RESUMO
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
Helicobacter pylori (H. pylori), a gram-negative microaerophilic bacterial pathogen that colonizes the stomachs of more than half of all humans, is linked to chronic gastritis, peptic ulcers and gastric cancer. Spiral-shaped H. pylori undergo morphologic conversion to a viable but not culturable coccoid form when they transit from the microaerobic stomach into the anaerobic intestinal tract. However, little is known about the morphological and pathogenic characteristics of H. pylori under prolonged anaerobic conditions. In this study, scanning electron microscopy was used to document anaerobiosis-induced morphological changes of H. pylori, from helical to coccoid to a newly defined fragmented form. Western blot analysis indicated that all three forms express certain pathogenic proteins, including the bacterial cytotoxin-associated gene A (CagA), components of the cag-Type IV secretion system (TFSS), the blood group antigen-binding adhesin BabA, and UreA (an apoenzyme of urease), almost equally. Similar urease activities were also detected in all three forms of H. pylori. However, in contrast to the helical form, bacterial motility and TFSS activity were found to have been abrogated in the anaerobiosis-induced coccoid and fragmented forms of H. pylori. Notably, it was demonstrated that some of the anaerobiosis-induced fragmented state cells could be converted to proliferation-competent helical bacteria in vitro. These results indicate that prolonged exposure to the anaerobic intestine may not eliminate the potential for H. pylori to revert to the helical pathogenic state.