title: Endothelin-1 inhibits thick ascending limb transport via Akt-stimulated nitric oxide production.
abstract: Endothelin-1 inhibits sodium reabsorption in the thick ascending limb (THAL) via stimulation of nitric oxide (NO) production. The mechanism whereby endothelin-1 stimulates THAL NO is unknown. We hypothesized that endothelin-1 stimulates THAL NO production by activating phosphatidylinositol 3-kinase (PI3K), stimulating Akt activity, and phosphorylating NOS3 at Ser1177. This enhances NO production and inhibits sodium transport. We measured 1) NO production by fluorescence microscopy using DAF2-DA, 2) Akt activity using a fluorescence resonance energy transfer-based Akt reporter, 3) phosphorylated NOS3 and Akt by Western blotting, and 4) NKCC2 activity by fluorescence microscopy. In isolated THAL, endothelin-1 (1 nmol/liter) increased NO production from 0.23 +/- 0.24 to 2.81 +/- 0.32 fluorescence units/min (p < 0.001; n = 5) but failed to stimulate NO production in THALs isolated from NOS3-/- mice. Wortmannin (150 nmol/liter), a PI3K inhibitor, reduced endothelin-1-stimulated NO by 83% (0.49 +/- 0.13 versus 3.31 +/- 0.49 fluorescence units/min for endothelin-1 alone; p < 0.006; n = 5). Endothelin-1 stimulated Akt activity by 0.16 +/- 0.02 arbitrary units as measured by fluorescence resonance energy transfer (p < 0.001; n = 5) and increased phosphorylation of Akt at Ser473 by 56 +/- 11% (p < 0.002; n = 7). Dominant-negative Akt blocked endothelin-1-induced NO by 60 +/- 8% (p < 0.001 versus control; n = 6), and an Akt inhibitor had a similar effect. Endothelin-1 increased phosphorylation of NOS3 at Ser1177 by 89 +/- 24% (p < 0.01; n = 7) but had no effect on Ser633. Endothelin-1 inhibited NKCC2 activity, an effect that was blocked by dominant-negative Akt and NOS inhibition. We conclude that endothelin-1 stimulates THAL NO production by activating PI3K, stimulating Akt activity, and phosphorylating NOS3 at Ser1177. This enhances NO production and inhibits sodium transport.
authors.affiliation: Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, Michigan 48202, USA.
authors.forename: Marcela
authors.initials: M
authors.lastname: Herrera
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Hong
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Ortiz
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Garvin
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000235:genetics; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism; D064466:Solute Carrier Family 12, Member 1; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D019332:Endothelin-1; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D000077191:Wortmannin; C578715:Slc12a1 protein, mouse; C578716:Slc12a1 protein, rat; C496315:Nos3 protein, mouse; C496316:Nos3 protein, rat