title: Critical involvement of pneumolysin in production of interleukin-1alpha and caspase-1-dependent cytokines in infection with Streptococcus pneumoniae in vitro: a novel function of pneumolysin in caspase-1 activation.
abstract: Pneumolysin is a pore-forming cytolysin known as a major virulence determinant of Streptococcus pneumoniae. This protein toxin has also been shown to activate the Toll-like receptor 4 (TLR4) signaling pathway. In this study, a mutant S. pneumoniae strain deficient in pneumolysin (Deltaply) and a recombinant pneumolysin protein (rPLY) were constructed. Upon infection of macrophages in vitro, the ability to induce the production of interleukin-1alpha (IL-1alpha), IL-1beta, and IL-18 was severely impaired in the Deltaply mutant, whereas there was no marked difference in the induction of tumor necrosis factor alpha (TNF-alpha) and IL-12p40 between the wild type and the Deltaply mutant of S. pneumoniae. When macrophages were stimulated with rPLY, the production of IL-1alpha, IL-1beta, and IL-18 was strongly induced in a TLR4-dependent manner, whereas lipopolysaccharide, a canonical TLR4 agonist, hardly induced these cytokines. In contrast, lipopolysaccharide was more potent than rPLY in inducing the production of TNF-alpha, IL-6, and IL-12p40, the cytokines requiring no caspase activation. Activation of caspase-1 was observed in macrophages stimulated with rPLY but not in those stimulated with lipopolysaccharide, and the level of activation was higher in macrophages infected with wild-type S. pneumoniae than in those infected with the Deltaply mutant. These results clearly indicate that pneumolysin plays a key role in the host response to S. pneumoniae, particularly in the induction of caspase-1-dependent cytokines.
authors.affiliation: Department of Microbiology, Kyoto University Graduate School of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Shereen
authors.initials: S
authors.lastname: Shoma
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Ikuo
authors.initials: I
authors.lastname: Kawamura
authors.forename: Takamasa
authors.initials: T
authors.lastname: Nomura
authors.forename: Hideki
authors.initials: H
authors.lastname: Hara
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Uchiyama
authors.forename: Sylvia
authors.initials: S
authors.lastname: Daim
authors.forename: Masao
authors.initials: M
authors.lastname: Mitsuyama
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020170:Caspase 1 / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D053582:Interleukin-1alpha / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000382:microbiology / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000378:metabolism*; D013301:Streptolysins / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D053582:Interleukin-1alpha; D013301:Streptolysins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C032290:plY protein, Streptococcus pneumoniae; D020170:Caspase 1