Besides the loss of blood and oxygen reaching the ischemic tissue, many secondary effects of ischemic stroke can cause additional tissue damage, including inflammation, oxidative stress, and proteomic disturbances. Receptor-interacting serine/threonine kinase 2 (RIPK2) is an important mediator in the post-stroke inflammatory cascade that responds to signals and molecular patterns released by dead or dying cells in the ischemic area. We hypothesize that RIPK2 signaling worsens injury and neurological recovery post-stroke and that global deletion of Ripk2 is protective following ischemic stroke in aged mice. Aged (18-24months) male mice were subjected to permanent middle cerebral artery occlusion (pMCAO). Vertical grid, weight grip, and open field were conducted at baseline and on days 1, 2, 3, 8, 15, and 22 post-stroke. Cognitive tests (novel object recognition and Y-maze) were performed at baseline and day 28 post-stroke. Infarct size was measured using cresyl violet staining, and reactive gliosis was measured using Iba1 and GFAP staining at day 28 post-stroke. Global deletion of Ripk2 (Ripk2-/- ) in aged mice resulted in smaller infarct volume and improved performance on vertical grid and weight grip tests compared to aged wildtype (WT) mice. Additionally, aged Ripk2 -/- mice had less Iba1 staining in the ipsilateral cortex than the aged WT control mice. This study further elucidates the role of RIPK2 signaling in the ischemic cascade and expands our knowledge of RIPK2 in stroke to aged mice. These results support the hypothesis that RIPK2 signaling worsens injury post-stroke and may be an attractive candidate for therapeutic intervention.

Past research has shown that as individuals age, there are decreases in within-network connectivity and increases in between-network connectivity, a pattern known as functional dedifferentiation. While the mechanisms behind reduced network segregation are not fully understood, evidence suggests that age-related differences in the dopamine (DA) system may play a key role. The DA D1-receptor (D1DR) is the most abundant and age-sensitive receptor subtype in the dopaminergic system, known to modulate synaptic activity and enhance the specificity of the neuronal signals. In this study from the DyNAMiC project (N=180, 20-79y), we set out to investigate the interplay among age, functional connectivity, and dopamine D1DR availability. Using a novel application of multivariate Partial Least squares (PLS), we found that older age, and lower D1DR availability, were simultaneously associated with a pattern of decreased within-network and increased between-network connectivity. Individuals who expressed greater distinctiveness of large-scale networks exhibited more efficient working memory. In line with the maintenance hypotheses, we found that older individuals with greater D1DR in caudate exhibited less dedifferentiation of the connectome, and greater working memory, compared to their age-matched counterparts with less D1DR. These findings suggest that dopaminergic neurotransmission plays an important role in functional dedifferentiation in aging with consequences for working memory function at older age.