Martens, Yuka A.

The immune system substantially influences age-related cognitive decline and Alzheimer’s disease (AD) progression, affected by genetic and environmental factors. In a Mayo Clinic Study of Aging cohort, we examined how risk factors like APOE genotype, age, and sex affect inflammatory molecules and AD biomarkers in cerebrospinal fluid (CSF). Among cognitively unimpaired individuals over 65 ( N = 298), we measured 365 CSF inflammatory molecules, finding age, sex, and diabetes status predominantly influencing their levels. We observed age-related correlations with AD biomarkers such as total tau, phosphorylated tau-181, neurofilament light chain (NfL), and YKL40. APOE4 was associated with lower Aβ42 and higher SNAP25 in CSF. We explored baseline variables predicting cognitive decline risk, finding age, CSF Aβ42, NfL, and REG4 to be independently correlated. Subjects with older age, lower Aβ42, higher NfL, and higher REG4 at baseline had increased cognitive impairment risk during follow-up. This suggests that assessing CSF inflammatory molecules and AD biomarkers could predict cognitive impairment risk in the elderly.

AbstractBackgroundThe accumulation of the amyloid‐β (Aβ) aggregates in the brain is a key pathological event in the development of Alzheimer’s disease (AD). The α‐secretase ADAM10 is responsible for cleavage of the amyloid precursor protein (APP) through a non‐amyloidogenic pathway, thereby preventing the generation of pathogenic Aβ in the brain. Secreted frizzled related protein‐1 (sFRP1), an endogenous antagonist of Wnt signaling, has recently been identified as a key negative modulator of ADAM10. Importantly, proteomic studies reveal that unregulated sFRP1 is one of the top Aβ‐correlated proteins in the human AD brains.MethodsWe determined the therapeutic potential of specific sFRP1 WAY316606 in the N2a/APP695swe cells and patient‐specific iPSC‐derived cerebral organoids.ResultsWe herein demonstrated that treatment of sFRP1 inhibitor WAY316606 resulted in augmentation of ADAM10 activity, upregulation of soluble APP‐α (sAPPα) production, and inhibition of Aβ generation in the N2a/APP695swe cells. Moreover, WAY316606 significantly enhanced ADAM10 activity, decreased Aβ production and inhibited tau phosphorylation in human AD patient‐specific iPSC‐derived cerebral organoids.ConclusionOur findings indicate that sFRP1 is a promising therapeutic target for AD.

AbstractBackgroundFor blood‐based biomarkers to fulfill their potential to revolutionize diagnosis and management of Alzheimer’s disease (AD), additional research in diverse populations remains critical. Here, we analyzed a biracial sample to assess the profiles of blood‐based AD biomarkers and their relationships to cognition and medical comorbidities.MethodsSelf‐reported African‐American (AA; n = 267) and non‐Hispanic White (NHW; n = 268) participants evaluated through the Mayo Jacksonville Alzheimer’s Disease Research Center were matched on age, sex, and clinical diagnosis. Plasma AD biomarkers (Aβ42/40, p‐tau181, GFAP, NfL) were measured using the Quanterix SiMoA HD‐X analyzer. Cognition was assessed with the Mini Mental State Examination. Wilcoxon rank sum tests were used to assess for differences in plasma biomarker levels by sex. Linear models tested for associations of race, chronic kidney disease (CKD), and vascular risk factors with plasma AD biomarker levels, covarying for age and sex. Additional models assessed for interactions between race and plasma biomarkers in predicting cognition, further covarying for education.ResultsThe sample included adults aged 43‐100 years, with 69% women. Education was higher in NHW participants (median 16 vs. 12 years, p<0.001). APOE (apolipoprotein E) ε4 positivity was higher in AA participants (43% vs. 34%; p = 0.04). There were no differences in plasma AD biomarker levels between AA and NHW participants. These findings were unchanged after stratifying by cognitive status (unimpaired versus impaired). Although the association between p‐tau181 and cognition appeared stronger in NHW participants while the association between Aβ42/40 and cognition appeared stronger in AA participants, these findings did not survive after excluding individuals with CKD. Women displayed higher GFAP (p = 0.002) and lower p‐tau181 (p = 0.001) levels than men. Diabetes was inversely associated with GFAP levels (p<0.001).ConclusionsIn a biracial, community‐based sample, we observed that sex differences, CKD, and vascular risk factors contributed to variation in plasma AD biomarkers, while self‐reported race did not. Our results reinforce the critical need to account for sex and systemic medical comorbidities in equitably deploying blood‐based AD biomarkers in the general population.

AbstractBackgroundThe causes of rapidly progressive dementia are heterogeneous, including neurodegenerative, vascular, and autoimmune/inflammatory diseases. Overlap in presenting symptoms and signs, results of cognitive testing, and findings on brain imaging and other common diagnostic tests confounds the etiologic diagnosis, contributing to diagnostic delays, missed opportunities for treatment, and poorer outcomes in patients with RPD. New tools and approaches are needed to improve diagnostic accuracy, with particular emphasis on improving early recognition of patients with potentially treatable causes of RPD.MethodsEstablished and emerging biomarkers of Alzheimer disease neuropathology (Aβ42/40, p‐tau181, p‐tau231), neuroaxonal and neuronal injury (neurofilament light [NfL], VILIP‐1, total tau), neuroinflammation (YKL‐40, sTREM2, GFAP, MCP‐1), and synaptic dysfunction (SNAP‐25, neurogranin) were measured in cerebrospinal fluid obtained at presentation from 78 prospectively accrued patients with RPD due to neurodegenerative (n = 35), vascular (n = 9), and autoimmune/inflammatory (n = 34) diseases, and 72 age‐ and sex‐similar cognitively normal individuals (controls). Causes of RPD were further classified as potentially treatment‐responsive or nonresponsive, referencing the extant literature. Biomarker levels were compared across etiologic diagnoses and by treatment responsiveness, referencing control values. Analyses were adjusted for the effects of age (ANCOVA).ResultsAlzheimer disease biomarkers (low Aβ42/40 and elevated p‐tau181 and p‐tau231) were associated with neurodegenerative causes of RPD (ANCOVA, p = 0.02 p = 0.30, p = 0.15), while high NfL (p = 0.61), low VILIP‐1 (p = 0.009), and elevated markers of inflammation (sTREM2, p = 0.009; YKL‐40, p<0.001) identified patients with autoimmune/inflammatory diseases (Figure). MCP‐1 levels were highest in patients with vascular causes of RPD (p = 0.08). 44 patients (56.4%) had potentially treatment‐responsive causes of RPD. Treatment responsiveness was associated with higher levels of CSF Aβ42/40 (p = 0.003), NfL (p<0.001), sTREM2 (p<0.001) and YKL‐40 (p<0.001); and lower levels of p‐tau‐181 and p‐tau231 (p<0.001, p<0.001) and VILIP‐1 (p<0.001).ConclusionSelected biomarkers measured in CSF at presentation associate with etiologic diagnosis and treatment responsiveness in patients with neurodegenerative, vascular, and autoimmune/inflammatory causes of RPD. Biomarker panels may be adapted to improve recognition of patients with treatment‐responsive causes of RPD early in the symptomatic course when treatments may be most effective.

AbstractBackgroundThe meningeal layers form a unique interface between the central nervous and peripheral immune systems. The lymphatic vasculature that is present in the meningeal dura and drains cerebrospinal fluid (CSF) becomes dysregulated during aging and in models of neurodegenerative disorders such as Alzheimer’s disease (AD). Apolipoprotein E (APOE), and the isoform APOE4 in particular, increases the risk for late‐onset sporadic AD. However, it is still poorly understood whether changes in meningeal lymphatic morphology and drainage are mediating the deleterious effects of APOE4 expression. In the present study, we investigate the effects of human APOE3 or APOE4 on meningeal lymphatic function and immunity.MethodWe evaluated the morphology of lymphatic vessels in dural whole mounts of age‐matched wild type, Apoe‐KO, APOE3, and APOE4 mice at 2‐3, and 11‐12 months. This assessment was performed in both male and female mice. The drainage function of meningeal lymphatics is being assessed in the same mice by in vivo imaging of CSF‐derived fluorescent tracers into the deep cervical lymph nodes. We have also performed RNAscope and protein measurements using murine meningeal tissue to investigate the main cellular source(s) of Apoe, and single‐cell RNA sequencing to explore the cell‐specific transcriptomic signatures linked to the changes in meningeal lymphatic function.ResultLymphatic vessel length is increased in 11‐12‐month‐old APOE4 male mice, when compared to their APOE3 counterparts. Interestingly, the same was not detected in female mice. Dural myeloid cells, expressing Itgam (encoding for CD11b), are the main source of Apoe mRNA transcripts, and one of the main sources of apoE protein in the brain dura mater. APOE4 expression and age markedly alter the transcriptional profile of meningeal myeloid cells, which show overexpression of lysosomal, antigen presentation, and complement genes.ConclusionAPOE4 expression leads to a sex‐dependent meningeal lymphatic vascular remodeling, which is associated with an exacerbated activation of meningeal macrophages. In future studies, we will test whether the changes in meningeal lymphatics observed in mice expressing APOE4 are mediated by myeloid cell derived APOE.

AbstractBackgroundAlzheimer’s disease (AD) is neuropathologically characterized by amyloid‐β (Aβ) plaques and tau neurofibrillary tangles often quantified by Thal phase and Braak stage, respectively. Aβ also frequently deposits in the cerebrovasculature with severity categorized by a cerebral amyloid angiopathy (CAA) score. These and related measures often show high variability within AD suggesting distinct underlying mechanisms, the identification of which may reveal important biological insights into AD pathophysiology. We hypothesize that, within the AD brain, neuropathology and levels of core AD‐related proteins are influenced by variations in DNA methylation (DNAm). To test this, we performed epigenome‐wide association studies (EWAS) using DNAm clusters from the temporal cortex (TCX) and cerebellum (CER) with AD‐related neuropathologic measures (Braak, Thal, and CAA) and brain biochemical levels of five proteins (apoE, Aβ40, Aβ42, tau, and p‐tau).MethodsDNAm from neuropathologically‐confirmed AD cases available through the Mayo Clinic brain bank was measured by reduced representation bisulfite sequencing (RRBS) from 471 brain samples, 200 of which had both TCX and CER measures. Neuropathology was scored by an experienced neuropathologist. TCX levels of five AD‐related proteins from three tissue fractions (buffer‐, detergent‐, and in‐soluble) were measured by ELISA (Liu 2020). CpG methylation (CpGm) was binned by a 15‐state chromatin model (Kundaje 2015) and averaged. Averaged CpGm clusters were tested for their association with each endophenotype through multi‐variable linear regression. The influence of CpGm clusters on expression levels of nearby genes was also investigated through multi‐variable regression.ResultsOur innovative binning method demonstrated expected and biologically relevant CpGm patterns. We identified multiple epigenome‐wide significant CpGm clusters unique to each AD‐related endophenotype and brain region. Comparisons between the TCX and CER further revealed brain region‐specific enrichment of distinct CpGm clusters. Significant CpGm clusters were further characterized by their influence on gene expression.ConclusionsAlthough all neuropathologic and biochemical endophenotypes tested are core to AD pathophysiology, our results suggest each has a distinct epigenetic architecture underlying their variability in the AD brain. By discovering brain region‐specific DNAm changes that contribute to each neuropathologic or biochemical outcome, we can identify core components of complex mechanisms that individually and jointly contribute to AD.

ObjectiveThis study was undertaken to apply established and emerging cerebrospinal fluid (CSF) biomarkers to improve diagnostic accuracy in patients with rapidly progressive dementia (RPD). Overlap in clinical presentation and results of diagnostic tests confounds etiologic diagnosis in patients with RPD. Objective measures are needed to improve diagnostic accuracy and to recognize patients with potentially treatment‐responsive causes of RPD.MethodsBiomarkers of Alzheimer disease neuropathology (amyloid‐β 42/40 ratio, phosphorylated tau [p‐tau181, p‐tau231]), neuroaxonal/neuronal injury (neurofilament light chain [NfL], visinin‐like protein‐1 [VILIP‐1], total tau), neuroinflammation (chitinase‐3‐like protein [YKL‐40], soluble triggering receptor expressed on myeloid cells 2 [sTREM2], glial fibrillary acidic protein [GFAP], monocyte chemoattractant protein‐1 [MCP‐1]), and synaptic dysfunction (synaptosomal‐associated protein 25kDa, neurogranin) were measured in CSF obtained at presentation from 78 prospectively accrued patients with RPD due to neurodegenerative, vascular, and autoimmune/inflammatory diseases; 35 age‐ and sex‐matched patients with typically progressive neurodegenerative disease; and 72 cognitively normal controls. Biomarker levels were compared across etiologic diagnoses, by potential treatment responsiveness, and between patients with typical and rapidly progressive presentations of neurodegenerative disease.ResultsAlzheimer disease biomarkers were associated with neurodegenerative causes of RPD. High NfL, sTREM2, and YKL‐40 and low VILIP‐1 identified patients with autoimmune/inflammatory diseases. MCP‐1 levels were highest in patients with vascular causes of RPD. A multivariate model including GFAP, MCP‐1, p‐tau181, and sTREM2 identified the 44 patients with treatment‐responsive causes of RPD with 89% accuracy. Minimal differences were observed between typical and rapidly progressive presentations of neurodegenerative disease.InterpretationSelected CSF biomarkers at presentation were associated with etiologic diagnoses and treatment responsiveness in patients with heterogeneous causes of RPD. The ability of cross‐sectional biomarkers to inform upon mechanisms that drive rapidly progressive neurodegenerative disease is less clear. ANN NEUROL 2024;95:299–313

ObjectiveTo improve the timely recognition of patients with treatment‐responsive causes of rapidly progressive dementia (RPD).MethodsA total of 226 adult patients with suspected RPD were enrolled in a prospective observational study and followed for up to 2 years. Diseases associated with RPD were characterized as potentially treatment‐responsive or non‐responsive, referencing clinical literature. Disease progression was measured using Clinical Dementia Rating® Sum‐of‐Box scores. Clinical and paraclinical features associated with treatment responsiveness were assessed using multivariable logistic regression. Findings informed the development of a clinical criterion optimized to recognize patients with potentially treatment‐responsive causes of RPD early in the diagnostic evaluation.ResultsA total of 155 patients met defined RPD criteria, of whom 86 patients (55.5%) had potentially treatment‐responsive causes. The median (range) age‐at‐symptom onset in patients with RPD was 68.9 years (range 22.0–90.7 years), with a similar number of men and women. Seizures, tumor (disease‐associated), magnetic resonance imaging suggestive of autoimmune encephalitis, mania, movement abnormalities, and pleocytosis (≥10 cells/mm3) in cerebrospinal fluid at presentation were independently associated with treatment‐responsive causes of RPD after controlling for age and sex. Those features at presentation, as well as age‐at‐symptom onset <50 years (ie, STAM3P), captured 82 of 86 (95.3%) cases of treatment‐responsive RPD. The presence of ≥3 STAM3P features had a positive predictive value of 100%.InterpretationSelected features at presentation reliably identified patients with potentially treatment‐responsive causes of RPD. Adaptation of the STAM3P screening score in clinical practice may minimize diagnostic delays and missed opportunities for treatment in patients with suspected RPD. ANN NEUROL 2024;95:237–248

Neuron-derived extracellular vesicles (NDEVs) are potential biomarkers of neurological diseases although their reliable molecular target is not well established. Here, we demonstrate that ATPase Na + /K + transporting subunit alpha 3 (ATP1A3) is abundantly expressed in extracellular vesicles (EVs) isolated from induced human neuron, brain, cerebrospinal fluid, and plasma in comparison with the presumed NDEV markers NCAM1 and L1CAM by using super-resolution microscopy and biochemical assessments. Proteomic analysis of immunoprecipitated ATP1A3 + brain-derived EVs shows higher enrichment of synaptic markers and cargo proteins relevant to Alzheimer’s disease (AD) compared to NCAM1 + or LICAM + EVs. Single particle analysis shows the elevated amyloid-β positivity in ATP1A3 + EVs from AD plasma, providing better diagnostic prediction of AD over other plasma biomarkers. Thus, ATP1A3 is a reliable target to isolate NDEV from biofluids for diagnostic research.