Current Medicinal Chemistry - Volume 17, Issue 33, 2010

The prevalent challenge facing tissue engineering today is the lack of adequate vascularization to support the growth, function, and viability of tissue substitutes that require blood vessel supply. Researchers rely on the increasing knowledge of angiogenic and vasculogenic processes to stimulate vascular network formation within three-dimensional tissue constructs. These processes are mainly endothelial cell-regulated, although in the context of tissue engineering, specific interactions with scaffold materials, growth factors and other cell types may require in vitro vascularization schemes to be altered accordingly. To better mimic the complete in vivo environment, increasing attention is given to the integration of co-cultures and mechanical conditioning in bioreactors. Such approaches show great promise for the enhancement of the functionality and clinical applicability of tissue engineering constructs. This paper reviews some scaffold materials used in tissue engineering and the effect of their properties on the vascularization process. Also, it specifically addresses the pivotal role of biomaterials vascularization in tissue engineering applications, along with the effect of angiogenic factors and adhesive molecules on angiogenesis. Assays and markers of angiogenesis are also outlined. One section highlights the need for bioreactor cultures and mechanical conditioning in controlling endothelial cell responses. Finally, we conclude with a brief section on the effects of oxygen concentration and hypoxia over microvessel formation.

In this review we describe in detail the available technologies used for investigating the substrate specificity of proteases. Critical comparison of the available detection methods and their choice for certain type of screening is discussed. We present successful strategies along with appropriate examples for the design and synthesis of combinatorial libraries of substrates using both chemical and biological approaches. Proteomic tools for the identification of natural substrates of proteases are also discussed.

Protein phosphorylation is a major regulatory mechanism of signal transduction cascades in eukaryotic cells, catalysed by kinases and reversed by protein phosphatases (PPs). Sequencing of entire genomes has revealed that ∼37percnt; of all eukaryotic genes encode kinases or PPs. Surprisingly, there appear to be 2-5 times fewer PPs than kinases. Over the past two decades it has become apparent that the diversity of Ser/Thr-specific PPs (STPP) was achieved not only by the evolution of new catalytic subunits, but also by the ability of a single catalytic subunit to interact with multiple interacting proteins. PP1, a STPP, is involved in the control of important cellular mechanisms. Several isoforms of PP1 are known in mammals: PP1α, PP1β and PP1γ . The various isoforms are highly similar, except for the N- and C-termini. The current view is that since PPs possess exquisite specificities in vivo, the key control mechanism must reside in the nature of the PP1 Interacting Protein (PIP) to which they bind. An increasing number of PIPs have been identified that are responsible for regulating the catalytic activity of PPs. Indeed, the diversity of such PIPs explains the need for relatively few catalytic subunit types, and makes them attractive targets for pharmacological intervention. This review will summarize the PIPs identified using the Yeast Two Hybrid methodology and alternative techniques, for instance bioinformatic and proteomic approaches. Further, it compiles 129 PP1-PIP relevant physiological interactions that are well documented in the literature. Finally, the use of PIPs as therapeutic targets will be addressed.

Cardiovascular disease is the largest cause of death in Western societies and it primarily results from atherosclerosis of large and medium-sized vessels. Atherosclerosis leads to myocardial infarction, when it occurs in the coronary arteries, or stroke, when it occurs in the cerebral arteries. Pathological processes involved in macrovascular disease include the accumulation of lipids which are retained by extracellular matrix (ECM) molecules, especially by the chondroitin sulfate/dermatan sulfate (CS/DS) proteoglycans (CS/DSPGs), such as versican, biglycan and decorin. The sulfation pattern of CS is a key player in protein interactions causing atherosclerosis. Several studies have shown that lipoproteins bind CSPGs via their glycosaminoglycan chains. Galactosaminoglycans, such as CS and DS, bind low density lipoproteins (LDL), affecting the role of these molecules in the arterial wall. In this article, the role of CS and versican in atherosclerosis and hyaluronan in atherogenesis as well as the up to date known mechanisms that provoke this pathological condition are presented and discussed.

Leishmaniasis, African sleeping sickness and Chagas disease, caused by the kinetoplastid parasites Leishmania spp, Trypanosoma brucei and Trypanosoma cruzi, respectively, are among the most important parasitic diseases, affecting millions of people and considered to be within the most relevant group of neglected tropical diseases. The main alternative to control such parasitosis is chemotherapy. Nevertheless, the current chemotherapeutic treatments are far from being satisfactory. This review outlines the current understanding of different drugs against leishmaniasis, African sleeping sickness and Chagas disease, their mechanism of action and resistance. Recent approaches in the area of anti-leishmanial and trypanocidal therapies are also enumerated, new modulators from the mode of action, development of new formulations of old drugs, therapeutic switching and “in silico” drug design.

DNA methylation is an epigenetic event involved in a variety array of processes that may be the foundation of genetic phenomena and diseases. DNA methyltransferase is a key enzyme for cytosine methylation in DNA, and can be divided into two functional families (Dnmt1 and Dnmt3) in mammals. All mammalian DNA methyltransferases are encoded by their own single gene, and consisted of catalytic and regulatory regions (except Dnmt2). Via interactions between functional domains in the regulatory or catalytic regions and other adaptors or cofactors, DNA methyltransferases can be localized at selective areas (specific DNA/nucleotide sequence) and linked to specific chromosome status (euchromatin/ heterochromatin, various histone modification status). With assistance from UHRF1 and Dnmt3L or other factors in Dnmt1 and Dnmt3a/Dnmt3b, mammalian DNA methyltransferases can be recruited, and then specifically bind to hemimethylated and unmethylated double-stranded DNA sequence to maintain and de novo setup patterns for DNA methylation. Complicated enzymatic steps catalyzed by DNA methyltransferases include methyl group transferred from cofactor Ado-Met to C5 position of the flipped-out cytosine in targeted DNA duplex. In the light of the fact that different DNA methyltransferases are divergent in both structures and functions, and use unique reprogrammed or distorted routines in development of diseases, design of new drugs targeting specific mammalian DNA methyltransferases or their adaptors in the control of key steps in either maintenance or de novo DNA methylation processes will contribute to individually treating diseases related to DNA methyltransferases.

Pharmacokinetic studies have become an integral part of modern drug development, but these studies are not regulatory needs for herbal remedies. This paper updates our current knowledge on the disposition pathways and pharmacokinetic properties of commonly used herbal medicines in humans. To retrieve relevant data, the authors have searched through computer-based literatures by full text search in Medline (via Pubmed), ScienceDirect, Current Contents Connect (ISI), Cochrance Library, CINAHL (EBSCO), CrossRef Search and Embase (all from inception to May 2010). Many herbal compounds undergo Phase I and/or Phase II metabolism in vivo, with cytochrome P450s (CYPs) and uridine diphosphate glucuronosyltransferases (UGTs) playing a major role. Some herbal ingredients are substrates of Pglycoprotein (P-gp) which is highly expressed in the intestine, liver, brain and kidney. As such, the activities of these drug metabolizing enzymes and drug transporters are determining factors for the in vivo bioavailability, disposition and distribution of herbal remedies. There are increasing pharmacokinetic studies of herbal remedies, but these studies are mainly focused on a small number of herbal remedies including St John's wort, milk thistle, sculcap, curcumin, echinacea, ginseng, ginkgo, and ginger. The pharmacokinetic data of a small number of purified herbal ingredients, including anthocyanins, berberine, catechins, curcumin, lutein and quercetin, are available. For the majority of herbal remedies used in folk medicines, data on their disposition and biological fate in humans are lacking or in paucity. For a herbal medicine, the pharmacological effect is achieved when the bioactive agents or the metabolites reach and sustain proper levels at their sites of action. Both the dose levels and fates of active components in the body govern their target-site concentrations after administration of an herbal remedy. In this regard, a safe and optimal use of herbal medicines requires a full understanding of their pharmacokinetic profiles. To optimize the use of herbal remedies, further clinical studies to explore their biological fate including the disposition pathways and kinetics in the human body are certainly needed.