eprintid: 10167859 rev_number: 12 eprint_status: archive userid: 699 dir: disk0/10/16/78/59 datestamp: 2023-06-08 11:24:39 lastmod: 2023-06-08 11:24:39 status_changed: 2023-06-08 11:24:39 type: thesis metadata_visibility: show sword_depositor: 699 creators_name: Maggio, Annalisa title: Exploring the crosstalk between lipid metabolism and interferon signalling in human monocytes ispublished: unpub divisions: UCL divisions: B02 divisions: C10 divisions: D17 note: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Licence (https://creativecommons.org/licenses/by-nc-nd/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. abstract: Liver X receptors (LXRs) are lipid-activated transcription factors that modulate lipid metabolism and help regulate inflammation. Current literature reports evidence of a crosstalk between lipid metabolism and immune programs. In fact, IFNα is an antiviral cytokine that reduces cholesterol and fatty acid synthesis upon viral infection. However, LXR and IFNα signalling crosstalk in human monocytes has not been thoroughly explored and its understanding could help discern their impact on metabolic and inflammatory conditions such as atherosclerosis. The hypothesis underpinning this research is that crosstalk between LXR and IFNα signalling affects lipid metabolism and cell function in human monocytes. Healthy human monocytes were isolated and treated with LXR agonist GW3965 (GW), IFNα ±GW, LXR antagonist (GSK) and vehicle controls for 24 hours. Gene expression (qPCR and RNA-Sequencing), cholesterol and glycosphingolipids (flowcytometry), and lipid content (lipidomics) were assessed in each group. LXR stimulation with GW upregulated LXR-target genes including cholesterol efflux-associated genes (e.g., ABCA1) resulting in decreased plasma membrane cholesterol. Notably, GW-stimulation of LXR was partially abrogated by co-stimulation with IFNα, resulting in downregulation of ABCA1 and increased membrane cholesterol. GW+IFNα co-stimulation downregulated genes involved in lipoprotein, phospholipid, and tri/diacylglyceride metabolism (e.g., PAPP2B), a finding that was recapitulated by lipidomic analysis, whereby di/triacylglycerols and phospholipids were downregulated compared to GW or IFNα alone. LXR/INFα co-stimulation also influenced genes associated with immune pathways: ferroptosis (ACSL1, upregulated) and PD-1-signalling (PD-1/PD-L1, downregulated). Functionally, GW+IFNα neutralised HLA-DR expression (compared with GW/INFα alone), increased membrane glycosphingolipids and decreased proinflammatory cytokine production (IL-1β/IL-6), potentially by altering plasma membrane cholesterol and glycosphingolipid expression. The co-stimulation also modulated genes not significantly regulated by GW or INFα alone. In conclusion, IFNα affects LXR-signalling by differentially regulating genes/lipids involved in metabolism and immunity, suggesting a crosstalk that could influence monocyte function. These findings have potential implications for understanding atherosclerosis-risk in inflammatory conditions. date: 2023-04-28 date_type: published full_text_type: other thesis_class: doctoral_embargoed thesis_award: Ph.D language: eng verified: verified_manual elements_id: 2015246 lyricists_name: Maggio, Annalisa lyricists_id: AMAGG94 actors_name: Maggio, Annalisa actors_id: AMAGG94 actors_role: owner full_text_status: restricted pages: 281 institution: UCL (University College London) department: Division of Medicine thesis_type: Doctoral citation: Maggio, Annalisa; (2023) Exploring the crosstalk between lipid metabolism and interferon signalling in human monocytes. Doctoral thesis (Ph.D), UCL (University College London). document_url: https://discovery.ucl.ac.uk/id/eprint/10167859/2/Thesis_Annalisa%20Maggio.pdf