Elvira Bailón

The effects of short-chain fatty acids on colon epithelial proliferation and survival depend on the cellular phenotype

Purpose: The short-chain fatty acids (SCFA) are produced via anaerobic bacterial fermentation of dietary fiber within the colonic lumen. Among them, butyrate is thought to protect against colon carcinogenesis. However, few studies analyze the effects of butyrate, and other SCFA, on normal epithelial cells and on epithelial regeneration during disease recovery. Since there are controversial in vitro studies, we have explored the effects of SCFA on different biological processes. Methods: We used both tumoral (HT-29) and normal (FHC) epithelial cells at different phenotypic states. In addition, we analyzed the in vivo activity of soluble dietary fiber and SCFA production in the proliferation rate and regeneration of intestinal epithelial cells. Results: The effect of butyrate on epithelial cells depends on the phenotypic cellular state. Thus, in nondifferentiated, high proliferative adenocarcinoma cells, butyrate significantly inhibited proliferation while increased differentiation and apoptosis, whereas other SCFA studied did not. However, in normal cells or in differentiated cultures as well as in in vivo studies, the normal proliferation and regeneration of damaged epithelium is not affected by butyrate or SCFA exposure. Conclusion: Although butyrate could exert antiproliferative effects in tumor progression, its production is safe and without consequences for the normal epithelium growth.

A comparative study of the preventative effects exerted by two probiotics, Lactobacillus reuteri and Lactobacillus fermentum, in the trinitrobenzenesulfonic acid model of rat colitis

The intestinal anti-inflammatory effects of two probiotics isolated from breast milk, Lactobacillus reuteri and L. fermentum, were evaluated and compared in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis. Colitis was induced in rats by intracolonic administration of 10 mg TNBS dissolved in 50% ethanol (0.25 ml). Either L. reuteri or L. fermentum was daily administered orally (5 x 10(8) colony-forming units suspended in 0.5 ml skimmed milk) to each group of rats (n 10) for 3 weeks, starting 2 weeks before colitis induction. Colonic damage was evaluated histologically and biochemically, and the colonic luminal contents were used for bacterial studies and for SCFA production. Both probiotics showed intestinal anti-inflammatory effects in this model of experimental colitis, as evidenced histologically and by a significant reduction of colonic myeloperoxidase activity (P<0.05). L. fermentum significantly counteracted the colonic glutathione depletion induced by the inflammatory process. In addition, both probiotics lowered colonic TNFalpha levels (P<0.01) and inducible NO synthase expression when compared with non-treated rats; however, the decrease in colonic cyclo-oxygenase-2 expression was only achieved with L.fermentum administration. Finally, the two probiotics induced the growth of Lactobacilli species in comparison with control colitic rats, but the production of SCFA in colonic contents was only increased when L. fermentum was given. In conclusion, L. fermentum can exert beneficial immunomodulatory properties in inflammatory bowel disease, being more effective than L. reuteri, a probiotic with reputed efficacy in promoting beneficial effects on human health.

A comparative study of the preventative effects exerted by three probiotics, Bifidobacterium lactis, Lactobacillus casei and Lactobacillus acidophilus, in the TNBS model of rat colitis.

Aims:  The intestinal anti‐inflammatory effects of three probiotics with immunomodulatory properties, Lactobacillus casei, Lactobacillus acidophilus and Bifidobacterium lactis, were evaluated and compared in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis.

The combination of fructooligosaccharides and resistant starch shows prebiotic additive effects in rats

Different types of dietary fiber can be distinguished considering their rate of fermentability, thus determining the location of the large intestine where they exert their beneficial effect. Their combination could be interesting to obtain health-promoting effects throughout the entire colon. The aim of the present study was to evaluate the synergistic effect of two dietary fibers with different fermentation patterns, fructooligosaccharides (FOS) (Beneo(®)-95) and resistant starch (Fibersol(®)-2), after their administration to healthy rats or in trinitrobenzenesulphonic acid-(TNBS) colitic rats, with an altered colonic immune response. In healthy rats, the administration of the combination of FOS and resistant starch induced changes in the intestinal microbiota, by increasing lactobacilli and bifidobacteria in caecum and colonic contents. Furthermore, its administration up-regulated the expression of the trefoil factor-3 and MUC-2 in comparison with untreated rats, thus improving the intestinal barrier function. The beneficial effects observed with this combination were confirmed in the TBNS model of rat colitis, since it was able to exert intestinal anti-inflammatory effect, associated with an increase of protective bacteria and up-regulation of epithelial defense mechanisms. In conclusion, the combination of two different dietary fibers may result in a synergistic prebiotic effect, and may confer greater health benefits to the host.

Butyrate in vitro immune-modulatory effects might be mediated through a proliferation-related induction of apoptosis

Survival and proliferation signals are two processes closely interrelated and finely controlled in most cell types, whose deregulation may lead to carcinogenesis. In the last decade, different studies have suggested that both cellular functions are also intimately associated with other cellular activities such as differentiation and cellular activation, especially in immune cells. The aim of this study was to evaluate the effects of the short-chain fatty acid (SCFA) butyrate on the proliferation and activation state of different cell types involved in inflammatory bowel disease. We focused on intestinal epithelial cells, macrophages and T-lymphocytes, using both primary non-transformed cultures and established cell lines. The results showed that low concentrations of butyrate inhibited the proliferation of all the immune cell types tested in this work, whereas it only induced apoptosis in activated T-lymphocytes, non-differentiated epithelial cells and macrophage cell lines, but not in differentiated epithelial cells or primary macrophages. Butyrate apoptosis induction was mediated by caspase-3/7 activation. This SCFA was only able to modify cell activation, measured as expression of inflammatory cytokines, in those cell types in which apoptosis was induced. In conclusion, our results suggest a cell type-specificity of the immune-modulatory effects of butyrate based on the proliferation/activation characteristic physiology of these processes in different cells types.

Antihypertensive Effects of Peroxisome Proliferator-Activated Receptor-β Activation in Spontaneously Hypertensive Rats

Activation of nuclear hormone receptor peroxisome proliferator-activated receptor &bgr;/&dgr; (PPAR&bgr;) has been shown to improve insulin resistance and plasma high-density lipoprotein levels, but nothing is known about its effects in genetic hypertension. We studied whether the PPAR&bgr; agonist GW0742 might exert antihypertensive effects in spontaneously hypertensive rats (SHRs). The rats were divided into 4 groups, Wistar Kyoto rat-control, Wistar Kyoto rat-treated (GW0742, 5 mg · kg−1 · day−1 by oral gavage), SHR-control, and SHR-treated, and followed for 5 weeks. GW0742 induced a progressive reduction in systolic arterial blood pressure and heart rate in SHRs and reduced the mesenteric arterial remodeling, the increased aortic vasoconstriction to angiotensin II, and the endothelial dysfunction characteristic of SHRs. These effects were accompanied by a significant increase in endothelial NO synthase activity attributed to upregulated endothelial NO synthase and downregulated caveolin 1 protein expression. Moreover, GW0742 inhibited vascular superoxide production, downregulated p22phox and p47phox proteins, decreased both basal and angiotensin II–stimulated NADPH oxidase activity, inhibited extracellular-regulated kinase 1/2 activation, and reduced the expression of the proinflammatory and proatherogenic genes, interleukin 1&bgr;, interleukin 6, or intercellular adhesion molecule 1. None of these effects were observed in Wistar Kyoto rats. PPAR&bgr; activation, both in vitro and in vivo, increased the expression of the regulators of G protein–coupled signaling proteins RGS4 and RGS5, which negatively modulated the vascular actions of angiotensin II. PPAR&bgr; activation exerted antihypertensive effects, restored the vascular structure and function, and reduced the oxidative, proinflammatory, and proatherogenic status of SHRs. We propose PPAR&bgr; as a new therapeutic target in hypertension.

A probiotic strain of Escherichia coli, Nissle 1917, given orally exerts local and systemic anti-inflammatory effects in lipopolysaccharide-induced sepsis in mice

Background and purpose:  Escherichia coli Nissle 1917 is a probiotic strain used in the treatment of intestinal immune diseases, including ulcerative colitis. The aim of the present study was to test if this probiotic bacterium can also show systemic immunomodulatory properties after oral administration.

Di-D-fructose dianhydride-enriched caramels: effect on colon microbiota, inflammation, and tissue damage in trinitrobenzenesulfonic acid-induced colitic rats.

In the present study we describe the preparation and chemical characterization of a caramel with a high (70%) content of difructose dianhydrides (DFAs) and glycosylated derivatives (DFAs). This product was obtained by thermal activation (90 degrees C) of highly concentrated (90% w/v) aqueous D-fructose solutions using the sulfonic acid ion-exchange resin Lewatit S2328 as caramelization catalyst. DFAs represent a unique family of cyclic fructans with prebiotic properties already present in low proportions (<15%) in commercial caramel. We report the antiinflammatory activity of the new DFA-enriched caramel in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis, an experimental model that resembles human inflammatory bowel disease (IBD), and compare its effects with those obtained with a commercial sucrose caramel and with linear fructooligosaccharides (FOS). For this purpose, the effects on colon tissue damage, gut microbiota, short-chain fatty acid (SCFAs) production, and different inflammatory markers were evaluated. The administration of DFA-enriched caramel to colitic rats showed intestinal antiinflammatory effect, as evidenced macroscopically by a significant reduction in the extent of the colonic damage induced by TNBS. This effect was similar to that obtained with FOS in the same experimental settings, whereas commercial caramel was devoid of any significant antiinflammatory effect. The beneficial effect was associated with the inhibition of the colonic levels of the proinflammatory cytokines, tumor necrosis factor alpha (TNF alpha) and interleukin 1beta (IL-1beta), and the reduction in colonic myeloperoxidase (MPO) activity and inducible nitric oxide synthase (iNOS) expression. The DFA-enriched caramel also promoted a more favorable intestinal microbiota, increasing lactobacilli and bifidobacteria counts as well as inducing higher concentrations of SCFAs in the luminal colonic contents. These results reinforce the concept of DFAs and glycosyl-DFAs as dietary beneficial compounds with prebiotic properties and suggest that the novel DFA-enriched caramel here reported may be an interesting candidate to be explored for the dietary treatment of human IBD.

Evaluation of the preventative effects exerted by Lactobacillus fermentum in an experimental model of septic shock induced in mice

The preventative effects of the probiotic Lactobacillus fermentum CECT5716 were evaluated in the lipopolysaccharide (LPS) model of septic shock in mice. The probiotic was administered suspended in drinking water at the final concentration of 108 colony-forming units/ml for 2 weeks before the induction of an endotoxic shock by an intraperitoneal injection of LPS (400 microg/200 microl per mouse). Blood and different organs were collected after 24 h to evaluate the severity of the endotoxic shock and the preventative effects of the probiotic. L. fermentum reduced TNF-alpha levels in blood, which promotes the major alterations observed during septic shock, as well as the infiltration of activated neutrophils into the lungs. Furthermore, free radical overproduction and oxidative stress were associated with a significant decrease in hepatic glutathione levels in septic mice, and with an excessive NO production attributed to the induction of the inducible isoform of NO synthase (iNOS). In fact, hepatic glutathione levels were significantly increased in the group of mice receiving the probiotic, and the increased iNOS expression both in the colon and lungs was down-regulated in those mice treated with L. fermentum. Finally, pre-treatment with L. fermentum may also exert its protective action modulating the expression of different cytokines in splenocyte-derived T cells such us IL-2, IL-5, IL-6 or IL-10. In conclusion, pre-treatment with L. fermentum may exert its protective action against LPS-induced organ damage in mice by a combination of several actions including its antioxidant properties and by reduction of the synthesis of the pro-inflammatory TNF-alpha and IL-6.

The intestinal anti-inflammatory effect of minocycline in experimental colitis involves both its immunomodulatory and antimicrobial properties

Some antibiotics, including minocycline, have recently been reported to display immunomodulatory properties in addition to their antimicrobial activity. The use of a compound with both immunomodulatory and antibacterial properties could be very interesting in the treatment of inflammatory bowel disease (IBD), so the aim of our study was to evaluate the anti-inflammatory effect of minocycline in several experimental models of IBD. Firstly, the immunomodulatory activity of the antibiotic was tested in vitro using Caco-2 intestinal epithelial cells and RAW 264.7 macrophages; minocycline was able to inhibit IL-8 and nitrite production, respectively. In vivo studies were performed in trinitrobenzenesulfonic acid (TNBS)-induced rat colitis and dextran sodium sulfate (DSS)-induced mouse colitis. The results revealed that minocycline exerted an intestinal anti-inflammatory effect when administered as a curative treatment in the TNBS model, modulating both immune and microbiological parameters, being confirmed in the DSS model; whereas none of the other antibiotics tested (tetracycline and metronidazole) showed anti-inflammatory effect. However, minocycline administration before the colitis induction was not able to prevent the development of the intestinal inflammation, thus showing that only its antimicrobial activity is not enough for the anti-inflammatory effect. In conclusion, minocycline displays an anti-inflammatory effect on different models of rodent colitis which could be attributed to the association of its antibacterial and immunomodulatory properties.