s-nitro-n-acetylpenicillamine and Neuroblastoma

Cholinergic cell lines were established by fusion of embryonic day 17 wild-type neurons from rat basal forebrain (BF) and upper brainstem (BS) with N18tg neuroblastoma cells. Isolated clones expressed choline acetyltransferase (ChAT) and neuronal nitric oxide synthase (nNOS) activities that were increased upon differentiation with retinoic acid. Clones from the BF expressed high levels of the tyrosine kinase type A (TrkA) receptor expression and activation of the mitogen-activated kinase ERK2 upon treatment with nerve growth factor. Like wild-type cholinergic populations, the six clones studied were variably resistant to nitric oxide (NO) excess from addition of S-nitroso-N-acetyl-D, L-penicillamine (SNAP). Of these, the BS2 clone exhibited resistance like in vivo BS cholinergic neurons, while the MS10 clone mimicked in vivo BF vulnerability. Apoptosis in response to NO excess was preceded by increases in mitochondrial responses bax/bcl-2 ratios, but cytochrome C was not released. Mitochondrial levels of apoptosis initiating factor (AIF) were either unchanged or increased, and only in MS clones was endonuclease G (EndoG) released. Microarray data indicated the existence of endoplasmic reticular (ER) stress and caspase-4 and caspase-12 were involved in the pathway to DNA fragmentation. The array data also indicated a survival role for mdm2, and its blockade rendered vulnerable the brainstem survivor clone BS2. Akt and ERK1/2 pathways were activated in response to NO and their blockade increased DNA fragmentation. Blockade of GSK-3 alpha/beta, a downstream target of Akt, reduced SNAP toxicity and this was more prominent in basal forebrain clones. We have identified two cholinergic cell lines useful for molecular studies of cholinergic vulnerability. We hypothesize that, in cholinergic neurons, control of ER stress signaling may be a major factor in differential vulnerability.

Topics: Animals; Brain; Cell Differentiation; Cell Fusion; Cell Survival; Cells, Cultured; Choline O-Acetyltransferase; DNA Fragmentation; Embryo, Mammalian; Enzyme Inhibitors; Gene Expression Regulation; Microarray Analysis; Nerve Growth Factor; Neuroblastoma; Neurons; Nitric Oxide Donors; Nitric Oxide Synthase Type I; Penicillamine; Rats; Signal Transduction; Stress, Physiological; Time Factors

Nitrogen monoxide (NO) is a cytotoxic effector molecule produced by macrophages that results in Fe mobilization from tumour target cells which inhibits DNA synthesis and mitochondrial respiration. It is well known that NO has a high affinity for Fe, and we showed that NO-mediated Fe mobilization is markedly potentiated by glutathione (GSH) generated by the hexose monophosphate shunt [Watts, R.N. & Richardson, D.R. (2001) J. Biol. Chem. 276, 4724-4732]. We hypothesized that GSH completes the coordination shell of an NO[bond]Fe complex that is released from the cell. In this report we have extended our studies to further characterize the mechanism of NO-mediated Fe mobilization. Native PAGE 59Fe-autoradiography shows that NO decreased ferritin-59Fe levels in cells prelabelled with [59Fe]transferrin. In prelabelled cells, ferritin-59Fe levels increased 3.5-fold when cells were reincubated with control media between 30 and 240 min. In contrast, when cells were reincubated with NO, ferritin-59Fe levels decreased 10-fold compared with control cells after a 240-min reincubation. However, NO could not remove Fe from ferritin in cell lysates. Our data suggest that NO intercepts 59Fe on route to ferritin, and indirectly facilitates removal of 59Fe from the protein. Studies using the GSH-depleting agent, L-buthionine-(S,R)-sulphoximine, indicated that the reduction in ferritin-59Fe levels via NO was GSH-dependent. Competition experiments with NO and permeable chelators demonstrated that both bind a similar Fe pool. We suggest that NO requires cellular metabolism in order to effect Fe mobilization and this does not occur via passive diffusion down a concentration gradient. Based on our results, we propose a model of glucose-dependent NO-mediated Fe mobilization.

Topics: Adenocarcinoma; Animals; Breast Neoplasms; Cell Membrane Permeability; Cell-Free System; Cytosol; Deferoxamine; Female; Ferritins; Fibroblasts; Glutathione; Humans; Iron; Iron Chelating Agents; Macrophage Activation; Mice; Neuroblastoma; Neuroectodermal Tumors, Primitive, Peripheral; Nitric Oxide; Nitric Oxide Donors; Nitrogen Oxides; Oxidation-Reduction; Penicillamine; S-Nitrosoglutathione; Spermine; Tumor Cells, Cultured

It is unclear what mechanisms lead to the degeneration of basal forebrain cholinergic neurons in Alzheimer's or other human brain diseases. Some brain cholinergic neurons express neuronal nitric oxide (NO) synthase (nNOS), which produces a free radical that has been implicated in some forms of neurodegeneration. We investigated nNOS expression and NO toxicity in SN56 cells, a clonal cholinergic model derived from the medial septum of the mouse basal forebrain. We show here that, in addition to expressing choline acetyltransferase (ChAT), SN56 cells express nNOS. Treatment of SN56 cells with retinoic acid (RA; 1 microM) for 48 h increased ChAT mRNA (+126%), protein (+88%), and activity (+215%) and increased nNOS mRNA (+98%), protein (+400%), and activity (+15%). After RA treatment, SN56 cells became vulnerable to NO excess generated with S-nitro-N-acetyl-DL-penicillamine (SNAP) and exhibited increased nuclear DNA fragmentation that was blocked with a caspase-3 inhibitor. Treatment with dexamethasone, which largely blocked the RA-mediated increase in nNOS expression, or inhibition of nNOS activity with methylthiocitrulline strongly potentiated the apoptotic response to SNAP in RA-treated SN56 cells. Caspase-3 activity was reduced when SNAP was incubated with cells or cell lysates, suggesting that NO can directly inhibit the protease. Thus, whereas RA treatment converts SN56 cells to a proapoptotic state sensitive to NO excess, endogenously produced NO appears to be anti-apoptotic, possibly by tonically inhibiting caspase-3.

Topics: Acetylcholine; Animals; Antineoplastic Agents; Apoptosis; Caspase 3; Caspases; Choline O-Acetyltransferase; DNA Fragmentation; Free Radicals; Gene Expression Regulation, Enzymologic; In Situ Nick-End Labeling; L-Lactate Dehydrogenase; Mice; Neuroblastoma; Neurons; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxidative Stress; Penicillamine; Phenotype; Receptors, Cholinergic; RNA, Messenger; Septal Nuclei; Tretinoin; Tumor Cells, Cultured

Fibroblast growth factor (FGF) has been shown to protect tissue damage in animal models of cerebral and myocardial ischemia. The cellular and molecular mechanisms of FGF effects have not been fully defined. In the present study, we have investigated the effect of FGF homologs on nitric oxide (NO)-mediated neuronal cell death. Addition of NO donor S-nitroso-N-acetylpenicillamine (SNAP) to cultures of human neuroblastoma SHSY-5Y cells resulted in a concentration-dependent cell death. TdT-mediated dUTP-X nick end labeling and oligonucleosome assays confirmed that NO-mediated cell death occurred through the apoptotic pathway. In the presence of 150 microM SNAP, about 40% of the cells in culture underwent apoptosis. Treatment with FGF-2 resulted in greater than 80% reduction in NO-induced cell death. FGF addition to cell cultures also enhanced cell survival without affecting cell proliferation. FGF-2 effectively inhibited NO-mediated apoptosis even when added 6 h after treatment with SNAP. Examination of other homologs of FGF on NO-mediated cell death showed that in SHSY-5Y cells, FGF-2 and FGF-4, but not other FGF homologs, inhibited NO-mediated apoptosis. These results show that FGF-2 was a potent cell survival factor and protected SHSY-5Y cells from NO-mediated apoptosis. These effects were limited to FGF-2 and FGF-4 homologs.

Topics: Apoptosis; Cell Division; Cell Survival; Cytoprotection; Fibroblast Growth Factor 2; Humans; Neuroblastoma; Neuroprotective Agents; Nitric Oxide; Penicillamine; Tumor Cells, Cultured