The mucus barrier : immune defence against gastrointestinal nematodes

Trichuriasis, caused by the intestinal nematode Trichuris, is a disease that affects up to a billion people worldwide. To date, most of our knowledge of this disease comes from the mouse model, Trichuris muris, which has been successfully used to dissect the immune-mediated effector mechanisms that elicit the expulsion of the nematode. Numerous studies have shown a temporal association between intestinal nematode expulsion and goblet cell hyperplasia; however their precise role in response to nematode infection remains elusive. Goblet cells found at mucosal surfaces secrete many constituent components of the mucus barrier, including the gel-forming mucins (Muc2 in the intestine); mucins are large multifunctional glycoproteins that provide the structural framework of the barrier. The studies presented in this thesis demonstrate that the mucosal barrier and in particular its mucin components, changes in response to acute and chronic T.muris infection. In animals resistant to chronic T. muris infection, IL-13-mediated increase in Muc2 production and secretion was observed at the site of infection. Critically, expulsion of the nematode was significantly delayed in the absence of Muc2. Further investigation subsequently showed that Muc5ac, a mucin normally expressed in non-intestinal mucosa was, in fact, expressed in the intestine following nematode infection and was associated with nematode expulsion in the resistant mice. Moreover, mice deficient in Muc5ac were susceptible to chronic infection, despite a strong underlying TH2-type immune response which is essential to eliminate the nematodes, suggesting that Muc5ac acts as a critical effector molecule. Several qualitative changes in the mucins were also noted during resistance: mucins were more highly charged and more sulphated during nematode expulsion. Overall, the changes within the mucus barrier during resistance result in altering the rheological properties of the mucus layer making it less porous and mucins were shown to directly 'damage' the nematodes during nematode expulsion as reflected by a significant reduction in ATP levels. Chronic infection was accompanied by decreased levels of low charged and highly sialylated Muc2. Additionally, we demonstrated that the excretory secretory products released by the nematode consist of serine proteases capable of depolymerising the Muc2 mucin network, which may be part of the nematodes regime to improve its niche and/or aid movement through the mucus layer. Overall, this resulted in a porous mucus layer and a favourable environment for the parasite.Data is presented to show that the intestinal mucus barrier and its constituent mucins are an integral part of the co-ordinated expulsion mechanisms that occur in animals resistant to T.muris infection and we identify a mechanism whereby the nematode exerts its effects on the mucin environment to promote its survival within the host.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

One-pot synthesis of pH-responsive Eudragit-mesoporous silica nanocomposites enable colonic delivery of glucocorticoids for the treatment of inflammatory bowel disease

Oral glucocorticoids are backbones for the acute management of inflammatory bowel disease (IBD). However, the clinical effectiveness of conventional oral dosage forms of glucocorticoids is hindered by their low delivery efficiency and systemic side effects. To overcome this problem, a smart drug delivery system with high loading capacity and colonic release by coating functionalized mesoporous silica nanoparticles (MSNs) with a pH‐responsive polymer Eudragit S100 is proposed. In vitro dissolution tests show that Eudragit‐coated MSNs can limit the burst release of loaded prednisolone and budesonide in the gastric environment with more than 60% of the drugs released only at colonic pH (i.e., pH ≥ 7). In vivo therapeutic efficacy of budesonide‐loaded nanoparticles is tested in a murine model of dextran sodium sulfate‐induced colitis. An oral budesonide dose of 0.2 mg kg−1 nanoparticles with Eudragit coating improves the disease activity index compared to other groups. Interestingly, both coated and uncoated nanoparticles show pathological improvements demonstrated by similar levels of histological colitis score. However, coated nanoparticles significantly decrease mRNA expression of the cytokines (Il‐1β, Il‐17, and Il‐10) particularly in proximal colon, indicating colonic delivery. Overall, this study demonstrates the effectiveness of a simple method to fabricate targeted nanomedicine for the treatment of IBD.Peer reviewe

Adult Non-Cystic Fibrosis Bronchiectasis Is Characterised by Airway Luminal Th17 Pathway Activation

Copyright © 2015 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.BACKGROUND: Non-cystic fibrosis (CF) bronchiectasis is characterised by chronic airway infection and neutrophilic inflammation, which we hypothesised would be associated with Th17 pathway activation. METHODS: Th17 pathway cytokines were quantified in bronchoalveolar lavage fluid (BALF), and gene expression of IL-17A, IL-1β, IL-8 and IL-23 determined from endobronchial biopsies (EBx) in 41 stable bronchiectasis subjects and 20 healthy controls. Relationships between IL-17A levels and infection status, important clinical measures and subsequent Pseudomonas aeruginosa infection were determined. RESULTS: BALF levels of all Th17 cytokines (median (IQR) pg/mL) were significantly higher in bronchiectasis than control subjects, including IL-17A (1.73 (1.19, 3.23) vs. 0.27 (0.24, 0.35), 95% CI 1.05 to 2.21, p<0.0001) and IL-23 (9.48 (4.79, 15.75) vs. 0.70 (0.43, 1.79), 95% CI 4.68 to 11.21, p<0.0001). However, BALF IL-17A levels were not associated with clinical measures or airway microbiology, nor predictive of subsequent P. aeruginosa infection. Furthermore, gene expression of IL-17A in bronchiectasis EBx did not differ from control. In contrast, gene expression (relative to medians of controls) in bronchiectasis EBx was significantly higher than control for IL1β (4.12 (1.24, 8.05) vs 1 (0.13, 2.95), 95% CI 0.05 to 4.07, p = 0.04) and IL-8 (3.75 (1.64, 11.27) vs 1 (0.54, 3.89), 95% CI 0.32 to 4.87, p = 0.02) and BALF IL-8 and IL-1α levels showed significant relationships with clinical measures and airway microbiology. P. aeruginosa infection was associated with increased levels of IL-8 while Haemophilus influenzae was associated with increased IL-1α. CONCLUSIONS AND CLINICAL RELEVANCE: Established adult non-CF bronchiectasis is characterised by luminal Th17 pathway activation, however this pathway may be relatively less important than activation of non-antigen-specific innate neutrophilic immunity

Glucocorticoids alleviate intestinal ER stress by enhancing protein folding and degradation of misfolded proteins

Endoplasmic reticulum (ER) stress in intestinal secretory cells has been linked with colitis in mice and inflammatory bowel disease (IBD). Endogenous intestinal glucocorticoids are important for homeostasis and glucocorticoid drugs are efficacious in IBD. In Winnie mice with intestinal ER stress caused by misfolding of the Muc2 mucin, the glucocorticoid dexamethasone (DEX) suppressed ER stress and activation of the unfolded protein response (UPR), substantially restoring goblet cell Muc2 production. In mice lacking inflammation, a glucocorticoid receptor antagonist increased ER stress, and DEX suppressed ER stress induced by the N-glycosylation inhibitor, tunicamycin (Tm). In cultured human intestinal secretory cells, in a glucocorticoid receptor-dependent manner, DEX suppressed ER stress and UPR activation induced by blocking N-glycosylation, reducing ER Ca2+ or depleting glucose. DEX up-regulated genes encoding chaperones and elements of ER-associated degradation (ERAD), including EDEM1. Silencing EDEM1 partially inhibited DEX's suppression of misfolding-induced ER stress, showing that DEX enhances ERAD. DEX inhibited Tm-induced MUC2 precursor accumulation, promoted production of mature mucin, and restored ER exit and secretion of Winnie mutant recombinant Muc2 domains, consistent with enhanced protein folding. In IBD, glucocorticoids are likely to ameliorate ER stress by promoting correct folding of secreted proteins and enhancing removal of misfolded proteins from the ER

Muc5ac: a critical component mediating the rejection of enteric nematodes

The mucin Muc5ac is essential for the expulsion of Trichuris muris and other gut-dwelling nematodes

A convergent evolutionary pathway attenuating cellulose production drives enhanced virulence of some bacteria

Bacteria adapt to selective pressure in their immediate environment in multiple ways. One mechanism involves the acquisition of independent mutations that disable or modify a key pathway, providing a signature of adaptation via convergent evolution. Extra-intestinal pathogenic Escherichia coli (ExPEC) belonging to sequence type 95 (ST95) represent a global clone frequently associated with severe human infections including acute pyelonephritis, sepsis, and neonatal meningitis. Here, we analysed a publicly available dataset of 613 ST95 genomes and identified a series of loss-of-function mutations that disrupt cellulose production or its modification in 55.3% of strains. We show the inability to produce cellulose significantly enhances ST95 invasive infection in a rat model of neonatal meningitis, leading to the disruption of intestinal barrier integrity in newborn pups and enhanced dissemination to the liver, spleen and brain. Consistent with these observations, disruption of cellulose production in ST95 augmented innate immune signalling and tissue neutrophil infiltration in a mouse model of urinary tract infection. Mutations that disrupt cellulose production were also identified in other virulent ExPEC STs, Shigella and Salmonella, suggesting a correlative association with many Enterobacteriaceae that cause severe human infection. Together, our findings provide an explanation for the emergence of hypervirulent Enterobacteriaceae clones

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation