Prorenin receptor (PRR)-mediated NADPH oxidase (Nox) signaling regulates VEGF synthesis under hyperglycemic condition in ARPE-19 cells

Abstract

The stimulation of angiotensin II (Ang II), the effector peptide of renin–angiotensin system, has been reported to increase the expression of vascular endothelial growth factor (VEGF) through the activation of the Ang II type 1 receptor (AT1R). In this study, we investigated whether hyperglycemia (HG, 33 mM glucose) in ARPE-19 cells could promote the expression of VEGF independently of Ang II through prorenin receptor (PRR), via an NADPH oxidase (Nox)-dependent mechanism. ARPE-19 cells were treated with the angiotensin converting enzyme (ACE) inhibitor perindopril to block the synthesis of Ang II. Treatment with HG induced VEGF expression in ARPE-19 cells, which was attenuated by pretreatment with the inhibitors of Nox, but not those of nitric oxide synthase, xanthine oxidase and mitochondrial O₂ synthesis. In addition, Nox-derived and H₂O₂ signaling in the regulation of VEGF was determined by using both polyethylene glycol (PEG)-catalase (CAT) and PEG-superoxide dismutase (SOD). We demonstrated that small interfering RNA (siRNA)-mediated knockdown of PRR, Nox2 and Nox4 significantly reduced the HG-induced stimulation of VEGF. On the other hand, Nox4 overexpression significantly potentiated PRR-induced stimulation of VEGF under hyperglycemia in ARPE-19 cells. Furthermore, Nox4 was shown to be associated with enhanced activities of ERK1/2 and NF-κB (p65), indicating their involvement in PRR-induced activation of VEGF under HG in ARPE-19 cells. Our results support the hypothesis that Nox4-derived reactive oxygen species (ROS) signaling is implicated in the hyperglycemia-induced increase of VEGF expression through PRR in ARPE-19 cells. However, further work is needed to evaluate the role of PRR and Nox-s in HG-induced stimulation of VEGF in vivo.

Keywords:

• Prorenin receptor
• retina
• NADPH oxidase (Nox)
• VEGF
• renin–angiotensin system (RAS)
• diabetic retinopathy

Acknowledgements

The authors thank Dr. David Lambeth, Emory University School of Medicine, for a gift of human Nox4 plasmid and Dr. Purnachandra Ganji (Emory University) for donating NF-κB (p65) antibody. The authors also thank Jane Abey, Curran S. Sidhu, and Julien Brock for technical assistance. The STR allele(s) analysis for ARPE-19 cell line authentication was supported in part by the Emory Integrated Genomics Core (EIGC), which is subsidized by the Emory University School of Medicine and is one of the Emory Integrated Core Facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research was supported by Research to Prevent Blindness (RPB), R01 EY004864 and P30 EY006360.