Interleukin-6 and alpha-2-macroglobulin indicate an acute-phase state in Alzheimer's disease cortices

Increased activity of Th-17 and Th-9 lymphocytes and a skewing of the post-thymic differentiation pathway are seen in Alzheimer's disease

Inflammatory mediators are responsible for the neuroinflammation observed in Alzheimer's disease (AD), a phenomenon that might be the culprit of disease or, possibly, a reaction to pathology. To better investigate inflammation in AD we performed an extensive immunophenotypic and functional analysis of amyloid-beta (Aβ) stimulated T lymphocytes in patients with a diagnosis of AD comparing data to those obtained in individuals with mild cognitive impairment (MCI) or aged-matched healthy individuals (HC). Results showed that IL-21- and IL-9-producing Aβ stimulated CD4(+) T cells, as well as IL-23- and IL-6-producing monocytes and CD4(+) T cells expressing the RORγ and NFATc1 transcriptional factors (TF), were significantly increased, whereas IL-10-producing monocytes were decreased in AD. Notably, GATA-3 TF-expressing CD4(+) T lymphocytes were significantly increased in MCI alone. Analysis of the post-thymic differentiation pathway indicated that Aβ specific naïve and central memory CD4(+) T lymphocytes were diminished whereas effector memory and terminally differentiated CD4(+) T lymphocytes were increased in AD and MCI compared to HC. Data herein indicate that cytokines (IL-21, IL-6, IL-23) and TF (RORγ) involved in the differentiation of Th-17 cells), as well as cytokines (IL-21, IL-22) generated by such cells, and IL-9, produced by Th-9 cells, are significantly increased in AD. This is accompanied by a shift of post-thymic differentiation pathways favoring the accumulation of differentiated, effector T lymphocytes. These data shed light on the nature of AD-associated neuroinflammation. A better understanding of the complexity of this phenomenon could facilitate the search for novel therapeutic strategies.

Locomotor impairment and cerebrocortical oxidative stress in portal vein ligated rats in vivo

BACKGROUND & AIMS

Oxidative/nitrosative stress plays an important role in the pathogenesis of hepatic encephalopathy and ammonia toxicity. The present study was undertaken in order to investigate the impact of portal vein ligation on cerebrocortical oxidative stress and its relation to locomotor activity.

METHODS

Cerebral protein tyrosine nitration, RNA oxidation, locomotor activity, and microglia activation were studied in rats that underwent portal vein ligation (PVL).

RESULTS

Two weeks after PVL, increased levels of protein tyrosine nitration and RNA oxidation were found in the brain. PVL rats exhibited hyperammonemia and reduced locomotor behaviour, but displayed no signs of microglia activation or upregulation of the mRNAs for interleukin-1ß and tumor necrosis factor-α. PVL also had no effect on astrocytic glutamate transporter or inducible nitric-oxide synthase expression. Only cerebral Il-6 mRNA levels were increased. Daily administration of indomethacin prevented PVL-induced protein tyrosine nitration, RNA oxidation, Il-6 mRNA increase, and the impairment of locomotor activity, but did not prevent PVL-induced hyperammonemia.

CONCLUSIONS

The data suggest that PVL triggers oxidative/nitrosative stress in the brain without activation of microglia and neuroinflammation. Prevention of protein tyrosine nitration and RNA oxidation by indomethacin also prevents the disturbances in locomotor activity pointing to a relevance of oxidative stress in the pathophysiology of HE.

Interleukin-6, a mental cytokine

Almost a quarter of a century ago, interleukin-6 (IL-6) was discovered as an inflammatory cytokine involved in B cell differentiation. Today, IL-6 is recognized to be a highly versatile cytokine, with pleiotropic actions not only in immune cells, but also in other cell types, such as cells of the central nervous system (CNS). The first evidence implicating IL-6 in brain-related processes originated from its dysregulated expression in several neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. In addition, IL-6 was shown to be involved in multiple physiological CNS processes such as neuron homeostasis, astrogliogenesis and neuronal differentiation. The molecular mechanisms underlying IL-6 functions in the brain have only recently started to emerge. In this review, an overview of the latest discoveries concerning the actions of IL-6 in the nervous system is provided. The central position of IL-6 in the neuroinflammatory reaction pattern, and more specifically, the role of IL-6 in specific neurodegenerative processes, which accompany Alzheimer's disease, multiple sclerosis and excitotoxicity, are discussed. It is evident that IL-6 has a dichotomic action in the CNS, displaying neurotrophic properties on the one hand, and detrimental actions on the other. This is in agreement with its central role in neuroinflammation, which evolved as a beneficial process, aimed at maintaining tissue homeostasis, but which can become malignant when exaggerated. In this perspective, it is not surprising that 'well-meant' actions of IL-6 are often causing harm instead of leading to recovery.

Neuroinflammation in Alzheimer's disease: mechanisms, pathologic consequences, and potential for therapeutic manipulation

The concept of neuroinflammation has evolved over the past two decades from an initially controversial viewpoint to its present status as a generally accepted idea whose mechanisms and consequences are still actively under research and debate, particularly with regard to Alzheimer's disease (AD). This review summarizes the current status of neuroinflammation research as it specifically relates to AD. Neuroinflammation is discussed mechanistically with emphasis on the role of redox signal transduction linked to the activation of central nervous system-relevant innate immune pathways. Redox signaling is presented both as a causal factor and a consequence of sustained neuroinflammation. Functional relationships are discussed that connect distinct neuroinflammatory components such as cytokines, eicosanoids, classic AD pathology (amyloid plaques and neurofibrillary tangles), and the recently emergent notion of "damage-associated molecular patterns". The interaction of these paracrine factors likely can produce positive as well as negative effects on the AD brain, ranging from plaque clearance by microglia in the short term to glial dysfunction and neuronal compromise if the neuroinflammation is chronically sustained and unmitigated. Recent disappointments in AD clinical trials of anti-inflammatory drugs are discussed with reference to possible explanations and potential avenues for future pharmacological approaches to the disease.

Rosuvastatin reduces microglia in the brain of wild type and ApoE knockout mice on a high cholesterol diet; implications for prevention of stroke and AD

We have previously shown that a high cholesterol (HC) diet results in increases in microglia load and levels of the pro-inflammatory cytokine interleukin-6 (IL-6) in the brains of wild type (WT) and apolipoprotein E knockout (ApoE-/-) mice. In the present investigation, we analyzed whether treatment with rosuvastatin, an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, would prevent the increases in inflammatory microglia and IL-6 levels in the brain and plasma of WT and ApoE-/- mice. We report that a HC diet resulted in an increased microglia load in the brains of WT and ApoE-/- mice, in support of our previous study. Treatment with rosuvastatin significantly decreased the microglia load in the brains of WT and ApoE-/- mice on a HC diet. Rosuvastatin treatment resulted in lowered plasma IL-6 levels in WT mice on a HC diet. However, in the present study the number of IL-6 positive cells in the brain was not significantly affected by a HC diet. A recent clinical study has shown that rosuvastatin reduces risk of ischemic stroke in patients with high plasma levels of the inflammatory marker C-reactive protein by 50%. The results from our study show that rosuvastatin reduces inflammatory cells in the brain. This finding is essential for furthering the prevention and treatment of neurodegenerative diseases such as Alzheimer's disease (AD) and stroke.

Aging and cerebrovascular dysfunction: contribution of hypertension, cerebral amyloid angiopathy, and immunotherapy

Age-related cerebrovascular dysfunction contributes to ischemic stroke, intracerebral hemorrhages (ICHs), microbleeds, cerebral amyloid angiopathy (CAA), and cognitive decline. Importantly, there is increasing recognition that this dysfunction plays a critical secondary role in many neurodegenerative diseases, including Alzheimer's disease (AD). Atherosclerosis, hypertension, and CAA are the most common causes of blood-brain barrier (BBB) lesions. The accumulation of amyloid beta (Aβ) in the cerebrovascular system is a significant risk factor for ICH and has been linked to endothelial transport failure and blockage of perivascular drainage. Moreover, recent anti-Aβ immunotherapy clinical trials demonstrated efficient clearance of parenchymal amyloid deposits but have been plagued by CAA-associated adverse events. Although management of hypertension and atherosclerosis can reduce the incidence of ICH, there are currently no approved therapies for attenuating CAA. Thus, there is a critical need for new strategies that improve BBB function and limit the development of β-amyloidosis in the cerebral vasculature.

Astrocytic A beta 1-42 uptake is determined by A beta-aggregation state and the presence of amyloid-associated proteins

Intracerebral accumulation of amyloid-beta (A beta) leading to A beta plaque formation, is the main hallmark of Alzheimer's disease and might be caused by defective A beta-clearance. We previously found primary human astrocytes and microglia able to bind and ingest A beta 1-42 in vitro, which appeared to be limited by A beta 1-42 fibril formation. We now confirm that astrocytic A beta-uptake depends on size and/or composition of A beta-aggregates as astrocytes preferably take up oligomeric A beta over fibrillar A beta. Upon exposure to either fluorescence-labelled A beta 1-42 oligomers (A beta(oligo)) or fibrils (A beta(fib)), a larger (3.7 times more) proportion of astrocytes ingested oligomers compared to fibrils, as determined by flow cytometry. A beta-internalization was verified using confocal microscopy and live-cell imaging. Neither uptake of A beta(oligo) nor A beta(fib), triggered proinflammatory activation of the astrocytes, as judged by quantification of interleukin-6 and monocyte-chemoattractant protein-1 release. Amyloid-associated proteins, including alpha1-antichymotrypsin (ACT), serum amyloid P component (SAP), C1q and apolipoproteins E (ApoE) and J (ApoJ) were earlier found to influence A beta-aggregation. Here, astrocytic uptake of A beta(fib) increased when added to the cells in combination with SAP and C1q (SAP/C1q), but was unchanged in the presence of ApoE, ApoJ and ACT. Interestingly, ApoJ and ApoE dramatically reduced the number of A beta(oligo)-positive astrocytes, whereas SAP/C1q slightly reduced A beta(oligo) uptake. Thus, amyloid-associated proteins, especially ApoJ and ApoE, can alter A beta-uptake in vitro and hence may influence A beta clearance and plaque formation in vivo.

Genomics of immune molecules: early detection of cognitive decline and new therapeutic interventions

Inflammation plays an important role in progressive degenerative diseases of the CNS, such as Alzheimer's disease, which represents the major cause of cognitive impairment in old age. Alzheimer's disease is a complex disease with multifactorial etiology and may represent a good model to investigate the multifaceted functions of immune responses in relation to cognitive decline. This review will discuss the following topics: relationships between inflammation and brain degenerative processes in Alzheimer's disease, the influence of genetic variations in cytokine genes upon the risk of developing Alzheimer's disease and/or the age at onset of the disease, the effects of gene allele polymorphism of immune molecules upon the turnover of these factors in the blood and brain of Alzheimer's disease patients and the association of genetic variations in some of this molecules with cognitive decline.

CSF Biomarkers for Alzheimer's Disease Diagnosis

Alzheimer's disease (AD) is the most common form of dementia that affects several million people worldwide. The major neuropathological hallmarks of AD are the presence of extracellular amyloid plaques that are composed of Aβ40 and Aβ42 and intracellular neurofibrillary tangles (NFT), which is composed of hyperphosphorylated protein Tau. While the amyloid plaques and NFT could define the disease progression involving neuronal loss and dysfunction, significant cognitive decline occurs before their appearance. Although significant advances in neuroimaging techniques provide the structure and physiology of brain of AD cases, the biomarker studies based on cerebrospinal fluid (CSF) and plasma represent the most direct and convenient means to study the disease progression. Biomarkers are useful in detecting the preclinical as well as symptomatic stages of AD. In this paper, we discuss the recent advancements of various biomarkers with particular emphasis on CSF biomarkers for monitoring the early development of AD before significant cognitive dysfunction.

Association between haplotype -88G/25G in A2M with Alzheimer's disease

Alpha 2-Macroglobulin gene (A2M) has been recognized as a candidate gene for late-onset Alzheimer's disease (AD), but the association between several polymorphisms in A2M gene and risk for AD remained controversial. Moreover, little is known regarding the effects of polymorphisms in A2M promoter region on AD susceptibility. Our study aimed to detect polymorphisms in A2M promoter region, and then evaluate their relationship to sporadic AD (SAD). One single nucleotide polymorphism (-88A/G) in proximal promoter region was found by sequencing, and further analyzed with an established 25T/G polymorphism in 179 SAD patients and 179 age-gender-matched controls. Allele A in -88A/G polymorphism was more prevalent in cases, with a 1.7-folded risk for SAD (OR=1.74, 95%CI 1.05-2.91, P=0.031), while G allele in 25T/G was less prevalent in cases, with a 43% reduced risk for SAD (OR=0.57, 95%CI 0.36-0.89, P=0.013). After adjusted the effects of age, gender and APOEvarepsilon4 allele status in logistic regression model, the protective effects of -88G and 25G on SAD still remained. Individuals who carried haplotype -88G/25G had a significant 44% reduced risk for SAD compared to those who did not carry (OR=0.56, 95%CI 0.34-0.94, P=0.027), while haplotype -88A/25T carriers had an increased risk for SAD compared to those who did not carry (OR=1.77, 95%CI 1.06-2.96, P=0.027). Our study supports that haplotype -88G/25G might play a protective role in the development of SAD, and the protective effects of -88G and 25G were independent of APOEvarepsilon4 allele.

Replication by the Epistasis Project of the interaction between the genes for IL-6 and IL-10 in the risk of Alzheimer's disease

Background

Chronic inflammation is a characteristic of Alzheimer's disease (AD). An interaction associated with the risk of AD has been reported between polymorphisms in the regulatory regions of the genes for the pro-inflammatory cytokine, interleukin-6 (IL-6, gene: IL6), and the anti-inflammatory cytokine, interleukin-10 (IL-10, gene: IL10).

Methods

We examined this interaction in the Epistasis Project, a collaboration of 7 AD research groups, contributing DNA samples from 1,757 cases of AD and 6,295 controls.

Results

We replicated the interaction. For IL6 rs2069837 AA × IL10 rs1800871 CC, the synergy factor (SF) was 1.63 (95% confidence interval: 1.10–2.41, p = 0.01), controlling for centre, age, gender and apolipoprotein E ε4 (APOEε4) genotype. Our results are consistent between North Europe (SF = 1.7, p = 0.03) and North Spain (SF = 2.0, p = 0.09). Further replication may require a meta-analysis. However, association due to linkage disequilibrium with other polymorphisms in the regulatory regions of these genes cannot be excluded.

Conclusion

We suggest that dysregulation of both IL-6 and IL-10 in some elderly people, due in part to genetic variations in the two genes, contributes to the development of AD. Thus, inflammation facilitates the onset of sporadic AD.

F-spondin plays a critical role in murine neuroblastoma survival by maintaining IL-6 expression

F-spondin is associated with the regulation of axonal growth and the development of the nervous system. Its mechanism of action, however, is not clearly understood. In this study, we found that murine neuroblastoma Neuro-2a cells expressed a significant level of IL-6, but only trace amounts of IL-12, tumor necrosis factor alpha and nitric oxide. Knock-down of F-spondin mRNA in murine neuroblastoma NB41A3 and Neuro-2a cells using small interfering RNAs led to decreased IL-6 levels along with lower resistance to serum starvation and cytotoxic amyloid beta(1-42) (Abeta(1-42)) peptide. Restoring decline of F-spondin or IL-6 induced by F-spondin knock-down through adding exogenous F-spondin, IL-6 or over-expressing F-spondin reversed the cell death induced by Abeta(1-42) peptide or serum starvation. The decrease of IL-6 level was positively correlated with decrease of NF-kappaB and inhibition of p38 mitogen-activated protein kinase (MAPK). Over-expressing MEKK, a kinase activator of the p38 MAPK pathway, increased IL-6 production, restored the decrease of p38 induced by F-spondin knock-down, and rescued the cells from death caused by Abeta(1-42) peptide. Taken together, these results suggest that F-spondin may play a critical role in murine neuroblastoma survival under adverse conditions by maintaining IL-6 level via a MEKK/p38 MAPK/NF-kappaB-dependent pathway.

Plasma biomarkers for mild cognitive impairment and Alzheimer's disease

PURPOSE OF REVIEW

With the move toward development of disease modifying treatments, there is a need for more specific diagnosis of early Alzheimer's disease (AD) and mild cognitive impairment (MCI), plasma biomarkers are likely to play an important role in this. We review the current state of knowledge on plasma biomarkers for MCI and AD, including unbiased proteomics and very recent longitudinal studies.

RECENT FINDINGS

With the use of proteomics methodologies, some proteins have been identified as potential biomarkers in plasma and serum of AD patients, including alpha-1-antitrypsin, complement factor H, alpha-2-macroglobulin, apolipoprotein J, apolipoprotein A-I. The findings of cross-sectional studies of plasma amyloid beta (A beta) levels are conflicting, but some recent longitudinal studies have shown that low plasma A beta 1-42 or A beta 1-40 levels, or A beta 1-42/A beta 1-40 ratio may be markers of cognitive decline. Other potential biomarkers for MCI and AD reflecting a variety of pathophysiological processes have been assessed, including isoprostanes and homocysteine (oxidative stress), total cholesterol and ApoE4 allele (lipoprotein metabolism), and cytokines and acute phase proteins (inflammation). A panel of 18 signal proteins was reported as markers of MCI and AD.

SUMMARY

A variety of potential plasma biomarkers for AD and MCI have been identified, however the findings need replication in longitudinal studies. This area of research promises to yield interesting results in the near future.

Immune and nervous systems share molecular and functional similarities: memory storage mechanism

One of the most complex and important features of both the nervous and immune systems is their data storage and retrieval capability. Both systems encounter a common and complex challenge on how to overcome the cumbersome task of data management. Because each neuron makes many synapses with other neurons, they are capable of receiving data from thousands of synaptic connections. The immune system B and T cells have to deal with a similar level of complexity because of their unlimited task of recognizing foreign antigens. As for the complexity of memory storage, it has been proposed that both systems may share a common set of molecular mechanisms. Here, we review the molecular bases of memory storage in neurons and immune cells based on recent studies and findings. The expression of certain molecules and mechanisms shared between the two systems, including cytokine networks, and cell surface receptors, are reviewed. Intracellular signaling similarities and certain mechanisms such as diversity, memory storage, and their related molecular properties are briefly discussed. Moreover, two similar genetic mechanisms used by both systems is discussed, putting forward the idea that DNA recombination may be an underlying mechanism involved in CNS memory storage.

Autoradiographical imaging of PPARgamma agonist effects on PBR/TSPO binding in TASTPM mice

Chronic inflammation is known to occur in the brains of Alzheimer's Disease (AD) patients, including the presence of activated microglia close to amyloid plaques. We utilised real time autoradiography and immunohistochemistry to investigate microglial activation and the potential anti-inflammatory effects of PPARgamma agonists in the Thy-1 APP695swe/Thy-1 PS-1.M146V (TASTPM) overexpressing transgenic mouse model of AD. An age dependent increase in specific [3H](R)-PK11195 binding to peripheral benzodiazepine receptors (PBR)/translocator protein (18 kDa) (TSPO) was observed in the cortex of TASTPM mice compared to wild type mice, indicative of microglial activation. This was consistent with immunohistochemical data showing age-dependent increases in CD68 immunoreactivity co-localised with amyloid beta (Abeta) deposits. In 10 month old TASTPM mice, pioglitazone (20 mg/kg) and ciglitazone (50 mg/kg) significantly reduced [3H](R)-PK11195 and [3H]DPA-713 binding in cortex and hippocampus, indicative of reduced microglial activation. In AD brain, significant [3H](R)-PK11195 and [3H]DPA-713 binding was observed across all stages of the disease. These results support the use of PBR/TSPO autoradiography in TASTPM mice as a functional readout of microglial activation to assess anti-inflammatory drugs prior to evaluation in AD patients.

Peptides and proteins in plasma and cerebrospinal fluid as biomarkers for the prediction, diagnosis, and monitoring of therapeutic efficacy of Alzheimer's disease

Alzheimer's disease (AD) affects millions of persons worldwide. Earlier detection and/or diagnosis of AD would permit earlier intervention, which conceivably could delay progression of this dementing disorder. In order to accomplish this goal, reliable and specific biomarkers are needed. Biomarkers are multidimensional and have the potential to aid in various facets of AD such as diagnostic prediction, assessment of disease stage, discrimination from normally cognitive controls as well as other forms of dementia, and therapeutic efficacy of AD drugs. To date, biomarker research has focused on plasma and cerebrospinal fluid (CSF), two bodily fluids believed to contain the richest source of biomarkers for AD. CSF is the fluid surrounding the central nervous system (CNS), and is the most indicative obtainable fluid of brain pathology. Blood plasma contains proteins that affect brain processes from the periphery, as well as proteins/peptides exported from the brain; this fluid would be ideal for biomarker discovery due to the ease and non-invasive process of sample collection. However, it seems reasonable that biomarker discovery will result in combinations of CSF, plasma, and other fluids such as urine, to serve the aforementioned purposes. This review focuses on proteins and peptides identified from CSF, plasma, and urine that may serve as biomarkers in AD.

Monocyte chemoattractant protein-1 plays a dominant role in the chronic inflammation observed in Alzheimer's disease

Chronic neuroinflammation correlates with cognitive decline and brain atrophy in Alzheimer's disease (AD), and cytokines and chemokines mediate the inflammatory response. However, quantitation of cytokines and chemokines in AD brain tissue has only been carried out for a small number of mediators with variable results. We simultaneously quantified 17 cytokines and chemokines in brain tissue extracts from controls (n = 10) and from patients with and without genetic forms of AD (n = 12). Group comparisons accounting for multiple testing revealed that monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and interleukin-8 (IL-8) were consistently upregulated in AD brain tissue. Immunohistochemistry for MCP-1, IL-6 and IL-8 confirmed this increase and determined localization of these factors in neurons (MCP-1, IL-6, IL-8), astrocytes (MCP-1, IL-6) and plaque pathology (MCP-1, IL-8). Logistic linear regression modeling determined that MCP-1 was the most reliable predictor of disease. Our data support previous work on significant increases in IL-6 and IL-8 in AD but indicate that MCP-1 may play a more dominant role in chronic inflammation in AD.

Monocytic, Th1 and th2 cytokine alterations in the pathophysiology of schizophrenia

A growing body of evidence suggests that changes in the serum levels and cellular production of various cytokines are associated with the immunological abnormalities of schizophrenia. Several studies have examined alterations in T helper type 1 (Th1) and T helper type 2 (Th2) cytokines in schizophrenia. We explored monocytic, Th1 and Th2 cytokines in 43 schizophrenia patients and 50 normal controls. The mitogen-induced production of tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), IL-4, gamma-interferon (IFN-gamma) and IL-2 was measured with enzyme-linked immunosorbent assays before and after antipsychotic treatment. IL-6 and TNF-alpha production by schizophrenic patients was significantly higher than by normal controls, while IL-2, IL-4 and IFN-gamma production was significantly lower in schizophrenic patients. After 6 weeks of antipsychotic treatment, IL-6 and TNF-alpha production was significantly decreased, while IL-4, IFN-gamma and IL-2 productions were not significantly changed. Our results suggest that increased monocytic cytokines and decreased Th1 and Th2 cytokines may be associated with the immunopathogenesis of acute psychotic schizophrenia, and that antipsychotics may play an important role in immune response by decreasing elevated monocytic cytokines.

Differences of peripheral inflammatory markers between mild cognitive impairment and Alzheimer's disease

Multiple pathogenic factors may contribute to the pathophysiology of Alzheimer's disease (AD). Peripheral markers have been used to assess biochemical alterations associated with AD and mild cognitive impairment (MCI) involved in its pathophysiology. The present study was conducted to evaluate inflammatory peripheral markers in elderly patients with MCI, patients with AD and normal elderly subjects. We measured plasma levels of different cytokines (IL-6, TNF-alpha and IFN-alpha) and platelet levels of cyclooxigenase-2 (COX-2) from 34 patients with MCI, 45 patients with AD and 28 age-matched control subjects. MCI and AD patients showed similarities in TNF-alpha and COX-2 levels, and differences in IL-6 and INF-alpha. Whereas augmented IL-6 levels have been found in AD patients, a significant increase in INF-alpha has been detected only in patients with MCI possibly associated with the depression stage frequently found in cognitive impairment. In conclusion, inflammatory response may be an early factor in AD development and these changes in circulating markers are possibly related to the progression of MCI to AD.

Heat shock proteins and amateur chaperones in amyloid-Beta accumulation and clearance in Alzheimer's disease

The pathologic lesions of Alzheimer’s disease (AD) are characterized by accumulation of protein aggregates consisting of intracellular or extracellular misfolded proteins. The amyloid-β (Aβ) protein accumulates extracellularly in senile plaques and cerebral amyloid angiopathy, whereas the hyperphosphorylated tau protein accumulates intracellularly as neurofibrillary tangles. “Professional chaperones”, such as the heat shock protein family, have a function in the prevention of protein misfolding and subsequent aggregation. “Amateur” chaperones, such as apolipoproteins and heparan sulfate proteoglycans, bind amyloidogenic proteins and may affect their aggregation process. Professional and amateur chaperones not only colocalize with the pathological lesions of AD, but may also be involved in conformational changes of Aβ, and in the clearance of Aβ from the brain via phagocytosis or active transport across the blood–brain barrier. Thus, both professional and amateur chaperones may be involved in the aggregation, accumulation, persistence, and clearance of Aβ and tau and in other Aβ-associated reactions such as inflammation associated with AD lesions, and may, therefore, serve as potential targets for therapeutic intervention.

Folic acid and polyunsaturated fatty acids improve cognitive function and prevent depression, dementia, and Alzheimer's disease--but how and why?

Low blood folate and raised homocysteine concentrations are associated with poor cognitive function. Folic acid supplementation improves cognitive function. Folic acid enhances the plasma concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). EPA, DHA, and arachidonic acid (AA) are of benefit in dementia and Alzheimer's disease by up-regulating gene expression concerned with neurogenesis, neurotransmission and connectivity, improving endothelial nitric oxide (eNO) generation, enhancing brain acetylcholine levels, and suppressing the production of pro-inflammatory cytokines. EPA, DHA, and AA also form precursors to anti-inflammatory compounds such as lipoxins, resolvins, and neuroprotectin D1 (NPD1) that protect neurons from the cytotoxic action of various noxious stimuli. Furthermore, various neurotrophins and statins enhance the formation of NPD1 and thus, protect neurons from oxidative stress and prevent neuronal apoptosis Folic acid improves eNO generation, enhances plasma levels of EPA/DHA and thus, could augment the formation of NPD1. These results suggest that a combination of EPA, DHA, AA and folic acid could be of significant benefit in dementia, depression, and Alzheimer's disease and improve cognitive function.

Genetic priming of a proinflammatory profile predicts low IQ in octogenarians

The purpose of the study was to test the hypothesis that single nucleotide polymorphisms (SNPs) within interleukin (IL)-18, TNF-alpha, IL-6 and IL-10 gene promoter regions are risk factors for cognitive decline in healthy octogenarians, and to isolate the strongest inflammatory biomarkers of cognitive function in the peripheral blood. The Wechsler Adult Intelligence Scale was administered to 112 individuals at ages 80 and 85. An IL-18 haplotype was an independent risk factor of poor Performance IQ. The TNF-308GA genotype was related to individual declines in Verbal IQ, and the IL-10-592 CC genotype was related to better Verbal IQ at the age of 80. Circulating levels of TNF-alpha, sTNFRs, and IL-6 were negatively correlated with IQ at age 85 and less strongly to IQ at age 80 with activation of the TNF system as the strongest biomarker. In conclusion, SNPs related to high proinflammatory or low anti-inflammatory activity are independent risk factors of reduced cognitive function in octogenarians. Only the IL-18 haplotype was associated with inflammation in the peripheral blood and only with regard to circulating TNF-alpha.

Peripheral inflammatory cytokines as biomarkers in Alzheimer's disease and mild cognitive impairment

BACKGROUND

Several lines of evidence in the literature have shown that inflammation is involved in the pathogenesis of Alzheimer's disease (AD). However, the results from the evaluation of serum inflammatory markers in AD patients have been controversial.

OBJECTIVE

To determine if any differences exist in the monocytic secretion pattern of IL-1beta, IL-6, IL-12 and TNF-alpha from mild cognitive impairment (MCI) and AD patients, when compared with healthy age-matched controls.

METHODS

To evaluate the percentage of peripheral monocytes secreting IL-1beta, IL-6, IL-12 and TNF-alpha along with the relative levels of these proteins, a cytofluorimetric analysis was conducted under basal conditions and after lipopolysaccharide-induced cell activation.

RESULTS

We found, in AD and MCI patients, a significant raise in the percentage of monocytes producing the studied cytokines (under basal conditions and after the exposure to an inflammatory stimulus), as well as a decreased competence of these cells to respond to inflammatory challenges, when compared with controls.

CONCLUSIONS

These results agree with a persistent inflammatory status in AD, reinforcing the hypothesis of a progressive impairment of the immune response in this disorder and suggesting that monocytes may be good targets to study the progression from MCI to AD.

The potential impact of sickness-motivated behavior on the expression of neuropsychiatric disturbances in systemic lupus erythematosus

Activation of the peripheral immune system is often accompanied by changes in cognition, ingestive behavior, sleep pattern, and sexual drive; collectively referred to as sickness behavior. Mounting evidence suggests that sickness behavior may be a purposeful attempt on the part of an organism to conserve energy and thereby facilitate recuperation. Illnesses characterized by chronic, uncontrolled immune reactivity such as systemic lupus erythematosus are also frequently associated with impaired emotionality and cognition; which, unlike sickness behavior, are conventionally thought to emanate from fixed structural lesions of the brain. Clinical observations, however, indicate that the neuropsychiatric disturbances in lupus may wax and wane in intensity and suggest the hypothesis that sickness-motivated behavior may significantly influence the neuropsychiatric manifestations of systemic lupus erythematosus and, perhaps, those of other autoimmune diseases associated with neuroinflammation. The hypothesis that patients with systemic lupus erythematosus undergo a reorganization of their motivational priorities, which influences cognitive performance and emotional output, may be examined using validated behavior paradigms in autoimmune MRL-MpJ-Tnfrsf6(lpr) (MRL-lpr/lpr) mice that spontaneously develop a lupus-like illness accompanied by disturbances in cognition and emotionality. Confirming that sickness-motivated behavior contributes to the aberrations in cognition and emotionality exhibited by an experimental model of systemic lupus erythematosus might have important therapeutic and prognostic implications by invoking the possibility that similar motivational effects may be influencing cognitive and/or emotional output in patients with neuropsychiatric lupus.

C/T conversion alters interleukin-1A promoter function in a human astrocyte cell line

Recently, association of an interleukin-1A promoter polymorphism (-889, thymine/thymine (T/T)) with Alzheimer's disease was reported, suggesting that this cytokine may play an important role in disease development. To understand the mechanism underlying the interleukin-1A promoter's role in Alzheimer's disease, a study comparing promoter function of an interleukin-1A polymorphism was performed in the SVG astroglia cell line. The effects of thymine and cytosine on transcriptional activity of the interleukin-1A promoter were analyzed by testing luciferase-reporter activity in transfected SVG cells. Our results demonstrate that cytosine/thymine conversion increases activity of the interleukin-1A promoter in SVG cells. Both sodium salicylate and lovastatin are able to block induced promoter activities in astroglial cells. Induced promoter activity by the polymorphism (T/T) may result in the upregulation of interleukin-1alpha protein and "cytokine cycle" amplification, which may promote disease development.

Proteome-based plasma biomarkers for Alzheimer's disease

Alzheimer's disease is a common and devastating disease for which there is no readily available biomarker to aid diagnosis or to monitor disease progression. Biomarkers have been sought in CSF but no previous study has used two-dimensional gel electrophoresis coupled with mass spectrometry to seek biomarkers in peripheral tissue. We performed a case-control study of plasma using this proteomics approach to identify proteins that differ in the disease state relative to aged controls. For discovery-phase proteomics analysis, 50 people with Alzheimer's dementia were recruited through secondary services and 50 normal elderly controls through primary care. For validation purposes a total of 511 subjects with Alzheimer's disease and other neurodegenerative diseases and normal elderly controls were examined. Image analysis of the protein distribution of the gels alone identifies disease cases with 56% sensitivity and 80% specificity. Mass spectrometric analysis of the changes observed in two-dimensional electrophoresis identified a number of proteins previously implicated in the disease pathology, including complement factor H (CFH) precursor and alpha-2-macroglobulin (alpha-2M). Using semi-quantitative immunoblotting, the elevation of CFH and alpha-2M was shown to be specific for Alzheimer's disease and to correlate with disease severity although alternative assays would be necessary to improve sensitivity and specificity. These findings suggest that blood may be a rich source for biomarkers of Alzheimer's disease and that CFH, together with other proteins such as alpha-2M may be a specific markers of this illness.

The role of pleiotropic effects of statins in dementia

High serum cholesterol is associated with ischemic heart disease. Recent reports also indicate that cholesterol modulates amyloid beta-peptide interactions in the brain. Statins are inhibitors of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMG-CoA reductase), the rate-limiting enzyme involved in cholesterol synthesis. Statin treatment significantly reduces the levels of low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL). In the past decade, cardiovascular mortality and morbidity has been reduced by the use of statins. However, evidence from in vivo and in vitro research has indicated that statins may confer multiple effects because of the inhibition of the production of intermediates in the mevalonate pathway. The aim of this review was to discuss the biological effects of statins on regulation of processes involved in the pathogenesis of dementia.

Anti-inflammatory effect of jeongshintang through suppression of p38 activation in human astrocytoma, U373MG cells

Jeongshintang (JST) is a Korean herbal prescription, which has been successfully used for cerebral diseases. However, the anti-inflammatory effect of JST on Alzheimer's disease (AD) is still not fully understood. In this study, we investigated the effects of JST in attenuating the inflammatory response induced by interleukin (IL)-1beta plus beta-amyloid [1-42] fragment (A beta) in the human astrocyte cell line, U373MG. The production of IL-6, IL-8, and prostaglandin (PG)E2 was significantly increased by IL-1beta plus A beta (1-42) in a time-dependent manner (P < 0.05). JST significantly inhibited the IL-1beta plus A beta (1-42)-induced IL-6, IL-8, and PGE2 production at 24 h (P < 0.05). Maximal inhibition rate of IL-6, IL-8, and PGE2 production by JST was about 54.40%, 56.01%, and 44.06% respectively. JST (0.01-1 mg/ml) also attenuated the expression of cyclooxygenase (COX)-2 and activation of p38 MAPK induced by IL-1beta and A beta (1-42). These results demonstrated that JST has an anti-inflammatory effect, which might explain its beneficial effect in the treatment of various neurodegenerative diseases such as AD.

Deficiency of TNF receptors suppresses microglial activation and alters the susceptibility of brain regions to MPTP-induced neurotoxicity: role of TNF-alpha

Enhanced expression of tumor necrosis factor (TNF) -alpha, is associated with the neuropathological effects underlying disease-, trauma- and chemically induced neurodegeneration. Previously, we have shown that deficiency of TNF receptors protects against MPTP-induced striatal dopaminergic neurotoxicity, findings suggestive of a role for TNF-alpha in neurodegeneration. Here, we demonstrate that deficiency of TNF receptors suppresses microglial activation and alters the susceptibility of brain regions to MPTP. MPTP-induced expression of microglia-derived factors, TNF-alpha, MCP-1, and IL-1alpha, preceded the degeneration of striatal dopaminergic nerve terminals and astrogliosis, as assessed by loss of striatal dopamine and TH, and an increase in striatal GFAP. Pharmacological neuroprotection with the dopamine reuptake inhibitor, nomifensine, abolished striatal dopaminergic neurotoxicity and associated microglial activation. Similarly, in mice lacking TNF receptors, microglial activation was suppressed, findings consistent with a role for TNF-alpha in striatal MPTP neurotoxicity. In the hippocampus, however, TNF receptor-deficient mice showed exacerbated neuronal damage after MPTP, as evidenced by Fluoro Jade-B staining (to identify degenerating neurons) and decreased microtubule-associated protein-2 (MAP-2) immunoreactivity. These effects were not accompanied by microglial activation, but were associated with increased oxidative stress (nitrosylation of tyrosine residues). These findings suggest that TNF-alpha exerts a neurotrophic/neuroprotective effect in hippocampus. The marked differences we observed in the regional density, distribution and/or activity of microglia and microglia-derived factors may influence the region-specific role for this cell type. Taken together, our results are indicative of a region-specific and dual role for TNF-alpha in the brain: a promoter of neurodegeneration in striatum and a protector against neurodegeneration in hippocampus.

Serum amyloid A (SAA)-induced remodeling of CSF-HDL

Inflammation is a risk factor for Alzheimer's disease. Serum amyloid A (SAA) is an acute phase protein that dissociates apolipoprotein AI (apoAI) from plasma HDL. In cerebrospinal fluid (CSF), the SAA concentration is much higher in subjects with Alzheimer's disease than in controls. CSF-HDL is rich in apoE, which plays an important role as a ligand for lipoprotein receptors in the central nervous system (CNS). To clarify whether SAA dissociates apoE from CSF-HDL, we added recombinant SAA to CSF and determined the apoE distribution in the CSF using native two-dimensional gel electrophoresis. We found that SAA dissociated apoE from CSF-HDL in a dose-dependent manner. This effect was more evident in apoE4 carriers than in apoE3 or apoE2 carriers. After a 24-h incubation at 37 degrees C, SAA continuously dissociated apoE from CSF-HDL. Amyloid beta (Abeta) fragments (1-42) were bound to large CSF-HDL but not to apoE dissociated by SAA. In conclusion, SAA dissociates apoE from CSF-HDL. We postulate that inflammation in the CNS may impair Abeta clearance due to the loss of apoE from CSF-HDL.

The acetylcholinesterase inhibitor, Donepezil, regulates a Th2 bias in Alzheimer's disease patients

The increased pro-inflammatory cytokine production was previously observed in Alzheimer's disease (AD). We sought to explore whether acetylcholinesterase inhibitor (AChEI) therapy ameliorates clinical symptoms in AD through down-regulation of inflammation. Expression and release of monocyte chemotactic protein-1 (MCP-1), a positive regulator of Th2 differentiation, and interleukin (IL)-4, an anti-inflammatory cytokine from peripheral blood mononuclear cells (PBMC) in AD patients, were investigated. PBMC were purified from AD patients at time of enrollment (T0) and after 1 month of treatment with AChEI (T1) and from healthy controls (HC). Supernatants were analyzed for cytokine levels by ELISA methods. mRNA expression were determined by RT-PCR. Expression and production of MCP-1 and IL-4 were significantly increased in AD subjects under therapy with the AChEI Donepezil, compared to the same AD patients at time of enrollment (P < 0.001). Our data suggest another possible explanation for the ability of Donepezil [diethyl(3,5-di-ter-butyl-4-hydroxybenzyl)phosphonate] to delay the progression of AD; in fact, Donepezil may modulate MCP-1 and IL-4 production, which may reflect a general shift towards type Th0/Th2 cytokines which could be protective in AD disease. The different amounts of MCP-1 and IL-4 observed might reflect the different states of activation and/or responsiveness of PBMC, that in AD patients could be kept in an activated state by pro-inflammatory cytokines.

Release of interleukin-6 via the regulated secretory pathway in PC12 cells

A growing body of evidence suggests that diverse growth factors such as neurotrophins (NTs), insulin-like growth factor-1 (IGF-1), and glial cell line-derived neurotrophic factor (GDNF) can be released via the regulated secretory pathway in neuronal cells, possibly representing a mechanism for preferentially supplying these growth factors to active synapses. Here we investigated whether interleukin-6 (IL-6), a member of the family of neuropoietic cytokines, can be released via stimulus-coupled secretion as well. IL-6 was expressed in PC12 cells, a neuronal model cell line that is frequently used for the study of vesicle release and trafficking. Regulated secretion of this cytokine was induced by 0.5 mM ATP and treatment with epidermal growth factor (EGF) and nerve growth factor (NGF). Release induced by 0.5 mM ATP but not by NGF or EGF depended on the presence of extracellular Ca(++). Furthermore, IL-6 colocalized with the dense core vesicle (DCV)-marker secretogranin-II (Sg-II) in transfected PC12 cells. Our data suggest that the neuropoietic cytokine IL-6 can be sorted to the regulated secretory pathway in neuronal cells and indicate a potential role for this cytokine in synaptic plasticity.

Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-alpha

Activated microglia are implicated in the pathogenesis of disease-, trauma- and toxicant-induced damage to the CNS, and strategies to modulate microglial activation are gaining impetus. A novel action of the tetracycline derivative minocycline is the ability to inhibit inflammation and free radical formation, factors that influence microglial activation. Minocycline is therefore being tested as a neuroprotective agent to alleviate CNS damage, although findings so far have yielded mixed results. Here, we showed that administration of a single low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (METH), a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in substantia nigra, increased the expression of mRNAs encoding microglia-associated factors F4/80, interleukin (IL)-1alpha, IL-6, monocyte chemoattractant protein-1 (MCP-1, CCL2) and tumor necrosis factor (TNF)-alpha. Minocycline treatment attenuated MPTP- or METH-mediated microglial activation, but failed to afford neuroprotection. Lack of neuroprotection was shown to be due to the inability of minocycline to abolish the induction of TNF-alpha and its receptors, thereby failing to modulate TNF signaling. Thus, TNF-alpha appeared to be an obligatory component of dopaminergic neurotoxicity. To address this possibility, we examined the effects of MPTP or METH in mice lacking genes encoding IL-6, CCL2 or TNF receptor (TNFR)1/2. Deficiency of either IL-6 or CCL2 did not alter MPTP neurotoxicity. However, deficiency of both TNFRs protected against the dopaminergic neurotoxicity of MPTP. Taken together, our findings suggest that attenuation of microglial activation is insufficient to modulate neurotoxicity as transient activation of microglia may suffice to initiate neurodegeneration. These findings support the hypothesis that TNF-alpha may play a role in the selective vulnerability of the nigrostriatal pathway associated with dopaminergic neurotoxicity and perhaps Parkinson's disease.

Interleukins, inflammation, and mechanisms of Alzheimer's disease

Alzheimer's disease (AD) is the most common progressive neurodegenerative form of dementia in the elderly and is characterized neuropathologically by neurofibrillary tangles (NFT), amyloid neuritic plaques (NP), and prominent synaptic and eventually neuronal loss. Although the molecular basis of AD is not clearly understood, a neuroinflammatory process, triggered by Abeta42, plays a central role in the neurodegenerative process. This inflammatory process is driven by activated microglia, astrocytes and the induction of proinflammatory molecules and related signaling pathways, leading to both synaptic and neuronal damage as well as further inflammatory cell activation. Epidemiologic data as well as clinical trial evidence suggest that nonsteroidal anti-inflammatory drug (NSAID) use may decrease the incidence of AD, further supporting a role for inflammation in AD pathogenesis. Although the precise molecular and cellular relationship between AD and inflammation remains unclear, interleukins and cytokines might induce activation of signaling pathways leading to futher inflammation and neuronal injury. This chapter will discuss the association between interleukins and neurodegeneration in AD and highlight the significance of genetic and clinical aspects of interleukins in disease expression and progression. As part of an emerging inflammatory signaling network underlying AD pathogenesis, beta-amyloid (Abeta) stimulates the glial and microglial production of interleukins and other cytokines, leading to an ongoing inflammatory cascade and contributing to synaptic dysfunction and loss, and later, neuronal death. Inflammatory pathways involving interleukin and cytokine signaling might suggest potential targets for intervention and influence the development of novel therapies to circumvent synaptic and neuronal dysfunction ultimately leading to AD neurodegeneration.

Purkinje neuron physiology is altered by the inflammatory factor interleukin-6

The cytokine interleukin-6 (IL-6) is produced by cells of the central nervous system (CNS) during a variety of neuroinflammatory states, in which it is thought to play a role in neuroprotection and/or neuropathology associated with neurological disease. In addition, CNS expression of IL-6 during non-pathological conditions may also occur, although the conditions for such IL-6 production remain elusive. Expression of IL-6 and its receptor and signal transducing elements by neurons and glia within the cerebellum implicate a role of IL-6 in modulating cerebellar function under normal conditions and in contributing to pathology and pathophysiology within the cerebellum during CNS disease states. Evidence for such a role of IL-6 comes from studies using transgenic mice that chronically express IL-6 within the CNS. These mice exhibit profound cerebellar pathology and significant alterations of Purkinje neuron electrical and synaptic activity. Additional evidence comes from in vitro studies using primary cultures of cerebellar cortex that have been chronically exposed to exogenously applied IL-6. Consistent with the IL-6 transgenic mice, chronic IL-6 treated Purkinje neurons in culture exhibit alterations of endogenous electrophysiological properties as well as changes in intracellular Ca2+ homeostasis and signaling. Despite these changes in Purkinje neuron physiology, chronic IL-6 does not affect the survival or morphology of Purkinje neurons in culture. Thus, by itself, IL-6 is able to modulate key components of cerebellar circuitry during periods of chronic expression, such as during neuroinflammation, and may be an important player in the movement disorders associated with a number of CNS disease states.

Cytokine production by a human microglial cell line: effects of beta-amyloid and alpha-melanocyte-stimulating hormone

Senile plaques in the Alzheimer's disease (AD) are formed by aggregation of beta-amyloid (Abeta) peptide. Abeta peptide has been shown to activate microglia and stimulate their production of inflammatory factors, such as cytokines. In the AD brain, the continued presence of amyloid plaques may keep microglia persistently activated, leading to chronic inflammation in the CNS. It is well established that alpha-melanocyte-stimulating hormone (alpha-MSH) gives rise to anti-inflammatory and anti-pyretic effects. The biological activities of alpha-MSH are mediated by one or more of the melanocortin receptor (MCR) subtypes, i.e. MCR1 - MCR5. The aim of the present study was to determine the effect of alpha-MSH alone and on Abeta-activated microglial cells with regard to the secretion of inflammatory cytokines, such as interleukin-6 (IL-6), and to determine which receptor subtype mediates the effects of alpha-MSH. The human microglial cell line, CHME3, was incubated for 24 h with freshly dissolved Abeta(1-40), interferon-gamma (IFN-gamma) and/or alpha-MSH. Freshly dissolved Abeta(1-40) (5-60 microM) resulted in a dose-dependent decrease in cell viability, along with a dose-dependent increase in IL-6 release. Neither IFN-gamma nor alpha-MSH affected the Abeta-induced secretion of IL-6, but resulted in a dose-dependent increase in basal IL-6 release. Agouti, the endogenous antagonist of MCR1 and 4, further increased the alpha-MSH-induced secretion of IL-6. RT-PCR showed the expression of MCR1, MCR3, MCR4 and MCR5 mRNA. The combined data suggest that the effect of alpha-MSH in increasing IL-6 release from the human microglial cell line is mediated by MCR3 or MCR5.

Beta-amyloid protein structure determines the nature of cytokine release from rat microglia

Activated microglia represent a major source of inflammatory factors in Alzheimer's disease and a possible source of cytotoxic factors. beta-Amyloid (Abeta) peptide, the predominant component in amyloid plaques, has been shown to activate microglia and stimulate their production of inflammatory factors. The present study was performed to analyze the responses of microglia to different forms of Abeta, with regard to release of the proinflammatory cytokines interleukin-1alpha (IL-1alpha), IL-1beta, tumor necrosis factor-alpha (TNF-alpha), IL-6, and interferon-gamma (IFN-gamma), as well as the IL-1 receptor antagonist (IL-1ra). Primary cultures of microglia from rat neonatal cerebral cortex were incubated with freshly dissolved Abeta1-40 or Abeta1-42, Abeta1-40 fibrils, Abeta1-40 betaamy balls, or vehicle. Abeta1-40 fibrils did not significantly stimulate any of these cytokines. Freshly dissolved Abeta1-40 resulted in a marked increase in the release of IL-1beta, and freshly dissolved Abeta1-42 significantly stimulated both IL-1alpha and IFN-gamma secretion. The Abeta1-40 betaamy balls stimulated the secretion of IL-1alpha and IL-1beta. Incubation with Abeta peptides did not affect the secretion of IL-1ra, IL-6, or TNF-alpha. In the case of IL-1beta, the response is correlated with the presence of Abeta peptide as monomers and oligomers.

Pattern of interleukin-6 receptor complex immunoreactivity between cortical regions of rapid autopsy normal and Alzheimer's disease brain

Involvement of the interleukin-6 receptor complex (IL-6RC) in neuroregulatory and immunological processes of the brain and particularly in Alzheimer's disease (AD) has been hypothesized. The functionally active IL-6RC consists of the cytokine IL-6, which acts through the ligand binding IL-6R and the signal transducing gp130. Using a new immunocytochemical protocol on rapid autopsy cryostat brain sections we studied the expression of the IL-6RC in Braak IV-V staged AD patients compared to normal age-matched controls (HC) across five different cortical regions. Inter-rater reliability of the method was high. The "baseline" expression in normal human brain was determined for IL-6,IL-6R and gp130 in all cortical regions. In normal tissue IL-6 expression was lower in parietal cortex. Higher IL-6R expression was shown in frontal, occipital and parietal cortex, lower expression in temporal cortex and cerebellum. In AD IL-6 expression levels were generally increased in parietal cortex and decreased in occipital cortex compared to controls. IL-6R expression levels were strongly increased in AD frontal and occipital cortex and decreased in temporal cortex and cerebellum. Our findings indicate an altered cortical immunoreactivity pattern of the functional IL-6RC in AD supporting the hypothesis of a disease-related role of IL-6 in AD pathophysiology.

Altered cytokine and acute phase response protein levels in the blood of children with Downs syndrome: relationship with dementia of Alzheimer's type

Downs syndrome (DS) subjects are at high risk of developing Alzheimer's disease (AD). Patients with AD often show altered levels of some immune molecules in their peripheral blood which correlate with cognitive impairment. However, whether the altered peripheral immune phenotype is a late and secondary phenomenon associated with dementia or an early impairment linked to mechanisms controlling neurodegeneration of the central nervous system (CNS) is still an unanswered question. Here we studied immune molecules in the blood of non demented children with DS to investigate whether altered peripheral immune phenotype could be present in these subjects without dementia, many years before the presentation of clinical signs of cognitive deterioration. Plasma levels of interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) were significantly higher in DS than in control children. Plasma levels of soluble intercellular adhesion molecule-3 (sICAM-3), soluble vascular cell adhesion molecule-1 (sVCAM-1) and C reactive protein (CRP) were also increased in DS. The increase of IL-6 and CRP from DS children was similar to that found in elderly patients with clinical AD. Peripheral altered immune phenotype in healthy young subjects with DS might be an early sign of CNS alterations leading many years later to cognitive deterioration and dementia.

Genetic studies of A2M and BACE1 genes in Chinese Han Alzheimer??s disease patients

We investigated insertion (Ins)/deletion(Del) polymorphism in alpha-2-macroglobulin (A2M), G/C variant in the beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and apolipoprotein E (APOE) gene epsilon2/epsilon3/epsilon4 polymorphism in 387 Chinese Han ethnic patients with Alzheimer's disease and healthy study participants. After stratification for APOEepsilon4 status, only the BACE1-G allele with APOEepsilon4 was significantly associated with Alzheimer's disease. Through meta-analysis of the Del or G allele by pooling Asian studies, only BACE1-G allele appeared to increase risk of developing Alzheimer's disease. Through combination-analysis of the data about the A2M-I/D and the A2M-Ile1000Val variants, the A2M gene was suggested to be associated with Alzheimer's disease.

Genotypes and haplotypes in the IL-1 gene cluster: analysis of two genetically and diagnostically distinct groups of Alzheimer patients

Increased risk of Alzheimer's disease (AD) has been associated with polymorphisms in the IL-1 gene cluster, and in particular with the IL-1alpha-889 T/T genotype. However, this association is still unclear, and needs further investigation. In order to clarify the role of these polymorphisms in the complex pathogenesis of AD we examined genotype and haplotype frequencies of the two C-to-T SNPs at position -889 and -551 in the IL-1alpha and IL-1beta genes, respectively, and of the 86 bp VNTR intron-2 polymorphisms in the IL-1Ra gene. The analysis was performed in two genetically and diagnostically distinct groups of sporadic AD from Italy and the USA. In the Italian group a significant association between the IL-1alpha-889 T/T genotype and AD (OR=3.022, 95% CI: 1.001-9.119) was found, whereas no difference was found in the group from the USA. Results were also compared with previously published studies that analyzed the same IL-1 polymorphisms in AD. In both groups, the analysis of the estimated haplotypes shows that AD patients and controls who carry the IL-1beta-511 C allele, were also more frequently carriers of the IL-1Ra 1 allele (haplotypes -C-1). The total frequency of the two -C-1 haplotypes (C-C-1 plus T-C-1) was about one half of the total frequency of the eight estimated haplotypes. This was confirmed by significant linkage disequilibrium between these two loci in both the Italian and USA groups. In the Italian group a weak association of the T-C-2 haplotype with the disease (OR=1.648, 95% CI: 1.519-1.788) was also found, whereas in the USA group no difference was found. Although ours and other published data on different samples of Caucasian and non-Caucasian AD show a great heterogeneity in the frequencies of the IL-1alpha-889, the IL-1beta-511 and the IL-1Ra VNTR gene polymorphisms, we confirm the role of the IL-1alpha-889 T/T genotype as a risk factor for sporadic AD, and show the presence of an allelic association between IL-1beta C and IL-1Ra 1 alleles in both the Italian and the USA groups, confirmed by the presence of significant levels of linkage disequilibrium between these two loci.

Chronic interleukin-6 exposure alters metabotropic glutamate receptor-activated calcium signalling in cerebellar Purkinje neurons

Chronic central nervous system expression of the cytokine interleukin-6 (IL-6) is thought to contribute to the histopathological, pathophysiological, and cognitive deficits associated with various neurological disorders. However, the effects of chronic IL-6 expression on neuronal function are largely unknown. Previous studies have shown that chronic IL-6 exposure alters intrinsic electrophysiological properties and intracellular Ca2+ signalling evoked by ionotropic glutamate receptor activation in cerebellar Purkinje neurons. In the current study, using primary cultures of rat cerebellum, we investigated the effects of chronic IL-6 exposure on metabotropic glutamate receptor (mGluR)-activated Ca2+ signalling and release from intracellular Ca2+ stores. Chronic exposure (6-10 days) of Purkinje neurons to 500 units/mL IL-6 resulted in elevated resting Ca2+ levels and increased intracellular Ca2+ signals evoked by the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) compared to untreated control neurons. Chronic IL-6 treatment also augmented Ca2+ signals evoked by brief 100 mm K+ depolarization, although to a lesser degree than responses evoked by DHPG. Depleting intracellular Ca2+ stores with sarcoplasmic-endoplasmic reticulum ATPase inhibitors (thapsigargin or cyclopiazonic acid) or blocking ryanodine receptor-dependent release from intracellular stores (using ryanodine) resulted in a greater reduction of DHPG- and K+-evoked Ca2+ signals in chronic IL-6-treated neurons than in control neurons. The present data show that chronic exposure to elevated levels of IL-6, such as occurs in various neurological diseases, alters Ca2+ signalling involving release from intracellular stores. The results support the hypothesis that chronic IL-6 exposure disrupts neuronal function and thereby may contribute to the pathophysiology associated with many neurological diseases.

Cholesterol at the crossroads: Alzheimer's disease and lipid metabolism

Alzheimer's Disease (AD) is a devastating disease that affects millions of elderly persons. Despite years of intense investigations, genetic risk factors that affect the majority of AD cases have yet to be determined. Recent studies suggest that cholesterol metabolism has integral part in AD pathogenesis, suggesting that genes that regulate lipid metabolism may also play roles in AD. This review will first describe emerging evidence that links cholesterol to the mechanisms thought to underlie AD. Based on this rationale, candidate genes located in regions implicated in AD that have roles in lipid metabolism will then be discussed.