bluuebunny/crossref_metadata_2025 huggingface dataset:
Folate deficiency aggravates SARS‐CoV‐2‐induced endothelial barrier disruption in Mthfr heterozygous knockout mice
Authors: Umar Meenakshi , Ismael Saifudeen , Volic Milla , Hall Gregory W , Bix Gregory J
Published: January 2025

Background

Increasing evidence suggests that SARS‐CoV‐2 infection may lead to early onset and aggravation of pre‐existing vascular dementia and Alzheimer’s disease. Methylene tetrahydrofolate reductase (Mthfr) is a critical enzyme in folate metabolism, also required for optimal brain function. Mthfr deficient mice display cognitive impairments and neurovascular deficits and polymorphisms in MTHFR increases dementia risk. Intriguingly, a globally prevalent polymorphism in MTHFR (C677T) is linked with the COVID‐19 incidence and mortality. Many studies have reported association of MTHFR polymorphisms with COVID‐19 severity suggesting it as a genetic risk factor of COVID‐19, however, there is a need of mechanistic evaluation of the underlying mechanism. In this study, we investigated the role of folate deficiency due to MTHFR polymorphism on SARS‐CoV‐2 mediated neuroinflammation and blood‐brain barrier disruption.

Method

C57 wild‐type (WT) and Mthfr heterozygous knockout (Mthfr±) mice were inoculated intranasally with mock or 1 × 104 PFU of the mouse adapted (MA10) strain of SARS‐CoV‐2 that is capable of infecting WT mice. After 3 days post‐infection, lung and brain were collected for pathological evaluation. Additionally, mouse brain microvascular endothelial cells (bEnd.3) cultured in folate‐sufficient and folate‐deficient medium were treated with SARS‐CoV‐2 spike proteins for 24h.

Result

Mthfr± mice showed slightly higher disease associated weight loss (10.5%) compared to WT mice (8.5%). In addition, lung viral load estimation indicated an elevated trend in Mthfr± infected mice (6.3±0.5 × 107 copies/100ng RNA) compared to WT (5.8±0.9 × 107 copies/100ng RNA). Blood‐brain barrier integrity, as measured by ZO‐1 mRNA level, was significantly reduced by MA10 infection in Mthfr± mice compared to WT and Mthfr± mice. Immunostaining further confirmed significant reduction in ZO‐1 expression in brain cortical regions of MA10 infected Mthfr± mice compared to WT infected mice. In addition, Mthfr+/ mice displayed less activated microglia in comparison to WT mice. Our preliminary in vitro study showed that folate deficiency decreased Claudin‐5 and Occludin mRNA expression in bEnd.3 cells. Additionally, exposure to SARS‐CoV‐2 spike proteins showed a further decrease in Claudin‐5 expression in folate‐deficient bEnd.3 cells.

Conclusion

SARS‐Cov‐2 infection may aggravate blood‐barrier disruption in the context of Mthfr disruption potentially increasing susceptibility to COVID‐19 morbidity and worsened post‐COVID neurocognitive effects.
Single vascular insult aggravates amyloid accumulation with age triggering glial activation in AD mice
Authors: Diwakar Latha , Gupta Mayank , Talukdar Ankita , Hussain Rehab
Published: January 2025

Background

Vascular pathology is often seen in cases of mixed dementia affecting elderly population including Alzheimer’s disease (AD). AD is generally characterized by the presence of amyloid‐β (Aβ) plaques and tau deposits. However, many factors influence the onset and progression of AD pathology. In the present study, we are looking for brain vascular pathology like blood brain barrier (BBB) breach by vascular insult and associated microglial activation in small vessels increase risk of developing pathology over age. It is often hypothesized that in presence of increased Aβ, vascular insults could synergistically trigger neuroinflammation leading to cognitive impairment accelerating neurodegeneration.

Method

Learning and memory deficits were performed in slow progressing APPswe mice injected with 2µg/2μl of ET‐1(endothelin‐1) bilaterally into lateral ventricles after 30 days of ET‐1 injection. BBB structural changes were assessed by immunohistochemistry for markers of endothelial cells and pericytes. Aβ plaque load and vascular deposition of Aβ were tested to understand the effect of vascular insult on AD pathology in double transgenic J20 mice. Further, microglial activation was estimated using specific markers.

Result

BBB breaching was increased after vasoconstriction following ET‐1 injection after 30 days with increasing age causing memory deficits in AD mice. The extent of structural changes in BBB increased with age indicating the susceptibility with mutation. Aβ plaque load and glial activation was increased in J20 mice after ET‐1 injection.

Conclusion

APP mutation increases susceptibility to ET‐1 induced single vascular insult bringing about BBB leakage, memory deficits, increased Aβ aggregation and glial activation with increasing age given enough time of 30 days to rescue. However, there was rescue in case of wild type mice.
Butyrate and Lauric acid effect on Astrocytes and Neurons in Alzheimer’s disease
Authors: Senarath R.M. Uththara Sachinthanie , Oikari Lotta E , Bharadwaj Prashant , Jayasena Vijay , Martins Ralph N , Fernando Warnakulasuriya Mary Ann Dipika Binosha
Published: January 2025

Background

Recently, there has been substantial interest in investigating the role of short‐chain fatty acids (SCFAs) and, medium chain fatty acids (MCFA) in the neuroinflammation associated with Alzheimer’s disease (AD). Specifically, butyrate (SCFA) and lauric acid (MCFA) have demonstrated potential in alleviating neuroinflammation and reducing toxicity associated with amyloid proteins. Additionally, they have been found to enhance mitochondrial function and reduce neuronal hyperactivity. However, the mechanisms by which butyrate and lauric acid either suppress or activate astrocytes and neurons, as well as how they influence Aβ‐mediated activation of astrocytes and neurons, remain unclear. This study aims to address this knowledge gap by investigating the independent and synergistic effects of butyrate and lauric acid on AD pathogenesis—a research endeavour not undertaken previously.

Method

Butyrate and lauric acid were administered independently and synergistically to cultures of astrocytes, neurons derived from induced pluripotent stem cells (iPSCs) obtained from healthy human control subjects. Inflammatory responses of astrocytes and neurons were measured under synthetic amyloid beta stimulating conditions similar to AD. Legend Plex Human Inflammatory Panel was used to quantify the response of inflammatory cytokines (Interleukin IL‐1β, IL‐6, IL‐8, IL‐18, IL‐33, etc.) to inflammatory stimuli. The statistical analysis was carried out using the GraphPad Prism version 10.1.2. One‐way ANOVA was used to analyse the data.

Result

Butyrate and lauric acid, independently and synergistically demonstrate a positive association with pro‐inflammatory cytokines. There were negative association with anti‐inflammatory cytokines in neuron, astrocytes and spontaneous co‐cultures of astrocytes and neurons.

Conclusion

The findings indicate that both butyrate and lauric acid inhibit inflammation in Alzheimer’s‐induced astrocytes and neurons. Ongoing investigations aim to evaluate their effects on various cytokines and determine the responsible genes through qPCR analysis.
Preserved transcriptional networks in immune signaling pathways associated with chronic disease identified in Alzheimer’s disease and Parkinson’s disease, cross‐tissue analysis
Authors: Strickland Samantha L , Tsai Wei , Chen Xuan , Cherukuri Yesesri , Allen Mariet , Quicksall Zachary , Wang Xue , Kantarci Kejal , Carrasquillo Minerva M. , Nho Kwangsik , Saykin Andrew J. , Petersen Ronald C. , Reddy Joseph S. , Ertekin‐Taner Nilüfer
Published: January 2025

Background

Systemic inflammation plays a pivotal role in many chronic diseases including Alzheimer’s disease (AD). Assessing the composition of immune pathways in neurodegenerative diseases can contribute to precision medicine. Using publicly available transcriptomic data, we sought to elucidate transcriptional networks pertinent to inflammatory pathways across brain regions and peripheral blood in AD/mild cognitive impairment (MCI) and peripheral blood in Parkinson’s disease (PD).

Method

For the AD/MCI vs. control dataset, we analyzed bulk‐RNAseq collected from 6 brain regions of donors from ROSMAP, Mayo Clinic, and Mount Sinai School of Medicine (MSSM) brain banks available from the AMP‐AD consortium. Ante‐mortem, blood RNAseq expression data was retrieved from the AMP‐AD Emory Vascular cohort and Mayo Clinic Study of Aging (MCSA). We also collected blood‐derived microarray expression data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). For the PD vs Control dataset, blood‐derived bulk‐RNAseq from the PDBP and PPMI cohorts were available through the AMP‐PD consortium. Following quality control, normalization, and residual generation to account for biological and technical variables, co‐expression network modules and their enriched pathways were identified using WGCNA within each dataset. Module/trait correlation tests for aging and diagnosis (cases [AD/MCI or PD] vs control) phenotypes were evaluated. Gene Ontology enrichment analyses were executed to identify enriched pathways and brain or blood cell types within the modules. Modules were tested for preservation across cohorts.

Result

We identified conserved immune signatures across brain regions and cohorts. Modules involved in immune response were preserved across all cohorts. Blood consensus modules involved in immune response were preserved in the brain and vice versa. Some immune modules were associated with AD/MCI, PD, and/or aging. Brain immune modules are significantly associated with aging and/or AD. Significant correlations (q<0.05) with PD diagnosis were present. In the MCSA and Emory vascular cohorts, there were no significant (q<0.05) associations between modules and diagnosis, while in ADNI there were nominal (p<0.05) associations.

Conclusion

Preserved transcriptional immune networks were identified across blood and brain and across two neurodegenerative diseases. Expanding gene co‐expression network analyses to other diseases and integrating additional omics measures and phenotypes can further strengthen these findings to unravel the immune signatures across complex diseases.
Genetically predicted levels of sex hormones are associated with cerebrovascular disease pathology in the Alzheimer’s disease brain
Authors: Libby Julia B. , Beecham Gary , Montine Thomas J. , Toga Arthur W. , Cuccaro Michael L. , Keene C Dirk , Larson Eric B , Crane Paul K. , Mukherjee Shubhabrata , Panizzon Matthew S. , Biber Sarah A , Kukull Walter A. , Bennett David A. , Schneider Julie A. , Barnes Lisa L. , De Jager Philip L. , Menon Vilas , Hohman Timothy J. , Dumitrescu Logan C.
Published: January 2025

Background

Cerebrovascular pathology frequently co‐occurs with Alzheimer’s disease (AD) pathology and the combinations of these forms of pathology may underly AD dementia. Sex hormones influence many aspects of cerebrovascular systems and may contribute to cerebrovascular pathology, but many studies of aging and AD do not measure hormones. Therefore, in this study, we explored whether a polygenic score predicting sex hormone levels relates to cerebrovascular pathology in the AD brain.

Method

Sex‐specific Polygenic Risk Scores (PRS) of the sex hormones testosterone (Nmales: 146,339; Nfemales: 142,778) and estradiol (Nmales: 147,690; Nfemales: 163,985) were built using a linkage‐disequilibrium (LD) clumping method from published sex‐stratified GWAS from UK Biobank, using individuals with an age range of 40‐69 years old. Each PRS was scaled before analysis. Genetic data and harmonized cerebrovascular pathology data were leveraged from non‐Hispanic White autopsy participants from three independent studies of aging and AD: Adult Changes in Thought (ACT), the National Alzheimer’s Coordinating Center (NACC), and the Religious Orders Study/Rush Memory and Aging Project (ROSMAP) (Nmales: 4,269; Nfemales: 4,609). Characteristics of the participants are described in Table 1. Sex‐specific logistic regression models were used to evaluate whether each PRS relate to cerebrovascular disease (CVD) outcomes, including presence or absence of macroscopic infarcts, microinfarcts, atherosclerosis, or arteriolosclerosis. Covariates included age at death, last clinical diagnosis before death, and education.

Result

Higher genetically predicted levels of testosterone in males were associated with the presence of macroscopic infarcts (Table 2; b = 0.11, p = 0.03). Interestingly, higher genetically predicted levels of estradiol in males were associated with the presence of arteriolosclerosis (Table 2; b = 0.13, p = 0.02). No significant associations were observed for the other CVD outcomes in men and none in women. Significant results did not survive corrections for multiple comparisons.

Conclusion

The results show that a PRS of sex hormones can be used to explore the effect of sex hormone levels on cerebrovascular pathology as it pertains to AD. The results also support the need for more studies investigating the role of sex hormones on sex‐specific phenotypes of cerebrovascular pathology in the presence of AD. Future work is needed to better understand the mechanisms behind the observed associations.
Targeted proteomic analysis of 3R and 4R tau in marmoset and human brain tissue
Authors: Shapley Sarah M , Huhe Hasi , Duong Duc M , Wu Fang , Carter Gregory W , Silva Afonso C , Rizzo Stacey J Sukoff , Seyfried Nicholas T
Published: January 2025

Background

The microtubule‐associated Tau gene (MAPT) undergoes alternative splicing to produce isoforms with varying combinations of microtubule‐binding region (MTBR) repeats (3R, 4R). The MTBR is the predominant region that forms paired helical filaments and neurofibrillary tangles fibrils in disease. Alzheimer’s disease (AD) is a mixed Tauopathy containing both 3R and 4R isoforms. Previously, marmosets have been shown to spontaneously develop the key pathological hallmarks of AD during advanced age, positioning them as a model system to overcome the rodent‐to‐human translational gap for AD. Yet, Tau isoform expression has been understudied in marmosets with conflicting reports of isoform expression. Recently, our lab found 3R and 4R Tau to be expressed in adult marmoset brains. Additionally, AD pathology related phospho‐epitopes of soluble (pT181, pT217, pT231) and insoluble (pS396/404 and pS202/205) Tau were conserved. The present study sought to comprehensively characterize Tau isoforms in marmosets and corroborate antibody‐based results with a targeted proteomics assay.

Method

Marmoset (n = 7), human AD (n = 4), human non‐demented control (n = 4), and mouse (n = 1) brain lysates were analyzed via targeted mass spectrometry. The detection of the 3R Tau isoform unique peptide, KVQIVY, was obtained through the use of the LysargiNase enzyme that cleaves N‐terminal to K/R residues. Recombinant 3R and 4R Tau (rTau) proteins were used to generate peptide spectral libraries and served as technical controls.

Result

Tau peptides were identified via retention time and co‐elution. The marmoset product ions mirrored the human peaks and highly corresponded to the 3R and 4R peptide library spectra, providing mass spectrometry evidence of both isoform expressions in marmoset brains. 3R Tau was enriched in the fetal marmoset. In conjunction, the 4R rTau isoform and mouse samples did not match the 3R recombinant library spectrum.

Conclusion

Overall, we found marmosets to be a promising translational model of AD that overcomes the limitations of mice concerning the expression of both 3R and 4R Tau isoforms. These data extend our previous findings from western blots in a cohort of unrelated marmosets. Additionally, proteotyping of other Tauopathies may lend insight for novel biomarkers and personalized therapeutics.
Examining additive risk for cerebrovascular dysfunction in a novel late‐onset Alzheimer’s disease model
Authors: Reagan Alaina M , Kotredes Kevin P , O'Rourke Rita , Herrick Sarah , Cossette Travis L , Sasner Michael , Howell Gareth R
Published: January 2025

Background

Mechanisms driving cerebrovascular decline during Alzheimer’s disease and related dementias (ADRD) are poorly understood. Methylenetetrahydrofolate reductase (MTHFR) is an enzyme in the folate/methionine pathway. Variants in MTHFR, notably 677C>T, are associated with ADRD. ∼30% of individuals carry at least one copy of MTHFR677C>T, causing a 50% decrease in MTHFR enzyme efficiency. Reduced efficiency can lead to elevated homocysteine in blood, resulting in vascular inflammation and increased risk for cerebrovascular damage. To examine vascular risk in a late‐onset Alzheimer’s disease (LOAD) model, MODEL‐AD created a mouse carrying known ADRD risk factors with the Mthfr677C>T variant. While plasma‐based protein biomarkers hold promise for identifying ADRD pathology, additional markers are necessary. Studies support eye exams as a synergistic strategy due to overlapping mechanisms of damage in retina and brain, so retinal phenotyping has been incorporated in our study.

Methods

The LOAD2.Mthfr677C>T model was created by the IU/JAX/PITT MODEL‐AD Center by incorporating the Mthfr677C>T allele with the LOAD2 alleles (hAbeta/APOE4/Trem2*R47H). Cerebrovascular health is assessed in 4, 12, 18 and 24 month‐old mice by immunofluorescence to examine barrier integrity in cells that make up the cerebrovascular unit: endothelium, smooth muscle, pericytes, basement membrane, tight junctions, and extracellular deposition of blood products. Differential expression of vascular related genes/proteins is being examined by RNA‐sequencing and proteomics. In vivo retinal imaging, including optical coherence tomography and fluorescence angiography, and ex vivo retinal IF was performed to assess and compare neuronal and vascular health in the retina to the brain.

Results

All mice have been aged, and in vivo assays completed. Compared to LOAD2 controls, LOAD2.Mthfr677C>T mice do not show significant changes in frailty, activity, or cognition. At 24 mos, transcriptomic and proteomic data suggest LOAD2 and LOAD2.Mthfr677C>T show some expression changes similar to those seen in human AD. By immunofluorescence, like LOAD2, Mthfr677C>T mice do not develop ThioS‐positive amyloid plaques, but assessment of vascular‐specific changes is in progress. Plasma and retinal biomarker analysis is also in progress.

Conclusions

MODEL‐AD continues to create strains that develop endophenotypes of LOAD for preclinical testing. Ultimately, this work will aid in the identification of novel therapeutic approaches that reduce cerebrovascular pathology in ADRDs.
Effects of Chronic Binge Alcohol Consumption on Alzheimer’s Disease Neuropathogenesis in 3xTg‐AD mice
Authors: Sloan Lucy J. , Chilton Paula M. , Rao Aakarsha V. , Zhang JingWen , Myers Scott A. , Reddy Sreelatha , Lee Jiyeon , Rodriguez Walter , Gobejishvili Leila , Chariker Julia , Rouchka Eric , Ghare Smita S. , McClain Craig J. , Barve Shirish
Published: January 2025

Background

Chronic, excessive alcohol consumption causes neurodegeneration and is associated with an increased risk for Alzheimer’s disease (AD) and other dementias. Moreover, there has been a consistent rise in alcohol consumption in older adults in the past few decades. However, there is minimal research showing how alcohol consumption affects AD neuropathogenesis and biological mechanisms remain unclear. We hypothesize that mid‐life chronic binge alcohol consumption accelerates AD neuropathology in the hippocampus, among the first brain regions affected by AD, through dysregulation of processes associated with AD pathogenesis.

Methods

Female triple transgenic (3xTg; n = 15) mice and non‐transgenic (NonTg) control mice (B6.129; n = 13) were given EtOH binges twice/week (4g/kg) by oral gavage for 3.5 months (from 6‐9.5 months) while untreated controls (3xTg n = 6 and NonTg n = 4) received sham gavages. Memory was evaluated with the novel object recognition test (NORT). RNA was extracted from the mid‐brain region of one hemisphere for RNA‐Sequencing (Illumina NextSeq2000; STAR/HTSeq/DESeq2 pipeline) and qPCR, while protein lysates from the opposite hemisphere’s midbrain region was used for Western blot (WB) analyses. Plasma neurofilament light chain (NfL) was measured with a MesoScale Discovery kit.

Results

One week after the final EtOH gavage, hippocampal‐dependent memory was significantly impaired in EtOH binged 3xTg mice, while NonTg mice were unaffected. Similarly, EtOH binge slightly increased plasma NfL in 3xTg mice, indicating persistent EtOH‐induced neurodegeneration, while nonTg mice showed a significant decrease. RNA‐seq from the mid‐brain region containing the hippocampus revealed that chronic EtOH binge significantly affected 8477 genes (4473 up‐ and 4004 down‐regulated) in 3xTg mice, while only 4 genes were significantly affected (2 up‐ and 2 down‐regulated) in nonTg mice. Enrichment analyses showed EtOH altered several processes associated with neurodegeneration in 3xTg mice including regulation of synaptic plasticity and autophagy.

Conclusions

Results indicate that 3xTg mice are more sensitive to EtOH‐mediated effects on neurodegeneration and memory impairment than nonTg controls. There was also significant EtOH‐induced dysregulation of AD‐related processes in the mid‐brain of 3xTg mice, a region affected early by AD neuropathology. Together, these data show that chronic mid‐life EtOH binging accelerates early AD neuropathology in 3xTg mice.
Sex dependent pleiotropic effects of Apolipoprotein (ApoE) 4 on executive function in mice and humans
Authors: Longmuir Madison , Arrar Aya , Onuska Kate M. , Spreng R. Nathan , Palmer Daniel , Bussey Timothy J , Saksida Lisa M , Prado Vania F , Prado Marco A.M. , Schmitz Taylor W. , Group PREVENT‐AD Research
Published: January 2025

Background

ApoE4 is the strongest genetic risk factor for late onset Alzheimer’s Disease (AD). However, ApoE4 has also been suggested to exhibit antagonistic pleiotropy, a phenomenon by which some allelic variations of a gene promote fitness during certain periods of life but may be detrimental in others. Previous work suggests that ApoE4 carriers exhibit superior performance on executive function tasks in early and middle age, while later in life (>70 years) ApoE4 carriers experience greater cognitive decline across multiple domains. We examined this ApoE4 antagonistic pleiotropy hypothesis using a cross‐species translational approach, focusing on cognitively unimpaired human adult ApoeE4 carriers and non‐carriers who were within a relatively younger age range (<70 years). We complement this using knock‐in mouse models that express humanized wild‐type App, MAPT, and ApoE3 or ApoE4 genes. To quantify executive function in both human and mouse, we used cross‐species touchscreen based Continuous Performance Task (CPT) to assess selective attention.

Method

Human participants were recruited from the PREVENT‐AD program at the Douglas Research Centre. Human touchscreen CPT testing was conducted using an MS SurfacePro. Mice were tested with the same task as humans using an operant chamber platform.

Result

Our initial behavioural results suggest that ApoE4 facilitates attentional processes in both older adults and mouse ApoE4 carriers, as indexed by discrimination performance on the CPT. Further strengthening this translational pattern, we found that the facilitative effect of ApoE4 on CPT was more pronounced in female ApoE4 carriers of both species. In mice, we were able to examine this ApoE‐dependent effect on attention longitudinally. Consistent with antagonistic pleiotropy hypothesis, ApoE4 female mice present a higher CPT performance early in life (6‐9 months of age) when compared to ApoE3 mice, but this difference was reduced by 12 months of age.

Conclusion

Taken together, these results support the ApoE4 antagonistic pleiotropy hypothesis, whereby ApoE4 carriership confers greater attentional performance early in life in both female humans and mice. These new mouse models, in combination with fully translatable touchscreen tests of cognition, can be used to explore potential mechanisms by which ApoE4 can affect different aspects of brain function across the life span
Reduced microglia Trem‐2 expression promotes LPS‐induced AD‐like pathology
Authors: Bhat Shahnawaz A
Published: January 2025

Background

Following the genome‐wide association studies (GWAS) discovery of microglia‐specific genes, particularly Trem‐2, SHIP‐1, and CD33, significantly associated with higher Alzheimer’s disease (AD) risk, the microglia TREM2 pathway has become central for regulating amyloid load, tissue damage, and limiting its spread. These discoveries have opened up the exciting possibility of therapeutic microglia TREM2 manipulation in AD. To date, however, several elements of TREM2 signaling remain unknown, ranging from the temporal activation pattern and receptor‐ligand binding to modulation of the brain microenvironment. This study aimed to investigate the consequences of reduced microglia Trem‐2 expression on oxidative stress, inflammatory response, and cognitive impairment. We hypothesized that a decrease in Trem‐2 expression would lead to an increase in oxidative stress markers, an up‐regulation of inflammatory cytokines, and a decline in cognitive function

Method

We mimicked the neuroinflammatory milieu of AD by using LPS as a neuroinflammatory tool in vitro (BV2 microglia) and in vivo (C57BL6 mice).

Result

We found that LPS‐induced reduction in Trem‐2 expression resulted in significantly higher levels of oxidative stress markers, including increased production of reactive oxygen species (increased DCFDA intensity), nitrite level, and reduced GSH content, both in vitro and in vivo. Likewise, we observed a significant increase in the level of tumor necrosis factor‐alpha (TNF‐α) in both the BV2 microglia and C57BL6 mice following LPS treatment. Furthermore, the MWM cognitive test revealed a decline in spatial memory and learning abilities in mice with decreased Trem‐2 expression compared to control mice.

Conclusion

These results emphasize the importance of Trem‐2 in maintaining a healthy brain environment and suggest that targeting Trem‐2 could be a potential therapeutic strategy for neurodegenerative diseases associated with microglia dysfunction.
Investigating the role of SORL1 in mediating AD‐specific endolysosomal phenotypes in neurons and microglia
Authors: DeRosa Brooke A. , Zhang Yalun , Golightly Charles G. , Coombs Lauren , Rothschild Lauren E. , Kunkle Brian W. , Cuccaro Michael L. , Vance Jeffery M. , Pericak‐Vance Margaret A , George‐Hyslop Peter St , Dykxhoorn Derek M.
Published: January 2025

Background

Dysregulation of endolysosomal trafficking is a major pathogenic mechanism in Alzheimer’s disease (AD). From the family of AD‐linked endosomal pathway genes, SORL1 stands out as one of the highest risk factors. SORL1 encodes an endocytic sorting receptor that mediates endosomal trafficking and processing of key AD‐associated molecules, including pathogenic forms of amyloid‐β (e.g., Aβ42) and amyloid precursor protein (APP). Using complementary cell‐based model systems, we investigated the role of a protein‐truncating SORL1 variant on endolysosomal trafficking and APP processing.

Method

Induced pluripotent stem cell (iPSC) lines were derived from two siblings affected with early onset AD (EOAD) who carried a rare protein‐truncating deletion in SORL1 (rs1343336951; p.C1431fs). SORL1+/+ isogenic control iPSC lines were created from the patient lines using CRISPR/Cas9. After validation, the iPSC lines were differentiated into forebrain neurons and analyzed for endosomal trafficking defects. Additional analyses were completed in HEK293‐APPswe cells overexpressing SORL1 wild‐type (WT) or the C1431fs variant. Studies are underway that examine SORL1+/C1431fs microglia for defects in endolysosomal function.

Result

SORL1+/C1431fs neurons have increased localization of APP in early endosomes (p = 0.002), endosomal swelling (p = 0.004), and greater numbers of early endosomes per cell (p = 0.018). We additionally observe SORL1+/C1431fs neurons trending toward increased secretion of Aβ42 compared to controls. In HEK293 cells, C1431fs increased secretion of Aβ42 (p < 0.01), Aβ40 (p < 0.01), as well as APP soluble α‐secretase (sAPPα; p < 0.01) and β‐secretase (sAPPβ; p < 0.01) cleavage products. We additionally found C1431fs led to increased secretion of soluble SORL1 (p < 0.01). Surface biotinylation revealed C1431fs led to lower levels of SORL1 detected at the cell surface (p < 0.05). Conversely, C1431fs increased the amount of surface APP (p < 0.05).

Conclusion

Our results indicate that a single gene copy of the SORL1 C1431fs variant is sufficient to induce neuronal defects in endosomal trafficking and APP processing. Our findings are consistent with previously reported results from similar studies of SORL1 in cultured neurons. Ongoing studies in SORL1+/C1431fs microglia and neurons will help broaden our understanding of the role SORL1 plays in regulating endolysosomal phenotypes in multiple cell types implicated in AD.
Cell type specific contributions of mTOR inhibition that drive neuroprotective mechanisms in Alzheimer’s disease
Authors: Haynes Kathryn A , Santos Diogo Francisco Silva , Williams Sean‐Paul Gerard , Hart Jason T , Lehman Alicia M , Eckels Seana E , Nepali Umesh , Reddy Aman , Finkel Toren , Rizzo Stacey J Sukoff
Published: January 2025

Background

Studies investigating mTOR signaling provide compelling and reproducible evidence of the extension of lifespan across model organisms by treatment with the mTOR inhibitor rapamycin, and preclinical data suggests neuroprotective benefits of rapamycin in models of Alzheimer’s disease (AD). Rapamycin has potent immunosuppressive and autophagy activating effects though it remains unknown whether rapamycin’s neuroprotective and lifespan enhancing effects are achieved through modulating systemic inflammation, augmenting autophagy, or via some combination of modifying both these factors. Relatedly, the cellular and molecular mechanisms that contribute to rapamycin’s neuroprotective effects in AD remain unclear. The purpose of these studies is to identify the brain‐specific cell types that contribute to the protective effects of mTOR inhibition in progressive AD.

Method

For these studies we crossed a transgenic mouse model of familial early onset amyloid plaque deposition (5XFAD; JAX#034848) with a mouse genetically engineered with reduced mTOR expression to ∼25% of WT levels (mTORΔ/Δ). Previous studies have demonstrated that these mTOR hypomorph mice exhibit a 20% extension in lifespan. We then generated chimeric mice by crossing mTORΔ/Δ/5XFAD carriers to neuronal‐, microglial‐, and astrocyte‐specific Cre+ lines, resulting in mTOR expression reduced to 25% of WT except in the specific Cre+ cell type. Male and female subjects were evaluated longitudinally across the lifespan for measures of healthspan using a frailty assessment and compared to WT littermate controls.

Result

Offspring from all crosses of mTORΔ/Δ; 5xFAD; and neuronal (Syn1‐cre; JAX#003966), astroglial (Gfap‐cre; JAX#012896) or microglial (Cx3cr1‐cre; JAX#025524) cre‐expressing mice were viable with cohorts bred to N = 10/sex/genotype/cre line for longitudinal lifespan and healthspan assessments. Evaluation of frailty scores assessed at 12 months of age reveal the expected increase in frailty in 5XFAD relative to WT littermate controls with reduced frailty scores in mTORΔ/Δ carrier mice including mTORΔ/Δ/5XFAD crosses.

Conclusion

The present interim results confirm and extend the protective effects of ubiquitous reduction of mTOR expression. Ongoing studies in Cre+ lines will determine in which cell types reduced mTOR signaling is necessary for neuroprotection by comprehensive characterization of these models in functional assessments, AD biomarkers and relevant pathology.
Automated image segmentation uncovers the association of a microglial subtype defined by High CD74 Expression with cognitive decline
Authors: Taga Mariko , Fujita Masashi , Parghi Neelang , De Jager Philip L.
Published: January 2025

Background

Stage III activated microglia have been associated with Alzheimer’s Disease (AD) and cognitive decline. Separately, recent single‐cell RNA‐sequencing revealed CD74 as a marker gene that is enriched in immunologically active microglial subtypes associated with AD.

Method

Post mortem tissue sections from the dorsolateral prefrontal cortex were stained simultaneously for (1) CD74, (2) IBA1 (a general microglial marker that outlines cellular processes), and (3) phosphoTau (AT8 antibody) to locate Tau proteinopathy. 154 aged individuals with and without AD from two brain collections were stained: ROS/MAP (n = 63) and NYBB (n = 91). To ensure unbiased results and facilitate high‐throughput data analysis, the entire tissue sections were scanned using a Nikon immunofluorescence scanner. An image analysis pipeline using CellProfiler software has been developed, to automatically delineate the grey and white matter and to extract microglial cell morphology and IBA1/CD74 intensities from a total of 483,733 neocortical microglia.

Result

In a meta‐analysis of the two datasets, the frequency of microglia with CD74 high expression (CD74high) is increased in individuals with a clinical diagnosis of AD dementia compared to those without (p = 0.01). These microglia exhibit significantly higher IBA1 intensity (p = 4.1 × 10‐20) and adopt a less complex, amoeboid shape (p = 1.1 × 10‐23) when compared to the remaining microglia. Results are consistent in samples from each of the contributing brain banks. Since we have a large surface area, we also analyzed the spatial distribution of CD74high cells and note heterogeneity in the distribution of these cells along the cortical ribbon, suggesting that their presence is influenced by regional factors. These topological analyses are ongoing, leveraging the tangle staining.

Conclusion

We report a potential role of CD74high microglial cells in cognitive decline and present evidence that they have a morphologic characteristic that is shared with stage III microglia. Thus, we have used a new automated image segmentation pipeline optimized for the characterization of microglia to define and explore the functional characteristics and topological features of a microglial subtype associated with AD that was originally defined using single cell transcriptomic profiles.
NIA Genetics of Alzheimer’s Disease Data Storage Site (NIAGADS) AI‐Enhanced Search
Authors: Greenfest‐Allen Emily , Valladares Otto , Gangadharan Prabhakaran , White Heather , Kuzma Amanda B , Kuksa Pavel P. , Lee Wan‐Ping , Leung Yuk Yee , Wang Li‐San
Published: January 2025

Background

NIAGADS is a national data repository that offers qualified investigators access to genomic data for Alzheimer’s disease (AD) and related dementia. In addition, NIAGADS has made substantial effort to curate, harmonize, standardize, and disseminate AD‐relevant variant, gene, and sequence annotations from publications, functional genomics datasets, and summary statistics deposited at NIAGADS. These results are made available to the public in a collection of interactive knowledgebases (AD Variant Portal, FILER Functional Genomics Repository, VariXam, Alzheimer’s GenomicsDB & Genome Browser), all of which are accessible programmatically via the NIAGADS API. However, as these offerings grow, navigating them can be challenging. Here, we introduce AI‐based enhancements to NIAGADS sites to help guide researchers and facilitate data discovery.

Method

We leverage OpenAI’s generative AI to build and train three large language models (LLMs) based on NIAGADS documentation, step‐by‐step recipes for data‐access requests, subject‐specific vocabularies, and the OpenAPI specification defining the NIAGADS API that allows programmatic access to the NIAGADS knowledgebases. For users of the API and to enhance search interfaces, we build on the LLMs to construct a framework for handling complex natural language instructions that decomposes an inquiry into tasks and subtasks and then plans, selects, and optionally executes API calls and parses the results.

Result

Developing these LLMs allows NIAGADS to improve user experiences by integrating topic‐specific chatbots and generative AI search tools into NIAGADS sites. Rule‐based chatbots that leverage conversational AI on the NIAGADS portal and Data Sharing Service will respond to inquiries with answers inferred from the LLMs, with responses improving with user feedback. These bots will also supplement help requests, suggesting solutions to common inquiries. Planner‐enhanced generative AI based on the API‐specification trained LLMs will be tied to knowledgebase searches and filters in resources such as the GenomicsDB and FILER to allow users to leverage natural language processing to ask sophisticated questions that require multiple API calls to resolve the answer.

Conclusion

Introducing AI‐enhanced search creates an interactive opportunity for NIAGADS users to learn new information or discover resources and tools they can use to supplement their research, which, in turn, improves NIAGADS ability to support AD genetics research.
Expression of the APOE4 allele influences the systemic environment to alter hippocampal phenotypes
Authors: Philippi Sarah M , Ferreira Ana Catarina , Hemmer Brittany M. , BP Kailash , Kapoor Manav , Raj Towfique , Castellano Joseph M.
Published: January 2025

Background

The apolipoprotein E (APOE) ε4 allele is the strongest genetic risk factor for Alzheimer’s disease (AD), increasing risk from 3‐12‐fold relative to the common ε3 allele. Seminal studies have revealed that age‐related changes in blood‐CNS communication regulate cognitive function. More recently, youth‐associated blood‐borne proteins revitalize the aged brain, improving hippocampal function and increasing adult neurogenesis and dendritic spine plasticity. Characterizing plasma proteomic changes across various systemic contexts may thus be critical for development of novel therapeutic strategies to combat AD. We hypothesized that the plasma proteome differs between APOE4 and APOE3 individuals, and these systemic changes account for differences in brain function according to APOE genotype.

Method

Using an aptamer‐based platform to profile the plasma proteome from human APOE4/4 and APOE3/3 subjects, we identified allele‐specific changes in protein expression and canonical pathways linked to CNS functions and processes. Next, we examined the plasma proteome in APOE knock‐in mice expressing human APOE3 or APOE4 and evaluated those pathways that are conserved across species. To examine molecular processes within the brain regulated by opposing APOE alleles from the systemic environment, we characterized transcriptomic changes in the hippocampi of mice in which blood is shared between APOE4 and APOE3 mice by parabiosis relative to isogenic control pairs.

Result

In both mouse and human subjects, expression of APOE4 is associated with perturbations of plasma proteins related to extracellular matrix (ECM) and inflammation pathways relative to expression of APOE3. Several pathways shown to be associated with APOE3 expression in the hippocampus and disrupted in APOE4‐KI hippocampus were found to be restored in APOE4‐KI mice exposed to APOE3 blood via parabiosis. Specific deleterious phenotypes were identified in the hippocampi of APOE3 mice exposed to APOE4 blood, suggesting that APOE4‐associated brain phenotypes are, in part, mediated by how APOE4 alters the systemic compartment.

Conclusion

We find that APOE alleles differentially alter the systemic environment to confer changes in brain phenotypes. Ongoing experiments focus on investigating the protective impact of the APOE3 systemic environment on molecular processes within the APOE4 hippocampus, which may ultimately inform our understanding of increased AD risk in APOE4 subjects.
Impact of APOE4 Allele on Cell‐Cell Communication and α‐Synuclein Aggregation in Lewy Body Dementia: Insights from Spatial Transcriptomics
Authors: Jin Yunjung , Wixom Alexander Q. , Li Zonghua , Liu Yuanhang , Koga Shunsuke , Sekiya Hiroaki , Santhakumar Hannah , Bu Guojun , Dickson Dennis W. , Zhao Na
Published: January 2025

Background

The aggregation of α‐synuclein protein, encoded by the SNCA gene, forms Lewy bodies (LBs) in neurons and is a key pathological feature of Lewy body dementia (LBD). Interestingly, the apolipoprotein E gene (APOE), primarily expressed in glial cells, is the strongest genetic modifier for LBD. The ε4 allele of this gene (APOE4) notably increases the risk of LBD. However, the specific mechanisms through which APOE‐regulated glial cells affect α‐synuclein aggregation in neurons are not yet fully understood.

Method

To explore this, we conducted spatial transcriptomics using the 10X Genomics Visium CytAssist platform on Formalin‐Fixed Paraffin‐Embedded tissue slides from the temporal cortex of human LBD brains (N = 4 brains in controls and N = 6 brains in LBD group, with an equal ratio of APOE3/3 and APOE3/4 genotypes). We defined the neuronal layers of the gray matter (Layers 1 to 6, L1‐6) and white matter in each brain based on the gene signature of each spot. We also identified LBs from hematoxylin and eosin (H&E) staining on the same slides, and annotated LB‐positive (LB+), LB‐surrounding and LB‐negative (LB‐) spots in each brain using Loupe Browser. We evaluated SNCA and APOE gene expression in each layer and analyzed cell‐cell communication using the CellChat tool across the layers.

Result

We observed that the SNCA gene was highly expressed in L5, which corresponded to the areas where most LBs were found. Notably, within LB+ spots across all layers, both SNCA and APOE gene expression levels were elevated in APOE3/4 cases compared to APOE3/3 cases. Furthermore, we identified cell‐cell communication networks between LB+ and LB‐surrounding spots, particularly in L4 and L5. These networks were enriched by microglia‐related signaling pathways, including APOE signaling, migration inhibitory factor (MIF) signaling, and colony stimulating factor 1 (CSF1) signaling. Interestingly, APOE3/4 brains exhibited significantly reduced interactions and lower interaction strength in these networks compared to APOE3/3 samples.

Conclusion

Our findings indicate that impaired cell‐cell communication, such as microglia‐mediated immune responses around LB regions, may be associated with the increased risk presented by the APOE4 allele in LBD brains.
NCRAD iPSCs: a vital resource for the Alzheimer’s disease research community
Authors: Nudelman Kelly N. , Jackson Trever , Marshall Jeanine D. , Faber Kelley M. , Ohlemacher Sarah K , Edler Michael C. , Foroud Tatiana M. , Meyer Jason S.
Published: January 2025

Background

The National Centralized Repository for Alzheimer’s Disease and Related Dementias (NCRAD) is continuing to develop a bank of induced pluripotent stem cells (iPSCs) that are available by request to the Alzheimer’s disease (AD) research community.

Methods

As part of the pipeline for quality control of received cell lines, DNA was extracted for all lines and was submitted for whole genome sequencing (WGS). Paired‐end WGS data was generated using the Illumina NovaSeq 6000 and processed following GATK best practices using the Sentieon pipeline. WGS data was annotated with Annovar, and data was reviewed for reported cell line variants and checked with Varsome and Franklin. Sequencing data was reviewed for all nonsynonymous and splicing variants in the APP, PSEN1, PSEN2, GRN, and MAPT genes. Additionally, DNA from cell lines was genotyped in‐house by NCRAD to generate apolipoprotein E (APOE) genotypes, and this data was compared with the WGS to confirm sample identity. Basic clinical and demographic data was also collected, including sex, case/control status, age, race, and ethnicity.

Results

To date, DNA has been extracted and genotyped at NCRAD for lines from 183 participants including generation of APOE genotypes passing quality control. Of these, 120 cell lines have returned WGS data passing quality control. Table 1 describes the demographic and clinical features for these lines, which include data for lines from 90 individuals as well as data for 30 isogenic lines. Of the 120 lines with available WGS, there are 13 case APP variant carriers, 13 case MAPT variant carriers, 8 case PSEN1 variant carriers, and 2 case PSEN2 variant carriers. Additionally, these cell lines included two control carriers of variants of uncertain significance (VUS) in GRN or PSEN2, as well as two cases carrying VUS in PSEN1 or APP.

Conclusions

NCRAD continues to expand iPSCs for the research community; adding WGS data to this resource provides an expanded scope for pre‐screening as well as functional research. Future directions include review of variants being tested in the Model Organism Development & Evaluation for Late‐Onset AD (MODEL‐AD) to provide additional value to researchers.
Carbonic anhydrase inhibitors improves cognitive functions in Tg2576 AD mice
Authors: Vazquez‐Torres Rafael , Parodi‐Rullan Rebecca M , Carey Ashley M , Fossati Silvia
Published: January 2025

Background

Over the years, Alzheimer’s Disease (AD) has been identified as a multifactorial disease, with cerebral vascular dysfunction being one of the most common and early pathological features. Vascular risk factors (VRF) are thought to further increase AD risk and pathology. Cerebral Amyloid Angiopathy (CAA) is defined as the accumulation of amyloid‐beta (Aβ) on the vascular wall. CAA occurs progressively with age in human AD brains, vascular dementias, and the Tg2576 AD mouse model. The Tg2576 develops significant amounts of parenchymal Aβ plaques and vascular amyloid deposits making it a valuable model to study CAA and AD. To study the contribution of VRF to CAA and AD pathology, we induced hyperhomocysteinemia (HHcy) and hypertension (HP) in Tg2576 mice. We have shown that carbonic anhydrase inhibitors (CAi) decreased vascular amyloid accumulation and neuroinflammation and prevented cognitive impairment in TgSwDI mice. Here, we evaluated the effects of HP and HHcy in AD and CAA pathology. In addition, we assessed the beneficial effects of CAi in the Tg2576 with/without the presence of VRF.

Methods

To induce VRF, male and female WT and Tg2576 mice were fed a HHcy inducing diet and/or were given L‐NAME (NO inhibitor to induce HP) in the water starting at 5 months of age. To test the effects of CAi, the FDA‐approved CAi (Acetazolamide) was added to the diet starting at 5 months of age. Animals were then tested in a battery of behavioral measures including spatial learning and memory (barnes maze, fear conditioning, novel object recognition, open field, and rotarod), at 12 months of age.

Result

The presence of HHcy or HT worsens spatial learning and memory in the WT and Tg2576 mice. Preliminary results may suggest that treatment with CAi improved spatial learning and memory in the WT and Tg2576 mice, in the presence or absence of VRFs.

Conclusion

Taken together, our results suggest that VRF affect learning and memory in AD/CAA and non‐AD/CAA animal models. Importantly, we demonstrate that CAi is a promising treatment for treating mixed AD and CAA pathology.