Increased expression of TREM2 in peripheral cells from mild cognitive impairment patients who progress into Alzheimer's disease.

BACKGROUND AND PURPOSE: Neuroinflammation plays a role in the aetiopathogenesis of Alzheimer's disease (AD). Triggering receptor expressed on myeloid cells 2 (TREM2), a cell surface receptor of the immunoglobulin superfamily, seems to have protective anti-inflammatory activity in AD. METHODS: Triggering receptor expressed on myeloid cells 2 expression was analysed in peripheral blood mononuclear cells from healthy subjects (CT) and from patients with either AD or mild cognitive impairment (MCI). MCI patients were re-evaluated at a 2-year follow-up to investigate their progression to AD (MCI-AD) or lack thereof (MCI-MCI). RESULTS: Triggering receptor expressed on myeloid cells 2 gene expression was higher in AD than CT patients, but was highest in MCI. At recruitment TREM2 levels were higher in MCI-AD than in MCI-MCI, and in MCI-AD were higher initially than at follow-up. TREM2 displayed a moderate degree of sensitivity and specificity for identifying MCI-AD in all MCI patients. Our data showed higher TREM2 levels in allele ε4 of apolipoprotein E (ApoE ε4) carriers than non-carriers in MCI and particularly in MCI-AD. CONCLUSIONS: These data seem to confirm the protective role of TREM2 in the pre-clinical stage of AD. Upregulation of TREM2 in MCI-AD could be a mechanism to counteract the activation of neuroinflammatory processes. It is possible that TREM2 and ApoE ε4 interact synergistically in the pre-clinical stage of AD. Therefore, TREM2 may be useful as an early peripheral biomarker for the development of AD.

Genome-wide haplotype association study identifies the FRMD4A gene as a risk locus for Alzheimer's disease.

Recently, several genome-wide association studies (GWASs) have led to the discovery of nine new loci of genetic susceptibility in Alzheimer's disease (AD). However, the landscape of the AD genetic susceptibility is far away to be complete and in addition to single-SNP (single-nucleotide polymorphism) analyses as performed in conventional GWAS, complementary strategies need to be applied to overcome limitations inherent to this type of approaches. We performed a genome-wide haplotype association (GWHA) study in the EADI1 study (n=2025 AD cases and 5328 controls) by applying a sliding-windows approach. After exclusion of loci already known to be involved in AD (APOE, BIN1 and CR1), 91 regions with suggestive haplotype effects were identified. In a second step, we attempted to replicate the best suggestive haplotype associations in the GERAD1 consortium (2820 AD cases and 6356 controls) and observed that 9 of them showed nominal association. In a third step, we tested relevant haplotype associations in a combined analysis of five additional case-control studies (5093 AD cases and 4061 controls). We consistently replicated the association of a haplotype within FRMD4A on Chr.10p13 in all the data set analyzed (OR: 1.68; 95% CI: (1.43-1.96); P=1.1 × 10(-10)). We finally searched for association between SNPs within the FRMD4A locus and Aß plasma concentrations in three independent non-demented populations (n=2579). We reported that polymorphisms were associated with plasma Aß42/Aß40 ratio (best signal, P=5.4 × 10(-7)). In conclusion, combining both GWHA study and a conservative three-stage replication approach, we characterised FRMD4A as a new genetic risk factor of AD.

Plasma microglial-derived extracellular vesicles are increased in frail patients with Mild Cognitive Impairment and exert a neurotoxic effect.

Extracellular vesicles (EVs) are mediators of cellular communication that can be released by almost all cell types in both physiological and pathological conditions and are present in most biological fluids. Such characteristics make them attractive in the research of biomarkers for age-related pathological conditions. Based on this, the aim of the present study was to examine the changes in EV concentration and size in the context of frailty, a geriatric syndrome associated with a progressive physical and cognitive decline. Specifically, total EVs and neural and microglial-derived EVs (NDVs and MDVs respectively) were investigated in plasma of frail and non-frail controls (CTRL), mild cognitive impairment (MCI) subjects, and in Alzheimer's disease (AD) patients. Results provided evidence that AD patients displayed diminished NDV concentration (3.61 × 109 ± 1.92 × 109 vs 7.16 × 109 ± 4.3 × 109 particles/ml) and showed high diagnostic performance. They are able to discriminate between AD and CTRL with an area under the curve of 0.80, a sensitivity of 78.95% and a specificity of 85.7%, considering the cut-off of 5.27 × 109 particles/ml. Importantly, we also found that MDV concentration was increased in frail MCI patients compared to CTRL (5.89 × 109 ± 3.98 × 109 vs 3.16 × 109 ± 3.04 × 109 particles/ml, P < 0.05) and showed high neurotoxic effect on neurons. MDV concentration discriminate frail MCI vs non-frail CTRL (AUC = 0.76) with a sensitivity of 80% and a specificity of 70%, considering the cut-off of 2.69 × 109 particles/ml. Altogether, these results demonstrated an alteration in NDV and MDV release during cognitive decline, providing important insight into the role of EVs in frailty status.

APOE and Alzheimer disease: a major gene with semi-dominant inheritance.

Apolipoprotein E (APOE) dependent lifetime risks (LTRs) for Alzheimer Disease (AD) are currently not accurately known and odds ratios alone are insufficient to assess these risks. We calculated AD LTR in 7351 cases and 10 132 controls from Caucasian ancestry using Rochester (USA) incidence data. At the age of 85 the LTR of AD without reference to APOE genotype was 11% in males and 14% in females. At the same age, this risk ranged from 51% for APOE44 male carriers to 60% for APOE44 female carriers, and from 23% for APOE34 male carriers to 30% for APOE34 female carriers, consistent with semi-dominant inheritance of a moderately penetrant gene. Using PAQUID (France) incidence data, estimates were globally similar except that at age 85 the LTRs reached 68 and 35% for APOE 44 and APOE 34 female carriers, respectively. These risks are more similar to those of major genes in Mendelian diseases, such as BRCA1 in breast cancer, than those of low-risk common alleles identified by recent GWAS in complex diseases. In addition, stratification of our data by age groups clearly demonstrates that APOE4 is a risk factor not only for late-onset but for early-onset AD as well. Together, these results urge a reappraisal of the impact of APOE in Alzheimer disease.

Pin1 contribution to Alzheimer's disease: transcriptional and epigenetic mechanisms in patients with late-onset Alzheimer's disease.

BACKGROUND: Neurofibrillary tangles and senile plaques are hallmarks of Alzheimer's disease (AD) although the molecular basis of their coexistence remains elusive. The peptidyl-prolyl cis/trans isomerase Pin1 acts on both tau and amyloid precursor protein to regulate their functions by influencing tau phosphorylation and amyloid precursor protein processing. OBJECTIVE: In order to identify potential biomarkers for AD in easily accessible cells and to gain insight into the relationship between the brain and peripheral compartments in AD pathology, we investigated Pin1 expression and activity in the peripheral blood mononuclear cells of subjects with late-onset AD (LOAD) and age-matched controls (CT). METHODS: Gene and protein expression, promoter methylation, Ser(16) phosphorylation and activity of Pin1 were evaluated in 32 samples from subjects with LOAD and in 28 samples from CT. RESULTS: In LOAD subjects, there was a statistically significant reduction in Ser(16) phosphorylation (-30%; p = 0.041) and promoter methylation (-8%; p = 0.001), whereas Pin1 expression was significantly increased (+74%; p = 0.018). CONCLUSION: The modifications of Pin1 found in LOAD subjects support its involvement in the pathogenesis of the disease with an important role being played by epigenetic mechanisms.

Nutritional Interventions for Early Dementia.

Nutrition plays a critical role in the definition of the individual's wellbeing. Nutritional interventions have been repeatedly advocated as of potential interest for preventing or delaying the cognitive decline, also in the context of neurodegenerative conditions. The idea of targeting the initial phases of dementia, when the process is theoretically still amenable of correction, via lifestyle modifications (including healthy diet or supplementation of specific micro-/macro-nutrients) is extremely appealing. In this perspective paper, we describe the most recent evidence on the topic and discuss how the nutritional assessment should be nested within a comprehensive approach to the aging person with initial signs of dementia for promoting his/her optimal management.

The Triggering Receptor Expressed on Myeloid Cells-2 (TREM-2) as Expression of the Relationship between Microglia and Alzheimer's Disease: A Novel Marker for a Promising Pathway to Explore.

Alzheimer's disease (AD) is a common neurodegenerative disorder, strongly related with age. It has been reported that genetic variants of the Triggering Receptor Expressed on Myeloid Cells-2 (TREM2), a cell-surface receptor expressed in microglial cells, greatly increase the risk of AD, thus suggesting an involvement of the microglia in the AD pathogenesis. The aim of this report is to provide an overview of the TREM2 and of its possible implication in the pathogenesis of AD.

Apolipoprotein E gene in physiological and pathological aging.

INTRODUCTION: The genetic background plays a role on longevity. The distribution of the apolipoprotein E gene (APOE) variants (ε2, ε3, ε4) may differ across age groups, especially in the oldest old and despite geographical and ethnic specificities. Since the ε4 variant is associated with Alzheimer's disease (AD), it might represent an opportunity for exploring the relationship of APOE with physiological and pathological aging. AIM: To explore the role played by APOE genotype/alleles on physiological and pathological brain aging. MATERIALS AND METHODS: The study was conducted in a cohort of centenarians (n = 106), and two cohorts of octogenarians (without cognitive decline, n = 351 controls; and with AD, n = 294). RESULTS: No significant differences in genotype/allele distributions were observed comparing controls to centenarians. The prevalence of ε2/ε3, ε3/ε3, ε3/ε4 and ε4/ε4 genotypes were significantly different in centenarians compared to AD. The prevalence of ε2 and ε3 alleles were significantly higher in centenarians, whereas the ε4 was less frequent. The ε4 allele was positively associated with AD, whereas a negative association was found for ε2 and ε3 alleles. CONCLUSIONS: Our study indicates that ε4 allele is strongly associated with AD. APOE significantly affects AD risk, but apparently not longevity.

Age-dependent expression of fibrosis-related genes and collagen deposition in the rat myocardium.

OBJECTIVES: We sought to characterize the evolution, during maturational growth and early ageing, of the messenger abundance of four genes involved in cardiac fibrosis regulation (procollagens alpha2(I) and alpha1(III), transforming growth factors beta1, and beta3) and corroborate it with the alterations in collagen deposition in cardiac interstitium and around coronary arteries. METHODS: Messenger RNA was quantified in LV and RV of 2-, 6-, 12- and 19-month-old male Sprague-Dawley rats (n = 5 per group) with Northern blot analysis. Collagen deposition was quantified with a semi-automated image analyser on Sirius red-stained sections of LV tissue. RESULTS: There was an age-related monotonous decrease of procollagen type I (COL-I) transcript abundance in LV (p < 0.001) but not in RV. Procollagen type III (COL-III) expression decreased rapidly during maturational growth, both in LV and RV. On the other hand, collagen deposition in myocardial interstitium and around coronary arteries was slightly augmented during the maturational period of life (2-12 months), but with a higher rate during early ageing (up to 19 months). This was not accompanied by a significant thickening of the wall of coronary arteries. Transforming growth factor beta1, (TGF-beta1) and transforming growth factor beta3 (TGF-beta3) transcript abundance showed no major variations during ageing. CONCLUSIONS: These results reflect a striking ventricular difference regarding the age-dependent expression of COL-I. The expression of TGF-beta(s), pleiotropic factors known to influence collagen pathway at different levels, does not seem to be profoundly altered during ageing. The discrepancy between protein and COL-I and COL-III mRNA levels indicates differences in age-related mRNA stability and/or regulation of collagen translation.

Left ventricular response to beta-adrenergic stimulation in aging rats.

The incidence of heart failure in the population increases steeply among older people. Overactivation of the sympathetic nervous system is associated to and responsible for worsening of heart failure. This study describes the influence of aging on short-term left ventricular (LV) adaptation to b-adrenergic stimulation in Wistar rats. In controls at 18 mo, interstitial fibrosis was increased with respect to 3-mo-old rats, whereas myocytes dimension and the messenger RNA (mRNA) abundance of atrial natriuretic peptide (ANP), a2(I) procollagen, transforming growth factor (TGF-b1, TGF-b3), and secreted protein, acidic and rich in cysteine (SPARC) were not different. To determine how aging affects LV adaptation to adrenergic stimulation, two groups of animals received isoproterenol (ISO, 1 mg/kg/d) for 3 days. There was no significant difference between young and older rats with respect to increase in LV weight, myocytes dimension, and mRNA abundance of all the genes considered, except a1(III) procollagen. These findings indicate that despite limited compensatory hypertrophy and higher fibrosis, LV from aged nonsenescent rats preserves the capacity to adapt to b-adrenergic stimulation through the upregulation of several genes encoding extracellular matrix-related proteins.

Age-dependent expression of fibrosis-related genes and collagen deposition in rat kidney cortex.

Because progressive fibrosis is a histological hallmark of the aging kidney, we sought to characterize the course of some fibrosis-related genes [pro-alpha2(I)collagen (COL-I), pro-alpha1(III)collagen (COL-III), and transforming growth factors beta1 and beta3 (TGF-beta1 and TGF-beta3)] of interstitial collagen accumulation [COL-I and COL-III proteins, hydroxyproline (PRO-OH), histology] and its degradation (matrix metalloproteinase MMP-1 and -2) during maturation and early aging in rats. During the lifespan considered we observed no changes in the mRNA, except that COL-I mRNA tended to be up-regulated from 2 to 19 months of age. However, progressive fibrosis was histologically detectable, with COL-I accumulation (p < .05 and p < .01 in 12-month- and 19-month-old rats vs the youngest), and confirmed by the PRO-OH tissue levels (p = .0001); COL-III seemed to be less involved. The MMP-1 protein level decreased significantly in the cortex of 12-month- and 19-month-old rats (p < .05), whereas MMP-2 protein level and activity remained essentially unchanged. These results show that, during aging of the kidney, (i) renal cortex fibrosis is explained by COL-I accumulation as a consequence of an altered balance between its synthesis and degradation, and (ii) the expression of the pleiotropic factor TGF-beta in the renal cortex is not modified.

Fibroblasts from Alzheimer's disease donors do not differ from controls in response to heat shock.

We investigated HSPs mRNA expression in cultured fibroblasts from control and AD patients. Northern blot analysis using probes for HSP70 and HSC73 revealed that HS induced a several fold increase in both mRNA. Under these condition the extent of mRNA increase was similar in controls and AD. HS elicited also a modest increase in sAPP release that was similar in control and AD. The results suggest that the ability of AD fibroblasts to produce a defensive response to HS is preserved.

-308(G/A) TNF-alpha gene polymorphism and risk of depression late in the life.

The relationship between major depression (MD) and dementia in the elderly is still not clear, but it is certain that the immune system and in particular, pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, play a key role in the mechanisms underlying the two neuro-psychiatric disorders. In our experience, the -308(G/A) single nucleotide polymorphism (SNP) in the TNF-alpha gene is associated with earlier age at onset in patients affected by Alzheimer's disease (AD). The aim of this study was to investigate the association between the -308(G/A) SNP and late-life MD in elderly people without dementia. Blood samples were obtained from 50 subjects, after screening with the geriatric depression scale (GDS>or=15) and mini-mental state examination (MMSE>or=24). The -308 (G/A) SNP was genotyped by SSP-PCR amplification. Two-hundred-fourty age-matched healthy volunteers were taken as the control group. We identified different genotype and allele distributions of the SNP in old depressed patients and healthy controls (HC). Our results evidenced a significantly higher percentage of the GG genotype in depressed subjects (84.0% vs. 68.3%; p=0.007) and consequently of the G allele (92.0% vs. 81.9%; p=0.05). The presence of the GG genotype raised the risk of developing MD (odds ratio=OR=2.433, confidence interval=Cl=1.09-5.43). Our findings suggested that the investigated TNF-alpha SNP may: (1) affect MD susceptibility; (2) be involved both in AD and MD development, but probably with a distinct role in the two pathologies.

PIN1 promoter polymorphisms are associated with Alzheimer's disease.

In our study, we analyzed the coding and promoter regions of the PIN1 gene in a group of 111 Alzheimer's disease (AD) patients looking for a possible genotype-phenotype correlation. The presence of SNPs - which could affect and modify the clinical phenotype of AD patients was also investigated. We identified two single nucleotide polymorphisms (SNPs) at positions -842 (G-->C) and -667 (C-->T) in the promoter region of the PIN1 gene. Our results evidenced a significantly higher percentage of -842C allele carriers in AD subjects with respect to healthy controls. We found that this allele significantly raised the risk of developing AD (OR 3.044, CI 1.42-6.52). The -842 and -667 SNPs were in linkage disequilibrium and combined to form haplotypes. The CC haplotype conferred a higher risk of developing AD (OR 2.95, confidence interval 1.31-6.82). Finally, protein expression analyses revealed that subjects carrying the -842 CC genotype or the CC haplotype showed reduced levels of the PIN1 protein in peripheral mononuclear cells.

Changes in expression of the albumin, fibronectin and type I procollagen genes in CCl4-induced liver fibrosis: effect of pyridoxol L,2-pyrrolidon-5 carboxylate.

The protective activity of pyridoxol L,2-pyrrolidon-5 carboxylate (metadoxine) was investigated in a rat model of carbon tetrachloride (CCL4)-induced hepatic fibrosis. After 6 weeks of CCl4 treatment, the animals developed fibrosis and inflammation of the liver while those treated with CCl4 + metadoxine had less severe lesions (P < 0.05). Since in liver fibroplasia there are quantitative changes of the extracellular matrix components and almost invariably a decrease in albumin synthesis, we have also investigated by Northern blot analysis the expression of the cellular fibronectin, pro-alpha 2(I)collagen and albumin genes. There were striking increases in fibronectin and pro-alpha 2(I)collagen mRNA contents in the livers of CCL4-treated animals and these enhancements were less evident in the metadoxine-treated rats. In contrast, albumin mRNA levels, almost identical in control and metadoxine-treated rats, were lower in the CCl4-treated animals. These data suggest that metadoxine might slow the development of CCl4-mediated liver fibrosis.

Glutathione pretreatment lessens the acute liver injury induced by carbon tetrachloride.

We explored the protective activity of glutathione (GSH) in a rat model of carbon tetrachloride-induced acute liver damage. Histological examination of livers from GSH-pretreated rats revealed minor damage, confirmed by biochemical parameters of liver cell necrosis evaluated both 24 and 48 hr after hepatotoxin delivery. In addition we quantified changes in hepatic steady-state levels of albumin, type I procollagen, transforming growth factor-beta 1 and tumour necrosis factor-alpha mRNAs. Even at the molecular level and above all for the albumin gene, it appears that GSH lessens the effect of the hepatotoxin, however the protection of the thiol is restricted to the first 24 hrs and is almost totally exhausted after 48 hr. Since, only 24 hr after CC14 delivery, GSH abundance determined in erythrocytes and liver is almost equal in the controls and in the GSH injected rats, but significantly higher than in the only intoxicated animals (P < 0.05, intraerythrocyte content), we conclude that the thiol pretreatment exerts an effective but transient protection.

Albumin and procollagen type I gene regulation in alcohol and viral-induced human liver disease.

Common features of chronic alcoholic liver disease are progressive hypoalbuminemia and liver fibrosis. The molecular mechanisms which account for these effects are still controversial. Therefore, in the present study we evaluated albumin and collagen gene expression in livers of alcohol abusers and patients with viral-induced liver disease. Albumin and pro-alpha 1 (I) collagen mRNA levels were determined in 30 patients who underwent diagnostic liver biopsy. Of 14 alcoholics, 7 had alcoholic hepatitis alone, while the other 7 had cirrhosis plus alcoholic hepatitis. Of 16 non-alcoholic patients with chronic viral infection, 6 had chronic active hepatitis and 10 cirrhosis plus chronic active hepatitis. Total RNA was extracted from a portion of each biopsy, hybridized with a human albumin or collagen cDNA clone and compared to 2 normal surgical specimens which served as controls. The Northern hybridization studies revealed that: despite the presence of inflammation and fibrosis, the albumin mRNA levels of alcoholics were similar to normal controls; these alcoholics had significantly higher levels of albumin mRNA than did patients with similar histological stages of disease due to viral infection; and all the categories of patients had markedly increased procollagen mRNA levels when compared to controls. Given these results it is tempting to speculate that alcohol may actually increase albumin mRNA content in man as it does in animals. Furthermore, the increased procollagen mRNA levels in fibrotic livers suggest that an increase in collagen synthesis may be a significant factor in the pathogenesis of hepatic fibrosis.