Permissive and repulsive cues and signalling pathways of axonal outgrowth and regeneration

The updates on metastatic mechanism and treatment of colorectal cancer

Colorectal cancer (CRC) is a main cause of cancer death worldwide. Metastasis is a major cause of cancer-related death in CRC. The treatment of metastatic CRC has progressed minimally. However, the potential molecular mechanisms involved in CRC metastasis have remained to be comprehensively clarified. An improved understanding of the CRC mechanistic determinants is needed to better prevent and treat metastatic cancer. In this review, based on evidence from a growing body of research in metastatic cancers, we discuss the cellular and molecular mechanisms involved in CRC metastasis. This review reveals both the molecular mechanisms of metastases and identifies new opportunities for developing more effective strategies to target metastatic relapse and improve CRC patient outcomes.

Neuroinflammation in the Central Nervous System: Exploring the Evolving Influence of Endocannabinoid System

Neuroinflammation is a complex biological process that typically originates as a protective response in the brain. This inflammatory process is triggered by the release of pro-inflammatory substances like cytokines, prostaglandins, and reactive oxygen and nitrogen species from stimulated endothelial and glial cells, including those with pro-inflammatory functions, in the outer regions. While neuronal inflammation is common in various central nervous system disorders, the specific inflammatory pathways linked with different immune-mediated cell types and the various factors influencing the blood-brain barrier significantly contribute to disease-specific characteristics. The endocannabinoid system consists of cannabinoid receptors, endogenous cannabinoids, and enzymes responsible for synthesizing and metabolizing endocannabinoids. The primary cannabinoid receptor is CB1, predominantly found in specific brain regions such as the brainstem, cerebellum, hippocampus, and cortex. The presence of CB2 receptors in certain brain components, like cultured cerebellar granular cells, Purkinje fibers, and microglia, as well as in the areas like the cerebral cortex, hippocampus, and cerebellum is also evidenced by immunoblotting assays, radioligand binding, and autoradiography studies. Both CB1 and CB2 cannabinoid receptors exhibit noteworthy physiological responses and possess diverse neuromodulatory capabilities. This review primarily aims to outline the distribution of CB1 and CB2 receptors across different brain regions and explore their potential roles in regulating neuroinflammatory processes.

Hypothermia evoked by stimulation of medial preoptic nucleus protects the brain in a mouse model of ischaemia

Therapeutic hypothermia at 32-34 °C during or after cerebral ischaemia is neuroprotective. However, peripheral cold sensor-triggered hypothermia is ineffective and evokes vigorous counteractive shivering thermogenesis and complications that are difficult to tolerate in awake patients. Here, we show in mice that deep brain stimulation (DBS) of warm-sensitive neurones (WSNs) in the medial preoptic nucleus (MPN) produces tolerable hypothermia. In contrast to surface cooling-evoked hypothermia, DBS mice exhibit a torpor-like state without counteractive shivering. Like hypothermia evoked by chemogenetic activation of WSNs, DBS in free-moving mice elicits a rapid lowering of the core body temperature to 32-34 °C, which confers significant brain protection and motor function reservation. Mechanistically, activation of WSNs contributes to DBS-evoked hypothermia. Inhibition of WSNs prevents DBS-evoked hypothermia. Maintaining the core body temperature at normothermia during DBS abolishes DBS-mediated brain protection. Thus, the MPN is a DBS target to evoke tolerable therapeutic hypothermia for stroke treatment.

Reduced hippocampal inhibition and enhanced autism-epilepsy comorbidity in mice lacking neuropilin 2

The neuropilin receptors and their secreted semaphorin ligands play key roles in brain circuit development by regulating numerous crucial neuronal processes, including the maturation of synapses and migration of GABAergic interneurons. Consistent with its developmental roles, the neuropilin 2 (Nrp2) locus contains polymorphisms in patients with autism spectrum disorder (ASD). Nrp2-deficient mice show autism-like behavioral deficits and propensity to develop seizures. In order to determine the pathophysiology in Nrp2 deficiency, we examined the hippocampal numbers of interneuron subtypes and inhibitory regulation of hippocampal CA1 pyramidal neurons in mice lacking one or both copies of Nrp2. Immunostaining for interneuron subtypes revealed that Nrp2^-/- mice have a reduced number of parvalbumin, somatostatin, and neuropeptide Y cells, mainly in CA1. Whole-cell recordings identified reduced firing and hyperpolarized shift in resting membrane potential in CA1 pyramidal neurons from Nrp2^+/- and Nrp2^-/- mice compared to age-matched wild-type controls indicating decrease in intrinsic excitability. Simultaneously, the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) are reduced in Nrp2-deficient mice. A convulsive dose of kainic acid evoked electrographic and behavioral seizures with significantly shorter latency, longer duration, and higher severity in Nrp2^-/- compared to Nrp2^+/+ animals. Finally, Nrp2^+/- and Nrp2^-/- but not Nrp2^+/+, mice have impaired cognitive flexibility demonstrated by reward-based reversal learning, a task associated with hippocampal circuit function. Together these data demonstrate a broad reduction in interneuron subtypes and compromised inhibition in CA1 of Nrp2^-/- mice, which could contribute to the heightened seizure susceptibility and behavioral deficits consistent with an ASD/epilepsy phenotype.

Functional Expression of Choline Transporters in Human Neural Stem Cells and Its Link to Cell Proliferation, Cell Viability, and Neurite Outgrowth

Choline and choline metabolites are essential for all cellular functions. They have also been reported to be crucial for neural development. In this work, we studied the functional characteristics of the choline uptake system in human neural stem cells (hNSCs). Additionally, we investigated the effect of extracellular choline uptake inhibition on the cellular activities in hNSCs. We found that the mRNAs and proteins of choline transporter-like protein 1 (CTL1) and CTL2 were expressed at high levels. Immunostaining showed that CTL1 and CTL2 were localized in the cell membrane and partly in the mitochondria, respectively. The uptake of extracellular choline was saturable and performed by a single uptake mechanism, which was Na⁺-independent and pH-dependent. We conclude that CTL1 is responsible for extracellular choline uptake, and CTL2 may uptake choline in the mitochondria and be involved in DNA methylation via choline oxidation. Extracellular choline uptake inhibition caused intracellular choline deficiency in hNSCs, which suppressed cell proliferation, cell viability, and neurite outgrowth. Our findings contribute to the understanding of the role of choline in neural development as well as the pathogenesis of various neurological diseases caused by choline deficiency or choline uptake impairment.

An imbalanced ratio between PC(16:0/16:0) and LPC(16:0) revealed by lipidomics supports the role of the Lands cycle in ischemic brain injury

Promoting brain recovery after stroke is challenging as a plethora of inhibitory molecules are produced in the brain preventing it from full healing. Moreover, the full scope of inhibitory molecules produced is not well understood. Here, using a high-sensitivity UPLC-MS-based shotgun lipidomics strategy, we semiquantitively measured the differential lipid contents in the mouse cerebral cortex recovering from a transient middle cerebral artery occlusion (MCAO). The lipidomic data were interrogated using the soft independent modeling of class analogy (SIMCA) method involving principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Statistics of the 578 confirmed lipids revealed 84 species were differentially changed during MCAO/reperfusion. The most dynamic changes in lipids occurred between 1 and 7 days post-MCAO, whereas concentrations had subsided to the Sham group level at 14 and 28 days post-MCAO. Quantitative analyses revealed a strong monotonic relationship between the reduction in phosphatidylcholine (PC)(16:0/16:0) and the increase in lysophosphatidylcholine (LPC)(16:0) levels (Spearman's Rs = -0.86) during the 1 to 7 days reperfusion period. Inhibition of cPLA2 prevented changes in the ratio between PC(16:0/16:0) and LPC(16:0), indicating altered Land's cycle of PC. A series of in vitro studies showed that LPC(16:0), but not PC(16:0/16:0), was detrimental to the integrity of neuronal growth cones and neuronal viability through evoking intracellular calcium influx. In contrast, PC(16:0/16:0) significantly suppressed microglial secretion of IL-1β and TNF-α, limiting neuroinflammation pathways. Together, these data support the role of the imbalanced ratio between PC(16:0/16:0) and LPC(16:0), maintained by Lands' cycle, in neuronal damage and microglia-mediated inflammatory response during ischemic recovery.

The regulatory and enzymatic functions of CRMPs in neuritogenesis, synaptic plasticity, and gene transcription

Collapsin response mediator proteins (CRMPs) are ubiquitously expressed in neurons from worms to humans. A cardinal feature of CRMPs is to mediate growth cone collapse in response to Semaphorin-3A signaling through interactions with cytoskeletal proteins. These are critical regulatory roles that CRMPs play during neuritogenesis and neural network formation. Through post-translational modifications, such as phosphorylation, O-GlcNAcylation, SUMOylation, and proteolytic cleavage, CRMPs participate in synaptic plasticity by modulating NMDA receptors, L- and N-type voltage-gated calcium channels (VGCCs), thus affecting neurotransmitter release. CRMPs also possess histone deacetylase (HDAC) activity, which deacetylates histone H4 during neuronal death. Calcium-dependent proteolytic cleavage of CRMPs results in the truncation of CRMPs, producing a large 54 kD fragment (p54). Translocation of the p54 fragment into the nucleus leads to deacetylation of nuclear histone H4 and de-repression of transcription factor E2F1 expression. Increased expression of E2F1 elevates the expression of genes in cell cycle and death. These new and exciting studies lead to the realization that CRMPs are multifunctional proteins with both regulatory and enzymatic functions. Increasing numbers of studies associate these functions of CRMPs with the development of mental and neurological disorders, such as schizophrenia, Alzheimer's diseases, brain trauma, and stroke. This review focuses on new evidence showing the regulatory and enzymatic functions of CRMPs and highlights recent understandings of CRMPs' roles in neurological diseases.

Combined Treatment With 2-(2-Benzofu-Ranyl)-2-Imidazoline and Recombinant Tissue Plasminogen Activator Protects Blood-Brain Barrier Integrity in a Rat Model of Embolic Middle Cerebral Artery Occlusion

Recombinant tissue plasminogen activator (rt-PA) is used to treat acute ischemic stroke but is only effective if administered within 4.5 h after stroke onset. Delayed rt-PA treatment causes blood-brain barrier (BBB) disruption and hemorrhagic transformation. The compound 2-(-2-benzofuranyl)-2-imidazoline (2-BFI), a newly discovered antagonist of high-affinity postsynaptic N-methyl-D-aspartate (NMDA) receptors, has been shown to have neuroprotective effects in ischemia. Here, we investigated whether combining 2-BFI and rt-PA can ameliorate BBB disruption and prolong the therapeutic window in a rat model of embolic middle cerebral artery occlusion (eMCAO). Ischemia was induced in male Sprague Dawley rats by eMCAO, after which they were treated with 2-BFI (3 mg/kg) at 0.5 h in combination with rt-PA (10 mg/kg) at 6 or 8 h. Control rats were treated with saline or 2-BFI or rt-PA. Combined therapy with 2-BFI and rt-PA (6 h) reduced the infarct volume, denatured cell index, BBB permeability, and brain edema. This was associated with increased expression of aquaporin 4 (AQP4) and tight junction proteins (occludin and ZO-1) and downregulation of intercellular adhesion molecule 1 (ICAM-1) and matrix metalloproteinases 2 and 9 (MMP2 and MMP9). We conclude that 2-BFI protects the BBB from damage caused by delayed rt-PA treatment in ischemia. 2-BFI may therefore extend the therapeutic window up to 6 h after stroke onset in rats and may be a promising therapeutic strategy for humans. However, mechanisms to explain the effects oberved in the present study are not yet elucidated.

Erythropoietin induces synaptogenesis and neurite repair after hypoxia ischemia-mediated brain injury in neonatal rats

The memory dysfunction is one of the disastrous outcomes for perinatal hypoxia ischemia. Erythropoietin (EPO) has been demonstrated as a neuroprotective agent with multiple effects in a series of neurological diseases. We hypothesized that disruption of neural network including synapses and neurites would contribute to memory dysfunction induced by hypoxia ischemia. The aim of the present study was to elucidate the involvement of EPO on synaptogenesis and neurite repair following perinatal hypoxia ischemia. Using a neonatal hypoxia ischemia rat model, we found that EPO rescued hypoxia ischemia-induced decrease of synaptic proteins including Synapsin1 and PSD95 rather than GluR1 in the cortex and hippocampus. In addition, EPO reduced the expression of APP (an axonal injury marker), induced the expression of microtubule-associated protein MAP-2 (a dendritic marker), and restored axonal density after hypoxia ischemia. These changes contributed to improving electrophysiological properties of synapses and spatial memory performance. In summary, our data revealed an important role of EPO in synaptogenesis and neurite repair, providing a new insight into cellular mechanisms underlying cognitive and memory dysfunction associated with perinatal hypoxia ischemia.

The cytosolic isoform of glutaredoxin 2 promotes cell migration and invasion

BACKROUND

Cytosolic glutaredoxin 2 (Grx2c) controls axonal outgrowth and is specifically induced in many cancer cell lines. We thus hypothesized that Grx2c promotes cell motility and invasiveness.

METHODS

We characterized the impact of Grx2c expression in cell culture models. We combined stable isotope labeling, phosphopeptide enrichment, and high-accuracy mass spectrometry to characterize the underlying mechanisms.

RESULTS

The most prominent associations were found with actin dynamics, cellular adhesion, and receptor-mediated signal transduction, processes that are crucial for cell motility. For instance, collapsin response mediator protein 2, a protein involved in the regulation of cytoskeletal dynamics, is regulated by Grx2c through a redox switch that controls the phosphorylation state of the protein as well. Cell lines expressing Grx2c showed dramatic alterations in morphology. These cells migrated two-fold faster and gained the ability to infiltrate a collagen matrix.

CONCLUSIONS

The expression of Grx2c promotes cell migration, and may negatively correlate with cancer-specific survival.

GENERAL SIGNIFICANCE

Our results imply critical roles of Grx2c in cytoskeletal dynamics, cell adhesion, and cancer cell invasiveness.

Past and Future of Neurotrophic Growth Factors Therapies in ALS: From Single Neurotrophic Growth Factor to Stem Cells and Human Platelet Lysates

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that typically results in death within 3–5 years after diagnosis. To date, there is no curative treatment and therefore an urgent unmet need of neuroprotective and/or neurorestorative treatments. Due to their spectrum of capacities in the central nervous system—e.g., development, plasticity, maintenance, neurogenesis—neurotrophic growth factors (NTF) have been exploited for therapeutic strategies in ALS for decades. In this review we present the initial strategy of using single NTF by different routes of administration to the use of stem cells transplantation to express a multiple NTFs-rich secretome to finally focus on a new biotherapy based on the human platelet lysates, the natural healing system containing a mix of pleitropic NTF and having immunomodulatory function. This review highlights that this latter treatment may be crucial to power the neuroprotection and/or neurorestoration therapy requested in this devastating disease.

Defining the Hallmarks of Metastasis

Metastasis is the primary cause of cancer morbidity and mortality. The process involves a complex interplay between intrinsic tumor cell properties as well as interactions between cancer cells and multiple microenvironments. The outcome is the development of a nearby or distant discontiguous secondary mass. To successfully disseminate, metastatic cells acquire properties in addition to those necessary to become neoplastic. Heterogeneity in mechanisms involved, routes of dissemination, redundancy of molecular pathways that can be utilized, and the ability to piggyback on the actions of surrounding stromal cells makes defining the hallmarks of metastasis extraordinarily challenging. Nonetheless, this review identifies four distinguishing features that are required: motility and invasion, ability to modulate the secondary site or local microenvironments, plasticity, and ability to colonize secondary tissues. By defining these first principles of metastasis, we provide the means for focusing efforts on the aspects of metastasis that will improve patient outcomes.

An overview of the cannabinoid type 2 receptor system and its therapeutic potential

PURPOSE OF REVIEW

This narrative review summarizes recent insights into the role of the cannabinoid type 2 (CB2) receptor as potential therapeutic target in neuropathic pain and neurodegenerative conditions.

RECENT FINDINGS

The cannabinoid system continues to receive attention as a therapeutic target. The CB2 receptor is primarily expressed on glial cells only when there is active inflammation and appears to be devoid of undesired psychotropic effects or addiction liability. The CB2 receptor has been shown to have potential as a therapeutic target in models of diseases with limited or no currently approved therapies, such as neuropathic pain and neurodegenerative conditions such as Alzheimer's disease.

SUMMARY

The functional involvement of CB2 receptor in neuropathic pain and other neuroinflammatory diseases highlights the potential therapeutic role of drugs acting at the CB2 receptor.

The Small GTPase RAC1/CED-10 Is Essential in Maintaining Dopaminergic Neuron Function and Survival Against α-Synuclein-Induced Toxicity

Parkinson's disease is associated with intracellular α-synuclein accumulation and ventral midbrain dopaminergic neuronal death in the Substantia Nigra of brain patients. The Rho GTPase pathway, mainly linking surface receptors to the organization of the actin and microtubule cytoskeletons, has been suggested to participate to Parkinson's disease pathogenesis. Nevertheless, its exact contribution remains obscure. To unveil the participation of the Rho GTPase family to the molecular pathogenesis of Parkinson's disease, we first used C elegans to demonstrate the role of the small GTPase RAC1 (ced-10 in the worm) in maintaining dopaminergic function and survival in the presence of alpha-synuclein. In addition, ced-10 mutant worms determined an increase of alpha-synuclein inclusions in comparison to control worms as well as an increase in autophagic vesicles. We then used a human neuroblastoma cells (M17) stably over-expressing alpha-synuclein and found that RAC1 function decreased the amount of amyloidogenic alpha-synuclein. Further, by using dopaminergic neurons derived from patients of familial LRRK2-Parkinson's disease we report that human RAC1 activity is essential in the regulation of dopaminergic cell death, alpha-synuclein accumulation, participates in neurite arborization and modulates autophagy. Thus, we determined for the first time that RAC1/ced-10 participates in Parkinson's disease associated pathogenesis and established RAC1/ced-10 as a new candidate for further investigation of Parkinson's disease associated mechanisms, mainly focused on dopaminergic function and survival against α-synuclein-induced toxicity.

Hypoxic conditioned medium derived from bone marrow mesenchymal stromal cells protects against ischemic stroke in rats

In recent years, studies have shown that the secretome of bone marrow mesenchymal stromal cells (BMSCs) contains many growth factors, cytokines, and antioxidants, which may provide novel approaches to treat ischemic diseases. Furthermore, the secretome may be modulated by hypoxic preconditioning. We hypothesized that conditioned medium (CM) derived from BMSCs plays a crucial role in reducing tissue damage and improving neurological recovery after ischemic stroke and that hypoxic preconditioning of BMSCs robustly improves these activities. Rats were subjected to ischemic stroke by middle cerebral artery occlusion and then intravenously administered hypoxic CM, normoxic CM, or Dulbecco modified Eagle medium (DMEM, control). Cytokine antibody arrays and label-free quantitative proteomics analysis were used to compare the differences between hypoxic CM and normoxic CM. Injection of normoxic CM significantly reduced the infarct area and improved neurological recovery after stroke compared with administering DMEM. These outcomes may be associated with the attenuation of apoptosis and promotion of angiogenesis. Hypoxic preconditioning significantly enhanced these therapeutic effects. Fourteen proteins were significantly increased in hypoxic CM compared with normoxic CM as measured by cytokine arrays. The label-free quantitative proteomics analysis revealed 163 proteins that were differentially expressed between the two groups, including 107 upregulated proteins and 56 downregulated proteins. Collectively, our results demonstrate that hypoxic CM protected brain tissue from ischemic injury and promoted functional recovery after stroke in rats and that hypoxic CM may be the basis of a potential therapy for stroke patients.

A Traveling Wave Ion Mobility Spectrometry (TWIMS) Study of the Robo1-Heparan Sulfate Interaction

Roundabout 1 (Robo1) interacts with its receptor Slit to regulate axon guidance, axon branching, and dendritic development in the nervous system and to regulate morphogenesis and many cell functions in the nonneuronal tissues. This interaction is known to be critically regulated by heparan sulfate (HS). Previous studies suggest that HS is required to promote the binding of Robo1 to Slit to form the minimal signaling complex, but the molecular details and the structural requirements of HS for this interaction are still unclear. Here, we describe the application of traveling wave ion mobility spectrometry (TWIMS) to study the conformational details of the Robo1-HS interaction. The results suggest that Robo1 exists in two conformations that differ by their compactness and capability to interact with HS. The results also suggest that the highly flexible interdomain hinge region connecting the Ig1 and Ig2 domains of Robo1 plays an important functional role in promoting the Robo1-Slit interaction. Moreover, variations in the sulfation pattern and size of HS were found to affect its binding affinity and selectivity to interact with different conformations of Robo1. Both MS measurements and CIU experiments show that the Robo1-HS interaction requires the presence of a specific size and pattern of modification of HS. Furthermore, the effect of N-glycosylation on the conformation of Robo1 and its binding modes with HS is reported. Graphical Abstract ᅟ.

Alpha 7 nicotinic receptors attenuate neurite development through calcium activation of calpain at the growth cone

The α7 nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel that plays an important role in cellular calcium signaling contributing to synaptic development and plasticity, and is a key drug target for the treatment of neurodegenerative conditions such as Alzheimer's disease. Here we show that α7 nAChR mediated calcium signals in differentiating PC12 cells activate the proteolytic enzyme calpain leading to spectrin breakdown, microtubule retraction, and attenuation in neurite growth. Imaging in growth cones confirms that α7 activation decreases EB3 comet motility in a calcium dependent manner as demonstrated by the ability of α7 nAChR, ryanodine, or IP3 receptor antagonists to block the effect of α7 nAChR on growth. α7 nAChR mediated EB3 comet motility, spectrin breakdown, and neurite growth was also inhibited by the addition of the selective calpain blocker calpeptin and attenuated by the expression of an α7 subunit unable to bind Gαq and activate calcium store release. The findings indicate that α7 nAChRs regulate cytoskeletal dynamics through local calcium signals for calpain protease activity.

Axon guidance pathways and the control of gene expression

Axons need to be properly guided to their targets to form synaptic connections, and this requires interactions between highly conserved extracellular and transmembrane ligands and their cell surface receptors. The majority of studies on axon guidance signaling pathways have focused on the role of these pathways in rearranging the local cytoskeleton and plasma membrane in growth cones and axons. However, a smaller body of work has demonstrated that axon guidance signaling pathways also control gene expression via local translation and transcription. Recent studies on axon guidance ligands and receptors have begun to uncover the requirements for these alternative mechanisms in processes required for neural circuit formation: axon guidance, synaptogenesis, and cell migration. Understanding the mechanisms by which axon guidance signaling regulates local translation and transcription will create a more complete picture of neural circuit formation, and they may be applied more broadly to other tissues where axon guidance ligands and receptors are required for morphogenesis. Developmental Dynamics 247:571-580, 2018. © 2017 Wiley Periodicals, Inc.

Human annulus signaling cues for nerve outgrowth: In vitro studies

The relationship between neurotrophins produced by human annulus cells, such as neurotrophin-4 (NT4) and brain-derived neurotrophic factor (BDNF) which function in neurite survival and outgrowth, and nerve ingrowth into the disc remains poorly understood. In this work, we tested F11 neurite growth during exposure to control media, media with added nerve growth factor (NGF), conditioned media (CM) harvested from previous human annulus culture, or co-culture with annulus cells. Co-culture of F11 cells with annulus cells significantly increased media levels of amphiregulin, BDNF, glial-derived neurotrophic factor, and vascular endothelial growth factor compared to levels from in culture of F11 cells alone (p ≤ 0.04). Cell-based assays of neurite growth revealed that BDNF levels present in CM bore a significant (p = 0.01) positive relationship to neurite length and accounted for 38.5% of the change in neurite length. NT4 levels produced during co-culture with annulus cells bore a significant (p = 0.04) positive relationship to neurite length and accounted for 40.9% of the change in length. Statement of clinical significance: In vitro findings point to a potential role of annulus cells related to nerve ingrowth in vivo, and may have relevance in the outer annulus (where cell numbers are high) or in regions where nerves penetrate into annular tears or fissures. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1456-1465, 2016.

IL-10 Promotes Neurite Outgrowth and Synapse Formation in Cultured Cortical Neurons after the Oxygen-Glucose Deprivation via JAK1/STAT3 Pathway

As a classic immunoregulatory and anti-inflammatory cytokine, interleukin-10 (IL-10) provides neuroprotection in cerebral ischemia in vivo or oxygen-glucose deprivation (OGD)-induced injury in vitro. However, it remains blurred whether IL-10 promotes neurite outgrowth and synapse formation in cultured primary cortical neurons after OGD injury. In order to evaluate its effect on neuronal apoptosis, neurite outgrowth and synapse formation, we administered IL-10 or IL-10 neutralizing antibody (IL-10NA) to cultured rat primary cortical neurons after OGD injury. We found that IL-10 treatment activated the Janus kinase 1 (JAK1)/signal transducers and activators of transcription 3 (STAT3) signaling pathway. Moreover, IL-10 attenuated OGD-induced neuronal apoptosis by down-regulating the Bax expression and up-regulating the Bcl-2 expression, facilitated neurite outgrowth by increasing the expression of Netrin-1, and promoted synapse formation in cultured primary cortical neurons after OGD injury. These effects were partly abolished by JAK1 inhibitor GLPG0634. Contrarily, IL-10NA produced opposite effects on the cultured cortical neurons after OGD injury. Taken together, our findings suggest that IL-10 not only attenuates neuronal apoptosis, but also promotes neurite outgrowth and synapse formation via the JAK1/STAT3 signaling pathway in cultured primary cortical neurons after OGD injury.

Potential role of estrogen in maintaining the imbalanced sympathetic and sensory innervation in endometriosis

Endometriosis, one of the most common benign gynecological diseases, affects millions of women of childbearing age. Endometriosis-associated pain is a major cause of disability and compromised quality of life in women. Neuropathic mechanisms are believed to play an important role. An imbalanced sympathetic and sensory innervation (reduced sympathetic innervation, with unchanged or increased sensory innervation in endometriotic lesions) has been demonstrated in endometriosis in recent studies. And it is believed to contribute to the pathogenesis of endometriosis-associated pain. It is primarily considered to be a natural adaptive program to endometriosis-associated inflammation. However, it is important to further clarify whether other potential modulating factors are involved in this dysregulation. It is generally accepted that endometriosis is an estrogen dependent disease. Higher estrogen biosynthesis and lower estrogen inactivation in endometriosis can lead to an excess of local estrogen in endometriotic lesions. In addition to its proliferative and anti-inflammatory actions, local estrogen in endometriosis also exerts potential neuromodulatory effects on the innervation in endometriosis. The aim of this review is to highlight the role of estrogen in mediating this imbalanced sympathetic and sensory innervation in endometriosis, through direct and indirect mechanisms on sympathetic and sensory nerves. Theoretical elaboration of the underlying mechanisms provides new insights in supporting the therapeutic role of estrogen in endometriosis-associated pain.

Turning On Lights to Stop Neurodegeneration: The Potential of Near Infrared Light Therapy in Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's disease are the two most common neurodegenerative disorders. They develop after a progressive death of many neurons in the brain. Although therapies are available to treat the signs and symptoms of both diseases, the progression of neuronal death remains relentless, and it has proved difficult to slow or stop. Hence, there is a need to develop neuroprotective or disease-modifying treatments that stabilize this degeneration. Red to infrared light therapy (λ = 600-1070 nm), and in particular light in the near infrared (NIr) range, is emerging as a safe and effective therapy that is capable of arresting neuronal death. Previous studies have used NIr to treat tissue stressed by hypoxia, toxic insult, genetic mutation and mitochondrial dysfunction with much success. Here we propose NIr therapy as a neuroprotective or disease-modifying treatment for Alzheimer's and Parkinson's patients.

Purines in neurite growth and astroglia activation

The mammalian nervous system is a complex, functional network of neurons, consisting of local and long-range connections. Neuronal growth is highly coordinated by a variety of extracellular and intracellular signaling molecules. Purines turned out to be an essential component of these processes. Here, we review the current knowledge about the involvement of purinergic signaling in the regulation of neuronal development. We particularly focus on its role in neuritogenesis: the formation and extension of neurites. In the course of maturation mammals generally lose their ability to regenerate the central nervous system (CNS) e.g. after traumatic brain injury; although, spontaneous regeneration still occurs in the peripheral nervous system (PNS). Thus, it is crucial to translate the knowledge about CNS development and PNS regeneration into novel approaches to enable neurons of the mature CNS to regenerate. In this context we give a general overview of growth-inhibitory and growth-stimulatory factors and mechanisms involved in neurite growth. With regard to neuronal growth, astrocytes are an important cell population. They provide structural and metabolic support to neurons and actively participate in brain signaling. Astrocytes respond to injury with beneficial or detrimental reactions with regard to axonal growth. In this review we present the current knowledge of purines in these glial functions. Moreover, we discuss organotypic brain slice co-cultures as a model which retains neuron-glia interactions, and further presents at once a model for CNS development and regeneration. In summary, the purinergic system is a pivotal factor in neuronal development and in the response to injury. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Embryonic stages in cerebellar afferent development

The cerebellum is important for motor control, cognition, and language processing. Afferent and efferent fibers are major components of cerebellar circuitry and impairment of these circuits causes severe cerebellar malfunction, such as ataxia. The cerebellum receives information from two major afferent types – climbing fibers and mossy fibers. In addition, a third set of afferents project to the cerebellum as neuromodulatory fibers. The spatiotemporal pattern of early cerebellar afferents that enter the developing embryonic cerebellum is not fully understood. In this review, we will discuss the cerebellar architecture and connectivity specifically related to afferents during development in different species. We will also consider the order of afferent fiber arrival into the developing cerebellum to establish neural connectivity.

Semaphorin3A elevates vascular permeability and contributes to cerebral ischemia-induced brain damage

Semaphorin 3A (Sema3A) increased significantly in mouse brain following cerebral ischemia. However, the role of Sema3A in stroke brain remains unknown. Our aim was to determine wether Sema3A functions as a vascular permeability factor and contributes to ischemic brain damage. Recombinant Sema3A injected intradermally to mouse skin, or stereotactically into the cerebral cortex, caused dose- and time-dependent increases in vascular permeability, with a degree comparable to that caused by injection of a known vascular permeability factor vascular endothelial growth factor receptors (VEGF). Application of Sema3A to cultured endothelial cells caused disorganization of F-actin stress fibre bundles and increased endothelial monolayer permeability, confirming Sema3A as a permeability factor. Sema3A-mediated F-actin changes in endothelial cells were through binding to the neuropilin2/VEGFR1 receptor complex, which in turn directly activates Mical2, a F-actin modulator. Down-regulation of Mical2, using specific siRNA, alleviated Sema3A-induced F-actin disorganization, cellular morphology changes and endothelial permeability. Importantly, ablation of Sema3A expression, cerebrovascular permeability and brain damage were significantly reduced in response to transient middle cerebral artery occlusion (tMCAO) and in a mouse model of cerebral ischemia/haemorrhagic transformation. Together, these studies demonstrated that Sema3A is a key mediator of cerebrovascular permeability and contributes to brain damage caused by cerebral ischemia.

Expression of netrin-1 and its receptors, deleted in colorectal cancer and uncoordinated locomotion-5 homolog B, in rat brain following focal cerebral ischemia reperfusion injury

Netrin-1 is currently one of the most highly studied axon guidance factors. Netrin-1 is widely expressed in the embryonic central nervous system, and together with the deleted in colorectal cancer and uncoordinated locomotion-5 homolog B receptors, netrin-1 plays a guiding role in the construction of neural conduction pathways and the directional migration of neuronal cells. In this study, we established a rat middle cerebral artery ischemia reperfusion model using the intraluminal thread technique. Immunofluorescence microscopy showed that the expression of netrin-1 and deleted in colorectal cancer in the ischemic penumbra was upregulated at 1 day after reperfusion, reached a peak at 14 days, and decreased at 21 days. There was no obvious change in the expression of uncoordinated locomotion-5 homolog B during this time period. Double immunofluorescence labeling revealed that netrin-1 was expressed in neuronal cells and around small vessels, but not in astrocytes and microglia, while deleted in colorectal cancer was localized in the cell membranes and protrusions of neurons and astrocytes. Our experimental findings indicate that netrin-1 may be involved in post-ischemic repair and neuronal protection via deleted in colorectal cancer receptors.

Neurorestorative therapy for stroke

Ischemic stroke is responsible for many deaths and long-term disability world wide. Development of effective therapy has been the target of intense research. Accumulating preclinical literature has shown that substantial functional improvement after stroke can be achieved using subacutely administered cell-based and pharmacological therapies. This review will discuss some of the latest findings on bone marrow-derived mesenchymal stem cells (BMSCs), human umbilical cord blood cells, and off-label use of some pharmacological agents, to promote recovery processes in the sub-acute and chronic phases following stroke. This review paper also focuses on molecular mechanisms underlying the cell-based and pharmacological restorative processes, which enhance angiogenesis, arteriogenesis, neurogenesis, and white matter remodeling following cerebral ischemia as well as an analysis of the interaction/coupling among these restorative events. In addition, the role of microRNAs mediating the intercellular communication between exogenously administered cells and parenchymal cells, and their effects on the regulation of angiogenesis and neuronal progenitor cell proliferation and differentiation, and brain plasticity after stroke are described.

Microenvironmental Influences on Metastasis Suppressor Expression and Function during a Metastatic Cell's Journey

Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches [1]. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive [2]. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass [3].Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [4, 5] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [3, 6, 7] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements.In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases [8]. Many physicians and patients opt for additional chemotherapy in order to "mop up" cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable.Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [9-11], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [12-16].The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases [14]. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers.Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth [17]. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease.In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves [18].

Trophic factors as modulators of motor neuron physiology and survival: implications for ALS therapy

Motor neuron physiology and development depend on a continuous and tightly regulated trophic support from a variety of cellular sources. Trophic factors guide the generation and positioning of motor neurons during every stage of the developmental process. As well, they are involved in axon guidance and synapse formation. Even in the adult spinal cord an uninterrupted trophic input is required to maintain neuronal functioning and protection from noxious stimuli. Among the trophic factors that have been demonstrated to participate in motor neuron physiology are vascular endothelial growth factor (VEGF), glial-derived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNTF) and insulin-like growth factor 1 (IGF-1). Upon binding to membrane receptors expressed in motor neurons or neighboring glia, these trophic factors activate intracellular signaling pathways that promote cell survival and have protective action on motor neurons, in both in vivo and in vitro models of neuronal degeneration. For these reasons these factors have been considered a promising therapeutic method for amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases, although their efficacy in human clinical trials have not yet shown the expected protection. In this minireview we summarize experimental data on the role of these trophic factors in motor neuron function and survival, as well as their mechanisms of action. We also briefly discuss the potential therapeutic use of the trophic factors and why these therapies may have not been yet successful in the clinical use.

Genome-wide association study combining pathway analysis for typical sporadic amyotrophic lateral sclerosis in Chinese Han populations

Sporadic amyotrophic lateral sclerosis (sALS) is a severe neurodegenerative disease that causes progressive motor neuron death. Although the etiology of sALS remains unknown, genetic variants are thought to predispose individuals to the disease. Several recent genome-wide association studies have identified a number of loci that increase sALS susceptibility, but these only explain a small proportion of the disease. To extend the current genetic evidence and to identify novel candidates of sALS, we performed a pooling genome-wide association study by 859,311 autosomal single-nucleotide polymorphisms of IlluminaHumanOmniZhongHua-8 combining pathway analysis in 250 typical sALS cases precluding age, clinical course, and phenotype interference and 250 control subjects from Chinese Han populations (CHP). The results revealed that 8 novel loci of 1p34.3, 3p21.1, 3p22.2, 10p15.2, 22q12.1, 3q13.11, 11q25, 12q24.33, and 5 previously reported loci of CNTN4 (kgp11325216), ATXN1 (kgp8327591), C9orf72 (kgp6016770), ITPR2 (kgp3041552), and SOD1 (kgp10760302) were associated with sALS from CHP. Furthermore, the pathway analysis based on the Gene Set Analysis Toolkit V2 showed that 10 top pathways were strongly associated with sALS from CHP, and among them, the 7 most potentially candidate pathways were phosphatidylinositol signaling system, Wnt signaling pathway, axon guidance, MAPK signaling pathway, neurotrophin signaling pathway, arachidonic acid metabolism, and T-cell receptor signaling pathway, a total of 39 significantly associate genes in 7 candidate pathways was suggested to involve in the pathogenesis of sALS from CHP. In conclusion, our results revealed several new loci and pathways related to sALS from CHP and extend the association evidence for partial loci, genes, and pathways, which were previously identified in other populations. Thus, our data provided new clues for exploring the pathogenesis of sALS.

Epigenetics of neural repair following spinal cord injury

Spinal cord injury results from an insult inflicted on the spinal cord that usually encompasses its 4 major functions (motor, sensory, autonomic, and reflex). The type of deficits resulting from spinal cord injury arise from primary insult, but their long-term severity is due to a multitude of pathophysiological processes during the secondary phase of injury. The failure of the mammalian spinal cord to regenerate and repair is often attributed to the very feature that makes the central nervous system special-it becomes so highly specialized to perform higher functions that it cannot effectively reactivate developmental programs to re-build novel circuitry to restore function after injury. Added to this is an extensive gliotic and immune response that is essential for clearance of cellular debris, but also lays down many obstacles that are detrimental to regeneration. Here, we discuss how the mature chromatin state of different central nervous system cells (neural, glial, and immune) may contribute to secondary pathophysiology, and how restoring silenced developmental gene expression by altering histone acetylation could stall secondary damage and contribute to novel approaches to stimulate endogenous repair.

Rho/Rho-associated kinase pathway in glaucoma (Review)

The Rho/ROCK pathway plays important roles in the modulation of the cytoskeletal integrity of cells, the synthesis of extracellular matrix components in the aqueous humor outflow tissue and the permeability of Schlemm's canal endothelial cells. The activation of the Rho/ROCK pathway results in trabecular meshwork (TM) contraction, and the inhibition of this pathway would provoke relaxation of TM with subsequent increase in outflow facility and, thereby, decrease intraocular pressure (IOP). ROCK inhibitors also serve as potent anti‑scarring agents via inhibition of transdifferentiation of tenon fibroblasts into myofibroblasts. Furthermore, the RhoA/ROCK pathway is involved in optic nerve neuroprotection. Inactivation of Rho/ROCK signaling increase ocular blood flow, improve retinal ganglion cell (RGC) survival and promote RGC axon regeneration. Considering the IOP modulation, potent bleb anti-scarring effect and neuroprotective properties of ROCK inhibitors, the Rho/ROCK pathway is an attractive target for anti-glaucoma therapy, and it may be used for human therapy in the near future.

Collapsin response mediator protein 3 deacetylates histone H4 to mediate nuclear condensation and neuronal death

CRMP proteins play critical regulatory roles during semaphorin-mediated neurite outgrowth, neuronal differentiation and death. Albeit having a high degree of structure and sequence resemblance to that of liver dihydropyrimidinase, purified rodent brain CRMPs do not hydrolyze dihydropyrimidinase substrates. Here we found that mouse CRMP3 has robust histone H4 deacetylase activity. During excitotoxicity-induced mouse neuronal death, calpain-cleaved, N-terminally truncated CRMP3 undergoes nuclear translocation to cause nuclear condensation through deacetylation of histone H4. CRMP3-mediated deacetylation of H4 leads to de-repression of the E2F1 gene transcription and E2F1-dependent neuronal death. These studies revealed a novel mechanism of CRMP3 in neuronal death. Together with previous well established bodies of literature that inhibition of histone deacetylase activity provides neuroprotection, we envisage that inhibition of CRMP3 may represent a novel therapeutic approach towards excitotoxicity-induced neuronal death.

Fast, non-competitive and reversible inhibition of NMDA-activated currents by 2-BFI confers neuroprotection

Excessive activation of the N-methyl-D-aspartic acid (NMDA) type glutamate receptors (NMDARs) causes excitotoxicity, a process important in stroke-induced neuronal death. Drugs that inhibit NMDA receptor-mediated [Ca(2+)]i influx are potential leads for development to treat excitotoxicity-induced brain damage. Our previous studies showed that 2-(2-benzofu-ranyl)-2-imidazoline (2-BFI), an immidazoline receptor ligand, dose-dependently protects rodent brains from cerebral ischemia injury. However, the molecular mechanisms remain unclear. In this study, we found that 2-BFI transiently and reversibly inhibits NMDA, but not AMPA currents, in a dose-dependent manner in cultured rat cortical neurons. The mechanism of 2-BFI inhibition of NMDAR is through a noncompetitive fashion with a faster on (Kon = 2.19±0.33×10(-9) M(-1) sec(-1)) and off rate (Koff = 0.67±0.02 sec(-1)) than those of memantine, a gold standard for therapeutic inhibition NMDAR-induced excitotoxicity. 2-BFI also transiently and reversibly blocked NMDA receptor-mediated calcium entry to cultured neurons and provided long-term neuroprotection against NMDA toxicity in vitro. Collectively, these studies demonstrated a potential mechanism of 2-BFI-mediated neuroprotection and indicated that 2-BFI is an excellent candidate for repositioning as a drug for stroke treatment.

Learning and memory: an emergent property of cell motility

In this review, we develop the argument that the molecular/cellular mechanisms underlying learning and memory are an adaptation of the mechanisms used by all cells to regulate cell motility. Neuronal plasticity and more specifically synaptic plasticity are widely recognized as the processes by which information is stored in neuronal networks engaged during the acquisition of information. Evidence accumulated over the last 25 years regarding the molecular events underlying synaptic plasticity at excitatory synapses has shown the remarkable convergence between those events and those taking place in cells undergoing migration in response to extracellular signals. We further develop the thesis that the calcium-dependent protease, calpain, which we postulated over 25 years ago to play a critical role in learning and memory, plays a central role in the regulation of both cell motility and synaptic plasticity. The findings discussed in this review illustrate the general principle that fundamental cell biological processes are used for a wide range of functions at the level of organisms.

Molecular mechanisms of peripheral nerve regeneration: emerging roles of microRNAs

MicroRNAs are small non-coding RNAs that suppress gene expression through target mRNA degradation or translation repression. Recent studies suggest that miRNA plays an important role in multiple physiological and pathological processes in the nervous system. In this review article, we described what is currently known about the mechanisms in peripheral nerve regeneration on cellular and molecular levels. Recently, changes in microRNA expression profiles have been detected in different injury models, and emerging evidence strongly indicates that these changes promote neurons to survive by shifting their physiology from maintaining structure and supporting synaptic transmission towards a regenerative phenotype. We reviewed the putative mechanisms involved in miRNA mediated post-transcriptional regulation and pointed out several areas where future research is necessary to advance our understanding of how targeting miRNA machinery can be used as a therapeutic approach for treating nerve injuries.

The neurorestorative benefit of GW3965 treatment of stroke in mice

BACKGROUND AND PURPOSE

GW3965, a synthetic liver X receptor agonist, elevates high-density lipoprotein cholesterol and has antiatherosclerosis and anti-inflammation properties. We tested the hypothesis that GW3965 treatment of stroke increases vascular remodeling, promotes synaptic protein expression and axonal growth in the ischemic brain, and improves functional outcome in mice.

METHODS

Mice were subjected to transient middle cerebral artery occlusion and treated without or with different doses of GW3965 (5, 10, or 20 mg/kg) starting 24 hours after middle cerebral artery occlusion daily for 14 days. Neurological functional tests, blood high-density lipoprotein cholesterol measurement, and immunostaining were performed. Mouse brain endothelial cells, primary cultured artery explants, and primary cortical neurons cultures were also used in vitro.

RESULTS

GW3965 treatment of stroke significantly increased blood high-density lipoprotein cholesterol level, synaptic protein expression, axonal density, angiogenesis and arteriogenesis, and Angiopoietin1, Tie2, and occludin expression in the ischemic brain and improved functional outcome compared with middle cerebral artery occlusion control animals (n=10; P<0.05). In vitro, GW3965 and high-density lipoprotein cholesterol also significantly increased capillary-like tube formation and artery explant cell migration as well as neurite outgrowth. Inhibition of Angiopoietin-1 attenuated GW3965-induced tube-formation, artery cell migration, and neurite outgrowth (n=6 per group; P<0.05).

CONCLUSIONS

These data indicate, for the first time, that GW3965 promotes synaptic protein expression and axonal growth and increases vascular remodeling, which may contribute to improvement of functional outcome after stroke. Increasing Angiopoietin-1/Tie2 signaling activity may play an important role in GW3965-induced brain plasticity and neurological recovery from stroke.

Neurovascular protection conferred by 2-BFI treatment during rat cerebral ischemia

Stroke is caused by vascular dysfunction and currently there are no effective therapeutics to stroke induced brain damage. In contrast to an intense emphasis on neuroprotection, relatively few studies have addressed means of vascular protection in cerebral ischemia. Here we discovered that the ligand to immidazolin receptor, 2-BFI, not only provided potent neuroprotection during middle cerebral artery occlusion in rat, which confirmed our previous reports, but also protected the integrity of the cerebral vasculature. Treatment with 2-BFI twice daily after the occlusion of the middle cerebral artery for 14 d significantly improved the neurological deficits, reduced brain infarction, and importantly, protected the cerebral vasculature as evidenced by the increased expression of an endothelial marker, von Willebrand factor, and better preservation of the cerebral vasculature, as viewed under a confocal microscope on rat brain perfused with FITC-labeled dextran. These results indicated that 2-BFI contributes to protection of neurovasculature. Understanding the molecular mechanisms could eventually lead to development of more effective therapies for stroke.

Human axonal survival of motor neuron (a-SMN) protein stimulates axon growth, cell motility, C-C motif ligand 2 (CCL2), and insulin-like growth factor-1 (IGF1) production

Spinal muscular atrophy is a fatal genetic disease of motoneurons due to loss of full-length survival of motor neuron protein, the main product of the disease gene SMN1. Axonal SMN (a-SMN) is an alternatively spliced isoform of SMN1, generated by retention of intron 3. To study a-SMN function, we generated cellular clones for the expression of the protein in mouse motoneuron-like NSC34 cells. The model was instrumental in providing evidence that a-SMN decreases cell growth and plays an important role in the processes of axon growth and cellular motility. In our conditions, low levels of a-SMN expression were sufficient to trigger the observed biological effects, which were not modified by further increasing the amounts of the expressed protein. Differential transcriptome analysis led to the identification of novel a-SMN-regulated factors, i.e. the transcripts coding for the two chemokines, C-C motif ligands 2 and 7 (CCL2 and CCL7), as well as the neuronal and myotrophic factor, insulin-like growth factor-1 (IGF1). a-SMN-dependent induction of CCL2 and IGF1 mRNAs resulted in increased intracellular levels and secretion of the respective protein products. Induction of CCL2 contributes to the a-SMN effects, mediating part of the action on axon growth and random cell motility, as indicated by chemokine knockdown and re-addition studies. Our results shed new light on a-SMN function and the underlying molecular mechanisms. The data provide a rational framework to understand the role of a-SMN deficiency in the etiopathogenesis of spinal muscular atrophy.

Divergent functions through alternative splicing: the Drosophila CRMP gene in pyrimidine metabolism, brain, and behavior

DHP and CRMP proteins comprise a family of structurally similar proteins that perform divergent functions, DHP in pyrimidine catabolism in most organisms and CRMP in neuronal dynamics in animals. In vertebrates, one DHP and five CRMP proteins are products of six genes; however, Drosophila melanogaster has a single CRMP gene that encodes one DHP and one CRMP protein through tissue-specific, alternative splicing of a pair of paralogous exons. The proteins derived from the fly gene are identical over 90% of their lengths, suggesting that unique, novel functions of these proteins derive from the segment corresponding to the paralogous exons. Functional homologies of the Drosophila and mammalian CRMP proteins are revealed by several types of evidence. Loss-of-function CRMP mutation modifies both Ras and Rac misexpression phenotypes during fly eye development in a manner that is consistent with the roles of CRMP in Ras and Rac signaling pathways in mammalian neurons. In both mice and flies, CRMP mutation impairs learning and memory. CRMP mutant flies are defective in circadian activity rhythm. Thus, DHP and CRMP proteins are derived by different processes in flies (tissue-specific, alternative splicing of paralogous exons of a single gene) and vertebrates (tissue-specific expression of different genes), indicating that diverse genetic mechanisms have mediated the evolution of this protein family in animals.

VEGF-induced growth cone enhancement is diminished by inhibiting tyrosine-residue 1214 of VEGFR-2

Axonal outgrowth is of paramount significance for establishing the intricate neuronal network both during embryogenesis and nerve regeneration. Vascular endothelial growth factor (VEGF), which is known for its essential role in vascular sprouting and its involvement in cancer, has recently been found to exert a trophic activity on neurons leading to an increased axonal outgrowth. Although two receptors, VEGFR-2 and neuropilin-1, were identified on neurons, the signaling pathways associated with them are not well understood. The aim of this study was to analyze the influence of VEGF on the growth cone morphology and motility of dorsal root ganglia (DRG) neurons. Moreover, we aimed for a deeper understanding of VEGFR-2 on growth cones that potentially mediates the stimulating and attractive effects. We cultivated chicken DRG in medium containing mouse VEGF and analyzed growth cone size. The data presented here show a positive effect of VEGF on growth cone size. Furthermore, we interrupted the activity of VEGFR-2 by either blocking the tyrosine residue 1214 (tyr1214) or by inhibiting the receptor phosphorylation with axitinib, a novel small molecule, which has recently entered phase III trials for cancer treatment. Disruption of the VEGFR-2 leads to a significantly diminished growth cone size. Based on these findings, we propose a positive effect of VEGF on peripheral nervous system growth cone size and show for the first time quantitative data to underline this hypothesis. Additionally, we propose that VEGFR-2 and especially the tyr1214-dependent pathway of VEGFR-2 are of importance in VEGF signaling in the growth cone of DRG neurons.

Niaspan increases axonal remodeling after stroke in type 1 diabetes rats

BACKGROUND AND OBJECTIVE

We investigated axonal plasticity in the bilateral motor cortices and the long term therapeutic effect of Niaspan on axonal remodeling after stroke in type-1 diabetic (T1DM) rats.

EXPERIMENTAL APPROACHES

T1DM was induced in young adult male Wistar rats via injection of streptozotocin. T1DM rats were subjected to 2h transient middle cerebral artery occlusion (MCAo) and were treated with 40 mg/kg Niaspan or saline starting 24 h after MCAo and daily for 28 days. Anterograde tracing using biotinylated dextran amine (BDA) injected into the contralateral motor cortex was performed to assess axonal sprouting in the ipsilateral motor cortex area. Functional outcome, SMI-31 (a pan-axonal microfilament marker), Bielschowsky silver and synaptophysin expression were measured. In vitro studies using primary cortical neuron (PCN) cultures and in vivo BDA injection into the brain to anterogradely label axons and terminals were employed.

RESULTS

Niaspan treatment of stroke in T1DM-MCAo rats significantly improved functional outcome after stroke and increased SMI-31, Bielschowsky silver and synaptophysin expression in the ischemic brain compared to saline treated T1DM-MCAo rats (p<0.05). Using BDA to anterograde label axons and terminals, Niaspan treatment significantly increased axonal density in ipsilateral motor cortex in T1DM-MCAo rats (p<0.05, n=7/group). Niacin treatment of PCN significantly increased Ang1 expression under high glucose condition. Niacin and Ang1 significantly increased neurite outgrowth, and anti-Ang1 antibody marginally attenuated Niacin induced neurite outgrowth (p=0.06, n=6/group) in cultured PCN under high glucose condition.

CONCLUSION

Niaspan treatment increased ischemic brain Ang1 expression and promoted axonal remodeling in the ischemic brain as well as improved functional outcome after stroke. Ang1 may partially contribute to Niaspan-induced axonal remodeling after stroke in T1DM-rats.

Inhibition of cyclin-dependent kinase 5 but not of glycogen synthase kinase 3-β prevents neurite retraction and tau hyperphosphorylation caused by secretable products of human T-cell leukemia virus type I-infected lymphocytes

Human T-cell leukemia virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurodegenerative disease characterized by selective loss of axons and myelin in the corticospinal tracts. This central axonopathy may originate from the impairment of anterograde axoplasmic transport. Previous work showed tau hyperphosphorylation at T(181) in cerebrospinal fluid of HAM/TSP patients. Similar hyperphosphorylation occurs in SH-SY5Y cells incubated with supernatant from MT-2 cells (HTLV-I-infected lymphocytes secreting viral proteins, including Tax) that produce neurite shortening. Tau phosphorylation at T(181) is attributable to glycogen synthase kinase 3-β (GSK3-β) and cyclin-dependent kinase 5 (CDK5) activation. Here we investigate whether neurite retraction in the SH-SY5Y model associates with concurrent changes in other tau hyperphosphorylable residues. Threonine 181 turned out to be the only tau hyperphosphorylated residue. We also evaluate the role of GSK3-β and CDK5 in this process by using specific kinase inhibitors (LiCl, TDZD-8, and roscovitine). Changes in both GSK3-β active and inactive forms were followed by measuring the regulatory phosphorylable sites (S(9) and Y(216) , inactivating and activating phosphorylation, respectively) together with changes in β-catenin protein levels. Our results showed that LiCl and TDZD-8 were unable to prevent MT-2 supernatant-mediated neurite retraction and also that neither Y(216) nor S(9) phosphorylations were changed in GSK3-β. Thus, GSK3-β seems not to play a role in T(181) hyperphosphorylation. On the other hand, the CDK5 involvement in tau phosphorylation was confirmed by both the increase in its enzymatic activity and the absence of MT-2 neurite retraction in the presence of roscovitine or CDK5 siRNA transfection.

Extracellular inhibitors, repellents, and semaphorin/plexin/MICAL-mediated actin filament disassembly

Multiple extracellular signals have been identified that regulate actin dynamics within motile cells, but how these instructive cues present on the cell surface exert their precise effects on the internal actin cytoskeleton is still poorly understood. One particularly interesting class of these cues is a group of extracellular proteins that negatively alter the movement of cells and their processes. Over the years, these types of events have been described using a variety of terms and herein we provide an overview of inhibitory/repulsive cellular phenomena and highlight the largest known protein family of repulsive extracellular cues, the Semaphorins. Specifically, the Semaphorins (Semas) utilize Plexin cell-surface receptors to dramatically collapse the actin cytoskeleton and we summarize what is known of the direct molecular and biochemical mechanisms of Sema-triggered actin filament (F-actin) disassembly. We also discuss new observations from our lab that reveal that the multidomain oxidoreductase (Redox) enzyme Molecule Interacting with CasL (MICAL), an important mediator of Sema/Plexin repulsion, is a novel F-actin disassembly factor. Our results indicate that MICAL triggers Sema/Plexin-mediated reorganization of the F-actin cytoskeleton and suggest a role for specific Redox signaling events in regulating actin dynamics.

What Are the bona fide GSK3 Substrates?

Nearly 100 proteins are proposed to be substrates for GSK3, suggesting that this enzyme is a fundamental regulator of almost every process in the cell, in every tissue in the body. However, it is not certain how many of these proposed substrates are regulated by GSK3 in vivo. Clearly, the identification of the physiological functions of GSK3 will be greatly aided by the identification of its bona fide substrates, and the development of GSK3 as a therapeutic target will be highly influenced by this range of actions, hence the need to accurately establish true GSK3 substrates in cells. In this paper the evidence that proposed GSK3 substrates are likely to be physiological targets is assessed, highlighting the key cellular processes that could be modulated by GSK3 activity and inhibition.

Crossed over repair of the femoral sensory and motor branches influences N-CAM

N-CAM, expressed by non-myelinating Schwann cells, was investigated by immunohistochemistry in transected rat femoral nerves, which were repaired either using a straight or a crossed over technique. N-CAM staining covered 30 and 11% of the cross-sectional area of sensory and motor branches, respectively, in uninjured nerves. After 3 days there was a transient smaller area of N-CAM staining following both the repairs. After a straight repair N-CAM area increased to the control values in both branches. In contrast, a crossed over repair resulted in a continuous increase of N-CAM in the motor branch, whereas the area in the sensory branch returned slowly to control values. N-CAM is influenced by an intentionally misdirected outgrowth of motor and sensory axons after nerve repair.