One-in-four adults hospitalized for community-acquired pneumonia (CAP) experience an adverse cardiac event. Clinical epidemiological studies, as well as those performed in mice, non-human primates, and with human autopsy samples indicate that Streptococcus pneumoniae (Spn), the leading cause of CAP, can invade the heart from the bloodstream and cause direct cardiotoxicity. Within the myocardium Spn cause focal areas of damage we have called microlesions and these disrupt contractility. One recent break-through in our understanding of Spn pathogenesis was the observation that pneumococci are taken up by cardiomyocytes and Spn kill these cells from within. What is more, the pore-forming toxin pneumolysin and Streptococcal pyruvate oxidase (SpxB) derived H2O2 were both requisite for cardiotoxicity. Herein, our goal is to gain an understanding of the events that take place within a cardiomyocyte immediately after Spn uptake. Along such lines, results from in vitro and in vivo experiments, including dual-species RNA sequencing of Spn- infected hearts, have revealed highly compelling connections between changes in carbon availability, H2O2 production, biofilm / cardiac microlesion formation, and pneumolysin production. Thus, we hypothesize that glucose restriction encountered by Spn within a cardiomyocyte, and again in cardiac microlesions, results in metabolic and gene expression changes that enhance bacterial cardiotoxicity. To test this hypothesis and learn how pneumolysin and H2O2 work together to kill cardiomyocytes we will:
AIM 1 : Determine how environmental glucose, metabolism, and virulence are interlinked. To elucidate the basis, extent, and consequences of these connections we will: 1) determine how purposeful shunting of pyruvate metabolism (by means of mutation) towards the production of acetate, lactate, and/or formate impacts gene expression under high and low glucose conditions; 2) identify how Spn gene expression changes in longitudinal fashion after bacterial uptake by a cardiomyocyte and how this is linked to changes in Spn metabolism; 3) determine the importance of metabolism-linked genes to Spn survival within a cardiomyocyte, killing of the cardiomyocyte, and the overall disease process.
AIM 2 : Determine how bacterial derived H2O2, together with pneumolysin, kills cardiomyocytes. SpxB derived H2O2 and pneumolysin are both required for Spn killing of cardiomyocytes; each alone is insufficient. To determine why we will: 1) determine how varying production of H2O2 and pneumolysin together modulate the form of cardiomyocyte death; 2) determine if H2O2 potentiates pneumolysin production, its release from Spn, or host cell membrane targeting; and, 3) determine if SpxB-derived H2O2 contributes to the ion dysregulation that has previously been implicated in pneumolysin-induced necroptosis.
This aim, at its completion, will advance our understanding of how Spn kills host cells.

Public Health Relevance

One-in-four adults hospitalized for community-acquired pneumonia experience an adverse cardiac event. This is, in part, the result of Streptococcus pneumoniae invasion of cardiomyocytes. Herein, we determine how glucose limitation experienced by intracellular pneumococci enhances their production of cytotoxic pneumolysin and hydrogen peroxide; together resulting in cardiomyocyte death.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI114800-06A1
Application #
9891766
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Lu, Kristina
Project Start
2014-11-01
Project End
2024-11-30
Budget Start
2019-12-10
Budget End
2020-11-30
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Alabama Birmingham
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Dela Cruz, Charles S; Wunderink, Richard G; Christiani, David C et al. (2018) Future Research Directions in Pneumonia. NHLBI Working Group Report. Am J Respir Crit Care Med 198:256-263
Pajuelo, David; Gonzalez-Juarbe, Norberto; Tak, Uday et al. (2018) NAD+ Depletion Triggers Macrophage Necroptosis, a Cell Death Pathway Exploited by Mycobacterium tuberculosis. Cell Rep 24:429-440
Gonzalez-Juarbe, Norberto; Bradley, Kelley M; Riegler, Ashleigh N et al. (2018) Bacterial Pore-Forming Toxins Promote the Activation of Caspases in Parallel to Necroptosis to Enhance Alarmin Release and Inflammation During Pneumonia. Sci Rep 8:5846
Spencer, Brady L; Shenoy, Anukul T; Orihuela, Carlos J et al. (2017) The Pneumococcal Serotype 15C Capsule Is Partially O-Acetylated and Allows for Limited Evasion of 23-Valent Pneumococcal Polysaccharide Vaccine-Elicited Anti-Serotype 15B Antibodies. Clin Vaccine Immunol 24:
González-Juarbe, Norberto; Bradley, Kelley Margaret; Shenoy, Anukul Taranath et al. (2017) Pore-forming toxin-mediated ion dysregulation leads to death receptor-independent necroptosis of lung epithelial cells during bacterial pneumonia. Cell Death Differ 24:917-928
Shenoy, Anukul T; Brissac, Terry; Gilley, Ryan P et al. (2017) Streptococcus pneumoniae in the heart subvert the host response through biofilm-mediated resident macrophage killing. PLoS Pathog 13:e1006582
Mangat, Mandeep; Amalakuhan, Bravein; Habib, Sheila et al. (2017) High endocan levels are associated with the need for mechanical ventilation among patients with severe sepsis. Eur Respir J 50:
Brissac, Terry; Shenoy, Anukul T; Patterson, LaDonna A et al. (2017) Cell invasion and pyruvate oxidase derived H2O2 are critical for Streptococcus pneumoniae mediated cardiomyocyte killing. Infect Immun :
Lizcano, Anel; Akula Suresh Babu, Ramya; Shenoy, Anukul T et al. (2017) Transcriptional organization of pneumococcal psrP-secY2A2 and impact of GtfA and GtfB deletion on PsrP-associated virulence properties. Microbes Infect 19:323-333
Ray, Christopher; Shenoy, Anukul T; Orihuela, Carlos J et al. (2017) Killing of Serratia marcescens biofilms with chloramphenicol. Ann Clin Microbiol Antimicrob 16:19

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