Current Drug Discovery Technologies (v.5, #4)

Ex Vivo and In Vivo Approaches to Study Mechanisms of Cardioprotection Targeting Ischemia/Reperfusion (I/R) Injury: Useful Techniques for Cardiovascular Drug Discovery by Ramesh Vidavalur, Snehasikta Swarnakar, Mahesh Thirunavukkarasu, Samson Samuel, Nilanjana Maulik (269-278).
The last few decades have seen significant advancement in the therapy of Ischemic Heart Diseases (IHD). This is a direct outcome of the increasing knowledge of the molecular mechanisms involved during an ischemic insult of the myocardium. Even then there is still a major unmet need for better strategies or drug therapies to reduce ventricular remodeling and improve post-ischemic myocardial function. The ex-vivo isolated working heart model and the in vivo myocardial infarction model are the best known techniques to elucidate the contribution of a drug therapy to confer cardioprotection in the event of an ischemic insult/reperfusion. Our review aims to provide an insight into the state of the art techniques that lay the foundations for cardiovascular drug discovery and present the prospects for further development from a preclinical perspective. The first section of the review provides an overview of the rat/mouse ex-vivo and in vivo models of myocardial ischemia. The following section will then present various applications of these clinically relevant models in characterizing cardiac functions, screening for drugs and identifying the drug induced changes in cardiac functions. Finally the role of these models in drug development is discussed with respect to functional relevance of drug treatment on heart rate, aortic flow, coronary flow, infarct size and the mechanisms by which these drugs promote myocardial protection. This review may serve as a basic knowledge for researchers who intend to study the efficacy of a drug in the treatment of ischemic heart diseases.

There is compelling evidence that airway smooth muscle cells may function as inflammatory cells in the airway system by producing multiple inflammatory cytokines in response to a large array of external stimuli such as acetylcholine, bradykinin, inflammatory cytokines, and toll-like receptor activators. However, how multiple extracellular stimuli interact in the regulation of inflammatory gene expression in an airway smooth muscle cell remains poorly understood. This review addresses the mechanistic systems biology of inflammatory gene expression in airway smooth muscle by discussing: a) redundancy underlying multiple stimulus-product relations in receptor-mediated inflammatory gene expression, and their regulation by convergent activation of Erk1/2 mitogen-activated protein kinase (MAPK), b) Erk1/2 MAPK-dependent induction of phosphatase expression as a negative feedback mechanism in the robust maintenance of inflammatory gene expression, and c) cyclooxygenase 2-dependent regulation of the differential temporal dynamics of early and late inflammatory gene expression. It is becoming recognized that a single-target approach is unlikely to be effective for the treatment of inflammatory airway diseases because airway inflammation is a result of complex interactions among multiple inflammatory mediators and cells types in the airway system. Understanding the mechanistic systems biology of inflammatory gene expression in airway smooth muscle and other cell types in the airway system may lead to the development of multi-target drug regimens for the treatment of inflammatory airway diseases such as asthma.

Potential Therapeutic Application of Chondroitin Sulfate/Dermatan Sulfate by Shuhei Yamada, Kazuyuki Sugahara (289-301).
Glycosaminoglycans (GAGs) are complex polysaccharides, which play important roles in cell growth, differentiation, morphogenesis, cell migration, and bacterial/viral infections. Major GAGs include heparin (Hep)/heparan sulfate, and chondroitin sulfate (CS)/dermatan sulfate (DS). Hep has been used for the treatment of thromboembolic disorders for more than 75 years, and has an established position in therapy today. CS/DS has attracted less attention and its clinical use is limited. However, CS/DS also have intriguing biological activities, which in turn should help in the development of CS/DS-based therapeutics. In this review, the following potential applications of CS/DS chains are discussed. (1) Sugar drugs for parasitic and viral infections. Particular CS variants appear to be involved in infections of various microbes, suggesting that CS/DS oligosaccharide sequences specifically interacting with microbes will lead to the development of inhibitory drugs for these infections. (2) Regenerative medicine. Biological activities of CS/DS chains possibly involve various growth factors, also known as Hep-binding growth factors. Specific CS/DS chains recruit growth/neurotrophic factors and/or potentiate their activities, suggesting that minute amounts of functional CS/DS chains can be utilized for tissue regeneration instead of signaling proteins. (3) Anti-tumor drugs. Specific saccharide structures in CS/DS chains appear to be involved in tumor cell proliferation and metastasis. The detection and identification of such CS/DS saccharide sequences would be an important contribution to cancer therapy.

Acute hypoxia is induced during coronary occlusion or when oxygen supply does not meet demand and can trigger cardiac arrhythmia. Cardiac ion channels shape the action potential and excitability of the heart. Acute hypoxia regulates the function of cardiac ion channels including the L-type Ca channel that is the main route for Ca influx into cardiac myocytes and shapes the plateau phase of the action potential. This article will review the evidence for alteration of ion channel function during hypoxia as a result of modification of thiol groups by reactive oxygen species. The effect of acute hypoxia on cardiac excitability will be examined and how this can lead to life threatening arrhythmias with particular reference to the L-type Ca channel. Recent evidence indicates the L-type channel is a suitable target for the development of drugs that can modify channel function during hypoxia or oxidative stress to prevent induction of arrhythmia or development of pathology.

Bivalent Ligands as Specific Pharmacological Tools for G Protein-Coupled Receptor Dimers by Isabelle Berque-Bestel, Frank Lezoualc'h, Ralf Jockers (312-318).
G protein-coupled receptors (GPCRs) are major drug targets and are organized in dimeric/oligomeric complexes. These dimers may be composed of identical (homodimer) or different (heterodimer) receptors. GPCR dimerization provides new opportunities for drug design. Different strategies have been developed to specifically target GPCR dimers. Bivalent ligands, which are composed of two functional pharmacophores linked by a spacer, are among the most promising strategies. Due to the constitutive nature of GPCR dimers, bivalent ligands are expected in most cases to bind to and stabilize preexisting dimers rather then to promote ligand-induced dimerization. Most studies on GPCR dimerization were conducted so far in heterologous expression systems. Due the development of heterodimerspecific tools such as bivalent ligands, dimerization has now been confirmed for an increasing number of receptors in native tissues. In this review, we will discuss general considerations for the design and synthesis of bivalent ligands and present the functional in vitro and in vivo properties of reported bivalent ligands.

The Osteogenic Differentiation of Adipose Tissue-Derived Precursor Cells in a 3D Scaffold/Matrix Environment by David Leong, Wee Nah, Anurag Gupta, Dietmar Hutmacher, Maria Woodruff (319-327).
This paper details an in-vitro study using human adipose tissue-derived precursor/stem cells (ADSCs) in three-dimensional (3D) tissue culture systems. ADSCs from 3 donors were seeded onto NaOH-treated medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffolds with two different matrix components; fibrin glue and lyophilized collagen. ADSCs within these scaffolds were then induced to differentiate along the osteogenic lineage for a 28-day period and various assays and imaging techniques were performed at Day 1, 7, 14, 21 and 28 to assess and compare the ADSC's adhesion, viability, proliferation, metabolism and differentiation along the osteogenic lineage when cultured in the different scaffold/matrix systems. The ADSC cells were proliferative in both collagen and fibrin mPCL-TCP scaffold systems with a consistently higher cell number (by comparing DNA amounts) in the induced group over the non-induced groups for both scaffold systems. In response to osteogenic induction, these ADSCs expressed elevated osteocalcin, alkaline phosphatase and osteonectin levels. Cells were able to proliferate within the pores of the scaffolds and form dense cellular networks after 28 days of culture and induction. The successful cultivation of osteogenic ADSCs within a 3D matrix comprising fibrin glue or collagen, immobilized within a robust synthetic scaffold is a promising technique which should enhance their potential usage in the regenerative medicine arena, such as bone tissue engineering.

Ultrasound Techniques for Drug Delivery in Cardiovascular Medicine by Luigi Landini, Maria Santarelli, Linda Landini, Vincenzo Positano (328-332).
In this review, we will give a critical update of published studies using ultrasound for targeted therapeutic use. We will briefly discuss the interaction mechanisms and their effects in non-invasive delivery of therapeutic agents. Moreover, the mechanisms by which ultrasonic contrast agents facilitate the delivery of drugs and genes into tissue will be discussed, together with recent applications and perspectives of targeted-microbubbles in cardiovascular medicine.

New Drug Delivery Systems Based on Chitosan by Ines Panos, Niuris Acosta, Angeles Heras (333-341).
The development of new delivery systems for the controlled release of drugs is one of the most interesting fields of research in pharmaceutical sciences. Microparticles can be used for the controlled release of drugs, vaccines, antibiotics, and hormones. To prevent the loss of encapsulated materials, the microcapsules should be coated with another polymer that forms a membrane on the surface. In addition there are several fundamental properties of polymers that are useful in solving drug delivery problems, as they can be combined with the drug covalently or ionically to overcome problems like solubility, stability or permeability. Chitosan is a copolymer of N-acetylglucosamine and glucosamine derived from chitin, which is extracted from crustaceans - shells. This polymer has become the focus of major interest in recent years because it has applications in several fields such as biomedicine, agriculture, the textile industry and the paper industry. There are many processes that can be used to encapsulate drugs within chitosan matrixes such as ionotropic gelation, spray drying, emulsification- solvent evaporation and coacervation. Combinations of these processes are also used in order to obtain microparticles with specific properties and performances. This review provides an overview of these four techniques applied directly to chitosan microparticulate systems.