Although it is generally recognized that the function of the immune system declines with age, the nature of the underlying defects is still poorly understood. We now demonstrate the predominance of CD8+CD28− T cell clonal expansions in elderly persons who fail to produce specific Abs following influenza vaccination. These clones express effector cell markers and are mostly CD45RA+. When isolated and put into culture, they are unable to proliferate, but produce IFN-γ (but no IL-5) upon stimulation with anti-CD3 or autoantigen. These autoreactive CD8+ type 1 effector cells seem to trigger a Th1 polarization, as CD4+ T cells from elderly persons without in vivo Ab production produce Th1, but only low amounts of Th2 cytokines upon in vitro stimulation with PHA. Therefore, the increased occurrence of CD8+CD28− clonal expansions may be decisive for the development of immune deficiency in the elderly.

SummaryA huge amount of evidence has implicated amyloid beta (Aβ β β β ) peptides and other derivatives of the amyloid precursor protein (β β β β APP) as central to the pathogenesis of Alzheimer's disease (AD). It is also widely recognized that age is the most important risk factor for AD and that the innate immune system plays a role in the development of neurodegeneration. Little is known, however, about the molecular mechanisms that underlie age-related changes of innate immunity and how they affect brain pathology. Aging is characteristically accompanied by a shift within innate immunity towards a pro-inflammatory status. Pro-inflammatory mediators such as tumour necrosis factor-α α α α or interleukin-1β β β β can then in combination with interferon-γ γ γ γ be toxic on neurons and affect the metabolism of β β β β APP such that increased concentrations of amyloidogenic peptides are produced by neuronal cells as well as by astrocytes. A disturbed balance between the production and the degradation of Aβ β β β can trigger chronic inflammatory processes in microglial cells and astrocytes and thus initiate a vicious circle. This leads to a perpetuation of the disease.

The appearance of inflammatory markers associated with amyloid plaques indicates a state of chronic inflammation in Alzheimer's disease (AD). Multiple epidemiological studies also suggest that patients taking anti-inflammatory drugs have a decreased risk of developing AD. Here we present evidence that inflammatory cytokines can alter the metabolism of the beta-amyloid precursor protein (betaAPP). We show that the combination of tumor necrosis factor alpha and interferon gamma triggers the production of beta-amyloid peptides and inhibits the secretion of soluble APPs by human neuronal and extraneuronal cells. The results demonstrate a new mechanism by which inflammatory components can exacerbate the fundamental pathology in AD.

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IntroductionThere is still a clear need for a widely available, inexpensive and reliable method to diagnose Alzheimer’s disease (AD) and monitor disease progression. Liquid chromatography–mass spectrometry (LC-MS) is a powerful analytic technique with a very high sensitivity and specificity.ObjectivesThe aim of the present study is to measure concentrations of 20 bile acids using the novel Kit from Biocrates Life Sciences based on LC-MS technique.MethodsTwenty bile acid metabolites were quantitatively measured in plasma of 30 cognitively healthy subjects, 20 patients with mild cognitive impairment (MCI) and 30 patients suffering from AD.ResultsLevels of lithocholic acid were significantly enhanced in plasma of AD patients (50 ± 6 nM, p = 0.004) compared to healthy controls (32 ± 3 nM). Lithocholic acid plasma levels of MCI patients (41 ± 4 nM) were not significantly different from healthy subjects or AD patients. Levels of glycochenodeoxycholic acid, glycodeoxycholic acid and glycolithocholic acid were significantly higher in AD patients compared to MCI patients (p < 0.05). All other cholic acid metabolites were not significantly different between healthy subjects, MCI patients and AD patients. ROC analysis shows an overall accuracy of about 66%. Discriminant analysis was used to classify patients and we found that 15/23 were correctly diagnosed. We further showed that LCA levels increased by about 3.2 fold when healthy subjects converted to AD patients within a 8–9 year follow up period. Pathway analysis linked these changes to a putative toxic cholesterol pathway.ConclusionIn conclusion, 4 bile acids may be useful to diagnose AD in plasma samples despite limitations in diagnostic accuracy.Electronic supplementary materialThe online version of this article (10.1007/s11306-017-1297-5) contains supplementary material, which is available to authorized users.

Traumatic brain injury (TBI) is a risk factor for the development of Alzheimer's disease (AD). After a traumatic brain injury depositions of amyloid beta (Abeta) in the brain parenchyma were found. In this study we investigated the expression pattern of beta-secretase (BACE-1) in ipsi- or contralateral hippocampus and cortex following controlled cortical TBI in rats. BACE-1 mRNA levels, estimated by real time RT-PCR, were elevated 24 h post injury, and persisting up to 72 h, in the ipsi- and contralateral hippocampus and cerebral cortex as compared to the sham-treated animals (p<0.01). The TBI-induced changes in BACE-1 mRNA are due to enhanced hippocampal and cortical expression of BACE-1 mRNA in neurons and reactive astrocytes as revealed by in situ hybridization. The alterations in hippocampal BACE-1 mRNA levels are accompanied by corresponding increases in BACE-1 protein levels in ipsi- and contralateral hippocampus and ipsilateral cortex as demonstrated by Western blot analysis. In contrast, in the contralateral cortex only a weak increase of traumatically induced BACE-1 protein production was found. The activity of BACE-1 as measured by the formation of the cleavage product of amyloid beta precursor protein, transiently increased up to 48 h after injury, but returned to basal level 7 days post injury. This study demonstrates that the beta-secretase is stimulated following TBI and may suggest a mechanism for the temporal increase of Abeta levels observed in patients with brain trauma.

Cerebrospinal fluid (CSF) biological markers may be of valuable help in the diagnosis of dementia. The aim of the present study was to evaluate CSF levels of 13 potential biomarkers in patients with Alzheimer’s disease (AD), frontotemporal lobe dementia, alcohol dementia, major depression and control patients without any neuropsychiatric disease. The study was performed using β-amyloid 1–42 (Aβ42), total tau and phosphorylated tau-181 (P-tau181) as core markers. The ratio P-tau181/Aβ42 could significantly distinguish AD patients from all other diagnostic subgroups. CSF levels of 5 growth factors (HGF, GDNF, VEGF, BDNF, FGF-2) and 3 cytokines/chemokines (TNF-α, TGF-β₁, MIP-1α) did not significantly differentiate between the studied groups. However, depending on the degree of neurodegeneration (as expressed by the ratio P-tau181/Aβ42), patients with AD displayed significantly increased CSF levels of nerve growth factor (NGF) as compared to healthy controls. CSF levels of monocyte chemoattractant protein 1 (MCP-1) were found to be significantly increased with age in all groups but did not distinguish AD patients from healthy controls. The results confirmed the suitability of the ratio P-tau181/Aβ42 for the diagnosis of AD, while CSF levels of NGF and MCP-1 are less specific and reliable for AD. It is suggested that the increase in NGF depends on the extent of neurodegeneration of the AD type and the increase in MCP-1 on age.

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