Abstract TP259: Neuroprotective Effects Of Ripk2 Deficiency In Experimental Ischemic Stroke

Abstract

Background: Receptor-interacting serine-threonine protein kinase 2 (Ripk2) is involved in the signaling pathways of members of the NOD family of cytosolic pattern recognition receptors. Ripk2 has been implicated in the caspase-1 pathway of hypoxia and ischemia-induced neuronal cell death, as well as the pathology of neuroinflammatory diseases like multiple sclerosis. Ischemic stroke is characterized by brain injury resulting from initial hypoxia/ischemia-induced cell death and secondary neuroinflammation. Hypothesis: Since Ripk2 is implicated in both pathways, we hypothesized that the genetic deletion of Ripk2 will improve outcomes for animals after experimental stroke. Methods: We utilized Ripk2 knockout ( Ripk2 -/- ) mice (3-4 months old) and subjected them to 45min of transient middle cerebral artery occlusion (tMCAO) along with wild-type (WT) control littermates. Infarct size was measured at 24h by TTC staining. RNA was isolated from the ipsilateral and contralateral cortices for RT-qPCR. Weight grip test, vertical grid test, and open field behavioral tests were conducted before and up to 21 days after tMCAO with novel object recognition and Y-maze tests occurring at day 28. Results: After 24h, Ripk2 -/- mice had significantly smaller infarct sizes than wild-type (WT) mice. Ripk2 -/- mice also had much lower expression of proinflammatory cytokines ( Tnfα, Il1β, and Il6 ) and chemokines ( Ccl2 and Cxcl1 ) in the ipsilateral cortex relative to WT, implicating a diminished proinflammatory response to ischemia/reperfusion injury in Ripk2 -/- animals. Ripk2 -/- mice displayed significantly better neurological deficit scores compared to WT at 24h, 48h, 7d, 14d, and 21d post-tMCAO. Ripk2 -/- mice also performed much better than WT at acute time points in a battery of behavioral tests, such as the weight grip test, vertical grid test, and open field test. Neurological assessment via novel object recognition and Y-maze tests showed no difference between genotypes at 28d. Conclusions: Our findings support the hypothesis that Ripk2 plays a detrimental role in the pathology of ischemic stroke. Understanding Ripk2’s role in stroke pathology may reveal a novel therapeutic target for the treatment of ischemic stroke.