Isolation and analysis of the rat genomic sequence encoding Cu/Zn superoxide dismutase

Transcriptional regulation of the Japanese flounder Cu,Zn-SOD (Jfsod1) gene in RAW264.7 cells during oxidative stress caused by causative bacteria of edwardsiellosis

Edwardsiellosis is one of the most important bacterial diseases in fish, sometimes causing extensive economic losses in the aquaculture industry. Our previous studies demonstrated that the Cu,Zn-SOD (sod1) activity has significantly increased in Japanese flounder, Paralichthys olivaceus, hepatopancreas infected by causative bacteria of edwardsiellosis Edwardsiella tarda NUF251. In this study, NUF251 stimulated intracellular superoxide radical production in mouse macrophage RAW264.7 cells, which was reduced by N-acetylcysteine. This result suggests that NUF251 infection causes oxidative stress. To evaluate the regulatory mechanism of Jfsod1 at transcriptional levels under oxidative stress induced by NUF251 infection, we cloned and determined the nucleotide sequence (1124 bp) of the 5'-flanking region of the Jfsod1 gene. The sequence analysis demonstrated that the binding sites for the transcription factors C/EBPα and NF-IL6 involved in the transcriptional regulation of the mammalian sod1 gene existed. We constructed a luciferase reporter system with the 5'-flanking region (-1124/-1) of the Jfsod1 gene, and a highly increased transcriptional activity of the region was observed in NUF251-infected RAW264.7 cells. Further studies using several mutants indicated that deletion of the recognition region of NF-IL6 (-272/-132) resulted in a significant decrease in the transcriptional activity of the Jfsod1 gene in NUF251-infected RAW264.7 cells. In particular, the binding site (-202/-194) for NF-IL6 might play a major role in upregulating the transcriptional activity of the 5'-flanking region of the Jfsod1 gene in response to oxidative stress induced by NUF251 infection. These results could be provided a new insight to understand the pathogenic mechanism of causative bacteria of edwardsiellosis.

Intracellular copper/zinc superoxide dismutase from bay scallop Argopecten irradians: its gene structure, mRNA expression and recombinant protein

Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Two unique and highly compartmentalized bay scallop Argopecten irradians superoxide dismutases: MnSOD and ecCuZnSOD, have been molecularly characterized in our previous study. To complete characterize the SOD family in A. irradians, a novel intracellular copper/zinc SOD from the A. irradians (Ai-icCuZnSOD) was obtained and characterized. The full-length cDNA of Ai-icCuZnSOD was 1047 bp with a 459 bp open reading frame encoding 152 amino acids. The genomic length of the Ai-icCuZnSOD gene was about 4279 bp containing 4 exons and 3 introns. The promoter region containing many putative transcription factor binding sites were analyzed. Furthermore, quantitative reverse transcriptase real-time PCR (qRT-PCR) analysis indicated that the highest expression of the Ai-icCuZnSOD was detected in gill and the expression profiles in hemocytes of bay scallops challenged with bacteria Vibrio anguillarum and lipopolysaccharide (LPS) were different. The result presented an increased expression after injection with LPS whereas no significant changes were observed after V. anguillarum injection. A fusion protein containing Ai-icCuZnSOD was produced in vitro. The rAi-icCuZnSOD is a stable enzyme, retaining more than 80% of its activity between 10 and 60 degrees C and keeping above 88% of its activity at pH values between 5.8 and 9. Ai-icCuZnSOD is more stable under alkaline than acidic conditions.

PPARγ activation abolishes LDL-induced proliferation of human aortic smooth muscle cells via SOD-mediated down-regulation of superoxide

Native LDL would be a mitogenic and chemotactic stimulus of VSMC proliferation and differentiation in the atherosclerotic lesion where endothelial disruption occurred. In previous studies, our group investigated the molecular mechanisms by which LDL induces IL-8 production and by which PPARalpha activation abolishes LDL effects in human aortic SMCs (hAoSMCs). Herein is the first report of PPARgamma activation by troglitazone (TG) exerting its inhibitory effects on LDL-induced cell proliferation via generation not of H(2)O(2), but of O2(.-), and the subsequent activation of Erk1/2 in hAoSMCs. Moreover, in this study TG abolished the LDL-accelerated G(1)-S progression to control levels via down-regulation of active cyclinD1/CDK4 and cyclinE/CDK2 complexes and up-regulation of p21(Cip1) expression. TG exerted its anti-proliferative effects through the up-regulation of basal superoxide dismutase (SOD) expression. This data suggests that the regulation of O2(.-) is located at the crossroads between LDL signaling and cell proliferation.

Characterization of a novel plant promoter specifically induced by heavy metal and identification of the promoter regions conferring heavy metal responsiveness

The bean (Phaseolus vulgaris) stress-related gene number 2 (PvSR2) gene responds to heavy metals but not to other forms of environmental stresses. To elucidate its heavy metal-regulatory mechanism at the transcriptional level, we isolated and characterized the promoter region (-1623/+48) of PvSR2. Deletions from the 5' end revealed that a sequence between -222 and -147 relative to the transcriptional start site was sufficient for heavy metal-specific induction of the promoter region of PvSR2. Detailed analysis of this 76-bp fragment indicated that heavy metal-responsive elements were localized in two regions (-222/-188 and -187/-147), each of which could separately confer heavy metal-responsive expression on the beta-glucuronidase gene in the context of a minimal cauliflower mosaic virus 35S promoter. Region I (-222/-188) contains a motif (metal-regulatory element-like sequence) similar to the consensus metal-regulatory element of the animal metallothionein gene, and mutation of this motif eliminated the heavy metal-inducible function of region I. Region II (-187/-147) had no similarity to previously identified cis-acting elements involved in heavy metal induction, suggesting the presence of a novel heavy metal-responsive element. Transformed tobacco (Nicotiana tabacum) seedlings expressing beta-glucuronidase under control of the PvSR2 promoter region (-687/+48) showed heavy metal-specific responsive activity that depended on the type and concentration of the heavy metal and the type of organ. These findings further our understanding of the regulation of PvSR2 expression and provide a new heavy-metal-inducible promoter system in transgenic plants.

Ero1-L, an ischemia-inducible gene from rat brain with homology to global ischemia-induced gene 11 (Giig11), is localized to neuronal dendrites by a dispersed identifier (ID) element-dependent mechanism

Many changes in neuronal gene expression occur in response to ischemia, and these may play a role in determining the fate of ischemic neurons. To identify genes induced in the rat brain following cerebral ischemia, a strategy was used that combines subtractive hybridization and differential screening. Among the genes identified was one referred to as global ischemia-inducible gene 11(Giig11). Sequence analysis indicated that Giig11 exhibited 97% and 91% identity to the known Ero1-L (S. cereviseae ero1-like oxidoreductase) of mouse and human origin, which is involved in oxidative endoplasmic reticulum protein folding. Rat Ero1-L/Giig11 also contains a l07-bp sequence that is nearly identical (> 95%) to the known dispersed repetitive identifier (ID), but which is lacking in mouse and human Ero1-L. Northern blotting showed that expression of the ID element and Ero1-L/Giig11 mRNA increased after global cerebral ischemia. In situ hybridization demonstrated increased expression of Ero1-L/Giig11 in the brain following ischemic injury, with the highest levels in the vulnerable hippocampal CA1 pyramidal neurons. Transfection of cultured primary hippocampal neurons with a plasmid containing green fluorescent protein (gfp) and Ero1-L/Giig11 cDNA (with and without the ID element) produced a gfp-Ero1-L/Giig11 fusion protein, and more fusion protein was localized into dendrites in the presence of the ID element, suggesting that the ID element promotes Ero1-L/Giig11 protein localization to dendrites. Therefore, Ero-1L/Giig11 may have a role in ischemia-induced neuronal repair or survival mechanisms directed at counteracting abnormalities in protein folding, maturation and distribution.

Superoxide dismutase multigene family: a comparison of the CuZn-SOD (SOD1), Mn-SOD (SOD2), and EC-SOD (SOD3) gene structures, evolution, and expression

Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Three unique and highly compartmentalized mammalian superoxide dismutases have been biochemically and molecularly characterized to date. SOD1, or CuZn-SOD (EC 1.15.1.1), was the first enzyme to be characterized and is a copper and zinc-containing homodimer that is found almost exclusively in intracellular cytoplasmic spaces. SOD2, or Mn-SOD (EC 1.15.1.1), exists as a tetramer and is initially synthesized containing a leader peptide, which targets this manganese-containing enzyme exclusively to the mitochondrial spaces. SOD3, or EC-SOD (EC 1.15.1.1), is the most recently characterized SOD, exists as a copper and zinc-containing tetramer, and is synthesized containing a signal peptide that directs this enzyme exclusively to extracellular spaces. What role(s) these SODs play in both normal and disease states is only slowly beginning to be understood. A molecular understanding of each of these genes has proven useful toward the deciphering of their biological roles. For example, a variety of single amino acid mutations in SOD1 have been linked to familial amyotrophic lateral sclerosis. Knocking out the SOD2 gene in mice results in a lethal cardiomyopathy. A single amino acid mutation in human SOD3 is associated with 10 to 30-fold increases in serum SOD3 levels. As more information is obtained, further insights will be gained.

Transcriptional activation of Cu/Zn superoxide dismutase and catalase genes by panaxadiol ginsenosides extracted from Panax ginseng

Superoxide dismutase (SOD) converts superoxide radical to H(2)O(2), which is in turn broken down to water and oxygen by catalase. Thus, SOD and catalase constitute the first coordinated unit of defence against reactive oxygen species. A wide variety of chemical and environmental factors are known to induce these antioxidant enzymes. Here, we examined the effect of ginseng saponins on the induction of SOD and catalase gene expression. To explore this possibility, the upstream regulatory promoter region of Cu/Zn superoxide dismutase (SOD1) and catalase genes were linked to the chloramphenicol acetyltransferase (CAT) structural gene and introduced into human hepatoma HepG2 cells. Total saponin and panaxatriol did not activate the transcription of SOD1 and catalase genes but panaxadiol increased the transcription of these genes about 2-3 fold. Among the panaxadiol ginsenosides, the Rb(2) subfraction appeared to be a major inducer of SOD1 and catalase genes. The specificity of the Rb(2) effect was further confirmed by time course- and dose-dependent induction experiments. These results suggest that the panaxadiol fraction and its ginsenosides could induce the antioxidant enzymes which are important for maintaining cell viability by lowering the level of oxygen radical generated from intracellular metabolism.

The activation of the rat copper/zinc superoxide dismutase gene by hydrogen peroxide through the hydrogen peroxide-responsive element and by paraquat and heat shock through the same heat shock element

Copper/zinc superoxide dismutase (SOD1) protects cells against oxidative hazards by the dismutation of superoxide radicals. The promoter activity of the SOD1 gene was increased 3-5-fold by hydrogen peroxide, paraquat (PQ) and heat shock. Functional analyses of the regulatory region of the SOD1 gene by deletions, mutations, and heterologous promoter systems confirmed the induction of the SOD1 gene by H(2)O(2) through the hydrogen peroxide-responsive element (HRE) (between nucleotides -533 and -520). Gel mobility shift assays showed that the existence of an H(2)O(2)-inducible protein bound to the oligonucleotide of the HRE. Similar analyses showed that the heat shock activated the SOD1 promoter through the heat shock element (HSE) (between nucleotides -185 and -171). A strong specific far-shifted complex with the oligonucleotide of the HSE was observed by the treatment of heat shock. When cells were treated with PQ, a strong far-shifted complex with the HSE was observed and was competed out by the cold HSE probe, indicating that PQ also activated the SOD1 promoter through the same HSE site. It is very interesting to note that chemical and physical stresses, such as PQ and heat shock, respectively, activated the SOD1 promoter through the same cis-element HSE. These results indicate that the SOD1 was inducible by H(2)O(2) through the HRE and by PQ and heat shock through the same HSE to protect cells from oxidative hazards.

Induction of the rat Cu/Zn superoxide dismutase gene through the peroxisome proliferator-responsive element by arachidonic acid

The Cu/Zn superoxide dismutase (SOD1) catalyzes the dismutation of superoxide radicals produced from biological oxidation and environmental stresses. From the sequence analysis of transcription factor binding sites, the peroxisome proliferator-responsive element (PPRE) was located between nt -797 and -786 of the 5'-flanking sequence of the SOD1 gene. A promoter region was fused to a chloramphenicol acetyl-transferase gene, and the resultant construct was transiently transfected into HepG2 cells. The expression of the SOD1 gene was induced by arachidonic acid (AA). Functional analyses of the PPRE site by deletion, mutations, and the heterologous promoter system confirmed the induction of the SOD1 gene by AA through the PPRE site. Gel mobility shift assays showed AA inducible binding of the peroxisome proliferator-activated receptor (PPAR) to the PPRE. The intensity of PPAR binding was also increased by the treatment of retinoic acid (RA) and 9-cis retinoic acid (9-cis RA). These results suggest that the PPRE participates in the induction of the rat SOD1 gene by the peroxisome proliferator.

Xenobiotic-responsive element for the transcriptional activation of the rat Cu/Zn superoxide dismutase gene

Cu/Zn superoxide dismutase (SOD1) catalyzes the dismutation of superoxide radicals produced from biological oxidation and environmental stresses. A number of xenobiotics are toxic because they generate free radicals, such as superoxide and hydroxyl radicals, through a redox cycle. The xenobiotic responsive element (XRE) was located between the nt -268 and -262 region of the 5'-flanking sequence of the SOD1 gene. Functional analyses of this element by deletion, mutations, and heterologous promoter systems confirmed that the expression of the SOD1 gene was induced by a xenobiotic through the XRE. Gel mobility shift assays showed the xenobiotic inducible binding of the receptor-ligand complex to XRE. The cytoplasmic fraction from nontreated HepG2 cells also contains the factor as a cryptic form and prominently reveals its DNA-binding activity by incubation with betaNF in vitro. These results suggest that the XRE participates in the induction of the rat SOD1 gene by xenobiotics.

A nitric oxide-releasing reagent, S-nitroso-N-acetylpenicillamine, enhances the expression of superoxide dismutases mRNA in the murine macrophage cell line RAW264-7

Murine interferon-gamma (IFN-gamma) stimulates the murine macrophage tumour cell line RAW264-7 to produce nitric oxide (NO). IFN-gamma induces expression of inducible NO synthase (iNOS), manganese superoxide dismutase (Mn-SOD) and copper zinc SOD (CuZn-SOD) in these cells. To investigate the mechanism of induction of SOD expression, we added S-nitroso-N-acetyl penicillamine (SNAP) to RAW264-7 cells. SNAP enhanced the expression of Mn-SOD and CuZn-SOD. These results suggest that when producing NO, RAW264-7 cells express SOD that might protect them from NO toxicity.

The enzymatic activity of Cu/Zn superoxide dismutase does not fluctuate in mouse spermatogenic cells despite mRNA changes

In the mammalian testis, multiple mRNAs encoding the copper zinc superoxide dismutase (SOD-1) are expressed in postmeiotic male germ cells. Here we relate SOD-1 mRNA levels to SOD-1 protein and enzyme activity levels in mouse spermatogenic cells. Although the sizes and relative amounts of the multiple SOD-1 mRNAs vary as male germ cells enter meiosis and proceed into the postmeiotic stages of spermatogenesis, the amount of SOD-1 protein and enzyme activity does not fluctuate significantly, suggesting a precise control of SOD-1 activity in male germ cells.

Sp1 and C/EBP-related factor regulate the transcription of human Cu/Zn SOD gene

The Cu/Zn superoxide dismutase (SOD1) is one of the key enzymes that protect cells against oxidative stress. It catalyzes the dismutation of superoxide radicals (O2-) to oxygen and hydrogen peroxide. To study the transcriptional regulation of the human Cu/Zn SOD gene, we began by analyzing the 1.5-kb upstream region of the gene (see Kim et al., 1994). The element from nucleotides (nt) -116 to -45 increased the transcriptional activity of Cu/Zn SOD. Analyses by DNase I footprinting and electrophoretic mobility shift assay (EMSA) showed that Sp1 binds to the region from nt -104 to -89 and C/EBP-related factors to the region from nt -64 to -55. Studies using two mutant versions of this promoter, in which the Sp1 and C/EBP-related factor binding sites were deleted, respectively, revealed that Sp1 and C/EBP-related factors activate the transcription of SOD1 gene. An Sp1 expression plasmid, pPacSp1, stimulated the SOD1-linked CAT expression. Cotransfection of the element from nt -116 to -45 with the C/EBP alpha expression vector, pMSV-C/EBP, increased the transcriptional activity of the Cu/Zn SOD in HepG2 cells, but barely in HeLa cells. Because Sp1 is a ubiquitously expressed transcriptional factor, the binding of Sp1 to the proximal upstream region of the Cu/Zn SOD might explain the expression of Cu/Zn SOD in a wide variety of cells.

Transcriptional activation of the Cu,Zn-superoxide dismutase gene through the AP2 site by ginsenoside Rb2 extracted from a medicinal plant, Panax ginseng

We report here that the ginseng saponins induce the transcription of Cu,Zn-superoxide dismutase gene (SOD1), which is one of the major antioxidant enzymes. Total saponins and panaxatriol did not elevate the level of SOD1, but panaxadiol significantly increased SOD1. Among the panaxadiol fractions, ginsenoside Rb2 was a more specific and more remarkable inducer of the SOD1 gene than ginsenoside Rb1. Deletion analyses of the SOD1 promoter revealed that the proximal promoter is responsible for this induction. Mobility shift assays with cis-elements in the proximal promoter region showed that specific binding of the AP2 transcription factor was significantly increased by treatment with ginsenoside Rb2. Mutations of the AP2 binding sites in the heterologous promoter and natural context systems abolished the transcriptional activation by ginsenoside Rb2. These results suggest that the SOD1 gene was greatly activated by ginsenoside Rb2 through transcription factor AP2 binding sites and its induction.

In male mouse germ cells, copper-zinc superoxide dismutase utilizes alternative promoters that produce multiple transcripts with different translation potential

Copper-zinc superoxide dismutase (SOD-1) is an enzyme that is widely expressed in eukaryotic cells and performs a vital role in protecting cells against free radical damage. In mouse testis, three different sizes of SOD-1 mRNAs of about 0.73, 0.80, and 0.93 kilobases (kb) are detected. The 0.73-kb mRNA is found in early stages of male germ cells and in all somatic tissues. The mRNAs of 0.80 and 0.93 kb are exclusively detected in post-meiotic germ cells. RNase H digestions and Northern blot analyses reveal that the three SOD-1 mRNAs are derived from two transcripts, a ubiquitously expressed transcript and a post-meiotic transcript, which differ by 114-120 nucleotides. RNase protection assays demonstrate that the additional nucleotides present in the post-meiotic mRNA are solely in the 5'-untranslated region. Using a probe derived from the 5'-untranslated region of the 0.93-kb SOD-1 mRNA, we have established that it originates from an alternative upstream promoter contiguous with the somatic SOD-1 promoter. Polysomal gradient analysis of the three mouse testis SOD-1 mRNAs reveals that the 0.93-kb SOD-1 mRNA is primarily non-polysomal, while the 0.80- and 0.73-kb SOD-1 mRNAs are mostly polysome associated. A faster migrating form of the 0.93-kb SOD-1 mRNA is present on polysomes as a result of partial deadenylation. In a cell-free translation system, the 0.73-kb SOD-1 mRNA translates about 2-fold more efficiently than the 0.93-kb SOD-1 mRNA. These data demonstrate that male germ cells transcribe two size classes of SOD-1 mRNAs with different translation potential by utilizing two different promoters, post-meiotic SOD-1 mRNAs undergo adenylation changes, and one of the post-meiotic SOD-1 mRNAs is transcribed during mid-spermiogenesis and translated days later in a partially deadenylated form.