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AIM:To evaluate the effect of inflammatory cytokines on arylamine N-acetyltransferase 1 (NAT1),which is a phase-Ⅱenzyme 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-γ,interleukin-1β,and tumor necrosis factor-α) 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 V_(max) without affecting the K_m.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. CONCLUSION:These findings indicate an association between inflammation and suppression of NAT1,which perhaps contributes to chemical-mediated toxicity and carcinogenesis.
AIM: 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-γ, interleukin-1β, and tumor necrosis factor-α) for 48 h, and the effect on NAT1 activity was assessed by high performance liquid chromatography, while the NAT1 expression was determined by reverse -transcription polymerase chain reaction. 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 V_ (max) without affecting the K_m.Cytokines also had a significant ant 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. More over, inflammatory cytokines and GSNO suppressed NAT1 mRNA expression. CONCLUSION: These findings indicate an association between inflammation and suppression of NAT1, which perhaps contributes to chemical-mediated toxicity and carcinogenesis.