HRD1 prevents atherosclerosis-mediated endothelial cell apoptosis by promoting LOX-1 degradation

Area of Science:

• Cardiovascular Biology
• Molecular Medicine
• Endothelial Cell Biology

Background:

• The E3 ubiquitin ligase HRD1 (3-hydroxy-3-methylglutaryl reductase degradation) is crucial for cardiac function, but its role in endothelial dysfunction and atherosclerosis (AS) remains largely unknown.
• Endothelial cells (ECs) are key players in AS pathogenesis, and their dysfunction contributes to disease progression.

Purpose of the Study:

• To investigate the role and biological functions of HRD1 in the context of atherosclerosis.
• To elucidate the molecular mechanisms underlying HRD1 regulation and its impact on endothelial cell apoptosis.

Main Methods:

• Quantitative analysis of HRD1 expression in atherosclerotic tissues and ECs treated with oxidized low-density lipoprotein (ox-LDL).
• Gene manipulation techniques (forced expression, deletion) to assess HRD1's effect on EC apoptosis.
• Chromatin immunoprecipitation (ChIP) assays to identify transcription factor binding to the HRD1 promoter.
• Co-immunoprecipitation and Western blotting to study protein-protein interactions and ubiquitination.
• In vitro studies using pravastatin to evaluate its effect on HRD1 expression and EC protection.

Main Results:

• HRD1 expression was significantly reduced in atherosclerotic intima and by ox-LDL in ECs.
• Forced HRD1 expression inhibited ox-LDL-induced EC apoptosis, while HRD1 downregulation exacerbated it.
• The transcription factor KLF2 directly bound to and positively regulated the HRD1 promoter, reversing ox-LDL-induced HRD1 decrease.
• HRD1 interacted with LOX-1, promoting its ubiquitination and proteasomal degradation, thereby reducing EC apoptosis.
• Pravastatin enhanced HRD1 expression in an ox-LDL-exposed EC model via a KLF2-dependent mechanism, and HRD1 interference abolished this protective effect.

Conclusions:

• Reduced HRD1 expression is a critical factor in ox-LDL-induced endothelial cell apoptosis and AS development.
• The KLF2-HRD1-LOX-1 axis represents a novel molecular pathway regulating endothelial cell function in AS.
• Restoration of HRD1 expression, potentially through KLF2 activation or other mechanisms, emerges as a promising therapeutic strategy for human AS.