Jeffrey C Horowitz

Publications (2)12.11 Total impact

• Article: Implicating Exudate Macrophages and Ly-6Chigh Monocytes in CCR2-Dependent Lung Fibrosis following Gene-Targeted Alveolar Injury.

  John J Osterholzer, Michal A Olszewski, Benjamin J Murdock, Gwo-Hsiao Chen, John R Erb-Downward, Natalya Subbotina, Keely Browning, Yujing Lin, Roger E Morey, Jeremy K Dayrit, Jeffrey C Horowitz, Richard H Simon, Thomas H Sisson
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  ABSTRACT: The alveolar epithelium is characteristically abnormal in fibrotic lung disease, and we recently established a direct link between injury to the type II alveolar epithelial cell (AEC) and the accumulation of interstitial collagen. The mechanisms by which damage to the epithelium induces lung scarring remain poorly understood. It is particularly controversial whether an insult to the type II AEC initiates an inflammatory response that is required for the development of fibrosis. To explore whether local inflammation occurs following a targeted epithelial insult and contributes to lung fibrosis, we administered diphtheria toxin to transgenic mice with type II AEC-restricted expression of the diphtheria toxin receptor. We used immunophenotyping techniques and diphtheria toxin receptor-expressing, chemokine receptor-2-deficient (CCR2-/-) mice to determine the participation of lung leukocyte subsets in pulmonary fibrogenesis. Our results demonstrate that targeted type II AEC injury induces an inflammatory response that is enriched for CD11b+ nonresident exudate macrophages (ExM) and their precursors, Ly-6Chigh monocytes. CCR2 deficiency abrogates the accumulation of both cell populations and protects mice from fibrosis, weight loss, and death. Further analyses revealed that the ExM are alternatively activated and that ExM and Ly-6Chigh monocytes express mRNA for IL-13, TGF-β, and the collagen genes, COL1A1 and COLIIIA1. Furthermore, the accumulated ExM and Ly-6Chigh monocytes contain intracellular collagen, as detected by immunostaining. Together, these results implicate CCR2 and the accumulation of ExM and Ly-6Chigh monocytes as critical determinants of pulmonary fibrosis induced by selective type II AEC injury.
  The Journal of Immunology 03/2013; · 5.79 Impact Factor
• Source

  Available from: Michal A Olszewski

  Article: PAI-1 promotes the accumulation of exudate macrophages and worsens pulmonary fibrosis following type II alveolar epithelial cell injury.

  John J Osterholzer, Paul J Christensen, Vibha Lama, Jeffrey C Horowitz, Noboru Hattori, Natalya Subbotina, Andrew Cunningham, Yujing Lin, Benjamin J Murdock, Roger E Morey, Michal A Olszewski, Daniel A Lawrence, Richard H Simon, Thomas H Sisson
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  ABSTRACT: Fibrotic disorders of the lung are associated with perturbations in the plasminogen activation system. Specifically, plasminogen activator inhibitor-1 (PAI-1) expression is increased relative to the plasminogen activators. A direct role for this imbalance in modulating the severity of lung scarring following injury has been substantiated in the bleomycin model of pulmonary fibrosis. However, it remains unclear whether derangements in the plasminogen activation system contribute more generally to the pathogenesis of lung fibrosis beyond bleomycin injury. To answer this question, we employed an alternative model of lung scarring, in which type II alveolar epithelial cells (AECs) are specifically injured by administering diphtheria toxin (DT) to mice genetically engineered to express the human DT receptor (DTR) off the surfactant protein C promoter. This targeted AEC injury results in the diffuse accumulation of interstitial collagen. In the present study, we found that this targeted type II cell insult also increases PAI-1 expression in the alveolar compartment. We identified AECs and lung macrophages to be sources of PAI-1 production. To determine whether this elevated PAI-1 concentration was directly related to the severity of fibrosis, DTR(+) mice were crossed into a PAI-1-deficient background (DTR(+) : PAI-1(-/-) ). DT administration to DTR(+) : PAI-1(-/-) animals caused significantly less fibrosis than was measured in DTR(+) mice with intact PAI-1 production. PAI-1 deficiency also abrogated the accumulation of CD11b(+) exudate macrophages that were found to express PAI-1 and type-1 collagen. These observations substantiate the critical function of PAI-1 in pulmonary fibrosis pathogenesis and provide new insight into a potential mechanism by which this pro-fibrotic molecule influences collagen accumulation. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
  The Journal of Pathology 01/2012; 228(2):170-80. · 6.32 Impact Factor