Mitochondrial Genome-Encoded Long Noncoding RNA Cytochrome B and Mitochondrial Dysfunction in Diabetic Retinopathy
Ghulam Mohammad, Jay Kumar, Renu A. Kowluru
Abstract
Aims: Mitochondrial dysfunction is closely associated with the development of diabetic complications. In diabetic retinopathy, electron transport chain is compromised and mitochondrial DNA (mtDNA) is damaged, downregulating transcription of mtDNA-encoded cytochrome B ( CYTB ) and its antisense long noncoding RNA, long noncoding RNA cytochrome B (Lnc CytB ). Our goal was to investigate the role of Lnc CytB in the regulation of CYTB and mitochondrial function in diabetic retinopathy. Methods: Using human retinal endothelial cells, genetically manipulated for Lnc CytB (overexpression or silencing), the effect of high glucose (20 m M d -glucose) on Lnc CytB - CYTB interactions (by chromatin isolation by RNA purification), CYTB gene expression (by real-time quantitative polymerase chain reaction), complex III activity, mitochondrial free radicals, and oxygen consumption rate (OCR, by Seahorse XF analyzer) was investigated. Key results were confirmed in the retinal microvessels from streptozotocin-induced diabetic mice. Results: High glucose decreased Lnc CytB-CYTB interactions, and while Lnc CytB overexpression ameliorated glucose-induced decrease in CYTB gene transcripts, complex III activity and OCR and increase in mitochondrial reactive oxygen species, Lnc CytB-siRNA further attenuated CYTB gene transcription, complex III activity, and OCR. Similar decrease in Lnc CytB - CYTB interactions and CYTB transcription was observed in diabetic mice. Furthermore, maintenance of mitochondrial homeostasis by overexpressing superoxide dismutase or sirtuin 1 in mice ameliorated diabetes-induced decrease in Lnc CytB - CYTB interactions and CYTB gene transcripts, and also improved complex III activity and mitochondrial respiration. Innovation and Conclusion: Lnc CytB downregulation in hyperglycemic milieu downregulates CYTB transcription, which inhibits complex III activity and compromises mitochondrial stability and OCR. Thus, preventing Lnc CytB downregulation in diabetes has potential of inhibiting the development of diabetic retinopathy, possibly via maintaining mitochondrial respiration. Antioxid. Redox Signal. 39, 817–828.