Long-term rivastigmine treatment in a routine clinical setting

Objective – The aim of the study was to observe the effects of long‐term rivastigmine treatment in patients with mild to moderate Alzheimer’s disease (AD) in a routine clinical setting. Methods – This was a prospective, open‐label, observational, multicentre, non‐randomized study. Outcome measures included the Mini Mental State Examination (MMSE), the Clinician’s Interview‐Based Impression of Change (CIBIC) and the Alzheimer’s Disease Assessment Scale – cognitive subscale (ADAS‐cog). Results – Of 217 patients initiated into rivastigmine treatment, 62% (n = 135) remained on treatment for 24 months. Most patients droped out due to nursing home placement or side effects. Eighty per cent and 67% of completers exhibited a symptomatic attenuation of cognitive decline (≤ 4‐point deterioration) as assessed by using the MMSE and ADAS‐cog respectively. Forty‐four per cent showed an unchanged/improved CIBIC rating. Conclusions – Over 60% of patients remained on treatment for 2 years in this routine clinical setting. In patients who remained on treatment, rivastigmine appeared to stabilize their condition and prevented or delayed symptomatic decline.     

Depression is associated with low plasma Abeta42 independently of cardiovascular disease in the homebound elderly

BACKGROUND: Depression often precedes the onset of Alzheimer's disease (AD) before the appearance of cognitive symptoms. Plasma Amyloid-beta peptide 42 (Abeta42) declines before and soon after the onset of AD, yet the relationship between plasma Abeta42 and depression is unclear. METHODS: We used 515 homebound elders aged 60 and older in a population-based, cross-sectional study to investigate associations between plasma Abeta levels and depression with and without cardiovascular co-morbidities. Depression was evaluated by using the Center for Epidemiological Studies Depression (CES-D) scale. Plasma Abeta40 and Abeta42 were measured. RESULTS: The elderly with depression had lower plasma Abeta42 (median: 15.3 vs. 18.9, p = 0.008) than those without depression. The CES-D score was inversely associated with plasma Abeta42 (p = 0.001) in subjects with no cardiovascular disease (CVD); however, in the presence of CVD, this association did not exist. Low plasma Abeta42 (OR = 0.41, p = 0.007) and the presence of CVD (OR = 1.84, p = 0.005) were independently associated with depression after adjusting for the confounders of age, stroke and apolipoprotein E4. CONCLUSIONS: Depressive symptoms are associated with low plasma Abeta42 independently of CVD. Prospective studies are needed to determine whether depression associated with low plasma Abeta42 is a separate depression subtype that could predict the onset of AD.     

β-Secretase activity in rat astrocytes: translational block of BACE1 and modulation of BACE2 expression

BACE1 and BACE2 are two closely related membrane-bound aspartic proteases. BACE1 is widely recognized as the neuronal β-secretase that cleaves the amyloid-β precursor protein, thus allowing the production of amyloid-β, i.e. the peptide that has been proposed to trigger the neurodegenerative process in Alzheimer's disease. BACE2 has ubiquitous expression and its physiological and pathological role is still unclear. In light of a possible role of glial cells in the accumulation of amyloid-β in brain, we have investigated the expression of these two enzymes in primary cultures of astrocytes. We show that astrocytes possess β-secretase activity and produce amyloid-β because of the activity of BACE2, but not BACE1, the expression of which is blocked at the translational level. Finally, our data demonstrate that changes in the astrocytic phenotype during neuroinflammation can produce both a negative as well as a positive modulation of β-secretase activity, also depending on the differential responsivity of the brain regions.     

Differential effects of oligomeric and fibrillar amyloid-beta 1-42 on astrocyte-mediated inflammation

Activated glia, as a result of chronic inflammation, are associated with amyloid-beta peptide (Abeta) deposits in the brain of Alzheimer's disease (AD) patients. In vitro, glia are activated by Abeta inducing secretion of pro-inflammatory molecules. Recent studies have focused on soluble oligomers (or protofibrils) of Abeta as the toxic species in AD. In the present study, using rat astrocyte cultures, oligomeric Abeta induced initial high levels of IL-1beta decreasing over time and, in contrast, fibrillar Abeta increased IL-1beta levels over time. In addition, oligomeric Abeta, but not fibrillar Abeta, induced high levels of iNOS, NO, and TNF-alpha. Our results suggest that oligomers induced a profound, early inflammatory response, whereas fibrillar Abeta showed less increase of pro-inflammatory molecules, consistent with a more chronic form of inflammation.     

Residues 17-20 and 30-35 of beta-amyloid play critical roles in aggregation

We examined the effects of co-incubating nine different Abeta peptide fragments with full-length Abeta1-40 (Abeta40) on protein aggregation. Six fragments enhanced aggregation of Abeta40 (Abeta1-28, 12-28, 17-28, 10-20, 25-35 and 17-40), while three others did not (Abeta1-11, 1-16, and 20-29). All of the peptides that enhanced aggregation contained either residues 17-20 or 30-35, indicating the importance of these regions for promoting aggregation of full-length Abeta. Abeta25-35 in particular increased both the rate and extent of aggregation of Abeta40 considerably as indicated by fluorescence staining. Atomic force microscope imaging (AFM) indicates the increase in fluorescence staining with Abeta25-35 is primarily due to increased formation of oligomers and protofibrils rather than formation of large amyloid fibrils. AFM images of Abeta25-35 when incubated alone also indicate formation of aggregates and long thin filaments. The increase in formation of the small toxic oligomeric morphology of Abeta40, along with formation of Abeta25-35 oligomers and thin filaments, represent two different potential pathways for Abeta25-35 toxicity. The critical roles of residues 17-20 and 30-35 of Abeta provide further insight into mechanism that underlie the formation of toxic aggregates in Alzheimer Disease (AD) and suggest targets for the design of beta-sheet breakers to modulate the aggregation and inhibit toxicity of full-length Abeta.     

CSF markers for pathogenic processes in Alzheimer’s disease: diagnostic implications and use in clinical neurochemistry

In view of current (acetylcholine esterase (AChE) inhibitors) and future (e.g. γ-secretase inhibitors) therapeutic compounds for treatment of Alzheimer’s disease (AD), the development and evaluation of cerebrospinal fluid (CSF) biomarkers for AD has become a rapidly growing research field. Diagnostic biomarkers for AD would be especially valuable as aids to diagnosis early in the course of the disease, when correct diagnosis is difficult, and when therapeutic compounds have the greatest potential for being effective. This paper reviews CSF biomarkers for AD, with emphasis on their role in the clinical diagnosis. The two most studied biochemical markers, CSF-tau and CSF-Aβ42, have high sensitivity to identify AD, but the specificity against other dementias is lower. The addition of phosphorylated tau (P-Tau) seems to increase the specificity for the diagnosis of AD, since normal levels are found in both frontotemporal and Lewy body dementia, and in cerebrovascular disease. These CSF markers may be useful as diagnostic aids, especially to discriminate early or incipient AD from age-associated memory impairment, depression, and some secondary dementias.     

Diagnostic markers for diagnosing dementia with Lewy bodies: CSF and MIBG cardiac scintigraphy study

OBJECTIVE: This study examined the diagnostic value of cerebrospinal fluid (CSF) markers and iodine-123 metaiodobenzylguanidine ((123)I-MIBG) cardiac scintigraphy in distinguishing dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). METHODS: CSF levels of amyloid beta1-42 (Abeta42) and 181-Thr phosphorylated tau (p-tau) were measured using enzyme linked immunosorbent assay (ELISA) kits. (123)I-MIBG cardiac scintigraphy was performed in patients with AD and DLB, and control (CTL) subjects. RESULTS: Increased CSF levels of p-tau in AD were found compared to DLB patients and CTL subjects (P<0.01), but there was no significant difference in CSF levels of Abeta42 between AD and DLB patients. The early and delayed heart to mediastinum (H/M) ratios of (123)I-MIBG cardiac scintigraphy were significantly decreased in patients with DLB compared to AD patients and CTL subjects (P<0.01). The receiver operating characteristic (ROC) analysis revealed that the diagnostic value of (123)I-MIBG cardiac scintigraphy was superior to that of CSF markers. CONCLUSIONS: (123)I-MIBG cardiac scintigraphy may be useful for discriminating between DLB and AD.     

Anti-amyloid beta activity of metallothionein-III is different from its neuronal growth inhibitory activity: structure-activity studies

Recent studies have shown that metallothionein-III (MT-III), but not MT-I or -II, antagonizes both the neurotrophic and neurotoxic effects of amyloid β peptides (Aβs). Further, its anti-Aβ-toxicity effect was attributed to the fact that it inhibits the formation of fibrillar Aβ. MT-III alone also affects neuron survival in culture—promoting at low but inhibiting at high concentrations. To characterize these biological activities of MT-III in relation to its neuronal growth inhibitory activity discovered by Uchida et al. [Neuron 7 (1991) 337–347], we here studied effects of the P7S/P9A double mutant, and the N- and C-terminal domains of MT-III on primary cultures of rat embryonic cortical neurons in the presence and absence of Aβ. Results show that (i) only the wild-type MT-III inhibited the formation of SDS-resistant Aβ aggregates and protected cortical neurons from the toxic effect of Aβ, and (ii) both the wild type and the N-terminal domain of MT-III promote neuron survival at low concentrations but inhibited it at high concentrations. On the basis of these findings, we conclude that the anti-Aβ activity of MT-III is different from its neuronal growth inhibitory activity and suggest that the increased trophic activity of AD brain extracts could be attributed to its low MT-III content.     

ER stress is involved in Abeta-induced GSK-3beta activation and tau phosphorylation

Intracellular neurofibrillary tangles, one of the characteristic hallmarks of Alzheimer's disease (AD), are mainly composed of hyperphosphorylated tau. The abnormal tau phosphorylation seems to be related to altered activity of kinases such as glycogen synthase kinase-3beta (GSK-3beta). Tau pathology is thought to be a later event during the progression of the disease, and it seems to occur as a consequence of amyloid-beta (Abeta) peptide accumulation. The aim of this work was to investigate whether soluble Abeta1-42, particularly oligomers that correspond to the neurotoxic species involved early in the development of AD, triggers tau phosphorylation by a mechanism involving activation of tau-kinase GSK-3beta. Several studies suggest that GSK-3beta plays a central role in signaling the downstream effects of endoplasmic reticulum (ER) stress. Therefore, the involvement of ER Ca(2+) release in GSK-3beta activation and tau phosphorylation induced by Abeta1-42 oligomers was evaluated using dantrolene, an inhibitor of Ca(2+) release through channels associated with ER ryanodine receptors. We observed that Abeta1-42 oligomers increase tau phosphorylation and compromises cell survival through a mechanism mediated by GSK-3beta activation. We also demonstrated that oligomeric Abeta1-42 induces ER stress and that ER Ca(2+) release is involved in oligomer-induced GSK-3beta activation and tau phosphorylation. This work suggests that GSK-3beta can be a promising target for therapeutic intervention in AD.     

CSF biomarkers in frontotemporal lobar degeneration: relations with clinical characteristics, apolipoprotein E genotype, and neuroimaging

In order to better understand the large variation in cerebrospinal fluid (CSF) tau and amyloid-beta(1-42) (Abeta42) in frontotemporal lobar degeneration (FTLD), relations between these biomarkers and clinical parameters, neuroimaging characteristics, and apolipoprotein E (ApoE) genotype were studied in 31 patients with FTLD, including 16 patients with the frontal variant and 15 with the temporal variant. CSF tau was highest in FTLD with predominant temporal involvement. In the frontal subgroup, CSF tau level was influenced by the number of ApoE epsilon3 alleles. In the temporal subgroup, CSF tau level was dependent on a combination of CSF Abeta42, age, disease duration, and disease severity. No relation with degree of atrophy or asymmetry on neuroimaging could be established. CSF Abeta42 variability remained unexplained. Future research could study the role of ApoE genotype and Abeta42 in FTLD, as well as establish measures for disease intensity.     

Protective effects of erythropoietin on tau phosphorylation induced by beta-amyloid

Neuropathological studies have demonstrated that the presence of neurofibrillary tangles (NFTs) is one of the most prominent pathologic characteristics of Alzheimer's disease (AD). The microtubule-associated protein tau is the major component of NFTs, and its abnormal hyperphosphorylation leads to the destabilization of microtubules, impaired axonal transport, and eventual death of the neurons. The hematopoietic cytokine erythropoietin (Epo) is now considered as a viable agent with regard to central nervous system injury in a variety of cellular systems. Here we report that Epo prevented tau hyperphosphorylation in SH-SY5Y cells exposed to the beta-amyloid peptide and that this effect may depend on the PI3K/Akt-GSK-3beta pathway. This study provides new molecular insight into the neuroprotective effect of Epo and suggests its possible therapeutic role in the management of AD.     

Cysteine proteases are the major beta-secretase in the regulated secretory pathway that provides most of the beta-amyloid in Alzheimer's disease: role of BACE 1 in the constitutive secretory pathway

This article focuses on beta-amyloid (Abeta) peptide production and secretion in the regulated secretory pathway and how this process relates to accumulation of toxic Abeta in Alzheimer's disease. New findings are presented demonstrating that most of the Abeta is produced and secreted, in an activity-dependent manner, through the regulated secretory pathway in neurons. Only a minor portion of cellular Abeta is secreted via the basal, constitutive secretory pathway. Therefore, regulated secretory vesicles contain the primary beta-secretases that are responsible for producing the majority of secreted Abeta. Investigation of beta-secretase activity in regulated secretory vesicles of neuronal chromaffin cells demonstrated that cysteine proteases account for the majority of the beta-secretase activity. BACE 1 is present in regulated secretory vesicles but provides only a small percentage of the beta-secretase activity. Moreover, the cysteine protease activities prefer to cleave the wild-type beta-secretase site, which is relevant to the majority of AD cases. In contrast, BACE 1 prefers to cleave the Swedish mutant beta-secretase site that is expressed in a minor percentage of the AD population. These new findings lead to a unifying hypothesis in which cysteine proteases are the major beta-secretases for the production of Abeta in the major regulated secretory pathway and BACE 1 is the beta-secretase responsible for Abeta production in the minor constitutive secretory pathway. These results indicate that inhibition of multiple proteases may be needed to decrease Abeta production as a therapeutic strategy for Alzheimer's disease.     

Huperzine A attenuates amyloid beta-peptide fragment 25-35-induced apoptosis in rat cortical neurons via inhibiting reactive oxygen species formation and caspase-3 activation.

Huperzine A, a novel Lycopodium alkaloid originally discovered in the Chinese herb Qian Ceng Ta (Huperzia serrata), is a reversible, potent, and selective acetylcholinesterase (AChE) inhibitor and has been extensively used for the treatment of Alzheimer's disease (AD) in China. The present studies were designed to investigate effects of huperzine A on amyloid beta-peptide fragment 25-35 (Abeta25-35)-induced neuronal apoptosis and potential mechanisms in primary cultured rat cortical neurons. After exposure of the cells to Abeta25-35 (20 microM), apoptotic cell death was observed as evidenced by a significant decrease in cell viability, alteration of neuronal morphology, and DNA fragmentation. Pretreatment of the cells with huperzine A (0.01-10 microM) prior to Abeta25-35 exposure significantly elevated the cell survival and reduced Abeta25-35-induced nuclei fragmentation. Reactive oxygen species (ROS)-based fluorescence, caspase-3-like fluorogenic cleavage, and Western blot analysis demonstrated that huperzine A reduced Abeta25-35-induced ROS formation in a dose-dependent manner, and 1 microM of huperzine A attenuated Abeta25-35-induced caspase-3 activity at 6, 12, 24, and 48 hr posttreatment. Our results provide the first direct evidence that huperzine A protects neurons against Abeta25-35-induced apoptosis via the inhibition of ROS formation and caspase-3 activity.     

White matter lesion severity is associated with reduced cognitive performances in patients with normal CSF Abeta42 levels

Objective – To identify possible associations between white matter lesions (WML) and cognition in patients with memory complaints, stratified in groups with normal and low cerebrospinal fluid (CSF) Aβ42 values. Material and Methods – 215 consecutive patients with subjective memory complaints were retrospectively included. Patients were stratified into two groups with normal (n = 127) or low (n = 88) CSF Aβ42 levels (cut‐off is 450 ng/l). Cognitive scores from the Mini‐Mental State Examination (MMSE) and the Neurobehavioral Cognitive Status Examination (Cognistat) were used as continuous dependent variables in linear regression. WML load was used as a continuous independent variable and was scored with a visual rating scale. The regression model was corrected for possible confounding factors. Results – WML were significantly associated with MMSE and all Cognistat subscores except language (repetition and naming) and attention in patients with normal CSF Aβ42 levels. No significant associations were observed in patients with low CSF Aβ42. Conclusions – WML were associated with affection of multiple cognitive domains, including delayed recall and executive functions, in patients with normal CSF Aβ42 levels. The lack of such associations for patients with low CSF Aβ42 (i.e. with evidence for amyloid deposition), suggests that amyloid pathology may obscure cognitive effects of WML.     

CSF Aβ42 and tau in Parkinson's disease with cognitive impairment

We tested the hypothesis that the CSF biomarker signature associated with Alzheimer's disease (AD) is present in a subset of individuals with Parkinson's disease and Dementia (PD‐D) or with PD and Cognitive Impairment, Not Dementia (PD‐CIND). We quantified CSF Aβ₄₂, total tau (T‐tau), and phospho‐tau (P181‐tau) using commercially available kits. Samples were from 345 individuals in seven groups (n): Controls ≤50 years (35), Controls >50 years (115), amnestic Mild Cognitive Impairment (aMCI) (24), AD (49), PD (49), PD‐CIND (62), and PD‐D (11). We observed expected changes in AD or aMCI compared with age‐matched or younger controls. CSF Aβ₄₂ was reduced in PD‐CIND (P < 0.05) and PD‐D (P < 0.01), whereas average CSF T‐tau and P181‐tau were unchanged or decreased. One‐third of PD‐CIND and one‐half of PD‐D patients had the biomarker signature of AD. Abnormal metabolism of Aβ₄₂ may be a common feature of PD‐CIND and PD‐D. © 2010 Movement Disorder Society     

The diagnostic value of tau protein, beta-amyloid (1-42) and their ratio for the discrimination of alcohol-related cognitive disorders from Alzheimer's disease in the early stages

BACKGROUND: Chronic and heavy alcohol abuse or dependence may result in impaired cognition and dementia. The increased risk of Alzheimer's disease (AD) in older individuals interferes with the differential diagnosis, especially when dealing with elderly patients with a long history of alcohol abuse. The aim of the present study was to evaluate the diagnostic value of the putative cerebrospinal fluid (CSF) biomarkers tau, beta-amyloid 1-42 (Abeta42) and their ratio in differentiating alcohol related cognitive disorder (ARCD) from AD. METHODS: Double-sandwich ELISA (Innotest htau antigen and beta-Amyloid (1-42), Innogenetics) were used to quantify the above markers in a total of 20 patients with ARCD, 33 AD patients with mild to moderate dementia and 50 mentally intact subjects. RESULTS: Tau protein successfully differentiated AD from normal ageing with 96% specificity and 93.9% sensitivity and from ARCD with 95% specificity, and 87.9% sensitivity. Abeta42 alone had a specificity of 88% and a sensitivity of 69.7% in differentiating AD from normal ageing, while the corresponding values for differentiating AD from ARCD were 80% and 84.8% respectively. The tau/Abeta42 ratio was better than tau alone for differentiating AD from normal ageing (specificity 94%, sensitivity 97%) and better than any of the candidate markers alone, for differentiating AD from ARCD (specificity 100%, sensitivity 97%). CONCLUSIONS: The combined use of CSF tau and Abeta42 may be a useful tool in the differential diagnosis of ARCD from AD, especially in the early stages, where diagnostic uncertainty is greater.     

Association of platelet-derived soluble glycoprotein VI in plasma with Alzheimer's disease

Accumulating evidence from epidemiological, clinical and experimental studies suggests that vascular risk factors and angiopathic mechanisms are involved in the pathogenesis of Alzheimer’s disease (AD). Platelets could be the missing link between AD and the vasculature.

Soluble glycoprotein VI (sGPVI) and β-thromboglobulin (β-TG) plasma and cerebrospinal fluid (CSF) levels as markers of platelet activity were measured in 30 AD patients and 20 age-matched healthy elderly controls by ELISA. The severity of dementia was assessed by mini-mental state examination (MMSE).

We found in AD patients significantly decreased sGPVI plasma levels (0.55 ± 0.18 ng/ml) as compared to healthy controls (0.75 ± 0.43 ng/ml; p = 0.033). In AD patients, sGPVI levels were positively correlated with β-TG plasma levels (r = 0.244, p = 0.05) and with cognitive status as measured by MMSE score (r = 0.271; p = 0.048). In unconcentrated CSF samples, levels of β-TG and sGPVI were below the detection limit of the assays in AD patients and healthy controls.

Our results suggest an association of sGPVI with the pathogenesis of AD. These findings encourage future research into whether sGPVI plasma levels may reflect or even mediate neuroprotective mechanisms in AD.     

Lack of association between IL-1β, TNF-α, and IL-10 gene polymorphisms and sporadic Parkinson's disease in an Italian cohort

Pascale E, Passarelli E, Purcaro C, Vestri AR, Fakeri A, Guglielmi R, Passarelli F, Meco G. Lack of association between IL‐1β, TNF‐α, and IL‐10 gene polymorphisms and sporadic Parkinson’s disease in an Italian cohort.
Acta Neurol Scand: 2011: 124: 176–181.
© 2010 John Wiley & Sons A/S. Objective – There is increasing evidence suggesting that neuroinflammation and microglia activation may play important roles in the pathway leading to neuronal cell death in Parkinson’s disease (PD). Chronic activation of microglia may cause neuronal damage through the release of potentially cytotoxic molecules, such as pro‐inflammatory cytokines. Different functional promoter polymorphisms within genes coding pro‐ or anti‐inflammatory cytokines involved in the immune reactions in the brain might influence the risk of developing PD or the age of disease onset. Aim – To investigate the interleukin (IL)‐1β‐511, tumor necrosis factor alpha (TNF‐α)‐308, and interleukin (IL)‐10‐1082 gene polymorphisms as susceptibility factors for PD. Methods;– We analyzed genotype and allele distributions of these polymorphisms in146 Italian patients with PD and 156 healthy controls. Results – None of the polymorphisms we investigated was found to be associated with PD or with age of disease onset. No significant differences between patients with PD and controls were found as regards the concomitant presence of variant alleles in the three polymorphisms studied. We found that only the combined genotype TNF‐α‐308GG/IL‐1β‐511T(+) is associated with a decreased risk of PD. Conclusion – Our results indicate that the cytokine gene polymorphisms we investigated are not related to the development of PD in the Italian population; further studies are warranted to clarify the role of the TNF‐α‐308GG/IL‐1β‐511T(+) combined genotype.