Increased Transendothelial Transport of CCL3 Is Insufficient to Drive Immune Cell Transmigration through the Blood-Brain Barrier under Inflammatory Conditions In Vitro

Mediators Inflamm. 2017:2017:6752756. doi: 10.1155/2017/6752756. Epub 2017 May 25.

Abstract

Many neuroinflammatory diseases are characterized by massive immune cell infiltration into the central nervous system. Identifying the underlying mechanisms could aid in the development of therapeutic strategies specifically interfering with inflammatory cell trafficking. To achieve this, we implemented and validated a blood-brain barrier (BBB) model to study chemokine secretion, chemokine transport, and leukocyte trafficking in vitro. In a coculture model consisting of a human cerebral microvascular endothelial cell line and human astrocytes, proinflammatory stimulation downregulated the expression of tight junction proteins, while the expression of adhesion molecules and chemokines was upregulated. Moreover, chemokine transport across BBB cocultures was upregulated, as evidenced by a significantly increased concentration of the inflammatory chemokine CCL3 at the luminal side following proinflammatory stimulation. CCL3 transport occurred independently of the chemokine receptors CCR1 and CCR5, albeit that migrated cells displayed increased expression of CCR1 and CCR5. However, overall leukocyte transmigration was reduced in inflammatory conditions, although higher numbers of leukocytes adhered to activated endothelial cells. Altogether, our findings demonstrate that prominent barrier activation following proinflammatory stimulation is insufficient to drive immune cell recruitment, suggesting that additional traffic cues are crucial to mediate the increased immune cell infiltration seen in vivo during neuroinflammation.

MeSH terms

  • Astrocytes / cytology
  • Astrocytes / metabolism
  • Biological Transport
  • Blood-Brain Barrier / metabolism*
  • Cell Adhesion Molecules / metabolism
  • Cell Line
  • Cell Movement / physiology*
  • Chemokine CCL3 / metabolism*
  • Electric Impedance
  • Endothelial Cells / cytology
  • Endothelial Cells / metabolism
  • Humans
  • Inflammation / genetics
  • Inflammation / metabolism*
  • Intercellular Adhesion Molecule-1 / metabolism
  • Leukocytes / cytology
  • Leukocytes / metabolism
  • Leukocytes, Mononuclear / cytology
  • Leukocytes, Mononuclear / metabolism
  • Receptors, CCR1 / genetics
  • Receptors, CCR1 / metabolism
  • Receptors, CCR5 / genetics
  • Receptors, CCR5 / metabolism
  • Vascular Cell Adhesion Molecule-1 / metabolism

Substances

  • CCR1 protein, human
  • CCR5 protein, human
  • Cell Adhesion Molecules
  • Chemokine CCL3
  • Receptors, CCR1
  • Receptors, CCR5
  • Vascular Cell Adhesion Molecule-1
  • Intercellular Adhesion Molecule-1