Histamine Challenge Research Articles

Intrinsic endothelial hyperresponsiveness to inflammatory mediators drives acute episodes in models of Clarkson disease.

Clarkson disease, or monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS), is a rare, relapsing-remitting disorder featuring the abrupt extravasation of fluids and proteins into peripheral tissues, which in turn leads to hypotensive shock, severe hemoconcentration, and hypoalbuminemia. The specific leakage factor(s) and pathways in ISCLS are unknown, and there is no effective treatment for acute flares. Here, we characterize an autonomous vascular endothelial defect in ISCLS that was recapitulated in patient-derived endothelial cells (ECs) in culture and in a mouse model of disease. ISCLS-derived ECs were functionally hyperresponsive to permeability-inducing factors like VEGF and histamine, in part due to increased endothelial nitric oxide synthase (eNOS) activity. eNOS blockade by administration of N(γ)-nitro-l-arginine methyl ester (l-NAME) ameliorated vascular leakage in an SJL/J mouse model of ISCLS induced by histamine or VEGF challenge. eNOS mislocalization and decreased protein phosphatase 2A (PP2A) expression may contribute to eNOS hyperactivation in ISCLS-derived ECs. Our findings provide mechanistic insights into microvascular barrier dysfunction in ISCLS and highlight a potential therapeutic approach.

A ligand-independent Tie2-activating antibody reduces vascular leakage in models of Clarkson disease.

Vascular dysfunction resulting from endothelial hyperpermeability is a common and important feature of critical illness due to sepsis, trauma, and other conditions associated with acute systemic inflammation. Clarkson disease [monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS)] is a rare, orphan disorder marked by spontaneous and recurrent episodes of hypotensive shock and peripheral edema due to widespread vascular leakage in peripheral tissues. Mortality from acute flares approaches 30% due to lack of effective therapies. We evaluated a monoclonal antibody (4E2) specific for the endothelial receptor tyrosine kinase Tie2 in ISCLS models. 4E2 activated Tie2 in ISCLS patient-derived endothelial cells and reduced baseline and proinflammatory mediator-induced barrier dysfunction. 4E2 also reduced mortality and/or vascular leakage associated with systemic histamine challenge or influenza infection in the SJL/J mouse model of ISCLS. These findings support a critical role for Tie2 dysregulation in ISCLS and highlight a viable therapeutic approach to this catastrophic disorder.

A Longitudinal Analysis of Equine Asthma Presentation and Response to Treatment Using Lung Function Testing and BAL Cytology Analysis in Combination with Owner Perception.

(1) Background: Equine asthma (EA) is a pervasive and important cause of poor performance and respiratory morbidity in horses. Diagnosis of EA includes an owner complaint, clinical scoring, lung function testing, and cytological analysis of bronchoalveolar lavage (BAL) cytology. There is a paucity of information about the longitudinal course of the disease using these outcome assessments; thus, this study sought to describe and quantify, in horses with more than one visit to a specialty pulmonary clinic in New England, the type and range of clinical presentations with an eventual diagnosis of EA. It also aimed to develop and compare the outcomes of scoring systems for owner complaints and veterinary assessments, document and assess the diagnostic methods used, and evaluate the response of the horses to treatment and time. (2) Methods: This study was a retrospective, cross-sectional, STROBE-compliant observational analysis of equine patients who visited the Tufts Cummings Hospital for Large Animals (HLA) for evaluation of equine asthma (EA) from 1999-2023. The horses were categorized as having mild-moderate (mEA) or severe EA (sEA) using the ACVIM consensus statement guidelines. After excluding those with inadequate documentation or only one visit (n = 936), a total of 76 horses were included in the study. Of the 197 visits, 138 (70.0%) resulted in a diagnosis of mEA and 45 (22.8%) resulted in a diagnosis of sEA. Demographic information, owner complaints, clinical examination and scoring, lung function testing, BAL cytology, and recommendations for environmental remediation and pharmacologic treatment were recorded for all the visits. The data were analyzed for agreement between owner complaints (complaint score, CS) and clinical examination findings (examination score, ES), changes in CS and ES, lung function testing, and BAL cytology over time, with 197 visits recorded. (3) Results: A comparison between the CS and ES showed that the owners were more likely than veterinarians to detect cough, and a decrease in cough was the most common owner observation after treatment. The response to the histamine challenge, used to detect airway hyperreactivity, was significantly improved with treatment or time in the horses with mEA, whereas baseline lung function did not significantly change in mEA or sEA. (4) Conclusions: Owners can be astute observers of clinical signs, especially cough, in EA. Tests of airway hyperreactivity are more successful in detecting changes in mEA than are baseline lung function testing and assessment of BAL cytology.

Recombinant human diamine oxidase prevents hemodynamic effects of continuous histamine infusion in guinea pigs

ObjectiveTo test whether recombinant human diamine oxidase (rhDAO) with a mutated heparin-binding motif (mHBM), which shows an increased alpha-distribution half-life, prevents histamine-induced hemodynamic effects.MaterialThirty-eight female guinea pigs were either pretreated with rhDOA_mHBM or buffer.Treatment and methodsGuinea pigs received a continuous infusion of histamine. Heart rate (HR), body core temperature and mean arterial pressure (MAP) were measured and blood was collected.ResultsContinuous intravenous infusion of 8 µg/kg/min histamine increased mean peak plasma histamine levels from 5 (± 0.3 SEM) to 28 ng/mL (± 4.9 SEM) after 30 min but had no effect on oxygen saturation. Guinea pigs pretreated with 4 mg/kg rhDAO_mHBM showed lower mean HR (p = 0.008), histamine plasma concentrations (p = 0.002), and higher body core temperatures at the end of the histamine challenge (p = 0.02) compared to controls. Cessation of histamine infusion led to a rebound increase in MAP, but this hemodynamic instability was prevented by rhDAO_mHBM. Pretreatment with 4 mg/kg rhDAO_mHBM reduced urinary histamine (p = 0.004) and 1-Methylhistamine (p < 0.0001) concentrations compared to controls.ConclusionsProphylactic infusion of rhDAO_mHBM prevents hemodynamic effects in a guinea pig model of continuous histamine infusion. These findings might help in the translation from animals to humans and in the selection of the optimal dosing of rhDAO_mHBM during human histamine challenge studies.

Placebo-Controlled Histamine Challenge Disproves Suspicion of Histamine Intolerance

Histamine intolerance (HIT) is frequently diagnosed in patients with polysymptomatic otherwise unexplained symptoms. To exclude HIT by a single-blind placebo-controlled histamine challenge (SBPCHC), to study clinical features of patients with positive challenge, and to examine the predictability of HIT by biomarkers. SBPCHC was performed in 59 patients with suspected HIT. History and clinical data, including serum diamine oxidase (DAO) and histamine skin test wheal size of patients with positive versus negative SBPCHC, were compared. Patients were predominantly middle-aged women (84.7%). Three-quarters reported improvement but never resolution of symptoms during a histamine-low diet. Histamine provocation was safe; only 1 patient was treated with antihistamines. Thirty-seven patients (62.7%) displayed symptoms to placebo. HIT was excluded in 50 patients (84.7%). Objective symptoms occurred in 4 of 59 cases (6.8%) after histamine but not after placebo challenge. These were diagnosed with "plausible HIT" because reactions occurring by chance could not be excluded. Another 5 patients (8.5%) were diagnosed with "possible HIT" after case-dependent detailed analysis. Patients with plausible/possible HIT had reported more gastrointestinal symptoms (P= .01), but comparable diet response and equal histamine skin prick test wheal sizes to those without HIT. Serum DAO activity tended to be lower in patients with HIT (P= .08), but was highly variable in those without, limiting its value as a biomarker. SBPCHC disproves HIT in the majority of patients. Placebo-controlled challenges are needed as placebo reactions were frequent. Gastrointestinal symptoms after food intake and reduced DAO levels are markers for HIT; however, specificity is not sufficient enough for making the diagnosis.

Myricetin alleviates ovalbumin-induced allergic rhinitis in mice by regulating Th1/Th2 balance

Objective: To evaluate the effect of myricetin on ovalbumin (OVA)-induced allergic rhinitis in mice. Methods: Mice were sensitized and challenged using OVA (5%, 500 mL) intraperitoneally and intranasally, respectively, on an alternative day for 14 days, followed by administration of myricetin (50, 100, and 200 mg/kg) till day 21. Nasal symptoms, biochemical parameters, protein expressions, and histopathology were observed. Results: OVA-induced increased nasal symptoms including rubbing, sneezing, and discharge were significantly reduced by myricetin (100 and 200 mg/kg) (P&lt;0.05). Myricetin also protected against histamine challenge and attenuated elevated serum immunoglobulin E (IgE; total and OVA-specific), total IgG1, and β-hexosaminidase levels, as well as leukotriene C4 and interleukins levels in nasal lavage fluid (P&lt;0.05). Western blot analysis showed that myricetin significantly upregulated the protein expression of T-box expressed in T cells, while downregulating the protein expression of GATA binding protein 3, NF-κB, and 1κВ-α (P&lt;0.05). Additionally, OVA-induced histopathological abberations in the nasal mucosa was markedly ameliorated by myricetin treatment (P&lt;0.05). Conclusions: Myricetin exerts anti-allergic effects against OVA-induced allergic rhinitis via regulating Th1/Th2 balance.

Effectiveness of Indonesian house dust mite allergenic extract in triggering allergic rhinitis sensitivity in a mouse model: A preliminary study

Perennial allergic rhinitis (AR) is a chronic upper respiratory disease, with inflammation mediated by immunoglobulin E in the nasal mucosa caused by house dust mites. Recently, allergen immunotherapy showed promising allergic healing in patients with a definite history of sensitization. Based on this finding, a product was developed using Indonesian house dust mite (IHDM). This study aimed to optimize the allergenic rhinitis mouse model that was generated using IHDM to test the in vivo sensitivity and safety of this product. Seven groups of mice were used for effectiveness testing - normal, negative control with IHDM challenge, positive control with 0.1% histamine challenge, and AR group by both IHDM-induced sensitization at 12.5, 50, 250, or 500 μg and IHDM challenge. Mice were sensitized by intraperitoneal administration of IHDM once a week for 3 consecutive weeks. Thereafter, the challenge was given intranasally 5 times on alternate days. The number of nose rubbing and sneezing was noted. Eosinophil infiltration was assessed histologically using hematoxylin and eosin staining. The expression of interleukin-5 (IL-5) mRNA in the nasal mucosa was determined using semi-quantitative reverse transcription-polymerase chain reaction. The induction of AR with IHDM significantly increased the number of nose rubbing and sneezing in the mouse model. Eosinophil infiltration was observed in the nasal mucosa; however, no significant change occurred in the expression of IL-5 mRNA. Overall, these data indicate that IHDM allergenic extract could be an effective sensitizing agent in a mouse model of AR. Although the use of IHDM is a limitation of this study because other sources of house dust mites might have different effects, this study provides a proper model for immunotherapy effectivity testing for in vivo pre-clinical studies.

Diamine oxidase knockout mice are not hypersensitive to orally or subcutaneously administered histamine

ObjectiveTo evaluate the contribution of endogenous diamine oxidase (DAO) in the inactivation of exogenous histamine, to find a mouse strain with increased histamine sensitivity and to test the efficacy of rhDAO in a histamine challenge model.MethodsDiamine oxidase knockout (KO) mice were challenged with orally and subcutaneously administered histamine in combination with the β-adrenergic blocker propranolol, with the two histamine-N-methyltransferase (HNMT) inhibitors metoprine and tacrine, with folic acid to mimic acute kidney injury and treated with recombinant human DAO. Core body temperature was measured using a subcutaneously implanted microchip and histamine plasma levels were quantified using a homogeneous time resolved fluorescence assay.ResultsCore body temperature and plasma histamine levels were not significantly different between wild type (WT) and DAO KO mice after oral and subcutaneous histamine challenge with and without acute kidney injury or administration of HNMT inhibitors. Treatment with recombinant human DAO reduced the mean area under the curve (AUC) for core body temperature loss by 63% (p = 0.002) and the clinical score by 88% (p < 0.001). The AUC of the histamine concentration was reduced by 81%.ConclusionsInactivation of exogenous histamine is not driven by enzymatic degradation and kidney filtration. Treatment with recombinant human DAO strongly reduced histamine-induced core body temperature loss, histamine concentrations and prevented the development of severe clinical symptoms.

Micropuncture closure following high density microarray patch application in healthy subjects.

The high-density microarray patch (HD-MAP) promises to be a robust vaccination platform with clear advantages for future global societal demands for health care management. The method of action has its base not only in efficient delivery of vaccine but also in the reliable induction of a local innate physical inflammatory response to adjuvant the vaccination process. The application process needs to induce levels of reactivity, which are acceptable to the vaccine, and from which the skin promptly recovers. 1×1cm HD-MAP patches containing 5000, 250-μm long microprojections were applied to the skin in 12 healthy volunteers. The return of skin barrier function was assessed by transepidermal water loss (TEWL) and reaction to topical histamine challenge. Skin barrier recovery by 48h was confirmed for all HD-MAP sites by recovered resistance to the effects of topical histamine application. Our previous observation, that the barrier disruption indicator TEWL returns to normal by 48h, is supported by this paper's demonstration of return of skin resistance to topical histamine challenge in twelve healthy subjects.

P14‐13: Correlation of airway hyperresponsiveness with peripheral blood eosinophilia by histamine challenge in young adult patients with chronic cough

P14‐13: Correlation of airway hyperresponsiveness with peripheral blood eosinophilia by histamine challenge in young adult patients with chronic cough

Long-term predictors of severe exacerbations and mortality in a cohort of well-characterised adults with asthma

BackgroundWe aimed to explore long-term predictors of severe exacerbations and mortality in adults with well-characterised asthma.Study design and methodsAdults (aged ≥ 15) with an objectively verified diagnosis of asthma were recruited from a Danish respiratory outpatient clinic between 1974 and 1990. All individuals were followed in Danish registries for vital status, hospital admissions for asthma and cause of death until end of 2017. Predictors of exacerbations were obtained from a repeated measures model. Standardised mortality rates (SMR) for all-causes were compared with the Danish background population. Hazard ratios for mortality were obtained from a cox proportional hazards model in a two-step process.ResultsAt baseline, the cohort comprised 1071 patients (mean age 38, SD 16, 61% women), of whom 357 (33%) died during follow-up, with 93 (26%) dying from asthma (primary diagnosis). We found an SMR of 1.24 (95% CI 1.11–1.37, p < 0.001) for all-cause mortality. Baseline predictors for asthma-related death and repeated severe exacerbations were increasing age, ever smoker, FEV1 < 80% pred., high blood eosinophils, longer duration of symptoms and use of SABA > twice daily. Being non-atopic, having a positive histamine challenge test and symptoms more than twice a week were also predictors of repeated exacerbations.ConclusionsMarkers of poor asthma control, including high use of SABA, are predictors of long-term exacerbation rate and mortality over 30 years in patients with well-characterised asthma. Improving asthma control, including lung function and reducing use of reliever medication, is vital for improving the long-term outcome of asthma.

Identifying bronchoconstriction from the ratio of diaphragm EMG to tidal volume

BackgroundA fall of ≥ 20 % in forced expiratory volume in the first second (FEV1) with a cumulative dose of histamine ≤ 7.8 μmol is considered to indicate bronchial hyperactivity, but no method exists for patients who cannot perform spirometry properly. Here we hypothesized that increases in respiratory central output measured by chest wall electromyography of the diaphragm (EMGdi-c) expressed as a function of tidal volume (EMGdi-c/VT) would have discriminative power to detect a ‘positive’ challenge test. MethodsIn a physiological study EMGdi was recorded from esophageal electrode (EMGdi-e) in 16 asthma patients and 16 healthy subjects during a histamine challenge test. In a second study, EMGdi from chest wall surface electrodes (EMGdi-c) was measured during a histamine challenge in 44 asthma patients and 51 healthy subjects. VT was recorded from a digital flowmeter during both studies. ResultsWith histamine challenge test the change in EMGdi-e/VT in patients with asthma was significantly higher than that in healthy subjects (104.2 % ± 48.6 % vs 0.03 % ± 17.1 %, p < 0.001). Similarly there was a significant difference in the change of EMGdi-c/VT between patients with asthma and healthy subjects (90.5 % ± 75.5 % vs 2.4 % ± 21.7 %, p < 0.001). At the optimal cut-off point (29 % increase in EMGdi-c/VT), the area under the ROC curve (AUC) for detection of a positive test was 0.91 (p < 0.001) with sensitivity 86 % and specificity 92 %. ConclusionsWe conclude that EMGdi-c/VT may be used as an alternative for the assessment of bronchial hypersensitivity and airway reversibility to differentiate patients with asthma from healthy subjects.

Can bronchoconstriction and bronchodilatation in horses be detected using electrical impedance tomography?

BackgroundElectrical impedance tomography (EIT) generates images of the lungs based on impedance change and was able to detect changes in airflow after histamine challenge in horses.ObjectivesTo confirm that EIT can detect histamine‐provoked changes in airflow and subsequent drug‐induced bronchodilatation. Novel EIT flow variables were developed and examined for changes in airflow.MethodsBronchoconstriction was induced using stepwise histamine bronchoprovocation in 17 healthy sedated horses. The EIT variables were recorded at baseline, after saline nebulization (control), at the histamine concentration causing bronchoconstriction (Cmax) and 2 and 10 minutes after albuterol (salbutamol) administration. Peak global inspiratory (PIFEIT) and peak expiratory EIT (PEFEIT) flow, slope of the global expiratory flow‐volume curve (FVslope), steepest FVslope over all pixels in the lung field, total impedance change (surrogate for tidal volume; VTEIT) and intercept on the expiratory FV curve normalized to VTEIT (FVintercept/VTEIT) were indexed to baseline and analyzed for a difference from the control, at Cmax, 2 and 10 minutes after albuterol. Multiple linear regression explored the explanation of the variance of Δflow, a validated variable to evaluate bronchoconstriction using all EIT variables.ResultsAt Cmax, PIFEIT, PEFEIT, and FVslope significantly increased whereas FVintercept/VT decreased. All variables returned to baseline 10 minutes after albuterol. The VTEIT did not change. Multivariable investigation suggested 51% of Δflow variance was explained by a combination of PIFEIT and PEFEIT.Conclusions and Clinical ImportanceChanges in airflow during histamine challenge and subsequent albuterol administration could be detected by various EIT flow volume variables.

A retrospective cohort study to evaluate the relationship of airway hyperresponsiveness to type 2 biomarkers in persistent asthma

irway hyperresponsiveness (AHR) is a hallmark of persistent asthma measured using direct or indirect airway bronchial challenge testing. The purpose of this study is to investigate the putative relationships between type 2 inflammatory biomarkers, airway geometry (FEV1 and FEF25-75) and specific IgE (RAST or skin prick) to AHR. We performed a retrospective analysis of our database (n = 131) of patients with asthma. Of these subjects, 75 had a histamine challenge and 56 had a mannitol challenge. Fractional exhaled nitric oxide (FeNO) and specific immunoglobulin E (IgE) but not blood eosinophils were significantly higher in patients with AHR to either histamine or mannitol. FEV1 % and FEF25 - 75 % were significantly lower in patients with AHR. Elevated Type 2 biomarkers including FeNO and specific IgE but not blood eosinophils were associated with AHR. Highlights: FeNO and specific IgE but not blood eosinophils are raised in patients with airway hyperresponsiveness.

Work-related Asthma in Crop Farmers

AIM: The objective of the study was to evaluate the influence of occupational exposure on asthma development among crop farmers. METHODS: A cross-sectional study was performed, comprising 87 crop farmers, and 80 office workers, matched by gender and age. Evaluation of subjects included completion of a standard questionnaire on chronic respiratory symptoms, spirometry tests, histamine challenge, serial peak expiratory flow rates (PEFR) measurements, and skin prick tests to occupational and common inhalant allergens. RESULTS: The prevalence of chronic respiratory symptoms in the past 12 months was higher, while the mean values of spirometric parameters were lower in crop farmers. Sensitization to workplace and common inhalant allergens was similar in both groups, whereas frequencies of bronchial hyperresponsiveness (BHR) and asthma were non-significantly higher in crop farmers. The prevalence of allergic was significantly higher compared to non-allergic asthma in both groups. Asthma was registered in 8% of crop farmers and was significantly associated with atopy, and positive family history of asthma. Occupational allergic asthma (OA) was registered in 2.3% of crop farmers, while the frequency of work-aggravated asthma was 5.7%. A causal relationship between workplace and asthma, suggesting allergic OA, was documented in two crop farmers with asthma, based on serial PEFR monitoring, but specific workplace agent causing asthma in the affected subjects was not identified. CONCLUSION: The obtained results can contribute in the detection of critical points for action, and serve as a predictive factor in the development of work-related asthma, indicating the need for reduction of adverse occupational exposures through adequate preventive measures, regular health examinations, obligatory use of respiratory protective equipment, and implementation of engineering controls.

Asthma in children during the COVID-19 pandemic: lessons from lockdown and future directions for management

Asthma in children during the COVID-19 pandemic: lessons from lockdown and future directions for management

Evaluation of histamine-provoked changes in airflow using electrical impedance tomography in horses.

Electrical impedance tomography(EIT) generates thoracic impedance images of the lungs and has been used to assess ventilation in horses. This technique may have application in the detection of changes in airflow associated with equine asthma. The objective was to determine if histamine-induced airflow changes observed with flowmetric plethysmography (Δflow) could also be explained using global and regional respiratory gas flow signals calculated from EITsignals. Experimental in vivo study. Six horses, sedated using detomidine were fitted with a thoracic EITbelt and flowmetric plethysmography hardware. Saline (baseline=BL) and increasing concentrations of histamine (C1-4) were nebulised into the face mask until a change in breathing pattern was clinically confirmed and Δflow increased greater or equal to 50%. After nebulisation Δflow and EIT images were recorded over 3minutes and peak global inspiratory (InFglobal ) and expiratory (ExFglobal ) flow as well as peak regional expiratory and inspiratory flow for the dorsal and the ventral area of the right and left lungs were evaluated. Delta flow, InFglobal and ExFglobal at subsequent concentrations were indexed to baseline (yi =Ci /BL-1). Indexed and nonindexed variables were evaluated for a difference from baseline at sequential histamine doses (time). Multiple linear regression assessment of variance in delta flow was also investigated. Consistent with histamine-provoked increases in Δflow, the global flow indices increased significantly. A significant increase in regional inspiratory flow was seen in the right and left ventral lung and dorsal right lung. Multiple regression revealed that the variance in ExFglobal , and right and left ventral expiratory flow best explained the variance in Δflow (r2 =.82). Low number of horses and horses were healthy. Standardised changes in airflow during histamine challenge could be detected using EIT gas flow variables.

Diagnostic value of volumetric capnography in patients with chronic cough variant asthma

OBJECTIVES:To evaluate the quantitative changes and diagnostic performance of volumetric capnography (VCap) parameters in patients with cough variant asthma.METHODS:This cross-sectional study enrolled 31 patients with cough variant asthma and 30 patients with chronic cough without asthma between November 2010 and March 2012. VCap measurements were recorded at baseline, during the five steps of the histamine challenge, and after bronchodilation with salbutamol. They were then compared between the baseline and histamine challenge, and between the two groups. Receiver operating characteristic curve analysis was performed for different VCap measurements.RESULTS:The slope of phase III (dc\\dv3) and the ratio of phase III slope to phase II slope (SR23%) decreased from baseline upon challenge with 1.1 mg histamine in cough variant asthma patients but increased in patients with chronic cough without asthma. Additionally, the change upon challenge with 1.1 mg histamine in dc\\dv3 from baseline (S6-S1dc\\dv3) in cough variant asthma patients had the largest area under the curve (AUC) (0.814, 95% CI: 0.697-0.931; p<0.001). The AUC for change upon challenge with 1.1 mg histamine in SR23% from baseline was 0.755 (95%CI: 0.632-0.878; p<0.001). At a cutoff of 19.8, S6-S1 dc\\dv3 had a sensitivity of 74.2% and specificity of 90.0% and at a cutoff of 40.7, S6-S1 SR23% had a sensitivity of 48.4% and specificity of 96.7%.CONCLUSION:Patients with cough variant asthma exhibit distinct VCap responses for dead space parameters upon challenge with histamine in comparison to patients with chronic cough. VCap parameters like phase III slope and phase III/phase II slope ratio could be used to aid the diagnosis of cough variant asthma.

Network-Based Functional Prediction Augments Genetic Association To Predict Candidate Genes for Histamine Hypersensitivity in Mice.

Genetic mapping is a primary tool of genetics in model organisms; however, many quantitative trait loci (QTL) contain tens or hundreds of positional candidate genes. Prioritizing these genes for validation is often ad hoc and biased by previous findings. Here we present a technique for prioritizing positional candidates based on computationally inferred gene function. Our method uses machine learning with functional genomic networks, whose links encode functional associations among genes, to identify network-based signatures of functional association to a trait of interest. We demonstrate the method by functionally ranking positional candidates in a large locus on mouse Chr 6 (45.9 Mb to 127.8 Mb) associated with histamine hypersensitivity (Histh). Histh is characterized by systemic vascular leakage and edema in response to histamine challenge, which can lead to multiple organ failure and death. Although Histh risk is strongly influenced by genetics, little is known about its underlying molecular or genetic causes, due to genetic and physiological complexity of the trait. To dissect this complexity, we ranked genes in the Histh locus by predicting functional association with multiple Histh-related processes. We integrated these predictions with new single nucleotide polymorphism (SNP) association data derived from a survey of 23 inbred mouse strains and congenic mapping data. The top-ranked genes included Cxcl12, Ret, Cacna1c, and Cntn3, all of which had strong functional associations and were proximal to SNPs segregating with Histh. These results demonstrate the power of network-based computational methods to nominate highly plausible quantitative trait genes even in challenging cases involving large QTL and extreme trait complexity.

Asthma and Chronic Obstructive Pulmonary Disease Associated With Occupational Exposure in Dairy Farmers - Importance of Job Exposure Matrices.

AIM:To evaluate the prevalence of chronic respiratory symptoms, lung function impairment, and chronic obstructive respiratory diseases in dairy farmers. Our objective is to then examine their relation to exposure duration and to explore the usefulness of job exposure matrices as tools for exposure assessment, and predictors for respiratory health impairment.METHODS:A cross-sectional study was performed, including 83 dairy farmers (mean age: 52.6 ± 8.7 years; mean exposure duration: 23.7 ± 7.6 years) and 80 office workers as a control group (mean age: 52.7 ± 8.2 years) matched for age, smoking habits, and socioeconomic status. Methods of evaluating examined subjects included a questionnaire on respiratory symptoms in the last 12 months, spirometry and histamine challenge, as well as the use of job exposure matrices (JEM).RESULTS:Dairy farmers had a significantly higher prevalence of cough (38.5), phlegm (27.7%), and wheezing (21.7%), than controls (p < 0.05). All mean baseline spirometric parameters were lower in dairy farmers compared to the controls, but statistical significance was confirmed only for MEF25, MEF50, and MEF75% (p = 0.010, p = 0.001, and p = 0.004, respectively). The prevalence of bronchial hyperresponsiveness, asthma, and chronic obstructive pulmonary disease was higher in dairy farmers but without statistical significance. JEM were useful tools for exposure assessment and predictors of factors for asthma and COPD development.CONCLUSION:The results suggest that occupational exposure among crop farmers is associated with a higher prevalence of respiratory symptoms, lung function impairment, and a higher prevalence of chronic respiratory diseases. JEM showed good potential for farming exposure evaluation and promoted their applicability within the diagnostic algorithm focused on respiratory health assessment.