P. aeruginosa augments irradiation injury via 15-lipoxygenase-catalyzed generation of 15-HpETE-PE and induction of theft-ferroptosis.

Haider H Dar,Svetlana N Samovich,Joel S Greenberger,Alexander A Kapralov,Andrew A Amoscato,Tamil S Anthonymuthu,Claudette M St Croix,Simon C Watkins,Michael W Epperly,Galina V Shurin,Vladimir A Tyurin,Hülya Bayır,Valerian E Kagan,Austin B Souryavong,Yulia Y Tyurina,Sally E Wenzel,Rama K Mallampalli

doi:10.1172/jci.insight.156013

Abstract

Total body irradiation (TBI) targets sensitive bone marrow hematopoietic cells and gut epithelial cells, causing their death and inducing a state of immunodeficiency combined with intestinal dysbiosis and nonproductive immune responses. We found enhanced Pseudomonas aeruginosa (PAO1) colonization of the gut leading to host cell death and strikingly decreased survival of irradiated mice. The PAO1-driven pathogenic mechanism includes theft-ferroptosis realized via (a) curbing of the host antiferroptotic system, GSH/GPx4, and (b) employing bacterial 15-lipoxygenase to generate proferroptotic signal — 15-hydroperoxy-arachidonoyl-PE (15-HpETE-PE) — in the intestines of irradiated and PAO1-infected mice. Global redox phospholipidomics of the ileum revealed that lysophospholipids and oxidized phospholipids, particularly oxidized phosphatidylethanolamine (PEox), represented the major factors that contributed to the pathogenic changes induced by total body irradiation and infection by PAO1. A lipoxygenase inhibitor, baicalein, significantly attenuated animal lethality, PAO1 colonization, intestinal epithelial cell death, and generation of ferroptotic PEox signals. Opportunistic PAO1 mechanisms included stimulation of the antiinflammatory lipoxin A4, production and suppression of the proinflammatory hepoxilin A3, and leukotriene B4. Unearthing complex PAO1 pathogenic/virulence mechanisms, including effects on the host anti/proinflammatory responses, lipid metabolism, and ferroptotic cell death, points toward potentially new therapeutic and radiomitigative targets.

Highlights

Exposure to ionizing radiation initiates generation of a multitude of reactive intermediates leading to DNA damage that trigger predominantly apoptotic death of sensitive cell populations – gut epithelium and bone marrow hematopoietic cells [1, 2]
We discovered that PAO1 dramatically boosts the injury caused by total body irradiation (TBI) as evidenced by i) markedly accelerated mortality of exposed mice, ii) enhanced recruitment and activation of innate immune cells, iii) production and release of pro-inflammatory cytokines and chemokines, iv) elevated levels of pro-inflammatory lipid mediators and oxidized phospholipids, v) accumulation of myeloperoxidase-specific lipid metabolites, vi) activation of ferroptotic cell death, and vii) protective effects of a 15-lipoxygenase (15-LOX) inhibitor, baicalein
After administration of PAO1 the day after TBI, we observed an astonishing decrease in the survival of mice such that 100% lethality occurred on day 5 after irradiation (Figure 1A)

Summary

Introduction

Exposure to ionizing radiation initiates generation of a multitude of reactive intermediates leading to DNA damage that trigger predominantly apoptotic death of sensitive cell populations – gut epithelium and bone marrow hematopoietic cells [1, 2] These events transition into a cascade of aberrant metabolic and immune responses including recruitment/activation of innate immune cells. The interaction of the gut microbiome and radiation is a bidirectional function whereby radiation can disrupt the microbiome by promoting dysbiosis which, in turn, affects the body’s responses to irradiation [5] In this chain of events, intestinal dysbiosis favoring colonization by pathogenic bacterial strains, blossoming in immune-compromised conditions, plays a very important role [6]. Among them, is a Gram-negative bacterium, Pseudomonas aeruginosa (PAO1), well known to be virulent and successful in immunosuppressed pro-inflammatory environments [79]

Methods

Results

Conclusion