title: Prostaglandin E2 induces chloride secretion through crosstalk between cAMP and calcium signaling in mouse inner medullary collecting duct cells.
abstract: Under conditions of high dietary salt intake, prostaglandin E2 (PGE2) production is increased in the collecting duct and promotes urinary sodium chloride (NaCl) excretion; however, the molecular mechanisms by which PGE2 increases NaCl excretion in this context have not been clearly defined. We used the mouse inner medullary collecting duct (mIMCD)-K2 cell line to characterize mechanisms underlying PGE2-regulated NaCl transport. When epithelial Na(+) channels were inhibited, PGE2 exclusively stimulated basolateral EP4 receptors to increase short-circuit current (Isc(PGE2)). We found that Isc(PGE2) was sensitive to inhibition by H-89 and CFTR-172, indicating that EP4 receptors signal through protein kinase A to induce Cl(-) secretion via cystic fibrosis transmembrane conductance regulator (CFTR). Unexpectedly, we also found that Isc(PGE2) was sensitive to inhibition by BAPTA-AM (Ca(2+) chelator), 2-aminoethoxydiphenyl borate (2-APB) (inositol triphosphate receptor blocker), and flufenamic acid (FFA) [Ca(2+)-activated Cl(-) channel (CACC) inhibitor], suggesting that EP4 receptors also signal through Ca(2+) to induce Cl(-) secretion via CACC. Additionally, we observed that PGE2 stimulated an increase in Isc through crosstalk between cAMP and Ca(2+) signaling; BAPTA-AM or 2-APB inhibited a component of Isc(PGE2) that was sensitive to CFTR-172 inhibition; H-89 inhibited a component of Isc(PGE2) that was sensitive to FFA inhibition. Together, our findings indicate that PGE2 activates basolateral EP4 receptors and signals through both cAMP and Ca(2+) to stimulate Cl(-) secretion in IMCD-K2 cells. We propose that these signaling pathways, and the crosstalk between them, may provide a concerted mechanism for enhancing urinary NaCl excretion under conditions of high dietary NaCl intake.
authors.affiliation: Division of Nephrology, Department of Medicine, Stanford University, Palo Alto, California; and.
authors.forename: Madhumitha
authors.initials: M
authors.lastname: Rajagopal
authors.forename: Sheela V
authors.initials: SV
authors.lastname: Thomas
authors.forename: Paru P
authors.initials: PP
authors.lastname: Kathpalia
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Alan C
authors.initials: AC
authors.lastname: Pao
mesh_terms: D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D001896:Boron Compounds; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002460:Cell Line; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005439:Flufenamic Acid / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors; D017136:Ion Transport; D007546:Isoquinolines / Q000494:pharmacology; D007679:Kidney Medulla / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D051379:Mice; D018408:Patch-Clamp Techniques; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000378:metabolism; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: C482900:3-((3-trifluoromethyl)phenyl)-5-((3-carboxyphenyl)methylene)-2-thioxo-4-thiazolidinone; D001565:Benzoates; D001896:Boron Compounds; C492109:CLCA1 protein, human; D018118:Chloride Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007546:Isoquinolines; D058309:Receptors, Prostaglandin E, EP4 Subtype; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013449:Sulfonamides; D053778:Thiazolidines; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D012965:Sodium Chloride; D004533:Egtazic Acid; D005439:Flufenamic Acid; D000242:Cyclic AMP; C109986:2-aminoethoxydiphenyl borate; D015232:Dinoprostone; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium
keywords: Ca2+-activated Cl- channel; EP4 receptor; collecting duct; cystic fibrosis transmembrane conductance regulator; prostaglandin E2