Current Medicinal Chemistry - Volume 15, Issue 21, 2008

Alzheimer's disease (AD) is a complex disease, involving multiple factors such as the production of aggregation- prone amyloid β (Aβ) peptides, the formation of fibrillarly tangles of microtubule-associating proteins, Tau, and the polymorphism of cholesterol binding protein, APOE4. While understanding the mechanism of AD and the involvement of key players should lead to rational drug discovery against this disease, a traditional screening approach should also work for identifying drugs using AD models. We have used a cellular AD model, in which a cell death was induced by ADcausing neurotoxicities, and then screened the genes, which rescued the cells from the cell death. This resulted in isolation of a gene encoding a novel 24-amino acid long peptide, termed Humanin (HN), which protected neuronal cells at ∼μM level. Surprisingly, these gene products and the synthetic peptides not only protected neurons from cell death induced by Aβ-related neurotoxicities, but also Aβ-unrelated neurotoxicities. While a broad range of activities of HN against ADrelated insults is discovered, the detailed mechanism of its action is still obscure. Structure analysis of HN showed that it is largely disordered and flexible at low peptide concentrations and heavily aggregates at high concentrations. Interestingly, one of the HN analogs, which is 10000-times more active than the parent HN molecule (i.e. active below nM range), was found to be monomeric. Based on findings of structural analyses, we propose here that membrane environment may enable HN to achieve high affinity for target protein(s) with multiple-transmembrane domains, such as G-protein coupled receptors.

Background: Endometriosis is an estrogen-dependent disease, associated with pelvic pain and infertility, with still limited knowledge of the pathogenesis, pathophysiology of related infertility and evolution. Objective: To investigate proteogenomic approaches and new trends of endometriosis treatment. Methods: A literature search was carried out for all articles on endometriosis related to immune system, and to nonhormonal, antiangiogenic and experimental therapies. Results/Conclusions: Classic endometriosis pharmacotherapy is represented by GnRH agonists, oral contraceptives and Type II progesterone receptor ligands. New proteomic and genomic technologies could help to clarify the aetiology of endometriosis and promise the rapid identification of a new generation of drugs with a specific molecular target, with the aim to ameliorate the patients' quality of life.

Molecular substructures and fragment descriptors are important tools for many computational applications in medicinal chemistry and drug design. Here we briefly review the history of molecular fragmentation methods and describe the currently most widely used approaches. Then we focus on random fragmentation methods that have only recently been introduced and discuss selected applications. It is shown that the generation and mining of random fragment populations makes it possible to identify novel types of fragment descriptors and generate similarity search tools that depart from conventional design approaches. Thus, random fragmentation schemes complement and further extend established fragment methods.

Lysophosphatidic acid (LPA, 1- or 2-acyl-sn-glycerol 3-phosphate) is a simple phospholipid but displays an intriguing cell biology that is mediated via interactions with both G-protein-coupled seven transmembrane receptors (GPCRs) and nuclear hormone receptors. So far, seven GPCRs (LPA1-5 and recently reported GPR87/LPA6 and P2Y5/LPA7) and a nuclear hormone receptor, PPARγ, have been identified. LPA is predominantly produced in blood and a plasma enzyme, autotaxin, is involved in its production. Recent gene manipulating studies of these proteins have shown that LPA is involved in both pathological and physiological states including brain development, neuropathy pain, implantation, protection against radiation-induced intestinal injury and blood vessel formation. In addition, lipids similar to LPA, such as sphingosine 1-phosphate (S1P) and 2-arachidonylglycerol (2-AG), share common cellular signaling pathways with LPA and are now considered as promising targets of human therapy including immunosuppressant and anti-obesity drugs. Thus, LPA is now one of the most attractive targets for prevention and treatment of various diseases. Receptor- selective antagonists and agonists as well as inhibitors of LPA producing enzymes are undoubtedly useful. Recognition of the ligand, LPA, by each receptor seems to be quite different, as LPA species with various fatty acids at either the sn-1 or sn-2 position of the hydroxy residue activate each receptor quite differently. In the last decade a series of LPA analogs in which the sn-1 or sn-2 hydroxy, acyl chain, glycerol and phosphate group are modified have been created and evaluated by several laboratories. Here we review recent advances in the development of LPA-receptor targeted compounds (agonists and antagonists) and anti-autotaxin inhibitors.

The expansion of fluorescent techniques for studying the ligand-receptor interaction resulted in a burst of the novel fluorescent ligands development. The discovery of the ligand, that is of high affinity to the receptor and whose localization could be easily visualized, even on the single cell level, gave the researchers a strong impulse to investigate that field of GPCR ligands. Moreover, paying attention to the “non pharmacological” advantages of these ligands, as well as the techniques to be used, fluorescent ligands are becoming treated more seriously, as the ligands themselves, and as novel, useful tools for studying GPCRs. Herein, we review results described in the literature, starting from the year 2000, in the field of the fluorescent GPCR small, non-peptide ligands according to the affinity to the selected receptors (histamine, adenosine, adrenergic, cannabinoid, muscarinie, neuropeptide Y and serotonine) as well as the fluorophores that have been used to tag the molecules.

Quorum sensing (QS) systems are bacterial cell-to-cell communication systems that use small molecules as signals. Since QS is involved in the regulation of virulence and biofilm formation in several pathogenic bacteria, it has been suggested as a new target for the development of novel antibacterial therapies. As such, interference with the signal receptors by using chemical compounds has been proposed as an alternative strategy for treatment of bacterial infections and has already shown promising results in combination with traditional antibiotic treatments. In Gram-negative bacteria, the best studied QS systems use N-acyl homoserine lactones (AHLs) as signal molecules. This review provides an overview of all new chemical structure types that inhibit AHL-mediated QS systems as reported during the last three years in scientific journals and in the patent literature. The compounds were classified into three main groups depending on their structure: AHL analogues, 2(5H)-furanones, and compounds that are not structurally related to AHLs. We discuss the biological assays used and the different strategies applied to discover these molecules, including new approaches such as molecular docking for in silico identification of lead structures and random high-throughput screening of large libraries of chemicals. Finally, we elaborate on structure-activity relationships and on the new insights in the mechanisms of action of the identified inhibitors, highlighting the potential of these small molecules in medicine.

Atherosclerosis being a leading death cause in many countries is a chronic inflammatory process in which inflammation, immune activation, and oxidative stress are interactively involved. Some epidemiological and many experimental studies suggest that development of atherosclerosis is associated with the amount of iron stored in the body. Transport of electrons between different forms of iron makes it essential for many fundamental cell functions and signaling. Under pathologic conditions iron may serves as a potential catalyst, particularly in the form of redox-active iron or labile iron, for free radical reactions in oxidative stress and cell damage of atherogenesis. Emerging evidence indicates that cellular iron may participate in various cellular signaling pathways, many of which have been implicated in atherogenesis. These include iron homeostatic control signaling, iron-induced oxidative-responsive transcription factors, ironinduced activation of inflammatory cytokines, and iron-dependent signaling in cell growth and apoptosis. This review highlights research progress on atherosclerosis-relevant iron signaling and revisits our hypothesis on iron and atherosclerosis. We propose that iron may contribute to the pathogenesis of atherosclerosis not only via changes in the body iron amount but also by its regulatory roles in redox-sensitive signaling and inflammatory immune responses of atherosclerosis.

Cetirizine, marketed as a racemic mixture containing both levocetirizine and dextrocetirizine, is a member of the second generation H1 antihistamines clinically used for the treatment of symptoms associated with seasonal allergic rhinitis. Recently, its single R-enantiomer levocetirizine has been approved by the FDA as the newest antihistamine. Cetirizine is a piperazine derivative related to the first generation H1 antagonist hydroxyzine, and is the major metabolite in the blood circulation after hydroxyzine administration in humans. The acid functionality of cetirizine in combination with one of the basic nitrogens of piperazine ring makes this compound a very unique zwitterion. The molecular structure of cetirizine allows its carboxylic group to interact with the basic nitrogen via folded conformers, therefore, it possesses relatively high lipophilicity at physiological pH (LogD = 1.5). While both cetirizine and hydroxyzine possess high affinity at the H1 receptor, the R-configured levocetirizine has much slower dissociation rate from the H1 receptor than Rhydroxyzine, making it an insurmountable antagonist. In addition, the pharmacokinetics of cetirizine significantly differs from those of the basic and lipophilic hydroxyzine. For example, cetirizine has much lower CNS penetration than hydroxyzine, which may be explained by the zwitterionic structure of cetirizine and its P-glycoprotein activity. Cetirizine exhibits high intestinal absorption in humans and its oral bioavailability is estimated to be greater than 70%. Very importantly, cetirizine, especially levocetirizine, has a negligible interaction with the liver enzymes, and is mainly excreted in the urine as the parent despite its high plasma protein binding (88∼96%). The recommended dose of levocetirizine is 5 mg once daily, while its pharmacokinetic half-life is about 7 h in humans. This review will focus on the physicochemical, pharmacological and pharmacokinetic properties of cetirizine and levocetirizine in comparison with those of hydroxyzine. The zwitterionic cetirizine displays distinct advantages over the basic hydroxyzine in several categories such as slow receptor dissociation rate, high selectivity, negligible liver enzyme interaction and low CNS penetration. Therefore, cetirizine, or its single isomer levocetirizine, might serve a good example for medicinal chemists to design zwitterionic drugs from a basic, acidic or neutral lead molecule for peripheral biological targets.