Role of Transforming Growth Factor β in Rat Bladder Smooth Muscle Cell Proliferation

  1. Maurits M. Barendrecht,
  2. Arthur C. M. Mulders,
  3. Henk van der Poel,
  4. Maurice J. B. van den Hoff,
  5. Martina Schmidt and
  6. Martin C. Michel
  1. Departments of Pharmacology and Pharmacotherapy (M.M.B., A.C.M.M., M.S., MC.M.), Urology (M.M.B.), and Anatomy and Embryology (M.v.d.H.), Academic Medical Center, Amsterdam, The Netherlands; Department of Urology, Netherlands Cancer Institute, Amsterdam, The Netherlands (H.v.d.P.); and Department of Molecular Pharmacology, Rijksuniversiteit Groningen, Groningen, The Netherlands (M.S.)
  1. Address correspondence to:
    Dr. Martin C. Michel, Department of Pharmacology and Pharmacotherapy, Academic Medical Center, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. E-mail: m.c.michel{at}amc.nl

Abstract

Conditions associated with hypertrophy of the urinary bladder have repeatedly been associated with an increased urinary excretion of transforming growth factor (TGF) β in both rats and patients. Because TGFβ can have both growth-promoting and -inhibiting effects, we have studied its effects on cell growth and death in primary cultures of rat bladder smooth muscle cells. TGFβ1, TGFβ2, or TGFβ3 did not cause apoptosis, but all three isoforms inhibited DNA synthesis with similar potency (EC50 of approximately 0.1 ng/ml) and efficacy. Such inhibition was antagonized by a specific TGFβ receptor antagonist and independent of the presence of serum. Mitogen-activated protein kinases (MAPKs) are involved in the control of cell growth, and all three TGFβ isoforms inhibited activation of the extracellular signal-regulated kinase, c-Jun NH2-terminal kinase, and p38 MAPK subfamilies. Nevertheless, the inhibitory effects of the TGFβ isoforms on DNA synthesis were not affected by presence of inhibitors of the three MAPK pathways. TGFβ did not alter cell size as measured by flow cytometry or mitochondrial activity, an integrated measure of cell size and number. We conclude that our data do not support the hypothesis that TGFβ is a mediator of rat bladder hypertrophy.

Footnotes

  • Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.

  • doi:10.1124/jpet.106.119115.

  • ABBREVIATIONS: BOO, bladder outlet obstruction; TGF, transforming growth factor; MAPK, mitogen-activated protein kinase; ERK, extracellular signal-regulated kinase; JNK, c-Jun NH2-terminal kinase; BSMC, bladder smooth muscle cell; FCS, fetal calf serum; PBS, phosphate-buffered saline; SB 431542, 4-(5-benzol[1,3]dioxol-5-yl-4-pyrldin-2-yl-1H-imidazol-2-yl)-benzamide hydrate; PD 98059, 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; SP 600125, 1,9-pyrazoloanthrone; SB 203580, 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole; BrdU, 5-bromo-2′-deoxyuridine; TBS/T, Tris-buffered saline + 0.1% (v/v) Tween 20; TUNEL, terminal deoxynucleotidyl transferase dUTP nick-end labeling; ANOVA, analysis of variance; FACS, fluorescence-activated cell sorting.

    • Received December 22, 2006.
    • Accepted April 6, 2007.
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  1. doi: 10.1124/jpet.106.119115 JPET July 2007 vol. 322 no. 1 117-122
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