The natural phenolic peperobtusin A induces apoptosis of lymphoma U937 cells via the Caspase dependent and p38 MAPK signaling pathways.

Our previous research found the ethyl acetate extract of Peperomia tetraphylla (EAEPT) inhibited the growth of U937 cells by blocking the cell cycle and prompted apoptosis via the reactive oxygen species (ROS)-medicated mitochondria pathway. While the compounds in EAEPT which possessed the anti-tumor activity were unclear. Peperobtusin A is a phenolic compound, which was isolated from the whole plant of Peperomia tetraphylla. In this work, we found that peperobtusin A had the anti-proliferative effects against human lymphoma U937 cells and induced apoptosis in a dose dependent manner. Peperobtusin A significantly enhanced the formation of intracellular ROS and induced the loss of mitochondrial membrane potential (Δψm). And peperobtusin A could increase the ratio of Bax/Bcl-2, induce the cleavage of Bid, Caspase-3, Caspase-8 and Caspase-9 and enhance the level of P-P38. Moreover, peperobtusin A induced the accumulation of cells at S phase. Through using of inhibitors such as antioxidant NAC, pan-caspase inhibitor Z-VAD-FMK, p38 MAPK specific inhibitor SB203580, we found that intracellular ROS generation, activation of Caspases and p38 MAPK played very important roles in the apoptosis induced by peperobtusin A in U937 cells. Our results indicated that intracellular ROS generation, the Caspase-dependent and p38 MAPK signaling pathways involved in apoptosis induced by peperobtusin A in U937 cells.