Neutrophil-Derived Myeloperoxidase and Hypochlorous Acid Critically Contribute to 20-Hydroxyeicosatetraenoic Acid Increases that Drive Postischemic Angiogenesis

Compensatory angiogenesis is an important adaptation for recovery from critical ischemia. We recently identified 20-hydroxyeicosatetrae-noic acid (20-HETE) as a novel contributor of ischemia-induced angiogenesis. However, the precise mechanisms by which ischemia promotes 20-HETE increases that drive angiogenesis are unknown. This study aims to address the hypothesis that inflammatory neutro-phil-derived myeloperoxidase (MPO) and hypochlorous acid (HOCl) critically contribute to 20-HETE increases leading to ischemic angio-genesis. Using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry, Laser Doppler Perfusion Imaging, and Microvascular Density analysis, we found that neutrophil depletion and MPO knock-out mitigate angiogenesis and 20-HETE production in the gracilis muscles of mice subjected to hindlimb ischemia. Furthermore, we found MPO and HOCl to be elevated in these tissues postischemia as assessed by immunofluorescence microscopy and in vivo live imaging of HOCl. Next, we demonstrated that the additions of either HOCl or an enzymatic system for generating HOCl to endothelial cells increase the expression of CYP4A11 and its product, 20-HETE. Finally, pharmacological interference of hypoxia inducible fac-tor (HIF) signaling results in ablation of HOCl-induced CYP4A11 transcript and significant reductions in CYP4A11 protein. Col-lectively, we conclude that neutrophil-derived MPO and its product HOCl activate HIF-1a and CYP4A11 leading to increased 20-HETE production that drives postischemic com-pensatory angiogenesis. SIGNIFICANCE STATEMENT Traditionally, neutrophil derived MPO and HOCl are exclusively associated in the innate immunity as potent bactericidal/virucidal factors. The present study establishes a novel paradigm by propos -ing a unique function for MPO/HOCl as signaling agents that drive critical physiological angiogenesis by activating the CYP4A11-20-HETE signaling axis via a HIF-1a-dependent mechanism. The find-ings from this study potentially identify novel therapeutic targets for the treatment of ischemia and other diseases associated with abnormal angiogenesis.

Automated summary

This study reveals that neutrophil-derived MPO and HOCl contribute to postischemic compensatory angiogenesis by activating the HIF-1α and CYP4A11 signaling pathway, leading to increased production of 20-HETE. These findings potentially identify novel therapeutic targets for the treatment of ischemia and diseases associated with abnormal angiogenesis.