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

Integrating the monoamine, neurotrophin and cytokine hypotheses of depression--a central role for the serotonin transporter?

Monoamine, in particular serotonergic neurotransmission has long been recognized as an important factor in the aetiology of depression. The serotonin transporter (SERT) is the primary regulator of serotonin levels in the brain and a key target for widely used antidepressant drugs, such as selective serotonin reuptake inhibitors (SSRIs). In realising the limitations of current antidepressant therapy, depression research has branched out to encompass other areas such as synaptic plasticity, neurogenesis and brain structural remodelling as factors which influence mood and behaviour. More recently, the immune system has been implicated in the development of depression and various intriguing observations have inspired the cytokine hypothesis of depression. Over the past two decades evidence of in vitro and in vivo regulation of SERT function by pro-inflammatory cytokines as well as by mechanisms of synaptic plasticity has been accumulating, offering a mechanistic link between the monoamine, neurotrophin and cytokine theories of depression. This review will focus firstly on the interconnected roles of serotonin and neurotrophins in depression and antidepressant therapy, secondly on the impact of the immune system on serotonin transporter regulation and neurotrophin signalling and finally we propose a model of reciprocal regulation of serotonin and neurotrophin signalling in the context of inflammation-induced depression.

Regional brain shrinkage over two years: individual differences and effects of pro-inflammatory genetic polymorphisms

We examined regional changes in brain volume in healthy adults (N=167, age 19-79years at baseline; N=90 at follow-up) over approximately two years. With latent change score models, we evaluated mean change and individual differences in rates of change in 10 anatomically-defined and manually-traced regions of interest (ROIs): lateral prefrontal cortex (LPFC), orbital frontal cortex (OF), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), caudate nucleus (Cd), putamen (Pt), insula (In), cerebellar hemispheres (CbH), and primary visual cortex (VC). Significant mean shrinkage was observed in the Hc, CbH, In, OF, and PhG, and individual differences in change were noted in all regions, except the OF. Pro-inflammatory genetic variants modified shrinkage in PhG and CbH. Carriers of two T alleles of interleukin-1β (IL-1β C-511T, rs16944) and a T allele of methylenetetrahydrofolate reductase (MTHFR C677T, rs1801133) polymorphisms showed increased PhG shrinkage. No effects of a pro-inflammatory polymorphism for C-reactive protein (CRP-286C>A>T, rs3091244) or apolipoprotein (APOE) ε4 allele were noted. These results replicate the pattern of brain shrinkage observed in previous studies, with a notable exception of the LPFC, thus casting doubt on the unique importance of prefrontal cortex in aging. Larger baseline volumes of CbH and In were associated with increased shrinkage, in conflict with the brain reserve hypothesis. Contrary to previous reports, we observed no significant linear effects of age and hypertension on regional brain shrinkage. Our findings warrant further investigation of the effects of neuroinflammation on structural brain change throughout the lifespan.

Neurotoxicity of cancer chemotherapy

There is accumulating clinical evidence that chemotherapeutic agents induce neurological side effects, including memory deficits and mood disorders, in cancer patients who have undergone chemotherapeutic treatments. This review focuses on chemotherapy-induced neurodegeneration and hippocampal dysfunctions and related mechanisms as measured by in vivo and in vitro approaches. These investigations are helpful in determining how best to further explore the causal mechanisms of chemotherapy-induced neurological side effects and in providing direction for the future development of novel optimized chemotherapeutic agents.

Cognitive effects of cancer systemic therapy: implications for the care of older patients and survivors

The number of patients with cancer who are age 65 years or older (hereinafter "older") is increasing dramatically. One obvious aspect of cancer care for this group is that they are experiencing age-related changes in multiple organ systems, including the brain, which complicates decisions about systemic therapy and assessments of survivorship outcomes. There is a consistent body of evidence from studies that use neuropsychological testing and neuroimaging that supports the existence of impairment following systemic therapy in selected cognitive domains among some older patients with cancer. Impairment in one or more cognitive domains could have important effects in the daily lives of older patients. However, an imperfect understanding of the precise biologic mechanisms underlying cognitive impairment after systemic treatment precludes development of validated methods for predicting which older patients are at risk. From what is known, risks may include lifestyle factors such as smoking, genetic predisposition, and specific comorbidities such as diabetes and cardiovascular disease. Risk also interacts with physiologic and cognitive reserve, because even at the same chronological age and with the same number of illnesses, older patients vary from having high reserve (ie, biologically younger than their age) to being frail (biologically older than their age). Surveillance for the presence of cognitive impairment is also an important component of long-term survivorship care with older patients. Increasing the workforce of cancer care providers who have geriatrics training or who are working within multidisciplinary teams that have this type of expertise would be one avenue toward integrating assessment of the cognitive effects of cancer systemic therapy into routine clinical practice.

Effect of intravenous infusion of dobutamine hydrochloride on the development of early postoperative cognitive dysfunction in elderly patients via inhibiting the release of tumor necrosis factor-α

To investigate the effects of dobutamine hydrochloride on early postoperative cognitive dysfunction (POCD) and plasma tumor necrosis factor (TNF)-α concentration in patients undergoing hip arthroplasty, 124 patients undergoing unilateral total hip arthroplasty, aged 70-92 years old, were randomly assigned to four groups (n=31) as follows: a control group of patients receiving only saline (intravenous infusion, i.v.); and groups receiving 2, 4, or 6μgkg(-1)min(-1) (i.v.) of dobutamine hydrochloride. Cognitive functions were assessed on the day before surgery (T1), and the 1st day (T2), 3rd day (T3), and 7th day (T4) postsurgery using the Mini Mental State Examination (MMSE). The plasma TNF-α protein level was determined 10min before anesthesia (Ta), and 10min (Tb), 30min (Tc), and 60min (Td) after anesthesia by an enzyme-linked immunosorbent assay. Cognitive disorder was observed within the first 3 days after hip arthroplastic surgery, and it had recovered 7 days after the operation in the control group of patients. Administration of 2 or 4μgkg(-1)min(-1) dobutamine hydrochloride was able to reverse the early POCD. Simultaneously, an increase of plasma TNF-α levels 30min after anesthesia was observed (41.34±9.61 vs. 27.75±5.45), which was significantly suppressed by the administration of low-dose dobutamine hydrochloride (29.23±7.32 vs. 41.34±9.61) but not by high-dose dobutamine hydrochloride (45.9±12.11 vs. 41.34±9.61). Together, our data indicated that the plasma concentration of TNFα was engaged in the effect of dobutamine hydrochloride on POCD.

Long-term systemic inflammation and cognitive impairment in a population-based cohort

OBJECTIVES

Evidence suggests inflammation is associated with cognitive impairment, but previous epidemiological studies have reported conflicting results.

DESIGN

Prospective population-based cohort.

SETTING

Epidemiology of Hearing Loss Study participants.

PARTICIPANTS

Individuals without cognitive impairment in 1998-2000 (N = 2,422; 1,947 with necessary data).

MEASUREMENTS

Cognitive impairment (Mini-Mental State Examination score <24 or diagnosis of dementia) was ascertained in 1998-2000, 2003-2005, and 2009-2010. Serum C-reactive protein (CRP) and interleukin-6 (IL-6) were measured in 1988-1990, 1998-2000, and 2009-2010; tumor necrosis factor-alpha was measured from 1998-2000.

RESULTS

Participants with high CRP in 1988-1990 and 1998-2000 had lower risk of cognitive impairment than those with low CRP at both time points (hazard ratio (HR) = 0.46, 95% confidence interval (CI) = 0.26-0.80). Risk did not differ according to 10-year IL-6 profile or baseline inflammation category in the whole cohort. In sensitivity analyses restricted to statin nonusers, those with high IL-6 at both times had greater risk of cognitive impairment than those with low IL-6 at both times (HR = 3.35, 95% CI = 1.09-10.30). In secondary analyses, each doubling of IL-6 change over 20 years was associated with greater odds of cognitive impairment in 2009-2010 in the whole cohort (odds ratio (OR) = 1.40, 95% CI = 1.04-1.89), whereas a doubling of CRP change over 20 years was associated with cognitive impairment only in statin nonusers (OR = 1.32, 95% CI = 1.06-1.65).

CONCLUSION

With data collected over 20 years, this study demonstrated greater likelihood of cognitive impairment in individuals with repeated high or increasing IL-6. The inconsistent CRP findings may reflect effects of statin medications, survival effects, or adverse effects associated with chronically low CRP. Further studies of long-term inflammation and cognitive impairment are needed.

CX3CL1 is up-regulated in the rat hippocampus during memory-associated synaptic plasticity

Several cytokines and chemokines are now known to play normal physiological roles in the brain where they act as key regulators of communication between neurons, glia, and microglia. In particular, cytokines and chemokines can affect cardinal cellular and molecular processes of hippocampal-dependent long-term memory consolidation including synaptic plasticity, synaptic scaling and neurogenesis. The chemokine, CX₃CL1 (fractalkine), has been shown to modulate synaptic transmission and long-term potentiation (LTP) in the CA1 pyramidal cell layer of the hippocampus. Here, we confirm widespread expression of CX₃CL1 on mature neurons in the adult rat hippocampus. We report an up-regulation in CX₃CL1 protein expression in the CA1, CA3 and dentate gyrus (DG) of the rat hippocampus 2 h after spatial learning in the water maze task. Moreover, the same temporal increase in CX₃CL1 was evident following LTP-inducing theta-burst stimulation in the DG. At physiologically relevant concentrations, CX₃CL1 inhibited LTP maintenance in the DG. This attenuation in dentate LTP was lost in the presence of GABA_A receptor/chloride channel antagonism. CX₃CL1 also had opposing actions on glutamate-mediated rise in intracellular calcium in hippocampal organotypic slice cultures in the presence and absence of GABA_A receptor/chloride channel blockade. Using primary dissociated hippocampal cultures, we established that CX₃CL1 reduces glutamate-mediated intracellular calcium rises in both neurons and glia in a dose dependent manner. In conclusion, CX₃CL1 is up-regulated in the hippocampus during a brief temporal window following spatial learning the purpose of which may be to regulate glutamate-mediated neurotransmission tone. Our data supports a possible role for this chemokine in the protective plasticity process of synaptic scaling.

Cognitive impairment in coeliac disease improves on a gluten-free diet and correlates with histological and serological indices of disease severity

BACKGROUND

Mild impairments of cognition or 'Brain fog' are often reported by patients with coeliac disease but the nature of these impairments has not been systematically investigated.

AIM

This longitudinal pilot study investigated relationships between cognitive function and mucosal healing in people with newly diagnosed coeliac disease commencing a gluten-free diet.

METHODS

Eleven patients (8 females, 3 males), mean age 30 (range 22-39) years, were tested with a battery of cognitive tests at weeks 0, 12 and 52. Information processing efficacy, memory, visuospatial ability, motoric function and attention were tested. Small bowel biopsies were collected via routine gastroscopy at weeks 12 and 52 and were compared to baseline Marsh scores. Cognitive performance was compared to serum concentrations of tissue transglutaminase antibodies, biopsy outcomes and other biological markers.

RESULTS

All patients had excellent adherence to the diet. Marsh scores improved significantly (P = 0.001, Friedman's test) and tissue transglutaminase antibody concentrations decreased from a mean of 58.4 at baseline to 16.8 U/mL at week 52 (P = 0.025). Four of the cognitive tests assessing verbal fluency, attention and motoric function showed significant improvement over the 12 months and strongly correlated with the Marsh scores and tissue transglutaminase antibody levels (r = 0.377-0.735; all P < 0.05). However, no meaningful patterns of correlations were found for nutritional or biochemical markers, or markers of intestinal permeability.

CONCLUSIONS

In newly diagnosed coeliac disease, cognitive performance improves with adherence to the gluten-free diet in parallel to mucosal healing. Suboptimal levels of cognition in untreated coeliac disease may affect the performance of everyday tasks.

Cognitive impairment in older patients with breast cancer before systemic therapy: is there an interaction between cancer and comorbidity?

PURPOSE

To determine if older patients with breast cancer have cognitive impairment before systemic therapy.

PATIENTS AND METHODS

Participants were patients with newly diagnosed nonmetastatic breast cancer and matched friend or community controls age > 60 years without prior systemic treatment, dementia, or neurologic disease. Participants completed surveys and a 55-minute battery of 17 neuropsychological tests. Biospecimens were obtained for APOE genotyping, and clinical data were abstracted. Neuropsychological test scores were standardized using control means and standard deviations (SDs) and grouped into five domain z scores. Cognitive impairment was defined as any domain z score two SDs below or ≥ two z scores 1.5 SDs below the control mean. Multivariable analyses evaluated pretreatment differences considering age, race, education, and site; comparisons between patient cases also controlled for surgery.

RESULTS

The 164 patient cases and 182 controls had similar neuropsychological domain scores. However, among patient cases, those with stage II to III cancers had lower executive function compared with those with stage 0 to I disease, after adjustment (P = .05). The odds of impairment were significantly higher among older, nonwhite, less educated women and those with greater comorbidity, after adjustment. Patient case or control status, anxiety, depression, fatigue, and surgery were not associated with impairment. However, there was an interaction between comorbidity and patient case or control status; comorbidity was strongly associated with impairment among patient cases (adjusted odds ratio, 8.77; 95% CI, 2.06 to 37.4; P = .003) but not among controls (P = .97). Only diabetes and cardiovascular disease were associated with impairment among patient cases.

CONCLUSION

There were no overall differences between patients with breast cancer and controls before systemic treatment, but there may be pretreatment cognitive impairment within subgroups of patient cases with greater tumor or comorbidity burden.

Proposed mechanisms for cancer- and treatment-related cognitive changes

OBJECTIVES

To review the proposed mechanisms of cognitive changes associated with non-central nervous system cancers and cancer treatment.

DATA SOURCES

Review and synthesis of databased publications and review articles.

CONCLUSION

Proposed mechanisms include cytokine upregulation, hormonal changes, neurotransmitter dysregulation, attentional fatigue, genetic predisposition, and comorbid symptoms.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses need to understand the multiple mechanisms that may contribute to the development of cancer- and treatment-related cognitive changes so that they can identify patients at high risk and help patients understand why these changes occur.

A cognitive computational model inspired by the immune system response

The immune system has a cognitive ability to differentiate between healthy and unhealthy cells. The immune system response (ISR) is stimulated by a disorder in the temporary fuzzy state that is oscillating between the healthy and unhealthy states. However, modeling the immune system is an enormous challenge; the paper introduces an extensive summary of how the immune system response functions, as an overview of a complex topic, to present the immune system as a cognitive intelligent agent. The homogeneity and perfection of the natural immune system have been always standing out as the sought-after model we attempted to imitate while building our proposed model of cognitive architecture. The paper divides the ISR into four logical phases: setting a computational architectural diagram for each phase, proceeding from functional perspectives (input, process, and output), and their consequences. The proposed architecture components are defined by matching biological operations with computational functions and hence with the framework of the paper. On the other hand, the architecture focuses on the interoperability of main theoretical immunological perspectives (classic, cognitive, and danger theory), as related to computer science terminologies. The paper presents a descriptive model of immune system, to figure out the nature of response, deemed to be intrinsic for building a hybrid computational model based on a cognitive intelligent agent perspective and inspired by the natural biology. To that end, this paper highlights the ISR phases as applied to a case study on hepatitis C virus, meanwhile illustrating our proposed architecture perspective.

Raised serum proinflammatory cytokines in Alzheimer's disease with depression

The purpose of the present study was to identify the changes in the levels of proinflammatory cytokines like IL-1β, IL-6 and TNF-α in peripheral circulation in Alzheimer's disease (AD) subjects and to correlate these with associated depression and cognitive deficit. Fifty five AD subjects and thirty seven age and sex matched controls were included in the study. The AD patients were grouped as AD with depression (n= 31) and AD without depression (n= 24). The serum levels of IL-1β, IL-6 and TNF-α were determined by immunoassay by commercially available kits. The serum levels of IL-6 and TNF-α were elevated in AD patients with depression compared to control (p<0.001) or AD without depression (p<0.001). The serum level of IL-1β was higher in AD patients with or without depression as compared to controls. Furthermore, a strong inverse correlation was observed between the MMSE scores and serum levels of IL-6 or TNF-α in AD subjects with depression. The study highlights the important role of peripheral IL-6 and TNF-α in AD associated depression and cognitive deficits.

Peripheral cytokines as a chemical mediator for postconcussion like sickness behaviour in trauma and perioperative patients: literature review

Besides brain injury and systemic infection, cognitive and concussion like sickness behaviour is associated with muscular trauma and perioperative patients, which represents a major obstacle to daily activities and rehabilitation. The neuroinflammatory response triggers glial activation and consequently the release of proinflammatory cytokines within the hippocampus. We review clinical studies that have investigated neurocognitive and psychosomatic symptoms related to muscular trauma and in perioperative conditions. These include impaired attention and executive and general cognitive functioning. The purpose of this literature review is to focus on the systemic inflammation and the role of proinflammatory cytokines IL1, IL6,and TNF and other inflammatory mediators which mediates the cognitive impairment and induces sickness behaviour. Moreover, this review will also help to determine if some patients could have long-term cognitive changes associated with musculoskeletal injuries or as a consequence of surgery and thereby will lead to efforts in reducing that risk.

Stress, schizophrenia and bipolar disorder

The role of stress in precipitating psychotic episodes in schizophrenia and bipolar disorder has long been acknowledged. However, the neurobiological mechanism/s of this association have remained elusive. Current neurodevelopmental models of psychosis implicate early dysfunction in biological systems regulating hypothalamic-pituitary-adrenal axis and immune function, with long-term effects on the development of the brain networks responsible for higher order cognitive processes and stress reactivity in later life. There is also increasing evidence of childhood trauma in psychosis, and its impact on the development of brain systems regulating stress. These findings are emerging in the context of a new era of epigenetic methods facilitating the study of environmental effects on gene expression. The evidence is thus converging: exposure to stress at critical periods in life may be an important factor in the development of the brain dysfunction that represents psychosis vulnerability, rather than merely interacting with an independent 'biological vulnerability' to manifest in psychosis.

Changes in serum cytokines in response to musculoskeletal surgical trauma

Background

Trauma induces local and subsequent systemic inflammatory reactions, and when the cytokine production is deregulated, a systemic inflammatory response syndrome with a potentially lethal outcome can occur. The understanding of the physiological mechanism of the cytokine network would be useful to better comprehend pathological conditions.

Methods

We analysed a panel of 30 cytokines in the serum of 20 patients operated with total hip replacement. Cytokine release was assessed postoperatively up to 6 days by a multiplex antibody bead kit and compared to pre-operative values.

Results

Surgery induced significant increments in serum levels of IL-2R at 6 days after surgery, in levels of IL-6 at 6 hours after surgery and at 1 day after surgery, in levels of IL-8 at 6 hours after surgery, in levels of IL-16 at 6 hours and at 1 day after surgery. Significant decreases in serum levels of IL-1Rα were found at the end of surgery, in levels of IL-12 at the end of surgery and at 6 hours after, and in levels of Eotaxin during all phases of the postoperative course.

Conclusions

The major findings were significant increases in systemic levels of the pro-inflammatory cytokines IL-6, IL-8, IL-16, while IL-12 was significantly decreased. Otherwise there were modest changes in the systemic cytokine kinetics and no significant expression of anti-inflammatory cytokines.

Markers of low-grade inflammation and endothelial dysfunction are related to reduced information processing speed and executive functioning in an older population - the Hoorn Study

Low-grade inflammation and endothelial dysfunction are related to cognitive decline and dementia, in a complex interplay with vascular factors and aging. We investigated, in an older population, low-grade inflammation and endothelial dysfunction in relation to detailed assessment of cognitive functioning. Furthermore, we explored this association within the context of vascular factors. 377 participants (73 ± 6 years) of the population-based Hoorn Study were included. In plasma samples of 2000-2001 (n=363) and/or 2005-2008 (n=323), biomarkers were determined of low-grade inflammation (CRP, TNF-alpha, IL-6, IL-8, SAA, MPO, and sICAM-1) and endothelial dysfunction (vWF, sICAM-1, sVCAM-1, sTM, sE-selectin). In 2005-2008, all participants underwent neuropsychological examination. Composite z-scores were computed for low-grade inflammation and endothelial dysfunction at both time points, and for six domains of cognitive functioning (abstract reasoning, memory, information processing speed, attention and executive functioning, visuoconstruction, and language). The association between low-grade inflammation and endothelial dysfunction, and cognitive functioning was evaluated with linear regression analysis. In secondary analyses, we explored the relation with vascular risk factors and cardiovascular disease. Low-grade inflammation and endothelial dysfunction were associated with worse performance on information processing speed and attention and executive functioning, in prospective and cross-sectional analyses (standardized betas ranging from -0.20 to -0.10). No significant relation with other cognitive domains was observed. Adjusting for vascular factors slightly attenuated the associations. Low-grade inflammation and endothelial dysfunction accounted for only 2.6% explained variance in cognitive functioning, on top of related vascular risk factors and cardiovascular disease. Bootstrapping analyses show that low-grade inflammation and endothelial dysfunction mediate the relation between vascular risk factors and cognitive functioning. This study shows that low-grade inflammation and endothelial dysfunction contribute to reduced information processing speed and executive functioning in an older population.

Significance of serum immune markers in identification of global functional impairment in the oldest old: cross-sectional results from the BELFRAIL study

The large burden and coexistence of physical disability, cognitive impairment, and depression in the oldest old makes summary markers of global functioning of great value, allowing for risk stratification. Inflammation may be a common underlying cause or represents a final common pathway. The present study investigated the association between elevated serum inflammatory markers and global functioning and its underlying aspects. A representative sample of 415 community-dwelling elderly subjects participating in the BELFRAIL study, with a mean age of 85 years, was included in the present analysis. Data on physical performance, dependence, and mental aspects of functioning and serum levels of 15 inflammatory proteins, including cytokines, chemokines, and acute-phase proteins, were assessed. Interleukin (IL)-6 was negatively associated with global functioning (odds ratio (OR) 4.35). The odds ratios for C-reactive protein (CRP) (OR 2.37) and the combined score of IL-6 and CRP (OR 2.59) were lower or not significant. IL-6 was significantly associated with physical dependence and cognitive function, and only a highly elevated serum level was associated with physical performance. Physical dependence was associated with a highly elevated CRP serum level. The proportion of functionally impaired older persons with elevated IL-6 was 81.93 %, giving a low positive predictive value (0.38), but a high negative predictive value (0.87). So, IL-6 is strongly associated with global functioning and all of the individual aspects of functioning, except suspected depression, in community-dwelling persons 80 years and older.

Neurocognitive disturbances associated with acute infectious mononucleosis, Ross River fever and Q fever: a preliminary investigation of inflammatory and genetic correlates

Disturbances in neurocognitive performance are a core feature of the acute sickness response to infection; however the underlying mechanisms remain unclear. The current study used a computerised battery to assess neurocognitive functioning in subjects enrolled in the Dubbo Infection Outcomes Study (n=107) - a prospective cohort of subjects followed from documented acute infection with Epstein Barr virus, Ross River virus, or Coxiella burnetii until recovery. Subjects were assessed when ill, and a subset again after complete recovery. Associations between sickness-related cognitive disturbances and single nucleotide polymorphisms (SNPs) in cytokine (interleukin [IL]-6, IL-10, tumor necrosis factor-α and interferon-γ) and neurobehavioral genes (serotonin transporter and catechol-O-methyltransferase) were explored. During acute infection, subjects exhibited slower matching-to-sample responses (p=0.03), poorer working memory capacity (p=0.014), mental planning (p=0.045), and dual attention task performance (p=0.02), and required longer to complete discordant Stroop trials (p=0.01) compared to recovery. Objective impairments correlated significantly with self-reported symptoms (p<0.05) as well as levels of the inflammation marker, C-reactive protein (p=0.001). Linear regression analysis identified an association between neurocognitive disturbance during acute illness and functional polymorphisms in inflammatory cytokine genes. Specifically, the high cytokine producing G allele of the IL-6-174G/C SNP was associated with poorer neurocognitive performance when subjects were ill (p=0.027). These findings confirm that acute infection impacts on neurocognitive performance, manifesting as slowed responses and impaired performance on complex tasks requiring higher-order functioning which has important real-world implications. The data provide the first preliminary evidence for a role of a genetic predisposition to more intense inflammatory responses in objective neurocognitive disturbances during acute infections. These associations require replication in a larger sample size.

Cytokines as mediators of chemotherapy-associated cognitive changes: current evidence, limitations and directions for future research

Objectives

While various clinical and pharmacological determinants for chemotherapy-associated cognitive impairment have been identified, conflicting evidence suggests that cytokines might play an intermediary role. The objective of this systematic review was to evaluate the current evidence pertaining to the associations among chemotherapy, cytokines induction and cognitive impairment in cancer patients.

Methods

A literature search with PubMed and SciVerse Scopus was conducted in March 2013 to gather relevant articles and abstracts that fulfilled the inclusion and exclusion criteria. This review included studies that had performed objective and/or subjective cognitive assessments and cytokine measurements on defined populations of cancer patients who received chemotherapy.

Results

High methodological heterogeneity existed among the selected studies which differed in cancer populations, subject characteristics, cognitive endpoints, types of cytokines tested and their measurement methods. Weak to moderate correlations were observed between IL-1β, IL-6, TNF-α levels, and different degrees of cognitive impairment. Different types of chemotherapy treatments might lead to varying presentations and severities of cytokine-induced cognitive impairment. Notably, the time concordance between the onset of cytokine induction and occurrence of cognitive impairment was not well elucidated. A number of confounding factors was identified to interfere with the expression levels of cytokines; these confounders included subjects' cancer types, ages, genders, genetics and psychosocial characteristics such as anxiety, depression and fatigue.

Conclusion

Although existing studies observed cognitive impairment and cytokine dysregulation in patients who receive chemotherapy, our results suggest that the intermediary role of cytokines in post-chemotherapy cognitive impairment is still controversial and requires further evaluation. A list of methodological recommendations is proposed to harmonize future studies of this subject matter.

Association between an interleukin 1 receptor, type I promoter polymorphism and self-reported attentional function in women with breast cancer

Subgroups of patients with breast cancer may be at greater risk for cytokine-induced changes in cognitive function after diagnosis and during treatment. The purposes of this study were to identify subgroups of patients with distinct trajectories of attentional function and evaluate for phenotypic and genotypic (i.e., cytokine gene polymorphisms) predictors of subgroup membership. Self-reported attentional function was evaluated in 397 patients with breast cancer using the Attentional Function Index before surgery and for six months after surgery (i.e., seven time points). Using growth mixture modeling, three attentional function latent classes were identified: High (41.6%), Moderate (25.4%), and Low-moderate (33.0%). Patients in the Low-moderate class were significantly younger than those in the High class, with more comorbidities and lower functional status than the other two classes. No differences were found among the classes in years of education, race/ethnicity, or other clinical characteristics. DNA was recovered from 302 patients' samples. Eighty-two single nucleotide polymorphisms among 15 candidate genes were included in the genetic association analyses. After controlling for age, comorbidities, functional status, and population stratification due to race/ethnicity, IL1R1 rs949963 remained a significant genotypic predictor of class membership in the multivariable model. Carrying the rare "A" allele (i.e., GA+AA) was associated with a twofold increase in the odds of belonging to a lower attentional function class (OR: 1.98; 95% CI: 1.18, 3.30; p=.009). Findings provide evidence of subgroups of women with breast cancer who report distinct trajectories of attentional function and of a genetic association between subgroup membership and an IL1R1 promoter polymorphism.

Interleukin-8 and interleukin-10, brain volume and microstructure, and the influence of calorie restriction in old rhesus macaques

Higher systemic levels of the proinflammatory cytokine interleukin-6 (IL-6) were found to be associated with lower gray matter volume and tissue density in old rhesus macaques. This association between IL-6, and these brain indices were attenuated by long-term 30 % calorie restriction (CR). To extend these findings, the current analysis determined if a CR diet in 27 aged rhesus monkeys compared to 17 normally fed controls reduced circulating levels of another proinflammatory cytokine, interleukin-8 (IL-8), and raised levels of anti-inflammatory interleukin-10 (IL-10). Further, these cytokines were regressed onto imaged brain volume and microstructure using voxel-wise regression analyses. CR significantly lowered IL-8 and raised IL-10 levels. Across the two dietary conditions, higher IL-8 predicted smaller gray matter volumes in bilateral hippocampus. Higher IL-10 was associated with more white matter volume in visual areas and tracts. Consuming a CR diet reduced the association between systemic IL-8 and hippocampal volumes. Conversely, CR strengthened associations between IL-10 and microstructural tissue density in the prefrontal cortex and other areas, particularly in a region of dorsal prefrontal cortex, which concurred with our prior findings for IL-6. Consumption of a CR diet lowered proinflammatory and increased anti-inflammatory cytokine concentrations, which lessened the statistical association between systemic inflammation and the age-related alterations in important brain regions, including the hippocampus.

Cognitive effects of cancer and its treatments at the intersection of aging: what do we know; what do we need to know?

There is a fairly consistent, albeit non-universal body of research documenting cognitive declines after cancer and its treatments. While few of these studies have included subjects aged 65 years and older, it is logical to expect that older patients are at risk of cognitive decline. Here, we use breast cancer as an exemplar disease for inquiry into the intersection of aging and cognitive effects of cancer and its therapies. There are a striking number of common underlying potential biological risks and pathways for the development of cancer, cancer-related cognitive declines, and aging processes, including the development of a frail phenotype. Candidate shared pathways include changes in hormonal milieu, inflammation, oxidative stress, DNA damage and compromised DNA repair, genetic susceptibility, decreased brain blood flow or disruption of the blood-brain barrier, direct neurotoxicity, decreased telomere length, and cell senescence. There also are similar structure and functional changes seen in brain imaging studies of cancer patients and those seen with "normal" aging and Alzheimer's disease. Disentangling the role of these overlapping processes is difficult since they require aged animal models and large samples of older human subjects. From what we do know, frailty and its low cognitive reserve seem to be a clinically useful marker of risk for cognitive decline after cancer and its treatments. This and other results from this review suggest the value of geriatric assessments to identify older patients at the highest risk of cognitive decline. Further research is needed to understand the interactions between aging, genetic predisposition, lifestyle factors, and frailty phenotypes to best identify the subgroups of older patients at greatest risk for decline and to develop behavioral and pharmacological interventions targeting this group. We recommend that basic science and population trials be developed specifically for older hosts with intermediate endpoints of relevance to this group, including cognitive function and trajectories of frailty. Clinicians and their older patients can advance the field by active encouragement of and participation in research designed to improve the care and outcomes of the growing population of older cancer patients.

Chronic depression as a model disease for cerebral aging

Conceptualizations of the underlying neurobiology of major depression have changed their focus from dysfunctions of neurotransmission to dysfunctions of neurogenesis and neuroprotection. The “neurogenesis hypothesis of depression” posits that changes in the rate of neurogenesis are the underlying mechanism in the pathology and treatment of major depression. Stress, neuroinflammation, dysfunctional insulin regulation, oxidative stress, and alterations in neurotrophic factors possibly contribute to the development of depression. The influence of antidepressant therapies, namely pharmacotherapy and neuroprotectants, on cellular plasticity are summarized. A dysfunction of complex neuronal networks as a consequence of neural degeneration in neuropsychiatric diseases has led to the application of deep brain stimulation. We discuss the way depression seen in the light of the neurogenesis hypothesis can be used as a model disease for cerebral aging. A common pathological mechanism in depression and cerebral aging—a dysfunction of neuroprotection and neurogenesis—is discussed. This has implications for new treatment methods.

Neuroprotective effects of prior exposure to enriched environment on cerebral ischemia/reperfusion injury in rats: the possible molecular mechanism

Increasing evidence shows that exposure to an enriched environment (EE) after cerebral ischemia/reperfusion injury is neuroprotective in animal models. Recent studies have demonstrated that animals housed in an enriched environment condition after an experimental stroke obtained a better functional outcome than those housed in a standard condition. However, little is known about the underlying mechanisms of neuroprotective effects of enriched environment exposure prior to injury. The current study examined the neuroprotective effects of prior enriched environment exposure after transient middle cerebral artery occlusion (MCAO) in rats. Male Sprague Dawley (SD) rats, weighing 55-65g at the beginning of the experiment, were randomly assigned to a pre-ischemic enriched environment (PIEE) or pre-ischemic standard condition (PISC) group for 1 month. They were weighed on days1, 7, 18, and 28, and their locomotor activity was tracked during the period between 9:00am and 3:00pm daily. After 1 month, ischemia was induced by occluding the middle cerebral artery for 90min, followed by reperfusion. After approximately 24h of the operation, functional outcomes were assessed using the beam-walking test and a neurological evaluation scale in all rats. We measured the expression of extracellular signal regulated protein kinases1/2 (ERK1/2) by western blotting and gene expression levels of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthasen (iNOS) by Real-Time PCR in the cortical area affected by ischemia. Finally, we measured the level of malondialdehyde (MDA) content, which is a biomarker of oxidative stress. The results showed that rats in the PIEE group had lighter weight than those in the PISC group. The functional outcomes of rats in the PIEE group were better than those in the PISC group, and substances associated with inflammation, such as MDA, nNOS, iNOS, and phospho-ERK1/2, were lower in the PIEE group compared with the PISC group. These results indicate that enriched environment may provide neuroprotection via ischemic preconditioning and enhance resilience to cerebral ischemia.

Dietary approach to decrease aging-related CNS inflammation

We demonstrate that the spontaneously hypertensive rat stroke-prone rat (SHRsp) undergoes premature aging of the CNS compared to the related normotensive Wistar Kyoto rat (WKY) as demonstrated by presence of activated microglia/macrophages, increased expression of inducible nitric oxide synthase and increased astrogliosis. We tested the hypothesis that dietary intake of phase 2 protein inducers would decrease these aging-associated degenerative changes. The source of dietary phase 2 protein inducers was dried broccoli sprouts of a cultivar containing high amounts of glucoraphanin that gives rise to phase 2 protein-inducing isothiocyanate sulforaphane. This diet significantly decreased the aging-related degenerative changes in the SHRsp CNS. We conclude that modest changes in diet may have profound effects on the aging CNS.

Cognitive frailty: rational and definition from an (I.A.N.A./I.A.G.G.) international consensus group

The frailty syndrome has recently attracted attention of the scientific community and public health organizations as precursor and contributor of age-related conditions (particularly disability) in older persons. In parallel, dementia and cognitive disorders also represent major healthcare and social priorities. Although physical frailty and cognitive impairment have shown to be related in epidemiological studies, their pathophysiological mechanisms have been usually studied separately. An International Consensus Group on "Cognitive Frailty" was organized by the International Academy on Nutrition and Aging (I.A.N.A) and the International Association of Gerontology and Geriatrics (I.A.G.G) on April 16th, 2013 in Toulouse (France). The present report describes the results of the Consensus Group and provides the first definition of a "Cognitive Frailty" condition in older adults. Specific aim of this approach was to facilitate the design of future personalized preventive interventions in older persons. Finally, the Group discussed the use of multidomain interventions focused on the physical, nutritional, cognitive and psychological domains for improving the well-being and quality of life in the elderly. The consensus panel proposed the identification of the so-called "cognitive frailty" as an heterogeneous clinical manifestation characterized by the simultaneous presence of both physical frailty and cognitive impairment. In particular, the key factors defining such a condition include: 1) presence of physical frailty and cognitive impairment (CDR=0.5); and 2) exclusion of concurrent AD dementia or other dementias. Under different circumstances, cognitive frailty may represent a precursor of neurodegenerative processes. A potential for reversibility may also characterize this entity. A psychological component of the condition is evident and concurs at increasing the vulnerability of the individual to stressors.

Circulating interleukin-6 concentration and cognitive decline in old age: the PROSPER study

BACKGROUND

Inflammation is involved in the pathogenesis of cardiovascular disease and cognitive decline. Interleukin-6 (IL-6) has a role in cardiovascular disease, but the association of IL-6 concentration and the functional IL-6 -174 polymorphism with cognitive decline has not been demonstrated unequivocally. The objective of this study was to investigate the associations between both high concentration of IL-6 and the -174 promoter polymorphism, and increased cognitive decline in old age.

METHODS

Over 5000 participants of the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) with a mean age of 75 years and a history of cardiovascular disease or its risk factors were included in this study. We determined baseline concentrations of IL-6 and genotype of the IL-6 -174 polymorphism, of which the C allele was previously shown to be associated with higher circulating concentrations of IL-6. A cognitive test battery was administered at baseline and repeatedly during follow-up (mean 39 months).

RESULTS

In the cross-sectional analysis of 5653 participants, higher IL-6 concentration was associated with worse executive cognitive function (P < 0.001), independent of cardiovascular disease status and risk factors. No association was found between IL-6 concentration and memory function (P > 0.14). In the prospective analysis, higher IL-6 concentration was associated with an increased rate of cognitive decline in both executive function (P = 0.002) and memory function (P = 0.002), again independent of cardiovascular disease status and risk factors. Although not associated with IL-6 concentrations, the IL-6 -174 CC genotype was associated with worse performance on the Stroop test (P = 0.045).

CONCLUSIONS

Higher circulating levels of IL-6 were associated with worse cognitive function and steeper cognitive decline and provide preliminary genetic evidence for a potential causal association. The findings support the importance of the need for further investigation of the IL-6 pathway in cognitive decline.

Evidence for a dysregulated immune system in the etiology of psychiatric disorders

There is extensive bi-directional communication between the brain and the immune system in both health and disease. In recent years, the role of an altered immune system in the etiology of major psychiatric disorders has become more apparent. Studies have demonstrated that some patients with major psychiatric disorders exhibit characteristic signs of immune dysregulation and that this may be a common pathophysiological mechanism that underlies the development and progression of these disorders. Furthermore, many psychiatric disorders are also often accompanied by chronic medical conditions related to immune dysfunction such as autoimmune diseases, diabetes and atherosclerosis. One of the major psychiatric disorders that has been associated with an altered immune system is schizophrenia, with approximately one third of patients with this disorder showing immunological abnormalities such as an altered cytokine profile in serum and cerebrospinal fluid. An altered cytokine profile is also found in a proportion of patients with major depressive disorder and is thought to be potentially related to the pathophysiology of this disorder. Emerging evidence suggests that altered immune parameters may also be implicated in the neurobiological etiology of autism spectrum disorders. Further support for a role of immune dysregulation in the pathophysiology of these psychiatric disorders comes from studies showing the immunomodulating effects of antipsychotics and antidepressants, and the mood altering effects of anti-inflammatory therapies. This review will not attempt to discuss all of the psychiatric disorders that have been associated with an augmented immune system, but will instead focus on several key disorders where dysregulation of this system has been implicated in their pathophysiology including depression, schizophrenia and autism spectrum disorder.

Acetylcholinesterase inhibitors reduce neuroinflammation and -degeneration in the cortex and hippocampus of a surgery stress rat model

Exogenous stress like tissue damage and pathogen invasion during surgical trauma could lead to a peripheral inflammatory response and induce neuroinflammation, which can result in postoperative cognitive dysfunction (POCD). The cholinergic anti-inflammatory pathway is a neurohumoral mechanism that plays a prominent role by suppressing the inflammatory response. Treatments with acetylcholinesterase inhibitors enhance cholinergic transmission and may therefore act as a potential approach to prevent neuroinflammation. In the presence or absence of acetylcholinesterase inhibitors, adult Wistar rats underwent surgery alone or were additionally treated with lipopolysaccharide (LPS). Physostigmine, which can overcome the blood-brain barrier or neostigmine acting only peripheral, served as acetylcholinesterase inhibitors. The expression of pro- and anti-inflammatory cytokines in the cortex, hippocampus, spleen and plasma was measured after 1 h, 24 h, 3 d and 7 d using Real-Time PCR, western blot analysis or cytometric bead array (CBA). Fluoro-Jade B staining of brain slices was employed to elucidate neurodegeneration. The activity of acetylcholinesterase was estimated using a spectrofluorometric method. Surgery accompanied by LPS-treatment led to increased IL-1beta gene and protein upregulation in the cortex and hippocampus but was significantly reduced by physostigmine and neostigmine. Furthermore, surgery in combination with LPS-treatment caused increased protein expression of IL-1, TNF-alpha and IL-10 in the spleen and plasma. Physostigmine and neostigmine significantly decreased the protein expression of IL-1 and TNF-alpha. Neuronal degeneration and the activity of acetylcholinesterase were elevated after surgery with LPS-treatment and reduced by physostigmine and neostigmine. Along with LPS-treatment, acetylcholinesterase inhibitors reduce the pro-inflammatory response as well as neurodegeneration after surgery in the cortex and hippocampus. This combination may represent a tool to break the pathogenesis of POCD.

Selective anesthesia-induced neuroinflammation in developing mouse brain and cognitive impairment

BACKGROUND

: Recent population studies have suggested that children with multiple exposures to anesthesia and surgery at an early age are at an increased risk of cognitive impairment. The authors therefore have established an animal model with single versus multiple exposures of anesthetic(s) in young versus adult mice, aiming to distinguish the role of different types of anesthesia in cognitive impairment.

METHODS

: Six- and 60-day-old mice were exposed to various anesthesia regimens. The authors then determined the effects of the anesthesia on learning and memory function, levels of proinflammatory cytokine interleukin-6 and tumor necrosis factor-α in brain tissues, and the amount of ionized calcium-binding adaptor molecule 1-positive cells, the marker of microglia activation, in the hippocampus.

RESULTS

: In this article, the authors show that anesthesia with 3% sevoflurane for 2 h daily for 3 days induced cognitive impairment and neuroinflammation (e.g., increased interleukin-6 levels, 151 ± 2.3% [mean ± SD] vs. 100 ± 9.0%, P = 0.035, n = 6) in young but not in adult mice. Anesthesia with 3% sevoflurane for 2 h daily for 1 day and 9% desflurane for 2 h daily for 3 days induced neither cognitive impairment nor neuroinflammation. Finally, an enriched environment and antiinflammatory treatment (ketorolac) ameliorated the sevoflurane-induced cognitive impairment.

CONCLUSIONS

: Anesthesia-induced cognitive impairment may depend on developmental stage, anesthetic agent, and number of exposures. These findings also suggest the cellular basis and the potential prevention and treatment strategies for anesthesia-induced cognitive impairment, which may ultimately lead to safer anesthesia care and better postoperative outcomes for children.

Brain changes in BDNF and S100B induced by ketogenic diets in Wistar rats

AIMS

We investigated the effects of ketogenic diet (KD) on levels of tumor necrosis factor alpha (TNF-α, a classical pro-inflammatory cytokine), BDNF (brain-derived neurotrophic factor, commonly associated with synaptic plasticity), and S100B, an astrocyte neurotrophic cytokine involved in metabolism regulation.

MAIN METHODS

Young Wistar rats were fed during 8weeks with control diet or two KD, containing different proportions of omega 6 and omega 3 polyunsaturated fatty acids. Contents of TNF-α, BDNF and S100B were measured by ELISA in two brain regions (hippocampus and striatum) as well as blood serum and cerebrospinal fluid.

KEY FINDINGS

Our data suggest that KD was able to reduce the levels of BDNF in the striatum (but not in hippocampus) and S100B in the cerebrospinal fluid of rats. These alterations were not affected by the proportion of polyunsaturated fatty acids offered. No changes in S100B content were observed in serum or analyzed brain regions. Basal TNF-α content was not affected by KD.

SIGNIFICANCE

These findings reinforce the importance of this diet as an inductor of alterations in the brain, and such changes might contribute to the understanding of the effects (and side effects) of KD in brain disorders.

Gene expression profile of the hippocampus of rats subjected to chronic immobilization stress

Objective

This study systematically investigated the effect of chronic stress on the hippocampus and its damage mechanism at the whole genome level.

Methods

The rat whole genome expression chips (Illumina) were used to detect gene expression differences in the hippocampus of rats subjected to chronic immobilization stress (daily immobilization stress for 3 h, for 7 or 21 days). The hippocampus gene expression profile was studied through gene ontology and signal pathway analyses using bioinformatics. A differentially expressed transcription regulation network was also established. Real-time quantitative polymerase chain reaction (RT-PCR) was used to verify the microarray results and determine expression of the Gabra1, Fadd, Crhr2, and Cdk6 genes in the hippocampal tissues.

Results

Compared to the control group, 602 differentially expressed genes were detected in the hippocampus of rats subjected to stress for 7 days, while 566 differentially expressed genes were expressed in the animals experiencing stress for 21 days. The stress significantly inhibited the primary immune system functions of the hippocampus in animals subjected to stress for both 7 and 21 days. Immobilization activated the extracellular matrix receptor interaction pathway after 7 day exposure to stress and the cytokine-cytokine receptor interaction pathway. The enhanced collagen synthesis capacity of the hippocampal tissue was the core molecular event of the stress regulation network in the 7-day group, while the inhibition of hippocampal cell growth was the core molecular event in the 21-day group. For the Gabra1, Fadd, Crhr2, and Cdk6 genes, RT-PCR results were nearly in line with gene chip assay results.

Conclusion

During the 7-day and 21-day stress processes, the combined action of polygenic, multilevel, and multi-signal pathways leads to the disorder of the immunologic functions of the hippocampus, hippocampal apoptosis, and proliferation disequilibrium.

Preliminary evidence of an association between an interleukin 6 promoter polymorphism and self-reported attentional function in oncology patients and their family caregivers

Subgroups of individuals may be at greater risk of cytokine-induced changes in attentional function. The purposes of this study were to identify subgroups of individuals with distinct trajectories of attentional function and evaluate for phenotypic and genotypic (i.e., cytokine gene polymorphisms) differences among these subgroups. Self-reported attentional function was evaluated in 252 participants (167 oncology patients and 85 family caregivers) using the Attentional Function Index before radiation therapy and at six additional assessments over 6 months. Three latent classes of attentional function were identified using growth mixture modeling: moderate (36.5%), moderate-to-high (48.0%), and high (15.5%) attentional function. Participants in the moderate class were significantly younger, with more comorbidities and lower functional status, than those in the other two classes. However, only functional status remained significant in multivariable models. Included in the genetic association analyses were 92 single nucleotide polymorphisms (SNPs) among 15 candidate genes. Additive, dominant, and recessive genetic models were assessed for each SNP. Controlling for functional status, only Interleukin 6 (IL6) rs1800795 remained a significant genotypic predictor of class membership in multivariable models. Each additional copy of the rare "G" allele was associated with a 4-fold increase in the odds of belonging to the lower attentional function class (95% confidence interval: [1.78, 8.92]; p = .001). Findings provide preliminary evidence of subgroups of individuals with distinct trajectories of attentional function and of a genetic association with an IL6 promoter polymorphism.

Elevated levels of interleukin 6 and C-reactive protein associated with cognitive impairment in heart failure

There is abundant evidence on inflammatory mechanisms in heart failure (HF) that are used for prognostication of the disease; however, data are lacking regarding the association between elevated cytokines, C-reactive protein (CRP), and cognition in HF. A cross-sectional pilot study of 38 patients with HF, aged 62 years (standard deviation± 9 years), predominantly men (68%) and Caucasian (79%) were screened for cognitive function using the Montreal Cognitive Assessment (MoCA). The study aimed to examine cognitive scores on MoCA with cytokines, interleukin 6 [IL-6] and tumor necrosis factor α [TNF-α], and CRP as indicators of early cognitive changes in HF. The result showed no direct correlation between cardiac variables and the MoCA score. The MoCA score, however, was inversely associated with IL-6 (r=-0.53, P=.001) and CRP (r=-0.34, P=.04), with no association to TNF-α. Regression analysis on the MoCA score and log-transformed IL-6 accounted for an additional 11% variation and remained statistically significant (P=.008) after controlling for covariates of education, living arrangements, and loneliness. The large effect size (R(2) =0.87) found in this pilot study provides rationale for a larger exploratory study to examine associations between cognitive function, cytokines, and CRP levels and help design future intervention studies.

Reduced hippocampal volume and verbal memory performance associated with interleukin-6 and tumor necrosis factor-alpha levels in chemotherapy-treated breast cancer survivors

Many survivors of breast cancer show significant cognitive impairments, including memory deficits. Inflammation induced by chemotherapy may contribute to hippocampal changes that underlie these deficits. In this cross-sectional study, we measured bilateral hippocampal volumes from high-resolution magnetic resonance images in 42 chemotherapy-treated breast cancer survivors and 35 healthy female controls. Patients with breast cancer were, on average, 4.8 ± 3.4 years off-therapy. In a subset of these participants (20 breast cancer, 23 controls), we quantified serum cytokine levels. Left hippocampal volumes and memory performance were significantly reduced and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNFα) concentrations were significantly elevated in the breast cancer group compared to controls. In the breast cancer group, lower left hippocampal volume was associated with higher levels of TNFα and lower levels of IL-6 with a significant interaction between these two cytokines suggesting a potential modulatory effect of IL-6 on TNFα. Verbal memory performance was associated with cytokine levels and left hippocampal volume in both groups. These findings provide evidence of altered hippocampal volume and verbal memory difficulties following breast cancer chemotherapy that may be mediated by TNFα and IL-6.

PPARγ activation prevents impairments in spatial memory and neurogenesis following transient illness

The detrimental effects of illness on cognition are familiar to virtually everyone. Some effects resolve quickly while others may linger after the illness resolves. We found that a transient immune response stimulated by lipopolysaccharide (LPS) compromised hippocampal neurogenesis and impaired hippocampus-dependent spatial memory. The immune event caused an ∼50% reduction in the number of neurons generated during the illness and the onset of the memory impairment was delayed and coincided with the time when neurons generated during the illness would have become functional within the hippocampus. Broad spectrum non-steroidal anti-inflammatory drugs attenuated these effects but selective Cox-2 inhibition was ineffective while PPARγ activation was surprisingly effective at protecting both neurogenesis and memory from the effects of LPS-produced transient illness. These data may highlight novel mechanisms behind chronic inflammatory and neuroinflammatory episodes that are known to compromise hippocampus-dependent forms of learning and memory.

Does brain reserve protect older women from vascular depression?

OBJECTIVES

Brain reserve theory, typically discussed in relation to dementia, was examined with regard to late-life depression symptomatology and cerebrovascular burden (CVB) in older-old women.

METHOD

It was predicted that in a 6-year longitudinal sample (Health and Retirement Study) of 1,355 stroke-free women aged 80 years and older, higher levels of depressive symptomatology (8-item Center for Epidemiologic Studies-Depression score) would be predicted by high CVB, less educational attainment, and the education × CVB interaction after controlling for age and cognitive functioning (Telephone Interview for Cognitive Status). A latent growth curve model was used to identify differences in depression symptomatology at baseline and over time. Logistic regression analyses were used to predict clinically significant depressive symptomatology at each wave based on CVB, education, and the education × CVB interaction.

RESULTS

Results indicate that among older women, greater educational attainment predicted fewer depression symptoms at baseline, but this advantage was partially eroded over time. The education × CVB interaction predicted clinically significant depressive symptoms at baseline when the benefits of education were most robust.

DISCUSSION

Brain reserve, characterized by educational attainment, may counterbalance the effect of high CVB with respect to depressive symptoms, thereby preserving mood in late life. These findings support the application of brain reserve theory to late-life depression.

Neuroinflammation, neurodegeneration, and depression

Neurodegeneration and depression are two common co-morbid conditions, particularly within the aging population. Research has linked neuroinflammation as a major contributing factor to both of these diseases. The key to neuroinflammation effects on neurodegeneration and depression appears to lie within the dysregulation of the control and release of pro- and anti-inflammatory cytokines. This can come from an internal or external insult to the system, or from changes in the individual due to aging that culminate in immune dysregulation. The need to reduce neuroinflammation has led to extensive research into neuroprotectants. We discuss the efficacy found with nicotine, alcohol, resveratrol, curcumin, and ketamine. Our main focus will be on what research tells us about the connections between neuroinflammation, neurodegeneration, and depression, and the hope that neuroprotectants research gives people suffering from neurodegeneration and depression stemming from neuroinflammation. We will conclude by making suggestions for future research in this area.

Estrogens need insulin-like growth factor I cooperation to exert their neuroprotective effects in post-menopausal women

BACKGROUND

The abrupt fall in estrogens levels during the menopausal transition may connote an hormonal state predisposing to neurodegenerative disorders, e.g. Alzheimer's disease (AD). Reportedly, the neurotrophic activity of estrogen involves an interaction with IGF-I.

AIM

To evaluate the leukocyte gene expression of progesterone receptor (PR-A/B) and interleukin 6 (IL-6), two parameters under the control of estrogens and involved in the pathogenesis of AD.

SUBJECTS

The study was conducted in non-demented women divided into two groups according to their pre- or post-menopausal state; each group being further divided into two subgroups based on their circulating levels of IGF-I (normal or low). An additional sample of AD-affected women served as a comparison group.

RESULTS

Estrogens maintained their full activity only when IGF-I levels were in the range of normalcy. On the contrary, if the concentrations of one or both hormones were reduced, estrogens were not anymore capable to control the gene expression of PR-A/B or IL-6.

CONCLUSIONS

Before administering hormone-based replacement therapy, characterization of the somatotropic function should be performed in the early phase of the menopause.

Increased resistance of immobilized-stressed mice to infection: correlation with behavioral alterations

Immobilization is an easy and convenient method to induce both psychological and physical stress resulting in restricted motility and aggression and is believed to be the most severe type of stress in rodent models. Although it has been generally accepted that chronic stress often results in immunosuppression while acute stress has been shown to enhance immune responses, the effects of IS on the host resistance to Escherichia coli (E. coli) infection and associated behavioral changes are still not clear. In a series of experiments aimed at determining the level of hypothalamic COX-2, HSP-90, HSP-70, SOD-1 and plasma level of corticosterone, cytokine, antibody titer and their association with behavioral activities, mice were infected with viable E. coli during acute and chronic IS by taping their paws. In this study we show that acute and chronic IS enhances the resistance of mice to E. coli infection via inhibiting the production of pro-inflammatory cytokines, free radicals, and by improving the exploratory behavior. Altogether, our findings support the notion that cytokines released during immune activation and under the influence of corticosterone can modulate the open field behavior both in terms of locomotor activity as well as exploration. One of the features observed with chronic stressor was a lower ability to resist bacterial infection, although in case of acute stress, a better clearance of bacterial infection was observed in vivo with improvement of exploratory behavior and cognitive functions.

Peripubertal viral-like challenge and social isolation mediate overlapping but distinct effects on behaviour and brain interferon regulatory factor 7 expression in the adult Wistar rat

A range of adverse, early life environmental influences such as viral infection and social deprivation are thought to increase risk of psychiatric illness later in life. Here, we used peripheral administration of the viral infection mimic polyriboinosinic-polyribocytidylic acid (polyI:C) to compare the consequences of peripubertal infection and isolation rearing. Isolation rearing induced deficits in sensorimotor gating and recognition memory while no changes in social interaction or spatial learning were observed. PolyI:C injection during the peripubertal period markedly increased expression of interferon-stimulated genes (Ifit2, Prkr, Mx2 and Irf7) in the hippocampal dentate gyrus demonstrating that peripheral administration of the viral mimic in the adolescent animal does have direct effects in the brain. Peripubertal infection mimicry induced a similar but later emerging behavioural deficit in prepulse inhibition implying the existence of a peripubertal window of opportunity for viral-mediated cytokine increases to impact brain development and function. PolyI:C treatment also impaired novel object recognition but did not alter spatial reference memory or social interaction. Combining the polyI:C challenge with social isolation did not exacerbate the behavioural deficits seen with isolation rearing alone. Using Irf7 as a marker, peripubertal viral infection mimicry, isolation rearing and a combination of both were all seen to produce a long-lasting molecular imprint on the interferon-associated signalling pathway in the principal neuron population of the hippocampal dentate gyrus. The data suggest that the sensitivity of brain structure and function to disruption by viral infection extends into the peripubertal period. Moreover, augmented interferon signalling in hippocampus may represent a common molecular imprint of environmental insults associated with neuropsychiatric illnesses like schizophrenia.

The impact of inflammation on cognitive function in older adults: implications for healthcare practice and research

Accumulating evidence suggests that levels of inflammation, an immune response, increase with age throughout the body and the brain. The effects of inflammation on the brain, both acute and chronic, have been associated with cognitive decline and risk of dementia in older adults. Factors believed to increase inflammation include certain health-related behaviors, such as smoking, poor diet, and inactivity as well as health conditions like diabetes, hypertension, and chronic obstructive pulmonary disease, most of which require medical intervention and monitoring. As such, nurses and healthcare professionals are likely to encounter patients who are at a high risk for future development of inflammation-related cognitive decline. A review of inflammatory processes and their relation to cognitive function in older adults is provided, along with factors that may increase or reduce inflammation. Implications for practice and research are discussed.

Postconcussion syndrome: a review of pathophysiology and potential nonpharmacological approaches to treatment

The incidence of all-cause concussions in the United States is estimated to range from 1.6 to 3.8 million annually, with the reported number of sport- or recreation-related concussions increasing dramatically, especially in youth sports.(1,2) Additionally, the use of roadside bombs in Iraq and Afghanistan has propelled the incidence of concussion and other traumatic brain injuries to the highest levels ever encountered by the US military. As a result, there has also been a marked increase in postconcussion syndrome (PCS) and the associated cognitive, emotional, and memory disabilities associated with the condition. Unfortunately, however, there have been no significant advancements in the understanding or treatment of PCS for decades. The current management of PCS mainly consists of rest, reduction of sensory inputs, and treating symptoms as needed. Recently, researchers investigating the underlying mechanisms of PCS have proposed that activation of the immune inflammatory response may be an underlying pathophysiology that occurs in those who experience prolonged symptoms after a concussion. This article reviews the literature and summarizes the immune inflammatory response known as immunoexcitotoxicity. This article also discusses the use of nonpharmacological agents for the management of PCS that directly address this underlying mechanism.

Changes in serum and cerebrospinal fluid cytokines in response to non-neurological surgery: an observational study

Background

Surgery launches an inflammatory reaction in the body, as seen through increased peripheral levels of cytokines and cortisol. However, less is known about perioperative inflammatory changes in the central nervous system (CNS).

Our aim was to compare inflammatory markers in serum and cerebrospinal fluid (CSF) before and after surgery and evaluate their association with measures of blood–brain barrier (BBB) integrity.

Methods

Thirty-five patients undergoing knee arthroplastic surgery with spinal anesthesia had CSF and serum samples drawn before, after and on the morning following surgery. Cytokines and albumin in serum and CSF and cortisol in CSF were assessed at all three points.

Results

Cytokines and cortisol were significantly increased in serum and CSF after surgery (Ps <0.01) and CSF increases were greater than in serum. Ten individuals had an increased cytokine response and significantly higher CSF/serum albumin ratios (Ps <0.01), five of whom had albumin ratios in the pathological range (>11.8). Serum and CSF levels of cytokines were unrelated, but there were strong correlations between CSF IL-2, IL-10 and IL-13, and albumin ratios (Ps <0.05) following surgery.

Conclusion

Cytokine increases in the CNS were substantially greater than in serum, indicating that the CNS inflammatory system is activated during peripheral surgery and may be regulated separately from that in the peripheral body. CSF cytokine increase may indicate sensitivity to trauma and is linked to BBB macromolecular permeability.

The association between systemic inflammation and cognitive performance in the elderly: the Sydney Memory and Ageing Study

Inflammation may contribute to cognitive decline and dementia. This study examined the cross-sectional relationships between markers of systemic inflammation (C-reactive protein, interleukins-1β, -6, -8, -10, -12, plasminogen activator inhibitor, serum amyloid A, tumour necrosis factor-α and vascular adhesion molecule-1) and cognitive function in 873 non-demented community-dwelling elderly participants aged 70-90 years. Regression analyses were performed to determine the relationships between cognitive domains and inflammatory markers, controlling for age, sex, education, cardiovascular risk factors, obesity and other metabolic factors, smoking, alcohol consumption, depression and presence of the apolipoprotein ε4 genotype. Regression analyses were repeated using four factors derived from a factor analysis of the cognitive tests. After Bonferroni correction for multiple testing, associations remained between raised levels of interleukin-12 and reduced performance in processing speed. Marked sex differences were noted in the abovementioned findings, with only females being significantly affected. Using the four factors derived from the factor analyses of cognitive test as dependent variables, interleukins-12 and -6 were both associated with the processing speed/executive function factor, even after controlling for relevant confounding factors. Thus, markers of systemic inflammation are related to cognitive deficits in a non-clinical community-dwelling elderly population, independent of depression, cardiovascular or metabolic risk factors, or presence of apolipoprotein ε4 genotype. Additional research is required to elucidate the pathophysiology and longitudinal development of these relationships.

Race-ethnicity and health trajectories: tests of three hypotheses across multiple groups and health outcomes

Racial-ethnic disparities in static levels of health are well documented. Less is known about racial-ethnic differences in age trajectories of health. The few studies on this topic have examined only single health outcomes and focused on black-white disparities. This study extends prior research by using a life course perspective, panel data from the Health and Retirement Study, and multilevel growth curve models to investigate racial-ethnic differences in the trajectories of serious conditions and functional limitations among blacks, Mexican Americans, and whites. We test three hypotheses on the nature of racial-ethnic disparities in health across the life course (aging-as-leveler, persistent inequality, and cumulative disadvantage). Results controlling for mortality selection reveal that support for the hypotheses varies by health outcome, racial-ethnic group, and life stage. Controlling for childhood socioeconomic status, adult social and economic resources, and health behaviors reduces but does not eliminate racial-ethnic disparities in health trajectories.