Bmal1 Downregulation Worsens Critical Limb Ischemia by Promoting Inflammation and Impairing Angiogenesis.

Lirong Xu,Qianyun Cheng,Junhao Jiang,Yang Shen,Yutong Liu,Ye Yuan,Xiaolang Jiang,Xu Li,Daqiao Guo,Changpo Lin

doi:10.3389/fcvm.2021.712903

Abstract

Critical limb ischemia (CLI) is the most advanced clinical stage of peripheral vascular disease with high mobility and mortality. CLI patients suffer from lower extremity rest pain, ulceration, and gangrene caused by insufficient blood and oxygen supply. Seeking for effective biomarkers and therapeutic targets is of great significance for improving the life quality of CLI patients. The circadian clock has been reported to be involved in the progression of kinds of cardiovascular diseases. Whether and how circadian genes play a role in CLI remains unknown. In this study, by collecting femoral artery and muscle specimens of CLI patients who underwent amputation, we confirmed that the circadian gene Bmal1 is downregulated in the CLI femoral artery and ischemic distal lower limb muscle. Furthermore, we verified that Bmal1 affects CLI by regulating lipid metabolism, inflammation, and angiogenesis. A hindlimb ischemia model performed in wild-type and Bmal1−/− mice confirmed that Bmal1 disruption would lead to impaired angiogenesis. In vitro experiments indicated that the decreased expression of Bmal1 would increase ox-LDL uptake and impair endothelial cell functions, including proliferation, migration, and tube formation. As for mechanisms, Bmal1 represses inflammation by inhibiting lipid uptake and by activating IL-10 transcription and promotes angiogenesis by transcriptionally regulating VEGF expression. In conclusion, we provide evidence that the circadian gene Bmal1 plays an important role in CLI by inhibiting inflammation and promoting angiogenesis. Thus, Bmal1 may be an effective biomarker and a potential therapeutic target in CLI.

Highlights

Critical limb ischemia (CLI) is an ischemic disease of the lower extremities caused by arterial stenosis and occlusion [1]
It was shown that there is a significant decreased expression of Bmal1 in CLI femoral artery specimens compared with the normal artery (Supplementary Figure 1A), suggesting that Bmal1 may play a protective role in the CLI occurrence and progression
Data are presented as mean ± SEM (n = 4, unpaired t-test). *p < 0.05 and **p < 0.01, Bmal1−/− vs. WT. (E) Dil-ox-LDL uptake by human umbilical vein endothelial cells (HUVECs), with the expression changes of Bmal1 measured by confocal microscopy

Summary

Introduction

Critical limb ischemia (CLI) is an ischemic disease of the lower extremities caused by arterial stenosis and occlusion [1]. It is a local manifestation of systemic atherosclerosis in the limbs. Bmal Disruption Aggravates CLI ischemic symptoms at the distal end of the artery [2]. There are numerous theories about the CLI etiology, including lipid deposition, inflammation, and thrombosis [2, 3]. Patients with peripheral arterial diseases often have accompanying kinds of severe comorbidities, including coronary artery disease, cerebrovascular disease, respiratory dysfunction, and end-stage renal disease [6]. It is urgent to clarify the detailed pathogenesis of CLI and seek out more efficient prediction and therapy methods

Objectives

Methods

Results

Conclusion