Abstract WP300: Ifi27l2a is a Novel Target for Dampening Microglial Inflammation Following Stroke

Microglia play a critical role in initiating and spreading inflammation and are involved in the chronic recovery phase following stroke. Microglia express multiple interferon-stimulated genes (ISGs) in response to inflammatory cues, including Ifi27l2a . However, the specific roles of individual ISGs, such as Ifi27l2a , have not been well-studied in the context of stroke. We tested the hypothesis that induction of Ifi27l2a in microglia contributes to the pro-inflammatory response following stroke.

We used Ifi27l2a heterozygote (Het) mice to determine the effect of partial reduction of Ifi27l2a in primary microglia and in an experimental stroke model. Primary microglia isolated from WT and Het brains were stimulated with LPS to investigate the role of Ifi27l2a in microglial activation in vitro . Permanent distal middle cerebral artery occlusion (pdMCAO) was performed in young mice (WT vs Het, male, 3 months old) to determine whether deletion of Ifi27l2a reduces microglial activation and improves functional outcome following stroke.

We found that LPS-induced expression of Il1b was markedly reduced in Het microglia compared to WT microglia (n=6, p<0.01). Moreover, other inflammation marker genes ( Il1a and Tnfa ) were significantly reduced in Het microglia compared to WT microglia in LPS-stimulated conditions (n=6, p<0.05). The levels of inducible forms of Mmp3 and Mmp9 , which are responsible for blood-brain barrier (BBB) dysfunction, were significantly reduced in Het microglia (n=3, p<0.01). However, Mmp2 expression was not altered by deletion of Ifi27l2a. These findings suggest that Ifi27l2a is involved in the process of BBB dysfunction and microglial inflammation. Lastly, gliosis (microgliosis and astrogliosis) was significantly reduced at 14 days post-stroke in the thalamus of Het brains, a known site of secondary injury in pdMCAO model (n=6, p<0.05). Foot fault tests showed improved functional outcome in Het mice (n=4-6, p<0.05).

Ifi27l2a appears to be a critical molecular switch for inflammatory mechanisms in the post-stroke brain. These findings suggest that interventions targeting Ifi27l2a regulation (even partial inhibition) could reduce harmful inflammation and promote improved functional outcome following stroke.