Agaricus blazei is well known as a traditional medicinal mushroom and it has been shown to exhibit immunostimulatory and anti-cancer activity. However, the cellular and molecular mechanism of apoptosis of cancer cells is poorly understood. In this study, we have investigated whether A. blazei extract (ABE) exerts anti-proliferative and apoptotic effects on human leukemia THP-1 cells. It was found that ABE induced a time- and dose-dependent increase in leukemia cells apoptosis through caspase-3 activation and PARP cleavage. Activation of caspase- 9 induced by ABE suggested that ABE-induced signaling was mediated through a mitochondrial death pathway. In addition, we observed an elevation of ROS and a consequent loss of mitochondrial membrane potential, further suggesting that ABE-induced death signaling was mediated through a mitochondrial oxygen stress pathway. The antioxidant Nacetylcysteine, however, opposed ABE-mediated mitochondrial dysfunction, caspase activation, and apoptosis, supporting the role of ROS in the apoptotic process. We conclude that ABE induces apoptosisin human leukemia cells through a reactive oxygen species and caspase-dependent mitochondrial pathway.

Agaricus blazeiMurill is an edible mushroom distributed in Brazil and presently cultivated in other areas, including Korea, Japan, and China. Its chemical components, including steroids and lectin and various polysaccharides have been widely studied. For this, we used U937/vector and U937/Bcl-2 cells, which were generated by transfection of the cDNA of the Bcl-2 gene. As compared with U937/vector, U937/Bcl-2 cells exhibited a 4-fold greater expression of Bcl-2. Treatment with 0.5 or 4 mg/ml A. blazei Murill for 24 h produced morphological features of apoptosis in U937/vector cells, respectively. This was associated with caspase-3 activation and PARP degradation. In contrast, A. blazei Murill-induced caspase-3 activation and PARP degradation and apoptosis were significantly inhibited by z-DEVD-fmk in U937 cells. Bcl-2 overexpressing cells exhibited sustained caspase-3 activation and expression levels of the Bcl-2 proteins during A. blazei Murill-induced apoptosis. In addition, these findings indicate that Bcl-2 inhibits A. blazei Murill-induced apoptosis by a mechanism that interferes with Bcl-2 degradation and activity of caspase-3 that is involved in the execution of apoptosi.