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Modulation of Activation‐Induced Cytidine Deaminase by Curcumin in Helicobacter pylori ‐Infected Gastric Epithelial Cells
Author(s) -
Zaidi Syed Faisal Haider,
Yamamoto Takeshi,
Refaat Alaa,
Ahmed Kanwal,
Sakurai Hiroaki,
Saiki Ikuo,
Kondo Takashi,
Usmanghani Khan,
Kadowaki Makoto,
Sugiyama Toshiro
Publication year - 2009
Publication title -
helicobacter
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.206
H-Index - 79
eISSN - 1523-5378
pISSN - 1083-4389
DOI - 10.1111/j.1523-5378.2009.00724.x
Subject(s) - curcumin , helicobacter pylori , cytidine deaminase , microbiology and biotechnology , chemistry , apoptosis , downregulation and upregulation , biology , enzyme , biochemistry , gene , genetics
Background: Anomalous expression of activation‐induced cytidine deaminase (AID) in Helicobacter pylori ‐infected gastric epithelial cells has been postulated as one of the key mechanisms in the development of gastric cancer. AID is overexpressed in the cells through nuclear factor (NF)‐κB activation by H . pylori and hence, inhibition of NF‐κB pathway can downregulate the expression of AID. Curcumin, a spice‐derived polyphenol, is known for its anti‐inflammatory activity via NF‐κB inhibition. Therefore, it was hypothesized that curcumin might suppress AID overexpression via NF‐κB inhibitory activity in H . pylori ‐infected gastric epithelial cells. Materials and Methods: MKN‐28 or MKN‐45 cells and H . pylori strain 193C isolated from gastric cancer patient were used for co‐culture experiments. Cells were pretreated with or without nonbactericidal concentrations of curcumin. Apoptosis was determined by DNA fragmentation assay. Enzyme‐linked immunosorbent assay was performed to evaluate the anti‐adhesion activity of curcumin. Real‐time polymerase chain reaction was employed to evaluate the expression of AID mRNA. Immunoblot assay was performed for the analysis of AID, NF‐κB, inhibitors of NF‐κB (IκB), and IκB kinase (IKK) complex regulation with or without curcumin. Results: The adhesion of H. pylori to gastric epithelial cells was not inhibited by curcumin pretreatment at nonbactericidal concentrations (≤10 μmol/L). Pretreatment with nonbactericidal concentration of curcumin downregulated the expression of AID induced by H . pylori . Similarly, NF‐κB activation inhibitor (SN‐50) and proteasome inhibitor (MG‐132) also downregulated the mRNA expression of AID. Moreover, curcumin (≤10 μmol/L) has suppressed H . pylori ‐induced NF‐κB activation via inhibition of IKK activation and IκB degradation. Conclusion: Nonbactericidal concentrations of curcumin downregulated H . pylori ‐induced AID expression in gastric epithelial cells, probably via the inhibition of NF‐κB pathway. Hence, curcumin can be considered as a potential chemopreventive candidate against H . pylori ‐related gastric carcinogenesis.