RT Journal Article
SR Electronic
T1 Tumor Necrosis Factor-α-Induced Cyclooxygenase-2 Expression via Sequential Activation of Ceramide-Dependent Mitogen-Activated Protein Kinases, and IκB Kinase 1/2 in Human Alveolar Epithelial Cells
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 493
OP 500
DO 10.1124/mol.59.3.493
VO 59
IS 3
A1 Ching-Chow Chen
A1 Yi-Tao Sun
A1 Jun-Jie Chen
A1 Ya-Jen Chang
YR 2001
UL http://molpharm.aspetjournals.org/content/59/3/493.abstract
AB The role of p44/42 mitogen-activated protein kinase (MAPK), p38, and c-Jun NH2-terminal kinase (JNK) in tumor necrosis factor (TNF)-α-induced cyclooxygenase (COX)-2 expression was studied in NCI-H292 epithelial cells. TNF-α-mediated COX-2 expression and COX-2 promoter activity were inhibited by the MAPK kinase inhibitor PD98059 or the p38 inhibitor SB203580. Treatment of cells for 10 min with TNF-α resulted in activation of p44/42 MAPK, p38, and JNK. C2-ceramide (a cell-permeable ceramide analog), bacterial neutral sphingomyelinase (Smase; an enzyme that degrades sphingomyelin to ceramide), and N-oleoylethanolamine (a ceramidase inhibitor) all induced activation of MAPKs, COX-2 expression, nuclear factor (NF)-κB DNA-protein binding, and COX-2 promoter activity. The inactive analog, dihydro-C2-ceramide, had no effect. SMase- or C2-ceramide-induced COX-2 expression and COX-2 promoter activity were also inhibited by PD98059 or SB203580. Glutathione, a neutral SMase inhibitor, attenuated TNF-α- or SMase-induced activation of MAPKs, COX-2 expression, and COX-2 promoter activity. TNF-α- or C2-ceramide-induced COX-2 promoter activity was inhibited by the dominant negative mutant of extracellular signal-regulated kinase 2, p38, JNK, IκB kinase (IKK)1, or IKK2. IKK activity was stimulated by either TNF-α or C2-ceramide, and these effects were inhibited by PD98059 or SB203580. All these results suggest that, in NCI-H292 epithelial cells, activation of MAPKs by ceramide contributes to the TNF-α signaling that occurs downstream of neutral SMase activation and results in the stimulation of IKK1/2, and NF-κB in the COX-2 promoter, followed by initiation of COX-2 expression.