# Epigenetic and O-glycosylation regulation of p66Shc mitigates mitochondrial oxidative stress in aortic dissection

## TL;DR

This study shows that aPC reduces aortic dissection by suppressing p66Shc through epigenetic and glycosylation mechanisms, protecting mitochondria from oxidative stress.

## Contribution

The study reveals a novel mechanism where aPC regulates p66Shc via epigenetic and O-glycosylation pathways to mitigate mitochondrial oxidative stress in aortic dissection.

## Key findings

- aPC downregulates p66Shc expression through epigenetic modifications.
- aPC increases O-glycosylation of p66Shc at Thr29, preventing mitochondrial translocation and ROS production.
- These mechanisms inhibit the progression of aortic dissection in a mouse model.

## Abstract

Background: Aortic dissection (AD) is a life-threatening vascular emergency with limited effective pharmacological treatments. Recent studies have identified Src homology 2 domain-containing transforming protein C1 (p66Shc) as a crucial mediator of oxidative stress, apoptosis, and inflammation in aortic cells, thereby contributing to cellular dysfunction and vascular remodeling implicated in AD development and progression. Despite its established role in promoting vascular dysfunction and remodeling, the protective potential of targeting p66Shc in AD remains unclear.

Methods: We quantified activated protein C (aPC) levels in clinical plasma samples from control subjects and AD patients using enzyme-linked immunosorbent assay (ELISA). To evaluate changes in p66Shc expression, we analyzed aortic tissues by Western blotting (WB), immunohistochemistry (IHC), and immunofluorescence (IF) staining. An in vivo AD model was established in thrombomodulin (TM)-mutant ApoE-/- mice, which display impaired TM-dependent PC activation, and exogenous PC was administered to evaluate its therapeutic effect. In parallel, mechanistic studies were performed in human endothelial cells using WB, co-immunoprecipitation (Co-IP), dual-label IF staining, chromatin immunoprecipitation (ChIP), luciferase reporter assays, and mitochondrial functional analyses.

Results: In this study, we demonstrate that aPC, a coagulation protease with known cytoprotective properties, downregulates p66Shc expression through epigenetic modifications. Additionally, aPC can modulate the expression of a cold shock protein Y-box-binding protein 1 (YB1), which acts as a transcription factor, leading to elevated O-linked N-acetylglucosamine transferase (OGT) levels. This upregulation enhances the O-glycosylation of p66Shc on its 29th tyrosine residue, preventing its mitochondrial translocation, preserving mitochondrial membrane potential, and reducing reactive oxygen species (ROS) production. Consequently, these molecular mechanisms inhibit the onset and progression of AD.

Conclusions: aPC epigenetically represses p66Shc transcription and promotes its O-glycosylation at Thr29 via the YB-1/OGT axis, thereby inhibiting mitochondrial ROS production and preventing vascular injury.