Cytokines and cognition--the case for a head-to-toe inflammatory paradigm

Chemical Complexity and the Genetics of Aging

We examine how aging is impacted by various chemical challenges that organisms face and by the molecular mechanisms that have evolved to regulate lifespan in response to them. For example, environmental information, which is detected and processed through sensory systems, can modulate lifespan by providing information about the presence and quality of food as well as presence and density of conspecifics and predators. In addition, the diverse forms of molecular damage that result from constant exposure to damaging chemicals that are generated from the environment and from metabolism pose an informatic and energetic challenge for detoxification systems, which are important in ensuring longevity. Finally, systems of innate immunity are vital for recognizing and combating pathogens but are also seen as of increasing importance in causing the aging process. Integrating ideas of molecular mechanism with context derived from evolutionary considerations will lead to exciting new insights into the evolution of aging.

Longitudinal trajectories of cognitive change in preclinical Alzheimer's disease: a growth mixture modeling analysis

Preclinical Alzheimer's disease (AD) refers to a period of time prior to diagnosis during which cognitive deficits among individuals who will go on to receive a diagnosis of AD are present. There is great interest in describing the nature of cognitive change during the preclinical period, in terms of whether persons decline in a linear fashion to diagnosis, or exhibit some stability of functioning, followed by rapid losses in performance. In the current study we apply Growth Mixture Modeling to data from The Kungsholmen Project to evaluate whether decline in Mini Mental State Examination (MMSE) scores during the preclinical period of AD follows a linear or quadratic function. At the end of a 7-year follow-up period, some individuals would be diagnosed with AD (n=71), whereas others would remain free of dementia (n=457). The results indicated that a two-group quadratic model of decline provided the best statistical fit measures, as well as the greatest estimates of sensitivity (67%) and specificity (86%). Differences in MMSE scores were apparent at baseline, but the preclinical AD group began to experience precipitous declines three years prior to diagnosis. Finally, persons who were misclassified as preclinical AD had fewer years of education and poorer MMSE scores at baseline.

Gene expression changes in peripheral mononuclear cells from schizophrenic patients treated with a combination of antipsychotic with fluvoxamine

Antipsychotic treatment combined with Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant can improve negative symptoms in schizophrenic patients that are unresponsive to antipsychotic drugs alone. The mechanism of this therapeutic effect is not clear. The current study examined molecular changes induced by the combined treatment in human peripheral mononuclear cells (PMC) in order to get insight into its mechanism of action. Gene expression profile of PMC from antipsychotic-treated patients was examined before addition of the SSRI fluvoxamine, and 3 and 6 weeks after. Gene expression patterns screened with a cDNA array, comprising 1176 genes, revealed homologous changes in a range of transcripts related to G-protein coupled receptors (GPCR). Genes related to GPCR-family were assayed using customized cDNA array and the results verified by real-time RT-PCR. The mRNA expression of chemokine receptors, IL8RA and CCR1, and of RGS7 was significantly down-regulated following fluvoxamine augmentation. The clinical assessments showed improvement in negative symptoms following the combined treatment. The transcriptional analysis suggests that the therapeutic mechanism of the combined antipsychotic-fluvoxamine treatment may involve genes associated with G-protein coupled receptors (GPCR). Our findings suggest that gene expression changes in PMC may be useful in investigating the mechanism of drug action in schizophrenia.

Molecular evidence for increased expression of genes related to immune and chaperone function in the prefrontal cortex in schizophrenia

BACKGROUND

Schizophrenia is characterized by complex gene expression changes. The transcriptome alterations in the prefrontal cortex have been the subject of several recent postmortem studies that yielded both convergent and divergent findings.

METHODS

To increase measurement precision, we used a custom-designed DNA microarray platform with long oligonucleotides and multiple probes with replicates. The platform was designed to assess the expression of > 1800 genes specifically chosen because of their hypothesized roles in the pathophysiology of schizophrenia. The gene expression differences in dorsolateral prefrontal cortex samples from 14 matched pairs of schizophrenia and control subjects were analyzed with two technical replicates and four data mining approaches.

RESULTS

In addition to replicating many expression changes in synaptic, oligodendrocyte, and signal transduction genes, we uncovered and validated a robust immune/chaperone transcript upregulation in the schizophrenia samples.

CONCLUSIONS

We speculate that the overexpression of SERPINA3, IFITM1, IFITM2, IFITM3, CHI3L1, MT2A, CD14, HSPB1, HSPA1B, and HSPA1A in schizophrenia subjects represents a long-lasting and correlated signature of an early environmental insult during development that actively contributes to the pathophysiology of prefrontal dysfunction.

Genomic expression pathways associated with brain injury after cardiopulmonary bypass

OBJECTIVES

Neurologic injury after cardiac surgery, often manifested as neurocognitive decline, is a common postoperative complication without clear cause. We studied acute variations in gene-expression profiles of patients with neurocognitive decline (NCD group) compared with those without neurocognitive decline (NORM group) after cardiopulmonary bypass.

METHODS

Forty-two patients undergoing coronary artery bypass grafting, valve procedures, or both by using cardiopulmonary bypass were administered a validated neurocognitive battery preoperatively and postoperatively at day 4. Neurocognitive decline was defined as 1 standard deviation from baseline on 25% or greater of tasks. Whole-blood mRNA was isolated preoperatively and at 6 hours after surgical intervention for fold-change calculation. Relative gene expression in the NCD versus the NORM group was assessed by using Affymetrix GeneChip U133 Plus 2.0 (>40,000 genes) from mRNA samples collected. Differential expression, clustering, gene ontology, and canonical pathway analysis were performed. Validation of microarray gene expression was performed with SYBR Green real-time polymerase chain reaction.

RESULTS

Patients with neurocognitive decline (17/42 [40.5%] patients) were associated with a significantly different gene-expression response compared with that of healthy patients. Compared with preoperative samples, 6-hour samples had 531 upregulated and 670 downregulated genes uniquely in the NCD group compared with 2214 upregulated and 558 downregulated genes uniquely in the NORM group (P < .001; lower confidence bound, > or =1.2). Compared with patients in the NORM group, patients with neurocognitive decline had significantly different gene-expression pathways involving inflammation (including FAS, IL2RB, and CD59), antigen presentation (including HLA-DQ1, TAP1, and TAP2), and cellular adhesion (including ICAM2, ICAM3, and CAD7) among others.

CONCLUSIONS

Patients with neurocognitive decline have inherently different genetic responses to cardiopulmonary bypass compared with those of patients without neurocognitive decline Genetic variations in inflammatory, cell adhesion, and apoptotic pathways might be important contributors to the pathophysiology of neurologic injury after cardiopulmonary bypass and could become a target for prevention and risk stratification.

Frailty: an emerging research and clinical paradigm--issues and controversies

Clinicians and researchers have shown increasing interest in frailty. Yet, there is still considerable uncertainty regarding the concept and its definition. In this article, we present perspectives on key issues and controversies discussed by scientists from 13 different countries, representing a diverse range of disciplines, at the 2006 Second International Working Meeting on Frailty and Aging. The following fundamental questions are discussed: What is the distinction, if any, between frailty and aging? What is its relationship with chronic disease? Is frailty a syndrome or a series of age-related impairments that predict adverse outcomes? What are the critical domains in its operational definition? Is frailty a useful concept? The implications of different models and approaches are examined. Although consensus has yet to be attained, work accomplished to date has opened exciting new horizons. The article concludes with suggested directions for future research.

Cognitive function in breast cancer patients prior to adjuvant treatment

PURPOSE

To compare the neuropsychological functioning of breast cancer patients with invasive cancer and noninvasive cancer prior to adjuvant treatment.

PATIENTS AND METHODS

Breast cancer patients (N = 132) with invasive (Stages 1-3, N = 110, age = 54.1 +/- 8.1) or noninvasive (Stage 0, N = 22, age = 55.8 +/- 8.0) disease completed a battery of neuropsychological and psychological instruments following surgery but prior to initiation of chemotherapy, radiation or hormonal therapy. Matched healthy controls (N = 45, age = 52.9 +/- 10.0) completed the same battery of instruments. For the patients, data on menstrual status, type of surgery, time of general anesthesia, CBC and platelets, nutritional status (B12 and folate), and thyroid function were collected.

RESULTS

Comparison of mean neuropsychological test scores revealed that all groups scored within the normal range; however, patients with Stage 1-3 cancer scored significantly lower than healthy controls on the Reaction Time domain (p = 0.005). Using a definition of lower than expected cognitive performance that corrected for misclassification error, Stage 1-3 patients were significantly (p = 0.002) more likely to be classified as having lower than expected overall cognitive performance (22%) as compared to Stage 0 patients (0%) and healthy controls (4%). No differences were observed between patients classified as having lower than expected cognitive performance compared to those classified as normal performance on measures of depression, anxiety, fatigue, menstrual status, surgery/anesthesia or any of the blood work parameters.

CONCLUSION

Patients with Stage 1-3 breast cancer were more likely to be classified as having lower than expected cognitive performance prior to adjuvant treatment as compared to Stage 0 patients and healthy controls, although correction for misclassification error produced a lower rate than previously reported.

Interleukin-1beta and caspase-1: players in the regulation of age-related cognitive dysfunction

Scientific research on the unprecedented and growing number of older adults in the United States and other industrialized countries has focused much attention on the health consequences of aging. Over the last few decades, inflammation in the brain and its implication in the progression of aging and age-related cognitive dysfunction has been an area of increasing importance to neuroscientists and is now considered as one of the most interesting and promising topics for aging research. One of the critical aspects of inflammatory processes is that the activation of one upstream inflammatory molecule initiates a cascade of self-sustaining inflammatory events which leads to the activation of a number of different downstream functions. Recently, a great deal of attention has been given to the interplay between inflammatory and apoptotic processes and the regulation of these processes by the caspases. The caspase family of proteases can be divided into proapoptotic and pro-inflammatory members. The present review summarizes recent observations of the interactions between the inflammatory cytokine interleuldn-1 (IL-1) beta and the inflammatory/apoptotic caspase-1 and their involvement in age-related impairments in cognition. A comprehensive understanding of these mechanisms could potentially lead to the development of preventive or protective therapies that reduce or inhibit the cognitive decline associated with aging and age-related neurodegenerative disease.

APOE and cytokines as biological markers for recovery of prevalent delirium in elderly medical inpatients

BACKGROUND

Delirium frequently occurs in the context of infection and other inflammatory conditions associated with elevated levels of cytokines. Cytokines used therapeutically can induce symptoms of delirium as an adverse effect. We hypothesized that a causal relationship might exist between delirium and cytokine production during illness. Further, we speculated that the APOE genotype of patients might influence their rate of recovery from delirium given that APOE is associated with amyloid deposition, increased susceptibility to exogenous neurotoxins, and can affect the immune response.

METHODS

A cohort of 164 acutely ill patients, 70 years or older, admitted to an elderly medical unit were studied within 3 days of hospital admission and re-assessed twice weekly until their discharge, to identify and follow the clinical course of delirium. The APOE genotype and the level of circulating cytokines were determined for 116 and 60 patients respectively.

RESULTS

Prevalent delirium was significantly (p < 0.05) associated with a previous history of dementia, age, illness severity, disability and low levels of circulating IGF-I. Recovery was significantly associated (p < 0.05) with lack of APOE 4 allele and higher initial IFN-gamma. A model incorporating gender, APOE epsilon 4 status and IGF-I levels predicted recovery or not from delirium in 76.5% of cases, with a sensitivity 0.77 and specificity 0.75.

CONCLUSIONS

A relationship between delirium with APOE genotype, IFN-gamma, and IGF-I, but not with IL-6, IL-1, TNF-alpha, and LIF was found. A predictive model of recovery was derived from gender, APOE status, and IGF-I levels. This model needs replication with further studies.

Inflammation and interleukin-1 signaling network contribute to depressive symptoms but not cognitive decline in old age

The association between inflammation and neuropsychiatric symptoms in old age is generally accepted but poorly understood. The purpose of this study was to examine whether inflammation precedes depressive symptoms and cognitive decline in old age, and to identify specific inflammatory pathways herein. We measured serum C-reactive protein (CRP) and lipopolysaccharide-induced production of Interleukin (IL)-1beta, IL-6, Tumor Necrosis Factor (TNF)-alpha, IL-1 receptor antagonist (ra), and IL-10 levels in 85-year-old participants free from neuropsychiatric symptoms at baseline (n=267). Participants were prospectively followed for depressive symptoms (Geriatric Depression Scale) and cognitive functioning (Mini Mental State Examination) from 85 to 90 years. Higher baseline CRP levels preceded accelerated increase in depressive symptoms (p<0.001). A higher production capacity of the pro-inflammatory cytokine IL-1beta preceded a greater increase of depressive symptoms (p=0.06), whereas that of its natural antagonist IL-1ra preceded a smaller increase of depressive symptoms (p=0.003). There was no relation of CRP, IL-1beta, and IL-1ra with cognitive decline. Our findings show that in old age inflammatory processes contribute to the development of depressive symptoms but not cognitive decline. A high innate IL-1ra to IL-1beta production capacity reflects a better ability to neutralize inflammation and may therefore protect against depressive symptoms.

Cognitive decline and markers of inflammation and hemostasis: the Edinburgh Artery Study

OBJECTIVES

To determine whether circulating markers of activated inflammation and hemostasis are associated with cognitive decline in older people.

DESIGN

Prospective cohort study (Edinburgh Artery Study).

SETTING

Eleven general practices in Edinburgh, Scotland.

PARTICIPANTS

A sample of 452 men and women followed for 16 years.

MEASUREMENTS

Biomarker data were collected in 1987/88, and cognitive assessment was first conducted in 1998/99, when the mean age of the sample +/- standard deviation was 73.1+/-5.0), and subsequently in 2002/03. Information was obtained on verbal declarative memory (Wechsler Logical Memory Test (LMT)), nonverbal reasoning (Raven's Standard Progressive Matrices), verbal fluency (Verbal Fluency Test), information processing speed (Wechsler Digit Symbol Test), and a general cognitive factor representing the variance common to the individual test scores.

RESULTS

In age-adjusted analyses, plasma fibrinogen, interleukin-6 (IL-6), and intercellular adhesion molecule 1 (ICAM-1) were negatively associated with performance on all cognitive measures in 2002/03 except the LMT (correlation coefficients from -0.10 to -0.24). In multivariate analyses controlling for demographic characteristics, depression, and cardiovascular morbidity and risk factors, fibrinogen independently predicted 4-year decline in nonverbal reasoning (P<.05). Also, when cognitive change was estimated from peak prior level, IL-6 turned out to be inversely related to decline in information processing speed (P<.05). Similarly, ICAM-1 was associated with a greater decline in general cognitive ability (P<.05) and nonverbal ability (P<.05).

CONCLUSION

Systemic markers of inflammation and hemostasis are associated with a progressive decline in general and specific cognitive abilities in older people, independent of major vascular comorbidity.

Timosaponin B-II improves memory and learning dysfunction induced by cerebral ischemia in rats

Sapogenins from Anemarrhenae asphodeloides was reported to improve the learning and memory abilities. In this study, we investigated the effect of Timosaponin B-II(TB-II), a purified extract from A. asphodeloidesb on rat vascular dementia (VD) produced by transient (2h) middle cerebral artery occlusion. The learning and memory abilities of rats were measured by water maze task and passive avoidance task. Daily oral administration of TB-II at two different dose levels of 100 and 200 mg/kg resulted in a significant improvement of the deficit in the learning of the water maze task, beginning 14 days after ischemia. Shortened mean escape latency was detected in TB-II group compared with model group during the same trial days. TB-II treatment also significantly reversed the ischemia-induced retention deficit determined by a one trial step-down type of passive avoidance task. Meanwhile, the expression of interleukin-10, an anti-inflammatory cytokine, and its receptor were significantly increased in TB-II treated VD rats. The results presented the first evidence of a neuroprotective effect of TB-II in the model of vascular dementia. We suggest that the anti-dementia effect by TB-II is derived at least in part from its anti-inflammatory properties.

Plasma levels of apolipoprotein E and cognitive function in old age

The relationship between structural variants of the apolipoprotein E gene, APOE epsilon2/epsilon3/epsilon4, and dementia is well established, whereas the relationship of plasma apoE levels with dementia is less clear. Plasma apoE levels are under tight genetic control but vary widely within the various genotypes indicating that the APOE epsilon2/epsilon3/epsilon4 locus explains only a small fraction of this variation. Here we studied the association of plasma apolipoprotein E (apoE) levels with cognitive function in the elderly population at large. Within the Leiden 85-plus Study, a prospective population-based study of subjects aged 85 years, we measured plasma apoE level and genotype at base line. During a 5-year follow-up period, cognitive function was annually assessed using the Mini Mental State Examination (MMSE) and a standardized neuropsychological test battery. Among epsilon3epsilon3 carriers (n = 324), high plasma apoE levels associated with impaired global cognitive function (-1.10 points change in MMSE score per one standard deviation increase of plasma apoE level, P = 0.001), as well as lower attention (P = 0.064), speed and memory function (all P < 0.05). Adjustment for cardiovascular risk factors and exclusion of all subjects who suffered a stroke did not materially change the associations. Similar estimates were obtained in epsilon3epsilon4 carriers (n = 100), but not in epsilon2epsilon3 carriers (n = 90). We conclude that in old age, in non-epsilon2-allele carriers, high plasma apoE levels are associated with cognitive impairments, independent of genotype, cardiovascular risk factors, and stroke.

Depressive symptoms as a predictor of cognitive decline: MacArthur Studies of Successful Aging

OBJECTIVE

The prevalence of dementia continues to rise, and yet, there are few known modifiable risk factors. Depression, as a treatable condition, may be important in the development of dementia. Our objective was to examine the association between depressive symptoms and longitudinal cognitive changes in older adults who were high-functioning at baseline.

METHODS

The authors analyzed data from a community-based cohort (aged 70-79 at baseline), who, at study entry, scored 7 or more (out of 9) on the Short Portable Mental Status Questionnaire (SPMSQ). Depressive symptoms were assessed at baseline using the depression subscale of the Hopkins Symptom Check List. Cognitive performance was measured at baseline and at seven-year follow up by the SPMSQ and by summary scores from standard tests of naming, construction, spatial recognition, abstraction, and delayed recall.

RESULTS

After adjusting for potential confounders, including age, education, and chronic health conditions such as diabetes, heart attack, stroke, and hypertension, a higher number of baseline depressive symptoms were strongly associated with greater seven-year decline in cognitive performance and with higher odds of incident cognitive impairment, i.e., decline in SPMSQ score to < or = 6 (adjusted odds ratio per quartile of depressive symptoms score: 1.34, 95% confidence interval: 1.10-1.68).

CONCLUSIONS

Depressive symptomatology independently predicts cognitive decline and incident cognitive impairment in previously high-functioning older persons.

Genetic Variants in P-Selectin and C-Reactive Protein Influence Susceptibility to Cognitive Decline After Cardiac Surgery

OBJECTIVES

We hypothesized that candidate gene polymorphisms in biologic pathways regulating inflammation, cell matrix adhesion/interaction, coagulation-thrombosis, lipid metabolism, and vascular reactivity are associated with postoperative cognitive deficit (POCD).

BACKGROUND

Cognitive decline is a common complication of coronary artery bypass graft (CABG) surgery and is associated with a reduced quality of life.

METHODS

In a prospective cohort study of 513 patients (86% European American) undergoing CABG surgery with cardiopulmonary bypass, a panel of 37 single-nucleotide polymorphisms (SNPs) was genotyped by mass spectrometry. Association between these SNPs and cognitive deficit at 6 weeks after surgery was tested using multiple logistic regression accounting for age, level of education, baseline cognition, and population structure. Permutation analysis was used to account for multiple testing.

RESULTS

We found that minor alleles of the CRP 1059G/C SNP (odds ratio [OR] 0.37, 95% confidence interval [CI] 0.16 to 0.78; p = 0.013) and the SELP 1087G/A SNP (OR 0.51, 95% CI 0.30 to 0.85; p = 0.011) were associated with a reduction in cognitive deficit in European Americans (n = 443). The absolute risk reduction in the observed incidence of POCD was 20.6% for carriers of the CRP 1059C allele and 15.2% for carriers of the SELP 1087A allele. Perioperative serum C-reactive protein (CRP) and degree of platelet activation were also significantly lower in patients with a copy of the minor alleles, providing biologic support for the observed allelic association.

CONCLUSIONS

The results suggest a contribution of P-selectin and CRP genes in modulating susceptibility to cognitive decline after cardiac surgery, with potential implications for identifying populations at risk who might benefit from targeted perioperative antiinflammatory strategies.

The relationship between cytokines and pain/depression: A review and current status

Cytokines are small protein molecules secreted in response to immune stimuli. Recent research has outlined important roles for proinflammatory cytokines in the cascade of normal physiologic responses to environmental stresses, encompassing so-called sickness behavior that is thought to be an adaptive response to infection and other illnesses. Cytokines are involved in signaling that activates central nervous system glial cells. This activation is part of a poorly understood interaction between immune challenge or injury and host that can lead to the development or facilitation of persistent mood symptoms or pathologic pain. This article reviews evidence that may enhance our understanding of how pathologic symptoms, such as mood disorders and neuropathic pain, may emerge from proinflammatory cytokine activation. Possible conceptualizations of these illnesses and potential treatment implications are explored.

Cytokines and C-Reactive Protein Production in Hip-Fracture-Operated Elderly Patients

BACKGROUND

The study aim was to determine the kinetics of serum pro- and anti-inflammatory cytokines and C-reactive protein (CRP) in hip-fracture patients over a month postfracture, and their relationship to postoperative (postop) complications and cognitive level.

METHODS

Forty-one elderly hip-fracture patients were prospectively followed. Serum was obtained during the first 10 hours postfracture and presurgery, 48-60 hours postop, 7 and 30 days postop, measuring CRP, interleukin-1beta (IL-1beta), IL-6, IL-8, tumor necrosis factor-alpha (TNF-alpha), IL-10, and IL-1 receptor antagonist (IL-1RA).

RESULTS

A significant increase was found postop for CRP, IL-6, TNF-alpha, IL-1RA (p <.001), IL-10 (p <.002), and IL-8 (p =.05). CRP kinetics curves were higher in patients with complications as a group, and in those suffering from infections, delirium, and cardiovascular complications (p <.05). IL-6 increase in patients with complications approached significance. Additional complications appeared in patients with impaired mental status (IMS) versus cognitively normal patients (p =.037). Higher kinetics curves in the IMS patients were found for CRP and IL-6 (p <.05). Analyzing the interaction effect of complications and IMS on CRP and cytokines production demonstrated that the increase in CRP was independently related to complications and IMS. IL-6, IL-8, and IL-10 were higher in IMS patients but not in patients with complications without IMS (p <.05).

CONCLUSIONS

Serum CRP and cytokines increased drastically in postop hip-fracture elderly patients. Only CRP significantly and independently increased in IMS patients and in patients with complications, whereas cytokines significantly increased only in IMS patients. This study raises questions about possible effects that cytokine generation, after hip-fracture repair, might have on cognition and complications.

Inflammation, cardiovascular disease, and metabolic syndrome as sequelae of violence against women: the role of depression, hostility, and sleep disturbance

Women who experience violence are significantly more likely to have serious health problems above and beyond any injuries they might incur. The intriguing question is why this is so. In this article, the author describes how three sequelae of violence against women-depression, hostility, and sleep disturbance-can increase the risk of disease. One possible mechanism by which these sequelae increase risk is by elevating levels of pro-inflammatory cytokines. These cytokines have an adaptive function in fighting infection and repairing injured tissues. However, chronically high levels of pro-inflammatory cytokines have been implicated in a wide range of diseases. The author focuses on two illnesses that have not received much attention in the violence against women (VAW) literature: cardiovascular disease and metabolic syndrome, the precursor to type 2 diabetes. Preliminary studies also suggest that treatments that can lower inflammation may be promising adjuncts for survivors of VAW.

Candidate mechanisms for chemotherapy-induced cognitive changes

The mechanism(s) for chemotherapy-induced cognitive changes are largely unknown; however, several candidate mechanisms have been identified. We suggest that shared genetic risk factors for the development of cancer and cognitive problems, including low-efficiency efflux pumps, deficits in DNA-repair mechanisms and/or a deregulated immune response, coupled with the effect of chemotherapy on these systems, might contribute to cognitive decline in patients after chemotherapy. Furthermore, the genetically modulated reduction of capacity for neural repair and neurotransmitter activity, as well as reduced antioxidant capacity associated with treatment-induced reduction in oestrogen and testosterone levels, might interact with these mechanisms and/or have independent effects on cognitive function.

Potential Mechanisms for Chemotherapy-Induced Impairments in Cognitive Function

PURPOSE/OBJECTIVES

To review the domains of cognitive function and their corresponding neuroanatomic structures as well as present current evidence for neurotoxicity associated with specific chemotherapeutic agents and potential mechanisms for chemotherapy-induced cognitive impairments.

DATA SOURCES

Published research articles, review articles, and textbooks.

DATA SYNTHESIS

Chemotherapy does not appear to cross the blood-brain barrier when given in standard doses; however, many chemotherapy drugs have the potential to cause cognitive impairments through more than one mechanism. In addition, patient factors may be protective or place individuals at higher risk for cognitive impairments.

CONCLUSIONS

Although evidence of chemotherapy-induced impairments in cognitive function exists, no clinical studies have attempted to elucidate the mechanisms for chemotherapy-induced impairments in cognitive function. In addition, further studies are needed to determine predictive factors, potential biomarkers, and relevant assessment parameters.

IMPLICATIONS FOR NURSING

The ability to identify high-risk patients has important implications for practice in regard to informed consent, patient education about the effects of treatment, and preventive strategies.

Modulation of inflammation in brain: a matter of fat

Neuroinflammation is a host defense mechanism associated with neutralization of an insult and restoration of normal structure and function of brain. Neuroinflammation is a hallmark of all major CNS diseases. The main mediators of neuroinflammation are microglial cells. These cells are activated during a CNS injury. Microglial cells initiate a rapid response that involves cell migration, proliferation, release of cytokines/chemokines and trophic and/or toxic effects. Cytokines/chemokines stimulate phospholipases A2 and cyclooxygenases. This results in breakdown of membrane glycerophospholipids with the release of arachidonic acid (AA) and docosahexaenoic acid (DHA). Oxidation of AA produces pro-inflammatory prostaglandins, leukotrienes, and thromboxanes. One of the lyso-glycerophospholipids, the other products of reactions catalyzed by phospholipase A2, is used for the synthesis of pro-inflammatory platelet-activating factor. These pro-inflammatory mediators intensify neuroinflammation. Lipoxin, an oxidized product of AA through 5-lipoxygenase, is involved in the resolution of inflammation and is anti-inflammatory. Docosahexaenoic acid is metabolized to resolvins and neuroprotectins. These lipid mediators inhibit the generation of prostaglandins, leukotrienes, and thromboxanes. Levels of prostaglandins, leukotrienes, and thromboxanes are markedly increased in acute neural trauma and neurodegenerative diseases. Docosahexaenoic acid and its lipid mediators prevent neuroinflammation by inhibiting transcription factor NFkappaB, preventing cytokine secretion, blocking the synthesis of prostaglandins, leukotrienes, and thromboxanes, and modulating leukocyte trafficking. Depending on its timing and magnitude in brain tissue, inflammation serves multiple purposes. It is involved in the protection of uninjured neurons and removal of degenerating neuronal debris and also in assisting repair and recovery processes. The dietary ratio of AA to DHA may affect neurodegeneration associated with acute neural trauma and neurodegenerative diseases. The dietary intake of docosahexaenoic acid offers the possibility of counter-balancing the harmful effects of high levels of AA-derived pro-inflammatory lipid mediators.

Assessing neurocognitive outcomes after critical illness: are delirium and long-term cognitive impairments related?

PURPOSE OF REVIEW

Critically ill patients have a high risk of developing neurologic dysfunction including delirium and long-term cognitive impairment. In this paper we examine possible relationships between delirium and long-term cognitive impairments and explore this in the context of critical illness.

RECENT FINDINGS

Critical illness and its treatment can lead to neurologic morbidity including neuropathological abnormalities, delirium, and cognitive impairments. The association between delirium and long-term cognitive impairments has been shown in a number of populations. Among intensive care unit cohorts, delirium appears to be one of many possible causes of cognitive impairments and may be a leading modifiable cause. The mechanisms of both delirium and intensive care unit related cognitive impairment remain unclear, although a variety of common mechanisms have been proposed.

SUMMARY

Potential neurologic consequences of critical illness include delirium and long-term cognitive impairments. Defining the extent of their association in intensive care unit cohorts is an important research priority due to the high prevalence of delirium and persistent cognitive impairments in critically ill patients. Future research should focus on strategies for the early identification of delirium and cognitive impairments, elucidating mechanisms of brain injury, and the development and implementation of therapeutic modalities designed to prevent or decrease delirium and cognitive morbidity.

Association between plasma inflammatory markers and irrational beliefs; the ATTICA epidemiological study

OBJECTIVE

Recent research data suggest that inflammation and/or depression are associated with the development and progression of cardiovascular disease (CVD). Considering that depression may arise as a response to irrational beliefs according to the Ellis model of psychological disturbances and therapy, we sought to evaluate whether irrational beliefs are associated with plasma inflammatory factors in cardiovascular disease-free people.

METHOD

From May 2001 to December 2002 we randomly enrolled 453 men (23-69 years old) and 400 women (24-71 years old) stratified by age and gender. C-reactive protein, interleukin-6, serum amyloid-A, tumor necrosis factor-alpha and white blood cells were measured in all participants. Detailed dietary characteristics of these people were assessed through a validated food frequency questionnaire. Subjects completed also the irrational beliefs inventory (IBI), which is a brief self-report measure consistent with the Ellis model of psychological disturbance and therapy and the Zung's Depression questionnaire.

RESULTS

The IBI scores were similar in men and women (53+/-11 vs. 53+/-10, p = 0.83). IBI score was positively correlated with C-reactive protein (rho = 0.14, p = 0. 02), interleukin-6 (rho = 0.11, p = 0.02), tumor necrosis factor-alpha (rho = 0.21, p = 0.014) and white blood cell counts (rho = 0.14, p = 0.02). These associations were confirmed even after adjusting for age, sex, years of school, body mass index, physical activity status, depression level and food items consumed by the participants.

CONCLUSION

These findings indicate that irrational beliefs are associated with increased inflammation process, among apparently healthy individuals.

Aging sensitizes mice to behavioral deficits induced by central HIV-1 gp120

The number of older adults with HIV-1 disease is increasing but little is known about how age influences behavioral deficits associated with HIV-1 infection. The purpose of this study was to determine in a murine model if aging influenced sickness behavior following central injection of HIV-1 gp120. In initial studies, behavioral deficits induced by acute and repeated intracerebroventricular (ICV) injection of gp120 were greater in aged mice than in adults. Furthermore, repeated ICV injection of gp120 increased hippocampal levels of IL-1 beta and IL-6 mRNA in aged mice but not in adults. To determine if IL-6, which is elevated in aged brain, affects expression of the gp120-binding target, CCR5, microglia (BV-2 cell line) were incubated with increasing concentrations of IL-6. Cell surface expression of CCR5 was increased by IL-6 in a dose-dependent manner. Additionally, IL-6 increased gp120-dependent chemotaxis. These results suggest that aging increases the sensitivity of mice to behavioral deficits caused by ICV gp120, perhaps by increasing expression of CCR5 and augmenting production of cytokines.

Sleep and psychiatric disorders: future directions

Understanding of the relationship between co-occurring sleep and psychiatric disorders has undergone a radical change. The longstanding perspective that sleep problems invariably are a symptom of a psychiatric disorder is giving way to understanding that complex bidirectional relationships may exist. This change has opened doors to new directions in research and led to changes in guidelines for clinical practice. This article discusses promising future directions for building on this foundation, including developing lines of research currently underway, studying mechanisms that underlie the relationships between sleep and psychiatric disorders; and developing treatment strategies that target these mechanisms to lead to better treatment of sleep disorders and psychiatric disorders.

Cytokines in schizophrenia and the effects of antipsychotic drugs

Growing evidence suggests that the immune, endocrine, and nervous systems interact with each other through cytokines, hormones, and neurotransmitters. The activation of the cytokine systems may be involved in the neuropathological changes occurring in the central nervous system (CNS) of schizophrenic patients. Numerous studies report that treatment with antipsychotic drugs affects the cytokine network. Hence, it is plausible that the influence of antipsychotics on the cytokine systems may be responsible for their clinical efficacy in schizophrenia. This article reviews current data on the cytokine-modulating potential of antipsychotic drugs. First, basic information on the cytokine networks with special reference to their role in the CNS as well as an up-to-date knowledge of the cytokine alterations in schizophrenia is outlined. Second, the hitherto published studies on the influence of antipsychotics on the cytokine system are reviewed. Third, the possible mechanisms underlying antipsychotics' potential to influence the cytokine networks and the most relevant aspects of this activity are discussed. Finally, limitations of the presented studies and prospects of future research are delineated.

Serologic markers of brain injury and cognitive function after cardiopulmonary bypass

OBJECTIVE

To examine the association between biochemical markers of brain injury (MBI) and the inflammatory response in relation to neurocognitive deficiency (NCD) after cardiopulmonary bypass (CPB).

SUMMARY BACKGROUND DATA

In cardiac surgery, NCD is a common but underdiagnosed complication with an unclear pathophysiology leading to significant morbidity. Despite extensive investigation, identification of a MBI for clinical use and clarifying the pathophysiology of NCD have not been achieved.

METHODS

Forty patients undergoing CABG and/or valve procedures using CPB were administered a validated neurocognitive battery preoperatively and postoperatively at day 4 and 3 months. S-100b, neuron specific enolase (NSE), and tau protein were assayed as MBIs preoperatively and postoperatively at 6 hours and day 4. C-reactive protein (CRP), interleukin (IL)-6, C3a, and total peroxide levels were also quantified from serum. Impact of cardiotomy suction and antifibrinolytics on markers of brain injury was assessed.

RESULTS

The incidence of early NCD was 40% (16 of 40). NSE and tau protein at the 6-hour time point were both significantly elevated in the presence of NCD (NCD group) compared with those without NCD (NORM group) (8.69 +/- 0.82 vs. 5.98 +/- 0.61; P = 0.018 and 68.8 vs. 29.2%; P = 0.015; respectively). S-100b increase was not different between the NCD and NORM groups. Cardiotomy suction significantly elevated S-100b levels, whereas NSE and tau were not significantly influenced. Aprotinin did not have an effect on NCD or levels of MBIs. Also, the NCD group had significantly elevated CRP and peroxide levels compared with the NORM group at postoperative day 4 while C3a was significantly elevated at 6 hours.

CONCLUSION

NSE and tau are better associated with NCD and less influenced by cardiotomy suction compared with S-100beta. Inflammatory and oxidative stress is associated with NCD post-CPB.

Surprising lack of sex differences in normal cognitive aging in twins

Sex differences in the etiology of normal cognitive functioning in aging remain largely unexplored. We conducted an investigation of genetic and environmental contributions to sex differences in level of cognitive performance and rate of decline in the Swedish Adoption/Twin Study of Aging (SATSA) (Finkel & Pedersen, 2004) data set. Behavioral genetic parameterizations of a latent growth curve model were fit to longitudinal data on 11 cognitive measures. Seven hundred and ninety-eight non-demented individuals had cognitive data across four waves of measurement covering 13 years. Participants ranged in age from 44 to 88 at first testing wave; 60% were female. Results indicated sex differences in mean performance for five cognitive measures and in rates of decline for Information and Card Rotations. Only Synonyms demonstrated sex differences in genetic and environmental contributions to mean performance: heritability was higher in men than women. Despite differential longevity and susceptibility to disease, there are no consistent indications that men and women show different patterns of cognitive aging.

Increase in core body temperature of Alzheimer's disease patients as a possible indicator of chronic neuroinflammation: a meta-analysis

BACKGROUND

Neuroinflammation contributes to the pathogenesis of Alzheimer's disease (AD). Increased pro-inflammatory cytokine levels have been reported in the brain and cerebro-spinal fluid of individuals affected by this neurodegenerative disorder. These same cytokines, including interleukin -1, interleukin-6 and tumor necrosis factor-alpha, are also believed to be involved in thermoregulation. Furthermore, their effects are thought to be mediated through the induction of cyclooxygenases resulting in increased production of inflammatory prostaglandins. Such increases have been observed in AD brains. We hypothesized that these increased levels of inflammatory mediators could lead to an increase in core body temperature in AD patients.

OBJECTIVE

To determine whether clinical signs of AD are accompanied by an increase in core body temperature.

METHODS

Analysis of the scientific literature identified six studies that used continuous rectal measurements of core body temperature in AD and control patients. Meta-analysis was performed on these published data.

RESULTS

Meta-analysis showed that the mean core body temperature in AD patients was significantly increased by 0.10 degrees C when compared to healthy elderly subjects. The two-sided p value was 0.0355, and the 95% confidence interval was 0.0068-0.1950. The severity of AD pathology did not appear to contribute significantly (p = 0.235) to the heterogeneity in the core body temperature among different groups of AD patients.

CONCLUSION

The significant increase in core body temperature in AD patients could be a direct consequence of local inflammatory reactions in the brain. Although the changes observed are probably too small to be of any diagnostic value, these observations lend further support to the neuroinflammatory hypothesis of AD pathology.

C-Reactive protein and inflammatory response associated to neurocognitive decline following cardiac surgery

BACKGROUND

It has been recognized that neurocognitive decline (NCD) often occurs as a complication in cardiac surgery. The early inflammatory response and C-reactive protein (CRP) was examined in relation to NCD and to a marker of axonal central nervous system (CNS) injury after cardiopulmonary bypass.

METHODS

A cohort of patients undergoing coronary artery bypass grafting and/or valve procedures using cardiopulmonary bypass were administered a neurocognitive battery preoperatively and postoperatively at 6 hours and day 4. CRP, interleukin 1 beta, and interleukin 10 were quantified from serum. Increase of serum tau protein after surgery was used as a marker of axonal CNS damage.

RESULTS

The rate of NCD was found to be 40.5% in this group. Surprisingly, known predictors of NCD did not differ significantly between patients with/without NCD. Patients with NCD had an early increase of CRP of a significantly higher magnitude than those without NCD (38.01 +/- 11.4 vs 16.49 +/- 3.5 mg/L, P = .042), interleukin 1ss (2.35 +/- 0.3 vs 1.20 +/- 0.2 pg/mL, P = .002), and interleukin 10 (29.77 +/- 4.7 vs 12.94 +/- 2.2 pg/mL, P < .001). Increase in serum Tau protein was significantly correlated to NCD (r = 0.50, P = .02).

CONCLUSION

Perioperative increases in CRP and inflammatory cytokines are associated with NCD in patients after cardiopulmonary bypass. Thus, it appears that inflammation plays a key role in NCD pathophysiology, likely via axonal CNS injury, and could become a target for prevention.

Age and Neuroinflammation: A Lifetime of Psychoneuroimmune Consequences

This article reviews the literature indicating that the innate immune cells of the brain become more reactive with age. Although it is unclear how glia reactivity increases, emerging evidence suggests these alterations allow exacerbated neuroinflammation and sickness behavior following peripheral immune activation. This amplified or prolonged exposure to inflammatory cytokines in the brain may impair neuronal plasticity and underlie a heightened neuroinflammatory response in the aged that also may lead to other neurobehavioral impairments such as delirium, depression, and, potentially, the onset of neurologic disease. Therefore pharmacologic strategies to decrease neuroinflammation associated with infection may be important for improving recovery from sickness and reducing neurobehavioral deficits in the elderly.

Burnout and risk of cardiovascular disease: evidence, possible causal paths, and promising research directions

Burnout is characterized by emotional exhaustion, physical fatigue, and cognitive weariness, resulting from prolonged exposure to work-related stress. The authors review the accumulated evidence suggesting that burnout and the related concept of vital exhaustion are associated with increased risk of cardiovascular disease and cardiovascular-related events. The authors present evidence supporting several potential mechanisms linking burnout with ill health, including the metabolic syndrome, dysregulation of the hypothalamic-pituitary-adrenal axis along with sympathetic nervous system activation, sleep disturbances, systemic inflammation, impaired immunity functions, blood coagulation and fibrinolysis, and poor health behaviors. The association of burnout and vital exhaustion with these disease mediators suggests that their impact on health may be more extensive than currently indicated.

The immune risk phenotype is associated with IL-6 in the terminal decline stage: findings from the Swedish NONA immune longitudinal study of very late life functioning

In the present NONA immune longitudinal study, we further examine the previously identified T cell immune risk phenotype (IRP), relative inflammatory activity, morbidity and 2-year mortality in very old individuals >90 years. T-cell subsets as well as the inflammatory markers IL-6, IL-10, C-reactive protein, transthyretin and albumin were evaluated. IRP and low-grade inflammation predicted 57% of observed deaths and 97% of survival over 2 years, and was not significantly affected by individuals' health status, suggesting that the physiological ageing processes of T-cell immunosenescence and low-grade inflammation are of primary importance in late life survival. IRP non-survivors showed only a minor inflammatory activity at baseline, but had in contrast to survivors developed increased activity at follow-up. The results suggest a sequence of stages for IRP individuals that begin with acquisition of CMV infection in earlier life, followed by generation of CD8+CD28- cells to control persistent CMV infection and eventually the development of an IRP. Intriguingly, we also found that rare individuals moved out of the IRP category by a process of immune suppression, including increases in IL-6 and IL-10 and decreases in the number of CD3+CD8+CD28- cells. The further characterisation of these exceptional individuals may allow insight into remedial approaches for those who remain in the IRP category until death.

Impaired natural immunity, cognitive dysfunction, and physical symptoms in patients with chronic fatigue syndrome: preliminary evidence for a subgroup?

OBJECTIVE

The diagnostic criteria of chronic fatigue syndrome (CFS) define a heterogeneous population composed of several subgroups. Past efforts to identify subgroup markers have met with mixed success. This study was designed to examine natural killer cell activity (NKCA) as a potential subgroup marker by comparing the clinical presentations of CFS patients with and without clinically reduced NKCA.

METHODS

Forty-one female CFS patients were classified into having either low or normal NKCA levels. These subgroups were then compared on objective measures of cognitive functioning and subjective assessments of fatigue, vigor, cognitive impairment, and daytime dysfunction.

RESULTS

Relative to CFS patients in the normal-NKCA subgroup, low-NKCA patients reported less vigor, more daytime dysfunction, and more cognitive impairment. In addition, low-NKCA patients performed less on objective measures of cognitive functioning relative to normal-NKCA patients.

CONCLUSIONS

The results are offered as preliminary evidence in support of using NKCA as an immunological subgroup marker in CFS. Findings are also discussed in terms of known associations between dysregulated immune functions, somatic symptoms, and psychological stress.

Age-related changes in neuroprotection: is estrogen pro-inflammatory for the reproductive senescent brain?

Estrogen replacement therapy (ERT) is widely prescribed to postmenopausal women for relief from the adverse vasomotor effects of menopause, to reduce bone loss, to improve cardiovascular health, and to protect against metabolic disorders. However, there is now greater awareness of the increased risk to benefit ratio from the recently concluded Women's Health Initiative Memory Study (WHIMS), which reported that ERT increased the risk of cognitive impairment and dementia in elderly women. Studies from the experimental literature indicate that while estrogen is neuroprotective in many instances, estrogen replacement can be deleterious in some cases. These differences may be partly due to the age and species of the experimental model. The majority of the experimental data comes from studies where the age or endocrine status of the animal model is not comparable to that of menopausal or postmenopausal women, such as those in the WHIMS study. In this review, we will focus on age-related changes in estrogen's neuroprotective effects and evidence that reproductive senescence-related changes in the blood-brain barrier and the immune system may result in deleterious consequences for ERT.

Hydrolytic and nonenzymatic functions of acetylcholinesterase comodulate hemopoietic stress responses

Glucocorticoid-initiated granulocytosis, excessive proliferation of granulocytes, persists after cortisol levels are lowered, suggesting the involvement of additional stress mediator(s). In this study, we report that the stress-induced acetylcholinesterase variant, AChE-R, and its cleavable, cell-penetrating C-terminal peptide, ARP, facilitate granulocytosis. In postdelivery patients, AChE-R-expressing granulocyte counts increased concomitantly with serum cortisol and AChE activity levels, yet persisted after cortisol had declined. Ex vivo, mononuclear cells of adult peripheral blood responded to synthetic ARP26 by overproduction of hemopoietically active proinflammatory cytokines (e.g., IL-6, IL-10, and TNF-alpha). Physiologically relevant ARP26)levels promoted AChE gene expression and induced the expansion of cultured CD34+ progenitors and granulocyte maturation more effectively than cortisol, suggesting autoregulatory prolongation of ARP effects. In vivo, transgenic mice overexpressing human AChE-R, unlike matched controls, showed enhanced expression of the myelopoietic transcription factor PU.1 and maintained a stable granulocytic state following bacterial LPS exposure. AChE-R accumulation and the consequent inflammatory consequences can thus modulate immune responses to stress stimuli.

The association between burnout, depression, anxiety, and inflammation biomarkers: C-reactive protein and fibrinogen in men and women

Following the demonstrated association of employee burnout or vital exhaustion with several risk factors for cardiovascular disease (CVD) and CVD risk, the authors investigated the possibility that one of the mechanisms linking burnout with CVD morbidity is microinflammation, gauged in this study by high-sensitivity C-reactive protein (hs-CRP) and fibrinogen concentrations. Their sample included 630 women and 933 men, all apparently healthy, who underwent periodic health examinations. The authors controlled for possible confounders including 2 other negative affective states: depression and anxiety. In women, burnout was positively associated with hs-CRP and fibrinogen concentrations, and anxiety was negatively associated with them. In men, depression was positively associated with hs-CRP and fibrinogen concentrations, but not with burnout or anxiety. Thus, burnout, depression, and anxiety are differentially associated with microinflammation biomarkers, dependent on gender.

Circulating biomarkers of cognitive decline and dementia

Plasma and serum biochemical markers proposed for cognitive decline of degenerative (Alzheimer's disease, AD) or vascular origin and predementia syndromes (mild cognitive impairment and other related entities) are based on pathophysiologic processes such as lipoprotein metabolism (total cholesterol, apolipoprotein E, 24S-hydroxy-cholesterol), and vascular disease (homocysteine, lipoprotein(a)); SP formation (amyloid beta(Abeta)-protein, Abeta autoantibodies, platelet APP isoforms), oxidative stress (isoprostanes, vitamin E), and inflammation (cytokines). This review will focus on the current knowledge on circulating serum and plasma biomarkers of cognitive decline and dementia that are linked to cholesterol homeostasis and lipoprotein abnormalities, senile plaque formation and amyloid precursor protein (APP) metabolism, oxidative stress, and inflammatory reactions. Special emphasis will, however, be placed on biomarkers related to lipoprotein metabolism and vascular disease. Analytically, most plasma and serum proteins or metabolites lack reproducibility, sensitivity, or specificity for the diagnosis, risk and progression assessment, or therapeutic monitoring of AD and other dementing disorders. Measures linked to lipoprotein metabolism and vascular disease, APP metabolism, oxidative stress, or inflammation appear altered in AD relative to controls, but lack sufficient discriminatory power. Measures combining several biomarkers or incorporating a range of proteins in plasma and small molecule metabolites are promising approaches for the development of plasma or serum-based diagnostic tests for AD and other dementing disorders, as well as for predementia syndromes.

Improvement of memory for context by inhibition of caspase-1 in aged rats

Impaired learning and memory is a common pathologic feature associated with numerous neurologic disorders. There is strong evidence that central inflammation contributes significantly to the progression of several neurodegenerative diseases as well as to the ageing process. For example, in aged rats an increase in interleukin-1beta (IL-1beta) is implicated in the decline of synaptic plasticity in the hippocampus and impaired performance on cognitive tasks such as contextual fear conditioning. IL-1beta is a proinflammatory cytokine initially synthesized in an inactive precursor form that is cleaved by caspase-1 to generate the biologically mature form. In the present study, cleavage of IL-1beta was chronically inhibited using a specific caspase-1 inhibitor (Ac-YVAD-CMK; 10 pmol) in both aged (22 month) and young (4 month) rats. Both groups received Ac-YVAD-CMK for 28 days intracerebroventricularly through a brain infusion cannula connected to an osmotic minipump. On day 20 the animals were trained in contextual fear conditioning, and memory for context was tested on day 22. Chronic infusion of a specific caspase-1 inhibitor in aged rats ameliorated age-related increases in hippocampal IL-1beta and improved memory for context.

The impact of medical illness on executive function

Executive function can be defined as one's ability to plan, initiate, sequence, monitor, and inhibit complex goal-directed behaviors. Although executive impairment is generally associated with dementia, recent studies have suggested that patients with chronic diseases, such as hypertension, chronic obstructive pulmonary disease, and diabetes, may also have executive deficits independent of psychiatric comorbidities. Because executive function is associated with functional outcomes, medication compliance, and the capacity to give informed consent, it is important that it be assessed. However, it is the authors' impression that executive function is not adequately assessed in medical settings, despite the availability of reliable measures. This article reviews the impact of medical illness on executive function and discusses practical diagnostic instruments and treatment strategies. The changes in functional status associated with executive impairment as well as pathophysiology and treatment strategies are also discussed.

The immune system and neuropsychiatric diseases

The immune system has a complex and dynamic relationship with the nervous system, both in health and disease. The immune system surveys the central and peripheral nervous systems, becoming activated in response to foreign substances, infectious particles or neoplasms. Conversely, the nervous system modulates immune system function both through the neuroendocrine axis and through vagus nerve efferents. In disease states, this dynamic relationship is perturbed, resulting in neuropsychiatric diseases. In this manuscript, we will summarize fundamental principles of the immune system and its interaction with the nervous system. We will describe the critical components of the adaptive and innate branches of the immune system and will describe important effectors and signalling pathways in each. By understanding the principles of the immune system and how these principles relate to nervous system function, the reader will be prepared to interpret subsequent manuscripts in this issue.

Cognitive impairment in preclinical Alzheimer's disease: a meta-analysis

To determine the size of the impairment across different cognitive domains in preclinical Alzheimer's disease (AD), a meta-analysis based on 47 studies involving 9,097 controls and 1,207 preclinical AD cases was conducted. There were marked preclinical deficits in global cognitive ability, episodic memory, perceptual speed, and executive functioning; somewhat smaller deficits in verbal ability, visuospatial skill, and attention; and no preclinical impairment in primary memory. Younger age (< 75 years) and shorter follow-up intervals (< 3 years) were associated with larger effect sizes for both global cognitive ability and episodic memory. For global cognitive ability, studies that used population-based sampling yielded larger effect sizes; for episodic memory, larger differences were seen in studies that preidentified groups in terms of baseline cognitive impairment. Within episodic memory, delayed testing and recall-based assessment resulted in the largest effect sizes. The authors conclude that deficits in multiple cognitive domains are characteristic of AD several years before clinical diagnosis. The generalized nature of the deficit is consistent with recent observations that multiple brain structures and functions are affected long before the AD diagnosis.

Interactive relations of central versus total obesity and blood pressure to cognitive function

OBJECTIVE

To examine the potential interactive relations of central versus total obesity and blood pressure (BP) to cognitive function.

METHOD

In all, 90 healthy, stroke, and dementia-free middle-aged and older adults (ages 54-81 years; 63% male; 93% White) underwent biomedical and neuropsychological assessment. Relations of central obesity (assessed by waist circumference (WC)) and systolic or diastolic BP to cognitive function were examined in multiple regression models. Next, body mass index (BMI) was substituted for WC in the models.

RESULTS

After statistical adjustment for age, education, gender, and other potential confounders including components of the metabolic syndrome (depending on the model), significant interactions of WC and systolic (or diastolic) BP were noted for the Grooved Pegboard - Dominant Hand and Stroop Interference scores, with marginally significant results for Grooved Pegboard - Nondominant Hand. In general, individuals with greater WC and higher BP performed most poorly on these measures. Similar results were obtained for BMI.

CONCLUSION

Independent of other confounders including facets of the metabolic syndrome, the combination of greater WC (or BMI) and higher (systolic or diastolic) BP was associated with diminished performance on tests of motor speed and manual dexterity, and executive function (i.e. response inhibition) accounting for 3-13% of the variance in these measures. In healthy older adults, there are similar, negative relations of central and total obesity to cognitive function that are potentiated by higher BP levels.

Emerging evidence of hepatitis C virus neuroinvasion

It has been reported that hepatitis C virus (HCV) infection is associated with cognitive dysfunction, fatigue and depression, which do not correlate with the severity of liver disease and cannot be accounted for by hepatic encephalopathy or drug abuse. There is also emerging evidence that HCV infection can have negative neurocognitive effects in HIV-infected cohorts. Magnetic resonance spectroscopy has suggested the likely existence of a biological basis for these effects. HCV replicative forms have recently been detected in autopsy brain tissue and the infected cells have been identified as CD68-positive (macrophages/microglia). These findings raise the possibility that HCV infection of the brain could be directly related to the reported neuropsychological and cognitive changes. HCV is not strictly hepatotropic, as it can also replicate in leukocytes, including monocytes/macrophages. The latter cells could provide access of HCV into the central nervous system ('Trojan horse' mechanism) in a process similar to that postulated for HIV-1. In support of this hypothetical mechanism come reports showing a close relationship between HCV sequences present in the brain and cerebrospinal fluid and sequences found in lymph nodes and peripheral blood mononuclear cells. However, despite some similarities there is a fundamental difference between HIV-1 and HCV infection as the latter does not progress into AIDS-type dementia.

High cholesterol diet results in increased expression of interleukin-6 and caspase-1 in the brain of apolipoprotein E knockout and wild type mice

Inflammation in the central nervous system is an early hallmark of many neurodegenerative diseases including Alzheimer's disease (AD). Recently, increasing evidence suggests that hypercholesterolemia during midlife and abnormalities in the cholesterol metabolism could have an important role in the pathogenesis of AD. In the present study, we have evaluated the effect of high cholesterol (HC) diet on the expression of interleukin-6 (IL-6), a cytokine involved in neurodegeneration, and caspase-1, that is responsible for the cleavage of the precursors of interleukin-1 beta (IL-1 beta) and interleukin-18 (IL-18) in the brain of apolipoprotein E (Apo E) knock-out (KO) and wild type (WT) mice. The density of IL-6-positive cells was increased in the hippocampus (p<0.0001) and the dorsal part of the cortex (p<0.001) of KO and WT mice on HC diet (KOHC and WTHC mice, respectively) compared to KO and WT mice on ND (KOND and WTND mice, respectively). KOHC mice had increased caspase-1 positive cells and staining intensity in the hippocampus in comparison with WTHC mice (p<0.01). In the hippocampus, the density of caspase-1 positive cells was also higher in KOHC compared to KOND mice (p<0.05) and KOHC compared with WTHC mice (p<0.01). There was a major increase in caspase-1 immunoreactivity and cell density in both the dosal part of the cortex (p<0.001) and the lateral part of the cortex (p<0.005) in KO and WT mice on HC diet compared to ND. The findings of the present study indicate that chronic exposure to HC diet increases the expression of the two important inflammatory mediators IL-6 and caspase-1 in the brain of KO and WT mice. In the case of caspase-1, we report a major difference in the effect of HC diet on the KO mice compared to WT mice in the hippocampus. Increased expression of inflammatory mediators involved in neurodegeneration could be a potential mechanism by which hypercholesterolemia and HC diet increase the risk of AD.

IL-6 induces regionally selective spinal cord injury in patients with the neuroinflammatory disorder transverse myelitis

Transverse myelitis (TM) is an immune-mediated spinal cord disorder associated with inflammation, demyelination, and axonal damage. We investigated the soluble immune derangements present in TM patients and found that IL-6 levels were selectively and dramatically elevated in the cerebrospinal fluid and directly correlated with markers of tissue injury and sustained clinical disability. IL-6 was necessary and sufficient to mediate cellular injury in spinal cord organotypic tissue culture sections through activation of the JAK/STAT pathway, resulting in increased activity of iNOS and poly(ADP-ribose) polymerase (PARP). Rats intrathecally infused with IL-6 developed progressive weakness and spinal cord inflammation, demyelination, and axonal damage, which were blocked by PARP inhibition. Addition of IL-6 to brain organotypic cultures or into the cerebral ventricles of adult rats did not activate the JAK/STAT pathway, which is potentially due to increased expression of soluble IL-6 receptor in the brain relative to the spinal cord that may antagonize IL-6 signaling in this context. The spatially distinct responses to IL-6 may underlie regional vulnerability of different parts of the CNS to inflammatory injury. The elucidation of this pathway identifies specific therapeutic targets in the management of CNS autoimmune conditions.

Low-dose endotoxemia and human neuropsychological functions

Epidemiological data demonstrate an association between systemic low-grade inflammation defined as 2- to 3-fold increases in circulating inflammatory mediators and age-related decline in cognitive function. However, it is not known whether small elevations of circulating cytokine levels cause direct effects on human neuropsychological functions. We investigated changes in emotional, cognitive, and inflammatory parameters in an experimental in vivo model of low-grade inflammation. In a double-blind crossover study, 12 healthy young males completed neuropsychological tests before as well as 1.5, 6, and 24 h after an intravenous injection of Escherichia coli endotoxin (0.2 ng/kg) or saline in two experimental sessions. Endotoxin administration had no effect on body temperature, cortisol levels, blood pressure or heart rate, but circulating levels of tumor necrosis factor (TNF) and interleukin (IL)-6 increased 2- and 7-fold, respectively, reaching peak values at 3 h, whereas soluble TNF-receptors and IL-1 receptor antagonist peaked at 4.5 h. The neutrophil count increased and the lymphocyte count declined. In this model, low-dose endotoxemia did not affect cognitive performance significantly but declarative memory performance was inversely correlated with cytokine increases. In conclusion, our findings demonstrate a negative association between circulating IL-6 and memory functions during very low-dose endotoxemia independently of physical stress symptoms, and the hypothalamo-pituitary-adrenal axis.