Hypertonicity stimulates PGE2 signaling in the renal medulla by promoting EP3 and EP4 receptor expression.
Hypertonicity in the renal medulla stimulates local cyclooxygenase 2 expression, leading to abundant PGE(2) production. Here we found that mRNA expression by the PGE(2)-activated G-protein-coupled receptors, EP3 and EP4 in the renal medulla was decreased by furosemide treatment, a procedure that reduces medullary hypertonicity. When HepG2 cells were cultured in hypertonic conditions by addition of salt or sorbitol, EP3 expression was induced. A specific EP3 agonist inhibited cAMP production, indicating receptor functionality, and this led to a substantial increase in cell survival in hypertonic media. Survival was independent of the SLC5A3 inositol transporter and aldose reductase expression, suggesting that EP3 promoted cell survival under hypertonic conditions independent of cellular organic osmolyte accumulation. Reduced cAMP production did not contribute to increased survival. EP4 expression was stimulated by hypertonicity in MDCK and HepG2 cells, which was associated with increased cAMP production in response to an EP4 agonist. Our study shows that local hypertonicity promotes PGE(2) signaling in the renal medulla by stimulating cognate receptor and cyclooxygenase 2 expression that likely regulates local hemodynamics and tubular transport.Kidney International (2009) 75, 278-284. doi:10.1038/ki.2008.498.
Department of Medicine, University of Maryland, Baltimore, Maryland 21201, USA.
Jeong-Ah
JA
Kim
Mee Rie
MR
Sheen
Sang Do
SD
Lee
Ju-Young
JY
Jung
H Moo
HM
Kwon
D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D004285:Dogs; D006801:Humans; D006982:Hypertonic Solutions / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology; D007679:Kidney Medulla / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000235:genetics / Q000378:metabolism*; D058308:Receptors, Prostaglandin E, EP3 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D012462:Saline Solution, Hypertonic / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013012:Sorbitol / Q000378:metabolism
D006982:Hypertonic Solutions; C545647:PTGER3 protein, human; C545650:PTGER4 protein, human; D012333:RNA, Messenger; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D012462:Saline Solution, Hypertonic; D013012:Sorbitol; D051546:Cyclooxygenase 2; D015232:Dinoprostone