Toxicoproteomics and its application to human health risk assessment

An integrated proteomic and transcriptomic approach to understanding azathioprine- induced hepatotoxicity in rat primary hepatocytes

Azathioprine, an immunosuppressant, has gained a prominent position in the clinic for prevention of graft rejection in organ transplants, as well as dermatological autoimmune diseases. However, according to a number of research reports, hepatotoxicity, as one of the side effects, is a major obstacle in azathioprine therapy. In this study, an integrated toxicoproteomic and toxicotranscriptomic analysis was performed using rat primary hepatocytes, in order to gain insight into the in-depth pathway map related to azathioprine-induced hepatotoxicity. For proteomic and transcriptomic analysis, rat primary hepatocytes were exposed to azathioprine at IC20 concentration for 24 h. In particular, 2D LC-MS/MS and informatics-assisted label-free strategy for proteomic analysis were applied in order to increase the number of identified proteins and to improve the confidence of the quantitation results. Among 119 differentially identified protein species, 69 were upregulated and 50 were downregulated in the azathioprine-treated group. At the mRNA level, results of transcriptomic analysis showed increased transcription of 340 genes and decreased transcription of 63 genes in the azathioprine-treated group. Based on the analysis of transcriptomic and proteomic results using the DAVID program, drug metabolism/oxidative stress enzymes, xenobiotic metabolism by cytochrome P450, fatty acid metabolism, primary bile acid biosynthesis, contraction, inflammation metabolism, and mitogen-activated protein kinase (MAPK) kinase (ERK/JNK/p38 kinase) pathways were affected in azathioprine-treated hepatotoxicity. The effects on genes and proteins related to several important pathways were confirmed by real-time PCR and immunoblot analysis, respectively. This study is the first to report on relevant pathways related to azathioprine-induced hepatotoxicity through performance of integrated transcriptomic and proteomic analyses.

Toxicoproteomic analysis of a mouse model of nonsteroidal anti-inflammatory drug-induced gastric ulcers

Nonsteroidal anti-inflammatory drugs (NSAIDs) are valuable agents; however, their use has been limited by their association with mucosal damage in the upper gastrointestinal tract. NSAIDs inhibit cyclooxygenase and consequently block the synthesis of prostaglandins, which have cytoprotective effects in gastric mucosa; these effects on prostaglandins have been thought to be major cause of NSAID-induced ulceration. However, studies indicate that additional NSAID-related mechanisms are involved in formation of gastric lesions. Here, we used a toxicoproteomic approach to understand cellular processes that are affected by NSAIDs in mouse stomach tissue during ulcer formation. We used fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS)-which consists of fluorogenic derivatization, separation and fluorescence detection by LC, and identification by LC-tandem mass spectrometry-in this proteomic analysis of pyrolic stomach from control and diclofenac (Dic)-treated mice. FD-LC-MS/MS results were highly sensitive; 10 differentially expressed proteins were identified, and all 10 were more highly expressed in Dic-treated mice than in control mice. Specifically, expression levels of 78 kDa glucose-regulated protein (GRP78), heat shock protein beta-1 (HSP27), and gastrin were more than 3-fold higher in Dic-treated mice than in control mice. This study represents a first step to ascertain the precise actors of early NSAID-induced ulceration.

Umbuzeiro G, DeMarini DM. The Salmonella mutagenicity assay: the stethoscope of genetic toxicology for the 21st century

OBJECTIVES

According to the 2007 National Research Council report Toxicology for the Twenty-First Century, modern methods (e.g., "omics," in vitro assays, high-throughput testing, computational methods) will lead to the emergence of a new approach to toxicology. The Salmonella mammalian microsome mutagenicity assay has been central to the field of genetic toxicology since the 1970s. Here we document the paradigm shifts engendered by the assay, the validation and applications of the assay, and how the assay is a model for future in vitro toxicology assays.

DATA SOURCES

We searched PubMed, Scopus, and Web of Knowledge using key words relevant to the Salmonella assay and additional genotoxicity assays.

DATA EXTRACTION

We merged the citations, removing duplicates, and categorized the papers by year and topic.

DATA SYNTHESIS

The Salmonella assay led to two paradigm shifts: that some carcinogens were mutagens and that some environmental samples (e.g., air, water, soil, food, combustion emissions) were mutagenic. Although there are > 10,000 publications on the Salmonella assay, covering tens of thousands of agents, data on even more agents probably exist in unpublished form, largely as proprietary studies by industry. The Salmonella assay is a model for the development of 21st century in vitro toxicology assays in terms of the establishment of standard procedures, ability to test various agents, transferability across laboratories, validation and testing, and structure-activity analysis.

CONCLUSIONS

Similar to a stethoscope as a first-line, inexpensive tool in medicine, the Salmonella assay can serve a similar, indispensable role in the foreseeable future of 21st century toxicology.

Proteins in ecotoxicology - how, why and why not?

The growing interest in the application of proteomic technologies to solve toxicology issues and its relevance in ecotoxicology research has resulted in the emergence of "ecotoxicoproteomics". There is a general consensus that ecotoxicoproteomics is a powerful tool to spot early molecular events involved in toxicant responses, which are responsible for the adverse effects observed at higher levels of biological organization, thus contributing to elucidate the mode of action of stressors and to identify specific biomarkers. Ultimately, early-warning indicators can then be developed and deployed in "in situ" bioassays and in environmental risk assessment. The number of field experiments or laboratory trials using ecologically relevant test-species and involving proteomics has been, until recently, insufficient to allow a critical analysis of the real benefits of the application of this approach to ecotoxicology. This article intends to present an overview on the applications of proteomics in the context of ecotoxicology, focusing mainly on the prospective research to be done in invertebrates. Although these represent around 95% of all animal species and in spite of the key structural and functional roles they play in ecosystems, proteomic research in invertebrates is still in an incipient stage. We will review applications of ecotoxicoproteomics by evaluating the technical methods employed, the organisms and the contexts studied, the advances achieved until now and lastly the limitations yet to overcome will be discussed.