Proteomic investigation of the aggregation phenomenon in Lactobacillus crispatus

Aggregation process affects the ability of Lactobacillus crispatus, a probiotic, to survive into the gastro-intestinal environment and to adhere to the intestinal mucosa. To elucidate mechanisms underlying this process, a comparative proteomic study was carried out on a wild type strain M247 and its spontaneous isogenic mutant Mu5, which had lost the aggregative phenotype. Results highlighted an overall lower amount of enzymes involved in carbohydrate transport and metabolism in strain M247 compared to strain Mu5, suggesting a reduction in the general growth rate, probably caused by nutrient limitation in cell aggregates, coherently with the phenotypic traits of the strains. Moreover, the up-regulation of a putative elongation factor Tu in the wild type M247 strain could suggest a role of this particular protein in the adhesion mechanism of L. crispatus.     

Protective effects of Lactobacillus rhamnosus [corrected] and Bifidobacterium infantis in murine models for colitis do not involve the vagus nerve

The vagus nerve is an important pathway signaling immune activation of the gastrointestinal tract to the brain. Probiotics are live organisms that may engage signaling pathways of the brain-gut axis to modulate inflammation. The protective effects of Lactobacillus rhamnosus [corrected] (LR) and Bifidobacterium infantis (BI) during intestinal inflammation were studied after subdiaphragmatic vagotomy in acute dextran sulfate sodium (DSS) colitis in BALB/c mice and chronic colitis induced by transfer of CD4(+) CD62L(+) T lymphocytes from BALB/c into SCID mice. LR and BI (1 x 10(9)) were given daily. Clinical score, myeloperoxidase (MPO) levels, and in vivo and in vitro secreted inflammatory cytokine levels were found to be more severe in mice that were vagotomized compared with sham-operated animals. LR in the acute DSS model was effective in decreasing the MPO and cytokine levels in the tissue in sham and vagotomized mice. BI had a strong downregulatory effect on secreted in vitro cytokine levels and had a greater anti-inflammatory effect in vagotomized- compared with sham-operated mice. Both LR and BI retained anti-inflammatory effects in vagotomized mice. In SCID mice, vagotomy did not enhance inflammation, but BI was more effective in vagotomized mice than shams. Taken together, the intact vagus has a protective role in acute DSS-induced colitis in mice but not in the chronic T cell transfer model of colitis. Furthermore, LR and BI do not seem to engage their protective effects via this cholinergic anti-inflammatory pathway, but the results interestingly show that, in the T cell, transfer model vagotomy had a biological effect, since it increased the effectiveness of the BI in downregulation of colonic inflammation.     

The aggregation-promoting factor of Lactobacillus crispatus M247 and its genetic locus

AIMS: Characterization of the aggregation-promoting factor (APF) of the human intestinal isolate Lactobacillus crispatus M247 and its homologous nonaggregating mutant Mu5. METHODS AND RESULTS: Western blot analysis revealed that the supernatant of both M247 and Mu5 contains a 28-kDa protein which cross reacts with the antiserum produced against the APF of Lact. gasseri 4B2. The apf genes of M247 and Mu5 strains were identical and were shown to be 672 nucleotides in length and encoding a protein of 223 amino acids with a predicted molecular weight of 24.0 kDa. CONCLUSION: Our results shows that the lost of aggregation in Mu5 is not related to a defect in secretion of the APF protein or a mutation in the apf gene. SIGNIFICANCE AND IMPACT OF THE STUDY: These results suggest that the mutation in Mu5 may be contained in another molecule involved in aggregation such as a possible receptor for APF.     

UNC5B receptor deletion exacerbates DSS‐induced colitis in mice by increasing epithelial cell apoptosis

The netrin-1 administration or overexpression is known to protect colon from acute colitis. However, the receptor that mediates netrin-1 protective activities in the colon during colitis remains unknown. We tested the hypothesis that UNC5B receptor is a critical mediator of protective function of netrin-1 in dextran sodium sulfate (DSS)-induced colitis using mice with partial deletion of UNC5B receptor. DSS colitis was performed in mice with partial genetic UNC5B deficiency (UNC5B^+/− mice) or wild-type mice to examine the role of endogenous UNC5B. These studies were supported by in vitro models of DSS-induced apoptosis in human colon epithelial cells. WT mice developed colitis in response to DSS feeding as indicated by reduction in bw, reduction in colon length and increase in colon weight. These changes were exacerbated in heterozygous UNC5B knockout mice treated with DSS. Periodic Acid-Schiff stained section shows damages in colon epithelium and mononuclear cell infiltration in WT mice, which was further increased in UNC5B heterozygous knockout mice. This was associated with large increase in inflammatory mediators such as cytokine and chemokine expression and extensive apoptosis of epithelial cells in heterozygous knockout mice as compared to WT mice. Overexpression of UNC5B human colon epithelial cells suppressed DSS-induced apoptosis and caspase-3 activity. Moreover, DSS induced large amount of netrin-1 and shRNA mediated knockdown of netrin-1 induction exacerbated DSS-induced epithelial cell apoptosis. Our results suggest that UNC5B is a critical mediator of cell survival in response to stress in colon.     

Dextran sodium sulfate-induced colitis in germ-free IQI/Jic mice.

This study presents a histological examination of dextran sodium sulfate (DSS)-induced colitis in germ-free (GF) mice. A comparison of the pathology between GF and conventionalized mice (CVz) was made to determine the role that intestinal microflora play in DSS-induced colitis. To induce colitis, GF and CVz IQI/Jic mice were given either 5% or 1% DSS orally. Administration of 5% DSS, a common concentration used to induce colitis in mice, caused gross rectal bleeding and a marked decrease in hematocrit as early as day one in GF mice. These mice died on day three due to massive bleeding into the intestinal lumen. In contrast, CVz mice did not die during the seven-day experimental period. Histopathological examination three days after administration of 5% DSS did not reveal any colitis lesions in GF mice, but CVz mice had developed moderate colitis in the large intestine. Administration of a low concentration of DSS (1%), which only induces mild basal crypt loss in CVz mice, caused severe colitis in the distal colon in GF mice, and they died on day 14. These data suggest that intestinal microflora are not necessary for the induction of colitis. Furthermore, DSS may be highly toxic to GF mice, and when given at a concentration of 5% it causes massive bleeding into the intestinal lumen resulting in death prior to development of colitis.     

The protective effect of the vagus nerve in a murine model of chronic relapsing colitis

The vagus nerve inhibits the response to systemic administration of endotoxin, and we have recently extended this observation to show that the vagus attenuates acute experimental colitis in mice. The purpose of the present study was to determine whether there is a tonic counterinflammatory influence of the vagus on colitis maintained over several weeks. We assessed disease activity index, macroscopic and histological damage, myeloperoxidase (MPO) activity, and Th1 and Th2 cytokine profiles in chronic colitis induced by administration of dextran sodium sulfate (DSS) in drinking water for three cycles during 5 days with 11 days of rest between each cycle (DSS 3, 2, 2%) in healthy and vagotomized C57BL/6 mice and in mice deficient in macrophage-colony stimulating factor (M-CSF). A pyloroplasty was performed in vagotomized mice. Vagotomy accelerated the onset and the severity of inflammation during the first and second but not the third cycle. Although macroscopic scores were not significantly changed, histological scores as well as MPO activity and colonic tissue levels of IL-1alpha, TNF-alpha, IFN-gamma, and IL-18 but not IL-4 were significantly increased in vagotomized mice compared with sham-operated mice that received DSS. In control mice (without colitis), vagotomy per se did not affect any inflammatory marker. Vagotomy had no effect on the colitis in M-CSF-derived macrophage-deficient mice. These results indicate that the vagus protects against acute relapses on a background of chronic inflammation. Identification of the molecular mechanisms underlying the protective role of parasympathetic nerves opens a new therapeutic avenue for the treatment of acute relapses of chronic inflammatory bowel disease.     

CD30 ligand is a target for a novel biological therapy against colitis associated with Th17 responses

We have previously found that CD30 ligand (CD30L; CD153)/CD30 signaling executed by the T-T cell interaction plays a critical role in Th17 cell differentiation, at least partly via downregulation of IL-2 production. In this study, we investigated the role of CD30L in the development of colitis experimentally induced by dextran sulfate sodium (DSS), in which IL-17A is involved in the pathogenesis. CD30L(-/-) mice were resistant to both acute colitis induced by administration of 3 to ～ 5% DSS and to chronic colitis induced by administration of 1.5% DSS on days 0-5, 10-15, and 20-25 as assessed by weight loss, survival rate, and histopathology. The levels of IFN-γ, IL-17A, and IL-10 were significantly lower but the IL-2 level higher in the lamina propria T lymphocytes of CD30L(-/-) mice than those in lamina propria T lymphocytes of wild-type mice after DSS administration. Soluble murine CD30-Ig fusion protein, which was capable of inhibiting Th17 cell differentiation in vitro, ameliorated both types of DSS-induced colitis in wild-type mice. Modulation of CD30L/CD30 signaling by soluble CD30 could be a novel biological therapy for inflammatory diseases associated with Th17 responses.     

Attenuation by dietary taurine of dextran sulfate sodium-induced colitis in mice and of THP-1-induced damage to intestinal Caco-2 cell monolayers

The effects of dietary taurine on the experimental colitis induced by dextran sulfate sodium (DSS) in mice were evaluated. C57BL/6 female mice were given 3% DSS in drinking water for 5 d to induce acute colitis. Taurine at 2% was added to the drinking water 5 d before and during the DSS-treatment to investigate its preventive effect. Taurine supplementation significantly attenuated the weight decrease, diarrhea severity, colon shortening, and the increase in the colonic tissue myeloperoxidase activity induced by DSS. Taurine also significantly inhibited the increase in the expression of a pro-inflammatory chemokine, macrophage inflammatory protein 2 (MIP-2), but not of interleukin (IL)-1beta or tumor necrosis factor (TNF)-alpha mRNA. Furthermore, taurine significantly protected the intestinal Caco-2 cell monolayers from the damage by macrophage-like THP-1 cells in an in vitro coculture system. These results suggest that taurine prevented DSS-induced colitis partly in association with (1) its inhibitory effects on the secretion of MIP-2 from the intestinal epithelial cells and on the infiltration of such inflammatory cells as neutrophils and (2) its cytoprotective functions on the epithelial barrier from the direct toxicity of DSS and from the inflammatory cell-induced injury.     

Lactobacillus reuteri Maintains a Functional Mucosal Barrier during DSS Treatment Despite Mucus Layer Dysfunction

Treatment with the probiotic bacterium Lactobacillus reuteri has been shown to prevent dextran sodium sulfate (DSS)-induced colitis in rats. This is partly due to reduced P-selectin-dependent leukocyte- and platelet-endothelial cell interactions, however, the mechanism behind this protective effect is still unknown. In the present study a combination of culture dependent and molecular based T-RFLP profiling was used to investigate the influence of L. reuteri on the colonic mucosal barrier of DSS treated rats. It was first demonstrated that the two colonic mucus layers of control animals had different bacterial community composition and that fewer bacteria resided in the firmly adherent layer. During DSS induced colitis, the number of bacteria in the inner firmly adherent mucus layer increased and bacterial composition of the two layers no longer differed. In addition, induction of colitis dramatically altered the microbial composition in both firmly and loosely adherent mucus layers. Despite protecting against colitis, treatment with L. reuteri did not improve the integrity of the mucus layer or prevent distortion of the mucus microbiota caused by DSS. However, L. reuteri decreased the bacterial translocation from the intestine to mesenteric lymph nodes during DSS treatment, which might be an important part of the mechanisms by which L. reuteri ameliorates DSS induced colitis.     

M3 muscarinic receptor-deficient mice retain bethanechol-mediated intestinal ion transport and are more sensitive to colitis

Acetylcholine (ACh) is an important regulator of intestinal epithelial ion transport via muscarinic or nicotinic ACh receptors. Previous studies emphasize the role of the M3 muscarinic receptor subtype in mediating the effects of cholinergic agonists on intestinal ion transport. With the prevalence of mouse models to study intestinal (patho)physiology, it is crucial that ion transport be understood in this species. Using M3 receptor-deficient (KO) mice and wild-type (WT) mice, we examined M3 receptor contributions to ion transport as well as its role in colitis induced by dextran sodium sulphate (DSS). In the Ussing chambers, ileal and colonic tissue from M3 KO and WT mice displayed similar baseline ion transport properties. Short-circuit current (ISC) responses to the muscarinic receptor agonist bethanechol were slightly decreased in ileal tissue from M3 KO mice compared with tissue from WT mice, whereas responses were not significantly different in colonic tissue. ISC responses to bethanechol were partially inhibited by pirenzepine in WT ileum, but not tetrodotoxin, suggesting involvement of a non-neuronal M1 muscarinic receptor. In the ileum, the M3 receptor may inhibit neuronally evoked ion transport, as indicated by the increased ISC responses to electrical stimulation in tissue from M3 KO mice. Furthermore, whereas all DSS-treated mice developed colitis, M3 KO mice displayed more rapid mass loss and more severe disease than DSS-treated WT mice, even following a reduction in the amount and time of DSS treatment. Thus, M3 receptor-KO mice are compensated in their ability to evoke muscarinic receptor-driven ion transport responses, but are more sensitive to DSS. This work highlights the need to dissect muscarinic receptor-mediated events in the mouse, as mice become increasingly valuable in enteric disease models.     

Role of TNFR-related 2 mediated immune responses in dextran sulfate sodium-induced inflammatory bowel disease

Previous work has suggested that the LIGHT-TR2 costimulatory pathway plays a role in the acute and chronic stages of dextran sulfate sodium (DSS)-induced colitis [Steinberg et al. (2008); Wang et al. (2005)]. To clarify the role of TNFR-related 2 (TR2) signaling in the maintenance of intestinal homeostasis, we generated a TR2 knock-out (KO) mouse. Using DSS to induce colitis, we compared the colitic symptoms and pathological changes in wild type (WT) and TR2 KO mice, and the production of cytokines by the diseased colons. We also studied the role of TR2 in suppressing innate and adaptive immunity in the DSS model. TR2 deficient mice were characterized by reduced symptoms of intestinal inflammation compared with wild-type mice, and reduced production of cytokines. We therefore generated a monoclonal antibody against mouse TR2 which was specific to TR2 and capable of blocking TR2 signals. With this antibody, we demonstrated that antagonizing TR2 during the development of DSS-induced colitis reduced the symptoms of inflammation. Our findings suggest that TR2 is an important mediator in colitis, and may serve as a therapeutic target in inflammatory bowel disease.     

Dominant Effects of the Diet on the Microbiome and the Local and Systemic Immune Response in Mice

Outside the nutrition community the effects of diet on immune-mediated diseases and experimental outcomes have not been appreciated. Investigators that study immune-mediated diseases and/or the microbiome have overlooked the potential of diet to impact disease phenotype. We aimed to determine the effects of diet on the bacterial microbiota and immune-mediated diseases. Three different laboratory diets were fed to wild-type mice for 2 weeks and resulted in three distinct susceptibilities to dextran sodium sulfate (DSS)-induced colitis. Examination of the fecal microbiota demonstrated a diet-mediated effect on the bacteria found there. Broad-spectrum antibiotics disturbed the gut microbiome and partially eliminated the diet-mediated changes in DSS susceptibility. Dietary changes 2 days after DSS treatment were protective and suggested that the diet-mediated effect occurred quickly. There were no diet-mediated effects on DSS susceptibility in germ-free mice. In addition, the diet-mediated effects were evident in a gastrointestinal infection model (Citrobacter rodentium) and in experimental autoimmune encephalomyelitis. Taken together, our study demonstrates a dominant effect of diet on immune-mediated diseases that act rapidly by changing the microbiota. These findings highlight the potential of using dietary manipulation to control the microbiome and prevent/treat immune-mediated disease.     

Complement-dependent injury and protection in a murine model of acute dextran sulfate sodium-induced colitis

Complement plays a key role in the pathophysiology of many inflammatory diseases, and in this study, we investigated the role of complement in the pathogenesis of inflammatory bowel disease. Compared to wild-type mice, mice deficient in C3 or factor B were protected from acute dextran sulfate sodium (DSS)-induced colitis. C1q/mannose-binding lectin (MBL) double-deficient mice, however, exhibited more severe colitis than wild-type mice. When mice were allowed to recover after DSS treatment, all C1q/MBL(-/-) mice died by day 2 of recovery period, and, surprisingly, all C3(-/-) and factor B(-/-) mice died by day 5. Serum endotoxin levels were significantly increased in complement-deficient mice prior to death, particularly in C1q/MBL(-/-) mice, and antibiotic treatment prevented the lethal effect of DSS in all complement-deficient mice. In contrast to complement deficiency, targeted complement inhibition with either complement receptor 2 (CR2)-Crry (blocks all pathways at C3 activation) or CR2-factor H (blocks alternative pathway) was highly protective at treating established acute colitis. Endotoxin levels remained low in complement-inhibited mice, and complement inhibition also reduced inflammatory cytokines, leukocyte infiltration, and tissue injury while improving wound repair and mucosal healing. CR2-factor H provided more effective protection than CR2-Crry. Thus, complement has both pathogenic and protective roles in acute DSS-induced colitis, and whereas the alternative pathway appears to play a key role in tissue inflammation and injury, the classical/lectin pathway provides important protection in terms of host defense and wound repair. Targeted inhibition of the alternative pathway may represent a therapeutic modality for treating acute phases of inflammatory bowel disease.     

LRRK2 deficiency mitigates colitis progression by favoring resolution of inflammation and restoring homeostasis of gut microbiota

Leucine rich-repeat kinase 2 (LRRK2) has been considered a susceptibility gene for ulcerative colitis (UC), and its protein abundance was enhanced in the peripheral blood mononuclear cells (PBMCs) from UC cohorts as compared to healthy volunteers. In preclinical models of colitis, Lrrk2 deficiency ameliorated dextran sodium sulfate (DSS)-induced colitis progression, whereas the processes were aggravated by R1441C mutation. While intestinal macrophages (MФs) from Lrrk2 knock-out (Lrrk2^?/?) mice exhibited a tendency to transit to alternatively activated MФs, R1441C MФs mutation facilitated the pro-inflammatory phenotype polarization, determined by RNA sequencing and qPCR. Moreover, we characterized their microbiota profiles and found that loss of Lrrk2 increased the bacterial richness and altered bacterial community structure, and this shift contributed to the alleviation of colitis development and progression. We proposed that Lrrk2 deficiency promotes M2 MФ transition and facilitates probiotics colonization, providing a protective role during colitis.     

Oral delivery of pancreatitis-associated protein by Lactococcus lactis displays protective effects in dinitro-benzenesulfonic-acid-induced colitis model and is able to modulate the composition of the microbiota

Antimicrobial peptides secreted by intestinal immune and epithelial cells are important effectors of innate immunity. They play an essential role in the maintenance of intestinal homeostasis by limiting microbial epithelium interactions and preventing unnecessary microbe-driven inflammation. Pancreatitis-associated protein (PAP) belongs to Regenerating islet-derived III proteins family and is a C-type (Ca⁺² dependent) lectin. PAP protein plays a protective effect presenting anti-inflammatory properties able to reduce the severity of colitis, preserving gut barrier and epithelial inflammation. Here, we sought to determine whether PAP delivered at intestinal lumen by recombinant Lactococcus lactis strain (LL-PAP) before and after chemically induced colitis is able to reduce the severity in two models of colitis. After construction and characterization of our recombinant strains, we tested their effects in dinitro-benzenesulfonic-acid (DNBS) and Dextran sulfate sodium (DSS) colitis model. After the DNBS challenge, mice treated with LL-PAP presented less severe colitis compared with PBS and LL-empty-treated mice groups. After the DSS challenge, no protective effects of LL-PAP could be detected. We determined that after 5 days administration, LL-PAP increase butyrate producer's bacteria, especially Eubacterium plexicaudatum. Based on our findings, we hypothesize that a treatment with LL-PAP shifts the microbiota preventing the severity of colon inflammation in DNBS colitis model. These protective roles of LL-PAP in DNBS colitis model might be through intestinal microbiota modulation.     

Acute colitis induced by dextran sulfate sodium progresses to chronicity in C57BL/6 but not in BALB/c mice: correlation between symptoms and inflammation

Exposure to dextran sulfate sodium (DSS) induces acute colitis, which is normally resolved after DSS removal. To study chronicity, mice are typically subjected to three to five cycles of weekly DSS exposures, each followed by a 1- to 2-wk rest period. Here, we describe a novel and convenient way of inducing chronic, progressive colitis by a single exposure to DSS. C57BL/6 mice exposed to DSS for 5 days developed acute colitis that progressed to severe chronic inflammation. The plasma haptoglobin levels remained high during the chronic phase, showing that the inflammation was active. Surprisingly, the mice regained their original weight along with the progression of colitis, and the only apparent symptom was loose feces. Histopathological changes 4 wk after DSS removal were dense infiltrates of mononuclear cells, irregular epithelial structure, and persistent deposits of collagen. A progressive production of the cytokines IL-1beta, IL-12 p70, and IL-17 correlated with the extensive cellular infiltration, whereas high IFN-gamma production was mainly found late in the chronic phase. Similar to C57BL/6 mice, BALB/c mice exposed to 5 days of DSS developed acute colitis as previously described. The acute colitis was accompanied by elevated plasma levels of haptoglobin and increased colonic levels of IL-1alpha/beta, IL-6, IL-18, and granulocyte colony-stimulating factor. However, soon after DSS removal, BALB/c mice recovered and were symptom free within 2 wk and completely recovered 4 wk after DSS removal in terms of histopathology, haptoglobin levels, and local cytokine production. In summary, these data stress the effect of genetic background on the outcome of DSS provocation. We believe that the present protocol to induce chronic colitis in C57BL/6 mice offers a robust model for validating future therapies for treatment of inflammatory bowel disease.     

Absence of stearoyl-CoA desaturase-1 does not promote DSS-induced acute colitis

Absence of stearoyl-CoA desaturase-1 (SCD1) in mice leads to chronic inflammation of the skin and increased susceptibility to atherosclerosis, while also increasing plasma inflammatory markers. A recent report suggested that SCD1 deficiency also increases disease severity in a mouse model of inflammatory bowel disease, induced by dextran sulfate sodium (DSS). However, SCD1-deficient mice are known to consume increased amounts of water, which would also be expected to increase the intake of DSS-treated water. The aim of this study was to determine the effect of SCD1 deficiency on DSS-induced acute colitis with DSS dosing adjusted to account for genotype differences in fluid consumption. Wild-type controls were treated with 3.5% DSS for 5 days to induce moderately severe colitis, while the concentration of DSS given to SCD1-deficient mice was lowered to 2.5% to control for increased fluid consumption. Colonic inflammation was assessed by clinical and histological scoring. Although SCD1-deficient mice consumed a total intake of DSS that was greater than that of wild-type controls, colonic inflammation, colon length and fecal blood were not altered by SCD1-deficiency in DSS-induced colitis, while diarrhea and total weight loss were modestly improved. Despite SCD1 deficiency leading to chronic inflammation of the skin and increased susceptibility to atherosclerosis, it does not accelerate inflammation in the DSS-induced model of acute colitis when DSS intake is controlled. These observations suggest that SCD1 deficiency does not play a significant role in colonic inflammation in this model.     

Role of M-CSF-dependent macrophages in colitis is driven by the nature of the inflammatory stimulus

Although macrophages are considered a critical factor in determining the severity of acute inflammatory responses in the gut, recent evidence has indicated that macrophages may also play a counterinflammatory role. In this study, we examined the role of a macrophage subset in two models of colitis. Macrophage colony-stimulating factor (M-CSF)-deficient osteopetrotic mice (op/op) and M-CSF-expressing heterozygote (+/?) mice were studied following the induction of colitis by either dinitrobenzene sulfonic acid (DNBS) or dextran sulfate sodium (DSS). DNBS induced a severe colitis in M-CSF-deficient op/op mice compared with +/? mice. This was associated with increased mortality and more severe macroscopic and microscopic injury. Colonic tissue myeloperoxidase (MPO) activity as well as concentrations of TNF-alpha, IL-1beta, and IL-6 were higher and IL-10 lower in op/op mice with DNBS colitis. The severity of inflammation and mortality was attenuated in op/op mice that had received human recombinant M-CSF prior to the induction of colitis. In contrast, op/op mice appeared less vulnerable to colitis induced by DSS. Macroscopic damage, microscopic injury, MPO activity, and tissue concentrations of TNF-alpha, IL-1beta, and IL-6 were all lower in op/op mice compared with +/? mice with DSS colitis, and no changes were seen in IL-10. Macrophage inflammatory protein-1alpha concentrations were increased in op/op but not +/? mice following colitis induced by DNBS but not DSS. These results indicate that M-CSF-dependent macrophages may play either a pro- or counterinflammatory role in acute experimental colitis, depending on the stimulus used to induce colitis.     

鼠衣原体改善DSS诱导的小鼠溃疡性结肠炎的作用研究

【目的】探讨鼠衣原体(Chlamydia muridarum)对小鼠溃疡性结肠炎的作用。【方法】取15只雌性C57BL/6J小鼠随机分为3组,每组5只动物,分别为空白对照组(Control)、肠炎模型组(DSS)、实验组(CM+DSS)。选取CM+DSS组小鼠予以2×10⁵ IFU的鼠衣原体灌胃处理,并在其感染后第29天开始,给予DSS组和CM+DSS组的小鼠2%DSS饮水,持续5d,每天监测小鼠体重和肠炎疾病评分,实验结束后检测小鼠结肠长度和结肠组织炎性改变。【结果】肠炎模型组的小鼠均表现出典型的肠炎症状(包括体重减轻、肠炎疾病评分、结肠长度和组织炎性改变);而经鼠衣原体预处理的小鼠(CM+DSS组)肠炎症状显著减轻,表现在肠炎疾病评分降低,体重和结肠长度有所恢复,肠组织炎性损伤减轻。【结论】鼠衣原体对DSS诱导的小鼠溃疡性结肠炎具有改善作用。     

Infection with a helminth parasite prevents experimental colitis via a macrophage-mediated mechanism

The propensity of a range of parasitic helminths to stimulate a Th2 or regulatory cell-biased response has been proposed to reduce the severity of experimental inflammatory bowel disease. We examined whether infection with Schistosoma mansoni, a trematode parasite, altered the susceptibility of mice to colitis induced by dextran sodium sulfate (DSS). Mice infected with schistosome worms were refractory to DSS-induced colitis. Egg-laying schistosome infections or injection of eggs did not render mice resistant to colitis induced by DSS. Schistosome worm infections prevent colitis by a novel mechanism dependent on macrophages, and not by simple modulation of Th2 responses, or via induction of regulatory CD4+ or CD25+ cells, IL-10, or TGF-beta. Infected mice had marked infiltration of macrophages (F4/80+CD11b+CD11c(-)) into the colon lamina propria and protection from DSS-induced colitis was shown to be macrophage dependent. Resistance from colitis was not due to alternatively activated macrophages. Transfer of colon lamina propria F4/80+ macrophages isolated from worm-infected mice induced significant protection from colitis in recipient mice treated with DSS. Therefore, we propose a new mechanism whereby a parasitic worm suppresses DSS-induced colitis via a novel colon-infiltrating macrophage population.