Drug Design Reviews - Online (Discontinued) - Volume 2, Issue 1, 2005

Type 2 diabetes mellitus (T2DM) represents an increasing epidemic in most of the countries throughout the Western world. One of the main determinants of such a situation is the growing incidence of overweight and obesity. However, the pathophysiological link between obesity and T2DM still remains unclear. The discovery of the circulating hormone resistin, which is produced mainly by adipocytes and appears to be increased in obesity and inflammation, seemed to clear up this connection. Some studies indicate that T2DM patients could have increased circulating concentrations of resistin, although these results need further confirmation. Seemingly, resistin opposes insulin action and impairs glucose tolerance and insulin sensitivity. In this sense, hyperinsulinemic clamp studies in rats support the notion that resistin selectively impairs insulin action in liver and increases hepatic glucose production. Furthermore, resistin knockout mice have evidenced that resistin has a physiological function in the maintenance of blood glucose during fasting through an increase of hepatic glucose output, which could be exacerbated in the obese state. These results support the notion that blockade of the biological effects of resistin might be a promising pharmaceutical target for the treatment of T2DM.

Many bacteria start production of pathogenicity factors when organised in aggregates, so-called biofilms, where they are much more protected against toxic agents. To form biofilms bacteria monitor their cell density by a process called quorum sensing using small, water soluble molecules which act as autoinducers. N-acyl homoserine lactones (AHL) where the acyl side chains vary in length and degree of oxidation and 4,5-dihydroxy-2,3-pentanedion or furanosyl borate diester formed from ribose-homocysteine have been identified as autoinducers but more must exist. Plants and animals exposed to a wet environment developed several strategies to control biofilms and embedded pathogenic bacteria in particular. The red macroalgae Delisea pulchra is devoid of biofilms at its surface and produces a number of secondary metabolites with a furanone ring interfering with the action of AHL. Taking the lead structure from these metabolites and from AHL several smaller molecules have been developed, which prevent biofilm formation in many bacteria. In the review the different approaches to control bacterial biofilms will be described focussing on the progress made in the development of autoinducer antagonists and problems caused by their specificity and toxicity for the host. The combination with antibiotics and first applications in animal models will be discussed.

During the past century human life expectancy has increased significantly due to improved health care, including the availability of vaccines and new pharmaceutical drugs. With the aging population on the rise, complex diseases such as Alzheimer's disease, Parkinson's disease and various types of cancers, combined with new diseases with debilitating consequences can reduce the general quality of life. This, together with the fact that the drug discovery and developmental process is competitive, lengthy, risky, and expensive with a high failure rate, poses challenging opportunities for the development of new drugs. Thus, the new drug development process demands approaches that aim to increase the probability of robust target identification with quick validation such that the subsequent failure rate can be reduced to manageable levels. This review will focus on new approaches, both genomic and proteomic, that have been developed over the last few years and successfully used to discover new genes and proteins, quantify and analyze gene and protein expressions and assign functionalities. In addition, we will also discuss the limitations of these technologies with the intention of setting reasonable expectations.

It is estimated that over 100,000 patients require a pleurodesis in USA each year. Pleurodesis, the iatrogenic induction of pleural fibrosis to obliterate the pleural cavity, is the most effective way to prevent re-accumulation of pleural fluid. Currently used pleurodesing agents - talc, tetracycline derivatives and bleomycin - effect pleurodesis by inducing an acute pleural injury and inflammation, which eventually heals with fibrosis. Pleural inflammation is associated with side effects such as pain, fever and potentially fatal respiratory failure. There is thus a desperate need for development of novel agents. We have shown that a potent pro-fibrotic and anti-inflammatory cytokine, transforming growth factor (TGF)-β, can produce a pleurodesis, and circumvents the induction of pleural inflammation. In vitro, TGF-β2 stimulates collagen synthesis by pleural mesothelial cells, as well as suppresses their interleukin-8 production. In animal models, intrapleural TGF-β2 produces pleurodesis faster than talc and with less local inflammatory reaction. Unlike existing pleurodesing agents, TGF-β2 remains effective even with co-administration of systemic corticosteroids. TGF-β3 is equally effective as TGF-β2. A single intrapleural injection of TGF-β2 does not induce any acute physiological complications or extrapulmonary side effects. The use of TGF-β for pleurodesis should be further assessed in phase I clinical trials.

Sphingolipids, including ceramide, sphingomyelin, and glycosphingolipids, are essential components of eukaryotic cell membranes. At the cell surface, they form species- and cell type-specific patterns that change with cell growth, differentiation, transformation and oncogenesis. Apart from their structural role, they serve as attachment sites for many pathogens and are critically involved in the regulation of inter- and intracellular communication events like cell adhesion, proliferation, differentiation, and apoptosis. In recent years, their involvement in the formation of membrane microdomains, termed rafts, and their contribution to diverse signaling cascades attracted particular attention. Accumulating evidence further demonstrates an important role for sphingolipids in the modulation of pharmacologically relevant membrane-bound enzymes and receptors. We present a brief overview of new therapeutic strategies based on the intervention in sphingolipid metabolism. Emphasis is placed on ceramide analogs and on selected low molecular weight compounds interfering with ceramide metabolism.

G protein-coupled receptors (GPCRs) are major targets for drug discovery. They offer innumerable therapeutic benefits through the promotion or inhibition of GPCR-mediated biochemical, physiological and disease processes. The detailed understanding of how GPCRs detect extracellular signals and transduce them to intracellular G proteins and second messenger pathways has led to the development and exploitation of chimeric and promiscuous G protein a subunits. These adaptors, such as qi5, Gα16 and 16z44, allow signals from diverse GPCRs to be directed to the generation of an easily detectable product. This has enabled almost any GPCR to be incorporated into screening platforms such as FLIPR, aequorin assays, yeast autocrine selection and microarrayed assays. In this review we will revisit the structure of GPCRs and heterotrimeric G proteins with particular reference to those regions that determine the specificity of their interaction. In light of this information we will follow the development of chimeric Gα subunits and the discovery of naturally promiscuous adaptors. Their utility is exemplified by their incorporation into high-throughput drug screening assays and GPCR deorphanization programs.

Nordihydroguaiaretic acid (NDGA) is a lignan present in the perspired resin of leaves of Larrea divaricata . This compound and its derivatives have “in vitro” inhibition against several viruses including HIV, herpes simplex I and II, and human papilloma. Junin virus is the etiologic agent of Argentine Hemorrhagic fever of great sanitary importance in Argentine. It is an endemo-epidemic illness transmitted to man by rodents (Calomys musculinus), which produces a 10-30 % of mortality in non-treated patients. At the moment, there is a vaccine made with the attenuated strain “Candid 1” but it is not manufactured in our country and the doses available are scarce regarding the quantity of people at risk. In order to find an antiviral agent, considering the existing evidence of antiviral activity of NDGA, we conducted an “in vitro” assay against Junin virus. The inhibition of replication as a function of the concentrations of the lignan showed that the virus replication was inhibited differently, according to the NDGA (8-17 mg / ml) concentration and type of treatment (pre, simultaneous and post-treatment). All concentrations of NDGA were able to inhibit 100% of Junin virus replication when the compound was added simultaneously with the virus.

(-)-Epigallocatechin-3-gallate (EGCG) is the most abundant of the green tea polyphenols. The properties ascribed to EGCG are anti-tumorigenic, anti-inflammatory, antioxidative, antiproliferative, antibacterial and antiviral effects. Recent studies also report pro-inflammatory and pro-apoptotic effects, with a mechanism of action through cell cycle progression inhibition. Its novel properties include inhibition of expression of the matrix metalloproteases-2 (MMP- 2) gene by direct binding. Studies have shown that EGCG interferes with HIV-1 viral infection by virion destruction and HIV-1 reverse transcriptase inhibition. Its anticancer activity includes suppression of ligand binding to different tyrosine kinase receptors (TKR), inhibition of protein kinase C (PKC), lipoxygenase (LOX), cycloxygenase (COX), and induction of apoptotic cell death. EGCG exerts its anti-carcinogenic property by down regulating COX-2. EGCG inhibited the catalytic activity of extra cellular signal regulated kinases (ERKs) and p38 mitogen-activated protein kinase (MAPK), which are upstream enzymes known to regulate COX-2 expression suggesting that these could be potential targets for the anti-tumor activity of EGCG. It selectively inhibits tyrosine kinase and MAPK in the transformed cells and downregulates Ras and Jun. In the present article we review the various mechanisms through which EGCG exerts its antiproliferative effects and its potential application as a natural drug against several proliferative diseases are discussed.