Retinol-binding protein 7 is an endothelium-specific PPARγ cofactor mediating an antioxidant response through adiponectin
Chunyan Hu, Henry L. Keen, Ko-Ting Lu, Xuebo Liu, Jing Wu, Deborah R. Davis, Stella-Rita C. Ibeawuchi, Silke Vogel, Frederick W. Quelle, Curt D. Sigmund
Chunyan Hu, Henry L. Keen, Ko-Ting Lu, Xuebo Liu, Jing Wu, Deborah R. Davis, Stella-Rita C. Ibeawuchi, Silke Vogel, Frederick W. Quelle, Curt D. Sigmund
View: Text | PDF
Research Article Vascular biology

Retinol-binding protein 7 is an endothelium-specific PPARγ cofactor mediating an antioxidant response through adiponectin

Abstract

Impaired PPARγ activity in endothelial cells causes oxidative stress and endothelial dysfunction which causes a predisposition to hypertension, but the identity of key PPARγ target genes that protect the endothelium remain unclear. Retinol-binding protein 7 (RBP7) is a PPARγ target gene that is essentially endothelium specific. Whereas RBP7-deficient mice exhibit normal endothelial function at baseline, they exhibit severe endothelial dysfunction in response to cardiovascular stressors, including high-fat diet and subpressor angiotensin II. Endothelial dysfunction was not due to differences in weight gain, impaired glucose homeostasis, or hepatosteatosis, but occurred through an oxidative stress–dependent mechanism which can be rescued by scavengers of superoxide. RNA sequencing revealed that RBP7 was required to mediate induction of a subset of PPARγ target genes by rosiglitazone in the endothelium including adiponectin. Adiponectin was selectively induced in the endothelium of control mice by high-fat diet and rosiglitazone, whereas RBP7 deficiency abolished this induction. Adiponectin inhibition caused endothelial dysfunction in control vessels, whereas adiponectin treatment of RBP7-deficient vessels improved endothelium-dependent relaxation and reduced oxidative stress. We conclude that RBP7 is required to mediate the protective effects of PPARγ in the endothelium through adiponectin, and RBP7 is an endothelium-specific PPARγ target and regulator of PPARγ activity.

Authors

Chunyan Hu, Henry L. Keen, Ko-Ting Lu, Xuebo Liu, Jing Wu, Deborah R. Davis, Stella-Rita C. Ibeawuchi, Silke Vogel, Frederick W. Quelle, Curt D. Sigmund

×

Figure 6

Adiponectin (AdipoQ) is an RBP7-dependent PPARγ target gene.

Options: View larger image (or click on image) Download as PowerPoint
Adiponectin (AdipoQ) is an RBP7-dependent PPARγ target gene. (A and B) S...
(A and B) Segments of the carotid artery were bisected and matched samples were incubated in vitro with vehicle (DMSO) or rosiglitazone (Rosi) for 24 hours. Quantification of AdipoQ (A) and FABP4 (B) expression was measured by quantitative real-time reverse transcription PCR (qRT-PCR) using GAPDH or β-actin as the normalization control. The level of induction by Rosi was compared between matched samples. *P < 0.05 control vs. RBP7-deficient by paired t test; n = 6–7 per group. (C) Endothelial (EC+) and non–endothelial (EC–) cells were magnetically sorted from dissociated single cells isolated from carotid arteries incubated in vitro with vehicle or Rosi for 24 hours. AdipoQ expression was measured by qRT-PCR. *P < 0.05 control vs. RBP7-deficient; #P < 0.05 control EC+ vs. EC– by 2-way ANOVA; n = 7–9 per group. (D) AdipoQ mRNA expression was quantified by qRT-PCR from aorta or carotid artery isolated from control or RBP7-deficient mice fed either normal diet (ND) or high-fat diet (HFD) (n = 12–14 per group). *P < 0.05 control, HFD vs. ND; #P < 0.05 HFD, RBP7 vs. control by 2-way ANOVA. Results are the mean ± SEM. (E and F) Dual immunofluorescence of carotid arteries from control and RBP7-deficient mice treated in vitro with Rosi (10 μM, 24 hours) or DMSO (E), or from control and RBP7-deficient mice fed either ND or HFD (F) was performed using antisera detecting AdipoQ (blue) or the endothelium-specific marker CD31 (red). Sections were also stained with DAPI (white/gray). Representative photomicrographs from n = 3–7 experiments per group are shown. Scale bars: 100 μm. Con, control; RBP7, retinol-binding protein 7; Veh, vehicle.