Ifi27l2a as a therapeutic target for stroke - Abstract Microglia (MG), the resident innate immune cells of the brain, play a critical role in the inflammatory response to stroke. Stroke predominantly affects older individuals. Unfortunately, with aging, MG become increasingly dysfunctional and, in conjunction with other cell types in the brain, contribute to worse outcome following stroke. However, the role of MG in the stroke brain is not exclusively bad, as MG also contribute to repair and recovery following stroke. Thus, the selective regulation of the MG inflammatory response at specific times in the aged brain could be of great therapeutic value for stroke patients. Using single-cell transcriptomic analysis (scRNAseq), we discovered a gene (interferon alpha-inducible protein 27-like protein 2A; Ifi27l2a) that was selectively and highly upregulated in aged MG and further upregulated in MG following stroke. Our initial analysis showed a positive correlation between Ifi27l2a expression and specific sets of pro-inflammatory cytokine and senescence-related genes. These and other studies suggested that Ifi27l2a might play a critical regulatory role in promoting the inflammatory response of MG in the post-stroke brain of mice. Analysis of human brain samples also showed increased expression of IFI27L2 (human isoform) in stroke brain, enhancing the translational relevance of our findings. Next, to define the functional role of Ifi27l2a, we performed a combination of in vitro and in vivo studies, which established a compelling causative role of Ifi27l2a in promoting MG proinflammatory function and in worsening stroke injury. We also established the potential for Ifi27l2a overexpression to induce matrix metalloproteinase (MMP) expression/activity and reactive oxygen species (ROS) production, which are two driving factors in blood brain barrier (BBB) disruption. Finally, using a mouse stroke model, we showed that partial deletion of Ifi27l2a (Ifi27l2a+/- mice) led to significantly improved outcome, as evidenced by reduced infarct volume and reduced microglial activation. Together, these data provide the first direct evidence for Ifi27l2a in modulating MG functionality and brain injury following stroke and establish Ifi27l2a-dependent signaling as a new therapeutic target. Our proposed aims will test the overall hypothesis that increased MG Ifi27l2a contributes to an exaggerated inflammatory response to ischemic stroke in the aged brain and that reducing MG Ifi27l2a expression can attenuate neuroinflammation, reduce BBB disruption, and improve outcome following stroke. If successful, these studies will lay the foundation for a novel strategy based on the selective attenuation of MG pro-inflammatory signaling in the treatment of stroke or other pathologies associated with neuroinflammation.
