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Chemistry Researcher Studies Human Health at the Molecular Level

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Courtney Christopher started college as a pre-med major but realized chemistry could hold answers to complex human health questions. Now as a postdoctoral research fellow in the Department of Chemistry, she’s uncovering novel links between a microbial derived metabolite, the gut microbiome, and conditions ranging from systemic inflammation to Alzheimer’s disease.

Most of her postdoctoral work at the University of Tennessee, Knoxville, has stemmed from her discovery of 2,3-dihydroxypropane-1-sulfonate (DHPS) in humans.  

“Prior to my work, DHPS did not have a known role in human metabolism,” she explained. Her principal investigator is UT Chemistry Professor Shawn R. Campagna, who helped discover the role of DHPS in marine microbial communities a decade ago. 

“My contributions have been identifying DHPS in humans, discovering that this metabolite does impact human physiology, and providing data and generating hypotheses that will lay the foundation for future studies to uncover how DHPS may be a key regulator of human health and inflammation,” Christopher said.

She’ll be discussing all of her DHPS discoveries and summarizing the findings on DHPS in human health at the University of Tennessee Health Science Center’s Neuroscience Institute seminar series this October in Memphis.

This past summer she delivered oral presentations at the American Society for Mass Spectrometry and the American Chemical Society conferences, and her collaborator presented at the American Society for Microbiology conference. 

Vaping to Alzheimer’s

In one study, published in the journal metabolites, Christopher discovered a connection between DHPS and metabolic dysregulation, comparing DHPS levels in the stool of vaping and smoking subjects compared to controls. 

“This work provided the first evidence that DHPS, a microbial metabolite with an unknown role in human physiology, may be linked to vaping and smoking-induced metabolic dyshomeostasis and a basis for future research investigating the role of DHPS in human health,” she said. “I also identified correlations to cholesterol metabolism, acetylated amino acids, neurotransmitters, and vitamin B metabolism, which may provide insight into the physiological role of DHPS.”

In another, she discovered a previously unrecognized link between DHPS and neurodegenerative diseases (NDDs) such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis (ALS). “The data suggest that cryptic sulfur metabolism via DHPS is a missing link in our current understanding of NDD onset and progression,” Christopher said.

Her hypothesis is that metabolic dyshomeostasis and increased flux through DHPS result in mitochondrial dysfunction and systemic inflammation in humans.

This academic year she is investigating the pathophysiological impact of DHPS dyshomeostasis on mitochondrial dysfunction. “Additionally, I plan to study how different intrinsic (biological sex, aging) and extrinsic factors (diet, diabetes, hypertension) are impacted by DHPS dyshomeostasis,” she said. 

Interdisciplinary Collaborations

Christopher was working on her bachelor’s degree in chemistry at Lincoln Memorial University when she first heard of the work in the Campagna Lab at UT using mass spectrometry-based metabolomics to investigate the etiology of Alzheimer’s disease. 

“I was so impressed with Dr. Campagna’s research on human health and his many interdisciplinary research collaborations with PIs (principal investigators) across the country.” She earned her PhD from UT in 2022.

“None of this work would have been possible without my mentor (Campagna) and incredible collaborators,” Christopher said, “Through the Biological and Small Molecule Mass Spectrometry Core (BSMMSC) in UT’s Department of Chemistry, I have had the opportunity to collaborate with brilliant scientists across the globe. They have given me scientific freedom to explore this new discovery and have provided invaluable support.”

Her collaborators include Assistant Professor Katie Morgan from the UT College of Nursing, as well as researchers from Augusta University, the Medical University of South Carolina, and Louisiana State University.

By Amy Beth Miller

A woman standing in a chemistry lab

Graduate Student Earns Prestigious ACS Fellowship

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Miranda Limbach, graduate student in the Department of Chemistry, was chosen as one of four recipients of a 2024 American Chemical Society Analytical Graduate Research Fellowship.

A member of Assistant Professor Thanh Do’s research group, Limbach is currently finishing a summer internship with Merck. When she returns, Limbach will begin her fifth year of graduate studies at the university.

The goal of Limbach’s PhD research is to identify the underlying principles governing the membrane permeability of macrocyclic peptides. Macrocyclic peptides are being explored as a means of drug delivery that would target protein-protein interactions, potentially leading to new ways to treat a variety of diseases.

This prestigious fellowship awarded by the Analytical Division of the ACS is designed to support research, promote the growth of the discipline, and to recognize future leaders in analytical chemistry. The award will provide support to Limbach for 9 months, which will allow her to focus fully on her research without holding a GTA position.

Other winners of the nationally competitive award are from the University of Wisconsin-Madison, Florida State University, and the California Institute of Technology.

The American Chemical Society (ACS) was founded in 1876 and is one of the world’s largest scientific organizations. In addition to hosting regular conferences devoted to exploring new and continuing research across the discipline of chemistry, the ACS provides accreditation for undergraduate chemistry degrees, offers a variety of fellowships and awards for students and researchers, and publishes more than 80 peer-reviewed journals.

Campagna Lab published in Frontiers In Microbiology

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The Campagna lab published their work “Comparative Decomposition of Humans and Pigs: Soil Biogeochemistry, Microbial Activity and Metabolomic Profiles” in Frontiers In Microbiology.

Vertebrate decomposition processes have important ecological implications and, in the case of human decomposition, forensic applications. Animals, especially domestic pigs (Sus scrofa), are frequently used as human analogs in forensic decomposition studies. However, recent research shows that humans and pigs do not necessarily decompose in the same manner, with differences in decomposition rates, patterns, and scavenging.

The objective of this study was to extend these observations and determine if human and pig decomposition in terrestrial settings have different local impacts on soil biogeochemistry and microbial activity. In two seasonal trials (summer and winter), we simultaneously placed replicate human donors and pig carcasses on the soil surface and allowed them to decompose. In both human and pig decomposition-impacted soils, they observed elevated microbial respiration, protease activity, and ammonium, indicative of enhanced microbial ammonification and limited nitrification in soil during soft tissue decomposition. Soil respiration was comparable between summer and winter, indicating similar microbial activity; however, the magnitude of the pulse of decomposition products was greater in the summer.

Using untargeted metabolomics and lipidomics approaches, they identified 38 metabolites and 54 lipids that were elevated in both human and pig decomposition-impacted soils. The most frequently detected metabolites were anthranilate, creatine, 5-hydroxyindoleacetic acid, taurine, xanthine, N-acetylglutamine, acetyllysine, and sedoheptulose 1/7-phosphate; the most frequently detected lipids were phosphatidylethanolamine and monogalactosyldiacylglycerol. Decomposition soils were also significantly enriched in metabolites belonging to amino acid metabolic pathways and the TCA cycle.

Comparing humans and pigs, they noted several differences in soil biogeochemical responses. Soils under humans decreased in pH as decomposition progressed, while under pigs, soil pH increased. Additionally, under pigs we observed significantly higher ammonium and protease activities compared to humans. We identified several metabolites that were elevated in human decomposition soil compared to pig decomposition soil, including 2-oxo-4-methylthiobutanoate, sn-glycerol 3-phosphate, and tryptophan, suggesting different decomposition chemistries and timing between the two species.

Together, this work shows that human and pig decomposition differ in terms of their impacts on soil biogeochemistry and microbial decomposer activities, adding to our understanding of decomposition ecology and informing the use of non-human models in forensic research.

The group also published their work “Enterococcus faecalis Readily Adapts Membrane Phospholipid Composition to Environmental and Genetic Perturbation” in Frontiers In Microbiology. 

The bacterial lipid membrane, consisting both of fatty acid (acyl) tails and polar head groups, responds to changing conditions through alteration of either the acyl tails and/or head groups. This plasticity is critical for cell survival as it allows maintenance of both the protective nature of the membrane as well as functioning membrane protein complexes. Bacteria that live in fatty-acid rich environments, such as those found in the human host, can exploit host fatty acids to synthesize their own membranes, in turn, altering their physiology. Enterococcus faecalis is such an organism: it is a commensal of the mammalian intestine where it is exposed to fatty-acid rich bile, as well as a major cause of hospital infections during which it is exposed to fatty acid containing-serum. Within, the group employed an untargeted approach to detect the most common phospholipid species of E. faecalis OG1RF via ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS).

The group examined not only how the composition responds upon exposure to host fatty acids but also how deletion of genes predicted to synthesize major polar head groups impact lipid composition. Regardless of genetic background and differing basal lipid composition, all strains were able to alter their lipid composition upon exposure to individual host fatty acids. Specific gene deletion strains, however, had altered survival to membrane damaging agents. Combined, the enterococcal lipidome is highly resilient in response to both genetic and environmental perturbation, likely contributing to stress survival.

Sharma Announced Winner of 2021 Emerging Leader in Molecular Spectroscopy

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Bhavya Sharma, assistant professor, has been named the winner of the 2021 Emerging Leader in Molecular Spectroscopy Award. The award will be presented to Sharma at the SciX 2021 conference this fall, where she will give a plenary lecture and be honored in an award symposium.

“We would like to extend congratulations to Professor Sharma for winning the 2021 Emerging Leader in Molecular Spectroscopy Award,” said Mike Hennessy Jr., president and CEO of MJH Life Sciences™, the parent company of Spectroscopy®. “Sharma is well deserving of this recognition for all of her excellent work as a molecular spectroscopist. We are proud to honor her with this award at the SciX conference this fall.”

Sharma received her Ph.D. from the University of Pittsburgh in 2011. She has become a leader in the area of neurochemical detection with various forms of Raman spectroscopy, including surface-enhanced Raman spectroscopy (SERS) and spatially offset Raman spectroscopy. Sharma has developed novel Raman spectroscopy methods for neurological detection, including surface-enhanced spatially offset Raman spectroscopy. Additionally, she is developing methods to demonstrate direct detection of molecules for the first time by combining SERS and multivariate analysis.

Sharma has published 26 papers and has given more than 40 oral and poster presentations at scientific conferences. She is a reviewer for multiple journals and received an Outstanding Reviewer award for the journal Analyst in 2018. As an active member of the Coblentz Society, Sharma has served on multiple award committees and was also a member of the program committee for the OSA Optical Sensors Conference for 2018 and 2019. Sharma has also been active in organizing sessions at various scientific conferences, including Pittcon, the SPIE Defense + Commercial Sensing Symposium, and SciX. 

Selected by an independent scientific committee, the Emerging Leader in Molecular Spectroscopy Award recognizes the achievements and aspirations of a talented young molecular spectroscopist who has made strides early in his or her career toward the advancement of molecular spectroscopy techniques and applications. The winner must be within 10 years of receiving his or her PhD. 

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Do Lab Published in Chemical Science

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The Do Lab recently published their work “α-CGRP disrupts amylin fibrillization and regulates insulin secretion: implications on diabetes and migraine” in Chemical Science.

Amber Gray and Aleksandra Antevska, graduate students, share first authorship on this piece.

Despite being relatively benign and not an indicative signature of toxicity, fibril formation and fibrillar structures continue to be key factors in assessing the structure–function relationship in protein aggregation diseases. The inability to capture molecular cross-talk among key players at the tissue level before fibril formation greatly accounts for the missing link toward the development of an efficacious therapeutic intervention for Type II diabetes mellitus (T2DM).

This research shows that human α-calcitonin gene-related peptide (α-CGRP) remodeled amylin fibrillization. Furthermore, while CGRP and/or amylin monomers reduce the secretion of both mouse Ins1 and Ins2 proteins, CGRP oligomers have a reverse effect on Ins1. Genetically reduced Ins2, the orthologous version of human insulin, has been shown to enhance insulin sensitivity and extend the life-span in old female mice.

Beyond the mechanistic insights, their data suggest that CGRP regulates insulin secretion and lowers the risk of T2DM. Our result rationalizes how migraine might be protective against T2DM. They envision the new paradigm of CGRP : amylin interactions as a pivotal aspect for T2DM diagnostics and therapeutics. Maintaining a low level of amylin while increasing the level of CGRP could become a viable approach toward T2DM prevention and treatment.

Campagna Lab Published in JNP

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The Campagna Lab published their work “Isoflurane anesthesia disrupts the cortical metabolome” in a collaborative piece in the Journal of Neurophysiology (JNP). 

Identifying similarities and differences in the brain metabolome during different states of consciousness has broad relevance for neuroscience and state-dependent autonomic function. This study focused on prefrontal cortex (PFC) as a brain region known to modulate states of consciousness.

Anesthesia was used as a tool to eliminate wakefulness. Untargeted metabolomic analyses were performed on microdialysis samples obtained from mouse PFC during wakefulness and during isoflurane anesthesia.

Analyses detected 2153 molecules, 91 of which could be identified. Analytes were grouped as detected during both wakefulness and anesthesia (n=61), and as unique to wakefulness (n=23) or anesthesia (n=7). Data were analyzed using univariate and multivariate approaches. Relative to wakefulness, during anesthesia there was a significant (q < 0.0001) four-fold change in 21 metabolites. During anesthesia 11 of these 21 molecules decreased and 10 increased.

The Kyoto Encyclopedia of Genes and Genomes database was used to relate behavioral state specific changes in the metabolome to metabolic pathways. Relative to wakefulness, most of the amino acids and analogs measured were significantly decreased during isoflurane anesthesia. Nucleosides and analogs were significantly increased during anesthesia. Molecules associated with carbohydrate metabolism, maintenance of lipid membranes, and normal cell functions were significantly decreased during anesthesia.

Significant state-specific changes also were discovered among molecules comprising lipids and fatty acids, monosaccharides, and organic acids. Considered together, these molecules regulate point to point transmission, volume conduction, and cellular metabolism. The results identify a novel ensemble of candidate molecules in PFC as putative modulators of wakefulness and the loss of wakefulness.

Campagna Gives Talk for Harvard’s MSI Seminar Series

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The Microbial Sciences Initiative (MSI) at Harvard University is an interdisciplinary science program aimed at a comprehensive understanding of the richest biological reservoir of the planet, the microbial world.

Shawn Campagna presented a talk for this series titled “Using Metabolomics to Understand the Function of Environmentally Relevant Microbial Consortia.”

 

ORI Names Campagna Interim Director of Strategic Programs

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President Randy Boyd shared some developments at the Oak Ridge Institute at UT (ORI at UT). A national search for the first executive director and vice provost of the Oak Ridge Institute at UT is underway.

Shawn Campagna
Shawn Campagna

ORNL Director Thomas Zacharia and Randy Boyd, in consultation with UT Knoxville Chancellor Donde Plowman and UT Health Science Center Chancellor Steve Schwab, have named Michelle Buchanan, ORNL deputy for science and technology, and Stacey Patterson, UT System vice president for research, as interim co-directors of ORI at UT until a director is named. Suresh Babu, a UT-ORNL Governor’s Chair for Advanced Manufacturing and Bredesen Center Director, will serve as ORI at UT’s interim education director. Shawn Campagna, UT Knoxville associate department head of chemistry and Director of Science Alliance, will serve as the interim director of strategic programs. Jean Mercer, UT Knoxville assistant vice chancellor for research and director of the office of sponsored programs, will serve as interim director of operations.

Sharma Lab Published in Analyst

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The Sharma Raman lab is an interdisciplinary research group working in the areas of Analytical and Physical Chemistry, Biology, and Materials Science. The group focuses on probing and characterizing the underlying chemistry and physics of biological processes. The long range research goal of the group is the use of innovative Raman spectroscopic methods to create new approaches to understand biology. Specifically, we are developing methods for early detection of disease (both in vitro and in vivo detection), as well as methods for chemical and biological sensing.

The Sharma Lab published their work “Raman spectroscopy and neuroscience: from fundamental understanding to disease diagnostics and imaging” in Analyst. 

Neuroscience would directly benefit from more effective detection techniques, leading to earlier diagnosis of disease. The specificity of Raman spectroscopy is unparalleled, given that a molecular fingerprint is attained for each species. It also allows for label-free detection with relatively inexpensive instrumentation, minimal sample preparation, and rapid sample analysis. This review summarizes Raman spectroscopy-based techniques that have been used to advance the field of neuroscience in recent years.

Sharma Lab Published in Analytical Chemistry and Analyst

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Terence MooreThe Sharma Raman Lab published their work “Direct Surface Enhanced Raman Spectroscopic Detection of Cortisol at Physiological Concentrations” in Analytical Chemistry.

Josh Moore is the first author on this piece and recently earned his PhD in the Chemistry program.

Cortisol is an important steroid hormone in vertebrate physiology and plays a role in acute and chronic stress response. Current methods for determination of cortisol concentrations in biofluids require extensive sample preparation and long run times. Raman spectroscopy is an attractive alternative because analysis is rapid and non-destructive to the sample.

The Sharma Lab has developed a surface-enhanced Raman spectroscopy (SERS)-based method for detection of cortisol in ethanol that shows a sigmoidal concentration response and a limit of detection of 177 nanomolar, which is in the physiologically relevant range. The method can be applied to more complex solvent environments through the use of multivariate analysis techniques, where principal components analysis (PCA) demonstrates a linear separation according to cortisol concentration in a serum mimic. “We are, to our knowledge, the first group to report on the detection of cortisol using label-free SERS, which does not require a Raman reporter molecule to obtain signal,” Moore said.

The Sharma Lab published their work “Surface-enhanced spatially-offset Raman spectroscopy (SESORS) for detection of neurochemicals through the skull at physiologically relevant concentrations” in Analyst. 

Detection techniques for neurotransmitters that are rapid, label-free, and non-invasive are needed to move towards earlier diagnosis of neurological disease. Surface-enhanced Raman spectroscopy (SERS) allows for sensitive and selective detection of target analytes. The combination of SERS with spatially offset Raman spectroscopy (SORS) in a technique termed surface enhanced spatially offset Raman spectroscopy (SESORS) permits a sensitive and selective detection of neurotransmitters through the skull.

In this piece, the group presents the SESORS detection of individual neurotransmitters and mixtures of neurotransmitters at physiologically relevant concentrations, while also establishing limits of detection.