RESUMEN
Bacteria-controlled regulation of host responses to infection is an important virulence mechanism that has been demonstrated to contribute to disease progression. Here we report that the human pathogen Streptococcus pyogenes employs the procarboxypeptidase TAFI (thrombin-activatable fibrinolysis inhibitor) to modulate the kallikrein/kinin system. To this end, bacteria initiate a chain of events starting with the recruitment and activation of TAFI. This is followed by the assembly and induction of the contact system at the streptococcal surface, eventually triggering the release of bradykinin (BK). BK is then carboxyterminally truncated by activated TAFI, which converts the peptide from a kinin B(2) receptor ligand to a kinin B(1) receptor (B1R) agonist. Finally, we show that streptococcal supernatants indirectly amplify the B1R response as they act on peripheral blood mononuclear cells to secrete inflammatory cytokines that in turn stimulate upregulation of the B1R on human fibroblasts. Taken together our findings implicate a critical and novel role for streptococci-bound TAFI, as it processes BK to a B1R agonist at the bacterial surface and thereby may redirect inflammation from a transient to a chronic state.
Asunto(s)
Bradiquinina/metabolismo , Carboxipeptidasa B2/metabolismo , Inflamación/microbiología , Sistema Calicreína-Quinina/inmunología , Receptor de Bradiquinina B1/metabolismo , Streptococcus pyogenes/inmunología , Células Cultivadas , Citocinas/inmunología , Activación Enzimática , Fibroblastos/inmunología , Humanos , Inflamación/enzimología , Pulmón/inmunología , Monocitos/inmunología , Receptor de Bradiquinina B2/inmunología , Regulación hacia Arriba/inmunologíaRESUMEN
Bradykinin is a potent mediator of inflammation that has been shown to participate in allergic airway inflammation. The biologic effects of bradykinin are mediated by binding and activation of its cognate receptor, the B(2) receptor (B(2)R). In the lung fibroblast cell line IMR-90, binding of bradykinin to B(2)R triggers down-regulation of receptor surface expression, suggesting that bradykinin-induced inflammation is transient and self-limited. Notably, subjects with chronic airway inflammation continue to respond to BK following a first challenge. B(2)Rs are expressed on many different lung cell types, including airway epithelial cells. We therefore compared IMR-90 cells with the human lung epithelial cell line BEAS2B and found that B(2)R expression in the two cell types is differently regulated by BK. Whereas BK induces down-regulation of B(2)R in IMR-90 cells, the same treatment leads to up-regulation of the receptor in BEAS2B cells. These results provide a possible explanation for the potency of bradykinin in inducing ongoing airway inflammation.
Asunto(s)
Bradiquinina/farmacología , Pulmón/citología , Pulmón/efectos de los fármacos , Receptor de Bradiquinina B2/metabolismo , Línea Celular , Citosol/efectos de los fármacos , Citosol/metabolismo , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Unión Proteica/efectos de los fármacos , Procesamiento Postranscripcional del ARN/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Receptor de Bradiquinina B2/genética , Especificidad por Sustrato , Factores de TiempoRESUMEN
BACKGROUND: Rhinovirus infection is a major cause of asthma exacerbations. While rhinovirus infection is known to generate kinins in the upper respiratory track, little is known about the effect of rhinovirus on kinin generation in the lower airway. We previously identified human tissue kallikrein (hTK) as the principal lung kininogenase during allergic airway inflammation. In this report we investigate the effect of experimental rhinovirus infection on hTK activity in the airways of atopic subjects with and without asthma. METHODS: Eight atopic subjects, 4 with asthma, underwent bronchoscopy with lavage. At least 1 month later, subjects were inoculated with rhinovirus, then underwent repeat bronchoscopy with lavage 4 and 18 days later. hTK mRNA was measured in nasal scrape samples by quantitative real-time PCR. hTK activity (chromogenic substrate assay) and IL-8 levels (ELISA) were assessed in the bronchoalveolar lavage fluid. RESULTS: At day 4 after rhinovirus inoculation, nasal hTK mRNA was modestly increased in both the rhinitis (1.7-fold) and asthmatic (2.1-fold) groups. A doubling or greater increase in hTK activity after rhinovirus infection was observed in all 4 asthmatic subjects (mean 19-fold increase) but only in 1 of 4 atopic subjects without asthma (mean 2-fold increase). Rhinovirus infection also increased the IL-8 protein level in bronchoalveolar lavage fluid, which correlated with hTK activity (R = 0.82). CONCLUSION: Experimental rhinovirus infection in allergic asthmatic subjects is accompanied by increased lower airway hTK activation, which parallels the appearance of IL-8. Rhinovirus-induced hTK activation may contribute to airway inflammation and asthmatic exacerbations.
Asunto(s)
Hipersensibilidad/enzimología , Infecciones por Picornaviridae/enzimología , Rhinovirus , Calicreínas de Tejido/metabolismo , Adulto , Activación Enzimática , Femenino , Humanos , Interleucina-8/biosíntesis , Masculino , Infecciones por Picornaviridae/inmunología , ARN Mensajero/análisis , Calicreínas de Tejido/genéticaRESUMEN
Kinins are potent proinflammatory peptides that are produced extracellularly and are rapidly degraded by extracellular peptidases and by intracellular peptidases accessed by kinins via receptor-mediated endocytosis. In this study, we developed model cell systems expressing the kinin B(2) receptor (B(2)R) and the metalloendopeptidase thimet oligopeptidase (EC 3.4.24.15; EP24.15) either individually or together to address 1) the cellular and functional relationship between these proteins and 2) the participation of EP24.15 in the metabolism of bradykinin (BK) after BK internalization via B(2)R. B(2)R was localized almost exclusively in the plasma membrane, whereas EP24.15 was localized both intracellularly and on the cell surface and secreted in the media. Intracellular EP24.15 was present throughout the cell, both cytosolic and particulate, with less nuclear localization and no colocalization with either the endoplasmic reticulum marker calnexin or the Golgi marker GM130. No direct colocalization of B(2)R and EP24.15 was observed using immunofluorescence microscopy. However, the two proteins coimmunoprecipitated specifically, and EP24.15 attenuated maximal B(2)R responsiveness without influencing the potency of BK to stimulate phosphoinositide hydrolysis and intracellular Ca(2+) mobilization. Cell surface-bound BK remained intact in cells overexpressing EP24.15 but was degraded intracellularly in an EP24.15-dependent manner upon B(2)R-mediated endocytosis. These results show that EP24.15 acts to negatively regulate B(2)R responsiveness, and it serves as an intracellular peptidase in the degradation of BK specifically internalized via this receptor.
Asunto(s)
Bradiquinina/metabolismo , Líquido Intracelular/enzimología , Metaloendopeptidasas/metabolismo , Receptor de Bradiquinina B2/fisiología , Transporte Biológico/efectos de los fármacos , Transporte Biológico/fisiología , Línea Celular , Relación Dosis-Respuesta a Droga , Humanos , Líquido Intracelular/efectos de los fármacos , Metaloendopeptidasas/fisiología , Unión Proteica/efectos de los fármacos , Unión Proteica/fisiología , Receptor de Bradiquinina B2/agonistasRESUMEN
An inappropriate host response to invading bacteria is a critical parameter that often aggravates the outcome of an infection. Staphylococcus aureus is a major human Gram-positive pathogen that causes a wide array of community- and hospital-acquired diseases ranging from superficial skin infections to severe conditions such as staphylococcal toxic shock. Here we find that S aureus induces inflammatory reactions by modulating the expression and response of the B1 and B2 receptors, respectively. This process is initiated by a chain of events, involving staphylococcal-induced cytokine release from monocytes, bacteria-triggered contact activation, and conversion of bradykinin to its metabolite desArg(9)bradykinin. The data of the present study implicate an important and previously unknown role for kinin receptor regulation in S aureus infections.