Unravelling the influence of circadian timing on anti-inflammatory mechanisms

About the Project

Immune mediated inflammatory diseases (IMIDs) are a diverse group of chronic conditions which affect over 1 million people in the UK and represent a significant health burden. They often show diurnal variation in symptom severity and biomarker abundance. Key examples include asthma, rheumatoid arthritis and inflammatory bowel disease, where symptoms are heightened at certain times of day. Recent work in our laboratory, using pre-clinical models of inflammatory arthritis, colitis and allergic lung inflammation, has revealed differences in the cellular composition of inflamed tissue between daytime and nighttime (DOI: 10.1016/j.isci.2025.113183; DOI: 10.1038/s41467-020-15525-0; DOI: 10.1101/2025.08.06.668949). We have demonstrated that a specific subset of anti-inflammatory cells, called regulatory T cells (Tregs), show daily variation in their function (e.g. trafficking, suppressive capacity) which drives diurnal transitions in inflammatory state.

Tregs are a subset of T lymphocytes defined by their expression of the transcription factor FoxP3. Tregs are crucial for maintenance of peripheral tolerance, preventing autoimmunity and limiting chronic inflammation. They are abundant within inflamed tissue, where they suppress the pro-inflammatory action of effector immune cells via contact dependent and independent mechanisms.

24h rhythms in the function of immune cells are mediated by the circadian clock and are a consequence of the actions of cell intrinsic molecular clocks and cell extrinsic rhythmic factors regulated by environment and behaviour, including hormones (such as glucocorticoids) and feeding-derived signals. This project sets out to reveal the influence of the circadian timing system on Treg function, exploring the relative importance of intrinsic clocks and rhythmic extrinsic signals for driving daily variation in function. Using in vivo and in vitro approaches we will establish mechanisms underpinning daily variation in inflammatory processes.

Methods utilised in this project will include: in vivo studies in mice; RNA sequencing; ex vivo cell culture and co-culture assays; flow cytometric cellular phenotyping and QPCR. We will use a murine model to isolate Tregs from inflamed tissue (gut) across a 24h cycle for RNA sequencing. Gene targets will be validated at the protein level using flow cytometry. This will enable assessment of temporal variation in the Treg transcriptome and function in an inflammatory environment and evaluation of circadian clock activity. To explore how time of day influences Treg trafficking to sites of inflammation we will use a combination of in vivo (Treg adoptive transfer) and in vitro (co-culture systems) approaches. The importance of specific signalling pathways for trafficking capacity will be confirmed via manipulation (e.g. genetic, pharmacological) of candidate factors. Finally, we will build on this knowledge and test the role of rhythmic extrinsic signals (glucocorticoid hormones and feeding derived signals) on rhythmic Treg behaviour using modification of food availability and genetic manipulation of Tregs. This will reveal drivers of rhythmic anti-inflammatory activity and open avenues for manipulation for therapeutic gain.