Epigenetic modifications in hyperhomocysteinemia: potential role in diabetic retinopathy and age-related macular degeneration

// Khaled Elmasry 1, 2, 3, 4 , Riyaz Mohamed 1, 3 , Isha Sharma 1, 3 , Nehal M. Elsherbiny 5 , Yutao Liu 2, 3 , Mohamed Al-Shabrawey 1, 2, 3, 4 and Amany Tawfik 1, 2, 3 1 Department of Oral Biology and Anatomy, Dental College of Georgia, Augusta University, Augusta, GA, USA 2 Department of Cellular Biology and Anatomy, Medical College of Georgia (MCG), Augusta University, Augusta, GA, USA 3 James and Jean Culver Vision Discovery Institute, MCG, Augusta University, August, GA, USA 4 Department of Human Anatomy and Embryology, Faculty of Medicine, Mansoura University, Mansoura, Egypt 5 Department of Biochemistry, Faculty of Pharmacy, Mansoura University, Mansoura, Egypt Correspondence to: Amany Tawfik, email: amtawfik@augusta.edu Keywords: epigenetic modifications; blood retinal barrier; diabetic retinopathy; age-related macular degeneration; hyperhomocysteinemia; Gerotarget Received: August 06, 2017 Accepted: January 24, 2018 Published: January 29, 2018 ABSTRACT To study Hyperhomocysteinemia (HHcy)-induced epigenetic modifications as potential mechanisms of blood retinal barrier (BRB) dysfunction, retinas isolated from three- week-old mice with elevated level of Homocysteine (Hcy) due to lack of the enzyme cystathionine β-synthase ( cbs –/– , cbs +/– and cbs +/+ ), human retinal endothelial cells (HRECs), and human retinal pigmented epithelial cells (ARPE-19) treated with or without Hcy were evaluated for (1) histone deacetylases (HDAC), (2) DNA methylation (DNMT), and (3) miRNA analysis. Differentially expressed miRNAs in mice with HHcy were further compared with miRNA analysis of diabetic mice retinas (STZ) and miRNAs within the exosomes released from Hcy-treated RPEs. Differentially expressed miRNAs were further evaluated for predicted target genes and associated pathways using Ingenuity Pathway Analysis. HHcy significantly increased HDAC and DNMT activity in HRECs, ARPE-19, and cbs mice retinas, whereas inhibition of HDAC and DNMT decreased Hcy-induced BRB dysfunction. MiRNA profiling detected 127 miRNAs in cbs +/– and 39 miRNAs in cbs –/– mice retinas, which were significantly differentially expressed compared to cbs +/+ . MiRNA pathway analysis showed their involvement in HDAC and DNMT activation, endoplasmic reticulum (ER), and oxidative stresses, inflammation, hypoxia, and angiogenesis pathways. Hcy-induced epigenetic modifications may be involved in retinopathies associated with HHcy, such as age-related macular degeneration and diabetic retinopathy.