Regulatory issues in aging pharmacology

Many current drugs increase the average lifespan by preventing fatal diseases or by slowing down the progressive degenerative diseases that increase mortality. The existing strategies and guidelines for the development and regulatory approval of new drugs are designed for such compounds. Rapid advances in understanding molecular mechanisms of aging make it possible to envisage future drugs that extend the lifespan by regulating aging mechanism outside of disease pathways. Strategies for development and regulatory approval of such drugs remain to be defined. Since the drug candidates will be given to healthy, elderly subjects, safety requirements will be extremely high. Clinical studies of many years' duration will be necessary to prove changes in longevity. These time intervals may exceed those of patent protection and thus minimize commercial incentives. Despite these challenges, two broadly defined pathways are feasible. First, it may be possible to obtain public funding for studies with voluntary participation of humans consuming existing drugs or natural compounds in the 'expected to be safe' category. Second, the development of novel drugs may proceed on the basis of well-defined biomarkers of aging that can serve as surrogate end points in clinical studies. The emerging approaches will prompt the regulatory agencies into taking the first steps towards regulatory guidance.     

两种模式生物核小体定位比较研究

在对两种模式生物酵母与果蝇胚胎期核小体定位进行研究时,发现不同物种间以及同一物种中不同表达模式基因上的核小体分布呈现出差显著异性。在总体上,转录起始位点附近的酵母核小体NFR区域比果蝇的NFR短。经基因中心对齐后,酵母与果蝇胚胎期沉默型基因的核小体缺失区域的两个边界中间处共同呈现了一个明确有着均匀间隔的核小体数n,且随着基因长度L的变长其周期性特性逐渐变模糊,但果蝇的图谱表现的更为复杂。结果表明,从单细胞酵母生物到多细胞果蝇生物间基因组的进化过程中,核小体组织的演化既有变异性,也具有保守性。     

双歧啤酒对延缓衰老作用的研究

目的研究双歧啤酒的延缓衰老作用。方法将老龄小鼠和黑腹果蝇随机分成纯净水对照组、市售啤酒对照组和双歧啤酒低、中、高三个剂量组,进行果蝇生存实验,检测小鼠血液中超氧化物歧化酶（SOD）、谷光甘肽过氧化物酶（GSH-PX）的活性和丙二醛（MDA）的含量。结果与对照组比较,双歧啤酒高、中剂量组能显著延长果蝇的半数死亡时间、平均寿命和平均最高寿命,提高老龄小鼠血液中SOD、GSH-PX的活性,降低老龄小鼠血液中MDA的含量。结论双歧啤酒具有延缓衰老的作用。     

The chakragati mouse: a mouse model for rapid in vivo screening of antipsychotic drug candidates

The chakragati (ckr) mouse is a serendipitously discovered insertional transgenic mutant that exhibits circling and hyperactivity. Studies of social behavior, sensorimotor gating and ventricular anatomy suggest that the ckr mouse models aspects of schizophrenia. The underlying genetic and neurodevelopmental mechanisms remain to be elucidated but appear to result in a hemispheric asymmetry in striatal D(2)-like dopamine receptors. The circling is inhibited by administration of antipsychotic drugs and so lends itself to in vivo prospective screening for novel molecules with antipsychotic-like activity. Using the ckr mouse we have applied an in vivo first approach to screening for antipsychotic drug candidates. This offers the advantage of early indication of central nervous system bioavailability and potential toxicological concerns. Additionally, in vivo first screening in the ckr mouse is not biased by any particular neurotransmitter hypothesis of the disease, and so has the potential to identify compounds modifying the behavioral output by novel mechanisms of interaction with the underlying brain circuitry. Thus, in contrast to the classical strategy of hypothesis-driven in vitro screening for drugs fitting a "receptor model" of the disease, the ckr mouse screen has greater potential to identify lead molecules for a new generation antipsychotics with novel mechanisms of action.     

Recent Advances in Drug Repositioning for the Discovery of New Anticancer Drugs

Drug repositioning (also referred to as drug repurposing), the process of finding new uses of existing drugs, has been gaining popularity in recent years. The availability of several established clinical drug libraries and rapid advances in disease biology, genomics and bioinformatics has accelerated the pace of both activity-based and in silico drug repositioning. Drug repositioning has attracted particular attention from the communities engaged in anticancer drug discovery due to the combination of great demand for new anticancer drugs and the availability of a wide variety of cell- and target-based screening assays. With the successful clinical introduction of a number of non-cancer drugs for cancer treatment, drug repositioning now became a powerful alternative strategy to discover and develop novel anticancer drug candidates from the existing drug space. In this review, recent successful examples of drug repositioning for anticancer drug discovery from non-cancer drugs will be discussed.     

国内抗凝血、抗血栓多糖的药理研究进展

目前已经发现许多多糖具有生物活性。综述了国内在多糖的抗凝血、抗血栓药理研究方面的近况。     

A personal account of the role of peptide research in drug discovery: the case of hepatitis C.

Although peptides themselves are not usually the end products of a drug discovery effort, peptide research often plays a key role in many aspects of this process. This will be illustrated by reviewing the experience of peptide research carried out at IRBM in the course of our study of hepatitis C virus (HCV). The target of our work is the NS3/4A protease, which is essential for maturation of the viral polyprotein. After a thorough examination of its substrate specificity we fine-tuned several substrate-derived peptides for enzymology studies, high-throughput screening and as fluorescent probes for secondary binding assays. In the course of these studies we made the key observation: that the protease is inhibited by its own cleavage products. Single analog and combinatorial optimization then derived potent peptide inhibitors. The crucial role of the NS4A cofactor was also addressed. NS4A is a small transmembrane protein, whose central domain is the minimal region sufficient for enzyme activation. Structural studies were performed with a peptide corresponding to the minimal activation domain, with a series of product inhibitors and with both. We found that NS3/4A is an induced fit enzyme, requiring both the cofactor and the substrate to acquire its bioactive conformation; this explained some puzzling results of 'serine-trap' type inhibitors. A more complete study on NS3 activation, however, requires the availability of the full-length NS4A protein. This was prepared by native chemical ligation, after sequence engineering to enhance its solubility; structural studies are in progress. Current work is focused on the P' region of the substrate, which, at variance with the P region, is not used for ground state binding to the enzyme and might give rise to inhibitors showing novel interactions with the enzyme.     

The use of transgenic systems in pharmaceutical research.

Those pharmaceutical companies whose goal is to generate novel innovative drugs are faced with the challenge that only a fraction of the compounds tested in clinical trials eventually become a registered drug. This problem of attrition is compounded by the fact that the clinical trial or development stage is by far the most costly phase of bringing a new drug to market, consuming around 80 per cent of the total spend. Transgenic technology represents an attractive approach to reducing the attrition rate of compounds entering clinical trials by increasing the quality of the target and compound combinations making the transition from discovery into development. Transgenic technology can impact at many points in the discovery process, including target identification and target validation, and provides models designed to alert researchers early to potential problems with drug metabolism and toxicity, as well as providing better models for human diseases. In target identification, transgenic animals harbouring large DNA fragments can be used to narrow down genetic regions. Genetic studies often result in the identification of large genomic regions and one way to decrease the region size is to do complementation studies in transgenic animals using, for example, inserts from bacterial artificial chromosome (BAC) clones. In target validation, transgenic animals can be used for in vivo validation of a specific target. Considerable efforts are being made to establish new, rapid and robust tools with general utility for in vivo validation, but, so far, only transgenic animals work reliably on a wide range of targets. Transgenic animals can also be used to generate better disease models. Predictive animal models to test new compounds and targets will significantly speed up the drug discovery process and, more importantly, increase the quality of the compounds taken further in the research and development process. Humanised transgenic animals harbouring the human target molecule can be used to understand the effect of a compound acting on the human target in vivo. Also, models mimicking human drug metabolism will provide a means of assessing the effect of human-specific metabolites and of understanding the pharmacokinetic properties of potential drugs. In toxicology studies, transgenic animals are providing more predictive models. A good example of this are those models routinely used to look for carcinogenicity associated with new compounds.     

Drosophila melanogaster as a model system for the evaluation of anti-aging compounds

Understanding the causes of aging is a complex problem due to the multiple factors that influence aging, which include genetics, environment, metabolism and reproduction, among others. These multiple factors create logistical difficulties in the evaluation of anti-aging agents. There is a need for good model systems to evaluate potential anti-aging compounds. The model systems used should represent the complexities of aging in humans, so that the findings may be extrapolated to human studies, but they should also present an opportunity to minimize the variables so that the experimental results can be accurately interpreted. In addition to positively affecting lifespan, the impact of the compound on the physiologic confounders of aging, including fecundity and the health span-the period of life where an organism is generally healthy and free from serious or chronic illness-of the model organism needs to be evaluated. Fecundity is considered a major confounder of aging in fruit flies. It is well established that female flies that are exposed to toxic substances typically reduce their dietary intake and their reproductive output and display an artifactual lifespan extension. As a result, drugs that achieve longevity benefits by reducing fecundity as a result of diminished food intake are probably not useful candidates for eventual treatment of aging in humans and should be eliminated during the screening process.     

A novel model of a biomechanically induced osteoarthritis-like cartilage for pharmacological in vitro studies

Excessive pressure or overload induces and aggravates osteoarthritic changes in articular cartilage, but the underlying biomechanical forces are largely ignored in existing pharmacological in vitro models that are used to investigate drugs against osteoarthritis (OA). Here, we introduce a novel in vitro model to perform pathophysiological and pharmacological investigations, in which cartilage explants are subjected to intermittent cyclic pressure, and characterize its ability to mimic OA-like tissue reactivity. Mechanical loading time-dependently increased the biosynthesis, content and retention of fibronectin (Fn), whereas collagen metabolism remained unchanged. This protocol upregulated the production and release of proteoglycans (PGs). The release of PGs from explants was significantly inhibited by a matrix metalloproteinase (MMP) inhibitor, suggesting the involvement of such proteinases in the destruction of the model tissue, similar to what is observed in human OA cartilage. In conclusion, the metabolic alterations in our new biomechanical in vitro model are similar to those of early human OA cartilage, and our pharmacological prevalidation with an MMP-inhibitor supports its value for further in vitro drug studies.     

A Theoretical Model for Utilizing Mammalian Pharmacology and Safety Data to Prioritize Potential Impacts of Human Pharmaceuticals to Fish

Due to the potential for long-term, low-level exposure of environmental species to pharmaceuticals in the environment, concerns over chronic ecotoxicity have been raised. Pharmaceuticals typically have specific enzyme and receptor-based modes of action, which are extensively studied in mammals during drug development. A survey of the literature demonstrated that there is conservation of many enzyme/receptor systems between mammalian and teleost systems. Based on this conservation of enzyme/receptor systems across teleost species, a model has been developed to utilize the information from mammalian pharmacology and toxicology studies to evaluate the potential for chronic receptor mediated responses in fish. In this model, a measured human therapeutic plasma concentration (H_TPC) is compared to a predicted steady state plasma concentration (F_SSPC) in fish, and an effect ratio (ER = H_TPC/F_SSPC) is computed. The lower the ER, the greater the potential for a pharmacological response in fish. Data collection and model validation will strengthen the applicability of this approach as a viable tool for prioritizing research initiatives that examine the potential impact of pharmaceuticals on fish.     

Systems pharmacology and enhanced pharmacodynamic models for understanding antibody-based drug action and toxicity

Pharmacokinetic (PK) and pharmacodynamic (PD) models seek to describe the temporal pattern of drug exposures and their associated pharmacological effects produced at micro- and macro-scales of organization. Antibody-based drugs have been developed for a large variety of diseases, with effects exhibited through a comprehensive range of mechanisms of action. Mechanism-based PK/PD and systems pharmacology models can play a major role in elucidating and integrating complex antibody pharmacological properties, such as nonlinear disposition and dynamical intracellular signaling pathways triggered by ligation to their cognate targets. Such complexities can be addressed through the use of robust computational modeling techniques that have proven powerful tools for pragmatic characterization of experimental data and for theoretical exploration of antibody efficacy and adverse effects. The primary objectives of such multi-scale mathematical models are to generate and test competing hypotheses and to predict clinical outcomes. In this review, relevant systems pharmacology and enhanced PD (ePD) models that are used as predictive tools for antibody-based drug action are reported. Their common conceptual features are highlighted, along with approaches used for modeling preclinical and clinically available data. Key examples illustrate how systems pharmacology and ePD models codify the interplay among complex biology, drug concentrations, and pharmacological effects. New hybrid modeling concepts that bridge cutting-edge systems pharmacology models with established PK/ePD models will be needed to anticipate antibody effects on disease in subpopulations and individual patients.     

Revealing mechanism of Caulis Sargentodoxae for the treatment of ulcerative colitis based on network pharmacology approach

Objective: The traditional Chinese medicine Caulis Sargentodoxae is widely used in the treatment of ulcerative colitis (UC), but the mechanism remains unknown. The present study aims to reveal its effective components, targets and pathways through network pharmacology and bioinformatics approaches.Materials and methods: Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) was used to identify effective components. The ligand-based targets prediction was achieved through SwissTargetPrediction and TargetNet. UC-related targets were identified using Gene Expression Omnibus (GEO) data and DisGeNET. The common targets of disease and components were constructed and analyzed by PPI network. Lastly, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses are used to explain the functions of these common targets. Components-Targets-Pathways network was visualized and analyzed to further reveal the connection between the components and targets.Results: Eight active components and 102 key targets were identified to play an important role in UC. These targets were related to regulation of protein serine/threonine kinase activity, positive regulation of cell motility, response to molecule of bacterial origin, response to toxic substance, ERK1 and ERK2 cascade, peptidyl-tyrosine modification, inositol lipid-mediated signaling, cellular response to drug, regulation of inflammatory response and leukocyte migration. Moreover, HIF-1 signaling pathway and PI3K-Akt signaling pathway were the key targets involved in UC-related signaling pathways.Conclusion: The eight active components of Caulis Sargentodoxae mainly play a therapeutic role for UC through synergistic regulation of HIF-1 signaling pathway and PI3K-Akt signaling pathway.     

Imaging in vivo neuronal transport in genetic model organisms using microfluidic devices

Microfluidic devices have been developed for imaging behavior and various cellular processes in Caenorhabditis elegans, but not subcellular processes requiring high spatial resolution. In neurons, essential processes such as axonal, dendritic, intraflagellar and other long-distance transport can be studied by acquiring fast time-lapse images of green fluorescent protein (GFP)-tagged moving cargo. We have achieved two important goals in such in vivo studies namely, imaging several transport processes in unanesthetized intact animals and imaging very early developmental stages. We describe a microfluidic device for immobilizing C. elegans and Drosophila larvae that allows imaging without anesthetics or dissection. We observed that for certain neuronal cargoes in C. elegans, anesthetics have significant and sometimes unexpected effects on the flux. Further, imaging the transport of certain cargo in early developmental stages was possible only in the microfluidic device. Using our device we observed an increase in anterograde synaptic vesicle transport during development corresponding with synaptic growth. We also imaged Q neuroblast divisions and mitochondrial transport during early developmental stages of C. elegans and Drosophila, respectively. Our simple microfluidic device offers a useful means to image high-resolution subcellular processes in C. elegans and Drosophila and can be readily adapted to other transparent or translucent organisms.     

Intraspecific variation for resource use in Drosophila

Individuals within natural populations of Drosophila tripunctata and D. falleni varied significantly in their responses to alternative types of food baits; no such variation was detected in D. putrida. The food type at which laboratory-reared D. melanogaster tended to settle in the field was influenced by the type of food on which they had been kept prior to release. Although flies apparently forgot their previous experience within hours, its effect on their behaviour can be manifested for at least 1 day in the field. Mark -recapture experiments on wild flies are shown to be very inefficient at detecting individual variation in behaviour.