PPARγ Gene Transfer Sustains Apoptosis, Inhibits Vascular Smooth Muscle Cell Proliferation, and Reduces Neointima Formation After Balloon Injury in Rats

Abstract

Objective-There is still debate as to whether antiatherosclerotic effect of PPAR␥ ligands is dependant on PPAR␥ gene itself or some other pathway. Methods and Results-To investigate the effect of PPAR␥ gene modulation on neointima formation after balloon injury, we delivered adenoviral vectors expressing the wild-type (WT) dominant negative (DN) PPAR␥, or a control gene (␤-galactosidase [BG]) into carotid artery after balloon injury in rosiglitazone (a PPAR␥ ligand)-treated (Rϩ) (3 mg/kg/d) and nontreated (RϪ) rats. Two weeks after gene delivery, in both Rϩ and RϪ animals, the PPAR␥-WT gene transfer showed a significantly lower intima-media ratio (IMR) than control group. Moreover, the delivery of a PPAR␥-DN form showed the highest IMR (in RϩWT, 0.51Ϯ0.15; RϩBG, 0.89Ϯ0.14; RϩDN, 1.20Ϯ0.18, PϽ0.05 and in RϪWT, 0.91Ϯ0.21; RϪBG, 1.44Ϯ0.23; RϪDN, 1.74Ϯ0.29, PϽ0.05). Proliferation and migration showed same result pattern as IMR. In addition, apoptotic indices were significantly higher in the PPAR␥-WT gene transferred group than in the PPAR␥-DN group. Conclusions-In vivo transfer of the PPAR␥-WT gene was found to inhibit smooth muscle proliferation, sustain apoptosis, and reduce neointima formation after balloon injury irrespective of rosiglitazone treatment. These results indicate that PPAR␥ overexpression itself has a protective role against restenosis after balloon injury. Key Words: PPAR␥ Ⅲ vascular smooth muscle Ⅲ neointima Ⅲ proliferation Ⅲ apoptosis P eroxisome proliferator activated receptor gamma (PPAR␥) is a crucial factor in many cellular signaling pathways and is known to regulate several transcription factors. Researches have provided many insights into the pleiotropic role that PPAR␥ plays in cell proliferation, migration, and differentiation and adipocyte differentiation. In fact, PPAR␥ activation inhibits vascular smooth muscle cell (VSMC) proliferation, 1,2 for which several mechanisms have been suggested; blocking the reentry of quiescent VSMCs into the cell cycle, 3 inhibiting VSMC migration by controlling the mitogen-activated protein kinase (MAPK) pathway and the production of matrix metalloproteinase (MMP), 4,5 and reducing inflammation by attenuating cytokine production and nuclear factor-B transcription activity. 6,7 In the field of endocrinology and metabolism, PPAR␥ has been identified as an insulin sensitizer and as an important regulator of glucose metabolism. In fact, the diabetic milieu is associated with endothelial dysfunction and several therapeutic interventions have been tested in this context. 8 Moreover, PPAR␥ is a good target for the treatment of restenosis because its expression is found in all cells composing blood vessels (ie, monocytes, macrophages, and endothelial and VSMCs).It has recently been reported that the in vitro rosiglitazone treatment (a PPAR␥ ligand) results in a significant reduction in restenosis after coronary stent insertion. 9 Because PPAR␥ is located at a nodal point where multiple cell signals merge to control the proliferation and migration of VSMCs, it ma...

Effects of PPAR.GAMMA. on hypertension, atherosclerosis, and chronic kidney disease

“…However, numerexpressed dominant-negative PPARγ in endothelium demonstrated the development of endothelial dysfunction in response to a high-fat diet [22]. PPARγ ligands have also been reported to reduce intimal and medial complex thickening in carotid arteries and in-stent restenosis after coronary intervention in both diabetic and non-diabetic patients [23] as well as neointima formation after balloon injury in rats [24] and in-stent restenosis in atherosclerotic rabbits [25]. In order to examine the direct effects of PPARγ ligands on endothelial gene expression, we performed DNA microarray analyses.…”

Peroxisome Proliferator-Activated Receptor-γ–Mediated Effects in the Vasculature

“…61 Rosiglitazone also inhibits c-fos gene expression and dominant-negative PPAR-␥ gene transfer abolishes this effect in cultured VSMCs treated with basic FGF. 70 Eukaryotic initiation factor 4E-binding protein (4E-BP)1 and SHIP2 (Src homology 2-containing inositol phosphatase 2) are also likely to mediate the growth inhibition of PPAR-␥ agonists. 71 Both 15d-PGJ2 and rosiglitazone decrease the phosphorylation of 4E-BP1 and SHIP2 that is elevated by Ang II in VSMCs when they inhibit the DNA synthesis in vitro.…”

“…55 PPAR-␥ gene transfer into VSMCs induces apoptosis while inhibiting proliferation and migration in vitro and in vivo. 70 This indicates that VSMC apoptosis may be antiatherogenic by counteracting proliferation and migration. PPAR-␥ agonists have been shown to induce apoptosis of VSMCs from humans or rodents.…”

Overexpression of the growth arrest-specific homeobox gene Gax inhibits proliferation, migration, cell cycle progression, and apoptosis in serum-induced vascular smooth muscle cells

“…It is reported that after carotid arteries injury, VSMCs proliferation in the intima was highest at the 7th day postinjury, whereas the rate of apoptosis in VSMCs was unchanged and lower than 1%, suggesting an insufficient rate of cell apoptosis concomitant with intimal hyperplasia (Kamenz et al, 2000). It has been demonstrated that increasing VSMCs apoptosis could decrease neointimal hyperplasia in vivo (Lim et al, 2006). Gax overexpression inhibits the proliferation of hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs) and promotes apoptosis in the PASMCs (Xia et al, 2011).…”