TNF-α induces cytosolic phospholipase A2 expression in human lung epithelial cells via JNK1/2- and p38 MAPK-dependent AP-1 activation.
BACKGROUND
Cytosolic phospholipase A2 (cPLA2) plays a pivotal role in mediating agonist-induced arachidonic acid (AA) release for prostaglandin (PG) synthesis during inflammation triggered by tumor necrosis factor-α (TNF-α). However, the mechanisms underlying TNF-α-induced cPLA2 expression in human lung epithelial cells (HPAEpiCs) were not completely understood.


RESULTS
We demonstrated that TNF-α induced cPLA2 mRNA and protein expression, promoter activity, and PGE2 secretion in HPAEpiCs. These responses induced by TNF-α were inhibited by pretreatment with the inhibitor of MEK1/2 (PD98059), p38 MAPK (SB202190), JNK1/2 (SP600125), or AP-1 (Tanshinone IIA) and transfection with siRNA of TNFR1, p42, p38, JNK2, c-Jun, c-Fos, or ATF2. We showed that TNF-α markedly stimulated p42/p44 MAPK, p38 MAPK, and JNK1/2 phosphorylation which were attenuated by their respective inhibitors. In addition, TNF-α also stimulated c-Jun and ATF2 phosphorylation which were inhibited by pretreatment with SP600125 and SB202190, respectively, but not PD98059. Furthermore, TNF-α-induced cPLA2 promoter activity was abrogated by transfection with the point-mutated AP-1 cPLA2 construct. Finally, we showed that TNF-α time-dependently induced p300/c-Fos/c-Jun/ATF2 complex formation in HPAEpiCs. On the other hand, TNF-α induced in vivo binding of c-Jun, c-Fos, ATF2, and p300 to the cPLA2 promoter in these cells. In an in vivo study, we found that TNF-α induced leukocyte count in BAL fluid of mice and cPLA2 mRNA levels in lung tissues via MAPKs and AP-1.


CONCLUSIONS
Taken together, these results demonstrated that TNF-α-induced cPLA2 expression was mediated through p38 MAPK- and JNK1/2-dependent p300/c-Fos/c-Jun/ATF2 complex formation in HPAEpiCs.
Department of Anesthetics, Chang Gung Memorial Hospital at Lin-Kou and College of Medicine, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan ; Department of Physiology and Pharmacology and Health Aging Research Center, College of Medicine, Chang Gung University, Kwei-San, Tao-Yuan, Taiwan.
I-Ta
IT
Lee
Chih-Chung
CC
Lin
Shin-Ei
SE
Cheng
Li-Der
LD
Hsiao
Yu-Chun
YC
Hsiao
Chuen-Mao
CM
Yang
D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism*; D048056:Mitogen-Activated Protein Kinase 9 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D048056:Mitogen-Activated Protein Kinase 9; D048055:Mitogen-Activated Protein Kinase 8; D048051:p38 Mitogen-Activated Protein Kinases; D054513:Group IV Phospholipases A2