Starling, Skylar C

Abstract INTRODUCTION Loss‐of‐function variants of the ABCA7 gene are associated with an increased risk of Alzheimer's disease (AD). How neuronal ABCA7 contributes to AD pathogenesis is unknown. METHODS Using neuron‐specific Abca7 KO mice (n Abca7 −/− ) with or without 5×FAD amyloid model background and post mortem AD brains, we investigated AD‐related phenotypes through comprehensive approaches including transcriptomics and lipidomics. RESULTS Lipidomics analysis detected altered lipid profiles in the brains and synaptosomes of 5×FAD; n Abca7 −/− mice compared to controls. Transcriptomics profiling revealed that neuronal ABCA7 deficiency altered the expression of genes and pathways related to mitochondrial homeostasis and apoptosis, particularly in excitatory neurons. Consistently, synaptosomes isolated from 5×FAD; n Abca7 −/− mice showed diminished mitochondria respiration and reduced synaptic protein levels, which is further supported by results from human AD brains. DISCUSSION Our findings reveal that neuronal ABCA7 plays a critical role in mitochondrial homeostasis important for neuronal function and survival in the presence of AD pathology. Highlights Neuronal ABCA7 deficiency exacerbates Aβ pathology and neuronal damage in 5×FAD mice. Neuronal ABCA7 deficiency alters brain transcriptomes and lipidomes of 5×FAD mice. Neuronal ABCA7 deficiency disturbs mitochondria functions in synaptosomes from 5×FAD mice. Neuronal ABCA7 expression associates with genes and pathways related to mitochondrial homeostasis in AD brains.

AbstractBackgroundThe immune system is substantially involved in the development and progression of age‐related cognitive decline and Alzheimer’s disease (AD).MethodAs genetic and environmental factors interactively impact these conditions, we investigated how risk factors such as APOE genotype, age, and sex influence immune activation markers and AD biomarkers in cerebrospinal fluid (CSF) in elderly individuals enrolled in the Mayo Clinic Study of Aging cohort. Among cognitively unimpaired individuals aged over 65 at the baseline visit (N=298), we measured 365 CSF immune activation markers using the proximity extension assay.ResultWe found that age, sex, and diabetes status are associated with altered CSF levels of immune activation markers independently of other factors. For CSF AD biomarkers, we observed significant positive correlations between age and total tau, phosphorylated tau‐181 (p‐tau181), neurofilament light (NfL), and YKL40. APOE4 was also associated with lower Aβ42 and higher SNAP25 in CSF. We further examined whether baseline visit variables can predict cognitive decline, represented by the conversion from CDR=0 to CDR>0. We found that age, Aβ42, NfL, and REG4 were independently correlated with CDR conversion risk. When the cohort was dichotomized by their median values, older participants with lower Aβ42, higher NfL, and higher REG4 at baseline developed cognitive impairment during the follow up with a c‐index of 0.762 while age alone had a c‐index of 0.699.ConclusionTogether, our results suggest that assessing CSF immune activation markers and AD biomarkers can improve the prediction of cognitive impairment risk in the elderly.

AbstractBackgroundThe immune system is substantially involved in the development and progression of age‐related cognitive decline and Alzheimer’s disease (AD).MethodAs genetic and environmental factors interactively impact these conditions, we investigated how risk factors such as APOE genotype, age, and sex influence immune activation markers and AD biomarkers in cerebrospinal fluid (CSF) in elderly individuals enrolled in the Mayo Clinic Study of Aging cohort. Among cognitively unimpaired individuals aged over 65 at the baseline visit (N=298), we measured 365 CSF immune activation markers using the proximity extension assay.ResultWe found that age, sex, and diabetes status are associated with altered CSF levels of immune activation markers independently of other factors. For CSF AD biomarkers, we observed significant positive correlations between age and total tau, phosphorylated tau‐181 (p‐tau181), neurofilament light (NfL), and YKL40. APOE4 was also associated with lower Aß42 and higher SNAP25 in CSF. We further examined whether baseline visit variables can predict cognitive decline, represented by the conversion from CDR=0 to CDR>0. We found that age, Aß42, NfL, and REG4 were independently correlated with CDR conversion risk. When the cohort was dichotomized by their median values, older participants with lower Aß42, higher NfL, and higher REG4 at baseline developed cognitive impairment during the follow up with a c‐index of 0.762 while age alone had a c‐index of 0.699.ConclusionTogether, our results suggest that assessing CSF immune activation markers and AD biomarkers can improve the prediction of cognitive impairment risk in the elderly.

AbstractBackgroundAlzheimer’s disease (AD) is a progressive neurodegenerative disease and the most prevalent form of late‐life dementia. The ε2 allele of the APOE gene encoding apolipoprotein E (APOE2) is associated with lower susceptibility to AD among the three genotypes (ε2, ε3, ε4), while APOE4 is the strongest genetic risk factor for late‐onset AD. APOE plays a critical role in maintaining synaptic plasticity and neuronal function by controlling lipid homeostasis, with APOE2 having a superior function. Gene therapy that increases APOE2 levels in the brain has, therefore, emerged as a potential therapeutic strategy to treat AD.MethodWe conjugated PEGylated liposomes with transferrin and Penetratin, a cell‐penetrating peptide, sufficiently deliver chitosan‐APOE2 cDNA plasmid complex into amyloid model AppNL‐G‐F knockin mice at 12‐month‐old. Biochemical studies and brain transcriptome analysis were employed to investigate how brain‐targeting liposome‐based APOE2 gene delivery influences amyloid‐β (Aβ)‐related pathologies in AppNL‐G‐F knockin mice.ResultOne month after APOE2 gene therapy, there was a trend of reduced insoluble Aβ levels in the mouse cortices. Furthermore, in the AppNL‐G‐F knockin mice that received the APOE2 gene therapy, brain transcriptome analysis through RNA‐sequencing identified the upregulation of genes/pathways related to neuronal development. This was supported by increases of Dlg4 and Syp mRNAs coding synaptic proteins in the experimental group. On the other hand, we found that APOE2 gene delivery increased soluble Aβ levels, including oligomers, as well as exacerbated neurite dystrophy and decreased synaptophysin.ConclusionOur results suggest that brain‐targeting liposome‐based APOE2 gene therapy is potentially beneficial for synaptic formation at the transcriptional level. Forced APOE2 expressions, however, may exacerbate Aβ toxicity by increasing the dissociation of Aβ oligomers from aggregates in the presence of considerable amyloid burden.

Abstract Background: The prognosis of patients with MM with CNS mets is poor. E6201 is an intravenous (IV) MEK inhibitor with activity against BRAF V600-mutated MM cell lines, including MAPK resistance alteration. A previous phase I trial demonstrated activity of E6201 in BRAF V600E mutated MM with a Maximal Tolerated Dose of 320mg/m2 given IV once a week x 3 weeks q 28 days. 2/23 (8.7%) of patients had a PR, 8/23 (34.8%) had SD. Two patients with MM and brain mets achieved near-CR which led to preclinical studies that demonstrated E6201 is unaffected by P-gp and BCRP transport and achieved higher brain to blood concentration (266%).In this trial, patients with BRAF mutation + MM with brain mets, single agent E6201 given at 320mg/m2 twice weekly x 3 weeks q 28 days was determined to be safe. One patient had CNS SD and a PR in lung mets, and a second patient achieved CNS stable disease and CR in a leg melanotic lesion. The drug was well-tolerated with one reversible AE thrombocytopenia (Gr 2). The final review showed intracranial response of SD in 2/4 (50%) patients and systemic SD in 3/4 (75%) patients. Methods: We are currently accruing to the dose escalation cohort of E6201 with dabrafenib 150 mg twice daily orally (n=up to 22 evaluable patients). E6201 is administered IV at 320mg/m2 twice weekly for 3 weeks every 28 days. Patients must have stage IV melanoma with BRAF mutation with at least one active lesion in the brain. Prior local therapy is allowed if done at least 3 weeks prior to cycle 1. Participants must be on a stable dose of steroids for at least 7 days and have an ECOG <!–=2. The study allows one prior BRAF/MEK inhibitor therapy. The primary objectives are to determine the MTD of E6201 when combined with dabrafenib and the response rate of brain mets. The secondary objectives include duration of response, extracranial response, progression free survival, overall survival, and impact of BRAF mutation subtype and safety of the combination. Clinicaltrials.gov: NCT05388877 References:1.Gampa G, et al. Brain distribution of a novel MEK inhibitor E6201: implications in the treatment of melanoma brain metastases. 2018. Drug Metab Dispos.2.Tibes R et al. Safety, pharmacokinetics, and preliminary efficacy of E6201 in patients with advanced solid tumors, including melanoma: results of a phase I study. 2018. Brit J of Cancer. 3.Babiker Gm et al, E6201, an intravenous MEK1 inhibitor, achieves an exceptional response in BRAF V600E mutated metastatic malignant melanoma with brain metastases. 2018. Inv New Drugs4.Gampa G, Kim M, Cook-Rostie N, Laramy JK, Sarkaria JN, Paradiso L, DePalatis L, Elmquist WF. Brain distribution of a novel MEK inhibitor E6201: Implications in the treatment of melanoma brain metastases. 2018. Drug Met Disp.–> Citation Format: Mahesh Seetharam, Roxana Dronca, Arkadiusz Z. Dudek, Garth Nelson, Matthew Block, Skylar Starling, Amber Baskin, Renee Bradshaw, Courtney Nelson, Kylee Andrews, Alisha Birgin, Cristina Watson, Yiyi Yan, Daruka Mahadevan, Svetomir Markovic, Tom Myers, Linda Paradiso, Hani Babiker. Phase 1 trial of MEK1 inhibitor E6201 plus dabrafenib in patients (pts) with BRAF V600-mutated metastatic melanoma (MM) with central nervous system (CNS) metastases (mets) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT157.

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.

Cerebrovasculature is critical in maintaining brain homeostasis; its dysregulation often leads to vascular cognitive impairment and dementia (VCID) during aging. VCID is the second most prevalent cause of dementia in the elderly, after Alzheimer’s disease (AD), with frequent cooccurrence of VCID and AD. While multiple factors are involved in the pathogenesis of AD and VCID, APOE4 increases the risk for both diseases. A major apolipoprotein E (apoE) receptor, the low-density lipoprotein receptor-related protein 1 (LRP1), is abundantly expressed in vascular mural cells (pericytes and smooth muscle cells). Here, we investigated how deficiency of vascular mural cell LRP1 affects the cerebrovascular system and cognitive performance using vascular mural cell–specific Lrp1 -KO mice ( smLrp1 –/– ) in a human APOE3 or APOE4 background. We found that spatial memory was impaired in the 13- to 16-month-old APOE4 smLrp1 –/– mice but not in the APOE3 smLrp1 –/– mice, compared with their respective littermate control mice. These disruptions in the APOE4 smLrp1 –/– mice were accompanied with excess paravascular glial activation and reduced cerebrovascular collagen IV. In addition, blood-brain barrier (BBB) integrity was disrupted in the APOE4 smLrp1 –/– mice. Together, our results suggest that vascular mural cell LRP1 modulates cerebrovasculature integrity and function in an APOE genotype–dependent manner.