Abstract WP24: Pharmacological Hypothermia (PH) Promotes Plasticity Through RNA Binding Motif 3 (RBM3)-Mediated Cold Shock Pathway Following Ischemic Stroke

Abstract

Background: Phenothiazine, including chlorpromazine and promethazine (C+P), induce hypothermia and neuroprotection after stroke. Immediately after stroke onset, there is a neuroplasticity window within which rehabilitation is especially effective. Recent studies have indicated that hypothermia-induced neuroplasticity involves the RBM3-mediated cold shock pathway, but it is unknown whether this pathway participates in neuroprotection and neuroplasticity in the context of pharmacological hypothermia (PH) induced by C+P after stroke. Methods: Adult Sprague-Dawley rats were divided in 3 groups: (1) sham; (2) stroke; (3) stroke treated with C+P before reperfusion. Long-term functional outcomes were determined by grid walk tests, rota-rod tests, beam balance tests, forelimb placing tests, adhesive tape touch and adhesive tape removal at 7 through 28 days. mRNA and protein quantities of cold shock pathway [RBM3, eukaryotic initiation factor 2 alpha (eIF2α), and reticulon 3 (RTN3)] and neuroplasticity [synaptophysin (SYN), post-synaptic density protein-95 (PSD-95), Tau, and recombinant growth associated protein 43 (GAP43)] were assessed by real-time PCR and western blot at day 1, 7 and 28 after reperfusion. Additionally, expression of RTN3 and eIF2α, and the co-localization of SYN and PSD95 was measured in primary neurons which subjected to oxygen/glucose deprivation (OGD) with RBM3 knockdown. Results: PH significantly improved functional outcomes at day 7 and 28. At day 1, mRNA and protein expression of RBM3 and RTN3 were significantly increased, and eIF2α was dephosphorylated by PH after stroke. mRNA and protein levels of SYN, Tau and GAP43 were all increased by PH at day 7 and 28. Furthermore, in OGD with shRBM3 group, levels of RTN3 and eIF2α dephosphorylation were significantly decreased, and the co-localization of SYN and PSD95 were significantly reduced compared with OGD group at 24 h without shRBM3. Conclusion: Our study has provided evidence, for the first time, for a novel mechanism underlying hypothermia in which the neuroplasticity and rehabilitation were achieved after ischemic stroke. Our findings suggest that the RBM3-induce cold shock pathway is a potential target of hypothermia for neuroprotection and neurorehabilitation.