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Ku KH, Dubinsky MK, Sukumar AN, Subramaniam N, Feasson MYM, Nair R, Tran E, Steer BM, Knight BJ, Marsden PA. In Vivo Function of Flow-Responsive Cis-DNA Elements of eNOS Gene: A Role for Chromatin-Based Mechanisms. Circulation 2021; 144:365-381. [PMID: 33910388 DOI: 10.1161/circulationaha.120.051078] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND eNOS (endothelial nitric oxide synthase) is an endothelial cell (EC)-specific gene predominantly expressed in medium- to large-sized arteries where ECs experience atheroprotective laminar flow with high shear stress. Disturbed flow with lower average shear stress decreases eNOS transcription, which leads to the development of atherosclerosis, especially at bifurcations and curvatures of arteries. This prototypic arterial EC gene contains 2 distinct flow-responsive cis-DNA elements in the promoter, the shear stress response element (SSRE) and the KLF (Krüppel-like factor) element. Previous in vitro studies suggested their positive regulatory functions on flow-induced transcription of EC genes including eNOS. However, the in vivo function of these cis-DNA elements remains unknown. METHODS Insertional transgenic mice with a mutation at each flow-responsive cis-DNA element were generated using a murine eNOS promoter-β-galactosidase reporter by linker-scanning mutagenesis and compared with episomal-based mutations in vitro. DNA methylation at the eNOS proximal promoter in mouse ECs was assessed by bisulfite sequencing or pyrosequencing. RESULTS Wild type mice with a functional eNOS promoter-reporter transgene exhibited reduced endothelial reporter expression in the atheroprone regions of disturbed flow (n=5). It is surprising that the SSRE mutation abrogated reporter expression in ECs and was associated with aberrant hypermethylation at the eNOS proximal promoter (n=7). Reporter gene silencing was independent of transgene copy number and integration position, indicating that the SSRE is a critical cis-element necessary for eNOS transcription in vivo. The KLF mutation demonstrated an integration site-specific decrease in eNOS transcription, again with marked promoter methylation (n=8), suggesting that the SSRE alone is not sufficient for eNOS transcription in vivo. In wild type mice, the native eNOS promoter was significantly hypermethylated in ECs from the atheroprone regions where eNOS expression was markedly repressed by chronic disturbed flow, demonstrating that eNOS expression is regulated by flow-dependent DNA methylation that is region-specific in the arterial endothelium in vivo. CONCLUSIONS We report, for the first time, that the SSRE and KLF elements are critical flow sensors necessary for a transcriptionally permissive, hypomethylated eNOS promoter in ECs under chronic shear stress in vivo. Moreover, eNOS expression is regulated by flow-dependent epigenetic mechanisms, which offers novel mechanistic insight on eNOS gene regulation in atherogenesis.
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Affiliation(s)
- Kyung Ha Ku
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.).,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Michelle K Dubinsky
- Institute of Medical Science (M.K.D., A.N.S., N.S., P.A.M.) University of Toronto, Ontario, Canada.,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Aravin N Sukumar
- Institute of Medical Science (M.K.D., A.N.S., N.S., P.A.M.) University of Toronto, Ontario, Canada.,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Noeline Subramaniam
- Institute of Medical Science (M.K.D., A.N.S., N.S., P.A.M.) University of Toronto, Ontario, Canada.,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Manon Y M Feasson
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.).,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Ranju Nair
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.).,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Eileen Tran
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.)
| | - Brent M Steer
- Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.)
| | - Britta J Knight
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.)
| | - Philip A Marsden
- Department of Laboratory Medicine and Pathobiology (K.H.K., M.Y.M.F., R.N., E.T., B.J.K., P.A.M.).,Institute of Medical Science (M.K.D., A.N.S., N.S., P.A.M.) University of Toronto, Ontario, Canada.,Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute (K.H.K., M.K.D., A.N.S., N.S., M.Y.M.F., R.N., B.M.B., P.A.M.).,Department of Medicine (P.A.M.), St Michael's Hospital, Toronto, Ontario, Canada
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Menge C. The Role of Escherichia coli Shiga Toxins in STEC Colonization of Cattle. Toxins (Basel) 2020; 12:toxins12090607. [PMID: 32967277 PMCID: PMC7551371 DOI: 10.3390/toxins12090607] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/16/2020] [Accepted: 09/18/2020] [Indexed: 11/20/2022] Open
Abstract
Many cattle are persistently colonized with Shiga toxin-producing Escherichia coli (STEC) and represent a major source of human infections with human-pathogenic STEC strains (syn. enterohemorrhagic E. coli (EHEC)). Intervention strategies most effectively protecting humans best aim at the limitation of bovine STEC shedding. Mechanisms enabling STEC to persist in cattle are only partialy understood. Cattle were long believed to resist the detrimental effects of Shiga toxins (Stxs), potent cytotoxins acting as principal virulence factors in the pathogenesis of human EHEC-associated diseases. However, work by different groups, summarized in this review, has provided substantial evidence that different types of target cells for Stxs exist in cattle. Peripheral and intestinal lymphocytes express the Stx receptor globotriaosylceramide (Gb3syn. CD77) in vitro and in vivo in an activation-dependent fashion with Stx-binding isoforms expressed predominantly at early stages of the activation process. Subpopulations of colonic epithelial cells and macrophage-like cells, residing in the bovine mucosa in proximity to STEC colonies, are also targeted by Stxs. STEC-inoculated calves are depressed in mounting appropriate cellular immune responses which can be overcome by vaccination of the animals against Stxs early in life before encountering STEC. Considering Stx target cells and the resulting effects of Stxs in cattle, which significantly differ from effects implicated in human disease, may open promising opportunities to improve existing yet insufficient measures to limit STEC carriage and shedding by the principal reservoir host.
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Affiliation(s)
- Christian Menge
- Friedrich-Loeffler-Institut/Federal Research Institute for Animal Health, Institute of Molecular Pathogenesis, D-07743 Jena, Germany
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3
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Molecular Biology of Escherichia Coli Shiga Toxins' Effects on Mammalian Cells. Toxins (Basel) 2020; 12:toxins12050345. [PMID: 32456125 PMCID: PMC7290813 DOI: 10.3390/toxins12050345] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 05/18/2020] [Accepted: 05/20/2020] [Indexed: 12/11/2022] Open
Abstract
Shiga toxins (Stxs), syn. Vero(cyto)toxins, are potent bacterial exotoxins and the principal virulence factor of enterohemorrhagic Escherichia coli (EHEC), a subset of Shiga toxin-producing E. coli (STEC). EHEC strains, e.g., strains of serovars O157:H7 and O104:H4, may cause individual cases as well as large outbreaks of life-threatening diseases in humans. Stxs primarily exert a ribotoxic activity in the eukaryotic target cells of the mammalian host resulting in rapid protein synthesis inhibition and cell death. Damage of endothelial cells in the kidneys and the central nervous system by Stxs is central in the pathogenesis of hemolytic uremic syndrome (HUS) in humans and edema disease in pigs. Probably even more important, the toxins also are capable of modulating a plethora of essential cellular functions, which eventually disturb intercellular communication. The review aims at providing a comprehensive overview of the current knowledge of the time course and the consecutive steps of Stx/cell interactions at the molecular level. Intervention measures deduced from an in-depth understanding of this molecular interplay may foster our basic understanding of cellular biology and microbial pathogenesis and pave the way to the creation of host-directed active compounds to mitigate the pathological conditions of STEC infections in the mammalian body.
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Exeni RA, Fernandez-Brando RJ, Santiago AP, Fiorentino GA, Exeni AM, Ramos MV, Palermo MS. Pathogenic role of inflammatory response during Shiga toxin-associated hemolytic uremic syndrome (HUS). Pediatr Nephrol 2018; 33:2057-2071. [PMID: 29372302 DOI: 10.1007/s00467-017-3876-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 11/01/2017] [Accepted: 12/07/2017] [Indexed: 01/22/2023]
Abstract
Hemolytic uremic syndrome (HUS) is defined as a triad of noninmune microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The most frequent presentation is secondary to Shiga toxin (Stx)-producing Escherichia coli (STEC) infections, which is termed postdiarrheal, epidemiologic or Stx-HUS, considering that Stx is the necessary etiological factor. After ingestion, STEC colonize the intestine and produce Stx, which translocates across the intestinal epithelium. Once Stx enters the bloodstream, it interacts with renal endothelial and epithelial cells, and leukocytes. This review summarizes the current evidence about the involvement of inflammatory components as central pathogenic factors that could determine outcome of STEC infections. Intestinal inflammation may favor epithelial leakage and subsequent passage of Stx to the systemic circulation. Vascular damage triggered by Stx promotes not only release of thrombin and increased fibrin concentration but also production of cytokines and chemokines by endothelial cells. Recent evidence from animal models and patients strongly indicate that several immune cells types may participate in HUS physiopathology: neutrophils, through release of proteases and reactive oxygen species (ROS); monocytes/macrophages through secretion of cytokines and chemokines. In addition, high levels of Bb factor and soluble C5b-9 (sC5b-9) in plasma as well as complement factors adhered to platelet-leukocyte complexes, microparticles and microvesicles, suggest activation of the alternative pathway of complement. Thus, acute immune response secondary to STEC infection, the Stx stimulatory effect on different immune cells, and inflammatory stimulus secondary to endothelial damage all together converge to define a strong inflammatory status that worsens Stx toxicity and disease.
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Affiliation(s)
- Ramon Alfonso Exeni
- Departamento de Nefrología, Hospital Municipal del Niño, San Justo, Provincia de Buenos Aires, Argentina
| | - Romina Jimena Fernandez-Brando
- Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental Medicine (IMEX-CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina
| | - Adriana Patricia Santiago
- Departamento de Nefrología, Hospital Municipal del Niño, San Justo, Provincia de Buenos Aires, Argentina
| | - Gabriela Alejandra Fiorentino
- Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental Medicine (IMEX-CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina
- Laboratorio, Hospital Municipal del Niño, San Justo, Provincia de Buenos Aires, Argentina
| | - Andrea Mariana Exeni
- Servicio de Nefrología, Hospital Austral, Pilar, Provincia de Buenos Aires, Argentina
| | - Maria Victoria Ramos
- Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental Medicine (IMEX-CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina
| | - Marina Sandra Palermo
- Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto de Medicina Experimental Medicine (IMEX-CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina.
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Abstract
Post-infectious hemolytic uremic syndrome (HUS) is caused by specific pathogens in patients with no identifiable HUS-associated genetic mutation or autoantibody. The majority of episodes is due to infections by Shiga toxin (Stx) producing Escherichia coli (STEC). This chapter reviews the epidemiology and pathogenesis of STEC-HUS, including bacterial-derived factors and host responses. STEC disease is characterized by hematological (microangiopathic hemolytic anemia), renal (acute kidney injury) and extrarenal organ involvement. Clinicians should always strive for an etiological diagnosis through the microbiological or molecular identification of Stx-producing bacteria and Stx or, if negative, serological assays. Treatment of STEC-HUS is supportive; more investigations are needed to evaluate the efficacy of putative preventive and therapeutic measures, such as non-phage-inducing antibiotics, volume expansion and anti-complement agents. The outcome of STEC-HUS is generally favorable, but chronic kidney disease, permanent extrarenal, mainly cerebral complication and death (in less than 5 %) occur and long-term follow-up is recommended. The remainder of this chapter highlights rarer forms of (post-infectious) HUS due to S. dysenteriae, S. pneumoniae, influenza A and HIV and discusses potential interactions between these pathogens and the complement system.
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Affiliation(s)
- Denis F. Geary
- Division of Nephrology, The Hospital for Sick Children, Toronto, Ontario Canada
| | - Franz Schaefer
- Division of Pediatric Nephrology, University of Heidelberg, Heidelberg, Germany
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Xu T, Marr E, Lam H, Ripp S, Sayler G, Close D. Real-time toxicity and metabolic activity tracking of human cells exposed to Escherichia coli O157:H7 in a mixed consortia. ECOTOXICOLOGY (LONDON, ENGLAND) 2015; 24:2133-2140. [PMID: 26423391 PMCID: PMC5597431 DOI: 10.1007/s10646-015-1552-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/16/2015] [Indexed: 06/01/2023]
Abstract
Escherichia coli O157:H7 is a significant human pathogen that is continually responsible for sickness, and even death, on a worldwide scale. While the pathology of E. coli O157:H7 infection has been well studied, the effect of it's multiple resulting cytotoxic mechanisms on host metabolic activity has not been well characterized. To develop a more thorough understanding of these effects, several bioluminescence assays were evaluated for their ability to track both toxicity and host metabolic activity levels in real-time. The use of continuously autobioluminescent human cells was determined to be the most favorable method for tracking these metrics, as its self-sufficient autobioluminescent phenotype was unaffected by the presence of the infecting bacteria and its signal could be measured without cellular destruction. Using this approach, it was determined that infection with as few as 10 CFU of E. coli O157:H7 could elicit cytotoxic effects. Regardless of the initial infective dose, an impact on metabolic expression was not observed until bacterial populations reached levels between 5 × 10(5) and 1 × 10(6) (R(2) = 0.933), indicating that a critical bacterial infection level must be reached prior to the onset of cytotoxic effects. Supporting this hypothesis, it was found that cells displaying infection-mediated metabolic activity reductions could recover to wild type metabolic activity levels if the infecting bacteria were removed prior to cell death. These results indicate that rapid treatment of E. coli O157:H7 infection could serve to limit host metabolic impact and reduce overall host cell death.
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Affiliation(s)
- Tingting Xu
- Center for Environmental Biotechnology, University of Tennessee, 676 Dabney Hall, 1414 Circle Drive, Knoxville, TN, 37996, USA
| | - Enolia Marr
- Center for Environmental Biotechnology, University of Tennessee, 676 Dabney Hall, 1414 Circle Drive, Knoxville, TN, 37996, USA
| | - Haylie Lam
- Center for Environmental Biotechnology, University of Tennessee, 676 Dabney Hall, 1414 Circle Drive, Knoxville, TN, 37996, USA
| | - Steven Ripp
- 490 BioTech, Inc., 2450 E. J. Chapman Drive, Knoxville, TN, 37996, USA
| | - Gary Sayler
- Center for Environmental Biotechnology, University of Tennessee, 676 Dabney Hall, 1414 Circle Drive, Knoxville, TN, 37996, USA
| | - Dan Close
- 490 BioTech, Inc., 2450 E. J. Chapman Drive, Knoxville, TN, 37996, USA.
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Petruzziello-Pellegrini TN, Moslemi-Naeini M, Marsden PA. New insights into Shiga toxin-mediated endothelial dysfunction in hemolytic uremic syndrome. Virulence 2013; 4:556-63. [PMID: 23955166 PMCID: PMC5359733 DOI: 10.4161/viru.26143] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Shiga toxin-producing E. coli represents a significant global health concern, especially as hypervirulent pathogens surface amidst outbreaks of hemolytic uremic syndrome (HUS). Shiga toxin (Stx) is key in the microangiopathic events underlying the disease and its central role is underscored by the unprecedented HUS outbreak in Germany in 2011. The mechanisms of Stx-mediated endothelial dysfunction have been a major focus of research that has contributed to the current understanding of the pathogenic changes in endothelial phenotype leading to HUS. Among the newer concepts are Stx-mediated gene regulation in the absence of protein synthesis inhibition, a potential role for complement activation, and accumulating evidence for detectable serum markers before the onset of the classic clinical features of HUS. Further investigation of newer therapeutic targets and potential prognostic markers is essential to assess their utility in mitigating disease and/or predicting outcomes and will provide an improved overall understanding of HUS pathogenesis.
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Page AV, Liles WC. Enterohemorrhagic Escherichia coli Infections and the Hemolytic-Uremic Syndrome. Med Clin North Am 2013; 97:681-95, xi. [PMID: 23809720 DOI: 10.1016/j.mcna.2013.04.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Enterohemorrhagic Escherichia coli (EHEC; Shiga toxin/verotoxin-producing E. coli) can cause bloody diarrhea and the hemolytic-uremic syndrome (HUS), typically following consumption of contaminated food (including ground beef, leafy greens, and sprouts) and water. Often associated with foodborne outbreaks, EHEC possess unique virulence factors that facilitate effective colonization of the human gastrointestinal tract and subsequent release of Shiga toxin. This article reviews the epidemiology, pathogenesis, clinical presentation, treatment, and prevention of EHEC infections, focusing on E. coli O157:H7, the serotype most common in North America, and E. coli O104:H4, the serotype responsible for the EHEC outbreak in Germany in 2011.
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Affiliation(s)
- Andrea V Page
- Division of Infectious Diseases, Department of Medicine, Mount Sinai Hospital, University Health Network, University of Toronto, 200 Elizabeth Street, Toronto, Ontario, M5G 2C4, Canada.
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Grabowski EF, Kushak RI, Liu B, Ingelfinger JR. Shiga toxin downregulates tissue factor pathway inhibitor, modulating an increase in the expression of functional tissue factor on endothelium. Thromb Res 2013; 131:521-8. [PMID: 23642803 DOI: 10.1016/j.thromres.2013.03.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 03/04/2013] [Accepted: 03/08/2013] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Endothelial expression of tissue factor (TF) may play a major role in (Stx)-related hemolytic uremic syndrome. We examined human umbilical vein endothelial cell (HUVEC) monolayers to determine the interaction between TF and TF pathway inhibitor (TFPI), hypothesizing that changes in TFPI modulate TF expression. MATERIALS AND METHODS We studied 1) cell surface expression of globotriasylceramide (Gb3, the receptor for Stx) with Stx-1 (10 pM), TNFα (20 Ng/ml), or Stx-1 plus TNFα compared to control, 2) gene expression of TF and TFPI, 3) total cellular and cell surface antigenic TF and TFPI, 4) TFPI secretion into supernatant, and 5) factor Xa production. RESULTS AND CONCLUSIONS Gb3 expression, negligible with control and Stx-1 alone, increased significantly with TNFα and with Stx-1 plus TNFα. TF mRNA increased 1.25 ± 0.32- fold (N = 9; p = 0.041) with Stx-1 alone vs. 2.82 ± 0.92-fold (N = 13; p < 0.0005) with TNFα alone. However, Stx-1 plus TNFα yielded a 6.51 ± 3.48-fold increase (N = 17; p < 0.0005). TFPI mRNA decreased with TNFα (p < 0.001) and Stx-1 plus TNFα (p < 0.0005). Total cellular and cell surface TF antigen increased significantly with TNFα, but no further with Stx-1 plus TNFα. Total TFPI cellular and cell surface antigen levels, and TFPI secretion decreased significantly with Stx-1 plus TNFα. Median factor Xa production for Stx-1 plus TNFα vs TNFα alone increased (p < 0.001) 3.24-fold. Our results indicate that a subinhibitory concentration of Stx-1 plus TNFα impairs TFPI gene expression, synthesis, cell-surface association, and secretion, leading to augmented functional TF.
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Affiliation(s)
- Eric F Grabowski
- Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
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Shi PL, Binnington B, Sakac D, Katsman Y, Ramkumar S, Gariepy J, Kim M, Branch DR, Lingwood C. Verotoxin A subunit protects lymphocytes and T cell lines against X4 HIV infection in vitro. Toxins (Basel) 2012; 4:1517-34. [PMID: 23242319 PMCID: PMC3528260 DOI: 10.3390/toxins4121517] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 11/24/2012] [Accepted: 12/06/2012] [Indexed: 11/23/2022] Open
Abstract
Our previous genetic, pharmacological and analogue protection studies identified the glycosphingolipid, Gb3 (globotriaosylceramide, Pk blood group antigen) as a natural resistance factor for HIV infection. Gb3 is a B cell marker (CD77), but a fraction of activated peripheral blood mononuclear cells (PBMCs) can also express Gb3. Activated PBMCs predominantly comprise CD4+ T-cells, the primary HIV infection target. Gb3 is the sole receptor for Escherichia coli verotoxins (VTs, Shiga toxins). VT1 contains a ribosome inactivating A subunit (VT1A) non-covalently associated with five smaller receptor-binding B subunits. The effect of VT on PHA/IL2-activated PBMC HIV susceptibility was determined. Following VT1 (or VT2) PBMC treatment during IL2/PHA activation, the small Gb3+/CD4+ T-cell subset was eliminated but, surprisingly, remaining CD4+ T-cell HIV-1IIIB (and HIV-1Ba-L) susceptibility was significantly reduced. The Gb3-Jurkat T-cell line was similarly protected by brief VT exposure prior to HIV-1IIIB infection. The efficacy of the VT1A subunit alone confirmed receptor independent protection. VT1 showed no binding or obvious Jurkat cell/PBMC effect. Protective VT1 concentrations reduced PBMC (but not Jurkat cell) proliferation by 50%. This may relate to the mechanism of action since HIV replication requires primary T-cell proliferation. Microarray analysis of VT1A-treated PBMCs indicated up regulation of 30 genes. Three of the top four were histone genes, suggesting HIV protection via reduced gene activation. VT blocked HDAC inhibitor enhancement of HIV infection, consistent with a histone-mediated mechanism. We speculate that VT1A may provide a benign approach to reduction of (X4 or R5) HIV cell susceptibility.
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Affiliation(s)
- Pei Lin Shi
- Department of Biochemistry, University of Toronto, Ontario M5G 1X8, Canada; E-Mail:
- Division of Molecular Structure and Function and Research Institute, The Hospital for Sick Children, Ontario M5G 1X8, Canada; E-Mail:
| | - Beth Binnington
- Division of Molecular Structure and Function and Research Institute, The Hospital for Sick Children, Ontario M5G 1X8, Canada; E-Mail:
| | - Darinka Sakac
- Canadian Blood Services, Toronto, Ontario M5G 2M1, Canada; E-Mails: (D.S.); (Y.K.)
| | - Yulia Katsman
- Canadian Blood Services, Toronto, Ontario M5G 2M1, Canada; E-Mails: (D.S.); (Y.K.)
| | - Stephanie Ramkumar
- Laboratory Medicine & Pathology, University of Toronto, Ontario M5G 1X8, Canada; E-Mails: (S.R.); (M.K.); (D.R.B.)
| | - Jean Gariepy
- Department of Medical Biophysics & Pharmaceutical Sciences, University of Toronto, Ontario M5G 1X8, Canada; E-Mail:
- Sunnybrook Research Institute, Sunnybrook Health Science Centre, Toronto M4N 3M5, Canada
| | - Minji Kim
- Canadian Blood Services, Toronto, Ontario M5G 2M1, Canada; E-Mails: (D.S.); (Y.K.)
- Laboratory Medicine & Pathology, University of Toronto, Ontario M5G 1X8, Canada; E-Mails: (S.R.); (M.K.); (D.R.B.)
| | - Donald R. Branch
- Canadian Blood Services, Toronto, Ontario M5G 2M1, Canada; E-Mails: (D.S.); (Y.K.)
- Laboratory Medicine & Pathology, University of Toronto, Ontario M5G 1X8, Canada; E-Mails: (S.R.); (M.K.); (D.R.B.)
- Department of Medicine, University of Toronto, Ontario M5G 1X8, Canada
- Division of Cell and Molecular Biology, Toronto General Research Institute of the University Health Network, Toronto, Ontario M5G 2M9, Canada
| | - Clifford Lingwood
- Department of Biochemistry, University of Toronto, Ontario M5G 1X8, Canada; E-Mail:
- Division of Molecular Structure and Function and Research Institute, The Hospital for Sick Children, Ontario M5G 1X8, Canada; E-Mail:
- Laboratory Medicine & Pathology, University of Toronto, Ontario M5G 1X8, Canada; E-Mails: (S.R.); (M.K.); (D.R.B.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-416-813-5998; Fax: +1-416-813-5993
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Shiga toxin-associated hemolytic uremic syndrome: advances in pathogenesis and therapeutics. Curr Opin Nephrol Hypertens 2012; 21:433-40. [PMID: 22660553 DOI: 10.1097/mnh.0b013e328354a62e] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
PURPOSE OF REVIEW Diarrhea-associated hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC) continues to be an important public health threat worldwide. Specific therapies are lacking and patient care remains largely supportive. This review discusses the lessons learned from recent events and summarizes key advances made toward understanding the basic mechanisms involved in the pathogenesis of typical HUS. RECENT FINDINGS The recent German outbreak of a hybrid organism resulted in an unprecedented number of HUS cases and drastically changed the face of typical (diarrhea-associated) HUS. New findings on the roles of complement and the CXCR4/SDF-1 pathway in HUS pathogenesis are summarized and novel therapeutic strategies are highlighted. SUMMARY A better understanding of STEC-mediated HUS underlies improved therapeutic approaches. New studies of the mechanistic basis of the disease, together with patient-based studies, have led to key findings with important clinical implications.
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Abstract
Endothelial cells are essential regulators of vascular tone. They accomplish this by sensing humoral mediators and transducing their effects to the underlying vascular smooth muscle as well as by synthesizing vasoactive molecules that act in a paracrine fashion. In the kidney, the local release of these endothelial mediators, together with the concourse of specialized endothelial cells in the glomerulus, contribute to regulate renal blood flow, glomerular filtration, and tubular function that are intimately linked to sodium balance because they mutually influence each other. Ultimately, renal circulation and tubular function have a profound influence in systemic blood pressure as a result of the overall regulation of volume homeostasis.
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Petruzziello-Pellegrini TN, Yuen DA, Page AV, Patel S, Soltyk AM, Matouk CC, Wong DK, Turgeon PJ, Fish JE, Ho JJD, Steer BM, Khajoee V, Tigdi J, Lee WL, Motto DG, Advani A, Gilbert RE, Karumanchi SA, Robinson LA, Tarr PI, Liles WC, Brunton JL, Marsden PA. The CXCR4/CXCR7/SDF-1 pathway contributes to the pathogenesis of Shiga toxin-associated hemolytic uremic syndrome in humans and mice. J Clin Invest 2012. [PMID: 22232208 DOI: 10.1172/jci57313)] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Hemolytic uremic syndrome (HUS) is a potentially life-threatening condition. It often occurs after gastrointestinal infection with E. coli O157:H7, which produces Shiga toxins (Stx) that cause hemolytic anemia, thrombocytopenia, and renal injury. Stx-mediated changes in endothelial phenotype have been linked to the pathogenesis of HUS. Here we report our studies investigating Stx-induced changes in gene expression and their contribution to the pathogenesis of HUS. Stx function by inactivating host ribosomes but can also alter gene expression at concentrations that minimally affect global protein synthesis. Gene expression profiling of human microvascular endothelium treated with Stx implicated a role for activation of CXCR4 and CXCR7 by their shared cognate chemokine ligand (stromal cell-derived factor-1 [SDF-1]) in Stx-mediated pathophysiology. The changes in gene expression required a catalytically active Stx A subunit and were mediated by enhanced transcription and mRNA stability. Stx also enhanced the association of CXCR4, CXCR7, and SDF1 mRNAs with ribosomes. In a mouse model of Stx-mediated pathology, we noted changes in plasma and tissue content of CXCR4, CXCR7, and SDF-1 after Stx exposure. Furthermore, inhibition of the CXCR4/SDF-1 interaction decreased endothelial activation and organ injury and improved animal survival. Finally, in children infected with E. coli O157:H7, plasma SDF-1 levels were elevated in individuals who progressed to HUS. Collectively, these data implicate the CXCR4/CXCR7/SDF-1 pathway in Stx-mediated pathogenesis and suggest novel therapeutic strategies for prevention and/or treatment of complications associated with E. coli O157:H7 infection.
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Petruzziello-Pellegrini TN, Yuen DA, Page AV, Patel S, Soltyk AM, Matouk CC, Wong DK, Turgeon PJ, Fish JE, Ho JJD, Steer BM, Khajoee V, Tigdi J, Lee WL, Motto DG, Advani A, Gilbert RE, Karumanchi SA, Robinson LA, Tarr PI, Liles WC, Brunton JL, Marsden PA. The CXCR4/CXCR7/SDF-1 pathway contributes to the pathogenesis of Shiga toxin-associated hemolytic uremic syndrome in humans and mice. J Clin Invest 2012; 122:759-76. [PMID: 22232208 DOI: 10.1172/jci57313] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 11/17/2011] [Indexed: 01/18/2023] Open
Abstract
Hemolytic uremic syndrome (HUS) is a potentially life-threatening condition. It often occurs after gastrointestinal infection with E. coli O157:H7, which produces Shiga toxins (Stx) that cause hemolytic anemia, thrombocytopenia, and renal injury. Stx-mediated changes in endothelial phenotype have been linked to the pathogenesis of HUS. Here we report our studies investigating Stx-induced changes in gene expression and their contribution to the pathogenesis of HUS. Stx function by inactivating host ribosomes but can also alter gene expression at concentrations that minimally affect global protein synthesis. Gene expression profiling of human microvascular endothelium treated with Stx implicated a role for activation of CXCR4 and CXCR7 by their shared cognate chemokine ligand (stromal cell-derived factor-1 [SDF-1]) in Stx-mediated pathophysiology. The changes in gene expression required a catalytically active Stx A subunit and were mediated by enhanced transcription and mRNA stability. Stx also enhanced the association of CXCR4, CXCR7, and SDF1 mRNAs with ribosomes. In a mouse model of Stx-mediated pathology, we noted changes in plasma and tissue content of CXCR4, CXCR7, and SDF-1 after Stx exposure. Furthermore, inhibition of the CXCR4/SDF-1 interaction decreased endothelial activation and organ injury and improved animal survival. Finally, in children infected with E. coli O157:H7, plasma SDF-1 levels were elevated in individuals who progressed to HUS. Collectively, these data implicate the CXCR4/CXCR7/SDF-1 pathway in Stx-mediated pathogenesis and suggest novel therapeutic strategies for prevention and/or treatment of complications associated with E. coli O157:H7 infection.
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Moon Y. Cellular alterations of mucosal integrity by ribotoxins: Mechanistic implications of environmentally-linked epithelial inflammatory diseases. Toxicon 2012; 59:192-204. [DOI: 10.1016/j.toxicon.2011.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 10/20/2011] [Accepted: 11/10/2011] [Indexed: 01/01/2023]
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Rescue from lethal Shiga toxin 2-induced renal failure with a cell-permeable peptide. Pediatr Nephrol 2011; 26:2031-9. [PMID: 21603905 PMCID: PMC3179571 DOI: 10.1007/s00467-011-1913-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/28/2011] [Accepted: 04/28/2011] [Indexed: 12/22/2022]
Abstract
Intestinal infection with Shiga toxin (Stx)-producing E.coli is a leading cause of hemolytic uremic syndrome and acute renal injury in otherwise healthy children in the US. Antibiotics are contraindicated and a therapeutic priority is agents that act intracellularly against the bacterial toxins that drive kidney injury. Our aim was to evaluate whether intravenous administration of a cell-permeable peptide (TVP) that binds to Stx2 will reduce disease severity and rescue juvenile baboons from a lethal Stx2 dose (50 ng/kg). TVP (5 mg/kg) was delivered i.v. simultaneously with toxin (prevention protocol) or at 6 or 24 h after toxin with daily 1 mg/kg supplements up to day 4 (rescue protocols). Biomarkers were monitored in blood and urine up to 28 days. TVP therapy resulted in either absence of clinical signs of acute kidney injury and normal urine output (prevention), or delayed and reduced BUN and creatinine levels (rescue) with concomitant survival. Delayed peptide administration significantly reduced thrombocytopenia, but surprisingly did not alter anemia even when monitored for 28 days in rescued survivors. This is the first successful cell-permeable therapeutic that counteracts Stx2 lethality in an animal model, which recapitulates many of the human responses to enteric infection.
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17
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Shiga toxin-associated hemolytic uremic syndrome: pathophysiology of endothelial dysfunction. Pediatr Nephrol 2010; 25:2231-40. [PMID: 20424866 DOI: 10.1007/s00467-010-1522-1] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 03/15/2010] [Accepted: 03/15/2010] [Indexed: 12/24/2022]
Abstract
Shiga toxin (Stx)-producing enterohemorrhagic Escherichia coli O157:H7 has become a global threat to public health, as a primary cause of a worldwide spread of hemorrhagic colitis complicated by diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure that mainly affects early childhood. Endothelial dysfunction has been recognized as the trigger event in the development of microangiopathic processes. Endothelial cells, mainly those located in the renal microvasculature, are primary targets of the toxic effects of Stx1 and 2. Stxs bound to their specific globotriaosylceramide (Gb3Cer) receptor on the cell surface trigger a cascade of signaling events, involving NF-κB activation, that induce expression of genes encoding for adhesion molecules and chemokines, and culminate in the adhesion of leukocytes to endothelial cells, thereby increasing the endothelial susceptibility to leukocyte-mediated injury. Activated endothelial cells in response to Stxs lose the normal thromboresistance phenotype and become thrombogenic, initiating microvascular thrombus formation. Evidence is emerging that complement activation in response to Stxs favors platelet thrombus formation on endothelial cells, which may play a role in amplifying the inflammation-thrombosis circuit in Stx-associated HUS.
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18
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He JZ, Ho JJD, Gingerich S, Courtman DW, Marsden PA, Ward ME. Enhanced translation of heme oxygenase-2 preserves human endothelial cell viability during hypoxia. J Biol Chem 2010; 285:9452-9461. [PMID: 20118244 DOI: 10.1074/jbc.m109.077230] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Heme oxygenases (HOs) -1 and -2 catalyze the breakdown of heme to release carbon monoxide, biliverdin, and ferrous iron, which may preserve cell function during oxidative stress. HO-1 levels decrease in endothelial cells exposed to hypoxia, whereas the effect of hypoxia on HO-2 expression is unknown. The current study was carried out to determine if hypoxia alters HO-2 protein levels in human endothelial cells and whether this enzyme plays a role in preserving their viability during hypoxic stress. Human umbilical vein endothelial cells (HUVECs), human aortic endothelial cells (HAECs), and human blood outgrowth endothelial cells were exposed to 21% or 1% O(2) for 48 or 16 h in the presence or absence of tumor necrosis factor-alpha (10 ng/ml) or H(2)O(2) (100 microm). In all three endothelial cell types HO-1 mRNA and protein levels were decreased following hypoxic incubation, whereas HO-2 protein levels were unaltered. In HUVECs HO-2 levels were maintained during hypoxia despite a 57% reduction in steady-state HO-2 mRNA level and a 43% reduction in total protein synthesis. Polysome profiling revealed increased HO-2 transcript association with polysomes during hypoxia consistent with enhanced translation of these transcripts. Importantly, inhibition of HO-2 expression by small interference RNA increased oxidative stress, exacerbated mitochondrial membrane depolarization, and enhanced caspase activation and apoptotic cell death in cells incubated under hypoxic but not normoxic conditions. These data indicate that HO-2 is important in maintaining endothelial viability and may preserve local regulation of vascular tone, thrombosis, and inflammatory responses during reductions in systemic oxygen delivery.
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Affiliation(s)
- Jeff Z He
- Terrence Donnelly Laboratories, Toronto, Ontario M5B 1W8; Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario M5B 1W8; Departments of Laboratory Medicine and Pathobiology, Toronto, Ontario M5S 1A8, Canada
| | - J J David Ho
- Medical Biophysics, Toronto, Ontario M5S 1A8, Canada
| | - Sheena Gingerich
- Nephrology, Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - David W Courtman
- Terrence Donnelly Laboratories, Toronto, Ontario M5B 1W8; Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario M5B 1W8
| | - Philip A Marsden
- Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario M5B 1W8; Nephrology, Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
| | - Michael E Ward
- Terrence Donnelly Laboratories, Toronto, Ontario M5B 1W8; Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario M5B 1W8; Departments of Laboratory Medicine and Pathobiology, Toronto, Ontario M5S 1A8, Canada; Divisions of Respirology, Toronto, Ontario M5S 1A8, Canada
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19
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Siegler RL, Pysher TJ, Tesh VL, Noris M, Cassis P, Taylor FB. Reduced Nitric Oxide Bioavailability In a Baboon Model of Shiga Toxin Mediated Hemolytic Uremic Syndrome (HUS). Ren Fail 2009; 27:635-41. [PMID: 16153006 DOI: 10.1080/08860220500200841] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND Although there is agreement that post-diarrheal hemolytic uremic syndrome (D+ HUS) is caused by Shiga toxin (Stx)-producing E. coli, little is known about factors that mediate the host response to these toxins and potentially contribute to pathogenesis. Nitric oxide (NO) is a candidate mediator by virtue of its antiplatelet and renal vasodilatory properties. METHODS We used a baboon model of HUS to measure plasma and urinary NO metabolites and expression of NO synthase (eNOS and iNOS) in renal tissue following the intravenous administration of Stx-1. RESULTS Plasma concentrations through 60 hours of observation did not differ significantly from controls. Urinary values (indexed against urinary creatinine) tended, however, to rise during the initial 12 hours following administration of Stx-1. This was followed by a sustained reduction that coincided with the development of hemolytic anemia (schistocytosis) and other features of HUS. However, immunohistochemical staining for eNOS and iNOS in tissue obtained immediately after death at a median of 59 hours showed similar levels in control and Stx-treated animals, despite the presence of a florid thrombotic microangiopathy and tubular injury in the Stx-treated group. CONCLUSION We propose that urinary NO metabolite reduction was due to NO inactivation subsequent to its avid binding to free hemoglobin released from lysed red blood cells, and that this contributed to the acute renal failure by facilitating vasoconstriction and platelet aggregation and adhesion within the renal microvasculature.
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Affiliation(s)
- Richard L Siegler
- Division of Nephrology and Hypertension, Department of Pediatrics, University School of Medicine, 30 N 1900 E #2B422, Salt Lake City, UT 84132, USA.
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20
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Petruzziello TN, Mawji IA, Khan M, Marsden PA. Verotoxin biology: molecular events in vascular endothelial injury. Kidney Int 2009:S17-9. [DOI: 10.1038/ki.2008.612] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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da Silva RF, Chambaz C, Stergiopulos N, Hayoz D, Silacci P. Transcriptional and post-transcriptional regulation of preproendothelin-1 by plaque-prone hemodynamics. Atherosclerosis 2007; 194:383-90. [PMID: 17324434 DOI: 10.1016/j.atherosclerosis.2007.01.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Revised: 01/22/2007] [Accepted: 01/23/2007] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Plaque-prone areas are exposed to a particular hemodynamic environment characterized by a low mean shear stress value and a cyclic reversal flow. This mechanical environment, also termed oscillatory shear stress (OSS), induces the expression of several pro-atherogenic genes in the endothelial cells including the preproendothelin-1 (ppET-1) gene. The present paper investigates the molecular mechanisms of this induction. METHODS AND RESULTS Several deletional mutants of ppET-1 gene promoter were cloned upstream of a luciferase gene and transiently transfected in bovine arterial endothelial cells that were further exposed to plaque-prone hemodynamics. After 24h of flow exposure, analysis of the transfected cells showed that a proximal promoter of 156 base pairs length retained OSS responsiveness. Mutation of an activator protein-1 (AP-1) binding site present in this minimal promoter completely abolished its activation by OSS. Consistently, electrophoresis mobility shift assay revealed a sustained activation of AP-1 transcription factor in endothelial cells exposed to OSS. In addition to the transcriptional activation, we demonstrated that OSS also induces a stabilization of ppET-1mRNA through the 3'-untranslated region (3'-UTR) of this gene. Fluvastatin, a drug known to improve endothelial function, was shown to prevent OSS up-regulation of the ppET-1 gene expression. Under this flow condition, fluvastatin affects ppET-1 gene expression via inhibition of its promoter activity without affecting ppET-1mRNA stability. CONCLUSIONS The present study demonstrate that plaque-prone hemodynamic induces ppET-1 gene expression by both transcriptional and post-transcriptional mechanisms via an activation of AP-1 transcriptional factor and stabilization of mRNA. The transcriptional up-regulation of ppET-1 was shown to be fluvastatin sensitive.
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Affiliation(s)
- Rafaela Fernandes da Silva
- Laboratory of Hemodynamics and Cardiovascular Technology, Building AI 1232, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland.
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23
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van Deel ED, Merkus D, van Haperen R, de Waard MC, de Crom R, Duncker DJ. Vasomotor control in mice overexpressing human endothelial nitric oxide synthase. Am J Physiol Heart Circ Physiol 2007; 293:H1144-53. [PMID: 17496213 DOI: 10.1152/ajpheart.00773.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nitric oxide (NO) plays a key role in regulating vascular tone. Mice overexpressing endothelial NO synthase [eNOS-transgenic (Tg)] have a 20% lower systemic vascular resistance (SVR) than wild-type (WT) mice. However, because eNOS enzyme activity is 10 times higher in tissue homogenates from eNOS-Tg mice, this in vivo effect is relatively small. We hypothesized that the effect of eNOS overexpression is attenuated by alterations in NO signaling and/or altered contribution of other vasoregulatory pathways. In isoflurane-anesthetized open-chest mice, eNOS inhibition produced a significantly greater increase in SVR in eNOS-Tg mice compared with WT mice, consistent with increased NO synthesis. Vasodilation to sodium nitroprusside (SNP) was reduced, whereas the vasodilator responses to phosphodiesterase-5 blockade and 8-bromo-cGMP (8-Br-cGMP) were maintained in eNOS-Tg compared with WT mice, indicating blunted responsiveness of guanylyl cyclase to NO, which was supported by reduced guanylyl cyclase activity. There was no evidence of eNOS uncoupling, because scavenging of reactive oxygen species (ROS) produced even less vasodilation in eNOS-Tg mice, whereas after eNOS inhibition the vasodilator response to ROS scavenging was similar in WT and eNOS-Tg mice. Interestingly, inhibition of other modulators of vascular tone [including cyclooxygenase, cytochrome P-450 2C9, endothelin, adenosine, and Ca-activated K(+) channels] did not significantly affect SVR in either eNOS-Tg or WT mice, whereas the marked vasoconstrictor responses to ATP-sensitive K(+) and voltage-dependent K(+) channel blockade were similar in WT and eNOS-Tg mice. In conclusion, the vasodilator effects of eNOS overexpression are attenuated by a blunted NO responsiveness, likely at the level of guanylyl cyclase, without evidence of eNOS uncoupling or adaptations in other vasoregulatory pathways.
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Affiliation(s)
- Elza D van Deel
- Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, The Netherlands
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24
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Te Loo DM, Monnens L, van der Velden T, Karmali M, van den Heuvel L, van Hinsbergh V. Shiga toxin-1 affects nitric oxide production by human glomerular endothelial and mesangial cells. Pediatr Nephrol 2006; 21:1815-23. [PMID: 16944213 DOI: 10.1007/s00467-006-0232-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2006] [Revised: 05/14/2006] [Accepted: 05/15/2006] [Indexed: 10/24/2022]
Abstract
Acute renal failure hallmarks the pathogenesis of the epidemic form of hemolytic uremic syndrome (D+HUS), which is caused by E. coli strains that produce Shiga-like toxin (Stx). In this study, we investigated the influence of Stx-1 on nitric oxide (NO) production by human glomerular microvascular endothelial cells (GMVEC) and human mesangial cells. NO synthesis by human mesangial cells is in the micromolar range and that of GMVEC in the picomolar range. Stx-1 reduced NO production in non-stimulated GMVEC (5 nmol/l Stx-1 required) without inhibition of protein synthesis. In non-stimulated and TNFalpha-pretreated mesangial cells, NO production was reduced with a maximal reduction at 10 fmol/l shiga toxin. The cellular iNOS antigen content in mesangial cells was reduced in a concentration-dependent way (10 fmol/l-100 pmol/l), while partial inhibition of protein synthesis required 10 nmol/l Stx-1 in these cells. Our in vitro data suggest that Stx may reduce NO synthesis during the course of HUS development, contributing to the aggravation of the thrombotic microangiopathy and renal failure as observed in HUS.
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Affiliation(s)
- D Maroeska Te Loo
- Department of Pediatrics, University Hospital Nijmegen, Nijmegen, The Netherlands
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25
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Moussay E, Stamm I, Taubert A, Baljer G, Menge C. Escherichia coli Shiga toxin 1 enhances il-4 transcripts in bovine ileal intraepithelial lymphocytes. Vet Immunol Immunopathol 2006; 113:367-82. [PMID: 16879873 DOI: 10.1016/j.vetimm.2006.06.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2006] [Revised: 04/04/2006] [Accepted: 06/19/2006] [Indexed: 11/27/2022]
Abstract
Shiga toxin 1 (Stx1) blocks the activation of bovine peripheral and intraepithelial lymphocytes (IEL), implying that the toxin has the potential to retard the host's immune response during intestinal colonization of cattle with human pathogenic Stx-producing Escherichia coli (STEC). Since Stx1 does not eliminate affected lymphocytes by causing cellular death, we assumed that Stx1 disturbs the integrity of the immune regulatory network. We therefore assessed the impact of Stx1 on the expression of selected chemokine and cytokine genes in vitro by real-time RT-PCR and by quantitation of intracellular cytokine proteins. While Stx1 did not alter the amount of mRNA specific for interleukin (IL)-2, IL-10, gamma interferon (IFN-gamma), transforming growth factor beta (TGF-beta), IL-8, 10kDa interferon inducible protein (IP-10), and monocyte chemoattractant protein 1 (MCP-1) in cultured ileal IEL (iIEL), minute concentrations of Stx1 led to an up to 40-fold increase of il-4 transcripts within 6-8h of incubation. Comparative experiments with peripheral lymphocytes revealed that the effect was specific for iIEL. The enhancement of il-4 transcripts in iIEL was not accompanied by apoptosis but required the enzymatic activity of the holotoxin. Nevertheless, iIEL retained their ability to synthesize proteins in the presence of Stx1: 40% of iIEL could be stimulated to synthesize IFN-gamma while less than 10% expressed IL-4 or TGF-beta. Furthermore, iIEL were found to produce granulocyte chemoattractants, but the release of these substances was not different in iIEL cultures incubated with or without Stx1. Although Stx1 did not affect the numbers of iIEL producing either cytokine, these findings point to an altered responsiveness of IEL during bovine STEC infections and shed light on the initial effects Stx1 exerts on the local adaptive immune system.
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Affiliation(s)
- Etienne Moussay
- Institute for Hygiene and Infectious Diseases of Animals, Frankfurter Strasse 85-89, Justus-Liebig-University, D-35392 Giessen, Germany
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Abstract
Enterohaemorrhagic Escherichia coli (EHEC) are the pathogenic subgroup of Shiga toxin (Stx)-producing E. coli. EHEC can cause non-bloody and bloody diarrhoea, and the haemolytic uraemic syndrome (HUS). HUS is a major cause of acute renal failure in children. E. coli O57:H7 is the predominant, but far from being the only, serotype that can cause HUS. The cascade leading from gastrointestinal infection to renal impairment is complex, with the microvascular endothelium being the major histopathological target. EHEC also produce non-Stx molecules, such as cytolethal distending toxin, which can contribute to the endothelial or vascular injury. Because there are no specific therapies for EHEC infections, efficient reservoir and human preventive strategies are important areas of ongoing investigations. This review will focus on the microbiology, epidemiology, and pathophysiology of EHEC-associated diseases, and illustrate future challenges and opportunities for their control.
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Affiliation(s)
- Helge Karch
- Institute for Hygiene, and National Consulting Laboratory on Haemolytic Uraemic Syndrome, University Hospital Münster, Robert Koch Str. 41, D-48149 Münster, Germany.
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Fish JE, Matouk CC, Rachlis A, Lin S, Tai SC, D'Abreo C, Marsden PA. The expression of endothelial nitric-oxide synthase is controlled by a cell-specific histone code. J Biol Chem 2005; 280:24824-38. [PMID: 15870070 DOI: 10.1074/jbc.m502115200] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Expression of endothelial nitric-oxide synthase (eNOS) mRNA is highly restricted to the endothelial cell layer of medium to large sized arterial blood vessels. Here we assessed the chromatin environment of the eNOS gene in expressing and nonexpressing cell types. Within endothelial cells, but not a variety of nonendothelial cells, the nucleosomes that encompassed the eNOS core promoter and proximal downstream coding regions were highly enriched in acetylated histones H3 and H4 and methylated lysine 4 of histone H3. This differentially modified chromatin domain was selectively associated with functionally competent RNA polymerase II complexes. Endothelial cells were particularly enriched in acetylated histone H3 lysine 9, histone H4 lysine 12, and di- and tri-methylated lysine 4 of histone H3 at the core promoter. Histone modifications at this region, which we have previously demonstrated to exhibit cell-specific DNA methylation, were functionally relevant to eNOS expression. Inhibition of histone deacetylase activity by trichostatin A increased acetylation of histones H3 and H4 at the eNOS proximal promoter in nonexpressing cell types and led to increased steady-state eNOS mRNA transcript levels. H3 lysine 4 methylation was also essential for eNOS expression, since treatment of endothelial cells with methylthioadenosine, a known lysine 4 methylation inhibitor, decreased eNOS RNA levels, H3 lysine 4 methylation, and RNA polymerase II loading at the eNOS proximal promoter. Importantly, methylthioadenosine also prevented the trichostatin A-mediated increase in eNOS mRNA transcript levels in nonendothelial cells. Taken together, these findings provide strong evidence that the endothelial cell-specific expression of eNOS is controlled by cell-specific histone modifications.
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Affiliation(s)
- Jason E Fish
- Department of Medical Biophysics, St. Michael's Hospital and University of Toronto, Toronto, Ontario M5S 1A8, Canada
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Alexandrescu DT, Maddukuri P, Wiernik PH, Dutcher JP. Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome Associated with High-Dose Interleukin-2 for the Treatment of Metastatic Melanoma. J Immunother 2005; 28:144-7. [PMID: 15725958 DOI: 10.1097/01.cji.0000154250.82007.4a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Various drugs have been associated with the development of thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Among the biologic agents, alpha-interferon therapy, used for treatment of hepatitis B and chronic myelogenous leukemia, has been associated with TTP in a few recent reports. The authors report the first case of TTP/HUS occurring in a metastatic melanoma patient receiving treatment with high-dose interleukin-2 (IL-2). A 57-year-old patient with malignant melanoma presented with seizures 3 days after completing the first week of high-dose IL-2, and the characteristic hematologic picture revealed TTP/HUS. This occurrence is unlikely to be explained by the association with malignant melanoma, which was not presenting with widespread visceral disease at the time of the occurrence, or by the use of other medications. Similar cytokine release profiles are encountered in TTP, HUS caused by Shiga toxin-1, HUS caused by E. coli O157, after IL-2 or IL-2-containing biochemotherapy, as well as in TTP caused by interferon-alpha. This cytokine profile could reflect a common cause, or just the presence of similar pathways involved.
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Affiliation(s)
- Doru T Alexandrescu
- Comprehensive Cancer Center, Our Lady of Mercy Medical Center, New York Medical College, Bronx, New York 10466, USA.
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Gorczynski RM, Chen Z, Clark DA, Kai Y, Lee L, Nachman J, Wong S, Marsden P. Structural and functional heterogeneity in the CD200R family of immunoregulatory molecules and their expression at the feto-maternal interface. Am J Reprod Immunol 2005; 52:147-63. [PMID: 15274657 DOI: 10.1111/j.1600-0897.2004.00192.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
PROBLEM We have shown that CD200Fc, a chimeric molecule including the extracellular domain of CD200 and a murine immunoglobulin (Ig)G2a Fc region, regulates immune responses and prevents T helper (Th)1 cytokine-triggered spontaneous abortions in mice. CD200 is expressed on a subpopulation of uterine decidua cells and on trophoblast, both in the mouse and human. The receptor(s) for CD200, CD200R(s), was not previously well-characterized. METHODS 5'-rapid amplification of cDNA ends (RACE), cDNA and genomic DNA clone analysis were used to identify a family of CD200Rs on mouse chromosome 16, juxtaposed to the CD200 gene, named CD200R1, R2, R3, and R4. Northern blot and reverse transcriptase polymerase chain reaction (RT-PCR) analysis was used to detect expression of different CD200R subtypes in different organs. Rabbit polyclonal and rat monoclonal antibodies (mAbs) to CD200R isoforms was used for fluorescence-activated cell sorter (FACS) analysis, to test for immunomodulatory effects on allogeneic mixed-lymphocyte responses in vitro, and for immunohistochemistry. RESULTS The CD200Fc was able to interact physically with each of the CD200Rs expressed on the cell surface. Northern blot and RT-PCR analyses indicated distinct patterns of CD200R isoform mRNA expression in different tissues and FACS analyses confirmed unique cell- and tissue-specific expression of the different CD200Rs. mAbs directed against the different isoforms modified the development of in vitro alloimmune responses. The addition of anti-CD200R1/R4 elicited immunomodulatory responses in vitro comparable to findings with CD200Fc, but different from the effects of anti-CD200R2-3. CONCLUSIONS These data provide evidence for a family of CD200R molecules in the mouse genome and defines the existence of previously unrecognized diversity in the CD200/CD200R immunomodulatory gene member family. Although this gene member family is clustered in the genome, the different CD200Rs and CD200 exhibit distinct expression patterns and functional properties. Restricted CD200R isoform expression at the feto-maternal interface suggests CD200:CD200R interactions may serve important function(s) determining the successful outcome of pregnancy.
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Klinge CM, Blankenship KA, Risinger KE, Bhatnagar S, Noisin EL, Sumanasekera WK, Zhao L, Brey DM, Keynton RS. Resveratrol and estradiol rapidly activate MAPK signaling through estrogen receptors alpha and beta in endothelial cells. J Biol Chem 2004; 280:7460-8. [PMID: 15615701 DOI: 10.1074/jbc.m411565200] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vascular endothelial cells (EC) are an important target of estrogen action through both the classical genomic (i.e. nuclear-initiated) activities of estrogen receptors alpha and beta (ERalpha and ERbeta) and the rapid "non-genomic" (i.e. membrane-initiated) activation of ER that stimulates intracellular phosphorylation pathways. We tested the hypothesis that the red wine polyphenol trans-resveratrol activates MAPK signaling via rapid ER activation in bovine aortic EC, human umbilical vein EC, and human microvascular EC. We report that bovine aortic EC, human umbilical vein EC, and human microvascular EC express ERalpha and ERbeta. We demonstrate that resveratrol and estradiol (E(2)) rapidly activated MAPK in a MEK-1, Src, matrix metalloproteinase, and epidermal growth factor receptor-dependent manner. Importantly, resveratrol activated MAPK and endothelial nitric-oxide synthase (eNOS) at nm concentrations (i.e. an order of magnitude less than that required for ER genomic activity) and concentrations possibly achieved transiently in serum following oral red wine consumption. Co-treatment with ER antagonists ICI 182,780 or 4-hydroxytamoxifen blocked resveratrol- or E(2)-induced MAPK and eNOS activation, indicating ER dependence. We demonstrate for the first time that ERalpha-and ERbeta-selective agonists propylpyrazole triol and diarylpropionitrile, respectively, stimulate MAPK and eNOS activity. A red but not a white wine extract also activated MAPK, and activity was directly correlated with the resveratrol concentration. These data suggest that ER may play a role in the rapid effects of resveratrol in EC and that some of the atheroprotective effects of resveratrol may be mediated through rapid activation of ER signaling in EC.
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Affiliation(s)
- Carolyn M Klinge
- Department of Biochemistry & Molecular Biology and Center for Genetics and Molecular Medicine, School of Medicine, University of Louisville, Kentucky 40292, USA.
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31
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Kitaichi K, Nakayama H, Ueyama J, Nadai M, Baba K, Takagi K, Takagi K, Ohta M, Hasegawa T. Down-regulation of cytochrome P450 proteins and its activities by Shiga-like toxin II from Escherichia coli O157:H7. Biochem Pharmacol 2004; 67:1427-35. [PMID: 15041460 DOI: 10.1016/j.bcp.2003.12.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2003] [Accepted: 12/01/2003] [Indexed: 11/25/2022]
Abstract
Escherichia coli O157:H7 infection frequently induces clinical complications such as hemolytic uremic syndromes and intestinal dysfunctions. These changes could alter the disposition of drugs, consequently changing their efficacy. However, the possible changes of drug-metabolizing activities by E. coli O157:H7 infection have not been addressed. Thus, we have investigated the effect of Shiga-like toxin type II (SLT-II), derived from E. coli O157:H7, on the hepatic cytochrome P450 (CYP) content and its activity in rats. SLT-II (2microg per animal, i.v.) time-dependently decreased total CYP content and the contents of CYP2C11 and CYP3A2 in hepatic microsomal preparations up to 24hr following injection. Consistently, SLT-II time-dependently decreased CYP activity in vivo, as represented by systemic clearance of antipyrine. An inhibitor of inducible nitric oxide synthase, S-methylisothiourea, restored the decreased systemic clearance of antipyrine by SLT-II, suggesting the involvement of the overproduction of nitric oxide by SLT-II. Moreover, dexamethasone restored the decreased systemic clearance of antipyrine by SLT-II. In the hepatic microsomal preparation, dexamethasone restored the SLT-II-induced decrease of CYP3A2 whereas S-methylisothiourea did not affect both CYP subtypes. Taken together, these results suggest that SLT-II might alter hepatic drug-metabolizing function during E. coli O157 infection and that more than one cytokines induced by SLT-II, including nitric oxide, might make a critical contribution to the decrease of CYP content and its activity.
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Affiliation(s)
- Kiyoyuki Kitaichi
- Department of Medical Technology, Nagoya University School of Health Sciences, 1-1-20, Daikominami, Higashi-ku, Nagoya 461-8673, Japan.
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32
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Mawji IA, Robb GB, Tai SC, Marsden PA. Role of the 3'-untranslated region of human endothelin-1 in vascular endothelial cells. Contribution to transcript lability and the cellular heat shock response. J Biol Chem 2004; 279:8655-67. [PMID: 14660616 DOI: 10.1074/jbc.m312190200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endothelin-1 (ET-1) is a potent vasoconstrictor peptide expressed in the vascular endothelium. Stringent control over ET-1 expression is achieved through a highly regulated promoter and rapid mRNA turnover. Since little is known about mechanisms governing ET-1 post-transcriptional regulation, and changes in ET-1 mRNA stability are implicated in disease processes, we characterized these pathways using a variety of functional approaches. We expressed human ET-1 and luciferase transcripts with or without a wild type ET-1 3'-untranslated region (3'-UTR) and found that the 3'-UTR had potent mRNA destabilizing activity. Deletion analysis localized this activity to two domains of the 3'-UTR we have termed destabilizing elements 1 and 2 (DE1 and DE2). Mutational studies revealed that DE1 functions as an AU-rich element (ARE) dependent on a 100-nucleotide region. This activity was further localized to a 10-nucleotide region at position 978-987 of the 3'-UTR. Depletion of AUF1 by RNA interference up-regulated ET-1 in endothelial cells suggesting AUF1-dependent regulation. Since AUF1 functions through the ubiquitin-proteasome pathway, we disrupted this pathway with heat shock and proteasome inhibitor in endothelial cells and observed stabilization of endogenous ET-1 mRNA. Chimeric transcripts bearing wild type ET-1 3'-UTRs were also stabilized in response to proteasome inhibition whereas DE1 mutants failed to respond. Taken together, these findings suggest a complex model of ARE-mediated mRNA turnover dependent on two 3'-UTR domains, DE1 and DE2. Furthermore, DE1 functions as an ARE directing mRNA half-life through the proteasome. Finally, this data provides evidence for a novel pathway of ET-1 mRNA stabilization by heat shock.
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Affiliation(s)
- Imtiaz A Mawji
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada
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33
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Yamasaki C, Nishikawa K, Zeng XT, Katayama Y, Natori Y, Komatsu N, Oda T, Natori Y. Induction of cytokines by toxins that have an identical RNA N-glycosidase activity: Shiga toxin, ricin, and modeccin. Biochim Biophys Acta Gen Subj 2004; 1671:44-50. [PMID: 15026144 DOI: 10.1016/j.bbagen.2004.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2003] [Revised: 11/17/2003] [Accepted: 01/09/2004] [Indexed: 11/29/2022]
Abstract
Shiga toxin (Stx) has an A1-B5 subunit structure, and the A subunit is an RNA N-glycosidase that inhibits cellular protein synthesis. We previously reported that in Caco-2 cells Stx induced cytokines and that the RNA N-glycosidase activity was essential for the cytokine induction. It is known that the binding of the Stx-B subunit to its receptor glycolipid, Gb3, mediates an A subunit-independent signal in some types of cells, but the involvement of this signal in the cytokine induction is unclear. In this study, we investigated whether RNA N-glycosidase itself induces cytokines. IL-8 production was enhanced by Stx, ricin, and modeccin, three toxins that inhibit protein synthesis through an identical RNA N-glycosidase activity, but not by two other types of protein synthesis inhibitors, diphtheria toxin and cycloheximide. The RNA N-glycosidase-type toxins showed a similar induction pattern of cytokine mRNAs. Brefeldin A, a Golgi apparatus inhibitor, completely suppressed the cytokine induction by the toxins. Analysis by using inhibitors of toxin binding and also Stx-B subunit showed that the cytokine-inducing activity was independent of Gb3-mediated signaling. These results indicate that RNA N-glycosidase itself induces the cytokine production and that intracellular transport of toxins through the Golgi apparatus is essential for the activity.
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Affiliation(s)
- Chisato Yamasaki
- Research Institute, International Medical Center of Japan, Tokyo 162-8655, Japan
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Matussek A, Lauber J, Bergau A, Hansen W, Rohde M, Dittmar KEJ, Gunzer M, Mengel M, Gatzlaff P, Hartmann M, Buer J, Gunzer F. Molecular and functional analysis of Shiga toxin-induced response patterns in human vascular endothelial cells. Blood 2003; 102:1323-32. [PMID: 12702508 DOI: 10.1182/blood-2002-10-3301] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is the major cause of hemolyticuremic syndrome (HUS) characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. EHEC produces one or more Shiga toxins (Stx1 and Stx2), and it was assumed that Stx's only relevant biologic activity was cell destruction through inhibition of protein synthesis. However, recent data indicate that in vivo the cytokine milieu may determine whether endothelial cells survive or undergo apoptosis/necrosis when exposed to Stxs. In this study, we analyzed the genome-wide expression patterns of human endothelial cells stimulated with subinhibitory concentrations of Stxs in order to characterize the genomic expression program involved in the vascular pathology of HUS. We found that Stxs elicited few, but reproducible, changes in gene expression. The majority of genes reported in this study encodes for chemokines and cytokines, which might contribute to the multifaceted inflammatory response of host endothelial cells observed in patients suffering from EHEC disease. In addition, our data provide for the first time molecular insights into the epidemiologically well-established higher pathogenicity of Stx2 over Stx1.
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Affiliation(s)
- Andreas Matussek
- Department of Microbiology, German Research Centre for Biotechnology, Braunschweig, Germany
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35
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Degousee N, Martindale J, Stefanski E, Cieslak M, Lindsay TF, Fish JE, Marsden PA, Thuerauf DJ, Glembotski CC, Rubin BB. MAP kinase kinase 6-p38 MAP kinase signaling cascade regulates cyclooxygenase-2 expression in cardiac myocytes in vitro and in vivo. Circ Res 2003; 92:757-64. [PMID: 12649265 DOI: 10.1161/01.res.0000067929.01404.03] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in delayed prostaglandin biosynthesis. The purpose of this study was to evaluate the role of the MAP kinase kinase 6 (MKK6)-p38 MAPK signaling cascade in the regulation of myocardial COX-2 gene expression, in vitro and in vivo. RT-PCR analysis identified p38alpha and p38beta2 MAPK mRNA in rat cardiac myocytes. Interleukin-1beta induced the phosphorylation of p38alpha and p38beta2 MAPK in cardiomyocytes and stimulated RNA polymerase II binding to the COX-2 promoter, COX-2 transcription, COX-2 protein synthesis, and prostaglandin E2 (PGE2) release. Infecting cardiomyocytes with adenoviruses that encode mutant, phosphorylation-resistant MKK6 or p38beta2 MAPK inhibited interleukin-1beta-induced p38 MAPK activation, COX-2 gene expression, and PGE2 release. Treatment with the p38alpha and p38beta2 MAPK inhibitor, SB202190, attenuated interleukin-1beta-induced COX-2 transcription and accelerated the degradation of COX-2 mRNA. Cells infected with adenoviruses encoding wild-type or constitutively activated MKK6 or p38beta2 MAPK, in the absence of interleukin-1beta, exhibited increased cellular p38 MAPK activity, COX-2 mRNA expression, and COX-2 protein synthesis, which was blocked by SB202190. In addition, elevated levels of COX-2 protein were identified in the hearts of transgenic mice with cardiac-restricted expression of wild-type or constitutively activated MKK6, in comparison with nontransgenic littermates. These results provide direct evidence that MKK6 mediated p38 MAPK activation is necessary for interleukin-1beta-induced cardiac myocyte COX-2 gene expression and PGE2 biosynthesis in vitro and is sufficient for COX-2 gene expression by cardiac myocytes in vitro and in vivo.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Animals, Newborn
- Calcium-Calmodulin-Dependent Protein Kinases/genetics
- Calcium-Calmodulin-Dependent Protein Kinases/metabolism
- Cells, Cultured
- Cyclooxygenase 2
- Dinoprostone/metabolism
- Enzyme Inhibitors/pharmacology
- Gene Expression Regulation, Enzymologic/drug effects
- Heart Ventricles/cytology
- Heart Ventricles/metabolism
- Imidazoles/pharmacology
- Interleukin-1/pharmacology
- Isoenzymes/genetics
- Isoenzymes/metabolism
- MAP Kinase Kinase 6
- MAP Kinase Signaling System/drug effects
- MAP Kinase Signaling System/physiology
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/genetics
- Mitogen-Activated Protein Kinases/metabolism
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Phosphorylation/drug effects
- Prostaglandin-Endoperoxide Synthases/genetics
- Prostaglandin-Endoperoxide Synthases/metabolism
- Pyridines/pharmacology
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Tubulin/metabolism
- p38 Mitogen-Activated Protein Kinases
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Affiliation(s)
- Norbert Degousee
- Division of Vascular Surgery, 200 Elizabeth St, EC5-302a, Toronto General Hospital, Toronto, Ontario, Canada M5G-2C4
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Hoey DEE, Sharp L, Currie C, Lingwood CA, Gally DL, Smith DGE. Verotoxin 1 binding to intestinal crypt epithelial cells results in localization to lysosomes and abrogation of toxicity. Cell Microbiol 2003; 5:85-97. [PMID: 12580945 DOI: 10.1046/j.1462-5822.2003.00254.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Verotoxins (VTs) are important virulence factors of enterohaemorrhagic Escherichia coli (EHEC), a group of bacteria associated with severe disease sequelae in humans. The potent cytotoxic activity of VTs is important in pathogenicity, resulting in the death of cells expressing receptor Gb3 (globotriaosylceramide). EHEC, particularly serotype O157:H7, frequently colonize reservoir hosts (such as cattle) in the absence of disease, however, the basis to avirulence in this host has been unclear. The objective of this study was assessment of interaction between VT and intestinal epithelium, which represents the major interface between the host and enteric organisms. Bovine intestinal epithelial cells expressed Gb3 in vitro in primary cell cultures, localizing specifically to proliferating crypt cells in corroboration with in situ immunohistological observations on intestinal mucosa. Expression of receptor by these cells contrasts with the absence of Gb3 on human intestinal epithelium in vivo. Despite receptor expression, VT exhibited no cytotoxic activity against bovine epithelial cells. Sub-cellular localization of VT indicated that this toxin was excluded from endoplasmic reticulum but localized to lysosomes, corresponding with abrogation of cytotoxicity. VT intracellular trafficking was unaffected by treatment of primary cell cultures with methyl-beta-cyclodextrin, indicating that Gb3 in these cells is not associated with lipid rafts but is randomly distributed in the membrane. The combination of Gb3 isoform, membrane distribution and VT trafficking correlate with observations of other receptor-positive cells that resist verocytotoxicity. These studies demonstrate that intestinal epithelium is an important determinant in VT interaction with major implications for the differential consequences of EHEC infection in reservoir hosts and humans.
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Affiliation(s)
- D E Elaine Hoey
- Department of Medical Microbiology, University of Edinburgh, Edingburgh, Scotland, UK
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37
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Stamm I, Wuhrer M, Geyer R, Baljer G, Menge C. Bovine lymphocytes express functional receptors for Escherichia coli Shiga toxin 1. Microb Pathog 2002; 33:251-64. [PMID: 12495672 DOI: 10.1006/mpat.2002.0527] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Interactions of Shiga toxins (Stxs) and immune cells contribute to the pathogenesis of diseases due to Stx-producing Escherichia coli (STEC) infections in humans and facilitate the persistence of infection in asymptomatically infected cattle. Our recent findings that bovine B and T lymphocytes express Gb(3)/CD77, the human Stx-receptor, prompted us to determine whether the bovine homologue also mediates binding and internalization of Stx1. In fact, Stx1 holotoxin and recombinant B subunit (rStxB1) bound to stimulated bovine peripheral blood mononuclear cells, especially to those subpopulations (B cells, BoCD8(+) T cells) that are highly sensitive to Stx1. Competition and HPTLC-binding studies confirmed that Stx1 binds to bovine Gb(3), but different receptor isoforms with varying affinities for rStxB1 were expressed during the course of lymphocyte activation. At least one of these isoforms mediated toxin uptake. An anti-StxB1 mouse monoclonal antibody, used as a model for bovine serum antibodies specific for Stx1, modulated rather than generally prevented rStxB1 binding to and internalization by the receptors. The presence of functional Stx1-receptors on bovine lymphocytes explains the immunomodulatory effect of Stx1 observed in cattle at a molecular level. Furthermore, expression of such receptors by bovine but not human T cells enlightens the background for the differential outcome of STEC infections in cattle and man, i.e., persistent infection and development of disease, respectively.
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Affiliation(s)
- Ivonne Stamm
- Institut für Hygiene und Infektionskrankheiten der Tiere der Justus-Liebig-Universität, Giessen, Germany
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Smith DGE, Naylor SW, Gally DL. Consequences of EHEC colonisation in humans and cattle. Int J Med Microbiol 2002; 292:169-83. [PMID: 12398208 DOI: 10.1078/1438-4221-00202] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
While many factors have been associated with human EHEC infection, the full role these play in both human and ruminant hosts are not yet clear despite much investigation. It is hoped that the continued intense international research effort into EHEC will provide further insights into the commensal versus pathogenic lifestyles of E. coli and lead to approaches to reduce EHEC carriage in ruminants as well as prevent or treat human disease.
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Affiliation(s)
- David G E Smith
- Medical Microbiology, Royal (Dick) School of Veterinary Studies, University of Edinburgh, United Kingdom
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Rutjes NWP, Binnington BA, Smith CR, Maloney MD, Lingwood CA. Differential tissue targeting and pathogenesis of verotoxins 1 and 2 in the mouse animal model. Kidney Int 2002; 62:832-45. [PMID: 12164865 DOI: 10.1046/j.1523-1755.2002.00502.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Both verotoxin (VT)1 and VT2 share the same receptor, globotriaosyl ceramide (Gb(3)). Although VT1 is slightly more cytotoxic in vitro and binds Gb(3) with higher affinity, VT2 is more toxic in mice and may be associated with greater pathology in human infections. In this study we have compared the biodistribution of iodine 125 ((125)I)-VT1 and (125)I-VT2 versus pathology in the mouse. METHODS (125)I-VT1 whole-body autoradiography defined the tissues targeted. VT1 and VT2 tissue distribution, clearance, and tissue binding sites were compared. The effect of a soluble receptor analogue, adamantylGb(3), on VT2/Gb3 binding and in vivo pathology was assessed. RESULTS (125)I-VT1 autoradiography identified the lungs and nasal turbinates as major, previously unrecognized, targets, while kidney cortex and the bone marrow of the spine, long bones, and ribs were also significant targets. VT2 did not target the lung, but accumulated in the kidney to a greater extent than VT1. The serum half-life of VT1 was 2.7 minutes with 90% clearance at 5 minutes, while that of VT2 was 3.9 minutes with only 40% clearance at 5 minutes. The extensive binding of VT1, but not VT2, within the lung correlated with induced lung disease. Extensive hemorrhage into alveoli, edema, alveolitis and neutrophil margination was seen only after VT1 treatment. VT1 targeted lung capillary endothelial cells. Identical tissue binding sites (subsets of proximal/distal tubules and collecting ducts) for VT1 and VT2 were detected by toxin overlay of serial frozen kidney sections. Glucosuria was found to be a new marker of VT1- and VT2-induced renal pathology and positive predictor of outcome in the mouse, consistent with VT-staining of proximal tubules. Lung Gb3 migrated on thin-layer chromatography (TLC) faster than kidney Gb(3), suggesting a different lipid composition. AdamantylGb(3), a soluble Gb(3) analogue, competed effectively for Gb3 binding by VT1 and VT2 in vitro. However, the effect in the mouse model (only measured against VT2, due to the lower LD(50), a concentration required for 50% lethality) was to increase, rather than reduce, pathology and further reduce the VT2 serum clearance rate. Additional renal pathology was seen in VT2 + adamantylGb(3)-treated mice. CONCLUSIONS The lung is a preferential (Gb(3)) "sink" for VT1, which explains the relatively slower clearance of VT2 and subsequent increased VT2 renal targeting and VT2 mortality in this animal model.
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Affiliation(s)
- Niels W P Rutjes
- Division of Infection, Immunity, Injury and Repair, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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Thorpe CM, Smith WE, Hurley BP, Acheson DW. Shiga toxins induce, superinduce, and stabilize a variety of C-X-C chemokine mRNAs in intestinal epithelial cells, resulting in increased chemokine expression. Infect Immun 2001; 69:6140-7. [PMID: 11553553 PMCID: PMC98744 DOI: 10.1128/iai.69.10.6140-6147.2001] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2001] [Accepted: 06/22/2001] [Indexed: 11/20/2022] Open
Abstract
Exposure of humans to Shiga toxins (Stxs) is a risk factor for hemolytic-uremic syndrome (HUS). Because Stx-producing Escherichia coli (STEC) is a noninvasive enteric pathogen, the extent to which Stxs can cross the host intestinal epithelium may affect the risk of developing HUS. We have previously shown that Stxs can induce and superinduce IL-8 mRNA and protein in intestinal epithelial cells (IECs) in vitro via a ribotoxic stress response. We used cytokine expression arrays to determine the effect of Stx1 on various C-X-C chemokine genes in IECs. We observed that Stx1 induces multiple C-X-C chemokines at the mRNA level, including interleukin-8 (IL-8), GRO-alpha, GRO-beta, GRO-gamma, and ENA-78. Like that of IL-8, GRO-alpha and ENA-78 mRNAs are both induced and superinduced by Stx1. Furthermore, Stx1 induces both IL-8 and GRO-alpha protein in a dose-response fashion, despite an overall inhibition in host cell protein synthesis. Stx1 treatment stabilizes both IL-8 and GRO-alpha mRNA. We conclude that Stxs are able to increase mRNA and protein levels of multiple C-X-C chemokines in IECs, with increased mRNA stability at least one mechanism involved. We hypothesize that ribotoxic stress is a pathway by which Stxs can alter host signal transduction in IECs, resulting in the production of multiple chemokine mRNAs, leading to increased expression of specific proteins. Taken together, these data suggest that exposing IECs to Stxs may stimulate a proinflammatory response, resulting in influx of acute inflammatory cells and thus contributing to the intestinal tissue damage seen in STEC infection.
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Affiliation(s)
- C M Thorpe
- Division of Geographic Medicine and Infectious Diseases, Department of Medicine, Tufts University School of Medicine, New England Medical Center, Boston, Massachusetts, USA.
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41
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Ruggenenti P, Noris M, Remuzzi G. Thrombotic microangiopathy, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. Kidney Int 2001; 60:831-46. [PMID: 11532079 DOI: 10.1046/j.1523-1755.2001.060003831.x] [Citation(s) in RCA: 343] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The term thrombotic microangiopathy (TMA) defines a lesion of vessel wall thickening (mainly arterioles or capillaries), intraluminal platelet thrombosis, and partial or complete obstruction of the vessel lumina. Depending on whether renal or brain lesions prevail, two pathologically indistinguishable but somehow clinically different entities have been described: the hemolytic uremic syndrome (HUS) and the thrombotic thrombocytopenic purpura (TTP). Injury to the endothelial cell is the central and likely inciting factor in the sequence of events leading to TMA. Loss of physiological thromboresistance, leukocyte adhesion to damaged endothelium, complement consumption, abnormal von Willebrand factor release and fragmentation, and increased vascular shear stress may then sustain and amplify the microangiopathic process. Intrinsic abnormalities of the complement system and of the von Willebrand factor pathway may account for a genetic predisposition to the disease that may play a paramount role in particular in familial and recurrent forms. Outcome is usually good in childhood, Shiga toxin-associated HUS, whereas renal and neurological sequelae are more frequently reported in adult, atypical, and familial forms of HUS and in TTP. Plasma infusion or exchange is the only treatment of proven efficacy. Bilateral nephrectomy and splenectomy may serve as rescue therapies in very selected cases of plasma resistant HUS or recurrent TTP, respectively.
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Affiliation(s)
- P Ruggenenti
- Mario Negri Institute for Pharmacological Research, Bergamo, Italy.
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Abstract
The aim of this review is to examine recent advances in experimental and clinical research relevant to the pathogenesis of diarrhea-associated hemolytic uremic syndrome with special reference to histopathologic findings, virulence factors of Shiga toxin-producing Escherichia coli, the host response, and the prothrombotic state. Despite significant advances during the past decade, the exact mechanism by which Shiga toxin-producing E. coli leads to hemolytic uremic syndrome remains unclear. Factors such as Shiga toxin, lipopolysaccharide, the adhesins intimin and E. coli-secreted proteins A, B, and D, the 60-MD plasmid, and enterohemolysin likely contribute to the pathogenesis. Data on the inflammatory response of the host, including leukocytes and inflammatory mediators, are updated. The pathogenesis of the prothrombotic state leading to thrombocytopenia secondary to endothelial cell damage and platelet activation is also discussed. A hypothetical sequence of events from ingestion of the bacteria to the development of full-blown hemolytic uremic syndrome is proposed.
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Affiliation(s)
- F Proulx
- Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, 3175 Chemin Côte Sainte-Catherine, Montreal, Canada, H3T-1C5.
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O'Loughlin EV, Robins-Browne RM. Effect of Shiga toxin and Shiga-like toxins on eukaryotic cells. Microbes Infect 2001; 3:493-507. [PMID: 11377211 DOI: 10.1016/s1286-4579(01)01405-8] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Shigella dysenteriae and Shiga-toxin-producing Escherichia coli (STEC) elaborate the AB holotoxins, Shiga or Shiga-like toxins (Stx). Stx play a major role in the pathogenesis of haemorrhagic colitis and haemolytic uremic syndrome. This review provides an overview of the mechanisms of action of Stx and a model of the pathogenesis of Stx-induced disease.
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Affiliation(s)
- E V O'Loughlin
- Department of Gastroenterology, The Royal Alexandra Hospital for Children, PO Box 3515, Parramatta 2124, Westmead NSW, Australia.
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Yamada Y, Fujii J, Murasato Y, Nakamura T, Hayashida Y, Kinoshita Y, Yutsudo T, Matsumoto T, Yoshida SI. Brainstem mechanisms of autonomic dysfunction in encephalopathy-associated Shiga toxin 2 intoxication. Ann Neurol 2001. [DOI: 10.1002/1531-8249(199906)45:6<716::aid-ana5>3.0.co;2-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hargrove GM, Dufresne J, Whiteside C, Muruve DA, Wong NC. Diabetes mellitus increases endothelin-1 gene transcription in rat kidney. Kidney Int 2000; 58:1534-45. [PMID: 11012888 DOI: 10.1046/j.1523-1755.2000.00315.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Mesangial cell hypertrophy and increased extracellular matrix (ECM) contribute to mesangial expansion in early progressive diabetic nephropathy. Previous studies suggest that the growth factor endothelin-1 (ET-1) is not only up-regulated in diabetes, but may mediate the effects of hyperglycemia on mesangial cell hypertrophy and ECM synthesis. In models of diabetes mellitus, the mechanisms underlying increased ET-1 peptide and mRNA remain unknown. Therefore, our purpose is to determine whether ET-1 gene activity increases in kidneys of streptozotocin (SZT)-treated rats. METHODS Male Sprague-Dawley rats were injected with either SZT or vehicle. Parameters including glucose, body weight, 24-hour urine volume, urinary protein, and urinary ET-1 excretion were recorded. All rats were sacrificed at 12 weeks postinjection. Prepro-ET-1 mRNA from whole kidneys was determined using both RNase protection and reverse transcription-polymerase chain reaction (RT-PCR). The abundance of ET-1 peptide in primary cultured mesangial cells was detected by indirect immunofluorescence following treatment with 5.6, 11.2, or 22.5 mmol/L D-glucose for 24 hours. Cellular ET-1 mRNA was measured using RT-PCR in control cells at time 0 and also following exposure to increasing concentrations of glucose for 24 hours. Rat mesangial cells were transfected with a luciferase reporter construct containing the rat ET-1 promoter (pET1. Luc), and relative ET-1 promoter activity was measured after a 24-hour exposure to 5.6 and 22.5 mmol/L of D- or L-glucose. RESULTS After 12 weeks of hyperglycemia, diabetic rats gained less weight (344 +/- 23.9 vs. 548.75 +/- 15.08 g), had increased urinary volume (158.6 +/- 24.32 vs. 8.38 +/- 1.56 mL/day), and had marked proteinuria (101.7 +/- 12.2 vs. 14.1 +/- 2.8 mg/day) compared with controls. Total urinary ET-1 peptide increased 26.4-fold in diabetic versus control rats (17.5083 +/- 5.405 vs. 0.6635 +/- 0.343 ng/day). ET-1 mRNA extracted from whole rat kidneys was increased 2.1-fold in diabetic versus control animals. Primary cultured rat mesangial cells demonstrated a significant increase in immunofluorescence labeling of ET-1 peptide and ET-1 mRNA in response to increasing concentrations of glucose. Furthermore, transfected mesangial cells exposed to 22.5 mmol/L D-glucose showed a 1.6-fold increase in ET-1 promoter activity relative to those treated with 5.6 mmol/L glucose. CONCLUSION Glucose increases ET-1 gene expression in the kidney of the SZT-treated rat model of diabetes mellitus. Furthermore, high glucose induces ET-1 expression in primary cultured rat mesangial cells and directly enhances ET-1 promoter activity. The greater relative increase in peptide compared with transcription suggests the potential participation of other mechanisms such as increased mRNA stability, protein stability, and/or enhanced translational efficiency.
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Affiliation(s)
- G M Hargrove
- Departments of Medicine and Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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Viisoreanu D, Polanowska-Grabowska R, Suttitanamongkol S, Obrig TG, Gear AR. Human platelet aggregation is not altered by Shiga toxins 1 or 2. Thromb Res 2000; 98:403-10. [PMID: 10828480 DOI: 10.1016/s0049-3848(00)00191-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The hemolytic uremic syndrome involves the presence of Shiga toxin producing strains of Escherichia coli and is associated with thrombocytopenia, platelet activation, and microthrombi formation. We have, therefore, investigated the ability of Shiga toxin isotypes 1 and 2 to cause or enhance platelet aggregation under resting or arterial-flow conditions using a sensitive quenched-flow system and single-particle counting. Incubation of platelets with Shiga toxins 1 or 2 at 10(-10) M or 10(-9) M for 0.5-2 hours failed to induce platelet aggregation under static or physiological flow conditions, either by themselves or in the presence of ADP or thrombin. Thus, these Shiga toxins do not appear to be able to influence platelet function directly, and their ability to cause platelet thrombi in vivo must result from indirect mechanisms.
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Affiliation(s)
- D Viisoreanu
- Department of Biochemistry & Molecular Genetics, University of Virginia, School of Medicine, Charlottesville 22908, USA
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Zhang WL, Bielaszewska M, Liesegang A, Tschäpe H, Schmidt H, Bitzan M, Karch H. Molecular characteristics and epidemiological significance of Shiga toxin-producing Escherichia coli O26 strains. J Clin Microbiol 2000; 38:2134-40. [PMID: 10834966 PMCID: PMC86746 DOI: 10.1128/jcm.38.6.2134-2140.2000] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/1999] [Accepted: 03/20/2000] [Indexed: 11/20/2022] Open
Abstract
Fifty-five Shiga toxin (Stx)-producing Escherichia coli (STEC) O26:H11 and O26:H(-) strains isolated from humans between 1965 and 1999 in Germany and the Czech Republic were investigated for their chromosomal and plasmid characteristics. All motile (n = 23) and nonmotile (n = 32) STEC O26 strains were shown to possess the identical flagellin subunit-encoding gene (fliC). We observed a striking recent shift of the stx genotype from stx(1) to stx(2) among the STEC O26 isolates. While stx(1) was the exclusive genotype identified in our collection until 1994, 94% of the isolates obtained after 1997 possessed stx(2) either alone (71%) or together with stx(1) (23%). Plasmid profiling demonstrated a remarkable heterogeneity with respect to plasmid sizes and combinations. Southern blot analysis of plasmid DNA with probes specific to potential accessory virulence genes revealed considerable additional variability in gene composition and arrangement. Pulsed-field gel electrophoresis (PFGE) differentiated 16 subgroups among the 55 STEC O26 strains. Using these techniques we demonstrate the emergence of a new clonal subgroup characterized by PFGE pattern A and a unique combination of virulence markers including stx(2) and a single, approximately 90-kb plasmid harboring the enterhemorrhagic E. coli hlyA and etp genes. The proportion of PFGE subgroup A strains among STEC O26 isolates rose from 30% in 1996 to more than 50% in 1999. Four clusters of infections with the clonal subgroup A were identified. We conclude that the STEC serogroup O26 is diverse and that pathogenic clonal subgroups can rapidly emerge during short intervals. The extensive genetic diversity of STEC O26 provides a basis for molecular subtyping of this important non-O157 STEC serogroup.
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Affiliation(s)
- W L Zhang
- Institut für Hygiene und Mikrobiologie der Universität Würzburg, 97080 Würzburg, Germany
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Kojima S, Yanagihara I, Kono G, Sugahara T, Nasu H, Kijima M, Hattori A, Kodama T, Nagayama KI, Honda T. mkp-1 encoding mitogen-activated protein kinase phosphatase 1, a verotoxin 1 responsive gene, detected by differential display reverse transcription-PCR in Caco-2 cells. Infect Immun 2000; 68:2791-6. [PMID: 10768974 PMCID: PMC97489 DOI: 10.1128/iai.68.5.2791-2796.2000] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The major cytotoxic effect of the verotoxins (VTs) produced by strains of VT-producing Escherichia coli is the inhibition of host-cell protein synthesis, but VTs are also suspected to play a role in apoptotic cell signaling and cytokine release. Four differentially expressed genes, including mkp-1 (encoding mitogen-activated protein kinase phospatase 1), were detected by differential display reverse transcription-PCR (DD RT-PCR) stimulated by VT1 in Caco-2 cells. Northern blot analysis showed the induction of mkp-1 mRNA 6 h after VT1 stimulation. Neither mutant VT1 (mutVT1), harboring two mutations in the A subunit (E167Q-R170L), nor cycloheximide induced mkp-1 mRNA, but mkp-1 mRNA was detected with both wild-type VT1 (wtVT1) and anisomycin, a 28S rRNA inhibitor. Therefore, we concluded that the A subunit of VT1 was essential for mkp-1 induction. Increased amounts of phosphorylated c-Jun protein were also found with wtVT1 and anisomycin. Although the precise mechanism of induction of MKP-1 is unknown, we hypothesized that 28S rRNA not only was a sensor for ribotoxic stress, but also was involved in the signal cascade of MKP-1. This is the first report of detection by DD RT-PCR of cellular genes induced by bacterial toxins.
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Affiliation(s)
- S Kojima
- Department of Bacterial Infections, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka Suita-City, Osaka, Japan 565-0871, USA
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Abstract
Shiga toxin-producing Escherichia coli (STEC) are emerging as a significant source of foodborne infectious disease in the developed world. Multistate outbreaks of E. coli O157 and non-O157 serogroups in the United States are facilitated by the centralization of food processing and distribution. Our ability to recognize the clonality of these clusters has been advanced by developments in molecular detection techniques and in the establishment of active surveillance practices. These studies have helped identify important risk factors for both sporadic and outbreak STEC infection, allowing us to develop appropriate prevention strategies. Identification of these factors is of critical importance because of the lack of adequate treatments available. This brief review of the literature discusses major developments in the epidemiology, pathogenesis, diagnosis, treatment, and prevention of STEC disease published in the past few years.
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Affiliation(s)
- JL Jaeger
- Division of Geographic Medicine and Infectious Diseases, New England Medical Center, 750 Washington Street, Boston, MA 02111, USA.
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Schmidt H, Scheef J, Huppertz HI, Frosch M, Karch H. Escherichia coli O157:H7 and O157:H(-) strains that do not produce Shiga toxin: phenotypic and genetic characterization of isolates associated with diarrhea and hemolytic-uremic syndrome. J Clin Microbiol 1999; 37:3491-6. [PMID: 10523540 PMCID: PMC85676 DOI: 10.1128/jcm.37.11.3491-3496.1999] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/1999] [Accepted: 07/23/1999] [Indexed: 11/20/2022] Open
Abstract
We have isolated one sorbitol-nonfermenting (SNF) Escherichia coli O157:H7 isolate and five sorbitol-fermenting (SF) E. coli O157:H(-) isolates that do not contain Shiga toxin (Stx) genes (stx). Isolates originated from patients with diarrhea (n = 4) and hemolytic-uremic syndrome (HUS) (n = 2). All isolates harbored a chromosomal eae gene encoding gamma-intimin as well as the plasmid genes E-hly and etp. The E. coli O157:H7 isolate was katP and espP positive. Respective sera obtained from the patient with HUS contained antibodies to the O157 lipopolysaccharide antigen. The stx-negative E. coli O157:H7 isolate is genetically related to stx-positive SNF E. coli O157:H7. All stx-negative SF E. coli O157:H(-) isolates belong to the same genetic cluster and are closely related to stx-positive SF E. coli O157:H(-) isolates. Our data indicate that stx-negative E. coli O157:H7/H(-) variants may occur at a low frequency and cannot be recognized by diagnostic methods that target Stx.
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Affiliation(s)
- H Schmidt
- Institut für Hygiene und Mikrobiologie der Universität Würzburg, 97080 Würzburg, Germany
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