Inhibition of NADPH Oxidase (NOX) 2 Mitigates Colitis in Mice with Impaired Macrophage AMPK Function

Macrophage adenosine monophosphate-activated protein kinase (AMPK) limits the development of experimental colitis. AMPK activation inhibits NADPH oxidase (NOX) 2 expression, reactive oxygen species (ROS) generation, and pro-inflammatory cytokine secretion in macrophages during inflammation, while increased NOX2 expression is reported in experimental models of colitis and inflammatory bowel disease (IBD) patients. Although there are reductions in AMPK activity in IBD, it remains unclear whether targeted inhibition of NOX2 in the presence of defective AMPK can reduce the severity of colitis. Here, we investigate whether the inhibition of NOX2 ameliorates colitis in mice independent of AMPK activation. Our study identified that VAS2870 (a pan-Nox inhibitor) alleviated dextran sodium sulfate (DSS)-induced colitis in macrophage-specific AMPKβ1-deficient (AMPKβ1^LysM) mice. Additionally, VAS2870 blocked LPS-induced TLR-4 and NOX2 expression, ROS production, nuclear translocation of NF-κB, and pro-inflammatory cytokine secretion in bone marrow-derived macrophages (BMDMs) from AMPKβ1^LysM mice, whereas sodium salicylate (SS; AMPK β1 activator) did not. Both VAS2870 and SS inhibited LPS-induced NOX2 expression, ROS production, and pro-inflammatory cytokine secretions in bone marrow-derived macrophages (BMDMs) from wildtype (AMPKβ1^fl/fl) mice but only VAS2870 inhibited these effects of LPSs in AMPKβ1^LysM BMDMs. Furthermore, in macrophage cells (RAW 264.7), both SS and VAS2870 inhibited ROS production and the secretion of pro-inflammatory cytokines and reversed the impaired autophagy induced by LPSs. These data suggest that inhibiting NOX2 can reduce inflammation independent of AMPK in colitis.

A33 EFFECTS OF THE NEXT GENERATION PROBIOTIC, AKKERMANSIA MUCINIPHILA, ON INTESTINAL INFLAMMATION AND BARRIER FUNCTION

Background

Inflammatory bowel disease (IBD), characterised by chronic intestinal inflammation, is hypothesised to arise from the interplay between susceptibility genes, the immune system, environmental factors, and gut microbiota. Akkermansia muciniphila is a symbiotic bacterium that accounts for 1-5% of the human fecal microbiota. This microbe has been hailed as a next-generation probiotic, principally with regard to its plethora of beneficial host interactions, including the ability to influence mucin secretion and strengthen the intestinal barrier.

Purpose

Though a clear-cut role and mechanism by which A. muciniphila influences inflammatory conditions is unknown, evidence indicates this microbe is depleted in IBD, suggesting it may have protective effects that are lost in these conditions. Here, we investigate the role and mechanism of A. muciniphila in intestinal inflammation and its influence on intestinal barrier function by utilizing barrier-disrupting models of colitis.

Method

Across several experimental models of intestinal inflammation including the chemically-induced dextran sulphate sodium (DSS) model, the parasitic-based model of Trichuris muris infection, and the spontaneous Muc2-/- model, A.muciniphila was administered by oral gavage. Disease activity index, macroscopic scoring and histological scoring were all performed to assess the severity of intestinal inflammation. Various pro- and anti-inflammatory cytokines were assessed within colonic tissue using commercially available ELISA kits.To investigate the effects that A. muciniphila has on barrier function in the context of colitis, reverse transcriptase qPCR was used to explore several factors, including several TJPs, AMPs, and mucins. To analyse the composition of the microbiota and changes in diversity with A. muciniphila supplementation, 16S rRNA sequencing of fecal samples was performed.

Result(s)

Though only minor benefits were derived from this microbe in germ-free mice, in specific pathogen-free (SPF) mice, administration of pasteurized A. muciniphila in a DSS recovery model ameliorated inflammation severity and promoted recovery compared to controls. When gavaged prior to DSS administration, both live and pasteurized A. muciniphila failed to diminish inflammatory markers indicating minimal preventative effects. T. muris-infected SPF mice treated with live A. muciniphila showed increased levels of Th2 and anti-inflammatory cytokines, decreased worm burden, and enhanced levels of the mucin, Muc5ac, compared with those receiving control broth or pasteurized bacteria. Further, both live and pasteurized A. muciniphila ameliorated the severity of inflammation in a mucin 2 deficient (Muc2^-/-) mouse model of spontaneous colitis, indicating that these protective effects are Muc2-independent.

Conclusion(s)

These observations provide us not only with an enhanced understanding of the role A. muciniphila plays in the pathogenesis of intestinal inflammatory conditions but also may fuel novel avenues of treatment for those with IBD.

Please acknowledge all funding agencies by checking the applicable boxes below

CIHR

Disclosure of Interest

None Declared

Disruption of autophagy by increased 5-HT alters gut microbiota and enhances susceptibility to experimental colitis and Crohn's disease

Autophagy, an essential intracellular recycling process, is linked to the pathogenesis of various diseases including Crohn’s disease (CD). Factors that lead to the development of impaired autophagy during intestinal inflammation remain largely unexplored. Here, we report the impact of the interaction between serotonin [5-hydroxytryptamine;(5-HT)] and autophagy in colitis in mouse and human studies. In mice, increased gut 5-HT inhibited autophagy and led to enhanced colitis susceptibility. Reciprocally, mice with reduced 5-HT exhibited up-regulated autophagy via the mammalian target of rapamycin pathway, which resulted in significantly decreased colitis. Deletion of autophagy gene, Atg7, in an epithelial-specific manner, in concert with reduced 5-HT, promoted the development of a colitogenic microbiota and abolished the protective effects conferred by reduced 5-HT. Notably, in control and patient peripheral blood mononuclear cells, we uncovered that 5-HT treatment inhibited autophagy. Our findings suggest 5-HT as a previously unidentified therapeutic target in intestinal inflammatory disorders such as CD that exhibits dysregulated autophagy.

A51 ENTERIC PARASITE INFECTION-INDUCED ALTERATION OF THE GUT MICROBIOTA REGULATES INTESTINAL GOBLET CELL BIOLOGY AND MUCIN PRODUCTION VIA TLR2 SIGNALING

Background

Goblet cells (GCs) are the major source of mucin which are the main components of the mucus layer that represents the front line of innate defense in the gastrointestinal (GI) tract. Hyperplasia of GCs and increased mucin production are observed in many enteric nematode infections such as Trichuris muris infection. Increased mucin production contributes to parasite clearance by trapping in mucus and inhibiting motility. The GI tract contains trillions of commensal microbes, and these microbes control mucin production from GCs by activating different signaling cascades. During nematode parasite infection due to the coexistence of parasites and microbiota in close proximity of GCs in gut, it is likely that this nematode-microbiota interaction plays an important role in mucin production. Toll-like receptors (TLRs), components of the innate immune system, sense gut microbiota stimuli. The human GC-like cell line, LS174T, expresses TLR2 mRNA which was enhanced by stimulation with synthetic TLR2 ligands. We hypothesize T. muris-induced altered microbiota modulates GC response and mucin production via TLR2 signaling.

Aims

To elucidate the role of T. muris-induced altered gut microbiota in the regulation of intestinal GC response and mucin production via host TLR2 signaling.

Methods

C57BL/6 mice were infected by gavage with ~300 T. muris eggs and infectivity was confirmed by worm burden. Microbiota was analyzed by 16s rRNA sequencing. Colonic GCs response, mucins and TLR2 expression and cytokines production were assessed in germ-free (GF) mice receiving non-infected and T. muris-infected microbiota (collected on day 36 post-infection to exclude worms). Muc2 and Muc5ac expression were assessed in wild-type (WT) and TLR2 deficient (TLR2-/-) mice transplanted with T. muris-infected microbiota following antibiotic treatment.

Results

We observed a difference in microbial composition between non-infected and T. muris infected mice. Transfer of T. muris-infected microbiota into GF mice significantly increased GC numbers and TLR2 expression as well as up-regulated Muc2 and Muc5ac expression and IL-4, IL-13 production compared to GF mice with non-infected microbiota. Antibiotic-treated TLR2-/- mice after receiving microbiota from T. muris-infected mice showed significantly decreased expression of Muc2 and Muc5ac compared to antibiotic-treated WT mice receiving the same microbiota.

Conclusions

T. muris-induced altered microbiota influences intestinal GC response and mucin production via TLR2. In addition to enhancing our understanding on the interaction of parasite with resident microbiota in host defense, this study provides new information on TLR2 based innate signaling in the regulation of GC biology and mucin production.

Funding Agencies

NSERC

A219 PROTECTIVE EFFECTS OF AKKERMANSIA MUCINIPHILA ON INTESTINAL BARRIER FUNCTION AND INFLAMMATION

Background

Akkermansia muciniphila, an anaerobic gram-negative bacteria, accounts for ~3% of human gut microbiota. Despite its mucolytic nature, A. muciniphila has been shown to stimulate mucin production, enhance anti-inflammatory regulatory T cell proliferation and improve gut barrier integrity. Interestingly, an inverse relationship has been established between A. muciniphila and several disease states including inflammatory bowel disease (IBD) suggesting it may have protective and anti-inflammatory effects. However, the precise role and mechanism of A. muciniphila in the pathogenesis of colitis remains unknown. Thus, we hypothesize that A. muciniphila may induce protective effects on intestinal inflammation by influencing host immune response and epithelial barrier integrity.

Aims

(1) To investigate the protective role of A. muciniphila in intestinal inflammation in a chemically induced model of IBD and (2) to investigate the protective role of A. muciniphila in intestinal inflammation and host defense in a model of enteric parasitic infection.

Methods

Colitis was induced in germ-free C57BL/6 mice with 2.5% dextran sulphate sodium (DSS) after treatment with either C57BL/6 wild-type (WT) cecal contents or WT cecal contents supplemented with A. muciniphila. Colitis severity was assessed by disease activity index (DAI), macroscopic and histological scores, myeloperoxidase (MPO) assay and cytokine expression. In addition, colitis was induced by Trichuris muris, an intestinal nematode, following treatment with A. muciniphila. Post-infection, the severity of intestinal inflammation was assessed by worm burden, goblet cell staining, cytokines analysis, MPO activity and Muc2 expression. Microbial composition was assessed by 16s rRNA gene sequencing.

Results

In preliminary studies, mice treated with A. muciniphila and administered DSS for 5 days yielded a significant decrease in DAI, macroscopic scoring, and MPO values compared with controls. IL-10 was also elevated in mice receiving A. muciniphila. Groups receiving A. muciniphila in the T. muris model trended toward decreased worm burden, IL-4, IL-13, as well as increased levels of IL-10, goblet cell expression, and Muc2 and Muc5ac expression. A significant decrease in MPO activity was also observed in the group receiving the A. muciniphila-supplemented gavage. Microbial analysis indicated that 3 weeks post-gavage Akkermansia levels were significantly elevated in groups receiving the A. muciniphila-supplemented WT cecal contents versus WT alone. This significance was maintained post-T. muris infection.

Conclusions

These findings suggest that A. muciniphila may have a protective role in the context of intestinal inflammation. This research has the potential to fuel the development of novel treatments by utilizing this protective role in IBD.

Funding Agencies

CIHR

A209 ROLE OF SEROTONIN-AUTOPHAGY AXIS IN REGULATION OF EPITHELIAL CELL FUNCTION AND MICROBIOTA COMPOSITION IN GUT

Background

Serotonin (5-hydroxytryptamine; 5-HT), an enteric signalling molecule mainly produced by the enterochromaffin (EC) cells of the intestinal epithelium regulates various processes of the gut. Tryptophan hydroxylase 1 (Tph1) is the rate-limiting enzyme of 5-HT biosynthesis in EC cells. In inflammatory bowel disease (IBD) and experimental colitis, there are alterations in 5-HT content and microbiota composition in the gut. Previously we reported, Tph1-deficient (Tph1-/-) mice with reduced 5-HT in the gut exhibit reduced susceptibility to colitis. The mechanism by which 5-HT regulates colitis is unknown. Autophagy, a catabolic process regulates the function of intestinal epithelial cells (IECs), gut microbiota, and protects against intestinal inflammation. Both aberrant 5-HT signalling and autophagy is implicated in colitis. It is unclear whether they interact in regulation of production of pro-inflammatory cytokines from IECs and gut microbiota composition in relation to colitis. Our hypothesis is, an increase in 5-HT signalling inhibits autophagy in the IECs, which results in up-regulation of colitis by increasing the production of pro-inflammatory cytokines, and by selection for a more colitogenic microbiota.

Aims

To define the role of 5-HT-autophagy axis in the production of pro-inflammatory cytokines from IECs and gut microbiota composition in intestinal inflammation.

Methods

We investigated level of autophagy with or without 5% dextran sodium sulphate (DSS) in colons, mucosal scraping and IECs of Tph1-/- and their wild-type (WT) littermates. In addition, autophagy and proinflammatory cytokine production were investigated in human colonic epithelial cells (HT-29) following stimulation by 5-HT. We evaluated colitis and gut microbiota composition in WT, Tph1-/-, epithelial-specific autophagy gene Atg7 deficient (Atg7ΔIEC), and Atg7ΔIECTph1-/- (double knock out; DKO) mice.

Results

Tph1 -/- mice, with less 5-HT in the gut than WT mice following DSS administration exhibited an up-regulation of autophagy markers in the colon, mucosal scraping and IECs along with reduction of colitis severity. 5-HT treatment of HT-29 cells resulted in down-regulation of autophagy and upregulation of pro-inflammatory cytokine, IL-8. DKO mice exhibited increased severity of DSS-colitis, and altered microbiota composition compared to Tph1-/- mice.

Conclusions

These findings suggest, an increase in 5-HT in colitis inhibits autophagy in the IECs that contribute to alteration of the gut microbiota and disease severity. Blocking 5-HT signalling may promote autophagy in the IECs and alleviate the severity of colitis. Understanding the contribution of 5-HT in autophagy may identify new therapeutic target in IBD and other intestinal inflammatory conditions that exhibit dysregulated autophagy.

Funding Agencies

CAG, CIHR

Autophagy: roles in intestinal mucosal homeostasis and inflammation

The intestinal mucosa is a site of multiple stressors and forms the barrier between the internal and external environment. In the intestine, a complex interplay between the microbiota, epithelial barrier and the local immune system maintains homeostasis and promotes a healthy gut. One of the major cellular catabolic processes that regulate this homeostasis is autophagy. Autophagy is required to maintain anti-microbial defense, epithelial barrier integrity and mucosal immune response. Dysregulation of the autophagy process causes disruption of several aspects of the intestinal epithelium and the immune system that can lead to an inappropriate immune response and subsequent inflammation. Genome-wide association studies have found an association between several risk loci in autophagy genes and inflammatory bowel disease. The aim of the current review is to provide an update on the role of autophagy in intestinal mucosal physiology and in the control of inappropriate inflammation.

First Report of the Aecial State of Melampsora larici-populina on Larix spp. in North America

Melampsora larici-populina Kleb. was reported for the first time in eastern North America during 2002, on Populus spp., its telial host (1). M. larici-populina, a heteroecious rust, alternates between species of Populus and Larix. Since M. larici-populina was observed again in 2003, we investigated the possibility that its basidiospores may infect larch (Larix spp.) resulting in spermogonia and aecia. Identification of Melampsora species from aeciospore morphology is difficult but urediniospores are distinctive. This is important since the native M. medusae also alternates between Populus and Larix spp. During the spring of 2004, aecia were observed on needles of exotic (Larix decidua Mill. and L. leptolepis (Siebold and Zucc.) Gordon) and indigenous (L. laricina (K. Koch)) larch in an arboretum in Lotbinière (Quebec, Canada) where M. larici-populina has previously been found. Larch needles with yellow blister-like fructifications were collected in May 2004 and fixed on top of petri plates to allow aeciospore release onto leaves of Jackii poplar (Populus balsamifera L. × P. deltoides Marsh.). After approximately 10 days, uredinia appeared on the abaxial surface of the poplar leaves. Some of the many needles collected yielded uredinia cultures on Jackii poplars. The majority of these cultures were identified as being M. larici-populina; one was M. medusae. M. larici-populina urediniospores were 32 to 48 μm long and possessed a characteristic apical bald spot. DNA was extracted from aecia and uredinia, and the internal transcribed spacer (ITS) of the ribosomal RNA gene was amplified in real-time polymerase chain reaction (PCR) by specific primers for M. medusae or M. larici-populina created from sequences (GenBank Accession Nos. AY429656 and AY429657). The 120 base pairs target fragments amplified only with the M. larici-populina specific primers with the 14 samples that were identified as M. larici-populina by morphological characteristics of the urediniospores. No PCR amplification was obtained with M. medusae primers. These results were not unexpected since larch has been previously reported as an aecial host of M. larici-populina elsewhere (2). The ability of M. larici-populina to overwinter and complete its life cycle has important consequences since it proves that it is established and can go through sexual reproduction. A complete life cycle in eastern North America may allow M. larici-populina to generate pathogenic variation that will challenge poplar breeders in this region. References: (1) L. Innes et al. Plant Dis. 88:85, 2004. (2) G. Newcombe et al. Plant Dis. 78:1218, 1994.

Knowledge, perception and behaviour of the general public concerning the addition of fluoride in drinking water

A telephone survey was carried out in 1994, in the Quebec City region, among 1006 people living in two municipalities where tap water is fluoridated and 1003 people living in two municipalities where there is no fluoridation. Knowledge of the main benefit associated with the use of fluoride (prevention of tooth decay) in drinking water was not different in fluorated versus non-fluoridated municipalities (20.4% vs 19.4%, p = 0.57). Knowledge of its main disadvantage (increase of dental fluorosis) was very low and similar in both groups (3.1% vs 2.0%, p = 0.11). Opposition to fluoridation was slightly higher in fluoridated areas (22.0% vs 18.3%, p = 0.04), and the use of fluoridated supplements for children was much less important in fluoridated areas (4.4% vs 12.4%, p = 0.001). No changes in the measures of association (odds ratios) were found after adjustment for the different characteristics of the participants (age, family income, education). Opposition to fluoridation was lower among those who believed their tap water was fluoridated (even if not): 19.9% vs 34.5%, p < 0.001. This study demonstrates that there is still need for public health education on the uses of fluorides.

Cyclic stretching force selectively up-regulates transforming growth factor-beta isoforms in cultured rat mesangial cells

Glomerular distention from increased intraglomerular pressure stretches mesangial cells (MCs). Stretching MCs in culture stimulates extracellular matrix accumulation, suggesting that this may be a mechanism for glomerular hypertension-associated glomerulosclerosis. We examined whether mechanical stretching serves as a stimulus for the synthesis and activation of the prosclerotic molecule transforming growth factor (TGF)-beta, thus providing a potential system for auto-induction of extracellular matrix. Rat MCs cultured on flexible-bottom plates were subjected to cyclic stretching for up to 3 days and then assayed for TGF-beta mRNA, secretion of TGF-beta, and localization of active TGF-beta by immunostaining. MCs contained mRNA for all three mammalian isoforms of TGF-beta. Cyclic stretching for 36 hours increased TGF-beta1 and TGF-beta3 mRNA levels approximately twofold, without altering the levels of TGF-beta2 mRNA. This was followed at 48 to 72 hours by the increased secretion of both latent and active TGF-beta1. Latent, but not active, TGF-beta3 secretion also increased whereas the levels of TGF-beta2 were unaffected by mechanical force. The stretching force in this system is unequally distributed over the culture membrane. Localization of active TGF-beta by immunostaining demonstrated that the quantity of cell-associated cytokine across the culture was directly proportional to the zonal amplitude of the stretching force. These results demonstrate that stretching force stimulates MCs to selectively release and activate TGF-beta1. This mechanical induction of TGF-beta1 may help explain the increased extracellular matrix associated with intraglomerular hypertension.

Weighing contaminant risks and nutrient benefits of country food in Nunavik

In view of the levels of human exposure to priority contaminants assessed in previous surveys in Nunavik, a series of risk reduction scenarios were produced to modelize the effects of different potential health advisories on limiting exposure of women of reproductive age to these contaminants, as well as on maximizing nutritional benefits derived from the consumption of country food. This paper presents part of the results, in particular as regards effects of reducing PCB intake by 46%, 65% and 86%.

Induction of interleukin-6 in axotomized sensory neurons

RNA from rat dorsal root ganglia was analyzed in search of potentially beneficial cytokines that are induced in dorsal root ganglia by nerve injury. By reverse transcription, the PCR, and Southern blotting, interleukin-6 mRNA was detected during development but not in normal adult dorsal root ganglia, reappeared within 1 d of sciatic nerve transection, was maximally increased after 2 and 4 d, and decreased below the threshold of detection within 1 week. By RNase protection assay, interleukin-6 mRNA was consistently present in RNA from dorsal root ganglia removed from rats 4 d following transection but not in control dorsal root ganglia. Interleukin-6 bioactivity was also present in dorsal root ganglia following nerve injury. By in situ hybridization, interleukin-6 mRNA was localized within large and medium-sized axotomized neurons. In summary, some sensory neurons respond to axotomy with a brisk transient increase in synthesis of interleukin-6. Injury to the sciatic nerve also induced mRNAs for interleukin-1 beta and tumor necrosis factor-alpha in dorsal root ganglia. The inductions of interleukin-1 beta and tumor necrosis factor-alpha mRNAs were later and more sustained than that of interleukin-6 mRNA. The cellular sources of these two cytokines have not been defined.

Seroepidemiologic study of three zoonoses (leptospirosis, Q fever, and tularemia) among trappers in Québec, Canada

This study was undertaken to evaluate the prevalence of antibodies against Francisella tularensis, Coxiella burnetii, and certain serovars of Leptospira interrogans among trappers in Québec, Canada. Muskrat trapping was identified as a risk factor for F. tularensis infection, whereas having a cat at home apparently protected trappers against infection by L. interrogans. High percentages of control sera were positive for antibodies against C. burnetii (15%) and L. interrogans (5%), most frequently serovar bratislava. This is the first report of human infection by serovar bratislava in North America.

Colocalization of NGF binding sites, trk mRNA, and low-affinity NGF receptor mRNA in primary sensory neurons: responses to injury and infusion of NGF

The distributions of mRNAs for the protooncogene trk and the low-affinity NGF receptor (LNGFR) were studied by hybridization with oligonucleotide probes on sections of adult rat primary sensory and sympathetic ganglia. For comparison with high-affinity binding sites, adjacent sections were processed for NGF receptor radioautography. Among neurons in lumbar dorsal root ganglia and trigeminal ganglia, trk mRNA and NGF-binding sites were closely colocalized; this finding together with previous direct evidence in other cell types is taken to indicate that trk protein is an essential component of the high-affinity NGF receptor in adult sensory neurons. In lumbar dorsal root ganglia and trigeminal ganglia, abundant LNGFR mRNA was found in all neurons with strong 125I-NGF labeling and on additional neurons lacking high-affinity NGF-binding sites. The presence of abundant LNGFR in neurons with high-affinity receptors could be the cause and/or consequence of their ability to respond to NGF. Neurons with abundant LNGFR mRNA but few high-affinity NGF-binding sites may have receptors for other members of the neurotrophin family. In nodose ganglia, neurons with high concentrations of LNGFR mRNA greatly outnumbered the small percentage with abundant trk mRNA. Following intrathecal infusion of NGF to otherwise normal dorsal root ganglia, the concentrations of LNGFR mRNA but not those of trk mRNA and NGF-binding sites were increased in NGF-responsive neurons. The usual single normal pattern of frequency histograms of LNGFR labeling indices became bimodal in response to NGF. Concentrations of NGF-binding sites, LNGFR mRNA, and trk mRNA were all decreased by peripheral nerve transection and restored by exogenous NGF, the restoration being complete for LNGFR mRNA and partial for trk mRNA and NGF-binding sites. The data indicate that NGF can regulate both LNGFR and trk mRNAs but do not clarify the possible contribution of the LNGFR protein to high-affinity binding sites.

KpnI RFLP at the human muscle-type phosphofructokinase (PFKM) gene locus

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NcoI RFLP in human brain creatine kinase gene (CKBB)

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