Endothelial cytochrome P450 -derived cholesterol limits angiogenesis.

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• The cytochrome P450 (CYP450) system, including CYP450 reductase (POR), is crucial for cellular processes.
• CYP51A1, a CYP450 isoenzyme, is essential for endogenous cholesterol biosynthesis.
• The role of intracellular cholesterol synthesis in endothelial function and angiogenesis is not well understood.

Purpose of the Study:

• To investigate the role of endothelial POR in intracellular cholesterol synthesis and its impact on endothelial function.
• To elucidate the molecular mechanisms linking POR deficiency, cholesterol metabolism, and angiogenesis.

Main Methods:

• Generated CRISPR/Cas9 knockouts of POR in primary human endothelial cells (EC).
• Studied an endothelial-specific, tamoxifen-inducible POR knockout mouse model (ecPOR-/-).
• Analyzed cholesterol metabolites, SREBP2 activation, angiogenesis assays (spheroids, aortic segments, retinal angiogenesis), RNAseq, and signaling pathway activation (PI3K/AKT/mTOR).

Main Results:

• POR deletion in ECs led to lanosterol accumulation and reduced desmosterol, indicating impaired cholesterol synthesis.
• POR deficiency promoted basal and VEGF-induced angiogenesis in vitro and in vivo.
• Mechanistically, POR deletion activated the SREBP2 pathway and upregulated PI3K/AKT/mTOR signaling, leading to enhanced angiogenesis.

Conclusions:

• Endothelial POR and CYP51A1 axis inhibition impairs cholesterol synthesis, activates SREBP2, and enhances angiogenesis.
• This study reveals a novel link between intracellular cholesterol metabolism and vascular growth via PI3K/AKT/mTOR signaling.
• Targeting the endothelial POR/CYP51A1 pathway may offer new strategies for modulating angiogenesis.