Liang J, Jiang D, Jung Y, Xie T, Ingram J, Church T, Degan S, Leonard M, Kraft M, Noble PW. Role of hyaluronan and hyaluronan-binding proteins in human asthma.
J Allergy Clin Immunol 2011;
128:403-411.e3. [PMID:
21570715 DOI:
10.1016/j.jaci.2011.04.006]
[Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/29/2011] [Accepted: 04/01/2011] [Indexed: 12/31/2022]
Abstract
BACKGROUND
The characteristics of human asthma are chronic inflammation and airway remodeling. Hyaluronan, a major extracellular matrix component, accumulates during inflammatory lung diseases, including asthma. Hyaluronan fragments stimulate macrophages to produce inflammatory cytokines. We hypothesized that hyaluronan and its receptors would play a role in human asthma.
OBJECTIVE
To investigate the role of hyaluronan and hyaluronan-binding proteins in human asthma.
METHODS
Twenty-one subjects with asthma and 25 healthy control subjects underwent bronchoscopy with endobronchial biopsy and bronchoalveolar lavage. Fibroblasts were cultured, and hyaluronan and hyaluronan synthase expression was determined at baseline and after exposure to several mediators relevant to asthma pathobiology. The expression of hyaluronan-binding proteins CD44, TLR (Toll-like receptor)-2, and TLR4 on bronchoalveolar lavage macrophages was determined by flow cytometry. IL-8 production by macrophages in response to hyaluronan fragment stimulation was compared.
RESULTS
Airway fibroblasts from patients with asthma produced significantly increased concentrations of lower-molecular-weight hyaluronan compared with those of normal fibroblasts. Hyaluronan synthase 2 mRNA was markedly increased in asthmatic fibroblasts. Asthmatic macrophages showed a decrease in cell surface CD44 expression and an increase in TLR2 and TLR4 expression. Macrophages from subjects with asthma showed an increase in responsiveness to low-molecular-weight hyaluronan stimulation, as demonstrated by increased IL-8 production.
CONCLUSION
Hyaluronan homeostasis is deranged in asthma, with increased production by fibroblasts and decreased CD44 expression on alveolar macrophages. Upregulation of TLR2 and TLR4 on macrophages with increased sensitivity to hyaluronan fragments suggests a novel proinflammatory mechanism by which persistence of hyaluronan fragments could contribute to chronic inflammation and airway remodeling in asthma.
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