D2.390 - Effects of Cigarette Smoke on Expression and Rhythmicity ofr Core Circadian Genes in Peripheral Blood Mononuclear Cells (PBMC) and Bronchial Epithelial Cells
Background
The circadian rhythm (CR) system is an important mechanism in mammals that directs physiological, immunological, and behavioural rhythms for 24 hours. There are CR-related autonomous oscillators in the central clock in the hypothalamus and peripheral organs such as the lung. Although studies suggest that inhaled irritants such as cigarette smoke cause CR disruption, which can lead to the increased risk for systemic pathologies including immune diseases, the underlying mechanisms are not clear.
Method
Our objectives were to investigate; (i) the expression and rhythmicity of core CR genes such as BMAL1, CLOCK, PER2, DBP and CRY1 in PBMCs from non-smokers and smokers, and (ii) the effects of cigarette smoke extract (CSE) on expression and oscillation of these genes in human bronchial epithelial cells (BEAS-2B) at different time points using a LumiCycle device.
Results
The mRNA expression of CR genes in PBMCs from both non-smokers (p=0.035) and smokers (p=0.029) were found to be rhythmic; however, there was no significant difference between smokers and non-smokers. According to BioDare analysis, while amplitude and period of CR did not change, the phase was significantly higher in smokers (median=16.52 hrs), as compared to non-smokers (median= 11.9 hrs, p<0.01). In LumiCycle analysis, oscillation was evident in BEAS-2B cells, and CSE altered the oscillation, leading to a significant phase increase from the median of 3.77 hrs to 10.17 hrs (p<0.05). Similarly, CSE significantly induced expression of both PER2 protein (medians= 0.749 vs 0.467, p<0.05) and mRNA (medians= 1.359 vs 0.794, p=0.01) in BEAS-2B cells, whereas only protein expression of CRY1 enhanced by CSE.
Conclusion
In summary, our findings demonstrated that the phase of BMAL-1 was increased in PBMCs from smokers, which was associated with an increase in the phase and expression of PER2 and CRY1 in BEAS-2B cell cultures by CSE. We believe our findings form a basis for understanding the relationship between CR and cigarette smoking.
