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Grape seed extract (GSE), rich in the bioflavonoids commonly known as procyanidins, is one of the most commonly consumed dietary supplements in the United States because of its several health benefits. Epidemiological studies show that many prostate cancer (PCA) patients use herbal extracts as dietary supplements in addition to their prescription drugs. Accordingly, in recent years, we have focused our attention on assessing the efficacy of GSE against PCA. Our studies showed that GSE inhibits growth and induces apoptotic death of human PCA cells in culture and in nude mice. Here, we performed detailed studies to define the molecular mechanism of GSE-induced apoptosis in advanced human PCA DU145 cells. GSE treatment of cells at various doses (50-200 micro g/ml) for 12-72 h resulted in a moderate to strong apoptotic death in a dose- and time-dependent manner. In the studies assessing the apoptotic-signaling pathway induced by GSE, we observed an increase in cleaved fragments of caspases 3, 7 and 9 as well as PARP in GSE-treated cells after 48 and 72 h of treatment. Pre-treatment of cells with general caspases inhibitor, z-Val-Ala-Asp(OMe)-FMK or caspase 3-like proteases inhibitor [z-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-FMK], almost completely (approximately 90%) inhibited the GSE-induced apoptotic cell death. In a later case, GSE-induced caspase-3 activity was completely inhibited. Selective caspase 9 inhibitor [z-Leu-Glu(OMe)-His-Asp(OMe)-FMK] showed only partial inhibition of GSE-induced apoptosis whereas GSE-induced protease activity of caspase 9 was completely inhibited. Upstream of caspase cascade, GSE showed disappearance of mitochondrial membrane potential and an increase in cytochrome c release in cytosol. Together, these results suggest that GSE possibly causes mitochondrial damage leading to cytochrome c release in cytosol and activation of caspases resulting in PARP cleavage and execution of apoptotic death of human PCA DU145 cells. Furthermore, GSE-caused caspase 3-mediated apoptosis also involves other pathway(s) including caspase 9 activation.

Roots and leaves of Zea mays L. cv. Ganga Safed‐2 seedlings grown with nutrient solution containing either 10 mM KNO3 or NH4Cl or 5 mM NH4NO3 had considerably higher glutamate synthase (NADH, EC 1.4.1.14) activity than the corresponding organs from seedlings grown without any nitrogen. The supply of inorganic nitrogen for a short time, i.e. 3 h, to roots and leaves excised from seedlings grown without nitrogen also increased the enzyme activity in these organs. This increase was more pronounced with nitrate than with ammonium nitrogen. When excised roots and leaves from NH4NO3‐grown seedlings were incubated in a minus nitrogen medium for 24 h, the enzyme activity declined considerably. This decline was inhibited to some extent by nitrogen, especially by nitrate. Inorganic nitrogen prevented similarly the decline in in vitro enzyme activity during 24 h storage at 25°C, more regularly for the root than for the leaf enzyme. The experiments demonstrate the role of inorganic nitrogen in the regulation of glutamate synthase activity.

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