The Inhibition of Insulin-stimulated Proliferation of Vascular Smooth Muscle Cells by Rosiglitazone Is Mediated by the Akt-mTOR-P70S6K Pathway

Abstract

PurposeThiazolidinediones (TZDs) are known to inhibit the proliferation of vascular smooth muscle cell (VSMC) by increasing the activity of p27Kip1 and retinoblastoma protein (RB). However, the upstream signaling mechanisms associated with this pathway have not been elucidated. The Akt-mTOR-P70S6 kinase pathway is the central regulator of cell growth and proliferation, and increases cell proliferation by inhibiting the activities of p27Kip1 and retinoblastoma protein (RB). Therefore, we hypothesized in this study that rosiglitazone inhibits VSMC proliferation through the inhibition of the Akt-TOR-P70S6K signaling pathway.Materials and MethodsRat aortic smooth muscle cells (RAoSMCs) were treated with 10 µM of rosiglitazone 24 hours before the addition of insulin as a mitogenic stimulus. Western blot analysis was performed to determine the inhibitory effect of rosiglitazone treatment on the Akt-mTOR-P70S6K signaling pathway. Carotid balloon injury was also performed in Otsuka Long-Evans Tokushima Fatty (OLETF) diabetic rats that were pretreated with 3 mg/kg of rosiglitazone.ResultsWestern blot analysis demonstrated significant inhibition of activation of p-Akt, p-m-TOR, and p-p70S6K in cells treated with rosiglitazone. The inhibition of the activation of the p-mTOR-p-p70S6K pathway seemed to be mediated by both the upstream PI3K pathway and MEK-ERK complex.ConclusionThe inhibitory effect of rosiglitazone on RAoSMC proliferation in vitro and in vivo is mediated by the inhibition of the Akt-mTOR-P70S6K pathway.

Vascular Endothelial Over-Expression of Human Soluble Epoxide Hydrolase (Tie2-sEH Tr) Attenuates Coronary Reactive Hyperemia in Mice: Role of Oxylipins and ω-Hydroxylases

“…The final concentrations, after standardization of dose (0.01, 0.1, 1, & 10 μM) response for the various drugs used in this study were 10 μM for rosiglitazone (PPARγ-agonist), t -AUCB ( trans -4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (a selective sEH-inhibitor, University of California, Davis) [36], and 1 μM DDMS (dibromo-dodecenyl-methylsulfimide, CYP4A-blocker). These concentrations are equal or lower than used in previous studies: rosiglitazone, 10 μM; [11, 37], t -AUCB, 10 μM; [11, 35], DDMS, 1 μM [38]. …”

Anti‐proliferative effect of rosiglitazone on angiotensin II‐induced vascular smooth muscle cell proliferation is mediated by the mTOR pathway

“…Rosiglitazone blocked Ang II‐induced stimulation of cell proliferation in rat aortic VSMCs. Rosiglitazone inhibits the mTOR signalling pathway, which includes p70S6K, and this plays a key role in cell growth (Park et al, 2008). Furthermore, Ang II triggered dissociation of the translation initiation factor, eIF‐4E (eukaryotic initiation factor 4E), from its regulatory binding protein 4EBP1 (Lu et al, 2005).…”

Deletion of soluble epoxide hydrolase enhances coronary reactive hyperemia in isolated mouse heart: role of oxylipins and PPARγ

“…The final concentrations, after standardization of dose (0.01, 0.1, 1, and 10 M) response for the various drugs used in this study were 10 M for T0070907 (PPAR␥-antagonist), rosiglitazone (PPAR␥Ϫ agonist), and 100 M for L-NAME (N -nitro-L-arginine methyl ester hydrochloride, a nonselective nitric oxide synthase inhibitor). These concentrations were selected on the basis of our dose-response studies (for T0070907 and rosiglitazone) and on the basis of the concentrations used in previous studies [rosiglitazone, 10 M; (40)], and [L-NAME, 100 M; (58)]. Time-matched control experiments with WT (sEH ϩ/ϩ ) mouse hearts, employing three consecutive inductions of CRH, showed no change in CRH response and in baseline heart functions, including CF, LVDP, and HR (data not shown).…”