Notoginsenoside R1 activates the NAMPT-NAD+-SIRT1 cascade to promote postischemic angiogenesis by modulating Notch signaling

Abstract

Nicotinamide phosphoribosyltransferase (NAMPT) maintains mitochondrial function and protects against cerebral ischemic injury by improving energy metabolism. Notoginsenoside R1 (R1), a unique constituent of Panax notoginseng, has been shown to promote the proliferation and tube formation of human umbilical vein endothelial cells. Whether R1 has proangiogenesis on the activation of NAMPT in ischemic stroke remains unclear. The purpose of this study was to investigate the pharmacodynamic effect and mechanism of R1 on angiogenesis after ischemic stroke. We used male Sprague-Dawley (SD) rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). R1 was administered via intraperitoneal (i.p.) injection immediately after ischemia induction. The promotion of R1 on angiogenesis were detected by immunofluorescence staining, 3D stereoscopic imaging and transmission electron microscopy detection. HBMEC cells were pretreated with different concentrations of R1 for 12 h before oxygen-glucose deprivation/reoxygenation (OGD/R) exposure. Afterward, scratch assay, EdU staining and tube formation were determined. Western blot analyses of proteins, including those involved in angiogenesis, NAMPT-SIRT1 cascade, VEGFR-2, and Notch signaling, were conducted. We showed that R1 significantly restored cerebral blood flow, improved mitochondrial energy metabolism and promoted angiogenesis. More importantly, incubation with 12.5-50 μM R1 significantly increased the migration, proliferation and tube formation of HBMECs in vitro. The promotion of R1 on angiogenesis were associated with the NAMPT-NAD⁺-SIRT1 cascade and Notch/VEGFR-2 signaling pathway, which was partially eliminated by inhibitors of NAMPT and SIRT1. We demonstrated that R1 promotes post-stroke angiogenesis via activating NAMPT-NAD⁺-SIRT1 cascade. The modulation of Notch signaling and VEGFR-2 contribute to the post-stroke angiogenesis. These findings offer insight for exploring new therapeutic strategies for neurorestoration via R1 treatment after ischemic stroke.

Keywords: Angiogenesis; Energy metabolism; Ischemic stroke; Neurorestoration; R1.