title: Streptococcus pneumoniae secretes hydrogen peroxide leading to DNA damage and apoptosis in lung cells.
abstract: Streptococcus pneumoniae is a leading cause of pneumonia and one of the most common causes of death globally. The impact of S. pneumoniae on host molecular processes that lead to detrimental pulmonary consequences is not fully understood. Here, we show that S. pneumoniae induces toxic DNA double-strand breaks (DSBs) in human alveolar epithelial cells, as indicated by ataxia telangiectasia mutated kinase (ATM)-dependent phosphorylation of histone H2AX and colocalization with p53-binding protein (53BP1). Furthermore, results show that DNA damage occurs in a bacterial contact-independent fashion and that Streptococcus pyruvate oxidase (SpxB), which enables synthesis of H2O2, plays a critical role in inducing DSBs. The extent of DNA damage correlates with the extent of apoptosis, and DNA damage precedes apoptosis, which is consistent with the time required for execution of apoptosis. Furthermore, addition of catalase, which neutralizes H2O2, greatly suppresses S. pneumoniae-induced DNA damage and apoptosis. Importantly, S. pneumoniae induces DSBs in the lungs of animals with acute pneumonia, and H2O2 production by S. pneumoniae in vivo contributes to its genotoxicity and virulence. One of the major DSBs repair pathways is nonhomologous end joining for which Ku70/80 is essential for repair. We find that deficiency of Ku80 causes an increase in the levels of DSBs and apoptosis, underscoring the importance of DNA repair in preventing S. pneumoniae-induced genotoxicity. Taken together, this study shows that S. pneumoniae-induced damage to the host cell genome exacerbates its toxicity and pathogenesis, making DNA repair a potentially important susceptibility factor in people who suffer from pneumonia.
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602; Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545;
authors.forename: Prashant
authors.initials: P
authors.lastname: Rai
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;
authors.forename: Marcus
authors.initials: M
authors.lastname: Parrish
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;
authors.forename: Ian Jun Jie
authors.initials: IJ
authors.lastname: Tay
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602; Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545;
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;
authors.forename: Shelley
authors.initials: S
authors.lastname: Ackerman
authors.affiliation: Animal Health Biotechnology, Temasek Life Sciences Laboratory, Singapore 117604.
authors.forename: Fang
authors.initials: F
authors.lastname: He
authors.affiliation: Animal Health Biotechnology, Temasek Life Sciences Laboratory, Singapore 117604.
authors.forename: Jimmy
authors.initials: J
authors.lastname: Kwang
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602; Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545;
authors.forename: Vincent T
authors.initials: VT
authors.lastname: Chow
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; bevin@MIT.edu.
authors.forename: Bevin P
authors.initials: BP
authors.lastname: Engelward
mesh_terms: D000818:Animals; D017209:Apoptosis; D004249:DNA Damage; D004260:DNA Repair; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D006861:Hydrogen Peroxide / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D006861:Hydrogen Peroxide
keywords: DNA damage; Ku80; Streptococcus pneumoniae; hydrogen peroxide; γH2AX