The Role of Apelin in the Retina of Diabetic Rats

Abstract

 

Purpose

 

The purpose of this study was to investigate the effect of apelin-13 on proliferative potential in diabetic retinopathy (DR), and its antagonist inhibitory effects.

 

Methods

 

Localization of apelin-13, GFAP, and VEGF were detected using immunofluorescence in the retina of diabetic rats. The mRNA and protein of apelin-13, GFAP, and VEGF in the retina of diabetic rats were measured using real-time PCR and western blot. Apelin-13 antagonist F13A was used to block apelin-13, and to study its effects in vivo.

 

Results

 

Strong staining of apelin-13, co-localized with GFAP and VEGF, was observed in the retina of diabetic rats. Apelin-13, GFAP, and VEGF mRNA and protein levels were significantly increased in the sample’s retina. Moreover, exogenous apelin-13 promoted retinal Müller cell proliferation in vivo. Simultaneously, apelin-13 induced GFAP and VEGF expression. F13A markedly reduced the retinal gliosis caused by diabetes. Furthermore, F13A suppressed both GFAP and VEGF expression in vivo.

 

Conclusions

 

Our results strongly suggest that apelin-13 is associated with the development of DR, and contributes to changes in the retina of diabetic rats. Apelin-induced promotion of cell proliferation lends support to the possibility that apelin-13 may play a role in the progression of DR to a proliferative phase. This possible role deserves further investigation, which may open new perspectives in the early prevention and treatment of DR.

 

 

Fig 1. Indirect immunofluorescence evaluation of apelin-13 and GFAP distribution in retina of normal rats (A), diabetic rats (B) and F13A-injected diabetic rats(C). Merged images contain three color channels representing apelin-13 (red), GFAP (green) and DAPI (blue). Densitometric quantification of GFAP activity (D), GCL, ganglion cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; ONL, outer nuclear layer.F13A, F13A-injected group. ** indicates p < 0.01. Scale bars: 50µm.

 

 

Fig 2. RT-PCR and Western blot analysis showed the mRNA (A) and protein (B) expression of apelin-13, GFAP and VEGF in diabetic rats, and representative Western blots are shown in Fig.3C ** indicates p<0.01 vs. CON. The expression of GFAP (D) and VEGF (E) in retina of apelin-13 injected rats, and expressed as arbitrary units is shown at the upper. ** indicates p<0.01 vs. VEH.

 

Keywords: 499 diabetic retinopathy • 637 pathology: experimental • 543 growth factors/growth factor receptors