Exploring the Regulatory Role of Bone Morphogenetic Proteins on Retinal Proteomes in Experimental Diabetes

Abstract

Purpose : Diabetic retinopathy (DR) is a major complication of diabetes. This study investigates alterations in the retinal proteome in streptozotocin (STZ)-induced diabetic mice, focusing on the impact of bone morphogenetic protein (BMP) inhibitors.

Methods : Using label-free mass spectrometry, we examined the retinal proteome in normal mice, 16-week-old STZ diabetic mice, and diabetic mice treated with BMP inhibitors (noggin or LDN193189) delivered via subcutaneous minipump. Pathway enrichment analysis Genomatix and Ingenuity were used to highlight significant differences in protein levels related to various biological processes. Crystallin (Crys) proteins (bcrys-b2 and bcrys-b3) in retina of control and STZ-induced diabetic mice were examined by western blot. Moreover, expression of crystallin proteins was studied in postmortem human vitreous of non-diabetic and diabetic subjects with DR by western blot.

Results : Proteomic analysis revealed 49 significantly altered proteins between STZ-diabetic and wild-type mice, indicating dysregulation in key pathways such as MAPK signaling, wnt regulation, autophagy, angiogenesis, TGFβ signaling, cell death, and oxidative stress in diabetic retinas. Interestingly, 10 out of 49 altered proteins in retina of diabetic mice belong to the Crystallin family, mostly β- and γ-crystallin. BMP inhibitors showed distinct effects on the Crystallin protein family: noggin treatment upregulated these proteins, while LDN193189 downregulated them. Western blot analyses of β-crystallin b2 and b3 further confirmed diabetes induced a significant decrease in mouse retina (0.0903 ± 0.0214-fold change vs control, P<0.05 for β-crystallin b2; 0.0447 ± 0.0322-fold change vs control, P<0.05 for β-crystallin b3). Additionally, there was a significant decrease in β-crystallin b2 in human vitreous from subjects with DR compared to non-diabetic subjects (0.32 ± 0.1103-fold change vs control, P<0.05).

Conclusions : Crystallin protein family are ameliorated in mouse retina and human vitreous during diabetes. Our results demonstrate that the Crystallin protein family is intricately regulated by BMP signaling. Noggin treatment has a protective effect by upregulating Crystallin proteins. Understanding these molecular alterations provides insights into the pathogenesis of DR and opens avenues for potential therapeutic interventions targeting BMP signaling to ameliorate the progression of DR.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.