PPARα-mediated peroxisome induction compensates PPARγ-deficiency in bronchiolar club cells

PLoS One. 2018 Sep 13;13(9):e0203466. doi: 10.1371/journal.pone.0203466. eCollection 2018.

Abstract

Despite the important functions of PPARγ in various cell types of the lung, PPARγ-deficiency in club cells induces only mild emphysema. Peroxisomes are distributed in a similar way as PPARγ in the lung and are mainly enriched in club and AECII cells. To date, the effects of PPARγ-deficiency on the overall peroxisomal compartment and its metabolic alterations in pulmonary club cells are unknown. Therefore, we characterized wild-type and club cell-specific PPARγ knockout-mice lungs and used C22 cells to investigate the peroxisomal compartment and its metabolic roles in the distal airway epithelium by means of 1) double-immunofluorescence labelling for peroxisomal proteins, 2) laser-assisted microdissection of the bronchiolar epithelium and subsequent qRT-PCR, 3) siRNA-transfection of PPARγand PPRE dual-luciferase reporter activity in C22 cells, 4) PPARg inhibition by GW9662, 5) GC-MS based lipid analysis. Our results reveal elevated levels of fatty acids, increased expression of PPARα and PPRE activity, a strong overall upregulation of the peroxisomal compartment and its associated gene expression (biogenesis, α-oxidation, β-oxidation, and plasmalogens) in PPARγ-deficient club cells. Interestingly, catalase was significantly increased and mistargeted into the cytoplasm, suggestive for oxidative stress by the PPARγ-deficiency in club cells. Taken together, PPARα-mediated metabolic induction and proliferation of peroxisomes via a PPRE-dependent mechanism could compensate PPARγ-deficiency in club cells.

MeSH terms

  • Anilides / pharmacology
  • Animals
  • Bronchi / metabolism*
  • Bronchi / pathology
  • Gene Expression Regulation*
  • Mice
  • Mice, Knockout
  • Oxidative Stress / drug effects
  • Oxidative Stress / genetics
  • PPAR alpha / antagonists & inhibitors
  • PPAR alpha / biosynthesis*
  • PPAR alpha / genetics
  • PPAR gamma / deficiency*
  • Peroxisomes / genetics
  • Peroxisomes / metabolism*
  • Pulmonary Emphysema / genetics
  • Pulmonary Emphysema / metabolism*
  • Pulmonary Emphysema / pathology

Substances

  • 2-chloro-5-nitrobenzanilide
  • Anilides
  • PPAR alpha
  • PPAR gamma

Grants and funding

The authors received no specific funding for this work.