Tandem mass tag-based proteomic analysis reveals cathepsin-mediated anti-autophagic and pro-apoptotic effects under proliferative diabetic retinopathy

Rui Niu,Jindan Wang,Jianqun Shen,Lijie Dong,Zetong Nie,Chao Geng,Bojie Hu,Yahong Li,Lin Liu,Yan Zhang,Yuwen Chang

doi:10.18632/aging.202217

Abstract

Proliferative diabetic retinopathy (PDR) is a severe complication of diabetes and can cause blindness. However, the available therapeutic modalities to PDR have unsatisfactory efficacies and incur adverse effects, which is due to the paucity in the understanding of pathogenic mechanisms responsible for the disease. In this study, tandem mass tag labeling technology combined with liquid chromatography and tandem mass spectrometry were utilized to identify differentially expressed proteins in vitreous humor of patients with rhegmatogenous retinal detachment and PDR. The data are available via ProteomeXchange with identifier PXD021788. Afterwards, the downregulated protein expression of Cathepsin B, D, and L was verified in vitreous and serum of another cohort. The gene expression profiling of the 3 cathepsins was confirmed in blood cells of an extra cohort. Furthermore, in high glucose (HG)-treated retinal vascular endothelial cell cultures recapitulating the cathepsin expression patterns, Cathepsin B or D downregulation mediated the HG-induced anti-autophagic and pro-apoptotic effects, thereby may contribute to vascular lesions under hyperglycemia. This study demonstrates previously undescribed expression patterns of cathepsins, reveals a novel cathepsin-involved pathogenic mechanism under PDR, and sheds light on potential therapeutic targets to this debilitating retinal disease.

Highlights

Diabetes mellitus (DM) is a lifelong metabolic disease hallmarked by hyperglycemia [1]
The proteomic results revealed that as compared with the RRD control group, the lysosomal proteases Cathepsin B (CTSB), Cathepsin D (CTSD), and Cathepsin L (CTSL) in the Proliferative diabetic retinopathy (PDR) group were significantly downregulated at the protein levels (Figure 1A and Table 2)
The downregulated expression of CTSB, CTSD, and CTSL genes at mRNA level was confirmed in the blood cells of an extra cohort (Figure 4G–4I)

Summary

Introduction

Diabetes mellitus (DM) is a lifelong metabolic disease hallmarked by hyperglycemia [1]. Hyperglycemia generates an adverse microenvironment in the eye, including oxidative stress [3], accumulation of advanced glycosylation end products [4], dysregulated polyol metabolism [5], production and release of inflammaotry factors [6], and over activation of protein kinase C pathway [7], which may lead to degenerative lesions in both retinal microvessels and neuroretina, retinal ischemia, hypoxia, neovascularization, and eventually PDR [8]. The available therapeutic modalities to PDR either generate disappointing efficacies or incur severe side effects. Vitrectomy is more invasive, and the postoperative www.aging-us.com complications hamper long-term recovery of visual acuity [13]. An effective and safe therapeutic modality to PDR is lacking, for which the primary reason is because the pathogenic mechanisms underlying this debilitating disease remain elusive. The mechanisms underlying PDR should be discerned to provide leads for improving the therapeutic strategies for the disease

Methods

Results

Conclusion