Search Results (5)

Eucalyptus camaldulensis of the Myrtaceae family shows high resistance to aluminum (Al) ions and contains various compounds such as steroids, terpenoids, saponins, flavonoids, glycosides, alkaloids, and tannins. Although the ellagitannin oenothein B (12) isolated from E. camaldulensis exhibits remarkable properties for Al detoxification, likely contributing to its Al resistance, other ellagitannin oligomers present in E. camaldulensis have not been investigated in detail. In this study, novel dimeric and trimeric ellagitannin oligomers eucarpanin D₂ (1) and eucamalin A (2), together with known gallotannins (7, 8, and 10), monomeric ellagitannins (4–6, and 11), and dimeric ellagitannins (3, 9, and 12–14), were isolated from E. camaldulensis leaves. The structures of these novel compounds were elucidated based on their chemical and physicochemical properties, including the orientations of tergalloyl groups in compounds 1 and 2. Similar to compound 12, previously isolated from the roots of E. camaldulensis, the ellagitannins demonstrated good Al detoxification properties. Hence, these tannins may play a critical role in the high Al resistance of E. camaldulensis in acidic soils. This paper reports for the first time the isolation of ellagitannin oligomers from the leaves of E. camaldulensis. Full article

Soluble oligomeric forms of Amyloid-β (Aβ) are considered the major toxic species leading to the neurodegeneration underlying Alzheimer’s disease (AD). Therefore, drugs that prevent oligomer formation might be promising. The atypical dipeptide GAL-201 is orally bioavailable and interferes as a modulator of Aβ aggregation. It binds to aggregation-prone, misfolded Aβ monomers with high selectivity and affinity, thereby preventing the formation of toxic oligomers. Here, we demonstrate that the previously observed protective effect of GAL-201 on synaptic plasticity occurs irrespective of shortages and post-translational modifications (tested isoforms: Aβ_1–42, Aβ(p3-42), Aβ_1–40 and 3NTyr(10)-Aβ). Interestingly, the neuroprotective activity of a single dose of GAL-201 was still present after one week and correlated with a prevention of Aβ-induced spine loss. Furthermore, we could observe beneficial effects on spine morphology as well as the significantly reduced activation of proinflammatory microglia and astrocytes in the presence of an Aβ_1–42-derived toxicity. In line with these in vitro data, GAL-201 additionally improved hippocampus-dependent spatial learning in the “tgArcSwe” AD mouse model after a single subcutaneous administration. By this means, we observed changes in the deposition pattern: through the clustering of misfolded monomers as off-pathway non-toxic Aβ agglomerates, toxic oligomers are removed. Our results are in line with previously collected preclinical data and warrant the initiation of Investigational New Drug (IND)-enabling studies for GAL-201. By demonstrating the highly efficient detoxification of β-sheet monomers, leading to the neutralization of Aβ oligomer toxicity, GAL-201 represents a promising drug candidate against Aβ-derived pathophysiology present in AD. Full article

Soluble amyloid β (Aβ) oligomers have been shown to be highly toxic to neurons and are considered to be a major cause of the neurodegeneration underlying Alzheimer’s disease (AD). That makes soluble Aβ oligomers a promising drug target. In addition to eliminating these toxic species from the patients’ brain with antibody-based drugs, a new class of drugs is emerging, namely Aβ aggregation inhibitors or modulators, which aim to stop the formation of toxic Aβ oligomers at the source. Here, pharmacological data of the novel Aβ aggregation modulator GAL-201 are presented. This small molecule (288.34 g/mol) exhibits high binding affinity to misfolded Aβ_1-42 monomers (K_D = 2.5 ± 0.6 nM). Pharmacokinetic studies in rats using brain microdialysis are supportive of its oral bioavailability. The Aβ oligomer detoxifying potential of GAL-201 has been demonstrated by means of single cell recordings in isolated hippocampal neurons (perforated patch experiments) as well as in vitro and in vivo extracellular monitoring of long-term potentiation (LTP, in rat transverse hippocampal slices), a cellular correlate for synaptic plasticity. Upon preincubation, GAL-201 efficiently prevented the detrimental effect on LTP mediated by Aβ_1-42 oligomers. Furthermore, the potential to completely reverse an already established neurotoxic process could also be demonstrated. Of particular note in this context is the self-propagating detoxification potential of GAL-201, leading to a neutralization of Aβ oligomer toxicity even if GAL-201 has been stepwise removed from the medium (serial dilution), likely due to prion-like conformational changes in Aβ_1-42 monomer aggregates (trigger effect). The authors conclude that the data presented strongly support the further development of GAL-201 as a novel, orally available AD treatment with potentially superior clinical profile. Full article

Glutathione is an important antioxidant that plays a crucial role in the cellular protection against oxidative stress and detoxification of electrophilic mutagens, and carcinogens. Glutathione transferases are enzymes catalyzing glutathione-dependent reactions that lead to inactivation and conjugation of toxic compounds, processes followed by subsequent excretion of the detoxified products. Degeneration and loss of neuromelanin-containing dopaminergic neurons in the nigrostriatal neurons generally involves oxidative stress, neuroinflammation, alpha-synuclein aggregation to neurotoxic oligomers, mitochondrial dysfunction, protein degradation dysfunction, and endoplasmic reticulum stress. However, it is still unclear what triggers these neurodegenerative processes. It has been reported that aminochrome may elicit all of these mechanisms and, interestingly, aminochrome is formed inside neuromelanin-containing dopaminergic neurons during neuromelanin synthesis. Aminochrome is a neurotoxic ortho-quinone formed in neuromelanin synthesis. However, it seems paradoxical that the neurotoxin aminochrome is generated during neuromelanin synthesis, even though healthy seniors have these neurons intact when they die. The explanation of this paradox is the existence of protective tools against aminochrome neurotoxicity composed of the enzymes DT-diaphorase, expressed in these neurons, and glutathione transferase M2-2, expressed in astrocytes. Recently, it has been reported that dopaminergic neurons can be protected by glutathione transferase M2-2 from astrocytes, which secrete exosomes containing the protective enzyme. Full article

Over the last decades, cerium oxide nanoparticles (CeO₂ NPs) have gained great interest due to their potential applications, mainly in the fields of agriculture and biomedicine. Promising effects of CeO₂ NPs are recently shown in some neurodegenerative diseases, but the mechanism of action of these NPs in Parkinson’s disease (PD) remains to be investigated. This issue is addressed in the present study by using a yeast model based on the heterologous expression of the human α-synuclein (α-syn), the major component of Lewy bodies, which represent a neuropathological hallmark of PD. We observed that CeO₂ NPs strongly reduce α-syn-induced toxicity in a dose-dependent manner. This effect is associated with the inhibition of cytoplasmic α-syn foci accumulation, resulting in plasma membrane localization of α-syn after NP treatment. Moreover, CeO₂ NPs counteract the α-syn-induced mitochondrial dysfunction and decrease reactive oxygen species (ROS) production in yeast cells. In vitro binding assay using cell lysates showed that α-syn is adsorbed on the surface of CeO₂ NPs, suggesting that these NPs may act as a strong inhibitor of α-syn toxicity not only acting as a radical scavenger, but through a direct interaction with α-syn in vivo. Full article