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Hofstaedter CE, O'Keefe IP, Met CM, Wu L, Vanderwoude J, Shin S, Diggle SP, Riquelme SA, Rasko DA, Doi Y, Harro JM, Kopp BT, Ernst RK. Pseudomonas aeruginosa Lipid A Structural Variants Induce Altered Immune Responses. Am J Respir Cell Mol Biol 2024; 71:207-218. [PMID: 38656811 DOI: 10.1165/rcmb.2024-0059oc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 04/23/2024] [Indexed: 04/26/2024] Open
Abstract
Pseudomonas aeruginosa causes chronic lung infection in cystic fibrosis (CF), resulting in structural lung damage and progressive pulmonary decline. P. aeruginosa in the CF lung undergoes numerous changes, adapting to host-specific airway pressures while establishing chronic infection. P. aeruginosa undergoes lipid A structural modification during CF chronic infection that is not seen in any other disease state. Lipid A, the membrane anchor of LPS (i.e., endotoxin), comprises the majority of the outer membrane of Gram-negative bacteria and is a potent Toll-like receptor 4 (TLR4) agonist. The structure of P. aeruginosa lipid A is intimately linked with its recognition by TLR4 and subsequent immune response. Prior work has identified P. aeruginosa strains with altered lipid A structures that arise during chronic CF lung infection; however, the impact of the P. aeruginosa lipid A structure on airway disease has not been investigated. Here, we show that P. aeruginosa lipid A lacks PagL-mediated deacylation during human airway infection using a direct-from-sample mass spectrometry approach on human BAL fluid. This structure triggers increased proinflammatory cytokine production by primary human macrophages. Furthermore, alterations in lipid A 2-hydroxylation impact cytokine response in a site-specific manner, independent of CF transmembrane conductance regulator function. It is interesting that there is a CF-specific reduction in IL-8 secretion within the epithelial-cell compartment that only occurs in CF bronchial epithelial cells when infected with CF-adapted P. aeruginosa that lacks PagL-mediated lipid A deacylation. Taken together, we show that P. aeruginosa alters its lipid A structure during acute lung infection and that this lipid A structure induces stronger signaling through TLR4.
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Affiliation(s)
| | | | | | - Ling Wu
- Department of Microbiology and
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jelly Vanderwoude
- Center for Microbial Dynamics and Infection, School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | | | - Stephen P Diggle
- Center for Microbial Dynamics and Infection, School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | | | - David A Rasko
- Institute for Genome Sciences
- Department of Microbiology and Immunology, and
- Center for Pathogen Research, University of Maryland, Baltimore, Baltimore, Maryland
| | - Yohei Doi
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
| | | | - Benjamin T Kopp
- Division of Pulmonary, Asthma, Cystic Fibrosis, and Sleep, Emory University, Atlanta, Georgia
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Hofstaedter CE, Chandler CE, Met CM, Gillespie JJ, Harro JM, Goodlett DR, Rasko DA, Ernst RK. Divergent Pseudomonas aeruginosa LpxO enzymes perform site-specific lipid A 2-hydroxylation. mBio 2024; 15:e0282323. [PMID: 38131669 PMCID: PMC10865791 DOI: 10.1128/mbio.02823-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/27/2023] [Indexed: 12/23/2023] Open
Abstract
Pseudomonas aeruginosa can survive in a myriad of environments, partially due to modifications of its lipid A, the membrane anchor of lipopolysaccharide. We previously demonstrated that divergent late acyltransferase paralogs, HtrB1 and HtrB2, add acyloxyacyl laurate to lipid A 2- and 2'-acyl chains, respectively. The genome of P. aeruginosa also has genes which encode two dioxygenase enzymes, LpxO1 and LpxO2, that individually hydroxylate a specific secondary laurate. LpxO1 acts on the 2'-acyloxyacyl laurate (added by HtrB2), whereas LpxO2 acts on the 2-acyloxyacyl laurate (added by HtrB1) in a site-specific manner. Furthermore, while both enzyme pairs are evolutionarily linked, phylogenomic analysis suggests the LpxO1/HtrB2 enzyme pair as being of ancestral origin, present throughout the Pseudomonas lineage, whereas the LpxO2/HtrB1 enzyme pair likely arose via horizontal gene transfer and has been retained in P. aeruginosa over time. Using a murine pulmonary infection model, we showed that both LpxO1 and LpxO2 enzymes are functional in vivo, as direct analysis of in vivo lipid A structure from bronchoalveolar lavage fluid revealed 2-hydroxylated lipid A. Gene expression analysis reveals increased lpxO2 but unchanged lpxO1 expression in vivo, suggesting differential regulation of these enzymes during infection. We also demonstrate that loss-of-function mutations arise in lpxO1 and lpxO2 during chronic lung infection in people with cystic fibrosis (CF), indicating a potential role for pathogenesis and airway adaptation. Collectively, our study characterizes lipid A 2-hydroxylation during P. aeruginosa airway infection that is regulated by two distinct lipid A dioxygenase enzymes.IMPORTANCEPseudomonas aeruginosa is an opportunistic pathogen that causes severe infection in hospitalized and chronically ill individuals. During infection, P. aeruginosa undergoes adaptive changes to evade host defenses and therapeutic interventions, increasing mortality and morbidity. Lipid A structural alteration is one such change that P. aeruginosa isolates undergo during chronic lung infection in CF. Investigating genetic drivers of this lipid A structural variation is crucial in understanding P. aeruginosa adaptation during infection. Here, we describe two lipid A dioxygenases with acyl-chain site specificity, each with different evolutionary origins. Further, we show that loss of function in these enzymes occurs in CF clinical isolates, suggesting a potential pathoadaptive phenotype. Studying these bacterial adaptations provides insight into selection pressures of the CF airway on P. aeruginosa phenotypes that persist during chronic infection. Understanding these adaptive changes may ultimately provide clinicians better control over bacterial populations during chronic infection.
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Affiliation(s)
- Casey E. Hofstaedter
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, Maryland, USA
- Medical Scientist Training Program, University of Maryland, Baltimore, Baltimore, Maryland, USA
| | - Courtney E. Chandler
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, Maryland, USA
| | - Charles M. Met
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, Maryland, USA
| | - Joseph J. Gillespie
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, Maryland, USA
| | - Janette M. Harro
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, Maryland, USA
| | - David R. Goodlett
- Departments of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - David A. Rasko
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, Maryland, USA
- Institute for Genome Sciences, University of Maryland, Baltimore, Baltimore, Maryland, USA
- Center for Pathogen Research, University of Maryland, Baltimore, Baltimore, Maryland, USA
| | - Robert K. Ernst
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, Maryland, USA
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, Maryland, USA
- Center for Pathogen Research, University of Maryland, Baltimore, Baltimore, Maryland, USA
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