Helicobacter pylori VacA enhances prostaglandin E2 production through induction of cyclooxygenase 2 expression via a p38 mitogen-activated protein kinase/activating transcription factor 2 cascade in AZ-521 cells.
Treatment of AZ-521 cells with Helicobacter pylori VacA increased cyclooxygenase 2 (COX-2) mRNA in a time- and dose-dependent manner. A p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, blocked elevation of COX-2 mRNA levels, whereas PD98059, which blocks the Erk1/2 cascade, partially suppressed the increase. Consistent with involvement of p38 MAPK, VacA-induced accumulation of COX-2 mRNA was reduced in AZ-521 cells overexpressing a dominant-negative p38 MAPK (DN-p38). Phosphatidylinositol-specific phospholipase C, which inhibits VacA-induced p38 MAPK activation, blocked VacA-induced COX-2 expression. In parallel with COX-2 expression, VacA increased prostaglandin E(2) (PGE(2)) production, which was inhibited by SB203580 and NS-398, a COX-2 inhibitor. VacA-induced PGE(2) production was markedly attenuated in AZ-521 cells stably expressing DN-p38. VacA increased transcription of a COX-2 promoter reporter gene and activated a COX-2 promoter containing mutated NF-kappaB or NF-interleukin-6 sites but not a mutated cis-acting replication element (CRE) site, suggesting direct involvement of the activating transcription factor 2 (ATF-2)/CREB-binding region in VacA-induced COX-2 promoter activation. The reduction of ATF-2 expression in AZ-521 cells transformed with ATF-2-small interfering RNA duplexes resulted in suppression of COX-2 expression. Thus, VacA enhances PGE(2) production by AZ-521 cells through induction of COX-2 expression via the p38 MAPK/ATF-2 cascade, leading to activation of the CRE site in the COX-2 promoter.
Hisatsune
Junzo
J
Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan.
Yamasaki
Eiki
E
Nakayama
Masaaki
M
Shirasaka
Daisuke
D
Kurazono
Hisao
H
Katagata
Yohtaro
Y
Inoue
Hiroyasu
H
Han
Jiahuai
J
Sap
Jan
J
Yahiro
Kinnosuke
K
Moss
Joel
J
Hirayama
Toshiya
T
D051698:Activating Transcription Factor 2 / Q000502:physiology*; D051696:Activating Transcription Factors / Q000502:physiology*; D001426:Bacterial Proteins / Q000502:physiology*; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics; D015232:Dinoprostone / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000502:physiology; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology*
D051698:Activating Transcription Factor 2; D051696:Activating Transcription Factors; D001426:Bacterial Proteins; D012333:RNA, Messenger; C074689:VacA protein, Helicobacter pylori; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone