Extracellular cyclophilin levels associate with parameters of asthma in phenotypic clusters

Abstract

Objective: Leukocyte persistence during chronic (quiescent) phases of asthma is a major hallmark of the disease. The mechanisms regulating these persistent leukocyte populations are not clearly understood. An alternative family of chemoattracting proteins, cyclophilins (Cyps), has recently been shown to contribute to leukocyte recruitment in animal models of allergic asthma. The goals of this study were to determine whether Cyps are present in asthma patients during the chronic phase of the disease and to investigate whether levels of Cyps associate with clinical parameters of disease severity.

Methods: Nasal wash samples from an urban cohort of 137 patients of age 6-20 years with physician-diagnosed asthma were examined for the presence of cyclophilin A (CypA), cyclophilin B (CypB), as well as several other classical chemokines. Linear, logistic, or ordinal regressions were performed to identify associations between Cyps, chemokines, and clinical parameters of asthma. The asthma cohort was further divided into previously established phenotypic clusters (cluster 1: n = 55; cluster 2: n = 31; and cluster 3: n = 51) and examined for associations.

Results: Levels of CypB in the asthma group were highly elevated compared to nonasthmatic controls, while a slight increase in Monocyte Chemotactic Protein-1 (MCP-1) was also observed. CypA and MCP-1 were associated with levels of eosinophil cationic protein (ECP; a marker of eosinophil activation). Cluster-specific associations were found for CypA and CypB and clinical asthma parameters [e.g. forced expiratory volume in 1 second (FEV(1)) and ECP].

Conclusions: Cyps are present in nasal wash samples of asthma patients and may be a novel biomarker for clinical parameters of asthma severity.

Figure 1. CypB and MCP-1 Increased in Asthma Patients During the Chronic Phase of Disease

Levels of extracellular CypA, CypB, and other classical chemokines were assessed in nasal wash samples from asthma patients and healthy control volunteers. CypA and CypB were measured by Western Blot analysis, and classical chemokines were measured by cytometric bead array or ELISA (eotaxin-2). Asthma group n = 137; control group n = 22. For analysis data were log₁₀ transformed, and a t-test was used to identify significant differences from the control group. *p<0.05; ***p<0.0001.

Figure 2. Levels of CypA, CypB, and MCP-1 by Asthma Cluster

Levels of extracellular CypA, CypB, and MCP-1 were measured in nasal wash samples as described above, and then grouped according to asthma phenotype (Table 1). Asthma cluster 1 n = 55; cluster 2 n = 31; cluster 3 n = 51; control group n = 22. Data were log₁₀ transformed, and t-tests were used to identify significant differences from the control group. No significant differences were observed.