Correlation of cytokine secretion by mononuclear cells of Alzheimer patients and their disease stage

A meta-analysis of bulk RNA-seq datasets identifies potential biomarkers and repurposable therapeutics against Alzheimer's disease

Alzheimer's disease (AD) poses a major challenge due to its impact on the elderly population and the lack of effective early diagnosis and treatment options. In an effort to address this issue, a study focused on identifying potential biomarkers and therapeutic agents for AD was carried out. Using RNA-Seq data from AD patients and healthy individuals, 12 differentially expressed genes (DEGs) were identified, with 9 expressing upregulation (ISG15, HRNR, MTATP8P1, MTCO3P12, DTHD1, DCX, ST8SIA2, NNAT, and PCDH11Y) and 3 expressing downregulation (LTF, XIST, and TTR). Among them, TTR exhibited the lowest gene expression profile. Interestingly, functional analysis tied TTR to amyloid fiber formation and neutrophil degranulation through enrichment analysis. These findings suggested the potential of TTR as a diagnostic biomarker for AD. Additionally, druggability analysis revealed that the FDA-approved drug Levothyroxine might be effective against the Transthyretin protein encoded by the TTR gene. Molecular docking and dynamics simulation studies of Levothyroxine and Transthyretin suggested that this drug could be repurposed to treat AD. However, additional studies using in vitro and in vivo models are necessary before these findings can be applied in clinical applications.

β-Amyloid peptide modulates peripheral immune responses and neuroinflammation in rats

Alzheimer's disease (AD) is characterized by immune system dysregulation, impacting both central and peripheral immune responses. The study aimed to investigate the mechanism behind the neurotoxic effects of β-amyloid (Aβ) peptide in the rat brain including the study of neuroinflammation, neurodegeneration, and alterations in peripheral immune responses (PIR). The neuroinflammation brought on by Aβ1-42 and is unknown to influence PIR. Animal models were prepared, after 28 days, control, sham, and treated rats were anaesthetized and inflammatory markers of hippocampus and serum levels (reactive oxygen species, nitrite, tumor necrosis factor-α, and interleukin-1β), and some markers of PIR (splenic mononuclear cells or MNC, cytotoxicity and phagocytic index of the white blood cells leukocyte adhesion inhibition index or LAI), as well as polymorphonuclear cells of the spleen, were assessed. In addition to changes in peripheral immune responses, the present study found that AD rats had higher blood levels of inflammatory markers. Based on the study, the immune system irregularities observed in AD rats in the peripheral regions might be connected to neuroinflammation, which is facilitated by a compromised blood-brain barrier. Hence, it is viable to propose that the neuroinflammatory condition in rats with Aβ-induced AD could modify immune responses in the peripheral areas with significantly higher levels of inflammatory cytokines markers in the hippocampal tissue in Aβ-injected AD rats.

A glance through the effects of CD4+ T cells, CD8+ T cells, and cytokines on Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Unfortunately, despite numerous studies, an effective treatment for AD has not yet been established. There is remarkable evidence indicating that the innate immune mechanism and adaptive immune response play significant roles in the pathogenesis of AD. Several studies have reported changes in CD8+ and CD4+ T cells in AD patients. This mini-review article discusses the potential contribution of CD4+ and CD8+ T cells reactivity to amyloid β (Aβ) protein in individuals with AD. Moreover, this mini-review examines the potential associations between T cells, heme oxygenase (HO), and impaired mitochondria in the context of AD. While current mathematical models of AD have not extensively addressed the inclusion of CD4+ and CD8+ T cells, there exist models that can be extended to consider AD as an autoimmune disease involving these T cell types. Additionally, the mini-review covers recent research that has investigated the utilization of machine learning models, considering the impact of CD4+ and CD8+ T cells.

Vitamin D and inflammatory cytokines association in mild cognitive impaired subjects

BACKGROUND

Mild cognitive impairment (MCI) is a prodromal stage of Alzheimer's disease (AD). The association of low Vitamin D and chronic inflammation in the onset of cognitive decline in the elderly population has been established but the variable population-based study is still lacking.

METHODOLOGY

The present study aims to investigate the level of plasma Vitamin D, pro-inflammatory cytokines IL-1β, IL-6, TNF-α, cognitive performance, and white matter changes in the elderly population in the North-Eastern part of Uttar Pradesh, India.

RESULTS

70 participants with (Mean age- 75.14 ± 1.24, Male/Female- 50/20) with an Mini Mental State Examination (MMSE) score of (24.82 ± 1.82) and Montreal Cognitive Assessment Test (MOCA) score (21.83 ± 1.75), were cognitive decline, against the 70 healthy controls (Mean Age-73.18 ± 1.43; Male/Female- 50/20) with MMSE score (28.1 ± 1.5) and MOCA (28.5 ± 1.65), White matter variable Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) values in MCI subject was found significantly altered in Right temporal lobe, Corpus Callosum (Right) and Hippocampus body (Right), Hippocampus body (left), Hippocampus head (Right) and Hippocampus head (Left)as compared with healthy controls. The level of cytokines IL-1β, IL-6, TNF-α, was significantly high in MCI subjects as compared with controls. Further lower Vitamin D level in plasma was detected in MCI as compared with healthy controls.

CONCLUSION

The result from the present study depicts that chronic inflammation and lower Vitamin D level influences neurodegeneration and decline in cognitive performance in the elderly population. These variables can be used as biomarkers for early identification of AD and interventional strategies can be designed for prevention at the prodromal stage of AD.

Astrocytic interleukin-3 programs microglia and limits Alzheimer's disease

Communication within the glial cell ecosystem is essential for neuronal and brain health1-3. The influence of glial cells on the accumulation and clearance of β-amyloid (Aβ) and neurofibrillary tau in the brains of individuals with Alzheimer's disease (AD) is poorly understood, despite growing awareness that these are therapeutically important interactions4,5. Here we show, in humans and mice, that astrocyte-sourced interleukin-3 (IL-3) programs microglia to ameliorate the pathology of AD. Upon recognition of Aβ deposits, microglia increase their expression of IL-3Rα-the specific receptor for IL-3 (also known as CD123)-making them responsive to IL-3. Astrocytes constitutively produce IL-3, which elicits transcriptional, morphological, and functional programming of microglia to endow them with an acute immune response program, enhanced motility, and the capacity to cluster and clear aggregates of Aβ and tau. These changes restrict AD pathology and cognitive decline. Our findings identify IL-3 as a key mediator of astrocyte-microglia cross-talk and a node for therapeutic intervention in AD.

Friend, Foe or Both? Immune Activity in Alzheimer's Disease

Alzheimer's disease (AD) is marked by the presence of amyloid beta (Aβ) plaques, neurofibrillary tangles (NFT), neuronal death and synaptic loss, and inflammation in the brain. AD research has, in large part, been dedicated to the understanding of Aβ and NFT deposition as well as to the pharmacological reduction of these hallmarks. However, recent GWAS data indicates neuroinflammation plays a critical role in AD development, thereby redirecting research efforts toward unveiling the complexities of AD-associated neuroinflammation. It is clear that the innate immune system is intimately associated with AD progression, however, the specific roles of glia and neuroinflammation in AD pathology remain to be described. Moreover, inflammatory processes have largely been painted as detrimental to AD pathology, when in fact, many immune mechanisms such as phagocytosis aid in the reduction of AD pathologies. In this review, we aim to outline the delicate balance between the beneficial and detrimental aspects of immune activation in AD as a more thorough understanding of these processes is critical to development of effective therapeutics for AD.

CREB signals as PBMC-based biomarkers of cognitive dysfunction: A novel perspective of the brain-immune axis

To date, there is no reliable biomarker for the assessment or determination of cognitive dysfunction in Alzheimer's disease and related dementia. Such a biomarker would not only aid in diagnostics, but could also serve as a measure of therapeutic efficacy. It is widely acknowledged that the hallmarks of Alzheimer's disease, namely, amyloid deposits and neurofibrillary tangles, as well as their precursors and metabolites, are poorly correlated with cognitive function and disease stage and thus have low diagnostic or prognostic value. A lack of biomarkers is one of the major roadblocks in diagnosing the disease and in assessing the efficacy of potential therapies. The phosphorylation of cAMP Response Element Binding protein (pCREB) plays a major role in memory acquisition and consolidation. In the brain, CREB activation by phosphorylation at Ser133 and the recruitment of transcription cofactors such as CREB binding protein (CBP) is a critical step for the formation of memory. This set of processes is a prerequisite for the transcription of genes thought to be important for synaptic plasticity, such as Egr-1. Interestingly, recent work suggests that the expression of pCREB in peripheral blood mononuclear cells (PBMC) positively correlates with pCREB expression in the postmortem brain of Alzheimer's patients, suggesting not only that pCREB expression in PBMC might serve as a biomarker of cognitive dysfunction, but also that the dysfunction of CREB signaling may not be limited to the brain in AD, and that a link may exist between the regulation of CREB in the blood and in the brain. In this review we consider the evidence suggesting a correlation between the level of CREB signals in the brain and blood, the current knowledge about CREB in PBMC and its association with CREB in the brain, and the implications and mechanisms for a neuro-immune cross talk that may underlie this communication. This Review will discuss the possibility that peripheral dysregulation of CREB is an early event in AD pathogenesis, perhaps as a facet of immune system dysfunction, and that this impairment in peripheral CREB signaling modifies CREB signaling in the brain, thus exacerbating cognitive decline in AD. A more thorough understanding of systemic dysregulation of CREB in AD will facilitate the search for a biomarker of cognitive function in AD, and also aid in the understanding of the mechanisms underlying cognitive decline in AD.

Women's Pregnancy Life History and Alzheimer's Risk: Can Immunoregulation Explain the Link?

BACKGROUND

Pregnancy is associated with improvement in immunoregulation that persists into the geriatric phase. Impaired immunoregulation is implicated in Alzheimer's disease (AD) pathogenesis. Hence, we investigate the relationship between pregnancy and AD.

METHODS

Cross-sectional cohort of British women (N = 95). Cox proportional hazards modeling assessed the putative effects of cumulative months pregnant on AD risk and the mutually adjusted effects of counts of first and third trimesters on AD risk.

RESULTS

Cumulative number of months pregnant, was associated with lower AD risk (β = -1.90, exp(β) = 0.15, P = .02). Cumulative number of first trimesters was associated with lower AD risk after adjusting for third trimesters (β = -3.83, exp(β) = 0.02, P < .01), while the latter predictor had no significant effect after adjusting for the former.

CONCLUSIONS

Our observation that first trimesters (but not third trimesters) conferred protection against AD is more consistent with immunologic effects, which are driven by early gestation, than estrogenic exposures, which are greatest in late gestation. Results may justify future studies with immune biomarkers.

Etoricoxib inhibits peripheral inflammation and alters immune responses in intracerebroventricular colchicine injected rats

The present study was designed to investigate the effectiveness of etoricoxib induced inhibition of neuroinflammation by studying the peripheral inflammatory markers and select immune parameters in intracerebroventricular colchicine injected rats (ICIR). Results showed time dependent upregulation of the inflammatory markers in the serum along with alterations of peripheral immune parameters in ICIR and dose-dependent recovery was observed upon administration of etoricoxib to ICIR; most of these effects were greater with the longer duration of study. The present study indicates that colchicine induced neuroinflammation may cause systemic inflammation and alteration of immune responses which are mediated by increased cox- 2 activity.

Acetyl Cholinesterase Inhibitors and Cell-Derived Peripheral Inflammatory Cytokines in Early Stages of Alzheimer's Disease

BACKGROUND

Clinical and preclinical studies firmly support the involvement of the inflammation in the pathogenesis of Alzheimer's disease (AD). Despite acetylcholinesterase inhibitors (AChEI) being widely used in AD patients, there is no conclusive evidence about their impact on the inflammatory response.

METHODS

This study investigates peripheral proinflammatory cytokines (interferon gamma [IFN-γ], tumor necrosis factor alpha [TNF-α], and interleukins 1β [IL-1β] and 6 [IL-6]) by firstly comparing peripheral blood mononuclear cell (PBMC)-derived secretion in drug-naïve and AChEI-treated AD patients versus healthy controls. A subset of those drug-naïve AD patients, who were prescribed the AChEI donepezil, was followed-up for 6 months to investigate if donepezil suppresses proinflammatory cell-derived cytokine secretion.

RESULTS

Patients with AD showed higher levels of PBMC-derived proinflammatory cytokines (IFN-γ, TNF-α, IL-1β, and IL-6) in comparison with healthy controls. On reexamination, previously drug-naïve AD patients who received donepezil treatment for 6 months displayed a decrease in cell-derived IFN-γ, TNF-α, IL-1β, and IL-6.

CONCLUSIONS

Proinflammatory PBMC-derived cytokines were increased in patients with AD in comparison with healthy controls and donepezil-reduced proinflammatory cytokines when examining drug-naïve AD patients before and after AChEI treatment.

PDGF/PDGFR axis in the neural systems

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) are expressed in several cell types including the brain cells such as neuronal progenitors, neurons, astrocytes, and oligodendrocytes. Emerging evidence shows that PDGF-mediated signaling regulates diverse functions in the central nervous system (CNS) such as neurogenesis, cell survival, synaptogenesis, modulation of ligand-gated ion channels, and development of specific types of neurons. Interestingly, PDGF/PDFGR signaling can elicit paradoxical roles in the CNS, depending on the cell type and the activation stimuli and is implicated in the pathogenesis of various neurodegenerative diseases. This review summarizes the role of PDGFs/PDGFRs in several neurodegenerative diseases such as Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, brain cancer, cerebral ischemia, HIV-1 and drug abuse. Understanding PDGF/PDGFR signaling may lead to novel approaches for the future development of therapeutic strategies for combating CNS pathologies.

The role of astrocytes in amyloid production and Alzheimer's disease

Alzheimer's disease (AD) is marked by the presence of extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs) and gliosis, activated glial cells, in the brain. It is thought that Aβ plaques trigger NFT formation, neuronal cell death, neuroinflammation and gliosis and, ultimately, cognitive impairment. There are increased numbers of reactive astrocytes in AD, which surround amyloid plaques and secrete proinflammatory factors and can phagocytize and break down Aβ. It was thought that neuronal cells were the major source of Aβ. However, mounting evidence suggests that astrocytes may play an additional role in AD by secreting significant quantities of Aβ and contributing to overall amyloid burden in the brain. Astrocytes are the most numerous cell type in the brain, and therefore even minor quantities of amyloid secretion from individual astrocytes could prove to be substantial when taken across the whole brain. Reactive astrocytes have increased levels of the three necessary components for Aβ production: amyloid precursor protein, β-secretase (BACE1) and γ-secretase. The identification of environmental factors, such as neuroinflammation, that promote astrocytic Aβ production, could redefine how we think about developing therapeutics for AD.

Interferon Gamma: Influence on Neural Stem Cell Function in Neurodegenerative and Neuroinflammatory Disease

Interferon-gamma (IFNγ), a pleiotropic cytokine, is expressed in diverse neurodegenerative and neuroinflammatory conditions. Its protective mechanisms are well documented during viral infections in the brain, where IFNγ mediates non-cytolytic viral control in infected neurons. However, IFNγ also plays both protective and pathological roles in other central nervous system (CNS) diseases. Of the many neural cells that respond to IFNγ, neural stem/progenitor cells (NSPCs), the only pluripotent cells in the developing and adult brain, are often altered during CNS insults. Recent studies highlight the complex effects of IFNγ on NSPC activity in neurodegenerative diseases. However, the mechanisms that mediate these effects, and the eventual outcomes for the host, are still being explored. Here, we review the effects of IFNγ on NSPC activity during different pathological insults. An improved understanding of the role of IFNγ would provide insight into the impact of immune responses on the progression and resolution of neurodegenerative diseases.

Cytokines and Cytokine Receptors Involved in the Pathogenesis of Alzheimer's Disease

Inflammatory mechanisms are implicated in the pathology of Alzheimer's disease (AD). However, it is unclear whether inflammatory alterations are a cause or consequence of neurodegeneration leading to dementia. Clarifying this issue would provide valuable insight into the early diagnosis and therapeutic management of AD. To address this, we compared the mRNA expression profiles of cytokines in the brains of AD patients with "non-demented individuals with AD pathology" and non-demented healthy control (ND) individuals. "Non-demented individuals with AD pathology" are referred to as high pathology control (HPC) individuals that are considered an intermediate subset between AD and ND. HPC represents a transition between normal aging and early stage of AD, and therefore, is useful for determining whether neuroinflammation is a cause or consequence of AD pathology. We observed that immunological conditions that produce cytokines in the HPC brain were more representative of ND than AD. To validate these result, we investigated the expression of inflammatory mediators at the protein level in postmortem brain tissues. We examined the protein expression of tumor necrosis factor (TNF)α and its receptors (TNFRs) in the brains of AD, HPC, and ND individuals. We found differences in soluble TNFα and TNFRs expression between AD and ND groups and between AD and HPC groups. Expression in the temporal cortex was lower in the AD brains than HPC and ND. Our findings indicate that alterations in immunological conditions involving TNFR-mediated signaling are not the primary events initiating AD pathology, such as amyloid plaques and tangle formation. These may be early events occurring along with synaptic and neuronal changes or later events caused by these changes. In this review, we emphasize that elucidating the temporal expression of TNFα signaling molecules during AD is important to understand the selective tuning of these pathways required to develop effective therapeutic strategies for AD.

Impairment of blood brain barrier is related with the neuroinflammation induced peripheral immune status in intracerebroventricular colchicine injected rats: An experimental study with mannitol

The neurodegeneration in AD patients may be associated with changes of peripheral immune responses. Some peripheral immune responses are altered due to neuroinflammation in colchicine induced AD (cAD) rats. The leaky blood brain barrier (BBB) in cAD-rats may be involved in inducing peripheral inflammation, though there is no report in this regard. Therefore, the present study was designed to investigate the role of BBB in cADrats by altering the BBB in a time dependent manner with injection (i.v.) of mannitol (BBB opener). The inflammatory markers in the brain and serum along with the peripheral immune responses were measured after 30 and 60min of mannitol injection in cAD rats. The results showed higher inflammatory markers in the hippocampus and serum along with alterations in peripheral immune parameters in cAD rats. Although the hippocampal inflammatory markers did not further change after mannitol injection in cAD rats, the serum inflammatory markers and peripheral immune responses were altered and these changes were greater after 60min than that of 30min of mannitol injection. The present study shows that the peripheral immune responses in cAD rats after 30 and 60min of mannitol injection are related to magnitude of impairment of BBB in these conditions. It can be concluded from this study that impairment of BBB in cAD rats is related to the changes of peripheral immune responses observed in that condition.

Cerebrospinal fluid inflammatory markers in amnestic mild cognitive impairment

AIMS

Inflammatory processes might play a significant role at the pathophysiology of Alzheimer's disease (AD). Neuroinflammation is characterized by activation of microglia and the release of inflammatory cytokines, such as interleukin (IL)-1β, IL-6 and tumor necrosis factor-α. Although, it is unknown what the real contribution of these inflammatory markers in the development of AD is. The purpose of the present study was to assess the possible relationship between inflammatory markers in the cerebrospinal fluid (CSF) of amnestic mild cognitive impairment patients (aMCI), aged 60 years or older, and compare with aged healthy controls.

METHODS

We examined concentrations of IL-1β, IL-6 and tumor necrosis factor-α in the CSF of aMCI patients and controls by enzyme immunoassay. aMCI diagnoses were based on anamnesis and Petersen criteria, corroborated by the Clinical Dementia Rating. Cognitive function was assessed by neuropsychological tests.

RESULTS

CSF levels of IL-1β (13.735 vs 22.932 pg/mL; P < 0.001) and tumor necrosis factor-α (1.913 vs 2.627 pg/mL; P = 0.002), but not IL-6 (4.178 vs 5.689 pg/mL; P = 0.106), were significantly reduced in the aMCI samples as compared with controls. Individuals with IL-1β < 17 pg/mL were at a 7.2 (CI 1.5-36; P: 0.016) increased odds of aMCI. There was a positive correlation between IL-1β levels and the Consortium to Establish a Registry for Alzheimer's Disease word list score (r_s  = 0.299; P = 0.046). Linear regression analysis showed that IL-1β levels might explain 13.7% (β = 24.545; P = 0.012) of the variance on this Consortium to Establish a Registry for Alzheimer's Disease subscore.

CONCLUSION

The present results show a pattern of cytokines expression in the CSF of aMCI patients that might be relevant to the pathogeny of prodromal AD. Geriatr Gerontol Int 2017; 17: 239-245.

Multiplex analyte assays to characterize different dementias: brain inflammatory cytokines in poststroke and other dementias

Both the inflammatory potential and cognitive function decline during aging. The association between the repertoire of inflammatory biomarkers and cognitive decline is unclear. Inflammatory cytokines have been reported to be increased, decreased, or unchanged in the cerebrospinal fluid and sera of subjects with dementia. We assessed 112 postmortem brains from subjects diagnosed with poststroke dementia (PSD), vascular dementia, mixed dementia, and Alzheimer's disease (AD), comparing those to poststroke nondemented (PSND) subjects and age-matched controls. We analyzed 5 brain regions including the gray and white matter from the frontal and temporal lobes for a panel of cytokine and/or chemokine analytes using multiplex-array assays. Of the 37 analytes, 14 were under or near the detection limits, 7 were close to the lowest detection level, and 16 cytokines were within the linear range of the assay. We observed widely variable concentrations of C-reactive protein (CRP) and serum amyloid A at the high end (1-150 ng/mg protein), whereas several of the interleukins (IL, interferon-gamma and tumor necrosis factor) at the low end (1-10 pg/mg). There were also regional variations; most notable being high concentrations of some cytokines (e.g., CRP and angiogenesis panel) in the frontal white matter. Overall, we found decreased concentrations of several cytokines, including IL-1 beta (p = 0.000), IL-6 (p = 0.000), IL-7 (p = 0.000), IL-8 (p = 0.000), IL-16 (p = 0.001), interferon-inducible protein-10 (0.044), serum amyloid A (p = 0.011), and a trend in IL-1 alpha (p = 0.084) across all dementia groups compared to nondemented controls. IL-6 and IL-8 were significantly lower in dementia subjects than in nondemented subjects in every region. In particular, lower levels of IL-6 and IL-8 were notable in the PSD compared to PSND subjects. Because these 2 stroke groups had comparable degree of vascular pathology, the lower production of IL-6 and IL-8 in PSD reaffirms a possible specific involvement of immunosenescence in dementia pathogenesis. In contrast, CRP was not altered between dementia and nondementia subjects or between PSD and PSND. Our study provides evidence not only for the feasibility of tracking cytokines in postmortem brain tissue but also suggests differentially impaired inflammatory mechanisms underlying dementia including AD. There was a diminished inflammatory response, possibly reflecting immunosenescence and cerebral atrophy, in all dementias. Strategies to enhance anti-inflammatory cytokines and boost the immune system of the brain may be beneficial for preventing cognitive dysfunction, especially after stroke.

Effects of naproxen on immune responses in a colchicine-induced rat model of Alzheimer's disease

BACKGROUND

The components of the immune system have been indicated to be linked with the neurotoxicity in Alzheimer's disease (AD). The participation of the immune system in the neurodegeneration in a rat model of colchicine-induced AD has not been explored.

METHODS

In the present study, hippocampal neurodegeneration along with reactive oxygen species (ROS), nitrite and TNF-α in the hippocampus and some systemic immune responses were measured after 15 and 21 days of intracerebroventricular colchicine injection in rats and again after oral administration of different doses of the anti-inflammatory drug naproxen in AD rats.

RESULTS

Chromatolysis and amyloid plaques were found along with higher ROS, nitrite and TNF-α levels in the hippocampus of colchicine-induced AD rats, and these changes were prevented by naproxen in a dose-dependent manner. Alterations in immunological parameters [increased phagocytic activity of white blood cells and splenic polymorphonuclear cells (PMN), increased cytotoxicity and decreased leucocyte adhesive inhibition index (LAI) of splenic mononuclear cells (MNC)] were also observed in colchicine-injected rats, which showed a dose-dependent recovery after oral administration of naproxen in AD rats. The number of plaques, chromatolysis of Nissl granules, TNF-α, nitrite and ROS levels in the hippocampus, phagocytic activity of splenic PMN and LAI of splenic MNC in AD rats showed greater changes in the 21- than in the 15-day study, and the recovery of these parameters after administration of naproxen differed between the two study durations.

CONCLUSION

The present study shows that colchicine-induced neurodegeneration is time dependent and mediated by cyclooxygenase-induced neuroinflammation, which is reflected in the systemic immunological responses.

Immunological functioning in Alzheimer's disease: differential effects of relative left versus right temporoparietal dysfunction

The cerebral hemispheres are differentially involved in regulating immunological functioning and the neuropathology associated with Alzheimer's disease (AD) is asymmetrical. Thus, subgroups of AD patients may exhibit different patterns of immunological dysfunction. We explored this possibility in a group of AD patients and found that patients with low white blood cell counts and low lymphocyte numbers exhibited better performance on tests of right temporoparietal functioning. Also, a significant positive relationship exists between lymph numbers and performance on a test of left temporoparietal functioning. Thus, some AD patients have greater immunological dysfunction based on relative left versus right temporoparietal functioning.

Hygiene and the world distribution of Alzheimer's disease: Epidemiological evidence for a relationship between microbial environment and age-adjusted disease burden

People living in sanitized environments may be at greater Alzheimer's risk. We compare Alzheimer's rates in different countries in light of countries' historical and contemporary pathogen prevalence, sanitation, and urbanization. We find that countries that are less urbanized, with more pathogens and lower degree of sanitation have lower Alzheimer's rates.

Background and objectives: Alzheimer’s disease (AD) shares certain etiological features with autoimmunity. Prevalence of autoimmunity varies between populations in accordance with variation in environmental microbial diversity. Exposure to microorganisms may improve individuals’ immunoregulation in ways that protect against autoimmunity, and we suggest that this may also be the case for AD. Here, we investigate whether differences in microbial diversity can explain patterns of age-adjusted AD rates between countries.

Methodology: We use regression models to test whether pathogen prevalence, as a proxy for microbial diversity, across 192 countries can explain a significant amount of the variation in age-standardized AD disability-adjusted life-year (DALY) rates. We also review and assess the relationship between pathogen prevalence and AD rates in different world populations.

Results: Based on our analyses, it appears that hygiene is positively associated with AD risk. Countries with greater degree of sanitation and lower degree of pathogen prevalence have higher age-adjusted AD DALY rates. Countries with greater degree of urbanization and wealth exhibit higher age-adjusted AD DALY rates.

Conclusions and implications: Variation in hygiene may partly explain global patterns in AD rates. Microorganism exposure may be inversely related to AD risk. These results may help predict AD burden in developing countries where microbial diversity is rapidly diminishing. Epidemiological forecasting is important for preparing for future healthcare needs and research prioritization.

Chronic neuron- and age-selective down-regulation of TNF receptor expression in triple-transgenic Alzheimer disease mice leads to significant modulation of amyloid- and Tau-related pathologies

Neuroinflammation, through production of proinflammatory molecules and activated glial cells, is implicated in Alzheimer's disease (AD) pathogenesis. One such proinflammatory mediator is tumor necrosis factor α (TNF-α), a multifunctional cytokine produced in excess and associated with amyloid β-driven inflammation and cognitive decline. Long-term global inhibition of TNF receptor type I (TNF-RI) and TNF-RII signaling without cell or stage specificity in triple-transgenic AD mice exacerbates hallmark amyloid and neurofibrillary tangle pathology. These observations revealed that long-term pan anti-TNF-α inhibition accelerates disease, cautions against long-term use of anti-TNF-α therapeutics for AD, and urges more selective regulation of TNF signaling. We used adeno-associated virus vector-delivered siRNAs to selectively knock down neuronal TNF-R signaling. We demonstrate divergent roles for neuronal TNF-RI and TNF-RII where loss of opposing TNF-RII leads to TNF-RI-mediated exacerbation of amyloid β and Tau pathology in aged triple-transgenic AD mice. Dampening of TNF-RII or TNF-RI+RII leads to a stage-independent increase in Iba-1-positive microglial staining, implying that neuronal TNF-RII may act nonautonomously on the microglial cell population. These results reveal that TNF-R signaling is complex, and it is unlikely that all cells and both receptors will respond positively to broad anti-TNF-α treatments at various stages of disease. In aggregate, these data further support the development of cell-, stage-, and/or receptor-specific anti-TNF-α therapeutics for AD.

Effects of non-steroidal anti-inflammatory drug treatments on cognitive decline vary by phase of pre-clinical Alzheimer disease: findings from the randomized controlled Alzheimer's Disease Anti-inflammatory Prevention Trial

OBJECTIVE

We examined the effects of non-steroidal anti-inflammatory drugs on cognitive decline as a function of phase of pre-clinical Alzheimer disease.

METHODS

Given recent findings that cognitive decline accelerates as clinical diagnosis is approached, we used rate of decline as a proxy for phase of pre-clinical Alzheimer disease. We fit growth mixture models of Modified Mini-Mental State (3MS) Examination trajectories with data from 2388 participants in the Alzheimer's Disease Anti-inflammatory Prevention Trial and included class-specific effects of naproxen and celecoxib.

RESULTS

We identified three classes: "no decline", "slow decline", and "fast decline", and examined the effects of celecoxib and naproxen on linear slope and rate of change by class. Inclusion of quadratic terms improved fit of the model (-2 log likelihood difference: 369.23; p < 0.001) but resulted in reversal of effects over time. Over 4 years, participants in the slow-decline class on placebo typically lost 6.6 3MS points, whereas those on naproxen lost 3.1 points (p-value for difference: 0.19). Participants in the fast-decline class on placebo typically lost 11.2 points, but those on celecoxib first declined and then gained points (p-value for difference from placebo: 0.04), whereas those on naproxen showed a typical decline of 24.9 points (p-value for difference from placebo: <0.0001).

CONCLUSIONS

Our results appeared statistically robust but provided some unexpected contrasts in effects of different treatments at different times. Naproxen may attenuate cognitive decline in slow decliners while accelerating decline in fast decliners. Celecoxib appeared to have similar effects at first but then attenuated change in fast decliners.

Ablation of TNF-RI/RII expression in Alzheimer's disease mice leads to an unexpected enhancement of pathology: implications for chronic pan-TNF-α suppressive therapeutic strategies in the brain

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by severe memory loss and cognitive impairment. Neuroinflammation, including the extensive production of pro-inflammatory molecules and the activation of microglia, has been implicated in the disease process. Tumor necrosis factor (TNF)-α, a prototypic pro-inflammatory cytokine, is elevated in AD, is neurotoxic, and colocalizes with amyloid plaques in AD animal models and human brains. We previously demonstrated that the expression of TNF-α is increased in AD mice at ages preceding the development of hallmark amyloid and tau pathological features and that long-term expression of this cytokine in these mice leads to marked neuronal death. Such observations suggest that TNF-α signaling promotes AD pathogenesis and that therapeutics suppressing this cytokine's activity may be beneficial. To dissect TNF-α receptor signaling requirements in AD, we generated triple-transgenic AD mice (3xTg-AD) lacking both TNF-α receptor 1 (TNF-RI) and 2 (TNF-RII), 3xTg-ADxTNF-RI/RII knock out, the cognate receptors of TNF-α. These mice exhibit enhanced amyloid and tau-related pathological features by the age of 15 months, in stark contrast to age-matched 3xTg-AD counterparts. Moreover, 3xTg-ADxTNF-RI/RII knock out-derived primary microglia reveal reduced amyloid-β phagocytic marker expression and phagocytosis activity, indicating that intact TNF-α receptor signaling is critical for microglial-mediated uptake of extracellular amyloid-β peptide pools. Overall, our results demonstrate that globally ablated TNF receptor signaling exacerbates pathogenesis and argues against long-term use of pan-anti-TNF-α inhibitors for the treatment of AD.

Presenilin 2 is the predominant γ-secretase in microglia and modulates cytokine release

Presenilin 1 (PS1) and Presenilin 2 (PS2) are the enzymatic component of the γ-secretase complex that cleaves amyloid precursor protein (APP) to release amyloid beta (Aβ) peptide. PS deficiency in mice results in neuroinflammation and neurodegeneration in the absence of accumulated Aβ. We hypothesize that PS influences neuroinflammation through its γ-secretase action in CNS innate immune cells. We exposed primary murine microglia to a pharmacological γ-secretase inhibitor which resulted in exaggerated release of TNFα and IL-6 in response to lipopolysaccharide. To determine if this response was mediated by PS1, PS2 or both we used shRNA to knockdown each PS in a murine microglia cell line. Knockdown of PS1 did not lead to decreased γ-secretase activity while PS2 knockdown caused markedly decreased γ-secretase activity. Augmented proinflammatory cytokine release was observed after knockdown of PS2 but not PS1. Proinflammatory stimuli increased microglial PS2 gene transcription and protein in vitro. This is the first demonstration that PS2 regulates CNS innate immunity. Taken together, our findings suggest that PS2 is the predominant γ-secretase in microglia and modulates release of proinflammatory cytokines. We propose PS2 may participate in a negative feedback loop regulating inflammatory behavior in microglia.

Systemic immune aberrations in Alzheimer's disease patients

The role of chronic inflammation in the pathogenesis of Alzheimer's disease (AD) has been implied in a plethora of studies. The objective of the present study was to evaluate the immune alterations and the immunological markers in patients suffering from AD. IL-1alpha, IL-2, IL-6, IL-8, IL-10, TNF-alpha cytokine and helper/inducer (CD4), suppressor/cytotoxic (CD8) T lymphocyte levels were investigated in patients with various degrees of cognitive impairment (mild-moderate and severe stage), as well as in age-matched non demented controls. Cytokines were measured using the ELISA immunoassay method and lymphocytes using flow cytometry. Results showed a significant TNF-alpha increase in patients of severe stage serum compared to controls as well as a significant decrease of CD4 lymphocyte subpopulation levels in patients of severe stage compared to those of mild-moderate stage patients and controls. No significant differences were observed on IL-1alpha, IL-2, IL-6, IL-8, IL-10 cytokine levels and on CD8, CD4/CD8 lymphocyte subpopulations levels between patients and controls neither between mild moderate and severe stage patients. CD4 lymphocyte subpopulation and cytokine IL-2 were revealed as having a significant relationship (positive and negative respectively) with the MMSE score of patients. Data suggest the existence of detectable changes of peripheral immune system in AD.

Neuroinflammation: implications for the pathogenesis and molecular diagnosis of Alzheimer's disease

During the past few years, an increasing set of evidence has supported the major role of deregulation of the interaction patterns between glial cells and neurons in the pathway toward neuronal degeneration. Neurons and glial cells, together with brain vessels, constitute an integrated system for brain function. Inflammation is a process related with the onset of several neurodegenerative disorders, including Alzheimer's disease (AD). Several hypotheses have been postulated to explain the pathogenesis of AD, but none provides insight into the early events that trigger metabolic and cellular alterations in neuronal degeneration. The amyloid hypothesis was sustained on the basis that Abeta-peptide deposition into senile plaques is responsible for neurodegeneration. However, recent findings point to Abeta oligomers as responsible for synaptic impairment in neuronal degeneration. Amyloid is only one among many other major factors affecting the quality of neuronal cells. Another explanation derives from the tau hypothesis, supported by the observations that tau hyperphosphorylations constitute a common feature of most of the altered signaling pathways in degenerating neurons. Altered tau patterns have been detected in the cerebrospinal fluids of AD patients, and a close correlation was observed between the levels of hyperphosphorylated tau isoforms and the degree of cognitive impairment. On the other hand, the anomalous effects of cytokines and trophic factors share in common the activation of tau hyperphosphorylation patterns. In this context, a neuroimmunological approach to AD becomes relevant. When glial cells that normally provide neurotrophic factors essential for neurogenesis are activated by a set of stressing events, they overproduce cytokines and NGF, thus triggering altered signaling patterns in the etiopathogenesis of AD. A solid set of discoveries has strengthened the idea that altered patterns in the glia-neuron interactions constitute early molecular events within the cascade of cellular signals that lead to neurodegeneration in AD. A direct correlation has been established between the Abeta-induced neurodegeneration and cytokine production and its subsequent release. In effect, neuroinflammation is responsible for an abnormal secretion of proinflammatory cytokines that trigger signaling pathways that activate brain tau hyperphosphorylation in residues that are not modified under normal physiological conditions. Other cytokines such as IL-3 and TNF-alpha seem to display neuroprotective activities. Elucidation of the events that control the transitions from neuroprotection to neurodegeneration should be a critical point toward elucidation of AD pathogenesis.

A proline-rich polypeptide complex (PRP) isolated from ovine colostrum. Modulation of H2O2 and cytokine induction in human leukocytes

A proline-rich polypeptide complex (PRP) has immunoregulatory properties and also shows beneficial effects in Alzheimer's disease (AD). It is known that the unregulated activation of microglial cells in AD may result in chronic inflammatory response. There is a link between the activation of immune cells on the periphery and in the central nervous system (CNS). Therefore, we studied the effect of the PRP on human peripheral blood mononuclear cells (PBMCs) stimulated by LPS with PHA (LP) or PMA as proinflammatory activators. PRP and its nonapeptide fragment (NP) inhibited by 40-60% production of H(2)O(2) induced by PMA. The peptides also inhibited activity of superoxide dismutase. Both peptide preparations showed differential effects on the secretion of cytokines. NP induced TNF-alpha only while PRP induced IL-6, IL-10 and TNF-alpha. On the other hand, the release of TNF-alpha and IL-10 induced by LP in PBMCs was inhibited by PRP while NP inhibited the release of IFN-gamma and IL-10. The results obtained showed that PRP may affect not only adaptive immunity but also innate immunity and thus may regulate secretions of mediators of inflammation. The regulatory effect of the PRP on the innate immunity may shed some light on understanding the beneficial effects of this polypeptide complex in AD patients.

Interferon-gamma and tumor necrosis factor-alpha regulate amyloid-beta plaque deposition and beta-secretase expression in Swedish mutant APP transgenic mice

Reactive astrocytes and microglia in Alzheimer's disease surround amyloid plaques and secrete proinflammatory cytokines that affect neuronal function. Relationship between cytokine signaling and amyloid-beta peptide (Abeta) accumulation is poorly understood. Thus, we generated a novel Swedish beta-amyloid precursor protein mutant (APP) transgenic mouse in which the interferon (IFN)-gamma receptor type I was knocked out (APP/GRKO). IFN-gamma signaling loss in the APP/GRKO mice reduced gliosis and amyloid plaques at 14 months of age. Aggregated Abeta induced IFN-gamma production from co-culture of astrocytes and microglia, and IFN-gamma elicited tumor necrosis factor (TNF)-alpha secretion in wild type (WT) but not GRKO microglia co-cultured with astrocytes. Both IFN-gamma and TNF-alpha enhanced Abeta production from APP-expressing astrocytes and cortical neurons. TNF-alpha directly stimulated beta-site APP-cleaving enzyme (BACE1) expression and enhanced beta-processing of APP in astrocytes. The numbers of reactive astrocytes expressing BACE1 were increased in APP compared with APP/GRKO mice in both cortex and hippocampus. IFN-gamma and TNF-alpha activation of WT microglia suppressed Abeta degradation, whereas GRKO microglia had no changes. These results support the idea that glial IFN-gamma and TNF-alpha enhance Abeta deposition through BACE1 expression and suppression of Abeta clearance. Taken together, these observations suggest that proinflammatory cytokines are directly linked to Alzheimer's disease pathogenesis.

Interleukin-2 inhibits NMDA receptor-mediated currents directly and may differentially affect subtypes

Using whole-cell patch-clamp recordings, this study investigated the effects of interleukin-2 (IL-2) on N-methyl-d-aspartate (NMDA) receptor-mediated currents (I(NMDA)) in rat cultured hippocampal neurons and human embryonic kidney (HEK) 293 cells expressing recombinant NMDA receptors. We found that IL-2 (0.01-1ng/ml) immediately and significantly decreased peak I(NMDA) in cultured neurons. Interestingly, the peak I(NMDA) induced in HEK 293 cells was also inhibited by IL-2. We also found that IL-2 differentially decreased the peak amplitudes of NR2A- and NR2B-containing NMDA receptor-mediated currents (I(NR2A) and I(NR2B)) by 54+/-5% and 30+/-4%, respectively. These results provide new evidence that IL-2 induces rapid inhibition of peak currents of NMDA receptor-mediated responses with possible NR1/NR2A and NR1/NR2B subtype-differentiation, and suggest that the inhibition is mediated by direct interaction between IL-2 and NMDA receptors.

Increased production of inflammatory cytokines in mild cognitive impairment

Recent studies indicate that chronic inflammation plays a pathogenic role in both the central nervous system (CNS) and periphery in Alzheimer's disease (AD). We have screened for cytokines differentially produced by peripheral blood mononuclear cells (PBMCs) isolated from subjects with mild cognitive impairment (MCI) and mild AD subjects who had progressed from MCI using a commercially available cytokine array. Following determination of expressed cytokines, we quantified levels of the proinflammatory cytokines TNF-alpha, IL-6, and IL-8, and the anti-inflammatory cytokine IL-10 using flow cytometry. We have found a significant increase in the levels of IL-6, IL-8, and IL-10 produced by PBMCs stimulated for 24 h with phytohemagglutinin (PHA) in MCI subjects compared to healthy elderly controls. However, in PBMCs stimulated for 48 h with lipopolysaccharide (LPS), lower TNF-alpha/IL-10, IL-6/IL-10, and IL-8/IL-10 ratios were seen in MCI subjects. There were no differences in plasma levels of IL-8 between aged controls, MCI, and mild AD, and the levels of circulating IL-6 and IL-10 were below detection limits. Our data indicate that changes in cytokine production by PBMCs may be detected early in MCI, and an alteration of the immune response may precede clinical AD.

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.

Expression and production of two selected beta-chemokines in peripheral blood mononuclear cells from patients with Alzheimer's disease

MCP-1 and RANTES are molecules that regulate monocyte and T-lymphocyte recruitment towards sites of inflammation. We sought to evaluate the role of these chemokines in Alzheimer's disease (AD), and the effect of acetylcholinesterase inhibitor (AchEI) therapy on their release from peripheral blood mononuclear cells (PBMC). MCP-1 and RANTES mRNA expressions were determined by RT-PCR and the amount of secreted chemokines was assayed using specific ELISA methods from purified PBMC from each AD patients (n = 40) at the time of enrolment (T0) and after 1 month of treatment with AchEI (T1) and from 20 healthy age and sex-matched subjects (HC). We found that expression and production of MCP-1 in AD patients was significantly lower than in HC subjects. After 1 month of therapy with AchEI (Donepezil), MCP-1 levels increased in each patient. However, higher levels were detected for RANTES in AD patients compared to control subjects and in AD patients treated with Donepezil. MCP-1 and RANTES have a compensatory role in balancing the impaired mechanisms involved in immune response during ageing. Our present findings suggest that these two chemokines are both involved in AD pathogenesis and might reflect different states of activation and/or responsiveness of PBMC from AD patients, contributing to the impaired of the peripheral immune system in these patients.

Diminished production of proinflammatory cytokines in patients with Alzheimer's disease

Cerebral inflammation as well as systemic immunological alterations have been reported in Alzheimer's disease (AD). We examined the production of the proinflammatory cytokines interleukin-6, interleukin-12, interferon-gamma, and tumor necrosis factor-alpha in whole blood cell cultures of AD patients and age-matched controls. The production of all measured cytokines after mitogen stimulation is significantly decreased in the AD group compared to controls. The results reflect an attenuated secretory activity of monocytes/macrophages, but also of T-helper cells. The data sustain the assumption that a systemic, possibly age-related alteration of immune mechanisms may play a pathogenetic role in the development of AD.

Flow cytometry as a method for studying effects of stressors on primary rat neurons

The mechanisms associated with cell death have been an important focus for neurobiology research. In the present study, the methodology of flow cytometry was used to optimize quantification of the toxic effects of tumor necrosis factor-alpha (TNF-alpha), trans-4-hydroxy-2-nonenal (4-HNE), and aged amyloid-beta (Abeta1-42) on rat primary cortical neurons. The fluorescent dyes annexin V-FITC and propidium iodide (PI) were used to identify populations of viable, early apoptotic, necrotic and late apoptotic cells by flow cytometry. Prior to exposure, the primary cultures showed 83% cell viability. Flow cytometry following labeling of cells with a specific neuronal marker, TUJ-1, revealed 82% pure neuronal populations, whereas approximately 7% were astrocytic as shown by glial fibrillary acidic protein positivity. Exposure of primary cultures to TNF-alpha, 4-HNE, and aged Abeta1-42 gave an increased number of early apoptotic cells. We show that flow cytometry is a suitable method for quantifying effects of different stressors on neurons in primary cultures. This technique could be useful for screening and testing of pharmacological compounds relevant to neurodegenerative disorders.

Lymphocytes as a neural probe: potential for studying psychiatric disorders

There is an increasing body evidence pointing to a close integration between the central nervous system (CNS) and immunological functions with lymphocytes playing therein a central role. The authors provide arguments to consider blood lymphocytes as a convenient probe of--an albeit--limited number of cellular functions, including gene expression. The use of brain biopsies of living patients is unrealistic for biochemical investigation, therefore lymphocytes may be a convenient and accessible alternative. Numerous studies showed similarities between receptor expression and mechanisms of transduction processes of cells in the nervous system (e.g. neurons and glia) and lymphocytes. In several neuropsychiatric disorders, alteration of metabolism and cellular functions in the CNS, as well as disturbances in the main neurotransmitter and hormonal systems are concomitant with altered function and metabolism of blood lymphocytes. We summarize relevant investigations on depression, stress, Alzheimer's disease (AD) and schizophrenia. New techniques such as cDNA microarray gene expression and proteomics may give clues to define molecular abnormalities in psychiatric disorders and could eventually reveal information for diagnostic and treatment purposes. Taken together, these considerations suggest that lymphocyte could reflect the metabolism of brain cells, and may be exploited as a neural and possible genetic probe in studies of psychiatric disorders.

Dexamethasone inhibits TNF-alpha synthesis more effectively in Alzheimer's disease patients than in healthy individuals

Inflammatory mechanisms are involved in the pathogenesis of Alzheimer's disease (AD). It is postulated that cytokine synthesis is altered in AD patients compared with nondemented subjects. Glucocorticoids play an important role in cytokine synthesis. We assessed the release of tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10) and interleukin-12 (IL-12) and its regulation by dexamethasone in AD patients in vitro. Cytokine levels were measured using the ELISA method in unstimulated, LPS-stimulated or whole-blood samples incubated with LPS and dexamethasone from 18 AD patients and 12 controls. The cytokine levels spontaneously produced by blood cells after incubation with LPS or LPS and dexamethasone did not differ significantly between groups. Dexamathasone inhibited TNF-alpha synthesis by LPS-stimulated blood cells more effectively in AD patients than in controls. These results suggest that cytokine synthesis in AD patients could be regulated by glucocorticoids in a different way than in nondemented subjects.

Peripheral cytokine release in Alzheimer patients: correlation with disease severity

Various studies suggested that inflammation is involved in the pathogenesis of Alzheimer's disease (AD). We investigated cytokine release from LPS-stimulated blood cells of 32 AD patients, with different disease severity, compared to 16 age-related controls. A significant decrease of IL-1beta and IL-6 secretion was observed in severely demented patients; TNF-alpha release was also decreased, but not significantly. By contrast, mild and moderate patients showed a cytokine release similar to controls. IL-1beta, IL-6 and TNF-alpha secretion was negatively correlated with the severity of dementia, quantified by the MMSE. Our data suggest that alterations of the immune profile are associated with AD progression.

Serum markers of monocyte/macrophage activation in patients with Alzheimer's disease and other types of dementia

OBJECTIVES

Recently an increase in serum neopterin has been described in patients with Alzheimer's disease (AD) that would be associated with an increased cell-mediated immune response. We have studied the serum levels of several monocyte/macrophage activation markers in patients with AD and other types of dementia.

DESIGN AND METHODS

Serum neopterin concentration, and the chitotriosidase (ChT), angiotensin-converting enzyme (ACE) and adenosine deaminase (ADA) activities were determined in 30 patients with AD, in 19 patients with other types of dementia, and in 24 nonaffected controls.

RESULTS

Neopterin concentration was significantly higher in the subgroup of AD patients with a global deterioration scale higher than in the other patients with AD, patients with other types of dementia and in the control group (p < 0.005). However, the activities of ChT, ACE and ADA, despite having a significant correlation with neopterin, did not present any statistically significant differences among the groups studied.

CONCLUSION

In the most advanced clinical stages of AD, as well as an increased immune activation, an impaired formation of tetrahydrobiopterin from dehydroneopterin triphosphate would contribute to an increase in the serum concentration of neopterin. However, the large overlap between the groups, limits the possible clinical value of serum neopterin in AD patients.

Immunologic and inflammatory mediators and cognitive decline in Alzheimer's disease

Local up-regulation of immune mediators is implicated in the development of AD; however, the systemic cell-mediated immune response in patients with AD may be impaired. Progression of AD from moderate to severe stages is accompanied by a progressive decline in cognitive function, independence, and behavioral and motor impairments and by the occurrence of recurrent infections, such as bronchitis and pneumonia. Several factors, including malnutrition, may be implicated in the reduced ability to mount an adequate immune response against invading pathogens in advanced stages of AD. The immune system has an important role in the development, progression, and potential treatment of AD and is involved in determining the subsequent sequelae and morbidity outcomes in patients with advanced-stage AD. A better understanding of the immune mediators that are involved in the local and systemic immune response in AD may assist in mediating the development of AD, halting its progression, and treating patients with anti-inflammatory drugs and immunization strategies.

Age-related inflammatory cytokines and disease

Aging is associated with chronic low-grade increases in circulating levels of inflammatory markers. A wide range of environmental factors, including smoking, infections, and obesity, genetic factors, and the declining function of sex hormones may contribute to systemic low-grade inflammatory activity in older individuals. Age-associated disease may exacerbate this phenomenon. The multifunctional cytokines TNF-alpha and IL-6 have been associated with morbidity and mortality in the elderly. Evidence supports the direct role of TNF-alpha in the pathogeneses of atherosclerosis, type 2 DM, and AD in older individuals. Age-related increases in systemic levels of TNF-alpha could provide a unifying basis for these disorders. Furthermore, TNF-alpha induces a catabolic state that causes frailty. Circulating levels of IL-6 seem to be a strong risk factor for frailty in the elderly, which could reflect its association with increased production of TNF-alpha. IL-6 also may be a risk factor for thromboembolic complications. In healthy, elderly populations, high circulating levels of TNF-alpha and IL-6 predict mortality, independent of comorbidity, indicating that TNF-alpha and IL-6 cause morbidity and mortality. In cohorts of frail, older individuals, TNF-alpha and IL-6 also act as disease markers. Circulating levels of TNF-alpha seem to be the best predictor of mortality in frail, elderly populations with a high mortality rate, whereas IL-6 seems to be the strongest risk marker in healthy, elderly populations. This finding could reflect that in relatively healthy old populations the increase in circulating levels of IL-6 represent a systemic response to local proinflammatory activities; however, when age-related inflammatory diseases progress, levels of TNF-alpha increase in the circulation and become gradually a stronger risk marker than IL-6. In conclusion low-grade elevations in levels of circulating cytokines are strong independent risk factors of morbidity and mortality in the elderly, and lifestyle factors and comorbidities may modulate these levels. Exercise and dietary interventions may be possible strategies to decrease inflammatory activity and improve the health status of the elderly.

Severe dementia and adverse outcomes of nursing home-acquired pneumonia: evidence for mediation by functional and pathophysiological decline

OBJECTIVES

To assess whether the severity of dementia is related to unfavorable outcomes of nursing home-acquired pneumonia and how this relationship is mediated.

DESIGN

Prospective cohort study.

SETTING

Psychogeriatric wards of 61 nursing homes in the Netherlands.

MEASUREMENTS

Dementia severity and the possible mediators swallowing disturbance, aspiration, insufficient food intake, weight loss, and dehydration were measured and related to the following outcomes: death (rate), cure rate, and increase in discomfort at the onset of pneumonia.

PARTICIPANTS

Demented patients (n = 374) treated with antibiotics for pneumonia.

RESULTS

Dementia severity was independently related to death rate within the first week after pneumonia (hazard rate ratio = 3.0 for the most severely demented quartile versus the least demented quartile, 95% confidence interval (CI) = 1.1-8.3) and to 3-month mortality (odds ratio (OR) 2.5, 95% CI = 1.1-5.4). The latter relation was in part mediated by aspiration and weight loss (OR dementia severity adjusted for these mediators declined from 2.5 to 1.9, 95% Cl = 0.8-4.3). Dementia severity was not related to cure rate within 2 weeks nor to an in-crease in discomfort after 3 days compared with before the pneumonia.

CONCLUSION

The functional and pathophysiological consequences of progressive dementia account in part for increased 3-month mortality after pneumonia. Mid-term mortality is expected to be high only in the most severely demented patients and in less severely demented patients who aspirated or who lost weight. Implications for end-of-life decision-making and effectiveness of preventive and curative interventions are discussed.

Activation of mitogen-activated protein kinase cascade and phosphorylation of cytoskeletal proteins after neurone-specific activation of p21ras. I. Mitogen-activated protein kinase cascade

Alterations in the phosphorylation state of the microtubule-associated protein tau have been associated with the pathogenesis of neurofibrillary degeneration as well as with a neuroprotective action against apoptotic cell death. Mitogen-activated protein kinases (MAPK) phosphorylate tau protein in vitro but the pathophysiological significance of this tau phosphorylation and its effects on neuronal viability is far from clear. Moreover, an in vivo model of activation of MAPK, a key candidate for in vivo tau phosphorylation, is still lacking. The aim of the present study and the accompanying paper was to establish an animal model of stimulated MAPK and to analyse the consequences on tau phosphorylation and the neuronal cytoskeleton. We took advantage of transgenic mice with neurone-specific expression of activated ras protein (p21H-ras(Val12)). The expression of the transgene in these animals is forced to a subset of neurones by the use of the synapsin I promoter. Activity of B-raf was elevated by 37%, while activity of MAPK (ERK1/ERK2) was increased by 25% associated with a subcellular redistribution from the cytoplasmic to the nuclear compartment. Kinases downstream of MAPK such as p90rsk and glycogen synthase kinase 3beta were only marginally affected. Activity of p70S6 kinase was unaltered. The present model might be useful to study the effects of activation of the MAPK cascade on tau phosphorylation and its cell biological sequelae.

T-helper-1 and T-helper-2 responses in psychiatric disorders

The expanding field of psychoneuroimmunology has markedly increased knowledge about the interference of the central nervous system and the immune system. Immunological abnormalities in psychiatric patients have been repeatedly described in the last century. Modern concepts of immunology and the growing knowledge of psychoneuroimmunology may help in understanding the distinct immunological mechanisms in psychiatric disorders. One of these concepts regarding the adaptive immune system is the discrimination between Th1-like cell-mediated and Th2-like antibody-related immune responses. This article systematically describes alterations of Th1- or Th2-specific parameters in the major psychiatric disorders schizophrenia, major depression, and Alzheimer's disease. There are several hints of associations of these two distinct arms of immune response with subgroups of schizophrenia and major depression. The immunological research in Alzheimer's disease has already led to a preclinical model of immunotherapy. Categorization of immune parameters may also help to identify a possible immune-related pathophysiology in psychotic and affective disorders, resulting in specific treatment strategies.

Disturbance of neuronal plasticity is a critical pathogenetic event in Alzheimer's disease

Brain areas affected by AD pathology are primarily those structures that are invovled in the regulation of "higher brain functions". The functions these areas subserve such as learning, memory, perception, self-awareness, and consciousness require a life-long re-fittng of synaptic contacts that allows for the acquistion of new epigenetic information, a process based on a particularly high degree of structural plasticity. Here, we outline a hypothesis that it is the "labile state fo differentiation" of a subset of neurons in the adult brain that allows for ongoing neuroplastic processes after development is completed but at the same time renders these neurons particularly vulnerable. Mechanisms of molecular and cellular control of neuronal differentiation and proliferation might, thus, not only play a role during development but critically involved in the pathogenesis of neurodegeneration.

Alzheimer's disease as a disorder of mechanisms underlying structural brain self-organization

Mental function has as its cerebral basis a specific dynamic structure. In particular, cortical and limbic areas involved in "higher brain functions" such as learning, memory, perception, self-awareness and consciousness continuously need to be self-adjusted even after development is completed. By this lifelong self-optimization process, the cognitive, behavioural and emotional reactivity of an individual is stepwise remodelled to meet the environmental demands. While the presence of rigid synaptic connections ensures the stability of the principal characteristics of function, the variable configuration of the flexible synaptic connections determines the unique, non-repeatable character of an experienced mental act. With the increasing need during evolution to organize brain structures of increasing complexity, this process of selective dynamic stabilization and destabilization of synaptic connections becomes more and more important. These mechanisms of structural stabilization and labilization underlying a lifelong synaptic remodelling according to experience, are accompanied, however, by increasing inherent possibilities of failure and may, thus, not only allow for the evolutionary acquisition of "higher brain function" but at the same time provide the basis for a variety of neuropsychiatric disorders. It is the objective of the present paper to outline the hypothesis that it might be the disturbance of structural brain self-organization which, based on both genetic and epigenetic information, constantly "creates" and "re-creates" the brain throughout life, that is the defect that underlies Alzheimer's disease (AD). This hypothesis is, in particular, based on the following lines of evidence. (1) AD is a synaptic disorder. (2) AD is associated with aberrant sprouting at both the presynaptic (axonal) and postsynaptic (dendritic) site. (3) The spatial and temporal distribution of AD pathology follows the pattern of structural neuroplasticity in adulthood, which is a developmental pattern. (4) AD pathology preferentially involves molecules critical for the regulation of modifications of synaptic connections, i.e. "morphoregulatory" molecules that are developmentally controlled, such as growth-inducing and growth-associated molecules, synaptic molecules, adhesion molecules, molecules involved in membrane turnover, cytoskeletal proteins, etc. (5) Life events that place an additional burden on the plastic capacity of the brain or that require a particularly high plastic capacity of the brain might trigger the onset of the disease or might stimulate a more rapid progression of the disease. In other words, they might increase the risk for AD in the sense that they determine when, not whether, one gets AD. (6) AD is associated with a reactivation of developmental programmes that are incompatible with a differentiated cellular background and, therefore, lead to neuronal death. From this hypothesis, it can be predicted that a therapeutic intervention into these pathogenetic mechanisms is a particular challenge as it potentially interferes with those mechanisms that at the same time provide the basis for "higher brain function".

Overproduction of IFN-gamma and TNF-alpha from natural killer (NK) cells is associated with abnormal NK reactivity and cognitive derangement in Alzheimer's disease

Alterations of natural killer (NK) function can be involved in the neuroimmune mechanism of neurodegeneration in dementia of the Alzheimer's type (DAT). NK cell cytotoxicity (NKCC) and the generation and release of IFN-gamma and TNF-alpha (spontaneous and modulated by IL-2) from pure NK cells (CD 16+, CD 56+, CD 3-) were studied together with circulating IFN-gamma and TNF-alpha levels and cognitive function in 22 old patients with DAT and 15 healthy old subjects. Higher (p < 0.001) IL-2 modulated NKCC (with IL-2 50 U/mL and 100 U/mL) was demonstrated in DAT patients (+35% and +99% from baseline) than in healthy subjects (+6% and +76% from baseline). Increased spontaneous and IL-2-induced release of IFN-gamma and TNF-alpha from NK cells were found in DAT patients compared to healthy subjects (p < 0.001), whereas no difference of serum IFN-gamma and TNF-alpha was demonstrated between DAT and control groups. Significant negative correlations among the spontaneous release of IFN-gamma and TNF-alpha from NK and the decrease of the score of cognitive function (MMSE) were found in patients with DAT. In conclusion, alterations of NKCC control and NK-derived cytokine release in DAT could be involved in the neuroinflammatory mechanism related to the progression of neurodegeneration and dementia.

Variability of interactions between neuroendocrine and immunological functions in physiological aging and dementia of the Alzheimer's type

A link between neuroendocrine and immunological changes has been suggested in the pathophysiology of dementia of the Alzheimer's type (DAT). Healthy young and old subjects and patients with DAT were recruited to evaluate the chrononeuroendocrine organization of cortisol, GH, and melatonin (MLT) secretions. The study was carried out together with the evaluation of natural killer (NK) cell function: cytotoxic activity (NKCC) and TNF-alpha and IFN-gamma release after exposure to IL-2 (100 U/mL). Moreover, a cerebral morphometric analysis of hippocampus and temporal lobe (MRI) was performed. The activation of hypothalamo-pituitary-adrenal (HPA) axis and the decrease of GH, and MLT nocturnal peaks were associated with normal NKCC and TNF-alpha/IFN-gamma in healthy elderly subjects, whereas in DAT patients the same neuroendocrine changes occurred together with abnormal NKCC (spontaneous and IL-2/IFN-beta-modulated) and with alterations of TNF-alpha/INF-gamma generation from NK. Moreover significant correlations among the increase of NKCC and TNF-alpha and the decrease of cognitive function were found in the DAT group. These correlations were associated with the impairment of nocturnal GH and MLT levels and with the relatively higher serum cortisol concentrations. Moreover, the impairment of cortisol suppression after dexamethasone (1 mg orally at 23:00) was significantly correlated with the increase of spontaneous release of TNF-alpha and with IL-2-modulated NKCC. Finally the imunoneuroendocrine alterations found in DAT were associated with the reduction of cerebral volume in hippocampus and temporal lobes. Taken together these data indicate that the immunoneuroendocrine balance is maintained in physiological aging, whereas NK immune dysregulation in DAT could contribute to altering the neuroendocrine functions and to extend the progression of neurodegeneration and dementia.

Local and systemic GM-CSF increase in Alzheimer's disease and vascular dementia

A growing body of evidence points out the potential role of inflammatory mechanisms in the pathophysiology of brain damage in dementia. The aim of the present study was to investigate patterns of local and systemic cytokine release in patients with Alzheimer's disease (AD) and vascular dementia (VAD). The intrathecal levels of cytokines were related to neuronal damage and cerebral apoptosis. Twenty patients with early AD and 26 patients with VAD were analyzed with respect to cerebrospinal fluid (CSF) and serum levels of pro- and anti-inflammatory cytokines. In addition, CSF levels of Fas/APO-1 and bcl-2, a measure for apoptosis, and Tau protein, a marker for neuronal degradation, were studied. Significantly increased CSF levels of GM-CSF but not of other cytokines were observed in both dementia groups. These patients displayed a significant correlation between the GM-CSF levels and the levels of Fas/APO-1 and Tau protein in CSF. Our study demonstrates an intrathecal production of GM-CSF, a cytokine stimulating microglial cell growth and exerting inflammatogenic properties. It is suggested that GM-CSF once secreted induces programmed cell death in the brain tissue of patients with dementia.

Platelet APP isoform ratios in asymptomatic young adults expressing an AD-related presenilin-1 mutation

The Alzheimer's disease (AD) related amyloid precursor protein (APP) is stored, cleaved and released similarly from neurons and from platelets. We have reported that the proportion of 120-130 to 110 kDa carboxyl-cleaved APP present in the platelets of AD patients is significantly lower than that of platelets of age-matched controls. This reduced APP isoform ratio, not seen in several other disease groups, is further reduced as the severity of AD increases. Since the neuropathology of AD is believed to begin many years before the onset of cognitive loss, we have also compared platelet APP ratios of four pre-symptomatic young adults carrying a presenilin-1 mutation to seven siblings homozygous for the normal PS-1 gene in an effort to determine whether reduced APP ratios are present before apparent cognitive loss in familial AD. Decreased platelet APP ratios were not seen in any of these subjects at this time. We will continue to monitor these subjects as they near the mean age of AD onset in these families. As the magnitude of the APP ratio reduction is proportional to the severity of cognitive loss in sporadic AD, these cognitively normal incipient AD subjects would not be expected to present significant reductions in this AD severity index at this time. Alternatively, the absence of platelet APP ratio reductions may result from a failure of platelets from familial PS-1 AD subjects to manifest altered APPs, as has been reported for PS-2 AD subjects, unlike those of sporadic AD patients. Continued monitoring of cognitive status in our sub-set of controls with AD-like low APP ratios may yet validate the ability of this assay to detect incipient sporadic AD.