Astrocytic-derived vascular remodeling factors are independently associated with blood brain barrier permeability in Alzheimer's disease.

Astrocytes in Alzheimer's disease (AD) exert a pivotal role in the maintenance of blood-brain barrier (BBB) integrity essentially through structural support and release of soluble factors. This study provides new insights into the vascular remodeling processes occurring in AD, and reveals, in vivo, a pathological profile of astrocytic secretion involving Vascular Endothelial Growth Factor (VEGF), Matrix Metalloproteinases (MMP)-9, MMP-2 and Endothelin-1 (ET-1). Cerebrospinal fluid (CSF) levels of VEGF, MMP-2/-9 were lower in patients belonging to the AD continuum, compared to aged-matched controls. CSF levels of VEGF and ET-1 positively correlated with MMP-9 but negatively with MMP-2, suggesting a complex vascular remodeling process occurring in AD. Only MMP-2 levels were significantly associated with CSF AD biomarkers. Conversely, higher MMP-2 (ß = 0.411, p < 0.001), ET-1 levels (ß = 0.344, p < 0.001) and VEGF (ß = 0.221, p = 0.022), were associated with higher BBB permeability. Astrocytic-derived vascular remodeling factors are altered in AD, disclosing the failure of important protective mechanisms which proceed independently alongside AD pathology.

Constitutive NOS Production Is Modulated by Alzheimer's Disease Pathology Depending on APOE Genotype.

Both the endothelial (eNOS) and the neuronal (nNOS) isoforms of constitutive Nitric Oxide Synthase have been implicated in vascular dysfunctions in Alzheimer's disease (AD). We aimed to explore the relationship between amyloid pathology and NO dynamics by comparing the cerebrospinal fluid (CSF) levels of nNOS and eNOS of 8 healthy controls (HC) and 27 patients with a clinical diagnosis of Alzheimer's disease and isolated CSF amyloid changes, stratified according to APOE ε genotype (APOE ε3 = 13, APOE ε4 = 14). Moreover, we explored the associations between NOS isoforms, CSF AD biomarkers, age, sex, cognitive decline, and blood-brain barrier permeability. In our cohort, both eNOS and nNOS levels were increased in APOE ε3 with respect to HC and APOE ε4. CSF eNOS inversely correlated with CSF Amyloid-ß42 selectively in carriers of APOE ε3; CSF nNOS was negatively associated with age and CSF p-tau only in the APOE ε4 subgroup. Increased eNOS could represent compensative vasodilation to face progressive Aß-induced vasoconstriction in APOE ε3, while nNOS could represent the activation of NO-mediated plasticity strategies in the same group. Our results confirm previous findings that the APOE genotype is linked with different vascular responses to AD pathology.

Blood-brain barrier permeability is associated with different neuroinflammatory profiles in Alzheimer's disease.

INTRODUCTION: Inflammation is an important player in Alzheimer's disease (AD), whose effects can be influenced by the blood-brain barrier (BBB). Here, we investigated the relationship between BBB permeability, indicated by cerebrospinal fluid (CSF)/plasma albumin quotient (Qalb), and CSF indexes of neuroinflammation in a cohort of biologically defined AD patients. METHODS: Fifty-nine consecutive patients with mild cognitive impairment (MCI) or early AD (Mini-Mental State Examination [MMSE] >22) underwent CSF analysis for inflammatory cytokines (interleukin [IL]-1ß, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, Il-10, IL-12, IL-13, IL-17, tumor necrosis factor-α [TNF-α], interferon-γ [IFN-γ], granulocyte-monocyte colony-stimulating factor [GM-CSF], granulocyte colony-stimulating factor [G-CSF]). Using backward stepwise linear regression analysis, we explored the potential influence of each cytokine CSF level on Qalb considering age, sex, and apolipoprotein E (APOE) as covariates. RESULTS: Higher levels of IL-4 (ß = 0.356, 0.005) and IL-8 (ß = 0.249, 0.05) were associated with higher Qalb values, while macrophage inflammatory protein-1α (MIP-1ß) (ß = -0.274; p = 0.032) and TNF-α (ß = -0.248; p = 0.031) showed a significant negative association with BBB permeability. Age was also positively associated with Qalb (ß = 0.283; p = 0.016). CONCLUSIONS: Despite the overall integrity of the BBB, its permeability could either influence or be influenced by central neuroinflammation, reflected by CSF cytokine levels. This is in line with previous studies that showed that patients with a more intact barrier are those with more prominent neurodegeneration. Our findings suggest that different neuroinflammatory profiles can be associated with different levels of BBB permeability in AD.

Different associations between amyloid-ßeta 42, amyloid-ßeta 40, and amyloid-ßeta 42/40 with soluble phosphorylated-tau and disease burden in Alzheimer's disease: a cerebrospinal fluid and fluorodeoxyglucose-positron emission tomography study.

BACKGROUND: Despite the high sensitivity of cerebrospinal fluid (CSF) amyloid beta (Aß)42 to detect amyloid pathology, the Aß42/Aß40 ratio (amyR) better estimates amyloid load, with higher specificity for Alzheimer's disease (AD). However, whether Aß42 and amyR have different meanings and whether Aß40 represents more than an Aß42-corrective factor remain to be clarified. Our study aimed to compare the ability of Aß42 and amyR to detect AD pathology in terms of p-tau/Aß42 ratio and brain glucose metabolic patterns using fluorodeoxyglucose-positron emission tomography (FDG-PET). METHODS: CSF biomarkers were analyzed with EUROIMMUN ELISA. We included 163 patients showing pathological CSF Aß42 and normal p-tau (A + T - = 98) or pathological p-tau levels (A + T + = 65) and 36 control subjects (A - T -). A + T - patients were further stratified into those with normal (CSFAß42 + /amyR - = 46) and pathological amyR (CSFAß42 + /amyR + = 52). We used two distinct cut-offs to determine pathological values of p-tau/Aß42: (1) ≥ 0.086 and (2) ≥ 0.122. FDG-PET patterns were evaluated in a subsample of patients (n = 46) and compared to 24 controls. RESULTS: CSF Aß40 levels were the lowest in A - T - and in CSFAß42 + /amyR - , higher in CSFAß42 + /amyR + and highest in A + T + (F = 50.75; p < 0.001), resembling CSF levels of p-tau (F = 192; p < 0.001). We found a positive association between Aß40 and p-tau in A - T - (ß = 0.58; p < 0.001), CSFAß42 + /amyR - (ß = 0.47; p < 0.001), and CSFAß42 + /amyR + patients (ß = 0.48; p < 0.001) but not in A + T + . Investigating biomarker changes as a function of amyR, we observed a weak variation in CSF p-tau (+ 2 z-scores) and Aß40 (+ 0.8 z-scores) in the normal amyR range, becoming steeper over the pathological threshold of amyR (p-tau: + 5 z-scores, Aß40: + 4.5 z-score). CSFAß42 + /amyR + patients showed a significantly higher probability of having pathological p-tau/Aß42 than CSFAß42 + /amyR - (cut-off ≥ 0.086: OR 23.3; cut-off ≥ 0.122: OR 8.8), which however still showed pathological values of p-tau/Aß42 in some cases (cut-off ≥ 0.086: 35.7%; cut-off ≥ 0.122: 17.3%) unlike A - T - . Accordingly, we found reduced FDG metabolism in the temporoparietal regions of CSFAß42 + /amyR - compared to controls, and further reduction in frontal areas in CSFAß42 + /amyR + , like in A + T + . CONCLUSIONS: Pathological p-tau/Aß42 and FDG hypometabolism typical of AD can be found in patients with decreased CSF Aß42 levels alone. AmyR positivity, associated with higher Aß40 levels, is accompanied by higher CSF p-tau and widespread FDG hypometabolism.

Cerebrospinal Fluid sTREM-2, GFAP, and ß-S100 in Symptomatic Sporadic Alzheimer's Disease: Microglial, Astrocytic, and APOE Contributions Along the Alzheimer's Disease Continuum.

BACKGROUND: Many transversal mechanisms act synergistically at different time-points in the cascade of Alzheimer's disease (AD), since amyloid-ß (Aß) deposition, tau pathology, and neuroinflammation influence each other. OBJECTIVE: We explored the contributions of microglia and astrocytes in patients with symptomatic sporadic AD stratified according to AT(N) system and APOE genotype. METHODS: We compared the cerebrospinal fluid (CSF) levels of sTREM-2 and markers of astrocytic activation (GFAP; ß-S100) from 71 patients with AD (23 A+T-,48 A+T+; 38 APOEɛ3, 33 APOEɛ4) and 30 healthy controls (HC). With multivariate analyses we investigated associations between glial biomarkers, Aß42, and p-tau in all subgroups. RESULTS: CSF sTREM-2 was higher in A+T+ [1.437 (0.264)] and A+T- [1.355 (0.213)] than in HC [1.042 (0.198); both p < 0.001]; GFAP and ß-S100 were comparable across groups. Considering all patients, sTREM-2 positively associated with Aß42 (p = 0.04) and p-tau (=0.016), with the first being present only in the A+T- subgroup (p = 0.023). GFAP positively associated with Aß42 in all patients (p = 0.020) and in the A+T+ subgroup (p = 0.04). Stratifying by APOE, a positive association of sTREM-2 and p-tau was confirmed selectively in carriers of ɛ4 (p = 0.018). Finally, sTREM-2 positively correlated with ß-S100 in all subgroups, and with GFAP in A+T+ (p = 0.042). CONCLUSION: Our results confirm the increase of CSF sTREM-2 in AD, which associates with reduced amyloidopathy in A+T- patients. Moreover, microglial activation seems to increase CSF tau levels in carriers of APOEɛ4, is associated with astrocytic reactivity (GFAP) in A+T+, and likely leads the acquisition of a more neurotoxic astrocytic phenotype (ß-S100).

Functional Correlates of Microglial and Astrocytic Activity in Symptomatic Sporadic Alzheimer's Disease: A CSF/18F-FDG-PET Study.

Glial and microglial cells contribute to brain glucose consumption and could actively participate in shaping patterns of brain hypometabolism. Here, we aimed to investigate the association between 18F-fluorodeoxyglucose (18F-FDG) uptake and markers of microglial and astrocytic activity in a cohort of patients with Alzheimer's Disease (AD). We dosed cerebrospinal fluid (CSF) levels of soluble Triggering Receptor Expressed on Myeloid cells (sTREM2), Glial Fibrillary Acidic Protein (GFAP), a marker of reactive astrogliosis, and ß-S100, a calcium-binding protein associated with a neurotoxic astrocytic profile. No associations were found between sTREM-2 and 18F-FDG uptake. Instead, 18F-FDG uptake was associated negatively with CSF ß-S100 in the left supramarginal gyrus, inferior parietal lobe and middle temporal gyrus (Brodmann Areas (BA) 21 and 40). Increased ß-S100 levels could negatively regulate neuronal activity in the temporo-parietal cortex to prevent damage associated with AD hyperactivity, or rather they could reflect neurotoxic astrocytic activation contributing to AD progression in key strategic areas. We also identified a trend of positive association of 18F-FDG uptake with CSF GFAP in the right fronto-medial and precentral gyri (BA 6, 9 and 11), which has been reported in early AD and could either be persisting as an epiphenomenon tied to disease progression or be specifically aimed at preserving functions in the frontal cortex. Overall, CSF markers of astrogliosis seem to correlate with cortical glucose uptake in symptomatic sporadic AD, highlighting the role of astrocytes in shaping regional hypometabolism and possibly clinical presentation.

Functional Correlates of Striatal Dopamine Transporter Cerebrospinal Fluid Levels in Alzheimer's Disease: A Preliminary 18F-FDG PET/CT Study.

The aim of our study was to investigate regional glucose metabolism with 18F-FDG positron emission tomography/computed tomography in a population of patients with Alzheimer's disease (AD) in relation to cerebrospinal (CSF) levels of striatal dopamine transporter (DAT). All patients underwent lumbar puncture and received a biomarker-based diagnosis of AD. Differences in regional brain glucose metabolism were assessed by Statistical Parametric Mapping version 12 with the use of age, gender, and MMSE as covariates in the analysis. A positive correlation between CSF DAT levels and glucose metabolism at the level of two brain areas involved in the pathophysiological process of Alzheimer's disease, the substantia nigra and the posterior cingulate gyrus, has been highlighted. Results indicate that patients with higher CSF DAT levels have a better metabolic pattern in two key zones, suggesting less advanced disease status in patients with more conserved dopaminergic systems.

Interplay between the catecholaminergic enzymatic axis and neurodegeneration/neuroinflammation processes in the Alzheimer's disease continuum.

BACKGROUND AND PURPOSE: The locus coeruleus (LC) provides dopamine/noradrenaline (DA/NA) innervation throughout the brain and undergoes early degeneration in Alzheimer's disease (AD). We evaluated catecholaminergic enzyme levels in the cerebrospinal fluid (CSF) of a group of patients biologically defined as within the AD continuum (ADc) and explored their relationship with AD biomarkers and cytokine/growth factor levels to investigate their interplay with neurodegenerative and neuroinflammatory processes. METHODS: The CSF concentration of DA transporter (DAT), tyrosine-hydroxylase (TH), DOPA-decarboxylase (DDC), and dopamine-ß-hydroxylase (DßH), as well as cytokine/growth factor levels, were analyzed in 41 ADc patients stratified according to CSF beta-amyloid (Aß)1-42 (A) and p-tau (T) in AD pathological changes (A+ T-) and AD (A+ T+) subgroups, as well as in 15 control subjects (A- T-). RESULTS: The ADc group had lower CSF levels of DAT and TH but increased DßH levels to compensate for NA synthesis. DDC levels were higher in the A+ T+ subgroup but comparable with controls in the A+ T- subgroup, probably because the DA system is resilient to the degeneration of LC neurons in the absence of tau pathology. Adjusting for age, sex, APOE genotype, and cognitive status, a significant association was found between TH and Aß1-42 (R2  = 0.25) and between DDC and p-tau (R2  = 0.33). Finally, TH correlated with interleukin (IL)-10 levels (p = 0.0008) and DßH with IL-1ß (p = 0.03), IL-4 (p = 0.02), granulocyte colony-stimulating factor (p = 0.007), and IL-17 (p = 0.01). CONCLUSIONS: Taken together, these findings suggest that catecholaminergic enzymes, functional markers of the catecholaminergic system, are closely linked to the neurodegenerative and neuroinflammatory processes in AD pathology.

Periodic sharp wave complexes identify a distinctive phenotype in Creutzfeldt-Jacob disease.

OBJECTIVE: The aim of our study was to evaluate the diagnostic and prognostic value of Electroencephalogram (EEG), brain Magnetic Resonance Imaging (MRI) and cerebrospinal fluid features, currently representing Creutzfeldt-Jacob Disease (CJD) diagnostic criteria. METHODS: A retrospective study on rapidly progressive dementia patients admitted at the Neurology Clinic of the University of Rome "Tor Vergata" between 2015 and 2020 was conducted. We evaluated clinical, EEG, cerebrospinal fluid and neuroradiological findings. RESULTS: Our analysis included 13 patients with probable CJD and 18 patients with non-CJD rapidly progressive dementia. Periodic sharp wave complexes were observed in 7/13 CJD and in 4/18 non-CJD patients (p =.151). The sub-analysis according to the EEG features revealed that CJD patients with earlier periodic sharp wave complexes had a significantly lower average survival time (p =.003), a shorter time to admission (p =.003) and lower levels of cerebrospinal fluid p-tau (p =.008) compared to CJD patients without periodic sharp wave complexes. Finally, they did not show signs of signal alteration on Fluid Attenuated Inversion Recovery images. CONCLUSIONS: Despite the lowest diagnostic specificity and sensibility among the CJD criteria, periodic sharp wave complexes could identify a distinctive phenotype hallmarked by a faster evolution, a reduced survival time and specific MRI and cerebrospinal fluid features. SIGNIFICANCE: The early presence of the typical EEG pattern may play a prognostic role in CJD.

Diabetes mellitus contributes to higher cerebrospinal fluid tau levels selectively in Alzheimer's disease patients with the APOE4 genotype.

BACKGROUND AND PURPOSE: Diabetes mellitus (DM) is considered a risk factor for Alzheimer's disease (AD) and shares some pathological pathways, such as activation of amyloid cascade and tau phosphorylation. The aim of the present study was to investigate to what extent DM could impact on neurodegeneration within the AD continuum, using ß amyloid (A: Aß1-42 ) and phosphorylated tau (T: p-tau) biomarkers to discriminate patients by Alzheimer's pathological change (A+/T-) and AD (A+/T+), according to the National Institute on Aging and Alzheimer's Association classification. In addition, we aimed to evaluate whether APOE genotype interacts with tau protein and glucose metabolism dysfunction to affect the pathological process. METHODS: For this retrospective observational study, 1350 patients were recruited. The patients underwent a complete clinical investigation, neuropsychological assessment, lumbar puncture for cerebrospinal fluid (CSF) biomarkers analysis and APOE genotyping. RESULTS: A total of 607 patients fulfilled the clinical criteria of mild cognitive impairment or early dementia. In A+T- patients (n = 350), DM did not influence CSF biomarker levels, while among A+T+ patients (n = 257) those with DM showed increased total tau (t-tau) levels compared to non-DM patients (DM: 919.4 ± 444 vs. non-DM: 773.1 ± 348.2; p = 0.04), but similar p-tau (p = 0.72) and Aß1-42  levels (p = 0.83). Furthermore, multivariable regression analyses showed a significant association between DM and t-tau CSF levels, adjusting for age and sex, in APOE E4+ carriers (coefficient 222.83, 95% confidence interval 47.49-398.1; p = 0.01), but not in APOE E4- (p = 0.53). CONCLUSIONS: The present study shows a clear dependency of CSF t-tau levels on DM for APOE E4+ AD patients, suggesting important differences between APOE E4-related and non-related disease, with key implications for AD pathophysiology and treatment.

Brain energy metabolism and neurodegeneration: hints from CSF lactate levels in dementias.

Mitochondrial dysfunction is pivotal in the development of neurodegenerative dementias, causing cellular death alongside disease-specific pathogenic cascades. Holding cerebrospinal fluid (CSF) lactates as an indirect measure of brain metabolic activity, we first compared CSF lactate levels from patients with Alzheimer's disease (AD)-stratified according to the ATN system and epsilon genotype-frontotemporal dementia (FTD) and dementia with Lewy body (DLB) to findings from healthy controls. With respect to controls, we detected lower CSF lactates in patients with AD and FTD but comparable levels in patients with DLB. Second, a correlation analysis between CSF lactates and biomarkers of neurodegeneration identified an inverse correlation between lactates and levels of t-tau and p-tau only in the Alzheimer's continuum. The reduction of CSF lactate correlates to the advent of tauopathy and cellular death in AD, implying that Aß pathology alone is not sufficient to induce neuronal metabolic impairment. The metabolic impairment in FTD patients has a similar explanation, as it is likely due to fast neuronal degeneration in the disease. The absence of CSF lactate reduction in patients with DLB may be related to the prevalent subcortical localization of the pathology.

Haemodynamic impairment along the Alzheimer's disease continuum.

BACKGROUND AND PURPOSE: Alzheimer's disease (AD) is considered a clinical and biological continuum identified via cerebrospinal fluid (CSF) or imaging biomarkers. Chronic hypoperfusion is held as one of the main features of Alzheimer's disease, as part of the processes causing neuronal degeneration. The mechanism responsible for such condition is still debated, although recently a direct connection with amyloid peptides has been shown. Here the aim was to investigate whether measures of hypoperfusion change along the AD continuum. METHODS: Seventy patients with mild AD were recruited and stratified according to their CSF biomarker profile-as indicated by the National Institute on Aging and Alzheimer's Association research framework-into patients with either isolated amyloid pathology (A+T-) or full-blown AD (A+T+), and further layered according to apolipoprotein E genotype. After evaluation of vascular risk factors, a transcranial Doppler was performed on each patient, to evaluate mean flow velocity and pulsatility index in the middle cerebral artery, and to calculate the breath-holding index. Patients were compared to a cohort of 17 healthy controls. RESULTS: The breath-holding index was reduced in the AD continuum and was inversely correlated to CSF amyloid ß42 levels. Such correlation was stronger in the A+T+ than in the A+T- group, and unexpectedly reached statistical significance only in the E3 and not in the E4 genotype carriers. CONCLUSIONS: These results suggest a tight and effective relationship between amyloid ß42, vascular hypoperfusion, cerebrovascular reactivity and epsilon genotype.

Beyond the motor account of amyotrophic lateral sclerosis: Verbal humour and its relationship with the cognitive and pragmatic profile.

BACKGROUND: Amyotrophic Lateral Sclerosis (ALS) was traditionally described as a disease restricted to the motor system. However, recent findings suggested that it also affects cognition, especially executive functions, social cognition, language and pragmatics. A relevant issue in current research is thus the description of the cognitive phenotype of ALS and the identification of the most vulnerable aspects. AIMS: The focus was on a communicative phenomenon placed at the crossroads of pragmatic and other cognitive domains, namely humour, which till now has been poorly explored in ALS. The first aim was to investigate whether ALS is associated with impairments in understanding and appreciating jokes. The second aim was to explore the predictors of humour comprehension and appreciation in patients, to confirm the involvement of pragmatic skills and to explore the role of other cognitive and clinical aspects. METHODS & PROCEDURES: A total of 30 non-demented patients with ALS and 27 controls were assessed with a task of verbal humour comprehension and appreciation, including two types of jokes: phonological and mental. We also administered a battery of pragmatic and other language tasks, and cognitive and socio-cognitive tasks. Mixed-effects models were used to test differences in the humour task between the two groups. Multiple regressions determined the best predictors of humour comprehension and appreciation in patients. OUTCOMES & RESULTS: Patients obtained lower comprehension accuracy scores than controls in the humour task, independently of the type of joke. Conversely, patients and controls did not differ in joke appreciation and both rated mental jokes as funnier than the phonological ones. Patients' comprehension accuracy was predicted by pragmatic skills and ALS severity, whereas appreciation was predicted by several clinical variables and, to a smaller extent, by language skills. CONCLUSIONS & IMPLICATIONS: The findings suggest that humour is a very vulnerable aspect in ALS, and that impairment in humour comprehension might be part of the larger cognitive impairment, being linked to pragmatic impairment. Clinical variables were also important, especially in relation to humour appreciation. More generally, these data speak in favour of pragmatics as a relevant aspect to sketch the cognitive phenotype of ALS. On the practical level, these findings point to the need of supporting communication at large, not only motor-related aspects such as dysarthria but also social-pragmatic aspects such as understanding jokes, to increase well-being in ALS. What this paper adds What is already known on this subject The literature of the last decades has shown that ALS comes with impairment in several cognitive domains, affecting especially executive functions as well as language. There is also initial evidence that the pragmatics of communication and humour comprehension are impaired, although non-serious talk has been documented in conversational interaction among people with ALS. What this paper adds to existing knowledge This study offers compelling evidence of an impairment in the comprehension of jokes in ALS, whereas the appreciation of joke funniness seems to be spared. The study also highlights the interplay of cognitive factors (especially pragmatics) and clinical factors (related to disease severity) in predicting the patients' performance in the humour task. What are the potential or actual clinical implications of this work? The study's findings call for the need of increased awareness among scholars as well as practitioners and caregivers of the profile of humour comprehension and appreciation in ALS. On a practical level, we highlight the need of assessing humour comprehension and adapting the communicative style accordingly. Second, we recommend that intervention programmes targeting communication in ALS go beyond speech-related difficulties and include pragmatic aspects such as humour. Considering the important communicative and social function of humour, as well as its use as a coping strategy, humour interventions are key to improve the quality of life of individuals with ALS.