title: Divergent roles of Smad3 and PI3-kinase in murine adriamycin nephropathy indicate distinct mechanisms of proteinuria and fibrogenesis.
abstract: Multiple transforming growth factor (TGF)-β-induced fibrogenic signals have been described in vitro. To evaluate mechanisms in vivo, we used an adriamycin nephropathy model in 129x1/Svj mice that display massive proteinuria by days 5 to 7 and pathological findings similar to human focal segmental glomerulosclerosis by day 14. TGF-β mRNA expression increased after day 7 along with nuclear translocation of the TGF-β receptor-specific transcription factor Smad3. Inhibiting TGF-β prevented both pathological changes and type-I collagen and fibronectin mRNA expression, but proteinuria persisted. Renal Akt was phosphorylated in adriamycin-treated mice, suggesting PI3-kinase activation. Expression of mRNA for the p110γ isozyme of PI3-kinase was specifically increased and p110γ colocalized with nephrin by immunohistochemistry early in disease. Nephrin levels subsequently decreased. Inhibition of p110γ by AS605240 preserved nephrin expression and prevented proteinuria. In cultured podocytes, adriamycin stimulated p110γ expression. AS605240, but not a TGF-β receptor kinase inhibitor, prevented adriamycin-induced cytoskeletal disorganization and apoptosis, supporting a role for p110γ in podocyte injury. AS605240, at a dose that decreased proteinuria, prevented renal collagen mRNA expression in vivo but did not affect TGF-β-stimulated collagen induction in vitro. Thus, PI3-kinase p110γ mediates initial podocyte injury and proteinuria, both of which precede TGF-β-mediated glomerular scarring.
authors.affiliation: Division of Kidney Diseases and Children's Memorial Research Center, Children's Memorial Hospital, Chicago, IL, USA.
authors.forename: Gal
authors.initials: G
authors.lastname: Finer
authors.forename: H William
authors.initials: HW
authors.lastname: Schnaper
authors.forename: Yashpal S
authors.initials: YS
authors.lastname: Kanwar
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Liang
authors.forename: Herbert Y
authors.initials: HY
authors.lastname: Lin
authors.forename: Tomoko
authors.initials: T
authors.lastname: Hayashida
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D058534:Class I Phosphatidylinositol 3-Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004317:Doxorubicin; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005355:Fibrosis; D005923:Glomerulosclerosis, Focal Segmental / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000517:prevention & control; D007150:Immunohistochemistry; D007668:Kidney / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D057507:Mice, 129 Strain; D010766:Phosphorylation; D050199:Podocytes / Q000201:enzymology / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011507:Proteinuria / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000517:prevention & control; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000378:metabolism*; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D024042:Collagen Type I; D005353:Fibronectins; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; C113267:nephrin; D004317:Doxorubicin; C509622:1-phosphatidylinositol 3-kinase p110 subunit, mouse; D058534:Class I Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt