Phenotype of palmitic acid transport and of signalling in alveolar type II cells from E/H-FABP double-knockout mice: contribution of caveolin-1 and PPARgamma

Biochim Biophys Acta. 2004 Mar 22;1636(2-3):196-204. doi: 10.1016/j.bbalip.2003.10.015.

Abstract

Based on the assumption that fatty-acid-binding proteins (FABPs) of the epidermal-type (E-FABP) and heart-type (H-FABP) in murine alveolar type II (TII) cells mediate the synthesis of dipalmitoyl phosphatidylcholine (DPPC), the main surfactant phospholipid, we analysed TII cells isolated from wild-type (wt) and E/H-FABP double-knockout (double-ko) mice. Application of labelled palmitic acid to these cells revealed a drop in uptake, beta-oxidation, and incorporation into neutral lipids and total phosphatidylcholine (PC) of TII cells from double-ko mice. Whereas incorporation of labelled palmitic acid into DPPC remained unchanged, degradation studies demonstrated a substantial shift in DPPC synthesis from de novo to reacylation. In addition, increased expression of mRNAs and proteins of caveolin-1 and PPARgamma, and an increase of the mRNA encoding fatty acid translocase (FAT) was observed in the double-ko phenotype. As caveolin-1 interacted with PPARgamma, we assumed that FAT, caveolin-1, and PPARgamma form a signalling chain for fatty acid or drug. Consequently, PPARgamma-selective pioglitazone was added to the diet of double-ko mice. We found that further activation of PPARgamma could 'heal' the E/H-FABP double-ko effect in these TII cells as transport and utilisation of labelled palmitic acid restored a wt phenocopy. This indicated that E-FABP and/or H-FABP are involved in the mediation of DPPC synthesis in wt TII cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Biological Transport
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Caveolin 1
  • Caveolins / physiology*
  • DNA Primers
  • Fatty Acid-Binding Protein 7
  • Fatty Acid-Binding Proteins
  • Mice
  • Mice, Knockout
  • Nerve Tissue Proteins*
  • Palmitic Acid / metabolism*
  • Polymerase Chain Reaction
  • Pulmonary Alveoli / metabolism*
  • RNA, Messenger / genetics
  • Receptors, Cytoplasmic and Nuclear / physiology*
  • Transcription Factors / physiology*

Substances

  • Carrier Proteins
  • Cav1 protein, mouse
  • Caveolin 1
  • Caveolins
  • DNA Primers
  • Fabp7 protein, mouse
  • Fatty Acid-Binding Protein 7
  • Fatty Acid-Binding Proteins
  • Nerve Tissue Proteins
  • RNA, Messenger
  • Receptors, Cytoplasmic and Nuclear
  • Transcription Factors
  • Palmitic Acid