Plasma neopterin level as a marker of peripheral immune activation in amnestic mild cognitive impairment and Alzheimer's disease

Sex-specific associations of kynurenic acid with neopterin in Alzheimer's disease

BACKGROUND

Sex differences in neuroinflammation could contribute to women's increased risk of Alzheimer's disease (AD), providing rationale for exploring sex-specific AD biomarkers. In AD, dysregulation of the kynurenine pathway (KP) contributes to neuroinflammation and there is some evidence of sex differences in KP metabolism. However, the sex-specific associations between KP metabolism and biomarkers of AD and neuroinflammation need to be explored further.

METHODS

Here we investigate sex differences in cerebrospinal fluid concentrations of seven KP metabolites and sex-specific associations with established AD biomarkers and neopterin, an indicator of neuroinflammation. This study included 311 patients with symptomatic AD and 105 age-matched cognitively unimpaired (CU) controls, followed for up to 5 years.

RESULTS

We found sex differences in KP metabolites in the AD group, with higher levels of most metabolites in men, while there were no sex differences in the CU group. In line with this, more KP metabolites were significantly altered in AD men compared to CU men, and there was a trend in the same direction in AD women. Furthermore, we found sex-specific associations between kynurenic acid and the kynurenic acid/quinolinic acid ratio with neopterin, but no sex differences in the associations between KP metabolites and clinical progression.

DISCUSSION

In our cohort, sex differences in KP metabolites were restricted to AD patients. Our results suggest that dysregulation of the KP due to increased inflammation could contribute to higher AD risk in women.

Kynurenine Metabolism and Alzheimer's Disease: The Potential Targets and Approaches

L-tryptophan, an essential amino acid, regulates protein homeostasis and plays a role in neurotransmitter-mediated physiological events. It also influences age-associated neurological alterations and neurodegenerative changes. The metabolism of tryptophan is carried majorly through the kynurenine route, leading to the production of several pharmacologically active enzymes, substrates, and metabolites. These metabolites and enzymes influence a variety of physiological and pathological outcomes of the majority of systems, including endocrine, haemopoietic, gastrointestinal, immunomodulatory, inflammatory, bioenergetic metabolism, and neuronal functions. An extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the kynurenine metabolites that influence cellular redox potential, immunoregulatory mechanisms, inflammatory pathways, cell survival channels, and cellular communication in close association with several neurodegenerative changes. The imbalanced state of kynurenine pathways has found a close association to several pathological disorders, including HIV infections, cancer, autoimmune disorders, neurodegenerative and neurological disorders including Parkinson's disease, epilepsy and has found special attention in Alzheimer's disease (AD). Kynurenine pathway (KP) is intricately linked to AD pathogenesis owing to the influence of kynurenine metabolites on excitotoxic neurotransmission, oxidative stress, uptake of neurotransmitters, and modulation of neuroinflammation, amyloid aggregation, microtubule disruption, and their ability to induce a state of dysbiosis. Pharmacological modulation of KP pathways has shown encouraging results, indicating that it may be a viable and explorable target for the therapy of AD.

The impact of uremic toxins on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia, pathologically characterized by accumulation of senile plaques and neurofibrillary tangles. Chronic kidney disease (CKD) is highly prevalent in elderly population closely associated with occurrence of dementia. Recent epidemiological and experimental studies suggest a potential association of CKD with AD. Both diseases share a panel of identical risk factors, such as type 2 diabetes; and hypertension. However, the relationship between CKD and AD is unclear. Lower clearance of a panel of uremic toxin including cystatin-C, guanidine, and adiponectin due to CKD is implied to contribute to AD pathogenesis. In this review we summarize the current evidence from epidemiological, experimental and clinical studies on the potential contribution of uremic toxins to AD pathogenesis. We describe outstanding questions and propose an outlook on the link between uremic toxins and AD.

Determination of Neopterin as a Prognostic Indicator Using Neopterin-Imprinted Cryogel Membranes

Neopterin (Neo) is thought of as a key biomarker for the diagnosis and prognosis of a wide variety of diseases associated with cellular immune response. Therefore, it has become a vital need to be able to specifically determine the Neo concentration in human serum. Molecularly imprinted cryogels have come into prominence among other affinity systems by combining advantages of Molecular Imprinting Technology (MIT) and cryogels. In this chapter, synthesis of novel Neopterin-imprinted cryogel membranes (Neo-mip), characterization studies of synthesized materials, and their use in the determination of Neo in human serum is described in detail. In addition, the evaluation of selective Neo adsorption properties of Neo-mip against competitors (Pterin and Glucose) is discussed. Neo-mip will come into prominence as important affinity materials for the selective Neo recognition in body fluids, prior to use in the health sector.

The Impact of Ageing on the CNS Immune Response in Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disease strongly associated with increasing age. Neuroinflammation and the accumulation of amyloid protein are amongst the hallmarks of this disease and most translational research to date has focused on targeting these two processes. However, the exact etiology of AD remains to be fully elucidated. When compared alongside, the immune response in AD closely resembles the central nervous system (CNS) immune changes seen in elderly individuals. It is possible that AD is a pathological consequence of an aged immune system secondary to chronic stimulation by a previous or ongoing insult. Pathological changes like amyloid accumulation and neuronal cell death may reflect this process of immunosenescence as the CNS immune system fails to maintain homeostasis in the CNS. It is likely that future treatments designed to modulate the aged immune system may prove beneficial in altering the disease course. The development of new tests for appropriate biomarkers would also be essential in screening for patients most likely to benefit from such treatments.

On the Possible Relevance of Bottom-up Pathways in the Pathogenesis of Alzheimer's Disease

Dementia is an increasing health problem in older aged populations worldwide. Age-related changes in the brain can be observed decades before the first symptoms of cognitive decline appear. Cognitive impairment has chronic inflammatory components, which can be enhanced by systemic immune activation. There exist mutual interferences between inflammation and cognitive deficits. Signs of an activated immune system i.e. increases in the serum concentrations of soluble biomarkers such as neopterin or accelerated tryptophan breakdown along the kynurenine axis develop in a significant proportion of patients with dementia and correlate with the course of the disease, and they also have a predictive value. Changes in biomarker concentrations are reported to be associated with systemic infections by pathogens such as cytomegalovirus (CMV) and bacterial content in saliva. More recently, the possible influence of microbiome composition on Alzheimer's disease (AD) pathogenesis has been observed. These observations suggest that brain pathology is not the sole factor determining the pathogenesis of AD. Interestingly, patients with AD display drastic changes in markers of immune activation in the circulation and in the cerebrospinal fluid. Other data have suggested the involvement of factors extrinsic to the brain in the pathogenesis of AD. However, currently, neither the roles of these factors nor their importance has been clearly defined.

Tetrahydrobiopterin Improves Recognition Memory in the Triple-Transgenic Mouse Model of Alzheimer's Disease, Without Altering Amyloid-β and Tau Pathologies

BACKGROUND

Alzheimer's disease (AD) is a multifactorial disease, implying that multi-target treatments may be necessary to effectively cure AD. Tetrahydrobiopterin (BH4) is an enzymatic cofactor required for the synthesis of monoamines and nitric oxide that also exerts antioxidant and anti-inflammatory effects. Despite its crucial role in the CNS, the potential of BH4 as a treatment in AD has never been scrutinized.

OBJECTIVE

Here, we investigated whether BH4 peripheral administration improves cognitive symptoms and AD neuropathology in the triple-transgenic mouse model of AD (3xTg-AD), a model of age-related tau and amyloid-β (Aβ) neuropathologies associated with behavior impairment.

METHODS

Non-transgenic (NonTg) and 3xTg-AD mice were subjected to a control diet (5% fat - CD) or to a high-fat diet (35% fat - HFD) from 6 to 13 months to exacerbate metabolic disorders. Then, mice received either BH4 (15 mg/kg/day, i.p.) or vehicle for ten consecutive days.

RESULTS

This sub-chronic administration of BH4 rescued memory impairment in 13-month-old 3xTg-AD mice, as determined using the novel object recognition test. Moreover, the HFD-induced glucose intolerance was completely reversed by the BH4 treatment in 3xTg-AD mice. However, the HFD or BH4 treatment had no significant impact on Aβ and tau neuropathologies.

CONCLUSION

Overall, our data suggest a potential benefit from BH4 administration against AD cognitive and metabolic deficits accentuated by HFD consumption in 3xTg-AD mice, without altering classical neuropathology. Therefore, BH4 should be considered as a candidate for drug repurposing, at least in subtypes of cognitively impaired patients experiencing metabolic disorders.

Tetrahydrobioterin (BH4) Pathway: From Metabolism to Neuropsychiatry

Tetrahydrobipterin (BH4) is a pivotal enzymatic cofactor required for the synthesis of serotonin, dopamine and nitric oxide. BH4 is essential for numerous physiological processes at periphery and central levels, such as vascularization, inflammation, glucose homeostasis, regulation of oxidative stress and neurotransmission. BH4 de novo synthesis involves the sequential activation of three enzymes, the major controlling point being GTP cyclohydrolase I (GCH1). Complementary salvage and recycling pathways ensure that BH4 levels are tightly kept within a physiological range in the body. Even if the way of transport of BH4 and its ability to enter the brain after peripheral administration is still controversial, data showed increased levels in the brain after BH4 treatment. Available evidence shows that GCH1 expression and BH4 synthesis are stimulated by immunological factors, notably pro-inflammatory cytokines. Once produced, BH4 can act as an anti- inflammatory molecule and scavenger of free radicals protecting against oxidative stress. At the same time, BH4 is prone to autoxidation, leading to the release of superoxide radicals contributing to inflammatory processes, and to the production of BH2, an inactive form of BH4, reducing its bioavailability. Alterations in BH4 levels have been documented in many pathological situations, including Alzheimer's disease, Parkinson's disease and depression, in which increased oxidative stress, inflammation and alterations in monoaminergic function are described. This review aims at providing an update of the knowledge about metabolism and the role of BH4 in brain function, from preclinical to clinical studies, addressing some therapeutic implications.

[Neopterin as a potential biomarker in neuropsychiatry]

The importance of finding predictors or biomarkers of neuropsychiatric pathology, as well as methods of its prevention, treatment and early diagnosis is beyond question. The level of neopterin in body fluids is one of the possible biomarkers. Increased levels of neopterin in biological fluids (e.g., serum, cerebrospinal fluid or urine) are closely associated with various diseases associated with cellular immune response. The data presented in the review indicate the relevance of the study of neopterin concentrations in body fluids in patients with mental illness for the development of diagnostic and prognostic tests or as a pharmacodynamic marker of drug action.

Time to test antibacterial therapy in Alzheimer's disease

Alzheimer's disease is associated with cerebral accumulation of amyloid-β peptide and hyperphosphorylated tau. In the past 28 years, huge efforts have been made in attempting to treat the disease by reducing brain accumulation of amyloid-β in patients with Alzheimer's disease, with no success. While anti-amyloid-β therapies continue to be tested in prodromal patients with Alzheimer's disease and in subjects at risk of developing Alzheimer's disease, there is an urgent need to provide therapeutic support to patients with established Alzheimer's disease for whom current symptomatic treatment (acetylcholinesterase inhibitors and N-methyl d-aspartate antagonist) provide limited help. The possibility of an infectious aetiology for Alzheimer's disease has been repeatedly postulated over the past three decades. Infiltration of the brain by pathogens may act as a trigger or co-factor for Alzheimer's disease, with Herpes simplex virus type 1, Chlamydia pneumoniae, and Porphyromonas gingivalis being most frequently implicated. These pathogens may directly cross a weakened blood-brain barrier, reach the CNS and cause neurological damage by eliciting neuroinflammation. Alternatively, pathogens may cross a weakened intestinal barrier, reach vascular circulation and then cross blood-brain barrier or cause low grade chronic inflammation and subsequent neuroinflammation from the periphery. The gut microbiota comprises a complex community of microorganisms. Increased permeability of the gut and blood-brain barrier induced by microbiota dysbiosis may impact Alzheimer's disease pathogenesis. Inflammatory microorganisms in gut microbiota are associated with peripheral inflammation and brain amyloid-β deposition in subjects with cognitive impairment. Oral microbiota may also influence Alzheimer's disease risk through circulatory or neural access to the brain. At least two possibilities can be envisaged to explain the association of suspected pathogens and Alzheimer's disease. One is that patients with Alzheimer's disease are particularly prone to microbial infections. The other is that microbial infection is a contributing cause of Alzheimer's disease. Therapeutic trials with antivirals and/or antibacterials could resolve this dilemma. Indeed, antiviral agents are being tested in patients with Alzheimer's disease in double-blind placebo-controlled studies. Although combined antibiotic therapy was found to be effective in animal models of Alzheimer's disease, antibacterial drugs are not being widely investigated in patients with Alzheimer's disease. This is because it is not clear which bacterial populations in the gut of patients with Alzheimer's disease are overexpressed and if safe, selective antibacterials are available for them. On the other hand, a bacterial protease inhibitor targeting P. gingivalis toxins is now being tested in patients with Alzheimer's disease. Clinical studies are needed to test if countering bacterial infection may be beneficial in patients with established Alzheimer's disease.

Probiotic Supplementation in Patients with Alzheimer's Dementia - An Explorative Intervention Study

Background:

Dysbiosis of intestinal microbiota in the elderly can cause a leaky gut, which may result in silent systemic inflammation and promote neuroinflammation - a relevant pathomechanism in the early course of Alzheimer’s disease.

Objective:

The rebalancing of the microbiome could benefically impact on gut inflammation and immune activation.

Methods:

In this study, routine laboratory tests in twenty outpatients (9 females, 11 males, aged 76.7 ± 9.6 years) with Alzheimer’s disease were investigated. The mean Mini Mental State Examination score was 18.5 ± 7.7. Biomarkers of immune activation – serum neopterin and tryptophan breakdown - as well as gut inflammation markers and microbiota composition in fecal specimens were analyzed in 18 patients be-fore and after probiotic supplementation for 4 weeks.

Results:

After treatment a decline of fecal zonulin concentrations and an increase in Faecalibacterium prausnitzii compared to baseline were observed. At the same time, serum kynurenine concentrations in-creased (p <0.05). Delta values (before - after) of neopterin and the kynurenine to tryptophan ratios (Kyn/Trp) correlated significantly (p <0.05).

Conclusion:

Results show that the supplementation of Alzheimer’s disease patients with a multispecies probiotic influences gut bacteria composition as well as tryptophan metabolism in serum. The correlation between Kyn/Trp and neopterin concentrations points to the activation of macrophages and/or dendritic cells. Further studies are warranted to dissect the potential consequences of Probiotic supplementation in the course of Alzheimer’s disease.

Differences in potential biomarkers of delirium between acutely ill medical and elective cardiac surgery patients

BACKGROUND/AIMS

The pathophysiology of delirium is poorly understood. Increasing evidence suggests that different pathways might be involved in the pathophysiology depending on the population studied. The aim of the present study was to investigate potential differences in mean plasma levels of neopterin, amino acids, amino acid ratios and homovanillic acid between two groups of patients with delirium.

METHODS

Data from acutely ill medical patients aged 65 years and older, and patients aged 70 years and older undergoing elective cardiac surgery, were used. Differences in biomarker levels between the groups were investigated using univariate ANOVA with adjustments for age, sex, comorbidities, C-reactive protein (CRP) and the estimated glomerular filtration rate (eGFR), where appropriate. Linear regression analysis was used to identify potential determinants of the investigated biochemical markers.

RESULTS

Eighty patients with delirium were included (23 acutely ill medical patients and 57 elective cardiac surgery patients). After adjustment, higher mean neopterin levels (93.1 vs 47.3 nmol/L, P=0.001) and higher phenylalanine/tyrosine ratios (1.39 vs 1.15, P=0.032) were found in acutely ill medical patients when compared to elective cardiac surgery patients. CRP levels were positively correlated with neopterin levels in acutely ill medical patients, explaining 28.4% of the variance in neopterin levels. eGFR was negatively correlated with neopterin in elective cardiac surgery patients, explaining 53.7% of the variance in neopterin levels.

CONCLUSION

In this study, we found differences in mean neopterin levels and phenylalanine/tyrosine ratios between acutely ill medical and elective cardiac surgery patients with delirium. Moreover, our findings may suggest that in acutely ill medical patients, neopterin levels are mainly determined by inflammation/oxidative stress whereas in elective cardiac surgery patients, neopterin levels are mainly driven by renal function/fluid status. These findings suggest that the markers and pathways that might be involved in the pathophysiology of delirium may differ between specific groups of patients.

The kynurenine pathway and cognitive performance in community-dwelling older adults. The Hordaland Health Study

INTRODUCTION

Tryptophan, its downstream metabolites in the kynurenine pathway and neopterin have been associated with inflammation and dementia. We aimed to study the associations between plasma levels of these metabolites and cognitive function in community-dwelling, older adults.

METHODS

This cross-sectional study included 2174 participants aged 70-72 years of the community-based Hordaland Health Study. Tryptophan, kynurenine, neopterin and eight downstream kynurenines were measured in plasma. Kendrick Object Learning Test (KOLT), Digit Symbol Test (DST) and the Controlled Oral Word Association Test (COWAT) were all outcomes in standardized Zellner's regression. The Wald test of a composite linear hypothesis of an association with each metabolite was adjusted by the Bonferroni method. Age, body mass index, C-reactive protein, depressive symptoms, diabetes, education, glomerular filtration rate, hypertension, previous myocardial infarction, prior stroke, pyridoxal 5'phosphate, sex and smoking were considered as potential confounders.

RESULTS

Higher levels of the kynurenine-to-tryptophan ratio (KTR) and neopterin were significantly associated with poorer, overall cognitive performance (p < 0.002). Specifically, KTR was negatively associated with KOLT (β -0.08, p = 0.001) and COWAT (β -0.08, p = 0.001), but not with DST (β -0.03, p = 0.160). This pattern was also seen for neopterin (KOLT: β -0.07; p = 0.001; COWAT: β -0.06, p = 0.010; DST: β -0.01, p = 0.800). The associations were not confounded by the examined variables. No significant associations were found between the eight downstream kynurenines and cognition.

CONCLUSION

Higher KTR and neopterin levels, biomarkers of cellular immune activation, were associated with reduced cognitive performance, implying an association between the innate immune system, memory, and language.

Evaluation of plasma levels of neopterin and soluble CD40 ligand in patients with acute ischemic stroke in upper Egypt: can they surrogate the severity and functional outcome?

BACKGROUND

Inflammation constitutes a major component of ischemic stroke pathology. The prognostic value of "neopterin" and soluble CD40 ligand (sCD40L), as a potential biomarker of ischemic stroke, has been less extensively studied.

OBJECTIVES OF THE STUDY

This study aims at assessing the serum levels of neopterin and sCD40L in acute ischemic stroke (AIS), to clarify its association with the severity, etiology, and risk factors of stroke, and to evaluate their relationship with the stroke functional outcome in our study sample within 90 days of follow-up.

STUDY SAMPLE

This case-control study was conducted on 100 patients with first-ever acute onset ischemic stroke and 25 control subjects.

METHODS

Participants were subjected to full history taking and detailed clinical and neurological examination. Brain imaging was performed after hospital admission. Blood tests were drawn for assessment of neopterin and sCD40L on the first day of admission.

RESULTS

High levels of neopterin and sCD40L was reported. Their levels were significantly higher in relation with survival status. There was a relationship between AIS and sCD40L levels and the severity of the stroke. Within 3 months of follow-up, these biomarkers were associated significantly with poor functional outcome, within a 90-day follow-up period, and mortality. These biomarkers were highly associated in patients with small vessel occlusion as an etiology for AIS.

CONCLUSION

Neopterin and sCD40L levels increased after AIS. Both biomarkers were strong and independent predictors of 90-day unfavorable clinical outcome and death in patients after AIS.

Interferon-γ Mediated Pathways And Mitogen Stimulated Proliferation During And After An Acute Infection

Background: Interferon-γ (IFN- γ) regulates the degradation of tryptophan to kynurenine via induction of indoleamine- 2,3-dioxygenase (IDO). Local tryptophan depletion and accumulation of toxic metabolites might impair the proliferative capacity of lymphocytes. The aim of this study was to assess the actual status of immune system activation of patients with bacterial infection in the acute phase and during convalescence in vivo and in vitro. Parameters of systemic immune system activation were evaluated for associations with proliferative responsiveness of immune cells, and compared with healthy controls. Methods: 24 patients with various acute bacterial infections were included in the group of acutely ill patients. Sixteen patients participated in a follow-up examination after convalescence. The control group consisted of 6 healthy people. To assess the status of immune system activation in vivo, inflammation parameters C-reactive protein and differential blood counts were determined. Neopterin concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Tryptophan and kynurenine measurements were performed with high pressure liquid chromatography (HPLC). Peripheral blood mononuclear cells (PBMCs) were isolated from the patients’ blood and stimulated with concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) in vitro proliferation rates were evaluated by ³H-thymidine incorporation and neopterin production and tryptophan degradation were determined in supernatants of mitogen stimulated PBMCs. Results: Patients with acute bacterial infections showed reduced tryptophan and elevated neopterin concentrations, which did not normalize after convalescence period. Higher plasma neopterin values and increased IDO-activity were associated with reduced proliferative responses in vitro after stimulation with PHA. Associations were observed during acute infection as well as convalescence. Conclusions: Results of this study show that increased immune system activation in vivo is associated with impaired proliferative responsiveness of immune cells in vitro in acute bacterial infections as well as during convalescence.

Neopterin preconditioning prevents inflammasome activation in mammalian astrocytes

Neopterin, a well-established biomarker for immune system activation, is found at increased levels in the cerebrospinal fluid of individuals affected by neurological/neurodegenerative diseases. Here, neopterin synthesis was investigated in different nerve cells (rodent and human) and in the mouse hippocampus under inflammatory stimuli. We also aimed to investigate whether neopterin preconditioning could modulate the inflammasome activation, a component of the innate immune system. Increased neopterin was detected in human nerve cells supernatants (highest secretion in astrocytes) exposed to lipopolysaccharide (LPS) and interferon-gamma (INF-γ) and in the hippocampus of mice receiving LPS (0.33mg/kg; intraperitoneal). In parallel to the hippocampal-increased neopterin, it was observed a significant increase in the expression of the rate-limiting enzyme of its biosynthetic pathway, and both phenomena occurred before the inflammasome activation. Moreover, a significant inhibition of the inflammasome activation was observed in neopterin pre-conditioned human astrocytes, when challenged with LPS, by reducing IL-1β, caspase-1 and ASC expression or content, components of the NLRP3 inflammasome. Mechanistically, neopterin might induce eletrophilic stress and consequently the nuclear translocation of the transcription factor Nrf-2, and the anti-inflammatory cytokines IL-10 and IL-1ra release, which would induce the inhibition of the inflammasome activation. Altogether, this strongly suggests an essential role of neopterin during inflammatory processes.

Clinical aspects and biomarkers of Alzheimer's disease in Down syndrome

Alzheimer's disease (AD) may affect in excess of 90% of individuals with Down syndrome (DS) after age 60, due to duplication of the APP gene in trisomy of chromosome 21, with neuropathology that is comparable to Sporadic AD and Familial AD (FAD). Previous literature suggested some unique features in clinical presentation of dementia in DS (DSd), which might be due to diagnostic difficulties, or represent a real difference compared to SAD or FAD. We review current knowledge on clinical diagnosis and presentation of dementia in DS in comparison with FAD due to APP mutations and APP duplication. We suggest that the clinical presentation in DS (prominent memory decline and behavioral symptoms, and early development of myoclonus and seizures) are similar to the clinical features associated with APP mutations that is known to have an increased Aβ42/ Aβ40 ratio, and highlight the relative lack of vascular complications associated with cerebral amyloid angiopathy in DS in comparison with those rare individuals with FAD due to duplication APP. We consider the biomarker evidence associated with DS and DSd with reference to Aβ peptide levels and oxidative stress, and suggest future directions for research to explore the potential mechanisms associated with the clinical presentation of DSd.

A Novel Method to Identify Differential Pathways in Hippocampus Alzheimer's Disease

Background

Alzheimer’s disease (AD) is the most common type of dementia. The objective of this paper is to propose a novel method to identify differential pathways in hippocampus AD.

Material/Methods

We proposed a combined method by merging existed methods. Firstly, pathways were identified by four known methods (DAVID, the neaGUI package, the pathway-based co-expressed method, and the pathway network approach), and differential pathways were evaluated through setting weight thresholds. Subsequently, we combined all pathways by a rank-based algorithm and called the method the combined method. Finally, common differential pathways across two or more of five methods were selected.

Results

Pathways obtained from different methods were also different. The combined method obtained 1639 pathways and 596 differential pathways, which included all pathways gained from the four existing methods; hence, the novel method solved the problem of inconsistent results. Besides, a total of 13 common pathways were identified, such as metabolism, immune system, and cell cycle.

Conclusions

We have proposed a novel method by combining four existing methods based on a rank product algorithm, and identified 13 significant differential pathways based on it. These differential pathways might provide insight into treatment and diagnosis of hippocampus AD.

The Serum Levels of Resistin and Its Relationship with Other Proinflammatory Cytokines in Patients with Alzheimer's Disease

Objective

The present study aims to analyze the levels of resistin, tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, IL-18, and C-reactive protein (CRP) in patients with Alzheimer's disease (AD) and also investigate a potential relationship between resistin levels and TNF-α, IL-1β, IL-6, IL-18, and CRP levels in patients with AD.

Methods

The study included fifty patients with AD and 30 healthy controls with normal cognitive functions. The serum resistin, TNF-α, IL-1β, IL-6, IL-18, and CRP levels were assessed. We performed a Mini-Mental State Examination (MMSE) to evaluate the general cognitive performance.

Results

The mean serum resistin, IL-1β, IL-18, and TNF-α levels were significantly higher in patients with AD compared with the controls (p=0.026, p=0.002, p=0.003, and p=0.038, respectively). The IL-6 and CRP levels did not differ between the groups (p=0.874 and p=0.941). The resistin levels were positively correlated with the levels of CRP and IL-18 (r=0.526, p＜0.001; r=0.402, p=0.004, respectively). MMSE scores and inflammatory markers were not correlated (p＞0.05 for all).

Conclusion

Serum resistin levels were significantly increased and correlated with some inflammatory markers in AD patients, suggesting that resistin might play a role in the inflammatory process of AD.

Age, but not anthelmintic treatment, is associated with urinary neopterin levels in semi-free ranging Barbary macaques

Studying host parasite interactions and their implications for evolution and ecology recently received increasing attention, particularly with regard to host physiology and immunity. Here we assess variation of urinary neopterin (uNEO), a marker of cellular immune activation and iummunosenescence, in response to age and anthelmintic treatment in semi-free ranging Barbary macaques (Macaca sylvanus). Urinary NEO levels were measured via enzyme-immunoassay from 179 urine samples of 43 individuals between 5–29 years of age. Efficiency of treatment was assessed by Mc Master flotation on repeated faecal samples, including 18 untreated individuals as control group. We used linear mixed models with age and parasite status as main effects, controlling for sex and physical condition, assessed through urinary C-Peptide-levels, with social group and ID as random factors. Urinary NEO levels significantly increased with age, suggesting that changes in aging Barbary macaque immune responses are consistent with immunosenescence described in human and nonhuman primates and can be detected via uNEO measurements. Anthelmintic treatment, however, had no influence on uNEO levels, potentially due to quick reinfections or attenuated immune responses in repeated infections. We conclude that uNEO is a potential non-invasive marker for immune function and particularly immunosenescence in wildlife.

Neopterin and hsCRP are not correlated in gestational diabetes mellitus

OBJECTIVE

To determine serum neopterin and high sensitive C-reactive protein (hsCRP) levels in patients with and without gestational diabetes mellitus (GDM).

METHODS

Neopterin and hsCRP levels were quantified in 28 women with GDM and 20 pregnant women with normal glucose tolerance (NGT). Postpartum neopterin and hsCRP levels were measured in a follow-up study.

RESULTS

Neopterin levels were significantly higher in women with GDM than in women with NGT (15.89 ± 8.19 nmol/L versus 10.4 ± 3.8 nmol/L, p < 0.008, respectively), however the levels significantly decreased after delivery in GDM group (15.89 ± 8.19 nmol/L versus 11.63 ± 5.96 nmol/L, p < 0.001). hsCRP levels were not different between women with and without GDM (5.74 ± 3.91 versus 5.73 ± 3.34, p = 0.9, respectively). In contrast, hsCRP levels decreased after delivery in patients with GDM (5.74 ± 3.91 versus 3.78 ± 2.78, p < 0.01). Neopterin levels were correlated with maternal age (r = 0.3, p = 0.02) and fasting glucose (r = 0.4, p = 0.004), postprandial glucose (r = 0.3, p = 0.01), HbA1c (r = 0.3, p = 0.02), whereas hsCRP levels were correlated with pre-pregnancy (r = 0.3, p = 0.04) and pregnancy body mass index (r = 0.4, p = 0.008). No correlation between serum neopterin and hsCRP levels was found (p = 0.9).

CONCLUSION

Neopterin levels increased in patients with GDM; hence, it may be related to inflammation. However, the lack of correlation between neopterin and hsCRP suggests the role of different attitudes of these two parameters in the course of pregnancy and GDM.

Cognitive ability in Down syndrome and its relationship to urinary neopterin, a marker of activated cellular immunity

BACKGROUND

Neopterin is an unconjugated pteridine that is secreted in large quantities by activated macrophages and can be used as a clinical marker of activated cellular immunity and oxidative stress. We aimed to investigate whether urinary neopterin levels are associated with cognitive function in people with Down syndrome (DS).

METHODS

Out of 32 adults with DS who originally participated in a longitudinal study, 25 were followed up at 4 years. Informants rated their adaptive behavior (ABAS) and the adults with DS attempted assessments of language skills and memory at both baseline and follow-up time points (Modified Memory Object Task, MOMT), and receptive vocabulary (British Picture Vocabulary Scale, BPVS).

RESULTS

Neopterin/creatinine levels were negatively correlated with change in the MOMT total score (Spearman's Rho=-0.517, p=0.020) and change in the MOMT delayed recall score (Spearman's Rho=-0.577, p=0.008) over time, i.e. higher neopterin/creatinine level was associated with worse performance on a test of cognitive ability over time.

CONCLUSION

Urine neopterin may have potential as a biomarker for memory decline in Down syndrome, and could potentially also help to track progression of mild cognitive impairment (MCI) to Alzheimer's disease in other high risk populations.

Neopterin acts as an endogenous cognitive enhancer

Neopterin is found at increased levels in biological fluids from individuals with inflammatory disorders. The biological role of this pteridine remains undefined; however, due to its capacity to increase hemeoxygenase-1 content, it has been proposed as a protective agent during cellular stress. Therefore, we investigated the effects of neopterin on motor, emotional and memory functions. To address this question, neopterin (0.4 and/or 4pmol) was injected intracerebroventricularly before or after the training sessions of step-down inhibitory avoidance and fear conditioning tasks, respectively. Memory-related behaviors were assessed in Swiss and C57BL/6 mice, as well as in Wistar rats. Moreover, the putative effects of neopterin on motor and anxiety-related parameters were addressed in the open field and elevated plus-maze tasks. The effects of neopterin on cognitive performance were also investigated after intraperitoneal lipopolysaccharide (LPS) administration (0.33mg/kg) in interleukin-10 knockout mice (IL-10(-/-)). It was consistently observed across rodent species that neopterin facilitated aversive memory acquisition by increasing the latency to step-down in the inhibitory avoidance task. This effect was related to a reduced threshold to generate the hippocampal long-term potentiation (LTP) process, and reduced IL-6 brain levels after the LPS challenge. However, neopterin administration after acquisition did not alter the consolidation of fear memories, neither motor nor anxiety-related parameters. Altogether, neopterin facilitated cognitive processes, probably by inducing an antioxidant/anti-inflammatory state, and by facilitating LTP generation. To our knowledge, this is the first evidence showing the cognitive enhancer property of neopterin.

No relationship between lipoprotein-associated phospholipase A2, proinflammatory cytokines, and neopterin in Alzheimer's disease

OBJECTIVE

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a reported risk factor for dementia. However, the relationship between Alzheimer's disease (AD) and Lp-PLA2 is still debatable and, to the best of our knowledge, no study has evaluated the associations between levels of Lp-PLA2, proinflammatory cytokines, and neopterin in AD.

METHODS

In total, 59 patients with AD and 38 non-demented individuals were included in the case-control study. Fasting serum concentrations of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), neopterin, and Lp-PLA2 were determined using ELISA. The associations between AD and each of the variables were analyzed by logistic regression.

RESULTS

The median Lp-PLA2 levels in AD and controls were similar (P=0.29, not significant). Median serum neopterin and IL-6 levels were significantly higher in patients with AD than in controls (P=0.0001 and P=0.03, respectively). In regression analyses, median neopterin levels, a lower level of education, and female gender were significantly associated with AD when compared with controls (OR, 31.44, 95% CI 3.59-275.28, P=0.002; OR, 4.35, 95% CI 1.13-16.61, P=0.032; OR, 7.25, 95% CI 1.88-28.00, P=0.004, respectively).

CONCLUSION

In contrast to previous evidence suggesting its role in dementia and AD, Lp-PLA2 enzyme levels were higher in the controls, and no relationship between Lp-PLA2 and either proinflammatory cytokines or neopterin was identified in AD. Elevated neopterin levels may be considered inflammatory markers of AD.

Neopterin as a potential cytoprotective brain molecule

Neopterin, a byproduct of the tetrahydrobiopterin de novo pathway, is found in increased levels in cerebrospinal fluid and plasma and significantly increases upon damage, infection or during immune system activation. The production of this compound seems almost restricted to the monocyte/macrophage linage cells, in response to interferon-γ stimulation. However, it is unclear whether and which nervous cells are able to synthesize neopterin, respond to any stressor applied extracellularly, or even the role of the compound in the central nervous system. Here we propose a potential cytoprotective role of neopterin in the brain, and show evidence that cultured rat astrocytes are responsive to the molecule; the pterin elicited increased hemeoxygenase-1 cellular content and decreased oxidative stress induced by mitochondrial dysfunction. Further studies are needed to clarify neopterin's cytoprotective effects in the central nervous system, and its potential role in different neuroinflammatory diseases.

Lowered Levels of Carbonyl Proteins after Vitamin B Supplementation in Patients with Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND

The critical role of neuro-inflammation and oxidative stress in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD) has become evident.

OBJECTIVE

The aim of this study is to assess the influence of vitamin supplementation on parameters of oxidative stress, inflammation as well as on cognition in patients with AD and mild cognitive impairment.

METHODS

In our study, patients with cognitive impairment and healthy controls were enrolled. All patients were intended to receive vitamin supplementation (vitamin B1, B6, B12 and folic acid) for 3 months. Mini Mental State Examination (MMSE) and laboratory markers [carbonyl proteins (CPs), malondialdehyde, tryptophan (Trp), kynurenine (Kyn), neopterin, folic acid, vitamin B12 level] were assessed for patients and controls at baseline and after 3 months. After half of the patients had been treated for 3 months, analyses were performed resulting in 3 subgroups: healthy controls without supplementation (15 subjects, 11 females), patients with vitamin supplementation (17 subjects, 10 females) and patients without vitamin supplementation (16 subjects, 9 females; baseline values prior to supplementation).

RESULTS

Age was significantly higher for the supplemented group (76.4 ± 6.7 years) compared to vitamin-naïve patients (63.3 ± 13.7 years; p < 0.01). The MMSE score was higher in the supplemented group (23.1 ± 4.8 vs. 20.3 ± 9.5) but did not reach significance. Levels of CPs were significantly higher in the vitamin-naïve patients (p < 0.05). Levels of Kyn and the Kyn/Trp ratio were significantly lower in vitamin-naïve patients compared to the supplemented group (p < 0.05). No significant difference was seen for the other markers.

CONCLUSION

Vitamin supplementation leads to reduced levels of CPs in patients. Pearson's correlation coefficient shows a negative relation (r = -0.69) between CPs and MMSE. Future trials should assess whether CPs might be suitable markers for monitoring of demented patients.

Neopterin as a Predictor of Functional Outcome and Mortality in Chinese Patients with Acute Ischemic Stroke

Immune responses and inflammation play an important role in the pathogenesis of ischemic stroke. We therefore evaluated the 6-month prognostic value of early measurement of serum neopterin levels, a marker of inflammation and immune system activation, in Chinese patients with acute ischemic stroke (AIS). Consecutive AIS patients admitted to the emergency department were identified. Clinical information was collected. Serum concentration of neopterin and NIH stroke scale (NIHSS) were measured at the time of admission. Functional outcome was measured by modified Rankin scale (mRS) 6 months after admission. Multivariate analyses were performed using logistic regression models. During the inclusion period, 312 patients with first-ever AIS were included and 290 completed follow-up. The results indicated that the serum neopterin levels were significantly (P < 0.0001) higher in acutely ischemic stroke patients as compared to normal controls. Neopterin was an independent prognostic marker of 6-month functional outcome and death [odds ratio (OR) 4.33 (1.83-10.32) and 6.68 (2.44-12.13), respectively, P < 0.0001 for both, adjusted for NIHSS, other predictors and vascular risk factors] in patients with AIS. Neopterin improved the area under the receiver operating characteristic curve of the NHISS score for functional outcome from 0.75 (95 % CI 0.69-0.83) to 0.85 (95 % CI 0.79-0.91; P < 0.001) and for mortality from 0.76 (95 % CI 0.68-0.85) to 0.87 (95 % CI 0.81-0.94; P < 0.001). Serum neopterin is a useful, independent tool to predict functional outcome and mortality 6 months after stroke.

Dissecting the Contribution of Vascular Alterations and Aging to Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive decline that afflicts as many as 45 % of individuals who survive past the age of 85. AD has been associated with neurovascular dysfunction and brain accumulation of amyloid-β peptide, as well as tau phosphorylation and neurodegeneration, but the pathogenesis of the disease is still somewhat unclear. According to the amyloid cascade hypothesis of AD, accumulation of amyloid-β peptide (Aβ) aggregates initiates a sequence of events leading to neuronal injury and loss, and dementia. Alternatively, the vascular hypothesis of AD incorporates the vascular contribution to the disease, stating that a primary insult to brain microcirculation (e.g., stroke) not only contributes to amyloidopathy but initiates a non-amyloidogenic pathway of vascular-mediated neuronal dysfunction and injury, which involves blood-brain barrier compromise, with increased permeability of blood vessels, leakage of blood-borne components into the brain, and, consequently, neurotoxicity. Vascular dysfunction also includes a diminished brain capillary flow, causing multiple focal ischemic or hypoxic microinjuries, diminished amyloid-β clearance, and formation of neurotoxic oligomers, which lead to neuronal dysfunction. Here we present and discuss relevant findings on the contribution of vascular alterations during aging to AD, with the hope that a better understanding of the players in the "orchestra" of neurodegeneration will be useful in developing therapies to modulate the "symphony".

Elevated Serum Levels of Neopterin at Admission Predicts Depression After Acute Ischemic Stroke: a 6-Month Follow-Up Study

Inflammation and cell-mediated immune activation are attributed to the pathogenesis and pathophysiology in depression. Our aim was to test the possible association between serum levels of neopterin and the development of post-stroke depression (PSD) in Chinese patients. The subjects were first-ever acute ischemic stroke patients who were hospitalized at the First Affiliated Hospital of Xinxiang Medical University during the period from December 2012 to December 2013. Clinical information and stroke severity were collected at admission. Neurological and neuropsychological evaluations were conducted at the 6-month follow-up. Serum neopterin levels were measured using fluorometry and a high performance liquid chromatography (HPLC) method. Multivariate analyses were performed using logistic regression models. During the study period, 226 patients were included and finished the 6-month follow-up. Sixty-nine patients (30.5 %) were diagnosed as having major depression at 6 months. Patients with major depression showed higher levels of serum neopterin (21.6[IQR, 18.9-25.7]nmol/L vs. 14.6[IQR, 12.2-18.4]nmol/L, P < 0.0001) at admission. In multivariate analyses, serum neopterin was an independent predictor of PSD at 6 months [odds ratio (OR): 1.952 (95 % CI, 1.358-2.805), P < 0.0001]. With an AUC of 0.850 (95 % CI, 0.797-0.902), neopterin showed a significantly greater discriminatory ability as compared with high-sensitivity C-reactive protein, age, body mass index, and National Institutes of Health and Stroke Scale score. Neopterin is a novel, independent predictor of the development of depression 6 months after stroke. This indicated that the elevated neopterin levels may play a significant role in the pathology of depression and that the pathways leading to inflammation and cell-mediated immune activation warrant further exploration.

Immunologic changes in frail older adults

Several studies have shown a heightened inflammatory state in frail older adults, marked by high serum levels of interleukin-6 and C-reactive protein and an increased number of circulating leukocytes. Activation of monocytes and macrophages, marked by increased levels of neopterin, may contribute to chronic inflammation in the frail older adult. However, the reduced mononuclear cell response to lipopolysaccharide in vitro suggests the existence of defective activation pathways within the innate immune system possibly due to desensitization. Conversely, the expansion of CD8(+) T cells, and specifically those expressing the CCR5 chemokine receptor, above and beyond the levels observed in senescence, points to the involvement of adaptive immune pathways. In line with these observations, frail older adults exhibit a reduced antibody response to pneumococcal and influenza vaccines. Collectively, these observations support the existence of a dysregulated immune system in frail older adults and highlight the need for strategies to improve its function.

ABBREVIATIONS

AIDS, acquired immunodeficiency syndrome; CCL, CC-chemokine receptor ligand; CCR, CC-chemokine receptor; CHS, Cardiovascular Health Study; CMV, cytomegalovirus; GTP, guanosine trisphosphate; HAART, highly active anti-retroviral therapy; HIV, human immunodeficiency virus; IDO, indoleamine-pyrrole 2,3-dioxygenase; IL, interleukin; IFN, interferon; MACS, Multicenter AIDS Cohort Study; NH2PPP, dihydro-neopterin trisphosphate; Tc, T cytotoxic; TCR, T-cell receptor; TEMRA, T effector memory cells re-expressing CD45RA; Th, T helper; TNF, tumor necrosis factor; WHAS, Women's Health and Aging Study.

Serum neopterin as an indicator of increased risk of renal allograft rejection

Acute rejection remains associated with poor graft outcome. An early predictor of acute renal transplant rejection is the long sought after goal for transplant immunologists. In this study we measured levels of serum neopterin at day 5 post-transplant in a cohort of 216 consecutive renal allograft recipients, and compared this with serum creatinine and acute rejection episodes during the first year post transplant. We compared serum neopterin in recipients from living donors (LD), donors after brain death (DBD) and donors after cardiac death (DCD). In all cases higher neopterin levels were correlated with acute rejection in the first year post transplant, but this was only significant in recipients of DCD kidneys who suffered acute cellular or vascular rejection (p=0.04, odds ratio 1.08, 95% CI 1.003-1.012). The neopterin/creatinine ratio, which takes into account the effect of kidney function on circulating neopterin levels, was significantly higher for all recipients who suffered biopsy proven cellular or vascular rejection in the first year post transplant, compared to all other patients (p=0.001, for an increase of 0.1, odds ratio=1.64, 95% CI 1.21-2.20). The ability to use non-invasive biomarkers in the transplant recipient has the potential to increase transplant survival for these patients.

Systemic immune system alterations in early stages of Alzheimer's disease

Immune activation and inflammation play significant roles in the pathogenesis of Alzheimer's disease (AD). To test whether AD patients showed systemic manifestations of inflammation, blood from 41 patients with early stages of AD and 31 aged-match elderly controls were evaluated. Cellular markers for monocyte/macrophage (MO) activation and CD8 T lymphocyte were increased in early AD patients. Expression of monocyte CCR2, the receptor for monocyte chemoattractant protein-1 (MCP-1), was decreased; however, plasma MCP-1 levels were significantly increased and were related to the degree of MO activation in AD. These findings suggest that AD pathogenesis may be influenced by systemic immunologic dysfunction and provides potential immunologic targets for therapeutic intervention.