Abstract 31: The Angiotensin Type 2-receptor Agonist, Compound 21, Provides Neuroprotection After Ischemia Reperfusion Injury Through Interleukin 10 Upregulation

Abstract

Introduction: We and others have shown that the angiotensin type 2 (AT2) receptor agonist, compound 21 (C21), provides neuroprotection and enhances recovery in rodent stroke models yet the mechanism involved is not known. Moreover, C21 treatment is associated with an anti-inflammatory response. Here we tested the hypothesis that C21 mediates neuroprotection by upregulating the neuroprotective and anti-inflammatory cytokine interleukin (IL)-10. Methods: Wistar rats (n=16) were subjected to 3 h MCA suture occlusion and treated at reperfusion with C21 (0.03 mg/kg) ± IL-10 neutralizing antibody (0.1 μg/kg) both given I.P. Endpoints at 24 h included: Infarct size, behavioral outcome, and molecular analysis. Primary rat neurons were used to test the direct neuroprotective effect of C21 in vitro. Results (Table): C21 treatment upregulated IL-10 expression (1797±89 vs 1333±84 pg/mg) and increased IL-10 downstream survival signals, STAT3 and AKT phosphorylation, in the stroked hemisphere compared to saline. Anti-IL-10 co-treatment blocked the C21 induced reduction in infarct size and inflammatory/apoptotic markers, and blunted the improvement in behavioral outcome, as well as survival signal activation. In vitro (n=4), C21 treatment failed to directly protect ischemic neurons against oxygen glucose deprivation/reperfusion (OGD/R) insult as measured by LDH release (other cell death markers are to be analyzed), but was able to upregulate IL-10 in normoxic neurons (0.3±0.02 vs 0.23±0.01) suggesting a potential indirect neuroprotective effect. Conclusion: C21 provides acute neuroprotection after ischemia reperfusion injury through neuronal IL-10 upregulation. Further understanding of the mechanism of action will pave the way for translating C21 and future AT2 agonists to the clinical stroke setting.