L1 Blood immune cells clock mechanism is altered in asthma, with a time-of-day dependent response to steroids in vitro

Asthma is a rhythmic disease, with symptoms, airway physiology and inflammation showing strong time-of-day differences. Biological rhythms in our bodies (circadian rhythms) occur through the action of clock genes, present in most cell types, including immune cell. Chronotherapy is administering a treatment at the most efficacious time of day. Previous studies suggest that 4:00pm is the most efficacious time of day for steroid administration in asthma.1 Objectives To determine if peripheral clocks in blood immune cells (PBMCs) differ in asthma compared to healthy. To determine if (PBMCs respond differently to steroids (dexamethasone, DEX), by time of day in asthma compared to healthy. 10 adults with mild/moderate asthma on regular ICS and 10 healthy individuals were studied overnight. Whole blood samples were collected at 9:00am, 4:00pm, 9:00pm and 4:00amand qPCRused to quantify clock gene expression (PER2). PBMCs extracted at 4:00pm and 4:00am, plated and cultured for 4 hours with either DEX alone, Lipopolysaccharide (LPS) or LPS with DEX. Supernatant was collected and analysed for cytokines using a Luminex 34-plex panel. Expression of PER2 was significantly different between asthma and healthy (p IL-6 expression increased following treatment with LPS by 356-fold at 4:00pm and 757-fold at 4:00am. Following combined LPS and DEX treatment mean differences in IL-6 expression were54-fold and 256-fold recorded at 4:00pm and 4:00am respectively, (figure 1b). This is the first time that clock gene expression has been measured in whole blood in asthma. Differences in expression of PER2 between asthma and health, suggest alteration in the clock mechanism in immune cells in asthma. Preliminary luminex data of IL-6 expression, presents an exciting possibility of a time-of-day dependent response to steroids in vitro. Further cytokine analysis will provide an insight on a mechanism behind changes in steroid efficacy and reveal possible pathways and chronotherapy targets which could be used in the clinic. Reference Pincus DJ, et al. Chronotherapy of asthma with inhaled steroids: The effect of dosage timing on drug efficacy. Journal of Allergy and Clinical Immunology 1995. 95(6): p. 1172–1178.