The YKL-40-increased bronchial smooth muscle cell proliferation and migration is PAR-2 dependant

Background: In asthma, the decrease in lung function has been associated with an increased mass of bronchial smooth muscle (BSM). However, the mechanism of such remodelling remains largely unknown. We focused our attention on chitinase 3-like 1 protein YKL-40, since we previously reported that it altered the physiological properties of BSM cells and is highly secreted by inflammatory cells and epithelial cells from severe asthmatics. Objectives: The objectives were to study the mechanisms underlying the effects of YKL-40 on human BSM cell proliferation and migration. Methods: YKL-40 was kindly provided by MedImmune. Human BSM cells were cultured from controls (n=7) and asthmatics (n=6). BSM cell proliferation was assessed using BrdU incorporation. Cell migration was evaluated using inserts. Transduction mechanisms were assessed using several inhibitors of signal transduction pathways (Pertussis toxin, Calphostin, PD98059, SB203580, LY294002). The involvement of protease activated receptor-2 (PAR-2) was evaluated using an anti-PAR-2 blocking antibody. Results: YKL-40 significantly increased by more than two fold BSM cell BrdU incorporation within 24h incubation and cell number within 48h. Following 24h incubation, YKL-40 significantly increased BSM cell migration. These effects were inhibited by blocking PAR-2 antibody in both asthmatic and control BSM cells. Transduction mechanisms of cell proliferation and migration involved Gi protein, protein kinase C, MAPK/ERK pathways. Conclusion: These results confirm that the chitinase YKL-40-induced BSM cell hyperplasia was PAR-2-dependant.