Gasdermin D restricts Burkholderia cenocepacia infection in vitro and in vivo

Shady Estfanous,Cierra Carafice,Tianliang Li,Daniel Baetzhold,Kyle Caution,Sameh Soror,Mikhail A Gavrilin,Kathrin Krause,Mostafa Eltobgy,Xiaoli Zhang,Kylene Daily,Haitao Wen,Amal O Amer,Hesham Haffez,Midhun N K Anne,Asmaa Badr,Kaitlin Hamilton,Arwa Abu Khweek

doi:10.1038/s41598-020-79201-5

Abstract

Burkholderia cenocepacia (B. cenocepacia) is an opportunistic bacterium; causing severe life threatening systemic infections in immunocompromised individuals including cystic fibrosis patients. The lack of gasdermin D (GSDMD) protects mice against endotoxin lipopolysaccharide (LPS) shock. On the other hand, GSDMD promotes mice survival in response to certain bacterial infections. However, the role of GSDMD during B. cenocepacia infection is not yet determined. Our in vitro study shows that GSDMD restricts B. cenocepacia replication within macrophages independent of its role in cell death through promoting mitochondrial reactive oxygen species (mROS) production. mROS is known to stimulate autophagy, hence, the inhibition of mROS or the absence of GSDMD during B. cenocepacia infections reduces autophagy which plays a critical role in the restriction of the pathogen. GSDMD promotes inflammation in response to B. cenocepacia through mediating the release of inflammasome dependent cytokine (IL-1β) and an independent one (CXCL1) (KC). Additionally, different B. cenocepacia secretory systems (T3SS, T4SS, and T6SS) contribute to inflammasome activation together with bacterial survival within macrophages. In vivo study confirmed the in vitro findings and showed that GSDMD restricts B. cenocepacia infection and dissemination and stimulates autophagy in response to B. cenocepacia. Nevertheless, GSDMD promotes lung inflammation and necrosis in response to B. cenocepacia without altering mice survival. This study describes the double-edged functions of GSDMD in response to B. cenocepacia infection and shows the importance of GSDMD-mediated mROS in restriction of B. cenocepacia.

Highlights

Burkholderia cenocepacia (B. cenocepacia) is an opportunistic bacterium; causing severe life threatening systemic infections in immunocompromised individuals including cystic fibrosis patients
In order to investigate whether gasdermin D (GSDMD) is cleaved during B. cenocepacia infection, bone marrow-derived macrophages from WT, gsdmd−/−, and casp11−/− mice were infected with B. cenocepacia at MOI of 10
These data indicate that CASP11 contributes to GSDMD cleavage during B. cenocepacia infection

Summary

Introduction

Burkholderia cenocepacia (B. cenocepacia) is an opportunistic bacterium; causing severe life threatening systemic infections in immunocompromised individuals including cystic fibrosis patients. Our in vitro study shows that GSDMD restricts B. cenocepacia replication within macrophages independent of its role in cell death through promoting mitochondrial reactive oxygen species (mROS) production. Burkholderia cenocepacia (B. cenocepacia) is an opportunistic aerobic Gram-negative facultative intracellular bacterium widely spread in the environment and can cause severe pulmonary infections in immunocompromised individuals and patients with underlying diseases such as cystic fibrosis (CF) and chronic granulomatous disease[1]. The inflammasome promotes the activation and release of pro-inflammatory cytokines interleukin-1beta (IL-1β) and IL-18 This is associated with the formation of pores within the host plasma membrane via the protein Gasdermin D (GSDMD) which often precedes cell d eath[6,7,8,9]. GSDMD restricts B. cenocepacia replication while promoting inflammation and neutrophil recruitment in the lungs of infected mice These results clarify the double-edged functions of GSDMD in response to B. cenocepacia

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Results

Conclusion