title: Podocyte injury-driven intracapillary plasminogen activator inhibitor type 1 accelerates podocyte loss via uPAR-mediated β1-integrin endocytosis.
abstract: Podocyte-endothelial cell cross-talk is paramount for maintaining the filtration barrier. The present study investigated the endothelial response to podocyte injury and its subsequent role in glomerulosclerosis using the podocyte-specific injury model of NEP25/LMB2 mice. NEP25/LMB2 mice showed proteinuria and local podocyte loss accompanied by thrombotic microangiopathy on day 8. Mice showed an increase of glomerular plasminogen activator inhibitor type 1 (PAI-1) mRNA and aberrant endothelial PAI-1 protein already on day 1, before thrombosis and proteinuria. A PAI-1-specific inhibitor reduced proteinuria and thrombosis and preserved podocyte numbers in NEP25/LMB2 mice by stabilization of β1-integrin translocation. Heparin loading significantly reduced thrombotic formation, whereas proteinuria and podocyte numbers were unchanged. Immortalized podocytes treated with PAI-1 and the urokinase plasminogen activator (uPA) complex caused significant cell detachment, whereas podocytes treated with PAI-1 or uPA alone or with the PAI-1/uPA complex pretreated with an anti-uPA receptor (uPAR) antibody failed to cause detachment. Confocal microscopy and cell surface biotinylation experiments showed that internalized β1-integrin was found together with uPAR in endocytotic vesicles. The administration of PAI-1 inhibitor or uPAR-blocking antibody protected cultured podocytes from cell detachment. In conclusion, PAI-1/uPA complex-mediated uPAR-dependent podocyte β1-integrin endocytosis represents a novel mechanism of glomerular injury leading to progressive podocytopenia. This aberrant cross-talk between podocytes and endothelial cells represents a feedforward injury response driving podocyte loss and progressive glomerulosclerosis.
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Namiko
authors.initials: N
authors.lastname: Kobayashi
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Ueno
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Kumi
authors.initials: K
authors.lastname: Ohashi
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Hanako
authors.initials: H
authors.lastname: Yamashita
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Yukina
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Shun
authors.initials: S
authors.lastname: Manabe
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hara
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan;
authors.forename: Yasutoshi
authors.initials: Y
authors.lastname: Takashima
authors.affiliation: Center for Translational and Advanced Research, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan;
authors.forename: Takashi
authors.initials: T
authors.lastname: Dan
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland;
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
authors.affiliation: Center for Translational and Advanced Research, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan;
authors.forename: Toshio
authors.initials: T
authors.lastname: Miyata
authors.affiliation: Department of Anatomy, Juntendo University School of Medicine, Bunkyo, Tokyo, Japan;
authors.forename: Hidetake
authors.initials: H
authors.lastname: Kurihara
authors.affiliation: Department of Internal Medicine, Institute of Medical Science, Tokai University School of Medicine, Isehara, Kanagawa, Japan; and.
authors.forename: Taiji
authors.initials: T
authors.lastname: Matsusaka
authors.affiliation: Department of Medicine, Rush University, Chicago, Illinois.
authors.forename: Jochen
authors.initials: J
authors.lastname: Reiser
authors.affiliation: Department of Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan; nagatam@md.tsukuba.ac.jp.
authors.forename: Michio
authors.initials: M
authors.lastname: Nagata
mesh_terms: D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D006493:Heparin; D006801:Humans; D039641:Integrin beta Chains / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D050199:Podocytes / Q000502:physiology*; D011897:Random Allocation; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism*; D013927:Thrombosis / Q000378:metabolism; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
chemical_list: D039641:Integrin beta Chains; D017395:Plasminogen Activator Inhibitor 1; D055293:Receptors, Urokinase Plasminogen Activator; D006493:Heparin; D014568:Urokinase-Type Plasminogen Activator
keywords: endocytosis; integrin; kidney; pathology; plasminogen activator inhibitor type 1; podocyte