Showing papers in "Current Medicinal Chemistry in 2008"

Green Tea Catechins and Cardiovascular Health : An Update

Abstract: Epidemiological, clinical and experimental studies have established a positive correlation between green tea consumption and cardiovascular health. Catechins, the major polyphenolic compounds in green tea, exert vascular protective effects through multiple mechanisms, including antioxidative, anti-hypertensive, anti-inflammatory, anti-proliferative, anti-thrombogenic, and lipid lowering effects. (1) Tea catechins present antioxidant activity by scavenging free radicals, chelating redox active transition-metal ions, inhibiting redox active transcription factors, inhibiting pro-oxidant enzymes and inducing antioxidant enzymes. (2) Tea catechins inhibit the key enzymes involved in lipid biosynthesis and reduce intestinal lipid absorption, thereby improving blood lipid profile. (3) Catechins regulate vascular tone by activating endothelial nitric oxide. (4) Catechins prevent vascular inflammation that plays a critical role in the progression of atherosclerotic lesions. The anti-inflammatory activities of catechins may be due to their suppression of leukocyte adhesion to endothelium and subsequent transmigration through inhibition of transcriptional factor NF-kB-mediated production of cytokines and adhesion molecules both in endothelial cells and inflammatory cells. (5) Catechins inhibit proliferation of vascular smooth muscle cells by interfering with vascular cell growth factors involved in atherogenesis. (6) Catechins suppress platelet adhesion, thereby inhibiting thrombogenesis. Taken together, catechins may be novel plant-derived small molecules for the prevention and treatment of cardiovascular diseases. This review highlights current developments in green tea extracts and vascular health, focusing specifically on the role of tea catechins in the prevention of various vascular diseases and the underlying mechanisms for these actions. In addition, the possible structure-activity relationship of catechins is discussed.

Hyperphosphorylation of microtubule-associated protein tau: a promising therapeutic target for Alzheimer disease.

Abstract: Alzheimer disease (AD) is the most common cause of dementia in adults. The current therapy for AD has only moderate efficacy in controlling symptoms, and it does not cure the disease. Recent studies have suggested that abnormal hyperphosphorylation of tau in the brain plays a vital role in the molecular pathogenesis of AD and in neurodegeneration. This article reviews the current advances in understanding of tau protein, regulation of tau phosphorylation, and the role of its abnormal hyperphosphorylation in neurofibrillary degeneration. Furthermore, several therapeutic strategies for treating AD on the basis of the important role of tau hyperphosphorylation in the pathogenesis of the disease are described. These strategies include (1) inhibition of glycogen synthase kinase-3beta (GSK-3beta), cyclin-dependent kinase 5 (cdk5), and other tau kinases; (2) restoration of PP2A activity; and (3) targeting tau O-GlcNAcylation. Development of drugs on the basis of these strategies is likely to lead to disease-modifying therapies for AD.

A Review of Coumarin Derivatives in Pharmacotherapy of Breast Cancer

Abstract: The coumarin (benzopyran-2-one, or chromen-2-one) ring system, present in natural products (such as the anticoagulant warfarin) that display interesting pharmacological properties, has intrigued chemists and medicinal chemists for decades to explore the natural coumarins or synthetic analogs for their applicability as drugs. Many molecules based on the coumarin ring system have been synthesized utilizing innovative synthetic techniques. The diversity oriented synthetic routes have led to interesting derivatives including the furanocoumarins, pyranocoumarins, and coumarin sulfamates (COUMATES), which have been found to be useful in photochemotherapy, antitumor and anti-HIV therapy, and as stimulants for central nervous system, antibacterials, anti-inflammatory, anti-coagulants, and dyes. Of particular interest in breast cancer chemotherapy, some coumarins and their active metabolite 7-hydroxycoumarin analogs have shown sulfatase and aromatase inhibitory activities. Coumarin based selective estrogen receptor modulators (SERMs) and coumarin-estrogen conjugates have also been described as potential antibreast cancer agents. Since breast cancer is the second leading cause of death in American women behind lung cancer, there is a strong impetus to identify potential new drug treatments for breast cancer. Therefore, the objective of this review is to focus on important coumarin analogs with antibreast cancer activities, highlight their mechanisms of action and structure-activity relationships on selected receptors in breast tissues, and the different methods that have been applied in the construction of these pharmacologically important coumarin analogs.

From single- to multi- target drugs in cancer therapy: when aspecificity becomes an advantage

Abstract: Targeted therapies by means of compounds that inhibit a specific target molecule represent a new perspective in the treatment of cancer. In contrast to conventional chemotherapy which acts on all dividing cells generating toxic effects and damage of normal tissues, targeted drugs allow to hit, in a more specific manner, subpopulations of cells directly involved in tumor progression. Molecules controlling cell proliferation and death, such as Tyrosine Kinase Receptors (RTKs) for growth factors, are among the best targets for this type of therapeutic approach. Two classes of compounds targeting RTKs are currently used in clinical practice: monoclonal antibodies and tyrosine kinase inhibitors. The era of targeted therapy began with the approval of Trastuzumab, a monoclonal antibody against HER2, for treatment of metastatic breast cancer, and Imatinib, a small tyrosine kinase inhibitor targeting BCR-Abl, in Chronic Myeloid Leukemia. Despite the initial enthusiasm for the efficacy of these treatments, clinicians had to face soon the problem of relapse, as almost invariably cancer patients developed drug resistance, often due to the activation of alternative RTKs pathways. In this view, the rationale at the basis of targeting drugs is radically shifting. In the past, the main effort was aimed at developing highly specific inhibitors acting on single RTKs. Now, there is a general agreement that molecules interfering simultaneously with multiple RTKs might be more effective than single target agents. With the recent approval by FDA of Sorafenib and Sunitinib--targeting VEGFR, PDGFR, FLT-3 and c-Kit--a different scenario has been emerging, where a new generation of anti-cancer drugs, able to inhibit more than one pathway, would probably play a major role.

Antioxidants and free radical scavengers for the treatment of stroke, traumatic brain injury and aging.

Abstract: The overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is a common underlying mechanism of many neuropathologies, as they have been shown to damage various cellular components, including proteins, lipids and DNA. Free radicals, especially superoxide (O2 .-), and non-radicals, such as hydrogen peroxide (H2O2), can be generated in quantities large enough to overwhelm endogenous protective enzyme systems, such as superoxide dismutase (SOD) and reduced glutathione (GSH). Here we review the mechanisms of ROS and RNS production, and their roles in ischemia, traumatic brain injury and aging. In particular, we discuss several acute and chronic pharmacological therapies that have been extensively studied in order to reduce ROS/RNS loads in cells and the subsequent oxidative stress, so-called “free-radical scavengers.” Although the overall aim has been to counteract the detrimental effects of ROS/RNS in these pathologies, success has been limited, especially in human clinical studies. This review highlights some of the recent successes and failures in animal and human studies by attempting to link a compounds chemical structure with its efficacy as a free radical scavenger. In particular, we demonstrate how antioxidants derived from natural products, as well as long-term dietary alterations, may prove to be effective scavengers of ROS and RNS.

Arbidol: a broad-spectrum antiviral compound that blocks viral fusion.

Abstract: Arbidol (ARB; ethyl-6-bromo-4-[(dimethylamino)methyl]-5-hydroxy-1-methyl-2-[(phenylthio)methyl]-indole-3-carboxylate hydrochloride monohydrate), is a Russian-made potent broad-spectrum antiviral with demonstrated activity against a number of enveloped and non-enveloped viruses. ARB is well known in Russia and China, although to a lesser extent in western countries. Unlike other broad-spectrum antivirals, ARB has an established molecular mechanism of action against influenza A and B viruses, which is different from that of available influenza antivirals, and a more recently established mechanism of inhibition of hepatitis C virus (HCV). For both viral infections the anti-viral mechanism involves ARB inhibition of virus-mediated fusion with target membrane and a resulting block of virus entry into target cells. However, ARB inhibition of fusion exploits different ARB modalities in case of influenza viruses or HCV. This review aims to summarize the available evidence of ARB effects against different groups of viruses, also, to compare various aspects of ARB anti-fusion mechanisms against influenza virus and HCV (with reference to different stringency of pH-dependence of these two viral fusogens) and to discuss further prospects for ARB and its improved derivatives of the parent compounds.

Substrates and inhibitors of human multidrug resistance associated proteins and the implications in drug development.

Abstract: Human contains 49 ATP-binding cassette (ABC) transporter genes and the multidrug resistance associated proteins (MRP1/ABCC1, MRP2/ABCC2, MRP3/ABCC3, MRP4/ABCC4, MRP5/ABCC5, MRP6/ABCC6, MRP7/ABCC10, MRP8/ABCC11 and MRP9/ABCC12) belong to the ABCC family which contains 13 members. ABCC7 is cystic fibrosis transmembrane conductance regulator; ABCC8 and ABCC9 are the sulfonylurea receptors which constitute the ATP-sensing subunits of a complex potassium channel. MRP10/ABCC13 is clearly a pseudo-gene which encodes a truncated protein that is highly expressed in fetal human liver with the highest similarity to MRP2/ABCC2 but without transporting activity. These transporters are localized to the apical and/or basolateral membrane of the hepatocytes, enterocytes, renal proximal tubule cells and endothelial cells of the blood-brain barrier. MRP/ABCC members transport a structurally diverse array of important endogenous substances and xenobiotics and their metabolites (in particular conjugates) with different substrate specificity and transport kinetics. The human MRP/ABCC transporters except MRP9/ABCC12 are all able to transport organic anions, such as drugs conjugated to glutathione, sulphate or glucuronate. In addition, selected MRP/ABCC members may transport a variety of endogenous compounds, such as leukotriene C(4) (LTC(4) by MRP1/ABCC1), bilirubin glucuronides (MRP2/ABCC2, and MRP3/ABCC3), prostaglandins E1 and E2 (MRP4/ABCC4), cGMP (MRP4/ABCC4, MRP5/ABCC5, and MRP8/ABCC11), and several glucuronosyl-, or sulfatidyl steroids. In vitro, the MRP/ABCC transporters can collectively confer resistance to natural product anticancer drugs and their conjugated metabolites, platinum compounds, folate antimetabolites, nucleoside and nucleotide analogs, arsenical and antimonial oxyanions, peptide-based agents, and in concert with alterations in phase II conjugating or biosynthetic enzymes, classical alkylating agents, alkylating agents. Several MRP/ABCC members (MRPs 1-3) are associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. Drug targeting of these transporters to overcome MRP/ABCC-mediated multidrug resistance may play a role in cancer chemotherapy. Most MRP/ABCC transporters are subject to inhibition by a variety of compounds. Based on currently available preclinical and limited clinical data, it can be expected that modulation of MRP members may represent a useful approach in the management of anticancer and antimicrobial drug resistance and possibly of inflammatory diseases and other diseases. A better understanding of their substrates and inhibitors has important implications in development of drugs for treatment of cancer and inflammation.

Novobiocin and additional inhibitors of the Hsp90 C-terminal nucleotide-binding pocket.

Abstract: The 90 kDa heat shock proteins (Hsp90), which are integrally involved in cell signaling, proliferation, and survival, are ubiquitously expressed in cells. Many proteins in tumor cells are dependent upon the Hsp90 protein folding machinery for their stability, refolding, and maturation. Inhibition of Hsp90 uniquely targets client proteins associated with all six hallmarks of cancer. Thus, Hsp90 has emerged as a promising target for the treatment of cancer. Hsp90 exists as a homodimer, which contains three domains. The N-terminal domain contains an ATP-binding site that binds the natural products geldanamycin and radicicol. The middle domain is highly charged and has high affinity for co-chaperones and client proteins. Initial studies by Csermely and co-workers suggested a second ATP-binding site in the C-terminus of Hsp90. This C-terminal nucleotide binding pocket has been shown to not only bind ATP, but cisplatin, novobiocin, epilgallocatechin-3-gallate (EGCG) and taxol. The coumarin antibiotics novobiocin, clorobiocin, and coumermycin A1 were isolated from several streptomyces strains and exhibit potent activity against Gram-positive bacteria. These compounds bind type II topoisomerases, including DNA gyrase, and inhibit the enzyme-catalyzed hydrolysis of ATP. As a result, novobiocin analogues have garnered the attention of numerous researchers as an attractive agent for the treatment of bacterial infection. Novobiocin was reported to bind weakly to the newly discovered Hsp90 C-terminal ATP binding site ( approximately 700 M in SkBr3 cells) and induce degradation of Hsp90 client proteins. Structural modification of this compound has led to an increase of 1000-fold in activity in anti-proliferative assays. Recent studies of structure-activity relationship (SAR) by Renoir and co-workers highlighted the crucial role of the C-4 and/or C-7 positions of the coumarin and removal of the noviose moiety, which appeared to be essential for degradation of Hsp90 client proteins. Unlike the N-terminal ATP binding site, there is no reported co-crystal structure of Hsp90 C-terminus bound to any inhibitor. The Hsp90 C-terminal domain, however, is known to contain a conserved pentapeptide sequence (MEEVD) which is recognized by co-chaperones. Cisplatin is a platinum-containing chemotherapeutic used to treat various types of cancers, including testicular, ovarian, bladder, and small cell lung cancer. Most notably, cisplatin coordinates to DNA bases, resulting in cross-linked DNA, which prohibits rapidly dividing cells from duplicating DNA for mitosis. Itoh and co-workers reported that cisplatin decreases the chaperone activity of Hsp90. This group applied bovine brain cytosol to a cisplatin affinity column, eluted with cisplatin and detected Hsp90 in the eluent. Subsequent experiments indicated that cisplatin exhibits high affinity for Hsp90. Moreover Csermely and co-workers determined that the cisplatin binding site is located proximal to the C-terminal ATP binding site. EGCG is one of the active ingredients found in green tea. EGCG is known to inhibit the activity of many Hsp90-dependent client proteins, including telomerase, several kinases, and the aryl hydrocarbon receptor (AhR). Recently Gasiewicz and co-workers reported that EGCG manifests its antagonistic activity against AhR through binding Hsp90. Similar to novobiocin, EGCG was shown to bind the C-terminus of Hsp90. Unlike previously identified N-terminal Hsp90 inhibitors, EGCG does not appear to prevent Hsp90 from forming multiprotein complexes. Studies are currently underway to determine whether EGCG competes with novobiocin or cisplatin binding. Taxol, a well-known drug for the treatment of cancer, is responsible for the stabilization of microtubules and the inhibition of mitosis. Previous studies have shown that taxol induces the activation of kinases and transcription factors, and mimics the effect of bacterial lipopolysaccharide (LPS), an attribute unrelated to its tubulin-binding properties. Rosen and co-workers prepared a biotinylated taxol derivative and performed affinity chromatography experiments with lysates from both mouse brain and macrophage cell lines. These studies led to identification of two chaperones, Hsp70 and Hsp90, by mass spectrometry. In contrast to typical Hsp90-binding drugs, taxol exhibits a stimulatory response. Recently it was reported that the geldanamycin derivative 17-AAG behaves synergistically with taxol-induced apoptosis. This review describes the different C-terminal inhibitors of Hsp90, with specific emphasis on structure-activity relationship studies of novobiocin and their effects on anti-proliferative activity.

Recent trends in targeted anticancer prodrug and conjugate design.

Abstract: Anticancer drugs are often nonselective antiproliferative agents (cytotoxins) that preferentially kill dividing cells by attacking their DNA at some level. The lack of selectivity results in significant toxicity to noncancerous proliferating cells. These toxicities along with drug resistance exhibited by the solid tumors are major therapy limiting factors that result into poor prognosis for patients. Prodrug and conjugate design involves the synthesis of inactive drug derivatives that are converted to an active form inside the body and preferably at the site of action. Classical prodrug and conjugate design have focused on the development of prodrugs that can overcome physicochemical (e.g., solubility, chemical instability) or biopharmaceutical problems (e.g., bioavailability, toxicity) associated with common anticancer drugs. The recent targeted prodrug and conjugate design, on the other hand, hinge on the selective delivery of anticancer agents to tumor tissues thereby avoiding their cytotoxic effects on noncancerous cells. Targeting strategies have attempted to take advantage of low extracellular pH, elevated enzymes in tumor tissues, the hypoxic environment inside the tumor core, and tumor-specific antigens expressed on tumor cell surfaces. The present review highlights recent trends in prodrug and conjugate rationale and design for cancer treatment. The various approaches that are currently being explored are critically analyzed and a comparative account of the advantages and disadvantages associated with each approach is presented.

Human Endotoxemia as a Model of Systemic Inflammation

Abstract: Systemic inflammation is a pathogenetic component in a vast number of acute and chronic diseases such as sepsis, trauma, type 2 diabetes, atherosclerosis, and Alzheimer's disease, all of which are associated with a substantial morbidity and mortality. However, the molecular mechanisms and physiological significance of the systemic inflammatory response are still not fully understood. The human endotoxin model, an in vivo model of systemic inflammation in which lipopolysaccharide is injected or infused intravenously in healthy volunteers, may be helpful in unravelling these issues. The present review addresses the basic changes that occur in this model. The activation of inflammatory cascades as well as organ-specific haemodynamic and functional changes after lipopolysaccharide are described, and the limitations of human-experimental models for the study of clinical disease are discussed. Finally, we outline the ethical considerations that apply to the use of human endotoxin model.

Protein Kinase CK2 in Human Diseases

Abstract: Protein kinase CK2 (formerly referred to as casein kinase II) is an evolutionary conserved, ubiquitous protein kinase. There are two paralog catalytic subunits, i.e. alpha (A1) and alpha' (A2). The alpha and alpha' subunits are linked to two beta subunits to produce a heterotetrameric structure. The catalytic alpha subunits are distantly related to the CMGC subfamily of kinases, such as the Cdk kinases. There are some peculiarities associated with protein kinase CK2, which are not found with most other protein kinases: (i) the enzyme is constitutively active, (ii) it can use ATP and GTP and (iii) it is found elevated in most tumors investigated and rapidly proliferating tissues. With the elucidation of the structure of the catalytic subunit, it was possible to explain why the enzyme is constitutively active [1] and why it can bind GTP [2]. Considerable information on the potential roles of CK2 in various disease processes including cancer has been gained in recent years, and the present review may help to further elucidate its aberrant role in many disease states. Its peculiar structural features [3-9] may be advantageous in designing tailor-made compounds with the possibility to specifically target this protein kinase [10]. Since not all the aspects of what has been published on CK2 can be covered in this review, we would like to recommend the following reviews; (i) for general information on CK2 [11-18] and (ii) with a focus on aberrant CK2 [19-22].

Acetylcholinesterase inhibitors as disease-modifying therapies for Alzheimer's disease.

Abstract: The therapeutic arsenal for the treatment of Alzheimer's disease (AD) remains confined to a group of four inhibitors of AChE and one NMDA receptor antagonist, which are used to provide a relief of the very late symptoms of the dementia, i.e. the cognitive and functional decline. In line with the growing body of evidence of the pivotal role of the beta-amyloid peptide (Abeta) in the pathogenesis of AD, alternative classes of drugs targeting mainly the formation or the aggregation of Abeta are actively pursued by the pharmaceutical industry, as they could positively modify the course of AD, stopping or slowing down disease progression. While the first amyloid-directed disease-modifying drugs go ahead with their clinical development and could reach the market as soon as 2009, mounting preclinical and clinical evidences is pointing towards a disease-modifying role also for currently marketed anti-Alzheimer AChE inhibitors (AChEIs), particularly for donepezil. In this review, the neuroprotective effects exhibited by currently commercialized AChEIs will be briefly discussed, together with the secondary mechanisms through which they could exert such effects. This review will focus also on particular classes of AChEIs, namely dual binding site AChEIs, which are being purposely designed to target Abeta aggregation and / or other biological targets that contribute to AD pathogenesis, thus constituting very promising disease-modifying anti-Alzheimer drug candidates.

Aggresome formation and neurodegenerative diseases: therapeutic implications.

Abstract: Accumulation of misfolded proteins in proteinaceous inclusions is a prominent pathological feature common to many age-related neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis. In cultured cells, when the production of misfolded proteins exceeds the capacity of the chaperone refolding system and the ubiquitin-proteasome degradation pathway, misfolded proteins are actively transported to a cytoplasmic juxtanuclear structure called an aggresome. Aggresome formation is recognized as a cytoprotective response serving to sequester potentially toxic misfolded proteins and facilitate their clearance by autophagy. Recent evidence indicates that aggresome formation is mediated by dynein/dynactin-mediated microtubule-based transport of misfolded proteins to the centrosome and involves several regulators, including histone deacetylase 6, E3 ubiquitin-protein ligase parkin, deubiquitinating enzyme ataxin-3, and ubiquilin-1. Characterization of the molecular mechanisms underlying aggresome formation and its regulation has begun to provide promising therapeutic targets that may be relevant to neurodegenerative diseases. In this review, we provide an overview of the molecular machinery controlling aggresome formation and discuss potential useful compounds and intervention strategies for preventing or reducing the cytotoxicity of misfolded and aggregated proteins.

Polyelectrolyte Multilayer Films: From Physico-Chemical Properties to the Control of Cellular Processes

Abstract: Polyelectrolyte multilayer films have been well characterized for almost two decades and there is now a growing interest for the development of biomimetic films that could be used in vitro or in vivo to control cellular behaviors. In this review, the important properties of multilayer films designed for cell/surface interactions will be highlighted. The first part will deal with the physico-chemical properties of polypeptide and polysaccharide multilayer films, including their growth, swellability, stability and mechanical properties. In the second part, we will focus on important properties influencing cellular behaviors: i) film biodegradability, ii) film mechanical properties, iii) film bioactivity achieved by either the intrinsic properties of the film components or the insertion of small peptides, proteins, or DNA. In particular, films thicker than one micron are particularly well suited for loading bioactive molecules due to their reservoir capacities.

Mechanisms Underlying Chemotherapy-Induced Neurotoxicity and the Potential for Neuroprotective Strategies

Abstract: Chemotherapy-induced neurotoxicity is a significant complication in the successful treatment of many cancers. Neurotoxicity may develop as a consequence of treatment with platinum analogues (cisplatin, oxaliplatin, carboplatin), taxanes (paclitaxel, docetaxel), vinca alkaloids (vincristine) and more recently, thalidomide and bortezomib. Typically, the clinical presentation reflects an axonal peripheral neuropathy with glove-and-stocking distribution sensory loss, combined with features suggestive of nerve hyperexcitability including paresthesia, dysesthesia, and pain. These symptoms may be disabling, adversely affecting activities of daily living and thereby quality of life. The incidence of chemotherapy-induced neurotoxicity appears critically related to cumulative dose and infusion duration, while individual risk factors may also influence the development and severity of neurotoxicity. Differences in structural properties between chemotherapies further contribute to variations in clinical presentation. The mechanisms underlying chemotherapy-induced neurotoxicity are diverse and include damage to neuronal cell bodies in the dorsal root ganglion and axonal toxicity via transport deficits or energy failure. More recently, axonal membrane ion channel dysfunction has been identified, including studies in patients treated with oxaliplatin which have revealed alterations in axonal Na+ channels, suggesting that prophylactic pharmacological therapies aimed at modulating ion channel activity may prove useful in reducing neurotoxicity. As such, improved understanding of the pathophysiology of chemotherapy-induced neurotoxicity will inevitably assist in the development of future neuroprotective strategies and in the design of novel chemotherapies with improved toxicity profiles.

Molecular Mechanisms of Anti-Inflammatory Activity Mediated by Flavonoids

Abstract: Flavonoids (or bioflavonoids) are naturally occurring compounds, ubiquitous in all vascular plants. These compounds have been considered to possess anti-inflammatory properties, both in vitro and in vivo. Although not fully understood, these health-promoting effects have been mainly related to their interactions with several key enzymes, signaling cascades involving cytokines and regulatory transcription factors, and antioxidant systems. The biological effects of flavonoids will depend not only on these pharmacodynamic features but also on their pharmacokinetics, which are dependent on their chemical structure, administered dose schedule and route of administration. Thus, the therapeutic outcome mediated by flavonoids will result from a complex and interactive network of effects, whose prediction require a deep and integrated knowledge of those pharmacokinetic and pharmacodynamic factors. The aim of the present review is thus to provide an integrated update on the bioavailability and biotransformation of flavonoids and the mechanisms of activity at the molecular, cellular, organ and organism levels that may contribute to their anti-inflammatory effects.

Modulation of neuro-inflammation and vascular response by oxidative stress following cerebral ischemia-reperfusion injury.

Abstract: The mechanisms leading to cellular damage from ischemia-reperfusion (I/R) injury are complex and multi-factorial. Accumulating evidence suggests an important role for oxidative stress in the regulation of neuro-inflammation following stroke. Gene expression studies have revealed that the increase in oxygen radicals post-ischemia triggers the expression of a number of pro-inflammatory genes. These genes are regulated by the transcription factor, nuclear factor-kappa-B (NF-kappaB) which is redox-sensitive. It is hypothesised that changes in the oxidative state may modulate alterations in the neuro-inflammatory response following an I/R injury. Furthermore, NF-kappaB is involved in the transcriptional regulation of adhesion molecules, which play an important role in leukocyte-endothelium interactions. Recent studies have demonstrated that adhesion molecule-mediated leukocyte recruitment is associated with increased tissue damage in stroke, while mice lacking key adhesion molecules conferred neuro-protection. Nevertheless, the involvement of oxidative stress in leukocyte recruitment and the subsequent regulated cell injury is yet to be elucidated. While leukocyte infiltration into the ischemic brain is detrimental, leukocyte accumulation in the microvasculature was shown to be one of the many factors implicated in reduced reperfusion. Although this "no-reflow" phenomenon was confirmed in a variety of animal models of cerebral ischemia, the exact mechanism is still uncertain. This review aims to highlight the impact that oxidative stress has in the regulation of post-ischemic neuro-inflammation and the implication for the cerebral microvasculature after injury.

Virtual screening and its integration with modern drug design technologies.

Abstract: Drug discovery is a highly complex and costly process, which demands integrated efforts in several relevant aspects involving innovation, knowledge, information, technologies, expertise, R investments and management skills. The shift from traditional to genomics- and proteomics-based drug research has fundamentally transformed key R strategies in the pharmaceutical industry addressed to the design of new chemical entities as drug candidates against a variety of biological targets. Therefore, drug discovery has moved toward more rational strategies based on our increasing understanding of the fundamental principles of protein-ligand interactions. The combination of available knowledge of several 3D protein structures with hundreds of thousands of small-molecules have attracted the attention of scientists from all over the world for the application of structure- and ligand-based drug design approaches. In this context, virtual screening technologies have largely enhanced the impact of computational methods applied to chemistry and biology and the goal of applying such methods is to reduce large compound databases and to select a limited number of promising candidates for drug design. This review provides a perspective of the utility of virtual screening in drug design and its integration with other important drug discovery technologies such as high-throughput screening (HTS) and QSAR, highlighting the present challenges, limitations, and future perspectives in medicinal chemistry.

Pharmacotherapy of acute lung injury and acute respiratory distress syndrome.

Abstract: Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are characterized by rapid-onset respiratory failure following a variety of direct and indirect insults to the parenchyma or vasculature of the lungs. Mortality from ALI/ARDS is substantial, and current therapy primarily emphasizes mechanical ventilation and judicial fluid management plus standard treatment of the initiating insult and any known underlying disease. Current pharmacotherapy for ALI/ARDS is not optimal, and there is a significant need for more effective medicinal chemical agents for use in these severe and lethal lung injury syndromes. To facilitate future chemical-based drug discovery research on new agent development, this paper reviews present pharmacotherapy for ALI/ARDS in the context of biological and biochemical drug activities. The complex lung injury pathophysiology of ALI/ARDS offers an array of possible targets for drug therapy, including inflammation, cell and tissue injury, vascular dysfunction, surfactant dysfunction, and oxidant injury. Added targets for pharmacotherapy outside the lungs may also be present, since multiorgan or systemic pathology is common in ALI/ARDS. The biological and physiological complexity of ALI/ARDS requires the consideration of combined-agent treatments in addition to single-agent therapies. A number of pharmacologic agents have been studied individually in ALI/ARDS, with limited or minimal success in improving survival. However, many of these agents have complementary biological/biochemical activities with the potential for synergy or additivity in combination therapy as discussed in this article.

Pharmacophore-based virtual screening.

Abstract: Virtual screening (VS) is an important component of cheminformatics and molecular modeling. An abundance of structural information, indicated by both the ever-increasing availability of 3-dimensional (3D) protein structures and the readiness of free conformational databases of commercially available compounds, such as ZINC, supplies a broad platform for VS. At the same time, new technology enables the implementation of more accurate and sophisticated pharmacophore models and the screening of millions of compounds within a manageable period. Therefore, VS is expected to play a more important role in future drug discovery efforts. This paper will examine and compare the advantages and disadvantages of VS against experimental high-throughput screening (HTS). It will also evaluate pharmacophore-based VS against docking-based VS. The strategies leading to successful pharmacophore-based VS are outlined, including how to enumerate a conformational database efficiently, how to select chemical features for a specific pharmacophore model, how to incorporate excluded volumes to enhance the geographical restrictions, and how to optimize a pharmacophore model. Successful examples of pharmacophore-based VS will be presented.

Fibrinolysis: the key to new pathogenetic mechanisms.

Abstract: The fibrinolytic system includes a broad spectrum of proteolytic enzymes with physiological and pathophysiological functions in several processes, such as haemostatic balance, tissue remodeling, tumor invasion, angiogenesis and reproduction. The main enzyme of the plasminogen activator system is plasmin, which is responsible for the degradation of fibrin into soluble degradation products. The activation of plasminogen into plasmin is mediated by two types of activators, urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). The activity of both is regulated by specific plasminogen activator inhibitors (PAIs). There are 3 types of PAIs described so far but the most important fibrinolytic inhibitor in vivo is PAI type 1 (PAI-1). Among others, the presence of metabolic syndrome and the -675 4G/5G promoter polymorphism are known to be modulators of PAI-1 levels. Besides their fibrinolytic profile, plasmin and plasminogen activators are implicated in tissue proliferation and cellular adhesion, as they can proteolytically degrade the extracellular matrix and regulate the activation of both growth factors and matrix metalloproteinases. By all these means, the fibrinolytic system is also involved in physiological processes, and in pathological situations such as thrombosis, arteriosclerosis, endometriosis and cancer. PAI 1 has been studied in different settings with thrombotic pathophysiology, such as coronary artery disease and ischaemic stroke. Controversial results have been published and concerns about study designs or presence of confounders have been claimed to be responsible of them. Recently, its involvement in adverse thrombotic events related to the modern drug-eluting coronary stents has renewed the interest of its study. PAI-1 also plays an important role in signal transduction, cell adherence, and migration. Indeed, studies of several types of cancers, including breast cancer, have shown that increased uPA and PAI-1 levels are associated with aggressive tumor behavior and poor prognosis. Endometriosis is defined by the presence of endometrial glands and stroma outside the uterus with marked ability to attach and invade the peritoneum. It is one of the most frequent benign gynecological diseases that affect women with pelvic pain or infertility during their reproductive age. Immune system disorders, genetic predisposition, altered peritoneal environment and endometrial alterations are believed to increase the susceptibility to endometriosis. The plasminogen activator system may be involved in this process, where local extracellular proteolysis plays a crucial role. Altered expression of several components of the fibrinolytic system in both eutopic and ectopic endometrium and peritoneal fluid of women with the disease has been implicated not only in the onset, but also in the progression of the endometriotic lesions.

Entry of oximes into the brain: A review

Abstract: The passage of hydrophilic drugs, such as oxime acetylcholinesterase reactivators, into the central nervous system is restricted by the blood-brain and the blood-cerebrospinal fluid barriers. The present review summarizes morphological and functional properties of the blood-brain barrier, blood-cerebrospinal fluid barrier and cerebrospinal fluid-brain interface and reviews the existing data on brain entry of oximes. Due to the virtual absence of transcytosis, lack of fenestrations and unique properties of tight junctions in brain endothelial cells, the blood-brain barrier only allows free diffusion of small lipophilic molecules. Various carriers transport hydrophilic compounds and extrude potentially toxic xenobiotics. The blood-cerebrospinal fluid barrier is formed by the choroid plexus epithelium, whose tight junctions are more permeable than those of brain endothelial cells. The major function of plexus epithelium cells is active transport of ions for the production of the cerebrospinal fluid. The cerebrospinal fluid-brain interface is not a biological barrier and allows free diffusion. However, in contrast to passage via the blood-brain barrier or the blood-cerebrospinal fluid barrier, direct penetration from the cerebrospinal fluid into the brain is very slow, since much longer distances have to be covered. A bulk flow of brain interstitial fluid and cerebrospinal fluid speeds up exchange between these two fluid compartments. Oximes, by reactivating acetylcholinesterase, are important adjunct therapeutics in organophosphate poisoning. They are very hydrophilic and therefore cannot diffuse freely into the central nervous system. Changes in brain acetylcholinesterase activity, oxime concentration and some biological effects elicited by oxime administration in the periphery indicate, however, that oximes can gain access to the brain to a certain degree, probably by carrier-mediated transport, reaching in the brain about 4-10% of their respective plasma levels. The clinical relevance of this effect is hotly debated. Possible strategies to improve brain penetration of oximes are discussed.

Alkannins and shikonins: a new class of wound healing agents.

Abstract: Alkannins and Shikonins (A/S) are chiral-pairs of naturally occurring isohexenylnaphthazarins. They are found in the external layer of the roots of at least a hundred and fifty species that belong mainly to the genera Alkanna, Lithospermum, Echium, Onosma and Arnebia of the Boraginaceae family. Their occurrence in Jatropha glandulifera, a member of the Euphorbiaceae, should be considered as an exception. Pharmaceutical formulations with wound healing properties based on A/S have been in the market for many years. Although their wound-healing, anti-inflammatory, antimicrobial, antioxidant, antithrombotic and antitumor properties have been extensively documented, significant insight into their specific molecular pathways and mechanisms was hindered until recently. With the establishment of viable synthetic and biosynthetic routes of A/S and the synthesis of specific derivatives that were discovered the last few years, the effects of those compounds in the molecular-cell biology of human tissues in health and disease have just started being explored in depth, revealing a new class of drugs that hold promise as the basis for many valuable therapeutic targets. In the recent years, a wealth of new information arising from research efforts, on the wound healing properties of A/S has been accumulated. In this paper we review the findings and advances on the molecular and biological properties of A/S that promote wound healing.

CRM1-mediated nuclear export of proteins and drug resistance in cancer.

Abstract: Expression levels of intact tumor suppressor proteins and molecular targets of anti-neoplastic agents are critical in defining cancer cell drug sensitivity; however, the intracellular location of a specific protein may be as important. Many tumor suppressor proteins must be present in the cell nucleus to perform their policing activities or for the cell to respond to chemotherapeutic agents. Nuclear proteins needed to prevent cancer initiation or progression or to optimize chemotherapeutic response include the tumor suppressor proteins p53, APC/beta-catenin, and FOXO family genes; negative regulators of cell cycle progression and survival such as p21(CIP1) and p27(KIP1;) and chemotherapeutic targets such as DNA topoisomerases I and IIalpha. Mislocalization of a nuclear protein into the cytoplasm can render it ineffective as a tumor suppressor or as a target for chemotherapy. Blocking nuclear export of any or all of these proteins may restore tumor suppression or apoptosis or, for topoisomerases I and IIalpha, reverse drug resistance to inhibitors of these enzymes. During disease progression or in response to the tumor environment, cancer cells appear to acquire intracellular mechanisms to export anti-cancer nuclear proteins. These mechanisms generally involve modification of nuclear proteins, causing the proteins to reveal leucine-rich nuclear export signal protein sequences. Subsequent export is mediated by CRM1. This review defines the general processes involved in nuclear export mediated by CRM1/RanGTP (exportin/XPO1), examines the functions of individual tumor suppressor nuclear proteins and nuclear targets of chemotherapy, and explores potential mechanisms of cancer cells to induce export of these proteins. Novel drugs that could potentially counteract nuclear export of specific proteins are also discussed.

Inflammatory markers in SIRS, sepsis and septic shock.

Abstract: Despite great advancement in the understanding of the pathophysiology and in the development of novel therapeutic approaches, mortality of sepsis still remains unacceptably high. Adequate laboratory diagnostics represents a major requirement for the improvement of this situation. For a better understanding of the immunological dysregulation in this disease, several markers are now available for routine diagnostics in the clinical laboratory. They include the cytokines interleukin (IL) -6, IL-8, procalcitonin and the LPS-binding protein (LBP). These novel markers will be compared to the conventional procedure of diagnosing inflammatory and infectious disease, such as measurements of C-reactive protein (CRP) as a major acute phase protein and differential blood counting. Important questions addressed in this review are the usefulness of these markers for early diagnosis, their role as prognostic markers and in the risk assessment of patients. Furthermore, we will discuss whether these parameters are to differentiate between systemic inflammatory response syndrome (SIRS) and sepsis at its different degrees. In the case of an infectious nature of the disease, it is important to differentiate between viral or bacterial origin and to monitor the responsiveness of antibiotic therapies. The literature was analysed with focus on the evidence for diagnostic and analytical performance. For this purpose international definition and staging criteria were used in context of criteria for assay performance including sensitivity, specificity, negative and positive predictive values, ROC analysis and other analytical criteria.

Self-adjuvanting lipopeptide vaccines.

Abstract: Despite the important role of adjuvants for vaccine development, relatively few adjuvants have been successfully incorporated into vaccines intended for human administration. This is in part due to the high toxicity associated with many experimental adjuvants. This lack of choice effectively hinders the ability to produce vaccines against many diseases, or to improve current vaccine formulations. The conjugation of immunostimulatory lipids to peptide antigens, to produce self-adjuvanting lipopeptide vaccines, has been tested in human clinical trials. These systems appear to have a number of advantages over more traditional adjuvants (e.g. alum salts) including the capacity for these vaccines to be administered via mucosal routes (e.g. orally or nasally) instead of by injection, elicitation of antigen-specific cytotoxic T-lymphocytes and mucosal immunity, as well as little-to-no observed toxicity. Several lipopeptide vaccine systems have been described in the literature, ranging from the conjugation of single fatty acid chains, to the conjugation of more complex lipids and glycolipids onto peptide antigens. The following review provides an overview of the most studied lipopeptide vaccine systems grouped into the following categories: 1) bacterial lipopeptides, including tri-palmitoyl-S-glyceryl cysteine (Pam3Cys) and di-palmitoyl-S--glyceryl cysteine (Pam2Cys); 2) the lipid-core peptide (LCP) and multiple antigen lipophilic adjuvant carrier (MALAC) systems; 3) single-chain palmitoylated peptides; and 4) glycolipids (e.g. monophosphoryl lipid A). The review also discusses the potential mechanisms of action for lipopeptide and glycolipopeptide vaccines, as well as structure activity relationships, and provides examples of studies utilising each system.

Visfatin: Structure, Function and Relation to Diabetes Mellitus and Other Dysfunctions

Abstract: Visfatin is a newly discovered adipocyte hormone with a direct relationship between plasma visfatin level and type 2 diabetes mellitus. Visfatin binds to the insulin receptor at a site distinct from that of insulin and causes hypoglycaemia by reducing glucose release from liver cells and stimulating glucose utilization in adipocytes and myocytes. Visfatin is upregulated by hypoxia, inflammation and hyperglycaemia and downregulated by insulin, somatostatin and statins. This hormone is found in the cytoplasm as well as the nucleus of cells and has been identified in many tissues and organs including the brain, kidney, lung, spleen and testis but preferentially expressed in visceral adipose tissue and upregulated in some animal models of obesity. Visceral adipose tissue is regarded to be more pernicious than subcutaneous adipose tissue. Visfatin is an endocrine, autocrine as well as paracrine peptide with many functions including enhancement of cell proliferation, biosynthesis of nicotinamide mono- and dinucleotide and hypoglycaemic effect. Visfatin, also known as a pre-B cell colony-enhancing factor, consists of 491 amino acids (aa) in human, chimpanzee, cattle, pig, rat and mouse, 490 aa in rhesus monkey, 285 aa in sheep, 587 in opossum and 588 aa in canines. Visfatin gene is well preserved during evolution. For example, the canine visfatin protein sequence is 96% and 94% identical to human and rodent visfatin, respectively. Since evidence of a direct link between visfatin genotype and human type 2 diabetes mellitus is still weak, more molecular, physiological and clinical studies are needed to determine the role of visfatin in the etiology and pathogenesis of type 2 diabetes mellitus.

Natural Products and their Derivatives as Cholinesterase Inhibitors in the Treatment of Neurodegenerative Disorders: An Update

Abstract: Alzheimers disease (AD) is the most common form of neurodegenerative disorders. If more effective therapies than the ones currently available are not developed that either prevent AD or other neurodegenerative or block progression of the diseases in its very early stages, the economic and societal cost of caring for AD patients will be devastating. Besides the neuropathologic hallmarks of the diseases, namely neurofibrillary tangles and AD neuritic plaques, the disease is characterized neurochemically by a consistent deficit in cholinergic neurotransmission, particularly affecting cholinergic neurons in basal forebrain. AD and other forms of dementia could be treated by the use of agents which restore the level of acetylcholine through inhibition of both two major forms of cholinesterase: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Moreover, the inhibition of AChE holds a key role not only to enhance cholinergic transmission in the brain but also to reduce the aggregation of β-amyloid and the formation of the neurotoxic fibrils in AD. Following this view, in recent years, an increased interest has emerged directed to finding drugs able to inhibit both of these events. This review summarizes and highlights recent advances in current knowdlege on natural products as cholinesterase inhibitors and how these compounds have also served as the starting points for semi-synthetic analogs with improved properties.

BK channel modulators: a comprehensive overview.

Abstract: The large Ca(2+)-activated K(+) channel (BK channel) reflects per excellence the dilemma of the molecular target driven drug discovery process. Significant experimental evidence suggests that the BK channels play a pivotal and specific role in many pathophysiological conditions supporting the notion that the channel represents an innovative and promising drug target. However, after more than ten years of intense research effort both in academia and industry, scientists have yet to witness the approval of a single BK channel modulator for clinical use. On the contrary, three BK openers that were progressed to clinical development have recently been discontinued (NS8, BMS204352 and TA1702) and, at the present time, only one drug candidate targeting BK channels (andolast) remains in the early phases of clinical development. Since biological studies keep strengthening the concept of BK channels as a potentially attractive target, the design and synthesis of potent and selective BK modulators continue based on novel chemical ideas. A comprehensive overview of BK channel modulators is therefore timely and important to the current medicinal chemist for review, summary, and classification of the multitude of chemical entities claimed to be BK-modulating agents. Such chemical entities are, herein, classified by both origin and chemical structure in 1) Endogenous BK channel modulators and structural analogues 2) Naturally-occurring BK channel inhibitors and blockers 3) Synthetic BK channel inhibitors and blockers 4) Marketed and/or investigational drugs with BK-modulating side properties and structural analogues 5) Naturally-occurring BK channel openers and structural analogues 6) Synthetic BK channel openers. This review is intended to provide readers with current opinion on the BK channel as a drug target, the chemical structures of BK channel modulators, the structural and chemical features involved in the BK channel modulating activity and, where and when possible, with highlights of structure-activity relationships.

Carbohydrate-metal complexes and their potential as anticancer agents.

Abstract: Platinum complex-based chemotherapy is one of the major treatment options of many malignancies. Although severe side effects occur, and only a limited spectrum of tumors can be cured, Pt compounds are used in every second therapy scheme. Thus, many different drug design strategies have been employed for improving the properties of anticancer drugs including pH or redox activation in the tumor, variation of the metal center and therefore the redox and ligand exchange properties, the application of multinuclear metal complexes, the development of targeted approaches, etc. Application of carbohydrate-metal complexes is an example of a targeted approach exploiting the biochemical and metabolic functions of diverse sugars in living organisms for transport and accumulation. Natural carbohydrates and synthetic derivatives possess a manifold of donors endowing them with the ability to coordinate metal centers and providing some additional advantages over other ligands, e.g., biocompatibility, non-toxicity, enantiomeric purity, water solubility, and well-explored chemistry. In recent years, several examples of carbohydrate compounds have been developed for diverse medicinal applications ranging from compounds with antibiotic, antiviral, or fungicidal activity and anticancer compounds. Herein, metal complexes with carbohydrate ligands are reviewed and the role of the carbohydrate carriers on the antineoplastic activity of these compounds, both in vitro and in vivo, is described.