Signaling through P13K/AKT mediates stretch and PDGF-BBdependent DNA synthesis in bladder smooth muscle cells

Rosalyn M. Adam, Jonathan A. Roth, Hong Lin Cheng, Dana C. Rice, Joseph Khoury, Stuart B. Bauer, Craig A Peters, Michael R. Freeman

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

Purpose: Smooth muscle cells (SMC) of the bladder undergo hypertrophy and hyperplasia following exposure to sustained mechanical overload. Although superficial similarities in the response of the heart and bladder to hypertrophic stimuli suggest that similar molecular mechanisms may be involved, this remains to be demonstrated. In this study we compared signal transduction pathway activation in primary culture bladder SMC and cardiac myofibroblasts in response to cyclic stretch. The effects of growth factor stimulation on pathway activation in bladder SMC were also investigated. Materials and Methods: Primary culture rodent bladder SMC or cardiac myofibroblasts were subjected to cyclic stretch-relaxation in the absence or presence of pharmacologic inhibitors of the phosphoinositide-3-kinase, (PI3K)/Akt, extracellular signal-regulated kinase-mitogen activated protein kinase (Erk-MAPK) or the p38 stress -activated protein kinase-2 (SAPK2) pathways. In parallel experiments human bladder SMC were treated with platelet-derived growth factor-BB (PDGF-BB), heparin-binding EGF-like growth factor (HB-EGF) or fibroblast growth factor-2 (FGF-2). In each case the extent of DNA synthesis was determined by uptake of tritiated thymidine, and activation of specific signaling intermediates was determined by immunoblot analysis using antibodies to the non-phosphorylated and phosphorylated (activated) forms of Akt, p38 and Erkl/2. Results: Akt and p38 were rapidly phosphorylated in stretched bladder SMC and cardiac myofibroblasts, and stretch-induced DNA synthesis in these cells was ablated with inhibitors of PI3K or p38 but not Erk-MAPK. Similarly, PDGF-BB up-regulated DNA synthesis in bladder SMC in a p38 and Akt-dependent manner. Conclusions: We conclude that distinct stimuli, such as mechanical stretch and PDGF-BB, promote DNA synthesis in bladder SMC through shared downstream signaling pathways. Furthermore, phenotypically similar cells from the bladder and heart show comparable pathway activation in response to stretch. These findings suggest that similar molecular mechanisms underlie the altered growth responses of the bladder and heart to mechanical overload. This study also provides the first report of Akt activation in bladder SMC and suggests that Akt, consistent with its pivotal role in cardiac hypertrophy, may also be a key regulator of remodeling in the SMC compartment of the bladder exposed to hypertrophic/hyperplastic stimuli in vivo.

Original languageEnglish (US)
Pages (from-to)2388-2393
Number of pages6
JournalJournal of Urology
Volume169
Issue number6
DOIs
StatePublished - Jun 1 2003

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Smooth Muscle Myocytes
Urinary Bladder
DNA
Myofibroblasts
1-Phosphatidylinositol 4-Kinase
Extracellular Signal-Regulated MAP Kinases
Mitogen-Activated Protein Kinase 11
Cardiomegaly
p38 Mitogen-Activated Protein Kinases
Fibroblast Growth Factor 2
Mitogen-Activated Protein Kinases
Thymidine
Hypertrophy
Hyperplasia
Rodentia
Signal Transduction
Intercellular Signaling Peptides and Proteins

Keywords

  • Mechanical
  • Platelet-derived growth factor
  • Protein-serine-threonine kinases
  • Stress

ASJC Scopus subject areas

  • Urology

Cite this

Adam, R. M., Roth, J. A., Cheng, H. L., Rice, D. C., Khoury, J., Bauer, S. B., ... Freeman, M. R. (2003). Signaling through P13K/AKT mediates stretch and PDGF-BBdependent DNA synthesis in bladder smooth muscle cells. Journal of Urology, 169(6), 2388-2393. https://doi.org/10.1097/01.ju.0000063980.99368.35

Signaling through P13K/AKT mediates stretch and PDGF-BBdependent DNA synthesis in bladder smooth muscle cells. / Adam, Rosalyn M.; Roth, Jonathan A.; Cheng, Hong Lin; Rice, Dana C.; Khoury, Joseph; Bauer, Stuart B.; Peters, Craig A; Freeman, Michael R.

In: Journal of Urology, Vol. 169, No. 6, 01.06.2003, p. 2388-2393.

Research output: Contribution to journalArticle

Adam, Rosalyn M. ; Roth, Jonathan A. ; Cheng, Hong Lin ; Rice, Dana C. ; Khoury, Joseph ; Bauer, Stuart B. ; Peters, Craig A ; Freeman, Michael R. / Signaling through P13K/AKT mediates stretch and PDGF-BBdependent DNA synthesis in bladder smooth muscle cells. In: Journal of Urology. 2003 ; Vol. 169, No. 6. pp. 2388-2393.
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AU - Adam, Rosalyn M.

AU - Roth, Jonathan A.

AU - Cheng, Hong Lin

AU - Rice, Dana C.

AU - Khoury, Joseph

AU - Bauer, Stuart B.

AU - Peters, Craig A

AU - Freeman, Michael R.

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N2 - Purpose: Smooth muscle cells (SMC) of the bladder undergo hypertrophy and hyperplasia following exposure to sustained mechanical overload. Although superficial similarities in the response of the heart and bladder to hypertrophic stimuli suggest that similar molecular mechanisms may be involved, this remains to be demonstrated. In this study we compared signal transduction pathway activation in primary culture bladder SMC and cardiac myofibroblasts in response to cyclic stretch. The effects of growth factor stimulation on pathway activation in bladder SMC were also investigated. Materials and Methods: Primary culture rodent bladder SMC or cardiac myofibroblasts were subjected to cyclic stretch-relaxation in the absence or presence of pharmacologic inhibitors of the phosphoinositide-3-kinase, (PI3K)/Akt, extracellular signal-regulated kinase-mitogen activated protein kinase (Erk-MAPK) or the p38 stress -activated protein kinase-2 (SAPK2) pathways. In parallel experiments human bladder SMC were treated with platelet-derived growth factor-BB (PDGF-BB), heparin-binding EGF-like growth factor (HB-EGF) or fibroblast growth factor-2 (FGF-2). In each case the extent of DNA synthesis was determined by uptake of tritiated thymidine, and activation of specific signaling intermediates was determined by immunoblot analysis using antibodies to the non-phosphorylated and phosphorylated (activated) forms of Akt, p38 and Erkl/2. Results: Akt and p38 were rapidly phosphorylated in stretched bladder SMC and cardiac myofibroblasts, and stretch-induced DNA synthesis in these cells was ablated with inhibitors of PI3K or p38 but not Erk-MAPK. Similarly, PDGF-BB up-regulated DNA synthesis in bladder SMC in a p38 and Akt-dependent manner. Conclusions: We conclude that distinct stimuli, such as mechanical stretch and PDGF-BB, promote DNA synthesis in bladder SMC through shared downstream signaling pathways. Furthermore, phenotypically similar cells from the bladder and heart show comparable pathway activation in response to stretch. These findings suggest that similar molecular mechanisms underlie the altered growth responses of the bladder and heart to mechanical overload. This study also provides the first report of Akt activation in bladder SMC and suggests that Akt, consistent with its pivotal role in cardiac hypertrophy, may also be a key regulator of remodeling in the SMC compartment of the bladder exposed to hypertrophic/hyperplastic stimuli in vivo.

AB - Purpose: Smooth muscle cells (SMC) of the bladder undergo hypertrophy and hyperplasia following exposure to sustained mechanical overload. Although superficial similarities in the response of the heart and bladder to hypertrophic stimuli suggest that similar molecular mechanisms may be involved, this remains to be demonstrated. In this study we compared signal transduction pathway activation in primary culture bladder SMC and cardiac myofibroblasts in response to cyclic stretch. The effects of growth factor stimulation on pathway activation in bladder SMC were also investigated. Materials and Methods: Primary culture rodent bladder SMC or cardiac myofibroblasts were subjected to cyclic stretch-relaxation in the absence or presence of pharmacologic inhibitors of the phosphoinositide-3-kinase, (PI3K)/Akt, extracellular signal-regulated kinase-mitogen activated protein kinase (Erk-MAPK) or the p38 stress -activated protein kinase-2 (SAPK2) pathways. In parallel experiments human bladder SMC were treated with platelet-derived growth factor-BB (PDGF-BB), heparin-binding EGF-like growth factor (HB-EGF) or fibroblast growth factor-2 (FGF-2). In each case the extent of DNA synthesis was determined by uptake of tritiated thymidine, and activation of specific signaling intermediates was determined by immunoblot analysis using antibodies to the non-phosphorylated and phosphorylated (activated) forms of Akt, p38 and Erkl/2. Results: Akt and p38 were rapidly phosphorylated in stretched bladder SMC and cardiac myofibroblasts, and stretch-induced DNA synthesis in these cells was ablated with inhibitors of PI3K or p38 but not Erk-MAPK. Similarly, PDGF-BB up-regulated DNA synthesis in bladder SMC in a p38 and Akt-dependent manner. Conclusions: We conclude that distinct stimuli, such as mechanical stretch and PDGF-BB, promote DNA synthesis in bladder SMC through shared downstream signaling pathways. Furthermore, phenotypically similar cells from the bladder and heart show comparable pathway activation in response to stretch. These findings suggest that similar molecular mechanisms underlie the altered growth responses of the bladder and heart to mechanical overload. This study also provides the first report of Akt activation in bladder SMC and suggests that Akt, consistent with its pivotal role in cardiac hypertrophy, may also be a key regulator of remodeling in the SMC compartment of the bladder exposed to hypertrophic/hyperplastic stimuli in vivo.

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