Emanuela Cova

An over-oxidized form of superoxide dismutase found in sporadic amyotrophic lateral sclerosis with bulbar onset shares a toxic mechanism with mutant SOD1

Recent studies suggest that Cu/Zn superoxide dismutase (SOD1) could be pathogenic in both familial and sporadic amyotrophic lateral sclerosis (ALS) through either inheritable or nonheritable modifications. The presence of a misfolded WT SOD1 in patients with sporadic ALS, along with the recently reported evidence that reducing SOD1 levels in astrocytes derived from sporadic patients inhibits astrocyte-mediated toxicity on motor neurons, suggest that WT SOD1 may acquire toxic properties similar to familial ALS-linked mutant SOD1, perhaps through posttranslational modifications. Using patients’ lymphoblasts, we show here that indeed WT SOD1 is modified posttranslationally in sporadic ALS and is iper-oxidized (i.e., above baseline oxidation levels) in a subset of patients with bulbar onset. Derivatization analysis of oxidized carbonyl compounds performed on immunoprecipitated SOD1 identified an iper-oxidized SOD1 that recapitulates mutant SOD1-like properties and damages mitochondria by forming a toxic complex with mitochondrial Bcl-2. This study conclusively demonstrates the existence of an iper-oxidized SOD1 with toxic properties in patient-derived cells and identifies a common SOD1-dependent toxicity between mutant SOD1-linked familial ALS and a subset of sporadic ALS, providing an opportunity to develop biomarkers to subclassify ALS and devise SOD1-based therapies that go beyond the small group of patients with mutant SOD1.

SOD1 Transcriptional and Posttranscriptional Regulation and Its Potential Implications in ALS

Copper-zinc superoxide dismutase (SOD1) is a detoxifying enzyme localized in the cytosol, nucleus, peroxisomes, and mitochondria. The discovery that mutations in SOD1 gene cause a subset of familial amyotrophic lateral sclerosis (FALS) has attracted great attention, and studies to date have been mainly focused on discovering mutations in the coding region and investigation at protein level. Considering that changes in SOD1 mRNA levels have been associated with sporadic ALS (SALS), a molecular understanding of the processes involved in the regulation of SOD1 gene expression could not only unravel novel regulatory pathways that may govern cellular phenotypes and changes in diseases but also might reveal therapeutic targets and treatments. This review seeks to provide an overview of SOD1 gene structure and of the processes through which SOD1 transcription is controlled. Furthermore, we emphasize the importance to focus future researches on investigating posttranscriptional mechanisms and their relevance to ALS.

Expression and immunolocalization of aquaporin-7 in rat gastrointestinal tract.

Background information. In the gastrointestinal tract of mammals, water can either be secreted with digestive juices or absorbed by the small and large intestine. Transcellular water movement can be mediated by the transmembrane protein family of AQPs (aquaporins), as has also been recently identified in the gastrointestinal tract. However, the localization, expression and functioning of AQPs in the gastrointestinal tract have not been completely characterized. For the present study, we investigated: (1) the expression of AQP7 in some portions of rat gastrointestinal tract by semiquantitative reverse transcriptase—PCR and by immunoblotting and (2) the cellular and subcellular localization of AQP7 by immunohistochemistry.

TNF and sTNFR1/2 plasma levels in ALS patients

The involvement of the immune system has been hypothesized in the pathogenesis of amyotrophic lateral sclerosis (ALS). In this study a significantly higher level of TNF-alpha and its soluble receptors, TNF-R1 and TNF-R2, has been found in plasma of patients affected by the sporadic form of ALS compared to normal subjects. The genetic analysis of the polymorphisms of TNF-alpha, TNF-R1 and TNF-R2 showed no statistically significant differences in alleles and genotype frequencies between patients and controls. These data suggest a participation of the immune system in response to as far unknown intracellular signals.

Modified expression of Bcl-2 and SOD1 proteins in lymphocytes from sporadic ALS patients

Markers of oxidative stress have been found in spinal cord, cortex, cerebrospinal fluid, and plasma of SALS patients. Mitochondrial and calcium metabolism dysfunction were also found in peripheral lymphocytes from SALS patients. In this study, we demonstrate that lymphocytes from SALS patients are more prone to undergo alteration of cell membrane integrity both in basal conditions and following oxidative stress induced by H2O2 treatment. The expression of the antioxidant proteins, Bcl-2, SOD1 and catalase in basal conditions, was significantly lower in lymphocytes from SALS patients than in lymphocytes from age and sex matched controls. Exposure to H2O2 induced a time-dependent decrease of Bcl-2 and SOD1 in control lymphocytes. Conversely, the levels of these proteins remained unchanged in SALS lymphocytes even after 18 h stress. Catalase expression was not significantly modified by oxidative stress. Our results demonstrate that two factors involved in the genesis and/or progression of the familial form of the disease with SOD1 mutation are altered also in the sporadic form of ALS and suggest that the oxidative stress protection pathway is deregulated in lymphocytes from ALS patients.

SOD1 mRNA expression in sporadic amyotrophic lateral sclerosis

The mutated Cu,Zn-superoxide dismutase gene (SOD1) (E.C. No. 1.15.1.1) is generally recognized as a pathological cause of 20% of the familial form of Amyotrophic Lateral Sclerosis (ALS). However, several pieces of evidence also show that wild-type SOD1, under conditions of cellular stress, is implicated in a significant fraction of sporadic ALS cases, which represent 90% of ALS patients. Herein, we describe an abnormally high level of SOD1 transcript in spinal cord, brain stem and lymphocytes of sporadic ALS patients. Protein expression studies show a similar or lower amount of SOD1 in affected brain areas and lymphocytes, respectively. No differences are found in brain regions (cerebellum and non-motor cerebral cortex) not involved in the ALS neurodegenerative processes. In this report, cell and disease specificity are shown since no mRNA SOD1 increase is observed in sporadic ALS fibroblasts or in lymphocytes of patients affected by Alzheimers disease. These findings provide new insight and understanding of the pathologic causes of sporadic forms of ALS and allow a possible explanation for the molecular involvement of wild-type SOD1.

Cytotoxicity of Helicobacter pylori on human gastric epithelial cells in vitro: role of cytotoxin(s) and ammonia

Objective To evaluate the respective roles of vacuolating cytotoxin(s) and urease-mediated ammonia production in Helicobacter pylori-induced cytotoxicity on cultured human gastric epithelial cells. Methods Monolayers of MKN 28 cell line were incubated with broth culture filtrates of two urease-positive H. pylori strains: CCUG 17874, cytotoxin-producing and C21, non-cytotoxin-producing. After incubation, highly sensitive quantitative assays were used to measure the ammonia levels in the cell medium, cell vacuolation and cell death. In order to evaluate the cytotoxic role of ammonia more accurately, we performed an ‘ammonia simulation’ by measuring cell vacuolation and cytolethality induced by incubation with definite concentrations of ammonium chloride. Cell damage was also studied morphologically. Results Both H. pylori strains produced ammonia and induced cell vacuolation and cytolethality. With the G21 strain, both cell vacuolation and cytolethality appeared virtually identical to ammonia simulation. With the CCUG 17874 strain, which induced a higher degree of cell vacuolation and cell death compared with the G21 strain, cell vacuolation and cytolethality appeared largely ammonia-independent. The vacuoles induced by each H. pylori strain and by ammonia simulation were similar to each other. In less severely affected cells, vacuole formation and ammonia simulation were regularly limited by smooth membranes and morphologically and topographically resembled dilated endosomes or trans Golgi vesicles. In more severely affected cells, large autophagic-like vacuoles containing cell debris were also prominent. Conclusions The vacuolating cytotoxin(s) and ammonia are major H. pylori virulence factors. The cytotoxin(s) seem to play a more prominent role than ammonia in cell vacuolation. Nevertheless, ammonia seems to damage cells by other mechanisms in addition to vacuolation. A common pathway for cytotoxin- and ammonia-induced cell vacuolation seems likely.

Time course of oxidant markers and antioxidant defenses in subgroups of amyotrophic lateral sclerosis patients

Oxidative stress markers have been found in nervous and peripheral tissues of familial and sporadic amyotrophic lateral sclerosis patients. Here, we evaluated the activity of some antioxidant enzymes glutathione peroxidase, glutathione reductase and Cu-Zn superoxide dismutase in erythrocyte, the marker of non-enzymatic antioxidant response (total antioxidant status), as well as plasma reactive oxygen species, at the enrolment and during disease progression in 88 patients affected by the sporadic form of amyotrophic lateral sclerosis. Our study has been performed along 72 months by grouping the patients according to the ALS functional rating score or rate of disease progression. Our results showed a significant impairment of erythrocytes glutathione peroxidase activity in all groups of patients that remained low during disease time course. SOD1 activity significantly decreased along disease course in subjects with a more impaired functional status. A decreasing activity of all assayed enzymes was found in patients who have a faster disease progression rate. By this work we have the evidence that different ALS phenotypes present with different profile of enzymatic and non-enzymatic antioxidant response.

Effect of nitric oxide on lymphocytes from sporadic amyotrophic lateral sclerosis patients: toxic or protective role?

Markers of oxidative and nitrosative stress have been found in spinal cord, cortex, cerebrospinal fluid and plasma of patients affected by amyotrophic lateral sclerosis (ALS), a fatal disorder characterised by progressive motor neuron degeneration. In this study, we investigated the effect of the NO-releasing agent, diethylamine NONOate (NONO), on lymphocytes from patients affected by the sporadic form of ALS (SALS) and controls by flow cytometry. In the same experimental conditions we investigated the expression of the antioxidant proteins, Bcl-2 and SOD1. Incubation with NONO induced cell damage in control lymphocytes but did not further damage the already affected untreated SALS lymphocytes. The incubation with NONO induced a time-dependent decrease of Bcl-2 and SOD1 in control lymphocytes. Surprisingly, in SALS lymphocytes the NONO treatment increased the expression of these proteins, which in basal conditions was depressed compared to control lymphocytes.

Significance of Ammonia in the Genesis of Gastric Epithelial Lesions Induced by Helicobacter pylori: An in vitro Study with Different Bacterial Strains and Urea Concentrations

Two Helicobacter pylori products cause cell damage both in vivo and in vitro: ammonia, from bacterial urease activity, and a vacuolating toxin named VacA. In this in vitro study, the vacuolating effect of H. pylori broth culture filtrate from a VacA-positive/urease-positive strain is compared with that of a VacA-negative/urease-positive strain and a VacA-negative/urease-negative strain. The effect of VacA and ammonia was evaluated with and without addition of 10 mM urea, a physiological concentration for the human stomach, and with and without addition of 0.5 mg/ml acetohydroxamic and (AHA), an urease inhibitor. Our data show that: (1) both urease-positive H. pylori strains caused cell vacuolation in the absence of urea, the VacA-positive strain being approximatively twice as potent as the VacA-negative strain; (2) addition of urea to the culture medium caused an approximatively 3-fold increase in the vacuolating activity of both urease-positive strains; (3) a VacA-negative/urease-negative strain did not exert any vacuolating effect, either in the presence or in the absence of urea; (4) the ratio between cell vacuolation induced by VacA-positive and VacA-negative strains was enhanced by the presence of AHA: ratio was about 2 in the absence of AHA and about 6 in the presence of AHA, either with or without urea added. The increment of vacuolation is likely due to an interaction between AHA and VacA. In conclusion, a VacA-negative/urease-positive strain becomes highly cytotoxic when physiological levels of urea are present in the incubation medium. This finding suggests that all urease-positive H. pylori strains, both with and without VacA expression, should be considered as potentially cytotoxic for the human gastric mucosa, although VacA enhances the severity of cell damage.