Liver X receptors (LXRs) are nuclear receptors involved in the regulation of lipid metabolism and inflammatory responses in the central nervous system. Defects in cholesterol homeostasis contribute to the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and Huntington's disease. Inflammatory responses could enhance the neurodegenerative process or act independently. The natural and synthetic LXR agonists induce the transcriptional activity of LXR target genes, thus attenuate the imbalance of cholesterol metabolism and overactivation of microglia and astrocytes in inflammation and are widely used in a variety of neurodegenerative diseases animal models. By developing more specific, potent, penetrable, and functional LXR agonist may lead to a better curative effect for neurodegenerative diseases and avoidance of potentially deleterious side effects. Here, we focus on recent advances in our understanding of the role of LXRs and their agonists in cholesterol homeostasis, inflammation, and the potential therapeutic effects in neurodegenerative diseases.

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Cerebellar Purkinje cell and granule cell development are coordinated by Bergmann glia, and are particularly sensitive to ethanol (EtOH) exposure. The liver X receptor (LXR) plays important roles in Bergmann glial development. However, the effect of LXR activation on EtOH-mediated impairment of Bergmann glia and subsequently on Purkinje cell dendritogenesis remains undetermined. Therefore, using immunohistochemistry, quantitative real-time PCR and Western blot, we tested the possible protection of LXR agonist T0901317 (T0) on Bergmann glia and Purkinje cell dendritogenesis in mice exposed to ethanol. Results showed that a brief exposure of EtOH on postnatal day (PD 5) significantly decreased the average body weight of mice at PD 6 without alteration in the brain weight. In EtOH-exposed mice, the number of migrating granule cells in the molecular layer was significantly decreased, and this effect was attenuated by pretreatment of T0. EtOH exposure also resulted in the significant reduction of calbindin-labeled Purkinje cells, their maximum dendrite length, and impairment of Purkinje cell dendritogenesis. Furthermore, EtOH induced the activation of microglia in the Purkinje cell layer and impaired the development of Bergmann glia. However, pretreatment of T0 effectively blocked all of these responses. These responses were found to be mediated by the inhibition of upregulated levels of β-catenin and transcription factor LEF1 in the cerebellum. Overall, the results suggest that activating LXRs on postnatal mice exposed to EtOH is protective to Bergmann glia, and thus may play a critical role in preventing EtOH-induced defects during cerebellar development.

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