Circadian Blood Profiling in Asthma

Abstract

Asthma is a chronic disease of the airways, Circadian rhythms are patterns of behaviours which follow a 24 hour cycle. Peripheral clocks are synchronised by the suprachiasmatic nucleus, with daily oscillations driven by the transcription-translation feedback loop. Asthma is a rhythmic disease with symptoms and clinical parameters varying by time of day. Main focus in asthma pathogenesis points to the lungs, however obtaining samples directly from the lung in humans requires an invasive procedure. Thus, this project focuses on possible alteration to clocks in blood immune cells. Furthermore, several clinical studies suggest timing of inhaled corticosteroids, might be beneficial with increased efficacy in the afternoon, therefore we hypothesised if this extends to in vitro treatment of cells. Aims: 1. To assess variation in airway narrowing (FEV1) and FeNO in both groups, 2. To determine changes in blood cortisol levels and in blood immune cell number in asthma and healthy, 3. To compare clock gene expression in whole blood and peripheral cell mononucleocyes (PBMCs) and assess clock gene rhythmicity, 4. To assess the response of cultured PBMCs to Dexamethasone (DEX) treatment at 4:00pm and 4:00am. Ten healthy volunteers and ten adults with atopic asthma were recruited. Samples were collected at 4:00pm, 9:00pm, 4:00am and 9:00am and RNA isolated, from which expression of the clock genes ARNTL1, PER2, PER3, NR1D1 and CRY1 was measured. PBMCs were isolated using ficoll density gradient method and cultured for 2 hours with lipopolysaccharide in the presence of absence DEX. The conditioned media was collected and cytokine analysis performed. Expression of PER2 and PER3 was increased in asthma at night, while expression of PER3 and NR1D1 was significantly rhythmicity in asthma. Cytokine analysis revealed an increase in DEX sensitivity at 4:00pm in asthma compared to healthy, while time of day differences in DEX response were recorded in individual analytes. The differences in local clocks are a novel finding, suggesting clock gene expression is altered in blood cells from asthmatics. An increase in DEX sensitivity in asthma at 4:00pm supports current chronotherapy studies suggesting steroids should be taken in the afternoon.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	John Blaikley (Supervisor), Hannah Durrington (Supervisor) & Polly Downton (Supervisor)