Butyrate upregulates stromelysin-1 production by intestinal mesenchymal cells

Causal association between gut microbiota and fibromyalgia: a Mendelian randomization study

Background

Fibromyalgia (FM) is a syndrome characterized by chronic and widespread musculoskeletal pain. A number of studies have implied a potential association between gut microbiota and FM. However, the casual association between gut microbiota and FM remains unknown.

Method

Mendelian randomization (MR) study was conducted using the summary statistics of genetic variants from the genome-wide association study (GWAS). Inverse variance weighted (IVW), combined with MR-Egger and weighted median were used to investigate the causal association between 119 gut microbiota genera and FM. Sensitivity analyses were performed on the MR results, including heterogeneity test, leave-one-out test and pleiotropy test.

Results

A total of 1,295 single nucleotide polymorphism (SNPs) were selected as instrumental variables (IVs), with no significant heterogeneity and pleiotropy according to the sensitivity analyses. Five gut microbiota genera were found to have significant casual association with FM. Coprococcus2 (OR = 2.317, p-value = 0.005, 95% CI: 1.289-4.167), Eggerthella (OR = 1.897, p-value = 0.001, 95% CI: 1.313-2.741) and Lactobacillus (OR = 1.576, p-value =0.020, 95% CI: 1.073-2.315) can increase the risk of FM. FamillyXIIIUCG001 (OR = 0.528, p-value = 0.038, 95% CI: 0.289-0.964) and Olsenella (OR = 0.747, p-value = 0.050, 95% CI: 0.557-1.000) can decrease the risk of FM.

Conclusion

This MR study found that gut microbiota is casually associated with FM. New insights into the mechanisms of FM mediated by gut microbiota are provided.

Impact of graded levels of coated calcium butyrate on growth performance and serological indices during pre-weaning stage in Holstein calves

The study aimed to analyze the impact of calcium butyrate supplementation in calf starter on growth performance indices associated with early rumen development to decrease the volume of milk or milk replacer feeding and enhance early starter intake in Holstein calves. For this purpose, twelve Holstein calves were randomly assigned into three treatments (n = 4/treatment); a control without coated calcium butyrate, T1, and T2 treatments supplemented with coated calcium butyrate 3 g and 6 g per day/head, respectively. Body weight was measured at days 7, 14, 21, 28, 35, 42, 49, and 56 of the trial, and the average daily weight gain and feed conversion ratio were determined. Blood samples were collected at 14, 28, 42, and 56 days of trial for serological parameters. Gut morphometry was performed at the end of trial at slaughtering by collecting duodenal samples. Furthermore, the meat was also evaluated for its quality parameters including pH and tenderness after slaughtering. The results indicated that the feed intake, average daily weight gain, feed conversion ratio, and gut morphometric parameters involving villus height and crypts depth of calves were improved in coated calcium butyrate-supplemented groups. Furthermore, the supplementation of calf starter with coated calcium butyrate significantly enhanced serum concentrations of glucose and total protein. Besides, Beta hydroxy butyrate (BHBA) levels of blood were also found to be elevated in both treatment groups. However, it was revealed that coated calcium butyrate supplementation had no significant effect on meat quality parameters. In conclusion, the supplementation of calf starter with coated calcium butyrate could improve calf performance.

A subset of gut leukocytes has telomerase-dependent "hyper-long" telomeres and require telomerase for function in zebrafish

BACKGROUND

Telomerase, the enzyme capable of elongating telomeres, is usually restricted in human somatic cells, which contributes to progressive telomere shortening with cell-division and ageing. T and B-cells cells are somatic cells that can break this rule and can modulate telomerase expression in a homeostatic manner. Whereas it seems intuitive that an immune cell type that depends on regular proliferation outbursts for function may have evolved to modulate telomerase expression it is less obvious why others may also do so, as has been suggested for macrophages and neutrophils in some chronic inflammation disease settings. The gut has been highlighted as a key modulator of systemic ageing and is a key tissue where inflammation must be carefully controlled to prevent dysfunction. How telomerase may play a role in innate immune subtypes in the context of natural ageing in the gut, however, remains to be determined.

RESULTS

Using the zebrafish model, we show that subsets of gut immune cells have telomerase-dependent"hyper-long" telomeres, which we identified as being predominantly macrophages and dendritics (mpeg1.1+ and cd45+mhcII+). Notably, mpeg1.1+ macrophages have much longer telomeres in the gut than in their haematopoietic tissue of origin, suggesting that there is modulation of telomerase in these cells, in the gut. Moreover, we show that a subset of gut mpeg1.1+ cells express telomerase (tert) in young WT zebrafish, but that the relative proportion of these cells decreases with ageing. Importantly, this is accompanied by telomere shortening and DNA damage responses with ageing and a telomerase-dependent decrease in expression of autophagy and immune activation markers. Finally, these telomerase-dependent molecular alterations are accompanied by impaired phagocytosis of E. coli and increased gut permeability in vivo.

CONCLUSIONS

Our data show that limiting levels of telomerase lead to alterations in gut immunity, impacting on the ability to clear pathogens in vivo. These are accompanied by increased gut permeability, which, together, are likely contributors to local and systemic tissue degeneration and increased susceptibility to infection with ageing.

Beyond Immunity: Underappreciated Functions of Intestinal Macrophages

The gastrointestinal tract hosts the largest compartment of macrophages in the body, where they serve as mediators of host defense and immunity. Seeded in the complex tissue-environment of the gut, an array of both hematopoietic and non-hematopoietic cells forms their immediate neighborhood. Emerging data demonstrate that the functional diversity of intestinal macrophages reaches beyond classical immunity and includes underappreciated non-immune functions. In this review, we discuss recent advances in research on intestinal macrophage heterogeneity, with a particular focus on how non-immune functions of macrophages impact tissue homeostasis and function. We delve into the strategic localization of distinct gut macrophage populations, describe the potential factors that regulate their identity and functional heterogeneity within these locations, and provide open questions that we hope will inspire research dedicated to elucidating a holistic view on macrophage-tissue cell interactions in the body's largest mucosal organ.

Long-term exposure to butyric acid induces excessive production of matrix metalloproteases in human gingival fibroblasts

OBJECTIVE

The purpose of this study was to clarify the relationship between bacteria-induced butyric acid and periodontal disease progression.

DESIGN

Normal human gingival fibroblasts were exposed to butyric acid (0, 1, 5, 10, and 15 mM) adjusted to a pH of 7.2-7.4 using sodium hydroxide for 0-96 h and cell viability was evaluated. In addition, the effects of butyric acid on the production of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in gingival fibroblasts were analyzed by real-time RT-PCR, ELISA, western blotting, and stromelysin zymography.

RESULTS

Butyric acid reduced the viability of gingival fibroblasts in a concentration- and time-dependent manner. Furthermore, butyric acid promoted production of MMP-1, MMP-3, and MMP-10 in gingival fibroblasts and suppressed TIMP-2 protein production.

CONCLUSIONS

Butyric acid promoted overproduction of MMPs, resulting in a disruption of the balance between MMPs and TIMPs expression in gingival fibroblasts. Our study suggests that the butyric acid produced by causative bacteria stimulates excessive MMP expression in periodontal tissue, leading to destruction of the tissue.

Gut microbiome and magnetic resonance spectroscopy study of subjects at ultra-high risk for psychosis may support the membrane hypothesis

Background:

The microbiota-gut-brain axis and membrane dysfunction in the brain has attracted increasing attention in the field of psychiatric research. However, the possible interactive role of gut microbiota and brain function in the prodromal stage of schizophrenia has not been studied yet.

Methods:

To explore this, we collected fecal samples and performed Magnetic Resonance Spectroscopy (MRS) scans in 81 high risk (HR) subjects, 19 ultra-high risk (UHR) subjects and 69 health controls (HC). Then we analyzed the differences in gut microbiota and choline concentrations in the anterior cingulate cortex (ACC).

Results:

Presences of the orders Clostridiales, Lactobacillales and Bacteroidales were observed at increase levels in fecal samples of UHR subjects compared to the other two groups. The composition changes of gut microbiota indicate the increased production of Short Chain Fatty Acids (SCFAs), which could activate microglia and then disrupt membrane metabolism. Furthermore, this was confirmed by an increase of choline levels, a brain imaging marker of membrane dysfunction, which is also significantly elevated in UHR subjects compared to the HR and HC groups.

Conclusion:

Both gut microbiome and imaging studies of UHR subjects suggest the membrane dysfunction in the brain and hence might support the membrane hypothesis of schizophrenia.

Diversity and functions of intestinal mononuclear phagocytes

The intestinal lamina propria (LP) contains a diverse array of mononuclear phagocyte (MNP) subsets, including conventional dendritic cells (cDC), monocytes and tissue-resident macrophages (mφ) that collectively play an essential role in mucosal homeostasis, infection and inflammation. In the current review we discuss the function of intestinal cDC and monocyte-derived MNP, highlighting how these subsets play several non-redundant roles in the regulation of intestinal immune responses. While much remains to be learnt, recent findings also underline how the various populations of MNP adapt to deal with the challenges specific to their environment. Understanding these processes should help target individual subsets for 'fine tuning' immunological responses within the intestine, a process that may be of relevance both for the treatment of inflammatory bowel disease (IBD) and for optimized vaccine design.

Macrophages in gastrointestinal homeostasis and inflammation

Monocyte-derived mononuclear phagocytes, particularly macrophages, are crucial to maintain gastrointestinal homeostasis in the steady state but are also important for protection against certain pathogens. However, when uncontrolled, they can promote immunopathology. Broadly two subsets of macrophages can be considered to perform the vast array of functions to complete these complex tasks: resident macrophages that dominate in the healthy gut and inflammation-elicited (inflammatory) macrophages that derive from circulating monocytes infiltrating inflamed tissue. Here, we discuss the features of resident and inflammatory intestinal macrophages, complexities in identifying and defining these populations and the mechanisms involved in their differentiation. In particular, focus will be placed on describing their unique ontogeny as well as local gastrointestinal signals that instruct specialisation of resident macrophages in healthy tissue. We then explore the very different roles of inflammatory macrophages and describe new data suggesting that they may be educated not only by the gut microenvironment but also by signals they receive during development in the bone marrow. Given the high degree of plasticity of gut macrophages and their multifaceted roles in both healthy and inflamed tissue, understanding the mechanisms controlling their differentiation could inform development of improved therapies for inflammatory diseases such as inflammatory bowel disease (IBD).

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

Macrophages in intestinal homeostasis and inflammation

The intestine contains the largest pool of macrophages in the body which are essential for maintaining mucosal homeostasis in the face of the microbiota and the constant need for epithelial renewal but are also important components of protective immunity and are involved in the pathology of inflammatory bowel disease (IBD). However, defining the biological roles of intestinal macrophages has been impeded by problems in defining the phenotype and origins of different populations of myeloid cells in the mucosa. Here, we discuss how multiple parameters can be used in combination to discriminate between functionally distinct myeloid cells and discuss the roles of macrophages during homeostasis and how these may change when inflammation ensues. We also discuss the evidence that intestinal macrophages do not fit the current paradigm that tissue-resident macrophages are derived from embryonic precursors that self-renew in situ, but require constant replenishment by blood monocytes. We describe our recent work demonstrating that classical monocytes constantly enter the intestinal mucosa and how the environment dictates their subsequent fate. We believe that understanding the factors that drive intestinal macrophage development in the steady state and how these may change in response to pathogens or inflammation could provide important insights into the treatment of IBD.

Macrophages in intestinal homeostasis and inflammation

The intestine contains the largest pool of macrophages in the body which are essential for maintaining mucosal homeostasis in the face of the microbiota and the constant need for epithelial renewal but are also important components of protective immunity and are involved in the pathology of inflammatory bowel disease (IBD). However, defining the biological roles of intestinal macrophages has been impeded by problems in defining the phenotype and origins of different populations of myeloid cells in the mucosa. Here, we discuss how multiple parameters can be used in combination to discriminate between functionally distinct myeloid cells and discuss the roles of macrophages during homeostasis and how these may change when inflammation ensues. We also discuss the evidence that intestinal macrophages do not fit the current paradigm that tissue-resident macrophages are derived from embryonic precursors that self-renew in situ, but require constant replenishment by blood monocytes. We describe our recent work demonstrating that classical monocytes constantly enter the intestinal mucosa and how the environment dictates their subsequent fate. We believe that understanding the factors that drive intestinal macrophage development in the steady state and how these may change in response to pathogens or inflammation could provide important insights into the treatment of IBD.

The Epigenetic Regulation of Wound Healing

Significance: Epigenetic regulatory mechanisms are essential for epidermal homeostasis and contribute to the pathogenesis of many skin diseases, including skin cancer and psoriasis. However, while the epigenetic regulation of epidermal homeostasis is now becoming active area of research, the epigenetic mechanisms controlling the wound healing response remain relatively untouched. Recent Advances: Substantial progress achieved within the last two decades in understanding epigenetic mechanisms controlling gene expression allowed defining several levels, including covalent DNA and histone modifications, ATP-dependent and higher-order chromatin chromatin remodeling, as well as noncoding RNA- and microRNA-dependent regulation. Research pertained over the last few years suggests that epigenetic regulatory mechanisms play a pivotal role in the regulation of skin regeneration and control an execution of reparative gene expression programs in both skin epithelium and mesenchyme. Critical Issues: Epigenetic regulators appear to be inherently involved in the processes of skin repair, and are able to dynamically regulate keratinocyte proliferation, differentiation, and migration, together with influencing dermal regeneration and neoangiogenesis. This is achieved through a series of complex regulatory mechanisms that are able to both stimulate and repress gene activation to transiently alter cellular phenotype and behavior, and interact with growth factor activity. Future Directions: Understanding the molecular basis of epigenetic regulation is a priority as it represents potential therapeutic targets for the treatment of both acute and chronic skin conditions. Future research is, therefore, imperative to help distinguish epigenetic modulating drugs that can be used to improve wound healing.

Use of pigs as a potential model for research into dietary modulation of the human gut microbiota

The human intestinal microbial ecosystem plays an important role in maintaining health. A multitude of diseases including diarrhoea, gastrointestinal inflammatory disorders, such as necrotising enterocolitis (NEC) of neonates, and obesity are linked to microbial composition and metabolic activity. Therefore, research on possible dietary strategies influencing microbial composition and activity, both preventive and curative, is being accomplished. Interest has focused on pre- and probiotics that stimulate the intestinal production of beneficial bacterial metabolites such as butyrate, and beneficially affect microbial composition. The suitability of an animal model to study dietary linked diseases is of much concern. The physiological similarity between humans and pigs in terms of digestive and associated metabolic processes places the pig in a superior position over other non-primate models. Furthermore, the pig is a human-sized omnivorous animal with comparable nutritional requirements, and shows similarities to the human intestinal microbial ecosystem. Also, the pig has been used as a model to assess microbiota–health interactions, since pigs exhibit similar syndromes to humans, such as NEC and partly weanling diarrhoea. In contrast, when using rodent models to study diet–microbiota–health interactions, differences between rodents and humans have to be considered. For example, studies with mice and human subjects assessing possible relationships between the composition and metabolic activity of the gut microbiota and the development of obesity have shown inconsistencies in results between studies. The present review displays the similarities and differences in intestinal microbial ecology between humans and pigs, scrutinising the pig as a potential animal model, with regard to possible health effects.

Histone deacetylase inhibitors upregulate MMP11 gene expression through Sp1/Smad complexes in human colon adenocarcinoma cells

MMP-11 (stromelysin-3) is a matrix metalloproteinase associated with tumor progression and poor prognosis. Its expression was initially described exclusively in stromal cells surrounding tumors, but more recently it has also been detected in macrophages and hepatocarcinoma cells. Here we show MMP-11 expression in human epithelial colon adenocarcinoma cell lines (Caco-2, HT-29 and BCS-TC2). Treatment of BCS-TC2 cells with butyrate and trichostatin A (TSA) (histone deacetylase inhibitors) increases MMP11 promoter activity and protein expression. Using electrophoretic mobility shift assay (EMSA) and supershift assays, we demonstrate for the first time that Sp1 is able to bind to the GC-boxes within the MMP11 proximal promoter region; this binding has been confirmed by chromatin immunoprecipitation. Sp1 is involved in MMP11 basal expression and it is essential for the upregulation of transcription by histone deacetylase inhibitors as deduced from mutant constructs lacking the Sp1 sites and by inhibition of its binding to the promoter with mithramycin. This regulation requires the formation of Sp1/Smad2 heterocomplexes, which is stimulated by an increase in the acetylation status of Smad after butyrate or TSA treatments. We have also found that ERK1/2-mitogen-activated protein kinase (MAPK), but not p38-MAPK or JNK, is involved in the upregulation of MMP11 by HDAC inhibitors.

Histone deacetylase inhibitors and their potential role in inflammatory bowel diseases

IBDs (inflammatory bowel diseases) are lifelong manifestations that significantly impair the quality of life of those who suffer from them. Although many therapies are now available, including immunomodulatory drugs such as Infliximab which have efficacy in IBD, not all patients respond and some patients generate autoantibodies against these drugs. Hence the search for novel treatments is ongoing. HDACs (histone deacetylases) are responsible for condensation of chromatin in the nucleus of cells and inhibition of gene transcription and are often dysregulated during cancer. HDAC inhibitors allow normal gene transcription to be restored and provide attractive therapeutic options, as they have been shown to be anti-inflammatory and anti-proliferative in cancer. Indeed, two HDAC inhibitors have been recently approved for the treatment of cutaneous T-cell lymphoma in the U.S.A. Recent research using animal models has shown that HDAC inhibitors may have a beneficial effect in colitis by boosting levels of Foxp3+ (forkhead box P3+) T-regulatory cells that dampen inflammation. In the present paper, we outline the background to IBD, HDACs and their inhibitors as well as discussing their current use in models of IBD.

Epigenetic regulation of key vascular genes and growth factors

The role of small RNAs in epigenetic regulation is an emerging field. This research may also open novel treatment strategies based on manipulation of the epigenetic status of the target tissues. Our objective is to review epigenetic regulation of key vascular genes and growth factors. Vascular endothelial growth factor A (VEGF-A) is one of the key players in regulating and maintaining cardiovascular functions and pathology. Although its epigenetic regulation is still not completely understood, expression of the VEGF gene can be manipulated by epigenetic mechanisms using small RNAs that are targeted to the gene promoter which results in the alteration of histone code. VEGF exerts its effects mostly through two receptors, VEGFR1 and VEGFR2, and their expression is also regulated by promoter DNA methylation in various cancer cells. These findings suggest the importance of epigenetic mechanisms in the regulation of vascular functions.

From the gut to the peripheral tissues: the multiple effects of butyrate

Butyrate is a natural substance present in biological liquids and tissues. The present paper aims to give an update on the biological role of butyrate in mammals, when it is naturally produced by the gastrointestinal microbiota or orally ingested as a feed additive. Recent data concerning butyrate production delivery as well as absorption by the colonocytes are reported. Butyrate cannot be detected in the peripheral blood, which indicates fast metabolism in the gut wall and/or in the liver. In physiological conditions, the increase in performance in animals could be explained by the increased nutrient digestibility, the stimulation of the digestive enzyme secretions, a modification of intestinal luminal microbiota and an improvement of the epithelial integrity and defence systems. In the digestive tract, butyrate can act directly (upper gastrointestinal tract or hindgut) or indirectly (small intestine) on tissue development and repair. Direct trophic effects have been demonstrated mainly by cell proliferation studies, indicating a faster renewal of necrotic areas. Indirect actions of butyrate are believed to involve the hormono-neuro-immuno system. Butyrate has also been implicated in down-regulation of bacteria virulence, both by direct effects on virulence gene expression and by acting on cell proliferation of the host cells. In animal production, butyrate is a helpful feed additive, especially when ingested soon after birth, as it enhances performance and controls gut health disorders caused by bacterial pathogens. Such effects could be considered for new applications in human nutrition.

Reactivity of mouse alveolar macrophages to cigarette smoke is strain dependent

Cigarette smoke (CS) is a main risk factor in chronic obstructive pulmonary disease (COPD), but only 20% of smokers develop COPD, suggesting genetic predisposition. Animal studies have shown that C57BL/6J mice are sensitive to CS and develop emphysema, whereas Institute of Cancer Research (ICR) mice are not. To investigate the potential factors responsible for the different susceptibility of ICR and C57BL/6J mice to CS, we evaluated in alveolar macrophages (AMs) isolated from these strains of mice the possible mechanisms involved in the inflammatory and oxidative responses induced by CS. Lactate dehydrogenase (LDH) release revealed that C57BL/6J AMs were more susceptible to CS extract (CSE) toxicity than ICR. Differences were observed in inflammatory and oxidative response after CSE exposure. Proinflammatory cytokines and matrix metalloproteinases (MMPs) were increased in C57BL/6J but not ICR AMs. Control C57BL/6J AMs showed a higher baseline production of reactive oxygen species (ROS) and H(2)O(2) with lower baseline levels of GSH, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and glutathione peroxidase (GPX2). This was associated with reduced histone deacetylase-2 (HDAC2) expression, activation of NF-κB, and higher basal levels of TNF-α and IL-6. CSE induced a decrease in HDAC2 protein levels in both C57BL/6J and ICR AMs; however, the level of HDAC2 was significantly lower in C57BL/6 than in ICR AMs. Furthermore, CSE enhanced NF-κB-dependent cytokine release only in C57BL/6J AMs. We suggest that an imbalance in oxidative stress decreases HDAC2 levels and facilitates NF-κB binding, resulting in a proinflammatory response in C57BL/6J but not in ICR AMs. These results could contribute in understanding the different susceptibility to CS of these strains of mice.

Genetic and epigenetic mechanisms and their possible role in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common disease associated with significant cardiovascular morbidity and mortality. The pathogenesis of AAA is poorly defined, making targeting of new therapies problematic. Current evidence favours an interaction of multiple environmental and genetic factors in the initiation and progression of AAA. Epigenetics is the term used to define the properties of the genome that are not explained by the primary sequence, but are due to the modifications of DNA and/or associated proteins. Previous research indicates the association of gene specific promoter DNA hyper-methylation and global DNA hypo-methylation with atherosclerosis. Evidence also suggests an important role for epigenetic processes such as histone acetylation in cardiovascular diseases including atherosclerosis and restenosis. Altered DNA methylation or histone acetylation occur in inflammation, cellular proliferation and remodelling processes and therefore maybe relevant to the pathology of AAA. Important risk factors for AAA, including cigarette smoking, older age, male gender and hypertension, have been linked with epigenetic effects and thus could act in this way to promote AAA. In this review, we discuss the potential role of epigenetic mechanisms in AAA. Since epigenetic alterations are to some extent reversible, further study of this area may identify new treatment targets for AAA.

Comparative effect of orally administered sodium butyrate before or after weaning on growth and several indices of gastrointestinal biology of piglets

Sodium butyrate (SB) provided orally favours body growth and maturation of the gastrointestinal tract (GIT) in milk-fed pigs. In weaned pigs, conflicting results have been obtained. Therefore, we hypothesised that the effects of SB (3 g/kg DM intake) depend on the period (before v. after weaning) of its oral administration. From the age of 5 d, thirty-two pigs, blocked in quadruplicates within litters, were assigned to one of four treatments: no SB (control), SB before (for 24 d), or after (for 11–12 d) weaning and SB before and after weaning (for 35–36 d). Growth performance, feed intake and various end-point indices of GIT anatomy and physiology were investigated at slaughter. The pigs supplemented with SB before weaning grew faster after weaning than the controls (P < 0·05). The feed intake was higher in pigs supplemented with SB before or after weaning (P < 0·05). SB provided before weaning improved post-weaning faecal digestibility (P < 0·05) while SB after weaning decreased ileal and faecal digestibilities (P < 0·05). Gastric digesta retention was higher when SB was provided before weaning (P < 0·05). Post-weaning administration of SB decreased the activity of three pancreatic enzymes and five intestinal enzymes (P < 0·05). IL-18 gene expression tended to be lower in the mid-jejunum in SB-supplemented pigs. The small-intestinal mucosa was thinner and jejunal villous height lower in all SB groups (P < 0·05). In conclusion, the pre-weaning SB supplementation was the most efficient to stimulate body growth and feed intake after weaning, by reducing gastric emptying and intestinal mucosa weight and by increasing feed digestibility.

A randomized placebo-controlled comparison of 2 prebiotic/probiotic combinations in preterm infants: impact on weight gain, intestinal microbiota, and fecal short-chain fatty acids

OBJECTIVE

To compare the effect of 2 prebiotic/probiotic products on weight gain, stool microbiota, and stool short-chain fatty acid (SCFA) content of premature infants.

PATIENTS AND METHODS

This randomized, blinded, placebo-controlled trial included 90 premature infants treated with either a dietary supplement containing 2 lactobacillus species plus fructooligosaccharides (CUL, Culturelle, ConAgra, Omaha, NE), a supplement containing several species of lactobacilli and bifidobacteria plus fructooligosaccharides (PBP, ProBioPlus DDS, UAS Laboratories, Eden Prairie, MN), or placebo (a dilute preparation of Pregestamil formula) twice daily for 28 days or until discharge if earlier. The primary outcome was weight gain. Secondary outcomes were stool bacterial analysis by culture and 16S rDNA quantitative polymerase chain reaction and stool SCFA content measured by high performance liquid chromatography.

RESULTS

Both prebiotic/probiotic combinations contained more bacterial species than noted on the label. No significant effect on infant growth of either prebiotic/probiotic supplement was observed. By cultures, 64% of infants receiving PBP became colonized with bifidobacteria, compared with 18% of infants receiving CUL and 27% of infants receiving placebo (chi-square, P = 0.064). No differences were noted between groups in colonization rates for lactobacilli, Gram-negative enteric bacteria, or staphylococci. By 16S rDNA polymerase chain reaction analysis, the bifidobacteria content in the stools of the infants receiving PBP was higher than in the infants receiving CUL or placebo (Kruskal-Wallis, P = 0.011). No significant differences in stool SCFA content were detected between groups. No adverse reactions were noted.

CONCLUSIONS

Infants receiving PBP were more likely to become colonized with bifidobacteria. No significant differences in weight gain or stool SCFA content were detected.

Inhibitory effects of short-chain fatty acids on matrix metalloproteinase secretion from human colonic subepithelial myofibroblasts

BACKGROUND AND AIMS

Short-chain fatty acids (SCFAs), such as acetate, propionate and butyrate, are the major by-product of bacterial fermentation of dietary fiber in the colon. In this report, we investigated how SCFAs modulate matrix metalloproteinase (MMP) secretion from human colonic subepithelial myofibroblasts (SEMFs).

MATERIALS AND METHODS

SEMFs were identified by expression of alpha-smooth muscle actin and vimentin. Cytokine-induced MMP-1 and MMP-3 levels were determined by enzyme-linked immunosorbent assay. Cytokine-induced MMP mRNA expression was analyzed by RT-PCR and real-time PCR methods.

RESULTS

Acetate had no effect on MMP secretion. Propionate and butyrate significantly attenuated IL-1 beta- and TNF-alpha-induced MMP-1 and MMP-3 secretion. Similar responses were also observed at the mRNA levels. Propionate and butyrate did not modulate IL-1 beta- and TNF-alpha-induced activation of mitogen-activated protein kinases (MAPKs), which play a crucial role in MMP induction. Trichostatin A, a histone-deacetylase inhibitor, reduced IL-1 beta-induced MMP-1 and MMP-3 mRNA expression, and suppressed TNF-alpha-induced MMP-3 mRNA expression.

CONCLUSION

SCFAs play an anti-inflammatory role through suppression of MMP secretion in the colon. Inhibitory effects of SCFAs on MMP secretion might be associated with their action of histone hyperacetylation.

Dietary modulation of GALT

Changes in diet greatly affect the mucosal immune system, particularly in diseases such as Crohn's disease and necrotizing enterocolitis. This article examines the hypothesis that alterations in the luminal environment of the intestine regulate the expression of genes in the enterocyte responsible for signaling to immune cells. Genes expressed by the epithelium orchestrate leukocytes in the lamina propria. For example, chemokine expression in the mouse intestinal epithelium, through transgenic means, induced the recruitment of neutrophils and lymphocytes into intestinal tissues. Diet alters the expression of the genes responsible for signaling by a variety of pathways. The introduction of a normal diet to a weanling mouse up-regulates MHC class II expression through a particular isoform of the class II transactivator, a protein that acts in the nucleus. SCFA concentrations in the intestinal lumen vary markedly with diet. SCFAs increase IL-8 and insulin-like growth factor binding protein-2 expression by inhibiting histone deacetylase activity in the enterocyte. Down-regulation of gene expression by butyrate can act through acetylation of the inhibitory transcription factor Sp3. The review therefore describes a number of molecular pathways, explaining how changes in diet may alter leukocyte recruitment by regulating enterocyte gene expression. Myofibroblasts enhance enterocyte chemotactic activity by cleaving inactive precursors; and myofibroblast genes also are regulated by SCFA. It is likely that other similar regulatory mechanisms remain to be discovered.

Effects of oral administration of bifidobacterium breve on fecal lactic acid and short-chain fatty acids in low birth weight infants

OBJECTIVES

Short-chain fatty acids (SCFAs) are known to provide energy to colonocytes, whereas overproduction of SCFAs can cause mucosal injury in premature infants. Our objective was to investigate the effects of the oral administration of Bifidobacterium breve M-16V (B breve) on fecal lactic acid and SCFAs in low birth weight (LBW) infants.

PATIENTS AND METHODS

Fecal lactic, acetic, propionic, and butyric acids from 66 premature infants were analyzed by high-performance liquid chromatography at 0, 2, and 4 weeks after birth. The subjects included 22 extremely LBW (ELBW, <1000 g), 22 very LBW (VLBW, <1500 g), and 22 LBW (<2500 g) infants. The infants were divided into two groups: those with and those without B. breve supplementation.

RESULTS

In the control groups, fecal acetic acid and total SCFA concentrations were significantly increased at 2 weeks in the VLBW and LBW infants (P < 0.05) and at 4 weeks in the ELBW, VLBW, and LBW infants (P < 0.01 for each) compared with those at week 0. Fecal lactic acid concentrations showed a similar pattern during follow-up, but the differences were not significant. Four weeks after B breve administration, the fecal butyric acid concentrations were significantly decreased in the ELBW and VLBW infants (P < 0.05 each), and the ratio of the acetic acid concentrations to the total SCFAs was significantly increased compared with those of the control groups in the ELBW (P < 0.05), VLBW (P < 0.05), and LBW infants (P < 0.01).

CONCLUSIONS

Oral administration of B breve reduces the production of butyric acid, which may be helpful in protecting LBW infants from digestive diseases such as necrotizing enterocolitis.

Mixtures of SCFA, composed according to physiologically available concentrations in the gut lumen, modulate histone acetylation in human HT29 colon cancer cells

Intake of fibre has beneficial properties on gut health. Butyrate, a product of bacterial gut fermentation, is thought to contribute to positive effects by retarding growth and enhancing apoptosis of tumour cells. One mechanism is seen in its capacity to modulate histone acetylation and thereby transcriptional activity of genes. Next to butyrate, propionate and acetate are also major products of gut fermentation and together they may exert different potencies of cellular effects than butyrate alone. Since virtually nothing is known on combination effects by SCFA mixtures, here we had the aim to assess how physiological relevant concentrations and mixtures of SCFA modulate histone acetylation in human colon cells. HT29 colon cancer cells were incubated with mixtures of butyrate, acetate and propionate and with the individual compounds as controls. Histone acetylation was determined with acid-urea gel electrophoresis and immunoblotting. Acetylated histones slowly increased over 24 h and persisted up to 72 h in butyrate-treated HT29 cells. Butyrate (5-40 mM) and propionate (20-40 mM) enhanced histone acetylation significantly after 24 h incubation, whereas acetate (2.5-80 mM) was ineffective. Mixtures of these SCFA also modulated histone acetylation, mainly due to additive effects of butyrate and propionate, but not due to acetate. In conclusion, physiological concentrations of propionate together with butyrate could have more profound biological activities than generally assumed. Together, these SCFA could possibly mediate important processes related to an altered transcriptional gene activation and thus contribute to biological effects possibly related to cancer progression or prevention.

Matrix metalloproteinases in inflammatory bowel disease: boon or a bane?

Matrix metalloproteinases (MMPs) are a family of Zn(2+)-dependent extracellular matrix (ECM) degrading endopeptidases that share common functional domains, activation mechanisms, and collectively have the capacity to degrade all types of ECM proteins. In addition to playing a central role in ECM turnover, MMPs proteolytically activate or degrade a variety of nonmatrix substrates including chemokines, cytokines, growth factors, and junctional proteins. Thus, they are increasingly recognized as critical players in inflammatory response. Indeed, accumulating data from several studies indicate that they are the predominant proteases involved in the pathogenesis of inflammatory bowel disease (IBD) via their influence on the function and migration of inflammatory cells, mucosal ulceration, as well as matrix deposition and degradation. Some MMPs are constitutively expressed and play a protective role in IBD through their effect on cellular homeostasis, while others are induced during inflammation-mediated tissue damage. This article focuses on the role of the various MMPs in IBD, discussing their physiologic and pathogenetic role in the context of intestinal defense, mucosal inflammatory response, and immune cell-epithelial interaction.

Hypoxia suppresses the production of matrix metalloproteinases and the migration of humanmonocyte-derived dendritic cells

As most solid tumors are hypoxic, dendritic cells (DC) in solid tumors are also exposed to hypoxia. While many adaptation responses of tumor cells to hypoxia are known, it is yet to be determined how hypoxia affects the functions of DC. To explore the effects of hypoxia on the functions of DC, we compared the expression of surface markers, cytokines, chemokine receptors and matrix metalloproteinases (MMP) of human monocyte-derived DC (hmDC) differentiated under hypoxia to those differentiated under normoxia. Both groups of hmDC expressed similar levels of surface markers and cytokines. However, expression of MMP-9 and membrane type-1-MMP, as well as migrating activity, was significantly suppressed in hmDC differentiated under hypoxia compared with their normoxia counterparts. We also demonstrated that trichostatin A restored the production of MMP-9 in hmDC, under hypoxia. Collectively, our findings show that a hypoxic microenvironment suppresses the production of MMP in hmDC, most probably through the deacetylation of promoter regions of MMP, thus suppressing the migrating activity of hmDC. Our results suggest that the hypoxic microenvironment in solid tumor tissues may suppress the function of DC.

Oxidative stress and cigarette smoke alter chromatin remodeling but differentially regulate NF‐κB activation and proinflammatory cytokine release in alveolar epithelial cells

Oxidative stress is implicated in lung inflammation due to its effect on proinflammatory gene transcription. Changes in gene transcription depend on chromatin remodeling and the relative activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Alterations in the nuclear histone acetylation:deacetylation balance may result in uncontrolled transcription of specific proinflammatory genes. We studied the effect of hydrogen peroxide (H2O2) and cigarette smoke condensate (CSC) on histone acetylation:deacetylation in human alveolar epithelial cells (A549). H2O2 and CSC significantly increased acetylation of histone H4 proteins and were associated with decreased HDAC activity and HDAC2 levels in A549 cells. Also, the decreased HDAC2 activity was due to protein modification by aldehydes and nitric oxide products. Pretreatment of A549 cells with N-acetyl-l-cysteine attenuated the oxidant-mediated reduction in HDAC activity. Treatment of A549 cells with CSC did not cause nuclear factor-kappaB (NF-kappaB) activation or expression and release of either interleukin (IL)-8 or IL-6. However, H2O2, tumor necrosis factor-alpha (TNF-alpha), and IL-1beta significantly increased NF-kappaB activation and expression of IL-8 compared with control cells. Interestingly, CSC dose dependently inhibited TNF-alpha- and IL-1beta-mediated NF-kappaB activation and IL-8 expression. Thus, H2O2 and CSC enhance acetylation of histone proteins and decrease histone deacetylase activity but differentially regulate proinflammatory cytokine release in alveolar epithelial cells.

Redox modulation of chromatin remodeling: impact on histone acetylation and deacetylation, NF-kappaB and pro-inflammatory gene expression

Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation products, such as 4-hydroxy-2-nonenal, acrolein and F2-isoprostanes, may play a role in enhancing inflammation through the activation and phosphorylation of stress kinases (JNK, ERK, p38) and redox-sensitive transcription factors such as NF-kappaB and AP-1. This increases the expression of genes regulating a battery of distinct pro-inflammatory mediators. Acetylation by histone acetyltransferase (HAT) of specific lysine residues on the N-terminal tail of core histones, results in uncoiling of the DNA and increased accessibility to transcription factor binding. In contrast, histone deacetylation by histone deacetylase (HDAC) represses gene transcription by promoting DNA winding thereby limiting access to transcription factors. Oxidative stress activates NF-kappaB resulting in expression of pro-inflammatory mediators through the activation of intrinsic HAT activity on co-activator molecules. In addition, oxidative stress also inhibits HDAC activity and in doing so enhances inflammatory gene expression which leads to a chronic inflammatory response. Oxidative stress can also increase complex formation between the co-activator CBP/p300 and the p65 subunit of NF-kappaB suggesting a further role of oxidative stress in chromatin remodeling. The antioxidant and/or anti-inflammatory effects of thiol molecules (glutathione, N-acetyl-L-cysteine and N-acystelyn), dietary polyphenols (curcumin-diferuloylmethane and resveratrol), the bronchodilator theophylline and glucocorticoids have all been shown to play a role in either controlling NF-kappaB activation or chromatin remodeling through modulation of HDAC activity and subsequently inflammatory gene expression in lung epithelial cells. Thus, oxidative stress regulates both signal transduction and chromatin remodeling which in turn impacts on pro-inflammatory responses in the lungs.

Matrix metalloproteinases in necrotising enterocolitis

Elevated cytokines, especially TNF-alpha, have been implicated in the pathogenesis of necrotising enterocolitis (NEC). We have previously shown that TNF-alpha drives the production of matrix degrading enzymes, the matrix metalloproteinases (MMPs), in the gut wall. In this study we have therefore investigated the role of MMPs in the pathogenesis of NEC in neonates. Nine newborn infant nonnecrotic resected bowels with confirmed NEC were studied and 8 newborn infants with neonatal bowel obstructions were used as controls. Immunostaining was used to identify the numbers of monocytes, macrophages, neutrophils, and T cells in the tissue. We used quantitative, competitive RT-PCR to analyze the number of TNF-alpha, IFN-gamma, MMP, and TIMP mRNA transcripts and western blotting to analyze MMP and TIMP protein production. Double labeling (immunostaining and in situ hybridization) was used to identify the phenotype of MMP mRNA expressing cells. We found increased numbers of monocytes, macrophages, and neutrophils in NEC tissue compared with controls. The number of T cells was unexpectedly low in NEC as was the number of IFN-gamma transcripts in comparison with the control samples. Increased numbers of transcripts for TNF-alpha were detected in NEC tissue, as was mRNA expression and protein production for stromelysin-1 and TIMP-1 but not collagenase, gelatinases, or TIMP-2. The cellular source of stromelysin-1 in NEC was alpha-smooth muscle actin positive cells. These results suggest that stromelysin-1, which has the ability to degrade the mucosal extra-cellular matrix, may be responsible for the extensive tissue injury in infants with NEC.

Oxidative stress, transcription factors and chromatin remodelling in lung inflammation

Oxidative stress has been implicated in the pathogenesis of several inflammatory lung disorders. Oxidants and inflammatory mediators such as tumour necrosis factor-alpha (TNF-alpha) activate transcription factors such as nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) leading to the expression of pro-inflammatory genes. The expression of many genes, including those encoding pro-inflammatory mediators involves the remodelling of the chromatin structure provided by histone proteins. Histone acetylation causes the unwinding of chromatin structure therefore allowing transcription factor access to promoter sites. Nuclear histone acetylation is a reversible process, and is regulated by a group of acetyltransferases (HATs) which promote acetylation, and deacetylases (HDACs) which promote deacetylation. In addition, several co-activators, transcription factors and nuclear proteins also have histone acetyltransferase activity. Both TNF-alpha and the oxidant, hydrogen peroxide (H2O2) alter histone acetylation/deacetylation, and the activation of NF-kappaB and AP-1, leading to the release of the pro-inflammatory cytokine interleukin-8 (IL-8) in human alveolar epithelial cells (A549). Pharmacological inhibition of HDAC leads to the increased HAT activity, AP-1 and NF-kappaB activation, and IL-8 release by H2O2 or TNF-alpha treatments. This suggests that the remodelling of chromatin by histone acetylation plays a role in the oxidant-mediated pro-inflammatory responses in the lungs.