MicroRNA-21 controls the circadian regulation of apoptosis in atherosclerotic lesions. MicroRNA-21 controls the circadian regulation of apoptosis in atherosclerotic lesions

Atherosclerosis is a leading cause of death due to the rupture of arterial lesions characterized by a necrotic core and inflammatory activity. Although lesion vulnerability follows a diurnal pattern with a higher incidence of rupture in the morning, the role of circadian rhythms in atherosclerotic lesions is unclear. Here we show that apoptosis in lesions follows a diurnal pattern that is controlled through the circadian regulation of the pro-apoptotic XIAP associated factor 1 (Xaf1) by the Mir21 strands. The increased apoptosis during the transition from the inactive to the active phase is not matched with the efferocytic removal of dead cells resulting in increased necrotic core formation. Lack of Mir21 expression in macrophages decreases atherosclerosis and necrotic core formation in mice, suggesting that Mir21-mediated diurnal apoptosis promotes lesion growth. In human atherosclerotic lesions, apoptosis also follows a diurnal pattern with a peak in the morning and oscillates in-phase with XAF1 expression and anti-phase with miR-21 expression. Thus, diurnal apoptosis regulated by a Mir21-controlled macrophage death clock may contribute to circadian regulation of lesion vulnerability. Overall design: Gene expression in aortic arches was compared between BM Mir21–/– mice and BM Mir21+/+ mice after 12 weeks of an HFD feeding period by microarray analysis (n=3 mice per group).

动脉粥样硬化（Atherosclerosis）是引发死亡的首要病因，其诱因是伴有坏死核心与炎症活性的动脉粥样硬化斑块破裂。尽管斑块易损性存在昼夜节律特征，清晨斑块破裂的发生率更高，但昼夜节律在动脉粥样硬化斑块中的作用仍不明确。本研究证实，斑块内的细胞凋亡（apoptosis）呈现昼夜节律模式，该模式由Mir21链通过对促凋亡因子XIAP相关因子1（Xaf1）的昼夜节律调控所介导。机体从静息期向活动期过渡时，凋亡水平升高，但这一过程未能通过胞葬作用有效清除死亡细胞，进而导致坏死核心形成增多。巨噬细胞中Mir21表达缺失可减轻小鼠的动脉粥样硬化病变与坏死核心形成，提示Mir21介导的昼夜节律性凋亡可促进斑块生长。在人类动脉粥样硬化斑块中，细胞凋亡同样呈现昼夜节律模式，于清晨达到峰值，且其振荡规律与XAF1表达同相、与miR-21表达反相。综上，由Mir21调控的巨噬细胞死亡时钟所介导的昼夜节律性凋亡，可能参与斑块易损性的昼夜节律调控。
整体实验设计：高脂饮食（High-Fat Diet, HFD）喂养12周后，通过微阵列分析（microarray analysis）比较骨髓（Bone Marrow, BM）Mir21基因敲除小鼠与野生型骨髓Mir21+/+小鼠的主动脉弓基因表达水平，每组纳入3只实验小鼠。