Quantification of inflammatory mediators to explore molecular mechanisms and sub-phenotypes of asthma

This thesis summarizes a series of studies using liquid chromatography coupled to mass spectrometry methodologies to quantify metabolites of fatty acids (i.e., oxylipins) and histamine in different samples from experimental models and clinical studies with the overall aim to define mechanisms and identify biomarkers for improved sub-phenotyping of asthma. Asthma is characterized by variable airflow obstruction, hyperresponsiveness and chronic inflammation in the airways. The substantial overlap among clinical descriptors has resulted in difficulties to establish diagnosis and predict response to treatment. Instead, a shift in focus towards identifying specific cellular and molecular mechanisms has emerged, aiming to define new treatable traits based on specific cellular and molecular pathways (defined as endotypes). Important pathobiological components involve the release of potent inflammatory mediators, such as histamine, prostaglandins (PGs) and leukotrienes (LTs), that cause bronchoconstriction and airway inflammation. A rapid hydrophilic interaction chromatography method failed to quantify the major histamine metabolite 1,4-methyl-5-imidazoleacetic acid (tele-MIAA) due to ion suppression from inorganic salts present in urine. Ion-pairing chromatography was therefore employed and the resulting increase in precision enabled the detection of higher baseline levels of tele-MIAA in females compared to males (3.0 vs. 2.1 μmol/mmol creatinine, respectively) (Paper I). In addition, levels of tele-MIAA reached up to 30 μmol/mmol creatinine in spot urine samples from mastocytosis patients. Three liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) methods quantified 130 oxylipins and were able to define kinetic release and enzymatic contribution of mast cell-derived mediators to smooth muscle contraction using isolated and intact airways from humans and guinea pigs in vitro. PGD2 levels were elevated 24-hour post anti-IgE stimulation of human bronchus, suggesting a prolonged mast cell activation (Paper II). Furthermore, exposure to house dust mite (HDM) induced strong release of lipoxygenase-derived LTB4, 5,15-DiHETE, 15-HETE and 15-HEDE along with eosinophilic infiltration in a C57BL/6 murine model of asthma. Interestingly, high levels of cysteinyl-leukotrienes (CysLTs) remained unchanged suggesting a different role of CysLTs in mice (Paper III). Urinary profiles of 11 eicosanoid metabolites in 100 healthy control subjects and 497 asthmatics defined normal baseline levels and revealed increased concentration of PGs, LTE4 and isoprostanes with asthma severity. Consensus clustering of 497 asthmatics identified a five-cluster model with distinct clinical characteristics, which included two new phenotypes, U1 and U5, with low levels of thromboxanes and PGs respectively (Paper IV). At the 12 to 18-month longitudinal time point for the 302 subjects with severe asthma, z-scored eicosanoid concentrations retained the five-cluster profile, despite technical and intra-subject variability. In conclusion, the developed bioanalytical methods were applied to define levels of histamine and eicosanoid metabolites in urine from healthy subjects. In addition, release of multiple oxylipins following mast cell-mediated bronchoconstriction and HDM-induced airway inflammation in model systems were explored to relate functions to levels of lipid mediators. For the first time, grouping of asthmatics according to profiles of eicosanoid metabolites in urine was performed and demonstrated sufficient resolution to identify five sub-phenotypes of asthma possessing distinct clinical characteristics. The presented approaches, for both in vitro and in vivo respiratory research, offer an opportunity to progress the development of new treatment options and suggests a panel of PGs, LTE4 and isoprostanes to be further validated as diagnostic markers in patients with asthma

Metabolomics analysis identifies sex-associated metabotypes of oxidative stress and the autotaxin-lysoPA axis in COPD.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease and a leading cause of mortality and morbidity worldwide. The aim of this study was to investigate the sex dependency of circulating metabolic profiles in COPD.Serum from healthy never-smokers (healthy), smokers with normal lung function (smokers), and smokers with COPD (COPD; Global Initiative for Chronic Obstructive Lung Disease stages I-II/A-B) from the Karolinska COSMIC cohort (n=116) was analysed using our nontargeted liquid chromatography-high resolution mass spectrometry metabolomics platform.Pathway analyses revealed that several altered metabolites are involved in oxidative stress. Supervised multivariate modelling showed significant classification of smokers from COPD (p=2.8×10-7). Sex stratification indicated that the separation was driven by females (p=2.4×10-7) relative to males (p=4.0×10-4). Significantly altered metabolites were confirmed quantitatively using targeted metabolomics. Multivariate modelling of targeted metabolomics data confirmed enhanced metabolic dysregulation in females with COPD (p=3.0×10-3) relative to males (p=0.10). The autotaxin products lysoPA (16:0) and lysoPA (18:2) correlated with lung function (forced expiratory volume in 1 s) in males with COPD (r=0.86; p<0.0001), but not females (r=0.44; p=0.15), potentially related to observed dysregulation of the miR-29 family in the lung.These findings highlight the role of oxidative stress in COPD, and suggest that sex-enhanced dysregulation in oxidative stress, and potentially the autotaxin-lysoPA axis, are associated with disease mechanisms and/or prevalence

The FADS1 rs174550 Genotype Modifies the n-3 and n-6 PUFA and Lipid Mediator Responses to a High Alpha-Linolenic Acid and High Linoleic Acid Diets

Scope: The fatty acid composition of plasma lipids, which is associated with biomarkers and risk of non-communicable diseases, is regulated by dietary polyunsaturated fatty acids (PUFAs) and variants of fatty acid desaturase (FADS). We investigated the interactions between dietary PUFAs and FADS1 rs174550 variant.Methods and results: Participants (n = 118), homozygous for FADS1 rs174550 variant (TT and CC) followed a high alpha-linolenic acid (ALA, 5 percent of energy (E-%)) or a high linoleic acid (LA, 10 E-%) diet during an 8-week randomized controlled intervention. Fatty acid composition of plasma lipids and PUFA-derived lipid mediators were quantified by gas and liquid chromatography mass spectrometry, respectively. The high-LA diet increased the concentration of plasma LA, but not its lipid mediators. The concentration of plasma arachidonic acid decreased in carriers of CC and remained unchanged in the TT genotype. The high-ALA diet increased the concentration of plasma ALA and its cytochrome P450-derived epoxides and dihydroxys, and cyclooxygenase-derived monohydroxys. Concentrations of plasma eicosapentaenoic acid and its mono- and dihydroxys increased only in TT genotype carriers.Conclusions: These findings suggest the potential for genotype-based recommendations for PUFA consumption, resulting in modulation of bioactive lipid mediators which can exert beneficial effects in maintaining health.</p

Urinary leukotriene E4 and prostaglandin D2 metabolites increase in adult and childhood severe asthma characterized by type 2 Inflammation : a clinical observational study

Rationale: New approaches are needed to guide personalized treatment of asthma.Objective: To test if urinary eicosanoid metabolites can direct asthma phenotyping.Methods: Urinary metabolites of prostaglandins (PG), cysteinyl-leukotrienes (LT) and isoprostanes were quantified in the Unbiased Biomarkers for the Prediction of Respiratory Diseases Outcomes (U-BIOPRED) study including 86 adults with mild-to-moderate asthma (MMA), 411 with severe asthma (SA), and 100 healthy controls (HC). Validation was performed in 302 SA subjects followed-up after 12-18 months, and externally in 95 adolescents with asthma.Measurement and Main Results: Metabolite levels in HC were unrelated to age, BMI and sex, except for the PGE2-pathway. Eicosanoid levels were generally greater in MMA relative to HC, with further elevations in SA, except for PGE2-metabolites in males, which were the same or lower in non-smoking asthmatics as in HC. Metabolite levels were unchanged in asthmatics adherent to oral corticosteroid treatment as documented by urinary prednisolone detection, whereas SA treated with omalizumab had lower levels of LTE4 and the PGD2 metabolite 2,3-dinor-11?-PGF2?. High levels of LTE4 and PGD2-metabolites were associated with lower lung-function, and increased levels of exhaled nitric oxide and eosinophil markers in blood, sputum and urine in U-BIOPRED and in adolescents with asthma. These type-2 (T2) asthma associations were reproduced in the follow-up visit of the U-BIOPRED study, and found to be as sensitive to detect T2 inflammation as the established biomarkers. Conclusions: Monitoring of urinary eicosanoids can identify T2 asthma and introduces a new non-invasive approach for molecular phenotyping of adult and adolescent asthma

Low levels of endogenous anabolic androgenic steroids in females with severe asthma taking corticosteroids

Rationale: patients with severe asthma are dependent upon treatment with high doses of inhaled corticosteroids (ICS) and often also oral corticosteroids (OCS). The extent of endogenous androgenic anabolic steroid (EAAS) suppression in asthma has not previously been described in detail. The objective of the present study was to measure urinary concentrations of EAAS in relation to exogenous corticosteroid exposure.Methods: urine collected at baseline in the U-BIOPRED (Unbiased Biomarkers for the Prediction of Respiratory Disease outcomes) study of severe adult asthmatics (SA, n=408) was analysed by quantitative mass spectrometry. Data were compared to that of mild-to-moderate asthmatics (MMA, n=70) and healthy subjects (HC, n=98) from the same study.Measurements and main results: the concentrations of urinary endogenous steroid metabolites were substantially lower in SA than in MMA or HC. These differences were more pronounced in SA patients with detectable urinary OCS metabolites. Their dehydroepiandrosterone sulfate (DHEA-S) concentrations were Conclusion The pronounced suppression of endogenous anabolic androgens in females might contribute to sex differences regarding the prevalence of severe asthma

Enhanced oxidative stress in smoking and ex-smoking severe asthma in the U-BIOPRED cohort

Oxidative stress is believed to be a major driver of inflammation in smoking asthmatics. The U-BIOPRED project recruited a cohort of Severe Asthma smokers/ex-smokers (SAs/ex) and non-smokers (SAn) with extensive clinical and biomarker information enabling characterization of these subjects. We investigated oxidative stress in severe asthma subjects by analysing urinary 8-iso-PGF2α and the mRNA-expression of the main pro-oxidant (NOX2; NOSs) and anti-oxidant (SODs; CAT; GPX1) enzymes in the airways of SAs/ex and SAn. All the severe asthma U-BIOPRED subjects were further divided into current smokers with severe asthma (CSA), ex-smokers with severe asthma (ESA) and non-smokers with severe asthma (NSA) to deepen the effect of active smoking. Clinical data, urine and sputum were obtained from severe asthma subjects. A bronchoscopy to obtain bronchial biopsy and brushing was performed in a subset of subjects. The main clinical data were analysed for each subset of subjects (urine-8-iso-PGF2α; IS-transcriptomics; BB-transcriptomics; BBr-transcriptomics). Urinary 8-iso-PGF2α was quantified using mass spectrometry. Sputum, bronchial biopsy and bronchial brushing were processed for mRNA expression microarray analysis. Urinary 8-iso-PGF2α was increased in SAs/ex, median (IQR) = 31.7 (24.5-44.7) ng/mmol creatinine, compared to SAn, median (IQR) = 26.6 (19.6-36.6) ng/mmol creatinine (p< 0.001), and in CSA, median (IQR) = 34.25 (24.4-47.7), vs. ESA, median (IQR) = 29.4 (22.3-40.5), and NSA, median (IQR) = 26.5 (19.6-16.6) ng/mmol creatinine (p = 0.004). Sputum mRNA expression of NOX2 was increased in SAs/ex compared to SAn (probe sets 203922_PM_s_at fold-change = 1.05 p = 0.006; 203923_PM_s_at fold-change = 1.06, p = 0.003; 233538_PM_s_at fold-change = 1.06, p = 0.014). The mRNA expression of antioxidant enzymes were similar between the two severe asthma cohorts in all airway samples. NOS2 mRNA expression was decreased in bronchial brushing of SAs/ex compared to SAn (fold-change = -1.10; p = 0.029). NOS2 mRNA expression in bronchial brushing correlated with FeNO (Kendal's Tau = 0.535; p< 0.001). From clinical and inflammatory analysis, FeNO was lower in CSA than in ESA in all the analysed subject subsets (p< 0.01) indicating an effect of active smoking. Results about FeNO suggest its clinical limitation, as inflammation biomarker, in severe asthma active smokers. These data provide evidence of greater systemic oxidative stress in severe asthma smokers as reflected by a significant changes of NOX2 mRNA expression in the airways, together with elevated urinary 8-iso-PGF2α in the smokers/ex-smokers group. Trial registration ClinicalTrials.gov-Identifier: NCT01976767

Selective inhibition of prostaglandin D-2 biosynthesis in human mast cells to overcome need for multiple receptor antagonists : Biochemical consequences

Background The major mast cell prostanoid PGD(2) is targeted for therapy of asthma and other diseases, because the biological actions include bronchoconstriction, vasodilation and regulation of immune cells mediated by three different receptors. It is not known if the alternative to selectively inhibit the biosynthesis of PGD(2) affects release of other prostanoids in human mast cells. Objectives To determine the biochemical consequences of inhibition of the hematopoietic prostaglandin D synthase (hPGDS) PGD(2) in human mast cells. Methods Four human mast cell models, LAD2, cord blood derived mast cells (CBMC), peripheral blood derived mast cells (PBMC) and human lung mast cells (HLMC), were activated by anti-IgE or ionophore A23187. Prostanoids were measured by UPLC-MS/MS. Results All mast cells almost exclusively released PGD(2) when activated by anti-IgE or A23187. The biosynthesis was in all four cell types entirely initiated by COX-1. When pharmacologic inhibition of hPGDS abolished formation of PGD(2), PGE(2) was detected and release of TXA(2) increased. Conversely, when the thromboxane synthase was inhibited, levels of PGD(2) increased. Adding exogenous PGH(2) confirmed predominant conversion to PGD(2) under control conditions, and increased levels of TXB2 and PGE(2) when hPGDS was inhibited. However, PGE(2) was formed by non-enzymatic degradation. Conclusions Inhibition of hPGDS effectively blocks mast cell dependent PGD(2) formation. The inhibition was associated with redirected use of the intermediate PGH(2) and shunting into biosynthesis of TXA(2). However, the levels of TXA(2) did not reach those of PGD(2) in naive cells. It remains to determine if this diversion occurs in vivo and has clinical relevance

Metabolomics analysis identifies sex-associated metabotypes of oxidative stress and the autotaxin-lysoPA axis in&nbsp;COPD.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease and a leading cause of mortality and morbidity worldwide. The aim of this study was to investigate the sex dependency of circulating metabolic profiles in COPD.Serum from healthy never-smokers (healthy), smokers with normal lung function (smokers), and smokers with COPD (COPD; Global Initiative for Chronic Obstructive Lung Disease stages I-II/A-B) from the Karolinska COSMIC cohort (n=116) was analysed using our nontargeted liquid chromatography-high resolution mass spectrometry metabolomics platform.Pathway analyses revealed that several altered metabolites are involved in oxidative stress. Supervised multivariate modelling showed significant classification of smokers from COPD (p=2.8×10-7). Sex stratification indicated that the separation was driven by females (p=2.4×10-7) relative to males (p=4.0×10-4). Significantly altered metabolites were confirmed quantitatively using targeted metabolomics. Multivariate modelling of targeted metabolomics data confirmed enhanced metabolic dysregulation in females with COPD (p=3.0×10-3) relative to males (p=0.10). The autotaxin products lysoPA (16:0) and lysoPA (18:2) correlated with lung function (forced expiratory volume in 1 s) in males with COPD (r=0.86; p&lt;0.0001), but not females (r=0.44; p=0.15), potentially related to observed dysregulation of the miR-29 family in the lung.These findings highlight the role of oxidative stress in COPD, and suggest that sex-enhanced dysregulation in oxidative stress, and potentially the autotaxin-lysoPA axis, are associated with disease mechanisms and/or prevalence