Lack of evidence for oxidative stress in sporadic amyotrophic lateral sclerosis fibroblasts.

BACKGROUND: It is conceivable that an early therapeutic intervention in amyotrophic lateral sclerosis (ALS) would lead to better results in terms of disease progression for these patients. One possible strategy to increase the sensitivity of the diagnosis is represented by the use of biological parameters reflecting, for example, oxidative stress alterations associated with ALS. Such biomarkers would be valuable tools both for a better diagnostic evaluation and for studying the impact of therapeutic interventions on the disease course. A special category of experimental models is represented by peripheral cells obtained directly from patients (ex vivo). OBJECTIVE: In this study, primary fibroblasts obtained from 10 sporadic ALS (SALS) patients and 10 healthy matched controls were used to investigate a panel of parameters related to the oxidative status. METHODS: Reactive oxygen species production, protein carbonylation and nitration, susceptibility to hydrogen peroxide exposure, p38-mitogen-activated protein kinase activation and adenosine triphosphate intracellular content were evaluated. RESULTS: No significant difference was observed in all investigated parameters between patient and control cells, and no correlation with the disease severity was found. CONCLUSION: Collectively, our data show no major alterations of the oxidative and bioenergetic status in SALS cultured fibroblasts, suggesting that these cells do not represent a useful model to study the oxidative dysfunction associated with SALS.

Role of a pre-existing neuropathy on the course of bortezomib-induced peripheral neurotoxicity.

We investigated a series of bortezomib-treated patients and correlated the course of bortezomib-induced peripheral neurotoxicity with the presence or absence of peripheral neuropathy at baseline. Forty-eight patients were examined with the total neuropathy score reduced version (TNSr), visual analogue score (VAS) for pain, and nerve conduction studies at baseline and after two and four cycles of chemotherapy. Twenty-three patients had a baseline TNSr = 0-2, and 25 patients had a baseline TNSr >2 (median = 6, range 3-13). The course of bortezomib-induced peripheral neurotoxicity was generally more severe in those patients with the highest baseline TNSr. However, among those subjects with a normal baseline TNSr, two patients developed a clinically relevant peripheral neuropathy with a marked increase in TNSr as early as after two cycles of bortezomib treatment (TNSr = 10 and 15, respectively), while after four cycles, three other patients with normal baseline TNSr had a TNSr of 11, 12, and 13. VAS reporting confirmed that painful neuropathy is frequent after bortezomib administration. Our results indicate that the course of bortezomib-induced peripheral neurotoxicity can be severe in subjects with normal neurological examination at baseline, and therefore, careful monitoring during treatment is suggested in these patients.

Impairment of glutamate transport and increased vulnerability to oxidative stress in neuroblastoma SH-SY5Y cells expressing a Cu,Zn superoxide dismutase typical of familial amyotrophic lateral sclerosis.

Human neuroblastoma SH-SY5Y cells transfected with either familial amyotrophic lateral sclerosis-typical G93A mutant or wild-type copper/zinc superoxide dismutase were compared to untransfected cells in term of glutamate transport. Vmax of glutamate uptake was reduced in mutant cells, with no change in Km. No difference in EAAT1, EAAT2 and EAAT3 glutamate transporter mRNAs and immunoreactive proteins was found, suggesting that one or more transporters are functionally inactivated, possibly due to increased oxidative stress induced by the G93A mutation. Mutant cells showed a marked sensitivity to oxidants, resulting in a more pronounced reduction of glutamate uptake. Short-term antioxidant treatment did not reverse the impairment of glutamate uptake in G93A cells. Interestlingly, N-acetylcysteine was partially effective in preventing glutamate uptake reduction due to exogenous oxidative insults. Since the inhibition of the EAAT2 transporter subtype had no effect on glutamate re-uptake in this model, our study suggests an impaired function of the EAAT1/3 transporter subtypes, possibly due to oxidative inactivation, in the presence of mutant copper/zinc superoxide dismutase. Therefore, this model might prove to be a valuable tool to study the effects of mutant copper/zinc superoxide dismutase associated with amyotrophic lateral sclerosis on glutamate transport in neuronal cells, without the specific contribution of glial cells. These findings might lead to the identification of new therapeutic strategies aimed at preventing the damage associated with ALS.

Leber hereditary optic neuropathy mtDNA mutations disrupt glutamate transport in cybrid cell lines.

Leber hereditary optic neuropathy (LHON) is a maternally inherited form of retinal ganglion cell degeneration leading to optic atrophy which is caused by point mutations in the mitochondrial genome (mtDNA). Three pathogenic mutations (positions 11778/ND4, 3460/ND1 and 14484/ND6) account for the majority of LHON cases and they affect genes that encode for different subunits of mitochondrial complex I. Excitotoxic injury to retinal ganglion cells and the optic nerve has been previously hypothesized, especially given the high susceptibility of this neural cell type to glutamate toxicity. Osteosarcoma-derived cytoplasmic hybrids (cybrids) generated from six unrelated LHON patients, two cell lines for each pathogenic mutation, were compared with cybrids obtained from three healthy controls. Molecular and biochemical analyses showed that excitatory amino acid transporter 1 (EAAT1)/GLAST is the most active glutamate transporter in this cellular model. The glutamate uptake maximal velocity was significantly reduced in all LHON cybrids compared with control cybrids. This reduction was correlated in a mutation-specific fashion with the degree of mitochondrial production of reactive oxygen species, which is enhanced in LHON cybrids. Our findings support the hypothesis that the genetically determined mitochondrial dysfunction in LHON patients leads to impaired activity of the EAAT1 glutamate transporter. This observation is particularly relevant since EAAT1 is the major means of glutamate removal in the inner retina and this prevents retinal ganglion cells being damaged as a result of excitotoxicity.

Chemotherapy-Induced Peripheral Neurotoxicity assessment: a critical revision of the currently available tools.

Chemotherapy-Induced Peripheral Neurotoxicity (CIPN) is a frequent, potentially severe and dose-limiting side-effect of cancer treatment. Despite its clinical relevance that limits the use of several antineoplastic agents and even the future development of new anticancer drugs, several crucial aspects of CIPN remain unsolved, one of which is how to assess its occurrence and severity in the most effective and reliable way. CIPN severity is generally assessed using Common Toxicity Criteria (CTC) scales, although it is well known that significant inter-observer disagreement exists using these scales. Moreover, most CTC scores mix impairment, disability and quality of life measures, which could lead to misinterpretation of the results and unpredictable under- or overestimation of the effect. This uncertainty may lead to different interpretations of the results of the same clinical trials by clinicians and also by regulatory agencies. The use of other types of scale based on clinical and instrumental examinations, or the use of self-administered questionnaires for patients, has not yet really improved the accuracy of CIPN assessment, although some of these tools are promising and deserve to be further validated. As a result, there is a general recognition that CIPN has still not been properly assessed and that improvements should be made. In this review, the available data regarding the different tools used to assess CIPN will be revised and their features will be critically examined, with a special focus on their reliability and reproducibility across examiners and, when available, through direct comparison.

Mitochondrial dysfunction due to mutant copper/zinc superoxide dismutase associated with amyotrophic lateral sclerosis is reversed by N-acetylcysteine.

We report that the expression of mutant G93A copper/zinc superoxide dismutase (SOD1), associated with familial amyotrophic lateral sclerosis, specifically causes a decrease in MTT reduction rate and ATP levels and an increase in both cytosolic and mitochondrial reactive oxygen species (ROS) production in human neuroblastoma SH-SY5Y cells compared to cells overexpressing wild-type SOD1 and untransfected cells. Exposure to N-acetylcysteine lowers ROS production and returns mitochondrial functional assays to control levels. No large aggregates of human SOD1 are detectable under basal growth conditions in any of the investigated cell lines. After proteasome activity inhibition, SOD1 aggregates can be detected exclusively in G93A-SOD1 cells, even though they do not per se enhance cell death compared to control cell lines. Our findings indicate that mitochondrial homeostasis is affected by mutant SOD1-generated ROS independently from the formation of aggregates and that this alteration is reversed by antioxidants.