Introduction
The circadian rhythm is characterized by biological oscillations
occurring into a period of 24 hours, being responsible for a normal
functioning of all organic systems, which may be influenced by
variations in the light, temperature, sleeping timing and quality and
different types of stress1 Shiftwork scale is
characterized by working time outside the standard hours of 7:00 am to
6:00 pm and it is believed to negatively affects circadian rhythm,
resulting in impairment of different organs and physiological
systems2.
In this way, is widely accepted that alterations in the circadian rhythm
can negatively affects the immune system3,4 endocrine
and metabolic response5, cardiovascular
response5 and also the pulmonary
response6. Specifically, on the immune-regulated
pulmonary response, it has been demonstrated that circadian rhythm
drives bronchoconstriction/bronchodilatation, airway resistance,
respiratory symptoms, which in summary may leads to exacerbation of
respiratory diseases, particularly to chronic respiratory diseases, such
as asthma4 and chronic obstructive pulmonary disease
(COPD)7. However, concerning the immune-regulated
pulmonary response, the effects of altered circadian rhythm on pulmonary
cytokines, has been never investigated.
In fact, the alterations of circadian rhythm may lead to dysfunction of
pulmonary but certainly of the systemic immune
response3,4,6. In this context, it has been
demonstrated that human monocytes obtained from individuals during the
night, specifically during the sleep timing, release increased amounts
of IL-12 (a pro-inflammatory cytokine) in response to endotoxin
stimulation, while monocytes obtained during the day, responded to
increased release of IL-10 (a immunoregulatory and anti-inflammatory
cytokine)8. In the same way, establishing a causal
nexus, some studies have demonstrated that the frequency and severity of
exacerbations of COPD and asthma are increased specially during the
night and in the early hours of the morning, which are hallmarks of the
interference of circadian rhythm4,7. However,
concerning the key role of humoral response, measured by analysis of
cytokines, at the moment, no study has evaluated the possible
alterations in the cytokine’s levels in the lungs in response to chronic
stress.
Thus, the present study investigated for the first time the effects of
chronic alteration of circadian rhythm in shiftwork scale policemen
compared to civil men working in a diurnal constant scale, on the
pulmonary immune response and function, as well as on the cellular and
humoral systemic immune response.