NADPH-diaphorase-containing neurons in cortex, subcortical white matter and neostriatum are selectively spared in Alzheimer's disease

To investigate the involvement of NADPH-diaphorase (NADPH-d)-containing neurons in Alzheimer's disease (AD), NADPH-d enzyme histochemistry in vibratome sections was applied to the superior frontal and superior temporal cortex and the neostriatum in 5 AD and 6 aged control brains. Overall there was a neuronal loss and atrophy in the cortex of AD. Despite slight morphological neuronal changes in the cortex of AD, we found no significant difference in the number of NADPH-d-positive neurons in both cortex and neostriatum between control and AD cases. These results provide further evidence for a selective preservation of NADPH-d neurons in AD. In order to check whether nNOS-immunoreactive neurons are identical to NADPH-d-positive neurons in the human brain, we examined the frontal and temporal cortex and neostriatum of normal human brains in serial cryostat sections. We found that nNOS-containing neurons paralleled NADPH-d-positive neurons in these brain regions. Copyrightz1999S.KargerAG,Basel

Treatment of Alzheimer's disease: an evaluation of the cholinergic approach

The cholinergic hypothesis claims that a decrease of acetylcholine (ACh) in the brain of patients with Alzheimer's Disease (AD) plays an important role in the deterioration of cognitive functioning. This hypothesis has led to extensive research in possible therapeutic approaches towards improving cholinergic transmission in AD patients. The different approaches have focused on the following six strategies: ACh precursors, ACh release, M1, M3, or M4 receptor agonists, M2 receptor antagonists, nicotinic agonists, and acetylcholinesterase inhibitors (AChEI). The aim of this review is to assess the effectiveness of the cholinergic approach for the treatment of AD.

Regulation of metallothionein-III (GIF) mRNA in the brain of patients with Alzheimer disease is not impaired

Contradictory results have been reported on the downregulation and role of the brain-specific protein metallothionein-III (MT-III, GIF) in Alzheimer disease (AD). In this article, the importance of MT-III downregulation in AD brain was re-evaluated in temporal and frontal cortex, hippocampus, and cerebellum of 11 AD patients and two groups of five and six control subjects, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify the levels of MT-III mRNA relative to the levels of three constitutive RNAs: beta-actin, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), and ribosomal RNA 18S (rRNA 18S). The distribution of MT-III was similar to that of each of the three constitutive RNAs. The relative levels of each of these RNAs was high in brain regions examined in both AD patients and control subjects. Our findings do not support a downregulation of MT-III mRNA in the frontal cortex as well as the temporal cortex and hippocampus of AD patients. However, the level of MT-III mRNA was not constant in the investigated samples, suggesting that MT-III mRNA regulation could be controlled by factors other than AD pathology. Brain-derived neurotrophic factor (BDNF) mRNA levels were hardly detectable by RT-PCR in human brain tissue; a trend for a decrease was apparent in the temporal cortex of AD patients. In conclusion, the content of MT-III mRNA in the brain of AD patients was not detectably impaired, whereas BDNF mRNA may be affected.

Amyloid precursor protein accumulation in Lewy body dementia and Alzheimer's disease

The presence of amyloid precursor protein (APP) and beta-amyloid protein (beta A4) was investigated in the cerebra of 4 patients with Alzheimer's disease (AD), 1 patient with Down's syndrome, 4 patients with dementia of the Lewy body type (DLB) and 4 age-matched, clinically nondemented controls, of which one displayed many amyloid plaques. The different types of amyloid plaques stained strongly with antibodies against beta A4. Antibodies against the C-terminal region of APP reacted only weakly with small swollen neurites and with globular deposits in neuritic-type plaques from patients with AD. The antibody against the N-terminal region of APP stained strongly cellular elements in the neuritic type plaques of patients with AD but not dense cored plaques. In contrast, patients with DLB displayed with this antibody a homogeneous staining of dense cored amyloid plaques. Some Lewy bodies stained with the antibody against the N-terminal region of APP as well. These results indicate that the processing of APP in AD and DLB could be different, to yield different fragments deposited in AD and DLB amyloid plaques.

Appearance of localized immunoreactivity for the alpha 4 integrin subunit and for fibronectin in brains from Alzheimer's, Lewy body dementia patients and aged controls

The localization of alpha 4 integrin subunit and of fibronectin in Alzheimer's disease (AD), Down's syndrome, Lewy body dementia (DLB) and normal brains was immunohistochemically investigated. Antibodies against the alpha 4 subunit and a fibronectin specific antibody stained 'neuritic' plaques in AD and Down's syndrome, while 'preamyloid' and 'burned-out' plaques remained negative. No alpha 4 integrin subunit or fibronectin immunoreactivity was detected in the plaques of DLB consistent with the absence of neuritic plaques. In addition, hippocampal pyramidal neurons and some neocortical neurons showed immunoreactivity with alpha 4 subunit and fibronectin antibodies in all aged individuals, but not in younger controls. These results suggest an age-related and localized expression of alpha 4 integrin subunit and fibronectin in the brain.

Heparan sulfate expression patterns in the amyloid deposits of patients with Alzheimer's and Lewy body type dementia

Heparan sulfate (HS), along with serum amyloid P component, has been identified in all types of amyloid investigated so far, regardless of the type of amyloid protein deposited. To assess whether unique or specific HS proteoglycans (HSPGs) may be involved in the formation of these lesions, we have investigated the accumulation of several distinct HSPG epitopes in the cerebra of patients with different forms of neurodegenerative disease. A panel composed of several antibodies revealed distinctive patterns of HSPG accumulation. In patients with dementia of the Lewy body type, the burned-out-type plaques and preamyloid-type plaques were strongly stained by both the anti-HS 'chain' and anti-HS 'stub' antibodies, but by none of the available anti-core protein antibodies. In Alzheimer's disease, the preamyloid-type plaques, dense-cored-type plaques, neuritic-type plaques and the neurofibrillary tangles were stained by the anti-'stub' antibody. The anti-'chain' and the anti-core protein antibodies, in contrast, failed to stain the preamyloid-type plaques and burned-out-type plaques, but stained the neuritic-type plaques in these patients. These data suggest differences in the types of HS and HSPG (fragments) that accumulate in amyloid lesions that may hallmark neurodegenerative disorders of different etiologies.

alpha 2-Macroglobulin expression in neuritic-type plaques in patients with Alzheimer's disease

Because it has been suggested that alpha 2M could be involved in the generation of amyloid peptide, attention was given to a possible association of alpha 2M expression and amyloid accumulation in the brain. Therefore, we investigated the presence of the proteinase inhibitor alpha 2-macroglobulin (alpha 2M) in the cerebra of 4 patients with Alzheimer's Disease (AD). One case of a patient with Down's syndrome, 2 cases of patients with Dementia of the Lewy Body type (DLB), 1 case of an aged, clinically nondemented person who displayed many amyloid plaques, and 3 normal aged control brains were also studied. The results obtained by immunocytochemistry with monoclonal antibodies directed against two different epitopes of human alpha 2M showed an association of alpha 2M, only with neuritic-type plaques in patients with AD. No alpha 2M immunoreactivity was found in either preamyloid-type plaques or burned out-type plaques in AD, DLB, or aged nondemented controls. The results do not support a direct role of this proteinase inhibitor in the formation of amyloid. Because alpha 2M is observed to be associated with reactive microglia in the outer border of the neuritic plaques, the data suggest that alpha 2M could be a marker for an inflammatory cellular process in these neuritic plaques.

Towards an improved survival of rat brain neurons in culture by cerebrospinal fluid of patients with senile dementia of Alzheimer's type

Neuronal cell survival was investigated in rat brain cortical cultures in the presence of increasing concentrations of human brain extracts or cerebrospinal fluid (CSF) from control and Senile Dementia of Alzheimer's type (SDAT) patients. Using hippocampal brain extracts, converted 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) was compared to the content of the neuronal marker MAP2 in foetal rat brain neuronal cultures in order to test converted MTT as a quantitative parameter for neuronal cell survival. A significant correlation was found between both parameters. SDAT frontal cortex brain extracts induced a two four-fold increase in neuronal cell survival at 25 to 125 micrograms protein extract, whereas control brain extracts induced at similar protein concentrations a decline in neuronal cell survival. The enhanced survival yielded by SDAT brain extracts was fully abolished in the presence of control brain extract. Control CSF concentration-dependently increased neuronal cell survival in postnatal rat brain neuronal cultures independent of the difference in the protein content of CSF samples and age of the patients. SDAT CSF also concentration-dependently enhanced neuronal cell survival, however, the effect was more pronounced compared to control CSF. These observations are in favour of the hypothesis that there might be a higher neurotrophic activity in SDAT brain tissue.

Mode of action of the triazolobenzodiazepines in the treatment of panic attacks: a hypothesis

Alprazolam (Xanax) or 8-chloro-1-methyl-6-phenyl-4H-S-triazolobenzodiazepine is a potent drug for the treatment of anxiety disorders. The chemical structure differs from the classical benzodiazepines by incorporation of the triazoloring. Due to the triazolo ring, the drug can have additional modes of action than the normal benzodiazepines. The triazolobenzodiazepines are potent inhibitors of the platelet-activating factor. This factor is a potent stimulator of the corticotropin-releasing hormone. This hormone has an effect on the hypothalamo-pituitary-adrenal axis but the corticotropin-releasing hormone is also known to be a stimulator of the locus coeruleus. The corticotropin-releasing hormone in patients with panic attacks is elevated. This could be a result of the hyperactive metabolism which is observed by positron emission tomographic (PET) studies of the right parahippocampal area.