Bronchial hyperresponsiveness to mannitol, airway inflammation and Asthma Control Test in atopic asthmatic children

Mannitol Challenge to Assess Therapy Response in Asthmatic Children: An Interventional Cohort Study

Bronchial provocation tests, such as the mannitol challenge, can be performed to identify and quantify the severity of bronchial hyperresponsiveness in asthmatic patients. Studies of the mannitol challenge as a monitoring tool in asthmatic children are limited. Our primary aim was to compare the bronchial hyperresponsiveness to mannitol in treatment-naive asthmatic children between baseline and three months after receiving the indicated asthma prophylaxis. Twenty-three asthmatic patients aged 4-16 years were analyzed in this prospective cohort study. All subjects underwent the mannitol challenge at baseline and after three months of treatment with budesonide ± formoterol. The difference in the provocative dose of mannitol to induce a 15% drop in FEV₁ (PD₁₅) between baseline and follow-up, as well as its association with the presence of exercise-induced or nocturnal asthma symptoms, were evaluated. The PD₁₅ value increased significantly post-treatment (228.5 mg [4.50-458.15]; p = 0.04). Independently of the evaluation time point, the PD₁₅ values were significantly lower in the presence of nocturnal asthma symptoms (490 mg [122-635] vs. 635 mg [635-635]; p = 0.03), whereas there was no association between the PD₁₅ value and the presence of exercise-induced asthma (p = 0.73). These results suggest that bronchial hyperresponsiveness to mannitol may be a potential monitoring tool in the pediatric asthmatic population, reflecting therapy response in children receiving prophylactic treatment.

MicroRNA-590-5p represses proliferation of human fetal airway smooth muscle cells by targeting signal transducer and activator of transcription 3

INTRODUCTION

Pediatric asthma has remained a health threat to children in recent years. The abnormal proliferation of airway smooth muscle (ASM) cells contributes to airway remodeling during development of asthma. MicroRNAs (miRNAs) are critical regulators of ASM cell proliferation during airway remodeling. miR-590-5p has been reported to regulate cell proliferation in various cell types. However, it remains unclear whether miR-590-5p regulates ASM cell proliferation. In this study, we aimed to investigate the potential role of miR-590-5p in regulating fetal ASM cell proliferation in vitro stimulated by platelet-derived growth factor (PDGF).

MATERIAL AND METHODS

miRNA, mRNA, and protein expression was detected by real-time quantitative polymerase chain reaction and western blot. Cell proliferation was detected by CCK-8 and BrdU assays. The target of miR-590-5p was confirmed by dual-luciferase reporter assay.

RESULTS

MiR-590-5p expression was significantly down-regulated in fetal ASM cells stimulated with PDGF (p < 0.05). Overexpression of miR-590-5p inhibited cell proliferation (p < 0.05), whereas the suppression of miR-590-5p promoted cell proliferation of fetal ASM cells stimulated with PDGF (p < 0.05). Signal transducer and activator of transcription 3 (STAT3) was identified as a target gene of miR-590-5p. In addition, miR-590-5p negatively regulated STAT3 expression (p < 0.05). Moreover, miR-590-5p also modulated downstream genes of STAT3 including cyclin D3 and p27 (p < 0.05). The restoration of STAT3 significantly reversed the inhibitory effect of miR-590-5p on fetal ASM cell proliferation.

CONCLUSIONS

MiR-590-5p inhibits proliferation of fetal ASM cells by down-regulating STAT3, thereby suggesting a novel therapeutic target for the treatment of pediatric asthma.

Exhaled nitric oxide and mannitol test to predict exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is diagnosed via exercise challenge on a treadmill, but such testing requires complex equipment and sufficient health-care resources. The fraction of exhaled nitric oxide (FeNO) test and mannitol bronchial provocation test (BPT) may serve as a surrogate for exercise testing.

METHODS

We compared the diagnostic utilities of the FeNO test and mannitol BPT in predicting EIB in asthmatic children. We retrospectively analyzed data from 60 asthmatic children aged 6-16 years. We compared the exercise BPT results, FeNO levels, and mannitol BPT data.

RESULTS

All subjects were divided into exercise-positive (n = 41) or -negative (n = 19) BPT groups. Of the 41 exercise-positive patients, 32 were mannitol BPT positive and nine were mannitol BPT negative. Of the 19 exercise-negative patients, nine and 10, respectively, were mannitol BPT positive and BPT negative. The maximum % forced expiratory volume in 1 s (FEV₁ ) decrease after exercise was positively correlated with FeNO (r = 0.556, P < 0.001), and with mannitol response-dose ratio (RDR; r = 0.416, P = 0.001). The receiver operating characteristic (ROC) curve for FeNO to discriminate between asthmatic subjects with and without EIB had an area under the curve (AUC) of 0.771 (95%CI: 0.643-0.870). The discriminatory ROC curve for mannitol RDR had an AUC of 0.763 (95%CI: 0.633-0.864). The AUC of FeNO and mannitol RDR did not differ significantly.

CONCLUSIONS

EIB significantly correlated with both FeNO and mannitol BPT data. Given that both methods similarly predicted EIB in asthmatic children, the simpler and safer FeNO test alone may be a clinically useful diagnostic tool.

Clinical and immunological effects of vitamin D supplementation during the pollen season in children with allergic rhinitis

INTRODUCTION

Vitamin D deficiency has been proposed as a potential contributing factor in patients with allergic diseases. We compared the clinical and immunological effects of vitamin D supplementation to placebo during the pollen season in children with allergic rhinitis.

MATERIAL AND METHODS

Thirty-eight children aged 5-12, sensitive to grass pollen, participated in a prospective, randomized, double-blind, placebo-controlled trial. Children received either vitamin D 1000 IU daily supplementation or placebo. We studied symptoms/medication score, lung function, exhaled nitric oxide concentration (FENO), methacholine bronchial provocation test and serum level of 25(OH)D, as well as; CD4+CD25+Foxp3+ cells, TLR4, IL-1, IL-6, TNF and the IL-10 and transforming growth factor β1 (TGF-β1) levels in cell culture supernatants.

RESULTS

Vitamin D therapy was effective in reduction of the symptoms/medication score (p = 0.0371). In vitamin D group an increase in the CD4+CD25+Foxp3+ cells (7.06 vs. 10.5%; p = 0.0013) and serum 25(OH)D concentration (49.6 vs. 96.6 ng/ml; p = 0.0001) and in control group an increase in FENO (15.6 vs. 21 ppb; p = 0.0331) and serum 25(OH)D level were observed (82.9 vs. 100.3 ng/ml; p = 0.0003).We revealed a higher increase from baseline in the percentage of CD4+CD25+Foxp3+ cells in the vitamin D group compared to the control group (p = 0.0058). A significant correlation between CD4+CD25+Foxp3+ cell induction and FENO reduction in the vitamin D group was observed (p = 0.0217).

CONCLUSIONS

Vitamin D 1000 IU as a supplementary treatment of grass pollen allergy in children with allergic rhinitis during the pollen season significantly reduced the symptoms/medication score. The study revealed an immunological effect of vitamin D.

Spirometry-adjusted fraction of exhaled nitric oxide increases accuracy for assessment of asthma control in children

Spirometry and exhaled nitric oxide are two important complimentary tools to identify and assess asthma control in children. We aimed to determine the ability of a new suggested spirometry-adjusted fraction of exhaled nitric oxide (NO) index in doing that. A random sample of 1602 schoolchildren were screened by a health questionnaire, skin prick tests, spirometry with bronchodilation and exhaled NO. A total of 662 children were included with median (IQR) exhaled NO 11(14) ppb. Receiver operating characteristic (ROC) curves using exhaled NO equations from Malmberg, Kovesi and Buchvald, and spirometry-adjusted fraction of exhaled NO values were applied to identify asthmatic children and uncontrolled asthma. Receiver operating characteristic (ROC) curves failed to identify asthmatic children (all AUC < 0.700). Spirometry-adjusted fraction of exhaled NO/FEV₁ (AUC = 0.712; P = .010) and NO/FEF_25%-75% (AUC = 0.735 P = .004) had a fair and increased ability to identify uncontrolled disease compared with exhaled NO (AUC = 0.707; P = .011) or the Malmberg equation (AUC = 0.701; P = .014). Sensitivity and specificity identifying non-controlled asthma were 59% and 81%, respectively, for the cut-off value of 9.7 ppb/L for exhaled NO/FEV₁ , and 40% and 100% for 15.7 ppb/L/s for exhaled NO/FEF_25%-75% . Exhaled NO did not allow to identify childhood asthma. Spirometry-adjusted fraction of exhaled NO performed better-assessing asthma control in children. Thus, although more validation studies are needed, we suggest its use in epidemiological studies to assess asthma control.

Bronchoprotective tolerance with indacaterol is not modified by concomitant tiotropium in persistent asthma

BACKGROUND

Tiotropium is a long acting muscarinic antagonist (LAMA), licensed as triple therapy with inhaled corticosteroid and long-acting beta-agonist (ICS/LABA). There may be a synergistic benefit between LAMA and LABA as a consequence of receptor cross-talk, which in turn could modify beta-2 receptor downregulation and associated tolerance induced by LABA.

OBJECTIVE

We hypothesize this mechanism may result in a reduction of airway hyperresponsiveness (AHR) when using triple therapy.

METHODS

We evaluated 14 non-smoking asthmatics using an open-label, randomized crossover design. ICS with Indacaterol and Tiotropium (IND/TIO) vs ICS with Indacaterol (IND) over 4 weeks with challenge performed after first and last doses at trough.

RESULTS

We found no significant difference in mannitol sensitivity, expressed as the provocative dose of mannitol required to reach a 15% drop in FEV₁ , or mannitol reactivity, expressed as the response dose ratio (RDR: max % fall in FEV₁ /cumulative dose), when comparing ICS/IND/TIO to ICS/IND. Geometric mean fold differences for RDR comparing single and chronic dosing were 3.26-fold (95% CI 1.46-7.29) and 2.51-fold (95% CI 1.32-4.79) for IND and IND/TIO, respectively. Furthermore, salbutamol recovery post-challenge was significantly blunted after chronic compared to single dosing with either ICS/IND (P<.005) or ICS/IND/TIO (P<.05).

CONCLUSION AND CLINICAL RELEVANCE

Our data suggest that concomitant tiotropium does not modify the bronchoprotective tolerance induced by Indacaterol, in turn suggesting that cross-talk may not be clinically relevant when using triple therapy. This study was registered on clinicaltrials.gov as NCT02039011.