Cell adhesion molecules in neural plasticity and pathology: similar mechanisms, distinct organizations?

Compulsive methamphetamine self-administration in the presence of adverse consequences is associated with increased hippocampal mRNA expression of cellular adhesion molecules

Methamphetamine (METH) is a popular but harmful psychostimulant. METH use disorder (MUD) is characterized by compulsive and continued use despite adverse life consequences. METH users experience impairments in learning and memory functions that are thought to be secondary to METH-induced abnormalities in the hippocampus. Recent studies have reported that about 50% of METH users develop MUD, suggesting that there may be differential molecular effects of METH between the brains of individuals who met criteria for addiction and those who did not after being exposed to the drug. The present study aimed at identifying potential transcriptional differences between compulsive and non-compulsive METH self-administering male rats by measuring global gene expression changes in the hippocampus using RNA sequencing. Herein, we used a model of METH self-administration (SA) accompanied by contingent foot-shock punishment. This approach led to the separation of animals into shock-resistant rats (compulsive) that continued to take METH and shock-sensitive rats (non-compulsive) that suppressed their METH intake in the presence of punished METH taking. Rats were euthanized 2 h after the last METH SA plus foot-shock session. Their hippocampi were immediately removed, frozen, and used later for RNA sequencing and qRT-PCR analyses. RNA sequencing analyses revealed differential expression of mRNAs encoding cell adhesion molecules (CAMs) between the two rat phenotypes. qRT-PCR analyses showed significant higher levels of Cdh1, Glycam1, and Mpzl2 mRNAs in the compulsive rats in comparison to non-compulsive rats. The present results implicate altered CAM expression in the hippocampus in the behavioral manifestations of continuous compulsive METH taking in the presence of adverse consequences. Our results raise the novel possibility that altered CAM expression might play a role in compulsive METH taking and the cognitive impairments observed in MUD patients.

Proteomic Response of Rat Pituitary Under Chronic Mild Stress Reveals Insights Into Vulnerability and Resistance to Anxiety or Depression

Chronic stress as one of the most significant risk factor can trigger overactivity of hypothalamic-pituitary-adrenal (HPA) axis in depression as well as anxiety. Yet, the shared and unique neurobiological underpinnings underlying the pituitary abnormality in these two disorders have not been made clear. We previously have established depression-susceptible, anxiety-susceptible and insusceptible groups using a valid chronic mild stress (CMS) model. In this work, the possible protein expression changes in the rat pituitary of these three groups were continuously investigated through the use of the comparative quantitative proteomics and bioinformatics approaches. The pituitary-proteome analysis identified totally 197 differential proteins as a CMS response. These deregulated proteins were involved in diverse biological functions and significant pathways potentially connected with the three different behavioral phenotypes, likely serving as new investigative protein targets. Afterwards, parallel reaction monitoring-based independent analysis found out that expression alterations in Oxct1, Sec24c, Ppp1cb, Dock1, and Coq3; Lama1, Glb1, Gapdh, Sccpdh, and Renbp; Sephs1, Nup188, Spp1, Prodh1, and Srm were specifically linked to depression-susceptible, anxiety-susceptible and insusceptible groups, respectively, suggesting that the same CMS had different impacts on the pituitary protein regulatory system. Collectively, the current proteomics research elucidated an important molecular basis and furnished new valuable insights into neurochemical commonalities and specificities of the pituitary dysfunctional mechanisms in HPA axis underlying vulnerability and resistance to stress-induced anxiety or depression.

Piriform cortex alterations in the Ts65Dn model for down syndrome

The piriform cortex is involved in olfactory information processing, that is altered in Down Syndrome. Moreover, piriform cortex has a crucial involvement in epilepsy generation and is one of the first regions affected in Alzheimer's Disease, both maladies being prevalent among Down Syndrome individuals. In this work, we studied the alterations in neuronal morphology, synaptology and structural plasticity in the piriform cortex of the Ts65Dn mouse model, which is the most used model for the study of this syndrome and mimics some of their alterations. We have observed that Ts65Dn piriform cortex displays: a reduction in dendritic arborisation, a higher density of inhibitory synapses (GAD67), a lower density of excitatory synapses (vGLUT1) and a higher density of inhibitory postsynaptic puncta (gephyrin). Under electron microscopy the excitatory presynaptic and postsynaptic elements were larger in trisomic mice than in controls. Similar results were obtained using confocal microscopy. There were less immature neurons in piriform cortex layer II in addition to a reduction in the expression of PSA-NCAM in the neuropil that subsequently can reflect impairment in structural plasticity. These data support the idea of an impaired environment with altered ratio of inhibition and excitation that involves a reduction in plasticity and dendritic atrophy, providing a possible substrate for the olfactory processing impairment observed in DS individuals.

Mass Defect-Based DiLeu Tagging for Multiplexed Data-Independent Acquisition

The unbiased selection of peptide precursors makes data-independent acquisition (DIA) an advantageous alternative to data-dependent acquisition (DDA) for discovery proteomics, but traditional multiplexed quantification approaches employing mass difference labeling or isobaric tagging are incompatible with DIA. Here, we describe a strategy that permits multiplexed quantification by DIA using mass defect-based N,N-dimethyl leucine (mdDiLeu) tags and high-resolution tandem mass spectrometry (MS2) analysis. Millidalton mass differences between mdDiLeu isotopologues produce fragment ion multiplet peaks separated in mass by as little as 5.8 mDa, enabling up to 4-plex quantification in DIA MS2 spectra. Quantitative analysis of yeast samples displayed comparable accuracy and precision for MS2-based DIA and MS1-based DDA methods. Multiplexed DIA analysis of cerebrospinal fluid revealed the dynamic proteome changes in Alzheimer's disease, demonstrating its utility for discovery of potential clinical biomarkers. We show that the mdDiLeu tagging approach for multiplexed DIA is a viable methodology for investigating proteome changes, particularly for low-abundance proteins, in different biological matrices.

Maternal social environment affects offspring cognition through behavioural and immune pathways in rats

The social environment of lactation is a key etiological factor for the occurrence of postpartum disorders affecting women and their children. Postpartum depression and anxiety disorders are highly prevalent in new mothers and negatively affect offspring's cognitive development through mechanisms which are still unclear. Here, using a rat model, we manipulated the maternal social environment during lactation and explored the pathways through which social isolation (vs. the opportunity for limited social interaction with another lactating female, from 1 day before parturition to postpartum day 16) and chronic social conflict (daily exposure to a male intruder from postpartum day 2 to day 16) affect offspring learning and memory, measured at 40 to 60 days of age. We specifically explored the consequences of these social treatments on two main hypothesized mediators likely to affect offspring neurophysiological development: the quality of maternal care and maternal inflammation factors (brain-derived neurotrophic factor, granulocyte-macrophage colony-stimulating factor, intercellular adhesion molecule 1, tissue inhibitor of metalloproteinases 1 and vascular endothelial growth factor) likely to influence offspring development through lactation. Maternal rats which had the opportunity to interact with another lactating female spent more time with their pups which, in turn, displayed improved working and reference memory. Social stress affected maternal plasma levels of cytokines that were associated with cognitive deficits in their offspring. However, females subjected to social stress were protected from these stress-induced immune changes and associated offspring cognitive impairment by increased social affiliation. These results underscore the effects of social interaction for new mothers and their offspring and can be used to inform the development of clinical preventative measures and interventions.

A Strategy for Discovery and Verification of Candidate Biomarkers in Cerebrospinal Fluid of Preclinical Alzheimer's Disease

Alzheimer's disease (AD), a progressive neurodegenerative disease, is characterized by the accumulation of senile plaques, neurofibrillary tangles, and loss of synapses and neurons in the brain. The pathophysiological process of AD begins with a long asymptomatic phase, which provides a potential opportunity for early therapeutic intervention. Therefore, it is crucial to define putative biomarkers via reliable and validated methods for early diagnosis of AD. Here, we characterized candidate biomarkers by discovery proteomics analysis of cerebrospinal fluid (CSF), revealing that 732 and 704 proteins with more than one unique peptide were identified in healthy controls and preclinical AD patients, respectively. Among them, 79 and 98 proteins were significantly altered in preclinical AD for women and men, respectively, many of which have been demonstrated with consistent regulation pattern in patients with mild cognitive impairment or AD dementia. In-house developed 5-plex isotopic N,N-dimethyl leucine (iDiLeu) tags were further utilized to verify candidate biomarkers, neurosecretory protein VGF (VGF) and apolipoprotein E (apoE). By labeling peptide standards with different iDiLeu tags, a four-point internal calibration curve was constructed to allow for determination of the absolute amount of target analytes in CSF through a single liquid chromatography-mass spectrometry run.

IL-1β suppresses cLTP-induced surface expression of GluA1 and actin polymerization via ceramide-mediated Src activation

BACKGROUND

Brain inflammation including increases in inflammatory cytokines such as IL-1β is widely believed to contribute to the pathophysiology of Alzheimer's disease. Although IL-1β-induced impairments in long-term potentiation (LTP) in acute hippocampal slices and memory functions in vivo have been well documented, the neuron-specific molecular mechanisms of IL-1β-mediated impairments of LTP and memory remain unclear.

METHODS

This study uses an in vitro approach in primary hippocampal neurons to evaluate the effect of IL-1β on chemical LTP (cLTP)-induced structural plasticity and signaling.

RESULTS

We found that IL-1β reduces both the surface expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 and the spine growth following cLTP. These effects of IL-1β were mediated by impairing actin polymerization during cLTP, as IL-1β decreased the cLTP-induced formation of F-actin, and the effect of IL-1β on cLTP-induced surface expression of GluA1 can be mimicked by latrunculin, a toxin that disrupts dynamics of actin filaments, and can be prevented by jasplakinolide, a cell-permeable peptide that stabilizes F-actin. Moreover, live-cell imaging demonstrated that IL-1β decreased the stability of the actin cytoskeleton in spines, which is required for LTP consolidation. We further examined the role of sphingolipid signaling in the IL-1β-mediated impairment of spine plasticity and found that both the neutral sphingomyelinase inhibitor GW4869 and the inhibitor of Src kinase PP2 attenuated the IL-1β-mediated suppression of cLTP-induced surface expression of GluA1 and actin polymerization.

CONCLUSIONS

These findings support a mechanism by which IL-1β, via the sphingomyelinase/ceramide/Src pathway, impairs structural spine remodeling essential for LTP consolidation and memory.

Hypocellularity in the Murine Model for Down Syndrome Ts65Dn Is Not Affected by Adult Neurogenesis

Down syndrome (DS) is caused by the presence of an extra copy of the chromosome 21 and it is the most common aneuploidy producing intellectual disability. Neural mechanisms underlying this alteration may include defects in the formation of neuronal networks, information processing and brain plasticity. The murine model for DS, Ts65Dn, presents reduced adult neurogenesis. This reduction has been suggested to underlie the hypocellularity of the hippocampus as well as the deficit in olfactory learning in the Ts65Dn mice. Similar alterations have also been observed in individuals with DS. To determine whether the impairment in adult neurogenesis is, in fact, responsible for the hypocellularity in the hippocampus and physiology of the olfactory bulb, we have analyzed cell proliferation and neuronal maturation in the two major adult neurogenic niches in the Ts656Dn mice: the subgranular zone (SGZ) of the hippocampus and the subventricular zone (SVZ). Additionally, we carried out a study to determine the survival rate and phenotypic fate of newly generated cells in both regions, injecting 5'BrdU and sacrificing the mice 21 days later, and analyzing the number and phenotype of the remaining 5'BrdU-positive cells. We observed a reduction in the number of proliferating (Ki67 positive) cells and immature (doublecortin positive) neurons in the subgranular and SVZ of Ts65Dn mice, but we did not observe changes in the number of surviving cells or in their phenotype. These data correlated with a lower number of apoptotic cells (cleaved caspase 3 positive) in Ts65Dn. We conclude that although adult Ts65Dn mice have a lower number of proliferating cells, it is compensated by a lower level of cell death. This higher survival rate in Ts65Dn produces a final number of mature cells similar to controls. Therefore, the reduction of adult neurogenesis cannot be held responsible for the neuronal hypocellularity in the hippocampus or for the olfactory learning deficit of Ts65Dn mice.

Insulin signaling regulates neurite growth during metamorphic neuronal remodeling

Although the growth capacity of mature neurons is often limited, some neurons can shift through largely unknown mechanisms from stable maintenance growth to dynamic, organizational growth (e.g. to repair injury, or during development transitions). During insect metamorphosis, many terminally differentiated larval neurons undergo extensive remodeling, involving elimination of larval neurites and outgrowth and elaboration of adult-specific projections. Here, we show in the fruit fly, Drosophila melanogaster (Meigen), that a metamorphosis-specific increase in insulin signaling promotes neuronal growth and axon branching after prolonged stability during the larval stages. FOXO, a negative effector in the insulin signaling pathway, blocked metamorphic growth of peptidergic neurons that secrete the neuropeptides CCAP and bursicon. RNA interference and CCAP/bursicon cell-targeted expression of dominant-negative constructs for other components of the insulin signaling pathway (InR, Pi3K92E, Akt1, S6K) also partially suppressed the growth of the CCAP/bursicon neuron somata and neurite arbor. In contrast, expression of wild-type or constitutively active forms of InR, Pi3K92E, Akt1, Rheb, and TOR, as well as RNA interference for negative regulators of insulin signaling (PTEN, FOXO), stimulated overgrowth. Interestingly, InR displayed little effect on larval CCAP/bursicon neuron growth, in contrast to its strong effects during metamorphosis. Manipulations of insulin signaling in many other peptidergic neurons revealed generalized growth stimulation during metamorphosis, but not during larval development. These findings reveal a fundamental shift in growth control mechanisms when mature, differentiated neurons enter a new phase of organizational growth. Moreover, they highlight strong evolutionarily conservation of insulin signaling in neuronal growth regulation.

Chromium modulates expressions of neuronal plasticity markers and glial fibrillary acidic proteins in hypoglycemia-induced brain injury

AIMS

This experiment investigated if chromium (Cr) as Cr-histidinate (CrHis) and Cr29 picolinate (CrPic) have a protective role in rats with hypoglycemia-induced brain injury, assessed by neuronal plasticity and regeneration potential.

MAIN METHODS

Male Sprague-Dawley rats were prospectively divided into 2 groups: control and hypoglycemic (induced by insulin administration, 15U/kg, i.p., n=56). Hypoglycemic rats were then received randomly 1) none, 2) dextrose (on the day of sampling), 3) CrHis, or 4) CrPic. Cr-chelates were delivered via drinking water (providing 8μg elemental Cr per day) for one week prior to the hypoglycemia induction. The expressions of neuroplasticity markers [neural cell adhesion molecule (NCAM), growth-associated protein-43 (GAP-43), glial fibrillary acidic protein (GFAP)], glucose transporters (GLUT), and nuclear transcription proteins [nuclear factor-kappa (NF-κB), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and 4-hydroxyl nonenal (HNE)] were determined using Western blot.

KEY FINDINGS

Hypoglycemia caused increases in the expressions of GLUT-1, GLUT-3, GFAP, NF-κB and HNE and decreases in the expression of NCAM's, GAP-43 and Nrf2 in the hippocampus, cerebellum, and cortex. Cr-chelates suppressed expressions of GLUTs, GFAP, NF-κB and HNE expressions and enhanced expressions of NCAM, GAP-43 and Nrf2, which were more notable for CrHis than for CrPic.

SIGNIFICANCE

In conclusion, hypoglycemia leads to cerebral injury and Cr-chelates, particularly CrHis have protective and regeneration potential in cerebral tissues through modulating neuroplasticity markers and nuclear transcription proteins as well as facilitating glucose transporters.

Significance of the cell adhesion molecules and sialic acid in neurodegeneration

The central nervous system (CNS) is a complex and precise mechanism that controls the most highest functions of the body. All of them depend on the cellular and molecular interactions called by neurobiologists "cellular plasticity". The CNS is a flexible structure but its regeneration after damage is strongly limited. Better understanding of cellular and molecular basis of brain repair can open new way in the development of therapeutic tools for neurodegeneration. Among many molecules that participate in the formation of neuronal networks, neural cell adhesion molecule (NCAM) and its sialylated derivative seem to play crucial role in the life of brain. In particular, polysialylated cell adhesion molecule (PSA-NCAM) is proposed to participate in the neuroprotective response in neurodegeneration by reducing of AMPA/NMDA receptors sensitivity to glutamate and facilitating disconnection of cell-cell interactions. These mechanisms protect from excitotoxic damage and promote dendritic/spine re-growth. This review briefly focuses on the expression and role of PSA-NCAM in neurodegenerative diseases and its potential application in therapy.

Synaptic functions of invertebrate varicosities: what molecular mechanisms lie beneath

In mammalian brain, the cellular and molecular events occurring in both synapse formation and plasticity are difficult to study due to the large number of factors involved in these processes and because the contribution of each component is not well defined. Invertebrates, such as Drosophila, Aplysia, Helix, Lymnaea, and Helisoma, have proven to be useful models for studying synaptic assembly and elementary forms of learning. Simple nervous system, cellular accessibility, and genetic simplicity are some examples of the invertebrate advantages that allowed to improve our knowledge about evolutionary neuronal conserved mechanisms. In this paper, we present an overview of progresses that elucidates cellular and molecular mechanisms underlying synaptogenesis and synapse plasticity in invertebrate varicosities and their validation in vertebrates. In particular, the role of invertebrate synapsin in the formation of presynaptic terminals and the cell-to-cell interactions that induce specific structural and functional changes in their respective targets will be analyzed.

Region and diagnosis-specific changes in synaptic proteins in schizophrenia and bipolar I disorder

Aberrant regulation of synaptic function is thought to play a role in the aetiology of psychiatric disorders, including schizophrenia and bipolar disorder. Normal neurotransmitter release is dependent on a complex group of presynaptic proteins that regulate synaptic vesicle docking, membrane fusion and fission, including synaptophysin, syntaxin, synaptosomal-associated protein-25 (SNAP-25), vesicle-associated membrane protein (VAMP), alpha-synuclein and dynamin I. In addition, structural and signalling proteins such as neural cell adhesion molecule (NCAM) maintain the integrity of the synapse. We have assessed the levels of these important synaptic proteins using Western blots, in three cortical regions (BA10, 40 and 46) obtained post-mortem from subjects with bipolar 1 disorder, schizophrenia or no history of a psychiatric disorder. In bipolar 1 disorder cortex (parietal; BA40), we found a significant increase in the expression of SNAP-25, and a significant reduction in alpha-synuclein compared with controls. These changes in presynaptic protein expression are proposed to inhibit synaptic function in bipolar 1 disorder. In schizophrenia, a significant reduction in the ratio of the two major membrane-bound forms of NCAM (180 and 140) was observed in BA10. The distinct functions of these two NCAM forms suggest that changes in the comparative levels of these proteins could lead to a destabilisation of synaptic signalling. Our data support the notion that there are complex and region-specific alterations in presynaptic proteins that may lead to alterations in synaptic activity in both schizophrenia and bipolar disorder.

Environmental Enrichment Induces Synaptic Structural Modification After Transient Focal Cerebral Ischemia in Rats

Environmental enrichment (EE), where animals are exposed to a complex novel environment, has been shown to induce synaptic plasticity in both intact and injured animals. The purpose of this study was to investigate the effects of EE on spatial memory and structural modifications of synaptic junctions in rats following transient focal cerebral ischemia. Adult male Sprague-Dawley rats underwent right middle cerebral artery occlusion (MCAO) for 40 min and reperfusion. On day 3 after MCAO or sham surgery, rats were randomly assigned for 14 days to enriched or standard environmental housing. Spatial memory was then tested by the Morris water maze. Parietal cortex and the CA1 region of hippocampus were processed for electron microscopy and stereological techniques were used to evaluate plasticity of synaptic junctions. EE after MCAO improved spatial memory, with shortened escape length, increased frequency of crossings at the location of the platform, and increased percentage of time spent in the quadrant where the platform was previously located. Synaptic ultrastructural analysis showed that EE after MCAO increased numeric synaptic density in parietal cortex, and induced structural changes in synaptic junctions, with a decreased width of synaptic clefts and increased thickness of postsynaptic densities (PSD) in parietal cortex and hippocampus, accompanying improved performance on the spatial memory task. Using Western blot analysis, we determined the expression of glutamate receptor NMDAR1, and PSD-95, the best characterized protein member of the PSD-95 family, that was abundantly expressed in the PSD of excitatory synapses. The results showed that the content of NMDAR1 was not altered in MCAO rats of EE; however, the phosphorylated NMDAR1 increased significantly when compared with the standard environment housing MCAO rats. In addition, EE inhibited the impaired expression of PSD-95 induced by MCAO in parietal cortex and hippocampus. These data suggest that improved spatial memory of cerebral ischemic rats by EE is associated with structural modifications of synaptic junctions in several brain regions.

The immunoglobulin superfamily of neuronal cell adhesion molecules: lessons from animal models and correlation with human disease

Neuronal cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) play a crucial role in the formation of neural circuits at different levels: cell migration, axonal and dendritic targeting as well as synapse formation. Furthermore, in perinatal and adult life, neuronal IgCAMs are required for the formation and maintenance of specialized axonal membrane domains, synaptic plasticity and neurogenesis. Mutations in the corresponding human genes have been correlated to several human neuronal disorders. Perturbing neuronal IgCAMs in animal models provides powerful means to understand the molecular and cellular basis of such human disorders. In this review, we concentrate on the NCAM, L1 and contactin subfamilies of neuronal IgCAMs summarizing recent functional studies from model systems and highlighting their links to disease pathogenesis.

WITHDRAWN: The Neural Cell Adhesion Molecule NCAM2/OCAM/RNCAM, a Close Relative to NCAM

Cell adhesion molecules (CAMs) constitute a large class of plasma membrane-anchored proteins that mediate attachment between neighboring cells and between cells and the surrounding extracellular matrix (ECM). However, CAMs are more than simple mediators of cell adhesion. The neural cell adhesion molecule (NCAM) is a well characterized, ubiquitously expressed CAM that is highly expressed in the nervous system. In addition to mediating cell adhesion, NCAM participates in a multitude of cellular events, including survival, migration, and differentiation of cells, outgrowth of neurites, and formation and plasticity of synapses. NCAM shares an overall sequence identity of approximately 44% with the neural cell adhesion molecule 2 (NCAM2), a protein also known as olfactory cell adhesion molecule (OCAM) and Rb-8 neural cell adhesion molecule (RNCAM), and the region-for-region sequence homology between the two proteins suggests that they are transcribed from paralogous genes. However, very little is known about the function of NCAM2, although it originally was described more than 20 years ago. In this review we summarize the known properties and functions of NCAM2 and describe some of the differences and similarities between NCAM and NCAM2.

Alteration of serum and tumoral neural cell adhesion molecule (NCAM) isoforms in patients with brain tumors

The neural cell adhesion molecule (NCAM) is involved in the intercellular junctions of neurons and glial cells. We investigated its relevance as a biomarker in gliomas which main characteristic is their high invasiveness. We studied by Western blot the pattern of serum NCAM bands in patients with gliomas (n = 34), with brain metastasis of different primary cancers (n = 27) and with benign brain tumors (n = 22)] compared with healthy controls (n = 69). For densitometric analysis NCAM bands > or = 130 kDa (HMW) and <130 kDa (LMW) were clustered. We observed that glioma patients presented higher NCAM HMW and lower NCAM LMW levels than control subjects (P < 0.01). A similar pattern was found in patients with brain metastasis or brain benign tumors, suggesting that the pattern of serum NCAM bands would be useful to detect brain tumor pathology. On the other hand, serum NCAM expression was not associated with the main clinicopathological features of gliomas, including overall survival. Interestingly, we found that 9/12 patients with glioma showed a significant decrease in NCAM HMW/LMW ratio between 1-3 months after successful tumor removal. Thus, serum NCAM could be a useful marker for monitoring treatment.NCAM expression was also analyzed at tissular level in 59 glioma sections from paraffined tumors. We observed that NCAM immunostaining was inversely correlated with the histological grade of malignancy, remaining this association in a multivariate analysis. Besides, loss of NCAM staining was significantly associated with bad prognosis in an univariate analysis.

A network dysfunction perspective on neurodegenerative diseases

Patients with Alzheimer's disease or other neurodegenerative disorders show remarkable fluctuations in neurological functions, even during the same day. These fluctuations cannot be caused by sudden loss or gain of nerve cells. Instead, it is likely that they reflect variations in the activity of neural networks and, perhaps, chronic intoxication by abnormal proteins that the brain is temporarily able to overcome. These ideas have far-reaching therapeutic implications.

MMP-2, VCAM-1 and NCAM-1 expression in the brain of rats with experimental autoimmune encephalomyelitis as a trigger mechanism for synaptic plasticity and pathology

The neural cell adhesion molecules (NCAMs), and vascular cell adhesion molecules (VCAMs) that regulate cell-to-extracellular matrix adhesion, and matrix metalloproteinases (MMPs), modulating the extracellular matrix (ECM), are considered to play an important role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). Clinical signs appearance and significant increases of MMP-2 expression in CA1 and CA3 subdomains of the hippocampus and around the central canal of the cervical spinal cord, with the clusters of VCAM-1(+) immunoreactive cells localized in the choroid plexus epithelium and hypothalamo-hypophyses portal vessel system indicate an inflammation in acute EAE. Decreased NCAM-1 expression in CA1 and CA3 fields of the hippocampus, and in a lesser degree in the basal ganglia, limbic structure and cervical spinal cord, support the concept that the demyelinating neuroinflammatory damage in an autoimmune brain affect synaptic organization of the brain, altering the balance between extracellular proteases and cell adhesion molecules which appears to be critical for both the brain plasticity and autoimmune processes.

PSA-NCAM in mammalian structural plasticity and neurogenesis

Polysialic acid (PSA) is a linear homopolymer of alpha2-8-N acetylneuraminic acid whose major carrier in vertebrates is the neural cell adhesion molecule (NCAM). PSA serves as a potent negative regulator of cell interactions via its unusual biophysical properties. PSA on NCAM is developmentally regulated thus playing a prominent role in different forms of neural plasticity spanning from embryonic to adult nervous system, including axonal growth, outgrowth and fasciculation, cell migration, synaptic plasticity, activity-induced plasticity, neuronal-glial plasticity, embryonic and adult neurogenesis. The cellular distribution, developmental changes and possible function(s) of PSA-NCAM in the central nervous system of mammals here are reviewed, along with recent findings and theories about the relationships between NCAM protein and PSA as well as the role of different polysialyltransferases. Particular attention is focused on postnatal/adult neurogenesis, an issue which has been deeply investigated in the last decade as an example of persisting structural plasticity with potential implications for brain repair strategies. Adult neurogenic sites, although harbouring all subsequent steps of cell differentiation, from stem cell division to cell replacement, do not faithfully recapitulate development. After birth, they undergo morphological and molecular modifications allowing structural plasticity to adapt to the non-permissive environment of the mature nervous tissue, that are paralled by changes in the expression of PSA-NCAM. The use of PSA-NCAM as a marker for exploring differences in structural plasticity and neurogenesis among mammalian species is also discussed.

Phosphorylation of actin-depolymerizing factor/cofilin by LIM-kinase mediates amyloid beta-induced degeneration: a potential mechanism of neuronal dystrophy in Alzheimer's disease

Deposition of fibrillar amyloid beta (fAbeta) plays a critical role in Alzheimer's disease (AD). We have shown recently that fAbeta-induced dystrophy requires the activation of focal adhesion proteins and the formation of aberrant focal adhesion structures, suggesting the activation of a mechanism of maladaptative plasticity in AD. Focal adhesions are actin-based structures that provide a structural link between the extracellular matrix and the cytoskeleton. To gain additional insight in the molecular mechanism of neuronal degeneration in AD, here we explored the involvement of LIM kinase 1 (LIMK1), actin-depolymerizing factor (ADF), and cofilin in Abeta-induced dystrophy. ADF/cofilin are actin-binding proteins that play a central role in actin filament dynamics, and LIMK1 is the kinase that phosphorylates and thereby inhibits ADF/cofilin. Our data indicate that treatment of hippocampal neurons with fAbeta increases the level of Ser3-phosphorylated ADF/cofilin and Thr508-phosphorylated LIMK1 (P-LIMK1), accompanied by a dramatic remodeling of actin filaments, neuritic dystrophy, and neuronal cell death. A synthetic peptide, S3 peptide, which acts as a specific competitor for ADF/cofilin phosphorylation by LIMK1, inhibited fAbeta-induced ADF/cofilin phosphorylation, preventing actin filament remodeling and neuronal degeneration, indicating the involvement of LIMK1 in Abeta-induced neuronal degeneration in vitro. Immunofluorescence analysis of AD brain showed a significant increase in the number of P-LIMK1-positive neurons in areas affected with AD pathology. P-LIMK1-positive neurons also showed early signs of AD pathology, such as intracellular Abeta and pretangle phosphorylated tau. Thus, LIMK1 activation may play a key role in AD pathology.

Behaviorally induced synaptogenesis and dendritic growth in the hippocampal region following transient global cerebral ischemia are accompanied by improvement in spatial learning

Reports have shown that damage to the adult brain can result in adaptive changes in regions adjacent or surrounding the site of the principal injury and that these changes may be modulated by rehabilitation training. In this study, we examined the influence of complex environment housing as a rehabilitation strategy on ischemia-induced synaptic and dendritic changes in the hippocampus. Thirty-six adult male Wistar rats were included in the study and assigned to either transient global cerebral ischemia or sham group. Following ischemic or sham surgery, rats were randomized to either complex environment housing (EC) or social condition (SC, paired housing) group during the rehabilitation period. Following 14 days of rehabilitation, rats were tested in the water maze. Our results showed that: (1) ischemic injury and EC housing were able to independently influence synaptogenesis and dendritic growth in the hippocampal area adjacent to the site of injury, and (2) EC housing-induced synaptic and dendritic changes were accompanied by enhanced functional recovery after transient global cerebral ischemia. These data suggest that behavioral experience during the rehabilitation period may be able to alter the neuronal circuitry in the surrounding region where primary neuronal damage was seen and that such modification may have contributed to functional improvement.

Elevated levels of neural recognition molecule L1 in the cerebrospinal fluid of patients with Alzheimer disease and other dementia syndromes

In this study we surveyed a total of 218 cerebrospinal fluid (CSF) samples from patients with different neurological diseases including Alzheimer disease, non-Alzheimer forms of dementia, other neurodegenerative diseases without dementia and normal controls to quantitate by capture ELISA the concentrations of the immunoglobulin superfamily adhesion molecules L1 and NCAM, and characterized by immunoblot analysis the molecular forms of L1 and NCAM. We found a significant increase of L1 and a strong tendency for increase of the soluble fragments of NCAM in the CSF of Alzheimer patients compared to the normal control group. The proteolytic fragments of L1, but not NCAM were also elevated in patients with vascular dementia and dementia of mixed type. Higher L1 concentrations were observed irrespective of age and gender. NCAM concentrations were independent of gender, but positively correlated with age and, surprisingly, also with incidence of multiple sclerosis. Thus, there was an influence of Alzheimer and non-Alzheimer dementias and neurodegeneration on L1, whereas age and neurodegeneration influenced NCAM concentrations. These observations point to an abnormal processing and/or shedding of L1 and NCAM in dementia-related neurodegeneration and age, respectively, reflecting changes in adhesion molecule-related cell interactions.

Neuroinflammation and regeneration in the early stages of Alzheimer's disease pathology

The initial stages of Alzheimer's disease pathology in the neocortex show upregulation of cell cycle proteins, adhesion and inflammation related factors, indicating the early involvement of inflammatory and regenerating pathways in Alzheimer's disease pathogenesis. These brain changes precede the neurofibrillary pathology and the extensive process of neurodestruction and (astro)gliosis. Amyloid beta deposition, inflammation and regenerative mechanisms are also early pathogenic events in transgenic mouse models harbouring the pathological Alzheimer's disease mutations, while neurodegenerative characteristics are not seen in these models. This review will discuss the relationship between neuroinflammation and neuroregeneration in the early stages of Alzheimer's disease pathogenesis.

Acoustic sensor for monitoring adhesion of Neuro-2A cells in real-time

Neuronal adhesion plays a fundamental role in growth, migration, regeneration and plasticity of neurons. However, current methods for studying neuronal adhesion cannot monitor this phenomenon quantitatively in real-time. In this work, we demonstrate the use of an acoustic sensor to measure adhesion of neuro-blastoma cells (Neuro-2A) in real-time. An acoustic sensor consisting of a quartz crystal sandwiched between gold electrodes was placed in a flow cell and filled with 600 microl of phosphate buffered saline (PBS). Two sets of in vitro experiments were performed using sensors that had uncoated gold electrodes and sensors that were coated with a known neuronal adhesion promoter (poly-l-lysine or PLL). The instantaneous resonant frequency and the equivalent motional resistance of the acoustic sensor were monitored every second. Cell Tracker was used to confirm neuronal adhesion to the surface. Addition of 10 microl of media and Neuro-2A cells into the above set-up elicited exponential changes in the resonant frequency and motional resistance of the quartz crystal with time to reach steady state in the range of 2-11 h. The steady-state change in resonant frequency in response to addition of neurons was linearly related to the number of Neuro-2A cells added (R2=0.94). Acoustic sensors coated with the adhesion promoter, PLL showed a much higher change in resonant frequency for approximately the same number of neurons. We conclude that the acoustic sensor has sufficient sensitivity to monitor neuronal adhesion in real-time. This has potential applications in the study of mechanisms of neuron-substrate interactions and the effect of molecular modulators in the extra cellular matrix.

Molecular mechanisms of dendritic spine development and remodeling

Dendritic spines are small protrusions that cover the surface of dendrites and bear the postsynaptic component of excitatory synapses. Having an enlarged head connected to the dendrite by a narrow neck, dendritic spines provide a postsynaptic biochemical compartment that separates the synaptic space from the dendritic shaft and allows each spine to function as a partially independent unit. Spines develop around the time of synaptogenesis and are dynamic structures that continue to undergo remodeling over time. Changes in spine morphology and density influence the properties of neural circuits. Our knowledge of the structure and function of dendritic spines has progressed significantly since their discovery over a century ago, but many uncertainties still remain. For example, several different models have been put forth outlining the sequence of events that lead to the genesis of a spine. Although spines are small and apparently simple organelles with a cytoskeleton mainly composed of actin filaments, regulation of their morphology and physiology appears to be quite sophisticated. A multitude of molecules have been implicated in dendritic spine development and remodeling, suggesting that intricate networks of interconnected signaling pathways converge to regulate actin dynamics in spines. This complexity is not surprising, given the likely importance of dendritic spines in higher brain functions. In this review, we discuss the molecules that are currently known to mediate the exquisite sensitivity of spines to perturbations in their environment and we outline how these molecules interface with each other to mediate cascades of signals flowing from the spine surface to the actin cytoskeleton.

Changes in number of synapses and mitochondria in presynaptic terminals in the dentate gyrus following cerebral ischemia and rehabilitation training

Damage to the adult brain can result in adaptive plasticity in regions adjacent to the site of the principal insult and that the plastic changes may be modulated by post-injury rehabilitation training. In this study, we examined the effects of rehabilitation training on synaptic morphology in the dentate gyrus following transient global cerebral ischemia and the metabolic correlates of the ultrastructural changes. Forty adult male Wistar rats were included in the study and assigned to either ischemia or sham group. Following ischemic or sham surgery, rats were randomized to either complex environment housing (EC), exercise (EX), or social condition (SC, paired housing) group. Electron microscopy and unbiased stereological methods were used to evaluate synaptic plasticity and the number and size of mitochondria in synaptic axon terminals. Increased number of granule neurons was seen in all ischemic groups and in the sham EC rats. Changes in the number of synapses per neuron in the outer and inner molecular layers of the dentate gyrus parallel those seen in granule neurons. Similarly, ischemia and behavioral experience in EC independently increased the number of synaptic mitochondria in presynaptic terminals in both the outer and inner molecular layers; however, no significant changes were seen in mitochondrial size. These data suggest a link between behavioral training and synaptic plasticity in the region adjacent to the injury and that the likely metabolic correlate of this synaptic plasticity is increased number of mitochondria at synaptic axon terminals.

Variable alternative spliced exon (VASE)-containing and VASE-lacking neural cell adhesion molecule in the dorsal and ventral hippocampus of SAMP8 mice

The neural cell adhesion molecule (NCAM) is involved in the development and synaptic plasticity of the brain. Differential splicing of the variable alternative spliced exon (VASE) in the fourth immunoglobulin domain can dramatically change the functional properties of NCAM. This paper discusses our analysis of the levels of different expression of VASE-containing NCAM (NCAM-VASE(+)) and VASE-lacking NCAM (NCAM-VASE(-)) mRNAs in the dorsal and ventral hippocampus of senescence-accelerated mice (SAM). We further investigated the individual level of NCAM-VASE(+) and NCAM-VASE(-) in relation to the capacity for spatial learning and memory as assessed by a Morris water maze task. The results showed that the levels of both NCAM-VASE(+) and NCAM-VASE(-) were increased significantly in dorsal but not ventral hippocampus in aged SAMP8 mice. The mean latencies to find the hidden platform of the learning task on the last day were positively correlated with the levels of NCAM-VASE(+) in the dorsal hippocampus of SAMP8, which reveals that the mice with high levels of NCAM-VASE(+) have poor learning performances. These results suggest that the up-regulation of NCAM-VASE(+) could be involved in the impairments of spatial learning and memory.

β-Amyloid-Induced Neurodegeneration and Protection by Structurally Diverse Microtubule-Stabilizing Agents

Deposition of beta-amyloid peptide (Abeta) and hyperphosphorylation of the tau protein are associated with neuronal dysfunction and cell death in Alzheimer's disease. Although the relationship between these two processes is not yet understood, studies have shown that both in vitro and in vivo exposure of neurons to Abeta leads to tau hyperphosphorylation and neuronal dystrophy. We previously reported that the microtubule-stabilizing drug paclitaxel (Taxol) protects primary neurons against toxicity induced by the Abeta(25-35) peptide. The studies in this report were undertaken to characterize the actions of paclitaxel more fully, to assess the effectiveness of structurally diverse microtubulestabilizing agents in protecting neurons, and to determine the time course of the protective effects of the drugs. Primary neurons were exposed to Abeta in the presence or absence of several agents shown to interact with microtubules, and neuronal survival was monitored. Paclitaxel protected neurons against Abeta(1-42) toxicity, and paclitaxel-treated cultures exposed to Abeta showed enhanced survival over Abeta-only cultures for several days. Neuronal apoptosis induced by Abeta was blocked by paclitaxel. Other taxanes and three structurally diverse microtubule-stabilizing compounds also significantly increased survival of Abeta-treated cultures. At concentrations below 100 nM, the drugs that protected the neurons did not produce detectable toxicity when added to the cultures alone. Although multiple mechanisms are likely to contribute to the neuronal cell death induced by oligomeric or fibrillar forms of Abeta, low concentrations of drugs that preserve the integrity of the cytoskeletal network may help neurons survive the toxic cascades initiated by these peptides.

Ergonomic Pain-Part 1: Etiology, Epidemiology, and Prevention

Work-related musculoskeletal disorders (MSDs) have reached a costly epidemic proportion in recent years, producing ergonomic pain as their most frequent clinical consequence. While work-related MSDs have declined in incidence, their prevalence continues. Individuals develop symptoms as a consequence of numerous factors that include force, sustained posture, repetitive motion, and vibration. Different combinations of these factors lend to different pathomechanical and pathophysiological consequences that appear to be unique to different regions of the body and related to distinctive work environmental and task characteristics. Federal and state agencies have made considerable attempts to regulate the work environment in a preventative fashion in order to reduce the incidence of ergonomic pain and other sequelae of work-related MSDs.

Neural cell adhesion molecule in human serum. Increased levels in dementia of the Alzheimer type

Memory impairment is a process associated with alterations in neuronal plasticity, synapses formation, and stabilization. As the neural cell adhesion molecule (NCAM) plays a key role in synaptic bond stabilization, we analyzed the usefulness of soluble NCAM isoforms in the diagnosis of patients with dementia of the Alzheimer type (DAT). NCAM was measured in the sera of 70 control subjects and 43 DAT patients (with different severity of cognitive impairment, GDS), employing Western blot and densitometric quantification. LMW-NCAM bands (100-130 kDa) decreased significantly with age independently of sex. DAT patients presented values of LMW-NCAM and HMW-NCAM significantly higher than healthy controls of similar age (higher than 130 kDa). Only LMW-NCAM was associated with GDS. Our results suggest that NCAM could be involved in the pathogenesis of DAT disorder and that serum NCAM levels could be useful as differential diagnostic markers of the disease.

Behaviorally-induced ultrastructural plasticity in the hippocampal region after cerebral ischemia

Behavioral training has been shown to induce synaptic plasticity in both intact and injured animals. Because of the possibility that the adaptive changes after ischemic damage may make the brain more malleable to behavioral training, we examined the effects of complex environment (EC) housing and exercise (EX) after global cerebral ischemia on synaptic structural alterations. Forty-two adult male Wistar rats were included in the study and assigned to either ischemia or sham group. Following ischemic or sham surgery, rats were randomized to either EC, EX, or social condition (SC, paired housing) group. CA1 was processed for electron microscopy and unbiased stereological techniques were used to evaluate plasticity. Significantly decreased neuron density was seen in anterior and medial CA1 in ischemic animals regardless of behavioral training. Neuron density in anterior CA1 was 31% less than the medial area. Synaptogenesis was influenced by cerebral ischemia and behavioral training in that all ischemic groups and sham EC animals showed greater number of synapses per neuron compared to the sham EX and SC groups. Analysis of synapse configuration showed that the synaptogenesis in ischemia EX and SC rats was formed mainly by synapses with single synaptic boutons, whereas in the ischemia EC and sham EC rats synaptogenesis was formed mainly by synapses with multiple synaptic boutons. Furthermore, housing of sham and ischemia rats in EC resulted in increased number of synapses with perforated postsynaptic density. Together, these data suggest that behavioral experience in EC after insult may be able to enhance synaptic plasticity.

Microglia, macrophages, perivascular macrophages, and pericytes: a review of function and identification

The phenotypic differentiation of systemic macrophages that have infiltrated the central nervous system, pericytes, perivascular macrophages, and the "real" resident microglial cells is a major immunocytochemical and immunohistochemical concern for all users of cultures of brain cells and brain sections. It is not only important in assessing the purity of cell cultures; it is also of fundamental importance in the assessment of the pathogenetic significance of perivascular inflammatory phenomena within the brain. The lack of a single membranous and/or biochemical marker allowing conclusive identification of these cells is still a major problem in neurobiology. This review briefly discusses the functions of these cells and catalogs a large number of membranous and biochemical markers, which can assist in the identification of these cells.

Expression of neuronal plasticity markers in hypoglycemia induced brain injury

The expression of neuroplasticity markers was analyzed in four brain regions, namely cerebral hemispheres (CH), cerebellum (CB), brain stem (BS) and diencephalon (DC) from insulin-induced hypoglycemic young adult rats. Significant decrease in neural cell adhesion molecule (NCAM) isoforms and growth-associated protein-43 (GAP-43) was observed following hypoglycemic injury from majority of brain regions studied. The glial fibrillary acidic protein (GFAP) level increased significantly in cerebral hemispheres and diencephalon regions, whereas, synaptophysin level increased in cerebellum, brain stem and diencephalon regions. The selective downregulation of the neuronal plasticity marker proteins (GAP-43 and NCAM), and enhanced expression of GFAP and synaptophysin suggests that in acute hypoglycemia, mechanisms other than energy failure may also contribute to neuronal cell damage in the brain.

Learning associated increase in heat shock cognate 70 mRNA and protein expression

The Morris water maze is a task widely used to investigate cellular and molecular changes associated with spatial learning and memory. This task has both spatial and aversive (swimming related stress) components. It is possible that stress may influence cellular modifications observed after learning the Morris water maze spatial task. Heat shock proteins, also known as stress proteins, are up-regulated in response to thermal stress, trauma, or environmental insults. In the rat hippocampus, psychophysiological stress increases the levels of heat shock protein 70 (HSC70). In this study, we investigated whether the expression of the hsc70 gene is modulated in the hippocampus during learning of the Morris water maze task. Five groups of rats were trained in the Morris water maze task for varying amounts of time (either 1, 2, 3, 4, or 5 days). Training consisted of 10 trials/day in which the animals were given 60s to find a submerged platform. Rats were sacrificed 24h after their last training trial. Results showed a significant increase in hsc70 mRNA and protein levels in the hippocampal formation after two and three days of training, respectively. The increase in mRNA and protein was associated with learning but not stress because the increase was not observed in the yoked control animals. These findings suggest that cellular and molecular changes can occur independent of stress. Moreover, the results are the first to implicate hsc70 expression in spatial learning.

Functional recovery of cholinergic basal forebrain neurons under disease conditions: old problems, new solutions?

Recognition of the involvement of cholinergic neurons in the modulation of cognitive functions and their severe dysfunction in neurodegenerative disorders, such as Alzheimer's disease, initiated immense research efforts aimed at unveiling the anatomical organization and cellular characteristics of the basal forebrain (BFB) cholinergic system. Concomitant with our unfolding knowledge about the structural and functional complexity of the BFB cholinergic projection system, multiple pharmacological strategies were introduced to rescue cholinergic nerve cells from noxious attacks; however, a therapeutic breakthrough is still awaited. In this review, we collected recent findings that significantly contributed to our better understanding of cholinergic functions under disease conditions, and to the design of effective means to restore lost or damaged cholinergic functions. To this end, we first provide a brief survey of the neuroanatomical organization of BFB nuclei with emphasis on major evolutionary differences among mammalian species, in particular rodents and primates, and discuss limitations of the translation of experimental data to human therapeutic applications. Subsequently, we summarize the involvement of cholinergic dysfunction in the pathogenesis of severe neurological conditions, including stroke, traumatic brain injury, virus encephalitis and Alzheimer's disease, and emphasize the critical role of pro-inflammatory cytokines as common mediators of cholinergic neuronal damage. Moreover, we review leading functional concepts on the limited recovery of cholinergic neurons and their impaired plastic re-modeling, as well as on the hampered interplay of the ascending cholinergic and monoaminergic projection systems under neurodegenerative conditions. In addition, recent advances in the dynamic labeling of living cholinergic neurons by fluorochromated antibodies, referred to as in vivo labeling, and novel neuroimaging approaches as potential diagnostic tools of progressive cholinergic decline are surveyed. Finally, the potential of cell replacement strategies using embryonic and adult stem cells, and multipotent neural progenitors, as a means to recover damaged cholinergic functions, is discussed.

Aberrant activation of focal adhesion proteins mediates fibrillar amyloid beta-induced neuronal dystrophy

Neuronal dystrophy is a pathological hallmark of Alzheimer's disease (AD) that is not observed in other neurodegenerative disorders that lack amyloid deposition. Treatment of cortical neurons with fibrillar amyloid beta (Abeta) peptides induces progressive neuritic dystrophy accompanied by a marked loss of synaptophysin immunoreactivity (Grace et al., 2002). Here, we report that fibrillar Abeta-induced neuronal dystrophy is mediated by the activation of focal adhesion (FA) proteins and the formation of aberrant FA structures adjacent to Abeta deposits. In the AD brain, activated FA proteins are observed associated with the majority of senile plaques. Clustered integrin receptors and activated paxillin (phosphorylated at Tyr-31) and focal adhesion kinase (phosphorylated at Tyr-297) are mainly detected in dystrophic neurites surrounding Abeta plaque cores, where they colocalize with hyperphosphorylated tau. Deletion experiments demonstrated that the presence of the LIM domains in the paxillin C terminus and the recruitment of the protein-Tyr phosphatase (PTP)-PEST to the FA complex are required for Abeta-induced neuronal dystrophy. Therefore, both paxillin and PTP-PEST appear to be critical elements in the generation of the dystrophic response. Paxillin is a scaffolding protein to which other FA proteins bind, leading to the formation of the FA contact and initiation of signaling cascades. PTP-PEST plays a key role in the dynamic regulation of focal adhesion contacts in response to extracellular cues. Thus, in the AD brain, fibrillar Abeta may induce neuronal dystrophy by triggering a maladaptive plastic response mediated by FA protein activation and tau hyperphosphorylation.

Chronic repetitive reaching and grasping results in decreased motor performance and widespread tissue responses in a rat model of MSD

This study investigated changes in motor skills and tissues of the upper extremity (UE) with regard to injury and inflammatory reactions resulting from performance of a voluntary forelimb repetitive reaching and grasping task in rats. Rats reached for food at a rate of 4 reaches/min, 2 h/day, and 3 days/week for up to 8 weeks during which reach rate, task duration and movement strategies were observed. UE tissues were collected bilaterally at weekly time points of 3-8 weeks and examined for morphological changes. Serum was tested for levels of interleukin-1alpha (IL-1) protein. The macrophage-specific antibody, ED1, was used to identify infiltrating macrophages and the ED2 antibody was used to identify resident macrophages. Rats were unable to maintain baseline reach rate in weeks 5 and 6 of task performance. Alternative patterns of movement emerged. Fraying of tendon fibrils was observed after 6 weeks in the mid-forelimb. After 4 weeks, a general elevation of ED1-IR macrophages were seen in all tissues examined bilaterally including the contralateral, uninvolved forelimb and hindlimbs. Significantly more resident macrophages were seen at 6 and 8 weeks in the reach limb. At 8 weeks, serum levels of IL-1alpha increased significantly above week 0. Our results demonstrate that performance of repetitive tasks elicits motor decrements, signs of injury and a cellular and tissue responses associated with inflammation.

Characterization of neuronal dystrophy induced by fibrillar amyloid beta: implications for Alzheimer's disease

Amyloid deposition, neuronal dystrophy and synaptic loss are characteristic pathological features of Alzheimer's disease (AD). We have used cortical neuronal cultures to assess the dystrophic effect of fibrillar amyloid beta (Abeta) and its relationship with neurotoxicity and synaptic loss. Treatment with fibrillar Abeta led to the development of neuritic dystrophy in the majority of the neurons present in the culture. Morphometric analysis and viability assays showed that neuronal dystrophy appeared significantly earlier and at lower Abeta concentrations than neurotoxicity, suggesting that both effects are generated independently by different cellular mechanisms. The development of dystrophic features required Abeta fibril formation and did not depend on the presence of the RHDS adhesive domain in the sequence of Abeta. Finally, a dramatic reduction in the density of synaptophysin immunoreactivity was closely associated with dystrophic changes in viable neurons. These results suggest that aberrant plastic changes and loss of synaptic integrity induced by fibrillar Abeta may play a significant role in the development of AD pathology.