The role of the Th2 CC chemokine ligand CCL17 in pulmonary fibrosis.

Increasing evidence suggests that the development of pulmonary fibrosis is a Th2-mediated process. We hypothesized that the CC chemokines that are associated with a Th2 profile (CCL17 and CCL22) have an important role in the development of pulmonary fibrosis. We measured CCL17 and CCL22 during the pathogenesis of bleomycin-induced pulmonary fibrosis. We found that both CCL17 and CCL22 were significantly elevated through day 20 as compared with control mice. Peak expression of CCL22 preceded the peak levels of CCL17, as measured by real-time quantitative PCR. CCR4 is the receptor for CCL17 and CCL22 therefore, to further characterize the role of CCL17 and CCL22, we measured CCR4 mRNA in lung tissue of bleomycin-treated mice by real-time quantitative PCR. CCR4 was significantly elevated in bleomycin-treated mice as compared with control mice. Immunolocalization demonstrated that CCR4 was expressed predominantly on macrophages. Neutralization of CCL17, but not CCL22, led to a reduction in pulmonary fibrosis. Immunolocalization of bleomycin-treated lung tissue and human idiopathic pulmonary fibrosis tissue specimens showed that epithelial cells expressed CCL17. These findings demonstrate a central role for Th2 chemokines and the macrophage in the pathogenesis of pulmonary fibrosis and are further support for the role of a Th2 phenotype in the pathogenesis of pulmonary fibrosis.

Depletion of CXCR2 inhibits tumor growth and angiogenesis in a murine model of lung cancer.

The Glu-Leu-Arg(+) (ELR(+)) CXC chemokines are potent promoters of angiogenesis and have been demonstrated to induce a significant portion of nonsmall cell lung cancer-derived angiogenic activity and support tumorigenesis. ELR(+) CXC chemokines share a common chemokine receptor, CXCR2. We hypothesized that CXCR2 mediates the proangiogenic effects of ELR(+) CXC chemokines during tumorigenesis. To test this postulate, we used syngeneic murine Lewis lung cancer (LLC; 3LL, H-2(b)) heterotopic and orthotopic tumor model systems in C57BL/6 mice replete (CXCR2(+/+)) and deficient in CXCR2 (CXCR2(-/-)). We first demonstrated a correlation of the expression of endogenous ELR(+) CXC chemokines with tumor growth and metastatic potential of LLC tumors. Next, we found that LLC primary tumors were significantly reduced in growth in CXCR2(-/-) mice. Moreover, we found a marked reduction in the spontaneous metastases of heterotopic tumors to the lungs of CXCR2(-/-) mice. Morphometric analysis of the primary tumors in CXCR2(-/-) mice demonstrated increased necrosis and reduced vascular density. These findings were further confirmed in CXCR2(+/+) mice using specific neutralizing Abs to CXCR2. The results of these studies support the notion that CXCR2 mediates the angiogenic activity of ELR(+) CXC chemokines in a preclinical model of lung cancer.

Interaction of IL-13 and C10 in the pathogenesis of bleomycin-induced pulmonary fibrosis.

The initial stimulus for inflammatory cell recruitment and the mechanisms responsible for the perpetuation and evolution of chronic inflammation, granulation tissue formation, and fibrosis have not been fully elucidated. Although interleukin (IL)-13, a Th2 cytokine, has been shown to have direct effects on fibroblasts that support fibroproliferation, it is also a potent inducer of a novel CC chemokine, C10, which is chemotactic for mononuclear phagocytes. The macrophage/mononuclear phagocyte has been shown to have a role in the pathogenesis of pulmonary fibrosis, serving as an important source of growth factors that regulate extracellular matrix synthesis. In this study we demonstrate that IL-13 and C10 are elevated in the pathogenesis of bleomycin-induced pulmonary fibrosis. Neutralization of IL-13, but not IL-4, attenuated bleomycin-induced pulmonary fibrosis and levels of C10, suggesting that IL-13 has an important role in the development of pulmonary fibrosis. IL-13 is a potent inducer of C10 in vivo, and neutralization of C10 attenuated bleomycin-induced pulmonary fibrosis and intrapulmonary macrophage numbers. This suggests that IL-13 has a role in the development of pulmonary fibrosis that is independent of its direct effect on fibroblasts and is evidence for an interaction between Th2 cytokines and specific CC chemokines.