The role of tissue transglutaminase in 1-methyl-4-phenylpyridinium (MPP+)-induced toxicity in differentiated human SH-SY5Y neuroblastoma cells

Tissue transglutaminase (TG2) can induce post-translational modification of proteins, resulting in protein cross-linking or incorporation of polyamines into substrates, and can also function as a signal transducing G protein. The role of TG2 in the formation of insoluble cross-links has led to its implication in some neurodegenerative conditions. Exposure of pre-differentiated SH-SY5Y cells to the Parkinsonian neurotoxin 1-methyl-4-phenylpyridinium ion (MPP+) resulted in significant dose-dependent reductions in TG2 protein levels, measured by probing Western blots with a TG2-specific antibody. Transglutaminase (TG) transamidating activity, on the other hand, monitored by incorporation of a polyamine pseudo-substrate into cellular proteins, was increased. Inhibitors of TG (putrescine) and TG2 (R283) exacerbated MPP+ toxicity, suggesting that activation of TG2 may promote a survival response in this toxicity paradigm.

Analysis of spatial patterns in histological sections of brain tissue

A method is described which enables the spatial pattern of discrete objects in histological sections of brain tissue to be determined. The method can be applied to cell bodies, sections of blood vessels or the characteristic lesions which develop in the brain of patients with neurodegenerative disorders. The density of the histological feature under study is measured in a series of contiguous sample fields arranged in a grid or transect. Data from adjacent sample fields are added together to provide density data for larger field sizes. A plot of the variance/mean ratio (V/M) of the data versus field size reveals whether the objects are distributed randomly, uniformly or in clusters. If the objects are clustered, the analysis determines whether the clusters are randomly or regularly distributed and the mean size of the clusters. In addition, if two different histological features are clustered, the analysis can determine whether their clusters are in phase, out of phase or unrelated to each other. To illustrate the method, the spatial patterns of senile plaques and neurofibrillary tangles were studied in histological sections of brain tissue from patients with Alzheimer's disease.

The visual complications of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder affecting middle-aged and elderly people. The disorder is of particular interest to Optometrists because it is associated with a range of visual problems including defects in eye movement and pupillary function. This article reviews the visual complications of PD and the pathological changes in the eye and brain which may explain these symptoms.

DNA Mutation of the progranulin (GRN) gene in familial frontotemporal lobar degeneration (FTLD):a study of the pathology of nine cases

Frontotemporal lobar degeneration (FTLD) with transactive response (TAR) DNA-binding protein of 43kDa (TDP-43) proteinopathy (FTLD-TDP) is a neurodegenerative disease characterized by variable neocortical and allocortical atrophy principally affecting the frontal and temporal lobes. Histologically, there is neuronal loss, microvacuolation in the superficial cortical laminae, and a reactive astrocytosis. A variety of TDP-43 immunoreactive changes are present in FTLD-TDP including neuronal cytoplasmic inclusions (NCI), neuronal intranuclear inclusions (NII), dystrophic neurites (DN) and, oligodendroglial inclusions (GI). Many cases of familial FTLD-TDP are caused by DNA mutations of the progranulin (GRN) gene. Hence, the density, spatial patterns, and laminar distribution of the pathological changes were studied in nine cases of FLTD-TDP with GRN mutation. The densities of NCI and DN were greater in cases caused by GRN mutation compared with sporadic cases. In cortical regions, the commonest spatial pattern exhibited by the TDP-43 immunoreactive lesions was the presence of clusters of inclusions regularly distributed parallel to the pia mater. In approximately 50% of cortical gyri, the NCI exhibited a peak of density in the upper cortical laminae while the GI were commonly distributed across all laminae. The distribution of the NII and DN was variable, the most common pattern being a peak of NII density in the lower cortical laminae and DN in the upper cortical laminae. These results suggest in FTLD-TDP caused by GRN mutation: 1) there are greater densities of NCI and DN than in sporadic cases of the disease, 2) there is degeneration of the cortico-cortical and cortico-hippocampal pathways, and 3) cortical degeneration occurs across the cortical laminae, the various TDP-43 immunoreactive inclusions often being distributed in different cortical laminae.

Parkinson's disease Part 1: symptoms, diagnosis and changes in the brain

Parkinson's disease is a common neurodegenerative disorder of middle-aged and elderly people. There are two aspects of the disease of special interest to optometrists. First, visual problems may be present in a proportion of patients with the disease. In addition, the disease is treated by a variety of drugs, some of which may have ocular complications. This article describes the incidence, symptoms, diagnosis, causes and changes in the brain in Parkinson's disease.

The incidence of corpora amylacea (CA) in the optic nerve of patients with Alzheimer's disease

Corpora amylacea (CA) are spherical or ovoid bodies 50-50 microns in diameter. They have been described in normal elderly brain as well as in a number of neurodegenerative disorders. In this study, the incidence of CA in the optic nerves of Alzheimer's disease (AD) patients was compared with normal elderly controls. Samples of optic nerves (MRC Brain Bank, Institute of Psychiatry) were taken from 12 AD patients (age range 69-94 years) and 18 controls (43-82 years). Optic nerves were fixed in 2% buffered glutaraldehyde, post-fixed in osmium tetroxide, embedded in epoxy resin and then sectioned to a thickness of 2 microns. Sections were stained with toluidine blue. CA were present in all of the optic nerves examined. In addition, a number of similarly stained but more irregularly shaped bodies were present. Fewer CA were found in the optic nerves of AD patients compared with controls. By contrast, the number or irregularly shaped bodies was increased in AD. In AD, there may be a preferential decline in the large diameter fibres which may mediate the M-cell pathway. Hence, the decline in the incidence of CA in AD may be associated with a reduction in these fibres. It is also possible that the irregualrly shaped bodies are a degeneration product of the CA.

The spatial patterns of the tau immunopositive neuronal cytoplasmic inclusions (NCI) in the tauopathies

Tau positive neuronal cytoplasmic inclusions (NCI) are the ‘hallmark’ pathological feature of several neurodegenerative diseases collectively known as the tauopathies. This study compared the spatial patterns of various types of NCI in selected tauopathies including the neurofibrillary tangles (NFT) in Alzheimer's disease (AD) and progressive supranuclear palsy (PSP), Pick bodies (PB) in Pick’s disease (PiD), and the tau positive (tau+) neurons in corticobasal degeneration (CBD). In the cerebral cortex of these disorders, the tau+ NCI were distributed in clusters and in a significant proportion of analyses, the clusters were distributed with a regular periodicity parallel to the pia mater. The inclusions in AD, PiD and CBD exhibited a similar range of spatial patterns but in PSP were less frequently clustered and more frequently randomly distributed. In gyri where the NCI were clustered, there was a significant difference in mean cluster size between disorders. Hence, clusters of NFT in AD were larger than those in PSP and the tau+ neurons in CBD and clusters of PB in PiD were larger than the tau+ neurons in CBD and the NFT in PSP. The cluster size of the tau+ neurons in CBD was similar to the NFT in PSP. The data suggest that the formation of clusters of NCI, regularly distributed parallel to the pia mater, is a common feature of the tauopathies indicating similar patterns of cortical degeneration and pathogenic mechanisms across different diseases. Furthermore, the data suggest that cortical degeneration affecting the short and long cortico-cortical pathways may be a characteristic of the tauopathies.

Reactive oxygen and nitrogen species production in cardiomyoblasts during hypoxia and reoxygenation

Hypoxia is a stress condition in which tissues are deprived of an adequate O2 supply; this may trigger cell death with pathological consequences in cardiovascular or neurodegenerative disease. Reperfusion is the restoration of an oxygenated blood supply to hypoxic tissue and can cause more cell injury. The kinetics and consequences of reactive oxygen and nitrogen species (ROS/RNS) production in cardiomyoblasts are poorly understood. The present study describes the systematic characterization of the kinetics of ROS/RNS production and their roles in cell survival and associated protection during hypoxia and hypoxia/reperfusion. H9C2 cells showed a significant loss of viability under 2% O2 for 30min hypoxia and cell death; associated with an increase in protein oxidation. After 4h, apoptosis induction under 2% O2 and 10% O2 was dependent on the production of mitochondrial superoxide (O2-•) and nitric oxide (•NO), partly from nitric oxide synthase (NOS). Both apoptotic and necrotic cell death during 2% O2 for 4h could be rescued by the mitochondrial complex I inhibitor; rotenone and NOS inhibitor; L-NAME. Both L-NAME and the NOX (NADPH oxidase) inhibitor; apocynin reduced apoptosis under 10% O2 for 4h hypoxia. The mitochondrial uncoupler; FCCP significantly reduced cell death via a O2-• dependent mechanism during 2% O2, 30min hypoxia. During hypoxia (2% O2, 4h)/ reperfusion (21% O2, 2h), metabolic activity was significantly reduced with increased production of O2-• and •NO, during hypoxia but, partially restored during reperfusion. O2-• generation during hypoxia/reperfusion was mitochondrial and NOX- dependent, whereas •NO generation depended on both NOS and non-enzymatic sources. Inhibition of NOS worsened metabolic activity during reperfusion, but did not effect this during sustained hypoxia. Nrf2 activation during 2% O2, a sustained hypoxia and reperfusion was O2-•/•NO dependent. Inhibition of NF-?B activation aggravated metabolic activity during 2% O2, 4h hypoxia. In conclusion, mitochondrial O2-•, but, not ATP depletion is the major cause of apoptotic and necrotic cell death in cardiomyoblasts under 2% O2, 4h hypoxia, whereas apoptotic cell death under 10% O2, 4h, is due to NOS-dependent •NO. The management of ROS/RNS rather than ATP is required for improved survival during hypoxia. O2-• production from mitochondria and NOS is cardiotoxic during hypoxia/reperfusion. NF-?B activation during hypoxia and NOS activation during reperfusion is cardiomyoblast protective.

Quantitative methods in neuropathology

The last decade has seen a considerable increase in the application of quantitative methods in the study of histological sections of brain tissue and especially in the study of neurodegenerative disease. These disorders are characterised by the deposition and aggregation of abnormal or misfolded proteins in the form of extracellular protein deposits such as senile plaques (SP) and intracellular inclusions such as neurofibrillary tangles (NFT). Quantification of brain lesions and studying the relationships between lesions and normal anatomical features of the brain, including neurons, glial cells, and blood vessels, has become an important method of elucidating disease pathogenesis. This review describes methods for quantifying the abundance of a histological feature such as density, frequency, and 'load' and the sampling methods by which quantitative measures can be obtained including plot/quadrat sampling, transect sampling, and the point-quarter method. In addition, methods for determining the spatial pattern of a histological feature, i.e., whether the feature is distributed at random, regularly, or is aggregated into clusters, are described. These methods include the use of the Poisson and binomial distributions, pattern analysis by regression, Fourier analysis, and methods based on mapped point patterns. Finally, the statistical methods available for studying the degree of spatial correlation between pathological lesions and neurons, glial cells, and blood vessels are described.

General features of Multiple System Atrophy

Multiple system atrophy (MSA) is a rare movement disorder and a member of a group of neurodegenerative diseases referred to collectively as the ‘parkinsonian syndromes’. Characteristic of these syndromes is that the patient exhibits symptoms of ‘parkinsonism’, viz., a range of problems involving movement, most typically manifest in Parkinson’s disease (PD) itself1, but also seen in progressive supranuclear palsy (PSP), and to some extent in dementia with Lewy bodies (DLB). MSA is a relatively ‘new’ descriptive term and is derived from three previously described diseases, viz., olivopontocerebellar atrophy, striato-nigral degeneration, and Shy-Drager syndrome. The classical symptoms of MSA include parkinsonism, ataxia, and autonomic dysfunction.6 Ataxia describes a gross lack of coordination of muscle movements while autonomic dysfunction involves a variety of systems that regulate unconscious bodily functions such as heart rate, blood pressure, bladder function, and digestion. Although primarily a neurological disorder, patients with MSA may also develop visual signs and symptoms that could be useful in differential diagnosis. The most important visual signs may include oculomotor dysfunction and problems in pupil reactivity but are less likely to involve aspects of primary vision such as visual acuity, colour vision, and visual fields. In addition, the eye-care practitioner can contribute to the management of the visual problems of MSA and therefore, help to improve quality of life of the patient. Hence, this first article in a two-part series describes the general features of MSA including its prevalence, signs and symptoms, diagnosis, pathology, and possible causes.

Visual signs and symptoms of Multiple System Atrophy

Multiple system atrophy (MSA) is a rare movement disorder and a member of a group of neurodegenerative diseases, which include Parkinson’s disease (PD) and progressive supranuclear palsy (PSP), and referred to as the ‘parkinsonian syndromes’. Although primarily a neurological disorder, patients with MSA may also develop visual signs and symptoms that could be useful in differential diagnosis. In addition, the eye-care practitioner may contribute to the management of visual problems of MSA patients and therefore, help to improve quality of life. This second article in the series considers the visual signs and symptoms of MSA with special reference to those features most useful in differential diagnosis of the parkinsonian syndromes.

NT2 derived neuronal and astrocytic network signalling

A major focus of stem cell research is the generation of neurons that may then be implanted to treat neurodegenerative diseases. However, a picture is emerging where astrocytes are partners to neurons in sustaining and modulating brain function. We therefore investigated the functional properties of NT2 derived astrocytes and neurons using electrophysiological and calcium imaging approaches. NT2 neurons (NT2Ns) expressed sodium dependent action potentials, as well as responses to depolarisation and the neurotransmitter glutamate. NT2Ns exhibited spontaneous and coordinated calcium elevations in clusters and in extended processes, indicating local and long distance signalling. Tetrodotoxin sensitive network activity could also be evoked by electrical stimulation. Similarly, NT2 astrocytes (NT2As) exhibited morphology and functional properties consistent with this glial cell type. NT2As responded to neuronal activity and to exogenously applied neurotransmitters with calcium elevations, and in contrast to neurons, also exhibited spontaneous rhythmic calcium oscillations. NT2As also generated propagating calcium waves that were gap junction and purinergic signalling dependent. Our results show that NT2 derived astrocytes exhibit appropriate functionality and that NT2N networks interact with NT2A networks in co-culture. These findings underline the utility of such cultures to investigate human brain cell type signalling under controlled conditions. Furthermore, since stem cell derived neuron function and survival is of great importance therapeutically, our findings suggest that the presence of complementary astrocytes may be valuable in supporting stem cell derived neuronal networks. Indeed, this also supports the intriguing possibility of selective therapeutic replacement of astrocytes in diseases where these cells are either lost or lose functionality.

The anti-inflammatory action of tetracyclines

For six decades tetracyclines have been successfully used for their broad spectrum antibiotic effects. However, non-antibiotic effects of tetracyclines have been reported. The anti-inflammatory effects of tetracycline drugs have been investigated in the context of a range of inflammatory diseases including sepsis and a number of neurodegenerative diseases. This thesis investigates the effects of a range of clinically important tetracyclines (oxytetracycline, doxycycline, minocycline and tigecycline) on the ability of the J774.2 cell line to produce nitric oxide when stimulated with the bacterial cell wall component, LPS. The proteome of J774.2 cells was analysed in response to LPS stimulation (1 µg/ml) with and without prior treatment with minocycline (50µg/ml), this allows the unbiased analysis of the cellular proteome in response to minocycline and LPS, protein spots of interest were excised and identified by nano-electrospray ionisation-linear ion trap mass spectroscopy. All of the tetracyclines that were investigated inhibited LPS-induced nitric oxide production in a dose dependent manner and this was due to the inhibition of inducible nitric oxide synthase expression. This is the first report to show that tigecycline inhibits inducible nitric oxide expression and nitric oxide production. Using two-dimensional gel electrophoresis and total protein staining eleven proteins were identified as being modulated by LPS. Of these eleven proteins; expression of some, but not all was modulated when the cells received a prior treatment with minocycline suggesting that minocycline does not completely block LPS-induced macrophage activation but probably specifically acts on particular inflammatory signaling pathways in macrophages. Three protein spots with a similar molecular weight but different pI values identified in this proteomic study were identified as ATP synthase ß chain. These different protein spots probably correspond to different phosphorylation states of the protein, suggesting that minocycline affects the balance of protein kinase and protein phosphatase activity in the immune response.

Spatial patterns of TDP-43 neuronal cytoplasmic inclusions (NCI) in fifteen cases of frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP)

Neuronal cytoplasmic inclusions (NCI) immunoreactive for transactive response DNA-binding protein (TDP-43) are the pathological hallmark of frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP). We studied the spatial patterns of the TDP-43 immunoreactive NCI in the frontal and temporal cortex of 15 cases of FTLD-TDP. The NCI were distributed parallel to the tissue boundary predominantly in regular clusters 50-400 µm in diameter. In five cortical areas, the size of the clusters approximated to the cells of the cortico-cortical pathways. In most regions, cluster size was smaller than 400 µm. There were no significant differences in spatial patterns between familial and sporadic cases. Cluster size of the NCI was not correlated with disease duration, brain weight, Braak stage, or disease subtype. The spatial pattern of the NCI was similar to that of neuronal inclusions in other neurodegenerative diseases and may reflect a common pattern of degeneration involving the cortico-cortical projections.

The visual cortex in Alzheimer disease:laminar distribution of the pathological changes in visual areas V1 and V2

Alzheimer’s disease (AD) is an important neurodegenerative disorder causing visual problems in the elderly population. The pathology of AD includes the deposition in the brain of abnormal aggregates of ?-amyloid (A?) in the form of senile plaques (SP) and abnormally phosphorylated tau in the form of neurofibrillary tangles (NFT). A variety of visual problems have been reported in patients with AD including loss of visual acuity (VA), colour vision and visual fields; changes in pupillary responses to mydriatics, defects in fixation and in smooth and saccadic eye movements; changes in contrast sensitivity and in visual evoked potentials (VEP); and disturbances in complex visual tasks such as reading, visuospatial function, and in the naming and identification of objects. In addition, pathological changes have been observed to affect the eye, visual pathway, and visual cortex in AD. To better understand degeneration of the visual cortex in AD, the laminar distribution of the SP and NFT was studied in visual areas V1 and V2 in 18 cases of AD which varied in disease onset and duration. In area V1, the mean density of SP and NFT reached a maximum in lamina III and in laminae II and III respectively. In V2, mean SP density was maximal in laminae III and IV and NFT density in laminae II and III. The densities of SP in laminae I of V1 and NFT in lamina IV of V2 were negatively correlated with patient age. No significant correlations were observed in any cortical lamina between the density of NFT and disease onset or duration. However, in area V2, the densities of SP in lamina II and lamina V were negatively correlated with disease duration and disease onset respectively. In addition, there were several positive correlations between the densities of SP and NFT in V1 with those in area V2. The data suggest: (1) NFT pathology is greater in area V2 than V1, (2) laminae II/III of V1 and V2 are most affected by the pathology, (3) the formation of SP and NFT in V1 and V2 are interconnected, and (4) the pathology may spread between visual areas via the feed-forward short cortico-cortical connections.