Natural compound bavachalcone promotes the differentiation of endothelial progenitor cells and neovascularization through the RORα-erythropoietin-AMPK axis.

Shuang Ling,Qian-Mei Zhou,Yuanyuan Chen,Jin-Wen Xu,Rong-Zhen Ni,Yan-Qi Dang,Yukio Yamori,Shuang Liang,Wei Feng,Katsumi Ikeda,Fujiang Guo,Yunyun Yuan

doi:10.18632/oncotarget.21036

Abstract

In cardiovascular diseases, endothelial function is impaired and the level of circulating endothelial progenitor cells (EPCs) is low. This study investigated whether the natural bioactive component bavachalcone (BavaC) induces the differentiation of EPCs and neovascularization in vivo; the underlying mechanisms were also examined. We observed that the treatment of rat bone marrow–derived cells with a very low dose of BavaC significantly promoted EPC differentiation. In our hindlimb ischemia models, low–dose BavaC administered orally for 14 days stimulated the recovery of ischemic hindlimb blood flow, increased circulating EPCs, and promoted capillary angiogenesis. The BavaC treatment of rat bone marrow cells for 24 h initiated the AMP–activated protein kinase (AMPK) activity required for the differentiation of EPCs. Further testing revealed that BavaC and CGP52608, a retinoic acid receptor–related orphan receptor α (RORα) activator, enhanced the activity of RORα1 and EPO luciferase reporter gene. BavaC treatment also elevated EPO mRNA and protein expression in vitro and in vivo and the circulating EPO levels in rats. By contrast, the RORα antagonist VPR66 inhibited BavaC–induced EPO reporter activity, and differentiation of bone marrow cells into endothelial progenitor cells. Overall, this study revealed that BavaC promotes EPC differentiation and neovascularization through a RORα–EPO–AMPK axis. BavaC can be used as a promising angiogenesis agent for enhancing angiogenesis and tissue repair.

Highlights

Erythropoietin (EPO), produced mainly in the renal interstitium, is a cytokine that stimulates erythrocyte differentiation [1,2]
We investigated whether EPO promotes endothelial progenitor cells (EPCs) differentiation by activating AMP–activated protein kinase (AMPK) activity and whether receptor α (RORα) modulates EPO expression in cells stimulated with BavaC or a small molecule RORα activator
The suspended cells cultured in the medium containing 1 or 2 μM BavaC showed earlier adherence than the control group on the fourth and seventh days. They were stained through immunofluorescence by using anti-CD34 or antivWF antibodies, and the results confirmed that these cells differentiated into EPCs (Figure 1B)

Summary

Introduction

Erythropoietin (EPO), produced mainly in the renal interstitium, is a cytokine that stimulates erythrocyte differentiation [1,2]. A previous study showed that EPO caused a significant mobilization of CD34+/CD45+ circulating endothelial progenitor cells (EPCs) in peripheral blood, and increased the number of functionally active EPCs [6]. Various signal transduction pathways are involved in the EPO-promoted differentiation and proliferation of EPCs. AMP-activated protein kinase (AMPK) is essential for the differentiation of EPCs, and can activate eNOS activity and mediate the effects of vasculogenesis in vivo [16]. A previous study demonstrated that AMPK transactivates eNOS through EPO [17]. The JAK2-STAT5 axis is another essential pathway for EPO signaling. A prior study suggested that EPO-induced endothelial cell proliferation involves the STAT5 phosphorylation and nuclear translocation pathway [22]. The aforementioned signaling pathways activated by EPO are essential for the proliferation and differentiation of EPCs

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Results

Conclusion