Drug-Induced Liver Injury (DILI) represents a major problem in drug development. The clinical signature of DILI is broad (acute or chronic; hepatocellular, cholestatic or mixed) and the detection in clinical trials is mainly based on routine lab findings. Cases meeting Hy's law criteria identifies a potentially serious problem. The mechanisms of the pathogenesis of DILI remain a challenging issue. Although exposure to reactive drug metabolites is usually a prerequisite, downstream stress responses, cell death mechanisms and the immune system have emerged as critical determinants of DILI. In the case of “direct” toxicity, acetaminophen (APAP) has received the most attention and highlights the importance of signal transduction, programmed necrosis, and the role of mitochondrial dysfunction. Knowledge gained from recent studies of APAP from our laboratory has implicated sustained JNK activation in a type of programmed necrosis. Interaction of P-JNK with a protein in the outer membrane called Sab is required for sustained JNK activation. Inhibition of JNK or silencing the expression of Sab prevents APAP induced necrosis in vitro and in vivo without altering APAP metabolism (GSH depletion). Further these two approaches prevent massive apoptosis in the TNF/galactosamine model underscoring the general importance of JNK activation and interaction with mitochondrial Sab in hepatotoxicity. The hypothesis consistent with both models is that mitochondria made vulnerable by APAP or TNF produce enhanced ROS production when JNK interacts with Sab. ROS then lead to sustained JNK activation and ultimately cell death. In the case of idiosyncratic DILI, several examples of striking HLA associations point to the important role of the adaptive immune system in mediating injury. Recent genetic studies have shown increased risk with certain HLA markers in studies of flucloxacillin, ticlopidine, ximelagatran, lumiracoxib, amoxicillin and clavulanic acid, and lapatanib. However, GWAS studies conducted by the U.S. Drug-Induced Liver Injury Network of a large population of cases of DILI from various causes have not shown strong or reproducible associations. These findings leave us with two issues concerning idiosyncratic DILI: (1) In those with HLA risk factors, only a small percentage of cases actually develop DILI; what else determines the development of DILI in these cases? (2) concerning drugs with negative GWAS data, are genetic factors still involved (rare variants or multiple common polymorphisms)? In conclusion, considerable progress in predicting and understanding the mechanisms of DILI have been made recently, but there remains much to be learned.
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds elicit a broad spectrum of species-specific effects. Hepatic steatosis is a classic response following exposure to TCDD characterized by increases in lipid accumulation, hepatocellular vacuolization, inflammation, and serum free fatty acids. Many of these effects resemble characteristics of metabolic syndrome (MetS), a multi-factorial disease that includes dyslipidemia, obesity, and can progress into non-alcoholic fatty liver disease (NAFLD) and , and diabetes. We have systematically integrated omic data from genome-wide chromatin immunoprecipitation (ChIPchip), microarray and metabolomic studies with complementary histopathology, and comparative analysis of in vivo and in vitro human, mice and rat models, as well as bioinformatic approaches to further elucidate the mechanisms involved in aryl hydrocarbon receptor (AhR)-mediated hepatic steatosis in female C57BL/6 mice. Our results suggest that TCDD induces hepatic steatosis due to alterations in lipid transport and metabolism that increase fat uptake and inhibit beta oxidation. Lipidomic and gene expression analyses also suggests that there is increased uptake of dietary fatty acids and regulation of fatty acid metabolism that alters saturated, mono-, and poly-unsaturated fatty acid ratios resulting in hepatoxicity. The integration of ChIP-chip data with the genomewide computational identification of dioxin response elements (DREs) is consistent with AhR-AhR nuclear translocator (ARNT)- mediated regulation for many of these responses. However, ~50% of AhR enriched regions in our ChIP-chip data did not contain a DRE. Bioinformatic analyses with supporting microarray data suggest that the AhR interacts with DNA to regulate gene expression by dimerizing with other transcription factors to alter lipid metabolism and transport. Collectively, these results not only further elucidate the mechanisms involved in TCDD-induced steatosis, but also suggest that TCDD and related compounds may contribute to the development of MetS and its associated diseases by increasing hepatic fat accumulation.
Chemicals are able to cause various types of allergic disease. Those of greatest importance in the context of toxicology and occupational medicine are skin sensitization resulting in allergic contact dermatitis, and sensitization of the resporatory tract associated with asthma and rhinitis. There is a need to understand the mechanisms through which allergic sensitization to chemicals is acquired and, based on an appreciation of relevant cell;ular and molecular processes, to develop tools for accurate assessments of human health hazards and risks. The two forms of chemical allergy mentioned above provide toxicologists with different challenges. Allergic contact dermatitis is the commonest manifestation of immunotoxicity in humans, and it is clear that many hundreds of chemicals have the potential to cause skin sensitization. There are methods available that support the identification and characterization of skin sensitization hazards and the development of accurate risk assessments. Currently, however, those approaches are based on in vivo models and the challenge now is to develop robust and reliable alternative approaches that will eventually obviate the need for animals. Chemical respiratory allergy poses different problems because in this case there are not yet available widely accepted methods for hazard identification. In this presentation recent developments in chemical allergy will be described with reference to the relationship between clinical disease, cellular and molecular mechanisms, and approaches to toxicological evaluation.
我々はこれまで、新しい分子イメージングの手法、中でもナノ形態学の手法を開発し医学生理学上の問題に応用することで解決してきた（ビデオ顕微鏡相関電顕法Setou et al., Science 2000, GFP蛍光細胞内観察 Setou et., Nature 2002, ナノ微粒子による可視化Taira et al., e-J.Surf.Sci. Nanotech. 2007, Moritake et al., J.Nanosci.Nanotech.2007,位相差電子顕微鏡による観察Setou et al., Medical Molecular Morphology 2006）。
ポストゲノム時代においては、これら通常のDNA, RNA, 蛋白質の可視化はもとより、翻訳後修飾や脂質や糖鎖も含めたプロテオーム、メタボロームの解析（Ikegami et al., PNAS2007, Yao et al., Cell 2007, Konishi and Setou., Nature Neuroscience 2009, Ikegami and Setou FEBS Lett 2009, Kimura et al., JBC 2010, Ikegami et al., PNAS2010）も重要である。さらにはメタボロームの時間的空間的変化すなわち多次元メタボロミクスを知ることが重要であると考えられている。
そこで、私たちは島津製作所等と共同で、質量分析を用いた顕微鏡法、高解像度Imaging Mass Spectrometry (質量顕微鏡)を開発している。現在、質量顕微鏡法を用いて、疾患モデルマウスやヒト病理標本の解析を行い、メタボローム動態の可視化に挑んでいる。（Shimma et al., Surf.Int.Anal 2006, Sugiura et al., Anal.Chem 2006, Shimma et al., J.Chrom B 2007, Hayasaka et al., RCM 2008, Shimma et al., Anal Chem 2008, Taira et al., Anal Chem 2008, Sugiura et al., Plos One 2008, Ageta et al., MMM 2009, Zaima et al., J.Oleo Sci 2009, Sugiura et al., JLR 2009, Shrivas et al., Anal Chem 2010, Inoue et al., JASMS 2010, Hayasaka et al., JASMS2010, Koizumi et al., Neuroscience 2010, Morita et al., Cancer Sci 2010）。
「質量顕微鏡法：イメージングマススペクトロメトリー実験プロトコール」 シュプリンガー社 瀬藤光利 編 2008
Imaging Mass Spectrometry シュプリンガー社 瀬藤光利 編 2010
The International Union of Toxicology (IUTOX) has had a long history of collaboration with its member societies. The Japanese Society of Toxicology (JSOT) has played a prominent role in Asia, promoting cooperation and progress in toxicology among its members in AsiaTox. A new Executive Committee for IUTOX was elected for 2010-2013, and one of its major goals is to enhance the formation of new toxicology societies in developing countries around the world. We believe that JSOT and AsiaTox can be important partners with IUTOX in that initiative. IUTOX believes that the recognition of toxicologists (with minimal requirements) through a Global Directory in cooperation with its member societies can foster the identity and development of the discipline of toxicology on a world-wide basis.
After establishing a Global Directory of toxicologists, IUTOX plans to work with its member societies to promote the harmonization of standards for senior toxicologists of the existing certifying bodies—DJST, ERT, DABT, and ATS.
These endeavors will require the cooperation, patience, and hard work of all involved to secure the greater professional recognition of toxicologists on a world-wide basis.
IUTOX will continue to support International Congresses, such as CTDC’s and ICT’s, to facilitate the exchange of scientific information among its member toxicologists and will continue to expand its support of activities and workshops in developing countries to provide opportunities for scientists to learn more about risk assessment and other topics in toxicology.
Adverse effects on the cardiovascular system (CVS) are amongst the most common reasons for attrition during drug discovery, development & post-marketing. This highlights the need for pre-clinical strategies that predict the effect of drugs on CVS function in man. In response to attrition resulting from drug-induced QT interval prolongation, sequential in silico-in vitro-in vivo pre-clinical strategies have evolved that aim to predict the outcome of the “Thorough QT/QTc Study”. Owing to the widespread nature of the QT problem, sufficient data are emerging that provide estimates of the predictive value of the pre-clinical results. Although pre-clinical strategies also aim to predict drug-induced changes in other CVS end-points (e.g. blood pressure; heart rate; contractility; PR & QRS intervals), quantitative information on the predictive value of these pre-clinical data are relatively rare. Providing that a high priority is given to assessing translation of these end-points, there is no reason why a better understanding cannot gradually be achieved. Whether current pre-clinical studies can predict CVS risk in “outcome trials”, such as those recently recommended for type II diabetes drugs, is a significant and potentially intractable challenge, however. Case studies will be used to illustrate these perspectives.
Safety assessment in early drug development relies heavily on in vitro and animal experiments. The outcome of these experiments should guide which kinds of side effects in humans can be expected. When drug development progresses in human clinical trials, progressively human safety data are becoming visible and can overrule animal data. In this context, bridging biomarkers as indicators for tissue damage in animals and that can be monitored in humans are gaining importance. There is a need for good understanding between the toxicologists and human safety specialists about the predictivity and validity of such biomarkers in terms of them being early indicators of tissue damage or just being associated with tissue damage as such or being potentially only a remote part of a pathway not important for the disease as such. Further, based on animal studies, safety concerns may emerge, for which no good surrogate markers exist. These are eg associated with aspects of covalent binging of drugs or their metabolites to proteins, processes of tumor development, genotoxicity and reproductive toxicity. In these areas of little caches of applying surrogate biomarkers or monitoring in the clinical context, it is important for the toxicologist to provide enhanced understanding of the mechanism of action in animal or in vitro studies to judge human relevance with little chances only to validate the risk assessment in the human context. In such latter cases, an enhanced effort of understanding between clinical and non-clinical safety scientists is needed. The presentation will include a few cases to illustrate this.
The Health and Environmental Sciences Institute (HESI) is the global branch of the International Life Sciences Institute (ILSI) whose mission is to stimulate and support scientific research and educational programs that contribute to the identification and resolution of health and environmental issues of concern to the public, scientific community, government agencies, and industry. HESI’s programs bring together scientists from around the world from academia, industry, regulatory agencies, and other governmental institutions to address and reach consensus on scientific questions that have the potential to be resolved through creative application of intellectual and financial resources. This “tripartite” approach forms the core of every HESI scientific endeavor. As a non-profit organization, HESI provides a unique, objective forum for initiating dialogue among scientists with different perspectives and expertise. Industry members provide primary financial support for HESI programs, but HESI also receives financial and in-kind support from a variety of U.S. and international government agencies.
Human exposure to DNA-damaging agents is an important health issue because it has the potential to cause adverse health consequences. In vitro assays are key elements of the battery of genotoxicity assays. During the past 15 years, accumulated evidence has shown that a large number of the mammalian in vitro positive findings were not confirmed in in vivo genotoxicity and/or carcinogenicity studies, raising the question of their relevance to human. The mission of the In Vitro Genetic Toxicity (IVGT) Testing Project Committee of ILSI Health and Environmental Sciences Institute (HESI), is to improve the scientific basis for interpretation of in vitro genetic toxicology data for purposes of more accurate human risk assessment. It is increasingly accepted that positive results should not be considered in isolation, and that weight of evidence and mode of action approaches should be preferred. To this aim, IVGT Committee 1) elaborates recommendations for follow-up testing strategies, 2) considers how quantitative data can be used to extrapolate from in vitro to in vivo exposures and from rodent to human risk assessment, 3) supports the improvement of existing assays, and 4) facilitates the evaluation and development of new technologies and approaches that would improve the prediction of effects in humans. Scientists from 15-20 industrial companies, as well as academic institutes and regulatory authorities are involved in this effort that could lead to innovation in risk assessment.