Alterations in immune functions during normal aging and Alzheimer's disease

Neutrophil-Mediated Progression of Mild Cognitive Impairment to Dementia

Cognitive impairment is a serious condition that begins with amnesia and progresses to cognitive decline, behavioral dysfunction, and neuropsychiatric impairment. In the final stage, dysphagia and incontinence occur. There are numerous studies and developed drugs for cognitive dysfunction in neurodegenerative diseases, such as Alzheimer's disease (AD); however, their clinical effectiveness remains equivocal. To date, attempts have been made to overcome cognitive dysfunction and understand and delay the aging processes that lead to degenerative and chronic diseases. Cognitive dysfunction is involved in aging and the disruption of inflammation and innate immunity. Recent reports have indicated that the innate immune system is prevalent in patients with AD, and that peripheral neutrophil markers can predict a decline in executive function in patients with mild cognitive impairment (MCI). Furthermore, altered levels of pro-inflammatory interleukins have been reported in MCI, which have been suggested to play a role in the peripheral immune system during the process from early MCI to dementia. Neutrophils are the first responders of the innate immune system. Neutrophils eliminate harmful cellular debris via phagocytosis, secrete inflammatory factors to activate host defense systems, stimulate cytokine production, kill pathogens, and regulate extracellular proteases and inhibitors. This review investigated and summarized the regulation of neutrophil function during cognitive impairment caused by various degenerative diseases. In addition, this work elucidates the cellular mechanism of neutrophils in cognitive impairment and what is currently known about the effects of activated neutrophils on cognitive decline.

Machine Learning-Based Routine Laboratory Tests Predict One-Year Cognitive and Functional Decline in a Population Aged 75+ Years

BACKGROUND

Cognitive and functional decline are common problems in older adults, especially in those 75+ years old. Currently, there is no specific plasma biomarker able to predict this decline in healthy old-age people. Machine learning (ML) is a subarea of artificial intelligence (AI), which can be used to predict outcomes Aim: This study aimed to evaluate routine laboratory variables able to predict cognitive and functional impairment, using ML algorithms, in a cohort aged 75+ years, in a one-year follow-up study.

METHOD

One hundred and thirty-two older adults aged 75+ years were selected through a community-health public program or from long-term-care institutions. Their functional and cognitive performances were evaluated at baseline and one year later using a functional activities questionnaire, Mini-Mental State Examination, and the Brief Cognitive Screening Battery. Routine laboratory tests were performed at baseline. ML algorithms-random forest, support vector machine (SVM), and XGBoost-were applied in order to describe the best model able to predict cognitive and functional decline using routine tests as features.

RESULTS

The random forest model showed better accuracy than other algorithms and included triglycerides, glucose, hematocrit, red cell distribution width (RDW), albumin, hemoglobin, globulin, high-density lipoprotein cholesterol (HDL-c), thyroid-stimulating hormone (TSH), creatinine, lymphocyte, erythrocyte, platelet/leucocyte (PLR), and neutrophil/leucocyte (NLR) ratios, and alanine transaminase (ALT), leukocyte, low-density lipoprotein cholesterol (LDL-c), cortisol, gamma-glutamyl transferase (GGT), and eosinophil as features to predict cognitive decline (accuracy = 0.79). For functional decline, the most important features were platelet, PLR and NLR, hemoglobin, globulin, cortisol, RDW, glucose, basophil, B12 vitamin, creatinine, GGT, ALT, aspartate transferase (AST), eosinophil, hematocrit, erythrocyte, triglycerides, HDL-c, and monocyte (accuracy = 0.92).

CONCLUSIONS

Routine laboratory variables could be applied to predict cognitive and functional decline in oldest-old populations using ML algorithms.

Assessment of the neuroprotective potential of d-cycloserine and l-serine in aluminum chloride-induced experimental models of Alzheimer’s disease: In vivo and in vitro studies

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles in the brain accompanied by synaptic dysfunction and neurodegeneration. No effective treatment has been found to slow the progression of the disease. Therapeutic studies using experimental animal models have therefore become very important. Therefore, this study aimed to investigate the possible neuroprotective effect of D-cycloserine and L-serine against aluminum chloride (AlCl₃)-induced AD in rats. Administration of AlCl₃ for 28 days caused oxidative stress and neurodegeneration compared to the control group. In addition, we found that aluminum decreases α-secretase activity while increasing β-secretase and γ-secretase activities by molecular genetic analysis. D-cycloserine and L-serine application resulted in an improvement in neurodegeneration and oxidative damage caused by aluminum toxicity. It is believed that the results of this study will contribute to the synthesis of new compounds with improved potential against AlCl₃-induced neurodegeneration, cognitive impairment, and drug development research.

Association of Peripheral Blood Cell Profile With Alzheimer's Disease: A Meta-Analysis

Background

Inflammation and immune dysfunction play significant roles in the pathogenesis of Alzheimer's disease (AD)-related dementia. Changes in peripheral blood cell profiles are a common manifestation of inflammation and immune dysfunction and have been reported in patients with AD or mild cognitive impairment (MCI). We systematically evaluated the association of peripheral blood cell counts and indices with AD or MCI through a meta-analysis.

Methods

We electronically searched sources to identify all case–control trials comparing peripheral blood cell counts and/or lymphocyte subsets between patients with AD or MCI and healthy controls (HCs). Meta-analyses were used to estimate the between-group standardized mean difference (SMD) and 95% confidence interval (CI).

Results

A total of 36 studies involving 2,339 AD patients, 608 MCI patients, and 8,352 HCs were included. AD patients had significantly decreased lymphocyte counts (SMD −0.345, 95% CI [−0.545, −0.146], P = 0.001) and significantly increased leukocyte counts (0.140 [0.039, 0.241], P = 0.006), neutrophil counts (0.309 [0.185, 0.434], P = 0.01), and neutrophil–lymphocyte ratio (NLR) (0.644 [0.310, 0.978], P < 0.001) compared to HCs. Similarly, significantly increased leukocyte counts (0.392 [0.206, 0.579], P < 0.001), NLR (0.579 [0.310, 0.847], P < 0.001), and neutrophil counts (0.248 [0.121, 0.376], P < 0.001) were found in MCI patients compared with HCs. A significantly decreased percentage of B lymphocytes (−1.511 [−2.775, −0.248], P = 0.019) and CD8⁺ T cells (−0.760 [−1.460, −0.061], P = 0.033) and a significantly increased CD4/CD8 ratio (0.615 [0.074, 1.156], P = 0.026) were observed in AD patients compared to HCs. Furthermore, significant changes in hemoglobin level and platelet distribution width were found in patients with AD or MCI compared with HCs. However, no significant difference was found between AD or MCI patients and HCs in terms of platelet counts, mean corpuscular volume, red cell distribution width, mean platelet volume, and CD4⁺ T, CD3⁺ T, or natural killer cell counts.

Conclusion

Changes in peripheral blood cell profiles, particularly involving leukocyte, lymphocyte, neutrophil, and CD8⁺ T cell counts, as well as the NLR and the CD4/CD8 ratio, are closely associated with AD. The diagnostic relevance of these profiles should be investigated in future.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Interconnections between Inflammageing and Immunosenescence during Ageing

Acute inflammation is a physiological response to injury or infection, with a cascade of steps that ultimately lead to the recruitment of immune cells to clear invading pathogens and heal wounds. However, chronic inflammation arising from the continued presence of the initial trigger, or the dysfunction of signalling and/or effector pathways, is harmful to health. While successful ageing in older adults, including centenarians, is associated with low levels of inflammation, elevated inflammation increases the risk of poor health and death. Hence inflammation has been described as one of seven pillars of ageing. Age-associated sterile, chronic, and low-grade inflammation is commonly termed inflammageing-it is not simply a consequence of increasing chronological age, but is also a marker of biological ageing, multimorbidity, and mortality risk. While inflammageing was initially thought to be caused by "continuous antigenic load and stress", reports from the last two decades describe a much more complex phenomenon also involving cellular senescence and the ageing of the immune system. In this review, we explore some of the main sources and consequences of inflammageing in the context of immunosenescence and highlight potential interventions. In particular, we assess the contribution of cellular senescence to age-associated inflammation, identify patterns of pro- and anti-inflammatory markers characteristic of inflammageing, describe alterations in the ageing immune system that lead to elevated inflammation, and finally assess the ways that diet, exercise, and pharmacological interventions can reduce inflammageing and thus, improve later life health.

Emerging cellular senescence-centric understanding of immunological aging and its potential modulation through dietary bioactive components

Immunological aging is strongly associated with the observable deleterious effects of human aging. Our understanding of the causes, effects, and therapeutics of aging immune cells has long been considered within the sole purview of immunosenescence. However, it is being progressively realized that immunosenescence may not be the only determinant of immunological aging. The cellular senescence-centric theory of aging proposes a more fundamental and specific role of immune cells in regulating senescent cell (SC) burden in aging tissues that has augmented the notion of senescence immunotherapy. Now, in addition, several emerging studies are suggesting that cellular senescence itself may be prevalent in aging immune cells, and that senescent immune cells exhibiting characteristic markers of cellular senescence, similar to non-leucocyte cells, could be among the key drivers of various facets of physiological aging. The present review integrates the current knowledge related to immunosenescence and cellular senescence in immune cells per se, and aims at providing a cohesive overview of these two phenomena and their significance in immunity and aging. We present evidence and rationalize that understanding the extent and impact of cellular senescence in immune cells vis-à-vis immunosenescence is necessary for truly comprehending the notion of an 'aged immune cell'. In addition, we also discuss the emerging significance of dietary factors such as phytochemicals, probiotic bacteria, fatty acids, and micronutrients as possible modulators of immunosenescence and cellular senescence. Evidence and opportunities related to nutritional bioactive components and immunological aging have been deliberated to augment potential nutrition-oriented immunotherapy during aging.

LW-AFC, a new formula from the traditional Chinese medicine Liuwei Dihuang decoction, as a promising therapy for Alzheimer's disease: Pharmacological effects and mechanisms

LW-AFC is a new formula derived from the Liuwei Dihuang decoction, a classical traditional Chinese medicine prescription. Based on our research, LW-AFC is a promising drug for Alzheimer's disease (AD). The studies were conducted primarily in two typical AD mouse models: SAMP8 and APP/PS1 mice. The results showed that LW-AFC could improve many cognitive behaviors, such as spatial learning and memory ability, passive and active avoidance response, and object recognition memory capability. In addition, LW-AFC could also alleviate the AD-like pathology in animal models, such as neuron loss and Aβ deposition. Subsequent studies found that LW-AFC could rebalance hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic-pituitary-gonadal (HPG) axis, and modulate the disturbance of immune system and gut flora. These data suggested that the anti-AD effects of LW-AFC might be mainly via modulating the neuroendocrine immunomodulation (NIM) network. As inhibiting the immune function by immunosuppressant could abolish the protective effects of LW-AFC against long-term potentiation (LTP) impairment model, it is likely that LW-AFC balancing the NIM network is initiated by modulating the immune system.

Neutrophil hyperactivation correlates with Alzheimer's disease progression

OBJECTIVE

Recent studies have underlined the effect of systemic inflammation on the pathophysiology of Alzheimer's disease (AD). Neutrophils are key components of early innate immunity and contribute to uncontrolled systemic inflammation if not tightly regulated. The aim of our study was to fully characterize human circulating neutrophils at different disease stages in AD.

METHODS

We analyzed neutrophil phenotypes and functions in 42 patients with AD (16 with mild cognitive impairment and 26 with dementia), and compared them to 22 age-matched healthy subjects. This study was performed directly in whole blood to avoid issues with data interpretation related to cell isolation procedures.

RESULTS

Blood samples from AD patients with dementia revealed neutrophil hyperactivation associated with increased reactive oxygen species production and increased levels of intravascular neutrophil extravascular traps. The homeostasis of circulating neutrophils in these patients also changed: The ratio between the harmful hyperreactive CXCR4^high /CD62L^low senescent and the CD16^bright /CD62L^dim immunosuppressive neutrophil subsets rose in the later stage of the disease. These abnormalities were greater in fast-decliner than in slow-decliner patients.

INTERPRETATION

Our results indicate that the inflammatory properties of circulating neutrophils shift as the percentage of aged neutrophils expands in patients with AD-changes that may play an instrumental role in establishing systemic chronic inflammation. Most important, our data strongly suggest that the neutrophil phenotype may be associated with the rate of cognitive decline and may thus constitute an innovative and prognostic blood biomarker in patients with AD. Ann Neurol 2018;83:387-405.

Aged mice display altered numbers and phenotype of basophils, and bone marrow-derived basophil activation, with a limited role for aging-associated microbiota

Background

The influence of age on basophils is poorly understood, as well as the effect of aging-associated microbiota on basophils. Therefore, we studied the influence of aging and aging-associated microbiota on basophil frequency and phenotype, and differentiation from basophil precursors.

Results

Basophils became more abundant in bone marrow (BM) and spleens of 19-month-old mice compared with 4-month-old mice. Aged basophils tended to express less CD200R3 and more CD123, both in BM and spleen. Differences in microbiota composition with aging were confirmed by 16S sequencing. Microbiota transfers from young and old mice to germ-free recipients revealed that CD11b tended to be lowered on splenic basophils by aging-associated microbiota. Furthermore, abundance of Alistipes, Oscillibacter, Bacteroidetes RC9 gut group, and S24-7 family positively correlated and CD123 expression, whereas Akkermansia abundance negatively correlated with basophils numbers.Subsequently, we purified FcεRIα⁺CD11c^-CD117^- BM-derived basophils and found that those from aged mice expressed lower levels of CD11b upon stimulation. Higher frequencies of IL-4⁺ basophils were generated from basophil precursors of aged mice, which could be reproduced in basophils derived from germ-free recipients of aging-associated microbiota.

Conclusions

Collectively, these results show the influence of aging on basophils. Furthermore, this study shows that aging-associated microbiota altered activation of BM-derived basophils in a similar fashion as observed in BM-derived basophils from aged mice.

Brain, immune system and selenium: a starting point for a new diagnostic marker for Alzheimer's disease?

The clinical diagnosis of Alzheimer's disease (AD) is based primarily on neuropsychological tests, which assess the involutive damage, and imaging techniques that evaluate morphologic changes in the brain. Currently available diagnostic tests do not show complete specificity and do not permit accurate differentiation between AD and other forms of senile dementia. The correlation of these tests with laboratory investigations based on biochemical parameters could increase the certainty of diagnosis. In recent years, several biochemical markers for the diagnosis of AD have been proposed, but in most cases they show a limited specificity and their application is invasive, requiring, in general, sampling of cerebrospinal fluid. Thus, the use of a peripheral biochemical marker could represent a valuable complement for the diagnosis of this disease. Several studies have shown a relationship between neurodegenerative disorders typical of the ageing process, weakening of the immune system and alterations in the levels of selenium and of the antioxidant selenoenzymes in brain tissues and blood cells. Among blood cells, neutrophil granulocytes uniquely express the selenoenzyme methionine sulfoxide reductase B1 (MsrB1). In a preliminary analysis carried out on neutrophils from subjects affected by AD, we observed a significant decline in MsrB1 activity compared to normal subjects. Therefore, we deem it of particular interest to explore the potential use of MsrB1 as a selective peripheral marker for the diagnosis of AD.

Altered peripheral profile of blood cells in Alzheimer disease: A hospital-based case-control study

Alzheimer disease (AD) has been made a global priority for its multifactorial pathogenesis and lack of disease-modifying therapies. We sought to investigate the changes of profile of blood routine in AD and its correlation with the disease severity.In all, 92 AD patients and 84 age and sex-matched normal controls were enrolled and their profiles of blood routine were evaluated.Alzheimer disease patients had increased levels of mean corpuscular hemoglobin, mean corpuscular volume, red cell distribution width-standard deviation, mean platelet volume,and decreased levels of platelet distribution width, red blood cell, hematocrit, hemoglobin, lymphocyte, and basophil compared with normal controls.Alterations in quantity and quality of blood cells may be involved in the pathogenesis of AD and contribute to the disease progression.

Possible Predictors of Involuntary Weight Loss in Patients with Alzheimer's Disease

Loss in body mass (∆BM) is a common feature in patients with Alzheimer’s disease (AD). However, the etiology of this phenomenon is unclear. The aim of this cohort study was to observe possible ∆BM in AD patients following a standard institutionalized diet. Secondary objective was to identify possible predictors of ∆BM. To this end, 85 AD patients (age: 76±4 yrs; stature: 165±3 cm; BM: 61.6±7.4 kg; mean±standard deviation) and 86 controls (CTRL; age: 78±5 yrs; stature: 166±4 cm; BM: 61.7±6.4 kg) were followed during one year of standard institutionalized diet (~1800 kcal/24h). BM, daily energy expenditure, albuminemia, number of medications taken, and cortisolism, were recorded PRE and POST the observation period. Potential predictors of ∆BM in women (W) and men (M) with AD were calculated with a forward stepwise regression model. After one year of standard institutionalized diet, BM decreased significantly in AD (-2.5 kg; p < 0.01), while in CTRL remained unchanged (-0.4 kg; p = 0.8). AD patients and CTRL exhibited similar levels of daily energy expenditure (~1625 kcal/24h). The combination of three factors, number of medications taken, albuminemia, and cortisolism, predicted ∆BM in W with AD. At contrary, the best predictor of ∆BM in M with AD was the cortisolism. Despite a controlled energy intake and similar energy expenditure, both W and M with AD suffered of ∆BM. Therefore, controlled diet did not prevent this phenomenon. The assessments of these variables may predict W and M with AD at risk of weight loss.

Can peripheral leukocytes be used as Alzheimer's disease biomarkers?

Alzheimer's disease (AD) is the leading cause of dementia in elderly populations throughout the world and its incidence is on the rise. Current clinical diagnosis of AD requires intensive examination that includes neuropsychological testing and costly brain imaging techniques, and a definitive diagnosis can only be made upon postmortem neuropathological examination. Additionally, antemortem clinical AD diagnosis is typically administered following onset of cognitive and behavioral symptoms. As these symptoms emerge relatively late in disease progression, therapeutic intervention occurs after significant neurodegeneration, thereby limiting efficacy. The identification of noninvasive diagnostic biomarkers of AD is becoming increasingly important to make diagnosis more widely available to clinics with limited access to neuropsychological testing or state-of-the-art brain imaging, reduce the cost of clinical diagnosis, provide a biological measure to track the course of therapeutic intervention, and most importantly, allow for earlier diagnosis--possibly even during the prodromal phase--with hopes of therapeutic intervention prior to appreciable neurodegeneration. Circulating leukocytes are attractive candidate AD biomarkers as they can be obtained in a minimally invasive manner and are easily analyzed by widely available flow cytometry techniques. In this review, we critically analyze the potential utility of peripheral leukocytes as biological markers for AD.

Aging and neutrophils: there is still much to do

Human neutrophils are activated by a wide array of compounds through their receptors. This elicits their classical functions, such as chemotaxis, phagocytosis, and the production of reactive oxygen species (ROS). Upon stimulation, neutrophils also produce lipid and immune mediators and can present antigen through the major histocompatibility complex I (MHC-I). The age-related impairment of the classical functions of neutrophils is well described, but experimental evidence showing alterations in the production of mediators and antigen presentation with aging are lacking. This review highlights the role of neutrophils in age-related pathologies such as Alzheimer's disease, atherosclerosis, cancer, and autoimmune diseases. Furthermore, we discuss how aging potentially affects the production and release of mediators by human neutrophils in ways that may contribute to the development of these pathologies.

Restriction of sulfur-containing amino acids alters claudin composition and improves tight junction barrier function

Restriction of sulfur-containing amino acids (SCAA) has been shown to elicit a similar increase in life span and decrease in age-related morbidity as caloric restriction. The singular importance of epithelial barrier function in both physiological homeostasis and prevention of inflammation raised the issue of examining the effect of SCAA restriction on epithelial tight junction structure and permeability. Using a well-described in vitro, epithelial model, the LLC-PK(1) renal epithelial cell line, we studied the effects of SCAA restriction in culture medium. Reduction of methionine by 90%, cysteine by 50%, and total elimination of cystine resulted in dramatically lower intracellular pools of these amino acids and their metabolite, taurine, but the intracellular pools of the non-SCAA were all elevated. Cell growth and differentiation were maintained, and both confluent cell density and transepithelial short circuit current were unaffected. Certain tight junctional proteins, such as occludin and claudins-1 and -2 were not altered. However, claudins-3 and -7 were significantly decreased in abundance, whereas claudins-4 and -5 were markedly increased in abundance. The functional result of these structural changes was improved barrier function, as evidenced by increased transepithelial electrical resistance and decreased transepithelial (paracellular) diffusion of D-mannitol.

Persistent human papillomavirus infection is associated with a generalized decrease in immune responsiveness in older women

The development of cervical cancer and its precursors are linked to persistent infection with oncogenic types of human papillomavirus (HPV). Host immune responses seem to be determinants of risk for this disease. However, little is known about the immunologic determinants of HPV persistence. Here, we examined the association between lymphoproliferative responses to antigens/mitogens and persistent HPV infection in women older than 45 years. Women included in this study were participants in a 10,000-woman population-based cohort study of cervical neoplasia in Costa Rica. Women older than 45 years and HPV DNA positive at a screening visit were selected as cases (n = 283). We selected a comparably sized control group of HPV DNA-negative women, matched to cases on age and time since enrollment (n = 261). At an additional clinical visit, women were cytologically and virologically rescreened, and cervical and blood specimens were collected. Proliferative responses to phytohemagglutinin (PHA), influenza virus (Flu), and HPV16 virus-like particle (VLP) were lower among women with persistent HPV infection [median counts per minute (cpm): 72,849 for PHA, 1,241 for Flu, and 727 for VLP] than for the control group (median cpm: 107,049 for PHA, 2,111 for Flu, and 2,068 for VLP). The decreases were most profound in women with long-term persistence and were only observed for the oldest age group (>/=65 years). Our results indicate that an impairment in host immunologic responses is associated to persistent HPV infection. The fact that effects were evident for all studied stimuli is suggestive of a generalized effect.

Omega-3 fatty acid ethyl-eicosapentaenoate, but not soybean oil, attenuates memory impairment induced by central IL-1β administration

Proinflammatory cytokine interleukin (IL)-1beta can cause cognitive impairment, activate the hypothalamic-pituitary-adrenal axis and impair monoaminergic neurotransmission in the rat. IL-1beta has also been shown to increase the concentration of the inflammatory mediator prostaglandin E2 (PGE2) in the blood. Omega (n)-3 fatty acids, such as eicosapentaenoic acid (EPA), which are components of fish oil, have been shown to reduce both the proinflammatory cytokines and the synthesis of PGE2. The purpose of this study was to determine whether dietary supplements of EPA would attenuate the inflammation-induced impairment of spatial memory by centrally administered IL-1beta. Rats were fed with a diet of coconut oil (contained a negligible quantity of fatty acids), soybean oil (contained mainly n-6 fatty acids), or a diet of coconut oil enriched with ethyl-EPA (E-EPA). The rats were then injected intracerebroventricularly with IL-1beta or saline. The results of this study demonstrated that the IL-1-induced deficit in spatial memory was correlated with an impairment of central noradrenergic and serotonergic (but not dopaminergic) function and an increase in the serum corticosterone concentration. IL-1beta also caused an increase in the hippocampal PGE2 concentration. These effects of IL-1 were attenuated by the chronic administration of E-EPA. By contrast, rats fed with the soybean oil diet showed no effect on the changes induced by the IL-1 administration.

T cell response to amyloid-beta and to mitochondrial antigens in Alzheimer's disease

Despite the vast amount of literature on non-specific immune mechanisms in Alzheimer's disease (AD), little is known about the role of antigen-specific immune responses. We investigated T cell reactivity to fragment 1-42 of amyloid-beta (Abeta) and to N-terminal peptides of human mitochondrial and control microbial proteins. Thirty subjects with a diagnosis of probable AD according to NINCDS-ADRDA criteria and 30 sex- and age-matched healthy controls were enrolled. T cell responses to Abeta fragment showed no significant differences between AD patients and controls. By contrast, the mean number of positive T cell responses to both human mitochondrial and microbial peptides was significantly decreased in AD patients compared to control subjects. No significant correlation was found between T cell responses and both the severity of cognitive impairment and duration of the disease. Our results suggest that antigen-specific immune responses are impaired in AD. Protective immune responses to harmful amyloidogenic substances may also be impaired, thus favoring their accumulation in the brain.

Advanced age negatively influences mesenteric lymph node T cell responses after burn injury

While the pathophysiology of burn injury is well established in young adults, the factors that contribute to pathogenesis and increased death in elderly burn patients are not defined. The purpose of this study is to determine the effects of burn injury on mesenteric lymph node (MLN) T cell responses in young and aged mice. MLN is a cluster of lymph nodes that drains various parts of the intestine and is known to play role in clearance bacteria originating from the intestinal lumen. Results presented here suggest a significant suppression in Con A-induced MLN cell proliferation and IL-2 production in uninjured aged mice compared with uninjured young mice. Following 24 h after injury, although, a significant decrease in lymph node cell proliferation and IL-2 production was observed in both young and aged mice compared with their respective sham-injured animals, the suppression was more in aged mice. In addition we found a reduction in IFN-gamma, a Th-1 cytokine by MLN T cells from aged burned mice relative to young burn (P<0.05) or sham-injured mice (P<0.01). The Th-2 cytokine IL-4, on the other hand, was significantly increased in both young and aged burn-injured mice MLN T cells compared with their respective sham-injured mice. These results show that burn injury causes a greater suppression in MLN T cells ability to proliferate and a more pronounced shift to Th-2 phenotype in aged mice as compared with young mice. Such decreases in T cell functions may impair MLN's ability to clear the bacterial pathogens originating from intestine and thereby contribute to increased pathogenesis in injured host.

Aging enhances lymphocyte cytokine defects after injury

Mortality and sepsis after a traumatic injury is greater in the elderly than in young individuals. The altered lymphocyte response observed to occur in healthy aged individuals is proposed to be a contributing factor to increased mortality. The immune response associated with the increased mortality was explored using a murine scald injury model. In the absence of injury, aged mice had depressed delayed-type hypersensitivity (DTH) and splenocyte proliferative responses relative to young mice. There was also an increase with age in the production of the TH2 cytokines interleukin (IL)-4 and IL-10 by splenocytes. There was no change in the TH1 cytokines IFNgamma or IL-12 with age. However, IL-2 production was significantly lower. Following injury, there was a further decrease in the DTH response of aged injured mice, compared with aged sham mice. In addition, there was a decrease in all of the cytokines examined, regardless of age. In contrast, IFNgamma and IL-2 were significantly lower in the aged injured animals compared with the young injured animals. These results suggest that the lack of an adequate amount of TH1 cytokines shortly after injury in the aged mice may parallel the increased incidence of sepsis and death that occurs in aged burn patients.

Stress-associated immunomodulation and its implications for responses to vaccination

The rapidly growing field of psychoneuroimmunology involves the elucidation of the complex interactions between the CNS, the endocrine system and the immune system and its effects on health. Although the mechanisms involved in this bidirectional communication is not yet fully understood, studies in psychoneuroimmunology have shown that stress, through the hypothalamic-pituitary-adrenal and the sympathetic-adrenal-medullary axes, can induce modulation of the immune system. In this review, we discuss human studies and animal models, which focus on psychological stress and its effects on the immune response to vaccination, emphasizing the implications of these effects on health.

Stress-induced immunomodulation and the implications for health

There are complex bi-directional interactions among the central nervous system (CNS), the endocrine system, and the immune system. Although the mechanisms of this bi-directional communication is not yet fully understood, studies in the field of psychoneuroimmunology (PNI) have shown that stress, through the hypothalamic-pituitary-adrenal (HPA) and the sympathetic-adrenal medullary (SAM) axes, can result in the dysregulation of the immune system. In this review, we discuss human studies and animal models, which focuses on psychological stress emphasizing the implications of these effects on wound healing and infectious diseases.

Leukocyte lysosomal enzymes in Alzheimer's disease and Down's syndrome

Previous studies suggested the possibility of accelerated lysosomal degradation of brain gangliosides in Alzheimer's disease (AD). As AD pathology affects both neural and nonneural tissues, the aim of this study was to determine possible changes of glycosphingolipid metabolism in available peripheral cells in AD and Down's syndrome (DS). The activities of several lysosomal enzymes involved in catabolism of gangliosides and sulfatides were measured in leukocytes from subjects with dementia of the Alzheimer type, DS, and age-matched controls, by fluorimetry and spectrophotometry using specific substrates. The results showed a statistically significant increase of beta-galactosidase activity in both dementia of the Alzheimer type and DS leukocytes when compared with age-matched controls (p <.01 and p <.05, respectively; Student's t test). Not significantly increased activities of beta-galactosidase, beta-hexosaminidase, beta-hexosaminidase A, and slightly decreased activity of arylsulfatase A were observed in control leukocytes with aging. Our results indicate that a metabolic dysfunction and the acceleration of at least some lysosomal catabolic pathways are present in AD and DS nonneural cells.

Impairment of mitogenic activation of peripheral blood lymphocytes in Alzheimer's disease

Cell-cycle dysregulation might be critically involved in the process of neurodegeneration in Alzheimer's disease (AD). We now provide evidence for a dysfunction of the cell division cycle as a more general cellular phenomenon of the disease. Peripheral blood lymphocytes, stimulated with mitogenic compounds, were less able to express CD69, an early proliferation marker, in AD patients than in age-matched controls. Expression levels of CD69 of both T-cells and B-cells correlated inversely with the Mini-mental Scale. The results suggest that a systemic failure of cellular proliferation control might be of critical importance for the pathomechanism of AD.

Presenilin mutations and calcium signaling defects in the nervous and immune systems

Presenilin-1 (PS1) is thought to regulate cell differentiation and survival by modulating the Notch signaling pathway. Mutations in PS1 have been shown to cause early-onset inherited forms of Alzheimer's disease (AD) by a gain-of-function mechanism that alters proteolytic processing of the amyloid precursor protein (APP) resulting in increased production of neurotoxic forms of amyloid beta-peptide. The present article considers a second pathogenic mode of action of PS1 mutations, a defect in cellular calcium signaling characterized by overfilling of endoplasmic reticulum (ER) calcium stores and altered capacitive calcium entry; this abnormality may impair synaptic plasticity and sensitize neurons to apoptosis and excitotoxicity. The calcium signaling defect has also been documented in lymphocytes, suggesting a contribution of immune dysfunction to the pathogenesis of AD. A better understanding of the calcium signaling defect resulting from PS1 mutations may lead to the development of novel preventative and therapeutic strategies for disorders of the nervous and immune systems.

Stress-induced immunomodulation: impact on immune defenses against infectious disease

It is now accepted that there are complex interactions among the central nervous system, the endocrine system, and the immune system. Although the mechanisms of this bi-directional communication is not yet fully understood, studies in the field of psychoneuroimmunology (PNI) have shown that stress, through the hypothalamic-pituitary-adrenal (HPA) and the sympathetic-adrenal medullary (SAM) axes, can induce modulation of the immune system. In this review, we discuss human studies and animal models, which focus on psychological stress and its effects on the immune defense against infectious agents, emphasizing the implications of these effects on health.