Expression of β-Amyloid Peptide at Different Time Points After Transient Focal Cerebral Ischemia in Rats

Background and Purpose： Previous studies have shown that one central issue in AD pathogenesis is the amyloid cascade hypothesis, and cerebral ischemia can provoke focal accumulation of β amyloid （Aβ）, while it is not clear that how about was the expression characteristic of Aβ after cerebral ischemia. In this experiment, we studied the expression characteristic of Aβ after cerebral ischemia. Methods： Rats were divided into two groups, normal-group, model -group.     

Inhibition of the ATP-sensitive potassium channel from mouse pancreatic β-cells by surfactants

1. We have used patch-clamp methods to study the effects of the detergents, Cremophor, Tween 80 and Triton X100 on the K_ATP channel in the pancreatic β-cell from mouse.
2. All three detergents blocked K_ATP channel activity with the following order of potency: Tween 80 (K_i<∼83 nM)>Triton X100 (K_i=350 nM)>Cremophor. In all cases the block was poorly reversible.
3. Single-channel studies suggested that at low doses, the detergents act as slow blockers of the K_ATP channel.
4. Unlike the block produced by tolbutamide, that produced by detergent was not affected by intracellular Mg²⁺-nucleotide, diazoxide or trypsin treatment, nor did it involve an acceleration of rundown or increase in ATP sensitivity of the chanel.
5. The detergents could block the pore-forming subunit, Kir6.2ΔC26, which can be expressed independently of SUR₁ (the regulatory subunit of the K_ATP channel). These data suggest that the detergents act on Kir6.2 and not SUR₁.
6. The detergents had no effect on another member of the inward rectifier family: Kir1.1a (ROMK1).
7. Voltage-dependent K-currents in the β-cell were reversibly blocked by the detergents with a far lower potency than that found for the K_ATP channel.
8. Like other insulin secretagogues that act by blocking the K_ATP channel, Cremophor elevated intracellular Ca²⁺ in single β-cells to levels that would be expected to elicit insulin secretion.
9. Given the role of the K_ATP channel in many physiological processes, we conclude that plasma borne detergent may have pharmacological actions mediated through blockage of the K_ATP channel

     

Inhibition of β-glucuronidase by chlorinated hydroquinones and benzoquinones

An earlier study of the metabolism of pentachlorophenol has shown that a metabolite, tetrachloro-p-hydroquinone, possessed pronounced inhibitory action on the activity of -glucuronidase from bacterial origin. Several other chlorinated hydroquinones and benzoquinones have now been studied with regard to their ability to inhibit -glucuronidase of various origin in vitro and in vivo.All the studied chlorinated hydroquinones and benzoquinones were found to be potent inhibitors of -glucuronidase of bacterial origin. D-glucaric acid-1.4-lactone was included for comparison and was found to be less active than the other studied compounds. The inhibition was found to be competitive in nature.No inhibitory effect of the benzo- and hydroquinones studied in vitro or in vivo could be demonstrated on -glucuronidase from livers. The result calls for precaution when using bacterial -glucuronidase to split urinary conjugates of glucuronic acid.

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Zusammenfassung Eine frühere Studie des Metabolismus von Pentachlorphenol hat gezeigt, daß ein Metabolit, Tetrachlor-p-hydrochinon, eine ausgesprochene Hemmwirkung auf die Aktivität der Bakterien--Glucuronidase besitzt. Verschiedene andere chlorierte Hydrochinone und Benzochinone sind jetzt auf ihre Fähigkeit, -Glucuronidase anderen Ursprungs zu hemmen, in vitro und in vivo, untersucht worden.Alle die untersuchten chlorierten Hydrochinone und Benzochinone zeigten sich als starke Hemmer der Bakterien -Glucuronidase. D-Glucarsäure-1.4-Lakton wurde zum Vergleich einbezogen und wurde weniger aktiv als die anderen Verbindungen befunden. Die Hemmung war kompetitiver Art.Kein Hemmungseffekt von Hydro-oder Benzochinonen konnte in vitro oder in vivo auf Leber--Glucuronidase gezeigt werden. Das Resultat mahnt zur Vorsieht, wenn Bakterien -Glucuronidase zur Spaltung von Harnkonjugaten der Glucuronsäure angewandt wird.

     

The Molecular Basis of β-Lactamase Catalysis and Inhibition

The -lactamases catalyze the hydrolysis of the lactam bond in -lactams, thus rendering the -lactam ineffective as an antibiotic. The increasing spread of resistance to -lactam antibiotics is largely due to this class of enzyme. Mechanistically these enzymes appear to be related to the transpeptidases and carboxypeptidases involved in the synthesis of the bacterial cell wall. Interest in the basic mechanism of action of the -lactamases has been spurred by the potential for mechanism-based drug design. The past seven years have seen a significant increase in our knowledge of the catalysis and inhibition of the -lactamases. The presence of an essential, conserved, serine residue which participates in the formation of a covalent acyl-enzyme intermediate in catalysis, inhibition and inactivation by -lactams has been established. Unfortunately, few additional details regarding the catalytic mechanism are well established. A generalized reaction pathway can be formulated for most -lactam inhibitors (reversible or irreversible). This scheme involves partitioning of the initially-formed acyl-enzyme by three pathways: 1) hydrolysis leading to turnover, 2) transient inhibition probably involving formation of an imine or enamine acyl-enzyme, or possibly involving a substantial conformational change in some cases, and 3) imine formation followed by additional covalent modification of the enzyme leading to irreversible inactivation. The flux through each of these pathways varies with the nature of the substrate and the particular -lactamase.     

Inhibition of ��-amyloid1-40 Peptide Aggregation and Neurotoxicity by Citrate

The accumulation of β-amyloid (Aβ) aggregates is a characteristic of Alzheimer''s disease (AD). Furthermore, these aggregates have neurotoxic effects on cells, and thus, molecules that inhibit Aβ aggregate formation could be valuable therapeutics for AD. It is well known that aggregation of Aβ depends on its hydrophobicity, and thus, in order to increase the hydrophilicity of Aβ, we considered using citrate, an anionic surfactant with three carboxylic acid groups. We hypothesized that citrate could reduce hydrophobicity and increase hydrophilicity of Aβ_1-40 molecules via hydrophilic/electrostatic interactions. We found that citrate significantly inhibited Aβ_1-40 aggregation and significantly protected SH-SY5Y cell line against Aβ_1-40 aggregates-induced neurotoxicity. In details, we examined the effects of citrate on Aβ_1-40 aggregation and on Aβ_1-40 aggregates-induced cytotoxicity, cell viability, and apoptosis. Th-T assays showed that citrate significantly inhibited Aβ_1-40 aggregation in a concentration-dependent manner (Th-T intensity: from 91.3% in 0.01 mM citrate to 82.1% in 1.0 mM citrate vs. 100.0% in Aβ_1-40 alone). In cytotoxicity and viability assays, citrate reduced the toxicity of Aβ_1-40 in a concentration-dependent manner, in which the cytotoxicity decreased from 107.5 to 102.3% as compared with Aβ_1-40 aggregates alone treated cells (127.3%) and the cell viability increased from 84.6 to 93.8% as compared with the Aβ_1-40 aggregates alone treated cells (65.3%). Furthermore, Hoechst 33342 staining showed that citrate (1.0 mM) suppressed Aβ_1-40 aggregates-induced apoptosis in the cells. This study suggests that citrate can inhibit Aβ_1-40 aggregation and protect neurons from the apoptotic effects of Aβ_1-40 aggregates. Accordingly, our findings suggest that citrate administration should be viewed as a novel neuroprotective strategy for AD.     

PiB-Conjugated,Metal-Based Imaging Probes: Multimodal Approaches for the Visualization of β-Amyloid Plaques

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Direct Formation of Nanospheres from Amphiphilic β-Cyclodextrin Inclusion Complexes

Purpose. The aim of this work was to develop and characterize a highly loaded nanoparticulate system based on amphiphilic -cyclodextrins (CDs) to facilitate the parenteral administration of poorly soluble antifungal model drugs bifonazole and clotrimazole. Methods. Inclusion complexes were characterized with spectroscopic techniques. Particle size distribution of nanospheres were determined by photon correlation spectroscopy (PCS). Nanospheres were assessed for hemolytic activity. Entrapped and released drug quantities were determined and minimum inhibitory concentration (MIC) values of drugs, amphiphilic -CDs, and drug loaded nanospheres were evaluated. Results. 1:1 inclusion complexes of model drugs with amphiphilic -CDs gave nanospheres <300 nm (polydispersity index < 0.15) by nanoprecipitation technique without using surfactants. By direct preparation from preformed inclusion complexes, loading was increased 2- to 8-fold depending on CD type and loading technique. Conventionally loaded CD nanospheres displayed immediate release whereas preloaded and highly loaded nanospheres liberated model drugs over a period of 1 h reducing the initial burst effect. MIC values of bifonazole and clotrimazole were lowered significantly when associated to amphiphilic -CD nanospheres. Conclusion. Amphiphilic -CDs form nonsurfactant, highly loaded nanospheres with lower hemolytic activity than that of natural CDs directly from inclusion complexes. They enhanced solubility and subsequently therapeutic efficacy of the model drugs.     

Peptide micelle-mediated curcumin delivery for protection of islet β-cells under hypoxia

Islet transplantation is one of many therapeutic approaches for the treatment of diabetes. During transplant procedures, the isolated islets are subjected to hypoxic conditions, and undergo the apoptotic process. Curcumin has a cytoprotective effect, and may therefore be useful for the protection of islets under hypoxia. However, curcumin is hydrophobic, and an efficient curcumin carrier is required for effective treatment. In this study, R3V6 peptide micelles, composed of a 3-arginine stretch and 6-valine stretch, were evaluated as a curcumin carrier to INS-1 insulinoma cells. Curcumin was loaded into R3V6 micelles at a weight ratio of 10:3 (R3V6:curcumin). The size and surface charge of the curcumin-loaded R3V6 micelles (R3V6-curcumin) were approximately 250?nm and 17.49?mV, respectively. R3V6-curcumin delivered curcumin to the INS-1 cells more efficiently than either curcumin alone or a simple mixture of R3V6 and curcumin. MTT assay indicated that under hypoxia, R3V6-curcumin protected INS-1 cells more efficiently than curcumin alone. TUNEL and reactive oxygen species (ROS) assays suggested that R3V6-curcumin reduced INS-1 cell apoptosis under hypoxia. These results demonstrate that R3V6 peptide micelles are an effective carrier of curcumin, and that R3V6-curcumin may improve the viability of pancreatic β-cells in islet transplantation.     

Antagonizing Effects of Soybean Isoflavones on β-Amyloid Peptide-Induced Oxidative Damage in Neuron Mitochondria of Rats

Soybean isoflavone (SIF) has been demonstrated to have neuroprotective effects induced by β‐amyloid peptides (Aβ) through suppressing oxidative stress; however, the explicit mechanisms still remain uncovered. In the present study, 32 Wistar rats were randomly divided into four groups: an Aβ1‐42‐treated group, a SIF + Aβ1‐42 group, a SIF‐treated group and a control group. We measured the protein content of 8‐hydroxydeoxyguanosine (8‐OhdG) and mRNA expression of 8‐oxoguanine DNA glycosylase (OGG1). The protein expression of OGG1, Bcl‐xl, Bad, beta subunit of ATP synthase (ATPB) and pyruvate dehydrogenase (PDH) in brain was also measured. The results showed that the level of 8‐OHdG in both SIF groups was significantly decreased compared to the Aβ1‐42‐treated group (p < 0.05), while the mRNA and protein expression of OGG1 in the SIF + Aβ1‐42 groups were up‐regulated compared with the Aβ1‐42‐treated groups (p < 0.05). The expression of Bcl‐xl was up‐regulated in the SIF‐treated group compared with the Aβ1‐42‐treated groups (p < 0.05), while the expression of Bad was down‐regulated in the two SIF‐treated groups (p < 0.05). Aβ1‐42 significantly down‐regulated the expression of ATPase and PDH proteins compared with the control group (p < 0.05). SIF reversed the down‐regulation effects on the mitochondrial energy metabolic enzymes induced by Aβ1‐42 (p < 0.05) in the rats. These results suggest that SIF alleviate the oxidative stress in neurons and mitochondria of rat brains mediated by Aβ1‐42, and these protective effects might be associated with the regulation of OGG1, Bad, Bcl‐xl, ATPB and PDH.     

Inhibition of Nuclear Transcription Factor-κB by Specific IκB Kinase Peptide Inhibitor

Pharmaceutical Research -     

Advances in the identification of γ-secretase inhibitors for the treatment of Alzheimer's disease

INTRODUCTION: In an attempt of altering the natural history of Alzheimer's disease (AD), several compounds have been developed with the aim of inhibiting γ-secretase, the enzymatic complex generating β-amyloid (Aβ) peptides (Aβ(1 - 40) and Aβ(1 - 42)), from amyloid precursor protein (APP). APP is believed to be involved in the pathophysiological cascade of AD. AREAS COVERED: This article briefly reviews the profile of γ-secretase inhibitors that have reached the clinic. The paper reviews studies from the primary English literature on γ-secretase inhibitors published before November 2011, searching through the PubMed database of NCBI by author and the following keywords: drugs targeting β-amyloid, γ-secretase inhibitors, dementia syndromes and Alzheimer's disease. EXPERT OPINION: Studies in both transgenic and non-transgenic animal models of AD have indicated that γ-secretase inhibitors, administered by the oral route, are able to lower brain Aβ concentrations. However, scanty data are available on the effects of these compounds on brain Aβ deposition after prolonged administration. γ-Secretase inhibitors may cause significant toxicity in experimental animals and in humans believed to be associated with the inhibition of the cleavage of Notch, a transmembrane receptor involved in regulating cell-fate decisions. Unfortunately, two large Phase III clinical trials of semagacestat in mild-to-moderate AD patients were prematurely interrupted because of the observation of a detrimental cognitive and functional effects of the drug, possibly due to its lack of selectivity on APP processing. New APP-selective γ-secretase inhibitors are being developed with the hope of overcoming the previous setbacks.     

Inhibition of dopa decarboxylase by the hydrazino analog of α-methyldopa

dl-σ-Methyl-α-hydrazino-3,4-dihydroxyphenylpropionic acid (HMD) is a potent inhibitor of DOPA decarboxylase in vitro. In vivo, the hydrazino acid inhibited the accumulation of serotonin in the kidneys of mice given 5-hydroxytryptophan (5HTP); it inhibited the urinary excretion of serotonin by 5-HTP-dosed rats; it decreased the rate of expiration of radioactive CO₂ by rats which were dosed with l-1-¹⁴C-tyrosine, phenylalanine or α-methyldopa. However, it did not affect the rate of expiration of ¹⁴C-O₂ by rats which were dosed with dl-l-¹⁴C-glutamic acid. HMD was concentrated by the kidneys in rats, but did not enter the brain to a measurable extent, and did not affect concentrations of endogenous serotonin in brain. It was itself decarboxylated in the rat to a greater extent after oral than after intraperitoneal administration. HMD apparently did not inhibit monoamine oxidase in vivo.     

Inhibition of α-Amylase and α-Glucosidase by New β-Aminopropionamidoxime Derivatives

Pharmaceutical Chemistry Journal - New antidiabetic agents are being sought because of the global problem with diabetes. Amidoxime derivatives are known to have antidiabetic activity....     

Formation arid antimicrobial activity of complexes of β-cyclodextrin and some antimycotic imidazole derivatives

Complex formation between -cyclodextrin and six antimycotic imidazole derivatives has been studied. The solubility of all drugs was increased in the presence of -cyclodextrin. The smallest increase (approx. 5-fold) was observed for miconazol, and the largest increase (approx. 160-fold) was observed for bifonazol. Apparent I:I-complex constants were measured and found to decrease in the order: bifonazol > ketoconazol > tioconazol > miconazol > itraconazol > clotrimazol. The complexes appeared to possess a low, if any, antimicrobial activity. Measurement of inhibition zone sizes, with four test organisms was used to study the release of the antimycotic drugs from topical preparations. The antimycotic drugs were more readily released from topical preparations containing \-cyclodextrin than from the same vehicles without -cyclodextrin. The rationale of -cyclodextrin addition to antimycotic topical preparations is discussed.     

Pharmacological treatment of the psychosis of Alzheimer's disease: what is the best approach?

Psychosis of Alzheimer's disease (PAD) forms part of the behavioural and psychological symptoms of dementia (BPSD). PAD includes symptoms of psychosis such as hallucinations or delusions, and may be associated with agitation, negative symptoms or depression. Even though the US FDA has not approved any medication for the treatment of PAD, atypical antipsychotics have been widely used and favoured by geriatric experts in the management of the condition in view of their modest efficacy and relative safety. However, the recent FDA warnings regarding the cardiac, metabolic, cerebrovascular and mortality risks associated with the use of these drugs in elderly patients with dementia have caused serious concerns regarding their use. Nevertheless, until an effective and safe medication is approved by the regulatory agencies for PAD, clinicians do not have a better choice than atypical antipsychotics for the management of the serious symptoms of this condition.     

Inhibition of acetylcholine turnover in rat hippocampus by intraseptal injections of β-endorphin and morphine

Summary Intraseptal administration of morphine (70 nmol) or -endorphin (0.7 nmol) reduced the rate of acetylcholine (ACh) turnover (TR_ACh) in rat hippocampus but not in striatum or cortex. These intraseptal injections failed to modify the ACh content and did not elicit analgesia. Naltrexone (15 mol/kg, i.p.) completely antagonized the decrease of hippocampal TR_ACh elicited by the two opiate receptor agonists. Furthermore, intraseptal injections of naltrexone partially blocked the decrease in hippocampal TR_ACh induced by intraperitoneal administration of morphine (70 mol/kg, i.p.). These data suggest that opiate agonists decrease hippocampal TR_ACh by regulating septal cholinergic neurons, and that this effect is not associated with analgesia.