Microbial transmission in the social microbiome and host health and disease.

Although social interactions are known to drive pathogen transmission, the contributions of socially transmissible host-associated mutualists and commensals to host health and disease remain poorly explored. We use the concept of the social microbiome-the microbial metacommunity of a social network of hosts-to analyze the implications of social microbial transmission for host health and disease. We investigate the contributions of socially transmissible microbes to both eco-evolutionary microbiome community processes (colonization resistance, the evolution of virulence, and reactions to ecological disturbance) and microbial transmission-based processes (transmission of microbes with metabolic and immune effects, inter-specific transmission, transmission of antibiotic-resistant microbes, and transmission of viruses). We consider the implications of social microbial transmission for communicable and non-communicable diseases and evaluate the importance of a socially transmissible component underlying canonically non-communicable diseases. The social transmission of mutualists and commensals may play a significant, under-appreciated role in the social determinants of health and may act as a hidden force in social evolution.

Gut complement induced by the microbiota combats pathogens and spares commensals.

Canonically, the complement system is known for its rapid response to remove microbes in the bloodstream. However, relatively little is known about a functioning complement system on intestinal mucosal surfaces. Herein, we report the local synthesis of complement component 3 (C3) in the gut, primarily by stromal cells. C3 is expressed upon commensal colonization and is regulated by the composition of the microbiota in healthy humans and mice, leading to an individual host's specific luminal C3 levels. The absence of membrane attack complex (MAC) components in the gut ensures that C3 deposition does not result in the lysis of commensals. Pathogen infection triggers the immune system to recruit neutrophils to the infection site for pathogen clearance. Basal C3 levels directly correlate with protection against enteric infection. Our study reveals the gut complement system as an innate immune mechanism acting as a vigilant sentinel that combats pathogens and spares commensals.

Veggies and Intact Grains a Day Keep the Pathogens Away.

In this issue of Cell, Desai et al. compare how dietary fiber affects the gut microbiota and susceptibility to disease. They find that a fiber-free diet promotes mucus-degrading bacteria and susceptibility to Citrobacter rodentium infection.

Gut microbial fatty acid isomerization modulates intraepithelial T cells.

The human gut microbiome constantly converts natural products derived from the host and diet into numerous bioactive metabolites1-3. Dietary fats are essential micronutrients that undergo lipolysis to release free fatty acids (FAs) for absorption in the small intestine4. Gut commensal bacteria modify some unsaturated FAs-for example, linoleic acid (LA)-into various intestinal FA isomers that regulate host metabolism and have anticarcinogenic properties5. However, little is known about how this diet-microorganism FA isomerization network affects the mucosal immune system of the host. Here we report that both dietary factors and microbial factors influence the level of gut LA isomers (conjugated LAs (CLAs)) and that CLAs in turn modulate a distinct population of CD4+ intraepithelial lymphocytes (IELs) that express CD8αα in the small intestine. Genetic abolition of FA isomerization pathways in individual gut symbionts significantly decreases the number of CD4+CD8αα+ IELs in gnotobiotic mice. Restoration of CLAs increases CD4+CD8αα+ IEL levels in the presence of the transcription factor hepatocyte nuclear factor 4γ (HNF4γ). Mechanistically, HNF4γ facilitates CD4+CD8αα+ IEL development by modulating interleukin-18 signalling. In mice, specific deletion of HNF4γ in T cells leads to early mortality from infection by intestinal pathogens. Our data reveal a new role for bacterial FA metabolic pathways in the control of host intraepithelial immunological homeostasis by modulating the relative number of CD4+ T cells that were CD4+CD8αα+.

Targeting PD-L2-RGMb overcomes microbiome-related immunotherapy resistance.

The gut microbiota is a crucial regulator of anti-tumour immunity during immune checkpoint inhibitor therapy. Several bacteria that promote an anti-tumour response to immune checkpoint inhibitors have been identified in mice1-6. Moreover, transplantation of faecal specimens from responders can improve the efficacy of anti-PD-1 therapy in patients with melanoma7,8. However, the increased efficacy from faecal transplants is variable and how gut bacteria promote anti-tumour immunity remains unclear. Here we show that the gut microbiome downregulates PD-L2 expression and its binding partner repulsive guidance molecule b (RGMb) to promote anti-tumour immunity and identify bacterial species that mediate this effect. PD-L1 and PD-L2 share PD-1 as a binding partner, but PD-L2 can also bind RGMb. We demonstrate that blockade of PD-L2-RGMb interactions can overcome microbiome-dependent resistance to PD-1 pathway inhibitors. Antibody-mediated blockade of the PD-L2-RGMb pathway or conditional deletion of RGMb in T cells combined with an anti-PD-1 or anti-PD-L1 antibody promotes anti-tumour responses in multiple mouse tumour models that do not respond to anti-PD-1 or anti-PD-L1 alone (germ-free mice, antibiotic-treated mice and even mice colonized with stool samples from a patient who did not respond to treatment). These studies identify downregulation of the PD-L2-RGMb pathway as a specific mechanism by which the gut microbiota can promote responses to PD-1 checkpoint blockade. The results also define a potentially effective immunological strategy for treating patients who do not respond to PD-1 cancer immunotherapy.

NMDA Receptors in the Basolateral Amygdala Complex Are Engaged for Pavlovian Fear Conditioning When an Animal's Predictions about Danger Are in Error.

It is widely accepted that Pavlovian fear conditioning requires activation of NMDA receptors (NMDARs) in the basolateral amygdala complex (BLA). However, it was recently shown that activation of NMDAR in the BLA is only required for fear conditioning when danger occurs unexpectedly; it is not required for fear conditioning when danger occurs as expected. This study tested the hypothesis that NMDARs in the BLA are engaged for Pavlovian fear conditioning when an animal's predictions regarding danger are in error. In each experiment, rats (females in Experiment 1 and males in Experiments 2-5) were conditioned to fear one stimulus, S1, when it was paired with foot-shock (S1→shock), and 48 h later, a second stimulus, S2, when it was presented in sequence with the already-conditioned S1 and foot-shock (S2→S1→shock). Conditioning to S2 occurred under a BLA infusion of the NMDAR antagonist, D-AP5 or vehicle. The subsequent tests of freezing to S2 alone and S1 alone revealed that the antagonist had no effect on conditioning to S2 when the shock occurred exactly as predicted by the S1, but disrupted this conditioning when the shock occurred earlier/later than predicted by S1, or at a stronger/weaker intensity. These results imply that errors in the timing or intensity of a predicted foot-shock engage NMDARs in the BLA for Pavlovian fear conditioning. They are discussed in relation to theories which propose a role for prediction error in determining how experiences are organized in memory and how activation of NMDAR in the BLA might contribute to this organization.SIGNIFICANCE STATEMENT This study is significant in showing that prediction error determines how a new experience is encoded with respect to a past experience and, thereby, whether NMDA receptors (NMDARs) in the basolateral amygdala complex (BLA) encode the new experience. When prediction error is small (e.g., danger occurs as and when expected), the new experience is encoded together with a past experience as part of the same "mental model," and NMDAR activation in the BLA is not needed for this encoding. By contrast, when prediction error is large (e.g., danger occurs at an unexpected intensity or time), the new experience is encoded separately from the past experience as part of a new mental model, and NMDAR activation in the BLA is needed for this encoding.

Remission and low disease activity are associated with lower healthcare costs: results from the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort.

OBJECTIVES: This study aims to determine the independent impact of definitions of remission/low disease activity (LDA) on direct/indirect costs (DCs, ICs) in a multicentre inception cohort. METHODS: Patients from 31 centres in 10 countries were enrolled within 15 months of diagnosis and assessed annually. Five mutually exclusive disease activity states (DAS) were defined as (1) remission off-treatment: clinical (c) SLEDAI-2K=0, without prednisone/immunosuppressants; (2) remission on-treatment: cSLEDAI-2K=0, prednisone ≤5 mg/day and/or maintenance immunosuppressants; (3) LDA-Toronto Cohort (TC): cSLEDAI-2K≤2, without prednisone/immunosuppressants; (4) modified lupus LDA state (mLLDAS): SLEDAI-2K≤4, no activity in major organs/systems, no new activity, prednisone ≤7.5 mg/day and/or maintenance immunosuppressants and (5) active: all remaining assessments.At each assessment, patients were stratified into the most stringent DAS fulfilled and the proportion of time in a DAS since cohort entry was determined. Annual DCs/ICs (2021 Canadian dollars) were based on healthcare use and lost workforce/non-workforce productivity over the preceding year.The association between the proportion of time in a DAS and annual DC/IC was examined through multivariable random-effects linear regressions. RESULTS: 1692 patients were followed a mean of 9.7 years; 49.0% of assessments were active. Remission/LDA (per 25% increase in time in a remission/LDA state vs active) were associated with lower annual DC/IC: remission off-treatment (DC -$C1372; IC -$C2507), remission on-treatment (DC -$C973; IC -$C2604,) LDA-TC (DC -$C1158) and mLLDAS (DC -$C1040). There were no cost differences between remission/LDA states. CONCLUSIONS: Our data suggest that systemic lupus erythematosus patients who achieve remission, both off and on-therapy, and reductions in disease activity incur lower costs than those experiencing persistent disease activity.

A qualitative investigation of the experiences of patients living with antiphospholipid antibodies.

OBJECTIVE: Substantial morbidity and mortality affect those with antiphospholipid antibodies (aPLs) and antiphospholipid syndrome (APS), yet patient experiences remain poorly understood. This research investigated patient experiences of aPL/APS diagnosis; effects on daily life; and healthcare and treatment. METHODS: Patients aged ≥18 years with APS per the Revised Sapporo criteria or with ≥1 positive aPL on ≥2 occasions were recruited from a Canadian multidisciplinary APS clinic to participate in semi-structured in-depth interviews. Interviews were conducted virtually and transcribed verbatim for subsequent thematic analysis. RESULTS: Twenty-one patients with aPLs/APS participated; 95.2% were female, mean (SD) age was 45.6 (15.0) years. Most (71.4%) had APS, and 71.4% had aPLs/APS with SLE. Results are presented around patient experiences of aPL/APS diagnosis, effects on daily life, and healthcare and treatment. Participants described medical complications/physical symptoms and the healthcare, lifestyle, and emotional impacts experienced around the time of aPLs/APS diagnosis. In addition to the physical and psychosocial impacts of living with aPLs/APS, patients reported modified leisure activities, altered employment trajectories, and positive and negative impacts on relationships. Impacts on family planning were also a critical component of the aPL/APS lived experience; participants shared experiences of miscarriage, other pregnancy complications, and medication-related challenges (e.g., with low-molecular-weight heparin injections). Challenging aspects of aPL/APS healthcare and treatment were also discussed, particularly related to the lifestyle, physical, and emotional burden of medication use. Although a lack of resources was described, participants expressed trust in healthcare providers when making management decisions or when seeking information. Suggestions for resources included the need for additional medication-related information, examples to help contextualize management behaviours, and additional information for those with aPLs/APS without SLE. CONCLUSION: Patients highlighted how the diverse manifestations of aPLs/APS, accentuated by management-related challenges, impose considerable physical and psychosocial burdens. Results will inform the development of patient resources aligned with patient priorities.

Author Correction: Conversion of human fibroblasts to angioblast-like progenitor cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Low dialysate sodium in children and young adults on maintenance hemodialysis: a prospective, randomized, crossover study.

BACKGROUND: The optimal dialysate sodium concentration (dNa) in children on hemodialysis (HD) is unknown. The aim of this study was to compare the effect on interdialytic weight gain (IDWG) and blood pressure (BP) of a low (135 mmol/l) and standard dNa (138 mmol/l) in children and young adults on maintenance HD. METHODS: This prospective single-blind randomized crossover study consisted of a randomized sequence of two phases: "standard dNa" of 138 mmol/L and "low dNa" of 135 mmol/L. Each phase lasted 4 weeks. Inclusion criteria were age < 25 years, hypertension, pre-HD serum Na (sNa) ≥ 130 mmol/L, and occurrence of symptoms in less than 25% of sessions. Primary outcomes were pre-HD systolic and diastolic BP and IDWG. RESULTS: Fifteen patients were recruited, mean age 17.8 ± 4.4 years. Pre-HD SBP and DBP were not different between the two treatments. Mean IDWG was significantly lower with low dNa than with standard dNa: 2.12 ± 1.39% vs. 2.77 ± 1.53%, respectively (p = 0.008). The first-hour refill index (a volume index based on blood-volume monitoring) was significantly lower with dNa 135 mmol/L (p = 0.018). The mean Na gradient (dNa-sNa) was - 2.53 ± 2.4 mmol/L with dNa 135 mmol/L and 0.17 ± 2.8 mmol/L with dNa 138 mmol/L (p = 0.0001). The incidence of symptomatic sessions was similar (1.0% vs. 1.0%). CONCLUSIONS: In a selected population of hypertensive pediatric and young adult HD patients, a dNa of 135 mmol/L was associated with a significant reduction of IDWG compared with a dNa of 138 mmol/L. Furthermore, long-term studies are needed to investigate the effect of lowering dNa on BP. A higher resolution version of the Graphical abstract is available as Supplementary information.

Sigma-2 Receptor Ligand Binding Modulates Association between TSPO and TMEM97.

Sigma-2 receptor (S2R) is a S2R ligand-binding site historically associated with reportedly 21.5 kDa proteins that have been linked to several diseases, such as cancer, Alzheimer's disease, and schizophrenia. The S2R is highly expressed in various tumors, where it correlates with the proliferative status of the malignant cells. Recently, S2R was reported to be the transmembrane protein TMEM97. Prior to that, we had been investigating the translocator protein (TSPO) as a potential 21.5 kDa S2R candidate protein with reported heme and sterol associations. Here, we investigate the contributions of TMEM97 and TSPO to S2R activity in MCF7 breast adenocarcinoma and MIA PaCa-2 (MP) pancreatic carcinoma cells. Additionally, the role of the reported S2R-interacting partner PGRMC1 was also elucidated. Proximity ligation assays and co-immunoprecipitation show a functional association between S2R and TSPO. Moreover, a close physical colocalization of TMEM97 and TSPO was found in MP cells. In MCF7 cells, co-immunoprecipitation only occurred with TMEM97 but not with PGRMC1, which was further confirmed by confocal microscopy experiments. Treatment with the TMEM97 ligand 20-(S)-hydroxycholesterol reduced co-immunoprecipitation of both TMEM97 and PGRMC1 in immune pellets of immunoprecipitated TSPO in MP cells. To the best of our knowledge, this is the first suggestion of a (functional) interaction between TSPO and TMEM97 that can be affected by S2R ligands.

The Impact of Fitness Status on Vascular and Baroreceptor Function in Healthy Women and Men.

BACKGROUND: Chronic endurance exercise training elicits desirable physiological adaptations in the cardiovascular system. The volume of exercise training required to generate healthy adaptations is unclear. This study assessed the effects of differing exercise training levels on arterial stiffness, compliance, and autonomic function. METHODS: Eighty healthy adults (38.5 ± 9.7 years; 44% female) defined as endurance-trained (ET, n = 29), normally active (NA, n = 27), or inactive (IN, n = 24) participated. Cardiovascular markers, including hemodynamics, large arterial compliance and small arterial compliance (LAC and SAC), carotid-femoral pulse wave velocity (PWV), and spontaneous baroreceptor sensitivity (BRS) were assessed. RESULTS: ET showed significantly greater LAC values (21.4 ± 6.5) than NA (16.9 ± 2.5; p = 0.002) and IN (14.7 ± 3.2 mL × mm Hg × 10; p = 0.028). Values for SAC and BRS were significantly higher in ET than IN (p < 0.001 and p = 0.028, respectively), but not NA. Compared to IN, PWV values for ET and NA were significantly lower (p < 0.003). After adjusting for covariates (age, sex, and SBP), significant associations with cardiovascular fitness status were noted for all markers but BRS. CONCLUSION: Endurance exercise increases LAC likely due to high-volume training; however, lower volumes of physical activity may be sufficient to positively benefit vascular health overall.

Economic burden of food allergy in Canada: Estimating costs and identifying determinants.

BACKGROUND: Limited data exist on the economic burden of food allergy (FA). OBJECTIVE: To assess FA-related direct (healthcare and out-of-pocket) and indirect (lost productivity) costs and their determinants in Canadian children and adults self-reporting FA. METHODS: FA-individuals self-reporting a convincing history or physician diagnosis were recruited through FA registries, an anaphylaxis registry, and advocacy associations, and electronically surveyed regarding FA-related healthcare use, out-of-pocket expenditures, and time lost from paid and unpaid labor. Direct and indirect costs (2020 Canadian dollars [CAD]) were stratified on severe reaction vs mild, moderate or no reaction, and children vs adults; multivariate regressions assessed the association between costs and sociodemographic and disease characteristics. RESULTS: Between May 2018 and July 2019, 2692 eligible individuals responded (2189 convincing history and 503 physician diagnosis only); 1020 experienced a severe reaction; 1752 were children. Per FA-individual, annual healthcare, out-of-pocket, and indirect costs were $1267, $2136, and $7950. Those with a severe reaction had higher healthcare and out-of-pocket costs than those with mild, moderate or no reaction. FA-children vs FA-adults had higher healthcare and out-of-pocket costs, and lower indirect costs. Multivariate results showed that lower age, a severe reaction ever, multiple FAs, and fair or poor general health were associated with higher healthcare and out-of-pocket costs. Higher age, lower household education and income, and fair or poor general health were associated with higher indirect costs. CONCLUSION: The economic burden of FA in Canada is substantial, particularly for those with a severe reaction ever, multiple FAs, and fair or poor general health. It is crucial that those most adversely affected are allocated appropriate resources to support disease management.

Symbionts exploit complex signaling to educate the immune system.

The mammalian immune system is tolerized to trillions of microbes residing on bodily surfaces and can discriminate between symbionts and pathogens despite their having related microbial structures. Mechanisms of innate immune activation and the subsequent signaling pathways used by symbionts to communicate with the adaptive immune system are poorly understood. Polysaccharide A (PSA) of Bacteroides fragilis is the model symbiotic immunomodulatory molecule. Here we demonstrate that PSA-dependent immunomodulation requires the Toll-like receptor (TLR) 2/1 heterodimer in cooperation with Dectin-1 to initiate signaling by the downstream phosphoinositide 3-kinase (PI3K) pathway, with consequent CREB-dependent transcription of antiinflammatory genes, including antigen presentation and cosignaling molecules. High-resolution LC-MS/MS analysis of PSA identified a previously unknown small molecular-weight, covalently attached bacterial outer membrane-associated lipid that is required for activation of antigen-presenting cells. This archetypical commensal microbial molecule initiates a complex collaborative integration of Toll-like receptor and C-type lectin-like receptor signaling mechanisms culminating in the activation of the antiinflammatory arm of the PI3K pathway that serves to educate CD4+ Tregs to produce the immunomodulatory cytokine IL-10. Immunomodulation is a key function of the microbiome and is a focal point for developing new therapeutic agents.

New Pharmacological Strategies against Pancreatic Adenocarcinoma: The Multifunctional Thiosemicarbazone FA4.

A new sigma-2 (σ2) receptor ligand (FA4) was efficiently synthesized and evaluated for cytotoxic, proapoptotic, and antimigratory activity on pancreatic ductal adenocarcinoma (PDAC) primary cell cultures, which restrained the aggressive and chemoresistant behavior of PDAC. This compound showed relevant antiproliferative activity with half maximal inhibitory concentration (IC50) values ranging from 0.701 to 0.825 µM. The cytotoxic activity was associated with induction of apoptosis, resulting in apoptotic indexes higher than those observed after exposure to a clinically relevant concentration of the gemcitabine, the first-line drug used against PDAC. Interestingly, FA4 was also able to significantly inhibit the migration rate of both PDAC-1 and PDAC-2 cells in the scratch wound-healing assay. In conclusion, our results support further studies to improve the library of thiosemicarbazones targeting the σ-2 receptor for a deeper understanding of the relationship between the biological activity of these compounds and the development of more efficient anticancer compounds against PDAC.

Fine-scale genetic structure reflects limited and coordinated dispersal in the colonial monk parakeet, Myiopsitta monachus.

The genetic structure of animal populations has considerable behavioural, ecological and evolutionary implications and may arise from various demographic traits. Here, we use observational field data and molecular genetics to determine the genetic structure of an invasive population of monk parakeets, Myiopsitta monachus, at a range of spatial scales, and investigate the demographic processes that generate the observed structure. Monk parakeets construct large nests that can house several pairs occupying separate chambers; these nests are often aggregated within nesting trees. We determined patterns of relatedness within compound nests, within nesting trees and between trees. Spatial autocorrelation analyses of pairwise genetic relatedness revealed fine-scale genetic structure with relatives of both sexes spatially clustered within, but not beyond, nesting trees. In addition, males were more related to males sharing their compound nests than to other males occupying the same nesting tree. By contrast, males and females within compound nests were not significantly more closely related than elsewhere in the same tree, and we found no evidence for inbreeding. Adults showed high breeding site fidelity between years despite considerable disturbance of nest sites. Natal dispersal was female-biased, but dispersal distances were relatively short with some natal philopatry observed in both sexes. Sibling coalitions, typically of males, were observed amongst both philopatric and dispersing birds. Our results show significant clustering of kin within compound nests and nesting trees resulting from limited and coordinated natal dispersal, with subsequent breeding site fidelity. The resulting genetic structure has implications for social behaviour in this unusual parrot species.

The value of hackathons in integrated knowledge translation (iKT) research: Waterlupus.

BACKGROUND: Despite a growing movement toward a knowledge-user-driven research process, our understanding of the generation, implementation and evaluation of specific approaches in the integrated knowledge translation (iKT) toolbox that aim to engage health and healthcare knowledge users is limited. Health hackathons offer an innovative approach with potential to generate direct and indirect health-related outcomes benefitting participants, knowledge users and the broader population. In May 2019, our research team hosted Waterlupus, a health hackathon to improve the economic lives of individuals with systemic lupus erythematosus (SLE) in Canada. Waterlupus was held with a multi-stakeholder group of 50 participants that included advocacy organization representatives, policy-makers, researchers, physicians, individuals with lived experience and students. While the hackathon generated viable solutions with the potential to positively impact the lives of individuals with SLE, understanding how participants perceived the hackathon as an iKT tool is critical in the planning and implementation of future iKT research. METHODS: Semi-structured in-depth telephone interviews were conducted with Waterlupus participants (n = 13) between August and November 2019 to (1) explore participant experiences of the hackathon; (2) investigate participant-identified hackathon outcomes; and (3) elicit recommendations for future iKT research using health hackathons. RESULTS: Participants provided feedback on the format and organization of Waterlupus, and identified direct and indirect outcomes to knowledge users, students and researchers beyond the innovations generated at the event. While the majority (n = 11) had never participated in a hackathon prior to Waterlupus, all 13 stated they would participate in future hackathons. Positive outcomes identified include connecting with students and other SLE stakeholders, the formation of professional and support networks, increased awareness of SLE, as well as the innovations generated. Participant recommendations for future health hackathons include the addition of stakeholders from industry or technology, and the need for clear and designated roles for stakeholders to ensure efficient use of resources. CONCLUSIONS: This work contributes to a limited literature regarding the use of health hackathons for social innovation, and offers knowledge-user suggestions relevant to the implementation of future iKT events, and hackathons specifically.

Microsatellite characterisation and sex-typing in two invasive parakeet species, the monk parakeet Myiopsitta monachus and ring-necked parakeet Psittacula krameri.

Invasive species can have wide-ranging negative impacts, and an understanding of the process and success of invasions can be vital to determine management strategies, mitigate impacts and predict range expansions of such species. Monk parakeets (Myiopsitta monachus) and ring-necked parakeets (Psittacula krameri) are both widespread invasive species, but there has been little research into the genetic and social structure of these two species despite the potential links with invasion success. The aim of this study was to isolate novel microsatellite loci from the monk parakeet and characterise them in both monk and ring-necked parakeets in order to facilitate future investigations into their behaviour and population ecology. Sex-typing markers were also tested in both species. Of the 20 microsatellite loci assessed in 24 unrelated monk parakeets, 16 successfully amplified and were polymorphic displaying between 2 and 14 alleles (mean = 8.06). Expected heterozygosity ranged from 0.43 to 0.93 and observed heterozygosity ranged from 0.23 to 0.96. Nine of the 20 loci also successfully amplified and were polymorphic in the ring-necked parakeet, displaying between 2 and 10 alleles. Suitable markers to sex both species and a Z-linked microsatellite locus were identified. A multiplex marker set was validated for monk parakeets. These novel microsatellite loci will facilitate fine and broad-scale population genetic analyses of these two widespread invasive species.

Ventilation heterogeneity and oscillometry predict asthma control improvement following step-up inhaled therapy in uncontrolled asthma.

BACKGROUND AND OBJECTIVE: Abnormal peripheral airway function is an important feature of asthma and relates to asthma symptoms and poor asthma control. We aimed to determine whether peripheral airway function, as measured by forced oscillatory impedance and multiple-breath nitrogen washout (MBNW), relates to symptom improvement in asthmatic participants with uncontrolled asthma, after stepping up to high-dose ICS/LABA treatment. METHODS: A total of 19 subjects (14 females, mean age: 29.9 ± 13.6 years) with uncontrolled asthma, as defined by an ACQ5 > 1.5, taking 500 µg/day fluticasone equivalent or less, underwent spirometry, plethysmography, fractional exhaled FeNO, forced oscillatory resistance (Rrs5Hz ) and reactance (Xrs5Hz ), and indices of MBNW ventilation heterogeneity (lung clearance index (LCI), diffusion-convection-dependent (Sacin) and convection-dependent (Scond)). Measurements were made before and after 8 weeks of treatment with fluticasone/formoterol combination inhaler 250/10 µg, 2 puffs twice daily. RESULTS: Treatment improved ACQ5 (P = 0.0002), FEV1 (P = 0.02), FVC (P = 0.04), FeNO (P = 0.0008), Xrs5Hz (P = 0.01), LCI (P = 0.0002), Sacin (P = 0.006) and Scond (P = 0.01). At baseline, ACQ5 correlated with Xrs5Hz (rs = 0.52, P = 0.03) and Rrs5Hz (rs = 0.55, P = 0.02). The improvement in ACQ5 was predicted by more abnormal baseline LCI (P = 0.03), Scond (P = 0.02) and Rrs5Hz (P = 0.006). Baseline Scond was the best predictor of a clinically meaningful improvement in asthma control (ΔACQ > 0.5, ROC-AUC = 0.91, P = 0.007). CONCLUSION: Step-up to high-dose combination treatment in uncontrolled asthma is associated with improved peripheral airway function as measured by Xrs5Hz and MBNW. Baseline MBNW and FOT parameters correlated with the improvement in symptoms and may predict a positive response to up-titration in uncontrolled asthmatic patients.