Neurotrophins and neurodegeneration

A multiclass extreme gradient boosting model for evaluation of transcriptomic biomarkers in Alzheimer's disease prediction

BACKGROUND

Patients with young-onset Alzheimer's disease (AD) (before the age of 50 years old) often lack obvious imaging changes and amyloid protein deposition, which can lead to misdiagnosis with other cognitive impairments. Considering the association between immunological dysfunction and progression of neurodegenerative disease, recent research has focused on identifying blood transcriptomic signatures for precise prediction of AD.

METHODS

In this study, we extracted blood biomarkers from large-scale transcriptomics to construct multiclass eXtreme Gradient Boosting models (XGBoost), and evaluated their performance in distinguishing AD from cognitive normal (CN) and mild cognitive impairment (MCI).

RESULTS

Independent testing with external dataset revealed that the combination of blood transcriptomic signatures achieved an area under the receiver operating characteristic curve (AUC of ROC) of 0.81 for multiclass classification (sensitivity = 0.81; specificity = 0.63), 0.83 for classification of AD vs. CN (sensitivity = 0.72; specificity = 0.73), and 0.85 for classification of AD vs. MCI (sensitivity = 0.77; specificity = 0.73). These candidate signatures were significantly enriched in 62 chromosome regions, such as Chr.19p12-19p13.3, Chr.1p22.1-1p31.1, and Chr.1q21.2-1p23.1 (adjusted p < 0.05), and significantly overrepresented by 26 transcription factors, including E2F2, FOXO3, and GATA1 (adjusted p < 0.05). Biological analysis of these signatures pointed to systemic dysregulation of immune responses, hematopoiesis, exocytosis, and neuronal support in neurodegenerative disease (adjusted p < 0.05).

CONCLUSIONS

Blood transcriptomic biomarkers hold great promise in clinical use for the accurate assessment and prediction of AD.

Lower Nerve Growth Factor Levels in Major Depression and Suicidal Behaviors: Effects of Adverse Childhood Experiences and Recurrence of Illness

Major depressive disorder (MDD) and its severe subtype, major dysmood disorder (MDMD), are distinguished by activation of inflammatory and growth factor subnetworks, which are associated with recurrence of illness (ROI) and adverse childhood experiences (ACEs). Nerve growth factor (NGF) plays a crucial role in facilitating neuro-immune communications and may regulate the inflammatory response.

METHODS

The present study examined the effects of ACEs and ROI on culture supernatant NGF, stem cell factor (SCF), stem cell GF (SCGF), hepatocyte GF (HGF), and macrophage colony-stimulating factor (M-CSF), in relation to a neurotoxicity (NT) cytokine profile.

RESULTS

NGF levels are lower in MDD (p = 0.003), particularly MDMD (p < 0.001), as compared with normal controls. ROI and ACE were significantly and inversely associated with NGF (≤0.003) and the NGF/NT ratio (≤0.001), whereas there are no effects of ACEs and ROI on SCF, SCGF, HGF, or M-CSF. Lowered NGF (p = 0.003) and the NGF/NT ratio (p < 0.001) are highly significantly and inversely associated with the severity of the current depression phenome, conceptualized as a latent vector extracted from the current severity of depression, anxiety, and suicidal behaviors. We found that one validated and replicable latent vector could be extracted from NGF, ROI, and the depression phenome, which therefore constitutes a novel ROI-NGF-pathway-phenotype. ACEs explained 59.5% of the variance in the latter pathway phenotype (p < 0.001).

CONCLUSIONS

The imbalance between decreased NGF and increased neurotoxic cytokines during the acute phase of severe depression may contribute to decreased neuroprotection, increased neuro-affective toxicity, and chronic mild inflammation.

Therapeutic application of mesenchymal stem cells derived exosomes in neurodegenerative diseases: A focus on non-coding RNAs cargo, drug delivery potential, perspective

Despite the massive efforts advanced over recent years in emerging therapies for neurodegenerative diseases, effective treatment for these diseases is still an urgent need. The application of mesenchymal stem cells (MSCs) derived exosomes (MSCs-Exo) as a novel therapy for neurodegenerative diseases holds great promise. A growing body of data now suggests that an innovative cell-free therapy, MSCs-Exo, may establish a fascinating alternative therapy due to their unique advantages over MSCs. Notable, MSCs-Exo can infiltrate the blood-brain barrier and then well distribute non-coding RNAs into injured tissues. Research shows that non-coding RNAs of MSCs-Exo are vital effectors that participate in the treatment of neurodegenerative diseases through neurogeneration and neurite outgrowth, modulation of the immune system, reducing neuroinflammation, repairmen of damaged tissue, and promotion of neuroangiogenesis. In addition, MSCs-Exo can serve as a drug delivery system for delivering non-coding RNAs to neurons in neurodegenerative conditions. In this review, we summarize the recent progress in the therapeutic role of non-coding RNAs of MSCs-Exo for various neurodegenerative diseases. This study also discusses the potential drug delivery role of MSCs-Exo and challenges and opportunities in the clinical translation of MSCs-Exo-based therapies for neurodegenerative diseases in the future.

Potential therapeutic strategies for photoreceptor degeneration: the path to restore vision

Photoreceptors (PRs), as the most abundant and light-sensing cells of the neuroretina, are responsible for converting light into electrical signals that can be interpreted by the brain. PR degeneration, including morphological and functional impairment of these cells, causes significant diminution of the retina's ability to detect light, with consequent loss of vision. Recent findings in ocular regenerative medicine have opened promising avenues to apply neuroprotective therapy, gene therapy, cell replacement therapy, and visual prostheses to the challenge of restoring vision. However, successful visual restoration in the clinical setting requires application of these therapeutic approaches at the appropriate stage of the retinal degeneration. In this review, firstly, we discuss the mechanisms of PR degeneration by focusing on the molecular mechanisms underlying cell death. Subsequently, innovations, recent developments, and promising treatments based on the stage of disorder progression are further explored. Then, the challenges to be addressed before implementation of these therapies in clinical practice are considered. Finally, potential solutions to overcome the current limitations of this growing research area are suggested. Overall, the majority of current treatment modalities are still at an early stage of development and require extensive additional studies, both pre-clinical and clinical, before full restoration of visual function in PR degeneration diseases can be realized.

Expression and Signaling Pathways of Nerve Growth Factor (NGF) and Pro-NGF in Breast Cancer: A Systematic Review

Breast cancer represents the most common type of cancer and is the leading cause of death due to cancer among women. Thus, the prevention and early diagnosis of breast cancer is of primary urgency, as well as the development of new treatments able to improve its prognosis. Nerve Growth Factor (NGF) is a neurotrophic factor involved in the regulation of neuronal functions through the binding of the Tropomyosin receptor kinase A (TrkA) and the Nerve Growth Factor receptor or Pan-Neurotrophin Receptor 75 (NGFR/p75NTR). In addition, its precursor (pro-NGF) can extert biological activity by forming a trimeric complex with NGFR/p75NTR and sortilin, or by binding to TrkA receptors with low affinity. Several examples of in vitro and in vivo evidence show that NGF is both synthesized and released by breast cancer cells, and has mitogen, antiapoptotic and angiogenic effects on these cells through the activation of different signaling cascades that involve TrkA and NGFR/p75NTR receptors. Conversely, pro-NGF signaling has been related to breast cancer invasion and metastasis. Other studies suggested that NGF and its receptors could represent a good diagnostic and prognostic tool, as well as promising therapeutic targets for breast cancer. In this paper, we comprehensively summarize and systematically review the current experimental evidence on this topic. INPLASY ID: INPLASY2022100017.

Emerging role of mesenchymal stromal cells (MSCs)-derived exosome in neurodegeneration-associated conditions: a groundbreaking cell-free approach

Accumulating proofs signify that pleiotropic effects of mesenchymal stromal cells (MSCs) are not allied to their differentiation competencies but rather are mediated mainly by the releases of soluble paracrine mediators, making them a reasonable therapeutic option to enable damaged tissue repair. Due to their unique immunomodulatory and regenerative attributes, the MSC-derived exosomes hold great potential to treat neurodegeneration-associated neurological diseases. Exosome treatment circumvents drawbacks regarding the direct administration of MSCs, such as tumor formation or reduced infiltration and migration to brain tissue. Noteworthy, MSCs-derived exosomes can cross the blood–brain barrier (BBB) and then efficiently deliver their cargo (e.g., protein, miRNAs, lipid, and mRNA) to damaged brain tissue. These biomolecules influence various biological processes (e.g., survival, proliferation, migration, etc.) in neurons, oligodendrocytes, and astrocytes. Various studies have shown that the systemic or local administration of MSCs-derived exosome could lead to the favored outcome in animals with neurodegeneration-associated disease mainly by supporting BBB integrity, eliciting pro-angiogenic effects, attenuating neuroinflammation, and promoting neurogenesis in vivo. In the present review, we will deliver an overview of the therapeutic benefits of MSCs-derived exosome therapy to ameliorate the pathological symptoms of acute and chronic neurodegenerative disease. Also, the underlying mechanism behind these favored effects has been elucidated.

Simultaneous PET/MRI: The future gold standard for characterizing motor neuron disease-A clinico-radiological and neuroscientific perspective

Neuroimaging assessment of motor neuron disease has turned into a cornerstone of its clinical workup. Amyotrophic lateral sclerosis (ALS), as a paradigmatic motor neuron disease, has been extensively studied by advanced neuroimaging methods, including molecular imaging by MRI and PET, furthering finer and more specific details of the cascade of ALS neurodegeneration and symptoms, facilitated by multicentric studies implementing novel methodologies. With an increase in multimodal neuroimaging data on ALS and an exponential improvement in neuroimaging technology, the need for harmonization of protocols and integration of their respective findings into a consistent model becomes mandatory. Integration of multimodal data into a model of a continuing cascade of functional loss also calls for the best attempt to correlate the different molecular imaging measurements as performed at the shortest inter-modality time intervals possible. As outlined in this perspective article, simultaneous PET/MRI, nowadays available at many neuroimaging research sites, offers the perspective of a one-stop shop for reproducible imaging biomarkers on neuronal damage and has the potential to become the new gold standard for characterizing motor neuron disease from the clinico-radiological and neuroscientific perspectives.

Adjuvant Lineage-Negative Cell Therapy as a Potential Silencer of the Complement-Mediated Immune System in ALS Patients

ALS remains a fatal, neurodegenerative motor neuron disease. Numerous studies seem to confirm that innate immune system is involved in the pathophysiology of ALS. Hence, the assessment of the complement system and attempts to modify its activity remain the target of medical intervention in ALS. In the present study, three intrathecal administrations of autologous bone marrow-derived lineage-negative (Lin^–) cells were performed every 6 weeks in 20 sporadic ALS patients. The concentrations of various complement components in the cerebrospinal fluid and plasma at different time points after cell injection were quantified using a Luminex multiplex. The results of the complement system were correlated with the level of leukocytes, neutrophils, lymphocytes, fibrinogen and CRP in the peripheral blood and the functional status of ALS patients using Norris and ALS-FRSr scales. The study showed a statistically significant decrease in plasma C3b concentration in all 7th days after cell application. In parallel, a peak decrease in neutrophil count and CRP level was observed on days 5–7, with a simultaneous maximum clinical improvement on days 7–28 of each Lin^– cell administration. Adjuvant Lin^– cell therapy appears to have the silencing potential on the complement-mediated immune system and thus suppress pro-inflammatory reactions responsible for neurodegeneration. However, further in-depth studies are necessary to address this issue.

Exposure to di-(2-ethylhexyl) phthalate reduces secretion of GDNF via interfering with estrogen pathway and downregulating ERK/c-fos signaling pathway in astrocytes

Di-(2-ethylhexyl) phthalate (DEHP) is a typical endocrine-disrupting chemical (EDC) that can increase the risk of central nervous system disease. This study aimed to investigate the in vitro and in vivo effects of DEHP exposure on GDNF secretion and the underlying mechanisms. Pregnant Wistar rats were randomly assigned into four groups and administered 0, 30, 300, or 750 mg/kg DEHP daily by oral gavage. In addition, primary astrocytes were exposed to mono-(2-ethylhexyl) phthalate (MEHP), the main metabolite of DEHP. Our results showed that DEHP exposure reduced GDNF levels and downregulated the ERK/c-fos signaling pathway in the cerebral cortex of male, but not female, offspring. Moreover, exogenous estrogen could overcome the decreased GDNF levels in astrocytes caused by MEHP exposure. MEHP also decreased p300 levels and downregulated the ERK/c-fos signaling pathway in primary astrocytes. Honokiol restored GDNF levels following MEHP exposure by activating the ERK/c-fos signaling pathway, while the inhibitor U0126 further reduced the GDNF levels. These results suggested that DEHP exposure could interfere with the normal effects of estrogen in the brain and downregulate the ERK/c-fos signaling pathway to decrease the GDNF secretion from astrocytes in the cerebral cortex.

Design, Synthesis, and Biological Evaluation of Novel 3-Aminomethylindole Derivatives as Potential Multifunctional Anti-Inflammatory and Neurotrophic Agents

The development of multifunctional molecules that are able to simultaneously interact with several pathological components has been considered as a solution to treat the complex pathologies of neurodegenerative diseases. Herein, a series of aminomethylindole derivatives were synthesized, and evaluation of their application for antineuroinflammation and promoting neurite outgrowth was disclosed. Our initial screening showed that most of the compounds potently inhibited lipopolysaccharide (LPS)-stimulated production of NO in microglial cells and potentiated the action of NGF to promote neurite outgrowth of PC12 cells. Interestingly, with outstanding NO/TNF-α production inhibition and neurite outgrowth-promoting activities, compounds 8c and 8g were capable of rescuing cells after injury by H₂O₂. Their antineuroinflammatory effects were associated with the downregulation of the LPS-induced expression of the inflammatory mediators inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Western blotting and immunofluorescence assay results indicated that the mechanism of their antineuroinflammatory actions involved suppression of the MAPK/NF-κB signal pathways. Further studies revealed that another important reason for the high comprehensive antineuroinflammatory activity was the anti-COX-2 capabilities of the compounds. All these results suggest that the potential biochemical multifunctional profiles of the aminomethylindole derivatives provide a new sight for the treatment of neurodegenerative diseases.

Evidence of p75 Neurotrophin Receptor Involvement in the Central Nervous System Pathogenesis of Classical Scrapie in Sheep and a Transgenic Mouse Model

Neurotrophins constitute a group of growth factor that exerts important functions in the nervous system of vertebrates. They act through two classes of transmembrane receptors: tyrosine-kinase receptors and the p75 neurotrophin receptor (p75^NTR). The activation of p75^NTR can favor cell survival or apoptosis depending on diverse factors. Several studies evidenced a link between p75^NTR and the pathogenesis of prion diseases. In this study, we investigated the distribution of several neurotrophins and their receptors, including p75^NTR, in the brain of naturally scrapie-affected sheep and experimentally infected ovinized transgenic mice and its correlation with other markers of prion disease. No evident changes in infected mice or sheep were observed regarding neurotrophins and their receptors except for the immunohistochemistry against p75^NTR. Infected mice showed higher abundance of p75^NTR immunostained cells than their non-infected counterparts. The astrocytic labeling correlated with other neuropathological alterations of prion disease. Confocal microscopy demonstrated the co-localization of p75^NTR and the astrocytic marker GFAP, suggesting an involvement of astrocytes in p75^NTR-mediated neurodegeneration. In contrast, p75^NTR staining in sheep lacked astrocytic labeling. However, digital image analyses revealed increased labeling intensities in preclinical sheep compared with non-infected and terminal sheep in several brain nuclei. This suggests that this receptor is overexpressed in early stages of prion-related neurodegeneration in sheep. Our results confirm a role of p75^NTR in the pathogenesis of classical ovine scrapie in both the natural host and in an experimental transgenic mouse model.

Antineurodegenerative Labdane Diterpenoid Glycosides from the Twigs of Pinus koraiensis

Eleven new labdane-type diterpenoid glycosides, koraiensides A-K (1-11), together with two known analogues were isolated from the twigs of Pinus koraiensis. Their structures were elucidated via NMR, HRMS, and ECD data, DP4+ statistical analysis, and hydrolysis. The metabolites were tested for induction of nerve growth factor in C6 glioma cells to evaluate their potential neuroprotective activity. The compounds were measured for production of nitric oxide levels in lipopolysaccharide (LPS)-activated murine microglia BV2 cells to assess their antineuroinflammatory activity. Compounds 10 and 13 showed NGF secretion inducing effects from C6 glioma cells (162.3 ± 13.9% and 162.7 ± 6.9%, respectively). Compound 6 showed an IC₅₀ value of 24.1 μM, implying significant inhibition of NO production.

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

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

All-Trans Retinoic Acid Exerts Neuroprotective Effects in Amyotrophic Lateral Sclerosis-Like Tg (SOD1*G93A)1Gur Mice

All-trans retinoic acid (ATRA), a ligand of retinoic acid receptors, could regulate various biological processes by activating retinoic acid signals. Recent studies suggested that ATRA displays multiple neuroprotective effects and thereby alleviates the disease progression in a variety of neurological diseases. Our previous studies found that the impaired retinoic acid signal decreased ALDH1A2, an essential synthetase of ATRA, in the spinal cord of ALS mice. Here, we evaluated the neuroprotective and neurorestorative effects of ATRA in a SOD1-G93A transgenic mice model of ALS. We administrated ATRA(3 mg/kg) daily from the onset stage to the progression stage for 5 weeks. Behavioral tests showed that ATRA improved the forelimb grip strength in ALS mice and may slow the disease progression, but not the body weight. ATRA could completely reverse the impaired retinoic acid receptor alpha (RARα) signal in the spinal cord of ALS mice. This effect was accompanied by enhancing the degradation of misfolded proteins via the ubiquitin-proteasome system, regulating the oxidative stress, inhibiting the astrocyte activation, and promoting the neurotrophic signal recovery. Our findings are the first to indicate that the damaged retinoic acid signal is involved in the pathogenesis of ALS, and ATRA could induce the functional neuroprotection via repairing the damaged retinoic acid signal.

Neuroprotective effects of brain-derived neurotrophic factor against amyloid beta 1-40-induced retinal and optic nerve damage

Brain-derived neurotrophic factor (BDNF) could be considered a potential neuroprotective therapy in amyloid beta (Aβ)-associated retinal and optic nerve degeneration. Hence, in this study we investigated the neuroprotective effect of BDNF against Aβ1-40-induced retinal and optic nerve injury. In this study, exposure to Aβ1-40 was associated with retinal and optic nerve injury. TUNEL staining showed significant reduction in the apoptotic cell count in the BDNF-treated group compared with Aβ1-40 group. H&E-stained retinal sections also showed a striking reduction in neuronal cells in the ganglion cell layer (GCL) of retinas fourteen days after Aβ1-40 exposure. By contrast, number of retinal cells was preserved in the retinas of BDNF-treated animals. After Aβ1-40 exposure, visible axonal swelling was observed in optic nerve sections. However, the BDNF-treated group showed fewer changes in optic nerve; axonal swelling was less frequent and less marked. In the present study, exposure to Aβ was associated with oxidative stress, whereas levels of retinal glutathione (GSH), superoxide dismutase (SOD) and catalase were significantly increased in BDNF-treated than in Aβ1-40-treated rats. Both visual object recognition tests using an open-field arena and a Morris water maze showed that BDNF improved rats' ability to recognise visual cues (objects with different shapes) after Aβ1-40 exposure, thus demonstrating that the visual performance of rats was relatively preserved following BDNF treatment. In conclusion, intravitreal treatment with BDNF prevents Aβ1-40-induced retinal cell apoptosis and axon loss in the optic nerve of rats by reducing retinal oxidative stress and restoring retinal BDNF levels.

Müller cells derived neurotrophin-3 inhibits hypoxia-induced photoreceptor apoptosis via the TrkC/ERK pathway

Neurotrophin-3 (NT-3), a neurotrophic factor that mainly binds to the tyrosine kinase C (trkC) receptor, has been shown to play a crucial role in proliferation, differentiation, and survival. However, the role of NT-3 in the hypoxia-induced retinopathy has not been investigated extensively. Here, we created a model of hypoxia (1% O₂) in vitro and found that hypoxia promoted the apoptosis of mouse cone photoreceptor-derived 661W cells, increased the expression of TrkC and cleaved caspase-3. In contrast, the hypoxia-mediated 661W cell apoptosis was markedly alleviated by co-culturing with primary mouse Müller cells. Further mechanism studies revealed that hypoxia increased the synthesis and secretion of NT-3 by Müller cells, and exogenous NT-3 stimulation increased the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 by binding to TrkC in 661W cells. Besides, both siRNA knockdown of TrkC expression and incubation with an ERK-specific inhibitor PD98059 triggered apoptosis in hypoxic 661W cells. Altogether, these data suggest that NT-3 originating from Müller cells protects photoreceptors from hypoxia-induced apoptosis through a TrkC/ERK-dependent pathway. Our findings may facilitate future studies on the therapeutic implications of NT-3 in the treatment of hypoxia-relevant retinal diseases.

Counter effects of Asiaticosids-D through putative neurotransmission on rotenone induced cerebral ganglionic injury in Lumbricus terrestris

Asiaticoside-D (AD) was shown to efficacy of ganglionic degenerated Lumbricus terrestris as a pioneering observation in our earlier research. Though, extract molecular mechanisms of AD for degenerative diseases (DDs) remains largely unknown. We investigated the neuroprotective effects of AD against ROT in cerebral ganglions (CGs) of degenerative L. terrestris. Worms were exposed to 0.4 ppm ROT for 7 days were subjected to co- treatment with 15 ppm of AD. After, CGs was removed. The levels oxidant, non-antioxidant, antioxidant status, ganglioside, ceramide and ceramide glycanase (CGase) were estimated. The m-RNA levels of dopamine transporter (DAT), octopamine transporter (OAT), innexins-9 (inx-9), ionotropic glutamate receptor 3 (iGlu3), heat shock proteins (hsp70), XPRLamide neuropeptide precursor, tyramine beta-hydroxylase (tbh-1) and β- adrenergic receptor kinase-2 (β-ARK2-3) by semi-qRT- PCR. The expression pattern of tyramine beta hydroxylase (TBH), glutamate receptor (iGluR), serotonin transporter (SERT), dopamine transporters (DAT), nerve growth factors (NGF), cytochrome C oxidase (COC), NADH dehydogenase subunit-1 (ND-1), neurotrophin receptor p75 (p75NTR), neuronal nitric oxiside synthase (nNOs) interleukin 1- beta (IL1-β) and tumor necrosis factor alpha (TNF-α) by western blotting. Glutaminergic, serotogenic and dopaminergic toxicity variations were also performed. The levels of oxidant, non-antioxidant, antioxidant status, lipids, proteins and m-RNAs were significantly altered (p < 0.001) on ROT-induced (group II) and their levels were significantly changes (p < 0.05) by ROT+AD in CGs. The sensitive study plan concluded the neuroprotective effects of AD against ROT induced degeneration in worms and suggest that the AD deserves future studies for its use as an effective alternative medicine that could minimize the morbidity of ganglionic degenerative diseases patients.

CDNF Protein Therapy in Parkinson's Disease

Neurotrophic factors (NTF) are a subgroup of growth factors that promote survival and differentiation of neurons. Due to their neuroprotective and neurorestorative properties, their therapeutic potential has been tested in various neurodegenerative diseases. Bioavailability of NTFs in the target tissue remains a major challenge for NTF-based therapies. Various intracerebral delivery approaches, both protein and gene transfer-based, have been tested with varying outcomes. Three growth factors, glial cell-line derived neurotrophic factor (GDNF), neurturin (NRTN) and platelet-derived growth factor (PDGF-BB) have been tested in clinical trials in Parkinson’s disease (PD) during the past 20 years. A new protein can now be added to this list, as cerebral dopamine neurotrophic factor (CDNF) has recently entered clinical trials. Despite their misleading names, CDNF, together with its closest relative mesencephalic astrocyte-derived neurotrophic factor (MANF), form a novel family of unconventional NTF that are both structurally and mechanistically distinct from other growth factors. CDNF and MANF are localized mainly to the lumen of endoplasmic reticulum (ER) and their primary function appears to be modulation of the unfolded protein response (UPR) pathway. Prolonged ER stress, via the UPR signaling pathways, contributes to the pathogenesis in a number of chronic degenerative diseases, and is an important target for therapeutic modulation. Intraputamenally administered recombinant human CDNF has shown robust neurorestorative effects in a number of small and large animal models of PD, and had a good safety profile in preclinical toxicology studies. Intermittent monthly bilateral intraputamenal infusions of CDNF are currently being tested in a randomized placebo-controlled phase I–II clinical study in moderately advanced PD patients. Here, we review the history of growth factor-based clinical trials in PD, and discuss how CDNF differs from the previously tested growth factors.

Müller cells as a target for retinal therapy

Müller cells are specialized glial cells that span the entire retina from the vitreous cavity to the subretinal space. Their functional diversity and unique radial morphology render them particularly interesting targets for new therapeutic approaches. In this review, we reflect on various possibilities for selective Müller cell targeting and describe how some of their cellular mechanisms can be used for retinal neuroprotection. Intriguingly, cross-species investigation of their properties has revealed that Müller cells also have an essential role in retinal regeneration. Although many questions regarding this subject remain, it is clear that Müller cells have unique characteristics that make them suitable targets for the prevention and treatment of numerous retinal diseases.

Neuroprotective Role of Phytochemicals

Neurodegenerative diseases are normally distinguished as disorders with loss of neurons. Various compounds are being tested to treat neurodegenerative diseases (NDs) but they possess solitary symptomatic advantages with numerous side effects. Accumulative studies have been conducted to validate the benefit of phytochemicals to treat neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). In this present review we explored the potential efficacy of phytochemicals such as epigallocatechin-3-galate, berberin, curcumin, resveratrol, quercetin and limonoids against the most common NDs, including Alzheimer's disease (AD) and Parkinson's disease (PD). The beneficial potentials of these phytochemicals have been demonstrated by evidence-based but more extensive investigation needs to be conducted for reducing the progression of AD and PD.

Vrk1 partial Knockdown in Mice Results in Reduced Brain Weight and Mild Motor Dysfunction, and Indicates Neuronal VRK1 Target Pathways

Mutations in Vaccinia-related kinase 1 (VRK1) have emerged as a cause of severe neuronal phenotypes in human, including brain developmental defects and degeneration of spinal motor neurons, leading to Spinal Muscular Atrophy (SMA) or early onset Amyotrophic Lateral Sclerosis (ALS). Vrk1 gene-trap partial Knockout (KO) mice (Vrk1GT3/GT3), which express decreased levels of Vrk1, are sterile due to impaired gamete production. Here, we examined whether this mouse model also presents neuronal phenotypes. We found a 20-50% reduction in Vrk1 expression in neuronal tissues of the Vrk1GT3/GT3 mice, leading to mild neuronal phenotypes including significant but small reduction in brain mass and motor (rotarod) impairment. Analysis of gene expression in the Vrk1GT3/GT3 cortex predicts novel roles for VRK1 in neuronal pathways including neurotrophin signaling, axon guidance and pathways implicated in the pathogenesis of ALS. Together, our studies of the partial KO Vrk1 mice reveal that even moderately reduced levels of Vrk1 expression result in minor neurological impairment and indicate new neuronal pathways likely involving VRK1.

Nanoparticle formulations that allow for sustained delivery and brain targeting of the neuropeptide oxytocin

Oxytocin is a promising candidate for the treatment of social-deficit disorders such as Autism Spectrum Disorder, but oxytocin cannot readily pass the blood-brain barrier. Moreover, oxytocin requires frequent dosing as it is rapidly metabolized in blood. We fabricated four polymeric nanoparticle formulations using poly(lactic-co-glycolic acid) (PLGA) or bovine serum albumin (BSA) as the base material. In order to target them to the brain, we then conjugated the materials to either transferrin or rabies virus glycoprotein (RVG) as targeting ligands. The formulations were characterized in vitro for size, zeta potential, encapsulation efficiency, and release profiles. All formulations showed slightly negative charges and sizes ranging from 100 to 278 nm in diameter, with RVG-conjugated BSA nanoparticles exhibiting the smallest sizes. No formulation was found to be immunogenic or cytotoxic. The encapsulation efficiency was ≥75% for all nanoparticle formulations. Release studies demonstrated that BSA nanoparticle formulation exhibited a faster initial burst of release compared to PLGA particles, in addition to later sustained release. This initial burst release would be favorable for clinical dosing as therapeutic effects could be quickly established, especially in combination with additional sustained release to maintain the therapeutic effects. Our size and release profile data indicate that RVG-conjugated BSA nanoparticles are the most favorable formulation for brain delivery of oxytocin.

Neuroprotective strategies for retinal disease

Diseases that affect the eye, including photoreceptor degeneration, diabetic retinopathy, and glaucoma, affect 11.8 million people in the US, resulting in vision loss and blindness. Loss of sight affects patient quality of life and puts an economic burden both on individuals and the greater healthcare system. Despite the urgent need for treatments, few effective options currently exist in the clinic. Here, we review research on promising neuroprotective strategies that promote neuronal survival with the potential to protect against vision loss and retinal cell death. Due to the large number of neuroprotective strategies, we restricted our review to approaches that we had direct experience with in the laboratory. We focus on drugs that target survival pathways, including bile acids like UDCA and TUDCA, steroid hormones like progesterone, therapies that target retinal dopamine, and neurotrophic factors. In addition, we review rehabilitative methods that increase endogenous repair mechanisms, including exercise and electrical stimulation therapies. For each approach, we provide background on the neuroprotective strategy, including history of use in other diseases; describe potential mechanisms of action; review the body of research performed in the retina thus far, both in animals and in humans; and discuss considerations when translating each treatment to the clinic and to the retina, including which therapies show the most promise for each retinal disease. Despite the high incidence of retinal diseases and the complexity of mechanisms involved, several promising neuroprotective treatments provide hope to prevent blindness. We discuss attractive candidates here with the goal of furthering retinal research in critical areas to rapidly translate neuroprotective strategies into the clinic.

Safety and feasibility of transcranial direct current stimulation in amyotrophic lateral sclerosis - a pilot study with a single subject experimental design

INTRODUCTION

Transcranial direct current stimulation (tDCS) has been explored as a neuromodulatory tool to prime motor function in several neurological disorders. Studies using tDCS in amyotrophic lateral sclerosis (ALS) are limited. We investigated the safety, feasibility and effects of long-term tDCS in an individual with ALS.

METHODS

A 36-year-old male diagnosed with clinically definite ALS received 12 sessions each of anodal, sham, and cathodal tDCS. Outcome measures included disease progression (revised ALS functional rating scale (ALSFRS-R)), clinical measures of endurance and mobility, and corticomotor excitability.

RESULTS

No adverse events or change in disease progression were noticed during the study. Small improvement in gait speed (15% increase) was noticed with anodal tDCS only.

CONCLUSIONS

This case study demonstrates the safety and feasibility of long-term facilitatory and inhibitory tDCS on a single participant with ALS. This study serves as a guideline for implementing tDCS in future ALS trials.

Kidins220 Correlates with Tau in Alzheimer's Disease Brain and Cerebrospinal Fluid

Identification of neurodegeneration-monitoring biomarkers would be of great clinical value for Alzheimer's disease (AD) diagnosis. Using N- or C-terminal antibodies, we studied the pro-survival synaptic effector, Kidins220, in the brain and cerebrospinal fluid (CSF) of controls and AD patients. Only the N-terminal antibody showed a positive correlation between Kidins220 and phosphorylated tau in AD brains. Using this antibody, Kidins220 was detected in CSF from AD patients where it positively correlated with CSF phosphorylated tau and tau. This study highlights the potential of Kidins220 as a CSF biomarker in AD.

Sex Differences in Risk for Alzheimer's Disease Related to Neurotrophin Gene Polymorphisms: The Cache County Memory Study

Neurotrophins, including nerve-growth factor and brain-derived neurotrophic factor, have been implicated in Alzheimer's disease (AD). Associations between AD and neurotrophin signaling genes have been inconsistent, with few studies examining sex differences in risk. We examined four single-nucleotide polymorphisms (SNPs) involved in neurotrophin signaling (rs6265, rs56164415, rs2289656, rs2072446) and risk for AD by sex in a population-based sample of older adults. Three thousand four hundred and ninety-nine individuals without dementia at baseline [mean (standard deviation) age = 74.64 (6.84), 58% female] underwent dementia screening and assessment over four triennial waves. Cox regression was used to examine time to AD or right censoring for each SNP. Female carriers of the minor T allele for rs2072446 and rs56164415 had a 60% (hazard ratio [HR] = 1.60, 95% confidence interval [CI] = 1.02-2.51) and 93% (HR = 1.93, 95% CI = 1.30-2.84) higher hazard for AD, respectively, than male noncarriers of the T allele. Furthermore, male carriers of the T allele of rs2072446 had a 61% lower hazard (HR = 0.39, 95% CI = 0.14-1.06) than male noncarriers at trend-level significance (p = .07). The association between certain neurotrophin gene polymorphisms and AD differs by sex and may explain inconsistent findings in the literature.

Effect of Estradiol on Neurotrophin Receptors in Basal Forebrain Cholinergic Neurons: Relevance for Alzheimer's Disease

The basal forebrain is home to the largest population of cholinergic neurons in the brain. These neurons are involved in a number of cognitive functions including attention, learning and memory. Basal forebrain cholinergic neurons (BFCNs) are particularly vulnerable in a number of neurological diseases with the most notable being Alzheimer's disease, with evidence for a link between decreasing cholinergic markers and the degree of cognitive impairment. The neurotrophin growth factor system is present on these BFCNs and has been shown to promote survival and differentiation on these neurons. Clinical and animal model studies have demonstrated the neuroprotective effects of 17β-estradiol (E2) on neurodegeneration in BFCNs. It is believed that E2 interacts with neurotrophin signaling on cholinergic neurons to mediate these beneficial effects. Evidence presented in our recent study confirms that altering the levels of circulating E2 levels via ovariectomy and E2 replacement significantly affects the expression of the neurotrophin receptors on BFCN. However, we also showed that E2 differentially regulates neurotrophin receptor expression on BFCNs with effects depending on neurotrophin receptor type and neuroanatomical location. In this review, we aim to survey the current literature to understand the influence of E2 on the neurotrophin system, and the receptors and signaling pathways it mediates on BFCN. In addition, we summarize the physiological and pathophysiological significance of E2 actions on the neurotrophin system in BFCN, especially focusing on changes related to Alzheimer's disease.

Low-Intensity Pulsed Ultrasound Enhances Nerve Growth Factor-Induced Neurite Outgrowth through Mechanotransduction-Mediated ERK1/2-CREB-Trx-1 Signaling

Enhancing the action of nerve growth factor (NGF) is a potential therapeutic approach to neural regeneration. To facilitate neural regeneration, we investigated whether combining low-intensity pulsed ultrasound (LIPUS) and NGF could promote neurite outgrowth, an essential process in neural regeneration. In the present study, PC12 cells were subjected to a combination of LIPUS (1 MHz, 30 or 50 mW/cm², 20% duty cycle and 100-Hz pulse repetition frequency, 10 min every other day) and NGF (50 ng/mL) treatment, and then neurite outgrowth was compared. Our findings indicated that the combined treatment with LIPUS (50 mW/cm²) and NGF (50 ng/mL) promotes neurite outgrowth that is comparable to that achieved by NGF (100 ng/mL) treatment alone. LIPUS significantly increased NGF-induced neurite length, but not neurite branching. These effects were attributed to the enhancing effects of LIPUS on NGF-induced phosphorylation of ERK1/2 and CREB and the expression of thioredoxin (Trx-1). Furthermore, blockage of stretch-activated ion channels with Gd³⁺ suppressed the stimulating effects of LIPUS on NGF-induced neurite outgrowth and the downstream signaling activation. Taken together, our findings suggest that LIPUS enhances NGF-induced neurite outgrowth through mechanotransduction-mediated signaling of the ERK1/2-CREB-Trx-1 pathway. The combination of LIPUS and NGF could potentially be used for the treatment of nerve injury and neurodegenerative diseases.

Development of Precision Small-Molecule Proneurotrophic Therapies for Neurodegenerative Diseases

Age-related neurodegenerative diseases, such as Alzheimer's disease, will represent one of the largest future burdens on worldwide healthcare systems due to the increasing proportion of elderly in our society. As deficiencies in neurotrophins are implicated in the pathogenesis of many age-related neurodegenerative disorders, it is reasonable to consider that global neurotrophin resistance may also become a major healthcare threat. Central nervous system networks are effectively maintained through aging by neuroprotective and neuroplasticity signaling mechanisms which are predominantly controlled by neurotrophin receptor signaling. Neurotrophin receptors are single pass receptor tyrosine kinases that form dimeric structures upon ligand binding to initiate cellular signaling events that control many protective and plasticity-related pathways. Declining functionality of the neurotrophin ligand-receptor system is considered one of the hallmarks of neuropathological aging. Therefore, it is imperative to develop effective therapeutic strategies to contend with this significant issue. While the therapeutic applications of cognate ligands for neurotrophin receptors are limited, the development of nonpeptidergic, small-molecule ligands can overcome these limitations, and productively regulate this important receptor system with beneficial effects. Using our advanced knowledge of the high-dimensionality complexity of receptor systems, the future generation of precision medicines targeting these systems will be an attainable goal.

Lichen-derived compounds show potential for central nervous system therapeutics

BACKGROUND

Natural products from lichens are widely investigated for their biological properties, yet their potential as central nervous system (CNS) therapeutic agents is less explored.

PURPOSE

The present study investigated the neuroactive properties of selected lichen compounds (atranorin, perlatolic acid, physodic acid and usnic acid), for their neurotrophic, neurogenic and acetylcholine esterase (AChE) activities.

METHODS

Neurotrophic activity (neurite outgrowth) was determined using murine neuroblastoma Neuro2A cells. A MTT assay was performed to assess the cytotoxicity of compounds at optimum neurotrophic activity. Neuro2A cells treated with neurotrophic lichen compounds were used for RT-PCR to evaluate the induction of genes that code for the neurotrophic markers BDNF and NGF. Immunoblotting was used to assess acetyl H3 and H4 levels, the epigenetic markers associated with neurotrophic and/or neurogenic activity. The neurogenic property of the compounds was determined using murine hippocampal primary cultures. AChE inhibition activity was performed using a modified Ellman's esterase method.

RESULTS

Lichen compounds atranorin, perlatolic acid, physodic acid and (+)-usnic acid showed neurotrophic activity in a preliminary cell-based screening based on Neuro2A neurite outgrowth. Except for usnic acid, no cytotoxic effects were observed for the two depsides (atranorin and perlatolic acid) and the alkyl depsidone (physodic acid). Perlatolic acid appears to be promising, as it also exhibited AChE inhibition activity and potent proneurogenic activity. The neurotrophic lichen compounds (atranorin, perlatolic acid, physodic acid) modulated the gene expression of BDNF and NGF. In addition, perlatolic acid showed increased protein levels of acetyl H3 and H4 in Neuro2A cells.

CONCLUSION

These lichen depsides and depsidones showed neuroactive properties in vitro (Neuro2A cells) and ex vivo (primary neural stem or progenitor cells), suggesting their potential to treat CNS disorders.

State-dependent increase in the levels of neurotrophin-3 and neurotrophin-4/5 in patients with bipolar disorder: A meta-analysis

Bipolar disorder (BD) is one of the most serious psychiatric disorders in the world, but its pathophysiology is still unclear. Regulation of neurotrophic factors have been thought to play a role in this process. There have been inconsistent findings regarding the differences in blood neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5) between patients with BD and healthy controls (HCs). The aim of the current meta-analysis is to examine the changes in the levels of NT-3 and NT-4/5 in BD patients at different affective states. Eight articles (including 465 BD patients and 353 HCs) were included in the analysis, and their results were pooled by using a random effects model. We found the levels of both NT-3 (p = 0.0046) and NT-4/5 (p = 0.0003) were significantly increased in BD patients, compared to HCs. Through subgroup analysis, this increase persisted only in patients in depressed state (p = 0.0038 for NT-3 and p = 0.0001 for NT-4/5), but not in manic or euthymic state. In addition, we found the differences in NT-3 and NT-4/5 were significantly associated with the duration of illness, but not by the mean age or female proportion. Our results suggest a state-dependent increase in NT-3 and NT-4/5 levels in patients with BD. Further studies are needed to examine dynamic changes of these neurotrophins in BD patients along the disease course.

[A new strategy for preventive and functional therapeutic methods for dementia--approach using natural products]

Alzheimer's disease (AD) has become a serious social problem in Japan. However, effective preventive and fundamental therapeutic methods for AD have not yet been developed. Using a new strategy in the course of our survey of numerous natural resouces having neurotrophic activity, we isolated a variety of active constituents and proved their pharmacological properties. As a result, we successfully found nobiletin, a compound with anti-dementia activity that comes from citrus peels. Also, we have demonstrated that nobiletin ameliorates cognitive impairment in several dementia model animals such as chronically amyloid β(Aβ) infused rats, amyloid precursor protein transgenic (APPTg) mice, olfactory-bulbectomized (OBX) mice, N-methyl-D-aspartate (NMDA) receptor antagonist (MK-801)-treated mice, senescence-accelated mice and bilaterial common carotid arteries occlusion mice. In a APPTg mouse of AD, nobiletin greatly improved memory impairment, and this was accompanied by a marked decrease in Aβ deposition. Also, in OBX mice memory impairment was markedly recoverd by nobiletin, accompanied by improvement of a decrease indensity of cholinergic neurons. Interestingly, nobiletin improves age-related congnitive impairment and decreased hyperphosphorylation of tau as well as oxidative stress in senescence-accelerated mice. In cultured cells, nobiletin reversed the Aβ-induced inhibition of glutamate-induced increases in cAMP response element binding protein (CREB) phosphorylation and modulated gen expression of thioredoxin-interacting protein and NMDA resceptor subunits. These results suggest that nobiletin prevents memory impairment and exhibits a protecting action against neurodgeneration in AD model animals. Nobiletin and citrus peels thus have potential as functional foods for prevention of dementia.

[Basic Research on Neurotrophic Factors and Its Application to Medical Uses]

The author has studied nerve growth factor (NGF) and its family of neurotrophic factors (neurotrophins) for over 40 years. During the first 20 years, my laboratory established a highly sensitive enzyme immunoassay for NGF and analyzed the regulatory mechanism of NGF synthesis in cultured primary cells. Fibroblast cells cultured from peripheral organs such as the heart and astrocytes from the brain produced a substantial amount of NGF in a growth-dependent manner. Furthermore, synthesis of NGF in these cells could be upregulated by catechol compounds including catecholamines. This observation might explain a physiological relation between the level of NGF mRNA and the density of innervation in the peripheral sympathetic nervous systems. Over the subsequent 20 years, my laboratory investigated the physiological functions of neurotrophic factors, including neurotrophins, during development or post-injury and found that brain-derived neurotrophic factor (BDNF) plays a role in the formation of the laminar structure of the cerebral cortex. In addition, my laboratory discovered that endogenous glial cell line-derived neurotrophic factor (GDNF) contributes to the amelioration of motor activity after spinal cord injury. Therefore we aimed to develop low-molecular weight compounds that generate neurotrophic factor-like intracellular signals to protect or ameliorate neurological/psychiatric diseases. 2-Decenoic acid derivatives and other similar molecules could protect or ameliorate in animal models of mood disorders such as depression and enhance recovery from spinal cord injury-induced motor paralysis. Compounds that can generate neurotrophin-like signals in neurons are expected to be developed as therapeutic drugs for certain neurological or psychiatric disorders.

The intersection between growth factors, autophagy and ER stress: A new target to treat neurodegenerative diseases?

One of the salient features of most neurodegenerative diseases is the aggregation of specific proteins in the brain. This proteostasis imbalance is proposed as a key event triggering the neurodegenerative cascade. The unfolded protein response (UPR) and autophagy pathways are emerging as critical processes implicated in handling disease-related misfolded proteins. However, in some conditions, perturbations in the buffering capacity of the proteostasis network may be part of the etiology of the disease. Thus, pharmacological or gene therapy strategies to enhance autophagy or UPR responses are becoming an attractive target for disease intervention. Here, we discuss current evidence depicting the complex involvement of autophagy and ER stress in brain diseases. Novel pathways to modulate protein misfolding are discussed including the relation between aging and growth factor signaling. This article is part of a Special Issue entitled SI:Autophagy.

Brain ischaemia induces shedding of a BDNF-scavenger ectodomain from TrkB receptors by excitotoxicity activation of metalloproteinases and γ-secretases

Stroke remains a leading cause of death and disability in the world with limited therapies available to restrict brain damage or improve functional recovery after cerebral ischaemia. A promising strategy currently under investigation is the promotion of brain-derived neurotrophic factor (BDNF) signalling through tropomyosin-related kinase B (TrkB) receptors, a pathway essential for neuronal survival and function. However, TrkB and BDNF-signalling are impaired by excitotoxicity, a primary pathological process in stroke also associated with neurodegenerative diseases. Pathological imbalance of TrkB isoforms is critical in neurodegeneration and is caused by calpain processing of BDNF high affinity full-length receptor (TrkB-FL) and an inversion of the transcriptional pattern of the Ntrk2 gene, to favour expression of the truncated isoform TrkB-T1 over TrkB-FL. We report here that both TrkB-FL and neuronal TrkB-T1 also undergo ectodomain shedding by metalloproteinases activated after ischaemic injury or excitotoxic damage of cortical neurons. Subsequently, the remaining membrane-bound C-terminal fragments (CTFs) are cleaved by γ-secretases within the transmembrane region, releasing their intracellular domains (ICDs) into the cytosol. Therefore, we identify TrkB-FL and TrkB-T1 as new substrates of regulated intramembrane proteolysis (RIP), a mechanism that highly contributes to TrkB-T1 regulation in ischaemia but is minor for TrkB-FL which is mainly processed by calpain. However, since the secreted TrkB ectodomain acts as a BDNF scavenger and significantly alters BDNF/TrkB signalling, the mechanism of RIP could contribute to neuronal death in excitotoxicity. These results are highly relevant since they reveal new targets for the rational design of therapies to treat stroke and other pathologies with an excitotoxic component.

C6 Glioma-Secreted NGF and FGF2 Regulate Neuronal APP Processing Through Up-Regulation of ADAM10 and Down-Regulation of BACE1, Respectively

Excessive accumulation of amyloid-β (Aβ) caused by cleavage of amyloid precursor protein (APP) is thought to be the primary cause of Alzheimer's disease (AD). Two key enzymes ADAM10 and BACE1 are involved in the initial cleavage of APP, resulting in the onset of two pathways, the amyloidogenic pathway and the non-amyloidogenic pathway, respectively. Altering APP metabolism towards the non-amyloidogenic pathway is thought to reduce Aβ production. It has been reported that, in vivo, exogenous neurotrophic factors make APP apt to entering the non-amyloidogenic pathway. Since astrocytes secrete a battery of neurotrophic factors, we investigated the role of astrocyte-derived factors in the dynamics of Aβ generation in neural cells. Results show that C6 glioma cell-conditioned medium (GCM), obtained from cultured astrocyte-derived C6 glioma cells, inhibit Aβ1-42 production and shift APP processing towards the non-amyloidogenic pathway in APPswe-HEK293 cells. Such effect is attributed to two key APP cleavage enzymes, ADAM10 and BACE1. Two neurotrophic factors in the GCM, nerve growth factor and fibroblast growth factor 2, are responsible for the up-regulation of ADAM10 and down-regulation of BACE1, respectively. Our findings enhance our understanding of the relationship between astrocytes and Aβ generation, indicating that stimulation of astrocytic neurotrophic factors could slow AD progression.

Update on the role of p75NTR in neurological disorders: A novel therapeutic target

As a low-affinity neurotrophins receptor, p75 neurotrophin receptor (p75NTR) is a transmembrane receptor involved in a diverse array of cellular responses, including apoptosis, survival, neurite outgrowth, migration, and cell cycle arrest, which may be related to some neurological disorders, such as Alzheimer's disease (AD), schizophrenia, major depressive disorder (MDD), posttraumatic stress disorder (PTSD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Indeed, a series of studies during the last decade has demonstrated that the p75NTR signaling plays key roles in most aspects of the neurological disorder diseases. In spite of the limited information available, this review still tried to summary the relationship between p75NTR and diverse neurological disorder diseases, and tried to further clarify the possible mechanism, which may provide a novel therapeutic target for the treatment of neurological disorders.

Development of a neuroprotective peptide that preserves survival pathways by preventing Kidins220/ARMS calpain processing induced by excitotoxicity

Kinase D-interacting substrate of 220 kDa (Kidins220), also known as ankyrin repeat-rich membrane spanning (ARMS), has a central role in the coordination of receptor crosstalk and the integration of signaling pathways essential for neuronal differentiation, survival and function. This protein is a shared downstream effector for neurotrophin- and ephrin-receptors signaling that also interacts with the N-methyl-d-aspartate type of glutamate receptors (NMDARs). Failures in neurotrophic support and glutamate signaling are involved in pathologies related to excitotoxicity and/or neurodegeneration, where different components of these dynamic protein complexes result altered by a combination of mechanisms. In the case of Kidins220/ARMS, overactivation of NMDARs in excitotoxicity and cerebral ischemia triggers its downregulation, which contributes to neuronal death. This key role in neuronal life/death decisions encouraged us to investigate Kidins220/ARMS as a novel therapeutic target for neuroprotection. As the main mechanism of Kidins220/ARMS downregulation in excitotoxicity is proteolysis by calpain, we decided to develop cell-penetrating peptides (CPPs) that could result in neuroprotection by interference of this processing. To this aim, we first analyzed in detail Kidins220/ARMS cleavage produced in vitro and in vivo, identifying a major calpain processing site in its C-terminal region (between amino acids 1669 and 1670) within a sequence motif highly conserved in vertebrates. Then, we designed a 25-amino acids CPP (Tat-K) containing a short Kidins220/ARMS sequence enclosing the identified calpain site (amino acids 1668–1681) fused to the HIV-1 Tat protein basic domain, able to confer membrane permeability to attached cargoes. Transduction of cortical neurons with Tat-K reduced Kidins220/ARMS calpain processing in a dose- and time-dependent manner upon excitotoxic damage and allowed preservation of the activity of pERK1/2 and pCREB, signaling molecules central to neuronal survival and functioning. Importantly, these effects were associated to a significant increase in neuronal viability. This Kidins220/ARMS-derived peptide merits further research to develop novel neuroprotective therapies for excitotoxicity-associated pathologies.

Characterizing autism spectrum disorders by key biochemical pathways

The genetic and phenotypic heterogeneity of autism spectrum disorders (ASD) presents a substantial challenge for diagnosis, classification, research, and treatment. Investigations into the underlying molecular etiology of ASD have often yielded mixed and at times opposing findings. Defining the molecular and biochemical underpinnings of heterogeneity in ASD is crucial to our understanding of the pathophysiological development of the disorder, and has the potential to assist in diagnosis and the rational design of clinical trials. In this review, we propose that genetically diverse forms of ASD may be usefully parsed into entities resulting from converse patterns of growth regulation at the molecular level, which lead to the correlates of general synaptic and neural overgrowth or undergrowth. Abnormal brain growth during development is a characteristic feature that has been observed both in children with autism and in mouse models of autism. We review evidence from syndromic and non-syndromic ASD to suggest that entities currently classified as autism may fundamentally differ by underlying pro- or anti-growth abnormalities in key biochemical pathways, giving rise to either excessive or reduced synaptic connectivity in affected brain regions. We posit that this classification strategy has the potential not only to aid research efforts, but also to ultimately facilitate early diagnosis and direct appropriate therapeutic interventions.

Neuritogenic Activity of Tetradecyl 2,3-Dihydroxybenzoate Is Mediated through the Insulin-Like Growth Factor 1 Receptor/Phosphatidylinositol 3 Kinase/Mitogen-Activated Protein Kinase Signaling Pathway

Tetradecyl 2,3-dihydroxybenzoate (ABG-001) is a lead compound derived from neuritogenic gentisides. In the present study, we investigated the mechanism by which ABG-001 induces neurite outgrowth in a rat adrenal pheochromocytoma cell line (PC12). Inhibitors of insulin-like growth factor 1 (IGF-1) receptor, phosphatidylinositol 3-kinase (PI3K), and extracellular signal-regulated kinase (ERK) 1/2 significantly decreased ABG-001-induced neurite outgrowth. Western blot analysis revealed that ABG-001 significantly induced phosphorylation of IGF-1 receptor, protein kinase B (Akt), ERK, and cAMP responsive element-binding protein (CREB). These effects were markedly reduced by addition of the corresponding inhibitors. We also found that ABG-001-induced neurite outgrowth was reduced by protein kinase C inhibitor as well as small-interfering RNA against the IGF-1 receptor. Furthermore, like ABG-001, IGF-1 also induced neurite outgrowth of PC12 cells, and low-dose nerve growth factor augmented the observed effects of ABG-001 on neurite outgrowth. These results suggest that ABG-001 targets the IGF-1 receptor and activates PI3K, mitogen-activated protein kinase, and their downstream signaling cascades to induce neurite outgrowth.

Deletion of the Neurotrophic Factor neudesin Prevents Diet-induced Obesity by Increased Sympathetic Activity

Some neurotrophic factors, which are potent regulators of neuronal development and function, have recently been implicated in the control of energy balance by increasing energy expenditure. We previously identified neudesin as a novel neurotrophic factor with potential roles in the central nervous system. Although neudesin is also expressed in various peripheral tissues including adipose tissue, its physiological roles have not yet been elucidated. We found that neudesin knockout (KO) mice were resistant to high-fat diet-induced obesity and obesity-related metabolic dysfunctions. neudesin KO mice exhibited increased energy expenditure due to increased sympathetic activity, which resulted in increased heat production and fatty acid oxidation in brown adipose tissue and enhanced lipolysis in white adipose tissue. Thus, neudesin, which may be a negative regulator of sympathetic activity, could represent a novel regulator of the development of obesity and obesity-related metabolic dysfunctions.

Serum brain-derived neurotrophic factor differences between the luteal and follicular phases in premenstrual dysphoric disorder

OBJECTIVE

We hypothesized that comparison of the serum brain-derived neurotrophic factor (BDNF) levels between women with premenstrual dysphoric disorder (PMDD) and women without PMDD in the luteal and follicular phases of their menstrual cycles would reflect the altered neuromodulator responses that compensate the underlying pathogenesis in PMDD.

METHOD

Twenty-nine participants without PMDD and 20 with PMDD were enrolled in the study. The serum BDNF, estrogen and progesterone levels were assessed at the follicular and luteal phases in their two consecutive menstrual cycles.

RESULTS

Participants with PMDD had significantly higher luteal serum BDNF levels than the control subjects. The serum BDNF levels were significantly higher in the luteal phase than in the follicular phase in women with PMDD. The difference in the serum BDNF levels between the luteal and follicular phases were significantly higher in the PMDD patients than in the control.

CONCLUSIONS

The higher serum BDNF levels in the luteal phase in the PMDD patients may reflect compensatory process that results in subsequent improvement of the PMDD-associated depressive symptoms in the follicular phase. The higher difference in the serum BDNF levels between the phases in PMDD patients may reflect an altered neuromodulator response.

A novel Prins cascade process for the stereoselective synthesis of oxa-bicycles

E- and Z-9-Methyldeca-3,8-dien-1-ols undergo smooth cyclization with aldehydes in the presence of 20 mol% AgSbF6 under extremely mild conditions to generate the corresponding oxa-bicycles in good yields with excellent selectivity. In fact, E-olefin affords the trans-product exclusively, whereas the Z-olefin gives the cis-product predominantly. In the case of E- or Z-8-methylnona-3,8-dien-1-ol, the product is formed via the termination of Prins cyclization with an allylic C-H bond through olefin migration. The termination of Prins cyclization with tethered olefin is an unprecedented reaction, which provides a useful motif of various natural products.

Systemically administered brain-targeted nanoparticles transport peptides across the blood-brain barrier and provide neuroprotection

Although growth factors and anti-apoptotic peptides have been shown to be neuroprotective in stroke models, translation of these experimental findings to clinic is hampered by limited penetration of peptides to the brain. Here, we show that a large peptide like the basic fibroblast growth factor (bFGF) and a small peptide inhibitor of caspase-3 (z-DEVD-FMK) can effectively be transported to the brain after systemic administration by incorporating these peptides to brain-targeted nanoparticles (NPs). Chitosan NPs were loaded with peptides and then functionalized by conjugating with antibodies directed against the transferrin receptor-1 on brain endothelia to induce receptor-mediated transcytosis across the blood-brain barrier (BBB). Pre-ischemic systemic administration of bFGF- or z-DEVD-FMK-loaded NPs significantly decreased the infarct volume after 2-hour middle cerebral artery occlusion and 22-hour reperfusion in mice. Co-administration of bFGF- or z-DEVD-FMK-loaded NPs reduced the infarct volume further and provided a 3-hour therapeutic window. bFGF-loaded NPs were histologically detected in the brain parenchyma and also restored ischemia-induced Akt dephosphorylation. The neuroprotection was not observed when receptor-mediated transcytosis was inhibited with imatinib or when bFGF-loaded NPs were not conjugated with the targeting antibody, which enables them to cross the BBB. Nanoparticles targeted to brain are promising drug carriers to transport large as well as small BBB-impermeable therapeutics for neuroprotection against stroke.

Stem cell treatment of degenerative eye disease

Stem cell therapies are being explored extensively as treatments for degenerative eye disease, either for replacing lost neurons, restoring neural circuits or, based on more recent evidence, as paracrine-mediated therapies in which stem cell-derived trophic factors protect compromised endogenous retinal neurons from death and induce the growth of new connections. Retinal progenitor phenotypes induced from embryonic stem cells/induced pluripotent stem cells (ESCs/iPSCs) and endogenous retinal stem cells may replace lost photoreceptors and retinal pigment epithelial (RPE) cells and restore vision in the diseased eye, whereas treatment of injured retinal ganglion cells (RGCs) has so far been reliant on mesenchymal stem cells (MSC). Here, we review the properties of non-retinal-derived adult stem cells, in particular neural stem cells (NSCs), MSC derived from bone marrow (BMSC), adipose tissues (ADSC) and dental pulp (DPSC), together with ESC/iPSC and discuss and compare their potential advantages as therapies designed to provide trophic support, repair and replacement of retinal neurons, RPE and glia in degenerative retinal diseases. We conclude that ESCs/iPSCs have the potential to replace lost retinal cells, whereas MSC may be a useful source of paracrine factors that protect RGC and stimulate regeneration of their axons in the optic nerve in degenerate eye disease. NSC may have potential as both a source of replacement cells and also as mediators of paracrine treatment.

The deubiquitinating enzyme UBPy/USP8 interacts with TrkA and inhibits neuronal differentiation in PC12 cells

The tropomyosin-related kinase (Trk) family of receptor tyrosine kinases controls synaptic function, plasticity and sustains differentiation, morphology, and neuronal cell survival. Understanding Trk receptors down-regulation and recycling is a crucial step to point out sympathetic and sensory neuron function and survival. PC12 cells derived from pheochromocytoma of the rat adrenal medulla have been widely used as a model system for studies of neuronal differentiation as they respond to nerve growth factor (NGF) with a dramatic change in phenotype and acquire a number of properties characteristic of sympathetic neurons. In this study we demonstrated that in PC12 cells the TrkA receptor interacts with the deubiquitinating enzyme USP8/UBPy in a NGF-dependent manner and that it is deubiquitinated in vivo and in vitro by USP8. USP8 overexpression blocked NGF-induced neurites outgrowth while the overexpression of the catalytically inactive mutant USP8/UBPy(C748A) caused a marked increase of cell differentiation. Localization and biochemical experiments have point out that USP8 and TrkA partially co-localize in endosomes after NGF stimulation. Finally we have studied the role played by USP8 on TrkA turnover; using specific siRNA for USP8 we found that USP8 knockdown increases TrkA half-life, suggesting that the deubiquitinating activity of USP8 promotes TrkA degradation.