Stretch activates heparin-binding EGF-like growth factor expression in bladder smooth muscle cells.
Cultured rat bladder smooth muscle cells (SMC) were grown on collagen-coated silicone membranes and subjected to continuous cycles of stretch-relaxation. Semiquantitative RT-PCR analysis revealed a time-dependent increase in heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) mRNA levels after stretch, with maximal levels appearing after 4 h. Immunostaining for proHB-EGF revealed higher levels of HB-EGF protein in the stretched than in the nonstretched SMC. The ANG II receptor type 1 antagonist losartan markedly suppressed stretch-activated HB-EGF expression. ANG II levels were 3.3-fold higher in the stretch- than in the non-stretch-conditioned media. Stretch stimulation of bladder SMC that had been transiently transfected with an HB-EGF promoter-luciferase expression construct resulted in an 11-fold increase in reporter activity. Mechanical stretch induced a 4.7-fold increase in tritiated thymidine incorporation rate, and this was reduced by 25% in the presence of losartan. We conclude that mechanical stretch activates HB-EGF gene expression in bladder SMC and that this is mediated in part by autocrine ANG II secretion.
Park
J M
JM
Urologic Laboratory, Department of Urology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Borer
J G
JG
Freeman
M R
MR
Peters
C A
CA
D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D004815:Epidermal Growth Factor / Q000235:genetics*; D005091:Exons; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006493:Heparin / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014158:Transcription, Genetic / Q000187:drug effects; D001743:Urinary Bladder / Q000166:cytology / Q000378:metabolism / Q000502:physiology*
D003470:Culture Media; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; C587885:Hbegf protein, rat; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2; D000804:Angiotensin II; D004815:Epidermal Growth Factor; D006493:Heparin