Carla Cuní-López

Lipid droplets are dynamic cellular organelles that store neutral lipids and coordinate metabolic and stress-response pathways. In the brain, lipid droplets in glial cells, including astrocytes, have been implicated in Alzheimer’s disease, but how genetic risk factors influence their composition and turnover remains poorly understood. APOE is the strongest genetic modulator of late-onset Alzheimer’s disease and exists in common variants that confer decreased, neutral, or increased risk. Here we show that APOE genotype shapes the lipid droplet proteome, lipidome, and degradation dynamics in human induced pluripotent stem cell-derived astrocytes. By comparing oleic acid-treated astrocytes carrying APOE2 , APOE3 , or APOE4 , we find that each variant is associated with distinct lipid droplet proteins and lipids. These molecular differences correspond to genotype-dependent changes in lipophagy, an autophagy-mediated pathway for lipid droplet clearance. Lipid droplets in APOE2 astrocytes undergo efficient autophagic turnover, whereas those in APOE4 astrocytes resist degradation. These findings identify impaired lipid droplet clearance as a potential mechanism linking APOE4 to Alzheimer’s disease risk.

Disrupted endocytosis is an early feature of Alzheimer’s disease (AD), but how genetic risk factors functionally impact this pathway remains unclear. Using isogenic human iPSC-derived astrocytes, we show that the AD risk variant, APOE4, impairs clathrin-mediated membrane curvature, clathrin-mediated endocytosis, and alters plasma membrane lipid saturation and tension. Compared to APOE3 astrocytes, APOE4 cells display an accumulation of flat clathrin structures, reduced maturation of clathrin-coated pits, decreased early endosomes, and reduced endocytic uptake. We then identify the AD risk gene INPP5D as a modifier that restores early endocytosis in APOE4 astrocytes by promoting clathrin curvature and maturation through a mechanism distinct from membrane tension regulation. Beyond effects on trafficking, INPP5D overexpression also reduces lipid droplet accumulation and attenuates inflammatory signaling, linking membrane dynamics to disease-associated astrocytic phenotypes. Together, these findings establish altered membrane mechanics as a proximal consequence of the APOE4 variant and identify endocytosis as a common node linking AD risk genes.

The scarcity of effective biomarkers and therapeutic strategies for predicting disease onset and progression in neurodegenerative diseases such as Alzheimer’s disease (AD) is a major challenge. Conventional drug discovery approaches have been unsuccessful in providing efficient interventions due to their ‘one-size-fits-all’ nature. As an alternative, personalised drug development holds promise to pre-select responders and identifying suitable indicators of drug efficacy. In this exploratory study, we have established a pipeline with the potential to guide patient stratification studies before clinical trials. This pipeline uses 2D and 3D in vitro models of monocyte-derived microglia-like cells (MDMi) from AD and mild cognitive impairment (MCI) patients, and matched healthy control (HC) individuals. By profiling cytokine responses in these models using multidimensional analyses, we have observed that the 3D model offers a more defined separation of profiles between individuals based on disease status. While this pilot study focuses on AD and MCI, future investigations incorporating other neurodegenerative disorders will be necessary to validate the pipeline’s findings and demonstrate its broader applicability.

The escalating issue of air pollution contributes to an alarming number of premature fatalities each year, thereby posing a significant threat to global health. The focus of recent research has shifted towards understanding its potential association with neurodegenerative diseases, specifically Alzheimer’s disease (AD). AD is recognised for its characteristic deposition of toxic proteins within the brain, leading to a steady deterioration of cognitive capabilities, memory failure, and, ultimately, death. There is burgeoning evidence implying that air pollution may be a contributing factor to this protein build up, thereby intensifying the course of AD. It has been demonstrated that the olfactory system, responsible for smell perception and processing, acts as a potential gateway for airborne pollutants to inflict brain damage. This review aims to elucidate the relationship between air pollution, olfactory deterioration, and AD. Additionally, this review aims to highlight the potential mechanisms through which pollutants might instigate the development of AD and the role of the olfactory system in disease pathogenesis. Moreover, the diverse model systems employed in exploring the correlation, public health policy ramifications, and prospective directions for future research will be discussed.

Background Air pollution, particularly from Diesel Exhaust Particles (DEP) and Wildfire Smoke (WFS), is increasingly recognised as a significant driver of neuroinflammation linked to brain diseases. However, the role of microglia in mediating these neuroinflammatory responses remains poorly understood. This study aimed to investigate the effects of air pollution on monocyte-derived microglia-like cells (MDMi) from both young (< 40 years of age), and (older > 60 years of age) healthy individuals, focusing on immune response, cytokine secretion, nitrosative stress, and phagocytic activity. Results Our study demonstrated that DEP and WFS extract (WFSE) significantly upregulated expression of the oxidative stress marker, heme-oxygenase-1 (HO-1) in MDMi after 24 hr, with levels normalising by 96 hr, indicating a transient oxidative stress response. Both DEP and WFSE elicited distinct inflammatory cytokine profiles. DEP induced a rapid response, increasing TNF-α, IL-6, IL-23, and IL-33 within 2 hr in young MDMi and 24 hr in aged MDMi. In contrast, WFSE triggered a delayed but sustained inflammatory response, with TNF-α, IFN-γ, IL-23, and IL-33 levels persisting at 96 hr in aged MDMi, highlighting an age-related vulnerability to air pollutant-induced inflammation. Both pollutants activated p38, ERK, and NF-κB pathways, with p38 activity resolving by 96 hours and ERK activation persisting, reflecting their distinct roles in cellular stress and inflammation. NF-κB p65 nuclear translocation, observed at 24 hours, highlighted its critical role in cytokine release and inflammation following exposure to DEP and WFSE. This is the first report of NF-κB activation in human microglia exposed to air pollutants. Conclusions These results highlight the distinct and potentially harmful effects of DEP and WFSE on immune and inflammatory responses in MDMi, particularly in ageing populations, with significant implications for brain health. DEP triggers acute oxidative stress and inflammatory responses, while WFSE induces more prolonged effects, especially in aged microglia. Both pollutants activate the MAPK and NF-κB pathways and exhibit unique cytokine profiles, underscoring their overlapping yet distinct mechanisms of action. These findings advance our understanding of air pollutant-induced neuroinflammation and its contribution to neurodegeneration, providing a foundation for developing targeted interventions to mitigate the neurotoxic effects of air pollution.

The escalating issue of air pollution contributes to an alarming number of premature fatalities each year, thereby posing a significant threat to global health. The focus of recent research has shifted towards understanding its potential association with neurodegenerative diseases, specifically Alzheimer's disease (AD). AD is recognised for its characteristic deposition of toxic proteins within the brain, leading to a steady deterioration of cognitive capabilities, memory failure, and ultimately, death. There is burgeoning evidence implying that air pollution may be a contributing factor to this protein build up, thereby intensifying the course of AD. It has been demonstrated that the olfactory system, responsible for smell perception and processing, acts as a potential gateway for airborne pollutants to inflict brain damage. This review aims to elucidate the relationship between air pollution, olfactory deterioration, and AD. Additionally, this review aims to highlight the potential mechanisms through which pollutants might instigate the development of AD and the role of the olfactory system in disease pathogenesis. Moreover, the diverse model systems employed in exploring the correlation, public health policy ramifications, and prospective directions for future research will be discussed.

The scarcity of effective biomarkers and therapeutic strategies for predicting disease onset and progression in Alzheimer’s disease (AD) is a major challenge to improve much-needed therapeutic outcomes. Conventional drug discovery approaches have been unsuccessful in providing efficient interventions due to their ‘one-size-fits-all’ nature. As an alternative, personalised drug development holds promise to pre-select responders and identify suitable drug efficacy indicators. In this study, we established a preclinical drug testing strategy by assessing the efficacy of anti-inflammatory drugs in 2D and 3D in vitro models of monocyte-derived microglia-like cells (MDMi) derived from AD and mild cognitive impairment (MCI) patients, and matched healthy individuals. We observed that the cytokine inflammatory profiles of MDMi in response to drugs clustered separately between cohorts, with the 3D model showing a more defined separation between healthy and patient donors than 2D. By ranking donor and cytokine responses to drugs, we identified that drug efficacy was limited in AD patients and involved cohort-specific responsive cytokines. Our findings suggest that MDMi models have the potential to predict disease progression, stratify responders and identify biomarkers for estimating the efficacy of microglia-targeted drugs. Together, our pipeline could serve as a valuable tool to enhance the clinical translational value of preclinical drug screens and ultimately improve drug outcomes for AD.

An early symptom of Alzheimer’s disease (AD) is an impaired sense of smell, for which the molecular basis remains elusive. Here, we generated human olfactory neurosphere-derived (ONS) cells from people with AD and mild cognitive impairment (MCI), and performed global RNA sequencing to determine gene expression changes. ONS cells expressed markers of neuroglial differentiation, providing a unique cellular model to explore changes of early AD-associated pathways. Our transcriptomics data from ONS cells revealed differentially expressed genes (DEGs) associated with cognitive processes in AD cells compared to MCI, or matched healthy controls (HC). A-Kinase Anchoring Protein 6 (AKAP6) was the most significantly altered gene in AD compared to both MCI and HC, and has been linked to cognitive function. The greatest change in gene expression of all DEGs occurred between AD and MCI. Gene pathway analysis revealed defects in multiple cellular processes with aging, intellectual deficiency and alternative splicing being the most significantly dysregulated in AD ONS cells. Our results demonstrate that ONS cells can provide a cellular model for AD that recapitulates disease-associated differences. We have revealed potential novel genes, including AKAP6 that may have a role in AD, particularly MCI to AD transition, and should be further examined.

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