Cardiac fibroblasts have functional TRPV4 activated by 4alpha-phorbol 12,13-didecanoate.

Vanilloid type transient receptor potential channel (TRPV) could be a potential environmental sensor to multiple stimuli in many types of cells. In this study, we provide the first evidence of functional vanilloid type 4 transient receptor potential channel (TRPV4) in rat cardiac fibroblasts (CFs). Expression of TRPV4 in CFs was analyzed at mRNA and protein level. Function of TRPV4 in CFs was evaluated using a selective TRPV4 agonist, 4alpha-phorbol 12,13-didecanoate (4alphaPDD) while measuring intracellular Ca(2+) concentration ([Ca(2+)](i)) and membrane currents. Analysis of expression of mRNA transcripts of TRPV subfamily revealed that TRPV2 and TRPV4 were expressed in CFs. Significant immunoreactivity to TRPV4 protein was also detected in CFs. When 4alphaPDD was applied to CFs, [Ca(2+)](i) was elevated in a concentration-dependent manner. The elevation of [Ca(2+)](i) was abolished by the removal of external Ca(2+) and by ruthenium red (RuR). 4alphaPDD also activated non-selective cation currents (NSCCs), which were suppressed by RuR. Moreover, pretreatment of CFs with short interference RNA (siRNA) targeting TRPV4 significantly reduced both 4alphaPDD-induced elevation of [Ca(2+)](i) and NSCC. These results provide strong evidence that endogenous TRPV4 functions as an important regulator of [Ca(2+)](i) in CFs.