Biology subjects

Ferris, H. A.

Publications and source records attributed to Ferris, H. A..

4 recordsLinked to original sources

bioRxiv2025

7-ketocholesterol contributes to microglia-driven increases in astrocyte reactive oxygen species in Alzheimer's disease

Oxidative stress is a prominent feature of Alzheimers disease. Within this context, cholesterol undergoes oxidation, producing the pro-inflammatory product 7-ketocholesterol (7-KC). In this study, we observe elevated levels of 7-KC in the brains of the 3xTg mouse model of AD. To further understand the contribution of 7-KC on the oxidative environment, we developed a method to express a genetically encoded fluorescent hydrogen peroxide (H2O2) sensor in astrocytes, the primary source of cholesterol in the brain. With this sensor, we discovered that 7-KC increases H2O2 levels in astrocytes in vivo, but not when directly applied to astrocytes in vitro. Interestingly, when 7-KC was applied to a microglia cell line alone or mixed astrocyte and microglia cultures, it resulted in microglia activation and increased oxidative stress in astrocytes. Depletion of microglia from 3xTg mice resulted in reduced 7-KC in the brains of these mice. Taken together, these findings suggest that 7-KC, acting through microglia, contributes to increased astrocyte oxidative stress in AD. This study sheds light on the complex interplay between cholesterol oxidation, microglia activation, and astrocyte oxidative stress in the pathogenesis of AD.

neuroscience↗

bioRxiv2023

Altered circadian behavior and light sensing in mouse models of Alzheimer's disease

Circadian symptoms have long been observed in Alzheimers disease (AD) and often appear before cognitive symptoms, but the mechanisms underlying circadian alterations in AD are poorly understood. We studied circadian re-entrainment in AD model mice using a "jet lag" paradigm, observing their behavior on a running wheel after a six hour advance in the light:dark cycle. Female 3xTg mice, which carry mutations producing progressive amyloid beta and tau pathology, re-entrained following jet lag more rapidly than age-matched wild type controls at both 8 and 13 months of age. This re-entrainment phenotype has not been previously reported in a murine AD model. Because microglia are activated in AD and in AD models, and inflammation can affect circadian rhythms, we hypothesized that microglia contribute to this re-entrainment phenotype. To test this, we used the colony stimulating factor 1 receptor (CSF1R) inhibitor PLX3397, which rapidly depletes microglia from the brain. Microglia depletion did not alter re-entrainment in either wild type or 3xTg mice, demonstrating that microglia activation is not acutely responsible for the re-entrainment phenotype. To test whether mutant tau pathology is necessary for this behavioral phenotype, we repeated the jet lag behavioral test with the 5xFAD mouse model, which develops amyloid plaques, but not neurofibrillary tangles. As with 3xTg mice, 7-month-old female 5xFAD mice re-entrained more rapidly than controls, demonstrating that mutant tau is not necessary for the re-entrainment phenotype. Because AD pathology affects the retina, we tested whether differences in light sensing may contribute to altered entrainment behavior. 3xTg mice demonstrated heightened negative masking, an SCN-independent circadian behavior measuring responses to different levels of light, and re-entrained dramatically faster than WT mice in a jet lag experiment performed in dim light. 3xTg mice show a heightened sensitivity to light as a circadian cue that may contribute to accelerated photic re-entrainment. Together, these experiments demonstrate novel circadian behavioral phenotypes with heightened responses to photic cues in AD model mice which are not dependent on tauopathy or microglia.

neuroscience↗

bioRxiv2022

Regulation of neuroinflammation by astrocyte-derived cholesterol.

Neurodegeneration and its concomitant loss of cognitive function are closely linked to neuroinflammation and lipid accumulation, particularly cholesterol. In the brain, astrocytes synthesize cholesterol and deliver it to surrounding cells via apolipoprotein E (apoE). Astrocyte activation increases apoE secretion and promotes neuronal cell death, yet the link between astrocyte-derived cholesterol and inflammation remains unclear. Here we show that pro-inflammatory cytokines stimulate cholesterol synthesis and release from astrocytes. Immune cells take up this cholesterol, which clusters pro-inflammatory receptors in lipid rafts, amplifying inflammatory signaling and gene expression. Astrocyte-specific knockout of cholesterol synthesis (via SREBP2 deletion) reduces inflammatory cytokine production in an Alzheimers disease (AD) mouse model and shortens neuroinflammation triggered by peripheral lipopolysaccharide (LPS) injection. These findings identify astrocyte-derived cholesterol as a paracrine signal that helps drive neuroinflammation in microglia and brain-resident macrophages.

neuroscience↗

bioRxiv2021

SOD1 Mediates Lysosome-to-Mitochondria Communication and its Dysregulation by Amyloid-β Oligomers

Altered mitochondrial DNA (mtDNA) occurs in neurodegenerative disorders like Alzheimers disease (AD); how mtDNA synthesis is linked to neurodegeneration is poorly understood. We discovered Nutrient-induced Mitochondrial Activity (NiMA), an inter-organelle signaling pathway where nutrient-stimulated lysosomal mTORC1 activity regulates mtDNA replication in neurons by a mechanism sensitive to amyloid-{beta} oligomers (A{beta}Os), a primary factor in AD pathogenesis. Using 5-ethynyl-2-deoxyuridine (EdU) incorporation into mtDNA of cultured neurons, along with photoacoustic and mitochondrial metabolic imaging of cultured neurons and mouse brains, we show these effects being mediated by mTORC1-catalyzed T40 phosphorylation of superoxide dismutase 1 (SOD1). Mechanistically, tau, another key factor in AD pathogenesis and other tauopathies, reduced the lysosomal content of the tuberous sclerosis complex (TSC), thereby increasing NiMA and suppressing SOD1 activity and mtDNA synthesis. A{beta}Os inhibited these actions. Dysregulation of mtDNA synthesis was observed in fibroblasts derived from TS patients, who lack functional TSC and elevated SOD1 activity was also observed in human AD brain. Together, these findings imply that tau and SOD1 couple nutrient availability to mtDNA replication, linking mitochondrial dysfunction to AD.

neuroscience↗