Current Medicinal Chemistry - Volume 13, Issue 25, 2006

In the last decades, the physiological and pharmacological properties of dopamine receptors were controversial principally because of the lack of selective ligand for some receptor subtypes. Since 1997, some specific D4 agonists have been described and have allowed a therapeutic approach. We report here, compounds described as D4 agonist and when available the SAR. The major studies for physiological implications and their potential biological applications are also reported and principally their interest in erectile dysfunction.

Structure-based Drug Design (SBDD) is an essential part of the modern medicinal chemistry, and has led to the acceleration of many projects, and even to drugs on the market. Programs that perform docking and scoring of ligands to receptors are powerful tools in the drug designer's armoury that enhance the process of SBDD. They are even deployed on the desktop of many bench chemists. It is timely to review the state of the art, to understand how good our docking programs are, and what are the issues. In this review we would like to provide a guide around the reliable aspects of docking and scoring and the associated pitfalls aiming at an audience of medicinal chemists rather than modellers. For convenience, we will divide the review into two parts: docking and scoring. Docking concerns the preparation of the receptor and the ligand(s), the sampling of conformational space and stereochemistry (if appropriate). Scoring concerns the evaluation of all of the ligand-receptor poses generated by docking. The two processes are not truly independent, and this will be discussed here in detail. The preparation of the receptor and ligand(s) before docking requires great care. For the receptor, issues of protonation, tautomerisation and hydration are key, and we will discuss current approaches to these issues. Even more important is the degree of sampling: can the algorithms reproduce what is observed experimentally? If they can, are the scoring algorithms good enough to recognise this pose as the best? Do the scores correlate with observed binding affinity? How does local knowledge of the target (for example hinge-binding to a kinase) affect the accuracy of the predictions? We will review the key findings from several evaluation studies and present conclusions about when and how to interpret and trust the results of docking and scoring. Finally, we will present an outline of some of the latest developments in the area of scoring functions.

Coronary heart disease (CHD) is the leading cause of mortality in Western societies, affecting about one third of the population before their seventieth year. Over the past decades modifiable risk factors of CHD have been identified, including smoking and diet. These factors when altered can have a significant impact on an individuals' risk of developing CHD, their overall health and quality of life. There is strong evidence suggesting that dietary intake of plant foods rich in fibre and polyphenolic compounds, effectively lowers the risk of developing CHD. However, the efficacy of these foods often appears to be greater than the sum of their recognised biologically active parts. Here we discuss the hypothesis that beneficial metabolic and vascular effects of dietary fibre and plant polyphenols are due to an up regulation of the colon-systemic metabolic axis by these compounds. Fibres and many polyphenols are converted into biologically active compounds by the colonic microbiota. This microbiota imparts great metabolic versatility and dynamism, with many of their reductive or hydrolytic activities appearing complementary to oxidative or conjugative human metabolism. Understanding these microbial activities is central to determining the role of different dietary components in preventing or beneficially impacting on the impaired lipid metabolism and vascular dysfunction that typifies CHD and type II diabetes. This approach lays the foundation for rational selection of health promoting foods, rational target driven design of functional foods, and provides an essential thus-far, overlooked, dynamic to our understanding of how foods recognised as “healthy” impact on the human metabonome.

The mucosal immune system comprises B cells that can mount potent antibody responses against a variety of mucosal pathogens. Mucosal B cell responses can play a decisive role in protection against mucosal pathogens. Induction of mucosal B cell responses can be achieved through mucosal vaccination. However, mucosal administration of antigens without the use of adjuvants or delivery systems can lead to tolerance rather than immunity, and thus considerable efforts have been focused on development of effective immunopotentiating adjuvants and delivery systems. However, because the ultimate goal of vaccination is the induction and maintenance of immunological memory, the underlying mechanisms for induction of long-term mucosal B cell memory need to be analyzed for the selection of appropriate adjuvants. Moreover, as the antigen unspecific innate immune system invoked by adjuvants contributes significantly to the development of antigen-specific B cell responses, and presumably B cell memory, optimal interaction of B cells with cellular components of the innate immune system is required. To better understand the mechanisms that lead to the induction of mucosal antibody responses, antibodies against single epitopes from specific B cell clones as opposed to antibodies against large poly proteins from multiple B cell clones can be studied. This review deals with the concept of mucosal B cell memory with special emphasis on efforts to devise effective prophylactic or therapeutic vaccines.

The efficient removal of unwanted cells, such as senescent, damaged, mutated or infected cells is crucial for the maintenance of normal liver function. In fact, apoptosis has emerged as a potential contributor to the pathogenesis of a number of hepatic disorders, such as viral hepatitis, autoimmune diseases, ethanolinduced injury, cholestasis, and hepatocellular carcinoma. In contrast to the effect of cytotoxic bile acids in the liver, ursodeoxycholic acid (UDCA) has increasingly been used for the treatment of various liver disorders. The clinical efficacy of this hydrophilic bile acid was first recognized by its use in traditional Asian medicine. However, many studies have subsequently confirmed that UDCA improves liver function by three major mechanisms of action, including protection of cholangiocytes against the cytotoxicity of hydrophobic bile acids, stimulation of hepatobiliary secretion, and inhibition of liver cell apoptosis. UDCA acts as a potent inhibitor of the classical mitochondrial pathway of apoptosis, but also interferes with alternate and upstream molecular targets such as the E2F-1/p53 pathway. Together, there is growing evidence that this hydrophilic bile acid may modulate gene expression to prevent cell death. Curiously, as a cholesterol-derived molecule, UDCA interacts with nuclear steroid receptors, such as the glucocorticoid receptor. Nuclear steroid receptors play crucial roles in mediating steroid hormone signaling involved in many biological processes, including apoptosis. Here, we review the anti-apoptotic mechanisms of UDCA in hepatic cells, and discuss a potential involvement of nuclear steroid receptors in mediating the survival effects of UDCA.

The assessment of S-100B in acute neurological disorders such as global hypoxia, ischaemic or haemorrhagic stroke and traumatic brain injury reflects severity of symptoms and outcome. However, the temporal profile of S-100B release depends on topography, intensity and pathophysiology of the damage e.g. immediate release after traumatic brain injury following the acute destruction of neuronal tissue or delayed release after ischaemic stroke in which gradual breakdown of the blood-brain barrier plays a crucial role. In chronic brain diseases, knowledge about the clinical value of quantification of S-100B is scarce and further evaluations are needed. This review considers both conditions for S-100B measurement and illustrates advantages and limitations in comparison with clinical and neuroimaging data.

Autoimmune diseases are believed to develop mainly from three factors comprising genetic predisposition, environmental factors and immune (dys-) regulation. In this context, specific nucleic acids of exogenous or endogenous origin that signal through nucleic acid-specific Toll-like receptors (TLRs) have gained much research attention. During ongoing autoimmune disease microbial nucleic acids contribute to flares of disease and its aggravation leading to end organ damage, through unfavourable immune modulation. Apart from exogenous sources, nucleic acid molecules of endogenous origin emerge as potential ligands for receptors of host defence, i.e. TLRs. Rapidly accumulating data on the role of nucleic acid-specific TLRs has not only provided insights about their pathogenic potential of endogenous nucleic acid molecules, but is also fuelling the development of novel immunotherapies.

The basal ganglia are a highly interconnected group of subcortical nuclei in the vertebrate brain that play a critical role not only in the control of movements but also in some cognitive and behavioral functions. Several recent studies have emphasized that serotonergic pathways in the central nervous system (CNS) are intimately involved in the modulation of the basal ganglia and in the pathophysiology of human involuntary movement disorders. These observations are supported by anatomical evidence demonstrating large serotonergic innervation of the basal ganglia. In fact, serotonergic terminals have been reported to make synaptic contacts with dopamine (DA)-containing neurons and γ-aminobutyric acid (GABA)-containing neurons in the striatum, globus pallidus, subthalamus and substantia nigra. These brain areas contain the highest concentration of serotonin (5-HT), with the substantia nigra pars reticulata receiving the greatest input. Furthermore, in these structures a high expression of 5-HT different receptor subtypes has been revealed. In this paper, evidence demonstrating the serotonergic control of basal ganglia functions will be reviewed, focusing on the role of the 5-HT2C receptor subtype. In addition, the involvement of 5-HT2C receptors in neurological disorders such as Parkinson's disease and other related motor disorders, and their management with drugs blocking the 5-HT2C receptor will be discussed.

There is continued interest in development of antisense reagents (ASRs), including especially antisense oligonucleotides and small interfering RNAs, for experimental as well as therapeutic purposes. Optimization of ASRs begins with target site selection. Here we review protocols which have been developed to empirically determine effective target sites in RNAs. Such library selection technologies have demonstrated clear utility, and in vitro identification of sites has generally proven effective for cellular applications. A few groups are developing large combinatorial libraries and approaches to adapt use of such libraries to individual target RNAs, as well as learning algorithms to help with the optimization of target sites, particularly with respect to small interfering RNAs.

It is now widely accepted that airway inflammation is the key factor underlying the pathogenesis of asthma. Inhaled corticosteroids remain the most important anti-inflammatory treatment for asthma. However, they are rather non-specific in their actions and their use raises concerns over side effects and compliance issues, particularly in children and adolescents. Moreover, a significant sub-group of asthmatic patients responds poorly or not at all to high-dose inhaled or systemic steroid treatment. Therefore, much effort is being made to develop novel more specific and safer therapy for asthma. Significant areas of drug development include humanised monoclonal antibodies (mAb) for asthma therapy including those against IL-4, IL-5, TNF and IL-13. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include: (1) the use of humanised blocking mAb to their receptors; (2) removal of cytokines or chemokines via binding to soluble receptors or small molecule receptor antagonists; and (3) drugs that block the signal transduction pathways activated following the interaction of cytokines or chemokines with their receptors. Another approach is to use anti-inflammatory cytokines directly or encourage their production thereby suppressing the allergic inflammatory process; these chemokines include IL-10, IL-12 and IFN-γ. Finally, a further promising area involves targeting the allergic portion of the asthma phenotype using humanised anti- IgE mAb. This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy.