RESUMO
The type I IFNs (IFN-α and -ß) are important for host defense against viral infections. In contrast, their role in defense against nonviral pathogens is more ambiguous. In this article, we report that IFN-ß signaling in murine bone marrow-derived macrophages has a cell-intrinsic protective capacity against Mycobacterium tuberculosis via the increased production of NO. The antimycobacterial effects of type I IFNs were mediated by direct signaling through the IFN-α/ß-receptor (IFNAR), as Ab-mediated blocking of IFNAR1 prevented the production of NO. Furthermore, M. tuberculosis is able to inhibit IFNAR-mediated cell signaling and the subsequent transcription of 309 IFN-ß-stimulated genes in a dose-dependent way. The molecular mechanism of inhibition by M. tuberculosis involves reduced phosphorylation of the IFNAR-associated protein kinases JAK1 and TYK2, leading to reduced phosphorylation of the downstream targets STAT1 and STAT2. Transwell experiments demonstrated that the M. tuberculosis-mediated inhibition of type I IFN signaling was restricted to infected cells. Overall, our study supports the novel concept that M. tuberculosis evolved to inhibit autocrine type I IFN signaling to evade host defense mechanisms.
Assuntos
Comunicação Autócrina/imunologia , Interferon Tipo I/imunologia , Viabilidade Microbiana/imunologia , Mycobacterium tuberculosis/imunologia , Transdução de Sinais/imunologia , Animais , Comunicação Autócrina/genética , Interferon Tipo I/genética , Janus Quinase 1/genética , Janus Quinase 1/imunologia , Camundongos , Camundongos Knockout , Viabilidade Microbiana/genética , Óxido Nítrico/genética , Óxido Nítrico/imunologia , Receptor de Interferon alfa e beta/genética , Receptor de Interferon alfa e beta/imunologia , Transdução de Sinais/genética , TYK2 Quinase/genética , TYK2 Quinase/imunologiaRESUMO
The synthesis of acyclic cucurbit[n]uril dendrimers G1-G3 that bear four dendrons on their aromatic sidewalls via thiolate S(N)2 chemistry is reported. G1-G3 are polycationic and can bind to pEGFP plasmid DNA as shown by dynamic light scattering (DLS), gel electrophoresis, and scanning electron microscopy (SEM). The gene delivery ability of G1-G3 is presented.
Assuntos
Dendrímeros/síntese química , Compostos Macrocíclicos/síntese química , Dendrímeros/química , Técnicas de Transferência de Genes , Compostos Macrocíclicos/química , Microscopia Eletrônica de Varredura , Estrutura Molecular , Plasmídeos/genética , Poliaminas/química , PolieletrólitosRESUMO
Mycobacterium tuberculosis (Mtb) has coevolved with humans for tens of thousands of years. It is thus highly adapted to its human host and has evolved multiple mechanisms to manipulate host immune responses to its advantage. One central host pathogen interaction modality is host cell death pathways. Host cell apoptosis is associated with a protective response to Mtb infection, whereas a necrotic response favors the pathogen. Consistently, Mtb inhibits host cell apoptosis signaling but promotes induction of programmed necrosis. The molecular mechanisms involved in Mtb-mediated host cell death manipulation, the consequences for host immunity, and the potential for therapeutic and preventive approaches will be discussed.
Assuntos
Apoptose/fisiologia , Mycobacterium tuberculosis/fisiologia , Apoptose/genética , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/fisiologia , Humanos , Imunoterapia/métodos , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/patogenicidade , Necrose/genética , Necrose/microbiologia , Necrose/fisiopatologia , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Tuberculose/microbiologia , Tuberculose/prevenção & controle , Tuberculose/terapiaRESUMO
The production of IL-1ß during the infection with Mycobacterium tuberculosis (Mtb) is important for successful host immune defense. In macrophages and dendritic cells the host cell inflammasome is crucial for generation of secreted IL-1ß in response to Mtb infections. In these cell types Mtb infection only activates the NLRP3-inflammasome. New reports demonstrate that nitric oxide has an important function in the negative regulation of the NLRP3-inflammasome to reduce tissue damage during Mtb infections. The type I interferon, IFN-ß, is induced after Mtb infections and can also suppress NLRP3-inflammasome activation. In contrast, IFN-ß increases activity of the AIM2-inflammasome after infection with intracellular pathogens such as Francisella tularensis and Listeria monocytogenes. Recent results demonstrate that non-tuberculous mycobacteria but not virulent Mtb induce the AIM2-inflammasome in an IFN-ß dependent matter. Indeed, Mtb inhibits AIM2-inflammasome activation via its ESX-1 secretion system. This novel immune evasion mechanism may help Mtb to allow the induction of low levels of IFN-ß to suppress the NLRP3-inflammasome without activating the AIM2-inflammasome.
Assuntos
Células Dendríticas/imunologia , Interações Hospedeiro-Patógeno , Evasão da Resposta Imune , Inflamassomos/imunologia , Inflamassomos/metabolismo , Macrófagos/imunologia , Mycobacterium tuberculosis/imunologia , Células Dendríticas/microbiologia , Macrófagos/microbiologiaRESUMO
Mycobacterium tuberculosis extracellular DNA gains access to the host cell cytosol via the ESX-1 secretion system. It is puzzling that this extracellular DNA of M. tuberculosis does not induce activation of the AIM2 inflammasome because AIM2 recognizes cytosolic DNA. In this study, we show that nonvirulent mycobacteria such as Mycobacterium smegmatis induce AIM2 inflammasome activation, which is dependent on their strong induction of IFN-ß production. In contrast, M. tuberculosis, but not an ESX-1-deficient mutant, inhibits the AIM2 inflammasome activation induced by either M. smegmatis or transfected dsDNA. The inhibition does not involve changes in host cell AIM2 mRNA or protein levels but led to decreased activation of caspase-1. We furthermore demonstrate that M. tuberculosis inhibits IFN-ß production and signaling, which was partially responsible for the inhibition of AIM2 activation. In conclusion, we report a novel immune evasion mechanism of M. tuberculosis that involves the ESX-1-dependent, direct or indirect, suppression of the host cell AIM2 inflammasome activation during infection.