Tissue microenvironments within chronic inflammatory disease sites, such as the synovial compartment within rheumatoid arthritis (RA) patients contains a plethora of factors to drive immune responses. However, one specific characteristic that is commonly found at these sites is the presence of tissue hypoxia. Therefore, both resident and infiltrating immune cells need to adapt to these microenvironments in order to survive and function to promote chronic inflammation. Adaptation to hypoxia requires a level of metabolic reprogramming for this purpose. Therefore, this thesis aimed to examine what the metabolic consequences were for human monocytes that were adapting into hypoxic sites and to interrogate what role these metabolic pathways had in driving specific functions in hypoxic conditions. Metabolomic analyses reveal that hypoxia induces metabolic alterations in human monocytes, including the decrease in abundance of carnitine metabolites, important for subsequent fatty acid oxidation (FAO), and increases in glycolytic metabolites. Furthermore, hypoxia exacerbated the release of pro- inflammatory mediators in LPS activated monocytes, such as CCL20 and IL-1β. Manipulation of carnitine metabolites identify a role for FAO in the production of CCL20, and in the regulation of IL-1β release. To mimic the RA synovial environment more thoroughly in vitro, human monocytes were cultured in cell culture medium containing RA synovial fluid (RA-SF) under hypoxic conditions. Further metabolomics analysis revealed that monocytes accumulate a number of metabolites in comparison to untreated and LPS activated cells, suggesting that monocytes may enter a stasis-like phase when challenged with RA-SF. This was reflected by low level release of pro-inflammatory mediators under these conditions. Nevertheless, media supplementation with carnitine increased CCL20 production under RA-SF treatment, highlighting FAO may have a role in CCL20 release in several inflammatory contexts. This body of work shows that distinct metabolic pathways regulated by the extracellular environment may act in conjunction for the production of pro- inflammatory mediators in chronic inflammatory disease. This thesis highlights the influencing nature of tissue microenvironments on the functional capacity of myeloid cells by harnessing its metabolic machinery.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:754367 |
| Date | January 2018 |
| Creators | Rodgers, Lewis Craig |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/30725/ |
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