Circadian Gene Bmal1 Regulates Diurnal Oscillations of Ly6Chi Inflammatory Monocytes

KD Nguyen, SJ Fentress, Y Qiu, K Yun, JS Cox… - Science, 2013 - science.org
KD Nguyen, SJ Fentress, Y Qiu, K Yun, JS Cox, A Chawla
Science, 2013science.org
Circadian clocks have evolved to regulate physiologic and behavioral rhythms in
anticipation of changes in the environment. Although the molecular clock is present in innate
immune cells, its role in monocyte homeostasis remains unknown. Here, we report that
Ly6Chi inflammatory monocytes exhibit diurnal variation, which controls their trafficking to
sites of inflammation. This cyclic pattern of trafficking confers protection against Listeria
monocytogenes and is regulated by the repressive activity of the circadian gene Bmal1 …
Circadian clocks have evolved to regulate physiologic and behavioral rhythms in anticipation of changes in the environment. Although the molecular clock is present in innate immune cells, its role in monocyte homeostasis remains unknown. Here, we report that Ly6Chi inflammatory monocytes exhibit diurnal variation, which controls their trafficking to sites of inflammation. This cyclic pattern of trafficking confers protection against Listeria monocytogenes and is regulated by the repressive activity of the circadian gene Bmal1. Accordingly, myeloid cell-specific deletion of Bmal1 induces expression of monocyte-attracting chemokines and disrupts rhythmic cycling of Ly6Chi monocytes, predisposing mice to development of pathologies associated with acute and chronic inflammation. These findings have unveiled a critical role for BMAL1 in controlling the diurnal rhythms in Ly6Chi monocyte numbers.
AAAS