AY04-05 Alaska IDeA Graduate Fellowship Awards

Persistent organic pollutants (POPs) manufactured and used outside US, accumulate in the arctic because they tend to precipitate and deposit in colder regions. These chemicals have a lipophilic nature and people inhabiting the arctic, such as Alaskan Natives are exposed to these contaminants through their traditional subsistence based diet which relies heavily on fatty tissues of the arctic marine biota. As a preliminary case control study of the relationship between POPs and breast cancer, a number of these chemicals were measured and detected in Alaskan Native Women. p,p-DDE, Hexachlorobenzene, and Trans-nonachlor were among the top 6 contaminants found, and were found in more than 70% of Alaska Native Women. Based on these results I propose to study the effects of DDE, HCB and Trans-nonachlor on BRCA1 (breast cancer susceptibility gene), whose expression was found to be downregulated in sporadic breast and ovarian cancers. Furthermore I propose to look at the transcriptional machinery that potentially regulates BRCA1 in the presence of the above chemicals by characterizing the BRG1 protein levels (a co-repressor of the gene and a chromatin remodeler. In conclusion, this study will measure the effects of HCB, DDE and Trans-nonachlor on BRCA1, thus determining at the molecular level if these chemicals pose a risk to breast cancer development, and it will also open the door to a less explored area of research, that of the effects of POPs on chromatin remodelers.

Natural deposits of perchlorate are rare, but anthropogenic sources are plentiful, making the possibility of widespread contamination very likely. I'm studying the effects of a toxin called perchlorate on vertebrates, using the threespine stickleback (Gasterosteus aculeatus) as a model. I'm conducting a series of experiments that will reveal perchlorate's effects on metabolism, behavior, reproductive output, fertility and fecundity, swimming performance, development and developmental abnormalities, endocrine function/disruption, perchlorate residue deposition, toxicokinetics and toxicodistribion, differential growth rates, and survivorship. Perchlorate is currently unregulated by the EPA, so my research will be useful to help establish appropriate nationwide exposure levels.

Dioxins are pollutants that have been found in Alaska’s soil and wildlife. They cause developmental abnormalities in vertebrates including the African clawed frog, a commonly used model of vertebrate development. In cells exposed to dioxin a toxic-reponse gene is activated in a process that requires the BRG1 protein. It is not known what role BRG1 may play in dioxin-induced developmental abnormalities. I am studying its possible roles by injecting embryos with antisense oligonucleotides that prevent the production of BRG1. By comparing development in the presence or absence of dioxin, and with or without BRG1 function, I will be able to infer BRG1’s role in dioxin-induced developmental abnormalities. To date I have demonstrated that injecting the antisense oligonucleotides affects developing embryos in a dose-dependent manner.

Ribbon seals were sampled in 2003 during a year of unusual ice coverage in Little Diomede Island, Alaska. Liver, kidney (n=36) and lumbar muscle (n=40) were collected for chemical feeding ecology and contaminant analysis and jaws for determination of age from cementum annuli in teeth. Only few gastric contents were sampled and analyzed, since ribbon seals were harvested during the annual molt of this species. They are generally not feeding during this time and stomachs will not yield any information. However, determination of long term diet and trophic position (about 1 month) is possible by means of stable carbon and nitrogen isotope analysis of muscle tissue. In addition, liver and kidney will be analyzed for stable isotopes to assess tissues with faster turnover (days to weeks) than muscle and to evaluate immediate dietary selection and trophic position of ribbon seals. Accumulation of various contaminants, in particular mercury is of concern to consumers of Alaskan subsistence foods. Bioaccumulation of mercury is not solely dependent on trophic level, but is rather relying on prey selection and animal age. Therefore, feeding ecology information and animal morphometrics are invaluable in understanding contaminant pathways. Seal tissues will further be analyzed for total and monomethyl mercury using cold vapor atomic absorption spectrometry. The purpose of this study is to provide baseline concentrations of THg and MeHg of apparently healthy ribbon seals taken during subsistence harvests in Little Diomede, Alaska and relate these to the trophic level of the sampled population. This information will be interpreted with regard to age and feeding ecology as determined by tooth cementum structure and stable carbon and nitrogen isotopes, respectively.

Serotonin type 3 receptor is a member of the ligand gated ion channel superfamily; of which nicotinic acetylcholine, g aminobutyric acid A, and glycine receptors are other members. The ligand-binding site of the homomeric 5-HT3A receptor is located in the amino terminal region. The aim of this proposal is to identify potentially important residues in the putative Loop B region of the murine 5-HT3A receptor binding domain, using alanine-scanning mutagenesis. Each amino acid in the Loop B region will be mutated to alanine. These alanine mutants will be characterized using radioligand binding, electrophysiological and immunofluorescence assays to determine the role of each residue in binding, gating or assembly of the receptor. In addition, Bikádi Zsolt from the Department of Molecular Pharmacology, Institute of Chemistry, Chemical Research Center Budapest, Hungary will be performing ligand-docking studies using homology model of the 5-HT3A receptor. Used in tandem, the results from these studies will help us understand better how ligand binding to the ion channel coupled receptors leads to channel opening. These studies will also help in enhancing the pharmacaphore model for 5-HT3 antagonists, which have been found to be useful in the treatment of early onset alcoholism (a public health problem in adolescents in Alaska), anxiety, irritable bowel syndrome and obsessive-compulsive disorder.

Currently, the immune status of Alaskan polar bears and ice seals is unknown. In recent decades, the two major stressors for polar bears have been identified as contaminants and climate change. The impetus behind the project is to establish clinical baseline data to monitor potential change in health and also the development of in vitro immune bioassays for testing the effects of contaminants and pathogens on immune functions (i.e., contaminant and potential pathogen interactions) of polar bears and ice seals. The proposed research will examine the hypothesis that polar bears with reduced immune status based on clinical and functional assays will be more susceptible to contaminants induced suppression in vitro based on challenge with a potential pathogen or model component thereof (e.g. protein, RNA, etc.), focusing on morbillivirus.

The bowhead whale (Balaena mysticetus) is an endangered mysticete and an important subsistence species to many native communities in both Alaska and Russia. The population health of the bowhead whale is intimately tied to offshore/coastal development and other human activities that influence ecosystem health. The native subsistence hunt provides a unique opportunity to examine this rare species and, likewise, the data to investigate the health status of the Bering Sea/Western Arctic populations. We will investigate the normal range of values (natural variability due to time of year harvested, age, and sex) for basic nutritional and health parameters (blubber characteristics, essential and non-essential elements), as well as the structure of selected tissues in the bowhead whale (Balaena mysticetus). We will identify parameters most important in assaying the health status of other mysticetes residing in the Bering Sea or Western Arctic that are harvested or stranded via gross and histopathologic observations. Finally, we will determine the role of the bowhead whale as a potential indicator of ecosystem health and develop an optimized protocol for assessing mysticete health for the Bering Sea and Western Arctic, and other regions. The research proposed in this study will provide techniques and baseline data that can be applied to other endangered marine populations, such as the northern right whale (Eubalaena glacialis).

Neuroprotection from Excitotoxic Insult in Hippocampus of a Hibernating Species Arctic Ground Squirrel- Austin Ross

Hibernation is a state in which Arctic Ground Squirrel (AGS), Spermophyllis parryii, are able to survive profound decreases in blood flow, heart rate, respiration rate, and cerebral perfusion. Interestingly, AGS rewarm intermittently throughout the hibernation season for approximately 24 hour periods between one to three week bouts of torpor. During their rewarming periods AGS experience a situation comparable in some respects to reperfusion after ischemia, yet they avoid neuronal damage. In this project, AGS hippocampus is used to investigate mechanisms of neuroprotection relevant to studies of potential stroke therapeutics. My hypothesis is that unique mechanisms in the hippocampus of hibernating species, such as regulation of glutamate receptor subunit expression, results in tolerance to excitotoxic insult.

The Role of Cav1 in the AhR Pathway - Enola Schaff

The plasma membrane is a dynamic and complex structure of proteins and lipids that mediate how environmental contaminants enter the cell and exert their toxic effects. Caveolins are a major class of plasma membrane proteins that regulate membrane structure, composition, and transport of compounds across the plasma membrane. Caveolins also mediate the function of a number of receptors found within the cell. My research examines the role of caveolin 1 (CAV1) in cellular toxicity of environmental contaminants that act by binding to and activating the aryl hydrocarbon receptor (AhR). Activation of this receptor is required for many of the toxic responses associated with exposure to dioxins (found in agent orange) and related contaminants (e.g., cigarette smoke, automobile exhaust, industrial incineration). The AhR functions in a number of cell types including endothelial cells, which help regulate immune function and blood pressure. Little is known about endothelial cell responses to environmental contaminants acting through the AhR. I am working with a new mouse endothelial cell model to examine how CAV1 influences AhR function. This will result in a novel model for studying the effects of environmental contaminants. Understanding how the structure and composition of the plasma membrane influences AhR function will lead to a better understanding of how these contaminants affect the health of humans and other organisms.

Structure-function studies of the Acetylcholine Binding Protein (AChBP) - Asha Suryanarayana

The Acetylcholine Binding Protein (AChBP) is a naturally occurring soluble protein and has been crystallized at 2.70 A resolution. The AChBP bears high degree of structural and functional homology to the extracellular domain of receptors belonging to ligand gated ion channel (LGIC) family, which includes 5-HT3, nACh, GABA and Glycine receptors. Due to this homology, results from AChBP-based studies are valuable in drawing conclusions about membrane-bound ligand gated ion channels, which are relatively difficult to study. The primary aim of this proposal is to study the structure of AChBP using mutagenesis. Mutational data from the 5-HT3R will also be used to guide these studies. To this end, we propose to purify AChBP in large quantities by stable expression in mammalian cell lines. Data from these studies will be useful in better understanding the ligand binding site of AChBP and all LGICs in general.

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Last updated, Winter 2005