Biotin-AEVD-FMK

Nitric oxide (NO) is a potent inhibitor of apoptosis in many cell types, including hepatocytes. We and others have described NO-dependent decreases in caspase activity in cells undergoing apoptosis. However, previous work has not determined whether NO disrupts the proteolytic processing and thus the activation of pro-caspases. Here we report that NO suppresses proteolytic processing and activation of multiple pro-caspases in intact cells, including caspase-3 and caspase-8. We found that both exogenous NO as well as endogenously produced NO via adenoviral inducible NO synthase gene transfer protected hepatocytes from tumor necrosid factor (TNF) alpha plus actinomycin D (TNFalpha/ActD)-induced apoptosis. Affinity labeling with biotin-VAD-fmk of all active caspase species in TNFalpha-mediated apoptosis identified four newly labeled spots (activated caspases) present exclusively in TNFalpha/ActD-treated cells. Both NO and the caspase inhibitor, Ac-DEVD-CHO, prevented the appearance of the four newly labeled spots or active caspases. Immunoanalysis of affinity labeled caspases demonstrated that caspase-3 was the major effector caspase. Western blot analysis also identified the activation of caspase-8 in the TNFalpha/ActD-treated cells, and the activation was suppressed by NO. Furthermore, NO inhibited several other events associated with caspase activation in cells, including release of cytochrome c from mitochondria, decrease in mitochondrial transmembrane potential, and cleavage of poly(ADP-ribose) polymerase in TNFalpha/ActD-treated cells. These findings indicate the involvement of multiple caspases in TNFalpha-mediated apoptosis in hepatocytes and establish the capacity of NO to inhibit not only active caspases but also caspase activation.

In rats, striatal histotoxic hypoxic lesions produced by the mitochondrial toxin malonate resemble those of focal cerebral ischemia. Intrastriatal injections of malonate induced cleavage of caspase-2 beginning at 6 h, and caspase-3-like activity as identified by DEVD biotin affinity-labeling within 12 h. DEVD affinity-labeling was prevented and lesion volume reduced in transgenic mice overexpressing BCL-2 in neuronal cells. Intrastriatal injection of the tripeptide, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk), a caspase inhibitor, at 3 h, 6 h, or 9 h after malonate injections reduced the lesion volume produced by malonate. A combination of pretreatment with the NMDA antagonist, dizocilpine (MK-801), and delayed treatment with zVAD-fmk provided synergistic protection compared with either treatment alone and extended the therapeutic window for caspase inhibition to 12 h. Treatment with cycloheximide and zVAD-fmk, but not with MK-801, blocked the malonate-induced cleavage of caspase-2. NMDA injections alone resulted in a weak caspase-2 cleavage. These results suggest that malonate toxicity induces neuronal death by more than one pathway. They strongly implicate early excitotoxicity and delayed caspase activation in neuronal loss after focal ischemic lesions and offer a new strategy for the treatment of stroke.

Aim:To investigate the anti-tumor function of ginsenoside Rg3 on hepatocellular carcinoma (HCC) in vitro and in vivo, and its mechanism.Methods:Hep1-6 and HepG2 cells were treated by Rg3 in different concentrations (0, 50, 100 and 200 μg/mL) in vitro. After incubation for 0, 6, 12, 24 and 48 h, cell viability was measured by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling. Caspase-3 activity was measured by chromophore p-nitroanilide and flow cytometry. Bcl-2 family proteins were ascertained by Western-blotting. Mitochondria membrane potential was detected by 5, 5', 6' 6' - tetrachloro-1, 1', 3, 3' - tetraethylbenzimidazolylcarbocyanine iodide. Forty liver tumor-bearing C57Bl6 mice were divided randomly into 4 groups for intra-tumor injection of saline, ginsenoside Rg3, cyclophosphamide (CTX) and ginsenoside Rg3 + CTX combination.Results:The survival time was followed up to 102 d. The mice in the Rg3 + CTX group showed significant increased survival time compared with those in the control group (P < 0.05). Rg3 could inhibit HCC cell proliferation and induce cell apoptosis in vitro in the concentration and time dependent manner. It also induced mitochondria membrane potential to decrease. Caspase-3 activation can be blocked by the inhibitor z-DEVD-FMK. Bax was up-regulated while Bcl-2 and Bcl-XL were down-regulated after Rg3 treatment.Conclusion:Our data suggested that Rg3 alone or combined with CTX inhibited tumor growth in vivo and prolonged mouse survival time by inducing HCC cell apoptosis via intrinsic pathway by expression alterations of Bcl-2 family proteins.