Comparative analysis of morphological and molecular motifs in bronchiolitis obliterans and alveolar fibroelastosis after lung and stem cell transplantation
Matrix metalloproteinases (MMPs) are a class of extra-cellular and membrane-bound proteases involved in a wide array of physiological and pathological processes including tissue remodeling, inflammation, and cytokine secretion and activation. MMP-13 has been shown to be involved in lung diseases such as acute lung injury, viral infections, and chronic obstructive pulmonary disease; however, the molecular pathogenesis of MMP-13 in these conditions is not well understood. In this study, we investigated the mechanisms and roles of MMP-13 secretion in human small airway epithelial cells (SAECs) and functional polymorphisms of the MMP13 gene. Polyinosinic–polycytidylic acid (poly(I:C)) and interferon β (IFN-β) stimulated the secretion of MMP-13 from SAECs by more than several hundred-fold. Stimulation of the secretion by poly(I:C) was abolished by SB304680 (p38 inhibitor), LY294002 (PI3K inhibitor), Janus kinase (JAK) inhibitor I, RNA-activated protein kinase (PKR) inhibitor, and Bay 11-7082 (NF-κB inhibitor), while stimulation by IFN-β was inhibited by all except Bay 11-7082. These data suggested that the secretion of MMP-13 was mediated through IFN receptor pathways independently of nuclear factor kappa B (NF-κB) and that poly(I:C) stimulated IFN secretion in an NF-κB-dependent manner from SAECs, leading to IFN-stimulated MMP-13 secretion. Chemical MMP-13 inhibitors and MMP-13 small interfering RNA (siRNA) inhibited IFN-stimulated secretion of interferon gamma-inducible protein 10 (IP-10) and regulated on activation, normal T-cell expressed and secreted (RANTES), suggesting that MMP-13 is involved in the secretion of these virus-induced proinflammatory chemokines. We identified a novel functional polymorphism in the promoter region of the MMP13 gene. The MMP13 gene may play important roles in defense mechanisms of airway epithelial cells.