Effect of Saccharomyces cerevisiae UFMG A-905 in a murine model of food allergy.

Food allergy is triggered when there is an abnormal activation of the immune system by food allergens. Currently, there is no curative therapy for this pathological condition. Due to the immunomodulatory properties of probiotics they are potential candidates as therapeutic tools for food allergy. Therefore, the aim of this study was to evaluate the probiotic effect of Saccharomyces cerevisiae UFMG A-905 (905) in an in vivo model of food allergy. Probiotic effect was assessed by clinical, histological, immunological and microbiological parameters analysis. Furthermore, we also evaluated if 905 after inactivation has an effect, as well as if such an effect is dose dependent. Our results showed that oral administration of only viable 905 promotes a significant attenuation of tissue injury and myeloperoxidase (MPO) activity levels. Moreover, the treatment reduced interleukin 17 levels, and administration of the supernatant from the yeast culture also promoted a significant decrease in MPO levels. However, considering the systemic parameters, immunoglobulin (Ig)E and IgG anti-ovalbumin, which are essentials for triggering the allergic process, there was no effect, suggesting that the yeast promotes a local but not a systemic effect in the model evaluated. In addition, we found that only high doses of viable 905 were able to attenuate the signs of inflammation. In conclusion, oral administration of 905 led to a local effect that depends on the viability of the yeast.

The cytosolic sensor STING is required for intestinal homeostasis and control of inflammation.

STING (stimulator of interferon genes) is a cytosolic sensor for cyclic dinucleotides and also an adaptor molecule for intracellular DNA receptors. Although STING has important functions in the host defense against pathogens and in autoimmune diseases, its physiological relevance in intestinal homeostasis is largely unknown. In this study, we show that STING-/- mice presented defective protective mechanisms of intestinal mucosa, including decreased number of goblet cells, diminished mucus production, and lower levels of secretory IgA, when compared with wild-type (WT) mice. Fecal content and microbiota DNA could activate STING, indicating a role of this molecule in gut. Microbiota composition was altered in STING-/- mice toward a more inflammatory profile, evidencing a reduction in the Allobacolum and Bifidobacterium groups along with increase in Disulfovibrio bacteria. Absence of STING lead to decrease in induced intraepithelial lymphocytes (IEL) and to increase in group 1 innate lymphoid cell (ILC1) as well as ILC3 frequencies and decrease in ILC2 in the colon. Development and function of Foxp3+ and LAP+ regulatory T cells were also compromised in STING-/- mice. Moreover, these mice were highly susceptible to dextran sodium sulfate-induced colitis, T-cell-induced colitis, and enteric Salmonella typhimurium infection when compared with WT animals. Therefore, our results identify an important role of STING in maintaining gut homeostasis and also a protective effect in controlling gut inflammation.

Prolonged ingestion of ovalbumin diet by sensitized mice improves the metabolic consequences induced by experimental food allergy.

The prevalence of food allergy is rising in the western world. Allergen restriction is the chosen treatment in this condition, but continuous ingestion of the antigen has shown positive results in clinical trials. In a previous study, we have shown several allergic and metabolic alterations after 7 days of ovalbumin (OVA) ingestion by sensitized mice. The aim of this study was to investigate whether prolonged ingestion of antigen by sensitized mice would reverse the metabolic consequences caused by experimental food allergy. For this, allergic and metabolic parameters were analysed after prolonged ingestion of an OVA diet by OVA-sensitized mice. As shown previously, after 7 days of OVA consumption, sensitized mice showed increased serum levels of anti-OVA immunoglobulin (Ig)E and IgG1, aversion to the antigen ingestion, marked body and adipose tissue weight loss, followed by adipose tissue inflammation and decreased serum levels of adipokines, glucose and triglycerides. However, after 14 days of oral challenge, sensitized mice showed an anti-OVA IgE level similar to the mice that were only sensitized, but the specific IgG1 did not change. With this prolonged ingestion of OVA, sensitized mice were protected from OVA-induced anaphylaxis when the antigen was given systemically at a dose of 2 mg/animal. Moreover, various parameters analysed were significantly ameliorated, including adipose tissue inflammation, body and adipose tissue loss, as well as serum levels of adipokines and triglycerides. Therefore, our data suggest that prolonged ingestion of OVA by sensitized mice results in an improvement of the metabolic consequences caused by experimental food allergy.

AVE 0991, a non-peptide mimic of angiotensin-(1-7) effects, attenuates pulmonary remodelling in a model of chronic asthma.

BACKGROUND AND PURPOSE: AVE 0991 (AVE) is a non-peptide compound, mimic of the angiotensin (Ang)-(1-7) actions in many tissues and pathophysiological states. Here, we have investigated the effect of AVE on pulmonary remodelling in a murine model of ovalbumin (OVA)-induced chronic allergic lung inflammation. EXPERIMENTAL APPROACH: We used BALB/c mice (6-8 weeks old) and induced chronic allergic lung inflammation by OVA sensitization (20 µg·mouse(-1) , i.p., four times, 14 days apart) and OVA challenge (1%, nebulised during 30 min, three times per·week, for 4 weeks). Control and AVE groups were given saline i.p and challenged with saline. AVE treatment (1 mg·kg(-1) ·per day, s.c.) or saline (100 µL·kg(-1) ·per day, s.c.) was given during the challenge period. Mice were anaesthetized 72 h after the last challenge and blood and lungs collected. In some animals, primary bronchi were isolated to test contractile responses. Cytokines were evaluated in bronchoalveolar lavage (BAL) and lung homogenates. KEY RESULTS: Treatment with AVE of OVA sensitised and challenged mice attenuated the altered contractile response to carbachol in bronchial rings and reversed the increased airway wall and pulmonary vasculature thickness and right ventricular hypertrophy. Furthermore, AVE reduced IL-5 and increased IL-10 levels in the BAL, accompanied by decreased Ang II levels in lungs. CONCLUSIONS AND IMPLICATIONS: AVE treatment prevented pulmonary remodelling, inflammation and right ventricular hypertrophy in OVA mice, suggesting that Ang-(1-7) receptor agonists are a new possibility for the treatment of pulmonary remodelling induced by chronic asthma.

Reciprocal interference of experimental dyslipidemia and food allergy in the evolution of both diseases.

Background. Food allergies have been shown to reduce serum triacylglycerol, glucose, cholesterol, and free fatty acid levels in mice. In turn, dyslipidemias, especially dyslipidemias presenting with low levels of HDL cholesterol, are important risk factors for the development of atherosclerosis. However, the consequences of food allergies on dyslipidemia and atherosclerosis have not been fully investigated. Methods. Food allergy was induced using an egg white solution (EWS) in ovalbumin- (OVA-) sensitized C57BL/6 and low-density lipoprotein receptor knockout mice (LDLr(-/-)) for 5 weeks and was confirmed by the high production of anti-OVA IgE and IgG1 antibodies in both mouse strains. Results. The allergic C57BL/6 mice exhibited EWS aversion that was associated with less visceral fat and high levels of anti-Ova IgE antibodies after 5 weeks of EWS intake compared to controls. However, LDLr(-/-) allergic mice showed reduced anti-Ova IgE levels that were similar to the nonsensitized group. The LDLr(-/-) allergic mice also demonstrated a reversal of food aversion and sustained visceral fat after 5 weeks of allergy. Although HDL cholesterol levels were reduced in both sensitized mouse strains, lipid deposition in thoracic and abdominal aorta as well as area and composition of atherosclerotic plaques as unaffected by chronic ingestion of EWS. Conclusion. LDLr(-/-) mice develop an attenuated food allergy, as they showed a reversal of food aversion and lower IgE production after 5 weeks of induced allergy. The development of atherosclerosis, in turn, was not accelerated in the allergic LDLr(-/-) group despite the more atherogenic lipid profile.

In vitro selection of ertapenem and piperacillin/tazobactam-resistant strains of Bacteroides fragilis and analysis of their virulence in gnotobiotic mice.

Ertapenem and piperacillin/tazobactam are beta-lactam antibiotics with a broad spectrum of activity, used for the treatment of mixed infections, in which Bacteroides fragilis plays an important etiological role. The aim of this study was to select strains of B. fragilis resistant to these drugs and correlate the phenotype profiles of these lineages with changes in the virulence of the original bacterium. B. fragilis ATCC 25285, sensitive to the drugs listed, was used in this study. Strains resistant to these drugs were obtained by multi-step method and this condition was confirmed by comparing the time-kill curve of the original strain with those curves obtained from derived-resistant strains. To assess the virulence, germ-free mice were challenged intragastrically with the original strain or those derived-resistant. The mouse infection by the piperacillin/tazobactam-resistant B. fragilis strain produced increased levels of C-reactive protein, alkaline phosphatase and white blood cells and reduced platelet counts, what may indicate that acquisition of piperacillin/tazobactam resistance may enhance the pathogenic properties of these B. fragilis strains.

Functional asymmetry in the descending cardiovascular pathways from dorsomedial hypothalamic nucleus.

Neurons in the dorsomedial hypothalamus (DMH) play a key role in mediating tachycardia elicited by emotional stress. DMH activation by microinjections of the GABA(A) antagonist evokes tachycardia and physiological changes typically seen in experimental stress. DMH inhibition abolishes the tachycardia evoked by stress. Based on anatomic evidences for lateralization in the pathways from DMH, we investigated a possible inter-hemispheric difference in DMH-evoked cardiovascular responses. In anesthetized rats we compared changes in heart rate (HR), renal sympathetic activity (RSNA), mesenteric blood flow (MBF) and tail vascular conductance produced by activation of right (R) and left (L) sides of the DMH. We also evaluated the tachycardia produced by air jet stress after inhibition of R or L DMH. There were always greater increases in RSNA when bicuculline was injected ipsilaterally to the side where these parameters were recorded (average DeltaRSNA: L=+50% and R=+26%; P<0.05). Compared to pre-injection values, right DMH activation caused pronounced decrease (0.87+/-0.1% vs. 0.4+/-0.11%/mm Hg; P<0.05), whereas bicuculline methiodide (BMI) into left DMH produced no significant changes (0.95+/-0.09% vs. 1.04+/-0.25%/mm Hg) in tail vascular conductance. R or L DMH disinhibition produced decreases in MBF, but no differences in the range of these changes were observed. Activation of the right DMH caused greater tachycardia compared to the left DMH activation (average DeltaHR: R=+92 bpm; L=+48 bpm; P<0.05). Tachycardia evoked by air jet stress was smallest after right DMH inhibition (average DeltaHR: R=+57 bpm and L=+134 bpm; P<0.05). These results indicate that the descending cardiovascular pathways from DMH are predominantly lateralized and the right DMH might exert a prominent control on heart rate changes during emotional stress.

Chronic antigen ingestion protects ovalbumin sensitized mice from severe manifestation of Leishmania major infection.

In the present work, the development of experimental leishmaniasis was examined in sensitized BALB/c mice that were chronically fed with antigen. After an oral challenge with egg white solution, the ovalbumin (Ova)-sensitized mice showed an increase in serum anti-Ova IgE and IgG1 antibodies. Lesions induced by Leishmania major infection were reduced by the ingestion of Ova in sensitized mice, as assessed by reduced footpad growth, lower parasite loads and improved pathological outcome compared to sham sensitized mice. Moreover, such findings were connected to a shift to a Th1 response involving higher IFN-gamma production and serum levels of IgG2a anti-Leishmania antigens. The data appear to corroborate the suggestion that chronic ingestion of an antigen by sensitized mice modulates the immunological system through a shift in cytokine release, exhibiting a healing response and resistance to L. major infection.

Protective effect of Lactobacillus sakei 2a against experimental challenge with Listeria monocytogenes in gnotobiotic mice.

AIM: Lactobacillus sakei 2a isolated from sausage and presenting an in vitro antagonistic activity against Listeria monocytogenes Scott A was tested for a protective effect in mice experimentally challenged with the enterobacteria. METHODS AND RESULTS: In the experimental group, germ-free mice (n = 24) were inoculated intragastrically with 0.1 ml of a suspension containing 10(8) colony forming units (CFU) of Lact. sakei and 4 days later the animals were challenged intragastrically with 0.1 ml of a suspension containing 10(8) CFU of L. monocytogenes. Control group (n = 24) was only inoculated with the bacterial pathogen. Faecal counts showed that L. monocytogenes reached similar population levels (10(9) CFU g(-1) of contents) in both the groups. Animals in the control group showed lower (P = 0.0004) survival frequency (58.3%) when compared with the experimental one (100%). Anatomopathological examination confirmed the mortality data. CONCLUSIONS: Lactobacillus sakei 2a can survive in the mammal digestive tract where showed a protective effect against L. monocytogenes. This phenomenon was not due to an antagonistic activity. SIGNIFICANCE AND IMPACT OF THE STUDY: Use of Lact. sakei 2a as a meat starter could inhibit not only L. monocytogenes growth in the fermented product but also pathogen virulence in the gastrointestinal tract.

Alcohol-induced gastritis prevents oral tolerance induction in mice.

Despite several reports on the immunological relationship between inflammatory bowel diseases and immunoregulatory mechanisms in the gut, systematic studies addressing the impact of inflammatory processes in the gastric mucosa on events, such as oral tolerance, are still limited. Herein, we report the establishment of a novel murine model of gastritis induced by short-term administration of ethanol. The major immumological features of this clinical entity are characterized, as well as its impact on the induction of oral tolerance. Our data demonstrate that ethanol ingestion during 4 consecutive days triggered an acute inflammatory reaction in the stomach referred as ethanol-induced gastritis and characterized by hyperaemia, oedema and mixed mononuclear/polymorphonuclear cell infiltrate. Besides local immunological changes, such as high levels of gastric interleukin (IL)-4 and interferon (IFN)-gamma, systemic alterations are also observed, including increased IL-4 synthesis, enhanced levels of serum IgE and absence of IL-10 production by spleen cells. Moreover, ethanol-induced gastritis prevents oral tolerance induction to ovalbumin (OVA) as demonstrated by unaltered anti-OVA humoral and cellular immune responses in treated animals. Tissue eosinophilia after footpad immunization with OVA suggests that oral treatment with ethanol induced an allergic-type reaction. Taken together, our findings indicate that short-term ethanol ingestion is associated with gastric inflammatory events able to break immunoregulatory mechanisms that maintain mucosal homeostasis and oral tolerance.

A model of chronic IgE-mediated food allergy in ovalbumin-sensitized mice.

Food allergy is most frequently the result of IgE-mediated hypersensitivity reactions. Here, we describe a chronic model in which some of the intestinal and systemic consequences of continuous egg white solution ingestion by ovalbumin-sensitized eight-week-old BALB/c mice, 6 animals per group, of both sexes, were investigated. There was a 20% loss of body weight that began one week after antigen exposure and persisted throughout the experiment (3 weeks). The sensitization procedure induced the production of anti-ovalbumin IgG1 and IgE, which were enhanced by oral antigen exposure (129% for IgG1 and 164% for IgE, compared to sensitization values). Intestinal changes were determined by jejunum edema at 6 h (45% Evans blue extravasation) and by a significant eosinophil infiltration with a peak at 48 h. By day 21 of continuous antigen exposure, histological findings were mild, with mast cell hyperplasia (100%) and increased mucus production (483%). Altogether, our data clearly demonstrate that, although immune stimulation was persistently occurring in response to continuous oral antigen exposure, regulatory mechanisms were occurring in the intestinal mucosa, preventing overt pathology. The experimental model described here reproduces the clinical and pathological changes of mild chronic food allergy and may be useful for mechanistic studies of this common clinical condition.

A model of chronic IgE-mediated food allergy in ovalbumin-sensitized mice

Food allergy is most frequently the result of IgE-mediated hypersensitivity reactions. Here, we describe a chronic model in which some of the intestinal and systemic consequences of continuous egg white solution ingestion by ovalbumin-sensitized eight-week-old BALB/c mice, 6 animals per group, of both sexes, were investigated. There was a 20 percent loss of body weight that began one week after antigen exposure and persisted throughout the experiment (3 weeks). The sensitization procedure induced the production of anti-ovalbumin IgG1 and IgE, which were enhanced by oral antigen exposure (129 percent for IgG1 and 164 percent for IgE, compared to sensitization values). Intestinal changes were determined by jejunum edema at 6 h (45 percent Evans blue extravasation) and by a significant eosinophil infiltration with a peak at 48 h. By day 21 of continuous antigen exposure, histological findings were mild, with mast cell hyperplasia (100 percent) and increased mucus production (483 percent). Altogether, our data clearly demonstrate that, although immune stimulation was persistently occurring in response to continuous oral antigen exposure, regulatory mechanisms were occurring in the intestinal mucosa, preventing overt pathology. The experimental model described here reproduces the clinical and pathological changes of mild chronic food allergy and may be useful for mechanistic studies of this common clinical condition.

Hepatic changes in mice chronically infected with Helicobacter trogontum

We infected NIH germ-free female mice with Helicobacter trogontum, a recently described intestinal bacterium of rats, in order to study the lesions it induced in the liver of this host. Fifteen mice were challenged with a single dose of H. trogontum (test group) and killed 6, 12 and 18 months after inoculation (5 animals/group). Nine animals were challenged with 0.85 percent saline alone (control group) and killed at the same times. Fragments from the liver, cecum and colon were obtained for microbiologic and histologic examination. Stool samples were also collected. H. trogontum was detected in the cecum, colon and/or stool samples of all test mice. As expected, the bacterium was not isolated from any specimen obtained from the control animals. On the other hand, although we could not cultivate the bacterium from the liver, 13 test animals (86.7 percent) presented histological changes in this organ. The 6-month group presented infiltration of mononuclear and polymorphonuclear cells in the hepatic parenchyma and the two other groups presented foci of mononuclear cells. The results suggest that H. trogontum can elicit a hepatic inflammatory response in mice since the only difference between control and test animals was the presence of H. trogontum in the latter. This result, together with the growing number of related reports in the literature, reinforces the possible role of Helicobacter infection in the pathogenesis of hepatobiliary diseases

Hepatic changes in mice chronically infected with Helicobacter trogontum.

We infected NIH germ-free female mice with Helicobacter trogontum, a recently described intestinal bacterium of rats, in order to study the lesions it induced in the liver of this host. Fifteen mice were challenged with a single dose of H. trogontum (test group) and killed 6, 12 and 18 months after inoculation (5 animals/group). Nine animals were challenged with 0.85% saline alone (control group) and killed at the same times. Fragments from the liver, cecum and colon were obtained for microbiologic and histologic examination. Stool samples were also collected. H. trogontum was detected in the cecum, colon and/or stool samples of all test mice. As expected, the bacterium was not isolated from any specimen obtained from the control animals. On the other hand, although we could not cultivate the bacterium from the liver, 13 test animals (86.7%) presented histological changes in this organ. The 6-month group presented infiltration of mononuclear and polymorphonuclear cells in the hepatic parenchyma and the two other groups presented foci of mononuclear cells. The results suggest that H. trogontum can elicit a hepatic inflammatory response in mice since the only difference between control and test animals was the presence of H. trogontum in the latter. This result, together with the growing number of related reports in the literature, reinforces the possible role of Helicobacter infection in the pathogenesis of hepatobiliary diseases.

Influences of alpha-tocopherol on cholesterol metabolism and fatty streak development in apolipoprotein E-deficient mice fed an atherogenic diet

Although the role of oxidized lipoproteins is well known in atherogenesis, the role of vitamin E supplementation is still controversial. There is also little information about cholesterol metabolism (hepatic concentration and fecal excretion) in the new models of atherosclerosis. In the present study, we evaluated the effect of moderate vitamin E supplementation on cholesterol metabolism and atherogenesis in apolipoprotein E (apo E)-deficient mice. Apo E-deficient mice were fed an atherogenic diet containing 40 or 400 mg/kg of alpha-tocopherol acetate for 6 weeks. Total cholesterol in serum and liver and 3-OH-alpha-sterols in feces, and fecal excretion of bile acids were determined and histological analyses of aortic lesion were performed. A vitamin E-rich diet did not affect body weight, food intake or serum cholesterol. Serum and hepatic concentrations of cholesterol as well as sterol concentration in feces were similar in both groups. However, when compared to controls, the alpha-tocopherol-treated mice showed a reduction of about 60 percent in the atherosclerotic lesions when both the sum of lesion areas and the average of the largest lesion area were considered. These results demonstrate that supplementation of moderate doses of alpha-tocopherol was able to slow atherogenesis in apo E-deficient mice and to reduce atherogenic lipoproteins without modifying the hepatic pool or fecal excretion of cholesterol and bile acids

Role of p38 mitogen-activated protein kinase in chemokine-induced emigration and chemotaxis in vivo.

It has been proposed that L-selectin engagement with ligand activates p38 mitogen-activated protein kinase (MAPK) and can impact on downstream events of leukocyte rolling, including adhesion, and emigration. Using a novel chemotactic assay in vivo, we visualized slow release of chemokine from an agarose gel positioned 350 microm from a postcapillary venule, which induced directed migration (chemotaxis) of neutrophils. In this system, keratinocyte-derived cytokine induced phosphorylation of p38 MAPK, which phosphorylated a downstream protein (ATF-2). This latter event was blocked by the concentration of p38 inhibitors used in this study. Mice were treated with two different p38 inhibitors: SKF86002 and SB203580. Neither inhibitor affected rolling or adhesion in microvessels. Intravenous treatment with SFK86002 (5, 10, and 20 mg/kg) 30 min before the inflammatory stimulus inhibited the total number of emigrated cells at a dose of 20 mg/kg (62%, p < 0.05), despite the presence of many adherent cells within the vessels. A similar inhibition was observed with 20 mg/kg of a second p38 inhibitor SB203580 (67%, p < 0.05). In addition to emigration, both p38 inhibitors impaired the ability of emigrated cells to migrate through the tissue toward the chemotactic stimulus. In fact, the majority of emigrated leukocytes in p38 inhibitor-treated animals remained within 50 microm of the venule. Superfusion of the tissue with SKF86002 (0.7 mM) to impact only on emigrated and not vascular leukocytes resulted in no impairment in emigration, but in a significant reduction in chemotaxis away from the vessel wall. Again, the majority of emigrated leukocytes remained within 50 microm of the blood vessel. Our results suggest that p38 does not affect rolling or adhesion, but that it is involved in leukocyte emigration and chemotaxis through interstitium in response to keratinocyte-derived cytokine in vivo.

Influences of alpha-tocopherol on cholesterol metabolism and fatty streak development in apolipoprotein E-deficient mice fed an atherogenic diet.

Although the role of oxidized lipoproteins is well known in atherogenesis, the role of vitamin E supplementation is still controversial. There is also little information about cholesterol metabolism (hepatic concentration and fecal excretion) in the new models of atherosclerosis. In the present study, we evaluated the effect of moderate vitamin E supplementation on cholesterol metabolism and atherogenesis in apolipoprotein E (apo E)-deficient mice. Apo E-deficient mice were fed an atherogenic diet containing 40 or 400 mg/kg of alpha-tocopherol acetate for 6 weeks. Total cholesterol in serum and liver and 3-OH-alpha-sterols in feces, and fecal excretion of bile acids were determined and histological analyses of aortic lesion were performed. A vitamin E-rich diet did not affect body weight, food intake or serum cholesterol. Serum and hepatic concentrations of cholesterol as well as sterol concentration in feces were similar in both groups. However, when compared to controls, the alpha-tocopherol-treated mice showed a reduction of about 60% in the atherosclerotic lesions when both the sum of lesion areas and the average of the largest lesion area were considered. These results demonstrate that supplementation of moderate doses of alpha-tocopherol was able to slow atherogenesis in apo E-deficient mice and to reduce atherogenic lipoproteins without modifying the hepatic pool or fecal excretion of cholesterol and bile acids.

Evaluation of the components of a commercial probiotic in gnotobiotic mice experimentally challenged with Salmonella enterica subsp. enterica ser. Typhimurium.

Vitacanis((R)), a probiotic preparation containing a Lactobacillus acidophilus, an Enterococcus faecium and a Saccharomyces cerevisiae, has been developed for the prevention of intestinal disorders in dogs and cats. In the present study, these microorganisms were tested jointly or singly during experimental infection of gnotobiotic mice with Salmonella Typhimurium. Four experimental groups consisting of animals given probiotics jointly or singly and a control group consisting of germfree mice were used. The groups were treated with one or three of the microorganisms (experimental) or PBS (control) 10 days before intragastric challenge with a suspension containing about 10(2) cells of the bacterial pathogen. A higher survival (P<0.05) was observed in gnotobiotic mice given E. faecium (82%). All the animals in the other groups died after the challenge but the survival time was longer (P<0.05) for groups given all three of the microorganisms (7.4+/-2.4 days) or given only L. acidophilus (7.2+/-2.9 days) than for the control mice (4.4+/-1.1 days) and the mice that received S. cerevisiae (4.9+/-1.6 days) mice. The survival data agreed with the histopathological findings which showed more severe liver and intestinal lesions in control mice and in mice given Saccharomyces. In vitro antagonistic assays showed inhibition growth of E. faecium and S. Typhimurium around the colonies of L. acidophilus and for S. Typhimurium around the colonies of E. faecium. However, in vivo, S. Typhimurium became similarly established in the digestive tract of gnotobiotic mice at levels ranging from 10(8) to 10(10)CFU/g of feces and remained at these high levels until the animals died or were sacrificed. Among the three probiotic components of the commercial product Vitacanis((R)), E. faecium was the only one that provided protection against challenge with S. Typhimurium. Protection was not due to the reduction of the intestinal populations of the pathogenic bacteria.

Gelatin intake increases the atheroma formation in apoE knock out mice.

The effect of gelatin ingestion on cholesterol metabolism and on atheroma formation was evaluated in both wild type (n=14) and apoprotein E (apoE) knock out (apoE(-/-)) (n=20) C57BL/6 7-week-old mice. Animals were fed a cholesterol-free isoproteic semi-purified diet containing 20% of casein (control diet) or 10% of casein plus 10% of gelatin (gel diet) for 8 weeks. In wild type mice, dietary gelatin caused a reduction in the serum triacylglycerols levels associated with an increase in the fecal excretion. No difference in blood cholesterol was seen at the sixth week of experiment. At the eighth week of experiment, there was a modest but significant reduction of serum total and high density lipoprotein (HDL) cholesterol in apoE(-/-) mice fed on gel diet compared to the control. Total cholesterol/HDL cholesterol ratio was 2-fold higher in the gel group than that seen in the control group (14.39 and 7.84, respectively). Histological analyzes showed a 2.2-fold increase in the dimension of the atherosclerotic plaques in the proximal aorta in apoE(-/-) mice fed on a gel diet compared to those fed on a control diet. The gel diet also promoted a reduction in the fecal excretion of bile acids. Hepatic cholesterol was similar in both groups. In conclusion, although gelatin reduced total serum cholesterol, this reduction was associated to a decrease of HDL cholesterol and consequent increase of total cholesterol/HDL cholesterol ratio, resulting in an acceleration of atherogenesis.

Saccharomyces boulardii stimulates sIgA production and the phagocytic system of gnotobiotic mice.

The effect of Saccharomyces boulardii on the immune system was evaluated, comparing germ-free Swiss/NIH mice monoassociated with the probiotic with germ-free mice. Saccharomyces boulardii colonized the gut of germ-free mice and survived the gastrointestinal conditions. An increase in sIgA production, both total and anti-S. boulardii, was observed in the intestinal contents of monoassociated mice when compared with germ-free controls. The number of Kupffer cells was significantly higher in monoassociated mice than in germ-free controls. In S. boulardii-monoassociated mice, clearance of Escherichia coli B41 was higher than in germ-free controls. TNF-alpha, IFN-gamma and IL-12 serum levels were higher at earlier time points in monoassociated mice when compared with germ-free mice. These results show that the yeast S. boulardii modulates the host immune responses. This effect may be of interest for improving the resistance to enteropathogenic bacterial infections.