Current Medicinal Chemistry - Volume 16, Issue 22, 2009

There is rapid development in the field of protein microarray technology with the promise of important advancements in the near future. Protein microarrays have been reportedly successful in serum tumor marker profiling as well as in drug discovery and medicinal chemistry when the effect of small molecules in protein-protein interaction is studied. Some of the bottlenecks of the technology are protein instability, problems with immobilization and stabilization of proteins to the corresponding surface, as well as aspecific and /or not preferred interactions and the lack of protein amplification techniques to generate sufficient amounts of low abundance proteins. For the time being, the number of genes in RNA expression chips is significantly greater than the number of proteins available for microchip based analysis of gene expression at the protein level. The automation and standardization routinely used with nucleic acid microarrays is not yet available in their protein chip counterparts. One of the emerging applications of protein microchips is biomarker discovery via chromatographic surface-based protein array techniques, which is applicable to minute amounts of samples with excellent detection limits using mass spectrometry based interrogation. In this paper the advantages, technical limitations and main biomedical application of protein microarrays are reviewed.

Drug-induced phospholipidosis is characterised by an excessive accumulation of polar phospholipids in cells or tissues. However, from a toxicological perspective the functional consequences of phospholipidosis remain uncertain and a regulatory position unclear. As a consequence, to minimize compound development risk pharmaceutical companies are beginning to proactively address phospholipidosis within drug discovery programs, and implement strategies to identify compounds predicted to show no phospholipidosis. Examples of optimization of compounds to minimize phospholipidosis, and the status of current in silico prediction models, are presented and discussed.

Recently, there has been widespread interest in the use of non-invasive methods for the assessment of airway inflammation in a variety of lung diseases including chronic obstructive pulmonary disease (COPD). Sputum induction is a semi-invasive technique the value of which is not restricted to sputum cell counts, as inflammatory mediators can also be measured in the supernatants. However, none of the measurable biomarkers in induced sputum is considered applicable in clinical practice. Despite the predominating sputum neutrophilia, there is increasing evidence that the presence of sputum eosinophilia predicts an objective response to steroid treatment in patients with COPD. The commonly used Exhaled Breath Condensate (EBC) methodologies in COPD patients have considerable variability due to technical issues concerning both sample collection and analysis. Despite the above limitations, biomarkers mainly related to neutrophil derived products and oxidative stress, have been assessed for disease monitoring and response to pharmacological treatment. Endogenous airway acidification, as assessed by EBC pH, represents a measurable marker associated with oxidative stress and sputum neutrophilia. The fraction of exhaled nitric oxide (FeNO) is the most extensively studied exhaled biomarker and increased levels of FeNO have been widely documented in patients with asthma. FeNO measurement in COPD is of limited value due to smoking effect. However, increased values of FeNO have been found in COPD patients with sputum eosinophila. Moreover, measuring FeNO in different exhalation rates may reestablish its value in COPD. Despite the limited use of non-invasive methods, the future direction is a challenge towards new biomarkers or a combination of them that will assist us to move from the research laboratory to daily clinical practice.

Phosphatidylinositol 3-kinases (PI3Ks) are a class of lipid kinases that phosphorylate phosphatidylinositol 4,5- bisphosphate (PIP2) at the 3-OH of the inositol ring to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3), which in turn activates Akt and the downstream effectors like mTOR, and therefore play important roles in cell growth, survival, etc. The phosphatase and tensin homolog deleted in chromosome ten (PTEN), acts as the catalytic antagonist of PI3K by dephosphorylating PIP3 to PIP2. PI3K has become an important drug target for cancer therapy, since gain-of-function mutations of PIK3CA encoding PI3Kα, as well as loss-of-function mutations of PTEN, have been frequently found in human cancers. The pharmaceutical development of PI3K inhibitors has made a great leap forward during the last 3 years. While PI3Kβ, &δ and γ isoform-specific PI3K inhibitors (TGX-221, IC87114 and AS-605240) have been developed for therapy of coronary heart disease, asthma, and glomerulonephritis, respectively, a promising PI3Kα specific inhibitor is not yet available. Correspondingly, almost all of the promising PI3K inhibitors under development for caner therapy, such as NVP-BEZ235, GDC-0941 and ZSTK474, are pan-PI3K isoform inhibitors. Each of these pan-PI3K inhibitors seems to induce a common G1 phase arrest. All have shown favorable in vivo anticancer efficacies and low toxicities, and therefore most have entered evaluation in clinical trials. P-Akt and p-S6 have been reported to be feasible pharmacodynamic biomarkers for monitoring the efficacy of these agents. In the process of discovery of these and other PI3K inhibitors, detailed structure-activity relationship studies were carried out. This review summarizes key advances in the development of PI3K inhibitors, which is preceded by an introduction of PI3K family and their functions.

Many litres of fluids are found outside cells in the human body. These fluids are rich in dissolved proteins that each have a characteristic three dimensional shape, necessary for normal function, which has been attained by the correct folding of their polypeptide chain(s). The structure of these extracellular proteins can be damaged by a variety of environmental stresses (e.g. heat and oxidation) leading to their partial unfolding and aggregation. This in turn can produce toxic soluble aggregates and/or large insoluble protein deposits, either of which can disrupt normal body function (e.g. in Alzheimer's disease and the systemic amyloidoses). A small family of abundant human blood proteins with the ability to inhibit the aggregation and deposition of stressed (partially unfolded) proteins has been discovered. These extracellular chaperones (ECs) form stable, soluble complexes with stressed proteins. It has been proposed that once bound to stressed proteins, ECs guide them to specific cell surface receptors that direct the “cargo” into lysosomes for degradation. Thus ECs and their receptors may be critical parts of a quality control system to protect the body against the deleterious effects of inappropriately aggregating extracellular proteins. This review focuses on the role of extracellular protein aggregation and deposition in disease, what little is known about mechanisms that act to control these processes, and, lastly, potential new targets for drug development. Newly identified potential drug targets include direct inhibition of protein aggregation, and manipulation of the expression levels of ECs and their receptors.

Mucus production is a cardinal feature of bronchial asthma, contributing to morbidity and mortality in the disease. Goblet cells are major mucus-producing cells, and goblet cell hyperplasia (GCH) is one feature of airway remodeling, defined as structural changes occurring in the airway. A number of studies have demonstrated that Th2-type cells play critical roles in this process and that particularly interleukin-13 (IL-13), among Th2-type cytokines, is a central mediator for GCH. However, the mechanism underlying how Th2 cytokines induce mucus production or GCH is poorly understood. Mouse calcium-activated chloride channel-3 (mCLCA-3; gob-5)/human CLCA-1 acts as a downstream molecule of Th2 cytokines, IL-4/IL-9/IL-13 signals, playing an important role in mucus production. Moreover, we have recently found that pendrin, an anion transporter, is induced by IL-13 and causes mucus production in airway epithelial cells. It is hoped that if we can clarify how mucus is produced, this will lead to development of novel therapeutic reagents to suppress mucus production in bronchial asthma.

Currently, the long-term usage of non-nucleoside reverse transcriptase inhibitors (NNRTIs) in HIV/AIDS patients eventually leads to the development of drug resistance and severe side effect. Therefore, it is imperative to look for the novel NNRTIs with potent and broad spectrum anti-mutant activity that are also safe and have excellent pharmacokinetic profiles. In this article, newly emerging NNRTIs scaffolds in recent three years, together with the underlying strategies for developing new generation HIV-1 NNRTIs with improved resilience to current drug resistant mutants, are reviewed and analysed.

The vascular endothelial growth factor (VEGF)/VEGF receptor pathways are essential for the regulation of angiogenesis during embryonic development and tumor progression. VEGF receptor 1 (VEGFR-1) has been shown to promote tumor growth and metastasis through the regulation of multiple biological functions in cancer cells, vasculature, stroma and other tumor-associated cells. VEGFR-1 signaling is required for the survival of endothelial cells and macrophages and the mobilization of cancer cells, endothelial cells, myeloid progenitors, and monocyte/macrophages. VEGFR- 1 was reported to have a function in eliciting epithelial-to-mesenchymal transition in cancer cells toward invasive and metastatic phenotype. Furthermore, VEGFR-1 was found to promote metastasis through initiating pre-metastatic niche by VEGFR-1 positive bone marrow progenitors. It was reported that VEGFR-1 had an active role in promoting inflammation through modulating immune cells and mediating immunosuppression by VEGFR-1 positive myeloid cells. Given that VEGFR-1 has a multi-functional role in promoting angiogenesis, inflammation, tumor growth and metastasis, VEGFR-1 has emerged as a promising therapeutic target for treatment of cancer as well as angiogenesis and inflammation associated disorders.

The translocator protein (18 kDa) (TSPO), formerly known as the peripheral benzodiazepine receptor (PBR), was originally identified as an alternate binding site for the central benzodiazepine receptor (CBR) ligand, diazepam, in the periphery, but has now been distinguished as a novel site. The TSPO is ubiquitously expressed in peripheral tissues but only minimally in the healthy brain and increased levels of TSPO expression have been noted in neuroinflammatory conditions such as Alzheimer's disease, Parkinson's disease and stroke. This increase in TSPO expression has been reported to coincide with the process of microglial activation, whereby the brain's intrinsic immune system becomes active. Therefore, by using recently developed high affinity, selective TSPO ligands in conjunction with functional imaging modalities such as positron emission tomography (PET), it becomes possible to study the process of microglial activation in the living brain. A number of high affinity ligands, the majority of which are C,N-substituted acetamide derivatives, have been successfully radiolabelled and used in in vivo studies of the TSPO and the process of microglial activation. This review highlights recent achievements (up to December 2008) in the field of functional imaging of the TSPO as well as the radiosyntheses involved in such studies.

This review, a sequel to part 1 in the series, collects about 107 chemical entities separated from the roots, leaves and flower buds of Panax ginseng, quinquefolius and notoginseng, and categorizes these entities into about 18 groups based on their structural similarity. The bioactivities of these chemical entities are described. The ‘Yin and Yang’ theory and the fundamentals of the ‘five elements’ applied to the traditional Chinese medicine (TCM) are concisely introduced to help readers understand how ginseng balances the dynamic equilibrium of human physiological processes from the TCM perspectives. This paper concerns the observation and experimental investigation of biological activities of ginseng used in the TCM of past and present cultures. The current biological findings of ginseng and its medical applications are narrated and critically discussed, including 1) its antihyperglycemic effect that may benefit type II diabetics; in vitro and in vivo studies demonstrated protection of ginseng on beta-cells and obese diabetic mouse models. The related clinical trial results are stated. 2) its aphrodisiac effect and cardiovascular effect that partially attribute to ginseng's bioactivity on nitric oxide (NO); 3) its cognitive effect and neuropharmacological effect that are intensively tested in various rat models using purified ginsenosides and show a hope to treat Parkinson's disease (PD); 4) its uses as an adjuvant or immunotherapeutic agent to enhance immune activity, appetite and life quality of cancer patients during their chemotherapy and radiation. Although the apoptotic effect of ginsenosides, especially Rh2, Rg3 and Compound K, on various tumor cells has been shown via different pathways, their clinical effectiveness remains to be tested. This paper also updates the antioxidant, anti-inflammatory, anti-apoptotic and immune-stimulatory activities of ginseng, its ingredients and commercial products, as well as common side effects of ginseng mainly due to its overdose, and its pharmacokinetics.