Prostaglandin Transporter (PGT/SLCO2A1) Protects the Lung from Bleomycin-Induced Fibrosis

PLoS One. 2015 Apr 29;10(4):e0123895. doi: 10.1371/journal.pone.0123895. eCollection 2015.

Abstract

Prostaglandin (PG) E2 exhibits an anti-fibrotic effect in the lung in response to inflammatory reactions and is a high-affinity substrate of PG transporter (SLCO2A1). The present study aimed to evaluate the pathophysiological relevance of SLCO2A1 to bleomycin (BLM)-induced pulmonary fibrosis in mice. Immunohistochemical analysis indicated that Slco2a1 protein was expressed in airway and alveolar type I (ATI) and II (ATII) epithelial cells, and electron-microscopic immunohistochemistry further demonstrated cell surface expression of Slco2a1 in ATI cells in wild type (WT) C57BL/6 mice. PGE2 uptake activity was abrogated in ATI-like cells from Slco2a1-deficient (Slco2a1-/-) mice, which was clearly observed in the cells from WT mice. Furthermore, the PGE2 concentrations in lung tissues were lower in Slco2a1-/- than in WT mice. The pathological relevance of SLCO2A1 was further studied in mouse BLM-induced pulmonary fibrosis models. BLM (1 mg/kg) or vehicle (phosphate buffered saline) was intratracheally injected into WT and Slco2a1-/- mice, and BLM-induced fibrosis was evaluated on day 14. BLM induced more severe fibrosis in Slco2a1-/- than in WT mice, as indicated by thickened interstitial connective tissue and enhanced collagen deposition. PGE2 levels were higher in bronchoalveolar lavage fluid, but lower in lung tissues of Slco2a1-/- mice. Transcriptional upregulation of TGF-β1 was associated with enhanced gene transcriptions of downstream targets including plasminogen activator inhitor-1. Furthermore, Western blot analysis demonstrated a significant activation of protein kinase C (PKC) δ along with a modest activation of Smad3 in lung from Slco2a1-/- mice, suggesting a role of PKCδ associated with TGF-β signaling in aggravated fibrosis in BLM-treated Slco2a1-/- mice. In conclusion, pulmonary PGE2 disposition is largely regulated by SLCO2A1, demonstrating that SLCO2A1 plays a critical role in protecting the lung from BLM-induced fibrosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bleomycin*
  • Bronchoalveolar Lavage Fluid
  • Cells, Cultured
  • Dinoprostone / analysis
  • Dinoprostone / immunology*
  • Gene Deletion
  • Gene Expression Regulation
  • Lung / drug effects
  • Lung / immunology
  • Lung / pathology*
  • Male
  • Mice, Inbred C57BL
  • Organic Anion Transporters / analysis
  • Organic Anion Transporters / genetics
  • Organic Anion Transporters / immunology*
  • Pulmonary Fibrosis / chemically induced*
  • Pulmonary Fibrosis / genetics
  • Pulmonary Fibrosis / immunology*
  • Pulmonary Fibrosis / pathology
  • RNA, Messenger / genetics
  • Rats, Wistar

Substances

  • Organic Anion Transporters
  • RNA, Messenger
  • Slco2a1 protein, mouse
  • Bleomycin
  • Dinoprostone

Grants and funding

This study was supported by a grant from Ono Pharmaceutical Co., Ltd. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.