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Arul Joseph Duraisamy, Renu A Kowluru; Epigenetic modifications and regulation of matrix metalloproteinase-9 in the development of diabetic retinopathy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1846.
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© ARVO (1962-2015); The Authors (2016-present)
Matrix metalloproteinase-9 (MMP-9) is activated in the retina in diabetes, and translocates into the mitochondria, damaging their membranes and accelerating capillary cell apoptosis. MMP-9 expression is regulated by DNA/histone modifications in the promoter sequence that controls activator protein -1 (AP-1) transcription factor binding. Dynamic balance between methyltransferase, Ezh2, and demethylase, KDM6B, regulates methyl modifications at the lysine 27 of histone 3 (H3K27), which, in di- and tri-methylated form, represses gene expression, but in mono-methylated form, it could activate the transcription. The present study aims to elucidate the role of H3K27 methylation in retinal MMP-9 transcriptional activation in diabetes.
Retinal microvessels were prepared by osmotic shock method from rats maintained diabetic (streptozotocin-induced) for 2 months. Lysine methylation of H3K27- (me1, me2 and me3), and also the recruitments of Ezh2 and KDM6B, at AP-1 region of MMP-9 promoter were analyzed in the crosslinked retinal microvessels by chromatin immunoprecipitation using antibodies specific for H3K27me1, H3K27me2, H3K27me3, Ezh2 and KDM6B.
Compared to the retinal microvessels from age-matched normal rats, microvessels from diabetic rats had increased H3K27me2 and H3K27me3 at the AP-1 binding region of the MMP-9 promoter, but H3K27me1 levels were similar in these two groups. Interestingly, at the same AP-1 region, the binding of Ezh2, and that of KDM6B, were also elevated.
Although diabetes increases the binding of demethylase, KDM6B, at AP-1 region of the MMP-9 promoter, concomitant increased binding of methyltransferase, Ezh2, at same site, maintains higher levels of H3K27me3/me2. Thus, demethylation of H3K27me2/me3 by KDM6B might not be efficient, and instead, diabetes could also be facilitating recruitment of other histone modifying enzymes at the MMP-9 promoter to increase its transcription.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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