RESUMO
UNLABELLED: ESSENTIALS: Extracellular histones are highly augmented in sites of neovessel formation, such as regeneration tissues. We studied histone effect on survival and angiogenic activity of mature and progenitor endothelial cells. Extracellular histones trigger apoptosis and pyroptosis and reduce angiogenesis in vivo and in vitro. Histone blockade can be useful as a therapeutic strategy to improve angiogenesis and tissue regeneration. BACKGROUND: Extracellular histones are highly augmented in sites of neovessel formation, like regeneration tissues. Their cytotoxic effect has been studied in endothelial cells, although the mechanism involved and their action on endothelial colony-forming cells (ECFCs) remain unknown. OBJECTIVE: To study the effect of histones on ECFC survival and angiogenic functions and compare it with mature endothelial cells. METHODS AND RESULTS: Nuclear morphology analysis showed that each human recombinant histone triggered both apoptotic-like and necrotic-like cell deaths in both mature and progenitor endothelial cells. While H1 and H2A exerted a weak toxicity, H2B, H3 and H4 were the most powerful. The percentage of apoptosis correlated with the percentage of ECFCs exhibiting caspase-3 activation and was zeroed by the pan-caspase inhibitor Z-VAD-FMK. Necrotic-like cell death was also suppressed by this compound and the caspase-1 inhibitor Ac-YVAD-CMK, indicating that histones triggered ECFC pyroptosis. All histones, at non-cytotoxic concentrations, reduced migration and H2B, H3 and H4 induced cell cycle arrest and impaired tubulogenesis via p38 activation. Neutrophil-derived histones exerted similar effects. In vivo blood vessel formation in the quail chorioallantoic membrane was also reduced by H2B, H3 and H4. Their cytotoxic and antiangiogenic effects were suppressed by unfractioned and low-molecular-weight heparins and the combination of TLR2 and TLR4 blocking antibodies. CONCLUSIONS: Histones trigger both apoptosis and pyroptosis of ECFCs and inhibit their angiogenic functions. Their cytotoxic and antiangiogenic effects are similar in mature endothelial cells and disappear after heparin addition or TLR2/TLR4 blockade, suggesting both as therapeutic strategies to improve tissue regeneration.
Assuntos
Inibidores da Angiogênese/farmacologia , Células Progenitoras Endoteliais/efeitos dos fármacos , Histonas/farmacologia , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Neovascularização Fisiológica/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Caspase 1/metabolismo , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Células Progenitoras Endoteliais/metabolismo , Células Progenitoras Endoteliais/patologia , Células Endoteliais da Veia Umbilical Humana/metabolismo , Células Endoteliais da Veia Umbilical Humana/patologia , Humanos , Piroptose/efeitos dos fármacos , Codorniz , Transdução de Sinais/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
BACKGROUND: Platelets mediate angiogenesis through the secretion of several factors, including the pro-angiogenic vascular endothelial growth factor (VEGF) and the anti-angiogenic endostatin. Although previous findings indicated that these molecules are packed into different alpha-granules and selectively released by specific stimulation of protease-activated receptor (PAR)-1 or PAR-4, recent evidences are against this hypothesis. OBJECTIVES: To elucidate the controversies about the VEGF and endostatin release and the overall angiogenic effect of PARs-stimulated platelets. METHODS: VEGF and endostatin were quantified by enzyme linked-immunosorbent assay (ELISA). Endothelial proliferation (pNPP assay), wound healing (scratch assay) and tubule formation (matrigel) of human microvascular endothelial cells (HMEC-1) and endothelial progenitor cells (EPC) were determined using supernatants from PAR-1- or PAR-4-stimulated platelets. RESULTS: Activation of washed platelets (WPs) by PAR-1- or PAR-4-activating peptide (AP) promoted the VEGF and endostatin secretion in a concentration-dependent manner, being PAR-1-AP more potent than PAR-4-AP. The release of both molecules was abrogated by pre-incubation of platelets with PAR antagonists. Activation of platelet-rich plasma (PRP) with either PAR-1-AP or PAR-4-AP induced a significant VEGF secretion. Quantification of platelet-endostatin secretion was not possible in PRP due to the high levels of plasmatic endostatin vs. platelet content. Releasates from PAR-1- or PAR-4-activated WPs promoted similar pattern of angiogenic responses of HMEC-1 or EPC. Moreover, proliferation of HMEC-1 mediated by PAR-stimulated PRP releasates was delayed and significantly lower compared with that induced by PAR-stimulated WPs. CONCLUSIONS: Our results are in contrast with the previously described differential release of VEGF and endostatin induced by the selective PAR-1 or PAR-4 stimulation, and support the notion that while circulating endostatin accounts for the maintenance of a systemic anti-angiogenic state, locally, the release of platelet alpha-granule content promotes angiogenesis.
Assuntos
Plaquetas/metabolismo , Endostatinas/metabolismo , Receptor PAR-1/agonistas , Receptores de Trombina/agonistas , Fator A de Crescimento do Endotélio Vascular/metabolismo , Plaquetas/efeitos dos fármacos , Células Endoteliais/metabolismo , Humanos , Neovascularização Fisiológica , Oligopeptídeos/farmacologia , Ativação Plaquetária/efeitos dos fármacosRESUMO
BACKGROUND: To further understand the role of platelets in the pathogenesis of viral infections we explored platelet interaction with Coxsackieviruses B (CVB) 1 and 3. CVB is a group of viruses that cause the majority of human enterovirus-related viral myocarditis; their receptor (CAR) is expressed on the platelet surface and there is a well-characterized CVB3-induced myocarditis murine model. METHODS: Human platelets were infected with CVB1 and 3 and viruses were detected in pellets and in supernatants. C57BL/6J mice with or without platelet depletion were inoculated with CVB3 and peripheral blood and heart samples collected at different times post-infection. RESULTS: CVB1 and 3 RNA and a capsid protein were detected in infected platelets. Despite the fact that titration assays in Vero cells showed increasing infectivity titers over time, supernatants and pellets from infected platelets showed similar levels, suggesting that platelets were not susceptible to a replicative infectivity cycle. CVB binding was CAR-independent and resulted in P-selectin and phosphatidylserine (PS) exposure. CVB3-infected mice showed a rapid thrombocytopenia that correlated with an increase in platelet PS exposure and platelet-leukocyte aggregates without modification of platelet P-selectin expression or von Willebrand factor levels. Mortality, viremia, heart viral titers and myocarditis were significantly higher in platelet-depleted than normal animals. Type I IFN levels were not changed but IgG levels were lower in infected and platelet-depleted mice. CONCLUSIONS: Our data reveal that platelets play a critical role in host survival and immune response against CVB3 infection.
Assuntos
Plaquetas/virologia , Infecções por Coxsackievirus/sangue , Infecções por Coxsackievirus/virologia , Enterovirus Humano B/patogenicidade , Miocardite/sangue , Miocardite/virologia , Animais , Plaquetas/imunologia , Plaquetas/metabolismo , Proteínas do Capsídeo/sangue , Proteínas do Capsídeo/genética , Chlorocebus aethiops , Infecções por Coxsackievirus/imunologia , Modelos Animais de Doenças , Enterovirus Humano B/genética , Enterovirus Humano B/imunologia , Enterovirus Humano B/metabolismo , Feminino , Interações Hospedeiro-Patógeno , Humanos , Imunoglobulina G/sangue , Masculino , Camundongos Endogâmicos C57BL , Miocardite/imunologia , Selectina-P/sangue , Fosfatidilserinas/sangue , RNA Viral/sangue , Trombocitopenia/sangue , Trombocitopenia/virologia , Fatores de Tempo , Células Vero , Replicação ViralRESUMO
Solid tumors are infiltrated by immune cells where macrophages and senescent T cells are highly represented. Within the tumor microenvironment, a cross-talk between the infiltrating cells may occur conditioning the characteristic of the in situ immune response. Our previous work showed that tumors induce senescence of T cells, which are powerful suppressors of lympho-proliferation. In this study, we report that Tumor-Induced Senescent (TIS)-T cells may also modulate monocyte activation. To gain insight into this interaction, CD4+ or CD8+TIS-T or control-T cells were co-incubated with autologous monocytes under inflammatory conditions. After co-culture with CD4+ or CD8+TIS-T cells, CD14+ monocytes/macrophages (Mo/Ma) exhibit a higher expression of CD16+ cells and a reduced expression of CD206. These Mo/Ma produce nitric oxide and reactive oxygen species; however, TIS-T cells do not modify phagocyte capacity of Mo/Ma. TIS-T modulated-Mo/Ma show a higher production of pro-inflammatory cytokines (TNF, IL-1ß and IL-6) and angiogenic factors (MMP-9, VEGF-A and IL-8) and a lower IL-10 and IP-10 secretion than monocytes co-cultured with controls. The mediator(s) present in the supernatant of TIS-T cell/monocyte-macrophage co-cultures promote(s) tubulogenesis and tumor-cell survival. Monocyte-modulation induced by TIS-T cells requires cell-to-cell contact. Although CD4+ shows different behavior from CD8+TIS-T cells, blocking mAbs against T-cell immunoglobulin and mucin protein 3 and CD40 ligand reduce pro-inflammatory cytokines and angiogenic factors production, indicating that these molecules are involved in monocyte/macrophage modulation by TIS-T cells. Our results revealed a novel role for TIS-T cells in human monocyte/macrophage modulation, which may have deleterious consequences for tumor progression. This modulation should be considered to best tailor the immunotherapy against cancer.
Assuntos
Linfócitos T CD4-Positivos/metabolismo , Ligante de CD40/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Citocinas/biossíntese , Proteínas de Membrana/metabolismo , Monócitos/metabolismo , Linfócitos T CD4-Positivos/citologia , Ligante de CD40/genética , Linfócitos T CD8-Positivos/citologia , Comunicação Celular , Sobrevivência Celular , Senescência Celular , Técnicas de Cocultura , Citocinas/metabolismo , Proteínas Ligadas por GPI/genética , Proteínas Ligadas por GPI/metabolismo , Regulação da Expressão Gênica , Células HeLa , Receptor Celular 2 do Vírus da Hepatite A , Humanos , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Receptor de Manose , Lectinas de Ligação a Manose/genética , Lectinas de Ligação a Manose/metabolismo , Metaloproteinase 9 da Matriz/genética , Metaloproteinase 9 da Matriz/metabolismo , Proteínas de Membrana/genética , Monócitos/citologia , Óxido Nítrico/metabolismo , Cultura Primária de Células , Espécies Reativas de Oxigênio/metabolismo , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Receptores de IgG/genética , Receptores de IgG/metabolismo , Transdução de Sinais , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
BACKGROUND AND PURPOSE: Platelets are major players in every step of vessel development through the local delivery of angiogenesis-modulating factors, including the pro-angiogenic protein VEGF and the anti-angiogenic endostatin. Although thrombin is a potent agonist and is highly elevated in angiogenesis-related diseases, studies regarding its action on the release of platelet angiogenic factors are scarce and controversial. Herein, we have investigated the role of thrombin not only in VEGF and endostatin release but also in net platelet angiogenic activity. EXPERIMENTAL APPROACH: Human platelets were stimulated with thrombin in the presence of the various inhibitors of the signalling pathways involved in platelet activation. Supernatants/releasates were used to determine the levels of angiogenic molecules and to induce angiogenic responses. KEY RESULTS: We found that thrombin induced the secretion of both VEGF and endostatin; however, the overall effect of the releasates was pro-angiogenic as they promoted tubule-like formation and increased the proliferation of endothelial cells. Both responses were only slightly suppressed in the presence of a VEGF receptor-neutralizing antibody. Pharmacological studies revealed that while inhibitors of PKC, p38, ERK1/2, Src kinases or PI3K/Akt exerted only partial inhibitory effects, aspirin fully blocked the pro-angiogenic activity of the releasate. CONCLUSIONS AND IMPLICATIONS: In contrast to current belief, platelet pro-angiogenic responses are independent of VEGF and appear to be the result of the combined action of several molecules. Moreover, our data reinforce the notion that aspirin is a good candidate for a therapeutic agent to treat angiogenesis-related diseases.
Assuntos
Plaquetas/metabolismo , Neovascularização Fisiológica/fisiologia , Trombina/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo , Aspirina/farmacologia , Proliferação de Células , Endostatinas/metabolismo , Células Endoteliais/metabolismo , Humanos , Técnicas In Vitro , Neovascularização Patológica/tratamento farmacológico , Neovascularização Patológica/fisiopatologia , Neovascularização Fisiológica/efeitos dos fármacos , Ativação Plaquetária/fisiologia , Inibidores da Agregação Plaquetária/farmacologia , Transdução de Sinais/fisiologia , Trombina/administração & dosagemRESUMO
BACKGROUND: Type I interferons (IFN-I) negatively regulate megakaryo/thrombopoiesis. However, expression of the IFN-I receptor (IFNAR) in the megakaryocytic lineage is poorly characterized. OBJECTIVES: To study the expression and functionality of IFNAR in the megakaryocytic lineage. METHODS AND RESULTS: Although IFNAR mRNA was found in every cell type studied, its protein expression showed differences between them. According to flow cytometry and immunofluorescence, IFNAR1 was observed in Meg-01, Dami, CD34+ cells and megakaryocytes, but not in proplatelets or platelets. Immunoblotting assays showed that IFNAR1 and IFNAR2 were highly expressed in all cell types, except in platelets where it was barely detectable. Regarding IFNAR1, 130- and 90-kDa bands were detected in Meg-01 and Dami, whereas 130- and 60-kDa bands were found in CD34+ cells and megakaryocytes. Activation of megakaryocytic IFNAR by IFN-ß induced pSTAT1/2 and upregulated the antiviral genes IRF7 and MXA. The latter response was completely suppressed by IFNAR blockade. In contrast, the low levels of IFNAR in platelets were not functional as pSTAT1/2, aggregation and P-selectin expression were not induced by IFN-I. In addition, megakaryocytes increased IFN-I transcript levels and produced IFN-ß upon stimulation with PolyI:C, a synthetic dsRNA that mimics viral infection. CONCLUSIONS: Early progenitors and mature megakaryocytes, but not platelets, express functional IFNAR and synthetize/release IFN-ß, revealing not only that megakaryo/thrombopoiesis regulation by IFN-I is associated with a specific interaction with its receptor, but also that megakaryocytes may play a role in the antiviral defense by being both IFN producers and responders.
Assuntos
Megacariócitos/metabolismo , Receptor de Interferon alfa e beta/fisiologia , Western Blotting , Linhagem Celular , Linhagem da Célula , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Imunofluorescência , Humanos , Megacariócitos/citologia , Reação em Cadeia da Polimerase em Tempo RealRESUMO
BACKGROUND: Hyperthermia is one of the main disturbances of homeostasis occurring during sepsis or hypermetabolic states such as cancer. Platelets are important mediators of the inflammation that accompanies these processes, but very little is known about the changes in platelet function that occur at different temperatures. OBJECTIVES: To explore the effect of higher temperatures on platelet physiology. METHODS: Platelet responses including adhesion, spreading (fluorescence microscopy), α(IIb)ß(3) activation (flow cytometry), aggregation (turbidimetry), ATP release (luminescence), thromboxane A(2) generation, alpha-granule protein secretion (ELISA) and protein phosphorylation from different signaling pathways (immunoblotting) were studied. RESULTS: Preincubation of platelets at temperatures higher than 37 °C (38.5-42 °C) inhibited thrombin-induced hemostasis, including platelet adhesion, aggregation, ATP release and thromboxane A(2) generation. The expression of P-selectin and CD63, as well as vascular endothelial growth factor (VEGF) release, was completely inhibited by hyperthermia, whereas von Willebrand factor (VWF) and endostatin levels remained substantially increased at high temperatures. This suggested that release of proteins from platelet granules is modulated not only by classical platelet agonists but also by microenvironmental factors. The observed gradation of response involved not only antiangiogenesis regulators, but also other cargo proteins. Some signaling pathways were more stable than others. While ERK1/2 and AKT phosphorylation were resistant to changes in temperature, Src, Syk, p38 phosphorylation and IkappaB degradation were decreased in a temperature-dependent fashion. CONCLUSIONS: Higher temperatures, such as those observed with fever or tissue invasion, inhibit the hemostatic functions of platelets and selectively regulate the release of alpha-granule proteins.
Assuntos
Plaquetas/metabolismo , Febre/sangue , Hemostasia , Ativação Plaquetária , Vesículas Secretórias/metabolismo , Trifosfato de Adenosina/metabolismo , Western Blotting , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Temperatura Alta , Humanos , Microscopia de Fluorescência , Nefelometria e Turbidimetria , Fosforilação , Adesividade Plaquetária , Agregação Plaquetária , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/metabolismo , Proteínas Quinases/metabolismo , Transdução de Sinais , Trombina/metabolismo , Tromboxano A2/metabolismo , Fatores de TempoRESUMO
BACKGROUND: Although platelets are anucleated cells, they express several transcription factors that exert non-genomic functions, including the positive and negative regulation of platelet activation. NF-kappaB is a major transcriptional regulator of genes involved in survival, proliferation and inflammation. OBJECTIVE: Because platelets play a critical role not only in hemostasis, but also in inflammation and tumor progression, we evaluated the role of NF-kappaB in platelet physiology. RESULTS: Immunofluorescence, Western blotting and ELISA studies revealed that platelets express IkappaBalpha and NF-kappaB, and that stimulation with thrombin triggers IkappaBalpha phosphorylation and degradation and the binding of platelet NF-kappaB p65 subunit to synthetic oligonucleotides containing the consensus sequence for NF-kappaB. Two specific unrelated inhibitors of NF-kappaB activation, BAY 11-7082 and Ro 106-9920, reduced PAC-1 and fibrinogen binding to integrin alpha(IIb)beta3 and restricted platelet spreading on immobilized fibrinogen. Both inhibitors impaired aggregation mediated by ADP, epinephrine, collagen or thrombin, but not arachidonic acid. ATP release, TXB2 formation, P-selectin expression, ERK phosphorylation and cPLA2 activity stimulated by thrombin were reduced in BAY 11-7082- or Ro 106-9920-treated platelets. Although bleeding time was not affected, ADP-induced platelet aggregation was impaired in mice treated with BAY 11-7082. CONCLUSIONS: Our results suggest that NF-kappaB may be a novel mediator of platelet responses. The blockade of platelet function by NF-kappaB inhibitors might be relevant in those clinical situations where these drugs are being considered for anti-tumor and/or anti-inflammatory therapy.
Assuntos
NF-kappa B/antagonistas & inibidores , NF-kappa B/fisiologia , Ativação Plaquetária , Animais , Células Cultivadas , Fosfatase 2 de Especificidade Dupla , Fibrinogênio/metabolismo , Humanos , Proteínas I-kappa B/metabolismo , Camundongos , Inibidor de NF-kappaB alfa , NF-kappa B/metabolismo , Fosforilação , Adesividade Plaquetária , Ligação ProteicaRESUMO
The HlyX, a putative hemolysin identified from the Leptospira genomes, was cloned, expressed in Escherichia coli, purified, and its hemolytic activity was confirmed. Mouse polyclonal antiserum against the recombinant HlyX recognized HlyX-related antigens in a panel of Leptospira species extracts and it was also able to abolish the hemolytic activity of HlyX. A mixture of HlyX and LipL32, a known hemolysin from Leptospira, induced hemolysis in a synergistic way that was fully inhibited by antiserum against either protein. Moreover, sera from patients with leptospirosis also recognized the recombinant HlyX, showing that it is presented to the host immune system during Leptospira infection.