Pathway and mechanism of oxidative stress in Alzheimer's disease

The Microbiome and Alzheimer's Disease: Potential and Limitations of Prebiotic, Synbiotic, and Probiotic Formulations

The Microbiome has generated significant attention for its impacts not only on gastrointestinal health, but also on signaling pathways of the enteric and central nervous system via the microbiome gut-brain axis. In light of this, microbiome modulation may be an effective therapeutic strategy for treating or mitigating many somatic and neural pathologies, including neurodegenerative disorders. Alzheimer's disease (AD) is a chronic neurodegenerative disease that interferes with cerebral function by progressively impairing memory, thinking and learning through the continuous depletion of neurons. Although its etiopathogenesis remains uncertain, recent literature endorses the hypothesis that probiotic, prebiotic and synbiotic supplementation alters AD-like symptoms and improves many of its associated disease biomarkers. Alternatively, a dysfunctional microbiota impairs the gut epithelial barrier by inducing chronic gastric inflammation, culminating in neuroinflammation and accelerating AD progression. The findings in this review suggest that probiotics, prebiotics or synbiotics have potential as novel biological prophylactics in treatment of AD, due to their anti-inflammatory and antioxidant properties, their ability to improve cognition and metabolic activity, as well as their capacity of producing essential metabolites for gut and brain barrier permeability.

Berberine alleviates amyloid β25-35-induced inflammatory response in human neuroblastoma cells by inhibiting proinflammatory factors

The present study investigated the effect of berberine (BBR) on amyloid β 25-35 (Aβ25-35)-induced inflammatory response in human neuroblastoma cells. To model the inflammatory response observed in the central nervous system of patients with Alzheimer's disease, SH-SY5Y and SK-N-SH neuroblastoma cells were induced by Aβ25-35 (5 µM) for 24 h. Subsequently, cells were treated with BBR or indomethacin for 2 h. The cell survival rate was determined by the MTT assay. The activity of lactate dehydrogenase (LDH) in the cell culture medium was examined by spectrophotometry. The expression levels of inflammatory factors prostaglandin E2 (PGE2) and tumor necrosis factor-α (TNF-α) were determined by ELISA assays. The mRNA and protein expression levels of interleukin (IL)-1β, cyclooxygenase 2 (COX-2) and tumor necrosis factor receptor 1 (TNFR1) were measured by reverse-transcription-quantitative polymerase chain reaction and Western blotting, respectively. The results indicated that, treatment with Aβ25-35 increased the expression levels of PGE2 and TNF-α, increased the activity of LDH, and up-regulated the mRNA and protein expression of COX-2, IL-1β, and TNFR1. Treatment with BBR down-regulated the expression levels of PGE2 and TNF-α, decreased the activity of LDH, and downregulated the mRNA and protein expression of COX-2, IL-1β, and TNFR1. Taken together, the present results suggested that BBR suppressed the inflammatory response induced by Aβ25-35 in neuroblastoma cells. The mechanism of action may be associated with the inhibition of proinflammatory factors.

Association between tea consumption and risk of cognitive disorders: A dose-response meta-analysis of observational studies

Background

The epidemiological evidence for a dose-response relationship between tea consumption and risk of cognitive disorders is sparse. The aim of the study was to summarize the evidence for the association of tea consumption with risk of cognitive disorders and assess the dose-response relationship.

Methods

We searched electronic databases of Pubmed, Embase, and Cochrane Library (from 1965 to Jan 19, 2017) for eligible studies that published in the international journals. A random-effects model was used to pool the most adjusted odds ratios (ORs) and the corresponding 95% confidence intervals (CIs).

Results

Seventeen studies involving 48,435 participants were included in our study. The meta-analysis showed that a higher tea consumption was associated with a significant reduction in the risk of cognitive disorders (OR=0.73, 95% CI: 0.65-0.82). When considering the specific types of tea consumption, the significantly inverse association is only found in green tea consumption (OR=0.64, 95% CI: 0.53-0.77) but not in black/oolong tea consumption (OR=0.75, 95% CI: 0.55-1.01). Dose-response meta-analysis indicated that tea consumption is linearly associated with a reduced risk of cognitive disorders. An increment of 100 ml/day, 300 ml/day, and 500 ml/day of tea consumption was associated with a 6% (OR=0.94, 95% CI: 0.92-0.96), 19% (OR=0.81, 95% CI: 0.74-0.88), and 29% (OR=0.71, 95% CI: 0.62-0.82) lower risk of cognitive disorders.

Conclusions

Tea consumption is inversely and linearly related to the risk of cognitive disorders. More studies are needed to further confirm our findings.

Carbonic anhydrase activity from the gilthead sea bream (Sparus aurata) liver: the toxicological effects of heavy metals

Many studies have shown that metal ions may lead to oxidative stress in biological systems. Accordingly, DNA damage, protein modification, enzyme inhibition and activation, lipid peroxidation and many other effects may occur in living organisms. Many different formations of metal ions may enter human cells along with water, air, and various foods, and humans are negatively affected by these conditions, either directly or indirectly. These effects may cause irreversible damage to human metabolism. In this study, the toxicological effects of heavy metals on carbonic anhydrase enzyme activity from the gilthead sea bream liver were investigated. The carbonic anhydrase enzyme was purified via affinity chromatography and had a specific activity of 6775.5EUmg(-1). The kinetics and characteristic properties, such as optimum pH, stable pH, optimum temperature, activation energy (Ea), activation enthalpy (ΔH), Q10, Km, and Vmax, were determined for the purified enzyme SDS-polyacrylamide gel electrophoresis showed a single band and molecular weight of the subunit was approximately 25kDa. Cd(II), Cu(II), Ni(II) and Ag(I) inhibited the enzyme activity in vitro. The type of inhibition and Ki values for these metals were calculated from Lineweaver-Burk plots as 17.74mM, 36.20mM, 12.85mM and 0.025mM for Cd(II), Cu(II), Ni(II) and Ag(I), respectively. All the metals were noncompetitive inhibitors.

Protective effect of galantamine against oxidative damage using human lymphocytes: a novel in vitro model

BACKGROUND AND AIMS

Neurodegenerative disorders such as Alzheimer's disease are characterized in the initial stages by an increase in reactive oxygen species that trigger apoptosis or programmed cell death. It has been suggested that the synthetic alkaloid galantamine may offer protection against this cell loss. This investigation sought to assess the protective effect of galantamine against oxidative damage induced by hydrogen peroxide (H2O2) using human lymphocytes cultured in vitro as a model.

METHODS

Cell death can be measured indirectly using cell viability testing with trypan blue. Determination of the galantamine concentrations used was made possible by the negative correlation found between galantamine concentration and average mitotic index (MI).

RESULTS

Average viability of lymphocytes treated with low and medium concentrations of galantamine was significantly higher than the control.

CONCLUSION

Galantamine does indeed demonstrate a protective capacity against cell damage induced by hydrogen peroxide. This finding supports the possible use of the drug in treatment of neurodegenerative diseases related to oxidative stress.

Antioxidant potential and radical-scavenging effects of flavonoids from the leaves of Psidium cattleianum grown in French Polynesia

Psidium cattleianum J. Sabine (Myrtaceae) is a traditional medicinal plant in French Polynesia. The leaves and roots possess many medicinal properties. These effects may be correlated with the presence of antioxidant compounds. Seven flavonoids along with a benzoic acid were isolated from the leaves of P. cattleianum. The compounds indicated strong antioxidant and radical-scavenging activities in ALP, DPPH(·), ABTS(·-) and ORAC assays. This study demonstrates that the leaves of P. cattleianum possess main compounds with interesting antioxidant and radical-scavenging activities, as clarified by four biological assays. Our findings may justify the use of these leaves in the traditional medicine of French Polynesia. Among the total eight known compounds, reynoutrin and luteolin were isolated for the first time from the genus Psidium.

Protective effects of 1,3-diaryl-2-propen-1-one derivatives against H₂O₂ -induced damage in SK-N-MC cells

Alzheimer's disease (AD) is an age-related neurodegenerative disorder of the central nervous system resulting in memory loss and dementia. Some of the associated pathogenic changes are amyloid peptide aggregation, excitotoxicity, oxidative stress and inflammation. Oxidative stress plays an indispensable role in the pathophysiology of AD. Therefore, antioxidant therapies appear to be promising approaches in dealing with AD patients. In that line, we evaluated the free radical scavenging capabilities of 13 different chalcones (1,3-diphenyl-2-propen-1-one) derivatives against the free-radical damaging effects of hydrogen peroxide (H₂O₂) on the SK-N-MC neuroblastoma cell line. Pretreatment of the cells for 3 h with 20 µ m of each of these derivatives (compounds 8-20) followed by exposure to 300 µ m H₂O₂ for 24 h indicated that all compounds, except compound 20, were capable of restoring the viabilities of cells relative to the control (H₂O₂ -treated) cells. The destructive effect of H₂O₂ on the adhesive behavior of the cells was almost totally restored by each of the derivatives. In addition, each of the derivatives except compounds 20 and 14 significantly reduced the extent of lipofuscin formation among the cells time-dependently. Despite these activities, some of the derivatives, such as compounds 12 and 19, did not reduce the H₂O₂ -induced intracellular ROS (reactive oxygen species) levels, meaning that these two derivatives act through a different mechanism other than free-radical scavenging activity. On the other hand, for those derivatives acting as anti-oxidants, structure-activity evaluation clearly revealed that the hydroxyl group of vanillin ring is required for their free-radical scavenging activities.