Mini Reviews in Medicinal Chemistry - Volume 6, Issue 12, 2006

The development of safe and effective gene delivery methods is a major challenge to enable gene therapy or DNA vaccines to become a reality. Currently there are two major approaches for delivery of genetic material, viral and non-viral. The majority of on-going clinical trials in gene therapy or DNA vaccines use retroviruses and adenoviruses for delivering genetic materials. Viral delivery systems are far more effective than non-viral delivery however there are concerns regarding toxicity, immunogenicity and possible integration of viral genetic material into the human genome. Given the negative charge of the phosphate backbone of DNA, polycationic molecules have been the major focus as carriers of DNA. There are several physiological barriers to overcome for effective systemic delivery of DNA. The ideal vector must be stable in the systemic circulation, escape the reticuloendothelial system, able to extravasate tissues, enter the target cell, escape lysosomal degradation and transport DNA to the nucleus to be transcribed. With increasing understanding of the physicochemical properties essential to overcome the various barriers, it is possible to apply rational design to the cationic carriers. A number of poly-amino acids, cationic block co-polymers, dendrimers and cyclodextrins have been rationally designed to optimize gene delivery. This review will discuss approaches that have been used to design various synthetic polycations with enhanced DNA condensing ability, serum stability and endosomolytic capability for efficient gene transfer in vitro and in vivo.

Carbohydrates have been proven as valuable scaffolds to display pharmocophores and the resulting molecules have demonstrated useful biological activity towards various targets including the somatostatin receptors (SSTR), integrins, HIV-1 protease, matrix metalloproteinases (MMP), multidrug resistance-associated protein (MRP), and as RNA binders. Carbohydrate-based compounds have also shown antibacterial and herbicidal activity.

Most biological molecules exhibit more than one function. In particular, many molecules have the ability to directly/ indirectly scavenge free radicals and thus act in living organisms as antioxidant. During oxidative stress, the increase of these molecules levels seems to be a biological response that in synergism with the other antioxidant defence systems may protect cells from oxidation. Among these structures, chondroitin sulphate is a biomolecule which has increasingly focused the interest of many research groups due to its antioxidant activity. This review briefly summarises the action of chondroitin sulphate in reducing molecular damage caused by free radicals and associated oxygen reactants.

Pro-inflammatory lipid mediators (i.e. eicosanoids), cytokines (i.e. TNF-α) and reactive oxygen species are targets of interest in the regulation of liver inflammation and oxidative stress. In the current review, we summarize recent advances in the pharmacological modulation of these pathways with especial emphasis on the participation of Kupffer cells, the liver resident macrophages and the cell type most directly related to the production of inflammatory mediators in this organ.

There appear to be compelling evidences presenting adiponectin as a key regulator of energy homeostasis. Over the past 10 years, much work has been done to identify the molecular mechanisms by which adiponectin functions in the body. We and other groups have demonstrated that adiponectin activates multiple signaling pathways, which mediate its anti-diabetic, anti-atherogenic and anti-inflammatory functions. Comprehensive analysis of the mechanism of adiponectin action may allow us to elucidate the etiology of metabolic syndrome associated diseases including diabetes and cardiovascular diseases, where dysfunction of adiponectin may contribute to pathogenesis of diseases. While regulation of adiponectin gene expression or secretion remains an interesting topic in studies of cell metabolism, further intensive studies are necessary to illustrate the molecular mechanisms. Importantly, identification of molecules in the adiponectin signaling pathways and in the regulation of adiponectin gene expression may provide novel targets for therapeutic drugs.

β-(1,3)-Glucans are widely distributed within microorganisms or seaweeds in which they act as membrane components or for energy storage, respectively. Since these glucans are not biosynthesized by mammals, they are likely to activate the immune system of their host. Since the discovery of their positive involvement as immunomodulator agents, numerous studies were published all around the glycosciences. These works deal with purification procedures, analytical chemistry, synthetic processes, chemical modification of the natural polysaccharides, determination of their physicochemical properties, and assessment of their biological and medicinal effects through in vitro and in vivo studies. This article aims at presenting some recent results linked to β-(1,3)-glucans through two closely connected points of view, i.e. biology and chemistry. Biological aspects will be focused more particularly on discovery of some receptors present on immunocompetent cells and scope and limitations of chemical synthesis and/or modifications will be described. Moreover, this paper will also introduce some new chemo-enzymatic synthetic methods using wild-type or mutant glycosidases and will be extended to novel opportunities of applications of β-(1,3)-glucans in nanotechnology resulting from a better understanding of their self-assembling propensity in aqueous media.

Non-steroidal anti-inflammatory drugs (NSAID) target the enzyme cyclooxygenase (COX) thus affording relieve from pain, inflammation or fever. As COX-dependently formed prostanoids not only mediate signals involved in inflammation and pain, but also regulate important physiological cardiovascular functions, some NSAID have recently been reported to be associated with arterial thrombosis or hypertension. This is in contrast to the well-known antiplatelet effects of low-dose aspirin, but in coherence with the specific effects of some NSAID on prostanoid formation in the vasculature. A correlation between the intake of selective inhibitors of the cyclooxygenase 2 (COX-2) isoform and atherothrombotic events has recently been established. Large retrospective analyses of clinical data have repeatedly shown this effect and in some cases have also observed potential hazards for other, rather non-selective NSAID. This review evaluates potential prothrombotic effects of NSAID in vascular ischemic disease in comparison to low-dose aspirin and selective COX-2 inhibitors and discusses pathophysiological backgrounds for such observations.

Tumor Associated Carbohydrate Antigens (TACAs) constitute powerful tools as tumor markers and as targets for anticancer immunotherapy. In this review, methods of production of glycopeptide-based vaccines, as well as results of preclinical and clinical studies in cancer patients are discussed.

Cyclooxygenase plays a pivotal role in the transformation of the arachidonic acid to prostaglandins (PGs) and thromboxane. It is composed of two kinds of enzymes, namely cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX- 2). Cyclooxygenase 1 is the constructive enzyme whereas the cyclooxygenase 2 is the inducible enzyme. Inhibiting cyclooxygenase 1 is always associated with some undesirable side-effects, while inhibiting cyclooxygenase 2 can result in therapeutic effect. This has led the researchers to strive for searching the selective inhibitors inhibiting the COX-2 instead of COX-1. It is very well known that pain and inflammation are alleviated through the inhibition of COX-2 inhibitors such as Aspirin, which has resulted in the recent years, in the emergence of a range of COX-2 inhibitors. Moreover, while evaluating the functions of the COX-2 inhibitions, their significant role in treating glaucoma, preventing and suppressing cancer through their inhibitory activity was clearly revealed and many studies further demonstrated that COX-2 is not only related to the inflammation of peripheral tissues but also to the inflammation manifested in the central nervous system. In addition, the nervous disorders also found an effective treatment with the administration of COX-2 inhibitors. The above-mentioned findings delineate the role of the COX-2 inhibitors as promising agents to be exploited in the treatment of many illnesses. This review will elucidate the functions of the COX-2 inhibitors briefly and introduce some common selective inhibitors of COX-2.

Calmodulin is a Ca2+ binding protein found in many eukaryotic cells. It is one of the most important intracellular mediators of Ca2+-dependant signaling in eukaryotic cells. It regulates diverse processes including mitosis, muscle contraction and nucleotide metabolism by modulating the activity of at least 30 different target enzymes in a calciumdependant manner. Calmodulin plays an important role in the regulation of processes, such as the assembly and disassembly of microtubules by controlling protein kinase activities, by exerting an indirect influence upon a wide variety of cellular processes. It is observed that multi-drug resistant cells have a greater intracellular concentration of calcium than nonresistant cells which contributes to their increased sensitivity to calmodulin antagonism compared with that of non resistant cells. Calmodulin mediated processes can be effectively inhibited by a variety of pharmacological agents of different chemical structures, eg:The calcium channel blocker verapamil and antipsychotic drugs like the Phenothiazines. Many bioisosteres of phenothiazines like phenoxazines and acridones have been prepared and these have also shown very good calmodulin antagonism. These calmodulin antagonists have been shown to modulate multi-drug resistance (MDR) in cancer cells. This review highlights concepts of identification and optimization of new inhibitors of calmodulin in reversing MDR in cancer cells.