Surfactant phospholipid DPPC downregulates monocyte respiratory burst via modulation of PKC

Am J Physiol Lung Cell Mol Physiol. 2005 Jun;288(6):L1070-80. doi: 10.1152/ajplung.00386.2004. Epub 2005 Jan 28.


Pulmonary surfactant phospholipids have been shown previously to regulate inflammatory functions of human monocytes. This study was undertaken to delineate the mechanisms by which pulmonary surfactant modulates the respiratory burst in a human monocytic cell line, MonoMac-6 (MM6). Preincubation of MM6 cells with the surfactant preparations Survanta, Curosurf, or Exosurf Neonatal inhibited the oxidative response to either lipopolysaccharide (LPS) and zymosan or phorbol 12-myristate 13-acetate (PMA) by up to 50% (P < 0.01). Preincubation of MM6 cells and human peripheral blood monocytes with dipalmitoyl phosphatidylcholine (DPPC), the major phospholipid component of surfactant, inhibited the oxidative response to zymosan. DPPC did not directly affect the activity of the NADPH oxidase in a MM6 reconstituted cell system, suggesting that DPPC does not affect the assembly of the individual components of this enzyme into a functional unit. The effects of DPPC were evaluated on both LPS/zymosan and PMA activation of protein kinase C (PKC), a ubiquitous intracellular kinase, in MM6 cells. We found that DPPC significantly inhibited the activity of PKC in stimulated cells by 70% (P < 0.01). Western blotting experiments demonstrated that DPPC was able to attenuate the activation of the PKCdelta isoform but not PKCalpha. These results suggest that DPPC, the major component of pulmonary surfactant, plays a role in modulating leukocyte inflammatory responses in the lung via downregulation of PKC, a mechanism that may involve the PKCdelta isoform.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1,2-Dipalmitoylphosphatidylcholine / pharmacology*
  • Carcinogens / pharmacology
  • Cells, Cultured
  • Down-Regulation
  • Enzyme Activation / drug effects
  • Humans
  • Lipopolysaccharides / pharmacology
  • Monocytes / drug effects*
  • Monocytes / metabolism
  • NADPH Oxidases / metabolism
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Protein Kinase C-alpha
  • Protein Kinase C-delta
  • Reactive Oxygen Species / metabolism*
  • Respiratory Burst / drug effects*
  • Tetradecanoylphorbol Acetate / pharmacology
  • Zymosan / pharmacology


  • Carcinogens
  • Lipopolysaccharides
  • Reactive Oxygen Species
  • 1,2-Dipalmitoylphosphatidylcholine
  • Zymosan
  • NADPH Oxidases
  • PRKCA protein, human
  • PRKCD protein, human
  • Protein Kinase C
  • Protein Kinase C-alpha
  • Protein Kinase C-delta
  • Tetradecanoylphorbol Acetate