It has already been shown that the renin-angiotensin system (RAS) is involved in intimal calcification. Infusion of Ang II into ApoE−/− mice enhances calcification processes via AT1 receptors. However, the role of the protective arm of the RAS, including the AT2R, in calcification processes has not yet been studied. Since AT2R stimulation counterbalances most of the AT1R actions, it may have a therapeutic potential for the treatment of intimal calcification. Here we would like to test the hypothesis that AT2 receptor inhibits intimal calcification and to elucidate the underlying molecular mechanisms.
1. ApoE−/− mice under high-fat diet will be infused with vehicle or with Ang II and treated either with the AT2R agonist C21, the AT2R antagonist PD123319 or with the AT1 receptor blocker olmesartan. Calcium deposition will be assessed by molecular imaging (ESR11). Expression of calcification-related genes, pro-inflammatory cytokines, receptor activator of nuclear factor-κB ligand (RANKL) system and angiotensin receptors will be analysed by qPCR and immunohistology.
2. Aortic VSMC will be isolated from WT or AT2R knock out mice, cultured in normal or osteogenic medium. Cells will be stimulated with Ang II or RANKL and treated with C21, PD123319 or with olmesartan. Calcification will be assessed by Alizarin Red staining. Differential gene expression will be analysed by Affymetrix GeneChip® Transcriptome Array, covering both coding and non-coding RNA and validated by qPCR. In addition, it will be investigated whether AT2R stimulation can prevent phenotypic switching of VSMC from contractile to synthetic VSMC (ESR3 and 7).
3. Differentially expressed genes in above-mentioned in vitro experiments will be analysed in samples from in vivo studies.
4. Relevant pathways will be dissected by GO and pathway analysis of microarray data (ESR8).