Abstract 309: Sirt3 Regulates Oxygen Sensors and Blood Vessel Formation in the Heart

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New blood vessels formation is driven by deprivation of nutrients and oxygen during myocardial ischemia. The interaction between nutrients and oxygen sensors in the regulation of new blood vessel formation still remains incompletely understood. Sirtuins belong to a family of NAD+-dependent deacetylases which are involved in the regulation of angiogenesis and energy hemostasis. In the present study, we investigated the functional role of Sirtuin 3 (Sirt3), a metabolic sensor, in the regulation of blood vessel formation and its interaction with oxygen sensors-prolyl hydroxylases (PHDs)/hypoxia-inducible factors (HIFs) system. The levels of PHD1-3, HIFs, and angiogenic growth factors as well as blood vessel formation were examined in the hearts of Sirt3 knockout (Sirt3 KO) mice and wild type (WT) mice. Our data showed that the expression of angiopoietin-1 and angiopoietin-2 was significantly reduced, whereas the expression of Tie-2 and VEGF was unchanged in the hearts of Sirt3 KO mice compared to WT mice. Intriguingly, loss of Sirt3 had different effects on the PHDs/HIFs system. The expression of PHD1, PHD2, and HIF1α was significantly up-regulated, but PHD3 and HIF2α expression was down-regulated in Sirt3 KO mice. Ex vivo angiogenesis assay revealed that vessel outgrowth was significantly reduced in Sirt3 KO mice compared to WT mice. Our immunohistochemistry study further confirmed that the arteriole formation was significantly reduced in the hearts of Sirt3 KO mice compared to that in WT mice. This was accompanied by a reduction of cardiac ejection fraction (EF %) and fraction shortening (FS %). Moreover, the phosphorylation level of Akt was dramatically decreased together with increased Wnt7b, caspase-3 expression and apoptosis in the hearts of Sirt3 KO mice. Therefore, our data implicates that Sirt3 is important in controlling of blood vessel growth and cell survival by affecting oxygen sensors and angiopoietins expression in the heart.

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