Abstract TP316: Histone Deacetylase 3 as a Novel Therapeutic Target for Ischemic Stroke

Abstract

Introduction: Histone deacetylase 3 (HDAC3) has been implicated as neurotoxic in several neurodegenerative conditions. However, the role of HDAC3 in ischemic stroke has not been thoroughly explored. We tested the hypothesis that selective inhibition of HDAC3 after stroke affords neuroprotection. Methods: To investigate the effects of ischemia on HDAC3 expression, adult male Wistar rats (n=6/group) were subjected to middle cerebral artery occlusion (MCAO) and sacrificed 24 h later. Double immunohistochemistry was performed with antibodies against HDAC3 and NeuN (a neuronal marker). To investigate whether selective HDAC3 inhibition affords neuroprotection after stroke, another set of rats (n=7/group) was subjected to 2-h MCAO, and randomly selected animals were treated 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 at 3 h, 1 d, and 3 d after MCAO. Rats were sacrificed 3 d after MCAO. Infarct volumes were measured with H&E. Immunostaining for Akt, TNF-alpha, toll-like receptor 4 (TLR4), cleaved poly (ADP-ribose) polymerase (PARP), and TUNEL assays were performed by blinded investigators. Results: The numbers of HDAC3+ cells and HDAC3+/NeuN+ neurons were increased in the peri-infarct cortex compared to the contralateral cortex (p<0.05). Total and neuronal HDAC3 expressions were positively and significantly correlated with infarct volumes (r=0.8, p<0.001; r=0.6, p=0.03; respectively). Selective HDAC3 inhibition improved functional outcome (p=0.01) and reduced infarct volume (p<0.001). RGFP966 treatment reduced apoptosis—as measured by the numbers of TUNEL+ and cleaved PARP+ cells—in the ischemic brain (p<0.05). Selective HDAC3 inhibition reduced total and neuronal TNF-alpha and TLR4 in the ischemic border compared to vehicle control (p<0.05). RGFP966 treatment also increased Akt expression in the ipsilateral cortex (p=0.007). Conclusions: HDAC3 is upregulated after stroke and correlates with infarct volumes. Selective HDAC3 inhibition after stroke improves functional outcome and decreases infarct volume. The neuroprotective effects of HDAC3 inhibition are associated with a reduction in apoptosis and attenuation of inflammation.