Abstract 067: Endothelial mTORC1 Signaling Regulates Vascular Function and Mediates Angiotensin II Actions

Abstract

The mechanistic target of rapamycin complex 1 (mTORC1) serves as an intracellular energy sensor through its downstream signaling components the S6-kinase and the ribosomal S6 protein with recent implications for hypertension. In this study, we tested the hypothesis that endothelial mTORC1 signaling is critical for the regulation of vascular endothelial function. We generated tamoxifen-inducible endothelial-specific Raptor deleted mice (Tek CreERT2 /Raptor F/F ) to disrupt mTORC1 signaling in the endothelium. Tamoxifen-treated wildtype littermates were used as controls. We confirmed endothelial-specific deletion of Raptor by RT-PCR in MACS-sorted endothelial cells. Interestingly, homozygous Raptor deletion cause endothelial dysfunction as indicated by the reduced vasorelaxation of tamoxifen-treated Tek CreERT2 /Raptor F/F mice aortic rings evoked to acetylcholine (Max relax: 34±11 vs 61±7% in controls; p<0.05), but not sodium nitroprusside (Max relax: 82 ±3 vs 84±2%). Restoring mTORC1 signaling in tamoxifen-treated Tek CreERT2 /Raptor F/F aortic rings with an adenoviral S6-kinase constitutively active construct (Ad-S6KCA; 24hrs) rescued the reduction in acetylcholine-mediated relaxation (Max relax: 54±6 vs 31±10% in Ad-GFP; p<0.05), demonstrating that the endothelial dysfunction is Tek CreERT2 /Raptor F/F mice is due to loss of mTORC1 signaling. Notably, aortic rings from heterozygous Tek CreERT2 /Raptor F/+ mice which have intact acetylcholine-induced vasorelaxation responses were protected from angiotensin II (Ang II)-induced endothelial dysfunction. Indeed, incubation of aortic rings from wildtype mice with Ang II (100nM; 24hrs) reduced acetylcholine-mediated vasorelaxation responses (Max relax: 3±8 vs 57±4 % in vehicle group; p<0.05). In contrast, aortic rings of tamoxifen-treated Tek CreERT2 /Raptor F/+ mice were partially protected from the endothelial dysfunction evoked by Ang II (Max relax: 36±9; p<0.05 vs wildtype controls). Our data indicate that endothelial mTORC1 signaling is required for the regulation of endothelial function. Our findings also highlight the importance of mTORC1 signaling in mediating the vascular endothelial effects of Ang II.