Day 3 :
- Toxicology Studies | Toxicology Risk Assessment | Toxicity Testing
Location: Hall-Canterbury
Chair
Carlos Horacio Laino
National University of La Rioja, Argentina
Co-Chair
Chunyuan Jin
New York University School of Medicine, USA
Session Introduction
Thomas Weber
Pacific Northwest National Laboratory, USA
Title: Aberrant regulation of oscillatory behavior in the extracellular signal regulated kinase (ERK) pathway: A toxicologists’ perspective?
Time : 09:30-09:55
Biography:
Thomas Weber completed his PhD at Texas A&M University followed by a NIEHS Post-doctoral fellowship at The University of Texas at Austin. He is currently a staff scientist at the Pacific Northwest National Laboratory. He has published 43 papers in reputed journals, 3 book chapters on cell signaling and protein phosphorylation in toxicology and a Reference Module in Biomedical Sciences (Elsevier publications). He is recipient of a US Patent, Federal Laboratory Consortium Award and R&D 100 award for development of technologies for cellular biomonitoring at the Pacific Northwest National Laboratory. Current projects in addition to studies on oscillatory behavior encompass molecular profiling of radiation resistance for consideration in clinical radiotherapy and medical countermeasures, development of lung organotypic platforms as toxicological screens and non-invasive biomonitoring using saliva as matrix.
Abstract:
Oscillatory behavior occurs in pathways central to toxicological responses, including ERK, NF-κB, p53-MDM2 and Ca2+, however, the specific biological information encoded by oscillations is incompletely understood. We are the first to demonstrate that ERK oscillations regulate unique gene expression patterns in multiple experimental model systems, indicating that transcriptional regulation is one output for oscillatory behavior. We will discuss our most advanced experimental human model system that highlights a linkage between ERK oscillations and a transcriptional co-activator (MED1) whose half-life and activity is directly regulated by ERK-dependent phosphorylation as a feasible mechanism. Several toxicants (oxygen free radicals, ionizing radiation, bromate) inhibit ERK oscillations, and exploit well established stress-responsive signaling pathways (e.g. p38) to inhibit ERK signaling. However, the ERK feedback control processes specifically regulated by the stress response are undefined. We will also discuss experimental evidence that the inappropriate regulation of negative feedback loops in the ERK pathway can result in aberrant activation of ERK signaling, a response that has received little attention in a toxicological context. Finally, we have observed negative selection of ERK oscillations in vitro which may be important in view of the increased emphasis placed on in vitro screening assays in toxicology. Transcriptional misregulation is a mechanism frequently associated with toxic outcomes, therefore, the aberrant regulation of ERK oscillations by toxicants warrants further consideration in view of the unique gene expression profiles associated with this dynamic signaling behavior.
Chunyuan Jin
New York University School of Medicine, USA
Title: Inhibition of chromatin assembly by major cigarette smoke component acrolein
Time : 09:55-10:20
Biography:
Chunyuan Jin has completed his PhD from Tokyo University and Postdoctoral studies with Dr. Gary Felsenfeld at NIH. He is an Assistant Professor of Environmental Medicine at NYU School of Medicine. He has published more than 25 papers in reputed journals such as Nature Genetics and Genes & Development.
Abstract:
Acrolein is a α,β-unsaturated aldehyde, which is abundant in cigarette smoke and coking fumes. It is a potential major carcinogen of smoking-related lung cancer, yet the underlying mechanisms are not fully understood. We find that acrolein form adducts with histones and acrolein-modified histones are resistant to acetylation. Cellular fractionation analyses further reveal that exposure of cells to acrolein specifically inhibits acetylations of N-terminal tails of cytosolic histones H3 and H4, modifications that are important for nuclear import and chromatin assembly. Accordingly, the association of H3/H4 with histone chaperone ASF1B and translocator protein importin 4 is disrupted and the nuclear import of H3 is inhibited in cells following acrolein exposure. Moreover, ChIP (chromatin immunoprecipitation) assays exhibit that the levels of histone H3 are drastically decreased at the majority of genomic loci tested and H3 amount in chromatin fragments is depleted by acrolein exposure. These data indicate that acrolein exposure leads to compromise of the chromatin assembly. Interestingly, in vitro plasmid supercoiling assays reveal that treatment of either histones or ASF1B with acrolein has no effect on formation of plasmid supercoiling, while exposure of histones to acrolein prior to histone acetylation leads to the inhibition of RSF (Remodeling and Spacing Factor) chromatin assembly, which requires acetylated histones for efficient assembly. The results suggest that acrolein-protein adduct formation itself does not directly interfere with nucleosome assembly. We propose that acrolein compromises chromatin assembly via reacting with histone lysine residues at the sites critical for chromatin assembly and prevents these sites from physiological modifications.
Mahsa Karbaschi
Florida International University, USA
Title: Rescue of cells from apoptosis increases DNA repair in UVB exposed cells: Implications for the DNA damage response
Time : 10:20-10:45
Biography:
Mahsa Karbaschi has completed her PhD in Cancer Studies and Molecular Medicine at the University of Leicester in the UK and Post-doctoral studies from Florida International University in Florida, US. Her research interest is in formation and repair of oxidatively damaged DNA and also in development of new methodologies for the evaluation of DNA damage.
Abstract:
Classically, the nucleotide excision repair (NER) of cyclobutane pyrimidine dimers (CPD) is a lengthy process (t1/2 > 48 h). Using the T4 endonuclease V-modified comet assay, we uniquely found a far more rapid repair of UVA-induced CPD (t1/2 = 4.5 h) in human skin keratinocytes. The repair of UVB-induced CPD began to slow within 1 h of irradiation, causing damage to persist for over 36 h. A similar trend was noted for the repair of oxidatively-modified purine nucleobases. Supportive of this differential repair, we noted an up-regulation of key genes associated with NER in UVA-irradiated cells, whereas the same genes were down regulated in UVB-irradiated cells. There were no significant differences in cell viability between the two treatments over the first 6 h post-irradiation, but after 24 h apoptosis had increased significantly in the UVB-irradiated cells. The role of apoptosis was confirmed using a pan-caspase inhibitor, which increased CPD repair, similar to that seen with UVA. These data indicate that the cellular ‘decision’ for apoptosis/DNA repair occurs far earlier than previously understood, and that the induction of apoptosis leads to lesion persistence, and not vice versa. This also highlights a new, potential increased carcinogenic risk from UVA-induced DNA damage as, rather than undergoing apoptosis, high levels of damage are tolerated and repaired, with the attendant risk of mutation.
Carlos Horacio Laino
National University of La Rioja, Argentina
Title: Innovation in the use of amitriptyline for pain treatment by combination with omega-3 fatty acids
Time : 11:05-11:30
Biography:
Carlos Horacio Laino received his PhD degree in Pharmacology from University of Buenos Aires, Argentina and completed his Post-graduate studies in the laboratory of the Research Department of Neuroscience, Center for Addiction and Mental Health, Research Foundation of Toronto, Canada. Then, he joined the National University of La Rioja (Argentina) in 2005 and is currently an Associate Professor of Pharmacology and Toxicology. He further received an award for Innovative Research Work from the National Innovation Submit & Showcase – Tech Connect World in 2013 and 2014. His research focuses on drug discovery in several therapeutic areas, especially pain.
Abstract:
Combination therapy is often used to increase the clinical utility of analgesic agents. The co-administration of two compounds may achieve analgesia at doses lower than those required for either compound alone, leading to enhanced pain relief and a reduction in adverse effects. A tricyclic antidepressant, such as amitriptyline, is often used to treat many types of persistent pain, with their efficacy in this regard being well established. These conditions include diabetic neuropathy, postherpetic neuralgia, headache, arthritis, and chronic back pain. The disadvantages of using amitriptyline include side effects such as cardiovascular problems (e.g., hypertension, postural hypotension and arrhythmias), drowsiness, dry mouth, nausea, changes in body weight and constipation. The aim of this study was to examine in rats the antinociceptive effect of omega-3 fatty acids alone as well as in combined chronic treatments with amitriptyline (AMI) in the hot plate test. We found that compared to control, omega-3 fatty acids dose-dependently increased the latency time, indicative of an antinociceptive effect, with the co-administration of AMI (20 mg/kg/day) and omega-3 fatty acids (0.72 g/kg/day) revealing a higher antinociceptive efficacy than the individual treatments. The combination of omega-3 fatty acids with amitriptyline might produce better analgesia, thereby increasing the efficacy of pain management and reducing side effects through the use of a smaller dose of antidepressant.
Xue Zhou
Huazhong University of Science and Technology, China
Title: Sirtuin-6 inhibits epithelial to mesenchymal transition via inactivation TGF-β/smad signaling in vitro and in vivo
Time : 11:30-11:55
Biography:
Dr. Xue Zhou got her B.S. degree in Environemtal Sciences from Wuhan University in 2003, and got her Ph.D. degree in Environmental Health Sciences from New York University in 2010. She is currently Associate Professor at School of Public Health, Huazhong University of Science and Technology. She has more than 20 publications in reputed journals.
Abstract:
Sirtuin6 (SIRT6), a member of NAD+-dependent deacetylases that plays a key role in aging, cancer, and metabolism, has been shown to have anti-fibrosis function in heart and liver, but whether SIRT6 plays a role in idiopathic pulmonary fibrosis (IPF) has been poorly explored. Epithelial to mesenchymal cell transition (EMT), a process by which fully differentiated epithelial cells convert to a mesenchymal phenotype, has been involved in the pathogenesis of IPF. In the present study, SIRT6 expression was upregulated in both TGF-β1-induced EMT in A549 cells and bleomycin (BLM)-induced EMT in mice. Forced expression of SIRT6 by adenovirus transfection of A549 cells significantly abrogated TGF-β1-induced EMT-like phenotype and EMT-associated cell behavior. In A549 cells, TGF-β1-induced activation of TGF-β1/smad3 signaling and increase of smad3-snail1 interaction was ameliorated by overexpression of SIRT6. Upregulation of EMT related transcription factors by TGF-β1 treatment was also restored by overexpression of SIRT6. Further in vivo studies showed that lung targeted delivery of SIRT6 using adeno-associated virus transfection blunted BLM-induced pulmonary EMT and fibrosis as evidenced by a reduction of epithelium undergoing EMT and collagen deposition. Our findings unravel a novel role of SIRT6 as a key modulator in the phenotypic conversion of epithelial to mesenchymal cells and suggest it as an attractive potential therapeutic target for IPF.
Grace-Anne Bent
The University of the West Indies, West Indies
Title: A Newly Modified QuEChERS Method for Multiresidue Analysis of Organochlorines and Organophosphates in Foods Consumed in Trinidad and Tobago
Time : 11:55-12:20
Biography:
Grace-Anne Bent has received PhD from University of the West Indies. She is a lecturer of analytical chemistry in the Department of Chemistry at The University of the West Indies, St. Augustine Campus, Trinidad and Tobago. Her research interests include food safety and security, investigating the chemistry of food and food related toxins in an effort to minimize human exposure by understanding their mechanisms of interaction (in vivo and in vitro). She has published a book and 7 journal articles. She is also the recipient of several research awards.
Abstract:
Pesticides are a group of plant protection chemicals aimed at eradicating pests to improve crop yields. However, pesticides are toxic and can result in carcinogenic and neurologic effects on humans and animals who come in contact with them. Humans can come in contact with pesticides by direct or indirect application in the field or by consuming foods that have pesticide residues remaining after application. Pesticide residue analysis has been given high priority globally since the world’s population became much more conscious about the health hazards caused by exposure to pesticide residues. In Trinidad and Tobago, there is still yet to be defined the maximum allowable limit of pesticide residues on produce. Thus, the need for the analysis of pesticide residue levels in foods which form part of a typical “Trinbago” diet. Traditionally, pesticide residue analysis is a laborious process that involves the use of many toxic and expensive chemicals, thus making the routine analysis of food crops for pesticides a deterrent for the average farmer. As such, the quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed which reduces the sample preparation time and the use of toxic chemicals tremendously. However, the analysis can still be quite expensive. This research aims at developing a cheaper variation to the traditional QuEChERS method. This method has been tested on select organochlorine (OC) and organophosphate (OP) pesticides in selected food matrices. Recoveries ranged from 60-125 % with a relative standard deviation < 20 %. The method was successfully tested on samples from the Chaguanas District, Central Trinidad.