Abstract 27: Mir-494 Elicits Th1 Shift and Neurotoxic Responses to Promote Acute Ischemic Brain Injurythrough Targeting Hdac2

Abstract

Background: T helpler type 1 (Th1)-shifted inflammation after acute ischemic stroke (AIS) affects neurological function. However, the molecular switch is poorly defined. The objective of this study is to identify functionally important and therapeutically relevant pathways downstream of microRNA (miR)-494 in modulation of neurotoxic Th1 shift after AIS. Methods: Blood samples from 76 AIS patients and 52 heathy controls were collected, and miR-494 levels were detected by quantitative real-time PCR. Overexpression or knockdown of microRNA-494 in vivo and in vitro was achieved by lentivirus vector. Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion and cortical neurons were subjected to oxygen-glucose deprivation (OGD). Chromatin immunoprecipitation sequencing using anti-HDAC2 antibody was performed to assess the mechanism behind the regulation of transcription. Results: MiRNA-494 levels were increased in lymphocytes of AIS patients, and is inversely correlated with NIHSS score. Conversely, in vivo inhibition of miR-494 by intravenous administration markly improved the neuronal survival and neurological outcome of ischemic mice. Moreover, lymphocytic miR-494 level of AIS patients is specially positively associated with a key Th1 cytokine interferon (IFN)-γ. Enforced expression of miR-494 actually leads to Th1 shift in vitro , and this conditioned medium advanced neuronal death and axonal damage upon OGD. Mechanistically, histone deacetylase 2 (HDAC2) is a direct miR-494 target whose repression blunted miR-494 antagomir-reduced Th1-shift and brain injury after ischemic stroke. Conclusions: This work illustrates a novel miR-494/HDAC2 axis in promoting Th1-shifted inflammation after AIS, represents a potential therapeutic target.