https://doi.org/10.1007/s00392-025-02625-4
1Universitätsklinikum Frankfurt Institut für Kardiovaskuläre Physiologie Frankfurt am Main, Deutschland; 2Universitätsklinikum Bonn Institut für Klinische Chemie und Klinische Pharmakologie Bonn, Deutschland; 3Goethe University Frankfurt Institute for Cardiovascular Physiology Frankfurt am Main, Deutschland
The cytochrome P450 reductase (POR)/ CYP51 monoxygenase is a redox system important for sterol synthesis. Cholesterol is an important membrane constituent and is involved in cell signaling. Cellular cholesterol is determined by uptake and de novo synthesis. High circulating cholesterol is linked to cardiovascular diseases but the role of endogenous cholesterol synthesis for endothelial function, in contrast, is unknown and was studied here. To inhibit cholesterol synthesis in endothelial cells, POR and CYP51 CRISPR knockout was performed in human aortic endothelial cells (HAEC) and in human umbilical vein endothelial cells (HUVEC). Furthermore, an endothelial-specific tamoxifen-inducible POR knockout mouse (ecPOR-/-) was generated. Knockout of POR and CYP51 in HAEC led to an accumulation of the CYP51 substrate lanosterol, whereas its product, desmosterol was reduced. Functionally, loss of endogenous cholesterol synthesis was linked to an increased basal and VEGF-stimulated angiogenic sprouting in HUVEC. Similarly, endothelial sprouting from aortic segments was increased in ecPOR-/- mice as compared to control mice. Importantly, increased angiogenesis was also observed in vivo in retina of ecPOR-/- mice. Cellular cholesterol levels are sensed by the SREBP2 (sterol regulatory element-binding proteins) system, and indeed, SREBP2 activation (cleavage and translocation to the nucleus) was increased after deletion of POR in cultured cells as well as in vivo (en face of aorta). Overexpression of the active, cleaved nuclear SREBP2 in cells increased angiogenesis similar to the knockout of POR and CYP51. RNAseq of POR-/- HAEC showed significant upregulation of cholesterol related genes LRP1, VLDLR and ABCG1, as well as pro-angiogenic genes such as VEGFA and ADM2. Remarkably, the complete set of genes from the cholesterol synthesis pathway was significantly downregulated. Altogether, inhibition of the endothelial POR/CYP51-axis impairs endogenous cholesterol production which correlates with the transcription of genes that promote angiogenesis.