RESUMO
Intestinal epithelial cells (IECs) form a physical and immunological barrier that separates the vast gut microbiota from host tissues. MyD88-dependent Toll-like receptor signaling is a key mediator of microbial-host cross-talk. We examined the role of epithelial MyD88 expression by generating mice with an IEC-targeted deletion of the Myd88 gene (MyD88(ΔIEC)). Loss of epithelial MyD88 signaling resulted in increased numbers of mucus-associated bacteria; translocation of bacteria, including the opportunistic pathogen Klebsiella pneumoniae, to mesenteric lymph nodes; reduced transmucosal electrical resistance; impaired mucus-associated antimicrobial activity; and downregulated expression of polymeric immunoglobulin receptor (the epithelial IgA transporter), mucin-2 (the major protein of intestinal mucus), and the antimicrobial peptides RegIIIγ and Defa-rs1. We further observed significant differences in the composition of the gut microbiota between MyD88(ΔIEC) mice and wild-type littermates. These physical, immunological, and microbial defects resulted in increased susceptibility of MyD88(ΔIEC) mice to experimental colitis. We conclude that MyD88 signaling in IECs is crucial for maintenance of gut homeostasis.
Assuntos
Colite/imunologia , Mucosa Intestinal/metabolismo , Infecções por Klebsiella/imunologia , Klebsiella pneumoniae/imunologia , Fator 88 de Diferenciação Mieloide/metabolismo , Infecções Oportunistas/imunologia , Animais , Linhagem Celular , Colite/complicações , Regulação para Baixo , Homeostase , Humanos , Imunidade nas Mucosas , Mucosa Intestinal/imunologia , Infecções por Klebsiella/complicações , Metagenoma/genética , Metagenoma/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Animais , Mucina-2/genética , Mucina-2/metabolismo , Fator 88 de Diferenciação Mieloide/genética , Infecções Oportunistas/complicações , Proteínas Associadas a Pancreatite , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Proteínas/genética , Proteínas/metabolismo , RNA Interferente Pequeno/genética , Receptores de Imunoglobulina Polimérica/genética , Receptores de Imunoglobulina Polimérica/metabolismo , Deleção de Sequência/genética , Transdução de Sinais/genética , Transdução de Sinais/imunologiaRESUMO
The polymeric immunoglobulin receptor (pIgR) transports IgA antibodies across intestinal epithelial cells (IECs). Expression of pIgR is upregulated by proinflammatory signaling pathways via activation of nuclear factor-κB (NF-κB). Here, we examined the contributions of the RelA-dependent classical and RelB-dependent alternative pathways of NF-κB to pIgR regulation in the HT-29 human IEC line following stimulation with tumor necrosis factor (TNF), lipopolysaccharide (LPS; Toll-like receptor 4 (TLR4) ligand), and polyinosinic: polycytidylic acid (pIC; TLR3 ligand). Whereas induction of proinflammatory genes such as interleukin-8 (IL-8) required only RelA, pIgR expression was regulated by complex mechanisms that involved both RelA and RelB. Upregulation of pIgR expression by ligation of the lymphotoxin-ß receptor suggested a direct role for the alternative NF-κB pathway. Inhibition of mitogen-activated protein kinases reduced the induction of IL-8, but enhanced the induction of pIgR by TNF and TLR signaling. Regulation of pIgR through unique signaling pathways could allow IECs to sustain high levels of IgA transport while limiting the proinflammatory responses.
Assuntos
Células Epiteliais , Mucosa Intestinal , NF-kappa B/metabolismo , Receptores de Imunoglobulina Polimérica/imunologia , Transdução de Sinais/imunologia , Células Epiteliais/imunologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/imunologia , Técnicas de Silenciamento de Genes , Células HT29 , Humanos , Fatores Imunológicos/metabolismo , Fatores Imunológicos/farmacologia , Interleucina-8/genética , Interleucina-8/imunologia , Mucosa Intestinal/imunologia , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , RNA Mensageiro/genética , Receptores de Imunoglobulina Polimérica/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Receptores Toll-Like/metabolismo , Fator de Transcrição RelA/genética , Fatores de Necrose Tumoral/metabolismo , Fatores de Necrose Tumoral/farmacologiaRESUMO
In an effort to develop a molecular classification scheme for Crohn's disease (CD), mucosal biopsies from 69 CD patients and 28 normal controls were analyzed for expression of the RelA subunit of nuclear factor (NF)-kappaB, A20 (a negative regulator of NF-kappaB), polymeric immunoglobulin receptor (pIgR), tumor necrosis factor (TNF), and interleukin (IL)-8. Principal component analysis was used to classify individuals into three subsets based on patterns of biomarker expression. Set 1 included normal subjects and CD patients with mild disease and good responses to therapy, thus defining "normal" biomarker expression. CD patients in set 2, characterized by low expression of all five biomarkers, had moderate to severe disease and poor responses to immunosuppressive and anti-TNF therapy. Patients in set 3, characterized by low expression of RelA, A20, and pIgR, normal TNF and elevated IL-8, had acute inflammation that responded well to therapy. Classification of CD patients by these biomarkers may predict disease behavior and responses to therapy.