The objective was to test the hypothesis that a described association between homozygosity for a 50bp deletion in the SOD1 promoter 1684bp upstream of the SOD1 ATG and an increased age of onset in SALS can be replicated in additional SALS and control sample sets from other populations. Our second objective was to examine whether this deletion attenuates expression of the SOD1 gene. Genomic DNA from more than 1200 SALS cases from Ireland, Scotland, Quebec and the USA was genotyped for the 50bp SOD1 promoter deletion. Reporter gene expression analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation studies were utilized to examine the functional effects of the deletion. The genetic association for homozygosity for the promoter deletion with an increased age of symptom onset was confirmed overall in this further study (p=0.032), although it was only statistically significant in the Irish subset, and remained highly significant in the combined set of all cohorts (p=0.001). Functional studies demonstrated that this polymorphism reduces the activity of the SOD1 promoter by approximately 50%. In addition we revealed that the transcription factor SP1 binds within the 50bp deletion region in vitro and in vivo. Our findings suggest the hypothesis that this deletion reduces expression of the SOD1 gene and that levels of the SOD1 protein may modify the phenotype of SALS within selected populations.
Aging adults are a growing segment of the U.S. population and are likely to exhibit increased susceptibility to many environmental toxicants. However, there is little information on the susceptibility of the aged to toxicants. The toxicity of toluene has been well characterized in young adult rodents but there is little information in the aged. Three approaches were used: (1) pharmacokinetic (PK), (2) cardiac biomarkers, and (3) whole-animal physiology to assess whether aging increases susceptibility to toluene in the Brown Norway (BN) rat. Three life stages, young adult, middle aged, and aged (4, 12, and 24 mo, respectively), were administered toluene orally at doses of 0, 0.3, 0.65, or 1 g/kg and subjected to the following: terminated at 45 min or 4 h post dosing, and blood and brain toluene concentration were measured; terminated at 4 h post dosing, and biomarkers of cardiac function were measured; or monitor heart rate (HR), core temperature (Tc), and motor activity (MA) by radiotelemetry before and after dosing. Brain toluene concentration was significantly elevated in aged rats at 4 h after dosing with either 0.3 or 1 g/kg. Blood toluene concentrations were unaffected by age. There were various interactions between aging and toluene-induced effects on cardiac biomarkers. Most notably, toluene exposure led to reductions in mRNA markers for oxidative stress in aged but not younger animals. Toluene also produced a reduction in cardiac endothelin-1 in aged rats. Higher doses of toluene led to tachycardia, hypothermia, and a transient elevation in MA. Aged rats were less sensitive to the tachycardic effects of toluene but showed a prolonged hypothermic response. Elevated brain levels of toluene in aged rats may be attributed to their suppressed cardiovascular and respiratory responses. The expression of several cardiac biochemical markers of toluene exposure in the aged may also reflect differential susceptibility to this toxicant.
Previous studies have shown that testosterone production by the Leydig cells of aged Brown Norway rats is reduced from the relatively high levels produced by Leydig cells of young rats and that this reduction is not secondary to decreased serum luteinizing hormone concentration. The free radical theory of aging proposes that imbalance between pro-oxidants and the antioxidant defense system ultimately results in oxidative damage to cellular processes. With this in mind, we hypothesized herein that age-related reductions in steroidogenesis by Brown Norway rat Leydig cells may be associated with the impairment of the antioxidant defense system of these cells. To begin to test this hypothesis, we compared the activities and steady-state mRNA and protein levels of the antioxidant enzymes copper zinc (CuZn) superoxide dismutase (CuZnSOD, SOD1), manganese (Mn) superoxide dismutase (MnSOD, SOD2), and glutathione peroxidase (GPx) and the levels of reduced and oxidized glutathione in Leydig cells isolated from the testes of young (4-month-old) and aged (20-month-old) Brown Norway rats. For some studies, Leydig cells were isolated separately from aged testes that either had regressed because of age-related losses of germ cells or that were nonregressed. SOD (total) and GPx activities were found to decrease significantly with age whether or not the testes were regressed. CuZnSOD and MnSOD mRNA levels decreased with aging, though the magnitude of the decreases were considerably lower than the respective decreases in enzyme activities. GPx mRNA levels also decreased, which is consistent with the decreases seen in enzyme activity. MnSOD protein expression declined with age, and to a lesser extent, CuZnSOD did as well. Reduced and oxidized glutathione also exhibited age-related reductions in cells from both normal and regressed aged testes. The age-related decreases in Leydig cell antioxidant enzyme activities, gene expression, and protein levels and in glutathione were consistent with the hypothesis that the loss of steroidogenic function that accompanies Leydig cell aging may result in part from a decrease in the fidelity of the cellular antioxidant defense system.
Manganese superoxide dismutase (MnSOD) protects cells against oxidative stress by eliminating superoxides. Hypothetically, decreased MnSOD levels in cancer might lead to increased oxidative stress and, thus, to increased sensitivity of cells to chemotherapy agents. Eighty-nine patients with acute myeloid leukemia (AML) were analyzed for a functional C to T polymorphism of MnSOD, which could potentially lead to decreased enzyme concentrations inside mitochondria. A significant survival advantage (p=0.02) was observed for those AML patients carrying T-containing alleles of MnSOD compared to the patients with the CC genotype. These preliminary results may indicate an important role for genetic factors regulating the cellular redox state in determining the outcome of leukemia chemotherapy.
The development of drug resistance of tumors is multifactorial and still poorly understood. Some cytotoxic drugs generate free radicals, and, therefore, antioxidant enzymes may contribute to drug resistance. We investigated the levels of manganese superoxide dismutase (Mn SOD), its inducibility, and its protective role against tumor necrosis factor-alpha and cytotoxic drugs (cisplatin, epirubicin, methotrexate, and vindesin) in human pleural mesothelioma (M14K) and pulmonary adenocarcinoma (A549) cells. We also studied other major antioxidant mechanisms in relation to oxidant and drug resistance of these cells. A549 cells were more resistant than M14K cells toward both oxidants (hydrogen peroxide and menadione) and all the cytotoxic drugs tested. M14K cells contained higher basal Mn SOD activity than A549 cells (28.3 +/- 3.4 vs. 1.8 +/- 0.3 U/mg protein), and Mn SOD activity was significantly induced by tumor necrosis factor-alpha only in A549 cells (+524%), but the induction did not offer any protection during subsequent oxidant or drug exposure. Mn SOD was not induced significantly in either of these cell lines by any of the cytotoxic drugs (0.007-2 microM, 48 h) tested when assessed by Northern blotting, Western blotting, or specific activity. A549 cells contained higher catalase activity than M14K cells (7.6 +/- 1.3 vs. 3.6 +/- 0.5 nmol O(2). min(-1). mg protein(-1)). They also contained twofold higher levels of glutathione and higher immunoreactivity of the heavy subunit of gamma-glutamylcysteine synthetase than M14K cells. Experiments with inhibitors of gamma-glutamylcysteine synthetase and catalase supported our conclusion that mechanisms associated with glutathione contribute to the drug resistance of these cells.
Three populations of brown trout (Salmo trutta) exposed to different metal levels in their natural environments, were studied with respect to antioxidants metallothionein (MT), superoxide dismutase (SOD) and catalase (CAT) as well as for corresponding mRNA levels. In addition, mRNA levels were studied for glutathione peroxidase (GPx) and glutathione reductase (GR). The Cd/Zn-exposed trout (Naustebekken River) had higher accumulated levels of Cd, Cu and Zn in gills, and higher levels of MT (both protein and mRNA) in liver and kidney as well as in gills compared to the Cu-exposed trout (Rugla River) and trout from an uncontaminated reference river (Stribekken River). Less MT found in the Cu-exposed trout may increase susceptibility to oxidative stress, but no higher levels of antioxidant mRNAs were found in gills of these trouts. The data indicated that chronic exposures of brown trout to Cd, Zn and/or Cu did not involve maintenance of high activities of SOD and CAT enzymes in gills, although SOD mRNA levels were higher in the Cd/Zn-exposed trout. In livers, mRNA levels of SOD, CAT and GPx were higher in the metal-exposed trout, but in the case of GR this was only seen in kidneys of Cd/Zn-exposed trout. However, both metal-exposed groups had higher activities of SOD enzyme in liver compared to the unexposed reference trout, and CAT activity was found to be higher in kidneys of Cu-exposed trout. The Cu-exposed trout did not seem to rely on MT production to avoid Cu toxicity in gills, but rather by keeping the Cu uptake at a low level. A coordinated expression of different stress genes may also be important in chronic metal exposure. It may be concluded that the observed metal effects relies on acclimation rather than on genetic adaptation in the metal exposed populations.
Air breathing, especially oxygen therapy, exposes the lung to reactive oxygen species (ROS). Antioxidant enzymes (AOEs) may protect the lung from ROS-mediated injury. Because expression of the key AOEs increases in several animal species during gestation, we investigated (1) the messenger RNA (mRNA) and activity levels of the key AOEs manganese and copper-zinc superoxide dismutases (MnSOD and CuZnSOD, respectively), catalase (CAT), and glutathione peroxidase (GPx) in adult lung samples and during ontogenesis; and (2) the difference in AOE expression between lung and liver. In the lung, the mRNA expression of MnSOD, CuZnSOD, and CAT increased toward adulthood, and GPx was unchanged. Pulmonary activities of MnSOD and CuZnSOD were unchanged, whereas CAT increased 3-fold from fetuses to adults. In the liver, the mRNA expression of MnSOD, CuZnSOD, and GPx increased, whereas that of CAT decreased toward adulthood. Hepatic activities of MnSOD and CuZnSOD increased 2-fold and 4-fold, respectively, whereas CAT was similar in fetuses and adults. Neonatal GPx activity was 2-fold higher in the lung and 6-fold higher in the liver compared with adults. The mRNA levels of MnSOD correlated positively with those of CuZnSOD and CAT in the lung, and GPx with those of MnSOD and CuZnSOD in the liver. Activities of MnSOD and CuZnSOD correlated positively in the liver. We conclude that the regulation of AOEs differs between human lung and liver, and is not tightly coordinated in either tissue.
Hyperglycemia-induced oxidative stress is one mechanism believed to underlie diabetic vascular disease. We tested the hypothesis that diabetic subjects heterozygous for extracellular superoxide dismutase (SOD3) R213G, which entails lower antioxidant capacity in tissues, have increased risk of cardiovascular disease and heart failure.
We used the prospective Copenhagen General Population Study and Copenhagen City Heart Study and genotyped 95,871 individuals for the rs1799895 R213G variation in the SOD3 gene, of which 4498 had diabetes. We used national hospitalization and death registers to assess cardiovascular disease and heart failure.
Out of 95,871 individuals, we identified 93,521 R213G non-carriers (213RR, 97.5%), 2336 heterozygotes (213RG, 2.4%) and 14 homozygotes (213GG, 0.01%). In diabetic subjects, the hazard ratio for cardiovascular disease in R213G heterozygotes compared to non-carriers was 2.32 (95% CI 1·44-3.75), with a corresponding hazard ratio in non-diabetic subjects of 0.97 (0·80-1.19) (p for interaction 0.002). For heart failure, the hazard ratios in R213G heterozygotes compared to non-carriers were 2.19 (1.28-3.76) in diabetic and 0.68 (0.49-0.92) in non-diabetic subjects (p for interaction
Three biochemical gene markers test the hypothesis that the European hake, Merluccius merluccius (L.), along the west European continental shelf are one race. The three polymorphic loci were serum transferrin (Tf), eye vitreous fluid butyric esterase (Es) and liver superoxide dismutase (Sod). Five transferrin alleles, three esterase alleles and two superoxide dismutase alleles were identified. Heterogeneity tests on genotype frequency distribution for twelve areas ranging from Norway to Biscay revealed no significant variation. The results using these genetic tags are consistent with the unit race hypothesis for hake throughout the sea areas sampled.
Brown trout (Salmo trutta) from two native populations from the Røros area in Central Norway, acclimated in mining-affected habitats to different levels of Cd/Zn and Cu, together with trout from a nearby unaffected river (reference) were transferred to a nearby lake with higher levels of Cu, Cd, and Zn than those in their respective native rivers. This experiment was conducted to gain information about the underlying resistance mechanisms developed in fish exposed to metal environments. The focus was on gill metal accumulation and transcription of the metal-responsive stress genes metallothionein-A (MT-A), Cu/Zn-superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and heat shock protein 70 (HSP-70). The only shared response shown between the three groups after transfer were Cu accumulation and MT-A induction. The Cu-acclimated trout produced mucus to reduce the uptake of Cu into the gills. The MT-A levels were highest in the Cd/Zn-acclimated trout both before and after transfer. Before transfer, antioxidant transcription (SOD and GPx) was higher in gills of Cu-acclimated compared to the Cd/Zn-acclimated trout, but increased transcription of antioxidant stress genes was observed after transfer in both metal-acclimated groups. The metal-acclimated trout groups also showed an increase in the transcription of HSP-70. Compared to the reference population not previously exposed to metals, stress gene transcription increased faster in the metal-acclimated populations. The exception was induction of CAT, which appeared to be depressed after transfer in Cd/Zn-acclimated trout. The data indicate that acclimation to chronic metal exposure involves different strategies to cope with different metals and that these strategies involve both physiological mechanisms (mucus production) as well as metal-related stress gene transcription.