Cigarette smoke-induced RANKL expression enhances MMP-9 production by alveolar macrophages

Area of Science:

• Pulmonary Medicine
• Immunology
• Cell Biology

Background:

• Cigarette smoke (CS) causes lung damage by increasing proteinase production, particularly matrix metalloproteinase-9 (MMP-9), by alveolar macrophages (AMs).
• The role of the receptor activator of nuclear factor-κB ligand (RANKL) pathway in CS-induced MMP-9 expression remains unclear.

Purpose of the Study:

• To investigate the expression and functional role of the RANKL/RANK pathway in CS-induced MMP-9 production.
• To explore the involvement of this pathway in the pathogenesis of chronic obstructive pulmonary disease (COPD).

Main Methods:

• Localization of RANKL and its receptor RANK in mouse lungs after long-term CS exposure.
• In vitro assessment of RANKL and RANK expression in macrophages stimulated with CS extract (CSE).
• Evaluation of the in vitro biological function of RANKL in CS-induced MMP-9 production.

Main Results:

• RANKL and RANK were significantly upregulated in AMs of CS-exposed mice compared to controls.
• CSE stimulation increased RANKL and RANK expression in macrophages in vitro.
• CSE and RANKL stimulation led to MMP-9 overexpression in AMs, which was partially inhibited by an anti-RANKL antibody.

Conclusions:

• The RANKL/RANK pathway plays a mediating role in CS-induced MMP-9 expression in AMs.
• This pathway represents a novel mechanism contributing to CS-associated emphysema development.