Toll-like receptor (TLR) 2 induced through TLR4 signaling initiated by Helicobacter pylori cooperatively amplifies iNOS induction in gastric epithelial cells.
Cell-surface Toll-like receptors (TLRs) initiate innate immune responses, such as inducible nitric oxide synthase (iNOS) induction, to microorganisms' surface pathogens. TLR2 and TLR4 play important roles in gastric mucosa infected with Helicobacter pylori (H. pylori), which contains lipopolysaccharide (LPS) as a pathogen. The present study investigates their physiological roles in the innate immune response of gastric epithelial cells to H. pylori-LPS. Changes in the expression of iNOS, TLR2, and TLR4, as well as downstream activation of mitogen-activated protein kinases and nuclear factor-kappaB (NF-kappaB), were analyzed in normal mouse gastric mucosal GSM06 cells following stimulation with H. pylori-LPS and interferon-gamma. Specific inhibitors for mitogen-activated protein kinases, NF-kappaB, and small interfering RNA for TLR2 or TLR4 were employed. The immunohistochemistry of TLR2 was examined in human gastric mucosa. H. pylori-LPS stimulation induced TLR2 in GSM06 cells, but TLR4 was unchanged. TLR2 induction resulted from TLR4 signaling that propagated through extracellular signal-related kinase and NF-kappaB activation, as corroborated by the decline in TLR4 expression on small interfering RNA treatment and pretreatment with inhibitors. The induction of iNOS and the associated nitric oxide production in response to H. pylori-LPS stimulation were inhibited by declines in not only TLR4 but also TLR2. Increased expression of TLR2 was identified in H. pylori-infected human gastric mucosa. TLR4 signaling initiated by H. pylori-LPS and propagated via extracellular signal-regulated kinase and NF-kappaB activation induced TLR2 expression in gastric epithelial cells. Induced TLR2 cooperated with TLR4 to amplify iNOS induction. This positive correlation may constitute a mechanism for stimulating the innate immune response against various bacterial pathogens, including H. pylori-LPS.
Uno
Kaname
K
Research Project of Biofunctional Reactive Species, Yamagata Promotional Organization for Industrial Technology, Yamagata, Japan.
Kato
Katsuaki
K
Atsumi
Tomoaki
T
Suzuki
Takehito
T
Yoshitake
Jun
J
Morita
Hidetoshi
H
Ohara
Shuichi
S
Kotake
Yashige
Y
Shimosegawa
Tooru
T
Yoshimura
Tetsuhiko
T
D002460:Cell Line; D005753:Gastric Mucosa / Q000187:drug effects / Q000382:microbiology / Q000473:pathology / Q000502:physiology*; D005786:Gene Expression Regulation; D016481:Helicobacter Infections / Q000473:pathology / Q000503:physiopathology; D016480:Helicobacter pylori / Q000276:immunology / Q000502:physiology*; D006801:Humans; D008070:Lipopolysaccharides / Q000633:toxicity; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics*; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics*
D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D052247:Nitric Oxide Synthase Type II