In the title "Control of Vascular Tone via Transformation of Hydrogen Peroxide" by Prof. Emeritus Roland Stocker from the Heart Research Institute, Australia, the regulation of vascular tone is intricately explored in a 57-minute lecture. The lecture focuses on the intrinsic pathways governing arterial relaxation, introducing Kynurenine as an endothelium-derived relaxing factor produced during inflammation. Prof. Stocker challenges the dogma surrounding Indoleamine 2,3-dioxygenase 1 (IDO1) as a reductive dioxygenase, unveiling its peroxidase activity and its role in redox signaling and oxidative stress in vessels. The presentation explores the impact of IDO1 on blood pressure in human sepsis and pre-clinical models, detailing its effects on hypotension and endothelial expression in mice. Prof. Stocker elucidates the mechanism of IDO1-mediated arterial relaxation and blood pressure lowering, revealing L-Trp-induced relaxation and the formation of the arterial relaxant cis-WOOH. The lecture highlights the novel role of cis-WOOH in oxidative activation of PKG1α, regulating arterial relaxation and blood pressure. The redox signaling by cis-WOOH is explored through thiol-dependent hydroperoxide metabolism, involving the reaction with GPx4, Prx2/4, and PKG1α in arteries. Prof. Stocker summarizes the intricate redox signaling mechanisms mediated by IDO1 and cis-WOOH, contributing to our understanding of vascular tone control.For further details, watch a video