Durrington, H. J. | Search bioRxiv

bioRxiv2025

The club cell circadian clock regulates temporal patterns in leukocyte trafficking in chronic allergic airways disease

RationaleAsthma displays temporally variable symptoms which worsen overnight, corresponding with a nocturnal increase in airway eosinophils. The molecular clock within the club cell of the bronchial epithelium is a key driver of lung rhythmic processes, however, its role in chronic allergic airways disease (AAD) is not known. Elucidating the role of the club cell clock in regulating rhythmic inflammation in AAD could lead to new therapeutic advances. ObjectivesTo investigate the club cell molecular clock regulation of leukocyte trafficking in chronic AAD. Methodsccsp-bmal1 KO mice (which lack a functional clock in club cells) and littermate control mice underwent a 5-week chronic house dust mite (HDM) model of AAD, following which leukocyte populations and cytokines from blood, lung and airway compartments were quantified in a 24-hour time-course. Airway epithelial cells were cultured and transepithelial electrical resistance measured to explore circadian variability in barrier permeability and impact of pharmacological modulation of the clock. Main ResultsLeukocyte populations accumulate in the blood, lung and airways of HDM exposed mice in a time-of-day dependent manner, with time of peak accumulation dependent on cell type. This temporal gating of leukocyte accumulation is controlled and coordinated by the club cell circadian clock, which also regulates airway barrier integrity. Targeting REVERBa (a component of the molecular circadian clock), was effective at modifying airway barrier permeability achieving reduced transepithelial leukocyte migration. ConclusionsThe club cell clock gates leukocyte trafficking signals and airway barrier integrity by time of day in chronic allergic airway inflammation.

immunology↗

bioRxiv2019

The circadian clock protein REVERBα inhibits pulmonary fibrosis development

Pulmonary inflammatory responses lie under circadian control; however the importance of circadian mechanisms in fibrosis is not understood. Here, we identify a striking change to these mechanisms resulting in a gain of amplitude and lack of synchrony within pulmonary fibrotic tissue. These changes result from an infiltration of mesenchymal cells, an important cell type in the pathogenesis of pulmonary fibrosis. Mutation of the core clock protein REVERB in these cells exacerbated the development of bleomycin-induced fibrosis, whereas mutation of REVERB in club or myeloid cells had no effect on the bleomycin phenotype. Knockdown of REVERB revealed regulation of the poorly described transcription factor TBPL1. Both REVERB and TBPL1 altered integrin{beta}1 focal adhesion formation, resulting in increased myofibroblast activation. The translational importance of our findings was established through analysis of two human cohorts. In the UK Biobank circadian strain markers (sleep length, chronotype and shift work) are associated with pulmonary fibrosis making them novel risk factors. In a separate cohort REVERB expression was increased in human idiopathic pulmonary fibrosis (IPF) lung tissue. Pharmacological targeting of REVERB inhibited myofibroblast activation in IPF fibroblasts and collagen secretion in organotypic cultures from IPF patients, suggesting targeting REVERB could be a viable therapeutic approach.\n\nSignificanceThe circadian clock plays an essential role in energy metabolism, and inflammation. In contrast the importance of the clock in the pathogenesis of fibrosis remains poorly explored. This study describes a striking alteration in circadian biology during pulmonary fibrosis where the relatively arrhythmic alveolar structures gain circadian but desynchronous rhythmicity due to infiltration by fibroblasts. Disruption of the clock in these cells, which are not widely implicated in circadian pathophysiology, results in a pro-fibrotic phenotype. Translation of these findings in humans revealed previously unrecognised important circadian risk factors for pulmonary fibrosis (sleep length, chronotype and shift work). In addition, targeting REVERB repressed collagen secretion from human fibrotic lung tissue making this protein a promising therapeutic target.

cell biology↗