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Nucleases from Prevotella intermedia can degrade neutrophil extracellular traps.

ABSTRACT: Periodontitis is an inflammatory disease caused by periodontal bacteria in subgingival plaque. These bacteria are able to colonize the periodontal region by evading the host immune response. Neutrophils, the host's first line of defense against infection, use various strategies to kill invading pathogens, including neutrophil extracellular traps (NETs). These are extracellular net-like fibers comprising DNA and antimicrobial components such as histones, LL-37, defensins, myeloperoxidase, and neutrophil elastase from neutrophils that disarm and kill bacteria extracellularly. Bacterial nuclease degrades the NETs to escape NET killing. It has now been shown that extracellular nucleases enable bacteria to evade this host antimicrobial mechanism, leading to increased pathogenicity. Here, we compared the DNA degradation activity of major Gram-negative periodontopathogenic bacteria, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans. We found that Pr. intermedia showed the highest DNA degradation activity. A genome search of Pr. intermedia revealed the presence of two genes, nucA and nucD, putatively encoding secreted nucleases, although their enzymatic and biological activities are unknown. We cloned nucA- and nucD-encoding nucleases from Pr. intermedia ATCC 25611 and characterized their gene products. Recombinant NucA and NucD digested DNA and RNA, which required both Mg2+ and Ca2+ for optimal activity. In addition, NucA and NucD were able to degrade the DNA matrix comprising NETs.

SUBMITTER: Doke M

PROVIDER: S-EPMC5516193 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Nucleases from Prevotella intermedia can degrade neutrophil extracellular traps.

Doke M M Fukamachi H H Morisaki H H Arimoto T T Kataoka H H Kuwata H H

Molecular oral microbiology 20160920 4

Periodontitis is an inflammatory disease caused by periodontal bacteria in subgingival plaque. These bacteria are able to colonize the periodontal region by evading the host immune response. Neutrophils, the host's first line of defense against infection, use various strategies to kill invading pathogens, including neutrophil extracellular traps (NETs). These are extracellular net-like fibers comprising DNA and antimicrobial components such as histones, LL-37, defensins, myeloperoxidase, and neu ...[more]

PMID: 27476978

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Project description:The pathogen Streptococcus equi subsp. zooepidemicus is associated with a wide range of animals, including humans, and outbreaks frequently occur in pigs, equines, and goats. Thus far, few studies have assessed interactions between the host immune system and S. equi subsp. zooepidemicus and how these interactions explain the wide host spectrum of S. equi subsp. zooepidemicus Neutrophils, the first line of innate immunity, possess a defense mechanism called neutrophil extracellular traps (NETs), which primarily consist of DNA and granule proteins that trap bacteria via charge interactions. Extracellular nucleases play important roles in the degradation of the DNA backbone of NETs. Here, two related extracellular nucleases, nuclease and 5'-nucleotidase (named ENuc and 5Nuc, respectively, in this study), were identified as being encoded by the SESEC_RS04165 gene and the SESEC_RS05720 gene (named ENuc and 5Nuc, respectively), and three related gene deletion mutant strains, specifically, the single-mutant ΔENuc and Δ5Nuc strains and the double-mutant ΔENuc Δ5Nuc strain, were constructed. The ΔENuc and Δ5Nuc single-mutant strains and the ΔENuc Δ5Nuc double-mutant strain demonstrated lower virulence than wild-type S. equi subsp. zooepidemicus when the mouse survival rate was evaluated postinfection. Furthermore, wild-type S. equi subsp. zooepidemicus more frequently traversed the bloodstream and transferred to other organs. Wild-type S. equi subsp. zooepidemicus induced fewer NETs and was able to survive in NETs, whereas only 40% of the ΔENuc Δ5Nuc double-mutant cells survived. S. equi subsp. zooepidemicus degraded the NET DNA backbone and produced deoxyadenosine, primarily through the action of ENuc and/or 5Nuc. However, the double-mutant ΔENuc Δ5Nuc strain lost the ability to degrade NETs into deoxyadenosine. Deoxyadenosine decreased RAW 264.7 cell phagocytosis to 40% of that of normal macrophages. Streptococcus equi subsp. zooepidemicus causes serious bacteremia in its hosts. However, little is known about how S. equi subsp. zooepidemicus interacts with the host innate immune system, particularly innate cells found in the blood. S. equi subsp. zooepidemicus is capable of evading NET-mediated killing via the actions of its potent extracellular nucleases, ENuc and 5Nuc, which directly degrade the NET DNA backbone to deoxyadenosine. In previous studies, other pathogens have required the synergism of nuclease and 5'-nucleotidase to engage in this self-protective process; however, ENuc and 5Nuc both possess nuclease activity and 5'-nucleotidase activity, highlighting the novelty of this discovery. Furthermore, deoxyadenosine impairs phagocytosis but not the intracellular bactericidal activity of macrophages. Here we describe a novel mechanism for S. equi subsp. zooepidemicus extracellular nucleases in NET degradation, which may provide new insights into the pathogen immune evasion mechanism and the prevention and treatment of bacterial disease.

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Nucleases from Prevotella intermedia can degrade neutrophil extracellular traps.

Publications

Nucleases from Prevotella intermedia can degrade neutrophil extracellular traps.

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