title: Differential activation of mitogen-activated protein kinases in experimental mesangioproliferative glomerulonephritis.
abstract: Multiple extracellular mitogens are involved in the pathogenesis of proliferative forms of glomerulonephritis (GN). In vitro studies demonstrate the pivotal role of mitogen-activated protein (MAP) kinases in the regulation of cellular proliferation. This study was conducted to examine whether these kinases, as a convergence point of mitogenic stimuli, are activated in mesangioproliferative GN in vivo. Therefore, anti-Thy1 GN was induced in rats using a monoclonal anti-Thy1.1 antibody (OX-7). Whole cortical tissue as well as isolated glomeruli were examined at different time points using kinase activity assays and Western blot analysis. A maximal increase in the number of glomerular mitotic figures (9.7-fold) was demonstrated 6 d after injection of the anti-Thy1.1 antibody. In parallel with this finding, a significant increase in cortical, and more dramatically glomerular, activity of extracellular signal-regulated kinase (ERK) was detected. Maximal activation of ERK was detectable on day 6. This activation of ERK was accompanied by an increase in the expression of MEK (MAP kinase/ERK kinase), the ERK-activating kinase. A marked induction of glomerular apoptosis at 2 h after injection of the anti-Thy1.1 antibody, which subsided subsequently, was demonstrated using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay as well as staining for single-stranded DNA. However, no significant activation of stress-activated protein kinase or p38 MAP kinase, both MAP kinases that are suggested to induce apoptosis and to inhibit cellular growth, was detectable at this early time point. Rather, on day 6 a dramatic decrease in the activity of p38 MAP kinase, which might have contributed to the overshooting glomerular cellular proliferation, was observed. Treatment of rats with heparin blunted glomerular proliferation as well as ERK activation and restored p38 MAP kinase activity. These observations point to ERK and p38 MAP kinase as putative mediators of the proliferative response in mesangioproliferative GN and suggest that upregulation of MEK is involved in the long-term regulation of ERK in vivo.
authors.affiliation: Medizinische Poliklinik, Division of Nephrology, University of Bonn, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Bokemeyer
authors.affiliation: Division of Nephrology, Medizinische Hochschule Hannover, Germany.
authors.forename: Tammo
authors.initials: T
authors.lastname: Ostendorf
authors.affiliation: Division of Nephrology, Medizinische Hochschule Hannover, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Kunter
authors.affiliation: Medizinische Poliklinik, Division of Nephrology, University of Bonn, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Lindemann
authors.affiliation: Medizinische Poliklinik, Division of Nephrology, University of Bonn, Germany.
authors.forename: Herbert J
authors.initials: HJ
authors.lastname: Kramer
authors.affiliation: Division of Nephrology, Medizinische Hochschule Hannover, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Floege
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D005920:Glomerular Mesangium / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D015432:Glomerulonephritis, Membranoproliferative / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D006493:Heparin / Q000494:pharmacology; D007518:Isoantibodies / Q000276:immunology; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D007518:Isoantibodies; C035678:anti-Thy antibody; D006493:Heparin; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases