title: Manganese superoxide dismutase modulates interleukin-1alpha levels in HT-1080 fibrosarcoma cells.
abstract: Reactive oxygen species of mitochondrial origin have been implicated in regulating the expression of several tumor necrosis factor (TNF)-induced genes. Manganese superoxide dismutase (Mn-SOD) is one of many genes, but only antioxidant enzyme, induced in response to tumor necrosis factor. Mn-SOD is a nuclear-encoded mitochondrial matrix protein and serves a protective function by detoxifying superoxide. To address the role of superoxide in regulating gene expression in response to TNF, we have constitutively overexpressed Mn-SOD in a human fibrosarcoma cell line and asked what effect this has on the expression of a number of TNF-responsive genes using reverse transcription-polymerase chain reaction. Of the TNF-induced transcripts analyzed, only interleukin-1alpha (IL-1alpha) was modulated in response to Mn-SOD overexpression. In all cases of Mn-SOD overexpression, IL-1alpha protein and mRNA levels were lowered constitutively and in response to TNF when compared to the parental and mock-transfected cell lines. The induction of IL-1alpha by TNF can also be decreased by growth in 3% oxygen as compared to growth in 21% O2; in addition, growth in low oxygen lowers the basal level of IL-1alpha protein. The effect of Mn-SOD overexpression on IL-1alpha expression can be overcome by treatment with the protein kinase C activator, phorbol 12-myristate 13-acetate. Mn-SOD overexpression and low oxygen alter IL-1alpha mRNA levels by decreasing the stability of the IL-1alpha mRNA. These findings indicate that both Mn-SOD and O2 may regulate the levels of a cellular oxidant involved in both basal and TNF-induced IL-1alpha expression, presumably superoxide.
authors.affiliation: Department of Biochemistry and Molecular Biology, Albany Medical College, Albany, New York 12208, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Melendez
authors.forename: K J
authors.initials: KJ
authors.lastname: Davies
mesh_terms: D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005354:Fibrosarcoma / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D007375:Interleukin-1; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D013482:Superoxide Dismutase