Creatine Kinase Is Decreased in Childhood Asthma

Abstract

Rationale: The identification of novel molecules associated with asthma may provide insights into the mechanisms of disease and their potential clinical implications. Objectives: To conduct a screening of circulating proteins in childhood asthma and to study proteins that emerged from human studies in a mouse model of asthma. Methods: We included 2,264 children from eight birth cohorts from the Mechanisms of the Development of ALLergy project and the Tucson Children's Respiratory Study. In cross-sectional analyses, we tested 46 circulating proteins for association with asthma in the selection stage and carried significant signals forward to a validation and replication stage. As CK (creatine kinase) was the only protein consistently associated with asthma, we also compared whole blood CK gene expression between subjects with and without asthma (n = 249) and used a house dust mite (HDM)-challenged mouse model to gain insights into CK lung expression and its role in the resolution of asthma phenotypes. Measurements and Main Results: As compared with the lowest CK tertile, children in the highest tertile had significantly lower odds for asthma in selection (adjusted odds ratio, 95% confidence interval: 0.31; 0.15-0.65; P = 0.002), validation (0.63; 0.42-0.95; P = 0.03), and replication (0.40; 0.16-0.97; P = 0.04) stages. Both cytosolic CK forms (CKM and CKB) were underexpressed in blood from asthmatics compared with control subjects (P = 0.01 and 0.006, respectively). In the lungs of HDM-challenged mice, Ckb expression was reduced, and after the HDM challenge, a CKB inhibitor blocked the resolution of airway hyperresponsiveness and reduction of airway mucin. Conclusions: Circulating concentrations and gene expression of CK are inversely associated with childhood asthma. Mouse models support a possible direct involvement of CK in asthma protection via inhibition of airway hyperresponsiveness and reduction of airway mucin.

Keywords: asthma; biomarkers; creatine kinase.

Figure 1.

Study design. BAMSE = Child (Barn), Allergy, Milieu, Stockholm, Epidemiological survey; BIB = Born in Bradford cohort; INMA-G = INfancia y Medio Ambiente - Gipuzkoa; INMA-S = INfancia y Medio Ambiente - Sabadell; INMA-V = INfancia y Medio Ambiente - Valencia; RHEA = Mother-Child cohort in Crete; ROBBIC = Rome and Bologna Birth Italian Cohorts - Rome; TCRS = Tucson Children’s Respiratory Study.

Figure 2.

CK-B concentrations in lung tissue during house dust mite (HDM) challenge model in mice. (A) Model set up for HDM or saline challenge and days of harvest. (B) RNA expression by real-time PCR for n = 5 mice/group (representative data of two independent experiments). (C) Protein expression by Western blot from a set of lung lysates for n = 5–6 mice/group. *P < 0.05 and **P < 0.01. CK-B = creatine kinase-B.

Figure 3.

The impact of creatine kinase-B inhibition (CK-Bi) on pulmonary function and airway mucin accumulation in a house dust mite (HDM) mouse model. (A) Model set up for HDM challenge, creatine kinase inhibitor dosing, and days of assessment. All analyses reported in B–F were completed on Day 19. (B) Rrs, (C) Rn, indicative of the conducting airways, and (D) Ers were assessed during methacholine challenge by the Flexivent system. (E) PAS scores of histological lung sections from Day 19 harvest. (F) Representative images of PAS-stained sections from HDM versus HDM + CK-Bi groups from Day 19 harvest. For pulmonary function tests: n = 8 (HDM); n = 10 (HDM + CK-Bi); n = 5 (vehicle); n = 5 (vehicle + CK-Bi). For PAS: n = 12 (HDM); n = 10 (HDM + CK-Bi); n = 5 (vehicle); n = 5 (vehicle + CK-Bi). *P < 0.05, **P < 0.01, and ***P < 0.001. Ave = average; Ers = total airway elastance; PAS = periodic acid–Schiff; Rn = Newtonian resistance; Rrs = total airway resistance.