Peripheral blood and airway tissue expression of transforming growth factor β by neutrophils in asthmatic subjects and normal control subjects

Abstract

Background: Airway remodeling may play an important role in asthma pathophysiology. Transforming growth factor β (TGF-β) has a critical role in the remodeling process. Although cellular sources for TGF-β have been previously investigated in asthma airways, the expression, release, or both of TGF-β from asthmatic airways and blood neutrophils has not been reported. Objective: The current study evaluated the TGF-β protein and messenger (m)RNA expression by airway and peripheral blood neutrophils in asthmatic and normal subjects. Methods: TGF-β protein expression by airway and peripheral blood neutrophils was detected by using immunocytochemistry. TGF-β protein levels in blood neutrophil supernatant were measured by using an enzyme immunoassay. TGF-β mRNA expression was evaluated by using reverse transcription-PCR. Results: Higher numbers of TGF-β+ cells and neutrophils were found in airway tissue of asthmatic (n = 15) compared with normal subjects (n = 10). Although neutrophils in both asthmatic and normal airway tissue expressed TGF-β protein and the percentage of neutrophils expressing TGF-β was similar between the two groups, the total number of TGF-β+ neutrophils was higher in the asthmatic subjects (P = .01). Peripheral blood neutrophils from asthmatic (n = 5) and normal subjects (n = 7) also expressed TGF-β protein and mRNA. Blood neutrophils from asthmatic subjects spontaneously released significantly higher levels of TGF-β than those from normal subjects (P = .007). Conclusion: These data suggest that airway and blood neutrophils from both asthmatic and normal subjects can express and release TGF-β. Higher levels of TGF-β expression-release from asthmatic neutrophils indicate that nentrophils may be involved in the airway remodeling process of asthmatic subjects.