Dynamic DNA methylation of matrix metalloproteinase-9 in the development of diabetic retinopathy

Area of Science:

• Ophthalmology
• Molecular Biology
• Epigenetics

Background:

• Diabetes elevates retinal matrix metalloproteinase-9 (MMP-9), leading to mitochondrial damage and capillary cell apoptosis, key events preceding retinopathy.
• Diabetes influences epigenetic modifications, including DNA methylation, with activated retinal DNA methyltransferase (Dnmt) observed in diabetic conditions.

Purpose of the Study:

• To investigate the role of DNA methylation in regulating MMP-9 expression in the context of diabetes.
• To elucidate the specific mechanisms involving DNA methyltransferase 1 (Dnmt1) and Tet2 in MMP-9 regulation under high glucose conditions.

Main Methods:

• Quantified 5-methylcytosine (5mC) and 5-hydroxymethyl cytosine (5hmC) levels, and binding of Dnmt1 and Tet2 to the MMP-9 promoter in retinal endothelial cells exposed to high glucose.
• Utilized Tet2-siRNA to validate the specific role of Tet2 in MMP-9 activation.
• Confirmed findings in retinal tissues from streptozotocin-induced diabetic mice.

Main Results:

• High glucose decreased 5mC but increased Tet2 binding and 5hmC levels at the MMP-9 promoter, despite increased Dnmt1 binding.
• Tet2 inhibition (using Tet2-siRNA) reduced 5hmC levels, MMP-9 transcription, and protected against mitochondrial damage.
• Diabetic mice exhibited similar dynamic DNA methylation changes in the retinal MMP-9 promoter.

Conclusions:

• Diabetic retinopathy progression involves active DNA methylation-hydroxymethylation maintaining retinal MMP-9 transcription.
• Targeting this epigenetic machinery offers a potential therapeutic strategy to preserve mitochondrial homeostasis and inhibit diabetic retinopathy development.