Creutzfeldt-Jakob disease and oxidative stress

Association of Oxidative Stress with Neurological Disorders

BACKGORUND

Oxidative stress is one of the main contributing factors involved in cerebral biochemical impairment. The higher susceptibility of the central nervous system to reactive oxygen species mediated damage could be attributed to several factors. For example, neurons use a greater quantity of oxygen, many parts of the brain have higher concentraton of iron, and neuronal mitochondria produce huge content of hydrogen peroxide. In addition, neuronal membranes have polyunsaturated fatty acids, which are predominantly vulnerable to oxidative stress (OS). OS is the imbalance between reactive oxygen species generation and cellular antioxidant potential. This may lead to various pathological conditions and diseases, especially neurodegenerative diseases such as, Parkinson's, Alzheimer's, and Huntington's diseases.

OBJECTIVES

In this study, we explored the involvement of OS in neurodegenerative diseases.

METHODS

We used different search terms like "oxidative stress and neurological disorders" "free radicals and neurodegenerative disorders" "oxidative stress, free radicals, and neurological disorders" and "association of oxidative stress with the name of disorders taken from the list of neurological disorders. We tried to summarize the source, biological effects, and physiologic functions of ROS.

RESULTS

Finally, it was noted that more than 190 neurological disorders are associated with oxidative stress.

CONCLUSION

More elaborated studies in the future will certainly help in understanding the exact mechanism involved in neurological diseases and provide insight into revelation of therapeutic targets.

Can a Micronutrient Mixture Delay the Onset and Progression of Symptoms of Single-Point Mutation Diseases?

Single-point mutation diseases in which substitution of one nucleotide with another in a gene occurs include familial Alzheimer's disease (fAD), familial Parkinson's disease (fPD), and familial Creutzfeldt-Jacob disease (fCJD) as well as Huntington's disease (HD), sickle cell anemia, and hemophilia. Inevitability of occurrence of these diseases is certain. However, the time of appearance of symptoms could be influenced by the diet, environment, and possibly other genetic factors. There are no effective approaches to delay the onset or progression of symptoms of these diseases. The fact that increased oxidative stress and inflammation significantly contribute to the initiation and progression of these point mutation diseases shows that antioxidants could be useful. The major objectives are (a) to present evidence that increased oxidative stress and chronic inflammation are associated with selected single-point mutation diseases, such as fAD, fPD, and fCJD, HD, sickle cell anemia, and hemophilia; (b) to describe limited studies on the role of individual antioxidants in experimental models of some of these diseases; and (c) to discuss a rationale for utilizing a comprehensive mixture of micronutrients, which may delay the development and progression of symptoms of above diseases by simultaneously reducing oxidative and inflammatory damages.Key teaching pointsSelected single-point mutation diseases and their pattern of inheritanceCharacteristics of each selected single-point mutation diseaseEvidence for increased oxidative stress and inflammation in each diseasePotential reasons for failure of single antioxidants in human studiesRationale for using a comprehensive mixture of micronutrients in delaying the onset and progression of single-point mutation diseases.

Altered Ca2+ homeostasis induces Calpain-Cathepsin axis activation in sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most prevalent form of human prion disease and it is characterized by the presence of neuronal loss, spongiform degeneration, chronic inflammation and the accumulation of misfolded and pathogenic prion protein (PrP^Sc). The molecular mechanisms underlying these alterations are largely unknown, but the presence of intracellular neuronal calcium (Ca²⁺) overload, a general feature in models of prion diseases, is suggested to play a key role in prion pathogenesis.

Here we describe the presence of massive regulation of Ca²⁺ responsive genes in sCJD brain tissue, accompanied by two Ca²⁺-dependent processes: endoplasmic reticulum stress and the activation of the cysteine proteases Calpains 1/2. Pathogenic Calpain proteins activation in sCJD is linked to the cleavage of their cellular substrates, impaired autophagy and lysosomal damage, which is partially reversed by Calpain inhibition in a cellular prion model. Additionally, Calpain 1 treatment enhances seeding activity of PrP^Sc in a prion conversion assay. Neuronal lysosomal impairment caused by Calpain over activation leads to the release of the lysosomal protease Cathepsin S that in sCJD mainly localises in axons, although massive Cathepsin S overexpression is detected in microglial cells. Alterations in Ca²⁺ homeostasis and activation of Calpain-Cathepsin axis already occur at pre-clinical stages of the disease as detected in a humanized sCJD mouse model.

Altogether our work indicates that unbalanced Calpain-Cathepsin activation is a relevant contributor to the pathogenesis of sCJD at multiple molecular levels and a potential target for therapeutic intervention.

Rapid screening and identification of phenolic antioxidants in Hydrocotyle sibthorpioides Lam. by UPLC-ESI-MS/MS

The aim of the study was to identify the phenolic compounds present in Hydrocotyle sibthorpioides (HS), Centella asiatica (CA) and Amaranthus viridis (AV) extracts and investigate their respective antioxidant activities. Herein, an ultra-high pressure liquid chromatography-mass spectrometer (UPLC-MS/MS) analytical method has been developed for the separation, and systematic characterization of the phenolic compounds in HS, CA and AV extracts and was compared along with ten standard phenolic compounds. Additionally, in vitro antioxidant activity of the phenolic compounds was also determined. The HS extract revealed excellent antioxidant activity such as 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (IC50=19.7 ± 1.2 μg/mL), total reduction capability (0.169 ± 0.003 at 100 μg/mL), nitric oxide radical scavenging activity (IC50=39.33 ± 3.2 μg/mL), metal chelating activity (IC50=56.51 ± 3.6 μg/mL) and inhibition of lipid peroxidation (IC50=12.34 ± 2.3 μg/mL) as compared to CA and AV extracts. Furthermore, catechin, epicatechin, quercetin and chlorogenic acid were found to be the major components responsible for the antioxidant activity of the HS extract as evidenced from UPLC-MS/MS. Taken together, this study demonstrates the promising antioxidant properties of the HS extract, which can further be utilized in various pharmaceutical, food, and agricultural applications.

Isoprostanes and neuroprostanes as biomarkers of oxidative stress in neurodegenerative diseases

Accumulating data shows that oxidative stress plays a crucial role in neurodegenerative disorders. The literature data indicate that in vivo or postmortem cerebrospinal fluid and brain tissue levels of F2-isoprostanes (F2-IsoPs) especially F4-neuroprotanes (F4-NPs) are significantly increased in some neurodegenerative diseases: multiple sclerosis, Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease. Central nervous system is the most metabolically active organ of the body characterized by high requirement for oxygen and relatively low antioxidative activity, what makes neurons and glia highly susceptible to destruction by reactive oxygen/nitrogen species and neurodegeneration. The discovery of F2-IsoPs and F4-NPs as markers of lipid peroxidation caused by the free radicals has opened up new areas of investigation regarding the role of oxidative stress in the pathogenesis of human neurodegenerative diseases. This review focuses on the relationship between F2-IsoPs and F4-NPs as biomarkers of oxidative stress and neurodegenerative diseases. We summarize the knowledge of these novel biomarkers of oxidative stress and the advantages of monitoring their formation to better define the involvement of oxidative stress in neurological diseases.

Antioxidant effect of estrogen on bovine aortic endothelial cells

OBJECTIVE

This study discussed the role of estrogen as an antioxidant in the damage of vascular endothelial cells.

DESIGN

We treated bovine aortic endothelial cells (bAEC) either with 1mM of H(2)O(2) alone or with 1 microM of 17beta-estradiol (E(2)) for 24h followed by 1mM of H(2)O(2) for 3h. The cell survival was evaluated by MTT assay, cellular apoptosis by fluorescence activated cell sorter (FACS) and Hoechst 33342 staining, oxidative stress by intracellular reactive oxygen species (ROS) and apoptosis after oxidative stress by western blotting for phospho-p38, p38, and Bcl-2.

RESULTS

MTT assay showed that bAEC viability was reduced to 55.7+/-3.0% and 39.1+/-3.7% after 30 and 60 min of H(2)O(2) treatment, respectively. E(2) and H(2)O(2) treated cells did not show significant decrease in the cell survival. Similarly the FACS analysis and Hoechst 33342 stain showed that the latter decreased cellular apoptosis induced by H(2)O(2). Intracellular ROS increased by 181.6+/-68.9% in the former and by 37.0+/-3.9% in the latter (P<0.05). The expression of phospho-p38 mitogen-activated protein kinase (MAPK) was higher in the latter.

CONCLUSIONS

E(2) mediates antioxidant effects on the oxidative stress induced by H(2)O(2). This antioxidant effect on bAEC may elucidate the scientific basis of hormone therapy for maintaining cardiovascular integrity in postmenopausal women.

Genomic and post-genomic analyses of human prion diseases

Prion diseases share common features of neurodegenerative disorders, infectious diseases and pathologies linked to misfolded proteins. Whether these aspects are independently and fortuitously present in prion diseases or are somewhat linked together remains unsettled, but the contribution of genomic, proteomic, metabolomic and spectroscopic techniques might give insights into this puzzle, and likely give hope for therapy to patients. Although the prion protein gene (PRNP) governs most of the clinical and pathological features of prion diseases and plays a pivotal role in determining host susceptibility, there are still many uncertainties and unknown risk factors that need to be clarified and identified. Several genes, other than PRNP, have recently been found to be associated with a risk of developing sporadic or variant Creutzfeldt-Jakob disease, but these novel data have been produced in a relatively small number of patients and controls and, therefore, need further confirmation. The same criticism applies to the identification of the over 20 new cerebrospinal fluid or plasma markers of disease. Some of these markers seem related to the massive brain damage that occurs, rather than being specific to prion infection. Nevertheless, genomic and post-genomic approaches have shown that these techniques are very powerful, and the best way to overcome the scantiness of samples would be to encourage strong collaboration between different centers of excellence in prion diseases. In this review, we describe the most recent and outstanding advances offered by genomics and post-genomics analyses in the field of human prion diseases.

Oxidation, glycoxidation, lipoxidation, nitration, and responses to oxidative stress in the cerebral cortex in Creutzfeldt-Jakob disease

Gel electrophoresis and Western blotting of frontal cortex homogenates have been carried out in sporadic Creutzfeldt-Jakob disease (CJD) cases and age-matched controls to gain understanding of the expression of glycation-end products (AGEs). N-Carboxymethyl-lysine (CML) and N-carboxyethyl-lysine (CEL) were used as markers of glycoxidation; 4-hydroxynonenal (4-HNE) and malondialdehyde-lysine (MDAL) as markers of lipoxidation; and nitrotyrosine (N-tyr) and neuronal, endothelial and inducible nitric oxide synthase (nNOS, eNos and iNos) as markers of protein nitration and as sources of NO production, respectively. Age receptor (RAGE) and Cu/Zn superoxide dismutase (SOD1) and Mn superoxide dismutase (SOD2) expression levels were also examined. The results showed a significant increase in the expression levels of AGE (p<0.05), CEL (p<0.001), RAGE (p<0.05), HNE-modified proteins (p<0.01), nNOS, iNOS and eNOS (p<0.01 and p<0.05, respectively), N-tyr (p<0.05), and SOD1 (p<0.05) and SOD2 (p<0.05). No relationship was observed between PrP genotype, PrP type, PrP burden, and expression levels of oxidative stress markers. The present findings demonstrate oxidative, glycoxidative, lipoxidative and nitrative protein damage, accompanied by increased oxidative responses, in the cerebral cortex in sporadic CJD. These results provide support for the concept that oxidative stress may have important implications in the pathogenesis of prion diseases.

Reactive oxygen species as signaling molecules in cardiovascular differentiation of embryonic stem cells and tumor-induced angiogenesis

Besides the well known pathophysiological impact of oxidative stress in cardiovascular disease, reactive oxygen species (ROS) generated at low concentrations exert a role as signaling molecules that are involved in signal transduction cascades of numerous growth factor-, cytokine-, and hormone-mediated pathways, and regulate biological effects such as apoptosis, cell proliferation, and differentiation. Embryonic stem cells have the capacity to differentiate into the cardiovascular cell lineage. Furthermore, upon confrontation culture with tumor tissue, they form blood vessel-like structures that induce tumor-induced angiogenesis within tumor tissues. The role of ROS in cardiovascular differentiation of embryonic stem cells appears to be antagonistic. Whereas continuous exposure to ROS results in inhibition of cardiomyogenesis and vasculogenesis, pulse chase exposure to low-level ROS enhances differentiation toward the cardiomyogenic as well as vascular cell lineage. This review summarizes the current knowledge of ROS-induced cardiovascular differentiation of embryonic stem cells as well as the role of ROS in tumor-induced angiogenesis.

Evaluation of oxidative stress measurements in obstructive sleep apnea syndrome

Assessment of reactive oxygen species (ROS) is highly important in neurodegenerative disorders and neuroleptic treatment. However, conflicting results have been reported, which may arise from methodological difficulties. Obstructive sleep apnea (OSA) syndrome with episodic hypoxia-reoxygenation is proposed as a human model for the investigation of ROS measurements. Despite a broad analytical approach comprising lipid peroxidation and amino acid oxidation products, oxidative DNA damage, and activity of the antioxidant defense, only plasma malondialdehyde (MDA) and urinary o,o'-dityrosine seemed to be appropriate, robust biomarkers of oxidative stress, which are also simple enough for routine clinical use. MDA concentrations correlated with a duration of nocturnal desaturation below 85% (r = 0.77, p<0.0005), and o,o'-dityrosine levels decreased after therapy (p<0.05) as a function of baseline concentrations (r = -0.61, p<0.05). Gender effects in ROS generation also have to be considered. At present, we recommend the application of several oxidative stress measurements at different time points, preferably involving plasma MDA and urinary o,o'-dityrosine.

Creutzfeldt-Jakob Disease and Homocysteine Levels in Plasma and Cerebrospinal Fluid

BACKGROUND

There is evidence that homocysteine contributes to various neurodegenerative disorders.

OBJECTIVE

To assess the values of homocysteine in patients with Creutzfeldt-Jakob disease (CJD) in both cerebrospinal fluid (CSF) and plasma.

METHODS

STUDY DESIGN

Case control study. Total homocysteine was quantified in CSF and plasma samples of CJD patients (n=13) and healthy controls (n=13).

RESULTS

Mean values in healthy controls: 0.15 micromol/l +/- 0.07 (CSF) and 9.10 micromol/l +/- 2.99 (plasma); mean values in CJD patients: 0.13 micromol/l +/- 0.03 (CSF) and 9.22 micromol/l +/- 1.81 (plasma). No significant differences between CJD patients and controls were observed (Mann-Whitney U, p >0.05).

CONCLUSIONS

The results indicate that the CSF and plasma of CJD patients showed no higher endogenous levels of homocysteine as compared to normal healthy controls. These findings provide no evidence for an additional role of homocysteine in the pathogenetic mechanisms underlying CJD neurodegeneration.

The risk of transmission of variant Creutzfeldt–Jakob disease via contact lenses and ophthalmic devices

This review collated the available information regarding the risk of transmission of variant Creutzfeldt-Jakob disease (vCJD) via contact lenses and other ophthalmic devices. The topics examined include: the emerging background science of the unconventional infective agent, the prion, particularly those factors affecting transmission; the estimates of the number of undiagnosed infective individuals; and evidence of infectivity in the external eye. Despite many uncertainties in the literature, we conclude that cross-infection is theoretically possible. An assessment of the extensive search for a complete inactivation procedure resulted in the recommendation of the use of sodium hypochlorite (NaOCl), which does not appear to distort rigid lenses. Further tests are required for other devices.

Increased lipid peroxidation in cerebrospinal fluid and plasma from patients with Creutzfeldt-Jakob disease

Oxidative pathomechanisms play an important role in neurodegenerative diseases like Alzheimer's disease (AD). It has been shown that lipid peroxidation in cerebrospinal fluid (CSF) and plasma is increased in AD. To assess the role of oxidative stress in Creutzfeldt-Jakob disease (CJD), we investigated the oxidizability of lipids, the lipid composition and the levels of the antioxidants ascorbate and alpha-tocopherol in CSF and plasma of 15 CJD patients and 12 neurologically healthy controls. CSF and plasma lipid peroxidation was increased in CJD patients and polyunsaturated fatty acids were reduced in CSF of these patients. Ascorbate levels were lower in CSF and plasma of CJD patients, while alpha-tocopherol was found to be decreased in CSF but not in plasma. These results support the hypothesis that oxidative mechanisms are involved in the pathogenesis of CJD and provide a rationale for the use of antioxidants in the therapy of this disease.

Lipid peroxidation in neurodegeneration: new insights into Alzheimer's disease

Imbalances of oxidative homeostasis and lipid peroxidation have been revealed as important factors involved in neurodegenerative disorders such as Alzheimer's disease. The brains of patients with Alzheimer's disease contain increased levels of lipid-peroxidation products such as 4-hydroxy-2-nonenal or acrolein, and enhanced lipid peroxidation can also be detected in cerebrospinal fluid and plasma from such patients. Recent research revealed that the interplay of transition metals, amyloid-beta peptide and lipid peroxidation might be responsible for increased oxidative stress and cell damage in this disease. In particular, the contrasting roles of amyloid-beta peptide, as a possible transition metal-chelating antioxidant for lipoproteins and a pro-oxidant when aggregated in brain tissue, has been the focus of discussion recently. In this context, lipid peroxidation has to be seen as an important part of the pathophysiological cascade in Alzheimer's disease, and its measurement in body fluids might serve as a therapy control for Alzheimer's disease and other neurodegenerative diseases.

Oxidative stress and an altered methionine metabolism in alcoholism

The exact mechanism of brain atrophy in patients with chronic alcoholism remains unknown. There is growing evidence that chronic alcoholism is associated with oxidative stress and with a derangement in sulphur amino acid metabolism (e.g. ethanol-induced hyperhomocysteinemia). Furthermore, it has been reported that homocysteine induces neuronal cell death by stimulating N-methyl-D-aspartate receptors as well as by producing free radicals. To further evaluate this latter hypothesis we analysed serum levels of both homocysteine and markers of oxidative stress (malondialdehyde) in alcoholic patients who underwent withdrawal from alcohol. Homocysteine and malondialdehyde were quantified by high performance liquid chromatography (HPLC) in serum samples of 35 patients (active drinkers). There was a significant correlation (P<0. 01) between blood alcohol concentration and elevated homocysteine (Spearman's r=0.71) and malondialdehyde (r=0.90) levels on admission. In addition, homocysteine and malondialdehyde levels were found to be significant decreased after 3 days of withdrawal treatment (Wilcoxon test: homocysteine, Z=-5.127; malondialdehyde, Z=-3.120; P<0.01). We postulate that excitatory neurotransmitters and mechanisms of oxidative stress in patients with chronic alcoholism may partly mediate excitotoxic neuronal damage and hereby cause brain shrinkage.