Deficiency of circadian gene cryptochromes in bone marrow-derived cells protects against atherosclerosis in LDLR-/- mice.

Cryptochromes are photoreceptors that mediate the circadian entrainment by light in plants and animals. They are also involved in magnetic field sensing in some animals. Recent studies suggest that cryptochromes play an essential role in metabolism and cardiovascular disease. However, the tissue-specific function of cryptochromes in atherosclerosis is unknown. We transplanted bone marrow from wild-type (WT) and cryptochrome 1/2 knockout (Cry1/2 KO) mice into irradiated recipient low-density lipoprotein receptor knockout (LDLR-/- ) mice and induced atherosclerosis with a high cholesterol diet for 12 weeks. There was a reduction in atherosclerotic plaques and macrophage accumulation in the aorta of LDLR-/- mice that received Cry1/2 KO bone marrow compared to mice that received WT bone marrow. Bone marrow-derived macrophages (BMDMs) from Cry1/2 KO mice exhibited impaired uptake of low-density lipoprotein, and subsequently, impaired foam cell formation. Analysis of macrophage mRNA circadian oscillations revealed that the circadian rhythm of the LDLR mRNAs was lost in Cry1/2 KO BMDMs. Reinstalling the circadian oscillatory LDLR mRNAs using adenovirus into the BMDMs was able to rescue the lipid uptake and foam cell formation function. However, the noncircadian oscillatory LDLR mRNAs exhibited reduced ability to rescue the macrophage functions. These findings indicate that cryptochromes in bone marrow-derived cells are critical mediators of atherosclerosis through regulation of the LDLR mRNA circadian rhythm. Therapeutic measures targeting cryptochromes in the macrophage may have important implications for atherosclerosis.