title: Altered expression of selected genes in kidney of rats with lithium-induced NDI.
abstract: Lithium treatment is associated with development of nephrogenic diabetes insipidus, caused in part by downregulation of collecting duct aquaporin-2 (AQP2) and AQP3 expression. In the present study, we carried out cDNA microarray screening of gene expression in the inner medulla (IM) of lithium-treated and control rats, and selected genes were then investigated at the protein level by immunoblotting and/or immunohistochemistry. The following genes exhibited significantly altered transcription and mRNA expression levels, and these were compatible with the changes in protein expression. 11beta-Hydroxysteroid dehydrogenase type 2 protein expression in the IM was markedly increased (198 +/- 25% of controls, n = 6), and immunocytochemistry demonstrated an increased labeling of IM collecting duct (IMCD) principal cells. This indicated altered renal mineralocorticoid/glucocorticoid responses in lithium-treated rats. The inhibitor of cyclin-dependent kinases p27 (KIP) protein expression was significantly decreased or undetectable in the IMCD cells, pointing to increased cellular proliferation and remodeling. Heat shock protein 27 protein expression was decreased in the IM (64 +/- 6% of controls, n = 6), likely to be associated with the decreased medullary osmolality in lithium-treated rats. Consistent with this, lens aldose reductase protein expression was markedly decreased in the IM (16 +/- 2% of controls, n = 6), and immunocytochemistry revealed decreased expression in the thin limb cells in the middle and terminal parts of the IM. Ezrin protein expression was upregulated in the IM (158 +/- 16% of controls, n = 6), where it was predominantly expressed in the apical and cytoplasmic domain of the IMCD cells. Increased ezrin expression indicated remodeling of the actin cytoskeleton and/or altered regulation of IMCD transporters. In conclusion, the present study demonstrates changes in gene expression not only in the collecting duct but also in the thin limb of the loop of Henle in the IM, and several of these genes are linked to altered sodium and water reabsorption, cell cycling, and changes in interstitial osmolality.
authors.affiliation: The Water and Salt Research Ctr., Bldg. 233/234, Institute of Anatomy, Univ. of Aarhus, DK-8000 Aarhus C, Denmark.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Rojek
authors.forename: Jakob
authors.initials: J
authors.lastname: Nielsen
authors.forename: Heddwen L
authors.initials: HL
authors.lastname: Brooks
authors.forename: Hong
authors.initials: H
authors.lastname: Gong
authors.forename: Young-Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Tae-Hwan
authors.initials: TH
authors.lastname: Kwon
authors.forename: Jørgen
authors.initials: J
authors.lastname: Frøkiaer
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
mesh_terms: D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2 / Q000235:genetics; D000276:Adjuvants, Immunologic / Q000633:toxicity*; D000449:Aldehyde Reductase / Q000235:genetics; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003598:Cytoskeletal Proteins; D018500:Diabetes Insipidus, Nephrogenic / Q000139:chemically induced / Q000235:genetics* / Q000503:physiopathology; D015870:Gene Expression / Q000187:drug effects; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics; D007668:Kidney / Q000187:drug effects* / Q000502:physiology*; D018021:Lithium Chloride / Q000633:toxicity*; D008297:Male; D009363:Neoplasm Proteins / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D009994:Osmolar Concentration; D010750:Phosphoproteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011921:Rats, Inbred WKY; D017208:Rats, Wistar; D025521:Tumor Suppressor Proteins / Q000235:genetics; D000099149:Ezrin
chemical_list: D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2; D000276:Adjuvants, Immunologic; D000449:Aldehyde Reductase; D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003598:Cytoskeletal Proteins; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018021:Lithium Chloride; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D000099149:Ezrin; C493962:Cdkn1b protein, rat; C486114:Hspb1 protein, rat