IL-13 potently stimulates eosinophilic and lymphocytic inflammation and alveolar remodeling in the lung, effects that depend on the induction of various matrix metalloproteinases (MMPs). Here, we compared the remodeling and inflammatory effects of an IL-13 transgene in lungs of wild-type, MMP-9–deficient, or MMP-12–deficient mice. IL-13–induced alveolar enlargement, lung enlargement, compliance alterations, and respiratory failure and death were markedly decreased in the absence of MMP-9 or MMP-12. Moreover, IL-13 potently induced MMPs-2, -12, -13, and -14 in the absence of MMP-9, while induction of MMPs-2, -9, -13, and -14 by IL-13 was diminished in the absence of MMP-12. A deficiency in MMP-9 did not alter eosinophil, macrophage, or lymphocyte recovery, but increased the recovery of total leukocytes and neutrophils in bronchoalveolar lavage (BAL) fluids from IL-13 transgenic mice. In contrast, a deficiency in MMP-12 decreased the recovery of leukocytes, eosinophils, and macrophages, but not lymphocytes or neutrophils. These studies demonstrate that IL-13 acts via MMPs-9 and -12 to induce alveolar remodeling, respiratory failure, and death and that IL-13 induction of MMPs-2, -9, -13, and -14 is mediated at least partially by an MMP-12–dependent pathway. The also demonstrate that MMPs-9 and -12 play different roles in the generation of IL-13–induced inflammation, with MMP-9 inhibiting neutrophil accumulation and MMP-12 contributing to the accumulation of eosinophils and macrophages.

Interleukin (IL)-13 is a key mediator of tissue fibrosis caused by T helper cell type 2 inflammation. We hypothesized that the fibrogenic effects of IL-13 are mediated by transforming growth factor (TGF)-β. To test this hypothesis we compared the regulation of TGF-β in lungs from wild-type mice and CC10-IL-13 mice in which IL-13 overexpression causes pulmonary fibrosis. IL-13 selectively stimulated TGF-β1 production in transgenic animals and macrophages were the major site of TGF-β1 production and deposition in these tissues. IL-13 also activated TGF-β1 in vivo. This activation was associated with decreased levels of mRNA encoding latent TGF-β–binding protein-1 and increased mRNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. TGF-β1 activation was abrogated by the plasmin/serine protease antagonist aprotinin. It was also decreased in progeny of crosses of CC10-IL-13 mice and MMP-9 null mice but was not altered in crosses with CD44 null animals. IL-13–induced fibrosis was also significantly ameliorated by treatment with the TGF-β antagonist soluble TGFβR-Fc (sTGFβR-Fc). These studies demonstrate that IL-13 is a potent stimulator and activator of TGF-β1 in vivo. They also demonstrate that this activation is mediated by a plasmin/serine protease- and MMP-9–dependent and CD44-independent mechanism(s) and that the fibrogenic effects of IL-13 are mediated, in great extent, by this TGF-β pathway.

The downstream of kinase (DOK)-1 is involved in the protein tyrosine kinase (PTK) pathway in mast cells, but the role of DOK-1 in the pathogenesis of asthma has not been defined. In this study, we have demonstrated a novel regulatory role of DOK-1 in airway inflammation and physiologic responses in a murine model of asthma using lentiviral vector containing DOK-1 cDNA or DOK-1-specific ShRNA. The OVA-induced inflammatory cells, airway hyperresponsiveness, Th2 cytokine expression, and mucus response were significantly reduced in DOK-1 overexpressing mice compared to OVA-challenged control mice. The transgenic introduction of DOK-1 significantly stimulated the activation and expression of STAT-4 and T-bet, while impressively inhibiting the activation and expression of STAT-6 and GATA-3 in airway epithelial cells. On the other hand, DOK-1 knockdown mice enhanced STAT-6 expression and its nuclear translocation compared to OVA-challenged control mice. When viewed in combination, our studies demonstrate DOK-1 regulates allergen-induced Th2 immune responses by selective stimulation and inhibition of STAT-4 and STAT-6 signaling pathways, respectively. These studies provide a novel insight on the regulatory role of DOK-1 in allergen-induced Th2 inflammation and airway responses, which has therapeutic potential for asthma and other allergic diseases.