Background: Inflammasome in microglia are critical to elicit inflammatory cascades in ischemic stroke. Histone deacetylases 3 (HDAC3) regulate acetylation states of histone and non-histone proteins and could be a powerful regulator of inflammatory process in stroke.
Methods: Primary microglia, BV2 cells subjected to oxygen glucose deprivation (OGD) or LPS stimulation were applied to mimic inflammatory response in vitro. Middle cerebral artery occlusion (MCAO) model were applied to mimic acute stroke in vivo. Ischemic infarct volume and neurological functions were evaluated through 2,3,5-triphenyltetrazolium chloride (TTC) staining and Neurological Severity Scores (NSS) respectively. Expression of HDAC3, AIM2 inflammasome were detected by western blotting, PCR. Immunofluorescence was used to detect M1/M2 polarization. Luciferase activity of absent in melanoma 2 (AIM2) reporter promoter constructs was measured by fluorospectrophotometer. AIM2 knockdown and over-expression leti-virus were constructed to decrease or increase AIM2 expression. HDAC3 inhibitor RGFP966 was used to inhibit acetylation activity of HDAC3.
Results: HDAC3 is widely distributed in cerebral cortex, lateral ventricular , hippocampus, cerebellar cortex ; HDAC3 and AIM2 expression were enhanced in LPS stimulated-microglia and MCAO model. A marked stimulatory effect of RGFP966 on H3K9Ac was observed in nuclear extracts form BV2 cells at the dosage of 15 uM. Treatment of RGFP966 increased both IL-4-stimulated expression of Ym-1 and CD206 at 4 h, 10 h, 24 h, 48 h. AIM2, NLRP-1 and NLRP3 significantly increased in MCAO+Vehicle group compared to sham group, but decreased in MCAO+RGFP966 group. RGFP966 inhibited the elevation of circulatory IL-18 and IL-1β induced by stroke. RGFP966 decreased infracted size and alleviated neurological deficit.
Conclusions: HDAC3i alleviated ischemic stroke injury through modulating AIM2 inflammasome and microglia polarization. Selective HDAC3 inhibitor-RGFP966 could be a potential medication for combating ischemic brain injury.