Date of Award

2021

Document Type

Dissertation

Degree Name

Philosophy (Ph.D)

Department

Pharmaceutical Sciences

First Advisor

Diane Hardej

Second Advisor

Blase Billack

Third Advisor

Louis Trombetta

Abstract

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are members of a family of compounds known as perfluoroalkyl substances (PFAS). This study aimed to determine the protective role of Nrf2 against the toxicity of these agents. Nrf2-/- and wild-type astrocytes from C57BL/6 mice were exposed to PFOS (75-600µM) and PFOA (400-1000µM) for 24 hours. Lactate dehydrogenase (LDH) and Neutral Red (NR) uptake assays showed cytotoxicity being significantly greater in nrf2-/- than in the wild-type astrocytes. Concentrations of 600µM PFOS and 800µM PFOA showed significant increases in reactive oxygen species, lipid peroxidation, and TUNEL positive cells in both cells types with significantly higher levels in nrf2-/- astrocytes as compared to wild-type astrocytes. The GSH/GSSG ratio was significantly decreased in nrf2-/- astrocytes when compared to wild-type astrocytes. Additionally, PFOS and PFOS caused dramatic ultrastructural alterations to the mitochondria. BHT pretreatment in wild-type cells decreased ROS production with exposure to both agents. Nrf2-/- and wild-type C57BL/6 male mice, were also used to address the toxicity of PFOS and PFOA as in vivo models. Brain and liver were chosen as target organs with the goal to assess Nrf2 involvement in each organ. 5 mg/kg PFOS and 5 mg/kg PFOA were used to treat nrf2-/- C57BL/6 mice for 15 days and wild-type C57BL/6 mice for 30 days. Animal weights, organ weights, hematoxylin & eosin stain, trichrome stain, GSH/GSSG ratio, 4-hydroxynonenal (4HNE), and apoptosis via using TUNEL assay were evaluated after exposing the in vivo models to PFOS and PFOA. PFOA and PFOS treatments resulted in toxicity in the liver with regard to the above parameters with toxicity being significantly greater in nrf2-/- mice than WT mice. No toxicity was detected in the hippocampus of either WT or nrf2-/- mice. Data from the current study concludes that PFOA and PFOS are toxic to astrocytes and to the liver in C57BL/6 mice and that nrf2-/- models are more sensitive to toxicity by these agents.

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