Abstract T P80: Inhibition of Ezh2 Leads to Decreased M1 and Enhanced M2 Microglia Phenotypes

Background: Ischemic stroke results in the activation of microglia, which may polarize toward a pro-inflammatory (M1) phenotype or an anti-inflammatory, neuroprotective (M2) phenotype. Thus, simultaneously suppressing the M1 response and promoting the M2 response could be beneficial in the treatment of stroke. Recently, the epigenetic modulator Jmjd3 has been shown to be essential for M2 polarization. However, Jmjd3 is antagonized by Ezh2 which is associated with M1 polarization. Thus, we hypothesized that inhibition of Ezh2 tilts the balance between Jmjd3 and Ezh2, thereby enhancing polarization toward an M2 phenotype and improved outcome in ischemic stroke. Methods: Mixed glial cultures were isolated from P0.5-P2 C57BL/6J mice and cultured for 14 days before microglial isolation. Microglia were rested for 24 hours before treatment every other day with 6uM GSK343 (Cayman Chemical) or DMSO vehicle control. After 7 days, microglia were stimulated with LPS or IL-4 and RNA was isolated at 4hr and 24hr post-stimulation for qRT-PCR analysis. Results: LPS-induced IL6 and IL1B expression was significantly abrogated by 71% and 53%, respectively (p<0.05), at 24hr when Ezh2 was inhibited. Additionally, Ezh2 inhibition both increased baseline expression of M2-associated genes ARG1, CD206, and IRF4 by 196%, 257%, and 395%, respectively (p<0.05), and rescued their expression in the presence of LPS at 24hr (p<0.05) in which they were otherwise significantly down-regulated. Conclusion: Pharmacological inhibition of Ezh2 limits microglial M1 polarization and enhances M2 polarization.