Browsing by Author "Sudduth, Tiffany L."
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Item Acute Communication Between Microglia and Nonparenchymal Immune Cells in the Anti-Aβ Antibody-Injected Cortex(Society for Neuroscience, 2025-01-29) Foley, Kate E.; Weekman, Erica M.; Krick, Katelynn E.; Johnson, Sherika N.; Sudduth, Tiffany L.; Wilcock, Donna M.; Neurology, School of MedicineAnti-Aβ immunotherapy use to treat Alzheimer's disease is on the rise. While anti-Aβ antibodies provide hope in targeting Aβ plaques in the brain, there still remains a lack of understanding regarding the cellular responses to these antibodies in the brain. In this study, we sought to identify the acute effects of anti-Aβ antibodies on immune responses. To determine cellular changes due to anti-Aβ antibody exposure, we intracranially injected 14 mo APP male and female mice with anti-Aβ IgG1 (6E10) or control IgG1 into the cortex. After 24 h or 3 d, we harvested the cortex and performed a glial cell-enriched preparation for single-cell sequencing. Cell types, proportions, and cell-to-cell signaling were evaluated between the two injection conditions and two acute timepoints. We identified 23 unique cell clusters including microglia, astrocytes, endothelial cells, neurons, oligos/OPCs, immune cells, and unknown. The anti-Aβ antibody-injected cortices revealed more ligand-receptor (L-R) communications between cell types, as well as stronger communications at only 24 h. At 3 d, while there were more L-R communications for the anti-Aβ antibody condition, the strength of these connections was stronger in the control IgG condition. We also found evidence of an initial and strong communication emphasis in microglia-to-nonparenchymal immune cells at 24 h, specifically in the TGFβ signaling pathway. We identify several pathways that are specific to anti-Aβ antibody exposure at acute timepoints. These data lay the groundwork for understanding the brain's unique response to anti-Aβ antibodies.Item Alzheimer's disease and inflammatory biomarkers positively correlate in plasma in the UK‐ADRC cohort(Wiley, 2024) Foley, Kate E.; Winder, Zachary; Sudduth, Tiffany L.; Martin, Barbara J.; Nelson, Peter T.; Jicha, Gregory A.; Harp, Jordan P.; Weekman, Erica M.; Wilcock, Donna M.; Neurology, School of MedicineIntroduction: Protein-based plasma assays provide hope for improving accessibility and specificity of molecular diagnostics to diagnose dementia. Methods: Plasma was obtained from participants (N = 837) in our community-based University of Kentucky Alzheimer's Disease Research Center cohort. We evaluated six Alzheimer's disease (AD)- and neurodegeneration-related (Aβ40, Aβ42, Aβ42/40, p-tau181, total tau, and NfLight) and five inflammatory biomarkers (TNF𝛼, IL6, IL8, IL10, and GFAP) using the SIMOA-based protein assay platform. Statistics were performed to assess correlations. Results: Our large cohort reflects previous plasma biomarker findings. Relationships between biomarkers to understand AD-inflammatory biomarker correlations showed significant associations between AD and inflammatory biomarkers suggesting peripheral inflammatory interactions with increasing AD pathology. Biomarker associations parsed out by clinical diagnosis (normal, MCI, and dementia) reveal changes in strength of the correlations across the cognitive continuum. Discussion: Unique AD-inflammatory biomarker correlations in a community-based cohort reveal a new avenue for utilizing plasma-based biomarkers in the assessment of AD and related dementias. Highlights: Large community cohorts studying sex, age, and APOE genotype effects on biomarkers are few. It is unknown how biomarker-biomarker associations vary through aging and dementia. Six AD (Aβ40, Aβ42, Aβ42/40, p-tau181, total tau, and NfLight) and five inflammatory biomarkers (TNFα, IL6, IL8, IL10, and GFAP) were used to examine associations between biomarkers. Plasma biomarkers suggesting increasing cerebral AD pathology corresponded to increases in peripheral inflammatory markers, both pro-inflammatory and anti-inflammatory. Strength of correlations, between pairs of classic AD and inflammatory plasma biomarker, changes throughout cognitive progression to dementia.Item Atorvastatin rescues hyperhomocysteinemia-induced cognitive deficits and neuroinflammatory gene changes(BMC, 2023-09-01) Weekman, Erica M.; Johnson, Sherika N.; Rogers, Colin B.; Sudduth, Tiffany L.; Xie, Kevin; Qiao, Qi; Fardo, David W.; Bottiglieri, Teodoro; Wilcock, Donna M.; Neurology, School of MedicineBackground: Epidemiological data suggests statins could reduce the risk of dementia, and more specifically, Alzheimer's disease (AD). Pre-clinical data suggests statins reduce the risk of dementia through their pleiotropic effects rather than their cholesterol lowering effects. While AD is a leading cause of dementia, it is frequently found co-morbidly with cerebral small vessel disease and other vascular contributions to cognitive impairment and dementia (VCID), which are another leading cause of dementia. In this study, we determined if atorvastatin ameliorated hyperhomocysteinemia (HHcy)-induced VCID. Methods: Wild-type (C57Bl6/J) mice were placed on a diet to induce HHcy or a control diet each with or without atorvastatin for 14 weeks. Mice underwent novel object recognition testing before tissue collection. Plasma total cholesterol and total homocysteine as well as related metabolites were measured. Using qPCR and NanoString technology, we profiled glial cell-associated gene expression changes. Finally, microglial morphology, astrocyte end feet, and microhemorrhages were analyzed using histological methods. Results: Atorvastatin treatment of HHcy in mice led to no changes in total cholesterol but decreases in total homocysteine in plasma. While HHcy decreased expression of many glial genes, atorvastatin rescued these gene changes, which mostly occurred in oligodendrocytes and microglia. Microglia in HHcy mice with atorvastatin were trending towards fewer processes compared to control with atorvastatin, but there were no atorvastatin effects on astrocyte end feet. While atorvastatin treatment was trending towards increasing the area of microhemorrhages in HHcy mice in the frontal cortex, it only slightly (non-significantly) reduced the number of microhemorrhages. Finally, atorvastatin treatment in HHcy mice led to improved cognition on the novel object recognition task. Conclusions: These data suggest that atorvastatin rescued cognitive changes induced by HHcy most likely through lowering plasma total homocysteine and rescuing gene expression changes rather than impacts on vascular integrity or microglial changes.Item Frontal Memory‐related Brainwaves Differentially Correlate with AD and Astrocyte Plasma Biomarkers(Wiley, 2025-01-09) Jiang, Yang; Wu, Xian; Katsumata, Yuriko; Clark, Maria F.; Foley, Kate E.; Wang, Baoxi; Sudduth, Tiffany L.; Wilcock, Donna M.; Jicha, Gregory A.; Norris, Christopher M.; Neurology, School of MedicineBackground: We currently lack in the dementia field accurate, noninvasive, quick, and affordable screening tools for brain dysfunctions associated with early subtle risk of mild cognitive impairment (MCI). Our Kentucky aging cohort demonstrates that asymptomatic older individuals with MCI‐like frontal memory‐related brainwave patterns convert to MCI within a short 5‐year period, as opposed to individuals with NC‐like patterns (1) that remain normal 10 years later (2). Astrocyte reactivity influences amyloid‐β effects on tau pathology in preclinical Alzheimer’s disease (3). Leveraging blood‐based AD and astrocyte biomarkers and the cognitive electroencephalogram (EEG) signatures (4), we test the hypothesis that predictive frontal memory‐related EEG changes correlate with preclinical and early AD plasma biomarkers. Method: 34 (19 women) older volunteers with or without MCI, average age 79 (SD 8.53) years old, from a longitudinal cohort followed by University of Kentucky ADRC participated. Each participant’s EEG was recorded (64‐ or 14‐channels) during a working memory (modified delayed match‐to‐sample) task. Principal component analysis (PCA) was performed on 64‐channel EEG data to create PC scores (PC1 & PC2). For multiple linear regression of EEG PC scores on multiple neurodegenerative plasma biomarkers including Aβ42/40, pTau181, total Tau, and GFAP (Astrocyte reactivity), we adjusted age, sex, education, and gap years between collection dates. Result: The 61% of variance in frontal signals can be explained by PC1 in normal cognition (NC) and MCI individuals, and PC2 counts for 35% of variance (Figure 1). The decreased brainwaves (MCI‐like) seen in left frontal sites significantly correlate with increased pTau181, GFAP, and PC2 (Figure 2). Curiously, right frontal EEG relations with pTau181, GFAP showed the opposite trend. Bilateral frontal signals showed negative correlations with Aβ42/40 and positive correlations with total Tau. Conclusion: Our results indicate that GFAP & pTau181 trend in similar asymmetry ways with frontal cognitive brainwaves, but Aβ42/40 & total Tau correlate to a different component of frontal EEG. That is, distinct cognitive brainwaves correlate with astrocyte reactivity differentially that influence pathologies of beta‐amyloid accumulations and Tau development. Cognitive pathophysiological signatures and AD–Astrocyte plasma biomarkers have great potential for predicting subtle cognitive decline and specific dementia risk in healthy normal individuals.Item Glial changes as result of cerebral amyloid angiopathy progression(Wiley, 2025-01-03) Krick, Katelynn E.; Johnson, Sherika N.; Rogers, Colin B.; Sudduth, Tiffany L.; Weekman, Erica M.; Wilcock, Donna M.; Anatomy, Cell Biology and Physiology, School of MedicineBackground: Cerebral Amyloid Angiopathy (CAA) occurs at the intersection of Alzheimer’s disease and vascular contributions to cognitive impairment and dementia (VCID). In the human brain it occurs when amyloid beta (Aβ) aggregates in small/medium‐sized cerebral blood vessels, which contribute to hypoperfusion and cognitive decline by altering vascular function and integrity. The current study seeks to track the progression of CAA and associated neuroinflammation and glial cell changes in Tg2576 mice. Method: Tg2576 mice were aged to 8‐, 14‐, 20‐, and 27‐months and assessed for CAA pathology via histology. Gene expression was evaluated in hippocampal tissue by qPCR and posterior cortex by nanostring (ncounter Mouse Neuroinflammation and Mouse CVD Pathophysiology panels; in progress) to compare 8‐ and 20‐month APP and wildtype groups. Protein expression was evaluated via digital spatial profiling in the same APP mice, grouped by age or CAA presence compared to wildtype controls. CAA presence was defined as Aβ surrounding lectin‐positive vessels. Regions of interest were categorized as either positive or negative for CAA based on this criterion. Result: Congophillic plaque deposition along the vasculature increased in width, length, and area in a time dependent manner in both the frontal cortex and hippocampus. Astrocyte marker GFAP and proinflammatory receptor TNFR1 gene expression both increased at 20 months compared to 8 months in the APP group. Of the protein profile assessed (Mouse Neural Cell Profiling and Mouse Glial Cell Subtyping), the most consistent changes were found in astrocyte markers. Both Aldh1l1 and S100B were increased at 20 months compared to 8 months of age in both APP and WT mice. GFAP protein expression was found to increase with both age and CAA. Conclusion: This study showed increased vascular amyloid deposition and astrocyte gene and protein expression over time, further supporting a role for astrocytes in etiology and/or reaction to CAA.Item Hyperhomocysteinemia-induced VCID results in visual deficits, reduced neuroinflammation and vascular alterations in the retina(Springer Nature, 2025-01-30) Weekman, Erica M.; Rogers, Colin B.; Sudduth, Tiffany L.; Wilcock, Donna M.; Neurology, School of MedicineOver recent years, the retina has been increasingly investigated as a potential biomarker for dementia. A number of studies have looked at the effect of Alzheimer's disease (AD) pathology on the retina and the associations of AD with visual deficits. However, while OCT-A has been explored as a biomarker of cerebral small vessel disease (cSVD), studies identifying the specific retinal changes and mechanisms associated with cSVD are lacking. Using our model of hyperhomocysteinemia-induced cSVD, we aimed to identify the effects of cSVD on visual sensitivity and cognition, retinal glial and vascular cells, and neuroinflammatory and cardiovascular gene expression changes. We placed C57Bl6/SJL mice on a HHcy-inducing diet, a model that has been well characterized to have vascular pathologies in the brain similar to pathologic cSVD. After 14 weeks on diet, mice underwent the Visual-Stimuli 4-arm Maze to identify visual deficits. Whole mount retinas were stained for vessels, microglia and astrocytes to identify glial and vascular changes. Finally, neuroinflammatory and cardiovascular gene expression was measured using NanoString's nCounter system. Ultimately, HHcy led to visual changes that specifically affected the reaction to blue and white light, slightly decreased vascular volume and significantly decreased interaction of microglia with the vasculature, as well as downregulation of inflammatory and vascular genes. These changes provide novel insights and reproduce some prior observations. These studies highlight retinal changes in association with cSVD and serve as a precaution when interpreting vision-dependent cognitive testing of cSVD models.Item Induction of VCID via hyperhomocysteinemia leads to vision and retina changes in mice(Wiley, 2025-01-03) Weekman, Erica M.; Rogers, Colin B.; Sudduth, Tiffany L.; Wilcock, Donna M.; Neurology, School of MedicineBackground: Diagnosis of Alzheimer’s disease (AD) via MRI is costly and can be limited by regional availability. With the recent advancements and discovery of amyloid in the retina, diagnosis of AD and the effect of AD pathology on the retina is becoming well characterized. However, the prevalence of vascular contributions to cognitive impairment and dementia (VCID) and its effects on the retina are less well known. With the retina being a highly vascularized tissue and the considerable overlap of AD with VCID, it is imperative to understand the effect of VCID on vision. Method: We placed 6‐month‐old mice on a diet deficient in B vitamins and enriched in methionine to induce hyperhomocysteinemia (HHcy). HHcy is a risk factor for VCID, stroke and AD, and has been well characterized in our lab. After 14 weeks on diet, mice underwent the Visual‐Stimuli 4‐arm Maze (ViS4M) to identify visual and cognitive abnormalities. After behavior, brains and eyes were harvested with the left eye fixed in 4% PFA for 24hrs and the right eye flash frozen for RNA extraction. The fixed retina was flat mounted and stained for vessels, GFAP, and IBA‐1 and the flash frozen retina was used for RNA isolation and NanoString analysis. Result: Over the seven days the mice were tested on the ViS4M, the mice on the HHcy diet showed impaired cognition and altered colored arm entries compared to control mice. HHcy mice made more 2 arm alternations than 3 or 4 arm alternations, suggesting diminished exploration. When we determined their arm transitions, we saw that the HHcy mice tended to avoid the blue arm, suggesting sensitivity to blue light. In the retina, we saw slightly less vessel volume in the HHcy diet mice along with reduced coverage of vessels by microglia and astrocytes combined. Conclusion: The high prevalence of VCID with AD along with the impact of AD pathology on the eye makes it critical to understand the effect of VCID on the retina. In our model of HHcy induced VCID, we determined that HHcy does impair both cognition and vision and affects vessels within the retina.Item Plasma neurofilament light as a biomarker for vascular contributions to cognitive impairment and dementia(Wiley, 2025-01-09) Kautz, Tiffany F.; Mathews, Julia J.; Bernal, Rebecca; Wang, Chen-Pin; Liu, Qianqian; Gonzales, Mitzi M.; Tracy, Russell P.; Parent, Danielle; Wilcock, Donna M.; Sudduth, Tiffany L.; Wang, Danny J. J.; Sagare, Abhay P.; Rosenberg, Gary A.; Lu, Hanzhang; Kramer, Joel H.; Decarli, Charles; Jin, Lee-Way; Maillard, Pauline; Singh, Herpreet; Schwab, Kristin; Helmer, Karl; Greenberg, Steven M.; Kivisäkk, Pia; Aparicio, Hugo J.; Beiser, Alexa S.; Ghosh, Saptaparni; Fornage, Myriam; Mosley, Thomas H.; Mbangdadji, Djass; Launer, Lenore J.; Gudnason, Vilmundur; Bis, Josh; Psaty, Bruce M.; Seshadri, Sudha; Satizabal, Claudia L.; Neurology, School of MedicineBackground: The MarkVCID consortium was established to address the paucity of biomarkers for vascular contributions to cognitive impairment and dementia (VCID), a leading cause of dementia. Plasma neurofilament light (NfL), a neuroaxonal injury marker elevated in several neurological and neurodegenerative diseases, was selected as one of the first biomarkers to be examined. We performed comprehensive instrumental and clinical validation of the Quanterix Simoa NfL assay using the first MarkVCID cohort. Method: Plasma NfL was measured using HD‐X and HD‐1 Simoa instruments. Samples from the MarkVCID consortium were used to evaluate intra‐ and inter‐plate reliability, test‐retest repeatability, and inter‐site reproducibility. We used linear regression models to assess the association of NfL in MarkVCID with general cognitive function (GCF) as the primary outcome (n=331). In secondary analyses we assessed NfL associations with white matter hyperintensities (WMH). Models were adjusted for potential confounders, including eGFR as renal function influences NfL clearance. We replicated our findings using cohorts from the CHARGE consortium (CARDIA, ARIC, FHS, AGES; n=4,772), the UKY ADRC (n=350), and the UCD ADRC (n=196). Result: We found the Quanterix Simoa platform to be reliable with low coefficients of variation (average CV<12%), high inter‐site reproducibility (overall ICC = 0.93) and high repeatability in test‐retest samples drawn within 30 days (ICC=0.968). There was strong consistency across Quanterix instruments (HD‐X and HD‐1; R2≥0.98) and kits (N4PA and single molecule NfL; ICC≥0.81). We observed consistent significant associations between higher NfL concentrations and worse GCF in MarkVCID (β=‐0.23; [95% CI ‐0.41; ‐0.01), CHARGE cohorts (meta‐analysis β=‐0.11; [95% CI ‐0.17; ‐0.06]), the UKY ADRC (β=‐0.16; [95% CI ‐0.27; ‐0.05]) and the UCD ADRC (UCD: β=‐0.28; [95% CI ‐0.48; ‐0.08). Secondary analyses revealed significant associations between elevated NfL concentrations and higher WMH burden in MarkVCID (when controlled for eGFR), CHARGE, and the UCD ADRC. Conclusion: We have found that NfL can be reliably measured using the Quanterix platform, making this marker ideal for multi‐site clinical trials. We observed consistent associations for plasma NfL concentrations with cognition and WMH in MarkVCID and across independent samples, providing evidence that it can be a useful biomarker for stratification in VCID trials.Item Synergistic effects of plasma S100b levels and MRI‐based water exchange rate across the blood‐brain‐barrier on memory performance among older adults(Wiley, 2025-01-09) Pappas, Colleen; Zachariou, Valentinos; Bauer, Christopher E.; Sudduth, Tiffany L.; Wilcock, Donna M.; Jicha, Gregory A.; Hartz, Anika M. S.; Shao, Xingfeng; Wang, Danny J. J.; Gold, Brian T.; Neurology, School of MedicineBackground: Non‐invasive biofluid and MRI measures of blood‐brain‐barrier (BBB) dysfunction may aid early detection of cerebral small vessel disease (cSVD). Plasma markers of astrocytic function and injury, such as S100 calcium‐binding protein B (S100b), have gained increased attention in relation to BBB integrity and cognition. Here we explored the inter‐relationships between plasma S100b levels, an MRI measure of water exchange rate across the BBB (kw), and cognitive performance among older adults. Method: The participant sample consisted of 74 older adults without dementia recruited from the University of Kentucky Sanders Brown Center on Aging. Relationships between S100b and cognition (memory, executive function) and MRI‐based BBB water exchange rate were tested. Plasma S100b levels (pg/mL) were measured using Meso Scale Discovery R‐PLEX assay at the University of Kentucky’s CCTS Biomarker Analysis Lab. Composite scores were created for memory and executive function. A diffusion‐prepared arterial spin labeling (DP‐ASL) MRI sequence was used to estimate water exchange rate across the BBB (expressed as kw). All data (S100b, cognition, MRI) were collected within 1 year of each other. Multiple linear regression models examined the impact of plasma S100b on memory, executive function, and kw. Covariates included age, gender, and education (for cognition models only). Additionally, kw was tested as moderator of the S100b‐cognition relationships using the PROCESS macro. Result: A negative relationship was observed between S100b and memory, where higher S100b levels were associated with poorer memory performance. A similar relationship was not observed with executive function. S100b was also not associated with kw. However, there was an interaction between S100b levels and kw in the parietal lobe on memory performance such that participants with both lower parietal kw and higher S100b showed the poorest memory performance. Conclusion: Our results indicate that S100b levels are negatively associated with memory performance, but not MRI‐based BBB kw. However, higher S100b levels coupled with lower MRI‐based water exchange rate further contributed to the strong negative effects observed for memory performance. This suggests that plasma S100b and BBB kw may be different proxies of BBB function and may have synergistic negative effects on cognition.