Nucleotide Binding Oligomerization Domain 1 Is an Essential Signal Transducer in Human Epithelial Cells Infected with Helicobacter pylori That Induces the Transepithelial Migration of Neutrophils

BACKGROUND/AIMS: The cytosolic host protein nucleotide binding oligomerization domain 1 (Nod1) has emerged as a key pathogen recognition molecule for innate immune responses in epithelial cells. The purpose of the study was to elucidate the mechanism by which Helicobacter pylori infection leads to transepithelial neutrophil migration in a Nod1-mediated manner. METHODS: Human epithelial cell lines AGS and Caco-2 were grown and infected with H. pylori. Interleukin (IL)-8 mRNA expression and IL-8 secretion were assessed, and nuclear factor kappaB (NF-kappaB) activation was determined. Stable transfections of AGS and Caco-2 cells with dominant negative Nod1 were generated. Neutrophil migration across the monolayer was quantified. RESULTS: Cytotoxin-associated gene pathogenicity island (cagPAI)(+) H. pylori infection upregulated IL-8 mRNA expression and IL-8 secretion in AGS and Caco-2 cells compared with controls. NF-kappaB activation, IL-8 mRNA expression and IL-8 secretion by cagPAI knockdown strains were reduced compared with those infected with the wild-type strain. NF-kappaB activation, IL-8 mRNA expression and IL-8 secretion in dominant-negative (DN)-Nod1 stably transfected cells were reduced compared with the controls. The transepithelial migration of neutrophils in DN-Nod1 stably transfected cells was reduced compared with that in controls. CONCLUSIONS: Signaling through Nod1 plays an essential role in neutrophil migration induced by the upregulated NF-kappaB activation and IL-8 expression in H. pylori-infected human epithelial cells.

Papel de los receptores tipo toll (TLRs) y receptores para dominios de oligomerización para la unión a nucleótidos (NLRs) en las infecciones virales / Role of toll-like receptors (TLRs) and nucleotide-binding oligomerization domain receptors (NLRs) in viral infections

Las células del sistema inmunitario (SI) son capaces de reconocer una gran variedad de microorganismos, a través de los receptores que se encuentran expresados y distribuidos a lo largo de su arquitectura celular. La interacción entre los patrones moleculares asociados a microorganismos o a daño (PMAM o PMAD) y los receptores reconocedores de patrones (RRP) presentes en las células del hospedero es un evento crítico que implica procesos intracelulares de señalización que finalizan en la expresión de mediadores tanto proinflamatorios como antivirales. Por consiguiente, de la integridad de estos receptores dependerá el buen funcionamiento de los distintos mecanismos de transducción de señal desde las membranas celulares al citoplasma y por ende, de la respuesta que el SI desencadene contra los patógenos entre ellos los agentes virales. De allí que, en esta revisión se discutirá el papel de los receptores tipo toll (TLRs) y receptores para dominios de oligomerización para la unión a nucleótidos (NLRs) en las infecciones virales, tomando como evidencia los estudios en humanos y ratones que a la fecha se conocen.

The immune system (IS) cells are capable of recognizing a wide variety of microorganisms, through receptors that are expressed and distributed throughout the cell architecture. The interaction between the pathogen-associated molecular patterns or damage-associated molecular patterns (PAMPs or DAMPs) and pattern recognition receptors (PRR), present in host cells, is a critical event that involves intracellular signaling processes that end up in the expression of both, proinflammatory and antiviral mediators. Accordingly, the proper functioning of the different mechanisms of signal transduction from the cell membrane to the cytoplasm will depend on the integrity of these receptors (PRR); and therefore, the IS response triggered against pathogens including viral agents. Hence, in this review we discuss the role of toll-like receptors (TLRs) and nucleotide-binding oligomerization domain receptors (NLRs) in viral infections, using as evidence the studies in humans and mice known to date.