Apoptosis induced by niacin-related compounds in HL-60 cells.

We have investigated whether niacin-related compounds act as inducers of apoptosis in HL-60 cells. In this study, we found that picolinic acid, dipicolinic acid, and isonicotinamide strongly induce apoptosis. After treatments with these compounds, apoptosis started within 4 h and was induced in about 50% of the cells within 8 h. These compounds induced apoptosis at 5-10 mM, but did not at 1 mM. An ICE-like protease inhibitor (Z-Asp-CH2-DCB) completely blocked the apoptosis, but a caspase-1 inhibitor (Ac-YVAD-CHO) and a caspase-3 inhibitor (Ac-DEVD-CHO) did not block the apoptosis, suggesting that other caspases have the critical roles in the execution process of apoptosis induced by niacin-related compounds.