Phospholipid peroxidation fuels ExoU phospholipase-dependent cell necrosis and supportsPseudomonas aeruginosa-driven pathology

Abstract

Regulated cell necrosis supports immune and anti-infectious strategies of the body; however, dysregulation of these processes drives pathological organ damage. Pseudomonas aeruginosa expresses a phospholipase, ExoU that triggers pathological host cell necrosis through a poorly characterized pathway. Here, we investigated the molecular and cellular mechanisms of ExoU-mediated necrosis. We show that cellular peroxidised phospholipids enhance ExoU phospholipase activity, which drives necrosis of immune and non-immune cells. Conversely, both the endogenous lipid peroxidation regulator GPX4 and the pharmacological inhibition of lipid peroxidation delay ExoU-dependent cell necrosis and improve bacterial elimination in vitro and in vivo. Our findings also pertain to the ExoU-related phospholipase from the bacterial pathogen Burkholderia thailandensis, suggesting that exploitation of peroxidised phospholipids might be a conserved virulence mechanism among various microbial phospholipases. Overall, our results identify an original lipid peroxidation-based virulence mechanism as a strong contributor of microbial phospholipase-driven pathology.

Caspase-1-driven neutrophil pyroptosis and its role in host susceptibility to Pseudomonas aeruginosa

“…Striking to us was the observation that expression of the key virulence factors ExoS or ExoU strongly influences neutrophils to go into NETosis whereas strains lacking ExoU or ExoS induced a complete rewiring of neutrophil death toward a Caspase-1-driven way. We hypothesize that the potent cytotoxic effect of these toxins towards various cell types, including neutrophils, may overcome inflammasome detection of Pseudomonas aeruginosa and triggers other neutrophil death programs [ 42 , 43 , 59 – 61 ]. Another non mutually exclusive guess is that these toxins directly interfere with the activation of the inflammasome pathway, thus removal of such toxins leads to an exacerbated inflammasome-response as previously reported for ExoU [ 40 ] and ExoS [ 62 ].…”

Dihydrolipoamide Acetyltransferase AceF Influences the Type III Secretion System and Resistance to Oxidative Stresses through RsmY/Z in Pseudomonas aeruginosa

“…Four major T3SS effectors have been identified in P. aeruginosa , namely, ExoY, ExoT, ExoU and ExoS [ 2 ]. ExoU has been shown to function as a phospholipase, which directly damages the host cell membrane and causes rapid necrotic death [ 4 ]. P. aeruginosa strains with the ability to inject ExoU are usually associated with poor clinical outcomes and increased mortality rates [ 5 ].…”

Caspase-1-driven neutrophil pyroptosis promotes an incomplete NETosis upon Pseudomonas aeruginosa infection

“…Striking to us was the observation that expression of the key virulence factors ExoS or ExoU strongly influences neutrophils to go into NETosis whereas strains lacking ExoU or ExoS induced a complete rewiring of neutrophil death toward a Caspase-1-driven way. We hypothesize that the potent cytotoxic effect of these toxins towards various cell types, including neutrophils, may overcome inflammasome detection of Pseudomonas aeruginosa and triggers other neutrophil death programs [41,42,54–56]. Another non mutually exclusive guess is that these toxins directly interfere with the activation of the inflammasome pathway, thus removal of such toxins leads to an exacerbated inflammasome-response as previously reported for ExoU [39] and ExoS [57].…”

“…Although the importance of NETosis in host immunity to infections has been well established (Brinkmann et al, 2004;Chen et al, 2018;Kovacs et al, 2020;Li et al, 2010), NETosis dysregulation also associates to autoimmunity, host tissue damages, aberrant coagulation and thrombus that all contribute to pathology such as sepsis or autoimmune lupus (Apel et al, 2021;Biron et al, 2018;Fuchs et al, 2010;Kahlenberg et al, 2013;Knackstedt et al, 2019;Kumar et al, 2015;Lefrançais et al, 2018;Martinod et al, 2015). Specifically, P. aeruginosa bacterial strains that express the necrotizing ExoU phospholipase virulence factor of the patatin-like phospholipase A2 family, promote organ damage-dependent acute respiratory distress syndrome (Bagayoko et al, 2021;Howell et al, 2013;Phillips et al, 2003;Sato et al, 2003).…”