Aggregation of α-synuclein in brain samples from subjects with glucocerebrosidase mutations

Recent studies show an increased frequency of mutations in the glucocerebrosidase gene (GBA1) in patients with α-synucleinopathies including Parkinson disease. Some patients with Gaucher disease (GD) develop parkinsonism with α-synuclein-positive inclusions post mortem. Proteins were extracted from the cerebral cortex of subjects with synucleinopathies with and without GBA1 mutations, controls and patients with GD. Patients with GBA1-associated synucleinopathies showed aggregation of oligomeric forms of α-synuclein in the SDS-soluble fraction, while only monomeric forms of α-synuclein were seen in subjects with GBA1 mutations without parkinsonism. Thus, brains from patients with GBA1-associated parkinsonism show biochemical characteristics typical of Lewy body disorders.     

Gaucher disease with parkinsonian manifestations: does glucocerebrosidase deficiency contribute to a vulnerability to parkinsonism?

Among the phenotypes associated with Gaucher disease, the deficiency of glucocerebrosidase, are rare patients with early onset, treatment-refractory parkinsonism. Sequencing of glucocerebrosidase in 17 such patients revealed 12 different genotypes. Fourteen patients had the common "non-neuronopathic" N370S mutation, including five N370S homozygotes. While brain glucosylsphingosine levels were not elevated, Lewy bodies were seen in the four brains available for study. The shared clinical and neuropathologic findings in this subgroup suggest that the deficiency in glucocerebrosidase may contribute to a vulnerability to parkinsonism.     

Gaucher disease and the synucleinopathies

Several recent observations suggest a connection between Gaucher disease, the inherited deficiency of glucocerebrosidase, and the synucleinopathies. Rare patients have been observed who develop both Gaucher disease and parkinsonism. Autopsy studies on these subjects reveal synuclein-positive Lewy bodies and inclusions. An increased incidence of synucleinopathies also has been noted in relatives of Gaucher probands. In complementary studies, screening of patients with parkinsonism has identified a greater than expected frequency of glucocerebrosidase mutations. These glucocerebrosidase mutation carriers have a wide spectrum of associated parkinsonian phenotypes, ranging from classic L-dopa-responsive Parkinson disease to a phenotype more characteristic of Lewy body dementia. Despite this association, the vast majority of Gaucher carriers and patients with Gaucher disease never develop parkinsonism. However, mutations in this gene are likely to be a contributing risk factor in subjects otherwise prone to developing synucleinopathies.     

Gaucher disease: complexity in a "simple" disorder

Gaucher disease, the recessively inherited deficiency of the enzyme glucocerebrosidase and the most common sphingolipidosis, has both non-neurological and neuronopathic forms and a continuum of diverse clinical manifestations. Studies of genotype-phenotype correlations reveal significant genotypic heterogeneity among clinically similar patients, and vastly different phenotypes among patients with the same mutations. The region surrounding the glucocerebrosidase gene (GBA) on chromosome 1q is particularly gene-rich, with a highly homologous pseudogene sequence 16 kb downstream. Recombination events within the GBA locus contribute to the etiology of some mutations in Gaucher disease. Studies of patients with Gaucher disease and atypical manifestations, including parkinsonism, myoclonic epilepsy, cardiac involvement and collodion skin, seek to define other genetic or environmental factors contributing to the phenotypes. Recent reports demonstrating an association between Gaucher disease and parkinsonism provide an example of heterozygosity for a Mendelian disorder acting as a risk factor for a complex disease. There are rare patients with Gaucher disease and differing genotypes who develop early onset, treatment-refractory parkinsonism. Neuropathology in a group of these patients showed alpha-synuclein-reactive Lewy bodies in brain regions specifically associated with Gaucher disease. Family studies of these probands suggested that the incidence of parkinsonism might be more frequent in obligate heterozygotes. In a complementary finding, the examination of GBA in autopsy samples from individuals with sporadic Parkinson disease identified alterations in the GBA sequence in 14% of the cohort. These studies provide evidence that altered glucocerebrosidase may contribute to a vulnerability to parkinsonism. Moreover, this research demonstrates how insights from rare, single gene disorders like Gaucher disease can provide a window into the etiology of more common, multifactorial genetic diseases.     

ER retention and degradation as the molecular basis underlying Gaucher disease heterogeneity

Gaucher disease (GD), an autosomal recessive disease, is characterized by accumulation of glucosylceramide mainly in cells of the reticuloendothelial system, due to mutations in the acid beta-glucocerebrosidase gene. Some of the patients suffer from neurological symptoms (type 2 and type 3 patients), whereas patients with type 1 GD do not present neurological signs. The disease is heterogeneous even among patients with the same genotype, implicating that a mutation in the glucocerebrosidase gene is required to cause GD but other factors play an important role in the manifestation of the disease. Glucocerebrosidase is a lysosomal enzyme, synthesized on endoplasmic reticulum (ER)-bound polyribosomes and translocated into the ER. Following N-linked glycosylations, it is transported to the Golgi apparatus, from where it is trafficked to the lysosomes. In this study, we tested glucocerebrosidase protein levels, N-glycans processing and intracellular localization in skin fibroblasts derived from patients with GD. Our results strongly suggest that mutant glucocerebrosidase variants present variable levels of ER retention and undergo ER-associated degradation in the proteasomes. The degree of ER retention and proteasomal degradation is one of the factors that determine GD severity.     

L-type Ca currents at CA1 synapses,but not CA3 or dentate granule neuron synapses,are increased in 3xTgAD mice in an age-dependent manner

Abnormal neuronal excitability and impaired synaptic plasticity might occur before the degeneration and death of neurons in Alzheimer's disease (AD). To elucidate potential biophysical alterations underlying aberrant neuronal network activity in AD, we performed whole-cell patch clamp analyses of L-type (nifedipine-sensitive) Ca²⁺ currents (L-VGCC), 4–aminopyridine-sensitive K⁺ currents, and AMPA (2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid) and NMDA (N-methyl-D-aspartate) currents in CA1, CA3, and dentate granule neurons in hippocampal slices from young, middle-age, and old 3xTgAD mice and age-matched wild type mice. 3xTgAD mice develop progressive widespread accumulation of amyloid β-peptide, and selective hyperphosphorylated tau pathology in hippocampal CA1 neurons, which are associated with cognitive deficits, but independent of overt neuronal degeneration. An age-related elevation of L-type Ca²⁺ channel current density occurred in CA1 neurons in 3xTgAD mice, but not in wild type mice, with the magnitude being significantly greater in older 3xTgAD mice. The NMDA current was also significantly elevated in CA1 neurons of old 3xTgAD mice compared with in old wild type mice. There were no differences in the amplitude of K⁺ or AMPA currents in CA1 neurons of 3xTgAD mice compared with wild type mice at any age. There were no significant differences in Ca²⁺, K⁺, AMPA, or NMDA currents in CA3 and dentate neurons from 3xTgAD mice compared with wild type mice at any age. Our results reveal an age-related increase of L-VGCC density in CA1 neurons, but not in CA3 or dentate granule neurons, of 3xTgAD mice. These findings suggest a potential contribution of altered L-VGCC to the selective vulnerability of CA1 neurons to tau pathology in the 3xTgAD mice and to their degeneration in AD patients.     

Selective neuronal death after transient forebrain ischemia in the Mongolian gerbil: a silver impregnation study

An important feature of ischemic brain damage is the exceptional vulnerability of specific neuronal populations and the relative resistance of others. Silver impregnation was used to delineate the extent and time-course of neuronal degeneration produced by 5 min of complete forebrain ischemia in the Mongolian gerbil. Lesions were confined to four brain regions: (1) hippocampal areas CA1, CA2-CA3a and CA4; (2) the dorsomedial portion of the lateral septal nucleus; (3) the dorsolateral portion of the striatum; and (4) the somatosensory neocortex. The ischemic lesion evolved with time in all four regions, but at different rates. Somatic argyrophilia developed rapidly in the striatum and hippocampal area CA4 (maximal in 24 h or less), at intermediate rates in the somatosensory neocortex, hippocampal areas CA1a and CA2-CA3a and the lateral septal nucleus (maximal in 2 days), and slowly in hippocampal area CA1b (maximal in 3 days). These results emphasize that the extent and rate of neuronal degeneration can vary even within a presumably homogeneous neuronal population, as evidenced by the different results in areas CA1a and CA1b. Similar results were obtained from analysis of brain sections stained with Cresyl Violet, hematoxylin-eosin or hematoxylin-eosin/Luxol Fast Blue. Terminal-like silver granules were observed in the projection fields of degenerated neurons. They also appeared, however, in the perforant path terminal zone of the hippocampal dentate molecular layer 1-2 days after transient ischemia and in stratum oriens and stratum radiatum of area CA1b prior to somatic degeneration. These granular deposits could not be clearly related to the degeneration of neuronal somata. Novel findings of this study include the degeneration of some dentate basket cells and lateral septal neurons and the appearance of terminal-like argyrophilia in the hippocampal formation without any obvious relation to somatic degeneration. Some of our results lend support to the hypothesis that ischemic neuronal cell death constitutes an excitotoxic process. Other results, however, suggest that the selective vulnerability of neurons to transient ischemia must involve factors beyond excitotoxicity.     

Glucosylsphingosine but not Saposin C,is the target antigen in Gaucher disease-associated gammopathy

In Gaucher disease type 1 (GD1), genetic deficiency of lysosomal glucocerebrosidase results in the accumulation of glucosylceramide and glucosylsphingosine (GlcSph), that underlie chronic lipid-mediated metabolic inflammation. An important age-related phenotype is high risk of monoclonal gammopathy (MG), including multiple myeloma. We identified GlcSph, a pathological lyso-sphingolipid exclusively elevated in GD, as a mediator of B cell activation and as an antigenic target for GD1-associated MG. Saposin C (SapC), is a lipid-binding protein and activator of lysosomal glucocerebrosidase, which when mutated, cause a rare variant of GD. Sera of GD1 patients with MG of diverse immunoglobulin types were compared to GD patients without gammopathy for reactivity against GlcSph and SapC. We show reactivity of clonal immunoglobulin in GD1 to GlcSph but not to SapC. In two patients with GD1 and gammopathy, GlcSph-reduction therapy with eliglustat resulted in reduction in clonal Ig. Together, our data show that GlcSph but not SapC is the antigenic target in GD1-associated MG and that therapy aimed at reducing the levels of immunogenic lipid resulted in reduction of clonal immunoglobulin in vivo.     

Glucocerebrosidase mutations in subjects with parkinsonism

Recent studies showing an association between glucocerebrosidase deficiency and parkinsonism in Gaucher disease prompted an examination of the glucocerebrosidase gene sequence (GBA) and enzyme activity in brain samples from 57 subjects carrying the diagnosis of Parkinson disease. Alterations in GBA were identified in 12 samples (21%) and were more frequent among the younger subjects. These included eight with mutations (N370S, L444P, K198T, and R329C) and four with probable polymorphisms (T369M and E326K). Our findings suggest that mutations in glucocerebrosidase may be a risk factor for the development of parkinsonism.     

A mutation in SCARB2 is a modifier in Gaucher disease

Lysosomal integral membrane protein type 2 (LIMP-2) is responsible for proper sorting and lysosomal targeting of glucocerebrosidase, the enzyme deficient in Gaucher disease (GD). Mutations in the gene for LIMP-2, SCARB2, are implicated in inherited forms of myoclonic epilepsy, and myoclonic epilepsy is part of the phenotypic spectrum associated with GD. We investigated whether SCARB2 mutations impact the Gaucher phenotype focusing on patients with myoclonic epilepsy, including a pair of siblings with GD who were discordant for myoclonic seizures. Sequencing of SCARB2 genomic and cDNA identified a heterozygous, maternally inherited novel mutation, c.1412A>G (p.Glu471Gly), in the brother with GD and myoclonic epilepsy, absent from his sibling and controls. Glucocerebrosidase activity, Western blots, real-time PCR, and immunofluorescence studies demonstrated markedly decreased LIMP-2 and glucocerebrosidase in cells from the sibling with (p.Glu471Gly) LIMP-2, and diminished glucocerebrosidase in lysosomes. The cells secreted highly glycosylated enzyme and showed mistrafficking of glucocerebrosidase. Sequencing of SCARB2 in 13 other subjects with GD and myoclonic epilepsy and 40 controls failed to identify additional mutations. The study provides further evidence for the association of LIMP-2 and myoclonic epilepsy, explains the drastically different phenotypes encountered in the siblings, and demonstrates that LIMP-2 can serve as a modifier in GD.     

Mutation analysis and genotype/phenotype relationships of Gaucher disease patients in Spain

Mutations in the glucocerebrosidase (GBA) gene cause Gaucher disease (GD). The aim of this study was to characterise the GBA mutations and analyze genotype/phenotype relationships in 193 unrelated patients from the Spanish GD Registry. We have identified 98.7% of the mutated GBA alleles, finding 56 different GBA mutations and 66 genotypes causing GD in Spain: 47 previously described mutations and 9 novel mutations (4 missense R395C, R463H, W312R and V398I, 1 nonsense R359X, 4 frameshift c.708delC, c.1214-1215delGC, c.1439-1445del7 and c.42-65del24). The most prevalent mutations were N370S and L444P, accounting for 68.7% of the mutated alleles. A wide phenotypic difference was observed within each genotypic group, and 9% of diagnosed type 1 patients developed neurological involvement including parkisonism, tremor, hypoacusia and eye movements. All of these findings indicate that there is a significant genotypic heterogeneity that explains the huge phenotypic variation among Spanish GD patients.     

Parvalbumin-immunoreactive neurons in the hippocampal formation of Alzheimer''s diseased brain

The number and topographic distribution of immunocytochemically stained parvalbumin interneurons was determined in the hippocampal formation of control and Alzheimer's diseased brain. In control hippocampus, parvalbumin interneurons were aspiny and pleomorphic, with extensive dendritic arbors. In dentate gyrus, parvalbumin cells, as well as a dense plexus of fibers and puncta, were associated with the granule cell layer. A few cells also occupied the molecular layer. In strata oriens and pyramidale of CA1–CA3 subfields, parvalbumin neurons gave rise to dendrites that extended into adjacent strata. Densely stained puncta and beaded fibers occupied stratum pyramidale, with less dense staining in adjacent strata oriens and radiatum. Virtually no parvalbumin profiles were observed in stratum lacunosum-moleculare or the alveus. Numerous polymorphic parvalbumin neurons and a dense plexus of fibers and puncta characterized the deep layer of the subiculum and the lamina principalis externa of the presubiculum. In Alzheimer's diseased hippocampus, there was an approximate 60% decrease in the number of parvalbumin interneurons in the dentate gyrus/CA4 subfield (P<0.01) and subfields CA1–CA2 (P<0.01). In contrast, parvalbumin neurons did not statistically decline in subfields CA3, subiculum or presubiculum in Alzheimer's diseased brains relative to controls. Concurrent staining with Thioflavin-S histochemistry did not reveal degenerative changes within parvalbumin-stained profiles. These findings reveal that parvalbumin interneurons within specific hippocampal subfields are selectively vulnerable in Alzheimer's disease. This vulnerability may be related to their differential connectivity, e.g., those regions connectionally related to the cerebral cortex (dentate gyrus and CA1) are more vulnerable than those regions connectionally related to subcortical loci (subiculum and presubiculum).     

Alzheimer's disease: is the decrease of the cholinergic innervation of the hippocampus related to intrinsic hippocampal pathology?

Consistent findings in the hippocampi of patients with Alzheimer's disease are the presence of neurofibrillary tangles in pyramidal neurons and the loss of choline acetyltransferase activity due to degeneration of hippocampal cholinergic terminals. The present study sought to clarify, in the brains of five patients with Alzheimer's disease and four controls, whether the loss of cholinergic terminals in the hippocampal stratum pyramidale in Alzheimer's disease is related to degenerative changes in hippocampal pyramidal cells. A polyclonal antibody to human choline acetyltransferase was employed to visualize immunohistochemically cholinergic terminals. Hippocampal neurons were stained with Cresyl Violet, neurofibrillary tangles with thioflavin S and a monoclonal antibody against phosphorylated neurofilament (RT97). Quantification of the stained structures was performed in CA4, CA1 and the subiculum, on five sections selected from the entire anteroposterior extent of each hippocampus. In the group of Alzheimer patients, the densities of cholinergic terminals were homogeneously diminished in the three hippocampal subregions in comparison with the controls (32-33%). In contrast, a significant loss of pyramidal neurons was found only in CA1, and the density of neurofibrillary tangles was markedly increased only in CA1 and the subiculum in Alzheimer's disease. These findings suggest that there is no relationship between the loss of cholinergic terminals and the degeneration of pyramidal cells in the hippocampus of patients with Alzheimer's disease.     

Molecular analysis of Turkish Gaucher disease patients: identification of novel mutations in glucocerebrosidase (GBA) gene

Gaucher disease (GD) is the most frequent lysosomal glycolipid storage disorder due to autosomal recessive deficiency of acid beta-glucosidase and is characterized by the accumulation of glucocerebroside. In this work we carried out molecular analysis of the glucocerebrosidase gene (GBA) in 57 unrelated patients and the alleleic frequencies of gene mutations in Turkish patients are reported. The most prevalent are L444P and N370S accounting for 42% and 30% in our patients. We identified three novel genetic alterations: two missense changes S356F, L296V that are associated with the severe phenotype of type 1 GD. 303-305delCAC was identified in a homozygous state in one patient type 1 or type 3.     

Parkinsonism among Gaucher disease carriers

An association between Gaucher disease and Parkinson disease has been demonstrated by the concurrence of Gaucher disease and parkinsonism in rare patients and the identification of glucocerebrosidase mutations in probands with sporadic Parkinson disease. Using a different and complementary approach, we describe 10 unrelated families of subjects with Gaucher disease where obligate or confirmed carriers of glucocerebrosidase mutations developed parkinsonism. These observations indicate that mutant glucocerebrosidase, even in heterozygotes, may be a risk factor for the development of parkinsonism. Understanding the relationship between altered glucocerebrosidase and the development of parkinsonian manifestations will provide insights into the genetics, pathogenesis, and treatment of Parkinson disease.     

Non-Aβ Component of Alzheimer’s Disease Amyloid (NAC) Revisited : NAC and α-Synuclein Are Not Associated with Aβ Amyloid

alpha-Synuclein (alphaSN), also termed the precursor of the non-Abeta component of Alzheimer's disease (AD) amyloid (NACP), is a major component of Lewy bodies and Lewy neurites pathognomonic of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). A fragment of alphaSN termed the non-Abeta component of AD amyloid (NAC) had previously been identified as a constituent of AD amyloid plaques. To clarify the relationship of NAC and alphaSN with Abeta plaques, antibodies were raised to three domains of alphaSN. All antibodies produced punctate labeling of human cortex and strong labeling of Lewy bodies. Using antibodies to alphaSN(75-91) to label cortical and hippocampal sections of pathologically proven AD cases, we found no evidence for NAC in Abeta amyloid plaques. Double labeling of tissue sections in mixed DLB/AD cases revealed alphaSN in dystrophic neuritic processes, some of which were in close association with Abeta plaques restricted to the CA1 hippocampal region. In brain homogenates alphaSN was predominantly recovered in the cytosolic fraction as a 16-kd protein on Western analysis; however, significant amounts of aggregated and alphaSN fragments were also found in urea extracts of SDS-insoluble material from DLB and PD cases. NAC antibodies identified an endogenous fragment of 6 kd in the cytosolic and urea-soluble brain fractions. This fragment may be produced as a consequence of alphaSN aggregation or alternatively may accelerate aggregation of the full-length alphaSN.     

A randomized trial comparing the efficacy and safety of imiglucerase (Cerezyme) infusions every 4 weeks versus every 2 weeks in the maintenance therapy of adult patients with Gaucher disease type 1

Imiglucerase (Cerezyme^®) has been the standard of care for treatment of Gaucher disease, a lysosomal storage disorder resulting from deficiency of glucocerebrosidase, since its approval in 1994. Infusions are typically given once every 2 weeks. However, many patients have expressed a desire for less frequent infusions as a matter of convenience. This clinical study assessed the safety and efficacy of intravenous imiglucerase infused once every 4 weeks (Q4) compared to once every 2 weeks (Q2) at the same total monthly dose in adult patients with clinically stable Gaucher disease type 1 (GD1). This was a 24-month, open-label, randomized, Phase 4, dose-frequency study conducted in 25 centers worldwide. Patients receiving imiglucerase were randomized to receive their monthly dose biweekly (n = 33) or every 4 weeks (n = 62). Changes from baseline in hemoglobin, platelets, liver and spleen volumes, bone crisis, and bone disease comprised a predefined composite endpoint; achievement or maintenance of established Gaucher disease therapeutic goals comprised a secondary endpoint. Sixty-three percent of Q4- and 81% of Q2-treated patients met the composite endpoint at Month 24; 89% of Q4- and 100% of Q2-treated patients met the therapeutic goals-based endpoint. The frequency of related adverse events was comparable between treatment groups. This study suggests that with comprehensive monitoring, a Q4 imiglucerase infusion regimen may be a safe and effective treatment option for the majority of clinically stable adult patients with GD1 but may not be appropriate for all GD1 patients. Continued monitoring in patients treated with Q4 dosing is required to assess long-term effectiveness.     

Distribution and kainate-mediated induction of the DNA mismatch repair protein MSH2 in rat brain

DNA repair is one of the most essential systems for maintaining the inherited nucleotide sequence of genomic DNA over time. Repair of DNA damage would be particularly important in neurons, because these cells are among the longest-living cells in the body. MSH2 is one of the proteins which are involved in the recognition and repair of a specific type of DNA damage that is characterized by pair mismatches. We studied the distribution of MSH2 in rat brain by immunohistochemical analysis. We found the level of MSH2 expression in rat brain to be clearly heterogeneous. The highest intensity of staining was found in the pyramidal neurons of the hippocampus and in the entorhinal and frontoparietal cortices. Positive cells were observed in the substantia nigra pars compacta, in cerebellar granular and Purkinje cells, and in the motor neurons of the spinal cord. We investigated the possible modulation of MSH2 expression after injection of kainate. Systemic administration of kainate induces various behavioural alterations and a typical pattern of neuropathology, with cell death in the hippocampal pyramidal neurons of the CA3/CA4 fields. Kainate injection also resulted in a marked, dose-dependent increase of MSH2 immunoreactivity in the hippocampal neurons of the CA3/CA4 fields. The effect was specific, since no changes in immunoreactivity were detected in the dentate gyrus nor in other brain areas. In summary, our data suggest that a mismatch DNA repair system, of which MSH2 protein is a representative component, is heterogeneously expressed in the rat brain and specifically induced by an experimental paradigm of excitotoxicity.     

Temporal and spatial expression of preprotachykinin A mRNA in the developing filial mice brain after maternal administration of monosodium glutamate at a late stage of pregnancy

In the early stages of brain development, exposure of excessive monosodium glutamate (MSG) to neurons causes animal functional and behavioral disorders in adulthood. To investigate the effects of excessive MSG during pregnancy on the neurons in the developing brain, in situ hybridization was used. In mice, the expression of preprotachykinin A mRNA (PPT A mRNA) was assessed in neurons of in the brain after MSG treatment. Brain tissue sections were hybridized with specific digoxigenin-labeled RNA probes. The number of cells that expressed PPT A mRNA gradually decreased from 10-day-old (10d) to 60-day-old (60d) MSG-treated and normal animals. In the MSG-treated and normal mice, the PPT A mRNA-positive neurons almost disappeared in 90-day-old (90d) mice. The expression of PPT A mRNA significantly decreased at 10d in most of the brain regions of MSG-treated mice including the cerebral cortex (CC), hippocampal subregions of CA1, CA2 (CA1, CA2), habenula nucleus (HAB), hypothalamic periventricular nucleus (PE), hypothalamic arcuate nucleus (AR), median eminence (ME), amygdala nucleus (AMY), endopiriform nucleus (EN), and hypothalamic ventromedial nucleus (VMH) and dorsomedial nucleus (DMH). In the hippocampal CA4 subregions (CA4), paraventricular nucleus (PV) and caudate putamen (CPU), however, they were not significantly altered. Furthermore, in CC, hippocampal CA3 subregion (CA3), PE and EN regions the number of PPT A mRNA-positive neurons decreased at 20 days old (20d), but increased significantly in CA2 and CPU. At 30 days old (30d), the positive neuron number decreased in AMY, and they did not change in other regions. At 60d, the number of positive neurons significantly decreased in PV and ME, but increased in AMY. In the other observed regions, no changes were found. These results show that maternal administration of excessive MSG at a late stage of pregnancy significantly decreases PPT A mRNA expression in most of the brain regions of filial mice. This suggests that glutamate-induced excitotoxicity may affect the metabolism of precursors of substance P in developing brain neurons. The present study provides insights into the plasticity and vulnerability of neuron in different brain regions to glutamate excitotoxicity.     

Immunohistochemical investigation of neurofibrillary tangles and their tau isoforms in brains of limbic neurofibrillary tangle dementia

Limbic neurofibrillary tangle dementia (LNTD) is a subset of senile dementia characterized by numerous neurofibrillary tangles (NFT) in the hippocampal area, although there is an absence or scarcity of amyloid deposits (AM) throughout the brain. In the present study, we immunohistochemically investigated regional numbers and tau isoforms of NFT in the hippocampal area of nine LNTD patients with anti-three-repeat (3R) tau-specific and anti-four-repeat (4R) tau-specific antibodies, differentiating NFT into three developmental stages of pretangles (PT), NFT and ghost tangles (GT). Consequently, most PT were 4R tau-positive, most GT were 3R tau-positive, and NFT were 3R tau-, 4R tau- or double-positive, suggesting that composition of tau isoforms may shift from a 4R tau-predominant pattern to a 3R tau-predominant pattern during the development of NFT. In addition, a large number of NFT showing different developmental stages and different rates of 3R tau- and 4R tau-positive neurons according to the region were found in the hippocampal area, suggesting that regions undergoing earlier NFT formation may show higher ratio of 3R tau-positive neurons to 4R tau-positive neurons, and that NFT formation may begin in the entorhinal and transentorhinal cortices, subsequently progress to the subiculum and CA1, and further to the CA2, amygdala and CA3-4, although progression to the neocortex is limited. Furthermore, 4R tau-positive astrocytes and grains were found in several patients, suggesting that LNTD is a form of tauopathy.