Akt/mammalian target of rapamycin signaling pathway regulates neurite outgrowth in cerebellar granule neurons stimulated by methylcobalamin

MST2 Acts via AKT Activity to Promote Neurite Outgrowth and Functional Recovery after Spinal Cord Injury in Mice

Spinal cord injury (SCI) constitutes a significant clinical challenge, and there is extensive research focused on identifying molecular activities that can facilitate the repair of spinal cord injuries. Mammalian sterile 20-like kinase 2 (MST2), a core component of the Hippo signaling pathway, plays a key role in apoptosis and cell growth. However, its role in neurite outgrowth after spinal cord injury remains unknown. Through comprehensive in vitro and in vivo experiments, we demonstrated that MST2, predominantly expressed in neurons, actively participated in the natural development of the CNS. Post-SCI, MST2 expression significantly increased, indicating its activation and potential role in the early stages of neural recovery. Detailed analyses showed that MST2 knockdown impaired neurite outgrowth and motor function recovery, whereas MST2 overexpression led to the opposite effects, underscoring MST2's neuroprotective role in enhancing neural repair. Further, we elucidated the mechanism underlying MST2's action, revealing its interaction with AKT and positive regulation of AKT activity, a well-established promoter of neurite outgrowth. Notably, MST2's promotion of neurite outgrowth and motor functional recovery was diminished by AKT inhibitors, highlighting the dependency of MST2's neuroprotective effects on AKT signaling. In conclusion, our findings affirmed MST2's pivotal role in fostering neuronal neurite outgrowth and facilitating functional recovery after SCI, mediated through its positive modulation of AKT activity. In conclusion, our findings confirmed MST2's crucial role in neural protection, promoting neurite outgrowth and functional recovery after SCI through positive AKT activity modulation. These results position MST2 as a potential therapeutic target for SCI, offering new insights into strategies for enhancing neuroregeneration and functional restoration.

Subacute combined degeneration of the spinal cord with cerebellar lesions: A case report

RATIONALE

Subacute combined degeneration of the spinal cord is a degenerative disease of the central and peripheral nervous systems caused by vitamin B12 deficiency, mainly involving the spinal cord posterior, lateral, and peripheral nerves, but rarely involving the cerebellum.

PATIENT CONCERNS

A 41-year-old woman presented with a 2-year history of walking unsteadily. Her hematologic examination revealed megaloblastic anemia and vitamin B12 deficiency. Electromyography showed multiple peripheral nerve damage (sensory fibers and motor fibers were involved). Imaging examination showed long T2 signal in the cervical, thoracic and lumbar spinal cord and cerebellum. Gastroscopy revealed autoimmune gastritis.

DIAGNOSES

Subacute combined degeneration of the spinal cord.

INTERVENTIONS

By supplementing with vitamin B12.

OUTCOMES

The patient's symptoms of limb weakness, diet, and consciousness were improved, and the muscle strength of both lower limbs recovered to grade IV.

LESSONS

The symptomatic people should seek medical treatment in time to avoid further deterioration of the disease. When esophagogastroduodenoscopy is performed as part of routine physical examination in asymptomatic people, it should be checked for the presence of autoimmune gastritis. Early diagnosis can prevent irreversible neuropathy.

Late-onset cobalamin C deficiency type in adult with cognitive and behavioral disturbances and significant cortical atrophy and cerebellar damage in the MRI: a case report

Background

Late-onset cobalamin C (cblC) deficiency is associated with a wide range of neurological and psychiatric symptoms, hematological manifestations, anorexia, renal failure, ocular abnormalities, dermatitis, and pancreatitis. However, the neuroimaging characteristics of late-onset cblC deficiency remain insufficiently documented. Common findings include diffuse white matter swelling, varying degrees of severe leukoaraiosis, hydrocephalus, corpus callosum atrophy, and symmetric bilateral basal ganglia lesions. In this report, we present a case of late-onset cblC deficiency in adults presenting with cerebellar ataxia as the primary symptom. The MRI findings revealed bilateral lateral cerebellar hemispheres exhibiting symmetric hyperintensity, primarily observed in diffusion-weighted imaging (DWI), which is a rarely reported imaging change in this context.

Case presentation

Our patient was a male who experienced symptoms starting at the age of 30 years, including unsteady walking, apparent cerebellar ataxia, and cognitive impairment upon nervous system examination. Brain magnetic resonance imaging (MRI) exhibited symmetric hyperintensity in the bilateral lateral cerebellar hemispheres, predominantly manifested in DWI, without any enhancement. Subsequently, significantly elevated blood total homocysteine and urinary methylmalonic acid levels were observed. Genetic analysis confirmed the presence of MMACHC compound heterozygous mutants c.482G > A and c.609G > A, thus confirming the diagnosis of cblC deficiency. These variants were classified as likely pathogenic following the guidelines of the American College of Medical Genetics and Genomics (ACMG) and were verified using Sanger sequencing. Following treatment, the patient experienced improvements in walking ability and cognition, a significant decrease in blood total homocysteine levels, and reversal of the imaging lesions.

In conclusion

Late-onset cblC deficiency presents with diverse clinical and imaging manifestations. Early diagnosis and treatment are crucial in achieving a favorable prognosis. This case serves as a reminder to clinicians not to overlook genetic metabolic disorders, particularly those causing multisite damage, in adult patients with undiagnosed neurological disorders, especially those affecting the cerebellum. Notably, methylmalonic acidemia should be considered within the spectrum of bilateral cerebellar lesions.

Exploring the Role of Metabolites in Cancer and the Associated Nerve Crosstalk

Since Otto Warburg's first report on the increased uptake of glucose and lactate release by cancer cells, dysregulated metabolism has been acknowledged as a hallmark of cancer that promotes proliferation and metastasis. Over the last century, studies have shown that cancer metabolism is complex, and by-products of glucose and glutamine catabolism induce a cascade of both pro- and antitumorigenic processes. Some vitamins, which have traditionally been praised for preventing and inhibiting the proliferation of cancer cells, have also been proven to cause cancer progression in a dose-dependent manner. Importantly, recent findings have shown that the nervous system is a key player in tumor growth and metastasis via perineural invasion and tumor innervation. However, the link between cancer-nerve crosstalk and tumor metabolism remains unclear. Here, we discuss the roles of relatively underappreciated metabolites in cancer-nerve crosstalk, including lactate, vitamins, and amino acids, and propose the investigation of nutrients in cancer-nerve crosstalk based on their tumorigenicity and neuroregulatory capabilities. Continued research into the metabolic regulation of cancer-nerve crosstalk will provide a more comprehensive understanding of tumor mechanisms and may lead to the identification of potential targets for future cancer therapies.

Megaloblastic wobbliness: A reversible neurological condition

BACKGROUND

Vitamin B12 deficiency has been associated with a very wide spectrum of neurologic manifestations and the majority of cases occur in infants, pregnant women, and elderly people. In children, common neurological complications include neuropathy, neuropsychiatric features, infantile tremor syndrome, developmental delay, cognitive decline, spastic paraparesis due to subacute combined degeneration of cord, seizures, encephalopathy, extrapyramidal features, and neuropathy. Vitamin B12 is known to cause sensory ataxia, along with impaired position and vibration sense, as well as variable spasticity, as a part of subacute combined degeneration of the spinal cord. However, only a few cases of isolated cerebellar ataxia caused by vitamin B12 deficiency have been reported in published literature.

METHODS AND RESULTS

We are reporting a case of isolated cerebellar ataxia progressing over months in a 13-year-old boy. He also had associated knuckle hyperpigmentation, megaloblastic anemia and his magnetic resonance imaging of the brain was normal. Complete blood count showed hemoglobin of 8.6 gm/dl and peripheral smear showed macrovalocytes and few hypersegmented neutrophils. Serum vitamin B12 level was low (134 pg/mL). He was started on daily intramuscular vitamin B12 supplementation and he showed a favorable response after the first week.

CONCLUSIONS

Clinicians need to consider vitamin B12 deficiency as one of the rare etiological possibilities in children presenting with isolated subacute onset/chronic ataxia, as supplementation of this vitamin is likely to cause a complete reversal of ataxia in such children.

BmK NSPK, a Potent Potassium Channel Inhibitor from Scorpion Buthus martensii Karsch, Promotes Neurite Outgrowth via NGF/TrkA Signaling Pathway

Scorpion toxins represent a variety of tools to explore molecular mechanisms and cellular signaling pathways of many biological functions. These toxins are also promising lead compounds for developing treatments for many neurological diseases. In the current study, we purified a new scorpion toxin designated as BmK NSPK (Buthus martensii Karsch neurite-stimulating peptide targeting K_v channels) from the BmK venom. The primary structure was determined using Edman degradation. BmK NSPK directly inhibited outward K⁺ current without affecting sodium channel activities, depolarized membrane, and increased spontaneous calcium oscillation in spinal cord neurons (SCNs) at low nanomolar concentrations. BmK NSPK produced a nonmonotonic increase on the neurite extension that peaked at ~10 nM. Mechanistic studies demonstrated that BmK NSPK increased the release of nerve growth factor (NGF). The tyrosine kinases A (TrkA) receptor inhibitor, GW 441756, eliminated the BmK NSPK-induced neurite outgrowth. BmK NSPK also increased phosphorylation levels of protein kinase B (Akt) that is the downstream regulator of TrkA receptors. These data demonstrate that BmK NSPK is a new voltage-gated potassium (K_v) channel inhibitor that augments neurite extension via NGF/TrkA signaling pathway. K_v channels may represent molecular targets to modulate SCN development and regeneration and to develop the treatments for spinal cord injury.

A Nanofiber Sheet Incorporating Vitamin B12 Promotes Nerve Regeneration in a Rat Neurorrhaphy Model

Outcomes of peripheral nerve repair after injury are often suboptimal. Therefore, developing biological approaches to augment nerve regeneration is important. In this in vivo study, we tested the hypothesis that augmentation with an electrospun nanofiber sheet incorporating methylcobalamin (MeCbl) would be effective for regeneration after peripheral nerve transection and repair.

Methods

Rats were divided into 3 groups that either underwent sciatic nerve repair with or without the MeCbl sheet, or a sham operation. At 4 and/or 8 weeks after the operation, sensory and motor functional recovery, along with histological findings, were compared among the groups using the toe-spreading test, mechanical and thermal algesimetry tests, tibialis anterior muscle weight measurements, electrophysiological analyses, which included nerve conduction velocity (NCV), compound muscle action potential (CMAP), and terminal latency (TL), and histological analyses involving the myelinated axon ratio, axon diameter, and total axon number.

Results

Compared with the repair group without the MeCbl sheet, the repair group with the MeCbl sheet showed significant recovery in terms of tibialis anterior muscle weight, NCV and CMAP, and also tended to improve in the toe-spreading test, mechanical and thermal algesimetry tests, and TL. Histological analyses also demonstrated that the myelinated axon ratios and axon diameters were significantly higher. Among these findings, the repair group with the MeCbl sheet demonstrated the same recovery in NCV as the sham group.

Conclusion

This study demonstrated that electrospun nanofiber MeCbl sheets promoted nerve regeneration and functional recovery, indicating that this treatment strategy may be viable for human peripheral nerve injuries.

Implication of homocysteine in protein quality control processes

Homocysteine (Hcy) is a key metabolite generated during methionine metabolism. The elevated levels of Hcy in the blood are reffered to as hyperhomocystenimeia (HHcy). The HHcy is caused by impaired metabolism/deficiency of either folate or B12 or defects in Hcy metabolism. Accumulating evidence suggests that HHcy is associated with cardiovascular and brain diseases including atherosclerosis, endothelial injury, and stroke etc. Vitamin B12 (cobalamin; B12) is a water-soluble vitamin essential for two metabolic reactions. It acts as a co-factor for methionine synthase and L-methylmalonyl-CoA mutase. Besides, it is also vital for DNA synthesis and maturation of RBC. Deficiency of B12 is associated with haematological and neurological disorders. Hyperhomocysteinemia (HHcy)-induced toxicity is thought to be mediated by the accumulation of Hcy and its metabolites, homocysteinylated proteins. Cellular protein quality control (PQC) is essential for the maintenance of proteome integrity, and cell viability and its failure contributes to the development of multiple diseases. Chaperones, unfolded protein response (UPR), ubiquitin-proteasome system (UPS), and autophagy are analogous strategies of PQC that maintain cellular proteome integrity. Recently, multiple studies reported that HHcy responsible for perturbation of PQC by reducing chaperone levels, activating UPR, and impairing autophagy. Besides, HHcy also induce cytotoxicity, inflammation, protein aggregation and apoptosis. It has been shown that some of the factors including altered SIRT1-HSF1 axis and irreversible homocysteinylation of proteins are responsible for folate and/or B12 deficiency or HHcy-induced impairment of PQC. Therefore, this review highlights the current understanding of HHcy in the context of cellular PQC and their pathophysiological and clinical consequences, epigenomic changes, therapeutic implications of B12, and chemical chaperones based on cell culture and experimental animal models.

CerefolinNAC Therapy of Hyperhomocysteinemia Delays Cortical and White Matter Atrophy in Alzheimer's Disease and Cerebrovascular Disease

We examined whether using a medical food therapy for hyperhomocysteinemia (HHcy) in patients with Alzheimer's disease (AD) or cognitive impairment due to cerebrovascular disease (CVD) with Cerefolin®/CerefolinNAC® (CFLN: L-methylfolate, methylcobalamin, and N-acetyl-cysteine) slowed regional brain atrophy. Thirty HHcy patients with AD and related disorders (ADRD) received CFLN (HHcy+CFLN: duration [μ ±  σ] = 18.6±16.1 months); a sub-sample of this group did not receive CFLN for varying periods of time (HHcy+NoCFLN: duration [μ ±  σ] = 12.6±5.6 months). Thirty-seven NoHHcy patients with ADRD did not receive CFLN (NoHHcy+NoCFLN: duration [μ ±  σ] = 13.3±17.7 months). No participant took supplemental B vitamins. Regional brain volumes were measured at baseline and end of study, and covariate-adjusted rates of hippocampal, cortical, and forebrain parenchymal (includes white matter) atrophy were predicted. The HHcy+CFLN group's hippocampal and cortical atrophy adjusted rates were 4.25 and 11.2 times slower than those of the NoHHcy+NoCFLN group (p < 0.024). The HHcy+CFLN group's forebrain parenchyma atrophy rate was significantly slower only for CVD; the rate of slowing was proportional to the degree of homocysteine lowering (p < 0.0001). CFLN was associated with significantly slowed hippocampal and cortical atrophy rates in ADRD patients with HHcy, and forebrain parenchymal atrophy rates in CVD patients with HHcy. The present results should be further validated.

mTOR-Dependent Cell Proliferation in the Brain

The mammalian Target of Rapamycin (mTOR) is a molecular complex equipped with kinase activity which controls cell viability being key in the PI3K/PTEN/Akt pathway. mTOR acts by integrating a number of environmental stimuli to regulate cell growth, proliferation, autophagy, and protein synthesis. These effects are based on the modulation of different metabolic pathways. Upregulation of mTOR associates with various pathological conditions, such as obesity, neurodegeneration, and brain tumors. This is the case of high-grade gliomas with a high propensity to proliferation and tissue invasion. Glioblastoma Multiforme (GBM) is a WHO grade IV malignant, aggressive, and lethal glioma. To date, a few treatments are available although the outcome of GBM patients remains poor. Experimental and pathological findings suggest that mTOR upregulation plays a major role in determining an aggressive phenotype, thus determining relapse and chemoresistance. Among several activities, mTOR-induced autophagy suppression is key in GBM malignancy. In this article, we discuss recent evidence about mTOR signaling and its role in normal brain development and pathological conditions, with a special emphasis on its role in GBM.

Microtopographical cues promote peripheral nerve regeneration via transient mTORC2 activation

Despite microsurgical repair, recovery of function following peripheral nerve injury is slow and often incomplete. Outcomes could be improved by an increased understanding of the molecular biology of regeneration and by translation of experimental bioengineering strategies. Topographical cues have been shown to be powerful regulators of the rate and directionality of neurite regeneration, and in this study we investigated the downstream molecular effects of linear micropatterned structures in an organotypic explant model. Linear topographical cues enhanced neurite outgrowth and our results demonstrated that the mTOR pathway is important in regulating these responses.

mTOR gene expression peaked between 48 and 72 h, coincident with the onset of rapid neurite outgrowth and glial migration, and correlated with neurite length at 48 h. mTOR protein was located to glia and in a punctate distribution along neurites. mTOR levels peaked at 72 h and were significantly increased by patterned topography (p < 0.05). Furthermore, the topographical cues could override pharmacological inhibition. Downstream phosphorylation assays and inhibition of mTORC1 using rapamycin highlighted mTORC2 as an important mediator, and more specific therapeutic target. Quantitative immunohistochemistry confirmed the presence of the mTORC2 component rictor at the regenerating front where it co-localised with F-actin and vinculin. Collectively, these results provide a deeper understanding of the mechanism of action of topography on neural regeneration, and support the incorporation of topographical patterning in combination with pharmacological mTORC2 potentiation within biomaterial constructs used to repair peripheral nerves.

Statement of Significance

Peripheral nerve injury is common and functionally devastating. Despite microsurgical repair, healing is slow and incomplete, with lasting functional deficit. There is a clear need to translate bioengineering approaches and increase our knowledge of the molecular processes controlling nerve regeneration to improve the rate and success of healing. Topographical cues are powerful determinants of neurite outgrowth and represent a highly translatable engineering strategy. Here we demonstrate, for the first time, that microtopography potentiates neurite outgrowth via the mTOR pathway, with the mTORC2 subtype being of particular importance. These results give further evidence for the incorporation of microtopographical cues into peripheral nerve regeneration conduits and indicate that mTORC2 may be a suitable therapeutic target to potentiate nerve regeneration.

Methylcobalamin prevents mutant superoxide dismutase-1-induced motor neuron death in vitro

Amyotrophic lateral sclerosis (ALS) is an incurable progressive neurodegenerative disorder that causes motor dysfunction. Treatments and drugs that slow progression of ALS have garnered great interest. In the present study, we show that the vitamin B12 analog methylcobalamin (MBL) effectively and dose dependently prevented embryonic stem cell-derived motor neuron death induced by cocultivation with astrocytes expressing mutant human superoxide dismutase-1 (G93A). Moreover, cotreatment of MBL with a conventional ALS drug, riluzole, further enhanced survival of motor neurons in this in-vitro ALS model. Our results show the potential use of MBL as a treatment for ALS and suggest a possible combination therapy strategy with other types of approved ALS drugs.

Role of major and brain-specific Sgce isoforms in the pathogenesis of myoclonus-dystonia syndrome

Loss-of-function mutations in SGCE, which encodes ε-sarcoglycan (ε-SG), cause myoclonus-dystonia syndrome (OMIM159900, DYT11). A "major" ε-SG protein derived from CCDS5637.1 (NM_003919.2) and a "brain-specific" protein, that includes sequence derived from alternative exon 11b (CCDS47642.1, NM_001099400.1), are reportedly localized in post- and pre-synaptic membrane fractions, respectively. Moreover, deficiency of the "brain-specific" isoform and other isoforms derived from exon 11b may be central to the pathogenesis of DYT11. However, no animal model supports this hypothesis. Gene-trapped ES cells (CMHD-GT_148G1-3, intron 9 of NM_011360) were used to generate a novel Sgce mouse model (C57BL/6J background) with markedly reduced expression of isoforms derived from exons 3' to exon 9 of NM_011360. Among those brain regions analyzed in adult (2month-old) wild-type (WT) mice, cerebellum showed the highest relative expression of isoforms incorporating exon 11b. Homozygotes (Sgce^{Gt(148G1)Cmhd/Gt(148G1)Cmhd} or Sgce^Gt/Gt) and paternal heterozygotes (Sgce^m+/pGt, m-maternal, p-paternal) showed 60 to 70% reductions in expression of total Sgce. Although expression of the major (NM_011360) and brain-specific (NM_001130189) isoforms was markedly reduced, expression of short isoforms was preserved and relatively small amounts of chimeric ε-SG/β-galactosidase fusion protein was produced by the Sgce gene-trap locus. Immunoaffinity purification followed by mass spectrometry assessments of Sgce^m+/pGt mouse brain using pan- or brain-specific ε-SG antibodies revealed significant reductions of ε-SG and other interacting sarcoglycans. Genome-wide gene-expression data using RNA derived from adult Sgce^m+/pGt mouse cerebellum showed that the top up-regulated genes were involved in cell cycle, cellular development, cell death and survival, while the top down-regulated genes were associated with protein synthesis, cellular development, and cell death and survival. In comparison to WT littermates, Sgce^m+/pGt mice exhibited "tiptoe" gait and stimulus-induced appendicular posturing between Postnatal Days 14 to 16. Abnormalities noted in older Sgce^m+/pGt mice included reduced body weight, altered gait dynamics, and reduced open-field activity. Overt spontaneous or stimulus-sensitive myoclonus was not apparent on the C57BL/6J background or mixed C57BL/6J-BALB/c and C57BL/6J-129S2 backgrounds. Our data confirm that mouse Sgce is a maternally imprinted gene and suggests that short Sgce isoforms may compensate, in part, for deficiency of major and brain-specific Sgce isoforms.

Enhancement of Peripheral Nerve Regrowth by the Purine Nucleoside Analog and Cell Cycle Inhibitor, Roscovitine

Peripheral nerve regeneration is a slow process that can be associated with limited outcomes and thus a search for novel and effective therapy for peripheral nerve injury and disease is crucial. Here, we found that roscovitine, a synthetic purine nucleoside analog, enhances neurite outgrowth in neuronal-like PC12 cells. Furthermore, ex vivo analysis of pre-injured adult rat dorsal root ganglion (DRG) neurons showed that roscovitine enhances neurite regrowth in these cells. Likewise, in vivo transected sciatic nerves in rats locally perfused with roscovitine had augmented repopulation of new myelinated axons beyond the transection zone. By mass spectrometry, we found that roscovitine interacts with tubulin and actin. It interacts directly with tubulin and causes a dose-dependent induction of tubulin polymerization as well as enhances Guanosine-5′-triphosphate (GTP)-dependent tubulin polymerization. Conversely, roscovitine interacts indirectly with actin and counteracts the inhibitory effect of cyclin-dependent kinases 5 (Cdk5) on Actin-Related Proteins 2/3 (Arp2/3)-dependent actin polymerization, and thus, causes actin polymerization. Moreover, in the presence of neurotrophic factors such as nerve growth factor (NGF), roscovitine-enhanced neurite outgrowth is mediated by increased activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) pathways. Since microtubule and F-actin dynamics are critical for axonal regrowth, the ability of roscovitine to activate the ERK1/2 and p38 MAPK pathways and support polymerization of tubulin and actin indicate a major role for this purine nucleoside analog in the promotion of axonal regeneration. Together, our findings demonstrate a therapeutic potential for the purine nucleoside analog, roscovitine, in peripheral nerve injury.

Mammalian Target of Rapamycin: Its Role in Early Neural Development and in Adult and Aged Brain Function

The kinase mammalian target of rapamycin (mTOR) integrates signals triggered by energy, stress, oxygen levels, and growth factors. It regulates ribosome biogenesis, mRNA translation, nutrient metabolism, and autophagy. mTOR participates in various functions of the brain, such as synaptic plasticity, adult neurogenesis, memory, and learning. mTOR is present during early neural development and participates in axon and dendrite development, neuron differentiation, and gliogenesis, among other processes. Furthermore, mTOR has been shown to modulate lifespan in multiple organisms. This protein is an important energy sensor that is present throughout our lifetime its role must be precisely described in order to develop therapeutic strategies and prevent diseases of the central nervous system. The aim of this review is to present our current understanding of the functions of mTOR in neural development, the adult brain and aging.

Current Perspectives on the Beneficial Role of Ginkgo biloba in Neurological and Cerebrovascular Disorders

Ginkgo biloba extract is an alternative medicine available as a standardized formulation, EGb 761^®, which consists of ginkgolides, bilobalide, and flavonoids. The individual constituents have varying therapeutic mechanisms that contribute to the pharmacological activity of the extract as a whole. Recent studies show anxiolytic properties of ginkgolide A, migraine with aura treatment by ginkgolide B, a reduction in ischemia-induced glutamate excitotoxicity by bilobalide, and an alternative antihypertensive property of quercetin, among others. These findings have been observed in EGb 761 as well and have led to clinical investigation into its use as a therapeutic for conditions such as cognition, dementia, cardiovascular, and cerebrovascular diseases. This review explores the therapeutic mechanisms of the individual EGb 761 constituents to explain the pharmacology as a whole and its clinical application to cardiovascular and neurological disorders, in particular ischemic stroke.

TIMP3 Attenuates the Loss of Neural Stem Cells, Mature Neurons and Neurocognitive Dysfunction in Traumatic Brain Injury

Mesenchymal stem cells (MSCs) have been shown to have potent therapeutic effects in a number of disorders including traumatic brain injury (TBI). However, the molecular mechanism(s) underlying these protective effects are largely unknown. Herein we demonstrate that tissue inhibitor of matrix metalloproteinase-3 (TIMP3), a soluble protein released by MSCs, is neuroprotective and enhances neuronal survival and neurite outgrowth in vitro. In vivo in a murine model of TBI, intravenous recombinant TIMP3 enhances dendritic outgrowth and abrogates loss of hippocampal neural stem cells and mature neurons. Mechanistically we demonstrate in vitro and in vivo that TIMP3-mediated neuroprotection is critically dependent on activation of the Akt-mTORC1 pathway. In support of the neuroprotective effect of TIMP3, we find that intravenous delivery of recombinant TIMP3 attenuates deficits in hippocampal-dependent neurocognition. Taken together, our data strongly suggest that TIMP3 has direct neuroprotective effects that can mitigate the deleterious effects associated with TBI, an area with few if any therapeutic options.

Methylcobalamin promotes the differentiation of Schwann cells and remyelination in lysophosphatidylcholine-induced demyelination of the rat sciatic nerve

Schwann cells (SCs) are constituents of the peripheral nervous system. The differentiation of SCs in injured peripheral nerves is critical for regeneration after injury. Methylcobalamin (MeCbl) is a vitamin B12 analog that is necessary for the maintenance of the peripheral nervous system. In this study, we estimated the effect of MeCbl on SCs. We showed that MeCbl downregulated the activity of Erk1/2 and promoted the expression of the myelin basic protein in SCs. In a dorsal root ganglion neuron–SC coculture system, myelination was promoted by MeCbl. In a focal demyelination rat model, MeCbl promoted remyelination and motor and sensory functional regeneration. MeCbl promoted the in vitro differentiation of SCs and in vivo myelination in a rat demyelination model and may be a novel therapy for several types of nervous disorders.

Evaluation of the impact of the cancer therapy everolimus on the central nervous system in mice

Cancer and treatments may induce cognitive impairments in cancer patients, and the causal link between chemotherapy and cognitive dysfunctions was recently validated in animal models. New cancer targeted therapies have become widely used, and their impact on brain functions and quality of life needs to be explored. We evaluated the impact of everolimus, an anticancer agent targeting the mTOR pathway, on cognitive functions, cerebral metabolism, and hippocampal cell proliferation/vascular density in mice. Adult mice received everolimus daily for 2 weeks, and behavioral tests were performed from 1 week after the last treatment. Everolimus-treated mice displayed a marked reduction in weight gain from the last day of the treatment period. Ex vivo analysis showed altered cytochrome oxidase activity in selective cerebral regions involved in energy balance, food intake, reward, learning and memory modulation, sleep/wake cycle regulation, and arousal. Like chemotherapy, everolimus did not alter emotional reactivity, learning and memory performances, but in contrast to chemotherapy, did not affect behavioral flexibility or reactivity to novelty. In vivo hippocampal neural cell proliferation and vascular density were also unchanged after everolimus treatments. In conclusion, two weeks daily everolimus treatment at the clinical dose did not evoke alteration of cognitive performances evaluated in hippocampal- and prefrontal cortex-dependent tasks that would persist at one to four weeks after the end of the treatment completion. However, acute everolimus treatment caused selective CO modifications without altering the mTOR effector P70S6 kinase in cerebral regions involved in feeding behavior and/or the sleep/wake cycle, at least in part under control of the solitary nucleus and the parasubthalamic region of the hypothalamus. Thus, this area may represent a key target for everolimus-mediating peripheral modifications, which has been previously associated with symptoms such as weight loss and fatigue.

Differential effects of antidepressant drugs on mTOR signalling in rat hippocampal neurons

Recent studies suggest that ketamine produces antidepressant actions via stimulation of mammalian target of rapamycin (mTOR), leading to increased levels of synaptic proteins in the prefrontal cortex. Thus, mTOR activation may be related to antidepressant action. However, the mTOR signalling underlying antidepressant drug action has not been well investigated. The aim of the present study was to determine whether alterations in mTOR signalling were observed following treatment with antidepressant drugs, using ketamine as a positive control. Using Western blotting, we measured changes in the mTOR-mediated proteins and synaptic proteins in rat hippocampal cultures. Dendritic outgrowth was determined by neurite assay. Our findings demonstrated that escitalopram, paroxetine and tranylcypromine significantly increased levels of phospho-mTOR and its down-stream regulators (phospho-4E-BP-1 and phospho-p70S6K); fluoxetine, sertraline and imipramine had no effect. All drugs tested increased up-stream regulators (phospho-Akt and phospho-ERK) levels. Increased phospho-mTOR induced by escitalopram, paroxetine or tranylcypromine was significantly blocked in the presence of specific PI3K, MEK or mTOR inhibitors, respectively. All drugs tested also increased hippocampal dendritic outgrowth and synaptic proteins levels. The mTOR inhibitor, rapamycin, significantly blocked these effects on escitalopram, paroxetine and tranylcypromine whereas fluoxetine, sertraline and imipramine effects were not affected. The effects of escitalopram, paroxetine and tranylcypromine paralleled those of ketamine. This study presents novel in vitro evidence indicating that some antidepressant drugs promote dendritic outgrowth and increase synaptic protein levels through mTOR signalling; however, other antidepressant drugs seem to act via a different pathway. mTOR signalling may be a promising target for the development of new antidepressant drugs.

Isolated cerebellar involvement in vitamin B12 deficiency: a case report

Deficiency of vitamin B12 causes megaloblastic anemia and nervous system demyelination. Structures affected in the nervous system include spinal cord, cranial and peripheral nerves, and brain white matter. A 9-year-old boy presented with knuckle hyperpigmentation and oral ulcers for 3 years, pallor and easy fatigability for 6 months, gait abnormalities for 3 months, and abnormal speech and behavioral abnormalities for 3 days. On examination, he had physical signs of megaloblastic anemia, mood swings with intermittent hallucinations, and features of cerebellar impairment. Blood investigations revealed megaloblastic anemia, and pernicious anemia was ruled out. Brain magnetic resonance imaging (MRI) revealed bilateral cerebellar signal changes. He received treatment for vitamin B12 deficiency and appropriate nutritional counseling. Three months later, he showed significant clinical and radiologic resolution. To our knowledge, isolated cerebellar involvement as the sole neurologic manifestation of vitamin B12 deficiency has not been described previously in children.

Relationships between cobalamin, epidermal growth factor, and normal prions in the myelin maintenance of central nervous system

Cobalamin (Cbl), epidermal growth factor (EGF), and prions (PrPs) are key molecules for myelin maintenance in the central and peripheral nervous systems. Cbl and EGF increase normal prion (PrP(C)) synthesis and PrP(C) levels in rat spinal cord (SC) and elsewhere. Cbl deficiency increases PrP(C) levels in rat SC and cerebrospinal fluid (CSF), and decreases PrP(C)-mRNA levels in rat SC. The administration of anti-octapeptide repeat PrP(C) region antibodies (Abs) to Cbl-deficient (Cbl-D) rats prevents SC myelin lesions and a local increase in tumor necrosis factor (TNF)-α levels, whereas anti-TNF-α Abs prevent SC myelin lesions and the increase in SC and CSF PrP(C) levels. As it is known that both Cbl and EGF regulate SC PrP(C) synthesis independently, and that Cbl regulates SC EGF synthesis, EGF may play both Cbl-independent and Cbl-dependent roles. When Cbl-D rats undergo Cbl replacement therapy, SC PrP(C) levels are similar to those observed in Cbl-D rats. In rat frontal cortex (which is marginally affected by Cbl deficiency in histological terms), Cbl deficiency decreases PrP(C) levels and the increase induced by Cbl replacement leads to their normalization. Increased nerve PrP(C) levels are detected in the myelin lesions of the peripheral neuropathy of Cbl-D rats, and CSF PrP(C) levels are also increased in Cbl-D patients (but not in patients with Cbl-unrelated neurological diseases). Various common steps in the downstream signaling pathway of Cbl, EGF, and PrP(C) underlines the close relationship between the three molecules in keeping myelin normal.

Methylcobalamin promotes proliferation and migration and inhibits apoptosis of C2C12 cells via the Erk1/2 signaling pathway

Methylcobalamin (MeCbl) is a vitamin B12 analog that has some positive effects on peripheral nervous disorders. Although some previous studies revealed the effects of MeCbl on neurons, its effect on the muscle, which is the final target of motoneuron axons, remains to be elucidated. This study aimed to determine the effect of MeCbl on the muscle. We found that MeCbl promoted the proliferation and migration of C2C12 myoblasts in vitro and that these effects are mediated by the Erk1/2 signaling pathway without affecting the activity of the Akt signaling pathway. We also demonstrated that MeCbl inhibits C2C12 cell apoptosis during differentiation. Our results suggest that MeCbl has beneficial effects on the muscle in vitro. MeCbl administration may provide a novel therapeutic approach for muscle injury or degenerating muscle after denervation.

Thyroid hormone-dependent development of early cortical networks: temporal specificity and the contribution of trkB and mTOR pathways

Early in neocortical network development, triiodothyronine (T3) promotes GABAergic neurons' population increase, their somatic growth and the formation of GABAergic synapses. In the presence of T3, GABAergic interneurons form longer axons and conspicuous axonal arborizations, with an increased number of putative synaptic boutons. Here we show that the increased GABAergic axonal growth is positively correlated with the proximity to non-GABAergic neurons (non-GABA). A differential innervation emerges from a T3-dependent decrease of axonal length in fields with low density of neuronal cell bodies, combined with an increased bouton formation in fields with high density of neuronal somata. T3 addition to deprived networks after the first 2 weeks of development did not rescue deficits in the GABAergic synaptic bouton distribution, or in the frequency and duration of spontaneous bursts. During the critical 2-week-period, GABAergic signaling is depolarizing as revealed by calcium imaging experiments. Interestingly, T3 enhanced the expression of the potassium-chloride cotransporter 2 (KCC2), and accelerated the developmental shift from depolarizing to hyperpolarizing GABAergic signaling in non-GABA. The T3-related increase of spontaneous network activity was remarkably reduced after blockade of either tropomyosin-receptor kinase B (trkB) or mammalian target of rapamycin (mTOR) pathways. T3-dependent increase in GABAergic neurons' soma size was mediated mainly by mTOR signaling. Conversely, the T3-dependent selective increase of GABAergic boutons near non-GABAergic cell bodies is mediated by trkB signaling only. Both trkB and mTOR signaling mediate T3-dependent reduction of the GABAergic axon extension. The circuitry context is relevant for the interaction between T3 and trkB signaling, but not for the interactions between T3 and mTOR signaling.

Biphasic modulation of NOS expression, protein and nitrite products by hydroxocobalamin underlies its protective effect in endotoxemic shock: downstream regulation of COX-2, IL-1β, TNF-α, IL-6, and HMGB1 expression

Background. NOS/^•NO inhibitors are potential therapeutics for sepsis, yet they increase clinical mortality. However, there has been no in vivo investigation of the (in vitro) ^•NO scavenger, cobalamin's (Cbl) endogenous effects on NOS/^•NO/inflammatory mediators during the immune response to sepsis. Methods. We used quantitative polymerase chain reaction (qPCR), ELISA, Western blot, and NOS Griess assays, in a C57BL/6 mouse, acute endotoxaemia model. Results. During the immune response, pro-inflammatory phase, parenteral hydroxocobalamin (HOCbl) treatment partially inhibits hepatic, but not lung, iNOS mRNA and promotes lung eNOS mRNA, but attenuates the LPS hepatic rise in eNOS mRNA, whilst paradoxically promoting high iNOS/eNOS protein translation, but relatively moderate ^•NO production. HOCbl/NOS/^•NO regulation is reciprocally associated with lower 4 h expression of TNF-α, IL-1β, COX-2, and lower circulating TNF-α, but not IL-6. In resolution, 24 h after LPS, HOCbl completely abrogates a major late mediator of sepsis mortality, high mobility group box 1 (HMGB1) mRNA, inhibits iNOS mRNA, and attenuates LPS-induced hepatic inhibition of eNOS mRNA, whilst showing increased, but still moderate, NOS activity, relative to LPS only. experiments (LPS+D-Galactosamine) HOCbl afforded significant, dose-dependent protection in mice Conclusions. HOCbl produces a complex, time- and organ-dependent, selective regulation of NOS/^•NO during endotoxaemia, corollary regulation of downstream inflammatory mediators, and increased survival. This merits clinical evaluation.

Cobalamin and normal prions: a new horizon for cobalamin neurotrophism

It is known that cobalamin (Cbl) deficiency damages myelin by increasing tumor necrosis factor (TNF)-α and decreasing epidermal growth factor (EGF) levels in rat central nervous system (CNS), and affects the peripheral nervous system (PNS) morphologically and functionally. It is also known that some polyneuropathies not due to Cbl deficiency are connected with increased TNF-α levels, and that various cytokines (including TNF-α) and growth factors regulate the in vitro synthesis of normal prions (PrP(C)s). Given that there is extensive evidence that PrP(C)s play a key role in the maintenance of CNS and PNS myelin, we investigated whether the PrP(C) octapeptide repeat (OR) region is involved in the pathogenesis of rat Cbl-deficient (Cbl-D) polyneuropathy. After intracerebroventricularly administering antibodies (Abs) against the OR region (OR-Abs) to Cbl-D rats to prevent myelin damage and maximum nerve conduction velocity (MNCV) abnormalities, and PrP(C)s to otherwise normal rats to reproduce PNS Cbl-D-like lesions, we measured PrP(C) levels and MNCV of the sciatic and tibial nerves. PrP(C) and TNF-α levels were increased in sciatic and tibial nerves of Cbl-D and saline-treated rats, and the OR-Abs normalized the myelin ultrastructure, TNF-α levels, and MNCV values of the sciatic and tibial nerves of Cbl-D rats. The same peripheral nerves of the otherwise normal PrP(C)-treated rats showed typical Cbl-D myelin lesions, significantly increased TNF-α levels, and significantly decreased MNCV values. These findings demonstrate that Cbl deficiency induces excess PrP(C)s and thereby excess OR regions, which seem to be responsible for the PNS myelin damage, as has recently been found in the case of CNS myelin damage [66]. Furthermore, excess TNF-α is also involved in the pathogenesis of Cbl-D polyneuropathy. In conclusion, we have extended the list of prion diseases by adding one caused by excess PrP(C)s and the polyneuropathies related to excess TNF-α.

mTOR kinase, a key player in the regulation of glial functions: relevance for the therapy of multiple sclerosis

The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase with a central role in the regulation of cell growth and proliferation, and several intracellular processes, such as mRNA transcription and translation, autophagy and cytoskeletal organization. The relevance of this pathway in the regulation of the immune system is well characterized. mTOR is essential for the proper activation and proliferation of effector T cells, restricts the development of regulatory T cells, and downregulates innate immune responses. Recently, a direct role of mTOR in the modulation of glial functions has also been recognized. Data from our group and others support the notion that mTOR is involved in microglial proinflammatory activation. The kinase regulates several intracellular processes in astrocytes, among which the rate of mRNA degradation of the inducible form of NO synthase. Therefore, the inhibition of mTOR kinase activity in glial cells results in anti-inflammatory actions, suggesting possible beneficial effects of mTOR inhibitors (like rapamycin) in the treatment of inflammatory-based pathologies of the central nervous system. In contrast, mTOR plays an important role in the regulation of oligodendrocyte development and myelination process as well as several neuronal functions, which may limit this therapeutic approach. Nevertheless, as reviewed here, there is robust evidence that rapamycin ameliorates the clinical course of both the relapsing-remitting and the chronic experimental autoimmune encephalomyelitis (EAE), and significantly reduces the hyperalgesia observed before clinical development of EAE. These findings may have important clinical implications for the therapy of multiple sclerosis.

Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D(2) receptors and 5-hydroxytryptamine (5-HT) 5-HT(1A) receptors, and antagonistic activity at 5-HT(2A) receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT(1A) receptor antagonist WAY-100635, but not the dopamine D(2) receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP(3)) receptors and BAPTA-AM, a chelator of intracellular Ca(2+), blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT(1A) receptor activation and Ca(2+) signaling via IP(3) receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug.

Insulin in the brain: sources, localization and functions

Historically, insulin is best known for its role in peripheral glucose homeostasis, and insulin signaling in the brain has received less attention. Insulin-independent brain glucose uptake has been the main reason for considering the brain as an insulin-insensitive organ. However, recent findings showing a high concentration of insulin in brain extracts, and expression of insulin receptors (IRs) in central nervous system tissues have gathered considerable attention over the sources, localization, and functions of insulin in the brain. This review summarizes the current status of knowledge of the peripheral and central sources of insulin in the brain, site-specific expression of IRs, and also neurophysiological functions of insulin including the regulation of food intake, weight control, reproduction, and cognition and memory formation. This review also considers the neuromodulatory and neurotrophic effects of insulin, resulting in proliferation, differentiation, and neurite outgrowth, introducing insulin as an attractive tool for neuroprotection against apoptosis, oxidative stress, beta amyloid toxicity, and brain ischemia.