Serum Cu/Zn superoxide dismutase activity is reduced in sporadic amyotrophic lateral sclerosis patients

A novel hypothesis on metal dyshomeostasis and mitochondrial dysfunction in amyotrophic lateral sclerosis: Potential pathogenetic mechanism and therapeutic implications

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor dysfunctions resulting from the loss of upper (UMNs) and lower (LMNs) motor neurons. While ALS symptoms are coincidental with pathological changes in LMNs and UMNs, the causal relationship between the two is unclear. For example, research on the extra-motor symptoms associated with this condition suggests that an imbalance of metals, including copper, zinc, iron, and manganese, is initially induced in the sensory ganglia due to a malfunction of metal binding proteins and transporters. It is proposed that the resultant metal dyshomeostasis may promote mitochondrial dysfunction in the satellite glial cells of these sensory ganglia, causing sensory neuron disturbances and sensory symptoms. Sensory neuron hyperactivation can result in LMN impairments, while metal dyshomeostasis in spinal cord and brain stem parenchyma induces mitochondrial dysfunction in LMNs and UMNs. These events could prompt intracellular calcium dyshomeostasis, pathological TDP-43 formation, and reactive microglia with neuroinflammation, which in turn activate the apoptosis signaling pathways within the LMNs and UMNs. Our model suggests that the degeneration of LMNs and UMNs is incidental to the metal-induced changes in the spinal cord and brain stem. Over time psychiatric symptoms may appear as the metal dyshomeostasis and mitochondrial dysfunction affect other brain regions, including the reticular formation, hippocampus, and prefrontal cortex. It is proposed that metal dyshomeostasis in combination with mitochondrial dysfunction could be the underlying mechanism responsible for the initiation and progression of the pathological changes associated with both the motor and extra-motor symptoms of ALS.

Focused Proteomics in Post-Mortem Human Spinal Cord

With a highly sensitive electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS) system, proteins were identified in minimal amounts of spinal cord from patients with the neurodegenerative disease amyotrophic lateral sclerosis (ALS) and compared to proteins in spinal cord from control subjects. The results show 18 versus 16 significantly identified (p < 0.05) proteins, respectively, all known to be found in the central nervous system. The most abundant protein in both groups was the glial fibrillary acidic protein, GFAP. Other proteins were, for example, hemoglobin alpha- and beta chain, myelin basic protein, thioredoxin, alpha enolase, and choline acetyltransferase. This study also includes the technique of laser microdissection in combination with pressure catapulting (LMPC) for the dissection of samples and specific neurons. Furthermore, complementary experiments with nanoLC-matrix assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS) confirmed the results of the ESI-FTICR MS screening and provided additional results of further identified proteins.

An increase of oxidized coenzyme Q-10 occurs in the plasma of sporadic ALS patients

We have compared plasma redox status of coenzyme Q-10 in 20 sporadic amyotrophic lateral sclerosis (sALS) patients with those in 20 healthy age/sex-matched controls. A significant increase in the oxidized form of coenzyme Q-10 (sALS=109.3+/-95.2 nM; controls=23.3+/-7.5 nM, P=0.0002) and in the ratio of oxidized form of coenzyme Q-10 to total coenzyme Q-10 (%CoQ-10) (sALS=12.0+/-9.3%; controls=3.2+/-0.9%, P<0.0001) were observed. Moreover, %CoQ-10 correlated significantly with the duration of illness (rho=0.494, P=0.0315). Our finding suggests systemic oxidative stress in the pathogenesis of sALS.

Apoptosis as a general cell death pathway in neurodegenerative diseases

Neurodegenerative processes are generally characterized by the long-lasting course of neuronal death and the selectivity of the neuronal population or brain structure involved in the lesion. Two main common forms of cell death that have been described in neurons as in other vertebrate tissues i.e., necrosis and apoptosis. Necrosis is the result of cellular "accidents", such as those occurring in tissues subjected to chemical trauma. The necrotizing cells swell, rupture and provoke an inflammatory response. Apoptosis, on the other hand, is dependent on the cell's "decision" to commit suicide and die, and therefore is referred to as "programmed cell death" (PCD). The course of apoptotic death is characterized by a massive morphological change, including cell shrinkage, nuclear (chromosome) condensation and DNA degradation. Activation of PCD in an individual cell is based on its own internal metabolism, environment, developmental background and its genetic information. Such a situation occurs in most of the neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's diseases and amyotrophic lateral sclerosis (ALS). In these pathological situations, specific neurons undergo apoptotic cell death characterized by DNA fragmentation, increased levels of pro-apoptotic genes and "apoptotic proteins" both, in human brain and in experimental models. It is of utmost importance to conclusively determine the mode of cell death in neurodegenerative diseases, because new "anti-apoptotic" compounds may offer a means of protecting neurons from cell death and of slowing the rate of cell degeneration and illness progression.

Blood oxidative stress in amyotrophic lateral sclerosis

It has been suggested that amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder resulting in motor neuron death, is associated with oxidative damage induced by free radicals. Our study aimed to get an assessment of the blood oxidative stress status in a population of 167 ALS patients (aged 59+/-13 years), treated or not with riluzole, compared with 62 age-matched healthy control subjects (aged 60+/-11 years) simultaneously included in the study. We determined the level of plasma lipid peroxidation (thiobarbituric acid-reactive substances, TBARS); the status of the major lipophilic plasma antioxidant defenses (vitamin E, vitamin A and beta-carotene); the activities of erythrocyte Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and of plasma and erythrocyte glutathione peroxidase (GSH-Px). Plasma selenium was also determined as a trace element essential to the activity of the GSH-Px. In comparison with controls, we observed in ALS patients (mean+/-S.D.) significantly higher TBARS values (ALS=1.34+/-0.28 micromol/l; controls=1.11+/-0. 20 micromol/l) and a significant enhancement of the erythrocyte SOD activity (ALS=710+/-114 U/g Hb; controls=667+/-93 U/g Hb). No differences were observed for selenium level, GSH-Px activity, plasma vitamin E, beta-carotene and vitamin A concentrations. These data confirm the presence of an oxidative stress in blood of ALS patients. The elevated plasma TBARS, without any deficiency in plasma lipophilic antioxidants such as vitamin E, vitamin A and beta-carotene, suggest an enhancement in the production of free radicals. No correlation was found in our study between the level of any of the blood oxidative stress markers and the disease duration. Comparison between patients treated or not with riluzole did not display any modification of the plasma TBARS concentration, but we observed a slight decrease of erythrocyte SOD activity in treated patients (treated=705+/-113 U/g Hb; not treated=725+/-118 U/g Hb), suggesting a possible activity of riluzole on the oxygenated free radical production.

Antioxidative and proapoptotic effects of riluzole on cultured cortical neurons

Riluzole is used clinically in patients with amyotrophic lateral sclerosis. As oxidative stress, in addition to excitotoxicity, may be a major mechanism of motoneuron degeneration in patients with amyotrophic lateral sclerosis, we examined whether riluzole protects against nonexcitotoxic oxidative injury. Probably reflecting its weak antiexcitotoxic effects, riluzole (1-30 microM) attenuated submaximal neuronal death induced by 24-h exposure to 30 microM kainate or NMDA, but not that by 100 microM NMDA, in cortical cultures. Riluzole also attenuated nonexcitotoxic oxidative injury induced by exposure to FeCl3 in the presence of MK-801 and CNQX. Consistent with its antioxidative effects, riluzole reduced Fe3+-induced lipid peroxidation, and inhibited cytosolic phospholipase A2. By contrast, riluzole did not attenuate neuronal apoptosis induced by staurosporine. Rather unexpectedly, 24-48-h exposure to 100-300 microM riluzole induced neuronal death accompanied by nuclear and DNA fragmentations, which was attenuated by caspase inhibitor carbobenzyloxy-Val-Ala-Asp-fluoromethyl ketone but not by protein synthesis inhibitor cycloheximide. The present study demonstrates that riluzole has direct antioxidative actions, perhaps in part by inhibiting phospholipase A2. However, in the same neurons, riluzole paradoxically induces neuronal apoptosis in a caspase-sensitive manner. Considering current clinical use of riluzole, further studies are warranted to investigate its potential cytolethal effects.

Cu/Zn superoxide dismutase activity at different ages in sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive disorder resulting from degeneration of motor neurons in the brain and spinal cord. Sporadic ALS (SALS) accounts for the majority of patients and the familial form (FALS) represents fewer than 10% of all cases. Since it was found that there are Cu/Zn superoxide dismutase (SODI) gene mutations in 20% of FALS patients and that FALS and SALS patients show similar clinical features, it has been postulated that both may share a common physiopathological mechanism. We studied Cu/Zn SOD1 activity in cytosolic extracts of erythrocytes from 125 normal individuals and 40 SALS patients. We found that enzyme activity does not change with age in control subjects and tends to decrease in most SALS patients older than 60 years. A subpopulation of five SALS patients had significantly increased SOD1 activity; four of these patients over 70 years old. There was no correlation between enzyme activity and time of onset of the disease, or clinical forms of the illness. The variation in SOD1 activity in ageing SALS patients compared with younger patients suggests that they may undergo an oxidative disbalance contributing to the development of the disease.

Amyotrophic lateral sclerosis: a lesson in deficiency diseases

Amyotrophic lateral sclerosis (ALS) is an age-dependent degeneration of motor neurons in the central nervous system. ALS is not caused by faulty nutrition. Recent data suggest that ALS could be an oxidative neurotoxicity induced by a mutation in the SOD1 protein. This finding extends beyond the simple loss of an antioxidant enzyme.