MicroRNAs in angiogenic response to oxidized phospholipids

MicroRNAs, a class of noncoding RNAs, are known to regulate gene expression at post-transcriptional level by either suppressing translation or inducing decay of mRNA mainly via base-paring to the 3-untranslated regions of transcripts. microRNAs are thought to regulate production of thousands of proteins. microRNAs were demonstrated to play important role in embryonic development and human pathology. Recent publications showed that miRNAs also modulate formation and growth of blood vessels. Angiogenesis in atherosclerotic lesions plays critical role in progression of disease and formation of vulnerable plaques. Recently, we have demonstrated that oxidized phospholipids known to be present in atherosclerotic plaque can stimulate angiogenesis in several in vitro and in vivo experimental models. In addition, oxidized phospholipids are known to affect inflammatory and thrombogenic properties of endothelial cells and therefore can further promote atherosclerosis and its complications. Altogether these data raise the question about the role of microRNAs in OxPL-induced angiogenesis. The goal of the proposed study is to identify microRNAs mediating angiogenic effects of OxPLs. It is planned to determine the profile of microRNAs expression in endothelial cells treated with oxidized phospholipids. At the second stage of the project we will examine effects of identified microRNAs on angiogenesis induced by OxPLs in vitro and in vivo. Next, we will identify genes expression of which depend on OxPL-regulated microRNAs. Finally we will study functional importance of identified microRNA-dependent genes in OxPL-induced angiogenesis. In summary, we will clarify mechanisms of OxPLs action and provide further insight into the role of miRNAs in the regulation of angiogenic status of endothelial cells by OxPLs. Our findings may help in identifying new therapeutic targets and development of new RNA-based therapies.

Atherosclerosis and its clinical complications, such as myocardial infarction and stroke, are the leading cause of death worldwide. Angiogenesis, the formation and growth of blood vessels, in atherosclerotic lesions plays a critical role in the progression of the disease. We have demonstrated that oxidized phospholipids (OxPL), which are known to be present in atherosclerotic plaques, can induce angiogenesis and inflammation, and therefore can further promote atherosclerosis and its complications. Moreover MicroRNAs (miRNAs) are known as modulators of the formation and growth of blood vessels. miRNAs are a class of noncoding RNAs and are known to regulate gene expression at post-transcriptional level by either suppressing translation or inducing decay of mRNA. The goal of this project was to identify miRNAs that are mediating the angiogenic effects of OxPL.We performed profiling of miRNA expression in endothelial cells treated with OxPL and found upregulation of miR-663 and miR-320a miRNAs. Both were inducing expression of the major angiogenic factor VEGF in endothelial cells. Moreover, knockdown of both miRNAs attenuated OxPL-induced expression of VEGF, thereby suggesting a critical role of these miRNAs in OxPL-induced angiogenesis. Finally we demonstrated that miR-320a and miR-663 effects on VEGF expression are mediated via regulation of the transcription factors NRF2 and ATF4. In addition, we found that miR-320a and miR-663 are involved in the regulation of the expression of electrophilic stress response cytoprotective genes via the NRF2 transcription factor and unfolded protein response genes via the ATF4 transcription factor. These findings allow hypothesizing that miR-663 and miR-320a play a general role in controlling ATF4- and NRF2-dependent genes.Our findings point to miR-663 and miR-320a as prominent therapeutic targets for the development of new RNA-based therapies aimed for the treatment of atherosclerotic disease.