Sulforaphane inhibits platelet-derived growth factor-induced vascular smooth muscle cell proliferation by targeting mTOR/p70S6kinase signaling independent of Nrf2 activation

Abstract

Activation of nuclear factor erythroid 2-related factor 2 (Nrf2, a transcription factor) and/or inhibition of mammalian target of rapamycin (mTOR) are implicated in the suppression of vascular smooth muscle cell (VSMC) proliferation. The present study has examined the likely regulatory effects of sulforaphane (SFN, an antioxidant) on Nrf2 activation and platelet-derived growth factor (PDGF)-induced mTOR signaling in VSMCs. Using human aortic VSMCs, nuclear extraction and siRNA-mediated downregulation studies were performed to determine the role of Nrf2 on SFN regulation of PDGF-induced proliferative signaling. Immunoprecipitation and/or immunoblot studies were carried out to determine how SFN regulates PDGF-induced mTOR/p70S6K/S6 versus ERK and Akt signaling. Immunohistochemical analysis was performed to determine SFN regulation of S6 phosphorylation in the injured mouse femoral artery. SFN (5 μM) inhibits PDGF-induced activation of mTOR without affecting mTOR association with raptor in VSMCs. While SFN inhibits PDGF-induced phosphorylation of p70S6K and 4E-BP1 (downstream targets of mTOR), it does not affect ERK or Akt phosphorylation. In addition, SFN diminishes exaggerated phosphorylation of S6 ribosomal protein (a downstream target of p70S6K) in VSMCs in vitro and in the neointimal layer of injured artery in vivo. Although SFN promotes Nrf2 accumulation to upregulate cytoprotective genes (e.g., heme oxygenase-1 and thioredoxin-1), downregulation of endogenous Nrf2 by target-specific siRNA reveals an Nrf2-independent effect for SFN-mediated inhibition of mTOR/p70S6K/S6 signaling and suppression of VSMC proliferation. Strategies that utilize local delivery of SFN at the lesion site may limit restenosis after angioplasty by targeting mTOR/p70S6K/S6 axis in VSMCs independent of Nrf2 activation.

Cinnamic aldehyde inhibits vascular smooth muscle cell proliferation and neointimal hyperplasia in Zucker Diabetic Fatty rats

“…Similar to our results, Yoo et al showed that the electrophile SFN was able to inhibit neointimal hyperplasia in a non-diabetic carotid artery balloon injury model [22]. Shawky and Segar showed that SFN inhibited VSMC proliferation and neointimal hyperplasia in a mouse femoral artery wire injury model [23]. This group has also previously shown that SFN is able to inhibit leptin-induced VSMC proliferation and suppress neointimal hyperplasia in diet-induced obese mice [24].…”

AKT/FOXO1 axis links cross-talking of endothelial cell and pericyte in TIE2-mutated venous malformations

“…In response to vascular injury, the activated in ammatory cells, platelets and SMCs release the growth factors, especially platelet-derived growth factor (PDGF), thereby leading to a switch of SMCs from a contractile phenotype to a synthetic phenotype [48][49][50]. PDGFB is described to be one of the most potent stimulants for SMCs proliferation and migration [51]. In early vascular development, synthetic phenotypic SMCs are required to migrate around lumens, proliferate and secrete extracellular matrix to promote intercellular connections.…”

Pioglitazone Attenuates Injury-Induced Neointima Formation in Mouse Femoral Artery Partially through the Activation of AMP-Activated Protein Kinase

“…The medial area was determined by subtraction of the IEL area from the EEL area (i.e., medial area = EEL area – IEL area) [25]. The cryosectioning, H&E staining, and EVG staining of the injured femoral arteries (from control and treated conditions) were performed in a blinded manner as described earlier [27]. …”