Role of chitosan in intestinal integrity: TLR4 and IFNAR signaling in the induction of E-cadherin and CD103 in mice.

Chitin and its derivative chitosan (Q) are abundant structural elements in nature. Q has modulatory and anti-inflammatory effects and also regulates the expression of adhesion molecules. The interaction between cells expressing the αEß7 integrin and E-cadherin facilitates tolerogenic signal transmission and localization of lymphocytes at the frontline for interaction with luminal antigens. In this study we evaluated the ability of orally administered Q to stimulate E-cadherin and CD103 expression in vitro and in vivo. Our findings show that Q promoted epithelial cell migration, accelerated wound healing and increased E-cadherin expression in IEC-18 cells and isolated intestinal epithelial cells (IECs) after Q feeding. The upregulation of E-cadherin was dependent on TLR4 and IFNAR signaling, triggering CD103 expression in lymphocytes. Q reinforced the E-cadherin-αEß7 axis, crucial for intestinal barrier integrity and contributed to the localization of lymphocytes on the epithelium.

Luminal bacteria coated with IgA and IgG during intestinal inflammation as a new and abundant stimulus for colonic macrophages.

In the gut, secretory immunoglobulin A is the predominant humoral response against commensals, although healthy hosts also produce microbiota-specific IgG antibodies. During intestinal inflammation, the content of IgG in the lumen increases along with the proportion of commensal bacteria coated with this antibody, suggesting signalling through the IgG-CD64 axis in the pathogenesis of inflammatory bowel diseases. In this work, we evaluated day by day the frequency of faecal bacteria coated with IgA and IgG during the development of DSS colitis. We studied the phenotype and phagocytic activity of F4/80+ CD64+ colonic macrophages, as well as the production of cytokines and nitric oxide by lamina propria or bone marrow-derived macrophages after stimulation with IgA+ , IgG+ and IgA+ IgG+ bacteria. We found that the percentage of faecal IgA+ IgG+ double-coated bacteria increased rapidly during DSS colitis. Also, analysis of the luminal content of mice with colitis showed a markedly superior ability to coat fresh bacteria. IgA+ IgG+ bacteria were the most potent stimulus for phagocytic activity involving CD64 and Dectin-1 receptors. IgA+ IgG+ bacteria observed during the development of DSS colitis could represent a new marker to monitor permeability and inflammatory progression. The interaction of IgA+ IgG+ bacteria with CD64+ F4/80+ macrophages could be part of the complex cascade of events in colitis. Interestingly, after stimulation, CD64+ colonic macrophages showed features similar to those of restorative macrophages that are relevant for tissue repair and healing.

Network Analysis of Inflammatory Bowel Disease Research: Towards the Interactome.

BACKGROUND AND AIMS: Modern views accept that inflammatory bowel diseases [IBD] emerge from complex interactions among the multiple components of a biological network known as the 'IBD interactome'. These diverse components belong to different functional levels including cells, molecules, genes and biological processes. This diversity can make it difficult to integrate available empirical information from human patients into a collective view of aetiopathogenesis, a necessary step to understand the interactome. Herein, we quantitatively analyse how the representativeness of components involved in human IBD and their relationships ha ve changed over time. METHODS: A bibliographic search in PubMed retrieved 25 971 abstracts of experimental studies on IBD in humans, published between 1990 and 2020. Abstracts were scanned automatically for 1218 IBD interactome components proposed in recent reviews. The resulting databases are freely available and were visualized as networks indicating the frequency at which different components are referenced together within each abstract. RESULTS: As expected, over time there was an increase in components added to the IBD network and heightened connectivity within and across functional levels. However, certain components were consistently studied together, forming preserved motifs in the networks. These overrepresented and highly linked components reflect main 'hypotheses' in IBD research in humans. Interestingly, 82% of the components cited in reviews were absent or showed low frequency, suggesting that many aspects of the proposed IBD interactome still have weak experimental support in humans. CONCLUSIONS: A reductionist and fragmented approach to the study of IBD has prevailed in previous decades, highlighting the importance of transitioning towards a more integrated interactome framework.

A selective window after the food-intake period favors tolerance induction in mesenteric lymph nodes.

Biological rhythms are periodic oscillations that occur in the physiology of the organism and the cells. The rhythms of the immune system are strictly regulated and the circadian alteration seems to have serious consequences. Even so, it is not clear how the immune cells of the intestinal mucosa synchronize with the external environment. Besides, little is known about the way in which biological rhythms affect the critical functions of intestinal immunity, such as oral tolerance. We studied fluctuations in the relevant parameters of intestinal immunity at four different times throughout the day. By using multivariate statistical tools, we found that these oscillations represent at least three different time frames with different conditions for tolerance induction that are altered in Per2ko mice lacking one of the clock genes. Our results allowed us to characterize a window in the final stage of the dark phase that promotes the induction of specific regulatory populations and favors its location in the lamina propria. We show here that, at the end of the intake, the entry of luminal antigens, soluble factors, and leukocyte populations converge in the mesenteric lymph nodes (MLN) and display the greatest potential of the tolerogenic machinery.

Soy genistein administered in soluble chitosan microcapsules maintains antioxidant activity and limits intestinal inflammation.

We used water-soluble Chitosan obtained by Maillard reaction with glucosamine to microencapsulate soy genistein (Ge) and preserve its biological activity for oral administration. Release of Ge was pH dependent with a super Case II mechanism at pH 1.2 and an anomalous transport with non-Fickian kinetics at pH 6.8. Microencapsulated Ge retained its antioxidant properties in vitro and its daily administration to mice attenuated clinical signs of acute colitis, limited inflammatory reaction and reduced oxidative stress and tissue injury as well. Remarkably, after feeding microencapsulated Ge the production of IL-10 in colonic tissue was restored to levels of untreated controls. According to statistical multivariate analysis, this cytokine was the parameter with the highest influence on the inflammatory/oxidative status. Microencapsulation of Ge with derivatized Chitosan becomes an interesting alternative to develop therapeutic approaches for oxidative inflammatory diseases; our findings suggest that the soy isoflavone could be incorporated into any functional food for application in intestinal inflammation.

Chitosan and cloxacillin combination improve antibiotic efficacy against different lifestyle of coagulase-negative Staphylococcus isolates from chronic bovine mastitis.

Bovine mastitis affects the health of dairy cows and the profitability of herds worldwide. Coagulase-negative staphylococci (CNS) are the most frequently isolated pathogens in bovine intramammary infection. Based on the wide range of antimicrobial, mucoadhesive and immunostimulant properties demonstrated by chitosan, we have evaluated therapy efficiency of chitosan incorporation to cloxacillin antibiotic as well as its effect against different bacterial lifestyles of seven CNS isolates from chronic intramammary infections. The therapeutic effects of combinations were evaluated on planktonic cultures, bacterial biofilms and intracellular growth in mammary epithelial cells. We found that biofilms and intracellular growth forms offered a strong protection against antibiotic therapy. On the other hand, we found that chitosan addition to cloxacillin efficiently reduced the antibiotic concentration necessary for bacterial killing in different lifestyle. Remarkably, the combined treatment was not only able to inhibit bacterial biofilm establishment and increase preformed biofilm eradication, but it also reduced intracellular bacterial viability while it increased IL-6 secretion by infected epithelial cells. These findings provide a new approach to prophylactic drying therapy that could help to improve conventional antimicrobial treatment against different forms of bacterial growth in an efficient, safer and greener manner reducing multiresistant bacteria generation and spread.

Migratory capacity and function of dendritic cells from mesenteric afferent lymph nodes after feeding a single dose of vitamin A.

Lamina propria dendritic cells (DCs) have a permanent turnover with constitutive migration to mesenteric lymph nodes and replenishment by progenitors. Luminal bacteria and dietary constituents provide key signals that endow DCs their unique properties in vivo. Taking into account that the intestinal immune system is greatly influenced by retinoids, we evaluated in B6 mice 3, 8, 16 and 24 h after feeding a single dose of vitamin A phenotype and function of cells present in mesenteric afferent lymph nodes as well as signals involved in migration. We studied the frequency of CD11c+MHC-II+CD103+CD86+ and RALDH+ DCs by flow cytometry, we determined CCL-21 and D6 levels in tissue homogenates by Western blot, and we co-cultured cells isolated from afferent lymphatics with sorted CD4+ lymphocytes to assess Foxp-3 induction and homing receptor expression. Sixteen hours after vitamin A administration, DCs isolated from afferent lymphatics were able to induce homing receptors and Foxp3 expression in CD4+ lymphocytes. Our results show that a single dose of vitamin A generated a stream of signals and amplified the tolerogenic activity of DCs migrating to lymphoid tissue.

Stress Induced Polarization of Immune-Neuroendocrine Phenotypes in Gallus gallus.

Immune-neuroendocrine phenotypes (INPs) stand for population subgroups differing in immune-neuroendocrine interactions. While mammalian INPs have been characterized thoroughly in rats and humans, avian INPs were only recently described in Coturnix coturnix (quail). To assess the scope of this biological phenomenon, herein we characterized INPs in Gallus gallus (a domestic hen strain submitted to a very long history of strong selective breeding pressure) and evaluated whether a social chronic stress challenge modulates the individuals' interplay affecting the INP subsets and distribution. Evaluating plasmatic basal corticosterone, interferon-γ and interleukin-4 concentrations, innate/acquired leukocyte ratio, PHA-P skin-swelling and induced antibody responses, two opposite INP profiles were found: LEWIS-like (15% of the population) and FISCHER-like (16%) hens. After chronic stress, an increment of about 12% in each polarized INP frequency was found at expenses of a reduction in the number of birds with intermediate responses. Results show that polarized INPs are also a phenomenon occurring in hens. The observed inter-individual variation suggest that, even after a considerable selection process, the population is still well prepared to deal with a variety of immune-neuroendocrine challenges. Stress promoted disruptive effects, leading to a more balanced INPs distribution, which represents a new substrate for challenging situations.

Physicochemical characterization of water-soluble chitosan derivatives with singlet oxygen quenching and antibacterial capabilities.

New water-soluble chitosan derivatives (WSCh) were obtained by Maillard reaction (MR) between glucosamine (GA) with both low and medium molecular weight chitosans (Ch). The WSCh showed larger solubility than the respective Ch, while their deacetylation degree (DD) decreased by approximately 12%. Infrared spectroscopy experiments of WSCh confirmed the formation of imine bonds after MR with intensified pyranose structure, and sugar molecules as polymer branches. However, a 6-times reduction of the molecular weight of WSCh was measured, indicating the breakdown of the polysaccharide chain during the MR. The polysaccharides quenched singlet molecular oxygen (1O2), with rate quenching constants correlating with the DD value of the samples, suggesting the important role of amino groups (-NH2) in the deactivation of 1O2. Additionally, all polysaccharides presented antimicrobial activity against pathogenic bacteria, e.g. Staphylococcus aureus, Escherichia coli, Salmonella sp., Enterococcus faecalis and Listeria ivanovii, as tested by their minimum inhibitory concentration (MIC). This way we obtained new water-soluble polysaccharides, with similar functional properties to those presented by native Ch, enhancing its potential application as carrier material for bioactive compounds.

Evaluation of the biofilm forming ability and its associated genes in Staphylococcus species isolates from bovine mastitis in Argentinean dairy farms.

Staphylococcus aureus and coagulase-negative staphylococci (CNS) are important causes of intramammary infection in dairy cattle, and their ability to produce biofilm is considered an important virulence property in the pathogenesis of mastitis. However, the published date on mechanisms and factors involved in infection persistence in the mammary gland remains unclear. The aim of this study was to investigate whether the main Staphylococcus species involved in bovine intramammary infections possess specific characteristics that promote colonization of the udder. We evaluated the biofilm-forming ability and distribution of adhesion- and biofilm-associated genes of Staphylococcus spp. isolated from bovine mastitis infected animals in Argentinean dairy farms. For this purpose, the phenotypic biofilm formation ability of 209 Staphylococcus spp. from bovine mastitis was investigated. All isolates produced biofilm in vitro, being 35,0% and 45,0% of the 127 S. aureus or 51,0% and 29,0% of the 82 CNS strong and moderate biofilm producers respectively. All S. aureus samples were PCR-positive for icaA, icaD, clfA, clfB and fnbpA genes, 76.3% were positive for fnbpB gene and 11.0% were positive for bap gene. In CNS isolates, the positive rates for icaA and icaD were 73.2%, while for clfA, clfB, fnbpA fnbpB and bap genes the percentage were lower. The results demonstrate that in Staphylococcus spp. biofilm formation, the polysaccharide and the adhesion- and biofilm-associated genes are of overall importance on bovine mastitis in Argentina. Therefore, future works should focus on these pathogenic specific factors for the development of more effective therapies of control, being essential to consider the ability of isolates to produce biofilm.

Intestinal mononuclear cells primed by systemic interleukin-12 display long-term ability to aggravate colitis in mice.

To address whether the burst of systemic interleukin-12 (IL-12) influences intestinal inflammation elicited by luminal stimuli, we induced IL-12 release by cDNA injection in C57BL/6 mice and simultaneously started dextran sulphate sodium administration. The sequence of the inflammatory response triggered by IL-12 release was characterized by assessing myeloperoxidase activity and histological damage in colon samples on days 1, 3, 5 and 7 after colitis induction. To evaluate the persistence of IL-12 priming, colitis was induced in mice 7 or 60 days after cDNA injection. Under IL-12 influence, the development of acute colitis presented a faster and selective infiltration of inflammatory mononuclear cells in the lamina propria. Recruitment was driven by systemic cytokines rather than luminal antigens. Interestingly, when colitis was triggered 7 or 60 days after the cytokine storm, cells maintained the ability to worsen clinical signs of intestinal inflammation. Together, a systemic IL-12 burst effectively primed intestinal cells that became more prone to develop inflammatory responses. Activation was long-lasting because intestinal cells maintained their inflammatory potential and their ability to aggravate colitis.

Systemic IL-12 burst expands intestinal T-lymphocyte subsets bearing the α4 ß7 integrin in mice.

The intestinal immune system is complex and displays unique anatomic and functional characteristics. Numerous immune cell subsets are located beneath the epithelial barrier and their activity is highly regulated. Using hydrodynamic shear of IL-12 cDNA to achieve systemic expression of IL-12 in mice, we evaluated the effect of a transient burst of this cytokine on the activation status of T cells from Peyer's patches (PPs), mesenteric lymph nodes (MLNs), and colonic lamina propria (LP). Following systemic IL-12 release, intestinal T lymphocytes became activated, exhibiting a CD44(high) CD62L(-) phenotype. After 5 days of the cytokine burst, the frequency of α4ß7(+) CD4(+) and CD8(+) cells increased, and CD8(+) α4ß7(+) cells mainly expressed T bet, a critical regulator of the Th1 differentiation program. The incremental increase in α4ß7 expression involved the IL-12 receptor-signal transducer and activator of transcription (STAT)-4 axis, and occurred independently of IFN-γ, IL-4, IL-10, and TNF-α signaling. Moreover, IL-12 priming exacerbated the outcome of acute dextran sodium sulphate (DSS)-induced colitis with higher scores of weight loss, blood in stool, and diarrhea and lower hematocrit. Together, our findings demonstrate that systemic polarizing signals could effectively expand the number of effector cells able to home to the LP and contribute to local inflammation.

Lack of TNFRI signaling enhances annexin A1 biological activity in intestinal inflammation.

We evaluated whether the lack of TNF-α signaling increases mucosal levels of annexin A1 (AnxA1); the hypothesis stems from previous findings showing that TNF-α neutralization in Crohn's disease patients up-regulates systemic AnxA1 expression. Biopsies from healthy volunteers and patients under anti-TNF-α therapy with remittent ulcerative colitis (UC) showed higher AnxA1 expression than those with active disease. We also evaluated dextran sulfate sodium (DSS)-acute colitis in TNF-α receptor 1 KO (TNFR1-/-) strain with impaired TNF-α signaling and C57BL/6 (WT) mice. Although both strains developed colitis, TNFR1-/- mice showed early clinical recovery, lower myeloperoxidase (MPO) activity and milder histopathological alterations. Colonic epithelium from control and DSS-treated TNFR1-/- mice showed intense AnxA1 expression and AnxA1+ CD4+ and CD8+ T cells were more frequent in TNFR1-/- animals, suggesting an extra supply of AnxA1. The pan antagonist of AnxA1 receptors exacerbated the colitis outcome in TNFR1-/- mice, supporting the pivotal role of AnxA1 in the early recovery. Our findings demonstrate that the TNF-α signaling reduction favors the expression and biological activity of AnxA1 in inflamed intestinal mucosa.

Immune neuroendocrine phenotypes in Coturnix coturnix: do avian species show LEWIS/FISCHER-like profiles?

Immunoneuroendocrinology studies have identified conserved communicational paths in birds and mammals, e.g. the Hypothalamus-Pituitary-Adrenal axis with anti-inflammatory activity mediated by glucocorticoids. Immune neuroendocrine phenotypes (INPs) have been proposed for mammals implying the categorization of a population in subgroups underlying divergent immune-neuroendocrine interactions. These phenotypes were studied in the context of the LEWIS/FISCHER paradigm (rats expressing high or low pro-inflammatory profiles, respectively). Although avian species have some common immunological mechanisms with mammals, they have also evolved some distinct strategies and, until now, it has not been studied whether birds may also share with mammals similar INPs. Based on corticosterone levels we determined the existence of two divergent groups in Coturnix coturnix that also differed in other immune-neuroendocrine responses. Quail with lowest corticosterone showed higher lymphoproliferative and antibody responses, interferon-γ and interleukin-1ß mRNA expression levels and lower frequencies of leukocyte subpopulations distribution and interleukin-13 levels, than their higher corticosterone counterparts. Results suggest the existence of INPs in birds, comparable to mammalian LEWIS/FISCHER profiles, where basal corticosterone also underlies responses of comparable variables associated to the phenotypes. Concluding, INP may not be a mammalian distinct feature, leading to discuss whether these profiles represent a parallel phenomenon evolved in birds and mammals, or a common feature inherited from a reptilian ancestor millions of years ago.

MCP-1/CCR2 interactions direct migration of peripheral B and T lymphocytes to the thymus during acute infectious/inflammatory processes.

Mature lymphocyte immigration into the thymus has been documented in mouse, rat, and pig models, and highly increases when cells acquire an activated phenotype. Entrance of peripheral B and T cells into the thymus has been described in healthy and pathological situations. However, it has not been proposed that leukocyte recirculation to the thymus could be a common feature occurring during the early phase of a Th1 inflammatory/infectious process when a large number of peripheral cells acquire an activated phenotype and the cellularity of the thymus is seriously compromised. The data we present here demonstrate that in well-established Th1 models triggered by different types of immunogens, for example, LPS treatment (a bacterial product), Candida albicans infection (a fungus), and after Trypanosoma cruzi infection (a parasite), a large number of mature peripheral B and T cells enter the thymus. This effect is dependent on, but not exclusive of, the available space in the thymus. Our data also demonstrate that MCP-1/CCR2 (where MCP-1 is monocyte chemoattractant protein-1) interaction is responsible for the infiltration of peripheral cells to the thymus in these Th1-inflammatory/infectious situations. Finally, systemic expression of IL-12 and IL-18 produced during the inflammatory process is ultimately responsible for these migratory events.

Macrophages activation by a purified fraction, free of nordihydroguaiaretic acid (NDGA), from Larrea divaricata Cav. as a potential novel therapy against Candida albicans.

Larrea divaricata Cav. (jarilla) is a plant with well-documented applications in Argentinean folk medicine. In order to determine if the treatment with a purified fraction named F1 was capable to maintain a state of priming of macrophages after 15 days of mice infection with Candida albicans. Infected and uninfected mice were used. The effect of F1 on: cytosolic protein levels, apoptosis, phagocytosis, reactive oxygen species production, nitric oxide (NO), cell activity, lysosomal activity and the tissue fungal burden were studied. The results showed that F1 increased macrophages yeast phagocytosis and reactive oxygen species and NO production. All these effects were related to a decrease of cell activity and possible apoptosis. In conclusion, it was observed that F1 could induce a state of long-term activation of macrophages, since we observed increased activity of macrophages 15 days after infection, and it could be related to the elimination of C. albicans. These data may suggest that F1 fraction could be useful against disseminated candidiasis in patients and further studies on this field are desirable.

Chitosan enhances transcellular permeability in human and rat intestine epithelium.

The intestinal epithelium regulates the transit of molecules from and into the organism. Several agents act as absorption enhancers inducing changes in both transcellular and paracellular routes. Chitosan is a non-toxic biocompatible polysaccharide widely used as dietary supplement and mucosal delivery. Chitosan triggers both the activation of intestinal epithelial cells and the release of regulatory factors relevant for its immunomodulatory activity. Yet, the interaction of chitosan with intestinal epithelial cells is poorly characterized. We studied the uptake of this polysaccharide, and we evaluated its effects in both the net water and ion movements across human and rat colon samples and the epithelial permeability. Herein, we demonstrate that chitosan increases the transcellular permeability to ions, water and protein markers in human and rat intestinal mucosa and decreases the water permeability across the paracellular pathway. These findings are relevant to understand the activity of the polysaccharide in the mucosal environment.

In vivo effect of three fractions of Larrea divaricata Cav. (jarilla) on the innate immune system: macrophage response against Candida albicans.

Larrea divaricata Cav. (jarilla) is a plant with well-documented applications in folk medicine in Argentina. In this study, we aimed to evaluate functional parameters of peritoneal macrophages isolated from mice injected with three fractions (F1, F2 and F3) of L. divaricata. The response of macrophages against Candida albicans was evaluated. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, apoptosis was evaluated using Giemsa, acridine orange/ethidium bromide and ladder assay, oxidative burst was assayed using nitroblue tetrazolium test and nitrite production using Griess assay. Cell stimulation and their ability to kill C. albicans in vitro were measured. The number and cell viability were similar to controls. However, we found that F1 induces pre-activation of macrophages, and this pre-activation is enhanced by C. albicans. The effects exerted by F1 make it more important than F2 and F3 for the treatment of disseminated candidiasis in patients with immunodeficiency diseases such as AIDS and chronic granulomatous disease, among others.

Signals elicited at the intestinal epithelium upon chitosan feeding contribute to immunomodulatory activity and biocompatibility of the polysaccharide.

Chitosan is a copolymer of N-acetylglucosamine and glucosamine derived from chitin with several applications in pharmaceutical and medical fields. This polysaccharide exhibits adjuvant properties in mucosal immune responses of humans, rats and mice. Characterization of signals elicited by chitosan at the intestinal epithelium could explain its immunomodulatory activity and biocompatibility. We fed normal rats with single doses of chitosan and 16h later, we purified intestinal epithelial cells (IECs) to assess immune and biochemical parameters. Following chitosan administration, mRNA expression and release of several cytokines and chemokines increased, injury markers maintained constitutive levels and MHC type II molecule expression was augmented. IEC supernatants showed higher levels of IL-10, IL-6 and TGF-beta. Arginase activity of IECs increased upon chitosan interaction in vivo and in vitro. Together, after chitosan feeding, mild activation of IECs occurs in vivo, with production of regulatory factors that could be relevant for its biocompatibility and immunomodulatory effects.