Oxalate selectively activates p38 mitogen-activated protein kinase and c-Jun N-terminal kinase signal transduction pathways in renal epithelial cells.
Oxalate, a metabolic end product, is an important factor in the pathogenesis of renal stone disease. Oxalate exposure to renal epithelial cells results in re-initiation of the DNA synthesis, altered gene expression, and apoptosis, but the signaling pathways involved in these diverse effects have not been evaluated. The effects of oxalate on mitogen- and stress-activated protein kinase signaling pathways were studied in LLC-PK1 cells. Exposure to oxalate (1 mM) rapidly stimulated robust phosphorylation and activation of p38 MAPK. Oxalate exposure also induced modest activation of JNK, as monitored by phosphorylation of c-Jun. In contrast, oxalate exposure had no effect on phosphorylation and enzyme activity of p42/44 MAPK. We also show that specific inhibition of p38 MAPK by 4(4-(fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)imidazole (SB203580) or by overexpression of a kinase-dead dominant negative mutant of p38 MAPK abolishes oxalate induced re-initiation of DNA synthesis in LLC-PK1 cells. The inhibition is dose-dependent and correlates with in situ activity of native p38 MAP kinase, determined as MAPK-activated protein kinase-2 activity in cell extracts. Thus, this study not only provides the first demonstration of selective activation of p38 MAPK and JNK signaling pathways by oxalate but also suggests that p38 MAPK activity is essential for the effects of oxalate on re-initiation of DNA synthesis.
Chaturvedi
Lakshmi S
LS
Biochemistry and Molecular Biology Laboratory, Vattikuti Urology Institute, Henry Ford Health Sciences Center, One Ford Place, Detroit, MI 48202, USA.
Koul
Sweaty
S
Sekhon
Avtar
A
Bhandari
Akshay
A
Menon
Mani
M
Koul
Hari K
HK
D000818:Animals; D004261:DNA Replication; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D007668:Kidney / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018374:LLC-PK1 Cells; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010070:Oxalates / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013552:Swine; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D007093:Imidazoles; D010070:Oxalates; D011725:Pyridines; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580