Interleukin-18 alters protein expressions of neurodegenerative diseases-linked proteins in human SH-SY5Y neuron-like cells

Chronic inflammation and oxidative stress (OS) are present in Alzheimer's disease (AD) brains in addition to neuronal loss, Amyloid-β (Aβ) plaques and hyperphosphorylated tau-protein neurofibrillary tangles (NFTs). Previously we showed that levels of the pro-inflammatory cytokine, interleukin-18 (IL-18), are elevated in post-mortem AD brains. IL-18 can modulate the tau kinases, Cdk5 and GSK3β, as well as Aβ-production. IL-18 levels are also increased in AD risk diseases, including type-2 diabetes and obesity. Here, we explored other IL-18 regulated proteins in neuron-like SH-SY5Y cells. Differentiated SH-SY5Y cells, incubated with IL-18 for 24, 48, or 72 h, were analyzed by two-dimensional gel electrophoresis (2D-DIGE). Specific altered protein spots were chosen and identified with mass spectrometry (MS) and verified by western immunoblotting (WIB). IL-18 had time-dependent effects on the SH-SY5Y proteome, modulating numerous protein levels/modifications. We concentrated on those related to OS (DDAH2, peroxiredoxins 2, 3, and 6, DJ-1, BLVRA), Aβ-degradation (MMP14, TIMP2), Aβ-aggregation (Septin-2), and modifications of axon growth and guidance associated, collapsin response mediator protein 2 (CRMP2). IL-18 significantly increased antioxidative enzymes, indicative of OS, and altered levels of glycolytic α- and γ-enolase and multifunctional 14-3-3γ and -ε, commonly affected in neurodegenerative diseases. MMP14, TIMP2, α-enolase and 14-3-3ε, indirectly involved in Aβ metabolism, as well as Septin-2 showed changes that increase Aβ levels. Increased 14-3-3γ may contribute to GSK3β driven tau hyperphosphorylation and CRMP2 Thr514 and Ser522 phosphorylation with the Thr555-site, a target for Rho kinase, showing time-dependent changes. IL-18 also increased caspase-1 levels and vacuolization of the cells. Although our SH-SY5Y cells were not aged, as neurons in AD, our work suggests that heightened or prolonged IL-18 levels can drive protein changes of known relevance to AD pathogenesis.

Pro-inflammatory interleukin-18 increases Alzheimer's disease-associated amyloid-β production in human neuron-like cells

Background

Alzheimer’s disease (AD) involves increased accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles as well as neuronal loss in various regions of the neocortex. Neuroinflammation is also present, but its role in AD is not fully understood. We previously showed increased levels of pro-inflammatory cytokine interleukin-18 (IL-18) in different regions of AD brains, where it co-localized with Aβ-plaques, as well as the ability of IL-18 to increase expression of glycogen synthase kinase-3β (GSK-3β) and cyclin dependent kinase 5, involved in hyperphosphorylation of tau-protein. Elevated IL-18 has been detected in several risk conditions for AD, including obesity, type-II diabetes, and cardiovascular diseases as well as in stress.

Methods

We differentiated SH-SY5Y neuroblastoma cells as neuron-like and exposed them to IL-18 for various times. We examined the protein levels of amyloid-β precursor protein (APP) and its processing products, its cleaving enzymes, involved in amyloidogenic processing of APP, and markers of apoptosis.

Results

IL-18 increased protein levels of the β-site APP-cleaving enzyme BACE-1, the N-terminal fragment of presenilin-1 and slightly presenilin enhancer 2, both of which are members of the γ-secretase complex, as well as Fe65, which is a binding protein of the C-terminus of APP and one regulator for GSK-3β. IL-18 also increased APP expression and phosphorylation, which preceded increased BACE-1 levels. Further, IL-18 altered APP processing, increasing Aβ40 production in particular, which was inhibited by IL-18 binding protein. Increased levels of soluble APPβ were detected in culture medium after the IL-18 exposure. IL-18 also increased anti-apoptotic bcl-xL levels, which likely counteracted the minor increase of the pro-apoptotic caspase-3. Lactate dehydrogenase activity in culture medium was unaffected.

Conclusions

The IL-18 induction of BACE-1, APP processing, and Aβ is likely to be linked to stress-associated adaptations in neurons during the course of normal functioning and development. However, in the course of wider changes in the aging brain, and particularly in AD, the effects of heightened or prolonged levels of IL-18 may contribute to the process of AD, including via increased Aβ.

Mild cognitive impairment associates with concurrent decreases in serum cholesterol and cholesterol-related lipoprotein subclasses

BACKGROUND AND OBJECTIVE

Accumulating evidence suggests that serum lipids are associated with cognitive decline and dementias. However, majority of the existing information concerns only serum total cholesterol (TC) and data at the level of lipoprotein fractions and subclasses is limited. The aim of this study was to explore the levels and trends of main cholesterol and triglyceride measures and eight lipoprotein subclasses during normal aging and the development of mild cognitive impairment by following a group of elderly for six years.

DESIGN

Longitudinal.

SETTING

City of Kuopio, Finland.

PARTICIPANTS

45 elderly individuals of which 20 developed mild cognitive impairment (MCI) during the follow-up.

MEASUREMENTS

On each visit participants underwent an extensive neuropsychological and clinical assessment. Lipoprotein levels were measured via 1H NMR from native serum samples.

RESULTS

Serum cholesterol and many primarily cholesterol-associated lipoprotein measures clearly decreased in MCI while the trends were increasing for those elderly people who maintained normal cognition.

CONCLUSION

These findings suggest that a decreasing trend in serum cholesterol measures in elderly individuals may suffice as an indication for more detailed inspection for potential signs of cognitive decline.

CERAD-neuropsychological battery in screening mild Alzheimer's disease

OBJECTIVES

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery (nb) is used as an evaluation tool for dementia. In Finland, CERAD-nb was introduced in 1999 and has been proposed to be used in primary health care. However, some of its parts need reassessment and focusing. The goal of this study was to examine the sensitivity and specificity of the subtests and their cut-off points most appropriate for identifying mild Alzheimer's disease (AD).

MATERIALS AND METHODS

The study population consisted of 171 patients with mild AD and 315 cognitively normal elderly. Both groups underwent CERAD-nb investigation as a part of a wider examination procedure.

RESULTS

The most efficient subtests to discriminate patients with mild AD from the normal elderly were Wordlist delayed recall and savings, Wordlist learning and Wordlist recognition and a new variable of Total recall. Optimal cut-off points for each subtest are suggested. The sensitivities of the verbal memory subtests varied between 0.75 and 0.94, the specificities between 0.80 and 0.93 and the areas under the receiver operating characteristics curve between 0.89 and 0.96.

CONCLUSIONS

The CERAD-nb is capable of differentiating cases with mild AD from normal elderly individuals particularly with its verbal memory subtests. New cut-off scores for CERAD's subtests validated in the study further enhance the differentiating power, and with these clarifications, CERAD-nb is considered appropriate to be used as a screening tool for AD even in primary health care.

Neuropsychiatric symptoms and quality of life in patients with very mild and mild Alzheimer's disease

BACKGROUND

Neuropsychiatric symptoms (NPS) are common manifestations of Alzheimer' s disease (AD).

OBJECTIVE

To examine the prevalence and significance of NPS in very mild and mild AD patients with emphasis on their influence on the well-being of the patients and their caregivers.

METHODS

The participants were 240 patient-caregiver dyads who participated in a prospective, controlled rehabilitation study (ALSOVA). Three Quality of Life (QoL) instruments were used; generic 15D, disease-specific QoL-AD and Visual Analog Scale (VAS). The disease-specific QoL-AD was both self-rated and caregiver rated. Other scales used were Mini-Mental State Examination (MMSE), Clinical Dementia Rating (CDR), ADCS-ADL, Neuropsychiatric Inventory (NPI) and Beck Depression Inventory (BDI).

RESULTS

NPS were present in 76.5% of patients with very mild AD (CDR 0.5) and in 84.9% of patients with mild to moderate AD (CDR 1). The most frequent symptoms were apathy, depression, irritability, and agitation. The strongest predictor of self-reported QoL-AD scores was depressive symptoms whereas functional decline and presence of NPS predicted poor caregiver ratings of patients' QoL. However, caregiver depression also influenced significantly their ratings.

CONCLUSION

NPS are common even in the early stages of AD. NPS were significantly associated with caregiver assessment of the patient's QoL but not with patients' self-assessed QoL. Depression decreases QoL, but may remain unrecognized in AD patients, emphasizing the need for careful and structured assessment of NPS before deciding on the appropriate treatment.

Amyloid and tau proteins in cortical brain biopsy and Alzheimer's disease

OBJECTIVE

Amyloid-β(Aβ) aggregates are presumed to be found in the brain at an early stage of Alzheimer's disease (AD) but have seldom been assessed by brain biopsy during life in often elderly patients.

METHODS

Between 1991 and 2006 we evaluated 468 patients with suspected normal pressure hydrocephalus with intraventricular pressure monitoring and a right frontal cortical biopsy sample immunostained for Aβ and hyperphosphorylated tau (HPτ). Adequate samples and the clinical follow-up data until death or the end of 2008, available in 433 cases, were reviewed for the clinical signs of dementia, including AD. Logistic regression analysis was used to analyze whether Aβ and/or HPτ in the biopsy samples obtained during life predicted development of cognitive impairment, in particular, AD.

RESULTS

Of the 433 frontal cortical samples, 42 (10%) displayed both Aβ and HPτ, 144 (33%) Aβ only, and 247 (57%) neither Aβ nor HPτ. In a median follow-up time of 4.4 years, 94 patients (22%) developed clinical AD. The presence of both Aβ and HPτ was strongly associated (odds ratio [OR], 68.2; 95% confidence interval [CI], 22.1-210) and Aβ alone significantly associated (OR, 10.8; 95% CI, 4.9-23.8) with the clinical diagnosis of AD.

INTERPRETATION

This is the largest follow-up study of patients assessed for the presence of Aβ and HPτ in frontal cortical brain biopsy samples. 1) The presence of Aβ and HPτ spoke strongly for the presence or later development of clinical AD; 2) Aβ alone was suggestive of AD; and 3) the absence of Aβ and HPτ spoke against a later clinical diagnosis of AD.

Plasma Abeta42 and Abeta40 as markers of cognitive change in follow-up: a prospective, longitudinal, population-based cohort study

BACKGROUND

Single measurements of plasma Aβ are not useful in the diagnostics of Alzheimer's disease (AD). However, changes in plasma Aβ levels during repeated testing may be helpful in the prediction and evaluation of progression of the incipient AD or mild cognitive impairment.

OBJECTIVE

To examine the relation of baseline and serial plasma Aβ levels to cognitive change in follow-up.

METHODS

269 subjects (52 cognitively impaired and 217 controls) from a population-based cohort were clinically followed up from 3 to 6 years. Serial plasma samples were available from 70 subjects who were followed up for 3 years and 43 subjects followed for 6 years. The plasma Aβ levels were measured using ELISA.

RESULTS

Subjects who declined cognitively during the follow-up had lower levels of plasma Aβ42 at the baseline. Plasma Aβ42 and the Aβ42/Aβ40 ratio decreased (-2.4 pg/ml for Aβ42 in 6 years) in those who declined in follow-up, whereas Aβ42 and the Aβ42/Aβ40 ratio increased in the subjects who remained cognitively stable or improved in follow-up. Subjects using acetylsalicylic acid, dipyridamole, antidiabetic or anticoagulant drugs as well as subjects with coronary heart disease had higher levels of Aβ40.

CONCLUSIONS

Low or decreasing plasma Aβ42 during the follow-up is associated with cognitive decline. Serial measurement of plasma Aβ42 may be useful in the detection of the subjects who are at risk for cognitive decline.

[Early detection of cognitive changes in memory diseases: new cut-off scores for the Finnish version of CERAD neuropsychological battery]

The evaluation of cognitive functions by using CERAD (Consortium to Establish a Registry for Alzheimer's Disease) is recommended as a tool in basic health care for screening of memory diseases. The reliability of this method, adopted in Finland in 1999, has been impaired by the fact that there have been no comprehensive Finnish norms to serve as the basis for the cut-off limits of the test tasks. This article presents the new, revised cut-off values for the CERAD procedure, based on the comparison of Finnish population-based normative data with those of persons having very mild or mild Alzheimer's disease.

[Update on current care guidelines. The diagnosis and medical treatment of memory disorders]

Any complaints from a patient about their memory should be examined. Diagnosis is based on international criteria. The basic evaluation consists of the medical history, clinical evaluation, cognitive tests and brain imaging, especially using MRI. When a diagnosis of Alzheimer's disease, AD with cerebrovascular disease or with Lewy Body disease, or Dementia associated with Parkinson's disease or LBD is made, evidence based medical therapy is indicated as part of comprehensive care. An acetylcholinesterase inhibitor or memantine can be used. These drugs are ineffective in the case of frontotemporal degenerations. For severe behavioural disorders, other psychoactive medications can be applied.

[Update on current care guidelines: diagnostics, treatment and rehabilitation of multiple sclerosis]

Treatment is initiated when the McDonald criteria for relapsing-remitting multiple sclerosis (RRMS) are fulfilled. High-risk patients with clinically isolated syndrome are followed using magnetic resonance imaging for one year after the first imaging. Interferon-beta or glatiramer acetate are the first-line immunomodulating drugs (IMD) for RRMS. MxA protein is measured 12 and 24 months after initiation of Interferon-beta to evaluate possible development of neutralizing antibodies. If MxA protein may not be detected repeatedly interferon-beta treatment is discontinued. If the disease is active in spite of treatment with first-line IMD, natalizumab may be considered as a second-line therapy. IMD is stopped when the transition to secondary progressive phase has occurred (or upon transition to secondary progressive phase).

An update on clinical proteomics in Alzheimer's research

Alzheimer's disease (AD) is a pathologically complex and aetiologically multifactorial dementing disorder affecting millions of people worldwide. The pathological brain changes are assumed to occur decades prior to the onset of clinical symptoms. The diagnosis of early AD remains problematic and is mainly based on clinical and neuropsychological findings after the onset of symptoms. Currently available drugs are able to delay the symptom progression of the disease but not to attenuate the progression of pathological brain changes. Many studies exploring AD proteomes have been conducted as the middle of 1990s as a consequence of recent advances in the development of both gel-based and gel-free proteomics approaches. It is hoped that proteomics can contribute to improving the understanding, diagnosis, and follow-up of the progression of AD. In this review, we summarise the present status of proteome alterations, with emphasis on quantitative approaches, in AD brain, CSF and blood, and their relevance to dementia research.

Combined risk effects of IDE and NEP gene variants on Alzheimer disease

Polymorphisms in genes encoding amyloid beta-peptide (A beta)-degrading enzymes neprilysin (NEP) and insulin-degrading enzyme (IDE) individually affect the susceptibility to Alzheimer disease (AD) among the Finnish population. Here we show that a combination of risk genotypes for NEP and IDE genes leads to a higher susceptibility to AD. Individuals with the combination of risk genotypes for NEP and IDE conferred a threefold higher susceptibility to AD when compared with individuals not carrying these genotypes. Although no significant interaction was observed between NEP and IDE genes, these data suggest that NEP and IDE exhibit an additive risk effect in AD.

Neurofilament ELISA validation

BACKGROUND

Neurofilament proteins (Nf) are highly specific biomarkers for neuronal death and axonal degeneration. As these markers become more widely used, an inter-laboratory validation study is required to identify assay criteria for high quality performance.

METHODS

The UmanDiagnostics NF-light (R)enzyme-linked immunoabsorbent assays (ELISA) for the neurofilament light chain (NfL, 68kDa) was used to test the intra-assay and inter-laboratory coefficient of variation (CV) between 35 laboratories worldwide on 15 cerebrospinal fluid (CSF) samples. Critical factors, such as sample transport and storage, analytical delays, reaction temperature and time, the laboratories' accuracy and preparation of standards were documented and used for the statistical analyses.

RESULTS

The intra-laboratory CV averaged 3.3% and the inter-laboratory CV 59%. The results from the test laboratories correlated with those from the reference laboratory (R=0.60, p<0.0001). Correcting for critical factors improved the strength of the correlation. Differences in the accuracy of standard preparation were identified as the most critical factor. Correcting for the error introduced by variation in the protein standards improved the correlation to R=0.98, p<0.0001 with an averaged inter-laboratory CV of 14%. The corrected overall inter-rater agreement was subtantial (0.6) according to Fleiss' multi-rater kappa and Gwet's AC1 statistics.

CONCLUSION

This multi-center validation study identified the lack of preparation of accurate and consistent protein standards as the main reason for a poor inter-laboratory CV. This issue is also relevant to other protein biomarkers based on this type of assay and will need to be solved in order to achieve an acceptable level of analytical accuracy. The raw data of this study is available online.

CSF biomarkers and incipient Alzheimer disease in patients with mild cognitive impairment

CONTEXT

Small single-center studies have shown that cerebrospinal fluid (CSF) biomarkers may be useful to identify incipient Alzheimer disease (AD) in patients with mild cognitive impairment (MCI), but large-scale multicenter studies have not been conducted.

OBJECTIVE

To determine the diagnostic accuracy of CSF beta-amyloid(1-42) (Abeta42), total tau protein (T-tau), and tau phosphorylated at position threonine 181 (P-tau) for predicting incipient AD in patients with MCI.

DESIGN, SETTING, AND PARTICIPANTS

The study had 2 parts: a cross-sectional study involving patients with AD and controls to identify cut points, followed by a prospective cohort study involving patients with MCI, conducted 1990-2007. A total of 750 individuals with MCI, 529 with AD, and 304 controls were recruited by 12 centers in Europe and the United States. Individuals with MCI were followed up for at least 2 years or until symptoms had progressed to clinical dementia.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive and negative likelihood ratios (LRs) of CSF Abeta42, T-tau, and P-tau for identifying incipient AD.

RESULTS

During follow-up, 271 participants with MCI were diagnosed with AD and 59 with other dementias. The Abeta42 assay in particular had considerable intersite variability. Patients who developed AD had lower median Abeta42 (356; range, 96-1075 ng/L) and higher P-tau (81; range, 15-183 ng/L) and T-tau (582; range, 83-2174 ng/L) levels than MCI patients who did not develop AD during follow-up (579; range, 121-1420 ng/L for Abeta42; 53; range, 15-163 ng/L for P-tau; and 294; range, 31-2483 ng/L for T-tau, P < .001). The area under the receiver operating characteristic curve was 0.78 (95% confidence interval [CI], 0.75-0.82) for Abeta42, 0.76 (95% CI, 0.72-0.80) for P-tau, and 0.79 (95% CI, 0.76-0.83) for T-tau. Cut-offs with sensitivity set to 85% were defined in the AD and control groups and tested in the MCI group, where the combination of Abeta42/P-tau ratio and T-tau identified incipient AD with a sensitivity of 83% (95% CI, 78%-88%), specificity 72% (95% CI, 68%-76%), positive LR, 3.0 (95% CI, 2.5-3.4), and negative LR, 0.24 (95% CI, 0.21-0.28). The positive predictive value was 62% and the negative predictive value was 88%.

CONCLUSIONS

This multicenter study found that CSF Abeta42, T-tau, and P-tau identify incipient AD with good accuracy, but less accurately than reported from single-center studies. Intersite assay variability highlights a need for standardization of analytical techniques and clinical procedures.

Tenomodulin variants, APOE and Alzheimer's disease in a Finnish case-control cohort

The tenomodulin gene (TNMD, locus Xq-22) encodes an angiogenesis inhibitor. It is an interesting candidate gene for Alzheimer's disease (AD), since it is expressed in brain, alterations in angiogenesis have been linked to AD and in our previous studies we have observed associations between TNMD and phenotypes, which are related to increased risk of AD. The common sequence variation in the TNMD was not associated with prevalence of AD among 526 cases and 672 controls. However, a significant interaction (p=0.002) between rs5966709 and the APOE ε4-allele status was observed in women. Among the ε4-allele carriers, the women with rs5966709-TT genotype had smaller risk for having AD than those with other genotypes (odds ratio 0.47, p=0.019, false discovery rate 10.4%). According to these results the sequence variation of TNMD is not associated with AD, but might modify the effect of APOE ε4-allele in women.

Cerebrospinal fluid tau as a marker of neuronal damage after epileptic seizure

PURPOSE

Whether repeated brief seizures can cause neuronal damage is controversial. Cerebrospinal fluid (CSF) total tau (T-tau) and phosphorylated tau (P-tau) measurements have been suggested for the diagnosis of Alzheimer's disease, and T-tau may also be a marker of axonal damage and neuronal degeneration. We studied T-tau and P-tau levels and P-tau/T-tau ratio in CSF after epileptic seizures in order to determine whether they are increased after seizures.

METHODS

A total of 54 patients with tonic-clonic or partial secondarily generalized seizures due to various etiologies were studied and CSF obtained within 48h after the seizure.

RESULTS

There were no statistical differences in the levels of T-tau (p=0.09, ANOVA) or P-tau (p=0.60) between different etiologic groups or controls. No patients with epilepsy of unknown origin had abnormal CSF T-tau whereas 11 patients with acute or remote symptomatic seizures had abnormal T-tau levels and the P-tau/T-tau ratio showed significant differences between the groups and controls (p=0.003).

CONCLUSIONS

Epileptic seizures with unknown etiology did not increase CSF tau levels. Abnormal tau levels were associated with either acute or remote symptomatic seizures with known etiology. The presence of elevated CSF tau increases the probability of symptomatic cause in a patient with a seizure.

Cerebrospinal fluid {beta}-amyloid 42 and tau proteins as biomarkers of Alzheimer-type pathologic changes in the brain

BACKGROUND

There is a clear need to develop an objective diagnostic test for Alzheimer disease (AD). Changes in the levels of cerebrospinal fluid (CSF) tau protein and beta-amyloid 42 (Abeta42) peptide in patients with AD have been well documented, but the relationship between these biomarkers and neuropathologic changes in the brain is not established.

OBJECTIVE

To study the relationship between antemortem CSF biomarker levels and Alzheimer-type neuropathologic changes in the brain.

DESIGN

Cross-sectional study to correlate levels of CSF Abeta42, total tau, and phosphorylated tau protein with neuropathologic changes in the brain.

SETTING

Academic research. Patients The study included 123 patients (79 with clinically diagnosed AD, 29 with other dementia, and 15 with other neurologic disease). All underwent clinical evaluation and provided antemortem lumbar CSF samples, and neuropathologic data were collected from September 11, 1990, to March 13, 2003, in the Department of Neuroscience and Neurology, University of Kuopio, Kuopio, Finland.

MAIN OUTCOME MEASURES

Levels of CSF Abeta42, total tau, and phosphorylated tau protein were measured using standard commercial immunoassays. Neuropathologic evaluations included the classic silver impregnation method and immunohistochemistry for Abeta, hyperphosphorylated tau, and alpha-synuclein.

RESULTS

Cerebrospinal fluid Abeta42 and tau protein levels were related to amyloid load and the presence of neurofibrillary pathologic abnormalities in the brain. Cerebrospinal fluid Abeta42 level correlated inversely with total Abeta load in the brain, and CSF tau level correlated with results of immunohistochemistry for hyperphosphorylated tau and with the presence of neocortical neurofibrillary tangles. In multivariate logistic regression analysis, the number of neuritic plaques in the brain remained a significant predictor of decreased CSF Abeta42 level and of increased CSF tau level. Based on the ratio of phosphorylated tau level to Abeta42 level, sensitivity was 91.6%, and specificity was 85.7%, with an overall accuracy of 90.2% for the presence of pathologic neuritic plaque in the brain.

CONCLUSIONS

Cerebrospinal fluid Abeta42 and tau proteins are biomarkers of AD-associated pathologic changes in the brain. The combination of abnormally low CSF Abeta42 level and abnormally high CSF tau level predicted the presence of AD pathologic features with high accuracy. This combination assay may be helpful in diagnosing the presence of AD pathologic changes in the brain.

A follow-up study of chromosome 19q13 in multiple sclerosis susceptibility

A possible role of allelic variation on chromosome 19q13 in multiple sclerosis (MS) susceptibility has been suggested. We tested association of sixteen 19q13 markers with MS in 459 families. Nominally significant associations were tested in an independent set of 323 families as well as in the pooled set of 782 families. We were not able to confirm previously suggested associations with APOE, GIPR, ZNF45, ILT6 and D19S585. In the screening dataset nominally significant associations were found with D19S867 and with APOE haplotype (p=0.007 in both), but these were not replicated in the independent dataset nor in the pooled analysis of 757 families. Thus, we were not able to detect any statistically significant allelic associations. Re-sequencing based approaches may be required for elucidating the role chromosome 19q13 with MS.

Use of a genetic isolate to identify rare disease variants: C7 on 5p associated with MS

Large case-control genome-wide association studies primarily expose common variants contributing to disease pathogenesis with modest effects. Thus, alternative strategies are needed to tackle rare, possibly more penetrant alleles. One strategy is to use special populations with a founder effect and isolation, resulting in allelic enrichment. For multiple sclerosis such a unique setting is reported in Southern Ostrobothnia in Finland, where the prevalence and familial occurrence of multiple sclerosis (MS) are exceptionally high. Here, we have studied one of the best replicated MS loci, 5p, and monitored for haplotypes shared among 72 regional MS cases, the majority of which are genealogically distantly related. The haplotype analysis over the 45 Mb region, covering the linkage peak identified in Finnish MS families, revealed only modest association at IL7R (P = 0.04), recently implicated in MS, whereas most significant association was found with one haplotype covering the C7-FLJ40243 locus (P = 0.0001), 5.1 Mb centromeric of IL7R. The finding was validated in an independent sample from the isolate and resulted in an odds ratio of 2.73 (P = 0.000003) in the combined data set. The identified relatively rare risk haplotype contains C7 (complement component 7), an important player of the innate immune system. Suggestive association with alleles of the region was seen also in more heterogeneous populations. Interestingly, also the complement activity correlated with the identified risk haplotype. These results suggest that the MS predisposing locus on 5p is more complex than assumed and exemplify power of population isolates in the identification of rare disease alleles.

PET amyloid ligand [11C]PIB uptake and cerebrospinal fluid beta-amyloid in mild cognitive impairment

BACKGROUND

In mild cognitive impairment (MCI), Alzheimer's disease (AD)-type cerebrospinal fluid (CSF) biomarker profiles predict rapid progression and conversion to AD. An increased brain amyloid burden in AD and MCI has been demonstrated with PET using [(11)C]PIB (Pittsburgh compound B). Little is known about the relationship between these biomarkers in MCI.

METHODS

We studied 15 patients with amnestic MCI and 22 controls with PET using [(11)C]PIB. In MCI patients, CSF levels of Abeta42, pTAU, totalTAU and the Abeta42/pTAU ratio were measured.

RESULTS

In MCI patients, CSF Abeta42 was abnormal in 53% of patients, totalTAU in 67%, pTAU in 64% and the Abeta42/pTAU ratio in 64%. A composite neocortical [(11)C]PIB uptake score was increased in 87% of the MCI patients. Only 54% of [(11)C]PIB-positive subjects showed AD-type Abeta42 values. During a 2-year follow-up, 6 MCI patients converted to AD, all of them had increased neocortical PIB scores at the MCI stage. Abnormal CSF Abeta42 was found in 3 patients, pTAU in 3 patients and Abeta42/pTAU ratio in 4 patients.

CONCLUSION

Follow-up studies are needed to confirm whether [(11)C]PIB uptake might be more sensitive than CSF Abeta42 concentration in detecting increased amyloid burden in MCI, as suggested by the results of this study.

[Use of CSF biomarkers in the diagnostics of memory diseases]

Alzheimer's disease is the most common cause of dementia. Early diagnosis of diseases leading to dementia is cost-effective. However, early diagnosis of Alzheimer's disease may be difficult and should not be based on exclusion of other reasons for dementia. A decreased CSF amyloid beta-peptide-42 level together with elevated tau or phosphorylated tau levels can differentiate patients with AD from control subjects or patients with other neurologic conditions with relatively high accuracy. We evaluated the use of these biomarkers in 452 patient cohort during 2005-2007 in clinical practice. Cerebrospinal fluid biomarkers seem to be useful especially to confirm Alzheimer's disease diagnosis.

Cerebrospinal fluid, serum and plasma protein oxidation in Alzheimer's disease

OBJECTIVES

Many studies have shown differences in carbonylation and nitration of individual proteins in brain and body fluids of Alzheimer's disease (AD) patients. Therefore, we wanted to examine whether total levels of these oxidative stress markers of proteins were altered in AD.

PATIENTS AND METHODS

Total levels of carbonyls and nitrotyrosine in cerebrospinal fluid, serum and plasma were measured in 22 AD patients and 18 age-matched controls using commercially available enzyme immunoassay kits.

RESULTS

Protein carbonylation in cerebrospinal fluid did not differ between AD patients and controls but was decreased in APOE epsilon4 carriers as compared with non-carriers. Serum but not plasma levels of carbonyls tended to be decreased in AD patients as compared with aged controls. Nitrotyrosine concentrations did not differ between the groups. Surrogate cerebrospinal fluid markers for AD, beta-amyloid (1-42) and tau, correlated with blood carbonyl and nitrotyrosine levels.

CONCLUSIONS

According to these preliminary data, changes in oxidative metabolism related to the pathogenesis of AD cannot be detected as increased cerebrospinal fluid, serum or plasma protein carbonylation or nitration.

No evidence for shared etiology in two demyelinative disorders, MS and PLOSL

Loss-of-function mutations of DAP12 and TREM2 cause a recessively inherited disease PLOSL, manifesting in brain white matter. The genes of the DAP12-TREM2 signaling receptor are located on 19q13.12 and 6p21.1, to which linkage has been observed also in families affected by another immune-mediated demyelinating disease, MS. We have tested if allelic variation in DAP12 or TREM2 predisposes also to MS by monitoring carrier frequency of the Finnish PLOSL mutation in Finnish MS cases and by studying DAP12 and TREM2 in MS by linkage and association. To conclude, the DAP12-TREM2 complex unlikely has a role in genetic susceptibility of MS.

Assessment of beta-amyloid in a frontal cortical brain biopsy specimen and by positron emission tomography with carbon 11-labeled Pittsburgh Compound B

OBJECTIVE

To compare carbon 11-labeled Pittsburgh Compound B ([11C]PiB) positron emission tomography (PET) findings in patients with and without Alzheimer disease lesions in frontal cortical biopsy specimens.

DESIGN

Cross-sectional study of [11C]PiB PET findings in patients with or without beta-amyloid (Abeta) aggregates in frontal cortical biopsy specimens.

SETTING

Two university hospitals in Finland. Patients Ten patients who had undergone intraventricular pressure monitoring with a frontal cortical biopsy (evaluated for Abeta aggregates and hyperphosphorylated tau) for suspected normal-pressure hydrocephalus.

INTERVENTIONS

[11C]PiB PET and evaluation for cognitive impairment using a battery of neuropsychological tests.

MAIN OUTCOME MEASURES

Immunohistochemical evaluation for Abeta aggregates and hyperphosphorylated tau in the frontal cortical biopsy specimen and [11C]PiB PET.

RESULTS

In patients with Abeta aggregates in the frontal cortical biopsy specimen, PET imaging revealed higher [11C]PiB uptake (P < .05) in the frontal, parietal, and lateral temporal cortices and in the striatum as compared with the patients without frontal Abeta deposits.

CONCLUSIONS

Our study supports the use of noninvasive [11C]PiB PET in the assessment of Abeta deposition in the brain. Large prospective studies are required to verify whether [11C]PiB PET will be a diagnostic aid, particularly in early Alzheimer disease.

Applicability of current staging/categorization of alpha-synuclein pathology and their clinical relevance

In Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) α-synuclein (αS) pathology is seen that displays a predictable topographic distribution. There are two staging/categorization systems, i.e. Braak’s and McKeith’s, currently in use for the assessment of αS pathology. The aim of these diagnostic strategies in pathology is, in addition to assess the stage/severity of pathology, to assess the probabilities of the related clinical symptomatology i.e. dementia and extrapyramidal symptoms (EPS). Herein, we assessed the applicability of these two staging/categorization systems and the frequency of dementia and EPS in a cohort of 226 αS-positive-subjects. These subject were selected from a large autopsy sample (n = 1,720), irrespective of the clinical presentation, based on the detection of αS-immunoreactivity (IR) in one of the most vulnerable nuclei; in the dorsal motor nucleus of vagus, substantia nigra and basal forebrain. The frequency of αS-IR lesions in this large cohort was 14% (248 out of 1,720). If applicable, each of the 226 subjects with all required material available was assigned a neuropathological stage/category of PD/DLB and finally the neuropathological data was analyzed in relation to dementia and EPS. 83% of subjects showed a distribution pattern of αS-IR that was compatible with the current staging/categorization systems. Around 55% of subjects with widespread αS pathology (Braak’s PD stages 5–6) lacked clinical signs of dementia or EPS. Similarly, in respect to those subjects that fulfilled the McKeith criteria for diffuse neocortical category and displaying only mild concomitant Alzheimer’s disease-related pathology, only 48% were demented and 54% displayed EPS. It is noteworthy that some subjects (17%) deviated from the suggested caudo-rostral propagation suggesting alternative routes of progression, perhaps due to concomitant diseases and genetic predisposition. In conclusion, our results do indeed confirm that current staging/categorization systems can readily be applied to most of the subjects with αS pathology. However, finding that around half of the subjects with abundant αS pathology remain neurologically intact is intriguing and raises the question whether we do assess the actual disease process.

Vascular risk factors and dementia in the general population aged >85 years: prospective population-based study

The aim of this study was to evaluate the association between dementia and common vascular risk factors including blood pressure, blood lipids, homocysteine and diabetes mellitus in a population of very old people. This study is a 9-year follow-up prospective population-based study monitoring 339 non-demented subjects aged 85 years or over in the city of Vantaa, Southern Finland. During the follow-up, those individuals with diabetes mellitus at the baseline and new incident stroke had a higher probability for developing dementia. History of hypertension or higher level of education were associated with a lower probability of dementia. It seems that the contribution of vascular risk factors to the risk of dementia may be age-dependent and their role in the very old subjects may be mediated through their influence on cerebrovascular morbidity. Thus, prevention of stroke and diabetes mellitus may reduce the risk of cognitive decline in the very old.

Interferon regulatory factor 5 (IRF5) gene variants are associated with multiple sclerosis in three distinct populations

Background:

IRF5 is a transcription factor involved both in the type I interferon and the toll-like receptor signalling pathways. Previously, IRF5 has been found to be associated with systemic lupus erythematosus, rheumatoid arthritis and inflammatory bowel diseases. Here we investigated whether polymorphisms in the IRF5 gene would be associated with yet another disease with features of autoimmunity, multiple sclerosis (MS).

Methods:

We genotyped nine single nucleotide polymorphisms and one insertion-deletion polymorphism in the IRF5 gene in a collection of 2337 patients with MS and 2813 controls from three populations: two case–control cohorts from Spain and Sweden, and a set of MS trio families from Finland.

Results:

Two single nucleotide polymorphism (SNPs) (rs4728142, rs3807306), and a 5 bp insertion-deletion polymorphism located in the promoter and first intron of the IRF5 gene, showed association signals with values of p<0.001 when the data from all cohorts were combined. The predisposing alleles were present on the same common haplotype in all populations. Using electrophoretic mobility shift assays we observed allele specific differences in protein binding for the SNP rs4728142 and the 5 bp indel, and by a proximity ligation assay we demonstrated increased binding of the transcription factor SP1 to the risk allele of the 5 bp indel.

Conclusion:

These findings add IRF5 to the short list of genes shown to be associated with MS in more than one population. Our study adds to the evidence that there might be genes or pathways that are common in multiple autoimmune diseases, and that the type I interferon system is likely to be involved in the development of these diseases.

The association study between DHCR24 polymorphisms and Alzheimer's disease

DHCR24 gene in chromosome 1 encodes seladin 1, a cholesterol synthesizing enzyme. Seladin 1 protects neurons from Abeta(42) mediated toxicity and participates in regulation of Abeta(42) formation by organizing the placement of APP cleaving beta-secretase in cholesterol-rich detergent-resistant membrane domains (DRMs). In Alzheimer's disease (AD) the level of seladin 1 in affected neurons is reduced, DRMs are disorganized and Abeta(42) formation is increased. To examine genetic association of the DHCR24 with AD, we genotyped four single nucleotide polymorphism (SNP) sites (rs638944, rs600491, rs718265, and rs7374) in 414 Finnish AD cases and 459 controls and calculated the allelic and genotypic distribution of both cases and controls. The single locus association analysis indicated that men carrying the T allele of rs600491 had an increased risk of AD (OR 1.7 95% CI 1.2-2.4; P = 0.004, Bonferroni corrected P = 0.048 with 12 tests). We estimated haplotypes of SNPs rs638944 and rs600491 between cases and controls and found overall distribution of haplotypes highly significant (P < 0.001). There was a common protective haplotype TC with frequency of 0.22 in cases and 0.30 in controls (P < 0.001) and a risk haplotype GC with frequency of 0.10 in cases and 0.05 in controls (P < 0.001). We also measured CSF Abeta(42), tau and phosphorylated tau (ptau) levels in a subgroup of AD cases (n = 44) and controls (n = 10) and found that AD cases that carry rs718265 GG had lower levels of Abeta(42) than other genotype carriers. Our findings indicate that DHCR24 gene may be associated with AD risk.

Expression of interleukin-18 is increased in the brains of Alzheimer's disease patients

The inflammatory cytokines can initiate nerve cell degeneration and enhance the plaque production typically found in Alzheimer's disease (AD). Interleukin-18 (IL-18) is an inflammatory cytokine, which can induce the expression of interferon-gamma. This interleukin shares similarities with the IL-1 family of proteins. Like IL-1 beta, IL-18 is cleaved by caspase-1 (ICE) to an active secreted form. We examined the expressions of IL-18, -1 beta and ICE in different brain regions from AD patients that were categorized with respect to the Braak stage, and age-matched with non-demented controls. The levels of total-RNA and protein of IL-18 and ICE were increased, especially in the frontal lobe of AD patients and this change was not modified by ApoE genotype. Immunohistochemistry of AD brain samples detected IL-18 in microglia, astrocytes, and surprisingly in neurons, and it is also co-localized not only with amyloid-beta plaques but also with tau. In CSF, elevated IL-18 level was detected only in men and it also correlated with CSF tau in MCI. IL-18 may thus be a potential biomarker for men. Plasma levels of IL-18 showed no correlation with the disease. In conclusion, amyloid-beta may induce the synthesis of IL-18, and IL-18 kinases involved in tau phosphorylation as a part of the amyloid-associated inflammatory reaction.

Atrial Fibrillation, Stroke, and Cognition

Background and Purpose— The aim of this study was to investigate the association between atrial fibrillation (AF), stroke, dementia, and their correlation with brain pathology in subjects aged 85 years or older.

Methods— This is a prospective 9-year follow-up population based study in Vantaa, a town in Southern Finland; 553 subjects (92% of the total population) aged 85 years or older were clinically examined by a neurologist. The presence of AF was collected from the medical records or examined by ECG or ambulatory ECG. Neuropathological examination was conducted in more than half of the clinically examined subjects.

Results— AF was significantly associated with stroke at baseline; 32% of patients with AF had clinical evidence of stroke compared with 16.7% of those without such evidence ( P <0.001). Dementia at baseline was significantly associated with age, clinical stroke, and the presence of apolipoprotein E ε4 allele, but not with sex, education, or vascular risk factors. Multiple regression analysis including neuropathological results showed that dementia was significantly associated with education (OR, 0.89; 95% CI, 0.80 to 0.98; P =0.019), the β-amyloid load in the brain (OR, 1.26; 95% CI, 1.13 to 1.39; P <0.001) and with the vascular pathology (OR, 2.03; 95% CI, 1.14 to 3.62; P =0.016), but not with sex, age at death, apolipoprotein E ε4 allele, or vascular risk factors.

Conclusions— AF is a significant and preventable risk factor for stroke but not for dementia in the very old. The etiology of dementia syndrome in the very old is multifactorial. Both Alzheimer disease pathology and vascular pathology, particularly multiple small infarcts, contribute to cognitive decline.

Multiplexed proteomic analysis of oxidation and concentrations of cerebrospinal fluid proteins in Alzheimer disease

BACKGROUND

Carbonylation is an irreversible oxidative modification of proteins that has been linked to various conditions of oxidative stress, aging, physiological disorders, and disease. Increased oxidative stress is thus also considered to play a role in the pathogenesis of age-related neurodegenerative disorders such as Alzheimer disease (AD). In addition, it has recently become evident that the response mechanisms to increased oxidative stress may depend on sex. Several oxidized carbonylated proteins have been identified in plasma and brain of AD patients by use of 2-dimensional oxyblotting.

METHODS

In this pilot study, we estimated the concentrations and carbonylation of the most abundant cerebrospinal fluid proteins in aging women and men, both AD patients suffering from mild dementia and individuals exhibiting no cognitive decline. Oxidized carbonylated proteins were analyzed with 2-dimensional multiplexed oxyblotting, mass spectrometry, and database searches.

RESULTS

Signals for beta-trace, lambda chain, and transthyretins were decreased in probable AD patients compared with controls. The only identified protein exhibiting an increased degree of carbonylation in AD patients was lambda chain. The concentrations of proteins did not generally differ between men and women; however, vitamin D-binding protein, apolipoprotein A-I, and alpha-1-antitrypsin exhibited higher extents of carbonylation in men.

CONCLUSIONS

None of the brain-specific proteins exhibited carbonylation changes in probable AD patients compared with age-matched neurological controls showing no cognitive decline. The carbonylation status of proteins differed between women and men. Two-dimensional multiplexed oxyblotting is applicable to study both the concentrations and carbonylation of cerebrospinal fluid proteins.

Genetic study evaluating LDLR polymorphisms and Alzheimer's disease

We genotyped SNPs rs11668477, rs12983082, rs11669576, rs2738444, rs5925 and rs1433099 in 405 Finnish AD cases and 463 controls and conducted a single allele and genotypic distribution comparison and estimated the haplotype frequencies between cases and controls and evaluated the level of biomarkers in haplotype carriers. We observed that T allele of rs2738444 was overrepresented in AD women with p=0.014 (Bonferroni corrected p=0.252). A specific haplotype block consisting of SNPs rs11669576, rs2738444 and rs5925 was identified and in women the haplotype GTT was overrepresented in AD cases when compared to controls with p=0.008. We measured CSF Abeta(42), tau and phosphorylated tau (ptau) levels in a subgroup of cases and controls and found that some genotypes were associated with increased levels of tau and ptau or a decreased Abeta(42) level in women. The specific risk haplotype GTT was associated with an increased level of tau and ptau in both men and women. Our findings suggest that LDLR gene may be associated with AD risk and its CSF biomarkers, especially in women.

CSF phosphorylated tau protein correlates with neocortical neurofibrillary pathology in Alzheimer's disease

Hyperphosphorylated tau protein (P-tau) in CSF is a core biomarker candidate of Alzheimer's disease. Hyperphosphorylation of tau is thought to lead to neurofibrillary changes, a neuropathological hallmark of this type of dementia. Currently, the question is unresolved whether CSF levels of P-tau reflect neurofibrillary changes within the brain of a patient with the illness. Twenty-six patients were included with intra-vitam CSF as well as post-mortem neuropathological data. In the CSF, P-tau phosphorylated at threonine 231 (P-tau231P) was analysed. Post-mortem, scores of neurofibrillary tangles (NFT) and neuritic plaques (NP) were assessed in frontal, temporal, parietal and hippocampal cortical areas. In the same cortical regions, load of hyperphosphorylated tau protein (HP-tau load) was determined. Concentrations of P-tau231P were measured in frontal cortex homogenates. We found significant correlations between CSF P-tau231P concentrations and scores of NFTs and HP-tau load in all neocortical regions studied. The score of NPs was correlated with CSF P-tau231P only within the frontal cortex. There was a correlation between P-tau231P in CSF and brain homogenates. These findings indicate that CSF P-tau231P may serve as an in vivo surrogate biomarker of neurofibrillary pathology in Alzheimer's disease.

Association Between Blood Pressure and Survival over 9 Years in a General Population Aged 85 and Older

OBJECTIVES

To investigate the association between blood pressure and mortality in people aged 85 and older.

DESIGN

Population-based prospective study with 9-year follow-up.

SETTING

Department of Neuroscience and Neurology and Department of Public Health and General Practice, University of Kuopio, and Department of Clinical Neurosciences, Helsinki University Hospital.

PARTICIPANTS

Of all 601 people living in the city of Vantaa born before April 1, 1906, whether living at home or in institutions and alive on April 1, 1991, 521 were clinically examined and underwent blood pressure measurement.

MEASUREMENTS

Blood pressure was measured using a standardized method in the right arm of the subject after resting for at least 5 minutes. Information on medical history for each participant was verified from a computerized database containing all primary care health records. Death certificates were obtained from the National Register; the collection of death certificates was complete.

RESULTS

After adjusting for age, sex, functional status, and coexisting diseases (earlier-diagnosed myocardial infarction, congestive heart failure, dementia, cancer, stroke, or hypertension), low systolic blood pressure (BP) was associated with risk of death.

CONCLUSION

Low systolic BP may be partially related to poor general health and poor vitality, but the very old may represent a select group of individuals, and the use of BP-lowering medications needs to be evaluated in this group.

Problems associated with biological markers of Alzheimer's disease

The etiopathogenesis of Alzheimer's disease (AD) is still unclear, although clinical diagnostic criteria exist and the neuropathology of AD has been studied in great detail during the last 20 years. The present study addresses certain problems in the search for biological markers for the diagnosis, as well as in the follow-up of the course of AD and its differential diagnosis and reports some of our own observations in comparison with other studies. These include protein, genetic and neuroimaging markers. The definitions of biological markers and search strategies are also discussed.

CSF Abeta42 and tau or phosphorylated tau and prediction of progressive mild cognitive impairment

Baseline CSF amyloid beta-peptide-42 (Abeta42), tau, and phosphorylated tau (P-tau) levels from 46 control subjects and 78 patients with mild cognitive impairment (MCI) were measured. Twenty-three patients with MCI developed dementia during the study. Abnormal biomarkers were found early in the course of Alzheimer disease (AD). The most predictive assay for AD among the patients with MCI was the combination of Abeta42 and P-tau.