IL-10 inhibits inflammation but does not affect fibrosis in the pulmonary response to bleomycin

doi:10.1016/j.yexmp.2003.12.010

Experimental and Molecular Pathology

Volume 76, Issue 3, June 2004, Pages 205-211

https://doi.org/10.1016/j.yexmp.2003.12.010 Get rights and content

Abstract

Bleomycin yields pulmonary injury characterized by inflammation that proceeds to fibrosis. The production of IL-10 by pulmonary macrophages is increased in the inflammation that accompanies bleomycin lung injury. In the present study, IL-10 deficient and wildtype mice received 0.075 units of bleomycin intratracheally at day 0 and were sacrificed at day 7 or day 14. At day 7, pulmonary inflammation was increased in IL-10-deficient mice as reflected by increased representation of CD3+ and CD4+ lymphocytes and GR-1+ pulmonary granulocytes in the bronchoalveolar lavage (BAL) fluid. Pulmonary interstitial CD80+ and CD86+ mononuclear cells were increased in situ. At day 14, mononuclear cell inflammation was comparable between groups but pulmonary eosinophils were increased in the wildtype. There was no difference in the degree of pulmonary fibrosis, as judged by histology or lung hydroxyproline content. Lung chemokine expression of MIP-1α/β, MIP-2, and eotaxin was increased at days 7 and 14 with a trend towards increased MCP-1 expression at day 14. The findings suggest an immunomodulatory role for IL-10 in the inflammatory response but not in the pulmonary fibrosis yielded by bleomycin.

Introduction

Bleomycin (BLM) yields a pulmonary fibroinflammatory response in mice (Adamson and Bowden, 1974) that mimics the histological changes of human chronic interstitial pneumonitis. IL-10 inhibits the activities of a variety of immunomodulatory Th1 cytokines (Andrea et al., 1993) and has been implicated in pathways leading to pulmonary fibrosis (Furuie et al., 1997).

IL-10 yields its anti-inflammatory effects by antagonizing the activities of IL-12 (Andrea et al., 1993) and the activities of certain Th1 cytokines, including TNF-α (Armstrong et al., 1996) and IFN-γ (Andrea et al., 1993). In addition, IL-10 down-regulates the accessory activities of dendritic cells (Qin et al., 1997) and macrophages (Bogdan et al., 1991), thereby limiting inflammation.

The role of IL-10 in vivo has previously been examined in murine models of pulmonary inflammation and fibrosis. Huaux et al. (2002) demonstrated that IL-10 decreased production of TNF-α in the pulmonary response to silica. They noted that pulmonary fibrosis was not inhibited by IL-10, suggesting that the proinflammatory and profibrotic pathways of fibroinflammatory pulmonary injury might be dissociated. Arai et al. (2000) showed that the introduction of human IL-10 gene into mice reduced inflammation and diminished hydroxyproline content in BLM-mediated lung injury.

Zhu et al. (2002) demonstrated decreased pulmonary inflammation in response to endotoxin challenge in mice that over-expressed IL-10. However, in the same model, IL-10 yielded increased inflammation in mice with null mutations for IL-13, IL-4, and STAT-6. In another study, when IL-10-deficient mice were challenged with Pseudomonas species (Chmiel et al., 2002a), they developed persistently increased pulmonary inflammation compared to wild-type controls. Considered together, these studies support an anti-inflammatory effect of IL-10 in pulmonary inflammation. However, it is uncertain whether exhibit IL-10 affects the development of pulmonary fibrosis in vivo.

When C57BL/6 mice are treated with BLM, pulmonary interstitial inflammation peaks at day 7 and pulmonary fibrosis is established at day 14 (Sharma et al., 1996). Following the intratracheal instillation of BLM, pulmonary macrophages show increased expression of IL-10 at day 5 that persists through the development of pulmonary fibrosis at day 14 (Sakamoto et al., 2002). To determine the effect of IL-10 in the pulmonary fibroinflammatory response, we investigated the immune phenotype of BLM lung injury in IL-10-deficient mice.

Section snippets

Mice

Female C57BL/6 was obtained from Charles River Laboratory (Wilmington, MA). IL-10^−/− (deficient) mice developed on a genetic background of C57BL/6 mice were purchased from Jackson Laboratories. Mice were housed five per cage in the Massachusetts General Hospital (MGH) Animal Care Barrier Facility. As IL-10-deficient mice are prone to developing inflammatory bowel disease, all mice were examined at the time of sacrifice for evidence of colitis and one of the mice examined showed evidence of that

Histopathology

There were no differences in the histology of untreated lungs of IL-10-deficient and wildtype mice (not shown). The pulmonary inflammatory response to BLM was examined in IL-10-deficient mice at days 7 and 14, corresponding to the peaks of pulmonary inflammation and fibrosis, respectively, in wildtype mice. Lung sections at day 7 showed increased interstitial mononuclear cell inflammation (3.2 ± 1.1 vs. 1.6 ± 0.8, P = 0.04) in IL-10-deficient mice compared to controls (Figs. 1A, B). Mononuclear

Discussion

In a previous study, IL-10 expression by pulmonary macrophages was demonstrated to increase markedly between days 5 and 14 in C57BL/6 mice in the fibroinflammatory response to BLM (11). To examine the specific effects of IL-10 in BLM lung injury, cellular, and fibrotic responses were examined in IL-10-deficient mice. IL-10-deficient mice showed increased pulmonary inflammation compared to wildtype controls at day 7. The pulmonary inflammatory response in IL-10-deficient mice was characterized

Acknowledgements

This research was supported by NIH Grant RO139054. We wish to thank Carole Leary for her expert technical assistance.

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IL-10 inhibits inflammation but does not affect fibrosis in the pulmonary response to bleomycin

Abstract

Introduction

Section snippets

Mice

Histopathology

Discussion

Acknowledgements

Am. J. Transplant.

Clin. Immunol. Immunopathol.

Immunity

Immunol. Today

Exp. Mol. Pathol.

Cytokine

Immunity

Am. J. Pathol.

J. Exp. Med.

Introduction of the interleukin-10 gene into mice inhibited bleomycin-induced lung injury in vivo

Am. J. Physiol., Lung Cell. Mol. Physiol.

Thorax

J. Exp. Med.

Eur. J. Immunol.

Am. J. Respir. Crit. Care Med.

Am. J. Respir. Crit. Care Med.

Immunology

J. Exp. Med.

Ann. Med.

J. Exp. Med.