Student Research Experiences

The future of environmental health and exposome-related research lies with current students. Their fresh perspectives and enthusiasm are invaluable to these projects and the advancement of the field. HERCULES offered students the opportunity to participate in pilot project research and was met with both an incredible interest and response to the work the Center is doing. Here are a few highlights of the research these students have been up to over the past year.

Nanoparticle Exposures and the Potential for Human Toxicity

Daniel Nguyen, MPH Candidate

Last semester I worked as a graduate research assistant with the HERCULES Center in collaboration with Dr. Christine Payne at Georgia Institute of Technology. Dr. Payne’s innovative research explored the impact of nanoparticle uptake into cells and how this internalization may alter gene expression. Therefore my task as a public health student was to summarize and synthesize the nanoparticle literature while exploring the potential for human toxicity due to nanoparticle exposure. This was directly related to my interests in how different environmental exposures may have implications in human toxicology, which may also be associated with certain disease or health outcomes. My reviews on the current literature served to provide significant methodologies that could possibly assist Dr. Payne’s future research in this field. At the end of my research assistant position, I presented a presentation that reviewed my findings relating to nanotoxicity and nanoparticle exposures from the environment and compiled all of the research into a summarized paper as a reference.

Graduate students, Daniel Nguyen and Dipesh Khanal presenting Dr. Payne’s pilot project at the recent HERCULES External Advisory Board Meeting.

Having the opportunity to work with the HERCULES Center and Dr. Payne has been pivotal in developing my public health skills. I believe working in tandem and communicating with a different audience, which in this case was biochemistry, is key to progressing the field of environmental health. It was rewarding to apply the competencies I had learned within the classroom and directly apply them in conducting the research involved with Dr. Payne’s study. Her mentorship, as well as the resources offered by the HERCULES Center, has been and continues to be supportive in my growth as a public health professional.

Metabolic Profiling in Alzheimer’s Disease–Environmental and Endogenous Metabolites

Erica Figueroa, MPH Candidate

Working in collaboration with William Hu, Doug Walker, and Dean Jones, the pilot project that I have been working on focuses on metabolic profiling in Alzheimer’s disease (AD) to identify any metabolomics changes associated with the disease, concentrating on both endogenous metabolites and environmental chemicals. AD is a heterogeneous disorder, with risk factors that come from genetic, epigenetic, and environmental situations, as well as other areas. Previous studies have found that a correlation exists between exposure to the organochlorine pesticide, DDT (through its metabolite DDE) and AD. This project further evaluates DDT, as well as other environmental chemicals. Plasma samples were collected from subjects with normal cognition (healthy controls), mild cognitive impairment, AD, and a non-AD dementia (frontotemporal dementia). The subjects were split into two groups: training and validation cohorts; the latter will serve to confirm the presence of metabolite/chemical matches. These samples were then analyzed using Fourier-transform mass spectrometry (LC-FTMS) and were fractionated with a formate gradient. The LTQ-FT spectrometer detects the samples after they are ionized with electrospray ionization in the positive mode.

Using the R programming software package, apLCMS, feature tables are created for all the detected metabolites, which include retention times, mass/charge ratios (m/z), and peak intensity values. These feature tables are used with the R package, xMSanalyzer, to detect attributes from the tables and provides a list of matches based on a target list of chemicals/metabolites. Different ion/adducts are associated with the R analysis matches, including those found for diethyl phthalate which was present in both cohorts, but further work is needed in order to determine which factors influence adduct formation to confirm these findings. Plasma DDE levels were not associated with AD in either cohort, but increased plasma DDT levels may be associated with AD. Further research is necessary to help explain why certain adducts for the metabolite/chemical matches are present over others. The next step is to eliminate chemicals and narrow down the list of candidates by identifying the most plausible ion/adduct formations in the environment for each chemical match.