Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Nov 24;23(23):14680.
doi: 10.3390/ijms232314680.

The Protective Role of Apelin in the Early Stages of Diabetic Retinopathy

Jing Feng  1 , Weiqiang Yang  1 , Fuxiao Luan  1 , Fang Ma  1 , Yingjie Wang  1 , Yiquan Zhang  1 , Xuhui Liu  1 , Li Chen  1 , Xiaofeng Hu  1 , Yong Tao  1
Affiliations

The Protective Role of Apelin in the Early Stages of Diabetic Retinopathy

Jing Feng et al. Int J Mol Sci. .

Abstract

Diabetic retinopathy (DR) is one of the most common and serious microvascular complications of diabetes. Although current treatments can control the progression of DR to a certain extent, there is no effective treatment for early DR. Apart from vascular endothelial growth factor, it has been noted that the apelin/APJ system contributes to the pathogenesis of DR. We used a high-fat diet/streptozotocin-induced type 2 diabetic mouse model. The mice were divided into a lentivirus control group (LV-EGFP), an apelin-overexpression group (LV-Apelin+), and an apelin-knockdown group (LV-Apelin-), all of which were administrated intravitreal injections. LV-Apelin+ ameliorated the loss of pericytes in DR mice, whereas LV-Apelin- aggravated the loss of pericytes. Similarly, LV-Apelin+ reduced the leakage of retinal vessels, whereas LV-Apelin- exacerbated it. The genes and signaling pathway related to cell adhesion molecules were downregulated, whereas the cell-cell tight junctions and anti-apoptotic genes were upregulated in response to apelin overexpression. However, the alterations of these same genes and signaling pathways were reversed in the case of apelin knockdown. Additionally, LV-Apelin+ increased ZO-1 and occludin levels, whereas LV-Apelin- decreased them. Our results suggest that apelin can reduce vascular leakage by protecting pericytes, which offers a promising new direction for the early treatment of DR.

Keywords: apelin; early stages of diabetic retinopathy; pericytes; protective role; vascular leakage.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Construction of an HFD/STZ-induced type 2 diabetic mouse model and different lentiviral vectors. (A) Experimental and dosing procedures for HFD/STZ-induced type 2 diabetes. (B) Body weight and blood glucose were measured every two weeks. Data are expressed as mean ± SD (n = 6). (C) The maps of LV-Apelin+ and LV-Apelin−. (D) The expression images of LV-EGFP were obtained through confocal laser scanning microscopy (CLSM) at four and eight weeks. Blue: DAPI, green: LV-EGFP. GCL: ganglion cell layer; INL: inner nuclear layer; ONL: outer nuclear layer.
Figure 2
Figure 2
The expression of apelin in DR mice treated with LV-EGFP, LV-Apelin+, or LV-Apelin−. (A) Representative apelin staining images by CLSM and (B) the quantification of the staining intensity indicated that apelin was moderately expressed in the LV-EGFP group and was primarily distributed in the GCL, while it was widely expressed in the LV-Apelin+ group and distributed in the GCL and INL. In the LV-Apelin− group, there was almost no expression of apelin. (C) The qRT-PCR results revealed that the mRNA expression of apelin was upregulated in the LV-Apelin+ group, but downregulated in the LV-Apelin− group. Blue: DAPI, red: apelin. GCL: ganglion cell layer; INL: inner nuclear layer; ONL: outer nuclear layer. Data were expressed as mean ± SD. LV-Apelin+ versus LV-EGFP; LV-Apelin− versus LV-EGFP; * p < 0.05, **** p < 0.0001 (n = 6).
Figure 3
Figure 3
The expression of pericytes in DR mice treated with LV-EGFP, LV-Apelin+, or LV-Apelin−. (A) Representative NG2 and CD31 staining images by CLSM and (B) the quantification of pericyte coverage indicated that there was a partial loss of pericytes in the LV-EGFP group, while the expression of pericytes increased in the LV-Apelin+ group but decreased in the LV-Apelin− group. Green: NG2, Red: CD31. Data were expressed as mean ± SD. LV-Apelin+ versus LV-EGFP; LV-Apelin− versus LV-EGFP; **** p < 0.0001 (n = 6).
Figure 4
Figure 4
Retinal leakage in DR mice treated with LV-EGFP, LV-Apelin+, or LV-Apelin−. (A) Representative dextran leakage images and (B) the quantification of dextran leakage revealed that the leakage of retinal vessels was moderate in the LV-EGFP group; however, it decreased in the LV-Apelin+ group and increased in the LV-Apelin− group. Data were expressed as mean ± SD. LV-Apelin+ versus LV-EGFP; LV-Apelin− versus LV-EGFP; **** p < 0.0001 (n = 6).
Figure 5
Figure 5
The mechanism underlying the protective role of apelin in the early stages of diabetic retinopathy. (A) The heatmap of differential gene expression showed that LV-Apelin+ upregulated genes related to tight junction, and anti-apoptosis downregulated genes related to the adhesion molecule and vascular permeability. In contrast, LV-Apelin− upregulated genes related to adhesion molecules and pericyte apoptosis, and downregulated genes related to tight junction genes (n = 2). (B) The results of GSEA were consistent with the differential gene expression analysis. (C) Representative Western blot images and (D) the quantification of the relative protein levels revealed that the levels of ZO-1 and occludin were increased by LV-Apelin+ but decreased by LV-Apelin−. The data were expressed as mean ± SD. LV-Apelin+ versus LV-EGFP; LV-Apelin− versus LV-EGFP; *** p < 0.001, **** p < 0.0001 (n = 3).
Figure 6
Figure 6
Effects on the cerebrum in DR mice treated with LV-EGFP, LV-Apelin+, or LV-Apelin−. Representative HE staining images revealed that the intravitreal injection of the LV had no obvious side effects on the cerebrum.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Groeneveld Y., Tavenier D., Blom J.W., Polak B.C.P. Incidence of sight-threatening diabetic retinopathy in people with Type 2 diabetes mellitus and numbers needed to screen: A systematic review. Diabet. Med. 2019;36:1199–1208. doi: 10.1111/dme.13908. - DOI - PMC - PubMed
    1. Cui Y., Zhang M., Zhang L., Zhang L., Kuang J., Zhang G., Liu Q., Guo H., Meng Q. Prevalence and risk factors for diabetic retinopathy in a cross-sectional population-based study from rural southern China: Dongguan Eye Study. BMJ Open. 2019;9:e023586. doi: 10.1136/bmjopen-2018-023586. - DOI - PMC - PubMed
    1. Arboleda-Velasquez J.F., Valdez C.N., Marko C.K., D’Amore P.A. From pathobiology to the targeting of pericytes for the treatment of diabetic retinopathy. Curr. Diabetes Rep. 2015;15:573. doi: 10.1007/s11892-014-0573-2. - DOI - PMC - PubMed
    1. Caporarello N., D’Angeli F., Cambria M.T., Candido S., Giallongo C., Salmeri M., Lombardo C., Longo A., Giurdanella G., Anfuso C.D., et al. Pericytes in Microvessels: From “Mural” Function to Brain and Retina Regeneration. Int. J. Mol. Sci. 2019;20:6351. doi: 10.3390/ijms20246351. - DOI - PMC - PubMed
    1. Park D.Y., Lee J., Kim J., Kim K., Hong S., Han S., Kubota Y., Augustin H.G., Ding L., Kim J.W., et al. Plastic roles of pericytes in the blood-retinal barrier. Nat. Commun. 2017;8:15296. doi: 10.1038/ncomms15296. - DOI - PMC - PubMed