Abstract 17895: Rictor in Perivascular Adipose Tissue Reduces Aortic Contraction by Controlling Inflammation
Introduction: Mammalian target of rapamycin (mTOR) controls essential functions such as cellular growth and metabolism. The multiprotein mTOR kinase complex exists in two forms- mTOR complex 1 (mTORC1) and mTORC2. Rictor is an essential component of mTORC2 in adipose tissue and contributes to anti-inflammation in fibroblasts. The function of rictor in perivascular adipose tissue (PVAT), which forms a structural support around the arteries and has anti-contractile activity, is not known. Therefore, we hypothesized that rictor in PVAT may modulate vascular function through its anti-inflammatory property.
Method: Adipose-specific rictor knockout mice (rictorad-/-) and littermate controls (rictorfl/fl) were fed with standard chow diet till 20 weeks of age. Expression of rictor and pro-inflammatory molecules in PVAT was analyzed using qRT-PCR, bioplex assay and immunofluorescence. To assess the vascular function, experiments were performed with aortic rings with or without endothelium in the presence or absence of PVAT with phenylephrine (PE; 10-9-3x10-6 M). Experiments were also performed in the presence of nitric oxide synthase inhibitor L-NAME or iNOS inhibitor 1400W. Infiltration of macrophages and leukocytes in stromal vascular fractions of PVAT were analysed with flow cytometry using specific antibodies F4/80 and CD45.2, respectively.
Results: In rictorad-/- mice, expression of rictor was significantly reduced in PVAT but not in aorta. The contractions to PE were increased by 2-fold in rings with PVAT from rictorad-/- mice (43±6% vs. 20±3 %, n=10-13). The overall contractility was increased in rings after removal of PVAT and the contractile differences were not significant (70±9% vs. 81±10%, n=10-13). Contractions remained higher even after pre-treatment with L-NAME or after endothelium denudation in rings with PVAT lacking rictor. Expression of IL-6, TNFα, MIP1α and iNOS were significantly increased in PVAT from rictorad-/- mice but an increase in macrophage or leukocyte levels were not detected in PVAT (n=4-5). Inhibition of iNOS activity with 1400W inhibited the increased contractile response in rings with PVAT from rictorad-/- mice (n=7-11).
Conclusion: mTORC2 in PVAT regulates normal vascular tone by controlling inflammation.
- © 2013 by American Heart Association, Inc.