ABSTRACT
Objective To investigate the effect of cholesterol on the proliferation and differentiation of neural stem cells (NSCs) in ob/ob obese mice, and to explore the possible mechanism of central nervous systym dysfunction caused by obesity. Methods Selected 64-month-old ob/ob and wild type (WT) mice, and cell proliferation antigen (Ki67) and doublecortin (DCX) immunofluorescenct staining were used to detect ob/ob mice lateral ventricle subventricular zone (SVZ) neurogenesis level. Cultured SVZ NSCs isolated from 184-month-old ob/ob and WT mice, and BrdU incorporation experiment and β-III-tubulin (Tuj1) immunofluorescent staining were employed to detect the self-renewal and differentiation ability of NSCs. Matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI- MS)was used to detect the lipid distribution in 4-month-old ob/ob and WT mice brain tissues, and measure the changes of cholesterol(ST) content and the expression genes related to cholesterol synthesis. Cultured 15 WT postnatal day 0(P0) mouse SVZ NSCs in vitro and electrotransfected with the small interfering RNA(siRNA) sequence of cholesterol synthesis rate-limiting enzyme 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (Hmgcr) verified the knockdown efficiency, to detecte the effect of Hmgcr gene knockdown on NSCs by BrdU incorporation experiment and Tuj1 immunofluorescent staining. Results Compared with the WT mice, the number of Ki67
ABSTRACT
The ongoing SARS-CoV-2 pandemic has brought an urgent need for animal models to study the pathogenicity of the virus. Herein, we generated and characterized a novel mouse-adapted SARS-CoV-2 strain, named MASCp36, that causes severe acute respiratory symptoms and mortality in standard laboratory mice. Particularly, this model exhibits age and gender related skewed distribution of mortality akin to severe COVID-19, and the 50% lethal dose (LD50) of MASCp36 was 58 PFU in 9-month-old, male BALB/c mice. Deep sequencing identified three amino acid substitutions, N501Y, Q493H, and K417N, subsequently emerged at the receptor binding domain (RBD) of MASCp36, during in vivo passaging. All three mutations in RBD significantly enhanced the binding affinity to its endogenous receptor, mouse ACE2 (mACE2). Cryo-electron microscopy (cryo-EM) analysis of human ACE2 (hACE2) or mACE2 in complex with the RBD of MASCp36 at 3.1 to 3.7 angstrom resolution elucidates molecular basis for the receptor-binding switch driven by specific amino acid substitutions. Interestingly, N501Y and Q493H enhanced the binding affinity to human ACE2 (hACE2); while triple mutations N501Y/Q493H/K417N decreased affinity to hACE2, thus led to the reduced infectivity of MASCp36 to human cells. Our study not only provides a robust platform for studying the pathogenesis of severe COVID-19 and rapid evaluation of coutermeasures against SARS-CoV-2, but also unveils the molecular mechanism for the rapid adaption and evolution of SARS-CoV-2 in human and animals. One sentence summaryA mouse adapted SARS-CoV-2 strain that harbored specific amino acid substitutions in the RBD of S protein showed 100% mortality in aged, male BALB/c mice.
ABSTRACT
Olfactory dysfunction caused by SARS-CoV-2 infection represents as one of the most predictive and common symptoms in COVID-19 patients. However, the causal link between SARS-CoV-2 infection and olfactory disorders remains lacking. Herein we demonstrate intranasal inoculation of SARS-CoV-2 induces robust viral replication in the olfactory epithelium (OE), resulting in transient olfactory dysfunction in humanized ACE2 mice. The sustentacular cells and Bowmans gland cells in OE were identified as the major targets of SARS-CoV-2 before the invasion into olfactory sensory neurons. Remarkably, SARS-CoV-2 infection triggers cell death and immune cell infiltration, and impairs the uniformity of OE structure. Combined transcriptomic and proteomic analyses reveal the induction of antiviral and inflammatory responses, as well as the downregulation of olfactory receptors in OE from the infected animals. Overall, our mouse model recapitulates the olfactory dysfunction in COVID-19 patients, and provides critical clues to understand the physiological basis for extrapulmonary manifestations of COVID-19.
ABSTRACT
Realgar nanoparticles (NPs) are increasingly used as therapeutic agents for their enhanced anti-proliferation effect and cytotoxicity on cancer cells. However, the alteration of particle size may enhance biological reactivity as well as toxicity. A LC/MS and GC/MS based metabolomics approach was employed to explore the mechanism of realgar NPs-induced hepatotoxicity and identify potential biomarkers. Male Sprague-Dawley rats were administrated intragastrically with realgar or realgar NPs at a dose of 1.0 g·kg·d for 28 days and toxic effects of realgar NPs on liver tissues were examined by biochemical indicator analysis and histopathologic examination. Increased levels of serum enzymes and high hepatic steatosis were discovered in the realgar NPs treated group. Multivariate data analysis revealed that rats with realgar NPs-induced hepatotoxicity could be distinctively differentiated from the animals in the control and realgar treated groups. In addition, 21 and 32 endogenous metabolites were apparently changed in the serum and live extracts, respectively. Realgar NPs might induce free fatty acid and triglyceride accumulation, resulting in hepatotoxicity. In conclusion, the present study represents the first comprehensive LC/MS- and GC/MS-based metabolomics analysis of realgar NPs-induced hepatotoxicity, which may help further research of nanotoxicity.
