TGF-beta1 inhibits Cx43 expression and formation of functional syncytia in cultured smooth muscle cells from human detrusor.
BACKGROUND
Human detrusor smooth muscle cells (hBSMCs) are coupled by connexin 43 (Cx43)-positive gap junctions to form functional syncytia. Gap junctional communication likely is necessary for synchronised detrusor contractions and is supposed to be altered in voiding disturbances. Other authors have shown that the pleiotropic cytokine TGF-beta1 upregulates Cx43 expression in human aortic smooth muscle cells.


OBJECTIVE
In this study, we examined the TGF-beta1 effects on Cx43 expression in cultured hBSMCs.


METHODS
hBSMC cultures, established from patients undergoing cystectomy, were treated with recombinant human TGF-beta1.


METHODS
Cx43 expression was then examined by Western blotting, real-time PCR, and immunocytochemistry. Dye-injection experiments were used to study the size of functional syncytia.


CONCLUSIONS
Dye-coupling experiments revealed stable formation of functional syncytia in passaged cell cultures (P1-P4). Stimulation with TGF-beta1 led to significant reduction of Cx43 immunoreactivity and coupling. Cx43 protein expression was significantly downregulated and Cx43 mRNA was only 30% of the control level. Interestingly, low phosphorylation species of Cx43 were particularly affected.


CONCLUSIONS
Our experiments demonstrated a significant down regulation of connexin 43 by TGF-beta1 in cultured hBSMCs. These findings support the view that TGF-beta1 is involved in the pathophysiology of urinary bladder dysfunction.
Neuhaus
Jochen
J
Department of Urology, University of Leipzig, Leipzig, Germany. jochen.neuhaus@medizin.uni-leipzig.de
Heinrich
Marco
M
Schwalenberg
Thilo
T
Stolzenburg
Jens-Uwe
JU
D000368:Aged; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000187:drug effects / Q000235:genetics*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000235:genetics; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D014158:Transcription, Genetic; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D001749:Urinary Bladder Neoplasms / Q000235:genetics / Q000473:pathology* / Q000601:surgery*
D018031:Connexin 43; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D053773:Transforming Growth Factor beta1