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Inflammatory changes associated with circadian variation in pulmonary function in subjects with mild asthma
E A B Kelly1, J J Houtman, N N Jarjour
1Pulmonary and Critical Care Medicine Section, Department of Medicine, University of Wisconsin, Madison, WI 53792, USA. eak@medicine.wisc.edu
Summary
Asthma patients experience daily lung function changes linked to increased airway CD4+ T cells and IL-5 production at night. These variations in inflammation and lung function occur continuously throughout the day and night.
Area of Science:
- Immunology
- Pulmonology
- Circadian Biology
Background:
- Asthma is characterized by nocturnal worsening of airway inflammation and reduced pulmonary function.
- Understanding circadian variations in asthma is crucial for effective management.
Purpose of the Study:
- To investigate daily changes in airway inflammation in mild atopic asthma.
- To explore the relationship between these inflammatory changes and pulmonary function variations.
Main Methods:
- Bronchoalveolar lavage (BAL) performed at 04:00 and 16:00 hours in 12 mild atopic asthma subjects.
- Analysis of BAL cells for lymphocyte phenotype and cytokine production (IL-5) after phytohaemagglutinin (PHA) stimulation.
- Measurement of pulmonary function, specifically forced expiratory volume in 1 second (FEV1).
Main Results:
- Higher numbers of BAL lymphocytes and CD4+ T cells were observed at 04:00 compared to 16:00.
- Lower FEV1 at 04:00 correlated with increased BAL lymphocytes and CD4+ cells.
- IL-5 production by BAL cells correlated with eosinophils and CD4+ cells, and IL-5 changes related linearly to FEV1 circadian variation.
Conclusions:
- Circadian variations in lung function in asthma are linked to elevated airway CD4+ T cells and their IL-5 generating capacity.
- These daily fluctuations in inflammation and lung function in mild asthma represent a continuous spectrum.