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Distinct ICAM-1 forms and expression pathways in synovial microvascular endothelial cells

W Carley1, G Ligon, S Phan

  • 1Bayer Research Center, West Haven, CT 06516, USA.

Cellular and Molecular Biology (Noisy-Le-Grand, France)
|April 1, 1999
PubMed

Insights

Human synovial endothelial cells (HSE) and human umbilical vein endothelium (HUVE) process intracellular adhesion molecule-1 (ICAM-1) differently. HSE cells show distinct ICAM-1 pathways, impacting its expression and release, unlike HUVE cells.

Area of Science:

  • Immunology
  • Cell Biology
  • Endothelial Biology

Background:

  • Intracellular Adhesion Molecule-1 (ICAM-1) plays a crucial role in endothelial cell function and immune responses.
  • Tumor Necrosis Factor alpha (TNF alpha) and Interferon gamma (IFN gamma) synergistically upregulate ICAM-1 in human synovial endothelial cells (HSE).
  • The synergistic effect of TNF alpha and IFN gamma on ICAM-1 is less pronounced in human umbilical vein endothelium (HUVE).

Purpose of the Study:

  • To investigate the distinct mechanisms of ICAM-1 regulation and expression in HSE versus HUVE cells.
  • To correlate intracellular and cell surface levels of ICAM-1 in response to inflammatory stimuli.
  • To elucidate the differential secretory pathways of ICAM-1 in these two human endothelial cell types.

Main Methods:

  • Quantitative analysis of ICAM-1 mRNA and protein levels using ELISA and RT-PCR.
  • Immunostaining and confocal microscopy to visualize ICAM-1 localization within endothelial cells.
  • Treatment with monensin, an endosomal processing inhibitor, to assess its impact on ICAM-1 expression and release.
  • Immunoprecipitation and gel electrophoresis to characterize cell-specific forms of ICAM-1.

Main Results:

  • HSE cells exhibited significantly higher ICAM-1 mRNA levels compared to HUVE cells upon stimulation with TNF alpha/IFN gamma.
  • HSE cells showed distinct vesicular cytoplasmic staining for ICAM-1, absent in HUVE cells.
  • Monensin treatment inhibited HSE cell surface ICAM-1 expression and soluble ICAM-1 release by up to 70%, with no effect on HUVE cells.
  • Immunoprecipitation revealed cell-specific forms of ICAM-1 in HSE and HUVE cells.

Conclusions:

  • HSE and HUVE cells possess distinct intracellular adhesion molecule-1 (ICAM-1) forms and differential secretory pathways.
  • The findings suggest unique functional properties of HSE and HUVE cells related to ICAM-1 regulation and trafficking.
  • These cell-specific differences in ICAM-1 processing are critical for understanding endothelial cell behavior in inflammatory conditions.

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