Abstract
BackgroundExcessive apoptosis of airway epithelium is reported to induce airway remodeling and inhibited airway epithelium repair is highly associated with development of asthma and chronic obstructive pulmonary disease. Der p 2 is a major allergen derived from Dermatophagoides pteronyssinus and commonly causes airway hypersensitiveness and asthma; however, the connection between Der p 2 and epithelial apoptosis remains unclear. This study was aimed to explore whether Der p 2 induces apoptosis of airway epithelial cells and the underlying mechanisms.ResultsOur results showed that recombinant Der p 2 (rDP2) inhibited cell growth and induced apoptosis of human bronchial epithelial cell BEAS-2B. Further investigation revealed that rDP2 increased intracellular reactive oxygen species, level of cytosolic cytochrome c and cleavage of caspase-9 and caspase-3. rDP2 also induced activation of p38 mitogen-activated protein kinase (P38) and c-Jun N-terminal kinase (JNK), and triggered proapoptotic signals including decrease of Bcl-2, increase of Bax and Bak, and upregulation of Fas and Fas ligand. In parallel, rDP2 inhibited glycogen synthase kinase 3beta and consequently enhanced degradation of cellular (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP). Involvement of toll-like receptor (TLR)2 in rDP2-induced apoptosis was also demonstrated using specific small inhibitory RNA.ConclusionsOur findings indicate that rDP2 suppresses cell growth and trigger apoptosis of BEAS-2B cells, which may attribute to induction of both intrinsic and extrinsic pathway via TLR2 and P38/JNK signaling and c-FLIP degradation. It suggests that Der p 2 may aggravate respiratory disorders through enhancement of apoptosis and the consequent airway injury.
Highlights
Excessive apoptosis of airway epithelium is reported to induce airway remodeling and inhibited airway epithelium repair is highly associated with development of asthma and chronic obstructive pulmonary disease
To confirm the recombinant Der p 2 (rDP2)-induced cell death, cell cycle distribution analysis was performed and the results revealed that rDP2 dose-dependently elevated subG1 phase up to 22.4 ± 1.3 % (P < 0.005 as compared to glutathione S-transferase (GST) treatment)
transferase dUTP nick end labeling (TUNEL) assay showed that apoptotic cell ratio was increased to 24.1 ± 4.2 % of control in response to rDP2 treatment (40 μg/mL) (P < 0.005 as compared to GST treatment), and no TUNEL-positive cell was detected in the control and the GST treatment (Fig. 1c)
Summary
Excessive apoptosis of airway epithelium is reported to induce airway remodeling and inhibited airway epithelium repair is highly associated with development of asthma and chronic obstructive pulmonary disease. Der p 2 is a major allergen derived from Dermatophagoides pteronyssinus and commonly causes airway hypersensitive‐ ness and asthma; the connection between Der p 2 and epithelial apoptosis remains unclear. This study was aimed to explore whether Der p 2 induces apoptosis of airway epithelial cells and the underlying mechanisms. In patients with chronic obstructive pulmonary disease and asthma, the epithelial barrier exhibits detachment of columnar ciliated cells, presence of epithelial cell aggregates in sputum, increased permeability to allergens and disturbed. House dust mite (HDM) is one of the most important sources of indoor allergens and has been known as a predominant causative of respiratory disorders such as airway hypersensitiveness, asthma and exacerbation of lung. Association between Der p 2 and epithelial apoptosis has been rarely explored
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