Immunosuppressive effect of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) through the inhibition of T-lymphocyte proliferation and IL-2 production.
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the predominant heterocyclic amine formed in cooked meat and fish and causes cancers in the colon, the mammary glands, and the lymphoid organs. In the present study, we investigated the immunological impact of PhIP using thymocytes isolated from Balb/c mice and a murine thymocyte-derived cell line, EL4. Treatment of the thymocytes with PhIP moderately inhibited T-cell mitogen-induced cell proliferation and interleukin (IL)-2 secretion. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that PhIP attenuated IL-2 mRNA expression in the thymocytes and EL4 cells stimulated with phytohemagglutinin (PHA) plus phorbol 12-myristate 13-acetate (PMA). In vitro transient transfection assay using a reporter gene construct containing IL-2 promoter showed that the decrease in the steady-state IL-2 mRNA level by PhIP is partially due to the attenuation of IL-2 mRNA synthesis at the transcriptional level. Furthermore, an electrophoretic mobility shift assay showed that PhIP inhibited DNA binding activity of nuclear factor for immunoglobulin kappa chain in B cells (NF-kappaB), activator protein-1 (AP-1) and nuclear factor of activated T cells (NF-AT), which are known to be responsible for IL-2 transcriptional activation. Concomitantly, PhIP inhibited the PMA/PHA-induced generation of reactive oxygen species (ROS) involved in activation of the transcription factors. These results suggest that PhIP has potential immunosuppressive effects by inhibiting T-cell proliferation and IL-2 expression through down regulation of ROS generation and thereby inhibiting NF-kappaB, AP-1 and NF-AT activation.
Yun
Cheol-Heui
CH
Laboratory Sciences Division, International Vaccine Institute, SNU Research Park, San 4-8 Bongcheon-7 dong, Kwanak-gu, Seoul 151-818, Republic of Korea.
Son
Chang Gue
CG
Jung
Uhee
U
Han
Seung Hyun
SH
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D007093:Imidazoles / Q000494:pharmacology*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008934:Mitogens / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000235:genetics; D010835:Phytohemagglutinins / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection / Q000379:methods
D004268:DNA-Binding Proteins; D007093:Imidazoles; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D008934:Mitogens; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C467907:Nfatc4 protein, mouse; D010835:Phytohemagglutinins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine