Current Medicinal Chemistry - Volume 13, Issue 18, 2006

Tumor necrosis factor apoptosis ligand (TRAIL) is a type II membrane-bound ligand displaying expression in a broad range of tissues and exhibiting a high grade of homology with the cytotoxic Fas ligand. Interest in TRAIL grew after evidence emerged, that induction of TRAIL-mediated signaling destroyed malignant cells while sparing normal cells. Employing the extrinsic pathway of apoptosis, TRAIL-stimulation is characterized by initial adaptor recruitment and the subsequent activation of caspases. Besides promoting apoptosis, stimulation of the TRAIL receptors may also activate survival signals via the transcription factor NF-κB. Moreover, evaluation of the physiological roles of TRAIL-mediated signaling pathways provides evidence for a regulatory function within the immune system. Thus a complex picture of TRAIL-mediated signaling evolves, underscoring the necessity to define its modes of action while assessing its therapeutic potential. This review outlines the current knowledge on the physiological role of TRAIL and discusses its therapeutic potential with particular focus on malignancies of the hematopoietic system.

Heparanase is an endo-beta-D-glucuronidase that degrades heparan sulfate glycosaminoglycan side chains of the proteoglycans in extracellular matrix and basement membrane. Heparanase enzymatic activity is important in the promotion of tumor angiogenesis, primary tumor growth, invasion, and metastasis. Expression of heparanase in many tumor types conversely correlates with prognosis. Much progress has been made in studying the regulation of heparanase expression, processing and activation. The interaction between heparanase and its substrate heparan sulfate has been well characterized. The fact that heparanase was identified as the single predominant heparan sulfate-degrading enzyme in human cancer sparked considerable interest in developing heparanase inhibitors for potential therapeutic applications. Recent progress in drug development led to several classes of heparanase inhibitors, including chemically modified natural products, small molecule inhibitors, and antibodies. Some of these inhibitors have demonstrated potent activities to inhibit tumor angiogenesis, tumor progress, or tumor metastasis. A leading compound, PI-88, is currently being evaluated in clinical phase II trials in patients with melanoma, liver, or lung cancers. This review summarizes the recent progress in heparanase biochemical research and the development of heparanase antagonists as novel anti-cancer therapeutics.

In recent years, numerous studies have validated the role of inflammation in the pathogenesis of atherosclerosis. Several of such studies have produced compelling evidence that inflammation participates in both, the initiation and perpetuation of the atherosclerotic process. Furthermore, epidemiological observations have found basal white blood cell (WBC) count is strongly associated with future cardiovascular disease (CVD), highlighting the participation of leukocytes in the pathogenesis of the ischemic damage that occurred during an acute coronary event, in particularly during the acute myocardial infarction (MI). Fundamentally, an acute MI triggers a systemic response to a necrotic insult characterized by leukocytosis and acute-phase protein synthesis. In this setting, elevated WBC count plays a central role in the reparative process that takes place to replace the necrotic tissue for collagen. In addition to be a proxy for the intensity of the peri-infarction inflammatory response, recent evidence has also shown that an elevated WBC counts, measured during the acute phase of MI, to be associated with adverse outcomes. This relationship holds true even when adjusting for classical prognostic variables some of which are surrogates for the extension of the infarctedarea. WBC count prognostic value in absence of necrosis marker elevation (like unstable angina), however, remains unclear and controversial. Additionally, and essentially due to its simplicity, cost-effectiveness and wide availability, WBC count has drawn the attention of researchers as a potential stratification tool in acute coronary syndromes (ACS). However, a formal comparison is needed between WBC count with other inflammatory markers such high-sensitive C-reactive protein to fully characterize its diagnostic accuracy.

Background: None of the genetic markers are selectively associated with elite athletes, but potential candidates are found in the renin-angiotensin system, which plays a key role in the regulation of cardiovascular physiology. The most extensively examined gene in connection with the hemodynamics category is the angiotensin converting enzyme (ACE). This review paper has focused on ACE I/D allele polymorphism regarding the evidence of the effects of physiological and pathophysiological drugs and has completed with an original work in the exercise physiology. Methods: In this study we examined genetic polymorphisms of ACE in female (n=26) and male (n=24) athletes as well as in a well-trained control group (n=24). MVVex, VE and VO2max were determined at rest and during an exhaustive step test. Results: The frequency of the ACE I allele was significantly higher (p<0.041) in the group showing a higher intensity of breathing metabolism. The ACE D allele frequency was significantly higher in the excellent endurance athletes group than in unsuccessful athletes (p<0.054). Conclusion: The ACE I allele is a genetic marker for higher endurance efficiency in acute physical activity and higher adaptation of the cardiovascular system. The measurement of acute physical status needs to be completed with examination of genotype, which is related to the athletic excellence also, because the D allele could be associated with good performance by endurance athletes in future world championships. Further studies are needed to assess the view that the ACE D allele has a significant role in athletic efficiency.

The maternal diabetic environment alters the embryo and the feto-placental development. The results of these alterations are: increased embryo resorption and malformation rates, placental dysfunction, fetal alterations that lead to increased neonatal morbidity and mortality rates, and also diseases that will be evident later in the adult life of the newborn. The etiology of these many maternal diabetes-induced complications are not yet understood in full. In this review the role of maternal diabetes as an inductor of a pro-inflammatory environment that impairs embryo and placental development is discussed. An overproduction of proinflammatory agents is found in the uterus during implantation and the developing embryo and placenta from experimental models of diabetes, as well as in placenta from diabetic women. In these tissues there are increases in reactive oxygen species, pro-inflammatory cytokines and prostaglandins, nitric oxide and peroxynitrites. These pro-inflammatory agents lead to the intrauterine activation of matrix metalloproteinases, proteases involved in remodeling the extracellular matrix during implantation and feto-placental development. Many of these pro-inflammatory agents have overlapping mechanisms of action and cross regulatory pathways that propagate the inflammatory processes. Antioxidants, PPARγ activators, and NF-κB inhibitors are able to reduce the concentrations of these agents in intrauterine gestational tissues. This article reviews the current understanding of maternal diabetes-induced changes in pro-inflammatory and anti-inflammatory pathways that affect the embryo and placental development in maternal diabetes, and stresses the need of a strict maternal control of the pathology to prevent deleterious consequences in the offspring.

The dopaminergic system plays a major role in neurological and psychiatric disorders such as Parkinson's disease, Huntington's disease, tardive dyskinea and schizophrenia. Knowledge on altered dopamine synthesis, receptor densities and status are important for understanding the mechanisms underlying the pathogenesis and therapy of diseases. PET provides a non-invasive tool to investigate these features in vivo, provided the availability of suitable radiopharmaceuticals. To investigate presynaptic function, PET-tracers have been developed to measure dopamine synthesis and transport. For the former the most commonly used tracers are 6-[18F]FDOPA and 6-[18F]FMT, whereas for the latter several 11C/18F-labeled tropane analogues are being clinically used. Postsynaptically, dopamine exerts actions through several subtypes of the dopamine receptor. The dopamine receptor family consists of 5 subtypes D1-D5. In order to investigate the role of each receptor subtype, selective and high-affinity PETradioligands are required. For the dopamine D1-subtype the most commonly used ligand is [11C]SCH 23390 or [11C]NNC 112, whereas for the D2/D3-subtype [11C]raclopride is a common tracer. [18 F]Fallypride is a suitable PET-tracer for the investigation of extrapyramidal D2-receptors. For the other subtypes no suitable radioligands have been developed yet. This paper gives an overview of the current status on dopamine PET-tracers and the development of new lead compounds as potential PET-tracers by medicinal chemistry.

Since the viral vector for gene therapy has serious problems, including oncogenesity and other adverse effects, non-viral carriers have attracted a great deal of attention. Non-viral carriers are expected to achieve gene therapy without serious side effects. However, the most critical issue of gene delivery by non-viral carriers is the low-expression efficiencies of the desired gene. In order to apply non-viral carriers for gene therapy in practical clinical usage, further understanding of the cellular barriers against gene delivery is a prerequisite. Moreover, additional intelligent concepts for gene delivery are also needed. We will summarize the features and shortcomings of currently developed non-viral delivery systems. Especially, we will address the current progress of cationic lipids (lipoplex) and cationic polymers (polyplex) in terms of transfection efficiency. Furthermore, our group has developed a system that responds to the particular intracellular signals of target disease cells. We have named this gene delivery system a drug delivery system based on responses cellular signal (D-RECS). We will introduce this new concept of intelligent non-viral delivery system that our group recently developed.

The pathogenic nature of many infectious bacteria is enhanced by their ability to form surfaceassociated, protected communities known as "biofilms." Due to various factors, bacteria in biofilm communities display significantly greater resistance to traditional antimicrobial therapies than their planktonic brethren. This resistance complicates many common bacterial infections, resulting in recurrent ear infections, bacterial endocarditis, chronic lung infection in cystic fibrosis, infectious kidney stones, and surface infection of implanted medical devices. Owing to the serious nature of many biofilm-mediated infections and the near-complete dearth of effective strategies for treating them, efforts are underway to further understand the nature of bacterial infections involving biofilms and to discover and develop effective therapies to combat them. Particularly, several classes of chemical compounds have shown promise in combating biofilms when used in conjunction with traditional antimicrobials. The vast majority of these compounds exert their anti-biofilm properties through disruption of "quorum sensing," a common means of intercellular communication in bacterial communities that allows coordinated expression of virulence factors and facilitates formation of the oft-complex architecture of mature bacterial biofilms. Other new chemical entities are effective against biofilms without necessarily affecting quorum sensing. This review summarizes salient research in the development of effective chemical countermeasures for Gram-negative and Grampositive bacterial infections involving biofilms.

The central role of cholinergic system in Alzheimer's disease (AD) pathway is becoming increasingly significant as reports linking the various components of cholinergic neurotransmission with the other pathological hallmarks emerge. This review, while addressing the molecular mechanisms associated with the pathological hallmarks of the disease and their close interactions, also makes an attempt to address the critical question that evades an answer: Given the significant role played by cholinergic system in AD pathway, why do the cholinergic-mechanism-based drugs are not successful in reversing or arresting the disease progress? Further, as molecules of diverse structural features were shown to inhibit amyloid aggregation, an understanding of the generic pathway of amyloid aggregation slowly emerges. For the first time, a coherent view of amyloid aggregation is presented in this review. The possible role of neuroinflammatory response in the events leading to the degeneration of cholinergic neurons is also discussed.

During the last decades, Photodynamic Therapy (PDT) has been established as a powerful alternative approved by health agencies of several countries for treatment of various malignant and some non-malignant diseases. PDT makes use of the light-induced destruction of target cells by formation of cytotoxic products in the presence of a photosensitizing agent and oxygen. The light-dependent tumor destructive properties of Hypericin have drawn attention to its promising application as a photosensitizer in the frame of PDT. Hypericin is a naturally occurring secondary metabolite in plants of the Hypericum genus, with Hypericum perforatum (St. John's wort) as it is a commonly known representative. This review focuses on the cellular mechanisms of Hypericin-based phototoxicity and provides an outlook for future application of Hypericin as a fluorescing and photosensitizing agent for diagnosis and treatment of cancerous diseases, respectively.

The relationships between structure, disintegration and antituberculotic in vitro activity were studied for over 200 derivatives of isonicotinic acid hydrazide (isoniazid, INH). Conclusive evidence reflects that many compounds do not withstand the in vitro conditions. A pH dependant partial hydrolysis to INH occurs in the case of hydrazones, in analogy to well-known benzoic acid esters. Hydrazides and amides are cleaved into isonicotinic acid. In general, antimycobacterial potencies drop against INH except for two outliers probably with additional unspecific toxicity of their residues. Analyzing the complexity and heterogeneity of molecular events, trends linked to hydrolysis are found when structural features are clustered. Hammett sigma constants correlate to pKα values possessing a twofold descriptive meaning: (i) the cardinal increase of partial positive charge of the reaction center towards nucleophilic water attack and (ii) the ionization crucial for mycobacterial cell permeation through porins or lipid barriers. We review the literature concluding that many so-called "novel leads" are nothing else than precursors of an INH-based scaffold. In addition, INH ringsubstitution or analogous backbones never achieve the efficiency of INH, itself a prodrug, which accumulates in Mycobacterium tuberculosis in form of its intrabacterial active principle(s) to which it is an optimal transport vehicle, evidencing that INH is not a promising lead compound at all.