Antiaggregatory Effects Research Articles

Clinical use of albumin.

Human albumin (HA) is the most abundant circulating protein in the plasma of healthy individuals (3.5–5 g/dL) since it represents approximately 50% of the total protein content. HA is a small globular protein (molecular weight: 66.5 kDa), consisting of a single chain of 585 amino acids organised in three repeated homologue domains (sites I, II, and III), each of which comprises two separate sub-domains (A and B). Under physiological conditions, about 10–15 grams of HA are produced in the liver by the hepatocytes every day, with none or very low intracellular storage. Its synthesis is stimulated by hormones, such as insulin, cortisol and growth hormone, while it is inhibited by pro-inflammatory substances, including interleukin-6 and tumour necrosis factor-α1,2. Once released in the circulation, about 30–40% is maintained in the blood stream, while the remainder is distributed in the interstitium, where its concentration is low (1.4 g/dL). The protein leaves the circulation at a rate of 5% per hour, returning to it via the lymphatic system in an amount comparable to the output. This results in a circulatory half-life of approximately 16–18 hours and in a much longer total half-life which varies from about 12 to 19 days in a healthy young adult. HA can be catabolised in many tissues, but mainly in the muscles, liver and kidneys1–4. HA is the main modulator of fluid distribution among the compartments of the body, providing approximately 70–80% of the total plasma oncotic pressure. Two thirds of the oncotic property derives from the direct osmotic effect related to its molecular mass and 1/3 from the Gibbs-Donnan effect, due to the negative net charge of the molecule which attracts positively charged molecules (i.e. sodium and, therefore, water) into the intravascular compartment. However, many other non-oncotic properties which are unrelated to the regulation of fluid compartmentalisation, and are mostly the result of the peculiar structure and conformation of the molecule, have been identified in the last two decades. HA binds and carries a great variety of hydrophobic molecules, such as endogenous (i.e., cholesterol, fatty acids, bilirubin, thyroxina) or exogenous substances (i.e., drugs and toxins), transition metal ions, and gas (nitric oxide [NO]), with consequent implications for their solubilisation, transport, metabolism, and detoxification3,4. HA is also the major source of extracellular reduced sulfhydryl groups, localised at the cysteine-34 (Cys-34) site, which act as potent scavengers of reactive oxygen species (ROS). The antioxidant function resides also in the capability to bind at the N-terminal portion of the molecule several metal ions, including copper, cobalt, nickel, zinc and iron. These ions are therefore inhibited to catalyse many chemical reactions generating free radicals3,5,6. As a result, HA represents the main circulating antioxidant system in the body. The HA molecule also contributes to the stabilisation of the endothelial layer and to the maintenance of the normal capillary permeability probably by reducing oxidative damage and modulating inflammation7,8. Finally, it exerts an antithrombotic effect which appears to be related to the capacity of binding NO at the Cys-34 site with subsequent formation of the complex albumin-NO, thus preventing the rapid inactivation of NO and ultimately prolonging its anti-aggregant effect on platelets9,10.

Nucleoside triphosphates inhibit ADP, collagen, and epinephrine-induced platelet aggregation: Role of P2Y1 and P2Y12 receptors

Platelets express two ADP receptors namely P2Y1 and P2Y12 that regulate ADP and other agonists-induced platelet aggregation. P2Y1 receptor activation causes platelet shape change while P2Y12 receptor activation induces platelet aggregation. Previously, anti-aggregatory effects of ATP on ADP-induced and pro-aggregatory effects on epinephrine-induced platelet aggregation have been reported. However, the effects of other nucleoside triphosphates on platelet aggregation have never been described. The aim of the present study was to characterise the effects of nucleoside triphosphates (ATP, UTP, GTP, and CTP) on agonist-induced platelet aggregation. The experiments were performed on platelet rich plasma freshly isolated from blood donated by healthy human volunteers. All the nucleoside triphosphates tested inhibited ADP- and collagen-induced platelet aggregation in a concentration-dependent manner with a rank order of potency, 2MeSATP >ATP ≥ α,β,methyleneATP>UTP >>CTP ≥ GTP. The IC50 values against ADP (10 μM)-induced platelet aggregation were 0.039 ± 0.013, 18 ± 7, 25 ± 6, 32 ± 9, 360 ± 130, and 400 ± 160 μM, respectively. Low concentrations of ATP induced platelet shape change which was due to contaminating ADP. However, higher concentrations antagonised ADP and MRS2365-induced platelet shape change. The ATP analogue α,β,methyleneATP and CTP but not UTP and GTP also antagonised ADP-induced platelet shape change. Similarly, low ATP concentrations potentiated epinephrine-induced platelet aggregation that was abolished by P2Y1 antagonist MRS2500 suggesting P2Y1 receptor activation due to contaminating ADP. Higher ATP concentrations, α,β,methyleneATP, UTP, CTP, and GTP antagonised epinephrine-induced platelet aggregation. Thus, the data demonstrate nucleoside triphosphates in general act as P2Y12 receptor antagonists and antagonise ADP-, collagen-, and epinephrine-induced platelet aggregation.

P.5.14 The co-chaperone DNAJB6 – mutated in LGMD1D – and its role in handling of aggregation-prone muscle proteins

Mutations in the co-chaperone DNAJB6 causing LGMD1Dhave so far been identified in Finnish, Italian, North American, Japanese, and Korean populations. All identified mutations are localized in a small area of the G/F-rich linker domain of DNAJB6. We have earlier studied the effect of wild-type and mutant DNAJB6 on the aggregation of polyQ-huntingtin and all the tested mutants show a significant loss of anti-aggregation effect. The molecular details of DNAJB6 functions in muscle are largely unknown. DNAJB6 is apparently very important for correct handling of proteins in muscle as the mutations all cause dystrophy with protein aggregations and autophagic rimmed vacuolar pathology. The importance of DNAJB6 in muscle protein turnover and anti-aggregation was studied in transiently transfected mammalian cell cultures using co-expression of wild-type and mutant DNAJB6 and aggregation-prone proteins, such as mutant desmin and myotilin. Aggregated proteins were filter trapped and visualised using antibodies. Soluble proteins were measured by western blotting. The anti-aggregation activity was calculated as the ratio of aggregated vs. soluble protein amounts. Both lysosomal or proteasomal activity was blocked using inhibitors (E64d/pepstatin A and MG132 respectively) for the assessment of their involvement in the aggregation processes. The studies are ongoing and detailed results will be presented.

Blockade of platelet alpha2B-adrenergic receptors in patients with coronary artery disease: a novel antiaggregant mechanism

Purpose: Platelets play a vital role in hemostasis and thrombosis. Catecholamines have a profound effect on platelet aggregation and atherothrombosis but the exact mechanism involved is insufficiently understood. In this report, we demonstrate the existence and role of alpha2B–adrenergic receptors (α2B–ARs) in platelets from patients with Coronary Artery Disease (CAD) compared to normal individuals. Methods: Sixteen healthy individuals and 7 patients with CAD who were under dual antiplatelet therapy with clopidogrel 75mg and acetylsalicylic acid 100mg were included. Blood samples were obtained from which platelets were isolated. The presence of α2B-ARs in platelets was proven by Western blot analysis and real time PCR. In order to investigate their function, we performed light transmittance aggregometry by examining the inhibitory effects of specific α2B-AR antibodies. Results: Pretreatment of human platelets with agents that selectively block α2B-ARs showed a substantial inhibition in platelet aggregation that had been induced by adenosine diphosphate (ADP), by epinephrine and by arachidonic acid. The percent aggregation decreased from 81.5±1.7% to 35.8±5% for ADP with α2B-Abs, from 72.2±1.9% to 25.5±4.3% for epinephrine with α2B-Abs, and from 87±2.1% to 47.9±6.2% for arachidonic acid with α2B-Abs, p<0.05 for all. Patients with CAD showed a significantly reduced expression of the receptor in the platelets (149.6±100.8 in normals versus 32.1±17.7, p = 0.015). Notably, pretreatment with α2B –Abs resulted in a significant further reduction of platelet aggregation. The ADP-treated plasma showed a significant reduction in platelet aggregation after pre-treatment with α2B-Abs (42±5.8% for the control group versus 31.7±2.2% for the group with α2B-Abs pretreatment, p< 0.001). When arachidonic acid was used to induce aggregation, pre-treatment with α2B -Abs reduced platelet aggregation from 41.2±7.3% to 28.2±7.5%, p= 0.006). Similarly, the presence of α2B-Abs decreased platelet aggregation induced by epinephrine from 44.4±22.1% to 19.1±7.2% (p = 0.01). Conclusions: Our results reveal that contrary to previous knowledge, the α2B–AR subtype does exist in platelets and is an important regulator of aggregation. Inhibition of α2B-ARs in platelets may offer a novel therapeutic opportunity in the prevention of atherothrombotic events. Interestingly, even in patients with coronary artery disease who were receiving dual antiplatelet therapy with aspirin and clopidogrel, the inhibition of α2B-ARs had an additional antiaggregant effect.

Antiplatelet effect of AMP-activated protein kinase activator and its potentiation by the phosphodiesterase inhibitor dipyridamole

AMP-activated protein kinase (AMPK) activates endothelial nitric oxide synthase (eNOS) via phosphorylation at the activating site. The eNOS-nitric oxide (NO)/soluble guanylate cyclase (sGC)-cGMP/cGMP-dependent protein kinase (PKG) signaling axis is a major antiaggregatory mechanism residing in platelets. Based on the hypothesis that direct activation of AMPK might be a potential strategy to inhibit platelet aggregation, the antiplatelet effect of AMPK activators was investigated. Treatment of isolated platelets with the AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) resulted in AMPK activation and a decrease in aggregation, which was abolished by pretreatment with the AMPK inhibitors compound C (CC) and ara-A. Such an AMPK-dependent antiaggregatory effect was also observed with other AMPK activators such as A-769662 and PT1. AICAR induced eNOS activation was followed by NO synthesis, cGMP production, and subsequent phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a PKG substrate. All these events were blocked by CC or ara-A pretreatment, and each event was inhibited by the eNOS inhibitor L-NAME, the sGC inhibitor ODQ, and the PKG inhibitor Rp-8-pCPT-cGMPS. Simultaneous treatment of dipyridamole, a phosphodiesterase (PDE) inhibitor, with AICAR potentiated the antiaggregatory effect by enhancing the cGMP elevation. Administration of AICAR increased platelet cGMP and prolonged FeCl3-induced arterial occlusion time in rats, which further increased in combination with dipyridamole. In conclusion, AMPK activators inhibited platelet aggregation by stimulating the eNOS-NO/sGC-cGMP/PKG signaling pathway. The antiplatelet effect of AMPK activators could be potentiated in combination with a PDE inhibitor through the common mechanism of elevating cGMP. Thus, AMPK may serve as a potential target for antiplatelet therapy.

Anti-aggregating effect of the naturally occurring dipeptide carnosine on aβ1-42 fibril formation.

Carnosine is an endogenous dipeptide abundant in the central nervous system, where by acting as intracellular pH buffering molecule, Zn/Cu ion chelator, antioxidant and anti-crosslinking agent, it exerts a well-recognized multi-protective homeostatic function for neuronal and non-neuronal cells. Carnosine seems to counteract proteotoxicity and protein accumulation in neurodegenerative conditions, such as Alzheimer’s Disease (AD). However, its direct impact on the dynamics of AD-related fibril formation remains uninvestigated. We considered the effects of carnosine on the formation of fibrils/aggregates of the amyloidogenic peptide fragment Aβ1-42, a major hallmark of AD injury. Atomic force microscopy and thioflavin T assays showed inhibition of Aβ1-42 fibrillogenesis in vitro and differences in the aggregation state of Aβ1-42 small pre-fibrillar structures (monomers and small oligomers) in the presence of carnosine. in silico molecular docking supported the experimental data, calculating possible conformational carnosine/Aβ1-42 interactions. Overall, our results suggest an effective role of carnosine against Aβ1-42 aggregation.

Anti-aggregation effect of AA-peptide on beta-amyloid peptides in Alzheimer's disease

Anti-aggregation effect of AA-peptide on beta-amyloid peptides in Alzheimer's disease

Searching for an endogenous anti-Alzheimer molecule: identifying small molecules in the brain that slow Alzheimer disease progression by inhibition of β-amyloid aggregation

Alzheimer disease is a neurodegenerative disorder that progresses with marked interindividual clinical variability. We postulate the existence of endogenous molecules within the human brain exerting an antiaggregant activity that will prevent/slow Alzheimer disease progression. We performed in silico studies to determine if the small endogenous molecules L-phosphoserine (L-PS) and 3-hydroxyanthranilic acid (3-HAA) could bind to the target region of ß-amyloid responsible for protein misfolding. In vitro assays measured the antiaggregation effect of these molecules at varying concentrations. In silico studies demonstrated that L-PS and 3-HAA, both endogenous brain molecules, were capable of binding to the histidine(13)-histidine-glutamine-lysine(16) (HHQK) region of ß-amyloid involved in misfolding: these interactions were energetically favoured. The in vitro assays showed that both L-PS and 3-HAA were capable of inhibiting ß-amyloid aggregation in a dose-dependent manner, with 3-HAA being more potent than L-PS. Studies were performed in silico and in vitro but not in vivo. We successfully identified 2 endogenous brain molecules, L-PS and 3-HAA, that were capable of binding to the region of ß-amyloid that leads to protein misfolding and neurotoxicity. Both L-PS and 3-HAA were able to inhibit ß-amyloid aggregation in varying concentrations; levels of these compounds in the brain may impact their effectiveness in slowing/preventing ß-amyloid aggregation.

Chronic exercise leads to antiaggregant, antioxidant and anti-inflammatory effects in heart failure patients

Heart failure (HF) patients are at an increased risk of thrombotic events. Here, we investigated the effects of exercise training on platelet function and factors involved in its modulation in HF. Thirty HF patients were randomized to 6 months of supervised exercise training or to a control group that remained sedentary. Exercise training consisted of 30 min of moderate-intensity treadmill exercise, followed by resistance and stretching exercises, performed three times a week. Blood was collected before and after the intervention for platelet and plasma obtainment. Peak VO2 increased after exercise training (18.0 ± 2.2 vs. 23.8 ± 0.5 mlO2/kg/min; p < 0.05). Exercise training reduced platelet aggregation induced by both collagen and ADP (approximately -6%; p < 0.05), as well as platelet nitric oxide synthase activity (0.318 ± 0.030 vs. 0.250 ± 0.016 pmol/10(8) cells; p < 0.05). No difference in the above-mentioned variables were observed in the control group. No significant difference was observed in intraplatelet cyclic guanosine monophosphate levels among groups. There was a significant increase in the activity of the antioxidant enzymes superoxide dismutase and catalase in plasma and platelets, resulting in a decrease in both lipid and protein oxidative damage. Systemic levels of the inflammatory markers C-reactive protein, fibrinogen, and tumour necrosis factor α were also reduced in HF after training. Our results suggest that regular exercise training is a valuable adjunct to optimal medical management of HF, reducing platelet aggregation via antioxidant and anti-inflammatory effects, and, therefore, reducing the risk of future thrombotic events.

Effects of low-dose aspirin and fish oil on platelet function and NF-kappaB in adults with diabetes mellitus

IntroductionMany diabetics are insensitive to aspirin's platelet anti-aggregation effects. The possible modulating effects of co-administration of aspirin and fish oil in subjects with diabetes are poorly characterized. Participants and methodsThirty adults with type 2 diabetes mellitus were treated with aspirin 81mg/d for 7 days, then with fish oil 4g/day for 28 days, then the combination of fish oil and aspirin for another 7 days. ResultsAspirin alone and in combination with fish oil reduced platelet aggregation in most participants. Five of 7 participants classified as aspirin insensitive 1 week after daily aspirin ingestion were sensitive after the combination. Although some platelet aggregation measures correlated positively after aspirin and fish oil ingestion alone and (in combination) in all individuals, correlation was only observed in those who were aspirin insensitive after ingestion of the combination. ConclusionsCo-administration of aspirin and fish oil may reduce platelet aggregation more than aspirin alone in adults with diabetes mellitus.

Does aspirin use prevent acute coronary syndrome in patients with pneumonia

The aim of this study was to test the hypothesis that aspirin would reduce the risk for acute coronary syndromes (ACSs) in patients with pneumonia. Pooled data suggest that pneumonia may trigger an ACS as a result of inflammatory reactions and the prothrombotic changes in patients with pneumonia. Hypothetically considering its antiaggregating and anti-inflammatory effects, aspirin might also be beneficial for the primary prevention of ACS in patients with pneumonia. One hundred and eighty-five patients with pneumonia who had more than one risk factor for cardiovascular disease were randomized to an aspirin group (n=91) or a control group (n=94). The patients in the aspirin group received 300 mg of aspirin daily for 1 month. ECGs were recorded on admission and 48 h and 30 days after admission to assess silent ischemia. The level of high-sensitivity cardiac troponin T was measured on admission and 48 h after admission. The primary endpoint was the development of ACS within 1 month. The secondary endpoints included cardiovascular death and death from any cause within 1 month. The χ-test showed that the rates of ACS at 1 month were 1.1% (n=1) in the aspirin group and 10.6% (n=10) in the control group (relative risk, 0.103; 95% confidence interval 0.005-0.746; P=0.015). Aspirin therapy was associated with a 9% absolute reduction in the risk for ACS. There was no significant decrease in the risk of death from any cause (P=0.151), but the aspirin group had a decreased risk of cardiovascular death (risk reduction: 0.04, P=0.044). This randomized open-label study shows that acetyl salicylic acid is beneficial in the reduction of ACS and cardiovascular mortality among patients with pneumonia.

Effects of imidazoline and nonimidazoline alpha-adrenergic agents, including xylazine, medetomidine, yohimbine, tolazoline, and atipamezole, on aggregation of bovine and equine platelets

To investigate effects of various imidazoline and nonimidazoline α-adrenergic agents on aggregation and antiaggregation of bovine and equine platelets. Blood samples obtained from 8 healthy adult cattle and 16 healthy adult Thoroughbreds. Aggregation and antiaggregation effects of various imidazoline and nonimidazoline α-adrenergic agents on bovine and equine platelets were determined via a turbidimetric method. Collagen and ADP were used to initiate aggregation. Adrenaline, noradrenaline, or α-adrenoceptor agents alone did not induce changes in aggregation of bovine or equine platelets or potentiate ADP- or collagen-induced platelet aggregation. Adrenaline and the α(2)-adrenoceptor agonist clonidine had an inhibitory effect on ADP- and collagen-induced aggregation of bovine platelets. The α(2)-adrenoceptor antagonists phentolamine and yohimbine also inhibited collagen-induced aggregation of bovine platelets. Noradrenaline, other α-adrenoceptor agonists (xylazine, oxymetazoline, and medetomidine), and α-adrenoceptor antagonists (atipamezole, idazoxan, tolazoline, and prazosin) were less effective or completely ineffective in inhibiting ADP- and collagen-induced aggregation of bovine platelets. The imidazoline α(2)-adrenoceptor agonist oxymetazoline submaximally inhibited collagen-induced aggregation of equine platelets, and the α(2)-adrenoceptor antagonist idazoxan, along with phentolamine and yohimbine, also inhibited collagen-induced aggregation of equine platelets. The imidazoline compound antazoline inhibited both ADP- and collagen-induced aggregation of equine platelets. Several drugs had effects on aggregation of platelets of cattle and horses, and effective doses of ADP and collagen also differed between species. The α(2)-adrenoceptor agonists (xylazine and medetomidine) and antagonists (tolazoline and atipamezole) may be used by bovine and equine practitioners without concern for adverse effects on platelet function and hemostasis.

Metformin in dermatology: an overview

For several decades, metformin has been used as an oral hypoglycaemic agent, where it is the first line of treatment in overweight and obese type 2 diabetic patients. This is because it decreases the hepatic glucose output and acts as an insulin sensitizer by increasing the glucose utilization by muscles and adipocytes. As a result of the improvement in glycaemic control, serum insulin concentrations decline slightly, thus improving hyperinsulinaemia and its signs. In addition, it has been shown that metformin has platelet anti-aggregating and antioxidant effects. These pharmacological properties have allowed metformin to be effective in non-diabetic situations including cutaneous conditions. This is an evidence-based review on the use of metformin in the treatment of skin disorders such as hirsutism, acne, hidradenitis suppurativa, acanthosis nigricans, psoriasis, skin cancer, among others. In addition, cutaneous side-effects such as leukocytoclastic vasculitis, bullous pemphigoid, psoriasiform drug eruption, lichen planus and acute alopecia have been associated with metformin use and are discussed in the article.

Effects of Imidazoline and Non-Imidazoline α-Adrenergic Agents on Rabbit Platelet Aggregation

Background/Aims: Imidazoline α₂-adrenergic agents exert complex effects on mammalian platelet aggregation. Although non-adrenergic, imidazoline (I) receptors have been revealed in human platelets, there is limited information about imidazoline’s action on platelet aggregation. This study aimed to investigate aggregatory and anti-aggregatory effects of various imidazoline or non-imidazoline α-adrenergic agents on rabbit platelets. Methods: Aggregatory responses of agents on rabbit platelets were examined by turbidimetric method. Radioligand binding assay to platelet I₁ and I₂ receptors was performed using [³H]-clonidine and [³H]-idazoxan, respectively. Results: Aggregation was not induced by α-adrenoceptor agonists alone. Adrenaline and noradrenaline produced dose-dependent potentiation of ADP- or collagen-induced aggregation. Imidazoline adrenoceptor agonists clonidine and p-aminoclonidine also potentiated ADP-induced platelet aggregation. The α₂-adrenoceptor antagonists and/or certain imidazoline adrenergic agents inhibited adrenaline-potentiated aggregation in a dose-dependent manner, whereas α₁-adrenoceptor antagonists and non-imidazoline α-adrenergic agents were either ineffective or less effective in inhibiting adrenaline-potentiated aggregation. Rabbit platelets did not have I₁ receptors, but had I₂ receptors, indicating that adrenaline-potentiated platelet aggregation was inhibited by idazoxan, but not by imidazoline compounds clonidine and oxymetazoline. Conclusions/Implications: These results demonstrated that α₂-adrenoceptor-blocking agents and/or imidazoline α-adrenergic agents effectively inhibit adrenaline-potentiated platelet aggregation. It is proposed that imidazoline structure in part plays a role in the inhibition of adrenaline-potentiated aggregation.

Inhibitory effects of black soybean on platelet activation mediated through its active component of adenosine

Owing to the beneficial health effects on human cardiovascular system, soybeans and soy-related products have been a focus of intensive research. Soy isoflavones are known to be primarily responsible for the soy-related biological effects including anti-platelet activity but its in vivo relevancy has not been fully verified. Here we compared the role of adenosine, an active ingredient abundant in black soybean (BB) extract, in the anti-platelet effects of BB, to that of soy isoflavones. At the concentrations existing in BB, isoflavones such as genistein and daidzein could not attenuate collagen-induced platelet aggregation, however, adenosine significantly inhibited platelet aggregation with an equivalent potency to BB, suggesting that adenosine may be the major bioactive component. Consistently, the anti-aggregatory effects of BB disappeared after treatment of adenosine receptor antagonists. The effects of BB are mediated by adenosine through intracellular cAMP and subsequent attenuation of calcium mobilization. Of note, adenosine and BB significantly reduced platelet fibrinogen binding and platelet adhesion, other critical events for platelet activation, which were not affected by isoflavones. Taken together, we demonstrated that adenosine might be the major active ingredient for BB-induced anti-platelet activity, which will shed new light on the roles of adenosine as a bioactive compound in soybeans and soy-related food.

Anti-aggregation Effects on Liposomes during Desiccation by Model Peptides of Group3 LEA Proteins

Anti-aggregation Effects on Liposomes during Desiccation by Model Peptides of Group3 LEA Proteins

2P212 グループ3 LEAタンパク質のモデルペプチドによるリポソームの乾燥誘導凝集抑制(13A.生体膜・人工膜:構造・物性,ポスター,日本生物物理学会年会第51回(2013年度))

2P212 グループ3 LEAタンパク質のモデルペプチドによるリポソームの乾燥誘導凝集抑制(13A.生体膜・人工膜:構造・物性,ポスター,日本生物物理学会年会第51回(2013年度))

Highly sensitive and selective colorimetric detection of iodide based on anti-aggregation of gold nanoparticles

A simple and reliable colorimetric detection method for iodide has been well established based on the anti-aggregation effect of AuNPs in this paper. This assay is highly sensitive and selective toward iodide over other interferent anions due to the high stability of the inorganic complex formed between Hg2+ and iodide. In the absence of iodide, T-rich single-stranded DNA (ssDNA) can specifically bind with Hg2+ to form a stable T–Hg2+–T complex, inducing the solution color change from wine-red to finally violet blue with increasing concentration of Hg2+. However, when Hg2+ is first treated with iodide, the T–Hg2+–T interaction will be interrupted, which results in the anti-aggregation of AuNPs. A linear response from 4 × 10−8 to 4 × 10−6 M was obtained for iodide, and a detection limit of 13 nM was achieved.

Pharmacological Characterization of 1-Nitrosocyclohexyl Acetate, a Long-Acting Nitroxyl Donor That Shows Vasorelaxant and Antiaggregatory Effects

Nitroxyl (HNO) donors have potential benefit in the treatment of heart failure and other cardiovascular diseases. 1-Nitrosocyclohexyl acetate (NCA), a new HNO donor, in contrast to the classic HNO donors Angeli's salt and isopropylamine NONOate, predominantly releases HNO and has a longer half-life. This study investigated the vasodilatative properties of NCA in isolated aortic rings and human platelets and its mechanism of action. NCA was applied on aortic rings isolated from wild-type mice and apolipoprotein E-deficient mice and in endothelial-denuded aortae. The mechanism of action of HNO was examined by applying NCA in the absence and presence of the HNO scavenger glutathione (GSH) and inhibitors of soluble guanylyl cyclase (sGC), adenylyl cyclase (AC), calcitonin gene-related peptide receptor (CGRP), and K(+) channels. NCA induced a concentration-dependent relaxation (EC(50), 4.4 µM). This response did not differ between all groups, indicating an endothelium-independent relaxation effect. The concentration-response was markedly decreased in the presence of excess GSH; the nitric oxide scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide had no effect. Inhibitors of sGC, CGRP, and voltage-dependent K(+) channels each significantly impaired the vasodilator response to NCA. In contrast, inhibitors of AC, ATP-sensitive K(+) channels, or high-conductance Ca(2+)-activated K(+) channels did not change the effects of NCA. NCA significantly reduced contractile response and platelet aggregation mediated by the thromboxane A(2) mimetic 9,11-dideoxy-11α,9α-epoxymethanoprostaglandin F(2)(α) in a cGMP-dependent manner. In summary, NCA shows vasoprotective effects and may have a promising profile as a therapeutic agent in vascular dysfunction, warranting further evaluation.

Molecular Interactions of Alzheimer's Biomarker FDDNP with Aβ Peptide

All-atom explicit solvent model and replica exchange molecular dynamics were used to investigate binding of Alzheimer's biomarker FDDNP to the Aβ10–40 monomer. At low and high concentrations, FDDNP binds with high affinity to two sites in the Aβ10–40 monomer located near the central hydrophobic cluster and in the C-terminal. Analysis of ligand- Aβ10–40 interactions at both concentrations identifies hydrophobic effect as a main binding factor. However, with the increase in ligand concentration the interactions between FDDNP molecules also become important due to strong FDDNP self-aggregation propensity and few specific binding locations. As a result, FDDNP ligands partially penetrate the core of the Aβ10–40 monomer, forming large self-aggregated clusters. Ligand self-aggregation does not affect hydrophobic interactions as a main binding factor or the location of binding sites in Aβ10–40. Using the Aβ10–40 conformational ensemble in ligand-free water as reference, we show that FDDNP induces minor changes in the Aβ10–40 secondary structure at two ligand concentrations studied. At the same time, FDDNP significantly alters the peptide tertiary fold in a concentration-dependent manner by redistributing long-range, side-chain interactions. We argue that because FDDNP does not change Aβ10–40 secondary structure, its antiaggregation effect is likely to be weak. Our study raises the possibility that FDDNP may serve as a biomarker of not only Aβ fibril species, but of monomers as well.