Inflammatory cytokines suppress arylamine N-acetyltransferase 1 in cholangiocarcinoma cells.
OBJECTIVE
To evaluate the effect of inflammatory cytokines on arylamine N-acetyltransferase 1 (NAT1), which is a phase-II enzyme involved in the biotransformation of aromatic and heterocyclic amines found in food, drugs and the environment.


METHODS
Human cholangiocarcinoma KKU-100 cells were treated with a mixture of proinflammatory cytokines (interferon-gamma, interleukin-1 beta and tumor necrosis factor-alpha) for 48 h, and the effect on NAT1 activity was assessed by high performance liquid chromatography, while NAT1 expression was determined by reverse-transcription polymerase chain reaction. The oxidative stress on the cells was examined by the formation of nitric oxide, superoxide anion and glutathione (GSH) levels. The cells were also treated with S-nitroso-glutathione (GSNO), a nitric oxide donor, to see if the responses were similar to those obtained with the inflammatory cytokines.


RESULTS
Cytokines suppressed NAT1 activity, reducing the Vmax without affecting the Km. Cytokines also had a significant impact on the induction of nitric oxide production and in reducing the redox ratios of glutathione (GSH) and GSH disulfide. Treatment with GSNO for 2-48 h reduced NAT1 activity without affecting the GSH ratio. Moreover, inflammatory cytokines and GSNO suppressed NAT1 mRNA expression.


CONCLUSIONS
These findings indicate an association between inflammation and suppression of NAT1, which perhaps contributes to chemical-mediated toxicity and carcinogenesis.
Buranrat
Benjaporn
B
Department of Pharmacology, Faculty of Medicine, Liver Fluke and Cholangiocarcinoma Research Center, Khon Kaen University, Khon Kaen 40002, Thailand.
Prawan
Auemduan
A
Sripa
Banchob
B
Kukongviriyapan
Veerapol
V
D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D001650:Bile Duct Neoplasms / Q000201:enzymology* / Q000473:pathology; D001653:Bile Ducts, Intrahepatic; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma / Q000201:enzymology* / Q000473:pathology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000502:physiology*; D053583:Interleukin-1beta / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000378:metabolism; D026422:S-Nitrosoglutathione / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D053583:Interleukin-1beta; D007527:Isoenzymes; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D007371:Interferon-gamma; D001191:Arylamine N-Acetyltransferase; C089384:N-acetyltransferase 1; D005978:Glutathione