Arginase 2 regulates cholesterol biosynthesis in endothelial cells

Area of Science:

• Biochemistry
• Cell Biology
• Vascular Biology

Background:

• Arginase 2 (Arg 2) is a mitochondrial enzyme impacting endothelial nitric oxide (NO) bioavailability and vascular function.
• Its role in endothelial cholesterol metabolism is currently unknown, despite implications in endothelial dysfunction.

Purpose of the Study:

• To investigate the role of Arginase 2 (Arg 2) in endothelial cholesterol metabolism.
• To determine if Arg 2 influences the mevalonate pathway and vascular homeostasis.

Main Methods:

• CRISPR/Cas9-mediated deletion of Arg 2 in human umbilical vein endothelial cells (HUVECs).
• Transcriptomic analyses (RNA sequencing), quantitative RT-PCR, and immunoblotting for gene expression validation.
• Overexpression of wild-type and mutant Arg 2, arginase activity assays, and cholesterol intermediate quantification (LC-MS).

Main Results:

• Arg 2 deletion significantly downregulated genes in the mevalonate and steroid biosynthesis pathways.
• Reduced protein levels of key cholesterol biosynthetic enzymes and decreased cellular sterol concentrations were observed.
• Overexpression of Arg 2 (wild-type or inactive mutant) enhanced the expression of these cholesterol biosynthesis enzymes.

Conclusions:

• Arginase 2 (Arg 2) plays a previously unrecognized role in promoting endothelial cholesterol biosynthesis.
• Arg 2 may regulate vascular homeostasis via the mevalonate pathway, independent of its enzymatic activity.
• This links amino acid and lipid metabolism, suggesting Arg 2's contribution to endothelial dysfunction and atherosclerosis.