Conclusion
TRPV1 receptor is successfully stimulated by capsaicin, piperine, and natural capsaicinoids. These agonists present desensitization and their effect is significantly reduced by a TRPV1-specific antagonist. In addition, PC-3 cell bioassays proved useful in the study of TRPV1 pharmacodynamics.
Methods
PC-3 cells expressing TRPV1 were incubated with Fluo-4. Fluorescence emission changes following exposition to agonists with and without preincubation with antagonists were assessed and referred to maximal fluorescence following the addition of ionomycin. Concentration-response curves were fitted to the Hill equation.
Purpose
TRPV1 is a multimodal channel mainly expressed in sensory neurons. We aimed to explore the pharmacodynamics of the TRPV1 agonists, capsaicin, natural capsaicinoids, and piperine in an in vitro bioassay using human PC-3 cells and to examine desensitization and the effect of the specific antagonist SB366791.
Results
Capsaicin and piperine had similar pharmacodynamics (E max 204.8 ± 184.3% piperine versus 176.6 ± 35.83% capsaicin, P = 0.8814, Hill coefficient 0.70 ± 0.50 piperine versus 1.59 ± 0.86 capsaicin, P = 0.3752). In contrast, capsaicinoids had lower E max (40.99 ± 6.14% capsaicinoids versus 176.6 ± 35.83% capsaicin, P < 0.001). All the TRPV1 agonists showed significant desensitization after the second exposition and their effects were strongly inhibited by SB366791.