Mechanism of fluoride-induced MAP kinase activation in pulmonary artery endothelial cells

Am J Physiol Lung Cell Mol Physiol. 2006 Jun;290(6):L1139-45. doi: 10.1152/ajplung.00161.2005. Epub 2006 Jan 13.

Abstract

In this study, we demonstrate that challenge of endothelial cells (EC) with NaF, a recognized G protein activator and protein phosphatase inhibitor, leads to a significant Erk activation, with increased phosphorylation of the well-known Erk substrate caldesmon. Inhibition of the Erk MAPK, MEK, by U0126 produces a marked decrease in NaF-induced caldesmon phosphorylation. NaF transiently increases the activity of the MEK kinase known as Raf-1 (approximately 3- to 4-fold increase over basal level), followed by a sustained Raf-1 inhibition (approximately 3- to 4-fold decrease). Selective Raf-1 inhibitors (ZM-336372 and Raf-1 inhibitor 1) significantly attenuate NaF-induced Erk and caldesmon phosphorylation. Because we have previously shown that Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) participates in Erk activation in thrombin-challenged cells, we next explored if CaMKII is involved in NaF-induced EC responses. We found that in NaF-treated EC, CaMKII activity increases in a time-dependent manner with maximal activity at 10 min (approximately 4-fold increase over a basal level). Pretreatment with KN93, a specific CaMKII inhibitor, attenuates NaF-induced barrier dysfunction and Erk phosphorylation. The Rho inhibitor C3 exotoxin completely abolishes NaF-induced CaMKII activation. Collectively, these data suggest that sequential activation of Raf-1, MEK, and Erk is modulated by Rho-dependent CaMKII activation and represents important NaF-induced signaling response. Caldesmon phosphorylation occurring by an Erk-dependent mechanism in NaF-treated pulmonary EC may represent a link between NaF stimulation and contractile responses of endothelium.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Butadienes / pharmacology
  • Cattle
  • Endothelium, Vascular / enzymology*
  • Endothelium, Vascular / physiology
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Fluorides / pharmacology*
  • Kinetics
  • Mitogen-Activated Protein Kinases / metabolism*
  • Models, Biological
  • Nitriles / pharmacology
  • Pulmonary Artery / enzymology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Sodium Fluoride / pharmacology

Substances

  • Butadienes
  • Enzyme Inhibitors
  • Nitriles
  • U 0126
  • Sodium Fluoride
  • Mitogen-Activated Protein Kinases
  • Fluorides