Transcription Factor ETS-1 and Reactive Oxygen Species: Role in Vascular and Renal Injury

Abstract

The E26 avian erythroblastosis virus transcription factor-1 (ETS-1) is a member of the ETS family and regulates the expression of a variety of genes including growth factors, chemokines and adhesion molecules. Although ETS-1 was discovered as an oncogene, several lines of research show that it is up-regulated by angiotensin II (Ang II) both in the vasculature and the glomerulus. While reactive oxygen species (ROS) are required for Ang II-induced ETS-1 expression, ETS-1 also regulates the expression of p47phox, which is one of the subunits of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and a major source of ROS in the kidney and vasculature. Thus, there appears to be a positive feedback between ETS-1 and ROS. ETS-1 is also upregulated in the kidneys of rats with salt-sensitive hypertension and plays a major role in the development of end-organ injury in this animal model. Activation of the renin angiotensin system is required for the increased ETS-1 expression in these rats, and blockade of ETS-1 or haplodeficiency reduces the severity of kidney injury in these rats. In summary, ETS-1 plays a major role in the development of vascular and renal injury and is a potential target for the development of novel therapeutic strategies to ameliorate end-organ injury in hypertension.

Keywords: ETS-1; reactive oxygen species; renal injury; vascular injury.

Figure 1

Domains of the most abundant isoform of ETS-1. Black circles are the lysine (K) sumoylation sites. Blue circles are the Ca²⁺-dependent serine (S) phosphorylation sites. The red circle is the Ras-dependent threonine (T) phosphorylation site. Note that the schematic domain lengths are not proportional to the numbers of amino acids within each domain.

Figure 2

Regulation of ETS-1 by angiotensin II and the functional consequences. Ang II: Angiotensin II; ROS: reactive oxygen species; NADPH: nicotinamide adenine dinucleotide phosphate.

Figure 3

Angiotensin II (Ang II) increases cortical ETS-1 expression. (A) Representative confocal photomicrographs showing low basal expression of ETS-1 (green) in control kidney cortex, which is predominantly glomerular and increased by Ang II. (Bar = 50 μm); (B) The renal cortical ETS-1 protein expression increases after 2 weeks of Ang II as assessed by Western blot (n = 6, * p < 0.05 vs. control) and returns to baseline after 4 weeks of Ang II. The expression of ETS-1 was not significantly modified by treatment with either ETS-1 dominant-negative (ETS-1 DN) or ETS-1 mutant (ETS-1 MU) peptide; (C) Densitometric analysis for ETS-1 showing significant increases in ETS-1 protein expression after 2 but not after 4 weeks of Ang II. Neither ETS-1 DN nor ETS-1 MU modified ETS-1 protein expression. Data expressed as mean ± SEM are normalized to GAPDH (* p < 0.05 vs. control; n = 6). The infusion of Ang II for 2 weeks resulted in increases in cortical ETS-1 mRNA expression as assessed by real-time reverse transcriptase polymerase chain reaction (n = 6; * p < 0.05 vs. control) and returns to baseline levels after 4 weeks of Ang II. GAPDH: glyceraldehyde 3-phosphate dehydrogenase. (Right panel).

Figure 4

A single injection of ETS-1 DN (10 mg/kg) inhibited the formation of neointimal hyperplasia (NH) in injured rat carotid arteries. Top, elastic Van Gieson-stained tissue sections of carotid arteries from rats treated with (A) saline vehicle (VEH); (B) ETS-1 DN; or (C) ETS-1 mutant (MU) 14 days after balloon injury. Bottom, composite data are shown as mean ± SEM (n = 6 per group). * p < 0.05 compared to the VEH group. (Bar = 50 μm).

Figure 5

Glomerular expression of transcription factor avian erythroblastosis virus E26 oncogen homolog-1 (ETS-1) in hypertensive Dahl salt-sensitive (DS) rats. Colocalization studies were performed to characterize the expression of ETS-1 in the glomerular endothelium (CD31), podocytes (synaptopodin), or mesangium (desmin). (A–C) show positive stain for CD31 (A, red), ETS-1 (B, green), and some areas in which there is colocalization of CD31 and ETS-1 indicating endothelial expression of ETS-1 (C, arrows); (D–F) show positive stain for synaptopodin (D, red), ETS-1 (E, green), and areas in which there is colocalization of ETS-1 and synaptopodin indicating expression of ETS-1 in podocytes (F, arrows); (G–I) show positive stain for desmin (G, red), ETS-1 (H, green); no clear evidence of colocalization of ETS-1 and desmin was observed (I), suggesting lack of expression of ETS-1 in mesangial areas (×40 magnification).