RESUMO
Buruli ulcer is an emerging chronic infectious skin disease caused by Mycobacterium ulcerans. Mycolactone, an exotoxin produced by the bacterium, is the only identified virulence factor so far, but the functions of this toxin and the mechanisms of disease progression remain unclear. By interfering Sec61 translocon, mycolactone inhibits the Sec61-dependent co-translational translocation of newly synthesized proteins, such as induced cytokines and immune cell receptors, into the endoplasmic reticulum. However, in regard to IL-1ß, which is secreted by a Sec61-independent mechanism, mycolactone has been shown to induce IL-1ß secretion via activation of inflammasomes. In this study, we clarified that cytokine induction, including that of IL-1ß, in infected macrophages was suppressed by mycolactone produced by M. ulcerans subsp. shinshuense, despite the activation of caspase-1 through the inflammasome activation triggered in a manner independent of mycolactone. Intriguingly, mycolactone suppressed the expression of proIL-1ß as well as TNF-α at the transcriptional level, suggesting that mycolactone of M. ulcerans subsp. shinshuense may exert additional inhibitory effect on proIL-1ß expression. Remarkably, constitutively produced IL-18 was cleaved and mature IL-18 was actually released from macrophages infected with the causative mycobacterium. IL-18-deficient mice infected subcutaneously with M. ulcerans exhibited exacerbated skin inflammation during the course of disease progression. On the other hand, IL-1ß controls bacterial multiplication in skin tissues. These results provide information regarding the mechanisms and functions of the induced cytokines in the pathology of Buruli ulcer.
Assuntos
Úlcera de Buruli , Mycobacterium ulcerans , Animais , Camundongos , Úlcera de Buruli/microbiologia , Inflamassomos/metabolismo , Interleucina-18/metabolismo , Mycobacterium ulcerans/metabolismo , Macrolídeos/metabolismo , Citocinas/metabolismo , Progressão da Doença , InflamaçãoRESUMO
Caspase activation results in pyroptosis, an inflammatory cell death that contributes to several inflammatory diseases by releasing inflammatory cytokines and cellular contents. Fusobacterium nucleatum is a periodontal pathogen frequently detected in human cancer and inflammatory bowel diseases. Studies have reported that F. nucleatum infection leads to NLRP3 activation and pyroptosis, but the precise activation process and disease association remain poorly understood. This study demonstrated that F. nucleatum infection exacerbates acute colitis in mice and activates pyroptosis through caspase-11-mediated gasdermin D cleavage in macrophages. Furthermore, F. nucleatum infection in colitis mice induces the enhancement of IL-1⺠secretion from the colon, affecting weight loss and severe disease activities. Neutralization of IL-1⺠protects F. nucleatum infected mice from severe colitis. Therefore, F. nucleatum infection facilitates inflammation in acute colitis with IL-1⺠from colon tissue by activating noncanonical inflammasome through gasdermin D cleavage.
Assuntos
Colite , Inflamassomos , Humanos , Animais , Camundongos , Inflamassomos/metabolismo , Fusobacterium nucleatum/metabolismo , Gasderminas , Colite/induzido quimicamente , Caspases/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismoRESUMO
Helicobacter pylori, a pathogenic bacterium that colonizes in the human stomach, harbors DNA repair genes to counter the gastric environment during chronic infection. In addition, H. pylori adapts to the host environment by undergoing antigenic phase variation caused by genomic mutations. The emergence of mutations in nucleotide sequences is one of the major factors underlying drug resistance and genetic diversity in bacteria. However, it is not clear how DNA repair genes contribute to driving the genetic change of H. pylori during chronic infection. To elucidate the physiological roles of DNA repair genes, we generated DNA repair-deficient strains of H. pylori (ΔuvrA, ΔuvrB, ΔruvA, Δnth, ΔmutY, ΔmutS, and Δung). We performed susceptibility testing to rifampicin in vitro and found that ΔmutY exhibited the highest mutation frequency among the mutants. The number of bacteria colonizing the stomach was significantly lower with ΔmutY strain compared with wild-type strains in a Mongolian gerbil model of H. pylori infection. Furthermore, we performed a genomic sequence analysis of the strains isolated from the Mongolian gerbil stomachs eight weeks after infection. We found that the isolated ΔmutY strains exhibited a high frequency of spontaneous G:C to T:A mutations. However, the frequency of phase variations in the ΔmutY strain was almost similar to the wild-type strain. These results suggest that MutY may play a role in modes of gastric environmental adaptation distinct from phase variation.
Assuntos
Adaptação Fisiológica , DNA Glicosilases/genética , Helicobacter pylori/genética , Mutação/genética , Estômago/microbiologia , Animais , Proteínas de Bactérias/genética , Reparo do DNA/genética , Modelos Animais de Doenças , Gerbillinae , Infecções por Helicobacter/microbiologia , Helicobacter pylori/crescimento & desenvolvimento , Taxa de Mutação , NF-kappa B/metabolismoRESUMO
Clinical studies have shown that Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is associated with aggressive periodontitis and can potentially trigger or exacerbate rheumatoid arthritis (RA). However, the mechanism is poorly understood. Here, we show that systemic infection with A. actinomycetemcomitans triggers the progression of arthritis in mice anti-collagen antibody-induced arthritis (CAIA) model following IL-1ß secretion and cell infiltration in paws in a manner that is dependent on caspase-11-mediated inflammasome activation in macrophages. The administration of polymyxin B (PMB), chloroquine, and anti-CD11b antibody suppressed inflammasome activation in macrophages and arthritis in mice, suggesting that the recognition of lipopolysaccharide (LPS) in the cytosol after bacterial degradation by lysosomes and invasion via CD11b are needed to trigger arthritis following inflammasome activation in macrophages. These data reveal that the inhibition of caspase-11-mediated inflammasome activation potentiates aggravation of RA induced by infection with A. actinomycetemcomitans. This work highlights how RA can be progressed by inflammasome activation as a result of periodontitis-associated bacterial infection and discusses the mechanism of inflammasome activation in response to infection with A. actinomycetemcomitans.
Assuntos
Aggregatibacter actinomycetemcomitans , Artrite Experimental , Caspases Iniciadoras , Inflamassomos , Macrófagos , Animais , Camundongos , Macrófagos/imunologia , Artrite Experimental/microbiologia , Artrite Experimental/imunologia , Interleucina-1beta/metabolismo , Artrite Reumatoide , Camundongos Endogâmicos C57BL , Lipopolissacarídeos , Infecções por Pasteurellaceae/microbiologiaRESUMO
Long-term infection of the stomach with Helicobacter pylori can cause gastric cancer. However, the mechanisms by which the bacteria adapt to the stomach environment are poorly understood. Here, we show that a small non-coding RNA of H. pylori (HPnc4160, also known as IsoB or NikS) regulates the pathogen's adaptation to the host environment as well as bacterial oncoprotein production. In a rodent model of H. pylori infection, the genomes of bacteria isolated from the stomach possess an increased number of T-repeats upstream of the HPnc4160-coding region, and this leads to reduced HPnc4160 expression. We use RNA-seq and iTRAQ analyses to identify eight targets of HPnc4160, including genes encoding outer membrane proteins and oncoprotein CagA. Mutant strains with HPnc4160 deficiency display increased colonization ability of the mouse stomach, in comparison with the wild-type strain. Furthermore, HPnc4160 expression is lower in clinical isolates from gastric cancer patients than in isolates derived from non-cancer patients, while the expression of HPnc4160's targets is higher in the isolates from gastric cancer patients. Therefore, the small RNA HPnc4160 regulates H. pylori adaptation to the host environment and, potentially, gastric carcinogenesis.
Assuntos
Adaptação Fisiológica/genética , Infecções por Helicobacter/patologia , Helicobacter pylori/fisiologia , RNA Bacteriano/metabolismo , Pequeno RNA não Traduzido/metabolismo , Neoplasias Gástricas/microbiologia , Animais , Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , Carcinogênese , Modelos Animais de Doenças , Mucosa Gástrica/microbiologia , Mucosa Gástrica/patologia , Regulação Bacteriana da Expressão Gênica/fisiologia , Genoma Bacteriano/genética , Gerbillinae , Infecções por Helicobacter/microbiologia , Helicobacter pylori/isolamento & purificação , Helicobacter pylori/patogenicidade , Interações entre Hospedeiro e Microrganismos , Humanos , Masculino , Mutação , RNA Bacteriano/genética , Pequeno RNA não Traduzido/genética , RNA-Seq , Neoplasias Gástricas/patologiaRESUMO
Group A Streptococcus (GAS) secretes deoxyribonucleases and evades neutrophil extracellular killing by degrading neutrophil extracellular traps (NETs). However, limited information is currently available on the interaction between GAS and NETs in the pathogenicity of GAS pharyngitis. In this study, we modified a mouse model of GAS pharyngitis and revealed an essential role for DNase in this model. After intranasal infection, the nasal mucosa was markedly damaged near the nasal cavity, at which GAS was surrounded by neutrophils. When neutrophils were depleted from mice, GAS colonization and damage to the nasal mucosa were significantly decreased. Furthermore, mice infected with deoxyribonuclease knockout GAS mutants (∆spd, ∆endA, and ∆sdaD2) survived significantly better than those infected with wild-type GAS. In addition, the supernatants of digested NETs enhanced GAS-induced cell death in vitro. Collectively, these results indicate that NET degradation products may contribute to the establishment of pharyngeal infection caused by GAS.
Assuntos
DNA/química , Armadilhas Extracelulares , Faringite/microbiologia , Faringe/microbiologia , Infecções Estreptocócicas/patologia , Animais , Apoptose , Desoxirribonucleases/metabolismo , Modelos Animais de Doenças , Humanos , Macrófagos/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Neutrófilos/microbiologia , Reação em Cadeia da Polimerase em Tempo Real , Streptococcus pyogenesRESUMO
In this study, the synthesis and evaluation of a number of esters of CS-758 as injectable prodrugs are described. Phosphoryl ester 1a was soluble in water (>30mg/mL) and was converted to CS-758 in human liver microsome. It was also converted to CS-758 in rats after iv administration, wherein the bioavailability of CS-758 was 53%. Compound 1a (iv) reduced the viable cell counts in kidneys in a murine systemic Candida albicans infection model, wherein the effect was comparable to or slightly superior to that of CS-758 (po). The prodrug 1a proved to be a promising injectable antifungal agent whose further evaluation is warranted.