Inflammatory leukocytes exhibit distinct rhythms in their recruitment to arteries and veins

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Acute cardiovascular complications occur predominantly at the onset of the behavioral activity phase and are the major cause of death in humans. Recent evidence points to a critical role for rhythmic leukocyte recruitment in the onset of vascular diseases. Whether rhythmically distinct leukocyte interactions between arteries and veins can drive vessel‐type‐specific cardiovascular complications is unknown. Here, we demonstrate rhythmic differences in the ability of leukocytes to adhere to arteries and veins in an acute inflammatory scenario. Using TNFα in combination with i.v. injected fluorescent antibodies, we performed in vivo imaging analyses of the carotid artery and the jugular vein of the same mice at different time points. Our data indicate that leukocyte recruitment to the jugular vein followed a robust rhythm (~3‐fold difference between day and night) whereas leukocyte adhesion to the carotid artery exhibited an altered oscillatory pattern. While similar circadian rhythmicity was detected in the expression of CD11b integrin levels on leukocytes adherent to both artery and vein, we observed an inverse oscillation in the expression of ICAM‐1 and VCAM‐1 between endothelial cells of these vessels. Altered rhythmicity resulted in a heightened susceptibility to vaso‐occlusion at different times (vein: 10 min at Zeitgeber time (ZT, time after light onset) 2 vs 5 min at ZT8; artery: 11 min at ZT2 vs 20 min at ZT8). Together, our data indicate distinct mechanisms that induce rhythmic leukocyte recruitment to arteries and veins and their potential implications in driving time‐of‐day‐dependent cardiovascular complications.Funded by the Emmy‐Noether‐Program of the German Research Foundation (DFG)