Effects of Developmental Ethanol Exposure on Cerebellar Microglia and Purkinje Cells

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Project Summary Fetal alcohol spectrum disorders (FASD) are the most common cause of non-heritable, preventable mental disability, occurring in almost 5% of births in the U.S. There is no known cure for FASD, and its mechanisms remain unclear. A wide range of cognitive, behavioral, and physical impairments have been reported in FASD, including deficits in behaviors related to the cerebellum. These changes in behavior may arise from ethanol's effects on the cellular level. The sole output of the cerebellum, Purkinje cells, as well as microglia, the immune cells of the Central Nervous System, are both impacted by developmental ethanol exposure. Reduced numbers of both neurons and microglia, as well as alterations in Purkinje cell excitability and firing have been reported. After developmental ethanol exposure, microglia display a phenotype associated with immune activation and release pro-inflammatory factors. Peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists can block this immune activation and have been shown to attenuate some of the inflammatory responses in microglia and reduce Purkinje cell loss in rodents. This suggests that microglia may be a therapeutic target in FASD. Microglia are known to shape neuronal circuit development and connectivity in the cerebellum, which is linked to microglial structural dynamics. How ethanol affects these dynamics and how that impacts microglia- Purkinje cell interactions is unknown. Additionally, it is not yet known when these changes occur and how they are maintained or progressively altered into adulthood. Elucidating how ethanol-induced changes in microglia mediate some of the pathological changes in cerebellar Purkinje cells may be critical for understanding the onset of FASD pathology. Furthermore, modulating microglial survival and activity during ethanol exposure through a PPAR-γ agonist may provide some answers and potential therapies for these diseases. Thus, I hypothesize that ethanol induces neuroimmune changes in cerebellar microglia that alter their dynamics and interactions with Purkinje cells, and reducing microglia-mediated inflammation through a PPAR-γ agonist mitigates the pathological effects of ethanol. To test this hypothesis, I will pursue two aims using a mouse model of FASD. The first will investigate how developmental ethanol and a PPAR-γ agonist affects microglial phenotype over time using in vivo two-photon imaging of microglial dynamics, immunohistochemistry, and quantitative real time PCR. The second will determine if Purkinje cell and microglia interactions are affected throughout life by developmental ethanol exposure and PPAR-γ agonist administration with two-photon imaging, immunohistochemistry, and electron microscopy. These experiments will elucidate the effects of cerebellar microglia on Purkinje cells in the cerebellum after developmental ethanol exposure and assess microglia as a potential target to mitigate disease pathology in a mouse model of FASD.