High-density lipoprotein regulates angiogenesis by affecting autophagy via miRNA-181a-5p

We previously demonstrated that normal high-density lipoprotein(nHDL)can promote angiogenesis,whereas HDL from patients with coronary artery disease(d HDL)is dysfunctional and impairs angiogenesis.Autophagy plays a critical role in angiogenesis,and HDL regulates autophagy.However,it is unclear whether n HDL and d HDL regulate angiogenesis by affecting autophagy.Endothelial cells(ECs)were treated with n HDL and d HDL with or without an autophagy inhibitor.Autophagy,endothelial nitric oxide synthase(e NOS)expression,miRNA expression,nitric oxide(NO)production,superoxide anion(O2^(·-))generation,EC migration,and tube formation were evaluated.n HDL suppressed the expression of miR-181a-5p,which promotes autophagy and the expression of e NOS,resulting in NO production and the inhibition of O2^(·-)generation,and ultimately increasing in EC migration and tube formation.d HDL showed opposite effects compared to n HDL and ultimately inhibited EC migration and tube formation.We found that autophagy-related protein 5(ATG5)was a direct target of miR-181a-5p.ATG5 silencing or miR-181a-5p mimic inhibited n HDL-induced autophagy,e NOS expression,NO production,EC migration,tube formation,and enhanced O2^(·-)generation,whereas overexpression of ATG5 or miR-181a-5p inhibitor reversed the above effects of d HDL.ATG5 expression and angiogenesis were decreased in the ischemic lower limbs of hypercholesterolemic low-density lipoprotein receptor null(LDLr^(-/-))mice when compared to C57BL/6 mice.ATG5 overexpression improved angiogenesis in ischemic hypercholesterolemic LDLr^(-/-)mice.Taken together,nHDL was able to stimulate autophagy by suppressing miR-181a-5p,subsequently increasing e NOS expression,which generated NO and promoted angiogenesis.In contrast,d HDL inhibited angiogenesis,at least partially,by increasing miR-181a-5p expression,which decreased autophagy and e NOS expression,resulting in a decrease in NO production and an increase in O2^(·-)generation.Our findings reveal a novel mechanism by which HDL affects angiogenesis by regulating autophagy and provide a therapeutic target for d HDL-impaired angiogenesis.

High-density lipoprotein regulates angiogenesis by long non-coding RNA HDRACA

Normal high-density lipoprotein(nHDL)can induce angiogenesis in healthy individuals.However,HDL from patients with coronary artery disease undergoes various modifications,becomes dysfunctional(dHDL),and loses its ability to promote angiogenesis.Here,we identified a long non-coding RNA,HDRACA,that is involved in the regulation of angiogenesis by HDL.In this study,we showed that nHDL downregulates the expression of HDRACA in endothelial cells by activating WW domain-containing E3 ubiquitin protein ligase 2,which catalyzes the ubiquitination and subsequent degradation of its transcription factor,Kruppel-like factor 5,via sphingosine 1-phosphate(S1P)receptor 1.In contrast,dHDL with lower levels of S1P than nHDL were much less effective in decreasing the expression of HDRACA.HDRACA was able to bind to Ras-interacting protein 1(RAIN)to hinder the interaction between RAIN and vigilin,which led to an increase in the binding between the vigilin protein and proliferating cell nuclear antigen(PCNA)mRNA,resulting in a decrease in the expression of PCNA and inhibition of angiogenesis.The expression of human HDRACA in a hindlimb ischemia mouse model inhibited the recovery of angiogenesis.Taken together,these findings suggest that HDRACA is involved in the HDL regulation of angiogenesis,which nHDL inhibits the expression of HDRACA to induce angiogenesis,and that dHDL is much less effective in inhibiting HDRACA expression,which provides an explanation for the decreased ability of dHDL to stimulate angiogenesis.