Abstract
Purpose :
In the pathogenesis of diabetic retinopathy, mitochondrial DNA (mtDNA) is damaged, compromising the electron transport chain (ETC) system, and accelerating retinal capillary cell death. The proteins, encoded by mtDNA have an important role in the proper functioning of the ETC system, and cytochrome B (CYTB) is one of the 13 mtDNA-encoded genes critical in the functioning of complex III. Diabetes also alters the levels of many nuclear DNA transcribed long non-coding RNAs (LncRNAs; RNAs with more than 200 nucleotides with no open reading frame for translation), and these LncRNAs have been implicated in diabetic retinopathy. However, mtDNA also transcribes three LncRNAs, but their role in diabetic retinopathy remains to be elucidated. Our aim was to investigate the role of mitochondrial encoded LncRNA Cytochrome B (LncCytB) in diabetic retinopathy.
Methods :
Human retinal endothelial cells, incubated in 5mM (normal) or 20mM (high) D-glucose were analyzed for LncCytB expression by qRT-PCR and its mitochondrial localization by RNA fluorescence in situ hybridization. The interactions between LncCytB and CYTB were evaluated by Chromatin isolation by RNA purification method. The role of LncCytB in the regulation of CYTB expression was determined in HRECs overexpressing LncCytB using full-length LncCytB, synthesized by T7 promoter based in-vitro transcription.
Results :
Compared to normal glucose, high glucose decreased LncCytB transcripts, and also attenuated its levels in the mitochondria. The interactions of LncCytB with CYTB were compromised and the activity of the complex III was reduced. Restoration of LncCytB ameliorated glucose-induced decrease in CYTB.
Conclusions :
Decreased interactions of LncCytB-CYTB in hyperglycemic milieu attenuate the processing of mtDNA-encoded CYTB, resulting in its decreased expression, and the ETC system is compromised. Thus, regulation of LncCytB could prevent ETC-mediated self-propagation of the vicious cycle of free radicals, and protect mitochondrial integrity in diabetic retinopathy.
This is a 2021 ARVO Annual Meeting abstract.