ALDH1A1 gene therapy attenuates acrolein-induced Müller cell dysfunction in diabetic retinopathy

Purpose : Diabetic retinopathy (DR) is a common neurovascular complication of diabetes. Acrolein (ACR), a toxic lipid aldehyde, triggers cellular dysfunction and death through FDP-lysine protein adduct formation. Our previous research has shown increased FDP-lysine levels in Müller cells during experimental diabetes, contributing to their dysfunction in DR. Aldehyde dehydrogenase 1A1 (ALDH1A1) plays a crucial role in detoxifying ACR in vivo and is downregulated in diabetic retinas. The aim of this study was to evaluate the efficacy of ALDH1A1 gene therapy in preventing ACR- and diabetes-induced Müller cell dysfunction.

Methods : Male Sprague-Dawley rats were divided into non-diabetic, streptozotocin (STZ)-induced diabetic, and STZ-induced diabetic rats treated with either control virus (AAV2.eGFP) or AAV2.ALDH1A1. AAV2 was intravitreally injected one week after diabetes induction, followed by electroretinography (ERG) 3-months later. Immunohistochemistry of retinal cryosections was used to confirm ALDH1A1 overexpression and to evaluate markers associated with Müller cell dysfunction. In addition, QMMuC-1 murine Müller cells were subjected to varying concentrations of ACR, both with and without exposure to AAV2.ALDH1A1 or control viruses. Quantitative RT-PCR and/or Western blotting were employed to evaluate ACR's impact on Müller cells, focusing on markers associated with inflammation, oxidative stress, and other indicators of cellular dysfunction.

Results : The diabetic control group displayed significant reductions in ERG A- and B-wave amplitudes after 3 months of diabetes. Administration of AAV2.ALDH1A1, but not AAV2 control viruses, prevented these reductions. Diabetic rats treated with AAV2.ALDH1A1 exhibited increased retinal ALDH1A1 expression and reduced glial cell activation and neurodegeneration compared to other diabetic groups. Exposure to low concentrations of ACR (1-10µM) resulted in FDP-lysine accumulation on QMMuC-1 proteins and increased mRNA expression of inflammatory cytokines (IL-18 and IL-6). These changes were associated with elevated HO-1 and decreased expression of Aqp4 and Kir4.1. AAV2-ALDH1A1 effectively counteracted ACR-induced changes in Müller cells, an effect not observed with AAV2 control viruses.

Conclusions : Our studies provide evidence that ALDH1A1 gene therapy may represent an effective approach for preventing ACR-induced Müller cell dysfunction during diabetes.