Search

Little is known about the early pathogenic events by which mutant superoxide dismutase 1 (SOD1) causes amyotrophic lateral sclerosis (ALS). This lack of mechanistic understanding is a major barrier to the development and evaluation of efficient therapies. Although protein aggregation is known to be involved, it is not understood how mutant SOD1 causes degeneration of motoneurons (MNs). Previous research has relied heavily on the overexpression of mutant SOD1, but the clinical relevance of SOD1 overexpression models remains questionable. We used a human induced pluripotent stem cell (iPSC) model of spinal MNs and three different endogenous ALS-associated SOD1 mutations (D90Ahom, R115Ghet or A4Vhet) to investigate early cellular disturbances in MNs. Although enhanced misfolding and aggregation of SOD1 was induced by proteasome inhibition, Cells 2022, it was not affected by activation of the stress granule pathway. Interestingly, we identified loss of mitochondrial, but not lysosomal, integrity as the earliest common pathological phenotype, which preceded elevated levels of insoluble, aggregated SOD1. A super-elongated mitochondrial morphology with impaired inner mitochondrial membrane potential was a unifying feature in mutant SOD1 iPSC-derived MNs. Impaired mitochondrial integrity was most prominent in mutant D90Ahom MNs, whereas both soluble disordered and detergent-resistant misfolded SOD1 was more prominent in R115Ghet and A4Vhet mutant lines. Taking advantage of patient-specific models of SOD1-ALS in vitro, our data suggest that mitochondrial dysfunction is one of the first crucial steps in the pathogenic cascade that leads to SOD1-ALS and also highlights the need for individualized medical approaches for SOD1-ALS.

PURPOSE: The human cornea, a tissue much exposed to oxidative stress, is rich in extracellular superoxide dismutase (SOD). In this study, the contents and distributions of the SOD isoenzymes in the normal human cornea were compared with those in corneas affected by keratoconus and bullous keratopathy. METHODS: The central and peripheral parts of normal human corneas were analyzed separately. Central corneal buttons were obtained from patients with keratoconus and bullous keratopathy who were undergoing primary keratoplasty or retransplantation. SOD enzymatic activities were determined by a direct spectrophotometric method, and extracellular SOD and the cytosolic Cu- and Zn-containing SOD (CuZn-SOD) proteins were determined with ELISA and studied with immunohistochemistry. RESULTS: The total SOD content, and particularly the extracellular SOD content, was lower in the central than in the peripheral normal cornea. CuZn-SOD and extracellular SOD were demonstrated in all three corneal layers. CuZn-SOD was found in cells, whereas extracellular SOD appeared to be localized on cell surfaces, in basal membranes, and in the stroma. In keratoconus, corneal levels of extracellular SOD were half those in the control corneas, whereas CuZn-SOD and the mitochondrial Mn-containing SOD levels were normal. In bullous keratopathy, apart from edematous dilution, SOD isoenzyme levels were essentially normal. In a remarkable finding, the same pattern in SOD isoenzyme levels as in the original disease was also found at retransplantation. CONCLUSIONS: Extracellular SOD and CuZn-SOD show markedly different distribution patterns within the human cornea. Extracellular SOD activity in the central cornea is halved in keratoconus, compared with that in normal control corneas. The finding of a similar reduction at retransplantation in keratoconus suggests reduced corneal extracellular SOD synthesis in cells of the host as a cause of the low enzyme levels.

The air pollutant ozone induces both airway inflammation and restrictions in lung function. These responses have been proposed to arise as a consequence of the oxidizing nature of ozone, depleting endogenous antioxidant defenses with ensuing tissue injury. In this study we examined the impact of an environmentally relevant ozone challenge on the antioxidant defenses present at the surface of the lung in two groups known to have profound differences in their antioxidant defense network: healthy control (HC) and mild asthmatic (MA) subjects. We hypothesized that baseline differences in antioxidant concentrations within the respiratory tract lining fluid (RTLF), as well as induced responses, would predict the magnitude of individual responsiveness. We observed a significant loss of ascorbate (ASC) from proximal (-45.1%, p <.01) and distal RTLFs (-11.7%, p <.05) in healthy subjects 6 h after the end of the ozone challenge. This was associated (Rs, -0.71, p <.01) with increased glutathione disulphide (GSSG) in these compartments (p =.01 and p <.05). Corresponding responses were not seen in asthmatics, where basal ASC concentrations were significantly lower (p <.01) and associated with elevated concentrations of GSSG (p <.05). In neither group was any evidence of lipid oxidation seen following ozone. Despite differences in antioxidant levels and response, the magnitude of ozone-induced neutrophilia (+20.6%, p <.01 [HC] vs. +15.2%, p =.01 [MA]) and decrements in FEV(1) (-8.0%, p <.01 [HC] vs. -3.2%, p <.05 [MA]) did not differ between the two groups. These data demonstrate significant differences between the interaction of ozone with RTLF antioxidants in MA and HC subjects. These responses and variations in basal antioxidant defense were not, however, useful predictive markers of group or individual responsiveness to ozone.

We have previously shown that human beta-cells are resistant to the toxic effects of alloxan. In order to further clarify this characteristic of human islets, we investigated whether these cells might transfer their alloxan resistance to alloxan-sensitive rat or mouse islets. Islets from two species (human-mouse or rat-mouse) were mixed into one graft, which was implanted into the subcapsular kidney space of nude mice. Alloxan or saline was injected intravenously two weeks after implantation and one week thereafter the mice were killed. The number of grafted and endogenous beta-cells were evaluated by a semi-quantitative method after immunohistochemistry. Human islet production of the scavenging enzymes extracellular superoxide dismutase and plasma glutathione peroxidase were analyzed with ELISA-techniques, and mouse and human islet hydrogen peroxide breakdown activity were monitored with a horseradish peroxidase-dependent assay. Mouse beta-cells transplanted together with human islets were protected against alloxan cytotoxicity. Rat islets did not protect mouse beta-cells against alloxan, suggesting that the mixing procedure as such did not impose the protection. Production of extracellular superoxide dismutase and plasma glutathione peroxidase by human islets was very low. Moreover, H2O2 breakdown in vitro, did not differ between human and mouse islets. Alloxan-insensitive human islets protect mouse beta-cells against alloxan-induced lesions, suggesting that yet to be identified extracellular factors are involved in human islet resistance to alloxan toxicity., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

The levels of the secreted, interstitially located extracellular superoxide dismutase (EC-SOD), the cytosolic copper-and-zinc-containing SOD (CuZn-SOD), and the mitochondrial manganese-containing SOD (Mn-SOD) were measured in the walls of human coronary arteries, proximal thoracic aortas, and saphenous veins. The blood vessel walls, particularly the arteries, were found to contain exceptionally large amounts of EC-SOD, whereas the levels of CuZn-SOD and Mn-SOD were relatively low compared with other tissues. Analysis of EC-SOD by immunohistochemistry indicates an even distribution in the vessel wall, including large amounts of the arterial intima. Arterial smooth muscle cells were found to secrete large amounts of EC-SOD and likely are the principal source of the enzyme in the vascular wall. The EC-SOD concentration in the human arterial wall extracellular space is high enough to efficiently suppress the putative pathological effects of the superoxide radical, such as oxidation of LDL and reaction with nitric oxide to form the deleterious peroxynitrite. The levels of EC-SOD in the aortic wall are found to vary widely among species and were on average 6440 U/g in humans, 4340 U/g in the cow, 2660 U/g in the pig, 160 U/g in the dog, 770 U/g in the mouse. There were only moderate differences in the amounts of CuZn-SOD and Mn-SOD. This wide variation in EC-SOD content suggests that the susceptibility to pathologies induced by superoxide radicals in the vascular wall interstitium should vary widely among species.

In 10 healthy persons all amalgam fillings were replaced with gold inlays. Blood and urinary levels were measured on 10 occasions during a 4-month period before and a 12-month period after amalgam removal. These variables were also measured three times in 10 healthy controls. A strong statistically significant relation was found between plasma mercury values and both the total number of amalgam surfaces (r = 0.71, p = 0.0006) and the total surface area of the fillings (r = 0.73, p = 0.0004). In the immediate postremoval phase plasma mercury rose three- to four-fold, whereas the urinary and erythrocyte mercury rose about 50%. These peak values declined to the preremoval level at about 1 month. Twelve months after the removal the plasma and urinary mercury levels were significantly reduced to 50% and 25%, respectively, of the initial values for the experimental group. Apart from the significantly lower plasma selenium values 5 and 10 days after removal no significant differences were found with regard to plasma selenium or erythrocyte glutathione peroxidase either within or between the experimental and the control groups. A large number of supplementary biochemical analyses did not show any influence on organ functions or any differences between the groups before or after the amalgam removal. Amalgam fillings considerably contributed to the plasma and urinary mercury levels.

Amalgam restorations were inserted in eight healthy persons, previously unprovided with dental restorations, who had several severe carious lesions. The mean number of surfaces restored were 16.1 (range, 11 to 22). The total mean calculated amount of mercury inserted was 2.9 g (range, 1.5 to 4.3 g). Blood and urinary levels were measured on seven occasions during a 4-month period before and a 3-month period after amalgam placement. One and 3 months after placement, the P-mercury mean values were almost equal to the preplacement values (3.3 nmol/l). After placement U-mercury increased continuously; 3 months after placement a statistically significantly higher (p less than 0.05) mean U-mercury value (0.58 nmol/mmol creatinine) was found compared with the mean preplacement value (0.34 nmol/mmol creatinine). No statistically significant correlation was found between the P- and U-mercury concentrations and the total number of amalgam surfaces. Selenium levels in plasma and urine and erythrocyte glutathione peroxidase showed no systematic change of pattern. The results show that the insertion of amalgam fillings contributed to the U-mercury concentration, but apparently even more extensive amalgam therapy and/or longer exposure periods are needed to affect the P-mercury concentration. No negative effects on the P- and U-selenium or the erythrocyte glutathione peroxidase levels could be found during the 3 months immediately after an extensive amalgam placement. The supplementary blood and urine analyses were not influenced by the insertion of amalgam fillings.