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PMID:14665434

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Citation

Martineau, LC, McVeigh, LI, Jasmin, BJ and Kennedy, CR (2004) p38 MAP kinase mediates mechanically induced COX-2 and PG EP4 receptor expression in podocytes: implications for the actin cytoskeleton. Am. J. Physiol. Renal Physiol. 286:F693-701

Abstract

A dynamic cytoskeleton allows podocytes to withstand significant mechanical stress on elevation of intraglomerular capillary pressure (Pgc). However, vasoactive hormones, such as prostaglandin E2 (PGE2), may challenge the integrity of the actin cytoskeleton, alter podocyte morphology, and compromise glomerular permeability. PGE2 synthesis correlates with the onset of proteinuria and increased Pgc following reduced nephron mass. We investigated the interplay among mechanical stress, cyclooxygenase (COX), E-prostanoid (EP) receptor expression, and the actin cytoskeleton, using an in vitro model of cell stretch. Immortalized mouse podocytes grown on flexible silicone membranes were cyclically stretched (5% elongation, 0.5 Hz) for 2 h. EP4 and COX-2 mRNA increased three- and sevenfold above nonstretched controls, whereas EP1 and COX-1 levels were unchanged. Six hours of stretch resulted in a threefold increase in PGE2-stimulated cAMP accumulation, a measure of EP4 receptor function, and an increase in COX-2 protein. The stretch-induced effects on COX-2/EP4 expression and EP4-induced cAMP production were attributable to p38 MAP kinase, as blockade of this pathway, but not of ERK or JNK, abrogated the response. These stretch-induced changes in expression were transcriptionally dependent as they were actinomycin D sensitive. Finally, we investigated the influence of enhanced EP4 signaling on the actin cytoskeleton. Addition of PGE2 resulted in actin filament depolymerization observable only in stretched cells. Our results indicate that key components of the eicosanoid pathway are upregulated by mechanically stimulated p38 MAP kinase in podocytes. Enhanced EP4 receptor signaling may undermine podocyte cytoskeletal dynamics and thereby compromise filtration barrier function under conditions of increased Pgc.

Links

PubMed Online version:10.1152/ajprenal.00331.2003

Keywords

Actins/metabolism; Animals; Cell Line, Transformed; Cyclooxygenase 2; Dinoprostone/metabolism; Enzyme Inhibitors/pharmacology; Isoenzymes/genetics; Isoenzymes/metabolism; Kidney Glomerulus/cytology; Kidney Glomerulus/enzymology; Mice; Mitogen-Activated Protein Kinases/antagonists & inhibitors; Mitogen-Activated Protein Kinases/metabolism; Prostaglandin-Endoperoxide Synthases/genetics; Prostaglandin-Endoperoxide Synthases/metabolism; RNA, Messenger/metabolism; Receptors, Prostaglandin E/genetics; Receptors, Prostaglandin E/metabolism; Receptors, Prostaglandin E, EP4 Subtype; Signal Transduction/physiology; Stress Fibers/metabolism; Stress, Mechanical; Up-Regulation; p38 Mitogen-Activated Protein Kinases

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

MOUSE:PE2R4

involved_in

GO:0051492: regulation of stress fiber assembly

ECO:0000314: direct assay evidence used in manual assertion

P

  • occurs_in:(CL:0000653)

Seeded From UniProt

complete

MOUSE:PE2R4

involved_in

GO:0071260: cellular response to mechanical stimulus

ECO:0000270: expression pattern evidence used in manual assertion

P

  • occurs_in:(CL:0000653)

Seeded From UniProt

complete


See also

References

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