Abstract 164: Bet Protein Degradation With The Proteolysis-targeting Chimera, Dbet1, Ameliorates Brain Damage And Neurological Deficits After Transient Cerebral Ischemia

Abstract

Introduction: Accumulating evidence indicates that b romodomain and e xtra- t erminal domain (BET) proteins play a pivotal role in the transcriptional regulation of the inflammatory response, and consequently, BET inhibition has emerged as a promising novel therapeutic strategy to reduce inflammation linked to many diseases, including ischemic brain injury. dBET1 is the first BET-targeted proteolysis-targeting chimera (PROTAC) that induces a rapid and efficient deletion of BET proteins in vivo . Hypothesis: In this study, we hypothesized that dBET1 protects against brain damage and neurological deficits in a transient cerebral ischemia mouse model through the regulation of the inflammatory process. Methods: Adult C57BL/6 WT mice were subjected to transient cerebral ischemia surgery (tMCAO) and were administered intraperitoneally with dBET1 (30 mg/kg) or vehicle at 4 and 24 hours after the stroke onset. Infarct volume, neurological deficits, blood-brain barrier integrity, and several inflammatory mediators were examined 48h after tMCAO. Results: The expression level of the BET protein, BRD4, in the cerebral cortex was remarkably lower in the dBET1-treated animals compared to the controls. dBET1 significantly reduced infarct volume (56.2±7.9%, P≤0.01, n=13-14) and improved the neurological performance in the open field test, vertical grid test, and neurological deficit scoring (P≤0.05, n=19-20). In dBET1-treated mice, in both ischemic striatum and cerebral cortex, the inflammation-associated reactive gliosis in astrocytes and microglia was significantly attenuated (P≤0.05, n=6), along with a reduction in stroke-mediated blood-brain barrier damage and neutrophil infiltration. Mechanistically, dBET1 produced a dramatic decrease in the expression levels of pro-inflammatory mediators, while it enhanced levels of anti-inflammatory mediators (P≤0.05, n=6). Conclusion: Overall, this study provides direct in vivo evidence that BET protein degradation with dBET1 suppresses neuroinflammation and leads to anatomical and functional protection against ischemic brain damage. Blocking BET proteins is a promising new strategy to reduce neuroinflammation and eventually improve functional outcomes in stroke.