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Mediterranean Spotted Fever: Current Knowledge and Recent Advances. Trop Med Infect Dis 2021; 6:tropicalmed6040172. [PMID: 34698275 PMCID: PMC8544691 DOI: 10.3390/tropicalmed6040172] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/17/2021] [Accepted: 09/21/2021] [Indexed: 12/15/2022] Open
Abstract
Mediterranean spotted fever (MSF) is an emerging tick-borne rickettsiosis of the spotted fever group (SFG), endemic in the Mediterranean basin. By virtue of technological innovations in molecular genetics, it has been determined that the causative agent of MSF is Rickettsia conorii subspecies conorii. The arthropod vector of this bacterium is the brown dog tick Rhipicephalus sanguineus. The true nature of the reservoir of R. conorii conorii has not been completely deciphered yet, although many authors theorize that the canine population, other mammals, and the ticks themselves could potentially contribute as reservoirs. Typical symptoms of MSF include fever, maculopapular rash, and a characteristic eschar (“tache noire”). Atypical clinical features and severe multi-organ complications may also be present. All of these manifestations arise from the disseminated infection of the endothelium by R. conorii conorii. Several methods exist for the diagnosis of MSF. Serological tests are widely used and molecular techniques have become increasingly available. Doxycycline remains the treatment of choice, while preventive measures are focused on modification of human behavior and vector control strategies. The purpose of this review is to summarize the current knowledge on the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of MSF.
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Abstract
A wide variety of pathogens reach the circulatory system during viral, parasitic, fungal, and bacterial infections, causing clinically diverse pathologies. Such systemic infections are usually severe and frequently life-threatening despite intensive care, in particular during the age of antibiotic resistance. Because of its position at the interface between the blood and the rest of the organism, the endothelium plays a central role during these infections. Using several examples of systemic infections, we explore the diversity of interactions between pathogens and the endothelium. These examples reveal that bacterial pathogens target specific vascular beds and affect most aspects of endothelial cell biology, ranging from cellular junction stability to endothelial cell proliferation and inflammation.
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Rickettsia rickettsii Whole-Cell Antigens Offer Protection against Rocky Mountain Spotted Fever in the Canine Host. Infect Immun 2019; 87:IAI.00628-18. [PMID: 30396898 PMCID: PMC6346123 DOI: 10.1128/iai.00628-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 10/30/2018] [Indexed: 01/24/2023] Open
Abstract
Rocky Mountain spotted fever (RMSF) is a potentially fatal tick-borne disease in people and dogs. RMSF is reported in the United States and several countries in North, Central, and South America. Rocky Mountain spotted fever (RMSF) is a potentially fatal tick-borne disease in people and dogs. RMSF is reported in the United States and several countries in North, Central, and South America. The causative agent of this disease, Rickettsia rickettsii, is transmitted by several species of ticks, including Dermacentor andersoni, Rhipicephalus sanguineus, and Amblyomma americanum. RMSF clinical signs generally include fever, headache, nausea, vomiting, muscle pain, lack of appetite, and rash. If untreated, it can quickly progress into a life-threatening illness in people and dogs, with high fatality rates ranging from 30 to 80%. While RMSF has been known for over a century, recent epidemiological data suggest that the numbers of documented cases and the fatality rates remain high in people, particularly during the last two decades in parts of North America. Currently, there are no vaccines available to prevent RMSF in either dogs or people. In this study, we investigated the efficacies of two experimental vaccines, a subunit vaccine containing two recombinant outer membrane proteins as recombinant antigens (RCA) and a whole-cell inactivated antigen vaccine (WCA), in conferring protection against virulent R. rickettsii infection challenge in a newly established canine model for RMSF. Dogs vaccinated with WCA were protected from RMSF, whereas those receiving RCA developed disease similar to that of nonvaccinated R. rickettsii-infected dogs. WCA also reduced the pathogen loads to nearly undetected levels in the blood, lungs, liver, spleen, and brain and induced bacterial antigen-specific immune responses. This study provides the first evidence of the protective ability of WCA against RMSF in dogs.
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Sahni A, Fang R, Sahni SK, Walker DH. Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2018; 14:127-152. [PMID: 30148688 DOI: 10.1146/annurev-pathmechdis-012418-012800] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Obligately intracytosolic rickettsiae that cycle between arthropod and vertebrate hosts cause human diseases with a spectrum of severity, primarily by targeting microvascular endothelial cells, resulting in endothelial dysfunction. Endothelial cells and mononuclear phagocytes have important roles in the intracellular killing of rickettsiae upon activation by the effector molecules of innate and adaptive immunity. In overwhelming infection, immunosuppressive effects contribute to the severity of illness. Rickettsia-host cell interactions involve host cell receptors for rickettsial ligands that mediate cell adhesion and, in some instances, trigger induced phagocytosis. Rickettsiae interact with host cell actin to effect both cellular entry and intracellular actin-based mobility. The interaction of rickettsiae with the host cell also involves rickettsial evasion of host defense mechanisms and exploitation of the intracellular environment. Signal transduction events exemplify these effects. An intriguing frontier is the array of rickettsial noncoding RNA molecules and their potential effects on the pathogenesis and transmission of rickettsial diseases.
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Affiliation(s)
- Abha Sahni
- The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-0609, USA; , , ,
| | - Rong Fang
- The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-0609, USA; , , ,
| | - Sanjeev K Sahni
- The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-0609, USA; , , ,
| | - David H Walker
- The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-0609, USA; , , ,
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Schroeder CLC, Narra HP, Sahni A, Rojas M, Khanipov K, Patel J, Shah R, Fofanov Y, Sahni SK. Identification and Characterization of Novel Small RNAs in Rickettsia prowazekii. Front Microbiol 2016; 7:859. [PMID: 27375581 PMCID: PMC4896933 DOI: 10.3389/fmicb.2016.00859] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 05/23/2016] [Indexed: 12/12/2022] Open
Abstract
Emerging evidence implicates a critically important role for bacterial small RNAs (sRNAs) as post-transcriptional regulators of physiology, metabolism, stress/adaptive responses, and virulence, but the roles of sRNAs in pathogenic Rickettsia species remain poorly understood. Here, we report on the identification of both novel and well-known bacterial sRNAs in Rickettsia prowazekii, known to cause epidemic typhus in humans. RNA sequencing of human microvascular endothelial cells (HMECs), the preferred targets during human rickettsioses, infected with R. prowazekii revealed the presence of 35 trans-acting and 23 cis-acting sRNAs, respectively. Of these, expression of two trans-acting (Rp_sR17 and Rp_sR60) and one cis-acting (Rp_sR47) novel sRNAs and four well-characterized bacterial sRNAs (RNaseP_bact_a, α-tmRNA, 4.5S RNA, 6S RNA) was further confirmed by Northern blot or RT-PCR analyses. The transcriptional start sites of five novel rickettsial sRNAs and 6S RNA were next determined using 5' RLM-RACE yielding evidence for their independent biogenesis in R. prowazekii. Finally, computational approaches were employed to determine the secondary structures and potential mRNA targets of novel sRNAs. Together, these results establish the presence and expression of sRNAs in R. prowazekii during host cell infection and suggest potential functional roles for these important post-transcriptional regulators in rickettsial biology and pathogenesis.
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Affiliation(s)
| | - Hema P. Narra
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Abha Sahni
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Mark Rojas
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Kamil Khanipov
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Jignesh Patel
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Riya Shah
- Department of Neuroscience, University of Texas at DallasDallas, TX, USA
| | - Yuriy Fofanov
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Sanjeev K. Sahni
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
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New insight into immunity and immunopathology of Rickettsial diseases. Clin Dev Immunol 2011; 2012:967852. [PMID: 21912565 PMCID: PMC3170826 DOI: 10.1155/2012/967852] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 06/17/2011] [Indexed: 02/01/2023]
Abstract
Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecular Rickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered.
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Beta interferon-mediated activation of signal transducer and activator of transcription protein 1 interferes with Rickettsia conorii replication in human endothelial cells. Infect Immun 2011; 79:3733-43. [PMID: 21690236 DOI: 10.1128/iai.05008-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Infection of the endothelial cell lining of blood vessels with Rickettsia conorii, the causative agent of Mediterranean spotted fever, results in endothelial activation. We investigated the effects of R. conorii infection on the status of the Janus kinase (JAK)-signal transducer and activator of transcription protein (STAT) signaling pathway in human microvascular endothelial cells (HMECs), the most relevant host cell type, in light of rickettsial tropism for microvascular endothelium in vivo. R. conorii infection induced phosphorylation of STAT1 on tyrosine 701 and serine 727 at 24, 48, and 72 h postinfection in HMECs. Employing transcription profile analysis and neutralizing antibodies, we further determined that beta interferon (IFN-β) production and secretion are critical for STAT1 activation. Secreted IFN-β further amplified its own expression via a positive-feedback mechanism, while expression of transcription factors interferon regulatory factor 7 (IRF7) and IRF9, implicated in the IFN-β-STAT1 feedback loop, was also induced. Metabolic activity of rickettsiae was essential for the IFN-β-mediated response(s) because tetracycline treatment inhibited R. conorii replication, IFN-β expression, and STAT1 phosphorylation. Inclusion of IFN-β-neutralizing antibody during infection resulted in significantly enhanced R. conorii replication, whereas addition of exogenous IFN-β had the opposite inhibitory effect. Finally, small interfering RNA-mediated knockdown further confirmed a protective role for STAT1 against intracellular R. conorii replication. In concert, these findings implicate an important role for IFN-β-mediated STAT1 activation in innate immune responses of vascular endothelium to R. conorii infection.
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Rickettsia rickettsii infection of human macrovascular and microvascular endothelial cells reveals activation of both common and cell type-specific host response mechanisms. Infect Immun 2010; 78:2599-606. [PMID: 20385756 DOI: 10.1128/iai.01335-09] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although inflammation and altered barrier functions of the vasculature, due predominantly to the infection of endothelial cell lining of small and medium-sized blood vessels, represent salient pathological features of human rickettsioses, the interactions between pathogenic rickettsiae and microvascular endothelial cells remain poorly understood. We have investigated the activation of nuclear transcription factor-kappa B (NF-kappaB) and p38 mitogen-activated protein (MAP) kinase, expression of heme oxygenase 1 (HO-1) and cyclooxygenase 2 (COX-2), and secretion of chemokines and prostaglandins after Rickettsia rickettsii infection of human cerebral, dermal, and pulmonary microvascular endothelial cells in comparison with pulmonary artery cells of macrovascular origin. NF-kappaB and p38 kinase activation and increased HO-1 mRNA expression were clearly evident in all cell types, along with relatively similar susceptibility to R. rickettsii infection in vitro but considerable variations in the intensities/kinetics of the aforementioned host responses. As expected, the overall activation profiles of macrovascular endothelial cells derived from human pulmonary artery and umbilical vein were nearly identical. Interestingly, cerebral endothelial cells displayed a marked refractoriness in chemokine production and secretion, while all other cell types secreted various levels of interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) in response to infection. A unique feature of all microvascular endothelial cells was the lack of induced COX-2 expression and resultant inability to secrete prostaglandin E(2) after R. rickettsii infection. Comparative evaluation thus yields the first experimental evidence for the activation of both common and unique cell type-specific host response mechanisms in macrovascular and microvascular endothelial cells infected with R. rickettsii, a prototypical species known to cause Rocky Mountain spotted fever in humans.
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Abstract
The vascular endothelium is the main target of a limited number of infectious agents, Rickettsia, Ehrlichia ruminantium, and Orientia tsutsugamushi are among them. These arthropod-transmitted obligately-intracellular bacteria cause serious systemic diseases that are not infrequently lethal. In this review, we discuss the bacterial biology, vector biology, and clinical aspects of these conditions with particular emphasis on the interactions of these bacteria with the vascular endothelium and how it responds to intracellular infection. The study of these bacteria in relevant in vivo models is likely to offer new insights into the physiology of the endothelium that have not been revealed by other models.
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Affiliation(s)
- Gustavo Valbuena
- Department of Pathology and Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0609, USA.
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Yang S, Wu X. Tolliod-like gene in Crassostrea ariakensis: Molecular cloning, structural characterization and expression by RLO stimulation. FISH & SHELLFISH IMMUNOLOGY 2009; 27:130-135. [PMID: 19105979 DOI: 10.1016/j.fsi.2008.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Revised: 11/28/2008] [Accepted: 11/28/2008] [Indexed: 05/27/2023]
Abstract
The BMP1/TLD-like proteinases are pleiotropic, astacin-like metalloproteinases. They play central roles in regulating the formation of the extracellular matrix (ECM) and signaling through various TGFbeta-like proteins in morphogenetic and homeostatic events. Here we describe the cloning, structural characterization and expression of Tolloid-like gene in the oyster, Crassostrea ariakensis (CaTLL). The full-length cDNA of CaTLL spans 3492 nucleotides including an open reading frame of 2811 nucleotides which encodes a hypothetical protein of 936 amino acids, with a molecular mass of approximately 103 kDa. The CaTLL molecule possessed structural features of several motifs including an N-terminal signal peptide sequence, a prodomain with an RTRR motif, an astacin-like domain that contains a conserved zinc-binding motif HELGHVIGFWHEH, five CUBs and two EGF domains with the arrangement CUB-CUB-EGF-CUB-EGF-CUB-CUB. The proteolytic domain of Ca-Tolloid shares more than 30% identity with other astacins of various animals from squail to mammals, indicating its conserved catalytic ability. RT-PCR and quantitative real-time PCR analyses revealed that CaTLL showed the lowest expression level in hemocytes of normal groups, but was affected significantly by the challenge of an obligate intracellular Gram-negative bacterium, Rickettsia-like organisms, suggesting that Ca-Tolloid might be involved in the molluscan immune response, and its function is more diverse than previously assumed.
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Affiliation(s)
- Shoubao Yang
- Laboratory of Marine Life Science and Technology, College of Animal Sciences, Zhejiang University, 268 Kaixuan Road, Hangzhou, Zhejiang 310029, China; Shaoxing College of Arts and Sciences, Zhejiang, China
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Sahni SK, Rydkina E. Host-cell interactions with pathogenic Rickettsia species. Future Microbiol 2009; 4:323-39. [PMID: 19327117 DOI: 10.2217/fmb.09.6] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Pathogenic Rickettsia species are Gram-negative, obligate intracellular bacteria responsible for the spotted fever and typhus groups of diseases around the world. It is now well established that a majority of sequelae associated with human rickettsioses are the outcome of the pathogen's affinity for endothelium lining the blood vessels, the consequences of which are vascular inflammation, insult to vascular integrity and compromised vascular permeability, collectively termed 'Rickettsial vasculitis'. Signaling mechanisms leading to transcriptional activation of target cells in response to Rickettsial adhesion and/or invasion, differential activation of host-cell signaling due to infection with spotted fever versus typhus subgroups of Rickettsiae, and their contributions to the host's immune responses and determination of cell fate are the major subtopics of this review. Also included is a succinct analysis of established in vivo models and their use for understanding Rickettsial interactions with host cells and pathogenesis of vasculotropic rickettsioses. Continued progress in these important but relatively under-explored areas of bacterial pathogenesis research should further highlight unique aspects of Rickettsial interactions with host cells, elucidate the biological basis of endothelial tropism and reveal novel chemotherapeutic and vaccination strategies for debilitating Rickettsial diseases.
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Affiliation(s)
- Sanjeev K Sahni
- Department of Microbiology & Immunology, University of Rochester School of Medicine & Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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Sahni SK, Kiriakidi S, Colonne MP, Sahni A, Silverman DJ. Selective activation of signal transducer and activator of transcription (STAT) proteins STAT1 and STAT3 in human endothelial cells infected with Rickettsia rickettsii. Clin Microbiol Infect 2009; 15 Suppl 2:303-4. [PMID: 19438651 DOI: 10.1111/j.1469-0691.2008.02248.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S K Sahni
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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Rydkina E, Turpin LC, Sahni SK. Activation of p38 mitogen-activated protein kinase module facilitates in vitro host cell invasion by Rickettsia rickettsii. J Med Microbiol 2008; 57:1172-1175. [PMID: 18719192 DOI: 10.1099/jmm.0.47806-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Elena Rydkina
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Loel C Turpin
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Sanjeev K Sahni
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Sahni SK, Rydkina E, Sahni A. The proteasome inhibitor MG132 induces nuclear translocation of erythroid transcription factor Nrf2 and cyclooxygenase-2 expression in human vascular endothelial cells. Thromb Res 2008; 122:820-5. [DOI: 10.1016/j.thromres.2008.01.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 01/21/2008] [Accepted: 01/22/2008] [Indexed: 11/27/2022]
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García-Herrera J, Marca MC, Brot-Laroche E, Guillén N, Acin S, Navarro MA, Osada J, Rodríguez-Yoldi MJ. Protein kinases, TNF-{alpha}, and proteasome contribute in the inhibition of fructose intestinal transport by sepsis in vivo. Am J Physiol Gastrointest Liver Physiol 2008; 294:G155-64. [PMID: 17962360 DOI: 10.1152/ajpgi.00139.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Lipopolysaccharide (LPS) endotoxin is a causative agent of sepsis. The aim of this study was to examine LPS effects on intestinal fructose absorption and to decipher mechanisms. Sepsis was induced by intravenous injection of LPS in rabbits. The ultrastructural study and DNA fragmentation patterns were identical in the intestine of LPS and sham animals. LPS treatment reduced fructose absorption altering both mucosal-to-serosal transepithelial fluxes and uptake into brush border membrane vesicles (BBMVs). Cytochalasin B was ineffective on fructose uptake, indicating that GLUT5, but not GLUT2, transport activity was targeted. GLUT5 protein levels in BBMvs were lower in LPS than in sham-injected rabbits. Thus lower fructose transport resulted from lower levels of GLUT5 protein. LPS treatment decreased GLUT5 levels by proteasome-dependent degradation. Specific inhibitors of PKC, PKA, and MAP kinases (p38MAPK, JNK, MEK1/2) protected fructose uptake from adverse LPS effect. Moreover, a TNF-alpha antagonist blocked LPS action on fructose uptake. We conclude that intestinal fructose transport inhibition by LPS is associated with diminished GLUT5 numbers in the brush border membrane of enterocytes triggered by activation of several interrelated signaling cascades and proteasome degradation.
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Valbuena G, Walker DH. The endothelium as a target for infections. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2007; 1:171-98. [PMID: 18039112 DOI: 10.1146/annurev.pathol.1.110304.100031] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The endothelial cells lining vascular and lymphatic vessels are targets of several infectious agents, including viruses and bacteria, that lead to dramatic changes in their functions. Understanding the pathophysiological mechanisms that cause the clinical manifestations of those infections has been advanced through the use of animal models and in vitro systems; however, there are also abundant studies that explore the consequences of endothelial infection in vitro without supporting evidence that endothelial cells are actual in vivo targets of infection in human diseases. This article defines criteria for considering an infection as truly endothelium-targeted and reviews the literature that offers insights into the pathogenesis of human endothelial-target infections.
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Rydkina E, Sahni A, Silverman DJ, Sahni SK. Comparative analysis of host-cell signalling mechanisms activated in response to infection with Rickettsia conorii and Rickettsia typhi. J Med Microbiol 2007; 56:896-906. [PMID: 17577053 DOI: 10.1099/jmm.0.47050-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Gram-negative intracellular bacteria Rickettsia conorii and Rickettsia typhi are the aetiological agents of Mediterranean spotted fever and endemic typhus, respectively, in humans. Infection of endothelial cells (ECs) lining vessel walls, and the resultant vascular inflammation and haemostatic alterations are salient pathogenetic features of both of these rickettsial diseases. An important consideration, however, is that dramatic differences in the intracellular motility and accumulation patterns for spotted fever versus typhus group rickettsiae have been documented, suggesting the possibility of unique and potentially different interactions with host cells. This study characterized and compared R. conorii- and R. typhi-mediated effects on cultured human ECs. The DNA-binding activity of nuclear transcription factor-kappaB (NF-kappaB) and the phosphorylation status of stress-activated p38 kinase were determined as indicators of NF-kappaB and p38 activation. R. conorii infection resulted in a biphasic activation of NF-kappaB, with an early increase in DNA-binding activity at 3 h, followed by a later peak at 24 h. The activated NF-kappaB species were composed mainly of RelA p65-p50 heterodimers and p50 homodimers. R. typhi infection of ECs resulted in only early activation of NF-kappaB at 3 h, composed primarily of p65-p50 heterodimers. Whilst R. conorii infection induced increased phosphorylation of p38 kinase (threefold mean induction) with the maximal response at 3 h, a considerably less-intense response peaking at about 6 h post-infection was found with R. typhi. Furthermore, mRNA expression of the chemokines interleukin (IL)-8 and monocyte chemoattractant protein-1 in ECs infected with either Rickettsia species was higher than the corresponding controls, but there were distinct differences in the secretion patterns for IL-8, suggesting the possibility of involvement of post-transcriptional control mechanisms or differences in the release from intracellular storage sites. Thus, the intensity and kinetics of host-cell responses triggered by spotted fever and typhus species exhibit distinct variations that could subsequently lead to differences in the extent of endothelial activation and inflammation and serve as important determinants of pathogenesis.
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Affiliation(s)
- Elena Rydkina
- Hematology-Oncology Unit, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Abha Sahni
- Hematology-Oncology Unit, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - David J Silverman
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Sanjeev K Sahni
- Hematology-Oncology Unit, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Amador P, García-Herrera J, Marca MC, de la Osada J, Acín S, Navarro MA, Salvador MT, Lostao MP, Rodríguez-Yoldi MJ. Inhibitory effect of TNF-α on the intestinal absorption of galactose. J Cell Biochem 2007; 101:99-111. [PMID: 17177295 DOI: 10.1002/jcb.21168] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Sepsis is a systemic response to infection in which toxins, such as bacterial lipopolysaccharide (LPS), stimulate the production of inflammatory mediators like the cytokine tumor necrosis factor alpha (TNF-alpha). Previous studies from our laboratory have revealed that LPS inhibits the intestinal absorption of L-leucine and D-fructose in rabbit when it was intravenously administered, and that TNF-alpha seems to mediate this effect on amino acid absorption. To extend this work, the present study was designed to evaluate the possible effect of TNF-alpha on D-galactose intestinal absorption, identify the intracellular mechanisms involved and establish whether this cytokine mediates possible LPS effects. Our findings indicate that TNF-alpha decreases D-galactose absorption both in rabbit intestinal tissue preparations and brush-border membrane vesicles. Western blot analysis revealed reduced amounts of the Na+/glucose cotransporter (SGLT1) protein in the plasma membrane attributable to the cytokine. On the contrary, TNF-alpha increased SGLT1 mRNA levels. Specific inhibitors of the secondary messengers PKC, PKA, the MAP kinases p38 MAP, JNK, MEK1/2 as well as the proteasome, diminished the TNF-alpha-evoked inhibitory effect. LPS inhibition of the uptake of the sugar was blocked by a TNF-alpha antagonist. In conclusion, TNF-alpha inhibits D-galactose intestinal absorption by decreasing the number of SGLT1 molecules at the enterocyte plasma membrane through a mechanism in which several protein-like kinases are involved.
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Affiliation(s)
- P Amador
- Department of Pharmacology and Physiology, Physiology Unit, Veterinary Faculty, University of Zaragoza, E-50013 Zaragoza, Spain
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Rydkina E, Sahni A, Baggs RB, Silverman DJ, Sahni SK. Infection of human endothelial cells with spotted Fever group rickettsiae stimulates cyclooxygenase 2 expression and release of vasoactive prostaglandins. Infect Immun 2006; 74:5067-74. [PMID: 16926398 PMCID: PMC1594856 DOI: 10.1128/iai.00182-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rickettsiae, a diverse group of obligately intracellular gram-negative bacteria, include etiologic agents of the spotted fever and typhus groups of diseases. Rocky Mountain spotted fever and boutonneuse fever, due to Rickettsia rickettsii and R. conorii, respectively, are characterized by widespread infection of the vascular endothelium, microvascular injury, and vasculitis. Cultured human endothelial cells (EC) are highly susceptible to infection and respond by altering the expression of adhesion molecules, regulatory cytokines, and the antioxidant enzyme heme oxygenase (HO). In the vasculature, HO regulates the cyclooxygenase (COX) enzymes, among which the inducible isozyme COX-2 facilitates the synthesis of prostaglandins (PGs). Using in vitro and ex vivo models of infection, we demonstrate here that R. rickettsii infection of human EC causes robust induction of COX-2 mRNA and protein expression but has no apparent effect on the constitutive COX-1 isoform. Cells infected with viable rickettsiae consistently displayed significantly increased secretion of 6-keto-PGF(1alpha) and PGE(2). R. rickettsii-induced COX-2 was sensitive to inhibitors of de novo transcription and the pyridinylimidazole-based compound SB 203580, suggesting that this transcriptional host cell response involves signaling through p38 mitogen-activated protein kinase. PG production by infected cells was abrogated by NS 398 (a selective COX-2 inhibitor) and indomethacin (a pan-COX inhibitor). Immunohistochemical staining of sections of infected umbilical cords and corresponding uninfected controls revealed comparatively more intense and abundant staining for COX-2 in infected endothelia. Induction of the endothelial COX-2 system and the resultant enhanced release of vasoactive PGs may contribute to the regulation of inflammatory responses and vascular permeability changes during spotted fever rickettsioses.
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Affiliation(s)
- Elena Rydkina
- Department of Medicine, Hematology-Oncology Unit, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Hance ME, Czar MJ, Azad A, Purkayastha A, Snyder EE, Crasta OR, Setubal JC, Sobral BW. The pathogen resource integration center: implications for Rickettsial research. Ann N Y Acad Sci 2006; 1063:459-65. [PMID: 16481560 DOI: 10.1196/annals.1355.066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Mark E Hance
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0477, USA
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Rydkina E, Silverman DJ, Sahni SK. Activation of p38 stress-activated protein kinase during Rickettsia rickettsii infection of human endothelial cells: role in the induction of chemokine response. Cell Microbiol 2005; 7:1519-30. [PMID: 16153249 DOI: 10.1111/j.1462-5822.2005.00574.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rickettsia rickettsii, a Gram-negative and obligate intracellular bacterium, preferentially infects the vascular endothelium during human infections leading to inflammation and dysfunction. The aim of this study was to determine whether R. rickettsii infection of endothelial cells (EC) activates p38 and/or c-jun N-terminal kinases (JNK) mitogen-activated protein (MAP) kinase, key regulatory proteins that control the response to inflammatory stimuli. We show that infection of cultured human EC results in the dose-dependent activation of p38, as assessed by increased phosphorylation and activity, without affecting the status of JNK. Rickettsia inactivation by heat or formaldehyde abolished the activation of p38 kinase and inhibition of cellular invasion by infection at low temperature, pre-treatment of host EC with cytochalasin D, or pre-incubation of rickettsiae with an irreversible phospholipase inhibitor led to a diminished p38 phosphorylation, suggesting requirement of invasion by viable rickettsiae for this host cell response. SB 203580, a p38-specific inhibitor, had no effect on infection-induced activation of the ubiquitous transcriptional regulator nuclear factor-kappa B, but effectively reduced the expression and secretion of important chemoattractant cytokines interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1 by R. rickettsii-infected EC. Selective inhibition of p38 activity may be exploited as an anti-inflammatory target to prevent rickettsial vasculitis and to develop new and improved chemotherapeutic agents.
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Affiliation(s)
- Elena Rydkina
- Department of Medicine, University of Rochester School of Medicine and Dentistry, NY, USA
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22
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Valbuena G, Walker DH. Changes in the adherens junctions of human endothelial cells infected with spotted fever group rickettsiae. Virchows Arch 2005; 446:379-82. [PMID: 15778845 DOI: 10.1007/s00428-004-1165-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Accepted: 10/25/2004] [Indexed: 11/25/2022]
Abstract
Rickettsiae of the spotted fever group are obligately intracellular bacteria that primarily infect the vascular endothelium, invade adjacent cells propelled by actin polymerization, and cause severe systemic diseases. Endothelial dysfunction and vascular leakage develop as a consequence; this effect is the pathophysiological mechanism that explains most clinical manifestations. Here we report that rickettsial infection of cultured primary human endothelial cells is associated with the formation of gaps in the interendothelial adherens junctions, occurring late during the course of in vitro infections but not early, even when rickettsial loads are significant.
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Affiliation(s)
- Gustavo Valbuena
- School of Medicine, Universidad de Los Andes, Bogota, DC, Colombia
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23
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Clifton DR, Rydkina E, Freeman RS, Sahni SK. NF-kappaB activation during Rickettsia rickettsii infection of endothelial cells involves the activation of catalytic IkappaB kinases IKKalpha and IKKbeta and phosphorylation-proteolysis of the inhibitor protein IkappaBalpha. Infect Immun 2005; 73:155-65. [PMID: 15618150 PMCID: PMC538953 DOI: 10.1128/iai.73.1.155-165.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rocky Mountain spotted fever, a systemic tick-borne illness caused by the obligate intracellular bacterium Rickettsia rickettsii, is associated with widespread infection of the vascular endothelium. R. rickettsii infection induces a biphasic pattern of the nuclear factor-kappaB (NF-kappaB) activation in cultured human endothelial cells (ECs), characterized by an early transient phase at 3 h and a late sustained phase evident at 18 to 24 h. To elucidate the underlying mechanisms, we investigated the expression of NF-kappaB subunits, p65 and p50, and IkappaB proteins, IkappaBalpha and IkappaBbeta. The transcript and protein levels of p50, p65, and IkappaBbeta remained relatively unchanged during the course of infection, but Ser-32 phosphorylation of IkappaBalpha at 3 h was significantly increased over the basal level in uninfected cells concomitant with a significant increase in the expression of IkappaBalpha mRNA. The level of IkappaBalpha mRNA gradually returned toward baseline, whereas that of total IkappaBalpha protein remained lower than the corresponding controls. The activities of IKKalpha and IKKbeta, the catalytic subunits of IkappaB kinase (IKK) complex, as measured by in vitro kinase assays with immunoprecipitates from uninfected and R. rickettsii-infected ECs, revealed significant increases at 2 h after infection. The activation of IKK and early phase of NF-kappaB response were inhibited by heat treatment and completely abolished by formalin fixation of rickettsiae. The IKK inhibitors parthenolide and aspirin blocked the activities of infection-induced IKKalpha and IKKbeta, leading to attenuation of nuclear translocation of NF-kappaB. Also, increased activity of IKKalpha was evident later during the infection, coinciding with the late phase of NF-kappaB activation. Thus, activation of catalytic components of the IKK complex represents an important upstream signaling event in the pathway for R. rickettsii-induced NF-kappaB activation. Since NF-kappaB is a critical regulator of inflammatory genes and prevents host cell death during infection via antiapoptotic functions, selective inhibition of IKK may provide a potential target for enhanced clearance of rickettsiae and an effective strategy to reduce inflammatory damage to the host during rickettsial infections.
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Affiliation(s)
- Dawn R Clifton
- Hemostasis and Thrombosis Program, Hematology-Oncology Unit, Department of Medicine, P.O. Box 610, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, NY 14642, USA
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Valbuena G, Walker DH. Expression of CX3CL1 (fractalkine) in mice with endothelial-target rickettsial infection of the spotted-fever group. Virchows Arch 2004; 446:21-7. [PMID: 15480764 DOI: 10.1007/s00428-004-1120-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Accepted: 08/19/2004] [Indexed: 12/16/2022]
Abstract
Fractalkine (CX3CL1) is a chemokine expressed mainly by endothelial cells, which are the major cellular targets of rickettsiae. We used immunohistochemistry to investigate the normal expression of CX3CL1 in mice and the kinetics of expression of this chemokine throughout the course of lethal and sublethal rickettsial infections in a mouse model of spotted-fever group rickettsioses. The peak of expression of fractalkine on day 3 of infection coincided with the time of infiltration of macrophages into infected tissues and preceded the peak of rickettsial content in tissues.
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Affiliation(s)
- Gustavo Valbuena
- Department of Pathology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0609, USA
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Sahni A, Guo M, Sahni SK, Francis CW. Interleukin-1beta but not IL-1alpha binds to fibrinogen and fibrin and has enhanced activity in the bound form. Blood 2004; 104:409-14. [PMID: 15039285 DOI: 10.1182/blood-2004-01-0126] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fibrin is formed at sites of injury or inflammation and provides the temporary matrix to support vascular cell responses that are also mediated by cytokines including interleukin-1 (IL-1). We have shown previously that fibroblast growth factor 2 (FGF-2) binds with high affinity to fibrin(ogen). Because IL-1 has a structure similar to FGF-2, we have investigated the possible binding of IL-1 to fibrin(ogen). Experiments using IL-1 immobilized on Sepharose beads and soluble iodine 125 ((125)I)-labeled fibrinogen demonstrated no specific interaction of IL-1alpha with fibrinogen, but IL-1beta showed saturable and specific binding. Scatchard analysis indicated a single binding site with an apparent K(d) = 1.5 nM and a maximum molar binding ratio of IL-1beta to fibrinogen of 1.8:1. Binding of (125)I-IL-1beta to Sepharose-immobilized fibrinogen also demonstrated a single binding site with an apparent K(d) of 3.5 nM. IL-1beta also bound specifically to fibrin monomer and polymerized fibrin with apparent K(d)s of 3.4 nM and 2.3 nM, respectively. IL-1beta displaced FGF-2 for binding to fibrin, indicating an interaction with the same or a closely related site. Compared with free form, fibrinogen-bound IL-1beta stimulated increased activation of endothelial cell nuclear factor kappaB (NF-kappaB), monocyte chemoattractant protein-1 (MCP-1) secretion, and nitric oxide (NO) synthesis. We conclude that IL-1beta binds with high affinity to fibrin(ogen) and demonstrates increased activity in the bound form.
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Affiliation(s)
- Abha Sahni
- Department of Medicine, PO Box 610, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY 14642, USA.
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Valbuena G, Bradford W, Walker DH. Expression analysis of the T-cell-targeting chemokines CXCL9 and CXCL10 in mice and humans with endothelial infections caused by rickettsiae of the spotted fever group. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:1357-69. [PMID: 14507644 PMCID: PMC1868304 DOI: 10.1016/s0002-9440(10)63494-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Rocky Mountain spotted fever and other related diseases are systemic infections caused by rickettsiae. These obligatory intracellular bacteria target the endothelium, offering an appealing model to study the interactions between endothelial cells and T lymphocytes. We investigated the mRNA expression of chemokines known to target CD8+ T cells and CD4(+) T-helper 1 cells in the lungs of C3H/HeN mice infected with Rickettsia conorii with the purpose of identifying evidence for a role of chemokines in the immune clearance of rickettsiae from the vasculature. The expression of the CXCR3 ligands CXCL9 and CXCL10 was significantly higher than the other chemokines investigated. We validated the relevance of these results in the animal model through the analysis of tissues from humans with Rocky Mountain spotted fever. We then characterized the kinetics and localization of expression of CXCL9 and CXCL10 in lungs, brain, and liver of mice infected with lethal or sublethal doses of R. conorii by a combination of quantitative real-time polymerase chain reaction and immunohistochemistry. Interestingly, the peak of expression of these chemokines occurred 4 days before CD8+ T cells infiltrated the infected tissues. Our results suggest that CXCL9 and CXCL10 may play a role early during the immune response against rickettsial infections.
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Affiliation(s)
- Gustavo Valbuena
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555, USA
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Joshi SG, Francis CW, Silverman DJ, Sahni SK. Nuclear factor kappa B protects against host cell apoptosis during Rickettsia rickettsii infection by inhibiting activation of apical and effector caspases and maintaining mitochondrial integrity. Infect Immun 2003; 71:4127-36. [PMID: 12819104 PMCID: PMC162038 DOI: 10.1128/iai.71.7.4127-4136.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Apoptotic host cell death is a critical determinant in the progression of microbial infections and outcome of resultant diseases. The potentially fatal human infection caused by Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever, involves the vascular endothelium of various organ systems of the host. Earlier studies have shown that survival of endothelial cells (EC) during this infection depends on their ability to activate the transcription factor nuclear factor kappa B (NF-kappa B). Here, we investigated the involvement of caspase cascades and associated signaling pathways in regulation of host cell apoptosis by NF-kappa B. Infection of cultured human EC with R. rickettsii with simultaneous inhibition of NF-kappa B induced the activation of apical caspases 8 and 9 and also the executioner enzyme, caspase 3, whereas infection alone had no significant effect. Inhibition of either caspase-8 or caspase-9 with specific cell-permeating peptide inhibitors caused a significant decline in the extent of apoptosis, confirming their importance. The peak caspase-3 activity occurred at 12 h postinfection and led to cleavage of poly(ADP-ribose) polymerase, followed by DNA fragmentation and apoptosis. However, the activities of caspases 6 and 7, other important downstream executioners, remained unchanged. Caspase-9 activation was mediated through the mitochondrial pathway of apoptosis, as evidenced by loss of transmembrane potential and cytoplasmic release of cytochrome c. These findings suggest that activation of NF-kappa B is required for maintenance of mitochondrial integrity of host cells and protection against infection-induced apoptotic death by preventing activation of caspase-9- and caspase-8-mediated pathways. Targeted inhibition of NF-kappa B may therefore be exploited to enhance the clearance of infections with R. rickettsii and other intracellular pathogens with similar survival strategies.
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Affiliation(s)
- Suresh G Joshi
- Hematology-Oncology Unit, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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28
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Sahni SK, Rydkina E, Joshi SG, Sporn LA, Silverman DJ. Interactions of Rickettsia rickettsii with endothelial nuclear factor-kappaB in a "cell-free" system. Ann N Y Acad Sci 2003; 990:635-41. [PMID: 12860701 DOI: 10.1111/j.1749-6632.2003.tb07438.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sanjeev K Sahni
- Hematology-Oncology Unit, Hemostasis and Thrombosis Program, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
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Abstract
The specter of bioterrorism employing genetically engineered Rickettsia resistant to all antibiotics should reawaken the world's desire to elucidate the pathogenesis of typhus and spotted fever rickettsioses in a search for mechanisms vulnerable to interdiction. The pathogenetic sequence includes rickettsial entry into the dermis, hematogenous dissemination to vascular endothelial cells (most critically in brain and lungs), increased vascular permeability, edema, and immunity mediated by NK cells, IFN-gamma, TNF-alpha, RANTES, antibodies, and cytotoxic T lymphocytes. Silverman has demonstrated the role of reactive oxygen species (ROS) produced by R. rickettsii-infected endothelial cells in peroxidative damage to cell membranes in vitro, and Heinzen has described actin-based rickettsial intracellular mobility and intercellular spread. At this point the availability of sequences of rickettsial genomes and excellent animal models of rickettsioses have yielded insufficient progress towards the identification of rickettsial virulence factors and knowledge of the importance of injury mediated by ROS, phospholipase A(2), protease(s) or other mechanisms in vivo. Attention to the rickettsiosis-associated procoagulant state led to determination that hemostatic mechanisms largely prevent major hemorrhage without disseminated intravascular coagulation or thrombosis-mediated ischemia. Particularly lacking is knowledge of early events in vivo at the portal of entry in skin (or lung), of the effects of the inoculum medium (arthropod saliva or feces), mediators produced by infected endothelium under conditions of flow and of the contributions in vivo of immune effectors to pathology, of the role of apoptosis in rickettsial infection, and of the endothelial cell alterations that account for increased vascular permeability. The host cell receptor for the Rickettsia ligand and the mechanism of rickettsial escape from the phagosome need to be elucidated.
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Affiliation(s)
- David H Walker
- University of Texas Medical Branch, Galveston, Texas 77555-0609, USA.
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Rydkina E, Sahni A, Silverman DJ, Sahni SK. Rickettsia rickettsii infection of cultured human endothelial cells induces heme oxygenase 1 expression. Infect Immun 2002; 70:4045-52. [PMID: 12117910 PMCID: PMC128148 DOI: 10.1128/iai.70.8.4045-4052.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2002] [Revised: 04/02/2002] [Accepted: 05/03/2002] [Indexed: 01/09/2023] Open
Abstract
Existing evidence suggests that oxidative insults and antioxidant defense mechanisms play a critical role in the host cell response during infection of endothelial cells by Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever. Heme oxygenase (HO), a rate-limiting enzyme in the pathway for heme catabolism, protects against oxidant damage in a variety of stress situations. Here, we report on the expression of the inducible and constitutive HO isozymes, HO-1 and HO-2, during R. rickettsii infection of endothelial cells. Steady-state levels for HO-1 mRNA were increased two- to threefold, as early as 4 h postinfection, whereas HO-2 mRNA was not affected. Induction of HO-1 mRNA was dependent on the dose of infection and occurred in a time-dependent manner, reaching maximal levels at 4 to 7 h. The increase in HO-1 mRNA occurred at the level of trancription as it was blocked by the transcriptional inhibitors, actinomycin D and alpha-amanitin. The eukaryotic protein synthesis inhibitor, cycloheximide, caused a >50% reduction in the infection-induced increase in HO-1 mRNA level, suggesting its dependence on de novo protein synthesis of host cell. The uptake of viable organisms appeared to be necessary, since inactivation of R. rickettsii by heat or formalin fixation, or incubation of cells with cytochalasin B to prevent entry resulted in marked inhibition of HO-1 response. N-Acetyl-L-cysteine, a known oxidant scavenger, inhibited the HO-1 induction by R. rickettsii. Finally, Western analysis with a specific monoclonal antibody revealed higher levels of HO-1 protein ( approximately 32 kDa), confirming that changes in HO-1 mRNA levels were followed by increases in the levels of protein. The findings indicate that R. rickettsii infection induces HO-1 expression in host endothelial cells and suggest an important role for this enzyme in cellular response to infection, possibly by serving a protective function against oxidative injury.
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Affiliation(s)
- Elena Rydkina
- Hematology-Oncology Unit, Vascular Medicine Progam, Department of Medicine, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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31
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Valbuena G, Feng HM, Walker DH. Mechanisms of immunity against rickettsiae. New perspectives and opportunities offered by unusual intracellular parasites. Microbes Infect 2002; 4:625-33. [PMID: 12048032 DOI: 10.1016/s1286-4579(02)01581-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Investigation of the biology, pathology and immunology of rickettsial diseases offers new insights useful not only for the field of rickettsiology, but more importantly for the understanding of general principles of host-intracellular parasite relationships and, in particular, the immune interaction between endothelial cells and immune cells in the context of infection.
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Affiliation(s)
- Gustavo Valbuena
- Department of Pathology and WHO Collaborating Center for Tropical Diseases, University of Texas Medical Branch, 301 University Boulevard, Galveston 77555-0609, USA
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32
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Qin Z, Wang Y, Chasea TN. A caspase-3-like protease is involved in NF-kappaB activation induced by stimulation of N-methyl-D-aspartate receptors in rat striatum. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 80:111-22. [PMID: 11038244 DOI: 10.1016/s0169-328x(00)00147-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Glutamate receptor stimulation reportedly activates NF-kappaB in vitro and in vivo, although underlying mechanisms remain to be elucidated. Here we evaluated the role of proteases in mediating N-methyl-D-aspartate (NMDA) receptor agonist-induced NF-kappaB activation and apoptosis in rat striatum. The intrastriatal infusion of quinolinic acid (QA, 60 nmol) had no effect on levels of NF-kappaB family proteins, including p65, p50, p52, c-Rel and Rel B. In contrast, QA decreased IkappaB-alpha protein levels by 60% (P<0. 05); other members of the IkappaB family, including IkappaB-beta, IkappaB-gamma, IkappaB-epsilon and Bcl-3, were not altered. The QA-stimulated degradation of IkappaB-alpha was completely blocked by the NMDA receptor antagonist MK-801. QA-induced IkappaB-alpha degradation and NF-kappaB activation were not affected by the proteasome inhibitor MG-132 (1-4 microg). On the other hand, the caspase-3 inhibitor Ac-DEVD.CHO (2-8 microgram) blocked QA-induced IkappaB-alpha degradation in a dose-dependent manner (P<0.05). Ac-DEVD.CHO (4 microgram) also substantially reduced QA-induced NF-kappaB activation (P<0.05), but had no effect on QA-induced AP-1 activation. Furthermore, Ac-DEVD.CHO, but not MG-132, dose-dependently attenuated QA-induced internucleosomal DNA fragmentation. These findings suggest that NF-kappaB activation by NMDA receptor stimulation involves IkappaB-alpha degradation by a caspase-3-like cysteine protease dependent mechanism. Caspase-3 thus appears to contribute to the excitotoxin-induced apoptosis in rat striatal neurons occurring at least partially as a consequence of NF-kappaB activation.
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Affiliation(s)
- Z Qin
- Experimental Therapeutics Branch, National Institute of Neurological Disorders and Stroke, NIH, Bldg 10, Rm 5C 103, 10 Center Dr. MSC 1406, 20892-1406, Bethesda, MD, USA
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Nakai M, Qin Z, Wang Y, Chase TN. NMDA and non-NMDA receptor-stimulated IkappaB-alpha degradation: differential effects of the caspase-3 inhibitor DEVD.CHO, ethanol and free radical scavenger OPC-14117. Brain Res 2000; 859:207-16. [PMID: 10719066 DOI: 10.1016/s0006-8993(00)01959-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The excitotoxic response of striatal neurons to NMDA and non-NMDA receptor agonists involves the nuclear translocation of transcription factor nuclear factor-kappa B (NF-kappaB) due to IkappaB-alpha degradation. Resultant augmentation in c-Myc, p53 and cyclin D1 expression presages the apoptotic-like destruction of these cells in vivo. To differentiate molecular events triggered by intrastriatally injected quinolinic acid (QA, 60 nmol) and kainic acid (KA, 2.5 nmol), we compared the effects of a caspase-3 inhibitor (DEVD.CHO, 8 microgram intrastriatally), a free radical scavenger (OPC-14117; 600 mg/kg, orally) and ethanol (2.14-8.6 micromol, intrastriatally or 25-100 mmol/kg, orally) on changes induced by these glutamatergic agonists on NF-kappaB cascade components and the apoptotic death of rat striatal neurons in vivo. The results indicated that the QA-induced degradation of IkappaB-alpha is almost totally mediated by a caspase-3-dependent mechanism, while KA-induced IkappaB-alpha degradation is only partially dependent on caspase-3. OPC-14117 attenuated the effects of QA but not KA on IkappaB-alpha degradation, suggesting that oxidative stress contributes to the QA- but not the KA-induced degradation of IkappaB-alpha. In contrast, ethanol inhibited the KA- but not the QA-induced degradation of IkappaB-alpha and the ensuing DNA fragmentation and loss of striatal GABAergic neurons. It would now appear that NF-kappaB activation in striatal neurons induced by NMDA or KA receptor stimulation involves different biochemical mechanisms. Since excitotoxicity associated with NF-kappaB activation may contribute to neuronal degenerative disorders such as Huntington's disease, a more detailed understanding of biochemical events underlying ionotrophic glutamate receptor-stimulated cell death may assist in the discovery of alternative approaches to interdicting the deleterious consequences of excitotoxic insult.
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Affiliation(s)
- M Nakai
- Experimental Therapeutics Branch, National Institute of Neurological Disorders and Stroke, NIH, Bldg. 10, Rm. 5C103, 10 Center Drive, MSC 1406, Bethesda, MD, USA
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Al-Okla S, Chatenay-Rivauday C, Klein JP, Wachsmann D. Involvement of alpha5beta1 integrins in interleukin 8 production induced by oral viridans streptococcal protein I/IIf in cultured endothelial cells. Cell Microbiol 1999; 1:157-68. [PMID: 11207549 DOI: 10.1046/j.1462-5822.1999.00016.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Using human endothelial cells, we define a mechanism that accounts for the induction of interleukin 8 (IL-8) by protein I/IIf, an adhesin from Streptococcus mutans serotype f. We report that protein I/IIf interactions with endothelial cells increased the tyrosine phosphorylation of three cellular components with relative mass of 145,000, 125,000 and 70,000 in endothelial cells. These proteins were identified as phospholipase Cgamma (PLCy), focal adhesion kinase (FAK) and paxillin after immunoprecipitation with monoclonal antibodies (mAbs) and immunoblotting with antiphosphotyrosine mAbs. These results suggested that beta1 integrins could be one of the components implicated in the modulin activity of protein I/IIf. By incubating protein I/IIf with either purified alpha5beta1 integrins or with alpha5beta1 integrins overexpressing CHO cells, we demonstrated that alpha5beta1 integrins act as cell receptors for protein I/IIf. We also showed that protein I/IIf interactions with alpha5beta1 integrins lead to IL-8 secretion. Using specific inhibitors, we demonstrated that protein I/IIf-induced IL-8 release involves mitogen-activated protein kinases (MAPKs), and that PLCgamma and PKC also seem to contribute to protein I/IIf stimulation. However, PI-3K activation is not involved in IL-8 release. Altogether, these results indicate that, after binding to alpha5beta1 integrins, protein I/IIf induces IL-8 release by activating the MAPKs signalling pathways.
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Affiliation(s)
- S Al-Okla
- INSERM U392, Université Louis Pasteur de Strasbourg, Faculté de Pharmacie, Illkirch, France
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Kalogeris TJ, Laroux FS, Cockrell A, Ichikawa H, Okayama N, Phifer TJ, Alexander JS, Grisham MB. Effect of selective proteasome inhibitors on TNF-induced activation of primary and transformed endothelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C856-64. [PMID: 10199816 DOI: 10.1152/ajpcell.1999.276.4.c856] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to assess the effects of two structurally distinct yet selective proteasome inhibitors (PS-341 and lactacystin) on leukocyte adhesion, endothelial cell adhesion molecule (ECAM) expression, and nuclear factor-kappaB (NF-kappaB) activation in tumor necrosis factor (TNF)-alpha-stimulated human umbilical vein endothelial cells (HUVEC) and the transformed, HUVEC-derived, ECV cell line. We found that TNF (10 ng/ml) significantly enhanced U-937 and polymorphonuclear neutrophil (PMN) adhesion to HUVEC but not to ECV; TNF also significantly enhanced surface expression of vascular cell adhesion molecule 1 and E-selectin (in HUVEC only), as well as intercellular adhesion molecule 1 (ICAM-1; in HUVEC and ECV). Pretreatment of HUVEC with lactacystin completely blocked TNF-stimulated PMN adhesion, partially blocked U-937 adhesion, and completely blocked TNF-stimulated ECAM expression. Lactacystin attenuated TNF-stimulated ICAM-1 expression in ECV. Pretreatment of HUVEC with PS-341 partially blocked TNF-stimulated leukocyte adhesion and ECAM expression. These effects of lactacystin and PS-341 were associated with inhibitory effects on TNF-stimulated NF-kappaB activation in both HUVEC and ECV. Our results demonstrate the importance of the 26S proteasome in TNF-induced activation of NF-kappaB, ECAM expression, and leukocyte-endothelial adhesive interactions in vitro.
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Affiliation(s)
- T J Kalogeris
- Department of Surgery, Louisiana State University Medical Center, Shreveport, Louisiana 71130, USA
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