ObjectiveTo investigate the ameliorative effects of quercetin on neuropsychiatric symptoms associated with vascular dementia （VaD） and to elucidate the molecular mechanism， specifically whether quercetin inhibits pro-inflammatory activation of microglia by modulation of the receptor-interacting serine/threonine-protein kinase 1 （RIPK1）/NOD-like receptor protein 3 （NLRP3）/Caspase-1 signaling pathway， thereby promoting myelin repair in the medial prefrontal cortex （mPFC）. MethodsA C57BL/6J mouse model of VaD with neuropsychiatric symptoms was established by bilateral common carotid artery stenosis （BCAS） combined with chronic restraint stress （CRS）. Mice were randomly divided into a sham group， a model group， low-dose， medium-dose， and high-dose quercetin groups （30， 60， 120 mg·kg^-1·d^-1）， and a fluoxetine group （10 mg·kg^-1·d^-1）. After intervention， depressive- and anxiety-like behaviors were assessed by the sucrose preference test （SPT）， forced swim test （FST）， open field test （OFT）， and elevated plus maze （EPM）. mPFC tissue was collected. Immunofluorescence （IF） was used to detect myelin basic protein （MBP） expression and microglial morphology. Western blot was used to measure the protein level of MBP， myelin oligodendrocyte glycoprotein （MOG）， myelin-associated glycoprotein （MAG）， inducible nitric oxide synthase （iNOS）， CD86， RIPK1， phosphorylated RIPK1 （Ser166）， NLRP3， and Caspase-1. Enzyme-linked immunosorbent assay （ELISA） was used to determine the level of tumor necrosis factor-alpha （TNF-α）， interleukin-6 （IL-6）， and interleukin-1β （IL-1β）. ResultsCompared with the sham group， the model group exhibited significant depressive- and anxiety-like behaviors （P<0.01）， significantly decreased protein expression of MBP， MOG， and MAG in the mPFC （P<0.01）， activated microglia （characterized by enlarged cell bodies， reduced protrusions， and upregulated iNOS and CD86 expressions， P<0.01）， and significantly elevated p-RIPK1/RIPK1 ratio， NLRP3， Caspase-1 protein expression， and level of TNF-α， IL-6， and IL-1β （P<0.01， P<0.05）. Compared with the model group， the quercetin treatment （especially at medium and high doses） significantly ameliorated these behavioral abnormalities （P<0.05， P<0.01）， increased the expression of MBP （protein and fluorescence intensity）， MOG， and MAG in the mPFC （P<0.05， P<0.01）， suppressed excessive microglial activation （characterized decreased cell bodies， increased protrusions， and downregulated iNOS and CD86 expressions， P<0.01）， and significantly reduced the p-RIPK1/RIPK1 ratio， NLRP3， Caspase-1 protein expression， and inflammatory cytokine levels （P<0.01）. ConclusionQuercetin effectively alleviates neuropsychiatric symptoms in VaD mice. Its mechanism may be associated with the inhibition of microglial inflammatory activation mediated by the RIPK1/NLRP3/Caspase-1 signaling pathway， thereby promoting myelin repair in the mPFC region.

OBJECTIVETo determine the physical and magnetic properties of superparamagnetic iron oxide (SPIO) nanoparticle prepared in our laboratory and evaluate its possibility for use as contrast agents in magnetic resonance imaging (MRI).

METHODSThe SPIO nanoparticle was obtained by means of classical coprecipitation in dextran solution and its size determined by electron microscopy and photon-correlation spectroscopy. The iron content was determined by phenanthroline photometry, and T(2) values as well as relaxivity evaluated with a clinical MR system at 1.5T.

RESULTSDextran-coated magnetite particles with a hydrodynamic diameter of 85.9 nm were prepared. The iron core size was 15 nm and the formation of Fe(3)O(4) crystal in SPIO nanoparticles was confirmed by X-ray diffraction (XRD) analysis. These particles possessed some characteristics of superparamagnetic and show a smaller spin-spin relaxation, with relaxivity and saturation magnetization of 0.1567 mmol(-1)/ms(-1) and 80 emu/g Fe, respectively.

CONCLUSIONSA stable SPIO nanoparticle with a dextran coating have been developed, and in vitro evaluation of its physical and magnetic properties suggests its potential for use as the contrast agent in MRI.

Humans ; Iron ; chemistry ; Magnetic Resonance Imaging ; methods ; Nanoparticles ; chemistry ; Oxides ; chemical synthesis ; chemistry ; X-Ray Diffraction