Current Topics in Medicinal Chemistry - Volume 17, Issue 18, 2017

Nitrones have been extensively used for the detection of transient free radicals using electron paramagnetic resonance. Since the mid-80's, nitrones have also been widely used as protective agents against oxidative stress in several biological models. Due to the high potency of nitrones, there has been extensive research on the development of derivatives with improved biological and spin trapping properties as well as enhanced intra-cellular compartmentalization. The chemical and pharmacological properties of nitrones depend mainly on the connectivity as well as on the nature and the position of the substituents on the nitrone group. Therefore, novel bioactive molecules have been designed and the development of specific nitrone derivatives is aimed at providing new therapeutic approaches and perspectives in prevention, treatment and rehabilitation. This review focuses on the effects that are exerted by the most promising nitrone antioxidants that are available. A comprehensive description of the unique molecular mechanism and mediators that are targeted by these compounds is given to guide and enable novel and successful approaches to the treatment of a broad spectrum of diseases associated with stress and aging. New promising nitrone compounds are now available for further development by translational medicine that exert superior bioactivity and efficacy.

Elucidating details of the relationship between molecular structure and a particular biological end point is essential for successful, rational drug discovery. Molecular docking is a widely accepted tool for lead identification however, navigating the intricacies of the software can be daunting. Our objective was therefore to provide a step-by-step guide for those interested in incorporating contemporary basic molecular docking and homology modelling into their design strategy. Three molecular docking programs, AutoDock4, SwissDock and Surflex-Dock, were compared in the context of a case study where a set of steroidal and non-steroidal ligands were docked into the human androgen receptor (hAR) using both rigid and flexible target atoms. Metrics for comparison included how well each program predicted the X-ray structure orientation via root mean square deviation (rmsd), predicting known actives via ligand ranking and comparison to biological data where available. Benchmarking metrics were discussed in terms of identifying accurate and reliable results. For cases where no three dimensional structure exists, we provided a practical example for creating a homology model using Swiss-Model. Results showed an rmsd between X-ray ligands from wild-type and mutant receptors and docked poses were 4.15Å and 0.83Å (SwissDock), 2.69Å and 8.80Å (AutoDock4) and 0.39Å and 0.71Å (Surflex-Dock) respectively. Surflex-Dock performed consistently well in pose prediction (less than 2Å) while Auto-Dock4 predicted known active non-steroidal antiandrogens most accurately. Introducing flexibility into target atoms produced the largest degree of change in ligand ranking in Surflex-Dock. We produced a viable homology model of the P2X1 purireceptor for subsequent docking analysis.

The zebrafish is fast becoming a leading and prominent model organism used by researchers for developmental biology, and research in modeling human diseases in zebrafish is being undertaken at a fast pace. Many therapeutic areas, including oncology and cardiovascular diseases to name a few all have zebrafish models based on known disease mechanisms that are translatable to modes of action in humans. Many novel assays have been and are continuing to be developed to study human disease in zebrafish. Prominent methods to identify novel drug targets within the organism include, chemical mutagenesis, insertional mutagenesis and high throughput small molecule screens. Methods to validate potential drug targets include reverse and forward genetics, transgenesis and gene knockout. This review summarizes the important contributions made using the zebrafish model in recent years to aid in drug discovery and target validations in the highly important medical field of cancer medicine, cardiovascular disease and the emerging role of the zebrafish model as a platform for toxicity screening.

Ascidians (tunicates; sea squirts) are marine animals which provide a source of diverse, bioactive natural products, and a model for toxicity screenings. Compounds isolated from ascidians comprise an approved anti-tumor drug and many others are potent drug leads. Furthermore, the use of invertebrate embryos for toxicological screening tests or analysis offers the possibility to image a large number of samples for high throughput screens. Ascidians are members of a sister clade to the vertebrates and make a vertebrate-like tadpole larva composed of less than 3000 cells in 18 hours. The neural complex of the ascidian larva is made of only 350 cells (of which 100 are neurons) and functional genomic studies have now uncovered numerous GRNs underpinning neural specification and differentiation. Numerous studies showed that brain formation in ascidians is sensitive to toxic insults especially from endocrine disruptors making them a suitable model to study neurodevelopmental defects. Modern techniques available for ascidians, including transgenic embryos where 3D time lapse imaging of GFPexpressing reporter constructs can be analyzed, now permit numerous end-points to be evaluated in order to test the specific mode of action of many compounds. This review summarizes the key evidence suggesting that ascidian embryos are a favorable embryological model to study neurodevelopmental toxicity of different compounds with molecular and cellular end-points. We predict that ascidians may become a significant source of marine blue biotechnologies in the 21st century.

Small molecule screens using C. elegans as a model are becoming increasingly popular as the number of high-throughput methodologies has steadily increased over the years. Here we focus on the biology that underlies this increased popularity and outline the reasons that make C. elegans an attractive model for drug discovery. We discuss successful C. elegans based drug discovery projects in the literature and future challenges ahead.

Robert Koch utilized animal model systems to put forward his postulates while discovering the etiological agents of anthrax and tuberculosis, Bacillus anthracis and Mycobacterium tuberculosis, respectively. After more than 130 years, we have achieved limited success towards understanding these two pestilences, which have propagated as scourge against humans. B. anthracis and M. tuberculosis are diverse organisms, which share a common evolutionary path in tropics. They adapt unique strategies to overcome unfavorable conditions and surpass the host defense mechanisms. B. anthracis is an endospore forming bacteria that primarily acts by releasing toxins in the host cells.. M. tuberculosis is an intracellular bacteria that resides within the host macrophages by blocking phagosome-lysosome fusion events and ensuring its own survival. The bacterium can remain dormant for long periods, and when activated, it spreads in lungs and other extrapulmonary sites leading to formation of necrotic granulomas. The two diseases are immunologically distinct examples of inducing primarily either humoral or cell mediated immunity. Natural immune response to the two diseases probably explains early success achieved with the anthrax vaccine, while the hunt for successful tuberculosis prevention is still on. For comprehensive understanding of these diseases, model systems are of utmost importance that can alleviate detailed assessment of disease etiology and introductory treatment regimes. In this review, we discuss the various in vitro and in vivo model systems used to study these two diseases, discussing their contributions and recent themes.

Targeted therapeutics is a new generation therapy that can increase the efficacy of chemotherapeutic drugs, by facilitating site-specific delivery with minimum off-target effects. Amongst the targeted therapy, nucleic-acid based aptamers are increasingly gaining interest due to their small size, long shelf-life and ease in synthesis. Further, lactoferrin, a milk protein belonging to the transferrin family is now an established multi-functional iron-binding protein. Its applicability as an immunomodulator, antimicrobial and an anti-cancer agent has made this protein highly valuable. Recent research has been focusing towards increasing the efficacy of lactoferrin by encapsulating them in novel nanoparticles, that facilities in providing their controlled and sustained release. This review focuses on the application of aptamers against solid tumors, specifically colorectal cancer (CRC) indicating the different anti-cancer targeted strategies to target anti-angiogenic vascular endothelial growth factor –A (VEGF-A) and epidermal growth factor receptor (EGFR) signalling. Additionally, it highlights the synergistic approach of functionalising aptamers with drug loaded nanoparticles to facilitate enhanced uptake, stability and increase in the retention time. Special emphasis is given on lactoferrin loaded aptamer functionalised nanoparticles as anticancer drug delivery systems. Apart from highlighting the role of these aptamernanocarriers in tumor specific targeting and induction of apoptosis, there applicability in nanotheranostics, involving detection, diagnosis and treatment is also discussed here.