Date of Award
2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Pharmaceutical Sciences
Department
Biomedical and Pharmaceutical Sciences
First Advisor
Angela L. Slitt
Abstract
Per- and polyfluoroalkyl substances are a class of nonbiodegradable synthetic aliphatic environmental toxicants that are ubiquitous in the environment. A small subset, specifically perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been designated as highly hazardous to human health by the Environmental Protection Agency (EPA) under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). PFOA and PFOS-associated adverse health effects include, but are not limited to, immune suppression, thyroid dysfunction, increased serum cholesterol, liver damage (i.e., alanine aminotransferase (ALT)), and developmental toxicity (i.e., low fetal birth weight and neurotoxicity). In this doctoral dissertation, it was hypothesized that environmental PFAS exposure may affect chemical-tissue disposition, dysregulate proteome homeostasis, and contribute to disease in vivo.
The field’s understanding of maternal-fetal PFAS exposure and association with adverse health outcomes is still emerging, with limited data available on neonatal neurotoxicity. In Manuscript I, assessment of neonatal brain exposure to PFAS during gestation and lactation resulting from maternal exposure to PFOA, PFOS, and perfluorohexanesulfonic acid (PFHxS) was conducted using banked brain cortex tissue from neonatal offspring of CD-1 dams that were fed either standard rodent or high fat (60% kcal from fat) diet, and administered either 1 mg/kg PFOA, 0.036 mg/kg PFOS, and 1 mg/kg PFHxS orally during gestation and lactation until postnatal day (PND) 21. It was hypothesized that PFOS, PFOA, and PFHxS administration to dams during gestation and lactation would result in PFAS transfer to offspring, with measurable concentrations in the brain. Furthermore, it was hypothesized that maternal PFAS exposure would result in alterations to the offspring's brain proteome. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to quantify brain PFAS concentrations and further explore the maternal disposition of PFAS to offspring. Sequential Window Acquisition of all Theoretical Fragment-Ion Spectra (SWATH) mass spectrometry was used to determine whether maternal exposure to PFAS during the perinatal and lactation period altered the offspring brain proteome using an untargeted, unbiased approach. Findings from Manuscript I reveal that maternal exposure to PFOA, PFOS, and PFHxS resulted in PFAS accumulation in the offspring's brain, with PFHxS reaching concentrations higher than PFOA at the same maternal dose. Moreover, administration of PFAS to dams, along with a high-fat diet, altered PFAS concentration and protein abundance in offspring brain. The findings in this dissertation were consistent with previous findings from Kaye et al. that describe altered PFAS activity depending on maternal diet. Importantly, this is the first study to directly measure PFOA, PFOS, and PFHxS concentrations in the offspring brain following maternal exposure, with an emphasis on a high-fat diet feeding regimen - an area that is still largely unexplored.
In Manuscripts II and III, environmental PFAS exposure was assessed in banked human liver and serum samples. While most human biomonitoring studies have measured PFAS in serum, few studies have characterized liver PFAS concentration or profile despite the liver being a primary site of PFAS accumulation. Some PFAS undergo little to no metabolism and are associated with prolonged tissue retention, whereas others have been hypothesized to not bioaccumulate in humans. Elevated PFOA and PFOS levels are linked to hepatotoxicity, but limited knowledge exists regarding the other PFAS that accumulate in human liver. In Manuscripts II and III, PFAS concentration and profile were assessed by measuring 54 PFAS in 200+ banked human livers. The analysis used an in-house developed and validated highly sensitive ENVI-CarbTM solid-phase extraction-liquid chromatography-high resolution mass spectrometry (SPE-LC-HRMS) method to detect and quantify both legacy and emerging PFAS, as well as linear and branched PFAS isomers.
Manuscript II specifically characterized PFAS liver accumulation in 211 banked liver specimens from adult donors collected over the past two decades in the United States to assess temporal trends, chemical composition, and individual-level predictors of liver accumulation. Of the 54 PFAS (including linear and branched) analyzed, 25 were detected in ³3 individuals, and 15 were detected in ³30 livers. Markedly, PFAS, as a sum, were detected in 99.5% of individuals. Liver PFAS concentrations demonstrate declining trends over the 24-year sampling period, changing chemical profiles, and interindividual variability driven by age, sex, and liver health. Manuscript II findings provide a comprehensive view of PFAS accumulation in the human liver over time and highlight the importance of considering age, sex, and liver health status when interpreting exposure biomarkers and risk of hepatotoxicity. Furthermore, the data presented herein strongly support that the liver is a major site of deposition for legacy and emerging PFAS. Notably, the decline in PFAS concentrations in livers over the last 24 years exemplifies the effectiveness of PFAS phaseouts (i.e., PFOS and PFOA) and regulatory actions, thereby affecting tissue burden in humans. However, the rise in liver accumulation of unregulated PFAS poses a potential risk for additional hepatic bioaccumulation and may increase the likelihood of exposure-associated adverse health effects in the liver. Within this study, the SPFAS reached levels of ≥30 ng/g in samples collected as recently as 2022. As a result, this work highlights the need for more robust PFAS phaseouts and regulatory action.
Manuscript III characterized PFAS concentrations in donor-matched human liver and serum specimens from a cohort collected in Kansas City, Kansas. Paired liver and serum specimens from the same donor control for exposure, and analysis of tissue-to-serum ratios can provide insight into bioaccumulation and tissue partitioning. In this study, 54 individual PFAS were quantified in matched liver and serum samples from 18 human donors using high-resolution LC-MS/MS. Individuals from this cohort were recruited from a liver clinic and were seeking care for possible liver disease. Thus, some of the study participants were diagnosed as having normal non-fatty liver, whereas others had biomarker-confirmed metabolic dysfunction-associated fatty liver disease (MAFLD). Of the 54 PFAS (including linear and branched) analyzed, 6 were detected in the liver in ³3 individuals, and 8 were detected in serum. Tissue matrix components using protein and lipid determination kits and untargeted proteomics were quantified to evaluate whether the observed liver-to-serum concentration ratios reflect known binding affinities and can be predicted using multivariable linear regression models. Manuscript III findings demonstrate that human donor-matched liver and serum PFAS accumulation patterns are highly variable across all donors and between physiology-based compartments. Paired specimen measurements demonstrate that the liver remains a reservoir for persistent and emerging compounds in humans despite the phase-out of legacy PFAS. Lastly, model predictions identified serum albumin as an independent predictor of liver: serum PFAS distribution (p < 0.05).
Recommended Citation
Agudelo Areiza, Juliana, "PER- AND POLYFLUOROALKYL SUBSTANCES (PFAS) EFFECTS ON TISSUE DISPOSITION, PROTEOME, AND HEALTH EFFECTS" (2025). Open Access Dissertations. Paper 4500.
https://digitalcommons.uri.edu/oa_diss/4500