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Mast cells are potent regulators of endothelial cell adhesion molecule ICAM-1 and VCAM-1 expression
H Meng1, M G Tonnesen, M J Marchese
1Department of Medicine, State University of New York at Stony Brook 11794, USA.
Abstract:
To investigate the possible role of mast cells (MC) in regulating leukocyte adhesion to vascular endothelial cells (EC), microvascular and macrovascular EC were exposed to activated MC or MC conditioned medium (MCCM). Expression of intercellular and vascular adhesion molecules (ICAM-1 and VCAM-1) on EC was monitored. Incubation of human dermal microvascular endothelial cells (HDMEC) and human umbilical vein endothelial cells (HUVEC) with activated MC or MCCM markedly increased ICAM-1 and VCAM-1 surface expression, noted as early as 4 hr. Maximal levels were observed at 16 hr followed by a general decline over 48 hr. A dose-dependent response was noted using incremental dilutions of MCCM or by varying the number of MC in coculture with EC. At a ratio as low as 1:1,000 of MC:EC, increased ICAM-1 was observed. The ICAM-1 upregulation by MCCM was > 90% neutralized by antibody to tumor necrosis factor alpha (TNF-alpha), suggesting that MC release of this cytokine contributes significantly to inducing EC adhesiveness. VCAM-1 expression enhanced by MCCM was partly neutralized (70%) by antibody to TNF-alpha; thus other substances released by MC may contribute to VCAM-1 expression. Northern blot analysis demonstrated MCCM upregulated ICAM-1 and VCAM-1 mRNA in both HDMEC and HUVEC. To evaluate the function of MCCM-enhanced EC adhesion molecules, T cells isolated from normal human donors were used in a cell adhesion assay. T-cell binding to EC was increased significantly after exposure of EC to MCCM, and inhibited by antibodies to ICAM-1 or VCAM-1. Intradermal injection of allergen in human atopic volunteers known to develop late-phase allergic reactions led to marked expression of both ICAM-1 and VCAM-1 at 6 hr, as demonstrated by immunohistochemistry. These studies indicate that MC play a critical role in regulating the expression of EC adhesion molecules, ICAM-1 and VCAM-1, and thus augment inflammatory responses by upregulating leukocyte binding.
Insights
Mast cells (MC) significantly increase leukocyte adhesion to endothelial cells (EC) by upregulating ICAM-1 and VCAM-1. This process, mediated partly by TNF-alpha, contributes to inflammatory responses in allergic reactions.
Area of Science:
- Immunology
- Cell Biology
- Vascular Biology
Background:
- Mast cells (MC) are key immune cells involved in allergic and inflammatory responses.
- Endothelial cells (EC) play a crucial role in regulating leukocyte trafficking to tissues.
- The interaction between MC and EC in leukocyte adhesion is not fully understood.
Purpose of the Study:
- To investigate the role of mast cells in regulating leukocyte adhesion to vascular endothelial cells.
- To determine the expression of adhesion molecules ICAM-1 and VCAM-1 on EC upon mast cell activation.
- To assess the functional consequences of mast cell-induced changes in EC adhesiveness.
Main Methods:
- Co-culture of microvascular and macrovascular endothelial cells with activated mast cells or mast cell conditioned medium (MCCM).
- Quantification of ICAM-1 and VCAM-1 surface expression using various techniques.
- Neutralization studies using antibodies against TNF-alpha.
- Northern blot analysis to assess mRNA levels of adhesion molecules.
- Leukocyte adhesion assays using T cells.
- Immunohistochemical analysis in human atopic volunteers.
Main Results:
- Activated MC or MCCM significantly increased ICAM-1 and VCAM-1 expression on EC within 4 hours, peaking at 16 hours.
- This upregulation was dose-dependent and observed even at low MC:EC ratios.
- TNF-alpha antibody neutralized >90% of ICAM-1 upregulation and 70% of VCAM-1 upregulation.
- MCCM increased ICAM-1 and VCAM-1 mRNA levels in EC.
- Increased T-cell binding to EC exposed to MCCM was observed, which was inhibited by anti-ICAM-1/VCAM-1 antibodies.
- Allergen injection in atopic volunteers induced marked ICAM-1 and VCAM-1 expression.
Conclusions:
- Mast cells play a critical role in regulating endothelial cell expression of ICAM-1 and VCAM-1.
- Mast cell-derived TNF-alpha significantly contributes to ICAM-1 and VCAM-1 upregulation.
- These mast cell-mediated changes in EC adhesiveness augment inflammatory responses by increasing leukocyte binding.
- The findings highlight the importance of the MC-EC interaction in the pathogenesis of allergic late-phase reactions.