Nematode ascarosides attenuate mammalian type 2 inflammatory responses

Metabolomic and functional analyses of small molecules secreted by intestinal nematodes in the activation of epithelial tuft cells

INTRODUCTION

Intestinal helminth parasites trigger the host immune response through epithelial sensory tuft cells, but helminth-derived molecules that may activate tuft cells are poorly characterized.

OBJECTIVES

The study aimed to identify small molecules released in vitro by two nematode parasites, that infect rodents (Nippostrongylus brasiliensis) and ruminants (Haemonchus contortus), and to test candidate ligands in an in vivo model of tuft cell differentiation.

METHODS

Small molecules were analyzed by hydrophilic interaction liquid chromatography (HILIC) of material released by adult parasites incubated in serum-free media, followed by mass spectrometry; selected molecules were administered to mice and tuft cell expansion enumerated after 5 days.

RESULTS

A range of different conditions (culture media, timing, oxygenation) were tested, and comparisons made between the conditions, and between the two nematode species at selected points. Common products across the conditions and species included carboxylic acids (malate, succinate), medium chain fatty acids (such as decanoic and undecanoic acids), purines (guanine, xanthine and their derivatives), and phosphocholine compounds. We selected 19 of the prominent molecules for in vivo testing by oral administration, including succinate, a known activator of tuft cell differentiation. Malate elicited a low but significant level of tuft cell expansion, while undecanoic acids with or without a bromine substitution were also able to induce significant differentiation comparable to succinate. Other molecules including phosphorylcholine had no effect.

CONCLUSION

Multiple molecular species including decanoic and undecanoic acids released by helminths may contribute to activation of tuft cells in vivo.

Identification and synthesis of 4'-ortho-aminobenzoyl ascarosides as sex pheromones of gonochoristic Caenorhabditis nigoni

Using a combination of RP-C18 chromatography, MS and NMR techniques, a new class of homologous modular ascarosides carrying a 4'-ortho-aminobenzoyl moiety was identified from Caenorhabditis nigoni and Caenorhabditis tropicalis. These compounds could not be detected using targeted ascaroside screens based on precursor ion screening for m/z 73.0294 [C3H5O2]-, which highlighted a limitation of the current protocols. Their structure assignment was established by total synthesis of AB-asc-C5 (SMID: abas#9) as a representative example in about 1% yield over 14 steps. To achieve this aim, a new method for the synthesis of orthogonally protected ascarosides has been developed which provides methyl 2-benzoyl-ascaroside as a highly versatile building block for regioselective ascaroside synthesis. Furthermore, a new synthesis for short chain C5 ascarosides was developed that employs selective reduction and Grubbs cross metathesis. The identity of synthetic AB-asc-C5 and the natural product isolated from C. nigoni was established by an NMR mixing experiment. Retention of C. nigoni males by the exclusively female produced AB-asc-C5 suggests a function as a sex pheromone component. Along with the indole ascarosides (icas), the new class of 4'-ortho-aminobenzoyl ascarosides (abas) represents a mechanism to translate bacterial food dependent L-tryptophan availability into species-specific signaling molecules.

Hookworm genes encoding intestinal excreted-secreted proteins are transcriptionally upregulated in response to the host's immune system

Hookworms are intestinal parasitic nematodes that chronically infect ~500 million people, with reinfection common even after clearance by drugs. How infecting hookworms successfully overcome host protective mechanisms is unclear, but it may involve hookworm proteins that digest host tissues, or counteract the host's immune system, or both. To find such proteins in the zoonotic hookworm Ancylostoma ceylanicum, we identified hookworm genes encoding excreted-secreted (ES) proteins, hookworm genes preferentially expressed in the hookworm intestine, and hookworm genes whose transcription is stimulated by the host immune system. We collected ES proteins from adult hookworms harvested from hamsters; mass spectrometry identified 565 A. ceylanicum genes encoding ES proteins. We also used RNA-seq to identify A. ceylanicum genes expressed both in young adults (12 days post-infection) and in intestinal and non-intestinal tissues dissected from mature adults (19 days post-infection), with hamster hosts that either had normal immune systems or were immunosuppressed by dexamethasone. In adult A. ceylanicum, we observed 1,670 and 1,196 genes with intestine- and non-intestine-biased expression, respectively. Comparing hookworm gene activity in normal versus immunosuppressed hosts, we observed almost no changes of gene activity in 12-day young adults or non-intestinal 19-day adult tissues. However, in intestinal 19-day adult tissues, we observed 1,951 positively immunoregulated genes (upregulated at least two-fold in normal hosts versus immunosuppressed hosts), and 137 genes that were negatively immunoregulated. Thus, immunoregulation was observed primarily in mature adult hookworm intestine directly exposed to host blood; it may include hookworm genes activated in response to the host immune system in order to neutralize the host immune system. We observed 153 ES genes showing positive immunoregulation in 19-day adult intestine; of these genes, 69 had ES gene homologs in the closely related hookworm Ancylostoma caninum, 24 in the human hookworm Necator americanus, and 24 in the more distantly related strongylid parasite Haemonchus contortus. Such a mixture of rapidly evolving and conserved genes could comprise virulence factors enabling infection, provide new targets for drugs or vaccines against hookworm, and aid in developing therapies for autoimmune diseases.

Hypoxia-inducible factor 2α promotes pathogenic polarization of stem-like Th2 cells via modulation of phospholipid metabolism

T helper 2 (Th2) cells orchestrate immunity against parasite infection and promote tissue repair but promote pathology in asthma and tissue fibrosis. Here, we examined the mechanisms driving pathogenic differentiation of Th2 cells. Single-cell analyses of CD4+ T cells from asthma and chronic rhinosinusitis patients revealed high expression of the hypoxia-inducible factor (HIF)2α in Th2 cells. In mice, HIF2α deficiency impaired Th2 differentiation and alleviated asthmatic inflammation. Single-cell and lineage tracing approaches delineated a differentiation trajectory from TCF1+Ly108+ stem-like Th2 cells to the ST2+CD25+ pathogenic progeny, depending on a HIF2α-GATA3 circuit that modulated phospholipid metabolism and T cell receptor (TCR)-phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT) activation via transcriptional regulation of the inositol polyphosphate multikinase (IPMK). Overexpression of IPMK in HIF2α-deficient cells promoted Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) synthesis and pathogenic Th2 cell differentiation, whereas pharmacological inhibition of HIF2α impaired pathogenic differentiation of Th2 cells and mitigated airway inflammation. Our findings provide insight into the contextual cues that promote Th2-mediated pathology and suggest HIF2α as a therapeutic target in asthma.

The production, function, and clinical applications of IL-33 in type 2 inflammation-related respiratory diseases

Epithelial-derived IL-33 (Interleukin-33), as a member of alarm signals, is a chemical substance produced under harmful stimuli that can promote innate immunity and activate adaptive immune responses. Type 2 inflammation refers to inflammation primarily mediated by Type 2 helper T cells (Th2), Type 2 innate lymphoid cells (ILC2), and related cytokines. Type 2 inflammation manifests in various forms in the lungs, with diseases such as asthma and chronic obstructive pulmonary disease chronic obstructive pulmonary disease (COPD) closely associated with Type 2 inflammation. Recent research suggests that IL-33 has a promoting effect on Type 2 inflammation in the lungs and can be regarded as an alarm signal for Type 2 inflammation. This article provides an overview of the mechanisms and related targets of IL-33 in the development of lung diseases caused by Type 2 inflammation, and summarizes the associated treatment methods. Analyzing lung diseases from a new perspective through the alarm of Type 2 inflammation helps to gain a deeper understanding of the pathogenesis of these related lung diseases. This, in turn, facilitates a better understanding of the latest treatment methods and potential therapeutic targets for diseases, with the expectation that targeting lL-33 can propose new strategies for disease prevention.

The nematode-trapping fungus Arthrobotrys oligospora detects prey pheromones via G protein-coupled receptors

The ability to sense prey-derived cues is essential for predatory lifestyles. Under low-nutrient conditions, Arthrobotrys oligospora and other nematode-trapping fungi develop dedicated structures for nematode capture when exposed to nematode-derived cues, including a conserved family of pheromones, the ascarosides. A. oligospora senses ascarosides via conserved MAPK and cAMP-PKA pathways; however, the upstream receptors remain unknown. Here, using genomic, transcriptomic and functional analyses, we identified two families of G protein-coupled receptors (GPCRs) involved in sensing distinct nematode-derived cues. GPCRs homologous to yeast glucose receptors are required for ascaroside sensing, whereas Pth11-like GPCRs contribute to ascaroside-independent nematode sensing. Both GPCR classes activate conserved cAMP-PKA signalling to trigger trap development. This work demonstrates that predatory fungi use multiple GPCRs to sense several distinct nematode-derived cues for prey recognition and to enable a switch to a predatory lifestyle. Identification of these receptors reveals the molecular mechanisms of cross-kingdom communication via conserved pheromones also sensed by plants and animals.

Immunosuppressive Ability of Trichinella spiralis Adults Can Ameliorate Type 2 Inflammation in a Murine Allergy Model

BACKGROUND

There is an increase in the global incidence of allergies. The hygiene hypothesis and the old friend hypothesis reveal that helminths are associated with the prevalence of allergic diseases. The therapeutic potential of Trichinella spiralis is recognized; however, the stage at which it exerts its immunomodulatory effect is unclear.

METHODS

We evaluated the differentiation of bone marrow-derived macrophages stimulated with T spiralis excretory-secretory products. Based on an ovalbumin-induced murine model, T spiralis was introduced during 3 allergy phases. Cytokine levels and immune cell subsets in the lung, spleen, and peritoneal cavity were assessed.

RESULTS

We found that T spiralis infection reduced lung inflammation, increased anti-inflammatory cytokines, and decreased Th2 cytokines and alarms. Recruitment of eosinophils, CD11b+ dendritic cells, and interstitial macrophages to the lung was significantly suppressed, whereas Treg cells and alternatively activated macrophages increased in T spiralis infection groups vs the ovalbumin group. Notably, when T spiralis was infected prior to ovalbumin challenge, intestinal adults promoted proportions of CD103+ dendritic cells and alveolar macrophages.

CONCLUSIONS

T spiralis strongly suppressed type 2 inflammation, and adults maintained lung immune homeostasis.

Multiple overlapping risk factors for childhood wheeze among children in Benin

BACKGROUND

The African continent is currently facing an epidemiological transition characterized by a shift from communicable to non-communicable diseases. Prominent amongst the latter are allergies and asthma. In that context, wheeze has multiple potential contributory factors that could include some of the endemic helminth infections, as well as environmental exposures, such as household air pollution. We sought to determine the relative importance of these risk factors among children in Benin.

METHODS

We included 964 children aged 6-14 years living in the commune of Comé, south-west Benin. All children were participants in the longitudinal monitoring cohort of the DeWorm3 trial designed to evaluate multiple rounds of community mass treatment with albendazole for interruption of the transmission of soil transmitted helminths (STH). We administered a standard ISAAC questionnaire to determine the presence of wheeze. In addition, we assessed exposure to household air pollution and to other potential allergy-inducing factors, dietary intake and anthropometry. Using STH infection status assessed at the pretreatment baseline timepoint, we used multivariate statistical modelling, controlling for covariates, to investigate associations between wheeze and the different factors measured.

RESULTS

The prevalence of wheezing history was 5.2%, of current wheezing was 4.6% and of severe wheezing was 3.1%, while STH infections were found in 5.6% of children. These profiles did not vary as a function of either age or gender. Infection with Ascaris lumbricoides, but not hookworm species, was significantly associated with both current wheeze (adjusted Odds Ratio (aOR) = 4.3; 95% CI [1.5-12.0]) and severe wheeze (aOR = 9.2; 95% CI [3.1-27.8]). Significant positive associations with current wheeze, independent of each other and of STH infection status, were also found for (i) use of open cookstoves (aOR = 3.9; 95% CI [1.3-11.5]), (ii) use of palm cakes for fire lighting (aOR = 3.4; 95% CI [1.1-9.9]), (iii) contact with domestic animals and/or rodents (aOR = 2.5; 95% CI [1.1-6.0]), (iv) being overweight (aOR = 9.7; 95% CI [1.7-55.9]). Use of open cookstoves and being overweight were also independent risk factors for severe wheeze (aOR = 3.9; 95% CI [1.1-13.7]) and aOR = 10.3; 95% CI [1.8-60.0], respectively).

CONCLUSIONS

Children infected with A. lumbricoides appear to be at elevated risk of wheeze. Deworming may be an important intervention to reduce these symptoms. Improving cooking methods to reduce household air pollution, modifying dietary habits to avoid overweight, and keeping animals out of the house are all additional measures that could also contribute to reducing childrens' risk of wheeze. Policymakers in LMIC should consider tailoring public health measures to reflect the importance of these different risk factors.

The Role of Noncoding RNA in Airway Allergic Diseases through Regulation of T Cell Subsets

Allergic rhinitis and asthma are common airway allergic diseases, the incidence of which has increased annually in recent years. The human body is frequently exposed to allergens and environmental irritants that trigger immune and inflammatory responses, resulting in altered gene expression. Mounting evidence suggested that epigenetic alterations were strongly associated with the progression and severity of allergic diseases. Noncoding RNAs (ncRNAs) are a class of transcribed RNA molecules that cannot be translated into polypeptides and consist of three major categories, microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Previous studies showed that ncRNAs were involved in the physiopathological mechanisms of airway allergic diseases and contributed to their occurrence and development. This article reviews the current state of understanding of the role of noncoding RNAs in airway allergic diseases, highlights the limitations of recent studies, and outlines the prospects for further research to facilitate the clinical translation of noncoding RNAs as therapeutic targets and biomarkers.

Liver group 2 innate lymphoid cells regulate blood glucose levels through IL-13 signaling and suppression of gluconeogenesis

The liver stores glycogen and releases glucose into the blood upon increased energy demand. Group 2 innate lymphoid cells (ILC2) in adipose and pancreatic tissues are known for their involvement in glucose homeostasis, but the metabolic contribution of liver ILC2s has not been studied in detail. Here we show that liver ILC2s are directly involved in the regulation of blood glucose levels. Mechanistically, interleukin (IL)-33 treatment induces IL-13 production in liver ILC2s, while directly suppressing gluconeogenesis in a specific Hnf4a/G6pc-high primary hepatocyte cluster via Stat3. These hepatocytes significantly interact with liver ILC2s via IL-13/IL-13 receptor signaling. The results of transcriptional complex analysis and GATA3-ChIP-seq, ATAC-seq, and scRNA-seq trajectory analyses establish a positive regulatory role for the transcription factor GATA3 in IL-13 production by liver ILC2s, while AP-1 family members are shown to suppress IL-13 release. Thus, we identify a regulatory role and molecular mechanism by which liver ILC2s contribute to glucose homeostasis.

Besides hepatocytes, resident immune cells of the liver are also contributing to the body’s energy homeostasis. Here authors show that group 2 innate lymphoid cells interact with a specific set of hepatocytes in suppressing gluconeogenesis and regulate blood glucose levels via Interleukin-13 signalling.