The vicious circle of UHRF1 down-regulation and KEAP1/NRF2/HO-1 pathway impairment promotes oxidative stress-induced endothelial cell apoptosis in diabetes

Background: Oxidative stress is recognized as a key factor in the induction of endothelial dysfunction in diabetes. However, the specific mechanisms have not been fully elucidated. We herein hypothesized that ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) might have a role in oxidative stress-induced endothelial cell (EC) apoptosis in diabetes.

Methods: Western blot, qPCR, wound healing assay, apoptosis assay, reactive oxygen species (ROS) detection, dual-luciferase reporter assay, methylation-specific PCR, bisulfite sequencing PCR and chromatin immunoprecipitation assay were performed.

Results: UHRF1 expression levels were significantly decreased in endothelial colony-forming cells derived from peripheral blood of participants with type 2 diabetes compared with individuals without diabetes. ECs treated with high glucose, palmitate or hydrogen peroxide in vitro also exhibited decreased UHRF1 protein levels. Silencing of UHRF1 led to decreased migration ability and increased apoptosis and ROS production in ECs, which might be related to impaired Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2)/haeme oxygenase-1 pathway. Mechanistically, UHRF1 is closely implicated in epigenetic regulation of chromatin modification status at KEAP1 genomic locus via histone acetylation. NRF2 down-regulation in turn inhibits UHRF1 protein level, which might be due to increased ROS generation.

Conclusion: Diabetes-induced oxidative stress can mediate down-regulation of UHRF1, which enhances ROS production by regulating KEAP1/p-NRF2 pathway through histone acetylation and might also form a self-perpetuating feedback loop with KEAP1/p-NRF2 to further promote oxidative stress-induced apoptosis of ECs in diabetes.