Host-recognition of pathogens and commensals in the mammalian intestine.

To peacefully coexist with the microbial inhabitants of the intestine, mammals have evolved elaborate and interconnected regulatory mechanisms to maintain immune homeostasis in the face of potential infection and tissue damage by pathogenic microorganisms. Physical barriers, antimicrobial factors and secretory antibodies act in concert to keep microbes at a distance from the epithelium and initiate repair mechanisms in the event of damage. Commensal bacteria are not ignored but dynamically controlled via many complex overlapping and intertwined mechanisms involving intestinal epithelial cells (IECs) and signals from the microbiota. Polarized IECs play a decisive role in homeostasis by regulating the expression and activity of the pattern-recognition receptors (PRRs), in different compartments of the intestine. The differential signaling and expression of receptors on apical and basal membranes of the epithelium also plays its part in distinguishing commensals from harmful invaders. In steady state conditions macrophages and dendritic cells (DCs) in the lamina propria (LP) are conditioned by environmental factors to induce immune tolerance. The distinction between pathogen and non-pathogen is linked to the ability of pathogens to invade and cause damage to the host cells and tissues. This induces local inflammatory responses and the attraction of capillary leukocytes by chemokines released from colonized and invaded epithelial cells. This bypasses the tolerogenic mechanisms controlling the responses of resident DCs and macrophages leading to pathogen killing and adaptive immune responses. Research on this topic has important implications for the development of novel therapeutic approaches to treat or prevent inflammatory bowel disease (IBD), inflammation-related cancer and other gut-related diseases and disorders.

Epithelial crosstalk at the microbiota-mucosal interface.

This article provides an overview of how intestinal epithelial cells (IEC) recognize commensals and how they maintain host-bacterial symbiosis. Endocrine, goblet cells, and enterocytes of the intestinal epithelium express a range of pattern recognition receptors (PRR) to sense the presence of microbes. The best characterized are the Toll-like receptors (TLR) and nucleotide oligomerization domain-like receptors (NLR), which play a key role in pathogen recognition and the induction of innate effectors and inflammation. Several adaptations of PRR signaling have evolved in the gut to avoid uncontrolled and potentially destructive inflammatory responses toward the resident microbiota. PRR signaling in IEC serve to maintain the barrier functions of the epithelium, including the production of secretory IgA (sIgA). Additionally, IECs play a cardinal role in setting the immunosuppressive tone of the mucosa to inhibit overreaction against innocuous luminal antigens. This includes regulation of dendritic cells (DC), macrophage and lymphocyte functions by epithelial secreted cytokines. These immune mechanisms depend heavily on IEC recognition of microbes and are consistent with several studies in knockout mice that demonstrate TLR signaling in the epithelium has a profoundly beneficial role in maintaining homeostasis.

[Accidents among postmen using motorbikes for mail deliveries in Tuscany in the period 2007-2009]. / Gli infortuni negli addetti ai recapiti postali in servizio con il motomezzo in Toscana negli anni 2007-2009.

BACKGROUND: Health risks for postmen using motorbikes for mail delivery may be influenced by stability, weight and ease of handling of the vehicle, traffic and slippery or irregular road surface. OBJECTIVES: To describe accidents that occurred among postmen in Tuscany and evaluate how many of these would have been prevented using the UNI EN 13595/2004 safety jacket. METHODS: Record linkage of data obtained from the employer--the main mail delivery company in Italy--and from the Italian Workers Compensation Authority on accidents that occurred in postmen in Tuscany who used motorbikes for deliveries during the period 2007-2009. Accident rates (with CI 95%) by age, sex, year and province were calculated; the differences were evaluated using chi2 test. RESULTS: 1,342 accidents requiring at least 3 days' sick absence were recorded in postmen in Tuscany in the period 2007-2009, with an increasing trend in young men. The average accident rate was 17.6 per 100 workers, with 42,419 sick absence days. The female rate was higher compared to men (19.4%, CI 95% 18.03-20.79 in women vs 15.5%, CI 95%: 14.15-16.89 in men). 68% of accidents occurred driving a motorbike. The index of severity was 6.79, which was higher than that calculated by INAIL for the whole Tuscan transport and communication work sector (5.31). 309 accidents (11,021 sick absence days) could have been mitigated or avoided using UNI EN 13595/2004 safety jackets (47% spinal, 30% shoulder, 23% elbow, arm and forearm). CONCLUSIONS: The frequency of accidents in postmen using motorbikes is extremely high. Several serious accidents could have been prevented using the UNI EN 13595/2004 safety jackets, suggesting the need to make their use obligatory by these workers.

The vasoactive peptides urotensin II and urotensin II-related peptide regulate astrocyte activity through common and distinct mechanisms: involvement in cell proliferation.

UII (urotensin II) and its paralogue URP (UII-related peptide) are two vasoactive neuropeptides whose respective central actions are currently unknown. In the present study, we have compared the mechanism of action of URP and UII on cultured astrocytes. Competition experiments performed with [125I]UII showed the presence of very-high- and high-affinity binding sites for UII, and a single high-affinity site for URP. Both UII and URP provoked a membrane depolarization accompanied by a decrease in input resistance, stimulated the release of endozepines, neuropeptides specifically produced by astroglial cells, and generated an increase in [Ca2+]c (cytosolic Ca2+ concentration). The UII/URP-induced [Ca2+]c elevation was PTX (pertussis toxin)-insensitive, and was blocked by the PLC (phospholipase C) inhibitor U73122 or the InsP3 channel blocker 2-APB (2-aminoethoxydiphenylborane). The addition of the Ca2+ chelator EGTA reduced the peak and abolished the plateau phase, whereas the T-type Ca2+ channel blocker mibefradil totally inhibited the Ca2+ response evoked by both peptides. However, URP and UII induced a mono- and bi-phasic dose-dependent increase in [Ca2+]c and provoked short- and long-lasting Ca2+ mobilization respectively. Similar mono- and bi-phasic dose-dependent increases in [3H]inositol incorporation into polyphosphoinositides in astrocytes was obtained, but the effect of UII was significantly reduced by PTX, although BRET (bioluminescence resonance energy transfer) experiments revealed that both UII and URP recruited Galphao-protein. Finally, UII, but not URP, exerted a dose-dependent mitogenic activity on astrocytes. Therefore we described that URP and UII exert not only similar, but also divergent actions on astrocyte activity, with UII exhibiting a broader range of activities at physiological peptide concentrations.

Faecalibacterium prausnitzii A2-165 has a high capacity to induce IL-10 in human and murine dendritic cells and modulates T cell responses.

Faecalibacterium prausnitzii strain A2-165 was previously reported to have anti-inflammatory properties and prevent colitis in a TNBS model. We compared the immunomodulatory properties of strain A2-165 to four different F. prausnitzii isolates and eight abundant intestinal commensals using human dendritic cells (DCs) and mouse BMDCs in vitro. Principal component analysis revealed that the cytokine response to F. prausnitzii A2-165 is distinct from the other strains in eliciting high amounts of IL-10 secretion. The mouse DNBS model of relapsing IBD was used to compare the protective effects of F. prausnitzii A2-165 and Clostridium hathewayi, a low secretor of IL-10, on the Th1-driven inflammatory response to DNBS; attenuation of disease parameters was only observed with F. prausnitzii. In an in vivo mouse model of nasal tolerance to ovalbumin, F. prausnitzii A2-165 enhanced ovalbumin-specific T cell proliferation and reduced the proportion of IFN-γ(+) T cells in CLNs. Similarly, in vitro F. prausnitzii A2-165 stimulated BMDCs increased ovalbumin-specific T cell proliferation and reduced the number of IFN-γ(+) T cells. These mechanisms may contribute to the anti-inflammatory effects of F. prausnitzii in colitis and support the notion that this abundant bacterium might contribute to immune homeostasis in the intestine via its anti-inflammatory properties.

Faecalibacterium prausnitzii Strain HTF-F and Its Extracellular Polymeric Matrix Attenuate Clinical Parameters in DSS-Induced Colitis.

A decrease in the abundance and biodiversity of intestinal bacteria within the Firmicutes phylum has been associated with inflammatory bowel disease (IBD). In particular, the anti-inflammatory bacterium Faecalibacterium prausnitzii, member of the Firmicutes phylum and one of the most abundant species in healthy human colon, is underrepresented in the microbiota of IBD patients. The aim of this study was to investigate the immunomodulatory properties of F. prausnitzii strain A2-165, the biofilm forming strain HTF-F and the extracellular polymeric matrix (EPM) isolated from strain HTF-F. For this purpose, the immunomodulatory properties of the F. prausnitzii strains and the EPM were studied in vitro using human monocyte-derived dendritic cells. Then, the capacity of the F. prausnitzii strains and the EPM of HTF-F to suppress inflammation was assessed in vivo in the mouse dextran sodium sulphate (DSS) colitis model. The F. prausnitzii strains and the EPM had anti-inflammatory effects on the clinical parameters measured in the DSS model but with different efficacy. The immunomodulatory effects of the EPM were mediated through the TLR2-dependent modulation of IL-12 and IL-10 cytokine production in antigen presenting cells, suggesting that it contributes to the anti-inflammatory potency of F. prausnitzii HTF-F. The results show that F. prausnitzii HTF-F and its EPM may have a therapeutic use in IBD.

[Survey on health status of workers exposed in the past to carcinogens in a glass factory in Leghorn, Italy]. / Indagine sullo stato di salute di ex-esposti ad agenti cancerogeni di una vetreria industriale.

BACKGROUND: For a few years now in Italy there has been wide discussion on the advisability of developing health surveillance programmes for workers who were exposed to occupational carcinogens in the past (incompliance with Italian D.Lgs. 626/94, art. No. 69). The purpose of the present paper was to contribute to the discussion on operative guidelines for public or private Occupational Health Services intending to address this issue. METHODS: A cross-sectional survey was undertaken on former workers of a glass factory located in Leghorn, Italy. Six hundred and seventy-seven workers discharged in the period 1/1/1942 - 30/6/1992, with at least 1 year of service, resident in the area of Leghorn, were identified from the personnel records of the company and invited to medical examination at the local public Occupational Health Service. A structured questionnaire was developed in order to standardize the collection of occupational and health histories. RESULTS: 370 subjects were examined and for each of them occupational and health histories were collected. Occupational exposure to carcinogens in the factory in the last decades was reconstructed using the workers' occupational histories and the available plant records: 3 periods with different production activities (1942/49, 1950/69, 1970/92), and 4 main carcinogens (asbestos, PAH, silica and glass fibres) were identified. Thirty cancers were recorded and 10 of these were occupationally related. CONCLUSIONS: The health survey allowed occupational exposures to carcinogens to be defined in a factory where historical environmental data were not available. It was also possible to assess individual past occupational risk and provide information to each former worker on his risk, on available preventive measures, and on possible diagnostic, therapeutic and insurance procedures available in relation to diseases related to the different hazards. Via this survey it was also possible to identify and notify the Italian Institute of Insurance against Occupational Diseases and Accidents of 6 cases of bladder cancer, i.e., cancers with long survival that would be impossible to identify via current health data bases.

Vectorial secretion of interleukin-8 mediates autocrine signalling in intestinal epithelial cells via apically located CXCR1.

BACKGROUND: In the intestinal mucosa, several adaptations of TLR signalling have evolved to avoid chronic inflammatory responses to the presence of commensal microbes. Here we investigated whether polarized monolayers of intestinal epithelial cells might regulate inflammatory responses by secreting IL-8 in a vectorial fashion (i.e. apical versus basolateral) depending on the location of the TLR stimulus. RESULTS: In the Caco-2 BBE model of polarized villus-like epithelium, apical stimulation with TLR2 and TLR5 ligands resulted in the apical secretion of IL-8. The CXCR1 receptor for IL-8 was expressed only on the apical membrane of Caco-2 BBE cells and differentiated epithelial cells in the human small intestine and colon. Transcriptome analyses revealed that Caco-2 BBE cells respond to stimulation with IL-8 supporting the hypothesis that IL-8 induces G protein-coupled receptor signalling. CONCLUSIONS: These results show that IL-8 induces autocrine signalling via an apical CXCR1 in Caco-2 BBE intestinal epithelial cells and that this receptor is also expressed on the apical surface of differentiated human intestinal epithelial cells in vivo, suggesting an autocrine function for IL-8 secreted in the lumen.