Several recently identified intracellular proteins associate with the tumor necrosis factor (TNF) receptor and activate nuclear transcription factor (NF)-κB, c-Jun kinase, and apoptosis. However, the mechanism is not understood. In the present report, we investigated the role of reactive oxygen intermediates in TNF-induced signaling. Overexpression of manganese superoxide dismutase (Mn-SOD) in human breast cancer MCF-7 cells completely abolished TNF-mediated NF-κB activation, IκBα degradation, p65 nuclear translocation, and NF-κB-dependent reporter gene expression. Besides TNF, phorbol ester-, okadaic acid-, ceramide-, and lipopolysaccharide-induced activation of NF-κB was blocked by Mn-SOD, indicating a common pathway of activation. H2O2-induced NF-κB activation, however, was potentiated. In addition, Mn-SOD blocked the TNF-mediated activation of activated protein-1, stress-activated c-Jun protein kinase, and mitogen-activated protein kinase kinase. TNF-induced antiproliferative effects and caspase-3 activation, indicators of apoptosis, were also completely suppressed by transfection of cells with Mn-SOD. Suppression of apoptosis induced by okadaic acid, H2O2, and taxol was also inhibited by Mn-SOD but not that induced by vincristine, vinblastine, or daunomycin. Overall, these results demonstrate that, in addition to several recently identified signaling molecules, reactive oxygen intermediates play a critical role in activation of NF-κB, activated protein-1, c-Jun kinase, and apoptosis induced by TNF and other agents. Several recently identified intracellular proteins associate with the tumor necrosis factor (TNF) receptor and activate nuclear transcription factor (NF)-κB, c-Jun kinase, and apoptosis. However, the mechanism is not understood. In the present report, we investigated the role of reactive oxygen intermediates in TNF-induced signaling. Overexpression of manganese superoxide dismutase (Mn-SOD) in human breast cancer MCF-7 cells completely abolished TNF-mediated NF-κB activation, IκBα degradation, p65 nuclear translocation, and NF-κB-dependent reporter gene expression. Besides TNF, phorbol ester-, okadaic acid-, ceramide-, and lipopolysaccharide-induced activation of NF-κB was blocked by Mn-SOD, indicating a common pathway of activation. H2O2-induced NF-κB activation, however, was potentiated. In addition, Mn-SOD blocked the TNF-mediated activation of activated protein-1, stress-activated c-Jun protein kinase, and mitogen-activated protein kinase kinase. TNF-induced antiproliferative effects and caspase-3 activation, indicators of apoptosis, were also completely suppressed by transfection of cells with Mn-SOD. Suppression of apoptosis induced by okadaic acid, H2O2, and taxol was also inhibited by Mn-SOD but not that induced by vincristine, vinblastine, or daunomycin. Overall, these results demonstrate that, in addition to several recently identified signaling molecules, reactive oxygen intermediates play a critical role in activation of NF-κB, activated protein-1, c-Jun kinase, and apoptosis induced by TNF and other agents. TNF 1The abbreviations used are: TNF, tumor necrosis factor; NF-κB, nuclear transcription factor-κB; IκB, inhibitory subunit of NF-κB; SOD, superoxide dismutase; Mn-SOD, manganese superoxide dismutase; ROI, reactive oxygen intermediate(s); DTT, dithiothreitol; CAT, chloramphenicol acetyltransferase; MTT, 3-(4,5-dihydro-6-(4-(3,4-dimethoxybenzoil)-1-piperazinyl)-2(1H)-quinolinone; PARP, poly(ADP-ribose) polymerase; PMA, phorbol 12-myristate 13-acetate; JNK, c-Jun N-terminal kinase; AP-1, activated protein-1; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-buffered saline; MAP kinase, mitogen-activated protein kinase; MEK, MAP kinase kinase; LPS, lipopolysaccharide.1The abbreviations used are: TNF, tumor necrosis factor; NF-κB, nuclear transcription factor-κB; IκB, inhibitory subunit of NF-κB; SOD, superoxide dismutase; Mn-SOD, manganese superoxide dismutase; ROI, reactive oxygen intermediate(s); DTT, dithiothreitol; CAT, chloramphenicol acetyltransferase; MTT, 3-(4,5-dihydro-6-(4-(3,4-dimethoxybenzoil)-1-piperazinyl)-2(1H)-quinolinone; PARP, poly(ADP-ribose) polymerase; PMA, phorbol 12-myristate 13-acetate; JNK, c-Jun N-terminal kinase; AP-1, activated protein-1; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-buffered saline; MAP kinase, mitogen-activated protein kinase; MEK, MAP kinase kinase; LPS, lipopolysaccharide. plays a major role in tumorigenesis, inflammation, viral replication, and septic shock (see Ref. 1Aggarwal B.B. Natarajan K. Eur. Cytokine Netw. 1996; 7: 93-124PubMed Google Scholar and references within). How a single molecule can mediate such a wide array of effects is not known, but these effects are known to be mediated through two different receptors, p60 (type I) expressed on all cell types and p80 (type II) expressed primarily on immune cells. Within the last 5 years, over 15 distinct proteins have been identified that associate with the cytoplasmic domain of the p60 receptor and are involved in activation of apoptosis, NF-κB, N-terminal c-Jun kinase (JNK), and mitogen-activated protein kinase (see Ref. 2Darnay B.G. Aggarwal B.B. J. Leukocyte Biol. 1997; 61: 559-566Crossref PubMed Scopus (168) Google Scholar and references within). Similarly, the cytoplasmic domain of the p80 receptor has been reported to associate with four proteins that play a role in activation of NF-κB and apoptosis. How any of these proteins mediate apoptosis or NF-κB activation is less clear. By using metabolic inhibitors, several studies have indicated that TNF-mediated activation of either NF-κB or apoptosis or activation of various kinases requires the production of various intermediates including reactive oxygen intermediates (ROI) (3Goossens V. Grooten J. De Vos K. Fiers W. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 8115-8119Crossref PubMed Scopus (556) Google Scholar). We conducted a series of experiments using superoxide dismutase (SOD) to explore the role of ROI. SOD is a family of antioxidant enzymes that convert harmful superoxide radicals into H2O2, which in turn is metabolized to harmless water and oxygen by catalase and glutathione peroxidase (4Bannister J.V. Bannister W.H. Rotilio G. Crit. Rev. Biochem. 1987; 22: 111-180Crossref PubMed Scopus (786) Google Scholar, 5Hassan H.M. Free Radical Biol. Med. 1988; 5: 377-385Crossref PubMed Scopus (154) Google Scholar). In mammalian cells, two main types of SOD are found;viz. manganese SOD (Mn-SOD), located in the mitochondria, and copper-zinc SOD, found in the cytoplasm. Previous studies have shown that overexpression of Mn-SOD blocks TNF-mediated cytotoxicity (6Wong G.H.W. Goeddel D.V. Science. 1988; 242: 941-944Crossref PubMed Scopus (836) Google Scholar, 7Wong G.H.W. Elwell J.H. Oberley L.W. Goeddel D.V. Cell. 1989; 58: 923-931Abstract Full Text PDF PubMed Scopus (764) Google Scholar, 8Li J.J. Oberley L.W. Cancer Res. 1997; 57: 1991-1998PubMed Google Scholar). How overexpression of Mn-SOD affects TNF-induced transcription factors including NF-κB and AP-1 is not known, however. It is also not known how overexpression of SOD affects TNF-induced activation of stress-activated protein kinase, also called JNK, and the growth modulatory kinases of the extracellular signal-regulated kinase family (MAP kinase kinase kinase/MAP kinase (MEK)/MAP kinase), implicated in the TNF-induced activation of AP-1 and NF-κB, respectively (9Karin M. J. Biol. Chem. 1995; 270: 16483-16486Abstract Full Text Full Text PDF PubMed Scopus (2256) Google Scholar,10Lee F.S. Hagler J. Chen Z.J. Cell. 1997; 88: 213-222Abstract Full Text Full Text PDF PubMed Scopus (659) Google Scholar). In the present report, we demonstrate that overexpression of Mn-SOD in human breast tumor MCF-7 cells blocks TNF-induced cytotoxicity and activation of caspase-3 (indicator of apoptosis), NF-κB, AP-1, JNK, and MEK. The effect of SOD was not specific to TNF, since other agents that activate NF-κB (e.g. PMA, interleukin-1, and okadaic acid) or induce apoptosis (e.g. okadaic acid and taxol) were also inhibited, thus suggesting that the ROI has a critical role in activation of signaling by a wide variety of agents. Penicillin, streptomycin, RPMI 1640 medium, and fetal calf serum were obtained from Life Technologies, Inc. Glycine, NaCl, and bovine serum albumin were obtained from Sigma. Bacteria-derived recombinant human TNF, purified to homogeneity with a specific activity of 5 × 107 units/mg, was kindly provided by Genentech, Inc. (South San Francisco, CA). Antibody against IκBα and double-stranded oligonucleotide having an AP-1 consensus sequence were obtained from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA). The rat MDR1bCAT plasmid −243RMICAT containing the chloramphenicol acetyl transferase (CAT) gene with either wild-type or mutated NF-κB binding site was kindly supplied by Dr. M. Tien Kuo of the University of Texas M. D. Anderson Cancer Center (Houston, TX). The characterization of these plasmids has been described previously in detail (11Zhou G. Kuo M.T. J. Biol. Chem. 1997; 272: 15174-15183Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar). Human breast MCF-7 cells were stably transfected with control (neo) and Mn-SOD genes similarly to what was described in detail previously (8Li J.J. Oberley L.W. Cancer Res. 1997; 57: 1991-1998PubMed Google Scholar). Two different Mn-SOD cDNAs were examined. Polymorphism in the Mn-SOD gene results in two different amino acids (either Ile or Thr) at position 58 in the human population (12Borgstahl G.E.O. Parge H.E. Hickey M.J. Boissinot M. Hallewell R.A. Lepock J.R. Cabelli D.E. Tainer J.A. Biochemistry. 1996; 35 (4297): 4297Crossref Scopus (162) Google Scholar). The replacement of Thr for Ile leads to a protein with about 50% activity and a reduction in protein stability after heat (12Borgstahl G.E.O. Parge H.E. Hickey M.J. Boissinot M. Hallewell R.A. Lepock J.R. Cabelli D.E. Tainer J.A. Biochemistry. 1996; 35 (4297): 4297Crossref Scopus (162) Google Scholar). Sense human Mn-SOD cDNA was originally obtained from Dr. Daret St. Clair. After the cDNA was ligated into the pcDNA3 plasmid (Invitrogen) containing a neomycin resistance marker, it was sequenced, which revealed that this cDNA contained an ACA codon for threonine at amino acid 58. Site-directed mutagenesis was performed to change ACA to ATA, the codon for isoleucine. 2H. J. Zhang, and W. in The change was by cDNA The MCF-7 cell was found to the of Mn-SOD. two types of plasmids were transfected into MCF-7 cells from at by a to that described previously (8Li J.J. Oberley L.W. Cancer Res. 1997; 57: 1991-1998PubMed Google Scholar). at these cells were transfected with pcDNA3 plasmids by or plasmids containing human Mn-SOD cDNA or human Mn-SOD cDNA the control of a × cells were transfected with of plasmids for using the to the Technologies, after the cells were and in with of for 15 were by a were in with of MCF-7 cells were in with fetal bovine and amino acids in of at NF-κB activation, were described A. B.G. S. Aggarwal B.B. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). nuclear from cells × were double-stranded NF-κB oligonucleotide of protein with of from the human NF-κB binding for 15 at and the was from oligonucleotide on polyacrylamide double-stranded mutated was used to the of binding of NF-κB to the The of binding was also by with the The were and were by a using the activation of AP-1, of nuclear indicated were with of the AP-1 consensus oligonucleotide (Santa Cruz Biotechnology, AP-1 binding for 15 at and by The of binding was by with and of was by a using the of were B.G. M. Aggarwal B.B. J. Biol. Chem. Full Text PDF PubMed Google from cells and on the of NF-κB and nuclear and from cells were on After the proteins were to with against or p65 and by B.G. M. Aggarwal B.B. J. Biol. Chem. Full Text PDF PubMed Google Scholar). The obtained were using using The effects of TNF on MCF-7 cells were by the of by the cells described previously K. B.G. Aggarwal B.B. J. Google Scholar). cells were at in of in of TNF were in an of and at for the last was to and cells were with the of a to the was in a The cytotoxicity was also by the K. J. 1989; PubMed Scopus Google Scholar). cells were in the or of the indicated in a of for at of in phosphate-buffered was to After a at of the 50% was After an at the at were using a with the a of cytotoxicity was of cytotoxicity of of control × TNF-induced apoptosis was by of M. K. S. Cell. 1995; Full Text PDF PubMed Scopus Google Scholar). cells × were with TNF for different at and by for on in of containing NaCl, and The was and the was protein was on a with and by was by the of into and Goeddel D.V. M. Cell. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). MCF-7 cells, with different of TNF for at were with phosphate-buffered and with containing NaCl, DTT, and of protein was on to and with the MAP kinase in the was with and the were by The c-Jun kinase was performed by a described Goeddel D.V. M. Cell. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). after of cells × with TNF for cell were by cells in containing and were with of for at were by with protein for at The were with × and kinase × DTT, were performed for 15 at with glutathione a in DTT, and of were with the addition of 15 of × for 5 and to was by with and the gel was by a the TNF-induced reporter gene MCF-7 and cells were transfected by the with the plasmids wild-type NF-κB binding and binding to the supplied by the After of the cells were for at with of TNF for and for activity described J. Scholar). In the present we investigated the effect of transfection of the Mn-SOD gene on the transcription factors NF-κB and AP-1 and the kinases of the MAP kinase family induced by We also the effect of this gene on apoptosis induced by TNF and a wide variety of other agents. all cells and transfected with the gene were used a Two different types of were was transfected with Mn-SOD cDNA and was used for the of the an in Mn-SOD protein by with or but a in Mn-SOD and were obtained from cells transfected with Mn-SOD The in protein over were and for and The in activity over and were and for and types of have in but the have specific activity the The in of protein for and were and cells or of production in these cells. other at to however. the stability of the cells were for the of SOD for cell of TNF by and cells were found to specific binding of TNF and and MCF-7 cells were with different of TNF, and nuclear were and for NF-κB by TNF activated NF-κB in and cells, in Mn-SOD cells, NF-κB activation was at TNF against the and p65 of NF-κB the on the gel NF-κB suppressed by Mn-SOD of and p65 was since to or or serum is also indicated from the that this with and that it not to a oligonucleotide with mutated NF-κB site was MCF-7 cells, for all experiments cells were used a effect of of Mn-SOD gene on activation of MCF-7 cells × and transfected and Mn-SOD were at with different of TNF for and nuclear were and for NF-κB described and of were from or TNF cells × for 15 with different and NF-κB and for NF-κB of of NF-κB by Mn-SOD. MCF-7 cells × were at either with or TNF for indicated After these nuclear were and for of activation NF-κB by Mn-SOD gene is of MCF-7 cells × and transfected with and Mn-SOD were at with different of TNF for nuclear were and for NF-κB described In cells, TNF activated NF-κB 15 and a in In NF-κB activation was after in cells. that the mechanism of NF-κB activation in different cell we transfected human cells. Mn-SOD suppressed TNF-induced NF-κB activation in these cells not that the effects of Mn-SOD are not cell The effect of Mn-SOD on NF-κB activation was not to a single of transfected MCF-7 cells, since other and with medium, and Mn-SOD activity also suppressed TNF-induced NF-κB activation expressed the other of Mn-SOD. The inhibitory effect was less in in and for the specific activity of the Mn-SOD, it was found that has overexpression of Mn-SOD activity In of Mn-SOD of TNF-induced NF-κB activation, but the for this is not clear. agents activate NF-κB by different 1997; PubMed Google Scholar). TNF-induced NF-κB activation is protein kinase that activated by is protein kinase we the effect of Mn-SOD on the activation of NF-κB by PMA, LPS, H2O2, okadaic acid, and we have shown all agents activated NF-κB in human cells the activation was less in cells, all activated NF-κB MCF-7 cells Mn-SOD transfection blocked NF-κB activation by all agents The NF-κB activation by the was by Mn-SOD, thus suggesting that NF-κB by a mechanism that is different from that of other agents. The of NF-κB to the is by the and of Mn-SOD also TNF-induced IκBα degradation, the cytoplasmic of IκBα proteins after of cells with TNF for different were by IκBα was of TNF and by in MCF-7 (neo) cells In cells, however, of IκBα was after TNF to In cells, of p65 in cytoplasmic of cells The nuclear of p65 protein in cells but not in cells, thus suggesting that in cells TNF is to p65 from results to that Mn-SOD blocks the binding of NF-κB protein to it also blocks NF-κB-dependent gene was also examined. The rat resistance gene an NF-κB binding the was ligated with reporter plasmid was transfected into and cells, and the cells were with and TNF activated activity by in cells, a in activity over the was in cells effects were since the plasmid with mutated NF-κB binding site was not activated on of cells with results thus demonstrate that Mn-SOD also blocks TNF-induced TNF is a of AP-1 (9Karin M. J. Biol. Chem. 1995; 270: 16483-16486Abstract Full Text Full Text PDF PubMed Scopus (2256) Google Scholar). Several that the for AP-1 activation from that of NF-κB activation M. J. PubMed Scopus Google Scholar). activation of AP-1 by TNF is through ROI is not we investigated the effect of Mn-SOD on TNF-induced AP-1 activation. shown in TNF activated AP-1 in a with activation at in cells. however, in activation of AP-1 with activation was since it was completely inhibited by the TNF is also a of kinase is activated in to different of and is for activation of shown in TNF activated in cells in a with activation with Mn-SOD in completely suppressed TNF-induced activation. results thus that ROI by TNF is also for activation. It has been reported that TNF a kinase, MAP kinase kinase kinase called which in turn a kinase, MAP kinase kinase called and that MAP kinase, mitogen-activated protein signal-regulated kinase. are that MAP kinase kinase kinase is for TNF-induced NF-κB activation, the of Mn-SOD affects TNF-induced activation of was was activated by TNF in a cells but not in MCF-7 cells results that activation of by TNF also through the of ROI. By cell and by we have previously shown that Mn-SOD blocks the antiproliferative effects of TNF (8Li J.J. Oberley L.W. Cancer Res. 1997; 57: 1991-1998PubMed Google Scholar). We by by that Mn-SOD completely MCF-7 cells from TNF-induced cytotoxicity TNF effects either by necrosis or apoptosis. of apoptosis is the activation of caspase-3 which leads to of from to TNF induced of in cells Mn-SOD cells were to after of TNF results thus that Mn-SOD also blocks TNF-induced activation of Besides TNF, MCF-7 cells are to effects of a wide variety of other agents including agents such vinblastine, vincristine, and and to and okadaic How Mn-SOD affects the cytotoxicity induced by these agents was also Mn-SOD completely the cells from okadaic and cytotoxicity these however, Mn-SOD effect on cytotoxicity induced by vincristine, vinblastine, and daunomycin. with were results thus that different agents induce cytotoxicity by different agents that induce apoptosis also to activate this activation is through ROI is not we also investigated the effect of Mn-SOD on NF-κB activation by various agents. The results shown in that all of the agents that induced cytotoxicity also activated NF-κB, but activation was suppressed by Mn-SOD. results that taxol cytotoxicity and NF-κB activation through the other agents through a different The of the present was to the role of ROI in TNF-induced activation of NF-κB, AP-1, JNK, MEK, and human breast cancer MCF-7 cells were transfected with the Mn-SOD cells were used Overexpression of Mn-SOD suppressed TNF-induced IκBα degradation, NF-κB activation, and NF-κB-dependent reporter gene expression. It also blocked TNF-induced activation of AP-1, JNK, MEK, and cytotoxicity (see The effects of Mn-SOD were not specific to TNF, since NF-κB activation by okadaic acid, PMA, LPS, and and apoptosis induced by okadaic acid, and were also of these results that ROI are intermediates for of a wide variety of TNF effects are not cell of the of Mn-SOD to Human breast MCF-7 cells are known to the p60 of the TNF receptor V. B.G. Natarajan K. Aggarwal B.B. J. Google Scholar). over 15 different proteins have been identified that associate with the cytoplasmic domain of the TNF receptor and are for of apoptosis and activation of NF-κB, JNK, MEK, and caspase-3 investigated How any of these proteins ROI is not clear. By using and of ROI has been implicated in TNF-induced NF-κB activation M.T. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, W. J. Med. PubMed Scopus Google Scholar, 1995; PubMed Scopus Google Scholar). are other however, that that not to activation of NF-κB but by activate NF-κB J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, J. 1995; Google Scholar). however, the that ROI are critical for TNF-induced NF-κB activation. It is not to the reactive oxygen from studies with cells is SOD to superoxide but also to of and other (4Bannister J.V. Bannister W.H. Rotilio G. Crit. Rev. Biochem. 1987; 22: 111-180Crossref PubMed Scopus (786) Google Scholar, 5Hassan H.M. Free Radical Biol. Med. 1988; 5: 377-385Crossref PubMed Scopus (154) Google Scholar). since the with SOD for SOD to of SOD transfection can to of and any from It is not with a single transfection to the transfection with enzymes however, of the reactive How TNF NF-κB is not understood. several kinases have been identified that play a critical role in TNF-induced NF-κB activation. MAP kinase kinase kinase, and a Ref. D. Cell. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). We found that the overexpression of Mn-SOD blocked the activation of TNF-induced MEK, suggesting that superoxide is for activation of this kinase. It is that the of NF-κB is to of MEK. Mn-SOD superoxide radicals to and oxygen J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). we found that NF-κB was by Mn-SOD. results that ROI involved in activation of NF-κB by TNF, and other agents from that of It is that TNF-induced NF-κB activation is through a superoxide that induced by is through a however, has been shown to J. PubMed Scopus Google and TNF-induced NF-κB activation, it the superoxide and mechanism of activation of NF-κB has also been interleukin-1, okadaic acid, and induce NF-κB activation of ROI J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Google Scholar, G. J. V. Eur. J. Biochem. 1996; 242: PubMed Scopus Google Scholar, J.A. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). results on Mn-SOD however, that NF-κB activation by okadaic acid requires superoxide of these be to different cell types by 1995; PubMed Scopus Google Scholar, J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google and also be to the of of ROI used indicated results that various including vincristine, and activate results J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). How any of these agents activate NF-κB is not results that agents that by different induced cytotoxicity and NF-κB activation in MCF-7 cells. Mn-SOD, however, blocked cytotoxicity and NF-κB activation. results that taxol for cytotoxicity and NF-κB activation through the superoxide and and and through an We found that Mn-SOD also blocked TNF-induced AP-1 activation. we activation, other recently that overexpression of Mn-SOD abolished the AP-1 activity in cells St. Cancer Res. 1997; 57: Google Scholar). on the of TNF-induced AP-1 by Mn-SOD was in of studies that that the activate AP-1 by M. J. PubMed Scopus Google Scholar). activation of AP-1 requires activation of JNK, we found that Mn-SOD also suppressed TNF-induced is a G. A. M. M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google however, that that the kinase is for activation of NF-κB and AP-1 but not JNK, indicating that TNF-induced AP-1 activation is We also that Mn-SOD the TNF-induced activation of an for TNF-induced apoptosis. are that Mn-SOD can TNF-induced cytotoxicity G.H.W. Elwell J.H. Oberley L.W. Goeddel D.V. Cell. 1989; 58: 923-931Abstract Full Text PDF PubMed Scopus (764) Google Scholar, 8Li J.J. Oberley L.W. Cancer Res. 1997; 57: 1991-1998PubMed Google is the to that it is through of caspase-3 activation. Mn-SOD blocked the effects not of TNF, but also of taxol and okadaic acid, suggesting that all of these agents cells through a superoxide to these H2O2-induced cytotoxicity was also blocked by Mn-SOD, suggesting that cytotoxicity and NF-κB by different The of effect of Mn-SOD on cytotoxicity induced by vincristine, vinblastine, and that these agents the cells by a mechanism of the superoxide Mn-SOD also blocked TNF-induced NF-κB-dependent gene expression. it has been shown that TNF-induced in human cells is blocked by overexpression of Mn-SOD J.A. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). NF-κB activation is for it is that of NF-κB shown in studies is involved in Mn-SOD has also been reported to the of human tumor cells Oberley L.W. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). several genes involved in NF-κB in 1997; PubMed Google it is that of NF-κB by Mn-SOD is with effects on studies that NF-κB plays an role in TNF-induced apoptosis Science. 1996; PubMed Scopus Google Scholar, D. Science. 1996; PubMed Scopus Google Scholar, Science. 1996; PubMed Scopus Google Scholar). How is not but Mn-SOD is of the genes that is through NF-κB Cell. Biochem. 1995; PubMed Scopus Google thus suggesting a results from and that various effects of TNF are mediated through the of superoxide TNF is also known to induce Mn-SOD gene in all cell types (6Wong G.H.W. Goeddel D.V. Science. 1988; 242: 941-944Crossref PubMed Scopus (836) Google Scholar). the in the mechanism of of The of cells to TNF-mediated be by by catalase and glutathione which to Overexpression of catalase has been shown to TNF and okadaic NF-κB activation Med. Biol. 1996; PubMed Scopus Google Scholar). Overall, it is that the of and antioxidant intermediates the signaling mechanism of various to TNF and other agents. In the we the other in the cells to are also involved in the of of