摘要：Cytosolic ROS, generated by NADPH oxidase 2 (Nox2) in diabetes, damage retinal mitochondria, which leads to the development of retinopathy. A small molecular weight G-protein essential for Nox2 activation, Rac1, is also transcriptionally activated via active DNA methylation-hydroxymethylation. DNA methylation is a dynamic process, and can also be regulated by histone modifications; diabetes alters retinal histone methylation machinery. Our aim is to investigate the role of histone methylation (H3K9me3) of
Rac1 promoter in dynamic DNA methylation- transcriptional activation. Using human retinal endothelial cells in 20 mM D-glucose, H3K9me3 at
Rac1 promoter was quantified by chromatin-Immunoprecipitation technique. Crosstalk between H3K9me3 and DNA methylation was examined in cells transfected with siRNA of histone trimethyl-transferase,
Suv39H1, or
Dnmt1, exposed to high glucose. Key parameters were confirmed in retinal microvessels from streptozotocin-induced diabetic mice, with intravitreally administered
Suv39H1-siRNA or
Dnmt1-siRNA. Compared to cells in normal glucose, high glucose increased H3K9me3 and Suv39H1 binding at
Rac1 promoter, and
Suv39H1-siRNA prevented glucose-induced increase 5 hydroxy methyl cytosine (5hmC) and
Rac1 mRNA. Similarly, in diabetic mice,
Suv39H1-siRNA attenuated increase in 5hmC and
Rac1 mRNA. Thus, H3K9me3 at
Rac1 promoter assists in active DNA methylation-hydroxymethylation, activating
Rac1 transcription. Regulation of Suv39H1-H3K9 trimethylation could prevent further epigenetic modifications, and prevent diabetic retinopathy.
