RESUMO
Despite increased appreciation for the role of nicotinic receptors in the modulation of and response to inflammation, the contribution of muscarinic receptors to mucosal homeostasis, clearance of enteric pathogens, and modulation of immune cell function remains relatively undefined. Uninfected and Nippostrongylus brasiliensis-infected wild-type and type 3 muscarinic receptor (M3R)-deficient (Chrm3(-/-)) mice were studied to determine the contribution of M3R to mucosal homeostasis as well as host defense against the TH2-eliciting enteric nematode N. brasiliensis Intestinal permeability and expression of TH1/TH17 cytokines were increased in uninfected Chrm3(-/-) small intestine. Notably, in Chrm3(-/-) mice infected with N. brasiliensis, small intestinal upregulation of TH2 cytokines was attenuated and nematode clearance was delayed. In Chrm3(-/-) mice, TH2-dependent changes in small intestinal function including smooth muscle hypercontractility, increased epithelial permeability, decreased epithelial secretion and absorption, and goblet cell expansion were absent despite N. brasiliensis infection. These findings identify an important role for M3R in host defense and clearance of N. brasiliensis, and support the expanding role of cholinergic muscarinic receptors in maintaining mucosal homeostasis.
Assuntos
Citocinas/metabolismo , Imunidade nas Mucosas , Mucosa Intestinal/metabolismo , Intestino Delgado/metabolismo , Nippostrongylus/patogenicidade , Receptor Muscarínico M3/metabolismo , Infecções por Strongylida/metabolismo , Células Th2/metabolismo , Animais , Células Cultivadas , Citocinas/imunologia , Modelos Animais de Doenças , Predisposição Genética para Doença , Homeostase , Interações Hospedeiro-Patógeno , Mucosa Intestinal/imunologia , Mucosa Intestinal/parasitologia , Intestino Delgado/imunologia , Intestino Delgado/parasitologia , Ativação de Macrófagos , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/parasitologia , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Nippostrongylus/imunologia , Fenótipo , Receptor Muscarínico M3/deficiência , Receptor Muscarínico M3/genética , Infecções por Strongylida/genética , Infecções por Strongylida/imunologia , Infecções por Strongylida/parasitologia , Células Th2/imunologia , Células Th2/parasitologia , Fatores de TempoRESUMO
The plasticity of macrophages is evident in helminthic parasite infections, providing protection from inflammation. Previously we demonstrated that the micronutrient selenium induces a phenotypic switch in macrophage activation from a classically activated (pro-inflammatory; M1/CAM) toward an alternatively activated (anti-inflammatory; M2/AAM) phenotype, where cyclooxygenase (COX)-dependent cyclopentenone prostaglandin J2 (15d-PGJ2) plays a key role. Here, we hypothesize that dietary selenium modulates macrophage polarization toward an AAM phenotype to assist in the increasing clearance of adult Nippostrongylus brasiliensis, a gastrointestinal nematode parasite. Mice on a selenium-adequate (0.08 ppm) diet significantly augmented intestinal AAM presence while decreasing adult worms and fecal egg production when compared with infection of mice on selenium-deficient (<0.01 ppm) diet. Further increase in dietary selenium to supraphysiological levels (0.4 ppm) had very little or no impact on worm expulsion. Normal adult worm clearance and enhanced AAM marker expression were observed in the selenium-supplemented Trsp(fl/fl)Cre(WT) mice that express selenoproteins driven by tRNA(Sec) (Trsp), whereas N. brasiliensis-infected Trsp(fl/fl)Cre(LysM) selenium-supplemented mice showed a decreased clearance, with lowered intestinal expression of several AAM markers. Inhibition of the COX pathway with indomethacin resulted in delayed worm expulsion in selenium-adequate mice. This was rescued with 15d-PGJ2, which partially recapitulated the effect of selenium supplementation on fecal egg output in addition to increasing markers of AAMs in the small intestine. Antagonism of PPARγ blocked the effect of selenium. These results suggest that optimal expression of selenoproteins and selenium-dependent production of COX-derived endogenous prostanoids, such as Δ(12)-PGJ2 and 15d-PGJ2, may regulate AAM activation to enhance anti-helminthic parasite responses.
Assuntos
Regulação da Expressão Gênica/imunologia , Ativação de Macrófagos , Macrófagos/imunologia , Nippostrongylus/imunologia , Selenoproteínas/imunologia , Infecções por Strongylida/imunologia , Animais , Suplementos Nutricionais , Macrófagos/parasitologia , Macrófagos/patologia , Masculino , Camundongos , Prostaglandina D2/análogos & derivados , Prostaglandina D2/imunologia , Selênio/farmacologia , Infecções por Strongylida/tratamento farmacológicoRESUMO
BACKGROUND: Dynamic interactions between the host and gastrointestinal microbiota play an important role for local and systemic immune homeostasis. Helminthic parasites modulate the host immune response, resulting in protection against autoimmune disease but also increased susceptibility to pathogen infection. The underlying mechanisms remain largely unknown. RESULTS: We showed that the type 2 immune response to enteric Nippostrongylus brasiliensis infection in mice was associated with altered intestinal mucin and AMP expression and shifts in microbiota composition. Most strikingly, infection reduced concentrations of intestinal segmented filamentous bacteria (SFB), known inducers of T helper 17 cells, and IL-17-associated gene expression. Infected mice deficient in IL-13 or STAT6 did not reduce SFB or IL-17, and exogenous IL-25 replicated the effects of parasite infection in wild type mice. CONCLUSIONS: Our data show that parasite infection acts through host type 2 immunity to reduce intestinal SFB and expression of IL-17, providing an example of a microbiota-dependent immune modulation by parasites.
Assuntos
Bactérias/imunologia , Imunidade , Nippostrongylus , Infecções por Strongylida/imunologia , Infecções por Strongylida/microbiologia , Animais , Peptídeos Catiônicos Antimicrobianos/metabolismo , Bactérias/classificação , Biomarcadores , Expressão Gênica , Imunomodulação , Interleucina-13/genética , Interleucina-13/metabolismo , Interleucina-17/genética , Interleucina-17/metabolismo , Mucosa Intestinal/metabolismo , Intestinos/imunologia , Intestinos/microbiologia , Camundongos , Mucinas/metabolismo , Fator de Transcrição STAT6/genética , Fator de Transcrição STAT6/metabolismo , Infecções por Strongylida/parasitologia , Células Th17/imunologia , Células Th17/metabolismoRESUMO
OBJECTIVES: Diarrhea is a leading cause of mortality and morbidity in children younger than 5 years in impoverished regions of the world. Our aim was to compare the fecal microbiota of healthy children with that of children with clinical diarrhea in a population from a tropical highland in Colombia, South America. Our hypothesis was that a reduced prevalence of inherent Lactobacillus and Bifidobacterium species would be associated with enteric viral and bacterial pathogens. METHODS: Children between 1 and 5 years of age from 2 different locations were evaluated for presence of clinical diarrhea. Nucleic acid, isolated from fecal samples, was used to determine by molecular protocols the abundance of inherent bacterial species and presence of enteric pathogens compared with clinically healthy children. The effect of host demographic factors on incidence of diarrhea was also analyzed. RESULTS: : The composition of the fecal microbiota was affected by host demographic factors: age, health status, location, and sex. In partial support of our hypothesis, the relative abundance of commensal Bifidobacterium and Lactobacillus species was inversely correlated with incidence of diarrhea regardless of location. CONCLUSIONS: Our results suggested that changes in fecal microbiota composition of children with clinical diarrhea are associated with certain demographic factors that should be considered before designing a prophylactic intervention. Delivery of certain Lactobacillus species and Bifidobacterium species or a diet rich in bifidogenic components that promote growth of Bifidobacterium species could provide a prophylactic effect to ameliorate the effect of diarrhea in children at risk.
Assuntos
Bifidobacterium , Colo/microbiologia , Diarreia/microbiologia , Fezes/microbiologia , Lactobacillus , Metagenoma , Bifidobacterium/genética , Bifidobacterium/isolamento & purificação , Criança , Pré-Escolar , Colômbia , DNA Bacteriano , Feminino , Humanos , Lactente , Lactobacillus/genética , Lactobacillus/isolamento & purificação , Masculino , Valores de Referência , Clima TropicalRESUMO
IL-13 has a prominent role in host defense against the gastrointestinal nematode Nippostrongylus brasiliensis; however, the role of IL-13Ralpha2 in the immune and functional response to enteric infection is not known. In the current study, we investigated changes in smooth muscle and epithelial cell function as well as alterations in gene expression of IL-13 and IL-4 and their receptors using laser-capture microdissection of specific cell types in the small intestine of N. brasiliensis-infected mice. An infection-induced up-regulation of IL-13Ralpha2 gene expression was confined to smooth muscle and was dependent on STAT6 and IL-13, but not on IL-4. In contrast, expression of IL-13Ralpha1 was reduced, indicating that changes in IL-13alpha2 expression serve to limit the biological effects of IL-13. The increased availability of IL-13 in IL-13Ralpha2(-/-) mice resulted in marked changes in constitutive epithelial and smooth muscle function. In addition, maximal changes in smooth muscle hypercontractility and epithelial cell resistance peaked earlier after infection in IL-13Ralpha2(-/-) compared with wild-type mice. This did not coincide with an earlier Th2 immune response as expression of IL-4 and IL-13 was attenuated in IL-13Ralpha2(-/-) mice and worm expulsion was similar to that of wild-type mice. These data show that IL-13Ralpha2 plays an important role in nematode infection by limiting the availability of IL-13 during infection, thereby regulating both the immune and biological effects of IL-13.
Assuntos
Subunidade alfa2 de Receptor de Interleucina-13/imunologia , Nippostrongylus/imunologia , Infecções por Strongylida/imunologia , Animais , Regulação da Expressão Gênica/imunologia , Imunidade , Interleucina-13 , Interleucina-4 , Camundongos , Camundongos Endogâmicos BALB C , Músculo Liso/metabolismo , Fator de Transcrição STAT6RESUMO
Infection with gastrointestinal nematodes exerts profound effects on both immune and physiological responses of the host. Helminth infection induces a hypercontractility of intestinal smooth muscle that is dependent on the Th2 cytokines, IL-4 and IL-13, and may contribute to worm expulsion. Protease-activated receptors (PARs) are expressed throughout the gut, and activation of PAR-1 was observed in asthma, a Th2-driven pathology. In the current study we investigated the physiologic and immunologic regulation of PAR-1 in the murine small intestine, specifically 1) the effect of PAR-1 agonists on small intestinal smooth muscle contractility, 2) the effects of Nippostrongylus brasiliensis infection on PAR-1 responses, 3) the roles of IL-13 and IL-4 in N. brasiliensis infection-induced alterations in PAR-1 responses, and 4) the STAT6 dependence of these responses. We demonstrate that PAR-1 activation induces contraction of murine intestinal smooth muscle that is enhanced during helminth infection. This hypercontractility is associated with an elevated expression of PAR-1 mRNA and protein. N. brasiliensis-induced changes in PAR-1 function and expression were seen in IL-4-deficient mice, but not in IL-13- or STAT6-deficient mice, indicating the dependence of IL-13 on the STAT6 signaling pathway independent of IL-4.
Assuntos
Jejuno/imunologia , Jejuno/metabolismo , Nippostrongylus/imunologia , Receptor PAR-1/biossíntese , Infecções por Strongylida/imunologia , Infecções por Strongylida/metabolismo , Animais , Relação Dose-Resposta a Droga , Feminino , Interleucina-13/administração & dosagem , Interleucina-13/deficiência , Interleucina-13/fisiologia , Interleucina-4/deficiência , Interleucina-4/genética , Interleucina-4/fisiologia , Jejuno/efeitos dos fármacos , Jejuno/parasitologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Músculo Liso/fisiologia , Oligopeptídeos/farmacologia , Receptor PAR-1/agonistas , Receptor PAR-1/metabolismo , Fator de Transcrição STAT6/deficiência , Fator de Transcrição STAT6/genética , Fator de Transcrição STAT6/fisiologia , Regulação para Cima/imunologiaRESUMO
Th2 immune responses to a number of infectious pathogens are dependent on B7-1/B7-2 costimulatory molecule interactions. We have now examined the Th2 immune response to Nippostrongylus brasiliensis (Nb) in B7-1/B7-2(-/-) mice and show that Th2 effector cells develop that can mediate worm expulsion and produce substantial Th2 cytokines comparable with wild-type infected mice; however, in marked contrast, B cell Ag-specific Ab production is abrogated after B7 blockade. To examine the mechanism of T cell activation, OVA-specific DO11.10 T cells were transferred to recipient mice, which were then immunized with a combination of Nb plus OVA or either alone. Only the combination of Nb plus OVA triggered T cell differentiation to OVA-specific Th2 cells, suggesting that Nb acts as an adjuvant to stimulate Ag-specific naive T cells to differentiate to effector Th2 cells. Furthermore, using the DO11.10 TCR-transgenic T cell adoptive transfer model, we show that blocking B7-1/B7-2 interactions does not impair nonparasite Ag-specific DO11.10 Th2 cell differentiation; however, DO11.10 T cell cycle progression and migration to the B cell zone are inhibited.