A Thromboxane A ₂ Receptor-Driven COX-2–Dependent Feedback Loop That Affects Endothelial Homeostasis and Angiogenesis

Abstract

Background: TP (thromboxane A 2 receptor) plays an eminent role in the pathophysiology of endothelial dysfunction and cardiovascular disease. Moreover, its expression is reported to increase in the intimal layer of blood vessels of cardiovascular high-risk individuals. Yet it is unknown, whether TP upregulation per se has the potential to affect the homeostasis of the vascular endothelium. Methods: We combined global transcriptome analysis, lipid mediator profiling, functional cell analyses, and in vivo angiogenesis assays to study the effects of endothelial TP overexpression or knockdown/knockout on the angiogenic capacity of endothelial cells in vitro and in vivo. Results: Here we report that endothelial TP expression induces COX-2 (cyclooxygenase-2) in a G i/o - and G q/11 -dependent manner, thereby promoting its own activation via the auto/paracrine release of TP agonists, such as PGH2 (prostaglandin H 2 ) or prostaglandin F 2 but not TxA2 (thromboxane A 2 ). TP overexpression induces endothelial cell tension and aberrant cell morphology, affects focal adhesion dynamics, and inhibits the angiogenic capacity of human endothelial cells in vitro and in vivo, whereas TP knockdown or endothelial-specific TP knockout exerts opposing effects. Consequently, this TP-dependent feedback loop is disrupted by pharmacological TP or COX-2 inhibition and by genetic reconstitution of PGH 2 -metabolizing prostacyclin synthase even in the absence of functional prostacyclin receptor expression. Conclusions: Our work uncovers a TP-driven COX-2–dependent feedback loop and important effector mechanisms that directly link TP upregulation to angiostatic TP signaling in endothelial cells. By these previously unrecognized mechanisms, pathological endothelial upregulation of the TP could directly foster endothelial dysfunction, microvascular rarefaction, and systemic hypertension even in the absence of exogenous sources of TP agonists.

Active RhoA Exerts an Inhibitory Effect on the Homeostasis and Angiogenic Capacity of Human Endothelial Cells

“…Production, purification, and titration of lentiviral vectors were performed as described previously. 33 Shortly, human embryonic kidney cells, 293T cell line T cells were seeded in 150 cm² dishes at a density of 8*10 6 cells per dish in DMEM high‐glucose medium supplemented with 10% FCS, 1% penicillin‐streptomycin mix, and 1% GlutaMAX. After 24 hours, the cells were used for transfection at ≈40% confluence.…”

Deciphering Complex Interactions in Bioactive Lipid Signaling

“…The history of the EICs dates back to the 1930s, when new biologically active lipids were found in human seminal plasma [ 10 ]. Since then, they have been shown to play a major role in key processes like inflammation [ 13 ] and maintenance of energy homeostasis [ 14 , 15 , 16 , 17 ].…”

Aspirin sensitivity of PIK3CA-mutated Colorectal Cancer: potential mechanisms revisited

“…The most relevant being prostaglandin E 2 (PGE 2 ), D 2 , F 2α , prostacyclin (PGI 2 ) and TxA 2 . While both COX isoforms lead to the biosynthesis of prostaglandins, TxA 2 synthesis predominantly depends on COX-1-derived precursors [ 132 , 133 , 144 ]. This dependence of TxA 2 formation on COX-1 activity is due to COX isoform-preferential coupling of synthases.…”

“…However, not only formation of the mentioned prostaglandins and thromboxane A 2 depend on the activity of COX enzymes, but also COX have been shown to be involved, for instance, in dihomoprostaglandin formation from adrenic acid [ 147 ] or in the (mostly COX-2-dependent) formation of the F2-isoprostane and thromboxane A 2 receptor agonist 8-iso-PGF 2α (8-iso-prostaglandin F 2α ) [ 144 , 148 ]. Uninhibited, COX also generate a small amount of the arachidonic acid derivates 11-(R)-hydroxyeicosatetraenoic acid (11-HETE), as well as a racemic mixture of 15-(S)- and (R)-hydroxyeicosatetraenoic acid (15-HETE), the majority being the (S)-enantiomer [ 137 , 149 ].…”