Roles of macrophage stimulating protein and tyrosine kinase receptor RON in smoke-induced airway inflammation of rats.

Objective: To investigate the roles of macrophage stimulating protein (MSP) and its tyrosine kinase receptor RON in smoke-induced airway inflammation of rats.
Methods: Inhalation of combustion smoke was administered in rats to induce airway inflammation. Alveolar macrophages (AM) of healthy and smoking rats were isolated at different time points, cultured and then treated with different concentrations of MSP for 24 h.
Results: When compared with healthy rats, MSP increased in the serum and bronchoalveolar lavage fluid (BALF) of smoking rats in a time dependent manner. In smoking rats, the RON expression in the lung and AM was higher than in healthy rats, and these increases were time dependent. MSP stimulated the production of malondialdehyde (MDA) and reduced superoxide dismutase (SOD) activity in rat AM cells in a dose dependent manner. MSP also stimulated the release of inflammatory factors TNF-α, IL-8, IL-1β and IL-10 in rat AM in a dose-dependent manner. Moreover, at the same MSP concentration, the contents of MDA, TNF-α, IL-8 and IL-1β in the AM of smoking rates were higher than in healthy rats, while the IL-10 content and SOD activity were lower than in healthy rats.
Conclusion: MSP and its receptor RON are involved in the smoke-induced airway inflammation in rats via promoting AM to release inflammatory cytokines and inducing the increase of oxygen free radical.