variety of in vitro models have been developed to understand the mechanisms underlying the regenerative failure of central nervous system (CNS) axons, and to guide pre-clinical development of regeneration-promoting therapeutics. These range from single-cell based assays that typically focus on molecular mechanisms to organotypic assays that aim to recapitulate in vivo behavior. By utilizing a combination of models, researchers can balance the speed, convenience, and mechanistic resolution of simpler models with the biological relevance of more complex models. This review will discuss a number of models that have been used to build our understanding of the molecular mechanisms of CNS axon regeneration.

Recreating blood-brain barrier physiology and structure on chip: A novel neurovascular microfluidic bioreactor

The blood-brain barrier (BBB) is a critical structure that serves as the gatekeeper between the central nervous system and the rest of the body. It is the responsibility of the BBB to facilitate the entry of required nutrients into the brain and to exclude potentially harmful compounds; however, this complex structure has remained difficult to model faithfully in vitro. Accurate in vitro models are necessary for understanding how the BBB forms and functions, as well as for evaluating drug and toxin penetration across the barrier. Many previous models have failed to support all the cell types involved in the BBB formation and/or lacked the flow-created shear forces needed for mature tight junction formation. To address these issues and to help establish a more faithful in vitro model of the BBB, we have designed and fabricated a microfluidic device that is comprised of both a vascular chamber and a brain chamber separated by a porous membrane. This design allows for cell-to-cell communication between endothelial cells, astrocytes, and pericytes and independent perfusion of both compartments separated by the membrane. This NeuroVascular Unit (NVU) represents approximately one-millionth of the human brain, and hence, has sufficient cell mass to support a breadth of analytical measurements. The NVU has been validated with both fluorescein isothiocyanate (FITC)-dextran diffusion and transendothelial electrical resistance. The NVU has enabled in vitro modeling of the BBB using all human cell types and sampling effluent from both sides of the barrier.

Nitric oxide regulates antagonistically phagocytic and neurite outgrowth inhibiting capacities of microglia

Traumatic injury or the pathogenesis of some neurological disorders is accompanied by inflammatory cellular mechanisms, mainly resulting from the activation of central nervous system (CNS) resident microglia. Under inflammatory conditions, microglia up-regulate the inducible isoform of NOS (iNOS), leading to the production of high concentrations of the radical molecule nitric oxide (NO). At the onset of inflammation, high levels of microglial-derived NO may serve as a cellular defense mechanism helping to clear the damaged tissue and combat infection of the CNS by invading pathogens. However, the excessive overproduction of NO by activated microglia has been suggested to govern the inflammation-mediated neuronal loss causing eventually complete neurodegeneration. Here, we investigated how NO influences phagocytosis of neuronal debris by BV-2 microglia, and how neurite outgrowth of human NT2 model neurons is affected by microglial-derived NO. The presence of NO greatly increased microglial phagocytic capacity in a model of acute inflammation comprising lipopolysaccharide (LPS)-activated microglia and apoptotic neurons. Chemical manipulations suggested that NO up-regulates phagocytosis independently of the sGC/cGMP pathway. Using a transwell system, we showed that reactive microglia inhibit neurite outgrowth of human neurons via the generation of large amounts of NO over effective distances in the millimeter range. Application of a NOS blocker prevented the LPS-induced NO production, totally reversed the inhibitory effect of microglia on neurite outgrowth, but reduced the engulfment of neuronal debris. Our results indicate that a rather simple notion of treating excessive inflammation in the CNS by NO synthesis blocking agents has to consider functionally antagonistic microglial cell responses during pharmaceutic therapy.

Fasudil alleviates traumatic optic neuropathy by inhibiting Rho signaling pathway

OBJECTIVES

The present study is to investigate the pathological changes in rabbits with traumatic optic neuropathy (TON), as well as the effect of fasudil on the lesions.

METHODS

A total of 144 New Zealand rabbits were successfully established as TON models. Twelve hours after surgery, the rabbits in control, dexamethasone, and fasudil groups were administrated with saline, dexamethasone, and fasudil via ear veins, respectively. Then, retinas of the rabbits were obtained at 72 h and on days 7, 14 and 21 after surgery. The pathological changes in retina and optic nerves were observed by hematoxylin and eosin staining and transmission electron microscopy. The expression levels of Rho-associated genes were measured using quantitative real-time polymerase chain reaction.

RESULTS

In control group, the axons were swelling, and mitochondria showed vacuolation after optic nerve crush. Mitochondria were swelled slightly in dexamethasone group. By contrast, nerves in fasudil group were repaired. Retinal ganglion cells in control group were reduced significantly due to optic nerve crush. The loss of retinal ganglion cells was alleviated in fasudil group. Quantitative real-time polymerase chain reaction showed that the expression of Rho-associated genes were down-regulated.

CONCLUSIONS

The present study demonstrates that fasudil inhibits the apoptosis of retinal ganglion cells and ameliorates damages of optic nerves in traumatic optic neuropathy.

New Insights into the Roles of Nogo-A in CNS Biology and Diseases

Nogos have become a hot topic for its well-known number Nogo-A's big role in clinical matters. It has been recognized that the expression of Nogo-A and the receptor NgR1 inhibit the neuron's growth after CNS injuries or the onset of the MS. The piling evidence supports the notion that the Nogo-A is also involved in the synaptic plasticity, which was shown to negatively regulate the strength of synaptic transmission. The occurrence of significant schizophrenia-like behavioral phenotypes in Nogo-A KO rats also added strong proof to this conclusion. This review mainly focuses on the structure of Nogo-A and its corresponding receptor-NgR1, its intra- and extra-cellular signaling, together with its major physiological functions such as regulation of migration and distribution and its related diseases like stroke, AD, ALS and so on.