Circadian Disruption and Consequences on Innate Immunity and Inflammatory Response

Abstract

Circadian rhythms control almost all aspects of physiology and behavior, allowing temporal synchrony of these processes between each other, as well as with the external environment. In the immune system, daily rhythms of leukocyte functions can determine the strength of the immune response, thereby regulating the efficiency of defense mechanisms to cope with infections or tissue injury. The natural light/dark cycle is the prominent synchronizing agent perceived by the circadian clock, but this role of light is highly compromised by irregular working schedules and unintentional exposure to artificial light at night (ALAN). The primary concern is disrupted circadian control of important physiological processes, underlying potential links to adverse health effects. Here, we first discuss the immune consequences of genetic circadian disruption induced by mutation or deletion of specific clock genes. Next, we evaluate experimental research into the effects of disruptive light/dark regimes, particularly light-phase shifts, dim ALAN, and constant light on the innate immune mechanisms under steady state and acute inflammation, and in the pathogenesis of common lifestyle diseases. We suggest that a better understanding of the mechanisms by which circadian disruption influences immune status can be of importance in the search for strategies to minimize the negative consequences of chronodisruption on health.

Keywords: chronodisruption; circadian rhythms; inflammation; innate immunity; light at night; phase shifts.

Figure 1

Comparison of three disruptive light/dark regimes and their effects on the immune measures based on the current knowledge in laboratory animals. ALAN—artificial light at night; LD—standard light/dark cycle of 12/12 h; LL—constant light; WAT—white adipose tissue; WBCs—white blood cells; ZT—Zeitgeber time.