025 | Understanding pathological remodeling of reactive astrocytes: Epigenetically-controled downregulation of homeostatic genes

Cellular and Molecular Neurobiology

Author: JOSE DANTE DANIEL GOMEZ CUAUTLE | Email: dantegcuautle@gmail.com

Jose Dante Daniel Gomez Cuautle , Alejandro Villareal , Alberto Javier Ramos

1° IBCN UBA-CONICET, Facultad de Medicina, Universidad de Buenos Aires

Astrocytes support neurons metabolically via nutrients, ionic balance, water regulation, neurotransmitter recycling, antioxidants, and the blood-brain barrier. After brain damage, some reactive astrocytes become pro-neurodegenerative, showing inflammation, and dropping their normal roles. We studied epigenetic impacts on homeostatic genes in these reactive astrocytes. Astrocytic cultures were exposed to LPS (25 ng/ml) or HMGB1 (500 ng/ml) for 18 hours, followed by recovery periods of 24, 72 hours, and 7 days. This exposure prompted reactive astrogliosis, evident through GFAP staining, morphological changes, and heightened IL-1B and IL-6 expression via qPCR. Remarkably, acute exposure resulted in enduring astroglial DNA hypermethylation and reduced expression of homeostatic genes (LDHA, glutamine synthase, Kcnj10, Slc16a1, Aqp4). Notably, the key DNA methylation regulator, MAFG-1, along with DNMT1 and DNMT3a, were also upregulated. Reduced homeostatic gene expression correlated with heightened promoter CG island methylation, observed through methylation-sensitive PCR 72 hours after LPS or HMGB1 exposure. Treating cells exposed to LPS or HMGB1 with decitabine, an FDA-approved DNMT1 inhibitor, halted gene downregulation. In summary, our findings reveal that reactive astrocyte pathological remodeling leads to lasting suppression of homeostatic gene expression through critical CG island methylation in promoters. Notably, DNMT inhibitors like decitabine can mitigate this process.