技术资料

Regeneration of insulin-producing β-cells from resident pancreas progenitors requires an understanding of both progenitor identity and lineage plasticity. One model suggested that a rare β-cell sub-population within islets demonstrated multi-lineage plasticity. We hypothesized that β-cells from young mice (postnatal day 7,P7) exhibit such plasticity and used a model of islet dedifferentiation toward a ductal epithelial-cell phenotype to test this theory. RIPCre;Z/AP(+/+) mice were used to lineage trace the fate of β-cells during dedifferentiation culture by a human placental alkaline phosphatase (HPAP) reporter. There was a significant loss of HPAP-expressing β-cells in culture,but remaining HPAP(+) cells lost insulin expression while gaining expression of the epithelial duct cell marker cytokeratin-19 (Ck19). Flow cytometry and recovery of β-cell subpopulations from whole pancreas vs. islets suggest that the HPAP(+)Ck19(+) cells had derived from insulin-positive,glucose-transporter-2-low (Ins(+)Glut2(LO)) cells,representing 3.5% of all insulin-expressing cells. The majority of these cells were found outside of islets within clusters of <5 β-cells. These insulin(+)Glut2(LO) cells demonstrated a greater proliferation rate in vivo and in vitro as compared to insulin(+)Glut2(+) cells at P7,were retained into adulthood,and a subset differentiated into endocrine,ductal,and neural lineages,illustrating substantial plasticity. Results were confirmed using RIPCre;ROSA- eYFP mice. Quantitative PCR data indicated these cells possess an immature β-cell phenotype. These Ins(+)Glut2(LO) cells may represent a resident population of cells capable of forming new,functional β-cells,and which may be potentially exploited for regenerative therapies in the future. View Publication

Gliomas represent approximately 30% of all central nervous system tumors and 80% of malignant brain tumors. To understand the molecular mechanisms underlying the malignant progression of low-grade gliomas with mutations in IDH1 (encoding isocitrate dehydrogenase 1),we studied paired tumor samples from 41 patients,comparing higher-grade,progressed samples to their lower-grade counterparts. Integrated genomic analyses,including whole-exome sequencing and copy number,gene expression and DNA methylation profiling,demonstrated nonlinear clonal expansion of the original tumors and identified oncogenic pathways driving progression. These include activation of the MYC and RTK-RAS-PI3K pathways and upregulation of the FOXM1- and E2F2-mediated cell cycle transitions,as well as epigenetic silencing of developmental transcription factor genes bound by Polycomb repressive complex 2 in human embryonic stem cells. Our results not only provide mechanistic insight into the genetic and epigenetic mechanisms driving glioma progression but also identify inhibition of the bromodomain and extraterminal (BET) family as a potential therapeutic approach. View Publication

BACKGROUND Tumor cells present high levels of oxidative stress. Cancer therapeutics exploiting such biochemical changes by increasing reactive oxygen species (ROS) production or decreasing intracellular ROS scavengers could provide a powerful treatment strategy. METHODS To test the effect of our compound,obtusaquinone (OBT),we used several cell viability assays on seven different glioblastoma (GBM) cell lines and primary cells and on 12 different cell lines representing various cancer types in culture as well as on subcutaneous (n = 7 mice per group) and two intracranial GBM (n = 6-8 mice per group) and breast cancer (n = 6 mice per group) tumor models in vivo. Immunoblotting,immunostaining,flow cytometry,and biochemical assays were used to investigate the OBT mechanism of action. Histopathological analysis (n = 2 mice per group) and blood chemistry (n = 2 mice per group) were used to test for any compound-related toxicity. Statistical tests were two-sided. RESULTS OBT induced rapid increase in intracellular ROS levels,downregulation of cellular glutathione levels and increase in its oxidized form,and activation of cellular stress pathways and DNA damage,subsequently leading to apoptosis. Oxidative stress is believed to be the main mechanism through which this compounds targets cancer cells. OBT was well tolerated in mice,slowed tumor growth,and statistically prolonged survival in GBM tumor models. The ratio of median survival in U251 intracranial model in OBT vs control was 1.367 (95% confidence interval [CI] of ratio = 1.031 to 1.367,P = .008). Tumor growth inhibition was also observed in a mouse breast cancer model (average tumor volume per mouse,OBT vs control: 36.3 vs 200.4mm(3),difference = 164.1mm(3),95% CI =72.6 to 255.6mm(3),P = .005). CONCLUSIONS Given its properties and efficacy in cancer killing,our results suggest that OBT is a promising cancer therapeutic. View Publication

BACKGROUND AND PURPOSE HIV-1 glycoprotein Gp120 induces apoptosis in rodent and human neurons in vitro and in vivo.HIV-1/Gp120 is involved in the pathogenesis of HIV-associated dementia (HAD) and inhibits proliferation of adult neural progenitor cells (NPCs) in glial fibrillary acidic protein (GFAP)/Gp120 transgenic (Tg) mice. As cannabinoids exert neuroprotective effects in several model systems,we examined the protective effects of the CB receptor agonist AM1241 on Gp120-mediated insults on neurogenesis. EXPERIMENTAL APPROACH We assessed the effects of AM1241 on survival and apoptosis in cultures of human and murine NPCs with immunohistochemical and TUNEL techniques. Neurogenesis in the hippocampus of GFAP/Gp120 transgenic mice in vivo was also assessed by immunohistochemistry. KEY RESULTS AM1241 inhibited in vitroGp120-mediated neurotoxicity and apoptosis of primary human and murine NPCs and increased their survival. AM1241 also promoted differentiation of NPCs to neuronal cells. While GFAP/Gp120 Tg mice exhibited impaired neurogenesis,as indicated by reduction in BrdU cells and doublecortin (DCX) cells,and a decrease in cells with proliferating cell nuclear antigen (PCNA),administration of AM1241 to GFAP/Gp120 Tg mice resulted in enhanced in vivo neurogenesis in the hippocampus as indicated by increase in neuroblasts,neuronal cells,BrdU cells and PCNA cells. Astrogliosis and gliogenesis were decreased in GFAP/Gp120 Tg mice treated with AM1241,compared with those treated with vehicle. CONCLUSIONS AND IMPLICATIONS The CB receptor agonist rescued impaired neurogenesis caused by HIV-1/Gp120 insult. Thus,CB receptor agonists may act as neuroprotective agents,restoring impaired neurogenesis in patients with HAD. View Publication

Extracellular matrix (ECM) composition and stiffness are major driving forces for the development and persistence of fibrotic diseases. Lysyl oxidase (LOX) and LOX-like (LOXL) proteins play crucial roles in ECM remodeling due to their collagen crosslinking and intracellular functions. Here,we systematically investigated LOX/L expression in primary fibroblasts and epithelial cells under fibrotic conditions,Bleomycin (BLM) induced lung fibrosis and in human IPF tissue. Basal expression of all LOX/L family members was detected in epithelial cells and at higher levels in fibroblasts. Various pro-fibrotic stimuli broadly induced LOX/L expression in fibroblasts,whereas specific induction of LOXL2 and partially LOX was observed in epithelial cells. Immunohistochemical analysis of lung tissue from 14 IPF patients and healthy donors revealed strong induction of LOX and LOXL2 in bronchial and alveolar epithelium as well as fibroblastic foci. Using siRNA experiments we observed that LOXL2 and LOXL3 were crucial for fibroblast-to-myofibroblast transition (FMT). As FMT could only be reconstituted with an enzymatically active LOXL2 variant,we conclude that LOXL2 enzymatic function is crucial for fibroblast transdifferentiation. In summary,our study provides a comprehensive analysis of the LOX/L family in fibrotic lung disease and indicates prominent roles for LOXL2/3 in fibroblast activation and LOX/LOXL2 in IPF. View Publication

3D constructs composed of differentiated immortalized primary normal human bronchial epithelial (NHBE) cells (CL-1548) were repeatedly exposed at the air-liquid interface to non-lethal concentrations of mainstream cigarette smoke (4 cigarettes a day,5days/week,8 repetitions in total) and e-cigarette vapor (50 puffs a day,5 days/week,8 repetitions in total) to build up a permanent burden on the cells. Samples were taken after 4,6 and 8 times of repeated smoke exposure and the cultures were investigated using histopathological methods Compared to the clean air-exposed cultures (process control) and incubator control,the aerosol-exposed cultures showed a reduction of ciliated,mucus-producing and club cells. At the end of the exposure phase,we even found metaplastic areas positive for CK13 antibody in the cultures exposed to mainstream cigarette smoke and e-liquid vapor,commonly seen in squamous cells as a marker for non-cornified squamous epithelium. The control cultures (incubator cells) showed no comparable phenotypical changes. In conclusion,our in vitro model presents a valuable tool to study the induction of phenotypical changes after exposure to hazardous airborne material. View Publication

Alzheimer's disease (AD) belongs to a category of adult neurodegenerative conditions,which are associated with intracellular and extracellular accumulation of neurotoxic protein aggregates. Understanding how these aggregates are formed,secreted and propagated by neurons has been the subject of intensive research,but so far no preventive or curative therapy for AD is available,and clinical trials have been largely unsuccessful. Here we show that deficiency of the lysosomal sialidase NEU1 leads to the spontaneous occurrence of an AD-like amyloidogenic process in mice. This involves two consecutive events linked to NEU1 loss-of-function--accumulation and amyloidogenic processing of an oversialylated amyloid precursor protein in lysosomes,and extracellular release of Aβ peptides by excessive lysosomal exocytosis. Furthermore,cerebral injection of NEU1 in an established AD mouse model substantially reduces β-amyloid plaques. Our findings identify an additional pathway for the secretion of Aβ and define NEU1 as a potential therapeutic molecule for AD. View Publication

Neurotrophin-3 (NT-3) and its high-affinity receptor TrkC play crucial trophic roles in neuronal differentiation,axon outgrowth,and synapse development and plasticity in the nervous system. We demonstrated previously that postsynaptic TrkC functions as a glutamatergic synapse-inducing (synaptogenic) cell adhesion molecule trans-interacting with presynaptic protein tyrosine phosphatase σ (PTPσ). Given that NT-3 and PTPσ bind distinct domains of the TrkC extracellular region,here we tested the hypothesis that NT-3 modulates TrkC/PTPσ binding and synaptogenic activity. NT-3 enhanced PTPσ binding to cell surface-expressed TrkC and facilitated the presynapse-inducing activity of TrkC in rat hippocampal neurons. Imaging of recycling presynaptic vesicles combined with TrkC knockdown and rescue approaches demonstrated that NT-3 rapidly potentiates presynaptic function via binding endogenous postsynaptic TrkC in a tyrosine kinase-independent manner. Thus,NT-3 positively modulates the TrkC-PTPσ complex for glutamatergic presynaptic assembly and function independently from TrkC kinase activation. Our findings provide new insight into synaptic roles of neurotrophin signaling and mechanisms controlling synaptic organizing complexes. Significance statement: Although many synaptogenic adhesion complexes have been identified in recent years,little is known about modulatory mechanisms. Here,we demonstrate a novel role of neurotrophin-3 in synaptic assembly and function as a positive modulator of the TrkC-protein tyrosine phosphatase σ complex. This study provides new insight into the involvement of neurotrophin signaling in synapse development and plasticity,presenting a molecular mechanism that may underlie previous observations of short- and long-term enhancement of presynaptic function by neurotrophin. Given the links of synaptogenic adhesion molecules to autism and schizophrenia,this study might also contribute to a better understanding of the pathogenesis of these disorders and provide a new direction for ameliorating imbalances in synaptic signaling networks. View Publication

Malignant gliomas are the most common and deadly primary malignant brain tumors. In vivo orthotopic models could doubtless represent an appropriate tool to test novel treatment for gliomas. However,methods commonly used to monitor the growth of glioma inside the mouse brain are time consuming and invasive. We tested the reliability of a minimally invasive procedure,based on a secreted luciferase (Gaussia luciferase),to frequently monitor the changes of glioma size. Gluc activity was evaluated from blood samples collected from the tail tip of mice twice a week,allowing to make a growth curve for the tumors. We validated the correlation between Gluc activity and tumor size by analysing the tumor after brain dissection. We found that this method is reliable for monitoring human glioma transplanted in immunodeficient mice,but it has strong limitation in immunocompetent models,where an immune response against the luciferase is developed during the first weeks after transplant. View Publication

One important function of endothelial cells in glioblastoma multiforme (GBM) is to create a niche that helps promote self-renewal of cancer stem-like cells (CSLC). However,the underlying molecular mechanism for this endothelial function is not known. Since activation of NOTCH signaling has been found to be required for propagation of GBM CSLCs,we hypothesized that the GBM endothelium may provide the source of NOTCH ligands. Here,we report a corroboration of this concept with a demonstration that NOTCH ligands are expressed in endothelial cells adjacent to NESTIN and NOTCH receptor-positive cancer cells in primary GBMs. Coculturing human brain microvascular endothelial cells (hBMEC) or NOTCH ligand with GBM neurospheres promoted GBM cell growth and increased CSLC self-renewal. Notably,RNAi-mediated knockdown of NOTCH ligands in hBMECs abrogated their ability to induce CSLC self-renewal and GBM tumor growth,both in vitro and in vivo. Thus,our findings establish that NOTCH activation in GBM CSLCs is driven by juxtacrine signaling between tumor cells and their surrounding endothelial cells in the tumor microenvironment,suggesting that targeting both CSLCs and their niche may provide a novel strategy to deplete CSLCs and improve GBM treatment. View Publication

Rotavirus,a leading cause of severe gastroenteritis and diarrhoea in young children,accounts for around 215,000 deaths annually worldwide. Rotavirus specifically infects the intestinal epithelial cells in the host small intestine and has evolved strategies to antagonize interferon and NF-κB signalling,raising the question as to whether other host factors participate in antiviral responses in intestinal mucosa. The mechanism by which enteric viruses are sensed and restricted in vivo,especially by NOD-like receptor (NLR) inflammasomes,is largely unknown. Here we uncover and mechanistically characterize the NLR Nlrp9b that is specifically expressed in intestinal epithelial cells and restricts rotavirus infection. Our data show that,via RNA helicase Dhx9,Nlrp9b recognizes short double-stranded RNA stretches and forms inflammasome complexes with the adaptor proteins Asc and caspase-1 to promote the maturation of interleukin (Il)-18 and gasdermin D (Gsdmd)-induced pyroptosis. Conditional depletion of Nlrp9b or other inflammasome components in the intestine in vivo resulted in enhanced susceptibility of mice to rotavirus replication. Our study highlights an important innate immune signalling pathway that functions in intestinal epithelial cells and may present useful targets in the modulation of host defences against viral pathogens. View Publication

The intestinal epithelium plays an essential role in nutrient absorption,hormone release,and barrier function. Maintenance of the epithelium is driven by continuous cell renewal by stem cells located in the intestinal crypts. The amount and type of diet influence this process and result in changes in the size and cellular make-up of the tissue. The mechanism underlying the nutrient-driven changes in proliferation is not known,but may involve a shift in intracellular metabolism that allows for more nutrients to be used to manufacture new cells. We hypothesized that nutrient availability drives changes in cellular energy metabolism of small intestinal epithelial crypts that could contribute to increases in crypt proliferation. We utilized primary small intestinal epithelial crypts from C57BL/6J mice to study (1) the effect of glucose on crypt proliferation and (2) the effect of glucose on crypt metabolism using an extracellular flux analyzer for real-time metabolic measurements. We found that glucose increased both crypt proliferation and glycolysis,and the glycolytic pathway inhibitor 2-deoxy-d-glucose (2-DG) attenuated glucose-induced crypt proliferation. Glucose did not enhance glucose oxidation,but did increase the maximum mitochondrial respiratory capacity,which may contribute to glucose-induced increases in proliferation. Glucose activated Akt/HIF-1alpha signaling pathway,which might be at least in part responsible for glucose-induced glycolysis and cell proliferation. These results suggest that high glucose availability induces an increase in crypt proliferation by inducing an increase in glycolysis with no change in glucose oxidation. View Publication