MAPK mediation of hypertonicity-stimulated cyclooxygenase-2 expression in renal medullary collecting duct cells.
We have previously shown that hypertonicity stimulates cyclooxygenase-2 (COX-2) expression in cultured medullary epithelial cells. The aims of the present study were (i) to examine the role of cytoplasmic signaling through MAPK pathways in tonicity regulation of COX-2 expression in collecting duct cells and (ii) to assess the possible contribution of COX-2 to the survival of inner medullary collecting duct (IMCD) cells under hypertonic conditions. In mIMCD-K2 cells, a cell line derived from mouse IMCDs, hypertonicity induced a marked increase in COX-2 protein expression. The stimulation was reduced significantly by inhibition of MEK1 (PD-98059, 5-50 microm) and p38 (SB-203580, 5-100 microm) and was almost abolished by the combination of the two compounds. To study the role of JNK in tonicity-stimulated COX-2 expression, IMCD-3 cell lines stably transfected with dominant-negative mutants of three JNKs (JNK-1, -2, and -3) were used. Hypertonicity-stimulated COX-2 protein expression was significantly reduced in dominant-negative JNK-2-expressing cells and was unchanged in dominant-negative JNK-1- and JNK-3-expressing cells compared with controls. The reduction of COX-2 expression was associated with greatly reduced viability of dominant-negative JNK-2-expressing cells during hypertonicity treatment. 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) (2-8 microm), an inhibitor of Src kinases, reduced the tonicity-stimulated COX-2 expression in a dose-dependent manner, whereas PP3, an inactive analog of PP2, had no effect. Inhibition of COX-2 activity by NS-398 (30-90 microm) and SC-58236 (10-20 microm) significantly reduced viability of mIMCD-K2 cells subjected to prolonged hypertonic treatment. We conclude that 1) all three members of the MAPK family (ERK, JNK-2, and p38) as well as Src kinases are required for tonicity-stimulated COX-2 expression in mouse collecting duct cells and that 2) COX-2 may play a role in cell survival of medullary cells under hypertonic conditions.
Yang
T
T
NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA.
Huang
Y
Y
Heasley
L E
LE
Berl
T
T
Schnermann
J B
JB
Briggs
J P
JP
D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009578:Nitrobenzenes / Q000494:pharmacology; D009994:Osmolar Concentration; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013449:Sulfonamides / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009578:Nitrobenzenes; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D011505:Protein-Tyrosine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D015232:Dinoprostone