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Larsen S, Seidelin JB, Davidsen J, Dahlgaard K, Nielsen CH, Bennett EP, Pedersen OB, Coskun M, Troelsen JT. CDX2 regulates interleukin-33 gene expression in intestinal epithelial cells (LS174T). FEBS Open Bio 2021; 11:1638-1644. [PMID: 33838073 PMCID: PMC8167865 DOI: 10.1002/2211-5463.13161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 03/18/2021] [Accepted: 04/08/2021] [Indexed: 01/22/2023] Open
Abstract
Dysregulation of interleukin-33 (IL-33) has been implicated in the pathogenesis of several autoimmune and inflammatory diseases, but few studies have examined transcriptional regulation of the IL33 gene. In the intestines, gene regulation is controlled by a transcription factor network of which the intestinal-specific transcription factor CDX2 is a key component. In this study, we investigated whether CDX2 regulates IL33 mRNA expression. We examined IL33 mRNA expression in primary colonic epithelial cells from healthy humans and epithelial cell lines, revealing high expression levels in primary colonic and LS174T cells. Combining genomics data (ChIP-seq, RNA-seq) and IL33 promoter analyses in LS174T cells revealed intronic enhancer activity in the IL33 gene that is dependent on CDX2 expression. Western blotting and qRT-PCR confirmed that IL33 expression is upregulated in a CDX2 concentration-dependent manner, thereby providing the first evidence that CDX2 regulates the expression of IL33.
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Affiliation(s)
- Sylvester Larsen
- Department of Science and Environment, Roskilde University, Denmark.,Department of Clinical Immunology, Naestved Hospital, Denmark
| | - Jakob Benedict Seidelin
- Department of Gastroenterology, Medical Section, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - Johanne Davidsen
- Department of Science and Environment, Roskilde University, Denmark.,Department of Surgical Gastroenterology, Zealand University Hospital, Køge, Denmark
| | - Katja Dahlgaard
- Department of Science and Environment, Roskilde University, Denmark
| | - Claus Henrik Nielsen
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Section 7521, Copenhagen University Hospital Rigshospitalet, Denmark
| | - Eric Paul Bennett
- Department of Odontology, Copenhagen Center for Glycomics, Faculty of Health Sciences, University of Copenhagen, Denmark
| | | | - Mehmet Coskun
- Department of Gastroenterology, Medical Section, Herlev Hospital, University of Copenhagen, Herlev, Denmark.,Department of Biology, The Bioinformatics Centre, Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Denmark
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Davidsen J, Jessen SB, Watt SK, Larsen S, Dahlgaard K, Kirkegaard T, Gögenur I, Troelsen JT. CDX2 expression and perioperative patient serum affects the adhesion properties of cultured colon cancer cells. BMC Cancer 2020; 20:426. [PMID: 32408894 PMCID: PMC7227097 DOI: 10.1186/s12885-020-06941-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/10/2020] [Indexed: 02/28/2023] Open
Abstract
Background Colon cancer is one of the most commonly diagnosed types of cancer with surgical resection of the tumor being the primary choice of treatment. However, the surgical stress response induced during treatment may be related to a higher risk of recurrence. The aim of this study was to examine the effect of surgery on adhesion of cultured colon cancer cells with or without expression of the tumour suppressor CDX2. Method We enrolled 30 patients undergoing elective, curatively intended laparoscopic surgery for colon cancer in this study. Blood samples were drawn 1 day prior to surgery and 24 h after surgery. The samples of pre- and postoperative serum was applied to wild type colon cancer LS174T cells and CDX2 inducible LS174T cells and adhesion was measured with Real-Time Cell-Analysis iCELLigence using electrical impedance as a readout to monitor changes in the cellular adhesion. Results Adhesion abilities of wild type LS174T cells seeded in postoperative serum was significantly increased compared to cells seeded in preoperative serum. When seeding the CDX2 inducible LS174T cells without CDX2 expression in pre- and postoperative serum, no significant difference in adhesion was found. However, when inducing CDX2 expression in these cells, the adhesion abilities in pre- and postoperative serum resembled those of the LS174T wild type cell line. Conclusions We found that the adhesion of colon cancer cells was significantly increased in postoperative versus preoperative serum, and that CDX2 expression affected the adhesive ability of cancer cells. The results of this study may help to elucidate the pro-metastatic mechanisms in the perioperative phase and the role of CDX2 in colon cancer metastasis.
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Affiliation(s)
- Johanne Davidsen
- Department of Science and Environment, Enhanced Perioperative Oncology (EPeOnc) Consortium, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark.,Center for Surgical Science, Enhanced Perioperative Oncology (EPeOnc) Consortium, Department of Surgery, Zealand University Hospital, Lykkebækvej 1, 4600, Køge, Denmark
| | - Stine Bull Jessen
- Department of Science and Environment, Enhanced Perioperative Oncology (EPeOnc) Consortium, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark.,Center for Surgical Science, Enhanced Perioperative Oncology (EPeOnc) Consortium, Department of Surgery, Zealand University Hospital, Lykkebækvej 1, 4600, Køge, Denmark
| | - Sara Kehlet Watt
- Center for Surgical Science, Enhanced Perioperative Oncology (EPeOnc) Consortium, Department of Surgery, Zealand University Hospital, Lykkebækvej 1, 4600, Køge, Denmark
| | - Sylvester Larsen
- Department of Science and Environment, Enhanced Perioperative Oncology (EPeOnc) Consortium, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark.,Department of Clinical Immunology, Naestved Hospital, Ringstedgade 77B, 4700, Naestved, Denmark
| | - Katja Dahlgaard
- Department of Science and Environment, Enhanced Perioperative Oncology (EPeOnc) Consortium, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark
| | - Tove Kirkegaard
- Center for Surgical Science, Enhanced Perioperative Oncology (EPeOnc) Consortium, Department of Surgery, Zealand University Hospital, Lykkebækvej 1, 4600, Køge, Denmark
| | - Ismail Gögenur
- Center for Surgical Science, Enhanced Perioperative Oncology (EPeOnc) Consortium, Department of Surgery, Zealand University Hospital, Lykkebækvej 1, 4600, Køge, Denmark
| | - Jesper T Troelsen
- Department of Science and Environment, Enhanced Perioperative Oncology (EPeOnc) Consortium, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark.
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Larsen S, Davidsen J, Dahlgaard K, Pedersen OB, Troelsen JT. HNF4α and CDX2 Regulate Intestinal YAP1 Promoter Activity. Int J Mol Sci 2019; 20:ijms20122981. [PMID: 31216773 PMCID: PMC6627140 DOI: 10.3390/ijms20122981] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 06/10/2019] [Accepted: 06/16/2019] [Indexed: 01/06/2023] Open
Abstract
The Hippo pathway is important for tissue homeostasis, regulation of organ size and growth in most tissues. The co-transcription factor yes-associated protein 1 (YAP1) serves as a main downstream effector of the Hippo pathway and its dysregulation increases cancer development and blocks colonic tissue repair. Nevertheless, little is known about the transcriptional regulation of YAP1 in intestinal cells. The aim of this study to identify gene control regions in the YAP1 gene and transcription factors important for intestinal expression. Bioinformatic analysis of caudal type homeobox 2 (CDX2) and hepatocyte nuclear factor 4 alpha (HNF4α) chromatin immunoprecipitated DNA from differentiated Caco-2 cells revealed potential intragenic enhancers in the YAP1 gene. Transfection of luciferase-expressing YAP1 promoter-reporter constructs containing the potential enhancer regions validated one potent enhancer of the YAP1 promoter activity in Caco-2 and T84 cells. Two potential CDX2 and one HNF4α binding sites were identified in the enhancer by in silico transcription factor binding site analysis and protein-DNA binding was confirmed in vitro using electrophoretic mobility shift assay. It was found by chromatin immunoprecipitation experiments that CDX2 and HNF4α bind to the YAP1 enhancer in Caco-2 cells. These results reveal a previously unknown enhancer of the YAP1 promoter activity in the YAP1 gene, with importance for high expression levels in intestinal epithelial cells. Additionally, CDX2 and HNF4α binding are important for the YAP1 enhancer activity in intestinal epithelial cells.
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Affiliation(s)
- Sylvester Larsen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
- Department of Clinical Immunology, Næstved Hospital, Ringstedgade 77B, 4700 Næstved, Denmark.
| | - Johanne Davidsen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
- Department of Surgery, Center for Surgical Science, Enhanced Perioperative Oncology (EPEONC) Consortium, Zealand University Hospital, Lykkebækvej 1, 4600 Køge, Denmark.
| | - Katja Dahlgaard
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
| | - Ole B Pedersen
- Department of Clinical Immunology, Næstved Hospital, Ringstedgade 77B, 4700 Næstved, Denmark.
| | - Jesper T Troelsen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
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Davidsen J, Larsen S, Coskun M, Gögenur I, Dahlgaard K, Bennett EP, Troelsen JT. The VTI1A-TCF4 colon cancer fusion protein is a dominant negative regulator of Wnt signaling and is transcriptionally regulated by intestinal homeodomain factor CDX2. PLoS One 2018; 13:e0200215. [PMID: 29975781 PMCID: PMC6033461 DOI: 10.1371/journal.pone.0200215] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 06/21/2018] [Indexed: 02/07/2023] Open
Abstract
Sequencing of primary colorectal tumors has identified a gene fusion in approximately 3% of colorectal cancer patients of the VTI1A and TCF7L2 genes, encoding a VTI1A-TCF4 fusion protein containing a truncated TCF4. As dysregulation of the Wnt signaling pathway is associated with colorectal cancer development and progression, the functional properties and transcriptional regulation of the VTI1A-TCF4 fusion protein may also play a role in these processes. Functional characteristics of the VTI1A-TCF4 fusion protein in Wnt signaling were analyzed in NCI-H508 and LS174T colon cancer cell lines. The NCI-H508 cell line, containing the VTI1A-TCF7L2 fusion gene, showed no active Wnt signaling, and overexpression of the VTI1A-TCF4 fusion protein in LS174T cells along with a Wnt signaling luciferase reporter plasmid showed inhibition of activity. The transcriptional regulation of the VTI1A-TCF4 fusion gene was investigated in LS174T cells where the activity of the VTI1A promoter was compared to that of the TCF7L2 promoter, and the transcription factor CDX2 was analyzed for gene regulatory activity of the VTI1A promoter through luciferase reporter gene assay using colon cancer cell lines as a model. Transfection of LS174T cells showed that the VTI1A promoter is highly active compared to the TCF7L2 promoter, and that CDX2 activates transcription of VTI1A. These results suggest that the VTI1A-TCF4 fusion protein is a dominant negative regulator of the Wnt signaling pathway, and that transcription of VTI1A is activated by CDX2.
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Affiliation(s)
- Johanne Davidsen
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
- Department of Surgery, Zealand University Hospital, Roskilde, Denmark
| | - Sylvester Larsen
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
- Department of Clinical Immunology, Naestved Hospital, Naestved, Denmark
| | - Mehmet Coskun
- Department of Gastroenterology, Herlev Hospital, Herlev, Denmark
| | - Ismail Gögenur
- Department of Surgery, Zealand University Hospital, Roskilde, Denmark
| | - Katja Dahlgaard
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Eric Paul Bennett
- Copenhagen Center for Glycomics, Department of Odontology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Pinto R, Hansen L, Hintze J, Almeida R, Larsen S, Coskun M, Davidsen J, Mitchelmore C, David L, Troelsen JT, Bennett EP. Precise integration of inducible transcriptional elements (PrIITE) enables absolute control of gene expression. Nucleic Acids Res 2017; 45:e123. [PMID: 28472465 PMCID: PMC5570051 DOI: 10.1093/nar/gkx371] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 03/30/2017] [Accepted: 04/27/2017] [Indexed: 12/22/2022] Open
Abstract
Tetracycline-based inducible systems provide powerful methods for functional studies where gene expression can be controlled. However, the lack of tight control of the inducible system, leading to leakiness and adverse effects caused by undesirable tetracycline dosage requirements, has proven to be a limitation. Here, we report that the combined use of genome editing tools and last generation Tet-On systems can resolve these issues. Our principle is based on precise integration of inducible transcriptional elements (coined PrIITE) targeted to: (i) exons of an endogenous gene of interest (GOI) and (ii) a safe harbor locus. Using PrIITE cells harboring a GFP reporter or CDX2 transcription factor, we demonstrate discrete inducibility of gene expression with complete abrogation of leakiness. CDX2 PrIITE cells generated by this approach uncovered novel CDX2 downstream effector genes. Our results provide a strategy for characterization of dose-dependent effector functions of essential genes that require absence of endogenous gene expression.
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Affiliation(s)
- Rita Pinto
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Ipatimup, Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Faculty of Medicine of the University of Porto, Porto, Portugal
- Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine and Odontology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lars Hansen
- Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine and Odontology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - John Hintze
- Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine and Odontology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Raquel Almeida
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Ipatimup, Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Faculty of Medicine of the University of Porto, Porto, Portugal
- Department of Biology, Faculty of Sciences of the University of Porto, Porto, Portugal
| | - Sylvester Larsen
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
- Department of Clinical Immunology, Naestved Hospital, Naestved, Denmark
| | - Mehmet Coskun
- Department of Gastroenterology, Medical Section, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark
- The Bioinformatics Centre, Department of Biology & Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Johanne Davidsen
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Cathy Mitchelmore
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Leonor David
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Ipatimup, Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Faculty of Medicine of the University of Porto, Porto, Portugal
| | | | - Eric Paul Bennett
- Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine and Odontology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Moloney NR, Davidsen J. Stationarity of extreme bursts in the solar wind. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:052812. [PMID: 25353849 DOI: 10.1103/physreve.89.052812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Indexed: 06/04/2023]
Abstract
Recent results have suggested that the statistics of bursts in the solar wind vary with solar cycle. Here, we show that this variation is basically absent if one considers extreme bursts. These are defined as threshold-exceeding events over the range of high thresholds for which their number decays as a power law. In particular, we find that the distribution of duration times and energies of extreme bursts in the solar wind ε parameter and similar observables are independent of the solar cycle and in this sense stationary, and show robust asymptotic power laws with exponents that are independent of the specific threshold. This is consistent with what has been observed for solar flares and, thus, provides evidence in favor of a link between solar flares and extreme bursts in the solar wind.
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Affiliation(s)
- N R Moloney
- London Mathematical Laboratory, 14 Buckingham Street, London WC2N 6DF, United Kingdom and Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - J Davidsen
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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Moloney NR, Davidsen J. Extreme value statistics and return intervals in long-range correlated uniform deviates. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 79:041131. [PMID: 19518197 DOI: 10.1103/physreve.79.041131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Indexed: 05/27/2023]
Abstract
We study extremal statistics and return intervals in stationary long-range correlated sequences for which the underlying probability density function is bounded and uniform. The extremal statistics we consider (e.g., maximum relative to minimum) are such that the reference point from which the maximum is measured is itself a random quantity. We analytically calculate the limiting distributions for independent and identically distributed random variables, and use these as a reference point for correlated cases. The distributions are different from that of the maximum itself (i.e., a Weibull distribution), reflecting the fact that the distribution of the reference point either dominates over or convolves with the distribution of the maximum. The functional form of the limiting distributions is unaffected by correlations, although the convergence is slower. We show that our findings can be directly generalized to a wide class of stochastic processes. We also analyze return interval distributions, and compare them to recent conjectures of their functional form.
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Affiliation(s)
- N R Moloney
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada AB T2N 1N4.
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Jensen S, Jensen L, Davidsen J, Gill J, Shnyder S, Bibby M, Høyrup P, Jørgensen K. 604 Secretory phospholipase A2 as tumour specific trigger for targeted delivery of a novel class of liposomal prodrug anticancer etherlipids. EJC Suppl 2004. [DOI: 10.1016/s1359-6349(04)80612-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
Contrary to the recently published results by Daerden and Vanderzande [Phys. Rev. E 53, 4723 (1996)], we show that the time correlation function in the random-neighbor version of the Bak-Sneppen model can be well approximated by an exponential giving rise to a 1/f(2) power spectrum.
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Affiliation(s)
- J Davidsen
- Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität, Olshausenstrasse 40, 24118 Kiel, Germany.
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Abstract
The effect of poly(ethylene glycol)-phospholipid (PE-PEG) lipopolymers on phospholipase A(2) (PLA(2)) hydrolysis of liposomes composed of stearoyl-oleoylphosphatidylcholine (SOPC) was investigated. The PLA(2) lag-time, which is inversely related to the enzymatic activity, was determined by fluorescence, and the zeta-potentials of the liposomes were measured as a function of PE-PEG lipopolymer concentration. A significant decrease in the lag-time, and hence an increase in enzymatic activity, was observed with increasing amounts of the negatively charged PE-PEG lipopolymers incorporated into the SOPC liposomes. The enhancement of the PLA(2) enzymatic activity might involve a stronger PLA(2) binding affinity towards the negatively charged and polymer covered PEG liposomes.
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Affiliation(s)
- J Davidsen
- Department of Pharmaceutics, The Royal Danish School of Pharmacy, Universitetsparken 2, 2100 Copenhagen, Denmark
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Davidsen J, Vermehren C, Frøkjaer S, Mouritsen OG, Jørgensen K. Enzymatic degradation of polymer covered SOPC-liposomes in relation to drug delivery. Adv Colloid Interface Sci 2001; 89-90:303-11. [PMID: 11215800 DOI: 10.1016/s0001-8686(00)00058-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Polyethylenoxide (PEG) covered liposomes are used as lipid-based drug-delivery systems. In comparison to conventional liposomes the polymer-covered liposomes display a long circulation half-life in the blood stream. We investigate the influence of polyethyleneoxide-distearoylphosphatidylethanolamine (DSPE-PEG750) lipopolymer concentration on phospholipase A2 (PLA2) catalyzed hydrolysis of liposomes composed of stearoyloleoylphosphatidylcholine (SOPC). The characteristic PLA2 lag-time was determined by fluorescence and the degree of lipid hydrolysis was followed by HPLC analysis. Particle size and zeta-potential were measured as a function of DSPE-PEG750 lipopolymer concentration. A significant decrease in the lag-time, and hence an increase in enzyme activity, was observed with increasing concentrations of the anionic DSPE-PEG750 lipopolymer lipids. The observed decrease in lag-time might be related to changes in the surface potential and the PLA2 lipid membrane affinity.
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Affiliation(s)
- J Davidsen
- Department of Pharmaceutics, The Royal Danish School of Pharmacy, Copenhagen O
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Davidsen J, Schuster HG. 1/f(alpha) noise from self-organized critical models with uniform driving. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 62:6111-5. [PMID: 11101941 DOI: 10.1103/physreve.62.6111] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2000] [Indexed: 11/07/2022]
Abstract
Using the well-known Olami-Feder-Christensen model as our paradigm, we show how to modify uniform driven self-organized critical models to generate 1/f(alpha) noise. This model can reproduce all the main features of 1/f(alpha) noise: (1) alpha is close to one and does not depend on the dimension of the system. (2) The 1/f(alpha) behavior is found for very low frequencies. (3) The spatial correlations do not obey a power law. That proves that spatially extended systems based on activation-deactivation processes do not have to be point-driven to produce 1/f(alpha) noise. The essential ingredient is a local memory of the activation-deactivation process.
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Affiliation(s)
- J Davidsen
- Institut fur Theoretische Physik und Astrophysik, Christian-Albrechts-Universitat, Olshausenstrasse 40, 24118 Kiel, Germany
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Chen M, Brøgger Christensen S, Zhai L, Rasmussen MH, Theander TG, Frøkjaer S, Steffansen B, Davidsen J, Kharazmi A. The novel oxygenated chalcone, 2,4-dimethoxy-4'-butoxychalcone, exhibits potent activity against human malaria parasite Plasmodium falciparum in vitro and rodent parasites Plasmodium berghei and Plasmodium yoelii in vivo. J Infect Dis 1997; 176:1327-33. [PMID: 9359735 DOI: 10.1086/514129] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Previous studies have shown that licochalcone A, an oxygenated chalcone, exhibits antileishmanial and antimalarial activities. The present study was designed to examine the antimalarial activity of an analog of licochalcone A, 2,4-dimethoxy-4'-butoxychalcone (2,4mbc). 2,4mbc inhibited the in vitro growth of both a chloroquine-susceptible (3D7) and a chloroquine-resistant (Dd2) strain of Plasmodium falciparum in a [3H]hypoxanthine uptake assay. The in vivo activity of 2,4mbc was tested in mice infected with Plasmodium berghei or Plasmodium yoelii and in rats infected with P. berghei. 2,4mbc administered either orally, intraperitoneally, or subcutaneously for 5 days protected the mice from otherwise lethal infections of these parasites. 2,4mbc administered orally for 5 days reduced parasitemia in the rats infected with P. berghei. These results demonstrate that 2,4mbc exhibits potent antimalarial activity and might be developed into a new antimalarial drug.
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Affiliation(s)
- M Chen
- Centre for Medical Parasitology, Department of Clinical Microbiology, University Hospital of Copenhagen, Denmark
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Davidsen J. Lighting for the aging eye. Inter Des 1991; 62:134-5. [PMID: 10109535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Davidsen J. Birthing center. A hospitable hospital room by Loebl Schlossman and Hackl. Inter Des 1990; 61:190-3. [PMID: 10107826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Davidsen J. AIDS hospice. Inter Des 1990; 61:204-5. [PMID: 10104395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Davidsen J. Easy street. David Guynes designs real-life rehabilitation settings. Inter Des 1990; 61:200-3. [PMID: 10104394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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