Triptolide suppresses interleukin-1beta-induced human beta-defensin-2 mRNA expression through inhibition of transcriptional activation of NF-kappaB in A549 cells.
The immunosuppressive effect of triptolide has been associated with suppression of T-cell activation. However, the immunosuppressive effects of triptolide on innate immunity in the epithelial barrier remain to be elucidated. Human beta-defensin (HBD)-2 is an inducible antimicrobial peptide and plays an important role in the innate immunity. We have previously demonstrated that IL-1beta induced HBD-2 mRNA expression in A549 cells through activation of nuclear factor-kappaB (NF-kappaB) transcriptional factor as well as p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), or phosphatidylinositol-3-kinase (PI3K). In this study, we investigated effects of triptolide on IL-1beta-induced HBD-2 mRNA expression in A549 cells. Triptolide inhibited IL-1beta-induced HBD-2 mRNA expression in a dose-dependent manner. Addition of triptolide did not suppress activation of p38 MAPK, JNK, or PI3K in response to IL-1beta. Triptolide inhibited IL-1beta-induced MAPK phosphatase-1 expression at the transcriptional level and resulted in sustained phosphorylation of JNK or p38 MAPK, explaining the little effect of triptolide on IL-1beta-induced phosphorylation of these kinases. Although triptolide partially suppressed IL-1beta-mediated degradation of IkappaB-alpha and nuclear translocation of p65 NF-kappaB, triptolide potently inhibited NF-kappaB promoter-driven luciferase activity in A549 cells. These results collectively suggest that the inhibitory effect of triptolide on IL-1beta-induced HBD-2 mRNA expression in A549 cells seems to be at least in part mediated through nuclear inhibition of NF-kappaB transcriptional activity, but not inhibition of p38 MAPK, JNK, or PI3K. This inhibition may explain the ability of triptolide to diminish innate immune response.
Jang
Byeong-Churl
BC
Chronic Disease Research Center and Institute for Medical Science, Keimyung University School of Medicine, Daegu, Korea.
Lim
Ki-Jo
KJ
Choi
In-Hak
IH
Suh
Min-Ho
MH
Park
Jong-Gu
JG
Mun
Kyo-Chul
KC
Bae
Jae-Hoon
JH
Shin
Dong-Hoon
DH
Suh
Seong-Il
SI
D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004224:Diterpenes / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000187:drug effects; D004852:Epoxy Compounds / Q000494:pharmacology; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D053583:Interleukin-1beta / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D010616:Phenanthrenes / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*; D023083:beta-Defensins / Q000235:genetics* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D018797:Cell Cycle Proteins; D004224:Diterpenes; D004852:Epoxy Compounds; D017874:Immediate-Early Proteins; D007166:Immunosuppressive Agents; D053583:Interleukin-1beta; D010616:Phenanthrenes; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D023083:beta-Defensins; C001899:triptolide; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases