Current Medicinal Chemistry - Volume 15, Issue 1, 2008

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-??B) 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-??B 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.

Nuclear magnetic resonance spectroscopy has been exploited to study the metabolic characteristics (phenotype) of genetic disorders by taking advantage of some unique characteristics of the technique. The first application, metabolic profiling for diagnosis and therapeutic monitoring in vitro, demonstrates the exceptional diversity of metabolites detected by NMR, and has resulted in new interest in significant metabolites largely ignored previously because other techniques do not detect them, e.g. betaine and creatine. Moreover, previously ‘unknown’ genetic disorders have been detected and characterised The same NMR technique can be effectively exploited for metabolic profiling of mutation models in yeast and mice, leading to a prominent role in the development of large scale metabolomic profiling to link genomic information with phenotype. The second application, magnetic resonance spectroscopy (MRS), exploits the unique possibility of studying human metabolism in vivo, which permits intracellular rather than extracellular metabolic profiling. When it is possible to detect the precise diagnostic metabolites in vivo, investigators have been able to link clinical status with cellular biochemistry, sometimes questioning the clinical value of extracellular (plasma) metabolite measurements. Thus, claims have been made that brain phenylalanine concentrations match more closely the clinical status of patients with phenylketonuria. These studies in vivo have also led to new diagnoses e.g. the disorders of creatine synthesis and transport, highlighting a new category of brain syndromes. Future applications of NMR are cautiously considered as they are critically dependent on continued improvement in resolution and sensitivity in turn generated by developments in magnet design and higher fields.

Drug discovery is a highly complex and costly process, which demands integrated efforts in several relevant aspects involving innovation, knowledge, information, technologies, expertise, R&D investments and management skills. The shift from traditional to genomics- and proteomics-based drug research has fundamentally transformed key R&D 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.

Accumulation of misfolded proteins in proteinaceous inclusions is a prominent pathological feature common to many agerelated 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.

Type II diabetes is a heterogeneous disease where environment and genetics are important factors for the expression of the disease. The high cost for treating complications of diabetes is a burden for public health systems and governments worldwide. Type II diabetes has been causing debilitation worldwide for many decades, and a single drug that safely treats the disease has yet to be discovered. Sulfonylureas, biguanides, α-glucosidase, meglitinides, DPP-4 inhibitors and thiazolidinediones are among the classes of oral hypoglycemic drugs available to treat Type II diabetes, but concerns exist regarding safety and efficacy of these drugs. In this article we present the pros and cons of the six classes and discuss some of the latest advances towards the development of new drugs for the treatment of Type II diabetes.

Phytoecdysteroids are structural analogs of the insect molting hormone ecdysone. Plants comprise rich sources of ecdysteroids in high concentration and with broad structural diversity. Ecdysteroids have a number of proven beneficial effects on mammals but the hormonal effects of ecdysteroids have been proven only in arthropods. Their structures are somewhat similar to those of the vertebrate steroid hormones but there are several structural differences between the two steroid groups. Despite of these essential structural differences, ecdysteroids exert numerous effects in vertebrates that are similar to those of vertebrate hormonal steroids, and they may serve as effective anabolic, hepatoprotective, immunoprotective, antioxidant and hypoglycemic agents. Ecdysteroids do not bind to the cytosolic steroid receptors, instead, they are likely to influence signal transduction pathways, like the anabolic steroids, possibly via membrane bound receptors. The application of phytoecdysteroids is a promising alternative to the use of anabolic-androgenic steroids because of the apparent lack of adverse effects. The prospective use of phytoecdysteroids may extend to treatments of pathological conditions where anabolic steroids are routinely applied. One of the most cited aspects of phytoecdysteroid application (on the Internet) is the increase of muscle size. However in this field too stringent research is needed as an adequate cytological explanation is not yet available for the anabolic. This paper reports on the most important structural differences between androgenic hormones, their synthetic analogs and ecdysteroids. The anabolic/hormonal effects and the possible mechanisms of action of these compounds are also discussed as concerns the skeletal muscle.

This is a review of the enzymatic mechanism of DNA methyltransferase Dnmt1 and analysis of its implications on regulation of DNA methylation in mammalian cells and design of novel mechanism-based inhibitors. The methylation reaction by Dnmt1 has different phases that depend on DNA substrate and allosteric regulation. Consequently, depending on the phase, the differences in catalytic rates between unmethylated and pre-methylated DNA can vary between 30-40 fold, 3-6 fold or only 1 fold. The allosteric site and the active site can bind different molecules. Allosteric activity depends on DNA sequence, methylation pattern and DNA structure (single stranded vs. double stranded). Dnmt1 binds poly(ADP-ribose) and some RNA molecules. The results on kinetic preferences, allosteric activity and binding preference of Dnmt1 are combined together in one comprehensive model mechanism that can address regulation of DNA methylation in cells; namely, inhibition of DNA methylation by poly(ADP-ribose), RNA-directed DNA methylation by methylated and unmethylated non-coding RNA molecules, and transient interactions between Dnmt1 and genomic DNA. Analysis of reaction intermediates showed that equilibrium between base-flipping and base-restacking events can be the key mechanism in control of enzymatic activity. The two events have equal but opposite effect on accumulation of early reaction intermediates and methylation rates. The accumulation of early reaction intermediates can be exploited to improve the current inhibitors of Dnmt1 and achieve inhibition without toxic modifications in genomic DNA. [1,2-dihydropyrimidin-2-one]-5-methylene-(methylsulfonium)-adenosyl is described as the lead compound.