DDAH1 promotes neurogenesis and neural repair in cerebral ischemia

Choline acetyltransferase(ChAT)-positive neurons in neural stem cell(NSC)niches can evoke adult neurogenesis(AN)and restore impaired brain function after injury,such as acute ischemic stroke(AIS).However,the relevant mechanism by which ChAT+neurons develop in NSC niches is poorly understood.Our RNA-seq analysis revealed that dimethylarginine dimethylaminohydrolase 1(DDAH1),a hydrolase for asymmetric NG,NG-dimethylarginine(ADMA),regulated genes responsible for the synthesis and transportation of acetylcholine(ACh)(Chat,Slc5a7 and Slc18a3)after stroke insult.The dual-luciferase reporter assay further suggested that DDAH1 controlled the activity of ChAT,possibly through hypoxia-inducible factor 1α(HIF-1α).KC7F2,an inhibitor of HIF-1α,abolished DDAH1-induced ChAT expression and suppressed neurogenesis.As expected,DDAH1 was clinically elevated in the blood of AIS patients and was positively correlated with AIS severity.By comparing the results among Ddah1 general knockout(KO)mice,transgenic(TG)mice and wild-type(WT)mice,we discovered that DDAH1 upregulated the proliferation and neural differentiation of NSCs in the subgranular zone(SGZ)under ischemic insult.As a result,DDAH1 may promote cognitive and motor function recovery against stroke impairment,while these neuroprotective effects are dramatically suppressed by NSC conditional knockout of Ddah1 in mice.

Mid-infrared active metasurface based on Si/VO_(2) hybrid meta-atoms

Active metasurfaces whose optical properties can be tuned by an external stimulus have attracted great research interest recently. Introduction of VO_(2)phase change material in all-dielectric metasurfaces has been demonstrated to modulate the resonance wavelength and amplitude in the visible to near-infrared wavelength range. In this study, we report a mid-infrared active metasurface based on Si∕VO_(2)hybrid meta-atoms. By incorporating VO_(2)thin films in different locations of Si∕VO_(2)all-dielectric nanodisks, we demonstrate different modulation amplitude of the electric or magnetic resonance scattering cross sections, leading to drastically different transmission spectrum upon VO_(2)insulator to metal phase transition. The physical mechanism is originated from the field profiles of the resonance modes, which interact with VO_(2)differently depending on its locations. Based on this mechanism, we experimentally demonstrated a large modulation of the transmittance from 82% to 28% at the 4.6 μm wavelength. Our work demonstrates a promising potential of VO_(2)-based active all-dielectric metasurface for mid-infrared photonic applications such as infrared camouflage, chemical/biomedical sensing, optical neuromorphic computing, and multispectral imaging.