TY - JOUR
T1 - Helicobacter pylori lipopolysaccharide activates Rac1 and transcription of NADPH oxidase Nox1 and its organizer NOXO1 in guinea pig gastric mucosal cells
AU - Kawahara, Tsukasa
AU - Kohjima, Motoyuki
AU - Kuwano, Yuki
AU - Mino, Hisano
AU - Teshima-Kondo, Shigetada
AU - Takeya, Ryu
AU - Tsunawaki, Shohko
AU - Wada, Akihiro
AU - Sumimoto, Hideki
AU - Rokutan, Kazuhito
PY - 2005/2
Y1 - 2005/2
N2 - Primary cultures of guinea pig gastric mucosal cells express NADPH oxidase 1 (Nox1), a homolog of gp91phox, and produce superoxide anion (O 2-) at a rate of ∼100 nmol·mg protein -1· h-1 in response to Helicobacter pylori (H. pylori) lipopolysaccharide (LPS) from virulent type I strains. The upregulated O2- production also enhances H. pylori LPS-stimulated tumor necrosis factor-α or cyclooxygenase-2 mRNA expression, which suggests a potential role for Nox1 in the pathogenesis of H. pylori-associated diseases. The H. pylori LPS-stimulated O2- production in cultured gastric mucosal cells was inhibited by actinomycin D as well as cycloheximide, suggesting that the induction is regulated at the transcriptional level. The LPS treatment not only increased the Nox1 mRNA to a greater extent but also induced expression of the message-encoding, Nox-organizing protein 1 (NOXO1), a novel p47phox homolog required for Nox1 activity. In addition, H. pylori LPS activated Rac1; i.e., it converted Rac1 to the GTP-bound state. A phosphoinositide 3-kinase inhibitor, LY-294002, blocked H. pylori LPS-induced Rac1 activation and O2- generation without interfering with the expression of Nox1 and NOXO1 mRNA. O2 - production inhibited by LY-294002 was completely restored by transfection of an adenoviral vector encoding a constitutively active Rac1 but not an inactive Rac1 or a constitutively active Cdc42. These findings indicate that Rac1 plays a crucial role in Nox1 activation. Thus the H. pylori LPS-stimulated O2- production in gastric mucosal cells appears to require two distinct events: 1) transcriptional upregulation of Nox1 and NOXO1 and 2) activation of Rac1.
AB - Primary cultures of guinea pig gastric mucosal cells express NADPH oxidase 1 (Nox1), a homolog of gp91phox, and produce superoxide anion (O 2-) at a rate of ∼100 nmol·mg protein -1· h-1 in response to Helicobacter pylori (H. pylori) lipopolysaccharide (LPS) from virulent type I strains. The upregulated O2- production also enhances H. pylori LPS-stimulated tumor necrosis factor-α or cyclooxygenase-2 mRNA expression, which suggests a potential role for Nox1 in the pathogenesis of H. pylori-associated diseases. The H. pylori LPS-stimulated O2- production in cultured gastric mucosal cells was inhibited by actinomycin D as well as cycloheximide, suggesting that the induction is regulated at the transcriptional level. The LPS treatment not only increased the Nox1 mRNA to a greater extent but also induced expression of the message-encoding, Nox-organizing protein 1 (NOXO1), a novel p47phox homolog required for Nox1 activity. In addition, H. pylori LPS activated Rac1; i.e., it converted Rac1 to the GTP-bound state. A phosphoinositide 3-kinase inhibitor, LY-294002, blocked H. pylori LPS-induced Rac1 activation and O2- generation without interfering with the expression of Nox1 and NOXO1 mRNA. O2 - production inhibited by LY-294002 was completely restored by transfection of an adenoviral vector encoding a constitutively active Rac1 but not an inactive Rac1 or a constitutively active Cdc42. These findings indicate that Rac1 plays a crucial role in Nox1 activation. Thus the H. pylori LPS-stimulated O2- production in gastric mucosal cells appears to require two distinct events: 1) transcriptional upregulation of Nox1 and NOXO1 and 2) activation of Rac1.
UR - http://www.scopus.com/inward/record.url?scp=19944427068&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=19944427068&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.00319.2004
DO - 10.1152/ajpcell.00319.2004
M3 - Article
C2 - 15469954
AN - SCOPUS:19944427068
VL - 288
SP - C450-C457
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6143
IS - 2 57-2
ER -