Pathogenic Potential of Eomesodermin-Expressing T-Helper Cells in Neurodegenerative Diseases

Eomesodermin-expressing (Eomes⁺) T-helper (Th) cells show cytotoxic characteristics in secondary progressive multiple sclerosis. We found that Eomes⁺ Th cell frequency was increased in the peripheral blood of amyotrophic lateral sclerosis and Alzheimer's disease patients. Furthermore, granzyme B production by Th cells from such patients was high compared with controls. A high frequency of Eomes⁺ Th cells was observed in the initial (acutely progressive) stage of amyotrophic lateral sclerosis, and a positive correlation between Eomes⁺ Th cell frequency and cognitive decline was observed in Alzheimer's disease patients. Therefore, Eomes⁺ Th cells may be involved in the pathology of amyotrophic lateral sclerosis and Alzheimer's disease. ANN NEUROL 2024;95:1093–1098     

Adipose-derived mesenchymal stem cell transplantation promotes adult neurogenesis in the brains of Alzheimer’s disease mice

In the present study,we transplanted adipose-derived mesenchymal stem cells into the hippocampi of APP/PS1 transgenic Alzheimer’s disease model mice.Immunofluorescence staining revealed that the number of newly generated(BrdU+)cells in the subgranular zone of the dentate gyrus in the hippocampus was significantly higher in Alzheimer’s disease mice after adipose-derived mesenchymal stem cell transplantation,and there was also a significant increase in the number of BrdU+/DCX+neuroblasts in these animals.Adipose-derived mesenchymal stem cell transplantation enhanced neurogenic activity in the subventricular zone as well.Furthermore,adipose-derived mesenchymal stem cell transplantation reduced oxidative stress and alleviated cognitive impairment in the mice.Based on these findings,we propose that adipose-derived mesenchymal stem cell transplantation enhances endogenous neurogenesis in both the subgranular and subventricular zones in APP/PS1 transgenic Alzheimer’s disease mice,thereby facilitating functional recovery.     

Roles of glial ion transporters in brain diseases

Glial ion transporters are important in regulation of ionic homeostasis, cell volume, and cellular signal transduction under physiological conditions of the central nervous system (CNS). In response to acute or chronic brain injuries, these ion transporters can be activated and differentially regulate glial functions, which has subsequent impact on brain injury or tissue repair and functional recovery. In this review, we summarized the current knowledge about major glial ion transporters, including Na⁺/H⁺ exchangers (NHE), Na⁺/Ca²⁺ exchangers (NCX), Na⁺–K⁺–Cl⁻ cotransporters (NKCC), and Na⁺–HCO₃⁻ cotransporters (NBC). In acute neurological diseases, such as ischemic stroke and traumatic brain injury (TBI), these ion transporters are rapidly activated and play significant roles in regulation of the intra- and extracellular pH, Na⁺, K⁺, and Ca²⁺ homeostasis, synaptic plasticity, and myelin formation. However, overstimulation of these ion transporters can contribute to glial apoptosis, demyelination, inflammation, and excitotoxicity. In chronic brain diseases, such as glioma, Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), glial ion transporters are involved in the glioma Warburg effect, glial activation, neuroinflammation, and neuronal damages. These findings suggest that glial ion transporters are involved in tissue structural and functional restoration, or brain injury and neurological disease development and progression. A better understanding of these ion transporters in acute and chronic neurological diseases will provide insights for their potential as therapeutic targets.     

Glial Na+‐dependent ion transporters in pathophysiological conditions

Sodium dynamics are essential for regulating functional processes in glial cells. Indeed, glial Na⁺ signaling influences and regulates important glial activities, and plays a role in neuron‐glia interaction under physiological conditions or in response to injury of the central nervous system (CNS). Emerging studies indicate that Na⁺ pumps and Na⁺‐dependent ion transporters in astrocytes, microglia, and oligodendrocytes regulate Na⁺ homeostasis and play a fundamental role in modulating glial activities in neurological diseases. In this review, we first briefly introduced the emerging roles of each glial cell type in the pathophysiology of cerebral ischemia, Alzheimer's disease, epilepsy, Parkinson's disease, Amyotrophic Lateral Sclerosis, and myelin diseases. Then, we discussed the current knowledge on the main roles played by the different glial Na⁺‐dependent ion transporters, including Na⁺/K⁺ ATPase, Na⁺/Ca²⁺ exchangers, Na⁺/H⁺ exchangers, Na⁺‐K⁺‐Cl^? cotransporters, and Na⁺‐ cotransporter in the pathophysiology of the diverse CNS diseases. We highlighted their contributions in cell survival, synaptic pathology, gliotransmission, pH homeostasis, and their role in glial activation, migration, gliosis, inflammation, and tissue repair processes. Therefore, this review summarizes the foundation work for targeting Na⁺‐dependent ion transporters in glia as a novel strategy to control important glial activities associated with Na⁺ dynamics in different neurological disorders. GLIA 2016;64:1677–1697     

Schooling mediates brain reserve in Alzheimer's disease: findings of fluoro-deoxy-glucose-positron emission tomography

Background

Functional imaging studies report that higher education is associated with more severe pathology in patients with Alzheimer''s disease, controlling for disease severity. Therefore, schooling seems to provide brain reserve against neurodegeneration.

Objective

To provide further evidence for brain reserve in a large sample, using a sensitive technique for the indirect assessment of brain abnormality (¹⁸F‐fluoro‐deoxy‐glucose‐positron emission tomography (FDG‐PET)), a comprehensive measure of global cognitive impairment to control for disease severity (total score of the Consortium to Establish a Registry for Alzheimer''s Disease Neuropsychological Battery) and an approach unbiased by predefined regions of interest for the statistical analysis (statistical parametric mapping (SPM)).

Methods

93 patients with mild Alzheimer''s disease and 16 healthy controls underwent ¹⁸F‐FDG‐PET imaging of the brain. A linear regression analysis with education as independent and glucose utilisation as dependent variables, adjusted for global cognitive status and demographic variables, was conducted in SPM2.

Results

The regression analysis showed a marked inverse association between years of schooling and glucose metabolism in the posterior temporo‐occipital association cortex and the precuneus in the left hemisphere.

Conclusions

In line with previous reports, the findings suggest that education is associated with brain reserve and that people with higher education can cope with brain damage for a longer time.The hypothesis of brain reserve capacity (BRC) was introduced almost 20 years ago to account for the repeated observation that pathology of Alzheimer''s disease and its clinical symptoms are not tightly linked. Intelligence or life experience may provide reserve in the form of skills that allow some people to attenuate symptoms of neurodegeneration better than others. Epidemiological, clinical and neuropathological studies suggest education as an important factor of such life experience. Bennett et al¹ recently showed, for example, that the association between the Alzheimer''s disease pathology and cognitive symptoms shortly before death was attenuated by the number of years of schooling. Better educated patients had more pathology than would have been predicted from their cognitive status. Epidemiological studies that support the BRC hypothesis show that the incidence of clinical Alzheimer''s disease is lower in people with more years of school education and that higher educated patients with Alzheimer''s disease experience faster cognitive decline.² Functional imaging studies also provide evidence for BRC. Considering reduced cerebral blood flow (CBF) and regional cerebral metabolic rate of glucose utilisation (rCGMglc) as indirect markers of Alzheimer''s disease pathology, patients with more years of schooling consistently had more pronounced deficits in regions typically affected by the pathology of Alzheimer''s disease.We aim to provide further evidence for the BRC hypothesis using positron emission tomography (PET) imaging with ¹⁸F‐fluoro‐2‐deoxy‐glucose (¹⁸F‐FDG) for the measurement of rCGMglc in patients with Alzheimer''s disease. We hypothesised that years of schooling and rCGMglc should be inversely associated in brain regions affected by Alzheimer''s disease pathology. We decided to readdress this issue for the following reasons:

• Most previous studies have used limited neuropsychological measures to control for clinical disease severity.
• Sample size was a limiting factor in some of the previous studies.
• Most of the previous studies used single‐photon emission‐computed tomography to measure CBF, although ¹⁸F‐FDG‐PET was found to be more sensitive to early functional changes in Alzheimer''s disease.³
• Some of the earlier studies focused on regions of interest.

A voxel‐based approach, however, seems more appropriate, having no exact a priori hypothesis of brain regions with a marked association between education and rCGMglc.     

Molecular mechanisms of glial swelling in vitro

The pathophysiological chain of events occurring during cerebral ischemia is still poorly understood on a molecular level. Therefore, an in vitro model to study glial swelling mechanisms, using C6 glial cells under controlled extracellular conditions, has been established. Flow cytometry serves to determine even small cell volume changes. In this report, the effects of anoxia and acidosis on glial swelling are summarized. Anoxia alone, or in combination with iodoacetate to inhibit anaerobic glycolysis, did not cause an increase of glial volume for up to 2 h. Acidification of the incubation medium below pH 6.8, on the other hand, was immediately followed by cell swelling to 115% of normal. Amiloride or the absence of bicarbonate and Na⁺ in the medium significantly reduced glial swelling. The data support the contention that swelling results from an activation of the Na⁺/H⁺-antiporter to control intracellular pH. It is suggested that swelling in an ischemic penumbra is promoted by this mechanism. Therapeutic approaches to control cerebral pH might be useful to protect brain tissue in cerebral ischemia.     

Acetylcholine Muscarinic M2 Receptor Stimulated [35S]GTPγS Binding Shows Regional Selective Changes in Alzheimer's Disease Postmortem Brain

Oxotremorine-M stimulated [³⁵S]GTPγS binding was used to assess acetylcholine muscarinic M2 receptor mediated G-protein function in superior frontal cortical, superior temporal cortical and hippocampal membranes from a series of Alzheimer's disease and matched control subjects. No significant differences were seen in basal [³⁵S]GTPγS binding between the groups. The maximal level of oxotremorine-M stimulated [³⁵S]GTPγS binding over basal was significantly increased in Alzheimer's disease superior temporal cortex, suggesting an enhanced muscarinic M2 receptor-G-protein coupling efficiency in this region. In contrast, the maximal level of oxotremorine-M stimulated [³⁵S]GTPγS binding over basal was unaltered in Alzheimer's disease superior frontal cortex and significantly reduced in Alzheimer's disease hippocampus. Western immunoblotting using antisera towards the α-subunits of those G-protein types known to couple muscarinic receptors, revealed that G_qαand G_iα, but not G_oα, levels were significantly reduced in Alzheimer's disease superior temporal cortex. Neither G_qα, G_iαnor G_oαlevels were significantly altered in Alzheimer's disease superior frontal cortex or hippocampus. These results suggest that the efficacy of muscarinic M₂receptor G-protein coupling shows regional selective changes in Alzheimer's disease postmortem brain with deficits occurring only in a region that shows severe pathology.     

MRI Temporal Lobe Volume Measures and Neuropsychologic Function in Alzheimer's Disease

The authors performed quantitation of the temporal lobes using magnetic resonance imaging in 20 patients with mild-tomoderate Alzheimer's disease, 20 age-matched aged control subjects, and 26 healthy young volunteers. Compared to young subjects, aged controls showed volume reductions in amygdala (17%, p=0.02), hippocampus (15%, p=0.0001) and temporal lobe (22%, p=0.0001). Compared to aged controls, Alzheimer's subjects showed further volume reductions in amygdala (33%, p=0.0001) and hippocampus (20%, p=0.006) but not temporal lobe (7%, p=0.15). In Alzheimer's subjects, left temporal lobe volume correlated strongly with the Mini Mental State (MMSE) score (adjusted r² =0.46, p=0.0006) whereas right amygdala volume correlated inversely with the noncognitive ADAS score (adjusted r²=0.46, p=0.0006). The authors conclude that significant volume changes occur in the temporal lobe in aging and in Alzheimer's disease, with the greatest percentage reductions in the amygdala in Alzheimer's disease. Temporal neocortical atrophy and temporal limbic atrophy might be associated with different patterns of performance and behavior in Alzheimer's patients.     

Distinctive patterns of alterations in proton efflux from goldfish retinal horizontal cells monitored with self‐referencing H+‐selective electrodes

The H⁺ hypothesis of lateral feedback inhibition in the outer retina predicts that depolarizing agents should increase H⁺ release from horizontal cells. To test this hypothesis, self‐referencing H⁺‐selective microelectrodes were used to measure extracellular H⁺ fluxes from isolated goldfish horizontal cells. We found a more complex pattern of cellular responses than previously observed from horizontal cells of other species examined using this technique. One class of cells had an initial standing signal indicative of high extracellular H⁺ adjacent to the cell membrane; challenge with glutamate, kainate or high extracellular potassium induced an extracellular alkalinization. This alkalinization was reduced by the calcium channel blockers nifedipine and cobalt. A second class of cells displayed spontaneous oscillations in extracellular H⁺ that were abolished by cobalt, nifedipine and low extracellular calcium. A strong correlation between changes in intracellular calcium and extracellular proton flux was detected in experiments simultaneously monitoring intracellular calcium and extracellular H⁺. A third set of cells was characterized by a standing extracellular alkalinization which was turned into an acidic signal by cobalt. In this last set of cells, addition of glutamate or high extracellular potassium did not significantly alter the proton signal. Taken together, the response characteristics of all three sets of neurons are most parsimoniously explained by activation of a plasma membrane Ca²⁺ ATPase pump, with an extracellular alkalinization resulting from exchange of intracellular calcium for extracellular H⁺. These findings argue strongly against the hypothesis that H⁺ release from horizontal cells mediates lateral inhibition in the outer retina.     

Interindividual differences in the levels of the glutamate transporters GLAST and GLT,but no clear correlation with Alzheimer's disease

Alzheimer's disease is a common progressive neurodegenerative disease of unknown etiology. Several different pathological processes have been identified in the brains of Alzheimer patients. To determine if reduced glutamate uptake is a contributing factor, we have measured the levels of the glutamate transporter proteins GLAST (EAAT1) and GLT (EAAT2) in human autopsy samples. The postmortem proteolysis of these proteins turned out to be fairly rapid. Brains from 10 Alzheimer and 10 control patients were therefore obtained with a relatively short postmortem delay (5 hr on average). GLT (N‐terminal and central parts), GLAST (C‐terminal), glial fibrillary acidic protein (GFAP) and inositol (1,4,5)‐triphosphate (IP₃)‐receptor immunoreactivities were determined in the cingulate and inferior temporal gyri by immunoblotting. The Na⁺‐dependent “binding” of D‐[³H]aspartate and the glutamate uptake after solubilization and reconstitution in liposomes were determined for comparison. An individual variation in GLAST and GLT levels was found, but no significant correlation with Alzheimer's disease, except for a 14% lower ratio of N‐terminal to central GLT immunoreactivity (P < 0.04). The levels of GLAST and GLT showed negative correlation in agreement with the idea that these proteins are differentially regulated. In conclusion, Alzheimer's disease brains can have both normal and reduced levels of GLAST and GLT. J. Neurosci. Res. 55:218–229, 1999. © 1999 Wiley‐Liss, Inc.     

The influence of calcium transients on intracellular pH in cortical neurons in primary culture

The objective of this study was to assess the influence of Ca²⁺ influx on intracellular pH (pH_i) of neocortical neurons in primary culture. Neurons were exposed to glutamate (100–500 μM) or KCl (50 mM), and pH_i was recorded with microspectroflurometric techniques. Additional experiments were carried out in which calcium influx was triggered by ionomycin (2 μM) or the calcium ionophore 4-Br-A23187 (2 μM). Glutamate exposure either caused no, or only a small decrease in pH_i (ΔpH ≈ 0.06 units). When a decrease was observed, a rebound rise in pH_i above control was observed upon termination of glutamate exposure. In about 20% of the cells, the acidification was more pronounced (ΔpH ≈ 0.20 units), but all these cells had high control pH_i values, and showed gradual acidification. Exposure of cells to 50 mM KCl consistently increased pH_i. Since this increase was similar in the presence and nominal absence of HCO₃⁻, it probably did not reflect influx of HCO₃⁻ via a Na⁺-HCO₃⁻ symporter. Furthermore, since it occurred in the absence of external Ca²⁺ (or a measurable rise in Ca_i²⁺) it seemed independent of Ca²⁺ influx. It is tentatively concluded that the rise in pH_i was due to reduced passive influx of H⁺ along the electrochemical gradient, which is reduced by depolarization. In Ca²⁺-containing solutions, depolarization led to a rebound increase in pH_i above control. This, and the rebound found after glutamate transients, may reflect Ca²⁺-triggered phosphorylation and upregulation of the Na⁺/H⁺ antiporter which extrudes H⁺ from the cell. Ionomycin and 4-Br-A23187 gave rise to a large rise in Ca_i²⁺ and to alkalinization of the cell (ΔpH ≈ 0.5). Since amiloride or removal of Na⁺ from the external solution did not alter the rise in pH_i, it was probably not due to accelerated H⁺ extrusion. However, removal of Ca²⁺ from extracellular fluid prevented the rise, suggesting that it was secondary to Ca²⁺/2H⁺ exchange across plasma membranes.     

Intracellular acidification of the leech giant glial cell evoked by glutamate and aspartate

Glutamate is an excitatory receptor agonist in both neurones and glial cells, and, in addition, glutamate is also a substrate for glutamate transporter in glial cells. We have measured intracellular and extracellular pH changes induced by bath application of glutamate, its receptor agonist kainate, and its transporter agonist aspartate, in the giant neuropile glial cell in the central nervous system of the leech Hirudo medicinalis, using double-barrelled pH-sensitive microelectrodes. The giant glial cells responded to glutamate and aspartate (100–500 μM), and kainate (5–20 μM) with a membrane depolarization or an inward current, and with a distinct intracellular acidification. Glutamate and aspartate (both 500 μM) evoked a decrease in intracellular pH (pH_i) by 0.187 ± 0.081 (n = 88) and 0.198 ± 0.067 (n = 86) pH units, respectively. With a resting pH_i of 7.1 or 80 nM H⁺, these acidifications correspond to a mean increase of the intracellular H⁺ activity by 42 nM and 45 nM. Kainate caused a decrease of pH_i by 0.1 − 0.35 pH units (n = 15). The glutamate/aspartate-induced decrease in pH_i was not significantly affected by the glutamate receptor blockers kynurenic acid (1 mM) and 6-cyano-7-dinitroquinoxaline-2,3-dione (CNQX, 50–100 μM), which greatly reduced the kainate-induced change in pH_i. Extracellular alkalinizations produced by glutamate and aspartate were not affected by CNQX. Reduction of the external Na⁺ concentration gradually decreased the intracellular pH change induced by glutamate/aspartate, indicating half maximal activation of the acidifying process at 5–10 mM external Na⁺ concentration. When all external Na⁺ was replaced by NMDG⁺, the pH_iresponses were completely suppressed (glutamate) or reduced to 10% (aspartate). When Na⁺ was replaced by Li⁺, the glutamate- and aspartate-evoked pH_i responses were reduced to 18% and 14%, respectively. Removal of external Ca²⁺ reduced the glutamate- and aspartate-induced pH_i responses to 93 and 72%, respectively. The glutamate/aspartate-induced intracellular acidifications were not affected by the putative glutamate uptake inhibitor amino-adipidic acid (1 mM). DL-aspartate-β-hydroxamate (1 mM), and dihydrokainate (2 mM), which caused some pH_i decrease on its own, reduced the glutamate/aspartate-induced pH_i responses by 40 and 69%, respectively. The putative uptake inhibitor DL-threo-β-hydroxyaspartate (THA, 1 mM) induced a prominent intracellular acidification (0.36 ± 0.05 pH units, n = 9), and the pH_i change evoked by glutamate or aspartate in the presence of THA was reduced to less than 10%. The results indicate that glutamate, aspartate, and kainate produce substantial intracellular acidifications, which are mediated by at least two independent mechanisms: 1) via activation of non-NMDA glutamate receptors and 2) via uptake of the excitatory amino acids into the leech glial cell. © 1997 Wiley-Liss Inc.     

Low levels of mutant ubiquitin are degraded by the proteasome in vivo

The ubiquitin‐proteasome system fulfills a pivotal role in regulating intracellular protein turnover. Impairment of this system is implicated in the pathogenesis of neurodegenerative diseases characterized by ubiquitin‐ containing proteinaceous deposits. UBB⁺¹, a mutant ubiquitin, is one of the proteins accumulating in the neuropathological hallmarks of tauopathies, including Alzheimer's disease, and polyglutamine diseases. In vitro, UBB⁺¹ properties shift from a proteasomal ubiquitin‐fusion degradation substrate at low expression levels to a proteasome inhibitor at high expression levels. Here we report on a novel transgenic mouse line (line 6663) expressing low levels of neuronal UBB⁺¹. In these mice, UBB⁺¹ protein is scarcely detectable in the neuronal cell population. Accumulation of UBB⁺¹ commences only after intracranial infusion of the proteasome inhibitors lactacystin or MG262, showing that, at these low expression levels, the UBB⁺¹ protein is a substrate for proteasomal degradation in vivo. In addition, accumulation of the protein serves as a reporter for proteasome inhibition. These findings strengthen our proposition that, in healthy brain, UBB⁺¹ is continuously degraded and disease‐related UBB⁺¹ accumulation serves as an endogenous marker for proteasomal dysfunction. This novel transgenic line can give more insight into the intrinsic properties of UBB⁺¹ and its role in neurodegenerative disease. © 2010 Wiley‐Liss, Inc.     

EFFECT OF COLLOIDAL SILVER AGAINST THE CYTOTOXICITY OF HYDROGEN PEROXIDE AND NAPHTHAZARIN ON PRIMARY CULTURED CORTICAL ASTROCYTES

One major pathogenesis in degenerative disorders of the central nervous system (CNS), including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and ischemia, is the oxidative stress induced by reactive oxygen species (ROS). The present study investigated the protective effect of colloidal silver, which is widely marketed as a dietary supplement for diseases like diabetes, AIDS, cancer, and various infections, upon the oxidative brain damage induced by H₂O₂ or naphthazarin treatment. LDH release from primary cultured astrocytes was enhanced by naphthazarin treatment, and this elevation of the LDH concentration in medium was blocked by colloidal silver treatment. However, hydrogen peroxide was little affected by the colloidal silver. Fluorescence of DCF (peroxides) increased in astrocytes incubated with hydrogen peroxide or naphthazarin compared to the control. When exposed to naphthazarin-induced cells, ROS formation appeared to be reduced by colloidal silver. However, intracellular ROS formation in hydrogen peroxide–treated cells slightly reduced by colloidal silver. These results suggest that colloidal silver has a protective activity against the oxidative stress induced by naphthazarin, but not by hydrogen peroxide.     

Octanol,a gap junction uncoupling agent,changes intracellular [H+] in rat astrocytes

Octanol rapidly closes gap junction channels but its mechanism of action is not known. Because intracellular [H⁺], pH_i, also affects the conductance of gap junctions, we studied octanol's effects on pH_i in cultured rat astrocytes, which are highly coupled cells. Octanol (1 mM) caused an acid shift in the pH_i of 90% of rat hippocampal astrocytes which averaged −0.19 ± 0.09 pH units in magnitude. In 58% of the cells tested, a biphasic change in pH_i was seen; octanol produced an initial acidification lasting ∼10 min that was followed by a persistent alkalinization. The related gap junction uncoupling agent, heptanol, had similar effects on pH_i. Octanol-induced changes in pH_i were similar in nominally HCO₃⁻-free and HCO₃⁻-containing solutions, although the rate of initial acidification was significantly greater in the presence of HCO₃⁻. The initial acidification was inhibited in the presence of the stilbene DIDS, an inhibitor of Na⁺/HCO₃⁻ cotransport, indicating that octanol caused acidification by blocking this powerful acid extruder. The alkalinization was inhibited by amiloride which blocks the Na⁺/H⁺ exchanger (NHE), an acid extruder, suggesting that the alkaline shift induced by octanol was caused by stimulation of NHE. As expected, octanol's effects on astrocytic pH_i were prevented by removal of external Na⁺, which blocks both Na⁺/HCO₃⁻ cotransport and NHE. Octanol had only small effects on intracellular Ca²⁺ (Ca²⁺_i) in astrocytes. Hepatocytes which, like astrocytes, are strongly coupled to one another, showed no change in pH_i with octanol application. Fluorescence recovery after photobleaching (FRAP) was used to study the effect of changes in astrocyte pH_i on degree of coupling in hippocampal astrocytes. Coupling was decreased by intracellular acid shifts ∼−0.2 pH units in size. Octanol's effects on astrocyte pH_i were complex but a prompt initial acidification was nearly always seen and could contribute to the uncoupling action of this drug in astrocytes. Because octanol uncouples hepatocytes without changing their pH_i, this compound clearly can influence gap junctional conductance independent of changes in pH_i. © 1996 Wiley-Liss, Inc.     

Presenilin-1 protein expression in familial and sporadic Alzheimer's disease

Mutations of the presenilin PS1 and PS2 genes are closely linked to aggressive forms of early-onset (<60 years) familial Alzheimer's disease. A highly specific monoclonal antibody was developed to identify and characterize the native PS1 protein. Western blot analyses revealed a predominant 32-kd immunoreactive polypeptide in a variety of samples, including PC12 cells transfected with human PS1 complementary DNA, brain biopsy specimens from demented patients, and postmortem samples of frontal neocortex from early-onset familial Alzheimer's disease cases (PS1 and PS2), lateonset sporadic Alzheimer's disease cases, and cases of other degenerative disorders. This truncated polypeptide contains the N-terminus of PS1 and appeared unchaged across cases. In 2 early-onset cases linked to missense mutations in the PS1 gene, a PS1 immunoreactive protein (～49 kd) accumulated in the frontal cortex. This protein was similar in size to full-length PS1 protein present in transfected cells overexpressing PS1 complementary DNA, and in lymphocytes from an affected individual with a deletion of exon 9 of the PS1 gene, suggesting that mutations of the PS1 gene perturb the endoproteolytic processing of the protein. Immunohistochemical studies of control brains revealed that PS1 is expressed primarily in neurons, with the protein localized in the soma and dendritic processes. In contrast, PS1 showed striking localization to the neuropathology in early-onset familial Alzheimer's disease and sporadic Alzheimer's disease cases. PS1 immunoreactivity was present in the neuritic component of senile plaques as well as in neurofibrillary tangles. Localization of PS1 immunoreactivity in familial and sporadic Alzheimer's disease suggests that genetically heterogeneous forms of the disease share a common pathophysiology involving PS1 protein.     

Inhibition of Hydrogen Sulfide Generation Contributes to 1-Methy-4-Phenylpyridinium Ion-Induced Neurotoxicity

Reactive oxygen species (ROS) overproduction contributes to the neurotoxicity of 1-methy-4-phenylpyridinium ion (MPP⁺). Increasing studies have shown that hydrogen sulfide (H₂S) is an endogenous antioxidant gas. We have hypothesized that MPP⁺-caused neurotoxicity may involve the imbalance of proportion to this endogenous protective antioxidant gas. The aim of this study is to evaluate whether MPP⁺ disturbs H₂S synthesis in PC12 cells, a clonal rat pheochromocytoma cell line, and whether disturbance of H₂S generation induced by MPP⁺ is an underlying mechanism of MPP⁺-induced neurotoxicity. We show that exposure of PC12 cells to MPP⁺ causes a significant decrease in H₂S generation and results in remarkable cell damage. We find that cystathionine-β-synthetase (CBS) is catalyzed in PC12 cells to generate H₂S, and that both expression and activity of CBS are inhibited by MPP⁺ treatment. Exposure of sodium hydrosulfide (NaHS), a donor of H₂S, extenuates MPP⁺-induced cytotoxicity and ROS accumulation in PC12 cells, while inhibition of CBS by amino-oxyacetate (AOAA) exacerbates the effects of MPP⁺. These results indicate that MPP⁺ neurotoxicity involves reduction of H₂S production, which is caused by inhibition of CBS. This study provides novel insights into cell death observed in neurodegenerative disease such as Parkinson’s disease.     

Metabolic reduction in the posterior cingulate cortex in very early Alzheimer's disease

This study investigated cerebral glucose metabolism in very early Alzheimer's disease, before a clinical diagnosis of probable Alzheimer's disease is possible, using [¹⁸F]fluorodeoxyglucose positron emission tomography. First, 66 patients with probable Alzheimer's disease with a spectrum of dementia severity (Mini-Mental State Examination score, 0–23) were recruited and studied. Cortical metabolic activity was analyzed topographically using three-dimensional stereotactic surface projections. Regression analysis was performed for each brain pixel to predict metabolic patterns of very early disease. Predictions were tested prospectively in a group of 8 patients who complained only of memory impairment without general cognitive decline (Mini-Mental State Examination score, 25 · 1) at the time of scanning but whose condition later progressed to probable Alzheimer's disease. Both results were compared to cerebral metabolic activity in 22 age-similar normal control subjects. Prediction and analysis of actual patients consistently indicated marked metabolic reduction (21–22%) in the posterior cingulate cortex and cinguloparietal transitional area in patients with very early Alzheimer's disease. Mean metabolic reduction in the posterior cingulate cortex was significantly greater than that in the lateral neocortices or parahippocampal cortex. The result suggests a functional importance for the posterior cingulate cortex in impairment of learning and memory, which is a feature of very early Alzheimer's disease.     

A diagnostic formulation for anosognosia in Alzheimer's disease

Objective

To determine the earliest symptoms of anosognosia in people with Alzheimer''s disease and to validate a criteria‐guided strategy to diagnose anosognosia in dementia.

Methods

A consecutive series of 750 patients with very mild or probable Alzheimer''s disease attending a memory clinic, as well as their respective care givers, was assessed using a comprehensive psychiatric evaluation.

Results

The factors of anosognosia for (1) basic activities of daily living (bADL), (2) instrumental activities of daily living (iADL), (3) depression and (4) disinhibition were produced by a principal component analysis on the differential scores (ie, caregiver score minus patient score) on the anosognosia questionnaire for dementia. A discrepancy of two or more points in the anosognosia‐iADL factor was found to have a high sensitivity and specificity to identify clinically diagnosed anosognosia in people with Alzheimer''s disease. By logistic regression analysis, the severity of dementia and apathy were both shown to be noticeably associated with anosognosia in people with Alzheimer''s disease.

Conclusion

Anosognosia in those with Alzheimer''s disease is manifested as poor awareness of deficits in iADL and bADL, depressive changes and behavioural disinhibition. The frequency of anosognosia is found to increase considerably with the severity of dementia. The validity of a specific set of criteria to diagnose anosognosia in people with Alzheimer''s disease was shown, which may contribute to the early identification of this condition.Anosognosia (from the Greek “nosos” (illness) and “gnosis” (knowledge)) is a term coined by Babinski to refer to the phenomenon of denial of hemiplegia.¹ From an etymological perspective, the term anosognosia may be construed as the lack of knowledge or awareness of an illness. Anosognosia has also been reported among patients with Wernicke''s aphasia, who do not attempt to correct paraphasias and who may become irritable with others when their jargon‐loaded speech is not properly understood. Anton''s syndrome occurs in patients with cortical blindness, who deny being blind and confabulate responses when asked to recognise visually presented objects. In the context of people with Alzheimer''s disease, anosognosia was construed as the denial or lack of awareness of impairments in activities of daily living (ADL) or about neuropsychological deficits.^2,3 Different strategies have been used to assess anosognosia in Alzheimer''s disease, and these are briefly described as follows (see Clare^4,5 for a thorough review).     

Chromosomal fragility associated with familial Alzheimer's disease

To test whether chromosomal instability is associated with familial Alzheimer's disease, we examined breakage on X chromosomes of fibroblasts derived from patients with familial Alzheimer's disease, using gene cotransfer methodology. The X chromosome is a convenient target for analyzing DNA breakage because of its numerous markers and ease of selection in rodent-human hybrid cells. Patients with familial Alzheimer's disease, including the large Nova Scotia Alzheimer's kindred, show a significantly lower cotransfer of the X-linked glucose-6-phosphate dehydrogenase (G6PD) gene with the selected HPRT gene in hybrid cells, indicating breakage between the markers. Lower cotransfer of the more distant X-linked gene, MIC-2, was statistically significant in this kindred, but not in other patients with familial Alzheimer's disease. The distance between MIC2 and HPRT is sixfold to ninefold greater than that between HPRT and G6PD, suggesting that there may be a “hot spot” for breakage in the latter interval on the X chromosome of patients with familial Alzheimer's disease. The somatic cell hybrid model provides insights into underlying mechanisms for chromosomal breakage induced by the Alzheimer defect. A hypothesis implicating a candidate gene, C₁-THF synthase, in the generation of chromosome instability in the pathogenesis of familial Alzheimer's disease, is presented.