title: Short- and long-term A3 adenosine receptor activation inhibits the Na+/H+ exchanger NHE3 activity and expression in opossum kidney cells.
abstract: The renal function of the A(3) adenosine receptor (A3AR) is poorly characterized. In this study, we report that the A3AR-selective agonist, 1-[2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purine-9-yl]-1-deoxy-N-methyl-b-D-ribofuranuronamide (2-Cl-IBMECA) regulates the Na+/H+ exchanger-3 (NHE3) in a dose- and time-dependent fashion. In opossum kidney (OK) cells, 2-Cl-IBMECA at high (10(-6) M) and low (10(-8) M) dose inhibits NHE3 by a multiphasic time course with an acute phase of NHE3 inhibition from 15 min to 1 h, followed by a chronic phase of NHE3 inhibition from 24 to 48 h. Pre-incubation with either the selective A3AR-antagonist MRS1523 (10(-7) M) or the protein kinase C inhibitor, Calphostin C (10(-8) M) completely blocked 10(-6) M 2-Cl-IBMECA-induced acute (15 min) and chronic (24 h) phases of NHE3 inhibition. In contrast, the acute inhibitory phase (15 min) of 10(-8) M 2-Cl-IBMECA was completely prevented only when Calphostin C (10(-8) M) was added in conjunction with the protein kinase A inhibitor, H89 (10(-7) M). Acute (15 or 30 min depending on the A3AR-agonist concentration) A3AR-dependent inhibition of NHE3 activity was accompanied by decrease in cell surface NHE3 protein with no change in total NHE3 antigen. Chronic (24 h) A3AR-mediated down-regulation of NHE3 was associated with reduction of surface NHE3, decreased total NHE3 protein (70%) and a paradoxical rise of NHE3 RNA (40%). In summary, these results indicate that A3AR directly regulates NHE3 at multiple levels in a complex pattern. A3AR-dependent short- and long-term inhibition of NHE3 may be a fundamental mechanism of net sodium and fluid balance.
authors.affiliation: Department of Physiology and Pathophysiology, University of Göttingen, Göttingen, Germany. francesca.disole@utsouthwestern.edu
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Sole
authors.forename: Robert
authors.initials: R
authors.lastname: Cerull
authors.forename: Victor
authors.initials: V
authors.lastname: Babich
authors.forename: Valeria
authors.initials: V
authors.lastname: Casavola
authors.forename: Corinna
authors.initials: C
authors.lastname: Helmle-Roth
authors.forename: Gerhard
authors.initials: G
authors.lastname: Burckhardt
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D058909:Adenosine A3 Receptor Agonists; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D009281:Naphthalenes / Q000378:metabolism; D009893:Opossums; D011493:Protein Kinase C / Q000378:metabolism; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*
chemical_list: D058909:Adenosine A3 Receptor Agonists; D000893:Anti-Inflammatory Agents; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D043684:Receptor, Adenosine A3; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D006859:Hydrogen; D012964:Sodium; D011493:Protein Kinase C; C058819:calphostin C; D000241:Adenosine; D006854:Hydrocortisone; C090034:2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide