NIH Plunk The Effects of Gestational and Lactational Exposure to Perfluorohexanoic Acid on Cerebellum Development in the Mouse - Project Summary Perfluorohexanoic acid (PFHxA) is a short-chain per- and polyfluoroalkyl substance (PFAS) used in industrial and consumer products, such as aqueous film forming foam (AFFF), food wrappers, stain repellants on furniture, and makeup. PFHxA use is not regulated in the United States. PFHxA is found ubiquitously in the environment significantly contaminating soil and water resulting in humans being exposed through ingestion. Epidemiology literature has reported PFHxA in maternal serum and breastmilk, and PFHxA crosses the placenta. Together, these data demonstrate that fetuses are exposed through the placenta and infants through breast feeding. In humans, PFHxA accumulates higher in the cerebellum than in most other brain regions. The cerebellum is critical to both motor and cognitive functions, is the home of 50% of the neurons, has a unique cytoarchitecture, and develops later than other regions making it an important region to study in the context of developmental toxicant exposures. While the health effects of PFHxA are still largely unstudied, it is well established that legacy PFAS alter immune function, including suppressing peripheral immune responses. However, the effects of PFHxA on the immune cells of the brain, microglia, have not been investigated. Microglia have the same mesodermal origins as peripheral immune cells, suggesting that developmental exposures may target microglial function. Interestingly, microglia in the cerebellum may be particularly sensitive to neurotoxicants compared to microglia in other brain regions as they have a unique transcriptomic profile. In addition to immune function, microglia play a critical role in brain development by aiding in angiogenesis, providing factors for myelin development, and pruning synapses thereby remodeling neural circuits. Thus developmental PFHxA exposure could affect their immune and neuroanatomical functions. Despite the importance of microglia in brain development and evidence that PFHxA enters the brain, PFHxA has not been investigated in the mammalian nervous system. Based on evidence from epidemiology studies on PFHxA as well as long-chain PFAS, I hypothesize that gestational and lactational exposure to PFHxA in a mouse model disrupts cerebellar development, affecting neuronal and glial phenotypes, as well as motor activity. Microglia may be uniquely affected by this exposure, becoming immunosuppressed. To test this hypothesis, I will pursue two aims using a mouse model representing human exposure to PFHxA during gestation and lactation. The first aim will investigate how gestational and lactational exposure to PFHxA affects neuron and glia phenotypes using RNA sequencing and immunohistochemistry (IHC). This aim will also investigate how this exposure affects animal behaviors, especially those related to the cerebellum. The second will determine if microglia are altered at the genetic, protein, and dynamic level by using RNA sequencing, IHC, and two-photon microscopy. These experiments will show, for the first time, whether PFHxA exposure during brain development is neurotoxic and will also guide regulators from multiple agencies when considering PFHxA exposure to humans.
