Sagrario Martín-Aragón

Differences of peripheral inflammatory markers between mild cognitive impairment and Alzheimer's disease.

Multiple pathogenic factors may contribute to the pathophysiology of Alzheimers disease (AD). Peripheral markers have been used to assess biochemical alterations associated with AD and mild cognitive impairment (MCI) involved in its pathophysiology. The present study was conducted to evaluate inflammatory peripheral markers in elderly patients with MCI, patients with AD and normal elderly subjects. We measured plasma levels of different cytokines (IL-6, TNF-alpha and IFN-alpha) and platelet levels of cyclooxigenase-2 (COX-2) from 34 patients with MCI, 45 patients with AD and 28 age-matched control subjects. MCI and AD patients showed similarities in TNF-alpha and COX-2 levels, and differences in IL-6 and INF-alpha. Whereas augmented IL-6 levels have been found in AD patients, a significant increase in INF-alpha has been detected only in patients with MCI possibly associated with the depression stage frequently found in cognitive impairment. In conclusion, inflammatory response may be an early factor in AD development and these changes in circulating markers are possibly related to the progression of MCI to AD.

Peripheral levels of glutathione and protein oxidation as markers in the development of Alzheimer's disease from Mild Cognitive Impairment.

There is a great interest in the relationship between Mild Cognitive Impairment (MCI) and the progression to Alzheimers disease (AD). Several studies show the importance of oxidative stress in the pathogenesis of AD. The purpose of this study was the link between oxidative damage, MCI and AD. It analysed protein carbonyls and erythrocyte glutathione system plasma levels of 34 subjects with MCI, 45 subjects with AD and 28 age-matched control subjects. The results showed an increase in protein modification, a decrease in GSH levels and GSH/GSSG ratio in AD and MCI patients compared to age-matched control subjects (p<0.05). The present study shows that some peripheral markers of oxidative stress appear in MCI with a similar pattern to that observed in AD, which suggests that oxidative stress might represent a signal of the AD pathology. AD and MCI are biochemically equivalent. MCI does not necessarily need to progress to AD on a biochemical level.

Quercetin and rutin exhibit antiamyloidogenic and fibril-disaggregating effects in vitro and potent antioxidant activity in APPswe cells.

AIMS Quercetin and rutin have been reported to exert numerous pharmacological activities, such as free-radical scavenging, effects on immune and inflammatory cell functions, and could have benefits in Alzheimers disease (AD) by mitigating cellular damage induced by reactive oxygen species (ROS). A key event in AD is the conversion of the β-amyloid (Aβ) peptide into amyloid plaques in the brain. Preventing Aβ aggregation is pursued as a therapeutic strategy for treating AD. In this study, antiamyloidogenic and antioxidant properties of quercetin and rutin were investigated. MAIN METHODS We investigated whether quercetin and rutin affect Aβ25-35 fibrillogenesis, BACE activity and the cellular redox status. KEY FINDINGS Quercetin and rutin inhibited the formation of Aβ fibrils and disaggregated Aβ fibrils. β-secretase enzyme (BACE) activity was significantly inhibited by rutin. To resemble the in vivo Aβ-induced neurotoxicity we used a cell system overexpressing APP Swedish mutation (APPswe), which is associated with early-onset familial AD, and may promote oxidative stress due to the enhanced Aβ production. Quercetin and rutin decreased almost completely ROS generation in H(2)O(2)-treated APPswe cells. Both flavonoids increased intracellular GSH content and the redox status, and for rutin this effect was concentration dependent. Besides, quercetin and rutin diminished the index of lipid peroxidation in comparison with control APPswe cells at all concentrations tested. SIGNIFICANCE Our findings may provide an explanation of the neuroprotective effect of quercetin and rutin, suggesting that they could be dietary phytochemicals able to revert the β-amyloid toxicity in vivo.

Modifications on antioxidant capacity and lipid peroxidation in mice under fraxetin treatment

Fraxetin belongs to an extensive group of natural phenolic antioxidants. We have investigated the modifications in endogenous antioxidant capacity; superoxide dismutase (SOD), catalase (CAT), total and selenium‐dependent glutathione peroxidases (GPx) and glutathione reductase (GR) and stress index; glutathione disulphide (GSSG)/reduced glutathione (GSH) ratio and thiobarbituric acid‐reactive substances (TBARs) in liver and brain supernatants of C57BL/6J male 12‐month‐old mice under fraxetin treatment for 30 days.

Effects of the antioxidant (6,7-dihydroxycoumarin) esculetin on the glutathione system and lipid peroxidation in mice

The attempt to retard senescence by environmental manipulation includes the use of nutrients or drugs that decrease the oxidative damage to tissues associated with aging. The effects of esculetin treatment (25 mg/kg, orally for 30 days), a phenolic antioxidant compound, on the glutathione system and lipid peroxidation were examined in liver supernatants from male C57BL/6J mice. The effects of esculetin were compared to treatment with 3,5-di-terc-butyl-4-hydroxytoluene (BHT), a well-known synthetic phenolic antioxidant. Reduced glutathione (GSH) concentration in liver supernatants was only increased significantly in esculetin-treated mice compared to control animals, whereas the concentration of oxidized glutathione (GSSG) was significantly decreased by BHT treatment compared to the control group. The GSSG/GSH ratio was significantly lower in esculetin and BHT groups than in the control group. The decrease in this ratio was greater in BHT-treated mice than in esculetin-treated mice. Increases in glutathione reductase (GR) activity were observed with both treatments, although BHT resulted in a superior induction of this activity compared to esculetin. The extent of decline in the GSSG/GSH ratio was correlated with the increase in GR activity. The formation of thiobarbituric acid-reactive substances (TBARs), an index of stress, was lower following treatment with esculetin and BHT compared to control mice (although not significant). This index was very similar for both treatments. Based on the level of TBARs obtained in this study, the accumulation of lipid peroxides declines when the GSH levels are enhanced or GSSG levels are decreased. Finally, we found similar antioxidant effects in vivo with esculetin and BHT treatments and a decrease in the oxidative damage evaluated. The enhancement of glutathione status following esculetin treatment could be a possible defense strategy for the organism under ‘stress conditions’ and may be related to the delay of age-dependent degenerative disorders.

Antioxidant action of Vaccinium myrtillus L.

Vaccinium myrtillus L. is a well‐known bilberry shrub belonging to the Ericaceae family. It has been reported to have multiple pharmacological activities from its anthocyanosidic fraction: ophthalmic, vasoprotective, antiinflammatory, wound‐healing, antiulcer and antiatherosclerosis. It is to be expected that several activities might be related to a possible antioxidant action from anthocyanosides. An anthocyanoside complex extract from Vaccinium myrtillus was tested for its ability to inhibit lipid peroxidation and to scavenge hydroxyl and superoxide radicals. An antiperoxidative action of this V. myrtillus extract was assayed by the Fe3+‐ADP/NADPH method in rat liver microsomes. Interaction of this anthocyanoside extract with hydroxyl radicals was evaluated in the Fe3+‐EDTA‐H2O2 deoxyribose system. The superoxide scavenging action of this plant extract was established according to the reaction of phenazine methasulphate in the presence of NADH and molecular oxygen. The anthocyanoside complex extract was able to inhibit lipid peroxidation (IC50 = 50.28 μg/mL) and to scavenge superoxide anion (IC50 < 25 μg/mL). The ability to remove hydroxyl radical exerted by this extract was detectable from 50 μg/mL of extract in the reaction mixture.

In vitro antiamyloidogenic properties of 1,4-naphthoquinones.

The aim of this study is to find out whether several 1,4-naphthoquinones (1,4-NQ) can interact with the amyloidogenic pathway of the amyloid precursor protein processing, particularly targeting at β-secretase (BACE), as well as at β-amyloid peptide (Aβ) aggregation and disaggregating preformed Aβ fibrils. Compounds bearing hydroxyl groups at the quinoid (2) or benzenoid rings (5, 6) as well as some 2- and 3-aryl derivatives (11-15) showed BACE inhibitory activity, without effect on amyloid aggregation or disaggregation. The halogenated compounds 8 and 10 were selective for the inhibition of amyloid aggregation. On the other hand, 1,4-naphthoquinone (1), 6-hydroxy-1,4-naphthoquinone (4) and 2-(3,4-dichlorophenyl)-1,4-naphthoquinone (26) did not show any BACE inhibitory activity but were active on amyloid aggregation and disaggregation preformed Aβ fibrils. Juglone (5-hydroxy-1,4-naphthoquinone (3), and 3-(p-hydroxyphenyl)-5-methoxy-1,4-napththoquinone (19) were active on all the three targets. Therefore, we suggest that 1,4-NQ derivatives, specially 3 and 19, should be explored as possible drug candidates or lead compounds for the development of drugs to prevent amyloid aggregation and neurotoxicity in Alzheimers disease.

Processing of the Platelet Amyloid Precursor Protein in the Mild Cognitive Impairment (MCI)

It has been suggested that mild cognitive impairment (MCI) patients deteriorate faster than the healthy elderly population and have an increased risk of developing dementia. Certain blood molecular biomarkers have been identified as prognostic markers in Alzheimer’s disease (AD). The present study was aimed to assess the status of the platelet amyloid precursor protein (APP) metabolism in MCI and AD subjects and establish to what extent any variation could have a prognostic value suggestive of predictive AD in MCI patients. Thirty-four subjects diagnosed with MCI and 45 subjects with AD were compared to 28 healthy elderly individuals for assessing for protein levels of APP, β-APP cleaving enzyme 1 (BACE1), presenilin 1 (PS1) and a disintegrin and metalloproteinase-10 (ADAM-10) by western blot, and for the enzyme activities of BACE1 and γ-secretase by using specific fluorogenic substrates, in samples of platelets. A similar pattern in the healthy elderly and MCI patients was found for BACE1 and PS1 levels. A reduction of APP levels in MCI and AD patients compared with healthy elderly individuals was found. Augmented levels of ADAM-10 in both MCI and AD were displayed in comparison with age-matched control subjects. The ratio ADAM-10/BACE1 was higher for the MCI group versus AD group. Whereas BACE1 and PS1 levels were only increased in AD regarding to controls, BACE1 and γ-secretase activities augmented significantly in both MCI and AD groups. Finally, differences and similarities between MCI and AD patients were observed in several markers of platelet APP processing. Larger sample sets from diverse populations need to be analyzed to define a signature for the presence of MCI or AD pathology and to early detect AD at the MCI stage.

Effects of fraxetin on glutathione redox status.

Abstract We have evaluated the effects of an oral treatment of mice with fraxetin (25 mg/kg for 30 days) on the glutathione system (GSH, GSSG, and GSSG/GSH ratio as stress index), glutathione reductase (GR) and glutathione peroxidase (GPx) in liver supernatants from male C57BL/6J mice (18-month old). A significant antioxidant effect in vivo was found under this treatment by a decrease in the GSSG/GSH ratio and an increased activity of GR compared with the control mice. GSSG rate and GSSG/GSH ratio were correlated with the decline of GPx activity. Our results of increased GR activity could be considered as a supercompensation in glutathione redox status that involves a decrease in the accumulation of GSSG, as well as, in GSSG /GSH ratio. Finally, we suggest that this possible mechanism of supercompensation could lead to an enhancement in the average life span.

Discovery of alkenylboronic acids as neuroprotective agents affecting multiple biological targets involved in Alzheimer’s disease

Alkenylboronic acids have shown important biological activities that contribute to neuroprotection. We have determined their influence on the β-amyloid (βA) aggregation process, β-secretase and acethylcholinesterase activities on cell-free systems, on the redox and lipid peroxidation status, and on the vulnerability to apoptotic death in an APPswe neuroblastoma cell line, before and after hydrogen peroxide treatment. We have discovered that 2-arylvinylboronic acids and some of their esters possess a set of properties which makes them highly useful as neuroprotective agents affecting multiple biological targets involved in AD. These properties are not paralleled by the related 2-arylboronic acids.