黑果枸杞花青素对Aβ_(42)致痴呆模型大鼠记忆力及抗氧化活性研究

采用双侧海马CA1区注射Aβ42构建阿尔茨海默症(Alzheimer′s disease,AD)动物模型,通过穿梭箱被动回避记录行为学数据;以大鼠血清和脑组织中的总超氧化物歧化酶(T-SOD)、过氧化氢酶(CAT)活力及还原型谷胱甘肽(GSH)、丙二醛(MDA)和蛋白质羰基(PC)含量作为评价指标,分析黑果枸杞花青素(OPC)样品对AD模型大鼠记忆力以及体内抗氧化活性的影响。结果表明,模型组动物的记忆能力显著下降,而黑果枸杞花青素组可改善AD模型大鼠的记忆损伤;同时,发现灌胃剂量为80 mg/kg的黑果枸杞花青素组能显著提高AD大鼠血清和脑组织中T-SOD、CAT活力和GSH含量,并降低MDA和蛋白质羰基含量水平。综合上述结果可知,本研究所述黑果枸杞花青素具有良好的增强体内抗氧化活性和提高AD大鼠记忆力的作用,并具有预防AD的潜在功效。     

Synthesis and pharmacological evaluation of 8- and 9-substituted benzolactam-v8 derivatives as potent ligands for protein kinase C, a therapeutic target for Alzheimer's disease

A central element in the pathophysiology of Alzheimer's disease (AD) is the formation of amyloid plaques, which result from abnormal processing of the amyloid precursor protein (APP). The processing of APP is largely provided by three key enzymes, namely the alpha-, beta-, and gamma-secretases. As the latter two contribute to the formation of neurotoxic Abeta fragments while alpha-secretase does not, a decrease in the amyloidogenic products can be brought about either by inhibition of the beta- and gamma-secretases or through the activation of alpha-secretase. It is now known that the activation of protein kinase C (PKC) enhances alpha-secretase activity and therefore represents a possible target for the development of agents urgently needed for the treatment of this devastating neurodegenerative disorder. In the present study, new benzolactam-V8-based PKC activators were synthesized and tested for their binding affinity toward PKCalpha. All compounds tested showed binding values in the nanomolar concentration range. In accordance with previous publications, 9-substitution dramatically increased PKC binding affinity in comparison with the corresponding 8-substituted analogues. In addition to the location of the side chain on the aromatic ring, the binding affinities of these benzolactams were found to depend on the orientation, length, and electronic properties of this appendage. An interesting decrease in binding affinity was found for the 9-thienyl analogue 13, suggesting adverse electronic interactions of the sulfur atom with PKC or parts of the cellular membrane.     

Head-to-tail cyclization of a heptapeptide eliminates its cytotoxicity and significantly increases its inhibition effect on amyloid β-protein fibrillation and cytotoxicity

Amyloid-β (Aβ) protein aggregation is the main hallmark of Alzheimer’s disease (AD). Inhibition of Aβ fibrillation is thus a promising therapeutic approach to the prevention and treatment of AD. Recently, we designed a heptapeptide inhibitor, LVFFARK (LK7). LK7 shows a promising inhibitory capability on Aβ fibrillation, but is prone to self-assembling and displays high cytotoxicity, which would hinder its practical application. Herein, we modified LK7 by a head-to-tail cyclization and obtained a cyclic LK7 (cLK7). cLK7 exhibits a different self-assembly behavior from LK7, and has higher stability against proteolysis than LK7 and little cytotoxicity to SH-SY5Y cells. Thermodynamic analysis revealed that both LK7 and cLK7 could bind to Aβ₄₀ by electrostatic interactions, hydrogen bonding and hydrophobic interactions, but the binding affinity of cLK7 for Aβ₄₀ (K_D = 4.96 µmol/L) is six times higher than that of LK7 (K_D = 32.2 µmol/L). The strong binding enables cLK7 to stabilize the secondary structure of Aβ₄₀ and potently inhibit its nucleation, fibrillation and cytotoxicity at extensive concentration range, whereas LK7 could only moderately inhibit Aβ₄₀ fibrillation and cytotoxicity at low concentrations. The findings indicate that the peptide cyclization is a promising approach to enhance the performance of peptide-based amyloid inhibitors.     

Aβ多肽与铜锌金属离子非共价复合物的电喷雾质谱研究

Cu^2＋ and Zn^2＋ ions were reported to be able to induce Aβ aggregation at nearly physiological concentrations in vitro and related to the pathogenesis of Alzheimer’s disease. The smaller peptides including Aβ(1-28) was chosen as the target peptide, which helped define the nature of the interaction of the full length peptide. And we studied the influences of the different conditions including the pH, temperature, apparatus conditions, concentration on the impact of complex of Zn^2＋, Cu^2＋ and Aβ. Our findings by the studies of ESI-MS revealed the stoichiometry of 1:1 for the peptide-metal complexes, and to bind up to four cations upon increasing the metal concentration.     

Effects of Intramolecular Distance between Amyloidogenic Domains on Amyloid Aggregation

Peptide/protein aggregation is implicated in many amyloid diseases. Some amyloidogenic peptides/proteins, such as those implicated in Alzheimer’s and Parkinson’s diseases, contain multiple amyloidogenic domains connected by “linker” sequences displaying high propensities to form turn structures. Recent studies have demonstrated the importance of physicochemical properties of each amino acid contained in the polypeptide sequences in amyloid aggregation. However, effects on aggregation related to the intramolecular distance between amyloidogenic domains, which may be determined by a linker length, have yet to be examined. In the study presented here, we created peptides containing two copies of KFFE, a simple four-residue amyloidogenic domain, connected by GS-rich linker sequences with different lengths yet similar physicochemical properties. Our experimental results indicate that aggregation occurred most rapidly when KFFE domains were connected by a linker of an intermediate length. Our experimental findings were consistent with estimated entropic contribution of a linker length toward formation of (partially) structured intermediates on the aggregation pathway. Moreover, inclusion of a relatively short linker was found to inhibit formation of aggregates with mature fibril morphology. When the results are assimilated, our study demonstrates that intramolecular distance between amyloidogenic domains is an important yet overlooked factor affecting amyloid aggregation.     

Cell interaction study of amyloid by using luminescent conjugated polythiophene: implication that amyloid cytotoxicity is correlated with prolonged cellular binding

Needles and noodles: Studying amyloid toxicity is important for understanding protein misfolding diseases. Using a luminescent conjugated polythiophene, we found that cell binding of nontoxic filamentous amyloids of insulin and β2-microglobulin was less efficient than that of toxic fibrillar amyloids; this suggests a correlation between amyloid toxicity and cell binding.     

The value of the biomarkers cathelicidin,milk amyloid A,and haptoglobin to diagnose and classify clinical and subclinical mastitis

Timely and objective diagnosis and classification of mastitis is crucial to ensure adequate management and therapeutic decisions. Analyzing specific biomarkers in milk could be advantageous compared with subjective or semiquantitative criteria, such as palpation of the udder in clinical mastitis cases or evaluation of somatic cell count using cow side tests (e.g., California Mastitis Test) in subclinical mastitis quarters. The objective of this study was to investigate the diagnostic value of 3 biomarkers; cathelicidin, milk amyloid A, and haptoglobin for the diagnosis of subclinical and clinical mastitis. Furthermore, the suitability of these biomarkers to differentiate between mild, moderate, and severe clinical mastitis and the influence of different pathogens on biomarker levels was tested. A total of 67 healthy cows, 119 cows with subclinical mastitis, and 212 cows with clinical mastitis were enrolled in the study. Although cathelicidin, haptoglobin, and milk amyloid A were measured in all samples from healthy cows and those with subclinical mastitis, haptoglobin, and cathelicidin results were only available from 121 out of 212 cows with clinical mastitis. Milk amyloid A was measured in all samples. In cows with clinical mastitis, the mastitic quarter and a second healthy quarter serving as a healthy in-cow control quarter were sampled. It was possible to differentiate between healthy quarters, quarters with subclinical mastitis, and quarters with clinical mastitis using all 3 biomarkers. Concerning cathelicidin, thresholds were 0.000 [sensitivity (Se) = 0.83, specificity (Sp) = 0.97] and 0.053 (Se = 0.98, Sp = 0.99) for normalized optical density at 450 nm (NOD450) for differentiating between healthy quarters and quarters with subclinical or clinical mastitis, respectively. Thresholds of 1.28 µg/mL (Se = 0.65, Sp = 0.76) and 1.81 µg/mL (Se = 0.77, Sp = 0.83) for milk amyloid A and 3.65 µg/mL (Se = 0.92, Sp = 0.94) and 5.40 µg/mL mL (Se = 0.96, Sp = 0.99) for haptoglobin were calculated, respectively. Healthy in-cow control quarters from cows with CM showed elevated milk amyloid A and haptoglobin levels compared with healthy quarters from healthy cows. Only the level of milk amyloid A was higher in severe clinical mastitis cases compared with mild ones. In contrast to clinical mastitis, cathelicidin and haptoglobin in subclinical mastitis quarters were significantly influenced by different bacteriological results. The measurement of cathelicidin, milk amyloid A, and haptoglobin in milk proved to be a reliable method to detect quarters with subclinical or clinical mastitis.