Abstract TP272: Selective Inhibition of Histone Deacetylase 3 Decreases Cerebral Edema and Blood-Brain Barrier Leakage

Abstract

Introduction: Histone deacetylase 3 (HDAC3) has been implicated as neurotoxic in several neurodegenerative conditions. However, its role in ischemic stroke has not been thoroughly explored. In this study, we examined HDAC3 expression after stroke and tested whether selective inhibition of HDAC3 decreases cerebral edema and blood-brain barrier (BBB) leakage after ischemia. Methods: To examine HDAC3 expression over time, adult male Wistar rats (n=6/group) were subjected to middle cerebral artery occlusion (MCAO) and sacrificed at different time points after stroke. Another set of adult male Wistar rats was subjected to 2-h MCAO, and randomly selected animals were treated i.p. with either vehicle (1% Tween 80) or a selective HDAC3 inhibitor (RGFP966, 10 mg/kg) at 2 and 24 h after MCAO. Behavioral tests were performed, and infarct volumes and cerebral edema were measured. Evans blue dye (EBD) assay was employed to assess BBB leakage. Immunostaining for HDAC3, CD31, claudin-5, occludin, and ZO-1; and Western Blot for TNF-alpha and matrix metalloproteinase-9 (MMP9) were performed. Results: Total and neuronal HDAC3 significantly increased in the peri-infarct cortex as early as 3 hours after ischemia. HDAC3 levels continued to be significantly elevated at 3 days and returned to baseline at 7 days. Selective HDAC3 inhibition improved functional outcome (p=0.01) and reduced infarct volumes (p<0.001). Compared to vehicle control, RGFP966 treatment significantly decreased cerebral edema (p<0.001) as well as BBB leakage, as measured by EBD assay. Immunostaining showed that RGFP966 significantly increased the expression of tight junction proteins (claudin-5, occludin, and ZO-1) in the peri-infarct area compared to vehicle control group. Western Blot showed that RGFP966 treatment significantly decreased the expression of TNF-alpha and MMP9 in the ischemic brain. Conclusions: HDAC3 is upregulated in the ischemic brain as early as 3 hours after stroke. Early administration of a selective HDAC3 inhibitor improves neurological functional outcome and decreases infarct volume, cerebral edema, and BBB leakage. BBB protection by selective inhibition of HDAC3 is mediated in part by upregulation of tight junction proteins and attenuation of TNF-alpha and MMP9.