title: Enhanced glycogen synthase kinase-3β activity mediates podocyte apoptosis under diabetic conditions.
abstract: Glycogen synthase kinase-3β (GSK-3β) is involved in the pathogenesis of various kidney diseases. This study was undertaken to examine the changes in GSK-3β activity in podocytes under diabetic conditions and to elucidate the functional role of GSK-3β in podocyte apoptosis. In vivo, 32 rats were injected with either diluent (n = 16, C) or with streptozotocin intraperitoneally (n = 16, DM), and 8 rats from each group were treated with 6-bromoindirubin-3'-oxime (BIO) for 3 months. In vitro, immortalized mouse podocytes were exposed to 5.6 mM glucose or 30 mM glucose (HG) with or without 10 μM BIO. Western blot analysis and TUNEL or Hoechst 33342 staining were performed to identify apoptosis. Urinary albumin excretion was significantly higher in DM rats, and this increase was significantly abrogated in DM rats by BIO treatment. The protein expression of Tyr216-phospho-GSK-3β was significantly increased in DM glomeruli and in cultured podocytes exposed to HG. Western blot analysis revealed that the protein expression of Bax and active fragments of caspase-3 were significantly increased, whereas phospho-Akt, β-catenin, and Bcl-2 protein expression were significantly decreased in DM glomeruli and HG-stimulated podocytes. Apoptosis, determined by TUNEL assay and Hoechst 33342 staining, was also significantly increased in podocytes under diabetic conditions. The changes in the expression of apoptosis-related molecules and the increase in the number of apoptotic cells in DM glomeruli as well as in HG-stimulated podocytes were significantly ameliorated by BIO. These findings suggest that enhanced GSK-3β activity within podocytes under diabetic conditions is associated with podocyte loss in diabetic nephropathy.
authors.affiliation: Department of Internal Medicine, Severance Biomedical Science Institute, BK21, College of Medicine, Yonsei University, 134 Shinchon-Dong, Seodaemoon-Gu, Seoul, 120-752, Korea.
authors.forename: Jisun
authors.initials: J
authors.lastname: Paeng
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Chang
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Lee
authors.forename: Bo Young
authors.initials: BY
authors.lastname: Nam
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Kang
authors.forename: Seonghun
authors.initials: S
authors.lastname: Kim
authors.forename: Hyung Jung
authors.initials: HJ
authors.lastname: Oh
authors.forename: Jung Tak
authors.initials: JT
authors.lastname: Park
authors.forename: Seung Hyeok
authors.initials: SH
authors.lastname: Han
authors.forename: Tae-Hyun
authors.initials: TH
authors.lastname: Yoo
authors.forename: Shin-Wook
authors.initials: SW
authors.lastname: Kang
mesh_terms: D000419:Albuminuria / Q000378:metabolism / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D005947:Glucose / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles / Q000494:pharmacology; D007678:Kidney Glomerulus / Q000378:metabolism / Q000473:pathology; D008297:Male; D010091:Oximes / Q000494:pharmacology; D010766:Phosphorylation; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013311:Streptozocin; D014443:Tyrosine / Q000378:metabolism
chemical_list: C483321:6-bromoindirubin-3'-oxime; D051017:Apoptosis Regulatory Proteins; D007211:Indoles; D010091:Oximes; D014443:Tyrosine; D013311:Streptozocin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D005947:Glucose