Tetradecanoyl phorbol acetate induces expression of Toll-like receptor 2 in U937 cells: involvement of PKC, ERK, and NF-κB
Section snippets
Materials and methods
Cell culture. U937 promonocytic leukemia cells were maintained at 37 °C in a humidified atmosphere of 95% air and 5% CO2 in RPMI 1640 medium supplemented with 10% heat-inactivated fetal bovine serum, 2 mM glutamine, 100 U/ml penicillin, and 100 μg/ml streptomycin. Typically, 3 × 105 cells/ml were seeded in T-25 flasks as 4 ml cultures, and maintained in the tissue culture incubator for 12–16 h before the addition of TPA or other reagents.
Drugs and materials. Antibodies against phospho-ERKs (p-ERKs),
TPA induces TLR2 mRNA expression in U937 cells
First of all, endogenous expression level of TLR2, TLR4, or CD14 was analyzed in human U937, HL60, and K562 cells by RT-PCR using respective primers. THP-1 cells served as positive sources for human TLR2 and TLR4 mRNA expressions. As shown in Fig. 1A, HL60 cells expressed both TLR2 and TLR4 mRNAs. On the other hand, U937 cells expressed only TLR4. K562 cells also expressed very low level of TLR4 mRNA. Expression of CD14 was detected in HL60 and THP-1 cells. TPA has been known to induce
Discussion
Macrophages are patrolling cells of the innate immune system and express TLRs. TLRs are a family of pattern recognition receptors recently identified as crucial signaling receptors mediating the innate immune recognition [3], [4]. Though TLRs may contribute to the resensitization of macrophages to invasive pathogens, however, the mechanism by which TLR expression is regulated in cells is largely unknown. In this study, we have investigated the molecular signaling mechanisms of TLR2 expression
Acknowledgments
This work was supported by Grant No. R13-2002-028-01001-0 from Basic Research Program of Korea Science and Engineering Foundation (KOSEF) to Chronic Diesase Research (CDR) Center at Keimyung University.
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These authors contributed equally to this work.