Synthesis and surface expression of CD14 by human endothelial cells

Area of Science:

• Immunology
• Cell Biology
• Vascular Biology

Background:

• Previous research indicated a lack of membrane-bound CD14 (mCD14) on human vascular endothelial cells.
• CD14 is a key receptor for lipopolysaccharide (LPS), a component of gram-negative bacteria.

Purpose of the Study:

• To investigate the expression of CD14 on human umbilical vein endothelial cells (HUVEC).
• To determine the functional role of endothelial CD14 in LPS-induced responses.

Main Methods:

• Optimized immunoassay conditions, including monoclonal antibody selection, for detecting CD14 on HUVEC.
• Flow cytometry to quantify CD14 expression on HUVEC and monocytes.
• Radiolabeling with L-methionine to assess CD14 synthesis by HUVEC.
• Upregulation studies using LPS, lysophosphatidic acid, and culture supplements.

Main Results:

• HUVEC express surface CD14, albeit at lower levels than monocytes (approx. 20-fold less).
• Surface CD14 expression on HUVEC decreases with increasing culture passages.
• HUVEC synthesize CD14, confirmed by L-methionine incorporation.
• LPS, lysophosphatidic acid, and culture supplements upregulate HUVEC CD14 expression in a protein synthesis-dependent manner.
• Endothelial mCD14 is essential for LPS-induced endothelial cell activation without serum, working with soluble CD14.

Conclusions:

• Human endothelial cells express CD14, challenging prior assumptions.
• Optimized assay conditions are critical for detecting endothelial CD14.
• Endothelial CD14 plays a significant role in LPS-mediated endothelial cell activation.
• These findings impact the understanding of LPS signaling in endothelial cells and sepsis pathogenesis.