| 1. |
- Ali, Zaheer, et al.
(författare)
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Intussusceptive Vascular Remodeling Precedes Pathological Neovascularization
- 2019
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : Lippincott Williams & Wilkins. - 1079-5642 .- 1524-4636. ; 39:7, s. 1402-1418
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Tidskriftsartikel (refereegranskat)abstract
- Objective—Pathological neovascularization is crucial for progression and morbidity of serious diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. While mechanisms of ongoing pathological neovascularization have been extensively studied, the initiating pathological vascular remodeling (PVR) events, which precede neovascularization remains poorly understood. Here, we identify novel molecular and cellular mechanisms of preneovascular PVR, by using the adult choriocapillaris as a model.Approach and Results—Using hypoxia or forced overexpression of VEGF (vascular endothelial growth factor) in the subretinal space to induce PVR in zebrafish and rats respectively, and by analyzing choriocapillaris membranes adjacent to choroidal neovascular lesions from age-related macular degeneration patients, we show that the choriocapillaris undergo robust induction of vascular intussusception and permeability at preneovascular stages of PVR. This PVR response included endothelial cell proliferation, formation of endothelial luminal processes, extensive vesiculation and thickening of the endothelium, degradation of collagen fibers, and splitting of existing extravascular columns. RNA-sequencing established a role for endothelial tight junction disruption, cytoskeletal remodeling, vesicle- and cilium biogenesis in this process. Mechanistically, using genetic gain- and loss-of-function zebrafish models and analysis of primary human choriocapillaris endothelial cells, we determined that HIF (hypoxia-induced factor)-1α-VEGF-A-VEGFR2 signaling was important for hypoxia-induced PVR.Conclusions—Our findings reveal that PVR involving intussusception and splitting of extravascular columns, endothelial proliferation, vesiculation, fenestration, and thickening is induced before neovascularization, suggesting that identifying and targeting these processes may prevent development of advanced neovascular disease in the future.Visual Overview—An online visual overview is available for this article.
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| 2. |
- Bengtsson, H. Jörgen, et al.
(författare)
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Interaction of the antidepressant mirtazapine with alpha2-adrenoceptors modulating the release of 5-HT in different rat brain regions in vivo.
- 2000
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Ingår i: Naunyn-Schmiedeberg's archives of pharmacology. - 0028-1298. ; 362:4-5, s. 406-12
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Tidskriftsartikel (refereegranskat)abstract
- Mirtazapine (MIR) is a novel antidepressant, reported to raise extracellular noradrenaline (NA) through blockade of alpha2-autoreceptors and serotonin (5-HT) output via (1) indirect activation of facilitatory alpha1-adrenoceptors on the cell bodies of ascending 5-HT neurones and (2) blockade of presynaptic release-modulating alpha2-heteroreceptors on 5-HT terminals in the forebrain. To further assess the effect of MIR on NA/5-HT system interplay, including putative regional differences in the effects of the drug on 5-HT release in rat forebrain, we used in vivo microdialysis in anaesthetised rats. Probes were implanted in the dorsal hippocampus (DH) and frontal cortex (FCx), representing median and dorsal raphe 5-HT projection areas, respectively. In the DH, MIR (10 mg/kg s.c.) completely blocked the 5-HT release-suppressing action of the selective alpha2-adrenoceptor agonist clonidine (0.1 mg/kg s.c.), but had no effect per se on the 5-HT output. Neither drug significantly changed the 5-HT levels in the FCx. MIR perfused locally (10 microM via reverse-dialysis) also failed to significantly elevate 5-HT output, and did not affect the clonidine response in either brain area. Thus, the data confirm the basic alpha2-adrenoceptor-blocking properties of MIR, but are only partly concordant with previous studies reporting an increase of 5-HT output after MIR alone. Moreover, we find no elevation in 5-HT by the reference alpha2-adrenoceptor antagonist idazoxan (0.3-1.0 mg/kg s.c.). The discrepancies encountered, and the potential ability of alpha2-adrenoceptor antagonists in general to raise the output of 5-HT, are discussed with particular reference to methodological and other factors that may influence the experimental outcome (e.g., brain regional aspects, different alpha2-adrenoceptor subtypes, potential differences in adrenoceptor tone under varying experimental conditions).
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| 3. |
- Jensen, Lasse, et al.
(författare)
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Disruption of the Extracellular Matrix Progressively Impairs Central Nervous System Vascular Maturation Downstream of beta-Catenin Signaling
- 2019
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : LIPPINCOTT WILLIAMS & WILKINS. - 1079-5642 .- 1524-4636. ; 39:7, s. 1432-1447
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Tidskriftsartikel (refereegranskat)abstract
- Objective- The Wnt/beta-catenin pathway orchestrates development of the blood-brain barrier, but the downstream mechanisms involved at different developmental windows and in different central nervous system (CNS) tissues have remained elusive. Approach and Results- Here, we create a new mouse model allowing spatiotemporal investigations of Wnt/beta-catenin signaling by induced overexpression of Axin1, an inhibitor of beta-catenin signaling, specifically in endothelial cells (Axin1(iEC)-(OE)). AOE (Axin1 overexpression) in Axin1(iEC)-(OE) mice at stages following the initial vascular invasion of the CNS did not impair angiogenesis but led to premature vascular regression followed by progressive dilation and inhibition of vascular maturation resulting in forebrain-specific hemorrhage 4 days post-AOE. Analysis of the temporal Wnt/beta-catenin driven CNS vascular development in zebrafish also suggested that Axin1(iEC)-(OE) led to CNS vascular regression and impaired maturation but not inhibition of ongoing angiogenesis within the CNS. Transcriptomic profiling of isolated, beta-catenin signaling-deficient endothelial cells during early blood-brain barrier-development (E11.5) revealed ECM (extracellular matrix) proteins as one of the most severely deregulated clusters. Among the 20 genes constituting the forebrain endothelial cell-specific response signature, 8 (Adamtsl2, Apod, Ctsw, Htra3, Pglyrp1, Spock2, Ttyh2, and Wfdc1) encoded bona fide ECM proteins. This specific beta-catenin-responsive ECM signature was also repressed in Axin1(iEC)-(OE) and endothelial cell-specific beta-catenin-knockout mice (Ctnnb1-KOiEC) during initial blood-brain barrier maturation (E14.5), consistent with an important role of Wnt/beta-catenin signaling in orchestrating the development of the forebrain vascular ECM. Conclusions- These results suggest a novel mechanism of establishing a CNS endothelium-specific ECM signature downstream of Wnt-beta-catenin that impact spatiotemporally on blood-brain barrier differentiation during forebrain vessel development.
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| 4. |
- Kele-Olovsson, Julianna M V
(författare)
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Regulation of midbrain dopaminergic neuron development by Wnts, sFRPs and bHLH proteins
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parkinson’s disease (PD) is a chronic neurodegenerative disorder. The main pathology is characterized by progressive degeneration of the dopaminergic (DA) neurons of the substantia nigra leading to loss of striatal dopamine innervation. The knowledge about the fundamental mechanisms behind the degenerative process has been limited. During recent years a promising approach is evolving based on DA cell replacement therapy. However, in order to find a cure for PD an increased understanding is required about the intrinsic and extrinsic signals involved in the development of DA progenitor cells during embryogenesis. This thesis identifies novel players in midbrain development and investigates the mechanisms by which three major signaling modulators, Wnts, soluble Frizzled Related Proteins (sFRPs) and basic-Helix-Loop-Helix (bHLH) family of proteins, regulate DA neuron development. Proneural genes belong to the bHLH family of transcription factors and are crucial regulators of neurogenesis and subtype specification in many areas of the nervous system. Their function in DA neuron development has been unknown. In this thesis it is reported that the proneural genes Neurogenin2 (Ngn2) and Mash1 have an intricate pattern of expression in the ventricular zone (VZ) of the ventral midbrain (vMB), where DA neurons are generated. To examine the function of these genes, mice were analyzed in which one or two of these genes were deleted (Ngn1,Ngn2 and Mash1) or substituted (Mash1 in the Ngn2 locus). Our results demonstrate that Ngn2 is required for the differentiation of Sox2+ VZ progenitors into Nurr1+ postmitotic DA neuron precursors in the intermediate zone (ImZ), and that it is also required for their subsequent differentiation into DA neurons in the marginal zone (MZ). Although Mash1 normally has no detectable function in DA neuron development, it could partially rescue the generation of DA neuron precursors in the absence of Ngn2. These results demonstrate that Ngn2 is uniquely required for the development of vMB DA neurons. The Wnt signaling pathway regulates several developmental processes in the mammalian CNS; neural patterning, cell fate determination, proliferation, differentiation, neuronal maturation, cell migration and axon guidance. Our results present evidence that Wnt-1, -3a, and -5a expression is differentially regulated during vMB development. Wnt-3a promoted the proliferation of precursor cells expressing the orphan nuclear receptor-related factor 1 (Nurr1) but did not increase the number of DA neurons. Conversely, Wnt-1 and -5a increased the number of rat vMB DA neurons in rat embryonic day 14.5 precursor cultures by two distinct mechanisms. Wnt-1 predominantly increased the proliferation of Nurr1-precursors. In contrast, Wnt-5a primarily increased the proportion of Nurr1 precursors that acquired a neuronal DA phenotype. These findings indicate that Wnts are key regulators of proliferation and differentiation of DA precursors during vMB neurogenesis and that different Wnts have specific and unique activity profiles. Furthermore temporal expression profiles of Wnt components during critical phases of MB development revealed Frizzled (Fz) 9, a Wnt receptor, to be highly expressed in DA progenitors but not in newborn DA neurons. A possible function of Fz9 during early MB development might be to regulate proliferation of DA progenitors and inhibit differentiation, since Fz9 reduced Wnt5a signaling in DA cells in vitro. Finally, we set to examine the function of sFRPs in the developing ventral midbrain. sFRPs are a secreted family of factors that sterically hinder the Wnt ligand-Fz receptor complex to form and thereby block the Wnt signling pathway. sFRP1-3, but not 4 were expressed in the developing vMB, during DA neurogenesis. We therefore examined whether sFRP1-3 could work as Wnt antagonists in a dopaminergic cell line. We found that high doses of sFRP1 and sFRP2, but not sFRP3, acted as competitive antagonists of Wnt signaling. Treatment of vMB precursor cultures with sFRP1 resulted in DA neuron cell death, an effect that is compatible with Wnt1 blocking. However, treatment with sFRP2 lead to increased proliferation of progenitors and increased number of DA neurons, an effect incompatible with a Wnt blocking activity. Analysis of the sFRP2-/- mice also suggested that sFRP2 does not block Wnt function. On the contrary, we found that sFRP2 is partially required for several sequential steps in DA neuron development, including DA neurogenesis, differentiation of DA precursors into neurons and neuritogenesis. Thus, our results unravel several novel functions of sFRPs and identify sFRP2 as a novel player in DA neuron development. In summary, these results presented identify several novel players in midbrain DA neuron development and reveal new functions of proneural bHLHs, Wnts and sFRPs, thereby extending our knowledge and identifying factors that may be used to develop novel DA cell replacement therapies for the treatment of PD.
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| 5. |
- Martowicz, Agnieszka, et al.
(författare)
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Endothelial beta-Catenin Signaling Supports Postnatal Brain and Retinal Angiogenesis by Promoting Sprouting, Tip Cell Formation, and VEGFR (Vascular Endothelial Growth Factor Receptor) 2 Expression
- 2019
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : LIPPINCOTT WILLIAMS & WILKINS. - 1079-5642 .- 1524-4636. ; 39:11, s. 2273-2288
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Activation of endothelial beta-catenin signaling by neural cell-derived Norrin or Wnt ligands is vital for the vascularization of the retina and brain. Mutations in members of the Norrin/beta-catenin pathway contribute to inherited blinding disorders because of defective vascular development and dysfunctional blood-retina barrier. Despite a vital role for endothelial beta-catenin signaling in central nervous system health and disease, its contribution to central nervous system angiogenesis and its interactions with downstream signaling cascades remains incompletely understood.Approach and Results: Here, using genetically modified mouse models, we show that impaired endothelial beta-catenin signaling caused hypovascularization of the postnatal retina and brain because of deficient endothelial cell proliferation and sprouting. Mosaic genetic analysis demonstrated that endothelial beta-catenin promotes but is not required for tip cell formation. In addition, pharmacological treatment revealed that angiogenesis under conditions of inhibited Notch signaling depends upon endothelial beta-catenin. Importantly, impaired endothelial beta-catenin signaling abrogated the expression of the VEGFR (vascular endothelial growth factor receptor)-2 and VEGFR3 in brain microvessels but not in the lung endothelium.Conclusions: Our study identifies molecular crosstalk between the Wnt/beta-catenin and the Notch and VEGF-A signaling pathways and strongly suggest that endothelial beta-catenin signaling supports central nervous system angiogenesis by promoting endothelial cell sprouting, tip cell formation, and VEGF-A/VEGFR2 signaling.
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| 6. |
- Mikaeloff, Flora, et al.
(författare)
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Trans cohort metabolic reprogramming towards glutaminolysis in long-term successfully treated HIV-infection
- 2022
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite successful combination antiretroviral therapy (cART), persistent low-grade immune activation together with inflammation and toxic antiretroviral drugs can lead to long-lasting metabolic flexibility and adaptation in people living with HIV (PLWH). Our study investigated alterations in the plasma metabolic profiles by comparing PLWH on long-term cART(>5 years) and matched HIV-negative controls (HC) in two cohorts from low- and middle-income countries (LMIC), Cameroon, and India, respectively, to understand the system-level dysregulation in HIV-infection. Using untargeted and targeted LC-MS/MS-based metabolic profiling and applying advanced system biology methods, an altered amino acid metabolism, more specifically to glutaminolysis in PLWH than HC were reported. A significantly lower level of neurosteroids was observed in both cohorts and could potentiate neurological impairments in PLWH. Further, modulation of cellular glutaminolysis promoted increased cell death and latency reversal in pre-monocytic HIV-1 latent cell model U1, which may be essential for the clearance of the inducible reservoir in HIV-integrated cells. Mikaeloff et al. use untargeted and targeted LC-MS/MS-based plasma metabolic profiling to discover dysregulated metabolism including that of glutaminolysis in individuals living with HIV. Furthermore, decreased levels of neurosteroids were detected suggesting a potential connection between HIV and neurological impairment.
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| 7. |
- Osman, Ahmed M., et al.
(författare)
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Radiation Triggers a Dynamic Sequence of Transient Microglial Alterations in Juvenile Brain
- 2020
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Ingår i: Cell Reports. - : CELL PRESS. - 2211-1247. ; 31:9
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Tidskriftsartikel (refereegranskat)abstract
- Cranial irradiation (IR), an effective tool to treat malignant brain tumors, triggers a chronic pro-inflammatory microglial response, at least in the adult brain. Using single-cell and bulk RNA sequencing, combined with histology, we show that the microglial response in the juvenile mouse hippocampus is rapid but returns toward normal within 1 week. The response is characterized by a series of temporally distinct homeostasis-, sensome-, and inflammation-related molecular signatures. We find that a single microglial cell simultaneously upregulates transcripts associated with pro- and anti-inflammatory microglial phenotypes. Finally, we show that juvenile and adult irradiated microglia are already transcriptionally distinct in the early phase after IR. Our results indicate that microglia are involved in the initial stages but may not be responsible for driving long-term inflammation in the juvenile brain.
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