Functional transient receptor potential vanilloid 1 is expressed in human urothelial cells.
OBJECTIVE
We investigated the expression and functional status of TRPV1 receptor in human urothelial cells.


METHODS
Human urothelium was cultured and TRPV1 receptor expression was studied by immunocytochemistry and reverse transcriptase-polymerase chain reaction. The influence of inflammatory mediators on TRPV1 mRNA levels was also studied. Functional assays (cobalt uptake measurements and whole cell voltage clamp records) were used to study the response of urothelial cells to capsaicin, temperature, low pH and inflammatory mediators. Capsaicin induced adenosine triphosphate release from urothelial cells was assessed by bioluminescence.


RESULTS
TRPV1 protein and mRNA were detected in human urothelial cells and mRNA more than tripled in the presence of inflammatory mediators. Nerve growth factor treatment alone did not affect TRPV1 mRNA expression. Capsaicin (100 nM and 1 microM) and heat (41C and 45C) evoked cobalt uptake and inflammatory mediators lowered the temperature threshold for TRPV1 activation to 37C. Capsaicin (1 microM) induced TRPV1 desensitization to further applications of the agonist. In whole cell patch clamp experiments 1 microM capsaicin and a heat ramp from 37C to 50C caused inward currents. The same concentration of capsaicin induced the release of about 7 fmol adenosine triphosphate per mg.


CONCLUSIONS
TRPV1 receptors expressed by human urothelial cells respond to capsaicin and thermal stimuli. Capsaicin evoked release of adenosine triphosphate suggests that human urothelial TRPV1 is involved in the afferent branch of the micturition reflex. Inflammatory mediators decrease the TRPV1 thermal threshold of activation to body temperature and increase its expression. This finding may be relevant for symptoms associated with cystitis.
Institute of Histology and Embryology, Instituto de Ciências Biomédicas Abel Salazar, University of Porto, Porto, Portugal.
Ana
A
Charrua
Carlos
C
Reguenga
João Miguel
JM
Cordeiro
Paulo
P
Correiade-Sá
Cleope
C
Paule
Istvan
I
Nagy
Francisco
F
Cruz
António
A
Avelino
D002478:Cells, Cultured; D006801:Humans; D050916:TRPV Cation Channels / Q000096:biosynthesis*; D001743:Urinary Bladder / Q000166:cytology* / Q000378:metabolism*; D019459:Urothelium / Q000166:cytology / Q000378:metabolism
D050916:TRPV Cation Channels; C494482:TRPV1 protein, human