Capsaicin is an active component of chili peppers. It selectively binds to TRPV1 which is a heat-activated calcium channel. Capsaicin causes the channel to open below 37 °C This is why capsaicin is linked to the sensation of heat.
Capsaicin is an agonist of transient receptor potential vanilloid subtype 1 (TRPV1), which is expressed in nociceptive sensory neurons and a range of secretory epithelia, including salivary glands. Capsaicin activates TRPV1, which modulates the permeability of tight junctions (TJ) by regulating the expression and function of putative intercellular adhesion molecules in an ERK-dependent manner. Capsaicin is found to inhibit the growth and proliferation of FaDu cells in a dose- and time-dependent manner. Cells treated with 50, 100, 200, and 300 μM Capsaicin show an augmented decrease in cell growth as the Capsaicin dose increases. In addition, the percentage of viable cells decreases as the incubation time increases. The observed IC50 value is around 150 μM.
Capsaicin (CAP)-treated animals (Group IV) show increased DNA fragmentation suggesting apoptosis when compare with B(a)P-induced lung cancer-bearing animals (Group II) that show reduced DNA fragmentation. CAP-treated Group IV animals show markedly increased expressions of p53, Bax and caspase-3 with remarkable decrease in the levels of anti-apoptotic protein Bcl-2, when compare with B(a)P-administered lung cancer animals of Group II. Capsaicin causes a dose-dependent reduction of tear secretion in female Wistar/ST rats. Significant effects are observed at doses of 20, 50 and 100?mg/kg. In addition, Capsaicin also causes corneal lesions, and significant effects are observed at doses of 50 and 100?mg/kg.
Capsaicin is dissolved in DMSO and stored, and then diluted with appropriate medium before use. FaDu cells are plated at a density of 1×105 cells/well on 24-well plate. After overnight growth, the cells are treated with various concentrations of Capsaicin (0 μM, 50 μM, 100 μM, 150 μM, 200 μM, 250 μM, 300 μM, and 350 μM) for 24, 48 and 72 hours, with medium replacement every 24 hours. At the end of treatment, 30 μL of the tetrazolium compound MTT, and 270 μL of fresh medium are added. After further incubation for 4 hours at 37°C, 200 μL of 0.1 N HCl in 10% SDS is added into each well to dissolve the tetrazolium crystals. Finally, the absorbance at a wavelength of 540 nm is recorded using an ELISA plate reader.