Multiple Taq I RFLPs at the human manganese superoxide dismutase (S0D2) locus on chromosome 6

In vitro metal uptake by recombinant human manganese superoxide dismutase

Metal uptake by the antioxidant defense metalloenzyme manganese superoxide dismutase (MnSOD) is an essential step in the functional maturation of the protein that is just beginning to be investigated in detail. We have extended earlier in vitro studies on metal binding by the dimeric Escherichia coli apo-MnSOD to investigate the mechanism of metal uptake by tetrameric human and Thermus thermophilus apo-MnSODs. Like the E. coli apo-MnSOD, these proteins also bind metal ions in vitro in a thermally activated, pH-sensitive process. However, metal uptake by the tetrameric apo-MnSODs exhibits a number of important differences. In particular, there is no indication of conformational gating requirement for metal binding for these proteins, and the reaction is first-order in metal ion. The high concentration of metal ion that is required to achieve physiologically relevant metallation rates for tetrameric human apo-MnSOD in vitro suggests the possibility that co-translational metal binding or chaperone interactions may be required in vivo.

Antioxidant enzyme gene expression in congestive heart failure following myocardial infarction

Increased oxidative stress and reduction in antioxidant enzymes have been suggested to be involved in the pathophysiology of congestive heart failure subsequent to myocardial infarction (MI). The objective of the present study was to characterize changes in the mRNA abundance and protein levels for the enzymatic antioxidants, superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase during the sequelae of congestive heart failure in rats. MI was produced by the ligation of the left coronary artery and hearts from controls and 1, 4 and 16 week PMI groups were analyzed. Losartan treatment (2 mg/ml in drinking water, daily) was started at 4 weeks and continued for 12 weeks. The mRNA levels for SOD were reduced by about 40% at 1-week PMI, were near to the control levels at 4-week PMI and at 16 weeks PMI, the levels were reduced by about 73% below the controls. GSHPx mRNA levels remained unchanged at all time points. The mRNA levels for catalase remained unchanged at 1 and 4 weeks PMI and were significantly reduced by about 44% at 16 weeks PMI as compared to the controls. The protein levels for MnSOD, CuZnSOD, GSHPx at 1 and 16 weeks remained unchanged in treated and untreated PMI groups. However, the protein levels for catalase was significantly increased in the control and PMI groups treated with Losartan. It is concluded that changes in the SOD and catalase activities during severe heart failure correlated with changes in mRNA for these enzymes. The precise mechanism/s for the improvement in antioxidant reserve and protein levels after Losartan treatment is/are unclear at this time.

Oxygen free radicals mediate the induction of manganese superoxide dismutase gene expression by TNF-alpha

In this study, the hypothesis that oxygen free radicals act as intracellular messengers is examined. Treatment of human oral carcinoma SCC-25 cells with 200 ng/ml human TNF-alpha for 6 h greatly increased manganese superoxide dismutase (MnSOD) gene expression as detected by western blotting, RT-PCR, and nuclear run-on experiments. In the presence of the oxygen free radical spin trapping reagent, 5,5-dimethyl pyrroline-N-oxide (DMPO), the induction of MnSOD gene expression by TNF-alpha was significantly reduced. Electron paramagnetic resonance experiments showed that the production of oxygen free radicals was enhanced in TNF-alpha treated cells. Taken together, these observations suggest that the induction of MnSOD expression by TNF-alpha is at least partially mediated by intracellular formation of oxygen free radicals, and that superoxide is most likely the initiating species involved in the mediation of MnSOD gene expression by TNF-alpha.

Effects of methionine on endogenous antioxidants in the heart

The deficiency of methionine, an essential amino acid, is associated with cardiovascular lesions. Because different types of cardiac pathologies are caused by a decrease in antioxidants, we examined the effects of methionine on myocardial antioxidant enzymes in hemodynamically assessed rats that were treated with methionine (10 mg/ml) in drinking water for 12, 24, and 48 h. Glutathione peroxidase (GSHPx) activity was significantly increased to 150.5 +/- 12.2 and 191.7 +/- 13.7% of the control value at 12 and 24 h, respectively, followed by a decline to 120 +/- 24.6% at 48 h. The mRNA levels of GSHPx at these time points were 151.2 +/- 12.0, 218.7 +/- 35.3, and 173.5 +/- 25.2%, respectively. Superoxide dismutase (SOD) activity was 144.3 +/- 3.7, 114.3 +/- 10.1, and 143.1 +/- 11. 2% at 12, 24, and 48 h, respectively. Catalase (Cat) activity was 272.4 +/- 5.4, 237.8 +/- 16.6, and 224.1 +/- 17.3% of the control value. The expression of Cat and SOD mRNA was unchanged at 12, 24, and 48 h. The lipid peroxidation was decreased by 24.4 +/- 11.2, 54. 9 +/- 0.1, and 6.4 +/- 2.1% at 12, 24, and 48 h, respectively. Methionine had no effect on the ventricular or aortic pressures, heart rate, and myocardial glutathione levels at any of the time points. The study shows that methionine has a significant effect on the myocardial antioxidant enzyme activities, and only changes in GSHPx enzyme activity correlated with the mRNA changes. These antioxidant changes may have a role in the beneficial effects of methionine in pathological rather than physiological conditions.

Post-transcriptional elevation of mouse brain Mn-SOD protein by mercuric chloride

Alterations in gene expression, protein content and enzyme activity of brain Mn-SOD following mercuric chloride (HgCl2) exposure were examined in ICR male mice. Subcutaneous administration of HgCl2 (1 mg Hg/kg) resulted in a significant increase (4-fold) in the brain Mn-SOD content at 6 h after injection while the total mercury concentration was about 0.11 microg/g of brain. The enhancement of Mn-SOD protein caused by HgCl2 was completely abolished by pretreatment with dexamethasone (3 mg/kg) 1 h prior to HgCl2 administration, suggesting involvement of inflammation in inorganic mercury-induced increase in the antioxidant enzyme. This increase in level of Mn-SOD content coincided with a substantial rise in the enzyme activity; however, Northern blot analysis revealed that the induction of protein level was not due to that of its gene expression. The results of the present study indicate that mouse brain Mn-SOD appears to undergo post-translational modification by the environmental toxic metal, and induction of the antioxidant enzyme could be of an initial response to the metal-induced oxidative stress.

Transfection and expression of MnSOD cDNA decreases tumor malignancy of human oral squamous carcinoma SCC-25 cells

Overexpression of human manganese-containing superoxide dismutase (MnSOD) activity has been demonstrated to suppress malignancy in human melanoma and breast carcinoma cells in vitro and in vivo. To study its effects on human oral squamous carcinoma cells, stable transfection and expression of MnSOD in SCC-25 cells have been conducted. The MnSOD-overexpressing cell clones were shown to have approximately two- to five-fold increased MnSOD activity compared to the wild-type parental- or vector control-transfected cell clones, respectively. Plating efficiency with different concentrations of serum was decreased in the high MnSOD activity cell clones. Soft agar assays demonstrated that the clonogenic fractions of high-expressing MnSOD clones were dramatically reduced. When inoculated in nude mice, tumor growth was markedly inhibited in MnSOD overexpressing cell clones compared with the wild-type or vector control transfected cell lines. Thus, gene therapy of human oral cancer by increasing the expression of MnSOD activity in target cells might be used to prevent or reduce human oral tumor malignancy.

Selective inhibition of the mouse brain Mn-SOD by methylmercury

Changes in mRNA levels, protein contents and enzyme activities for brain Cu,Zn- and Mn-SOD by methylmercury chloride (MMC) administration, were examined, over a period of 12 days in ICR male mice. After subcutaneous administration of MMC (10 mg/kg) to mice, brain mercury content reached a maximum at 2 days and remained at that level for at least 5 days. MMC exposure resulted in a time-dependent decrease in the Mn-SOD activity: the enzyme activity at 5 days after exposure to MMC was about 60% of control level whereas this exposure was without effect on the Cu,Zn-SOD activity, indicating differential sensitivity of SOD isozymes to the metal. However, levels of mRNA and protein synthesis for Mn-SOD were unaffected by MMC administration. The direct effect of MMC on the both SOD activities were further examined with purified enzyme preparations. After each SOD isozyme (10 U) was incubated with 0.2 mM MMC for 24 h at pH 7.8, the enzyme activities for Cu,Zn- and Mn-SOD were 90% and 37% of control, respectively. Incubations at a ratio of SOD to MMC (1 : 600) for 24 h resulted in a substantial decrease in the enzyme activity of the Mn form; this isozyme-selective inactivation was noted at alkaline pH. A combination of isoelectric focusing-agarose gel electrophoresis (IEF-AGE) and synchrotron radiation X-ray fluorescence (SR-XRF) analysis revealed that Mn-SOD rather than Cu,Zn-SOD underwent modification. Furthermore, a decrease in native form of Mn-SOD protein after MMC exposure was confirmed by gel filtration chromatography. These results indicate that Mn-SOD, but not Cu,Zn-SOD, is susceptible to modification by MMC and the resulting alteration in structure appears to cause a loss of enzyme activities.

Altered levels of scavenging enzymes in embryos subjected to a diabetic environment

Maternal diabetes during pregnancy is associated with an increased rate of congenital malformations in the offspring. The exact molecular etiology of the disturbed embryogenesis is unknown, but an involvement of radical oxygen species in the teratological process has been suggested. Oxidative damage presupposes an imbalance between the activity of the free oxygen radicals and the antioxidant defence mechanisms on the cellular level. The aim of the present study was to investigate if maternal diabetes in vivo, or high glucose in vitro alters the expression of the free oxygen radical scavenging enzymes superoxide dismutase (CuZnSOD and MnSOD), catalase and glutathione peroxidase in rat embryos during late organogenesis. We studied offspring of normal and diabetic rats on gestational days 11 and 12, and also evaluated day-11 embryos after a 48 hour culture period in 10 mM or 50 mM glucose concentration. Both maternal diabetes and high glucose culture caused growth retardation and increased rate of congenital malformations in the embryos. The CuZnSOD and MnSOD enzymes were expressed on gestational day 11 and both CuZnSOD, MnSOD and catalase were expressed on day 12 with increased concentrations of MnSOD transcripts when challenged by a diabetic milieu. There was a good correlation between mRNA, protein, and activity levels, suggesting that the regulation of these enzymes occurs primarily at the pretranslational level. Maternal diabetes in vivo and high glucose concentration in vitro induced increased MnSOD expression, concomitant with increased total SOD activity, and a tentative decrease in catalase expression and activity in the embryos. These findings support the notion of enhanced oxidative stress in the embryo as an etiologic agent in diabetic teratogenesis.

Multilocus genetic determinants of LDL particle size in coronary artery disease families

Recent interest in atherosclerosis has focused on the genetic determinants of low-density lipoprotein (LDL) particle size, because of (i) the association of small dense LDL particles with a three-fold increased risk for coronary artery disease (CAD) and (ii) the recent report of linkage of the trait to the LDL receptor (chromosome 19). By utilizing nonparametric quantitative sib-pair and relative-pair analysis methods in CAD families, we tested for linkage of a gene or genes controlling LDL particle sizes with the genetic loci for the major apolipoproteins and enzymes participating in lipoprotein metabolism. We confirmed evidence for linkage to the LDL receptor locus (P=.008). For six candidate gene loci, including apolipoprotein(apo)B, apoAII, apo(a), apoE-CI-CII, lipoprotein lipase, and high-density lipoprotein-binding protein, no evidence for linkage was observed by sib-pair linkage analyses (P values ranged from .24 to .81). However, in addition, we did find tentative evidence for linkage with the apoAI-CIII-AIV locus (chromosome 11) (P=.06) and significant evidence for linkage of the cholesteryl ester transfer protein locus (chromosome 16) (P=.01) and the manganese superoxide dismutase locus (chromosome 6) (P=.001), thus indicating multilocus determination of this atherogenic trait.

Sub-milliMorgan map of the proximal part of mouse Chromosome 17 including the hybrid sterility 1 gene

We have generated a high-resolution genetic map, 0.071 cM per backcross animal, of the 13 cM T-H2 region of the mouse Chromosome (Chr) 17. The map contains two phenotypic loci, T and Hst1, 12 RFLP markers, and 24 microsatellite loci. The Hst1 gene was mapped to a chromosomal interval contained within a single 580-kb YAC clone. The FFEH11 YAC is 0.44 cM long and carries, besides the Hst1 gene, five polymorphic DNA markers and recombination breakpoints of six backcross animals. Two candidate genes for Hst1 were identified based on their location and testicular expression. These are Tbp and D17Ph4e. The submilliMorgan map of the T-H2 region revealed significant clustering of (CA)n loci. The clustering, if shown to be a common feature in the mouse genome, may cause gaps in the physical map of the mouse genome.

Absence of mutations in the Mn superoxide dismutase or catalase genes in familial amyotrophic lateral sclerosis

Familial amyotrophic lateral sclerosis (FALS) is an autosomal dominant, adult onset, neurological disorder caused by the degeneration of motor neurons of the cortex, brainstem and spinal cord. Recently, the defective gene in some FALS families was identified as the Cu/Zn superoxide dismutase (SOD1) gene. However, SOD1 mutations are present in approximately 20% of patients with FALS. We have tested the genes of two more free radical detoxifying enzymes, Mn superoxide dismutase (SOD2) and catalase by single strand conformation analysis (SSCA) for mutations in the remaining FALS cases. No mutations were found in the catalase enzyme in 73 unrelated FALS cases; mutations were not detected in the 66% of the SOD2 gene analyzed. FALS does not appear to be caused by mutations in the SOD2 nor the catalase genes.

Cu/Zn superoxide dismutase-like immunoreactivity in Lewy body-like inclusions of sporadic amyotrophic lateral sclerosis

Cu/Zn superoxide dismutase (SOD)-like immunoreactivity (LI) was found within Lewy body-like inclusions (LBIs) in the spinal cords of patients with sporadic amyotrophic lateral sclerosis (ALS) by using an antibody to human Cu/ZnSOD. LBIs were detected in the anterior horn cells in 10 of 20 patients with sporadic ALS. In each of these patients, 7 to 60% of LBIs showed Cu/ZnSOD-LI. No Cu/ZnSOD-LI was detected in intact neurons and glia in the 20 ALS patients, as well as in these cells in 10 normal control individuals. The skein-like inclusions and Bunina bodies, which were found in all of the 20 ALS cases, showed no Cu/ZnSOD-LI. Thus, Cu/ZnSOD appears to play roles in the production and/or degradation process of LBIs.

Linkage analysis of the genetic determinants of high density lipoprotein concentrations and composition: evidence for involvement of the apolipoprotein A-II and cholesteryl ester transfer protein loci

We have tested for evidence of linkage between the genetic loci determining concentrations and composition of plasma high density lipoproteins (HDL) with the genes for the major apolipoproteins and enzymes participating in lipoprotein metabolism. These genes include those encoding various apolipoproteins (apo), including apoA-I, apoA-II, apoA-IV, apoB, apoC-I, apoC-II, apoC-III, apoE, and apo(a), cholesteryl ester transfer protein (CETP), HDL-binding protein, lipoprotein lipase, and the low density lipoprotein (LDL) receptor. Polymorphisms of these genes, and nearby highly polymorphic simple sequence repeat markers, were examined by quantitative sib-pair linkage analysis in 30 coronary artery disease families consisting of a total of 366 individuals. Evidence for linkage was observed between a marker locus D16S313 linked to the CETP locus and a locus determining plasma HDL-cholesterol concentration (P = 0.002), and the genetic locus for apoA-II and a locus determining the levels of the major apolipoproteins of HDL, apoA-I and apoA-II (P = 0.009 and 0.02, respectively). HDL level was also influenced by the variation at the apo(a) locus on chromosome 6 (P = 0.02). Thus, these data indicate the simultaneous involvement of at least two different genetic loci in the determination of the levels of HDL and its associated lipoproteins.

Genetic susceptibility markers in Danish patients with type 1 (insulin-dependent) diabetes--evidence for polygenicity in man. Danish Study Group of Diabetes in Childhood

Fifty-five Danish families with two offspring concordant for type 1 diabetes--identified through a nationwide population-based survey, and 57 "true sporadic" cases--matched with familial cases for age at onset, but with no IDDM-affected first-degree relatives and long disease duration, and 110 control subjects were typed for putative genetic susceptibility markers for type 1 diabetes identified from a pathogenetic model. The markers included MHC class I, II and III loci, the manganese superoxide dismutase (MnSOD) locus (chr. 6q), interleukin-1 beta (IL1B), the IL-1 receptor antagonist (IL1RN), and the IL-1 type 1 receptor (IL1RI) loci (each chr. 2q). No significant differences between familial and sporadic cases were found within the MHC region (including the following loci: HLA-DQ, -DR, heat shock protein (HSP) 70, tumour necrosis factor (TNF), HLA-B and -A). In both groups of patients 11% were negative for both DQA1*0301-DQB1*0302 and DQA1*0501-DQB1*0201 genotypes, and 7% of the type 1 diabetics had genotypes unable to encode a susceptibility DQ alpha beta heterodimer. Disease association was found for the IL1RN (p = 0.04) and for the IL1RI (p = 0.03). When comparing controls and only familial cases with type 1 diabetes for the IL1RN polymorphism a difference was observed (p = 0.003). For the IL1B RFLP a trend for difference was observed between familial cases and control subjects (p = 0.046), whereas no differences between sporadic cases and control subjects could be demonstrated neither at the IL1B nor at the IL1RN loci. A difference in the MnSOD pattern was observed between sporadic cases and controls (p = 0.04).

Regional localization of a trophoblast antigen-related sequence and 16 other sequences to human chromosomes 6q using somatic cell hybrids

Using a panel of 13 hybrid cell lines, we have regionally localized 22 markers to the long arm of chromosome 6. Revised or new locations are provided for 17 of the markers, and preliminary assignments to chromosome 6 of 11 loci are confirmed. The location of NT5, previously determined by antigen expression in hybrids, has been confirmed at 6q14-q15 by using a cDNA probe. Other DNA probes include one new anonymous sequence, designated D6S130, that maps to 6q12 and 4 VNTR probes that map to the proterminal band, 6q27. Probe CRI-L1065 also maps to 6q21, CRI-994 maps to 6q21-qter, and CRI-L322 maps to 6q14-15, information that may assist the merging of physical and genetic maps.

Genetic mapping of the t-complex region on mouse chromosome 17 including the Hybrid sterility-1 gene

t-haplotypes occupy a region on chromosome (Chr) 17 which slightly overlaps the ends of the T-H-2 interval. The wild-type form of this 14 centi-Morgan (cM) region was mapped in a multilocus backcross (C57BL/10-T x C3H)F1 x C57BL/10 using 15 DNA probes on Southern blots of the DNA extracted from 53 animals which were recombinants in the T-H-2 interval. Each recombinant was also progeny-tested to ascertain its Hybrid sterility-1 (Hst-1) genotype by crossing to PWB/Ph, a Mus musculus-derived inbred strain. The limit of resolution of the cross was 0.27 cM. The map distances have been determined for the DNA loci in the T-H-2 interval and the Hst-1 gene was mapped in close vicinity to the D17Rp17 locus.

Manganese superoxide dismutase: nucleotide and deduced amino acid sequence of a cDNA encoding a new human transcript

Three human cDNA libraries were screened with a human manganese superoxide dismutase (Mn-SOD) cDNA under moderately stringent conditions to characterize a large 4-6 kb RNA species which hybridizes to Mn-SOD in RNA blot analyses. A new 4.2 kb Mn-SOD cDNA clone (Mn-SOD 1) was isolated. Its long 3426 nucleotide 3'-untranslated sequence contains both of the 240 base 3'-untranslated sequences of the 1 kb Mn-SOD 4 and 5 cDNAs. This is a fully processed, cytoplasmic RNA species and raises the possibility of a role for particular 3'-untranslated sequence selection in Mn-SOD gene regulation.

Human pepsinogen C (progastricsin) polymorphism: evidence for a single locus located at 6p21.1-pter

A series of six clones containing the entire human pepsinogen C gene (PGC) was identified in a cosmid vector library by using cDNA and oligonucleotide probes. The 10.7-kb PGC gene includes nine exons and exhibits a high degree of sequence identity (60%) with the functionally related pepsinogen A genes. The predicted amino acid sequence was identical with the partial amino-terminal and carboxyl-terminal sequences of purified pepsinogen C. An informative restriction fragment length polymorphism was detected with several restriction enzymes and involved an insertion or deletion of 100 bp of intron sequence located between exons 7 and 8. Evidence that there is only a single PGC gene in humans is presented. The PGC gene and the prolactin gene were regionally localized to 6p21.1-pter by analysis of mouse X human somatic cell hybrids.

Mapping of the Sod-2 locus into the t complex on mouse chromosome 17

A human DNA probe specific for the superoxide dismutase gene was used to identify the corresponding mouse gene. Under the chosen hybridizing conditions, the probe detected DNA fragments most likely carrying the mouse Sod-2 gene. Mapping studies revealed that the Sod-2 gene resides in the proximal inversion of the t complex on mouse chromosome 17. All complete t haplotypes tested showed restriction fragment length polymorphism which is distinct from that found in all wild-type chromosomes tested. The Sod-2 locus maps in the same region as some of the loci that influence segregation of t chromosomes in male gametes. The possibility that the Sod-2 locus is related to some of the t-complex distorter or responder loci is discussed. The data indicate that the human homolog of the mouse t complex has split into two regions, the distal region remaining on the p arm of human chromosome 6, while the proximal region has been transposed to the telomeric region of this chromosome's q arm.