Heart rate reduction with ivabradine in the early phase of atherosclerosis is protective in the endothelium of ApoE-deficient mice

Ivabradine, a heart rate reducing agent, protects the vascular system by unidentified mechanisms. We sought to determine the effects of the treatment with ivabradine, started before plaque formation, on early transcriptional changes and endothelium lesions in regions of aorta subjected to disturbed blood flow. Six week-old apolipoprotein E-deficient (ApoE-/-) mice, fed a low-fat diet, were treated with ivabradine to determine the effect on transcriptional changes (2-and 4-week treatment) and on lesions formation (19-week treatment) in the endothelium of the aortic arch. Microarrays analysis (60k probes) of endothelium-enriched RNA was carried out to detect changes in gene expression induced by treatment. Endothelium damage was assessed by en-face immunofluorescence staining for vascular endothelial (VE) cadherin. According to microarray analysis, 930 transcripts were affected by the treatment. We found downregulation of pro-apoptotic and pro-inflammatory genes, the majority of which are nuclear factor-κB (NF-κB)-and/or angiotensin II-regulated genes, and upregulation of anti-inflammatory genes. Many shear stress-responsive genes were affected by the treatment and the MAPK, Notch signalling and sterol metabolic processes were among the most significantly affected pathways. Consistently, we observed increased levels of Hes5, a Notch target gene, together with a reduction of endothelium damage, in the lower aortic arch of treated- compared with untreated- mice. We concluded that an early treatment with ivabradine protected the endothelium of the aortic arch of ApoE-/- mice. Activation of the Notch signalling could be part of the mechanism underlying this protection.