抄録
Background: Endothelial senescence is one of the major mechanisms contributing to vascular ageing, a complex process tightly associated with vascular inflammation, endothelial dysfunction and atherosclerosis. Angiotensin (Ang)-(1-7) is a heptapeptide of the renin-angiotensin system (RAS), which opposes several vasoactive and inflammatory actions of Ang II. Little is known on the capacity of Ang-(1-7) to protect against vascular ageing. In this study, we tested whether Ang-(1-7) could mitigate the senescence of cultured human umbilical vein endothelial cells (HUVEC) evoked by different stimuli. We further aimed to identify protective cellular pathways activated by Ang-(1-7), with particular focus on the antioxidant and anti-inflammatory Nrf2/heme oxygenase (HO)-1 axis and the anti-ageing protein klotho.
Methods: Cultured HUVEC were stimulated with Ang II (100 nM) or the cytokine interleukin-1β (2,5 ng/ml) for 18 h. Cell senescence was quantified by positive senescence-associated β-galactosidase (SA-β-gal+) staining. Vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were quantified by flow cytometry, while leukocyte-endothelium adhesion was determined using a flow chamber assay. Nrf2, HO-1 and klotho levels were determined by Western blot.
Results: Both Ang II and IL-1β; enhanced the fraction of SA-β-gal+ cells, together with increased expression of ICAM-1 and VCAM-1, resulting in a higher leukocyte adhesion to HUVEC monolayers. Ang-(1-7) (100 nM) attenuated all these actions through a mechanism that was prevented by the Mas receptor antagonist A779 (1 μM). Ang-(1-7) enhanced the levels of intracellular klotho, but also those of Nrf2 and HO-1. Interestingly, the HO-1 inhibitor Sn protoporphyrin (1 μM) dampened the anti-senescence action of both Ang-(1-7) and recombinant klotho (1 nM). Moreover, klotho silencing abolished the anti-senescence action of Ang-(1-7).
Conclusions: Ang-(1-7) counteracts endothelial cell senescence triggered by both RAS-dependent and -independent stimuli. An intracellular crosstalk between klotho and the Nrf2/HO-1 pathway seems to be on the basis of these protective properties of Ang-(1-7). Overall, the Ang-(1-7)/Mas axis arises as a novel pharmacological tool to attenuate endothelial senescence and vascular ageing.
