IL-1beta modulation of H,K-ATPase alpha-subunit gene transcription in Helicobacter pylori infection.
Helicobacter pylori infection of the human gastric body induces hypochlorhydria by perturbing acid secretion. H. pylori inhibits parietal cell H,K-ATPase alpha-subunit (HKalpha) gene and protein expression, providing a mechanistic basis for clinical hypochlorhydria. Given that H. pylori infection increases gastric mucosal IL-1beta, an acid secretory inhibitor, we investigated the role of IL-1beta in H. pylori-mediated inhibition of HKalpha transcription. Human gastric adenocarcinoma (AGS) cells were transfected with promoter-reporter constructs containing human HKalpha 5'-flanking sequence deletions. IL-1beta (10 ng/ml) had no effect on the transcriptional activity of six progressively shorter deletion constructs of the HKalpha promoter (HKalpha2179-HKalpha340) and significantly stimulated the activity of HKalpha206, HKalpha177, HKalpha165, and HKalpha102 deletion constructs (80%, 100%, 46%, and 35%, respectively). H. pylori inhibited the transcriptional activity of HKalpha2179, HKalpha206, HKalpha177, and HKalpha165; IL-1beta relieved the H. pylori inhibition of HKalpha2179 and HKalpha206 activity but not HKalpha177 and HKalpha165 activity. AGS cell pretreatment with a MEK1/2 inhibitor prevented the IL-1beta-mediated stimulation, but p38 and JNK pathway inhibitors did not. IL-1beta mRNA levels in AGS cells were low and unaffected by H. pylori, and ELISAs of H. pylori-conditioned AGS culture media showed no measurable IL-1beta secretion. These data indicate that an IL-1beta-dependent cis-response element lies downstream of -206 nt in the HKalpha promoter and that IL-1beta-mediated upregulation of HKalpha transcription is affected by an ERK1/2 kinase signal pathway. We conclude that an IL-1beta-responsive HKalpha cis element positively regulates HKalpha gene transcription in shortened deletion constructs and that H. pylori-induced inhibition of HKalpha transcription is not mediated by IL-1beta.
Saha
Arindam
A
Department of medicine, Medical University of South Carolina, 96 Jonathan Lucas St., Charleston, SC 29425, USA.
Hammond
Charles E
CE
Gooz
Monika
M
Smolka
Adam J
AJ
D024506:5' Flanking Region; D000230:Adenocarcinoma / Q000473:pathology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D005753:Gastric Mucosa / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D017930:Genes, Reporter; D017506:H(+)-K(+)-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics; D016481:Helicobacter Infections / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D016480:Helicobacter pylori; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism* / Q000494:pharmacology; D008156:Luciferases; D020935:MAP Kinase Signaling System; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021122:Protein Subunits; D012333:RNA, Messenger / Q000096:biosynthesis; D013274:Stomach Neoplasms / Q000473:pathology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation
D053583:Interleukin-1beta; D047428:Protein Kinase Inhibitors; D021122:Protein Subunits; D012333:RNA, Messenger; D008156:Luciferases; D017506:H(+)-K(+)-Exchanging ATPase