Permeability of the blood-brain barrier to neurotrophins

Delayed intramuscular human neurotrophin-3 improves recovery in adult and elderly rats after stroke

There is an urgent need for a therapy that reverses disability after stroke when initiated in a time frame suitable for the majority of new victims. We show here that intramuscular delivery of neurotrophin-3 (NT3, encoded by NTF3) can induce sensorimotor recovery when treatment is initiated 24 h after stroke. Specifically, in two randomized, blinded preclinical trials, we show improved sensory and locomotor function in adult (6 months) and elderly (18 months) rats treated 24 h following cortical ischaemic stroke with human NT3 delivered using a clinically approved serotype of adeno-associated viral vector (AAV1). Importantly, AAV1-hNT3 was given in a clinically-feasible timeframe using a straightforward, targeted route (injections into disabled forelimb muscles). Magnetic resonance imaging and histology showed that recovery was not due to neuroprotection, as expected given the delayed treatment. Rather, treatment caused corticospinal axons from the less affected hemisphere to sprout in the spinal cord. This treatment is the first gene therapy that reverses disability after stroke when administered intramuscularly in an elderly body. Importantly, phase I and II clinical trials by others show that repeated, peripherally administered high doses of recombinant NT3 are safe and well tolerated in humans with other conditions. This paves the way for NT3 as a therapy for stroke.

Alzheimer's Disease: Mechanism and Approach to Cell Therapy

Alzheimer’s disease (AD) is the most common form of dementia. The risk of AD increases with age. Although two of the main pathological features of AD, amyloid plaques and neurofibrillary tangles, were already recognized by Alois Alzheimer at the beginning of the 20th century, the pathogenesis of the disease remains unsettled. Therapeutic approaches targeting plaques or tangles have not yet resulted in satisfactory improvements in AD treatment. This may, in part, be due to early-onset and late-onset AD pathogenesis being underpinned by different mechanisms. Most animal models of AD are generated from gene mutations involved in early onset familial AD, accounting for only 1% of all cases, which may consequently complicate our understanding of AD mechanisms. In this article, the authors discuss the pathogenesis of AD according to the two main neuropathologies, including senescence-related mechanisms and possible treatments using stem cells, namely mesenchymal and neural stem cells.

Nerve growth factor for the treatment of spinocerebellar ataxia type 3: an open-label study

BACKGROUND

Spinocerebellar ataxia type 3 (SCA3) is the most common subtype of SCA worldwide, and runs a slowly progressive and unremitting disease course. There is currently no curable treatment available. Growing evidence has suggested that nerve growth factor (NGF) may have therapeutic effects in neurodegenerative diseases, and possibly also in SCA3. The objective of this study was to test the efficacy of NGF in SCA3 patients.

METHODS

We performed an open-label prospective study in genetically confirmed adult (>18 years old) SCA3 patients. NGF was administered by intramuscular injection (18 μg once daily) for 28 days consecutively. All the patients were evaluated at baseline and 2 and 4 weeks after treatment using the Chinese version of the scale for assessment and rating of ataxia (SARA).

RESULTS

Twenty-one SCA3 patients (10 men and 11 women, mean age 39.14 ± 7.81 years, mean disease duration 4.14 ± 1.90 years, mean CAG repeats number 77.57 ± 2.27) were enrolled. After 28 days of NGF treatment, the mean total SARA score decreased significantly from a baseline of 8.48 ± 2.40 to 6.30 ± 1.87 (P < 0.001). Subsections SARA scores also showed significant improvements in stance (P = 0.003), speech (P = 0.023), finger chase (P = 0.015), fast alternating hand movements (P = 0.009), and heel-shin slide (P = 0.001).

CONCLUSIONS

Our preliminary data suggest that NGF may be effective in treating patients with SCA3.

Role of the endogenous nitric oxide inhibitor asymmetric dimethylarginine (ADMA) and brain-derived neurotrophic factor (BDNF) in depression and behavioural changes: clinical and preclinical data in chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) exhibit a high prevalence of neuropsychiatric alterations, including depression and behavioural changes. CKD is also associated with decreased physical activity not fully explained by co-morbidities. In patients without CKD, the brain-derived neurotropic factor (BDNF) as well as the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA) had been suspected to be involved in major depression. The aim of our study was to examine the role of ADMA and BDNF in the behaviour of haemodialysis patients (CKD5D) as well as in a rat model of 5/6 nephrectomy and chronic ADMA infusion alone.

METHODS

Eleven (5F/6M) CKD5D patients underwent Beck Depression Inventory (BDI) testing along with analysis of ADMA and BDNF. Male Sprague-Dawley rats were randomly assigned to four groups: (i) saline infusion; (ii) ADMA (250 µg/kg/day) infusion via osmotic mini pumps; (iii) 5/6 nephrectomy; (iv) untreated controls. After 28 days, the animals underwent behavioural tests measuring anxiety, locomotion and investigative behaviour. Animals were sacrificed, blood samples were drawn and analysed and hippocampal immunohistology for BDNF was performed.

RESULTS

In CKD5D patients, decreased BDNF levels correlated with higher scores of depression (Pearson r = -0.8156, P = 0.002). ADMA infusion led to a significant decrease of BDNF while the decrease of BDNF in 5/6 nephrectomy was not significant. However, an attenuated hippocampal BDNF expression could be detected in 5/6 nephrecomized animals. Decreased spontaneous locomotor activity was shown in ADMA-infused rats [15.9 (13.5-26.1) lines crossed/min] and 5/6 nephrectomy [14.6 (6.1-20.2) lines crossed/min] when compared with controls [32.5 (15.3-42.4) lines crossed/min]. Anxiety-like behaviour tested by hole investigation time was significantly more pronounced in 5/6 nephrectomy [24 (6-44) s] when compared with ADMA infusion [64 (28-93) s] and controls [33 (26-65) s].

CONCLUSIONS

Progressive renal failure in rats is accompanied by a marked increase of ADMA and a decrease in BDNF. 5/6 nephrectomy leads to significantly decreased exploratory behaviour and locomotion. Both behaviours could be reproduced by ADMA infusion alone. Indicators of anxiety were more pronounced in ADMA-infused animals when compared with 5/6 nephrectomized rats. Furthermore, an inverse relationship of BDNF and BDI in 11 CKD5D patients was shown.

Elevated neurotrophin-3 and neurotrophin 4/5 levels in unmedicated bipolar depression and the effects of lithium

BACKGROUND

Bipolar disorder (BD) has been associated with diverse abnormalities in neural plasticity and cellular resilience. Neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5) support synaptic neuronal survival and differentiation. NT-3 and NT-4/5 levels were found to be altered in BD, potentially representing a physiological response against cellular stress. However, the use of psychopharmacological agents and heterogeneous mood states may constitute important biases in such studies. Thus, we aimed to assess NT-3 and NT-4/5 levels in medication-free BD type I or II individuals in a current depressive episode, before and after 6 weeks of lithium monotherapy and matched with healthy controls.

METHODS

Twenty-three patients with BD type I or II during a depressive episode and 28 healthy controls were studied. Patients were required to have a 21-item Hamilton Depression Rating Scale score ≥18 and had not undergone any psychopharmacological treatment for at least 6 weeks prior to study entry. Patients were treated with lithium for 6 weeks and plasma NT-3 and NT-4/5 levels were determined at baseline and endpoint using ELISA method.

RESULTS

Baseline plasma levels of both NT-3 and NT-4/5 were significantly increased in acutely depressed BD subjects in comparison to healthy controls (p=0.040 and 0.039, respectively). The NT-3 and NT-4/5 levels did not significantly change after lithium treatment. NT-3 and NT-4/5 levels were positively correlated to illness duration in BD (p=0.032 and 0.034, respectively).

CONCLUSION

Our findings suggest that NT-3 and NT-4/5 levels are increased in the depressive phase of BD, which seems directly associated with illness duration. The increased levels of NT-3 and NT-4/5 may underlie a biological response to cellular stress associated with the course of BD.

Molecular hydrogen in drinking water protects against neurodegenerative changes induced by traumatic brain injury

Traumatic brain injury (TBI) in its various forms has emerged as a major problem for modern society. Acute TBI can transform into a chronic condition and be a risk factor for neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, probably through induction of oxidative stress and neuroinflammation. Here, we examined the ability of the antioxidant molecular hydrogen given in drinking water (molecular hydrogen water; mHW) to alter the acute changes induced by controlled cortical impact (CCI), a commonly used experimental model of TBI. We found that mHW reversed CCI-induced edema by about half, completely blocked pathological tau expression, accentuated an early increase seen in several cytokines but attenuated that increase by day 7, reversed changes seen in the protein levels of aquaporin-4, HIF-1, MMP-2, and MMP-9, but not for amyloid beta peptide 1-40 or 1-42. Treatment with mHW also reversed the increase seen 4 h after CCI in gene expression related to oxidation/carbohydrate metabolism, cytokine release, leukocyte or cell migration, cytokine transport, ATP and nucleotide binding. Finally, we found that mHW preserved or increased ATP levels and propose a new mechanism for mHW, that of ATP production through the Jagendorf reaction. These results show that molecular hydrogen given in drinking water reverses many of the sequelae of CCI and suggests that it could be an easily administered, highly effective treatment for TBI.

Intranasal nerve growth factor bypasses the blood-brain barrier and affects spinal cord neurons in spinal cord injury

The purpose of this work was to investigate whether, by intranasal administration, the nerve growth factor bypasses the blood-brain barrier and turns over the spinal cord neurons and if such therapeutic approach could be of value in the treatment of spinal cord injury. Adult Sprague-Dawley rats with intact and injured spinal cord received daily intranasal nerve growth factor administration in both nostrils for 1 day or for 3 consecutive weeks. We found an increased content of nerve growth factor and enhanced expression of nerve growth factor receptor in the spinal cord 24 hours after a single intranasal administration of nerve growth factor in healthy rats, while daily treatment for 3 weeks in a model of spinal cord injury improved the deficits in locomotor behaviour and increased spinal content of both nerve growth factor and nerve growth factor receptors. These outcomes suggest that the intranasal nerve growth factor bypasses blood-brain barrier and affects spinal cord neurons in spinal cord injury. They also suggest exploiting the possible therapeutic role of intranasally delivered nerve growth factor for the neuroprotection of damaged spinal nerve cells.

Elevated levels of plasma brain derived neurotrophic factor in rapid cycling bipolar disorder patients

Impaired neuroplasticity may be implicated in the pathophysiology of bipolar disorder, involving peripheral alterations of the neurotrophins brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3). Evidence is limited by methodological issues and is based primarily on case-control designs. The aim of this study was to investigate whether BDNF and NT-3 levels differ between patients with rapid cycling bipolar disorder and healthy control subjects and whether BDNF and NT-3 levels alter with affective states in rapid cycling bipolar disorder patients. Plasma levels of BDNF and NT-3 were measured in 37 rapid cycling bipolar disorder patients and in 40 age- and gender matched healthy control subjects using enzyme-linked immunosorbent assay (ELISA). In a longitudinal design, repeated measurements of BDNF and NT-3 were evaluated in various affective states in bipolar disorder patients during a 6-12 months period and compared with repeated measurements in healthy control subjects. Careful attention was given to standardization of all procedures and adjustment for potential confounders of BDNF and NT-3. In linear mixed models, adjusting for demographical and lifestyle factors, levels of BDNF were significantly elevated in bipolar disorder patients in euthymic- (p<0.05), depressed- (p<0.005) and manic/hypomanic (p<0.005) states compared with healthy control subjects. Within bipolar disorder patients, adjusting for medication, there was no significant difference in BDNF levels between affective states, with equally elevated levels present in euthymic-, depressive- and manic/hypomanic patients. Levels of BDNF were higher in patients with longer duration of illness compared with patients with shorter duration of illness. We found no difference in NT-3 levels between bipolar disorder patients in any affective state compared with healthy control subjects and no difference in NT-3 levels between affective states in bipolar disorder patients. The results suggest that BDNF may be a marker related to illness stage in bipolar disorder, not varying with affective states in rapid cycling bipolar disorder patients. Due to the nature of comparison, it cannot be excluded that the finding of elevated BDNF levels in bipolar disorder patients compared with healthy controls could be influenced by medication.

Cord blood immune biomarkers in small for gestational age births

Fetal growth restriction is a risk factor for development of adulthood diseases, but the biological mechanism of this association remains unknown. Limited biomarkers have been studied in settings of preterm birth and maternal inflammation, but the relationship between a wide range of immune biomarkers and fetal growth has not been studied. The hypothesis of this study was that fetal growth restriction is associated with altered immune biomarker levels. We examined the relationship between small for gestational age (SGA) status and 27 umbilical cord blood immune biomarkers. This study was part of a large-scale cohort study of preterm birth and low birth weight conducted at Boston Medical Center, an inner city, predominantly minority patient population. Growth status was determined based on birth weight standardized to an internal reference. There were 74 SGA births and 319 appropriate for age (AGA) births with complete clinical and biomarker data. Adjusting for covariates and using AGA as reference, SGA births had lower levels of log IL-1β (ng/l; β -0.38, 95% CI -0.57, -0.19, P < 0.01), log BDNF (β -0.29, 95% CI -0.55, -0.03, P < 0.05) and log NT-3 (β -0.46, 95% CI -0.77, -0.15, P < 0.01). No associations were found between other biomarkers and SGA. In conclusion, three biomarkers were selectively associated with SGA status. Our results provide information that could be used to guide additional studied aimed at determining mechanisms that contribute to fetal growth.

Agile delivery of protein therapeutics to CNS

A variety of therapeutic proteins have shown potential to treat central nervous system (CNS) disorders. Challenge to deliver these protein molecules to the brain is well known. Proteins administered through parenteral routes are often excluded from the brain because of their poor bioavailability and the existence of the blood-brain barrier (BBB). Barriers also exist to proteins administered through non-parenteral routes that bypass the BBB. Several strategies have shown promise in delivering proteins to the brain. This review, first, describes the physiology and pathology of the BBB that underscore the rationale and needs of each strategy to be applied. Second, major classes of protein therapeutics along with some key factors that affect their delivery outcomes are presented. Third, different routes of protein administration (parenteral, central intracerebroventricular and intraparenchymal, intranasal and intrathecal) are discussed along with key barriers to CNS delivery associated with each route. Finally, current delivery strategies involving chemical modification of proteins and use of particle-based carriers are overviewed using examples from literature and our own work. Whereas most of these studies are in the early stage, some provide proof of mechanism of increased protein delivery to the brain in relevant models of CNS diseases, while in few cases proof of concept had been attained in clinical studies. This review will be useful to broad audience of students, academicians and industry professionals who consider critical issues of protein delivery to the brain and aim developing and studying effective brain delivery systems for protein therapeutics.

Neurotrophic factors in women with crack cocaine dependence during early abstinence: the role of early life stress

BACKGROUND

Neurotrophic factors have been investigated in the pathophysiology of alcohol and drug dependence and have been related to early life stress driving developmental programming of neuroendocrine systems.

METHODS

We conducted a follow-up study that aimed to assess the plasma levels of glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT3) and neurotrophin-4/5 (NT4/5) in crack users during 3 weeks of early abstinence in comparison with healthy controls. We performed a comprehensive clinical assessment in female inpatients with crack cocaine dependence (separated into 2 groups: participants with (CSA+) and without (CSA-) a history of childhood sexual abuse) and a group of nonuser control participants.

RESULTS

Our sample included 104 women with crack cocaine dependence and 22 controls; of the women who used crack cocaine, 22 had a history of childhood sexual abuse and 82 did not. The GDNF plasma levels in the CSA+ group increased dramatically during 3 weeks of detoxification. In contrast, those in the CSA- group showed lower and stable levels of GDNF under the same conditions. Compared with the control group, BDNF plasma levels remained elevated and NGF levels were reduced during early abstinence. We found no differences in NT3 and NT4/5 between the patients and controls. However, within-group analyses showed that the CSA+ group exhibited higher levels of NT4/5 than the CSA- group at the end of detoxification.

LIMITATIONS

Some of the participants were using neuroleptics, mood stabilizers or antidepressants; our sample included only women; memory bias could not be controlled; and we did not investigate the possible confounding effects of other forms of stress during childhood.

CONCLUSION

This study supports the association between early life stress and peripheral neurotrophic factor levels in crack cocaine users. During early abstinence, plasmastic GDNF and NT4/5 were the only factors to show changes associated with a history of childhood sexual abuse.

Fibroblast growth factor 19 entry into brain

Background

Fibroblast growth factor (FGF)-19, an endocrine FGF protein mainly produced by the ileum, stimulates metabolic activity and alleviates obesity. FGF19 modulates metabolism after either intravenous or intracerebroventricular injection, and its receptor FGFR4 is present in the hypothalamus. This led to the question whether blood-borne FGF19 crosses the blood-brain barrier (BBB) to exert its metabolic effects.

Methods

We determined the pharmacokinetics of FGF19 permeation from blood to brain in comparison with its distribution in peripheral organs. Multiple-time regression analysis after intravenous bolus injection, in-situ brain perfusion, and HPLC assays were performed.

Results

FGF19 was relatively stable in blood and in the brain compartment. Significant influx was seen in the presence of excess unlabeled FGF19 in blood. This coincided with a slower decline of ¹²⁵I-FGF19 in blood which suggested there was decreased clearance or peripheral tissue uptake. In support of an altered pattern of peripheral processing of ¹²⁵I-FGF19 by excess unlabeled FGF19, the high influx to liver was significantly attenuated, whereas the minimal renal uptake was linearly accelerated. In the present setting, we did not detect a saturable transport of FGF19 across the BBB, as the entry rate of ¹²⁵I-FGF19 was not altered by excess unlabeled FGF19 or its mouse homologue FGF15 during in-situ brain perfusion.

Conclusion

FGF19 remained stable in the blood and brain compartments for up to 10 min. Its influx to the brain was non-linear, non-saturable, and affected by its blood concentration and distribution in peripheral organs. Liver showed a robust and specific uptake of FGF19 that could be inhibited by the presence of excess unlabeled FGF19, whereas kidney clearance was dose-dependent.

Nerve growth factor: basic studies and possible therapeutic applications

The nerve growth factor (NGF) belongs to a family of neurotrophic factors called neurotrophins. It was discovered as a molecule that stimulates the survival and maturation of developing neurons in the peripheral nervous system and has later been shown to protect adult neurons in the degenerating mammalian brain. Basic and clinical studies have been undertaken to use NGF as a therapeutic agent aimed at restoring and maintaining neuronal function in the central nervous system and to determine the mechanisms to safely deliver the molecule into the brain. Recent studies have also recognized that the role of NGF extends far beyond the horizon of nerve cells and even beyond the peripheral and central nervous system. Studies published from our laboratory have shown that topical application of NGF possesses a protective action on human pressure ulcer, corneal ulcer and glaucoma. Here, we will review these studies, supporting the therapeutic potential of NGF.

Modelling the endothelial blood-CNS barriers: a method for the production of robust in vitro models of the rat blood-brain barrier and blood-spinal cord barrier

Background

Modelling the blood-CNS barriers of the brain and spinal cord in vitro continues to provide a considerable challenge for research studying the passage of large and small molecules in and out of the central nervous system, both within the context of basic biology and for pharmaceutical drug discovery. Although there has been considerable success over the previous two decades in establishing useful in vitro primary endothelial cell cultures from the blood-CNS barriers, no model fully mimics the high electrical resistance, low paracellular permeability and selective influx/efflux characteristics of the in vivo situation. Furthermore, such primary-derived cultures are typically labour-intensive and generate low yields of cells, limiting scope for experimental work. We thus aimed to establish protocols for the high yield isolation and culture of endothelial cells from both rat brain and spinal cord. Our aim was to optimise in vitro conditions for inducing phenotypic characteristics in these cells that were reminiscent of the in vivo situation, such that they developed into tight endothelial barriers suitable for performing investigative biology and permeability studies.

Methods

Brain and spinal cord tissue was taken from the same rats and used to specifically isolate endothelial cells to reconstitute as in vitro blood-CNS barrier models. Isolated endothelial cells were cultured to expand the cellular yield and then passaged onto cell culture inserts for further investigation. Cell culture conditions were optimised using commercially available reagents and the resulting barrier-forming endothelial monolayers were characterised by functional permeability experiments and in vitro phenotyping by immunocytochemistry and western blotting.

Results

Using a combination of modified handling techniques and cell culture conditions, we have established and optimised a protocol for the in vitro culture of brain and, for the first time in rat, spinal cord endothelial cells. High yields of both CNS endothelial cell types can be obtained, and these can be passaged onto large numbers of cell culture inserts for in vitro permeability studies. The passaged brain and spinal cord endothelial cells are pure and express endothelial markers, tight junction proteins and intracellular transport machinery. Further, both models exhibit tight, functional barrier characteristics that are discriminating against large and small molecules in permeability assays and show functional expression of the pharmaceutically important P-gp efflux transporter.

Conclusions

Our techniques allow the provision of high yields of robust sister cultures of endothelial cells that accurately model the blood-CNS barriers in vitro. These models are ideally suited for use in studying the biology of the blood-brain barrier and blood-spinal cord barrier in vitro and for pre-clinical drug discovery.

Reduced serum nerve growth factor in patients with late-life depression

INTRODUCTION

Nerve growth factor (NGF) is one of the most abundant neurotrophic factors in the central nervous system and has been involved in several neuropsychiatric disorders.

METHODS

We recruited 77 age- and gender-matched elderly subjects (38 with late-life depression, 17 with previous major depressive episode, and 22 healthy subjects in the comparison group). Serum concentration of NGF was determined by enzyme-linked immunosorbent assay.

RESULTS

NGF levels were significantly reduced in the depressed patients (p = 0.002) as compared with healthy elderly controls. Elderly control subjects with previous depressive episode also showed a significant reduction in NGF levels as compared with controls (p <0.01); NGF levels were similar between patients with current depressive episode and previous depressive episode (p = 0.2).

CONCLUSION

The present findings provide additional evidence to the relevance of reduced neurotrophic support in the pathophysiology of late-life depression. Also, reduced serum NGF level may be a state marker of depression in elderly subjects.

Cytokine signaling modulates blood-brain barrier function

The blood-brain barrier (BBB) provides a vast interface for cytokines to affect CNS function. The BBB is a target for therapeutic intervention. It is essential, therefore, to understand how cytokines interact with each other at the level of the BBB and how secondary signals modulate CNS functions beyond the BBB. The interactions between cytokines and lipids, however, have not been fully addressed at the level of the BBB. Here, we summarize current understanding of the localization of cytokine receptors and transporters in specific membrane microdomains, particularly lipid rafts, on the luminal (apical) surface of the microvascular endothelial cells composing the BBB. We then illustrate the clinical context of cytokine effects on the BBB by neuroendocrine regulation and amplification of inflammatory signals. Two unusual aspects discussed are signaling crosstalk by different classes of cytokines and genetic regulation of drug efflux transporters. We also introduce a novel area of focus on how cytokines may act through nuclear hormone receptors to modulate efflux transporters and other targets. A specific example discussed is the ATP-binding cassette transporter-1 (ABCA-1) that regulates lipid metabolism. Overall, cytokine signaling at the level of the BBB is a crucial feature of the dynamic regulation that can rapidly change BBB function and affect brain health and disease.

Nerve growth factor: from the early discoveries to the potential clinical use

The physiological role of the neurotrophin nerve growth factor (NGF) has been characterized, since its discovery in the 1950s, first in the sensory and autonomic nervous system, then in central nervous, endocrine and immune systems. NGF plays its trophic role both during development and in adulthood, ensuring the maintenance of phenotypic and functional characteristic of several populations of neurons as well as immune cells. From a translational standpoint, the action of NGF on cholinergic neurons of the basal forebrain and on sensory neurons in dorsal root ganglia first gained researcher's attention, in view of possible clinical use in Alzheimer's disease patients and in peripheral neuropathies respectively. The translational and clinical research on NGF have, since then, enlarged the spectrum of diseases that could benefit from NGF treatment, at the same time highlighting possible limitations in the use of the neurotrophin as a drug. In this review we give a comprehensive account for almost all of the clinical trials attempted until now by using NGF. A perspective on future development for translational research on NGF is also discussed, in view of recent proposals for innovative delivery strategies and/or for additional pathologies to be treated, such as ocular and skin diseases, gliomas, traumatic brain injuries, vascular and immune diseases.

Serum brain-derived neurotrophic factor, nerve growth factor and neurotrophin-3 levels in dementia

The aim of this study is to measure serum levels of neurotropic factor (NF) in patients with dementia. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) were determined in Alzheimer's dementia patients without medication (AD; n: 22), Alzheimer's dementia patients receiving cholinesterase inhibitor (CEI) treatment (AD + CEI; n: 32) and vascular dementia patients receiving CEI treatment (VaD + CEI; n: 27) and the age-matched control group (n: 20). NGF levels were detected to be significantly higher in the control group than in AD group (P < 0.001). BDNF and NT-3 levels in AD group were not significantly different from control group's levels. NGF levels in AD + CEI group were significantly higher than in AD group (P < 0.05). There was also no significant difference in serum neurotrophic factor levels between AD + CEI and VaD + CEI group. A positive correlation between BDNF and Mini Mental State Examination (MMSE) scores (r: 0.422, P < 0.01) in AD group and a negative correlation between BDNF and MMSE scores in the AD + CEI group (r: -0.357, P < 0.005) were obtained. In conclusion, our results suggest that while serum NGF levels are associated with the presence of dementia, serum BDNF levels may be associated with the severity of Alzheimer's dementia. However, future studies are required to determine the importance of NFs.

Effect of cell therapy on metabolite content in brain structures of children with consequences of severe brain injury: 1H magnetic resonance spectroscopy study

The effect of intravenous injection of human umbilical cord blood cells on the levels of N-acetylaspartate, creatine and phosphocreatine, choline-containing compounds, glutamine and glutamate, and myoinositol in morphologically intact areas of the cortex, white matter, and hippocampus of children with consequences of traumatic brain injury was studied by single voxel 1H magnetic resonance spectroscopy. It was shown that cell therapy increases the content of N-acetylaspartate, a marker of functional integrity of neurons, in the white matter and in the cortex at the boundary between the frontotemporal and parietal lobes and reduces neurological deficit.

Brainpeps: the blood-brain barrier peptide database

Peptides are able to cross the blood-brain barrier (BBB) through various mechanisms, opening new diagnostic and therapeutic avenues. However, their BBB transport data are scattered in the literature over different disciplines, using different methodologies reporting different influx or efflux aspects. Therefore, a comprehensive BBB peptide database (Brainpeps) was constructed to collect the BBB data available in the literature. Brainpeps currently contains BBB transport information with positive as well as negative results. The database is a useful tool to prioritize peptide choices for evaluating different BBB responses or studying quantitative structure-property (BBB behaviour) relationships of peptides. Because a multitude of methods have been used to assess the BBB behaviour of compounds, we classified these methods and their responses. Moreover, the relationships between the different BBB transport methods have been clarified and visualized.

Brain-derived neurotrophic factor in post-partum depressive mothers

Postpartum depression (PPD) is the most common psychiatric complication observed in women after they give birth. Some women are particularly sensitive to hormonal changes, starting in early menarche, thus increasing their vulnerability to psychological stressing agents that are triggered by environmental and physiological factors throughout their lives. Decreased serum brain-derived neurotrophic factor (BDNF) levels have been associated to different neuropsychiatric conditions and BDNF has been considered as a candidate marker for such dysfunctions. The goal of this study was to compare the levels of BDNF between mothers who suffer from PPD and healthy control mothers as well as to searching for associations between BDNF levels and the severity of PPD. This is a case-control study including 36 mothers with PPD and 36 healthy control mothers. PPD was defined according to the Beck Depression Inventory (BDI). Serum BDNF was assayed with the sandwich ELISA method.

RESULTS

Serum levels of BDNF were significantly lower in women with PPD than in control mothers (P ≤ 0.03). A significant negative correlation between BDI score and serum BDNF levels was observed (P ≤ 0.02 and r = -0.29). Our study demonstrated that low BDNF levels are associated with PPD. This result point out to the potential usage of BDNF in the screening of PPD, which could promote early treatment and, therefore, reduce the burden to the PPD women and to the health system.

Changes in plasma and platelet BDNF levels induced by S-citalopram in major depression

BACKGROUND

Neuroplastic processes are thought to be involved in the pathophysiology of major depression. It has been reported that serum brain-derived neurotrophic factor (BDNF) is decreased in depressed patients.

OBJECTIVES

Compare BDNF levels in depressed patients and healthy controls in platelet poor plasma and in washed platelets. Observe the effects of 8- and 24-week treatment with S-citalopram on these levels.

METHODS

We assessed the levels of BDNF in platelet poor plasma and in washed platelets from 18 major depression patients, and compared them with 14 healthy controls. Blood samples were obtained from patients before and during treatment (8 and 24 weeks) with a selective serotonin reuptake inhibitor, S-citalopram.

RESULTS

A significant decrease in severity of depressive symptoms was observed from the first month of treatment with S-citalopram, and symptoms continued decreasing until the 6th month. Plasma BDNF levels in untreated patients appeared significantly increased (p<0.01) but reached values similar to those of controls at the 24th week. In contrast, levels of platelet BDNF appeared significantly decreased (p<0.05), but treatment also normalized levels so that values obtained were equivalent to those of controls.

CONCLUSIONS

Untreated depressed patients showed increased plasma BDNF levels and decreased platelet BDNF levels, as compared with control subjects, and tend to normalize during treatment with S-citalopram for 24 weeks, with BDNF reaching levels similar to those in healthy controls at the 24th week in both samples. We observed that improvement in depressive symptoms was accompanied by normalization of plasma and platelet BDNF levels.

Increased neurotrophin-3 in drug-free subjects with bipolar disorder during manic and depressive episodes

Bipolar disorder (BD) has been increasingly associated with abnormalities in neuroplasticity. Previous studies demonstrated that neurotrophin-3 (NT-3) plays a role in the pathophysiology of mood disorders. The influence of medication in these studies has been considered a limitation. Thus, studies with drug-free vs. medicated patients are necessary to evaluate the role of medication in serum NT-3 levels. About 10 manic and 10 depressive drug-free, and 10 manic and 10 depressive medicated patients with BD type I were matched with 20 controls for sex and age. Patients were assessed using SCID-I, YMRS and HDRS. Serum NT-3 levels in drug-free and medicated patients is increased when compared with controls (2.51+/-0.59, 2.56+/-0.44 and 1.97+/-0.33, respectively, p<0.001 for drug-free/medicated vs. control). Serum NT-3 levels do not differ between medicated and drug-free patients. When analyzing patients according to mood states, serum NT-3 levels are increased in both manic and depressive episodes, as compared with controls (2.47+/-0.43, 2.60+/-0.59 and 1.97+/-0.33, respectively, p<0.001 for manic/depressive patients vs. controls). There is no difference in serum BDNF between manic and depressive patients. Results suggest that increased serum NT-3 levels in BD are likely to be associated with the pathophysiology of manic and depressive symptoms.

Serum MIP-1 alpha level: a biomarker for the follow-up of lentiviral therapy in mucopolysaccharidosis IIIB mice

Mucopolysaccharidosis (MPS) IIIB is an inherited lysosomal storage disorder caused by deficiency of alpha-N-acetylglucosaminidase (NAGLU). The disease is characterized by mild somatic features and severe neurological involvement, with high mortality rates. Although some therapeutic approaches have been applied to the murine model of the disease, no effective therapy is available. Moreover, assessing therapeutic efficacy is challenged by the lack of markers to for progression and severity. In this study, we examined the effect of brain-directed lentiviral (LV) gene therapy on serum levels of macrophage inflammatory protein 1 alpha (MIP-1alpha) and brain-derived neurotrophic factor (BDNF) proteins in the murine model of MPS IIIB to identify novel serum biomarkers. The cytokine MIP-1alpha was elevated in MPS IIIB mouse serum, and following gene therapy, it was reduced to normal levels. For neurotrophin BDNF, the difference in serum levels between MPS IIIB and normal mice was not statistically significant; after LV gene therapy, an increase in protein was found in treated mice, although the values were not statistically significant. Our studies suggest MIP-1alpha as the first serum biomarker that could be used to monitor disease progression and treatment for MPS IIIB disease.

Brain-derived neurotrophic factor in infants <32 weeks gestational age: correlation with antenatal factors and postnatal outcomes

Neurotrophins (NTs) play important roles in brain growth and development. Cord blood (CB) brain-derived neurotrophic factor (BDNF) concentrations increase with gestational age but data regarding postnatal changes are limited. We measured BDNF concentrations after birth in 33 preterm infants <32-wk gestation. Serum was collected at birth (CB), at day 2, between day 6 and 10 (D6), at day 30 (D30), and at day 60 (D60). BDNF concentrations fell on D2 (p = 0.03), recovered by D6 (p = 0.10), and continued to rise thereafter at D30 (p = 0.06) and D60 (p = 0.01) compared with CB. CB BDNF concentrations positively correlated with duration of rupture of membranes (r = 0.43, p = 0.04). Antenatal steroids (ANS, p = 0.02), postnatal steroids (PNS, p = 0.04), and retinopathy of prematurity (ROP, p = 0.02) were identified as significant factors in multivariate analyses. The median (25-75th interquartile range) CB BDNF concentrations were higher in infants who received a complete course ANS compared with those who received a partial course [1461 (553-2064) versus 281 (171-536) pg/mL, p = 0.04]. BDNF concentrations negatively correlated with the use of PNS at D30 (r = -0.53, p = 0.002) and at D60 (r = -0.55, p = 0.009). PNS use was associated with reduced concentrations of BDNF at D30 [733 (101-1983) versus 2224 (1677- 4400) pg/mL, p = 0.004] and at D60 [1149 (288-2270) versus 2560 (1337-5166) pg/mL, p = 0.01]. BDNF concentrations on D60 in infants who developed ROP (n = 16) were lower than those who did not develop ROP (n = 7) [1417 (553-2540) versus 3593 (2620-7433) pg/mL, respectively, p = 0.005]. Our data suggests that BDNF concentrations rise beyond the first week of age. BDNF concentrations correlate with factors that influence neurodevelopment outcomes.

Increased serum neurotrophin-4/5 levels in bipolar disorder

Neurotrophins are central to several aspects of central nervous system function, and emerging evidence links these growth factors to mood disorders. The purpose of this study was to investigate serum neurotrophin-4/5 (NT-4/5) levels in patients with bipolar disorder, both within mood episodes and in euthymia. Patients with bipolar I disorder (n=154) and controls (n=30) had their NT-4/5 serum levels assayed using an ELISA. Levels of NT-4/5 levels were significantly higher in bipolar disorder patients than in controls; NT-4/5 levels were increased in mania, depression and euthymia, but not significantly different between BD mood states. As far as are aware, this is the first study showing NT-4/5 immunocontent alterations in bipolar disorder. A tentative explanation would be that NT-4/5 increases is compensating for ongoing oxidative damage in dopaminergic neurons.

Delivery of peptide and protein drugs over the blood-brain barrier

Peptide and protein (P/P) drugs have been identified as showing great promises for the treatment of various neurodegenerative diseases. A major challenge in this regard, however, is the delivery of P/P drugs over the blood-brain barrier (BBB). Intense research over the last 25 years has enabled a better understanding of the cellular and molecular transport mechanisms at the BBB, and several strategies for enhanced P/P drug delivery over the BBB have been developed and tested in preclinical and clinical-experimental research. Among them, technology-based approaches (comprising functionalized nanocarriers and liposomes) and pharmacological strategies (such as the use of carrier systems and chimeric peptide technology) appear to be the most promising ones. This review combines a comprehensive overview on the current understanding of the transport mechanisms at the BBB with promising selected strategies published so far that can be applied to facilitate enhanced P/P drug delivery over the BBB.

Decreased serum neurotrophin 3 in chronically medicated schizophrenic males

There is evidence that major psychiatric disorders such as schizophrenia (SZ) are associated with deregulation of synaptic plasticity with downstream alterations of neurotrophins. NT3 is an important neurotrophin in the central nervous system, and performs key biological functions, such as promoting the survival, differentiation, and plasticity of neurons. NT3 has a central role in the early neuronal development; enhancing the survival of dopaminergic neurons, suggesting possible involvement in the physiopathology of dopamine related neuropsychiatric disorders such as SZ. Variations in the NT3 gene increase the risk of SZ. Three groups of chronically medicated DSM-IV patients with SZ, on treatment with clozapine (n=12), haloperidol (n=12), risperidone (n=12) and 10 healthy controls had 5 ml blood samples collected by venipuncture. NT3 serum levels were assessed using sandwich-ELISA and were significantly lower in SZ patients (p<0.005) when compared to either controls. These findings suggest that the NT3 signaling system may play a role in the pathophysiology of SZ and might be related to the course of illness or to treatment variables. Longitudinal studies are warranted.

Increased leptin permeation across the blood-brain barrier after chronic alcohol ingestion

Leptin, a polypeptide mainly produced in the periphery, crosses the blood-brain barrier (BBB) by receptor-mediated transport to exert multiple central nervous system actions including decreased food intake. The reciprocal interactions between leptin transport and alcohol drinking are not clear. In this study, we tested whether alcohol increases leptin entry into brain and, if this occurs, whether it is a consequence of a generalized increase in the permeability of the BBB. BBB permeability to albumin, the increased permeation of which indicates BBB disruption, as well as to leptin was measured after alcohol ingestion. CD1 and B6 mice ingested a 5% liquid alcohol diet or its isocaloric control for 2 weeks. Alcohol ingestion resulted in increased blood-alcohol levels, decreased blood-leptin concentrations, and increased permeation of radioactively labeled leptin across the BBB as shown by in situ perfusion. Although the increased influx of the vascular marker albumin into brain showed partial disruption of the BBB, the influx of (125)I-leptin still could be suppressed by excess unlabeled leptin, indicating persistence of its saturable transport system. When given a choice of either alcohol or control diet, even the alcohol-preferring B6 mice showed a significantly greater preference for the control liquid diet, and there was no evidence of BBB disruption or alterated leptin transport. Furthermore, acute alcohol intoxication induced by intraperitoneal injection of 20% alcohol did not result in BBB disruption or increased leptin permeation 4 h later. Thus, partial disruption of the BBB and increased permeation of leptin in both CD1 and B6 mice were only induced by chronic alcohol ingestion. The results showing increased leptin permeation across the BBB lead to the speculation that leptin may serve as a homeostatic feeding signal in these mice.

Developmental changes of leptin receptors in cerebral microvessels: unexpected relation to leptin transport

The adipokine leptin participates not only in the regulation of feeding and obesity in adults but also in neonatal development. It crosses the blood-brain barrier (BBB) by receptor-mediated transport. Leptin concentrations in blood differ between neonates and adults. We determined the developmental changes of leptin receptor subtypes in the cerebral microvessels composing the BBB and examined their expected correlation with leptin transport across the BBB. Total RNA was extracted from enriched cerebral microvessels of mice 1, 7, 14, and 60 d of age for real-time RT-PCR analysis of leptin receptor subtypes. In cerebral microvessels from neonates, ObRa, ObRb, ObRc, and ObRe mRNA were all higher than in adults, but ObRd was not detectable. Hypothalamus showed similar age-related changes except for ObRb, which was higher in adults. The homologous receptor gp130 did not show significant age-related changes in either region. Despite the increase of leptin receptors, leptin permeation across the BBB after iv injection was less in the neonates. In situ brain perfusion with blood-free buffer showed no significant difference in the brain uptake of leptin between neonates and adults, indicating an antagonistic role of leptin-binding proteins in the circulation, especially the soluble receptor ObRe. The results are consistent with our previous finding that ObRe antagonizes leptin endocytosis in cultured endothelia and transport from blood to brain in mice. Overall, the developmental changes observed for leptin receptors unexpectedly failed to correlate with the entry of leptin into brain, and this may indicate different functions of the receptors in neonates and adults.

Cytokine transport across the injured blood-spinal cord barrier

Spinal cord injury (SCI) induces dynamic changes of the blood-spinal cord barrier and even the more distant blood-brain barrier. Besides an immediate increase of paracellular permeability resulting from the direct impact of the injury, the transport systems for selective cytokines undergo regulatory changes. Since many of the transported molecules play essential roles in neuroregeneration, we propose that this altered peripheral tissue / CNS interaction benefits remodeling of the spinal cord and functional recovery after SCI. This review examines the transport of cytokines and neurotrophic factors into the spinal cord, emphasizing the upregulation of two cytokines--tumor necrosis factor alpha (TNF) and leukemia inhibitory factor (LIF)--during the course of SCI. The increased transport of TNF and LIF after SCI remains saturable and does not coincide with generalized BBB disruption, highlighting a pivotal regulatory role for the blood-spinal cord barrier.

Tumor necrosis factor and stroke: role of the blood-brain barrier

The progression and outcome of stroke is affected by the intricate relationship between the blood-brain barrier (BBB) and tumor necrosis factor alpha (TNFalpha). TNFalpha crosses the intact BBB by a receptor-mediated transport system that is upregulated by CNS trauma and inflammation. In this review, we discuss intracellular trafficking and transcytosis of TNFalpha, regulation of TNFalpha transport after stroke, and the effects of TNFalpha on stroke preconditioning. TNFalpha can activate cytoprotective pathways by pretreatment or persistent exposure to low doses. This explains the paradoxical observation that transport of this proinflammatory cytokine improves the survival and function of hypoxic cells and of mice with stroke. The dual effects of TNFalpha may be related to differential regulation of TNFalpha trafficking downstream to TNFR1 and TNFR2 receptors. As we better understand how peripheral TNFalpha affects its own transport and modulates neuroregeneration, we may be in a better position to pharmacologically manipulate its regulatory transport system to treat stroke.

Nesfatin-1 crosses the blood-brain barrier without saturation

Nesfatin-1 is an 82 amino acid peptide that suppresses food intake after intracerebroventricular injection. Nesfatin-1 and its precursor NUCB2 were identified by subtraction cloning in cell lines of both neuronal and adipocytic origin. This provides a strong basis for studies to determine how peripherally derived nesfatin-1 permeates the blood-brain barrier (BBB) to participate in its CNS actions and whether pharmacological delivery by the peripheral route is feasible. In this study, nesfatin-1 remained stable in blood at least 20 min after intravenous injection and permeated the BBB by a non-saturable mechanism. The influx rate of nesfatin-1 after intravenous delivery was 0.27+/-0.11 microl/g-min, and 0.3% of nesfatin-1 reached brain parenchyma 10 min after injection. The lack of saturation of influx was shown by use of excess unlabeled nesfatin-1 in multiple-time regression analysis, capillary depletion, and in situ brain perfusion. After intracerebroventricular injection, nesfatin-1 had a half-time disappearance of 23.8 min, which was not significantly different from that of albumin. This indicates that nesfatin-1 exited the brain by bulk absorption of cerebrospinal fluid without a specific efflux transport system. We conclude that the permeation of nesfatin-1 is a non-saturable process in either the blood-to-brain or brain-to-blood direction. Thus, the limited penetration under physiological conditions does not limit the pharmacological delivery of this satiety peptide as a potential therapeutic agent.

Adipokines and the blood-brain barrier

Just as the blood-brain barrier (BBB) is not a static barrier, the adipocytes are not inert storage depots. Adipokines are peptides or polypeptides produced by white adipose tissue; they play important roles in normal physiology as well as in the metabolic syndrome. Adipokines secreted into the circulation can interact with the BBB and exert potent CNS effects. The specific transport systems for two important adipokines, leptin and tumor necrosis factor alpha, have been characterized during the past decade. By contrast, transforming growth factor beta-1 and adiponectin do not show specific permeation across the BBB, but modulate endothelial functions. Still others, like interleukin-6, may reach the brain but are rapidly degraded. This review summarizes current knowledge and recent findings of the rapidly growing family of adipokines and their interactions with the BBB.

Serum neurotrophin-3 is increased during manic and depressive episodes in bipolar disorder

Accumulating evidence suggest that neural changes and cognitive impairment may accompany the course of bipolar disorder. Such detrimental effects of cumulative mood episodes may be related to changes in neurotrophins that take place during mood episodes but not during euthymic phases. The present study investigated serum neurotrophin-3 (NT-3) levels in patients with bipolar disorder during manic, depressed, and euthymic states, using an enzyme-linked immunosorbent assay (sandwich-ELISA). Serum NT-3 levels were increased in manic (p<0.001) and depressed (p<0.001) BD patients, as compared with euthymic patients and normal controls. These findings suggest that the NT-3 signaling system may play a role in the pathophysiology of BD.

Systemic and acquired immune responses in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized clinically by a progressive cognitive decline and dementia. AD brains are marked by amyloid plaques and neurofibrillary tangles, neuronal cell loss, and a prominent activation of glial cells, and innate immune responses. A growing number of studies in AD have also reported alterations in systemic immune responses including changes in lymphocyte and macrophage distribution and activation, the presence of autoantibodies, or abnormal cytokine production. Studies in animal models for AD support the notion that immune cells infiltrate the brain and may modulate the disease. Here we will review evidence for systemic alterations in immune responses and a role for acquired immunity in AD and discuss their potential contribution to the disease.

Differential responses to the application of exogenous NT-3 are observed for subpopulations of motor and sensory neurons depending on the presence of skeletal muscle

We examined the effects of a single injection of exogenous NT-3, administered at embryonic day (E) 13.5, on the survival of two populations of motor neurons and two populations of sensory neurons. Both wild-type and double knockout, Myf5-/-:MyoD-/-, mutant embryos were examined to determine the effects of the aforementioned neurotrophin on motor and sensory neuron survival in the presence and absence, respectively, of skeletal muscle. We found that, although NT-3 rescues select populations of motor neurons in the absence of muscles, there is a lack of increase in neuron survival when skeletal muscle is present. Additionally, NT-3 was found to rescue a select population of proprioceptive sensory neurons in the absence of target tissue, while, at times, exacerbating neuron cell death when target tissues are present. Lastly, we found that neurons in the spinal cord and brainstem show both a regional and functional specificity in their response to the administration of NT-3 in utero. Our results indicate the possibility that different pathways are involved in the survival of neurons during naturally occurring programmed cell death and during excessively occurring programmed cell death.

Repetitive transcranial magnetic stimulation for ALS

Repetitive transcranial magnetic stimulation (rTMS) of brain can modulate cortical neurotransmission, a novel paradigm of repetitive stimulation termed continuous theta-burst stimulation (cTBS) produces a pronounced and prolonged suppression of motor cortex excitability. The aim of this preliminary study was to investigate whether cTBS of motor cortex could have any beneficial effect in patients with amyotrophic lateral sclerosis (ALS). We performed a double-blind, placebo-controlled trial. Twenty patients with definite ALS were randomly allocated to blinded active or placebo stimulation. Repetitive stimulation of the motor cortex was performed for five consecutive days every month for six consecutive months. The primary outcome was the rate of decline as evaluated with the ALS functional rating scale. The treatment was well tolerated by the patients. Fifteen patients (seven active and eight sham) completed the study and were included in the 6-months analysis. Both active and sham patients deteriorated during treatment, however, active patients showed a modest but significant slowing of the deterioration rate. Though we cannot be sure whether the effects observed can be attributed to cTBS, because of the restricted number of patients studied, further investigation on a larger group of ALS patients is warranted. The results of the pilot study might open up a new therapeutic perspective in ALS based on neuromodulation.

Possible role of nerve growth factor in the pathogenesis of alcohol dependence

BACKGROUND

Recent studies have raised the possibility that nerve growth factor (NGF) is abnormally regulated in the central nervous system (CNS) of animal models of chronic ethanol treatment. The goals of this study were to determine whether prolonged alcohol consumption is associated with the plasma NGF levels and to assess the effect of a positive family history of alcohol dependence on plasma NGF levels in the alcohol-dependent patients.

METHODS

We used the enzyme-linked immunosorbent assay (ELISA) to determine the concentrations of peripheral NGF in patients with alcohol dependence and in a control group.

RESULTS

The plasma NGF concentrations in the alcohol-dependent patients were significantly lower than in the controls (71.9 vs 110.5 pg/mL, respectively). Moreover, the alcohol-dependent patients with positive family histories showed a greater decrease in their NGF levels than those subjects with negative family histories (64.7 vs 83.3 pg/mL, respectively).

CONCLUSIONS

Our study suggests that the NGF levels may be a trait marker for the development of alcohol dependence.

Delivery of 125I-cobrotoxin after intranasal administration to the brain: a microdialysis study in freely moving rats

In order to determine the contribution of intranasal (i.n.) administration to the uptake of large molecular weight (MW) substances into central nervous system (CNS), concentration in brain of the centrally acting polypeptide cobrotoxin (NT-I) versus time profiles were studied using dual-probe microdialysis in awake free-moving rats. NT-I, radiolabeled with sodium (125)I-Iodide ((125)I-NT-I), was administered at the dose of 105 microg/kg intravenously and intranasally in the same set of rat (n=15). The (125)I-NT-Inasal preparations were formulated with borneol/menthol eutectic mixture (+BMEM) as an absorption enhancer and without (-BMEM). After application, the dialysates sampled simultaneously from olfactory bulb and cerebellar nuclei were measured in a gamma-counter for radioactivity. The real concentrations of NT-I were recalculated by in vivo recoveries of microdialysis probes. The results showed that the area under the curve (AUC) value in cerebellar nuclei (2283.51+/-34.54 min ng/ml) following i.n. administration (+BMEM) was significantly larger than those (AUC(olfactory)=1141.92+/-26.42 min ng/ml; AUC(cerebellar)=1364.62+/-19.35 min ng/ml) after intravenous (i.v.) bolus, respectively. A prolonged time values to peak concentrations after i.n. application (+BMEM) were observed compared with those following i.v. administration. Also, following i.n. application (+BMEM) the measured time value to peak concentration in cerebellar nuclei (85 min) was statistically longer than that in olfactory bulb (75 min), which could be plausibly an indication for NT-I delivery into brain via nose-brain pathway in the presence of absorption enhancer. i.n. administration (-BMEM) had little or no ability of NT-I delivering into brain. In conclusion, i.n. administration (+BMEM) significantly enhanced brain transport of NT-I with uneven distribution in discrete regions of brain compared with i.v. administration. Additionally, multi-probe microdialysis technique should be considerably valuable in brain delivery studies.

Physical exercise in multiple sclerosis: supportive care or a putative disease-modifying treatment

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease affecting young adults and leading to considerable disability. For many years, patients have been advised to avoid physical activity. Today, however, an increasing number of studies have shown beneficial effects of exercise training in MS. It has been reported that such programs not only improve fitness parameters but can also enhance quality of life and beneficially affect some suggestive disability measures. Pilot studies even indicate a neuroprotective potential. This review summarizes the findings of the major clinical trials on exercise in MS. Possible biological effect mediators, such as neurotrophic factors or anti-inflammatory cytokines, will be discussed. Exercise management guidelines will be proposed and possible further research strategies are presented.

Permeation of hepatocyte growth factor across the blood-brain barrier

Hepatocyte growth factor (HGF), mainly produced and acting in the periphery, attenuates cerebral ischemia-induced cell death and thus shows therapeutic potential in CNS regeneration. Accordingly, we tested its ability to permeate the blood-brain barrier (BBB). HGF was stable in the circulating blood of adult mice for up to 20 min, as HPLC showed intact (125)I-HGF in both serum and brain homogenate. Multiple time regression analysis revealed a rapid blood-to-brain influx rate of 0.38 +/- 0.07 microl/g min, faster than might be expected for a protein of this size. Although excess unlabeled HGF failed to inhibit of the influx of (125)I-HGF in mice, the use of a higher dose of unlabeled HGF in cellular uptake studies showed the presence of saturable endocytosis. Furthermore, capillary depletion studies showed that about 32% of the HGF present in brain entered the parenchymal compartment in contrast to the 11% entrapped in endothelial cells 10 min after intravenous bolus injection. The amount of HGF that crossed the BBB in intact form was substantial and could be physiologically important in the CNS.

Peripheral immune activation by lipopolysaccharide decreases neurotrophins in the cortex and hippocampus in rats

Lipopolysaccharide (LPS), a cell wall component of Gram-negative bacteria, induces neuronal death, decreases neurogenesis, and impairs synaptic plasticity and memory, but the mechanisms for these effects are not well understood. We hypothesize that neurotrophin levels in the brain are influenced by LPS. To test this hypothesis, we determined effects of LPS on brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and NT-3 levels in the brain after intraperitoneal injection of saline or LPS (0.1, 0.3 or 1.0mg/kg) in rats. LPS significantly decreased BDNF in the hippocampus (-20%), frontal cortex (-19%), parietal cortex (-63%), temporal cortex (-29%), and occipital cortex (-41%). LPS also significantly decreased NGF levels by 10-20% in the hippocampus and different cortical regions, except in the occipital cortex. Finally, LPS decreased NT-3 by 15-25% in the frontal cortex. These observations indicate that the neuroprotection mediated by neurotrophins in the brain are compromised by systemic immune activation induced by LPS.