Dysregulation of Cytosolic c-di-GMP in Edwardsiella piscicida Promotes Cellular Non-Canonical Ferroptosis.

Ying Wen,Dahai Yang,Xiangshan Zhou,Qin Liu,Ying Wang,Gabriel Núñez,Yuanxing Zhang,Shouwen Chen

doi:10.3389/fcimb.2022.825824

Abstract

Programmed cell death plays an important role in modulating host immune defense and pathogen infection. Ferroptosis is a type of inflammatory cell death induced by intracellular iron-dependent accumulation of toxic lipid peroxides. Although ferroptosis has been associated with cancer and other sterile diseases, very little is known about the role of ferroptosis in modulating host-pathogen interactions. We show that accumulation of the secondary messenger bis-(3′,5′)-cyclic dimeric GMP (c-di-GMP) in the pathogenic bacterium Edwardsiella piscicida (E. piscicida) triggers a non-canonical ferroptosis pathway in infected HeLa cells. Moreover, we observed that the dysregulation of c-di-GMP in E. piscicida promotes iron accumulation, mitochondrial dysfunction, and production of reactive oxygen species, all of which that can be blocked by iron chelator. Importantly, unlike classical ferroptosis that is executed via excess lipid peroxidation, no lipid peroxidation was detected in the infected cells. Furthermore, lipoxygenases inhibitors and lipophilic antioxidants are not able to suppress morphological changes and cell death induced by E. piscicida mutant producing excess c-di-GMP, and this c-di-GMP dysregulation attenuates bacterial virulence in vivo. Collectively, our results reveal a novel non-canonical ferroptosis pathway mediated by bacterial c-di-GMP and provide evidence for a role of ferroptosis in the regulation of pathogen infection.

Highlights

Programmed cell death is comprised of non-lytic, immunologically silent forms of cellular demise such as apoptosis and lytic and pro-inflammatory forms of necrosis that include pyroptosis, necroptosis, and ferroptosis (Jorgensen et al, 2017)
These results indicate that the transposon gene insertion in the E. piscicida 1906I mutant promotes robust cell death associated with ruptured membrane
As an important secondary messenger widely distributed in diverse bacteria, increasing evidence suggest that c-di-GMP plays a role in bacterial pathogenesis

Summary

Introduction

Programmed cell death is comprised of non-lytic, immunologically silent forms of cellular demise such as apoptosis and lytic and pro-inflammatory forms of necrosis that include pyroptosis, necroptosis, and ferroptosis (Jorgensen et al, 2017). The death of an infected cell promotes the elimination of intracellular pathogen and the release of intracellular contents including cytokines and DAMPs, which further contributes to pathogen clearance and host immune defense. The intracellular host pattern recognition receptor NLRC4 can sense bacterial flagellins of various bacteria including Legionella pneumophila (Katagiri et al, 2012), Listeria Monocytogenes (Cervantes et al, 2008; Warren et al, 2008), Burkholderia thiailandensis (Miao et al, 2010), and Salmonella typhimurium (Yang et al, 2013) triggering caspase 1-mediated pyroptosis and secretion of the inflammatory cytokines IL-1b and IL-18 which enhances immune responses and limits bacterial invasion. Very little is known about the function of ferroptosis during pathogen infection

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