Drug Design Reviews - Online (Discontinued) - Volume 1, Issue 2, 2004

IBD include two major pathologies, ulcerative colitis (UC) and Crohn's Disease (CD), both characterized by an exaggerated response of the mucosal immune system to stimuli originated from the intestinal flora. Alterations in intestinal permeability and regional and systemic immune responses may play a role in disease outcome. In UC and CD release of Tumor Necrosis Factor (TNF)-α has been invoked as one of the major factor in the chronicity of the inflammation and this sustained production of TNF-α can be supported by plasma endotoxins detectable in a large percentage of IBD patients. In this framework, the role of enteric bacteria in the pathogenesis of IBD is discussed. The availability of Infliximab, a chimeric monoclonal antibody (MoAb) against TNF-α, has represented a therapeutical advance in the treatment of CD patients. In CD patients with moderately active disease, a single infusion of Infliximab led to a significant reduction in their score on a standard CD activity index and one third of the total achieved actual clinical remission. However, the response lasted from a few weeks to six months or more. Same pattern of responsiveness was seen in patients with perianal and cutaneous fistulas. According to some completed trials, serial administration of the drug seems to be more efficacious to maintain the initial response., however this indication has not yet been approved. The mechanisms of action of Infliximab are, then, described and personal data with a cytofluorimetric method for the immune follow-up of CD patients under Infliximab treatment are reported. Finally, among the side effects of Infliximab, cases of active tuberculosis have been described after the initial treatment.

Vascular targeting is distinct from inhibition of angiogenesis, which aims at inhibiting tumor growth and inducing regression by destruction of the tumor vasculature. A fundamental principle of this approach is that tumor vasculature is different from that in normal tissues. The interest in vascular-targeted anticancer therapy arises from the dependence of tumor cells on a functional blood vessel system for survival, proliferation and metastatic dissemination. Hence, the possibility to indirectly inhibit tumor growth and survival by impairing neovessel formation or function. Vascular targeting agents impair the integrity and functionality of tumor vessels, leading to shutdown of the tumor vascular system and consequent tumor cell death. This article reviews recent studies on the use of specific vascular targeting agents and suggests that targeting of the vasculature of diseased organs could underlie a new pharmacological approach to the treatment of malignancies.

In search of less toxic and more effective anticancer agents, the cell cycle has become an intense subject of research. Cell cycle deregulation associated with the cancerous state occurs through alterations of proto-oncogenes resulting in cellular transformation and tumorigenesis, and therefore, cell cycle oncoproteins are medicinally targetable with chemicals having useful specificity. For example, identification of Cdk (cyclin-dependent protein kinase) deregulation in many cancer cells stimulated interest in the targeting of these enzymes to inhibit the growth of transformed cells. As a result, several Cdk inhibitors have entered clinical trials. More recently, an understanding of the contribution of dual specificity Cdc25 (cell division cycle 25) phosphatases to cancer cell growth has also emerged during the past decade and makes them attractive drug targets. Cdc25s are key Cdk activating proteins and act by dephosphorylation of conserved Cdk Tyr15 and Thr14 residues. Cdc25A and Cdc25B were also discovered to be proto-oncogenes and their overexpression has been found in many cancer cells. Although the strong genetic link between Cdc25s and the molecular pathology of cancer has been rationalized to develop small-molecule inhibitors, the literature on Cdc25 inhibition is in it's infancy. Fortunately, the structure and catalytic mechanism(s) of Cdc25s have been solved to drive the design and development of specific and potent inhibitors of Cdc25 activity. This review summarizes some of the efforts directed toward the discovery of potent and specific inhibitors of Cdc25s, including several K-vitamin based structures discovered by our group, as well as their likely mechanisms of cell growth inhibition.

Lafutidine is a newly developed antiulcer drug, having histamine H2 receptor antagonistic and mucosal protective activity. This compound showed a potent and long-lasting inhibition on tiotidine binding and histamine-induced cyclic-3',5'-adenosine monophosphate production in CHO cells expressing human H2 receptors. The duration of the antisecretory activity in dogs and rats was substantially longer than that of famotidine or cimetidine. Lafutidine prevented gastric lesions as induced by a variety of noxious agents, and structure-activity relationships reveal that the presence of furfurylsulfinyl, pyridyl and amide moiety are chemically important for the gastroprotective activity. The mucosal protective effect of lafutidine was attenuated by pretreatment with the antagonist of calcitonin gene-related peptide (CGRP8-37) and the blocker of nitric oxide (NO) production, NG-nitro-L-arginine, as well as chemical ablation of capsaicin-sensitive sensory neurons, suggesting that this action appears through capsaicin-sensitive afferent neurons and is mediated by CGRP and NO. Lafutidine also exhibits a protective activity against the experimentally-induced mucosal lesions in digestive tissues other than the stomach; including acid reflux esophagitis; indomethacin-induced small intestinal lesions; colonic inflammation induced by dextran sulfate sodium. Furthermore, lafutidine also promotes healing of gastric ulcers and reduces the ulcer relapse after discontinuation of the treatment. Given the above results, we conclude that lafutidine has a protective action throughout the gastrointestinal tract from the esophagus to large intestine, and these pharmacological effects are mediated by both the histamine H2 receptor antagonism and facilitation of the sensory neuronal mechanism involving CGRP and NO.

Recognition of peptide / MHC complexes by TCR is a highly sensitive interaction. Even subtle changes in the index peptide amino acid sequence can drastically alter T cell responses. Such peptide variants or analog peptides are termed altered peptide ligands (APLs). Some APLs can act as partial agonists, as they induce only some T cell effecter function but not others, such as cytokine secretion, proliferation or cytolysis. Other APLs, so-called antagonists, inhibit subsequent T cell responses to the index peptide, when presented on the same antigenpresenting cell (APC) as haeindex peptide. Naturally occurring APLs have first been observed in viral diseases (HBV, HIV), and more recently in a number of other diseases. The mechanism of APL antagonism is not fully understood. Inhibition of protective T cell responses by APL antagonism represents a powerful means for immune evasion, not only by pathogens but also in cancer. Inhibition of auto reactive T cell responses by APLs, on the other hand, can provide a new strategy for the treatment of autoimmune diseases. This review will discuss the relevance of APL antagonism in infectious diseases, in autoimmunity, in cancer and the mechanism of APL antagonism.

The kernels of Prunus mume, the medicinal plants, contain immunomodulating polysaccharide P-1 that is pectic, bioactive and extractable with sodium hydroxide. To study the immunochemical properties of P-1, an anti-P-1 antibody was prepared in rabbits. P-1 digested with pectinase was separated into three peaks by ion-exchange chromatography. The fraction that exhibited the strongest immunoreactivity with the antibody was P-1-3, the most acidic fraction containing GalA (54.42 %). The polysaccharide fraction extracted from the kernels by pectinase digestion instead of alkaline extraction showed little immunoreactivity with the anti-P-1 antibody. However, it became immunoreactive after sodium hydroxide treatment. These observations suggested that the majority of epitopes in P-1 were covered by sodium hydroxide-sensitive moieties. The localization of P-1 in kernels was investigated by immunohistoch-emical analysis. Sections of the kernels were treated with aqueous sodium hydroxide and then stained with an anti-P-1 antibody and anti- IgG labeled with peroxidase. Most P-1 was localized in the periphery of the sections and interfascicular tissues. Therefore, it was shown that the bioactive polysaccharide P-1 performed an important role in relation to the germination and growth of plants. This method could determine the distribution of pectic polysaccharide in plants.

Cellular machinery is protected from the surrounding by two-layer lipid membrane that is impermeable for most substances unnecessary for cellular metabolism. Unfortunately, from a cellular point of view, most new generation drugs, designed to act on gene regulation and transcription, are also considered to be unnecessary for metabolism and therefore showing poor, if any, intracellular localization. To overcome this obstacle, several chemical and physical methods have been developed, improving the uptake, but, on the other hand, also showing some unwanted side effects or limitations for in vivo applications. This dictates the continuing need for improved drug delivery and one way seems to be the relatively new class of compounds - cell-penetrating peptides (CPPs). Discovered approximately a decade ago, the content of this class is growing rapidly, containing now more than 100 compounds, which shows the intensity of work in this field. CPPs have already been shown to translocate cellular membranes in an unknown, seemingly receptor-independent and non-endocytotic manner. Moreover, they are able to deliver cargoes exceeding their own size up to 100-fold into a cellular milieu both in vitro and in vivo. The variety of different cargoes includes, but is not limited to: DNA, antisense PNA, oligonucleotides and small proteins. Recent data argues though that endocytosis is involved and contributes in some cases to the main part of the translocation. This review summarizes data on mechanisms of cell-penetrating peptides.

This literature review presents an historical perspective and basic principles of the isolated-perfused heart and gives examples of its current usage together with some personal research data. Heart function, both under conditions of health and disease, is regulated at the molecular, cellular, organ and whole organism level. To address regulation of the heart at various levels, a vast variety of experimental models ranging from man to a single molecule are needed. The isolated mammalian heart preparation, perfused with a blood-free medium, whole blood, or blood components according to Langendorff, has provided reliable information on the condition of the working musculature, the conduction system and the coronary vessels in various conditions. Due to the technical ease by which these functions of the heart can be analyzed, the preparation has been frequently used as a research tool. The molecularly based understanding of the heart will hopefully be a source for new treatments of common cardiac conditions, such as heart failure, cardiomyopathy and dysrhythmias. Thus, the isolated-perfused heart will be further used to test the heart's function under various circumstances. Advances in the conditions that increase stability and extend the life of this preparation could also contribute to its prolonged and expandable usage.