The relationships between neuroglial and neuronal changes in Alzheimer's disease, and the related controversies II: gliotherapies and multimodal therapy.

Since the original description of Alzheimer´s disease (AD), research into this condition has mainly focused on assessing the alterations to neurons associated with dementia, and those to the circuits in which they are involved. In most of the studies on human brains and in many models of AD, the glial cells accompanying these neurons undergo concomitant alterations that aggravate the course of neurodegeneration. As a result, these changes to neuroglial cells are now included in all the "pathogenic cascades" described in AD. Accordingly, astrogliosis and microgliosis, the main components of neuroinflammation, have been integrated into all the pathogenic theories of this disease, as discussed in this part of the two-part monograph that follows an accompanying article on gliopathogenesis and glioprotection. This initial reflection verified the implication of alterations to the neuroglia in AD, suggesting that these cells may also represent therapeutic targets to prevent neurodegeneration. In this second part of the monograph, we will analyze the possibilities of acting on glial cells to prevent or treat the neurodegeneration that is the hallmark of AD and other pathologies. Evidence of the potential of different pharmacological, non-pharmacological, cell and gene therapies (widely treated) to prevent or treat this disease is now forthcoming, in most cases as adjuncts to other therapies. A comprehensive AD multimodal therapy is proposed in which neuronal and neuroglial pharmacological treatments are jointly considered, as well as the use of new cell and gene therapies and non-pharmacological therapies that tend to slow down the progress of dementia.

The relationships between neuroglial alterations and neuronal changes in Alzheimer's disease, and the related controversies I: Gliopathogenesis and glioprotection.

Since Alois Alzheimer described the pathology of Alzheimer's disease in 1907, an increasing number of studies have attempted to discover its causes and possible ways to treat it. For decades, research has focused on neuronal degeneration and the disruption to the neural circuits that occurs during disease progression, undervaluing in some extent the alterations to glial cells even though these alterations were described in the very first studies of this disease. In recent years, it has been recognized that different families of neuroglia are not merely support cells for neurons but rather key and active elements in the physiology and pathology of the nervous system. Alterations to different types of neuroglia (especially astroglia and microglia but also mature oligodendroglia and oligodendroglial progenitors) have been identified in the initial neuropathological changes that lead to dementia, suggesting that they may represent therapeutic targets to prevent neurodegeneration. In this review, based on our own studies and on the relevant scientific literature, we argue that a careful and in-depth study of glial cells will be fundamental to understanding the origin and progression of Alzheimer's disease. In addition, we analyze the main issues regarding the neuroprotective and neurotoxic role of neuroglial changes, reactions and/or involutions in both humans with Alzheimer's disease and in experimental models of this condition.

Reflections on Cerebellar Neuropathology in Classical Scrapie.

In this review, the most important neuropathological changes found in the cerebella of sheep affected by classical natural scrapie are discussed. This disease is the oldest known of a group of unconventional "infections" caused by toxic prions of different origins. Scrapie is currently considered a "transmissible spongiform encephalopathy" (due to its neuropathological characteristics and its transmission), which is the paradigm of prion pathologies as well as many encephalopathies (prion-like) that present aberrant deposits of insoluble protein with neurotoxic effects due to errors in their catabolization ("misfolding protein diseases"). The study of this disease is, therefore, of great relevance. Our work data from the authors' previous publications as well as other research in the field. The four most important types of neuropathological changes are neuron abnormalities and loss, neurogliosis, tissue vacuolization (spongiosis) and pathological or abnormal prion protein (PrP) deposits/deposition. These findings were analyzed and compared to other neuropathologies. Various aspects related to the presentation and progression of the disease, the involution of different neuronal types, the neuroglial responses and the appearance of abnormal PrP deposits are discussed. The most important points of controversy in scrapie neuropathology are presented.

Defective Insulin Signalling, Mediated by Inflammation, Connects Obesity to Alzheimer Disease; Relevant Pharmacological Therapies and Preventive Dietary Interventions.

BACKGROUND: Recent evidence suggests that obesity, besides being a risk factor for cardiovascular events, also increases the risk of Alzheimer's disease. Insulin resistance is common in all cases of obesity and appears to be the linkage between both diseases. Obesity, often associated with excessive fat and sugar intake, represents a preclinical stage toward insulin resistance during which nutrition intervention is likely to have maximum effect. OBJECTIVE: In this way, healthy lifestyles lifetime to prevent obesity-related modifiable risk factors such as inflammation, oxidative stress and metabolic disorders could be simultaneously beneficial for preserving cognition and controlling the Alzheimer's disease. METHOD: This review relates extensive research literature on facts linking nutrients and dietary patterns to obesity and Alzheimer's disease. In addition briefly presents molecular mechanisms involved in obesity- induced insulin resistance and the contribution of peripheral inflammatory and defective insulin signalling pathways, as well as ectopic lipids accumulation to Alzheimer's development through brain inflammation, neuronal insulin resistance, and cognitive dysfunction seen in Alzheimer's disease. RESULTS: The work relates current and emerging pharmacological and non-pharmacological therapies for the management of obesity, insulin resistance and Alzheimer's considering them as disorders with common molecular features. CONCLUSION: The findings of this review validate the importance of some nutritional interventions as possible approach to prevent or delay simultaneously progression of Alzheimer's disease and obesity.

Brain local and regional neuroglial alterations in Alzheimer's Disease: cell types, responses and implications.

From birth to death, neurons are dynamically accompanied by neuroglial cells in a very close morphological and functional relationship. Three families have been classically considered within the CNS: astroglia, oligodendroglia and microglia. Many types/subtypes (including NGR2+ cells), with a wide variety of physiological and pathological effects on neurons, have been described using morphological and immunocytochemical criteria. Glio-glial, glio-neuronal and neuro-glial cell signaling and gliotransmission are phenomena that are essential to support brain functions. Morphofunctional changes resulting from the plasticity of all the glial cell types parallel the plastic neuronal changes that optimize the functionality of neuronal circuits. Moreover, neuroglia possesses the ability to adopt a reactive status (gliosis) in which, generally, new functions arise to improve and restore if needed the neural functionality. All these features make neuroglial cells elements of paramount importance when attempting to explain any physiological or pathological processes in the CNS, because they are involved in both, neuroprotection/neurorepair and neurodegeneration. There exist diverse and profound, regional and local, neuroglial changes in all involutive processes (physiological and pathological aging; neurodegenerative disorders, including Alzheimer ´s disease -AD-), but today, the exact meaning of such modifications (the modifications of the different neuroglial types, in time and place), is not well understood. In this review we consider the different neuroglial cells and their responses in order to understand the possible role they fulfill in pathogenesis, diagnosis and treatment (preventive or palliative) of AD. The existence of differentiated and/or concurrent pathogenic and neuro-protective/neuro-restorative astroglial and microglial responses is highlighted.

Blood-based biomarkers of Alzheimer's disease: diagnostic algorithms and new technologies.

New concepts about Alzheimer's disease (AD), considered as a clinical-biological entity, make essential the definition of biomarkers that could be used for the in vivo diagnosis of the disorder before dementia develops. Different types of genetic, biochemical and neuroimaging markers have been described, highlighting some of the changes that occur in the brain during the course of the disease, yet there is little proof of their pathognomonic and diagnostic value. Furthermore, many of the assays used are difficult to perform, the equipment/reagents are expensive or potentially hazardous (e.g.; use of radioactive compounds, CSF extraction). Thus, there is a need to define more suitable and convenient approaches, such as the determination of blood parameters that are easy to obtain and that can be repeated as necessary without contraindications. These data can be used by algorithms that combine specific and non-specific changes to classify patients at different stages of AD and/or distinguish AD from other related diseases with a greater specificity and reliability (> 80%). The blood parameters considered in this review are varied, including: ß-amyloid, tau, apolipoproteins and proteins, as well as the metabolic behavior of blood cells, etc. Among the proteins, cytokines/chemokines and other cell factors related to both neuro-inflammatory and peripheral-inflammatory processes in AD are of prime importance. New technologies to detect and quantify these substances, reasonably priced such as the vibrational spectroscopy, panels of parameters and algorithms to assess the results, would be fundamental for the early AD diagnosis and to define new potential therapies.

Vibrational spectroscopic analysis of peripheral blood plasma of patients with Alzheimer's disease.

Using Raman and infrared spectroscopy, we monitored spectral changes occurring in the blood plasma of patients with Alzheimer's disease (AD) in relation to healthy controls. The protein secondary structure as reflected by amide I band involves ß-sheet enrichment, which may be attributable to Aß peptide formation and to increasing proportion of the globulins that are ß-sheet rich. Likewise, the behavior of the infrared 1200-1000-cm(-1) region and the Raman 980-910- and 450-400-cm(-1) regions can be explained in terms of the said plasma composition change. Further, the 744-cm(-1) Raman band from healthy control plasma shows frequency upshifting in the course of AD, which may be generated by the platelets collected in blood plasma. Linear discrimination analysis and receiver operating characteristic (ROC) analysis have been used to distinguish between patients with AD and age-matched healthy controls with a diagnostic accuracy of about 94%.

Ultrastructural changes in the progress of natural Scrapie regardless fixation protocol.

Because few studies regarding ultrastructural pathological changes associated with natural prion diseases have been performed, the present study primarily intended to determine consistent lesions at the subcellular level and to demonstrate whether these changes are evident regardless of the fixation protocol. Thus far, no assessment method has been developed for classifying the possible variations according to the disease stage, although such an assessment would contribute to clarifying the pathogenesis of this neurodegenerative disease. Therefore, animals at different disease stages were included here. This study presents the first description of lesions associated with natural Scrapie in the cerebellum. Vacuolation, which preferentially occurs around Purkinje cells and which displays a close relation with glial cells, is one of the most novel observations provided in this study. The disruption of hypolemmal cisterns in this neuronal type and the presence of a primary cilium in the granular layer both represent the first findings concerning prion diseases. The possibility of including samples regardless of their fixation protocol is confirmed in this work. Therefore, a high proportion of tissue bank samples that are currently being wasted can be included in ultrastructural studies, which constitute a valuable source for information regarding physiological and pathological samples.

Astroglial cell subtypes in the cerebella of normal adults, elderly adults, and patients with Alzheimer's disease: a histological and immunohistochemical comparison.

Objectives and experimental design Cerebella of young adults, elderly adults, and patients with Alzheimer's disease (AD) (with and without cerebellar amyloid deposits) were studied by Golgi staining and glial fibrillary acid protein (GFAP) immunocytochemical methods. Observations Three subtypes of Golgi epithelial cells and nine subtypes of stellate neuroglia (both normal and hypertrophic) were defined by their morphology, their GFAP-reactivity, their specific location in the cortical layers, and their responses in senility and AD. The GFAP immunoreaction was subtype specific. In aged and AD cerebella, different morphological and GFAP-immunoreactive subtype-specific changes were observed: in the white matter, the subtypes were always GFAP-immunopositive, but in the grey matter some astroglial subtypes showed a variable or no increase in GFAP staining. The astrocytes at the limits of the granule cell layer showed more and longer processes. Variations were seen in one or more folia, involving one or more subtypes and affecting different numbers of cells of each subtype. No clear differences were seen in glial reactivity between beta-amyloid positive and ß-amyloid (Aß) negative AD cerebella. No important relationships were found between Aß deposits. In aged and AD cerebella, different subtypes expressed new proteins (APP, calretinin). Conclusions The existence of different glial subtypes in different locations suggests they have different functions. General and local variations in these subtypes suggest that both general and local induction factors must also exist. The responses of glial cells to as-yet undefined stimuli might lead to general or local neuronal changes important in senility and the pathogenic course of AD.

Morphological approach to assess the involvement of astrocytes in prion propagation.

Transmissible Spongiform Encephalopathies (TSEs) are a group of neurodegenerative disorders affecting animals and humans and for which no effective treatment is available to date. Vacuolation, neuronal/neurite degeneration, deposition of pathological prion protein (PrPsc) and gliosis are changes typically found in brains from TSE affected individuals. However, the actual role of this last feature, microgliosis and astrocytosis, has not been precisely determined. The overall objective of this work is to assess the involvement of glial cells as components of the host protective system in prion propagation; specifically, to analyze the behavior of astroglial cells in prion progression. To achieve this aim, histopathological and immunohistochemical techniques were carried out on samples from cerebella using Scrapie as the prototype of natural TSEs as this made it possible to assess different stages of the disease; specifically, ages and genotypes from Scrapie-affected animals corresponding to different sources, by using optical, confocal and electron microscopy. The results provided in the present study demonstrate the indisputable involvement of astroglia in prion progression by showing specific changes of this glial population matching up to the evolution of the disease. Moreover, cerebellar lesions mainly associated to Purkinje cells that have not previously been reported in animal prion diseases in natural transmission are described here. The close relationship between PrPsc and GFAP hiperimmunoreactivity and Purkinje cells, alongside the evident thickening of their neurites at terminal stages demonstrated in this study, suggest that these neurons are the main target of this neurodegenerative disease.

Variability in the effects of nicotine on different regions of the brain: changes in the concentration of superoxide dismutase isoforms.

Previous studies have shown that rats subjected to subchronic treatment with nicotine experience changes in COX-2 (a marker of pro-inflammatory systems) and accumulate lipid hydroperoxides (a marker of oxidative stress) in the CNS (CNSMC, 2010; 10:180-206) (hippocampus, frontoparietal cortex and cerebellar cortex). Such changes are specific to each region since each contains different types of neuronal and glial cells with different nicotine receptors. They also differ in animals exposed to a source of oxidative stress, such as D-amphetamine. This paper discusses the changes in other markers of oxidative stress - the isozymes of superoxide dismutase Mn-SOD and Cu/Zn-SOD - in nicotine- and nicotine + D-amphetamine-treated rats. The biochemical and histochemical changes observed were specific to each region (in general very marked in the frontoparietal cortex and the hippocampus but less so in the cerebellar cortex) and each type of neuronal and glial cell. The SODs induced by nicotine may exert a neuroprotective effect via the reduction of oxidative stress. This might be beneficial in the treatment of neurodegenerative diseases. The fact that nicotine did not greatly increase the SODs in the rats treated with D-amphetamine may indicate that the effect of nicotine is partially or totally abolished in situations of oxidative stress. However, since ROS and lipid hydroperoxide levels are also reduced when nicotine is administered to such animals, it could be argued that nicotine is beneficial.

Discrimination analysis of blood plasma associated with Alzheimer's disease using vibrational spectroscopy.

In this study we have determined whether Raman and infrared spectroscopy of blood plasma differentiates Alzheimer's disease (AD) from normal aging of healthy controls. Spectroscopic analysis was conducted on blood plasma samples from 8 mild AD, 16 moderate AD, 11 severe AD, and 12 normal elderly control persons using Fourier transform spectrometers and a near-infrared laser beam as excitation source for Raman spectroscopy. Spectra were processed employing discriminant analysis to determine whether band areas and frequency-intensity relationships might reveal biochemical differences associated with AD. Seven spectral biomarkers were identified in the Raman regions of 1700-1600 cm-1 (protein secondary structure), 980-910 cm-1 (protein α-helices), 790-730 cm-1 (protein tertiary structure), and 440-390 cm-1 (protein backbone) and in the infrared regions of 1700-1600 cm-1 (protein secondary structure) and 1150-1000 cm-1 (oxidative stress). This discriminant analysis model differentiated AD from normal aging of elderly control persons with a sensitivity of 89% and specificity of 92%. Moreover, specificity increases to 100% for the detection of mild AD. In summary, our results open the possibility of using this spectroscopic approach as a non-invasive, rapid, and relatively inexpensive procedure for early accurate diagnosis of AD.

Objective assessment of olfactory function using functional magnetic resonance imaging.

OBJECTIVE: To show the results of a device that generates automated olfactory stimuli suitable for functional magnetic resonance imaging (fMRI) experiments. MATERIAL AND METHODS: Ten normal volunteers, 5 women and 5 men, were studied. The system allows the programming of several sequences, providing the capability to synchronise the onset of odour presentation with acquisition by a trigger signal of the MRI scanner. The olfactometer is a device that allows selection of the odour, the event paradigm, the time of stimuli and the odour concentration. The paradigm used during fMRI scanning consisted of 15-s blocks. The odorant event took 2s with butanol, mint and coffee. RESULTS: We observed olfactory activity in the olfactory bulb, entorhinal cortex (4%), amygdala (2.5%) and temporo-parietal cortex, especially in the areas related to emotional integration. CONCLUSIONS: The device has demonstrated its effectiveness in stimulating olfactory areas and its capacity to adapt to fMRI equipment.

Infrared spectroscopic analysis of mononuclear leukocytes in peripheral blood from Alzheimer's disease patients.

Peripheral mononuclear leukocytes from Alzheimer's disease (AD) patients were analyzed by infrared spectroscopy and their spectroscopic properties were compared with those from age-matched healthy controls. Two-dimensional correlation analysis of mean spectra measured at various disease stages shows that the protein secondary structure from AD patients involves ß-sheet enrichment and carbonyl intensity increase relative to healthy controls. The area percentages of ß-sheets, which were obtained by using a peak ratio second-derivative spectral treatment, were used for receiver operating characteristic (ROC) analysis to distinguish between patients with AD and age-matched healthy controls. The critical concentration and area under the curve (AUC) were determined by this curve analysis which showed a good performance for this quantitative assay. The results were 90% sensitivity and 90.5% specificity for determinations involving mild and moderate AD patients, and 82.1% sensitivity and 90.5% specificity for determinations involving patients at the three AD stages (mild, moderate, and severe). The AUC was greater than 0.85 in both scenarios. Taken together these results show that healthy controls are distinguished from mild and moderate AD patients better than from patients with severe disease and suggest that this infrared analysis is a promising strategy for AD diagnostics.

Changes induced by natural scrapie in the calretinin-immunopositive cells and fibres of the sheep cerebellar cortex.

Calretinin (CR)-immunopositive cells and fibres in the cerebellar cortex (vermal archicerebellum and neocerebellum) of scrapie-affected, ARQ/ARQ, Rasa Aragonesa breed sheep were studied in comparison with healthy, young and aged, ARQ/ARQ, Rasa Aragonesa animals and with Manchega breed sheep. The scrapie-affected sheep showed signs of both cellular involution and hypertrophic/hyperimmunoreactive responses in all neuronal subtypes; the distribution of the neuronal subtypes in the archi- and neocerebellum, however, did not change compared with controls. The results suggest that the different CR expression and/or CR content of cerebellar cortical neurons in scrapie-affected sheep are more related to their specific functions than any neuroprotective response. The reduction in the cell density of some CR-immunopositive neuronal subsets (i.e. unipolar brush cells) is contradictory to the supposed neuroprotective role of the calcium binding protein CR. However, the hyperimmunoreactivity of many CR-immunopositive neuronal subsets (e.g. the Purkinje cells) suggests the involvement of an over-expression of CR (transitory or restricted to selected neurons) as an adaptative mechanism to fight against the neurodegeneration caused by this prion disease. The changes in the number of immunopositive cells and the hypertrophic/hyperimmunoreactive response seen in scrapie-affected and aged sheep suggests that some different and some similar mechanisms are at work in this disease and aging.

Quality of life in patients with smell loss due to upper respiratory tract infections.

PURPOSE: Upper respiratory tract infections (URTIs) are among the most frequent causes of dysosmias. It has been reported that acute anosmic patients often experience a feeling of personal isolation, display less interest in eating, and feel emotionally impaired. Our goal is to describe the quality of life (QOL) in patients with URTI olfactory loss. MATERIAL AND METHODS: A retrospective and descriptive patient-based study was performed. From 2002 to 2007, 51 patients with URTI olfactory loss (40 women [78.4%] and 11 men [21.6%]) were studied. The mean age was 53.3 ± 1.8 years. Olfactory function was assessed using the Connecticut Chemosensorial Clinical Research Center test. All patients completed the QOL questionnaire Rhinosinusitis Disability Index. The following were determined: total score; visual analogue scale from 1 to 10; and functional, emotional, and physical domains. Descriptive analysis and Mann-Whitney U nonparametric test were used. RESULTS: Rhinosinusitis Disability Index data showed that questions f2, f4, p8, and p20 reached the highest score. The patients' mean overall rating of the severity of olfactory impairment was 3.9 ± 2.8, which fell into the moderate category. CONCLUSIONS: The patients' mean overall rating of the severity of olfactory impairment fell into the moderate category. The follow-up time span is important to assess the QOL of patients.

Characterization of a clinical olfactory test with an artificial nose.

Clinical olfactory tests are used to address hyposmia/anosmia levels in patients with different types of olfactory impairments. Typically, a given test is employed clinically and then replaced by a new one after a certain period of use which can range from days to several months. There is a need to assess control quality of these tests and also for a procedure to quantify their degradation over time. In this paper we propose a protocol to employ low-cost artificial noses for the quantitative characterization of olfactory tests used in clinical studies. In particular, we discuss a preliminary study on the Connecticut Chemosensorial Clinical Research Center Test kit which shows that some odorants, as sensed by an artificial nose, seem to degrade while others are potentiated as the test ages. We also discuss the need to establish a map of correspondence between human and machine olfaction when artificial noses are used to characterize or compare human smell performance in research and clinical studies.

Diversity and variability of the effects of nicotine on different cortical regions of the brain - therapeutic and toxicological implications.

Nicotine/nicotine agonists or allosteric modulators of nicotine receptors have been suggested as the most important therapeutic agents in the prevention and clinical control of cognitive impairment which characterize neuropsychiatric and neurodegenerative disorders such as schizophrenia, attention deficit/hyperactivity disorder and Alzheimer's disease. Both clinical studies and animal experiments support the important role of the nicotinic systems in learning, different kind of memory and cognition. For development of nicotinic treatments we have a well characterized lead compound, nicotine. However, the neural nicotinic mechanisms underlying cognitive functions are not well known because the side effects of nicotine overdose have hindered the development of this therapeutical line. The new development of non-toxic, brain specific nicotine drugs need a full knowledge of these mechanism and a reevaluation of the nicotine effects. This review aims to analyze the different kind of effects of nicotine on the Central Nervous System (CNS), especially on the cortex and hippocampus. Nicotine effects are, theoretically and/or practically, of variable character depending on daily dose and time of treatment; on the subtype and density of the different nicotinic receptors existing in the distinct brain regions; on the processes of desensitization and tolerance of nicotinic receptors and on other neuronal factors. Nicotine produces the above mentioned activation of the cognitive functions acting directly or indirectly on cortical neurons. In some experiments, high doses of nicotine can impair memory. This substance induces increases in the glycolytic pathway and Krebs cycle of neurons, as well as brain blood flow. Nicotine also produces an increase in NGF immunoreactivity in frontoparietal cortex. All these neuronal changes may cause different positive effects such as neuroprotection, neuroplasticity and better performance of synaptic circuits. The benefit of other neuronal changes can be matter of discussion such as some modifications in synaptic transmission, the COX-2 increase in frontoparietal cortex and hippocampus or the changes in the antioxidant systems. Finally, other neuronal changes can be of negative effect such as the induction of apoptosis and oxidative stress (DNA damage, ROS and lipid peroxide increase). All these described effects explain both the beneficial and neurotoxic consequences of the activation of the nicotinic receptors. The diversity and variability of the nicotinic effects should take into account when nicotine agonists will be used as a possible cognitive treatment.

Calretinin-immunopositive cells and fibers in the cerebellar cortex of normal sheep.

Calretinin (CR)-immunopositive cells and fibers in the cerebellar cortex (vermal archicerebellum--lobules X and IX--and neocerebellum--lobules VIIb and VIII) of two and 4-year-old Manchega and Rasa Aragonesa sheep were studied. CR-immunoreactivity was seen in subsets of all neurons and afferent fibers described in the cerebellar cortex. Generally, immunopositive cells were seen in very high densities in lobules X and IX, and in low density in lobule VIIb. Apparently, all unipolar brush cells were CR-immunopositive and showed a greater variety of shape than had been reported in other species. CR-immunoreactivity of Purkinje cells was either absent or varied from low to medium intensity. Few granule cell perikarya were immunostained (<5%) but a large number of their axons were CR-immunopositive. Subsets of stellate and basket cells were CR-immunoreactive--quite different to what is seen in most of mammalian species. Strongly CR-immunopositive mossy and climbing fibers, isolated or grouped, were observed in all lobules. Although we found neither a difference in CR-immunoreactivity between the two breds of sheep, nor between the two ages examined, we observed important differences in CR-immunoreactivity between sheep and other mammalian species. Our observation of neuronal clusters and groups of fibers with very high CR-immunopositivity supports the idea of a heterogeneous species-specific functional organization for the cerebellar cortex within an apparent homogeneous histological structure maintained throughout mammalian evolution. The results also suggest that the varied levels of CR expression may be related to the specific functions of these immunopositive neurons and fibers rather than to a general neuroprotective role played by calretinin in the cerebellar cortex.