Unselective Inhibition Research Articles

New Selective Inhibitors of α‐Glucosidase for the Treatment of Type 2 Diabetes Mellitus

AbstractType 2 diabetes mellitus is a metabolic dreadful disease caused by an uncontrolled glucose level in the bloodstream, particularly high after a meal. Inhibitors of glucosidases, involved in the digestion of carbohydrates, can regulate this post‐prandial increase in glucose concentration. The traditional drugs act as competitive inhibitors of both pancreatic α‐amylase and α‐glucosidases and this unselective inhibition is behind severe gastrointestinal side effects related to the concomitant inhibition of α‐amylase. We described herein some perglycosylated cyclodextrins as efficient and selective inhibitors of α‐glucosidase with low micromolar IC50 (3.64‐7.98 μM) compared to the acarbose (IC50 212 μM), clinically used for patients suffering from type 2 diabetes. On the other hand, they do not inhibit α‐amylase (IC50>500 μM). Structure/activity relationship rationalization suggests multiple interactions between the described inhibitors and α‐glucosidase, which support the existence of both active site and allosteric interactions.

Photocaged Histone Deacetylase Inhibitors as Prodrugs in Targeted Cancer Therapy.

Histone deacetylases (HDACs) play a key role in the control of transcription, cell proliferation, and migration. FDA-approved histone deacetylase inhibitors (HDACi) demonstrate clinical efficacy in the treatment of different T-cell lymphomas and multiple myeloma. However, due to unselective inhibition, they display a wide range of adverse effects. One approach to avoiding off-target effects is the use of prodrugs enabling a controlled release of the inhibitor in the target tissue. Herein, we describe the synthesis and biological evaluation of HDACi prodrugs with photo-cleavable protecting groups masking the zinc-binding group of the established HDACi DDK137 (I) and VK1 (II). Initial decaging experiments confirmed that the photocaged HDACi pc-I could be deprotected to its parent inhibitor I. In HDAC inhibition assays, pc-I displayed only low inhibitory activity against HDAC1 and HDAC6. After irradiation with light, the inhibitory activity of pc-I strongly increased. Subsequent MTT viability assays, whole-cell HDAC inhibition assays, and immunoblot analysis confirmed the inactivity of pc-I at the cellular level. Upon irradiation, pc-I demonstrated pronounced HDAC inhibitory and antiproliferative activities which were comparable to the parent inhibitor I. Additionally, only phototreated pc-I was able to induce apoptosis in Annexin V/PI and caspase-Glo 3/7 assays, making pc-I a valuable tool for the development of light-activatable HDACi.

Effects of anti-cyclooxygenases (COX-1 and COX-2), structure activity relationship, molecular docking and in silico ADMET of some synthesized chalcones

Purpose: To develop effective cancer chemopreventive and anti-inflammatory agents, a series of chalcones were prepared by reacting suitable aromatic aldehyde with appropriate acetophenones.
 Methods: Twenty-four synthesized chalcones (namely, 1 - 24) were assessed for their in vitro anti-cyclooxygenase-1 (COX-1) and anti-cyclooxygenase-2 (COX-2) activity in a COX catalyzed prostaglandin synthesis bioassay. Molecular docking was done to investigate the ligand-protein interactions, and selectivity on both enzymes. ADMET (absorption, distribution, metabolism, excretion, toxicity) modeling and software were also used.
 Results: The compounds inhibited both COX-1 and COX-2. Two compounds (3 and 19) demonstrated more marked COX-2 inhibition than compound 1. Indomethacin as a standard anti-cyclooxygenase shows unselective inhibition of 81.44 ± 6.5 and 91 ± 9.5, respectively. The in silico data revealed that a chalcone skeleton with C=O at 4-position, C2–C3 double bond and OH at 5-position are necessary properties for anti-cyclooxygenase effects. It was also revealed that the propenone moiety comprises of an appropriate scaffold which proposes a new acyclic 1,3-diphenylprop-2-en-1-ones with selective anti-COX effects. A molecular modeling investigations where these chalcones 1, 3 and 19 were docked in the active site of COX-2 depicted that the p-CH3 substituent on the C-4- phenyl ring A are oriented in the vicinity of the COX-2 secondary pocket Phe381, Gly526, Tyr385 and Val349.
 Conclusion: Based on the screening for oral bioavailability, in silico ADMET, and toxicity risk assessment, this study shows that these compounds could be a cornerstone for the development of new pharmaceuticals in the battle against COX-associated inflammatory disorders.

Binding mechanism of selective cathepsin K/S inhibition revealed from molecular simulations

Cathepsin K and S are two isoforms of cysteine protease with diverse biological functions in the aspect of osteoporosis and autoimmune diseases. Accordingly, the homologous sequence and similar binding site features among CTSK/S may lead to unselective inhibition and side effects. To address such issue, various computational strategies were applied in the current study to explore the selectivity mechanism of CTSK/S inhibitors, including sequence alignment, molecular docking, MD simulations, MM/GBSA energy calculation, and so on. Our findings highlight the notable effects of CTSK residues Glu59 and Tyr67, as well as CTSS residue Asn67, on inhibition selectivity. Overall, this study provides an informative guideline for the rational design of CTSK/S selective inhibitors.

Carborane Analogues of Fenoprofen Exhibit Improved Antitumor Activity.

Fenoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) against rheumatoid arthritis, degenerative joint disease, ankylosing spondylitis and gout. Like other NSAIDs, fenoprofen inhibits the synthesis of prostaglandins by blocking both cyclooxygenase (COX) isoforms, COX-1 the "house-keeping" enzyme and COX-2 the induced isoform from pathological stimuli. Unselective inhibition of both COX isoforms results in many side effects, but off-target effects have also been reported. The steric modifications of the drugs could afford the desired COX-2 selectivity. Furthermore, NSAIDs have shown promising cytotoxic properties. The structural modification of fenoprofen using bulky dicarba-closo-dodecaborane(12) (carborane) clusters and the biological evaluation of the carborane analogues for COX inhibition and antitumor potential showed that the carborane analogues exhibit stronger antitumor potential compared to their respective aryl-based compounds.

Prostaglandin D2 inhibits mediator release and antigen induced bronchoconstriction in the Guinea pig trachea by activation of DP1 receptors

The mechanism by which cyclooxygenase (COX) inhibition increases antigen-induced responses in airways remains unknown.Male albino guinea pigs were sensitized to ovalbumin (OVA). Intact rings of the trachea were isolated and mounted in organ baths for either force measurements or lipid mediator release analysis by UPLC-MS/MS or EIA following relevant pharmacological interventions.First, challenge with OVA increased the release of all primary prostanoids (prostaglandin (PG) D2/E2/F2α/I2 and thromboxanes). This release was eliminated by unselective COX inhibition (indomethacin) whereas selective inhibition of COX-2 (lumiracoxib) did not inhibit release of PGD2 or thromboxanes. Additionally, the increased levels of leukotriene B4 and E4 after OVA were further amplified by unselective COX inhibition. Second, unselective inhibition of COX and selective inhibition of the prostaglandin D synthase (2-Phenyl-Pyrimidine-5-Carboxylic Acid (2,3-dihydro-indol-1-yl)-amide) amplified the antigen-induced bronchoconstriction which was reversed by exogenous PGD2. Third, a DP1 receptor agonist (BW 245c) concentration-dependently reduced the antigen-induced constriction as well as reducing released histamine and cysteinyl-leukotrienes, a response inhibited by the DP1 receptor antagonist (MK-524). In contrast, a DP2 receptor agonist (15(R)-15-methyl PGD2) failed to modulate the OVA-induced constriction.In the guinea pig trachea, endogenous PGD2 is generated via COX-1 and mediates an inhibitory effect of the antigen-induced bronchoconstriction via DP1 receptors inhibiting mast cell release of bronchoconstrictive mediators. Removal of this protective function by COX-inhibition results in increased release of mast cell mediators and enhanced bronchoconstriction.

Unruptured Intracranial Aneurysms.

Unruptured Intracranial Aneurysms.

Differential inhibition of cardiac and neuronal Na+ channels by the selective serotonin-norepinephrine reuptake inhibitors duloxetine and venlafaxine

Duloxetine and venlafaxine are selective serotonin-norepinephrine-reuptake-inhibitors used as antidepressants and co-analgesics. While venlafaxine rather than duloxetine induce cardiovascular side-effects, neither of the substances are regarded cardiotoxic. Inhibition of cardiac Na+-channels can be associated with cardiotoxicity, and duloxetine was demonstrated to block neuronal Na+-channels. The aim of this study was to investigate if the non-life threatening cardiotoxicities of duloxetine and venlafaxine correlate with a weak inhibition of cardiac Na+-channels.Effects of duloxetine, venlafaxine and amitriptyline were examined on endogenous Na+-channels in neuroblastoma ND7/23 cells and on the α-subunits Nav1.5, Nav1.7 and Nav1.8 with whole-cell patch clamp recordings.Tonic block of the cardiac Na+-channel Nav1.5 and rat-cardiomyocytes (CM) revealed a higher potency for duloxetine (Nav 1.5 IC50 14±1µM, CM IC50 27±3µM) as compared to venlafaxine (Nav 1.5 IC50 671±26µM, CM IC50 452±34µM). Duloxetine was as potent as the cardiotoxic antidepressant amitriptyline (IC50 13±1µM). While venlafaxine almost failed to induce use-dependent block on Nav1.5 and cardiomyocytes, low concentrations of duloxetine (1, 10µM) induced prominent use-dependent block similar to amitriptyline. Duloxetine, but not venlafaxine stabilized fast and slow inactivation and delayed recovery from inactivation. Duloxetine induced an unselective inhibition of neuronal Na+-channels (IC50 ND7/23 23±1µM, Nav1.7 19±2µM, Nav1.8 29±2).Duloxetine, but not venlafaxine inhibits cardiac Na+-channels with a potency similar to amitriptyline. These data indicate that an inhibition of Na+-channels does not predict a clinically relevant cardiotoxicity.

Selectivity and Sparseness in Randomly Connected Balanced Networks

Neurons in sensory cortex show stimulus selectivity and sparse population response, even in cases where no strong functionally specific structure in connectivity can be detected. This raises the question whether selectivity and sparseness can be generated and maintained in randomly connected networks. We consider a recurrent network of excitatory and inhibitory spiking neurons with random connectivity, driven by random projections from an input layer of stimulus selective neurons. In this architecture, the stimulus-to-stimulus and neuron-to-neuron modulation of total synaptic input is weak compared to the mean input. Surprisingly, we show that in the balanced state the network can still support high stimulus selectivity and sparse population response. In the balanced state, strong synapses amplify the variation in synaptic input and recurrent inhibition cancels the mean. Functional specificity in connectivity emerges due to the inhomogeneity caused by the generative statistical rule used to build the network. We further elucidate the mechanism behind and evaluate the effects of model parameters on population sparseness and stimulus selectivity. Network response to mixtures of stimuli is investigated. It is shown that a balanced state with unselective inhibition can be achieved with densely connected input to inhibitory population. Balanced networks exhibit the “paradoxical” effect: an increase in excitatory drive to inhibition leads to decreased inhibitory population firing rate. We compare and contrast selectivity and sparseness generated by the balanced network to randomly connected unbalanced networks. Finally, we discuss our results in light of experiments.

Inhibition in Multiclass Classification

The role of inhibition is investigated in a multiclass support vector machine formalism inspired by the brain structure of insects. The so-called mushroom bodies have a set of output neurons, or classification functions, that compete with each other to encode a particular input. Strongly active output neurons depress or inhibit the remaining outputs without knowing which is correct or incorrect. Accordingly, we propose to use a classification function that embodies unselective inhibition and train it in the large margin classifier framework. Inhibition leads to more robust classifiers in the sense that they perform better on larger areas of appropriate hyperparameters when assessed with leave-one-out strategies. We also show that the classifier with inhibition is a tight bound to probabilistic exponential models and is Bayes consistent for 3-class problems. These properties make this approach useful for data sets with a limited number of labeled examples. For larger data sets, there is no significant comparative advantage to other multiclass SVM approaches.

On the Pro-Metastatic Stress Response to Cancer Therapies: Evidence for a Positive Co-Operation between TIMP-1, HIF-1α, and miR-210

In contrast to expectations in the past that tumor starvation or unselective inhibition of proteolytic activity would cure cancer, there is accumulating evidence that microenvironmental stress, such as hypoxia or broad-spectrum inhibition of metalloproteinases can promote metastasis. In fact, malignant tumor cells, due to their genetic and epigenetic instability, are predisposed to react to stress by adaptation and, if the stress persists, by escape and formation of metastasis. Recent recognition of the concepts of dynamic evolution as well as population and systems biology is extremely helpful to understand the disappointments of clinical trials with new drugs and may lead to paradigm-shifts in therapy strategies. This must be complemented by an increased understanding of molecular mechanism involved in stress response. Here, we review new roles of Hypoxia-inducible factor-1 (HIF-1), one transcription factor regulating stress response-related gene expression: HIF-1 is crucial for invasion and metastasis, independent from its pro-survival function. In addition, HIF-1 mediates pro-metastatic microenvironmental changes of the proteolytic balance as triggered by high systemic levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), typical for many aggressive cancers, and regulates the metabolic switch to glycolysis, notably via activation of the microRNA miR-210. There is preliminary evidence that TIMP-1 also induces miR-210. Such positive-regulatory co-operation of HIF-1α, miR-210, and TIMP-1, all described to correlate with bad prognosis of cancer patients, opens new perspectives of gaining insight into molecular mechanisms of metastasis-inducing evasion of tumor cells from stress.

Differential effects on cell motility, embryonic stem cell self-renewal and senescence by diverse Src kinase family inhibitors

The Src family of non-receptor tyrosine kinases (SFKs) has been shown to play an intricate role in embryonic stem (ES) cell maintenance. In the present study we have focused on the underlying molecular mechanisms responsible for the vastly different effects induced by various commonly used SFK inhibitors. We show that several diverse cell types, including fibroblasts completely lacking SFKs, cannot undergo mitosis in response to SU6656 and that this is caused by an unselective inhibition of Aurora kinases. In contrast, PP2 and PD173952 block motility immediately upon exposure and forces cells to grow in dense colonies. The subsequent halt in proliferation of fibroblast and epithelial cells in the center of the colonies approximately 24 h post-treatment appears to be caused by cell-to-cell contact inhibition rather than a direct effect of SFK kinase inhibition. Interestingly, in addition to generating more homogenous and dense ES cell cultures, without any diverse effect on proliferation, PP2 and PD173652 also promote ES cell self-renewal by reducing the small amount of spontaneous differentiation typically observed under standard ES cell culture conditions. These effects could not be mirrored by the use of Gleevec, a potent inhibitor of c-Abl and PDGFR kinases that are also inhibited by PP2.

Targeting HDACs in Pediatric Oncology

The analysis of the human acetylome has revealed that about 2000 proteins are regulated through reversible acetylation in a given cell, suggesting that this post-translational modification system may be equally important as protein phosphorylation. The acetylome is at least partially controlled by the human histone deacetylase (HDAC) family consisting of 11 members. It is now becoming clear that this family of enzymes regulate the acetylation status of numerous cellular proteins beyond histones and the term protein/lysine deacetylases has recently been introduced. The contribution of individual HDACs to cancer biology in general and in pediatric malignancies in particular is largely unknown, although it has been shown in numerous tumor models that their unselective inhibition results in anti-cancer effects. We have discovered that high expression of distinct and so far poorly studied HDAC family members is associated with unfavorable clinical outcome in neuroblastoma, medulloblastoma, and ependymoma tumors. Functionally, these HDACs suppress differentiation and apoptosis, and promote clonogenic survival and proliferation in cultured cells. Of note, cancer stem cells isolated from a patient with chemotherapy-resistant anaplastic ependymoma showed sensitivity to HDACs targeting. Selective targeting of individual HDACs through novel small molecule compounds recapitulate the anti-cancer phenotype observed with siRNA mediated knockdown. Translation of these findings in an early phase I/II clinical trial in pediatric oncology is currently underway.

SLC4A7 sodium bicarbonate co-transporter controls mitochondrial apoptosis in ischaemic coronary endothelial cells

Bicarbonate transport has been shown to participate in apoptosis under ischaemic stress. However, the precise transporting mechanisms involved in ischaemic apoptosis are unknown and were thus the aim of the present study. Rat coronary endothelial cells (EC) were exposed to simulated in vitro ischaemia for 2 h, and apoptosis was subsequently determined by chromatin staining and caspase-3 activity analysis. By examining the expression of bicarbonate transporters (BT) in EC by reverse transcriptase polymerase chain reaction and western blotting, a marked expression of the electroneutral sodium bicarbonate co-transporter (SLC4A7) was defined. To analyse the potential role of this transporter during apoptosis, a selective inhibitor (S0859, Sanofi-Aventis) was applied. Treatment with S0859 significantly increased caspase-3 activity and elevated the number of apoptotic EC. These results were comparable with an unselective inhibition of all BT due to withdrawal of bicarbonate in the anoxic medium. Knockdown of SLC4A7 in EC by transfecting appropriate siRNA similarly increased apoptosis of EC under simulated ischaemia. The initial characterization of the participating mechanisms of SLC4A7-dependent apoptosis revealed an activation of the mitochondrial pathway of apoptosis, i.e. cleavage of caspase-9 and binding of Bax to mitochondria. In contrast, no activation of the endoplasmic reticulum-dependent pathway (caspase-12 cleavage) or the extrinsic apoptotic pathway (caspase-8 cleavage) was found. Finally, a mitochondrial localization of SLC4A7 was demonstrated. The electroneutral sodium bicarbonate co-transporter SLC4A7 localizes in mitochondria and suppresses the ischaemia-induced activation of the mitochondrial pathway of apoptosis in coronary EC.

Targeting of HDAC8 and investigational inhibitors in neuroblastoma

Histone deacetylase (HDAC) inhibitors are an emerging class of promising novel anticancer drugs. However, little is known which one of the 11 classical HDAC family members is the most relevant drug target for therapy. The first Phase I/II trials show that unselective inhibition of HDACs causes a variety of side effects. Therefore, identification and selective targeting of the most critical tumor entity-relevant HDAC family member may reduce unspecific effects and increase antitumor efficacy in the future. Here, we review the clinical relevance of a particular HDAC family member, HDAC8, in neuroblastoma biology, a highly malignant embryonal childhood cancer. HDAC8 expression correlates with poor outcome in neuroblastoma and selective HDAC8 inhibition induces differentiation. In contrast, the targeting of other HDAC family members results in a completely different phenotype. Because HDAC8-selective inhibitors are available, HDAC8 may be a potential drug target for neuroblastoma differentiation therapy using selective inhibitors, avoiding unspecific side effects.

Stimulus Feature Selectivity in Excitatory and Inhibitory Neurons in Primary Visual Cortex

Although several lines of evidence suggest that stimulus selectivity in somatosensory and visual cortices is critically dependent on unselective inhibition, particularly in the thalamorecipient layer 4, no comprehensive comparison of the responses of excitatory and inhibitory cells has been conducted. Here, we recorded intracellularly from a large population of regular spiking (RS; presumed excitatory) and fast spiking (FS; presumed inhibitory) cells in layers 2-6 of primary visual cortex. In layer 4, where selectivity for orientation and spatial frequency first emerges, we found no untuned FS cells. Instead, the tuning of the spike output of layer 4 FS cells was significantly but moderately broader than that of RS cells. However, the tuning of the underlying synaptic responses was not different, indicating that the difference in spike-output selectivity resulted from differences in the transformation of synaptic input into firing rate. Layer 4 FS cells exhibited significantly lower input resistance and faster time constants than layer 4 RS cells, leading to larger and faster membrane potential (V(m)) fluctuations. FS cell V(m) fluctuations were more broadly tuned than those of RS cells and matched spike-output tuning, suggesting that the broader spike tuning of these cells was driven by visually evoked synaptic noise. These differences were not observed outside of layer 4. Thus, cell type-specific differences in stimulus feature selectivity at the first level of cortical sensory processing may arise as a result of distinct biophysical properties that determine the dynamics of synaptic integration.

Rolle des L-Arginin/NO-Stoffwechselweges im akuten Nierenversagen

Role of the L-arginine/NO-pathway in acute renal failure ■ Summary Regulation of renal hemodynamics – in particular intraglomerluar hemodynamics -is closely related to the L-arginine/ NO-pathway. Almost all forms of acute renal failure (ARF) are characterized by a reduction in renal plasma flow (RPF) and increased renal vascular resistance. NO, metabolized from L-arginine, is capable of improving renal function due to its vasorelaxing properties in almost all models of ARF, whereas unselective inhibition of nitric oxide synthase (NOS) generally exerts contrary effects. Increased tubular generation of oxygen radicals in the early course of ischemic ARF indicates increased oxidative stress. Simultaneously regulatory changes in expression of iNOS (inducible NOS) and eNOS (endothelial NOS) are observed. Apart from the positive functional effects with L-arginine supplementation a remarkable reduction in the formation of oxygen radicals and reduced overexpression of iNOS are observed. This is important, because in ischemic ARF increased expression of iNOS is accompanied by increased formation of oxygen radicals and peroxynitrite. Both substances are highly reactive and exert many cytotoxic effects. eNOS-derived NO probably plays such an important role in maintaining and improving renal and intraglomerular hemodynamics that negative effects from iNOS-derived NO are overcome. The roles of NOS are different for different types of NOS and also depend on the time course of ARF. Future management strategies should focus on the interplay between antioxidants and NO regulators and the correlation of reactive oxygen species and NO.

Sympatho-modulatory therapies in perioperative medicine

With increasing life expectancy and improved surgical technology an ever-larger number of elderly patients with cardiovascular disease, or significant cardiovascular risk factors will undergo major surgery. More than 5% of an unselected surgical population undergoing non-cardiac surgery will suffer from perioperative cardiovascular complications including myocardial infarction and cardiac death. The incidence of adverse cardiac events may even reach 30% in high-risk patients undergoing vascular surgery causing a substantial financial burden of perioperative health care costs. 59 Thus, all therapeutic measures should be undertaken to reach the challenging goal of a lower incidence of perioperative cardiovascular complications. Gaining control over sympathetic nervous system activity, that is blunting the adrenergic response to the surgical trauma, traditionally represents an important aspect of anaesthetic practice. 21 Anaesthesiology has been regarded as the ‘practice of autonomic nervous system medicine’. While variable and moderate changes in sympathetic nervous system activity function as a servo-control mechanism and are even required to maintain and optimize cardiac performance, undue liberation of excitotoxic substances such as catecholamines and inflammatory cytokines, particularly during emergence from anaesthesia and the painful postoperative period, facilitates the occurrence of cardiovascular complications. 83 84 At this point, the life-supporting adrenergic drive (‘fight-or-flight-response’) turns into a potentially hazardous life-threatening maladaptation. In support of this concept, the beneficial effects of antiadrenergic treatment regimens in perioperative medicine have been confirmed, in observational studies, metaanalyses 55 1 66 and randomized controlled clinical trials. 43 54 59 63 80 84 However, the seemingly established concept of ‘sympatholysis’ as an effective cardioprotective treatment modality needs considerable refinement in the light of the many new experimental and clinical findings. The parlance of ‘sympatholytic’ protection erroneously equates annihilation of any type of adrenergic stimulation with cardioprotection and should be replaced by ‘sympathomodulatory’protection. The present review summarizes findings from large-scale heart failure trials and discusses basic and clinical aspects of individual sympatho-modulatory therapies, as currently used in perioperative medicine, including b-adrenergic antagonism, a2-agonism, and regional anaesthetic techniques. For limitation of space, reviews will often be cited where further references to the primary literature may be found.

1‐N‐Substituted Thiocarbamoyl‐3‐phenyl‐5‐thienyl‐2‐pyrazolines: Synthesis and Evaluation as MAO Inhibitors

Twelve new 1-N-substituted thiocarbomoyl-3-phenyl-5-thienyl-2-pyrazoline derivatives were synthesized and evaluated their for antidepressant, anxiogenic and mammalian monoamine oxidase (MAO)-A and Binhibitory activities by in vivo and in vitro tests. MAO was isolated and purified from the mitochondrial pellet of bovine liver homogenates and human platelets. All of the new compounds inhibited the total MAO activity of liver homogenates and the inhibition was found to be time-dependent. Four compounds (3 i-3 l) inhibited MAO-B selectively and irreversibly in a classical non-competitive manner with IC(50) values in the range of 22.00-91.50 microM. The rest of the compounds appeared to be non-selective reversible inhibitors. It was suggested that the p-methoxy group on the phenyl ring in the compounds increased the inhibitory effect and selectivity toward MAO-B. The reversible and unselective inhibition of MAO by the remaining compounds was suggested to be related to their properties of acting ability to act as both as substrate and inhibitor at the same time. However, none of the novel compounds showed antidepressant activity as expected suggesting formation of inactive metabolites. We conclude that the compounds appeared as which functioned as selective MAO-B inhibitors might have promising features as therapeutic properties in the treatment of Parkinson disease. In vivo studies are needed to verify this hypothesis.

Severe nose bleeding after intake of acetylsalicylic acid: von Willebrand disease type 2A

This case report of a school boy with a history of severe and repeated episodes of epistaxis presents a short overview of the clinical and laboratory findings which lead to confirm the suspected diagnosis of von Willebrand disease (vWD). Suspicion of defective primary haemostasis should arise when unusual (because of their number or duration) mucosal bleeds appear in an otherwise normal and healthy patient. Because of its definitive inhibitory effect on platelet aggregation, acetylsalicylic acid (more than other non-steroidal anti-inflammatory drugs exerting unselective inhibition of cyclooxygenase) is a strong factor in triggering or sustaining the bleeding disorders in these patients. Among the congenital disorder of primary haemostasis, vWD is by far the most frequent one. The difficulties of laboratory diagnosis of vWD are stressed; the promises and pitfalls of new in vitro methods for measuring primary haemostasis (PFA-100 analyzer) are discussed. An accurate diagnosis of the specific type of vWD is of critical importance for correct patient management as well as for genetic counseling.