UC Riverside

Organophosphate flame retardants (OPFR) are semi-volatile additive flame retardants that are found in a variety of products that contain polyurethane foam, textiles, and plasticizers. As products age, these chemicals can leach from their end-use products into the air and adhere to certain environmental media such as dust. Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is an organophosphate ester-based flame retardant widely used within the United States. TDCIPP has been detected in breast milk, hair follicles, and placental tissue in biomonitoring studies, and previous research has found a significant association between TDCIPP exposure and adverse health effects within human populations. Therefore, the global presence of TDCIPP within indoor air and dust poses a potential public health concern, particularly for pregnant mothers who may be exposed to TDCIPP-contaminated dust or air via ingestion or inhalation. However, the potential mechanisms underlying TDCIPP-induced effects on DNA methylation, epigenome plasticity, and cellular metabolism during early embryonic development has yet to be fully understood. Moreover, little is known about whether 1) TDCIPP alters key developmental timepoints regulated by DNA methylation and 2) TDCIPP-induced impacts on DNA methylation impact viability and metabolism within human embryonic cells. Within Chapter 2, we utilized immunohistochemistry, high-content screening, and in situ-based protocols to develop a method that allows us to track 5-mC across multiple stages of development and dose concentrations within early embryogenesis of zebrafish embryos. Within Chapter 3, we utilized bisulfite amplicon sequencing (BSAS), bioinformatics, in vitro assays, and in situ-based protocols to understand how TDCIPP exposure impacts cytosine methylation and 5-mC formation within developing zebrafish embryos. Within Chapter 4, we relied on human embryonic kidney (HEK293) cells to determine whether TDCIPP affects cell viability, reactive oxygen species (ROS) production, global 5-mC methylation, cell membrane integrity, mitochondria abundance, and intracellular ATP production by utilizing a combination of in vitro, in situ, and real-time cell analysis methods. Overall, the findings from this dissertation have increased our understanding about how TDCIPP alters early embryonic development, cellular metabolism, and global DNA/RNA methylation within zebrafish and human cells.