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BACKGROUND: CpG ODN are synthetic single stranded DNA sequences that act as immunostimulants. They have been increasingly used to treat several cancers, however, thrombocytopenia is a potential recognized side effect of some sequences. OBJECTIVES: We tested the ability of two CpG ODN (ODN 2395 and ISIS 120704) to induce thrombocytopenia when administered to BALB/c mice and determined mechanisms associated with thrombocytopenia. METHODS: BALB/c mice were pre-bled and then injected with titrated doses of CpG ODNs and platelet counts were determined. The mice were treated IVIg or with various inhibitors and antagonists of toll-like receptor 9 (TLR9) and spleen tyrosine kinase (Syk) to determine their effects on the thrombocytopenia. RESULTS AND CONCLUSIONS: Compared with saline-treated mice or mice treated with 2'-O-methoxyethyl (MOE)-modified antisense (ASO) ODN, both ODN 2395 and ISIS 120704 induced an acute dose-dependent thrombocytopenia within 3 and 24 hours respectively. The thrombocytopenia was associated with significant increases in plasma monocyte chemoattractant protein 1 (MCP1). Intravenous immunoglobulin (IVIg) administration significantly rescued the CpG ODN-induced thrombocytopenia, as did treatment with either a Syk-inhibitor or TLR9 antagonists. In vitro, CpG ODN could activate human platelets and this correlated significantly with enhanced IVIg- and Syk-dependent phagocytosis by THP-1 monocytes. These results suggest that CpG ODN induce an acute inflammatory-associated (IVIg-sensitive) thrombocytopenia that can be alleviated by Syk- or TLR9-blockade, and an IVIg- and Syk-dependent platelet clearance pathway appears primarily responsible for the thrombocytopenia. Whether these results are applicable to humans still has to be elucidated.
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OBJECTIVE: To evaluate the effect of platelet:erythrocyte (P:E) ratios on Plasmodium falciparum erythrocyte invasion. BACKGROUND: Recent reports have shown that platelets are directly involved in the immune response towards P. falciparum during erythrocyte invasion. However, the literature both supports and conflicts with a role for platelets in limiting invasion. Also, the effect of platelet numbers on invasion (parasitemia) has not been thoroughly investigated. METHODS/MATERIALS: The P. falciparum strains FCR3S1.2 and W2mef were cultured with group O erythrocytes. The cultures were synchronised and supplemented with pooled platelets at P:E ratios ranging from 1:100 to 1:2. Parasitemia was measured at 40 h by flow cytometry and by microscopy of blood smears. RESULTS: A linear relationship was observed between reduced invasion and increased platelet numbers at P:E ratios ranging from 1:100 to 1:20. However, this effect was reversed at lower ratios (1:10-1:2). Microscopic evaluation revealed aggregation and attachment of platelets to erythrocytes, but not specifically to parasitised erythrocytes. CONCLUSION: We have shown that under physiological P:E ratios (approx. 1:10-1:40), platelets inhibited P. falciparum invasion in a dose-dependent manner. At ratios of 1:10 and below, platelets did not further increase the inhibitory effect and, although the trend was reversed, inhibition was still maintained.
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Malária Falciparum , Plasmodium falciparum , Plaquetas , Eritrócitos , Humanos , ParasitemiaRESUMO
In addition to their hemostatic role, platelets play a significant role in immunity. Once activated, platelets release extracellular vesicles (EVs) formed by the budding of their cytoplasmic membranes. Because of their heterogeneity, platelet EVs (PEVs) are thought to perform diverse functions. It is unknown, however, whether the proteasome is transferred from platelets to PEVs or whether its function is retained. We hypothesized that functional protein processing and antigen presentation machinery are transferred to PEVs by activated platelets. Using molecular and functional assays, we found that the active 20S proteasome was enriched in PEVs, along with major histocompatibility complex class I (MHC-I) and lymphocyte costimulatory molecules (CD40L and OX40L). Proteasome-containing PEVs were identified in healthy donor blood, but did not increase in platelet concentrates that caused adverse transfusion reactions. They were augmented, however, after immune complex injections in mice. The complete biodistribution of murine PEVs after injection into mice revealed that they principally reached lymphoid organs, such as spleen and lymph nodes, in addition to the bone marrow, and to a lesser extent, liver and lungs. The PEV proteasome processed exogenous ovalbumin (OVA) and loaded its antigenic peptide onto MHC-I molecules, which promoted OVA-specific CD8+ T-lymphocyte proliferation. These results suggest that PEVs contribute to adaptive immunity through cross-presentation of antigens and have privileged access to immune cells through the lymphatic system, a tissue location that is inaccessible to platelets.
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Plaquetas/imunologia , Vesículas Extracelulares/imunologia , Antígenos de Histocompatibilidade Classe I/imunologia , Complexo de Endopeptidases do Proteassoma/imunologia , Animais , Apresentação de Antígeno , Plaquetas/química , Vesículas Extracelulares/química , Antígenos de Histocompatibilidade Classe I/análise , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Complexo de Endopeptidases do Proteassoma/análiseRESUMO
SARS-CoV-2 has spread rapidly worldwide, causing the COVID-19 pandemic. Platelet activation and platelet-leukocyte complex formation are proposed to contribute to disease progression. Here, we report platelet and leukocyte activation during acute and convalescent COVID-19 in patients recruited between May-July 2020. Blood samples were analyzed by flow cytometry and ELISA using paired comparison between inclusion (day 0) and 28 days later. The majority of patients were mildly or moderately ill with significantly higher cytokine levels (IL-6 and IL-10) on day 0 as compared with day 28. Platelet activation and granule release were significantly higher on day 0 compared with day 28, as determined by ADP- or thrombin-induced surface CD62P expression, baseline released CD62P, and thrombin-induced platelet-monocyte complex formation. Monocyte activation and procoagulant status at baseline and post activation were heterogeneous but generally lower on day 0 compared with day 28. Baseline and thrombin- or fMLF-induced neutrophil activation and procoagulant status were significantly lower on day 0 compared with day 28. We demonstrate that during the acute phase of COVID-19 compared with the convalescent phase, platelets are more responsive while neutrophils are less responsive. COVID-19 is associated with thromboembolic events where platelet activation and interaction with leukocytes may play an important role.
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Plaquetas , COVID-19 , Convalescença , Monócitos , Ativação de Neutrófilo , Neutrófilos , Ativação Plaquetária , SARS-CoV-2/metabolismo , Doença Aguda , Adulto , Idoso , Idoso de 80 Anos ou mais , Plaquetas/metabolismo , Plaquetas/patologia , COVID-19/sangue , COVID-19/patologia , Feminino , Citometria de Fluxo , Humanos , Interleucina-10/sangue , Interleucina-6/sangue , Masculino , Pessoa de Meia-Idade , Monócitos/metabolismo , Monócitos/patologia , Neutrófilos/metabolismo , Neutrófilos/patologiaRESUMO
Platelets are the primary cellular mediators of hemostasis and this function firmly acquaints them with a variety of inflammatory processes. For example, platelets can act as circulating sentinels by expressing Toll-like receptors (TLR) that bind pathogens and this allows platelets to effectively kill them or present them to cells of the immune system. Furthermore, activated platelets secrete and express many pro- and anti-inflammatory molecules that attract and capture circulating leukocytes and direct them to inflamed tissues. In addition, platelets can directly influence adaptive immune responses via secretion of, for example, CD40 and CD40L molecules. Platelets are also the source of most of the microvesicles in the circulation and these miniscule elements further enhance the platelet's ability to communicate with the immune system. More recently, it has been demonstrated that platelets and their parent cells, the megakaryocytes (MK), can also uptake, process and present both foreign and self-antigens to CD8+ T-cells conferring on them the ability to directly alter adaptive immune responses. This review will highlight several of the non-hemostatic attributes of platelets that clearly and rightfully place them as integral players in immune reactions.
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Imunidade Adaptativa , Plaquetas/imunologia , Imunidade Inata , Biomarcadores/sangue , Plaquetas/metabolismo , Humanos , Imunomodulação , Inflamação/sangue , Inflamação/imunologia , Megacariócitos/imunologia , Megacariócitos/metabolismo , Transfusão de PlaquetasRESUMO
: Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder mediated by antiplatelet autoantibodies and antigen-specific T cells that either destroy platelets peripherally in the spleen or impair platelet production in the bone marrow. There have been a plethora of publications relating to the pathophysiology of ITP and since January of 2019, at least 50 papers have been published on ITP pathophysiology. PURPOSE OF REVIEW: To summarize the literature relating to the pathophysiology of ITP including the working mechanisms of therapies, T-cell and B-cell physiology, protein/RNA/DNA biochemistry, and animal models in an attempt to unify the perceived abnormal immune processes. RECENT FINDINGS: The most recent pathophysiologic irregularities associated with ITP relate to abnormal T-cell responses, particularly, defective T regulatory cell activity and how therapeutics can restore these responses. The robust literature on T cells in ITP points to the notion that ITP is a disease initiated by faulty self-tolerance mechanisms very much like that of other organ-specific autoimmune diseases. There is also a large literature on new and existing animal models of ITP and these will be discussed. It appears that understanding how to specifically modulate T cells in patients with ITP will undoubtedly lead to effective antigen-specific therapeutics. CONCLUSIONS: ITP is predominately a T cell disorder which leads to a breakdown in self tolerance mechanisms and allows for the generation of anti-platelet autoantibodies and T cells. Novel therapeutics that target T cells may be the most effective way to perhaps cure this disorder.
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Púrpura Trombocitopênica Idiopática/fisiopatologia , Animais , Linfócitos B/imunologia , Linfócitos B/patologia , Modelos Animais de Doenças , Humanos , Imunidade Celular , Púrpura Trombocitopênica Idiopática/imunologia , Púrpura Trombocitopênica Idiopática/patologia , Púrpura Trombocitopênica Idiopática/terapia , Linfócitos T/imunologia , Linfócitos T/patologiaRESUMO
Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder in which autoantibodies and/or autoreactive T cells destroy platelets and megakaryocytes in the spleen and bone marrow, respectively. Thrombopoietin receptor agonists (TPO-RA e.g. Romiplostim and Eltrombopag) have made a substantial contribution to the treatment of patients with ITP, which are refractory to first-line treatments and approximately 30% demonstrate sustained elevated platelet counts after drug tapering. How TPO-RA induce these sustained responses is not known. We analyzed the efficacy of a murine TPO-RA in a well-established murine model of active ITP. Treatment with TPO-RA (10 ug/kg, based on pilot dose escalation experiments) significantly raised the platelet counts in ITP-mice. Immunomodulation was assessed by measuring serum IgG anti-platelet antibody levels; TPO-RA-treated mice had significantly reduced IgG anti-platelet antibodies despite the increasing platelet counts. These results suggest that TPO-RA is not only an efficacious therapy but also reduces anti-platelet humoral immunity in ITP.
Assuntos
Autoanticorpos/imunologia , Plaquetas/imunologia , Plaquetas/metabolismo , Contagem de Plaquetas , Púrpura Trombocitopênica Idiopática/etiologia , Púrpura Trombocitopênica Idiopática/metabolismo , Receptores de Trombopoetina/agonistas , Animais , Autoimunidade , Biópsia , Plaquetas/efeitos dos fármacos , Modelos Animais de Doenças , Suscetibilidade a Doenças , Humanos , Imunomodulação , Camundongos , Camundongos Knockout , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/patologiaRESUMO
Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli (EHEC), that cause gastrointestinal infection leading to hemolytic uremic syndrome. The aim of this study was to investigate if Stx signals via ATP and if blockade of purinergic receptors could be protective. Stx induced ATP release from HeLa cells and in a mouse model. Toxin induced rapid calcium influx into HeLa cells, as well as platelets, and a P2X1 receptor antagonist, NF449, abolished this effect. Likewise, the P2X antagonist suramin blocked calcium influx in Hela cells. NF449 did not affect toxin intracellular retrograde transport, however, cells pre-treated with NF449 exhibited significantly higher viability after exposure to Stx for 24 hours, compared to untreated cells. NF449 protected HeLa cells from protein synthesis inhibition and from Stx-induced apoptosis, assayed by caspase 3/7 activity. The latter effect was confirmed by P2X1 receptor silencing. Stx induced the release of toxin-positive HeLa cell- and platelet-derived microvesicles, detected by flow cytometry, an effect significantly reduced by NF449 or suramin. Suramin decreased microvesicle levels in mice injected with Stx or inoculated with Stx-producing EHEC. Taken together, we describe a novel mechanism of Stx-mediated cellular injury associated with ATP signaling and inhibited by P2X receptor blockade.
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Infecções por Escherichia coli/tratamento farmacológico , Síndrome Hemolítico-Urêmica/tratamento farmacológico , Receptores Purinérgicos P2X1/genética , Toxina Shiga/genética , Trifosfato de Adenosina/metabolismo , Animais , Benzenossulfonatos/farmacologia , Plaquetas/microbiologia , Escherichia coli Êntero-Hemorrágica/efeitos dos fármacos , Escherichia coli Êntero-Hemorrágica/patogenicidade , Infecções por Escherichia coli/genética , Infecções por Escherichia coli/microbiologia , Infecções por Escherichia coli/patologia , Células HeLa , Síndrome Hemolítico-Urêmica/genética , Síndrome Hemolítico-Urêmica/microbiologia , Síndrome Hemolítico-Urêmica/patologia , Humanos , Camundongos , Antagonistas do Receptor Purinérgico P2X/farmacologia , Toxina Shiga/antagonistas & inibidoresRESUMO
Transfusion-related acute lung injury (TRALI) is one of the leading causes of transfusion-related fatalities and is characterized by the onset of acute respiratory distress within 6 hours upon blood transfusion. Specific therapies are unavailable. Preexisting inflammation is a risk factor for TRALI and neutrophils (polymorphonuclear neutrophils [PMNs]) are considered to be the major pathogenic cells. Osteopontin (OPN) is a multifunctional protein expressed at sites of inflammation and, for example, is involved in pulmonary disorders, can regulate cellular migration, and can function as a PMN chemoattractant. We investigated whether OPN is involved in TRALI induction by promoting PMN recruitment to the lungs. Using a previously established murine TRALI model, we found that in contrast to wild-type (WT) mice, OPN knockout (KO) mice were resistant to antibody-mediated PMN-dependent TRALI induction. Administration of purified OPN to the OPN KO mice, however, restored the TRALI response and pulmonary PMN accumulation. Alternatively, blockade of OPN in WT mice using an anti-OPN antibody prevented the onset of TRALI induction. Using pulmonary immunohistochemistry, OPN could be specifically detected in the lungs of mice that suffered from TRALI. The OPN-mediated TRALI response seemed dependent on macrophages, likely the cellular source of OPN and OPN polymerization, and independent from the OPN receptor CD44, interleukin 6 (IL-6), and other PMN chemoattractants including macrophage inflammatory protein-2 (MIP-2). These data indicate that OPN is critically required for induction of antibody-mediated murine TRALI through localization to the lungs and stimulation of pulmonary PMN recruitment. This suggests that anti-OPN antibody therapy may be a potential therapeutic strategy to explore in TRALI patients.
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Neutrófilos/patologia , Osteopontina/metabolismo , Lesão Pulmonar Aguda Relacionada à Transfusão/metabolismo , Lesão Pulmonar Aguda Relacionada à Transfusão/patologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
Transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI) are syndromes of acute respiratory distress that occur within 6 hours of blood transfusion. TACO and TRALI are the leading causes of transfusion-related fatalities, and specific therapies are unavailable. Diagnostically, it remains very challenging to distinguish TACO and TRALI from underlying causes of lung injury and/or fluid overload as well as from each other. TACO is characterized by pulmonary hydrostatic (cardiogenic) edema, whereas TRALI presents as pulmonary permeability edema (noncardiogenic). The pathophysiology of both syndromes is complex and incompletely understood. A 2-hit model is generally assumed to underlie TACO and TRALI disease pathology, where the first hit represents the clinical condition of the patient and the second hit is conveyed by the transfusion product. In TACO, cardiac or renal impairment and positive fluid balance appear first hits, whereas suboptimal fluid management or other components in the transfused product may enable the second hit. Remarkably, other factors beyond volume play a role in TACO. In TRALI, the first hit can, for example, be represented by inflammation, whereas the second hit is assumed to be caused by antileukocyte antibodies or biological response modifiers (eg, lipids). In this review, we provide an up-to-date overview of TACO and TRALI regarding clinical definitions, diagnostic strategies, pathophysiological mechanisms, and potential therapies. More research is required to better understand TACO and TRALI pathophysiology, and more biomarker studies are warranted. Collectively, this may result in improved diagnostics and development of therapeutic approaches for these life-threatening transfusion reactions.
Assuntos
Transfusão de Componentes Sanguíneos/efeitos adversos , Reação Transfusional/etiologia , Lesão Pulmonar Aguda Relacionada à Transfusão/etiologia , Humanos , PrognósticoRESUMO
The acute respiratory distress syndrome (ARDS) is a serious and common complication of multiple medical and surgical interventions, with sepsis, pneumonia, and aspiration of gastric contents being common risk factors. ARDS develops within 1 week of a known clinical insult or presents with new/worsening respiratory symptoms if the clinical insult is unknown. Approximately 40% of the ARDS cases have a fatal outcome. Transfusion-related acute lung injury (TRALI), on the other hand, is characterized by the occurrence of respiratory distress and acute lung injury, which presents within 6 h after administration of a blood transfusion. In contrast to ARDS, acute lung injury in TRALI is not attributable to another risk factor for acute lung injury. 'Possible TRALI', however, may have a clear temporal relationship to an alternative risk factor for acute lung injury. Risk factors for TRALI include chronic alcohol abuse and systemic inflammation. TRALI is the leading cause of transfusion-related fatalities. There are no specific therapies available for ARDS or TRALI as both have a complex and incompletely understood pathogenesis. Neutrophils (polymorphonuclear leukocytes; PMNs) have been suggested to be key effector cells in the pathogenesis of both syndromes. In the present paper, we summarize the literature with regard to PMN involvement in the pathogenesis of both ARDS and TRALI based on both human data as well as on animal models. The evidence generally supports a strong role for PMNs in both ARDS and TRALI. More research is required to shed light on the pathogenesis of these respiratory syndromes and to more thoroughly establish the nature of the PMN involvement, especially considering the heterogeneous etiologies of ARDS.
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Transfusion-related acute lung injury (TRALI) is a syndrome of respiratory distress upon blood transfusion and is the leading cause of transfusion-related fatalities. Whether the gut microbiota plays any role in the development of TRALI is currently unknown. We observed that untreated barrier-free (BF) mice suffered from severe antibody-mediated acute lung injury, whereas the more sterile housed specific pathogen-free (SPF) mice and gut flora-depleted BF mice were both protected from lung injury. The prevention of TRALI in the SPF mice and gut flora-depleted BF mice was associated with decreased plasma macrophage inflammatory protein-2 levels as well as decreased pulmonary neutrophil accumulation. DNA sequencing of amplicons of the 16S ribosomal RNA gene revealed a varying gastrointestinal bacterial composition between BF and SPF mice. BF fecal matter transferred into SPF mice significantly restored TRALI susceptibility in SPF mice. These data reveal a link between the gut flora composition and the development of antibody-mediated TRALI in mice. Assessment of gut microbial composition may help in TRALI risk assessment before transfusion.
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Quimiocina CXCL2/sangue , Microbioma Gastrointestinal , Pulmão/metabolismo , Neutrófilos/metabolismo , Lesão Pulmonar Aguda Relacionada à Transfusão/microbiologia , Animais , Pulmão/patologia , Camundongos , Neutrófilos/patologia , Lesão Pulmonar Aguda Relacionada à Transfusão/patologiaRESUMO
Certain kidney diseases are associated with complement activation although a renal triggering factor has not been identified. Here we demonstrated that renin, a kidney-specific enzyme, cleaves C3 into C3b and C3a, in a manner identical to the C3 convertase. Cleavage was specifically blocked by the renin inhibitor aliskiren. Renin-mediated C3 cleavage and its inhibition by aliskiren also occurred in serum. Generation of C3 cleavage products was demonstrated by immunoblotting, detecting the cleavage product C3b, by N-terminal sequencing of the cleavage product, and by ELISA for C3a release. Functional assays showed mast cell chemotaxis towards the cleavage product C3a and release of factor Ba when the cleavage product C3b was combined with factor B and factor D. The renin-mediated C3 cleavage product bound to factor B. In the presence of aliskiren this did not occur, and less C3 deposited on renin-producing cells. The effect of aliskiren was studied in three patients with dense deposit disease and this demonstrated decreased systemic and renal complement activation (increased C3, decreased C3a and C5a, decreased renal C3 and C5b-9 deposition and/or decreased glomerular basement membrane thickness) over a follow-up period of four to seven years. Thus, renin can trigger complement activation, an effect inhibited by aliskiren. Since renin concentrations are higher in renal tissue than systemically, this may explain the renal propensity of complement-mediated disease in the presence of complement mutations or auto-antibodies.
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Amidas/farmacologia , Ativação do Complemento/efeitos dos fármacos , Complemento C3/química , Fumaratos/farmacologia , Glomerulonefrite Membranoproliferativa/metabolismo , Glomerulonefrite Membranoproliferativa/terapia , Renina/química , Amidas/uso terapêutico , Quimiotaxia/efeitos dos fármacos , Criança , Complemento C3/metabolismo , Complemento C3a/química , Complemento C3a/metabolismo , Complemento C3b/química , Complemento C3b/metabolismo , Complemento C4/química , Complemento C5a/química , Complemento C5a/metabolismo , Complemento C5b/química , Complemento C5b/metabolismo , Fator B do Complemento/química , Fator D do Complemento/química , Feminino , Fumaratos/uso terapêutico , Membrana Basal Glomerular/patologia , Glomerulonefrite Membranoproliferativa/patologia , Humanos , Mastócitos/fisiologia , Renina/antagonistas & inibidores , Renina/metabolismoRESUMO
OBJECTIVES: Transfusion-related acute lung injury is characterized by the onset of respiratory distress and acute lung injury following blood transfusion, but its pathogenesis remains poorly understood. Generally, a two-hit model is presumed to underlie transfusion-related acute lung injury with the first hit being risk factors present in the transfused patient (such as inflammation), whereas the second hit is conveyed by factors in the transfused donor blood (such as antileukocyte antibodies). At least 80% of transfusion-related acute lung injury cases are related to the presence of donor antibodies such as antihuman leukocyte or antihuman neutrophil antibodies. The remaining cases may be related to nonantibody-mediated factors such as biolipids or components related to storage and ageing of the transfused blood cells. At present, transfusion-related acute lung injury is the leading cause of transfusion-related fatalities and no specific therapy is clinically available. In this article, we critically appraise and discuss recent preclinical (bench) insights related to transfusion-related acute lung injury pathogenesis and their therapeutic potential for future use at the patients' bedside in order to combat this devastating and possibly fatal complication of transfusion. DATA SOURCES: We searched the PubMed database (until August 22, 2017). STUDY SELECTION: Using terms: "Transfusion-related acute lung injury," "TRALI," "TRALI and therapy," "TRALI pathogenesis." DATA EXTRACTION: English-written articles focusing on transfusion-related acute lung injury pathogenesis, with potential therapeutic implications, were extracted. DATA SYNTHESIS: We have identified potential therapeutic approaches based on the literature. CONCLUSIONS: We propose that the most promising therapeutic strategies to explore are interleukin-10 therapy, down-modulating C-reactive protein levels, targeting reactive oxygen species, or blocking the interleukin-8 receptors; all focused on the transfused recipient. In the long-run, it may perhaps also be advantageous to explore other strategies aimed at the transfused recipient or aimed toward the blood product, but these will require more validation and confirmation first.
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Lesão Pulmonar Aguda Relacionada à Transfusão/etiologia , Humanos , Lesão Pulmonar Aguda Relacionada à Transfusão/prevenção & controle , Lesão Pulmonar Aguda Relacionada à Transfusão/terapiaRESUMO
Fiber and penton base overproduced in adenovirus (Ad) infected cells can be secreted prior to progeny release and thereby regulate progeny spread. We aimed to investigate the mechanisms of fiber and penton base secretion in Ad2- or Ad5-infected A549 cells. Our flow cytometry analyses detected abundant surface fiber molecules, but little penton base molecules at 12h post infection. Immunogold staining combined with transmission electron microscopic analyses revealed separate, non-co-localized release of fiber and penton base in the proximity of the plasma membrane. Depolymerization of microtubule and actin cytoskeletons, and inhibition of Rock kinase and myosin II activity together demonstrated cytoskeletal network-dependent fiber secretion. Inhibition of intracellular calcium [Ca2+]i signaling caused diminished fiber secretion, which was associated with diminished progeny production. Thus, fiber and penton base are actively and separately secreted during the early stages of Ad2 or Ad5 infection, their secretion may play important role in Ad life cycle.
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Infecções por Adenovirus Humanos/patologia , Adenovírus Humanos/metabolismo , Proteínas do Capsídeo/metabolismo , Capsídeo/metabolismo , Células A549 , Citoesqueleto de Actina/metabolismo , Adenovírus Humanos/classificação , Sinalização do Cálcio/fisiologia , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Citometria de Fluxo , Células HEK293 , Humanos , Microscopia Eletrônica de Transmissão , Microtúbulos/metabolismo , Miosina Tipo II/antagonistas & inibidores , Receptores Virais/metabolismo , Quinases Associadas a rho/antagonistas & inibidoresRESUMO
Complement activation occurs during enterohemorrhagic Escherichia coli (EHEC) infection and may exacerbate renal manifestations. In this study, we show glomerular C5b-9 deposits in the renal biopsy of a child with EHEC-associated hemolytic uremic syndrome. The role of the terminal complement complex, and its blockade as a therapeutic modality, was investigated in a mouse model of E. coli O157:H7 infection. BALB/c mice were treated with monoclonal anti-C5 i.p. on day 3 or 6 after intragastric inoculation and monitored for clinical signs of disease and weight loss for 14 d. All infected untreated mice (15 of 15) or those treated with an irrelevant Ab (8 of 8) developed severe illness. In contrast, only few infected mice treated with anti-C5 on day 3 developed symptoms (three of eight, p < 0.01 compared with mice treated with the irrelevant Ab on day 3) whereas most mice treated with anti-C5 on day 6 developed symptoms (six of eight). C6-deficient C57BL/6 mice were also inoculated with E. coli O157:H7 and only 1 of 14 developed disease, whereas 10 of 16 wild-type mice developed weight loss and severe disease (p < 0.01). Complement activation via the terminal pathway is thus involved in the development of disease in murine EHEC infection. Early blockade of the terminal complement pathway, before the development of symptoms, was largely protective, whereas late blockade was not. Likewise, lack of C6, and thereby deficient terminal complement complex, was protective in murine E. coli O157:H7 infection.
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Complemento C6/antagonistas & inibidores , Complexo de Ataque à Membrana do Sistema Complemento/antagonistas & inibidores , Infecções por Escherichia coli/imunologia , Síndrome Hemolítico-Urêmica/imunologia , Animais , Pré-Escolar , Complemento C6/imunologia , Complexo de Ataque à Membrana do Sistema Complemento/imunologia , Modelos Animais de Doenças , Escherichia coli Êntero-Hemorrágica , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BLRESUMO
Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli, which are non-invasive strains that can lead to hemolytic uremic syndrome (HUS), associated with renal failure and death. Although bacteremia does not occur, bacterial virulence factors gain access to the circulation and are thereafter presumed to cause target organ damage. Stx was previously shown to circulate bound to blood cells but the mechanism by which it would potentially transfer to target organ cells has not been elucidated. Here we show that blood cell-derived microvesicles, shed during HUS, contain Stx and are found within patient renal cortical cells. The finding was reproduced in mice infected with Stx-producing Escherichia coli exhibiting Stx-containing blood cell-derived microvesicles in the circulation that reached the kidney where they were transferred into glomerular and peritubular capillary endothelial cells and further through their basement membranes followed by podocytes and tubular epithelial cells, respectively. In vitro studies demonstrated that blood cell-derived microvesicles containing Stx undergo endocytosis in glomerular endothelial cells leading to cell death secondary to inhibited protein synthesis. This study demonstrates a novel virulence mechanism whereby bacterial toxin is transferred within host blood cell-derived microvesicles in which it may evade the host immune system.
Assuntos
Toxinas Bacterianas/metabolismo , Células Sanguíneas/metabolismo , Micropartículas Derivadas de Células/metabolismo , Escherichia coli Êntero-Hemorrágica/metabolismo , Infecções por Escherichia coli/metabolismo , Adolescente , Adulto , Animais , Células Sanguíneas/microbiologia , Micropartículas Derivadas de Células/microbiologia , Células Cultivadas , Criança , Pré-Escolar , Infecções por Escherichia coli/patologia , Feminino , Interações Hospedeiro-Patógeno , Humanos , Lactente , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Transporte ProteicoRESUMO
Polycomb ring finger oncogene BMI1 (B cell-specific Moloney murine leukemia virus integration site 1) plays a critical role in development of several types of cancers. Here, we report an inverse relationship between levels of BMI1 expression and adenovirus (Ad) progeny production. Enforced BMI1 expression in A549 cells impaired Ad progeny production. In contrast, knocking-down of endogenous BMI1 expression enhanced progeny production of a conditionally replicating Ad and wild-type Ad5 and Ad11p. Ad vectors overexpressing BMI1 were not impaired in the replication of progeny genomes and in the expression of E1A and Ad structural proteins. However, 293 cells infected by Ad vector overexpressing BMI1 contained a large proportion of morphologically irregular Ad particles. This effect was reversed in 293 cells pre-treated with the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) in parallel with the production of infectious Ad particles. Our findings suggest an inhibitory role of BMI1 in Ad morphogenesis that can be implied in Ad tropism and Ad-mediated cancer therapy.