Abstract Body: Background: Aging increases risk for the development of vascular cognitive impairment and dementia (VCID). Impaired bioenergetics, mitochondrial oxidative phosphorylation (OxPhos) and glycolysis, in the brain microvascular endothelium induce neurovascular uncoupling, which is one of the underlying mechanisms of VCID. Angiotensin (Ang)-(1-7) and Alamandine (Ala) are vascular protective peptides of renin angiotensin system. Ang-(1-7) is generated by angiotensin-converting enzyme-2 (ACE2) from Ang II, and produces vascular protective effects by acting on Mas receptor (MasR). Ala has been shown to be derived from Ang A by ACE2 or from Ang-(1-7) by an enzyme, which is yet to be characterized, with decarboxylase activity or Mas related G-protein-coupled receptor, member D (MrgD), respectively. This study evaluated the effect of aging on cellular bioenergetics in brain microvasculature (BMV) and tested the potential beneficial effects of Ang-(1-7) or Ala.
Methods: BMVs were obtained from Young (Y) and Old (O) mice of age 3 - 4 and 22 – 24 months, respectively, by using ultracentrifugation method. Protein expression of receptors or mitochondrial complexes in BMVs were evaluated by western blotting. Seahorse bioanalyzer was used to determine OxPhos and glycolysis in BMVs.
Results: Expression of MasR or MrgD was higher in the O-BMVs compared to the Young (P < 0.05, n = 4). Expression of mitochondrial respiratory complex proteins, II, IV and V, was lower in the O-BMVs (vs Y-BMVs, P < 0.05, n = 4). MitoStress test revealed that the basal and maximal respiration, and the spare capacity are lower in the O-BMVs compared to the Y-BMVs (P < 0.05). Ang-(1-7) or Ala (100 nM) increased the basal and maximal respiration, spare capacity and ATP production in the O-BMVs compared to the untreated (P < 0.05). Glycolysis rate assay (GRA) showed that basal glycolysis and basal proton efflux rate were lower in the O-BMVs (P < 0.01 vs Y-BMVs) that were increased by Ang-(1-7) or Ala.
Conclusion: The study shows that aging is associated with impaired cellular bioenergetics in the brain microvasculature and that the angiotensin peptides, Ang-(1-7) or Ala, restore the bioenergetics therefore have the potential to reverse neurovascular uncoupling in aging.