Capsaicin-induced death of human haematological malignant cell lines is independent of TRPV1 activation

The effect of the plant-derived vanilloid, capsaicin (CAP), on the metabolic activity of THP-1, U266B1 and U937 hematological malignancy cells was determined. CAP reduced metabolic activity in a concentration-dependent manner in the three cell lines. A biphasic effect was observed on THP-1 cells (EC₅₀: IC₅₀ (95% CI) 32.9 (19.9-54.3)/219 (144-246) µmol/l). U266B1 cells were more resistant to CAP than THP-1 and U937. Metabolic activity was significantly inhibited by CAP in U937 compared to U266B1 cells (IC₅₀: 197 versus 431 µmol/l, respectively, p < 0.008). Transient receptor potential vanilloid-1 (TRPV1) and CB1 antagonists (SB452533 and AM251, respectively) suppressed the CAP-induced increase in THP-1 cell metabolic activity (p < 0.001). AM251 and SB452533 appeared to act as partial agonists and displayed a synergistic effect with CAP in U937 cells. CAP inhibits the metabolic activity of malignant hematological cells through non-TRPV1-dependent mechanisms.