Purinergic Preconditioning Induces Epigenomic and Transcriptomic Changes Resembling Epilepsy-associated Microglial States

Microglia, as the main immune effector cells in the central nervous system (CNS), play a crucial role in a diverse range of neuropathological conditions through their exacerbated activation. Microglial inflammatory responses can be influenced by prior exposures to noxious stimuli, such as increased levels of extracellular adenosine and ATP. These conditions are characteristic of brain insults like epileptic seizures and could potentially shape subsequent responses through epigenetic regulation. In this study, we investigated DNA methylation and expression changes in microglia-like cells differentiated from monocytes following ATP-mediated preconditioning. First, during differentiation, we demonstrate that microglia-like cells acquire standard microglial features, including whole transcriptomes and methylomes like in vivo profiles. We show a predominant DNA demethylation in genomic sequences enriched in binding motifs of microglia lineage transcription factors like PU.1, consistent with the relevance of this factor in in vivo microglia. TLR-mediated activation, after a first exposure to ATP, promotes exacerbated pro-inflammatory activation compared to cells not pre-exposed to ATP. These changes are accompanied by DNA methylation and transcriptional reprogramming associated with the acquisition of trained immunity and altered immune-related functions such as with antigen presentation, phagocytosis and cytokine signaling. Finally, the reprogramming associated with ATP-mediated preconditioning leads to profiles found in microglial subsets linked to epilepsy. Purine-driven microglia immune preconditioning drives epigenetic and transcriptional changes that could contribute to altered functions of microglia during seizure development and progression, particularly associated with neuroinflammation.