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Increased PMN adherence on endothelial cells after hypoxia: involvement of PAF, CD18/CD11b, and ICAM-1
T Arnould1, C Michiels, J Remacle
1Laboratoire de Biochimie Cellulaire, Facultés Universitaires, Notre-Dame de la Paix, Namur, Belgium.
Abstract:
Ischemia is a well-known situation occurring in several diseases. There is a large body of evidence for the accumulation of neutrophils in the microvascular injury and the transformation of ischemic tissue into an inflammatory territory. However, the molecular mechanisms underlying this phenomenon are still poorly understood. The effects of hypoxia were investigated on human umbilical vein endothelial cells (HUVEC) in culture, and a very strong activation of these cells was obtained with an induction of the platelet-activating factor (PAF) synthesis which was optimal after 90 min of hypoxia. PAF was chemically identified by gas chromatography-mass spectrometry. Along with incubation under hypoxia, a constant increase in the adherence of unstimulated human polymorphonuclear neutrophils (PMN) to endothelial cells was observed. The role of PAF and of adhesion glycoproteins in this hypoxia-induced neutrophil adherence to HUVEC was then assessed. The adherence was mediated by PAF after 90 min of hypoxia as indicated by the inhibition obtained with PAF receptor antagonists and with PAF synthesis inhibition. When tested on HUVEC incubated for 120 min under hypoxia, PAF antagonists could not inhibit the PMN adherence, whereas inhibition of PAF during hypoxia could block the process, suggesting a role of PAF acting as a second messenger. In addition, the inhibitory effects obtained using monoclonal antibodies indicate that this increased adherence was also mediated by intracellular adhesion molecule 1 on HUVEC and by CD18/CD11b on neutrophils. GMP-140 seems also to be involved after 90 min hypoxia but not after 120 min hypoxia, which correlated well with the presence of PAF.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Hypoxia induces platelet-activating factor (PAF) synthesis in endothelial cells, promoting neutrophil adhesion. This PAF-mediated adhesion involves specific cell adhesion molecules, crucial for understanding inflammatory responses in ischemic tissues.
Area of Science:
- Molecular Biology
- Cell Biology
- Immunology
Background:
- Ischemia, a common condition in various diseases, leads to neutrophil accumulation in microvascular injury and tissue inflammation.
- The precise molecular mechanisms driving hypoxia-induced inflammation remain incompletely understood.
Purpose of the Study:
- To investigate the effects of hypoxia on human umbilical vein endothelial cells (HUVEC).
- To elucidate the role of platelet-activating factor (PAF) and adhesion glycoproteins in hypoxia-induced neutrophil adherence to HUVEC.
Main Methods:
- Hypoxia exposure of cultured HUVEC.
- Measurement of PAF synthesis and chemical identification (gas chromatography-mass spectrometry).
- Assessment of polymorphonuclear neutrophil (PMN) adherence to HUVEC.
- Use of PAF receptor antagonists, PAF synthesis inhibitors, and monoclonal antibodies against ICAM-1 and CD18/CD11b.
Main Results:
- Hypoxia strongly activated HUVEC, inducing optimal PAF synthesis after 90 minutes.
- Neutrophil adherence to HUVEC increased with hypoxia duration.
- PAF mediated neutrophil adherence at 90 minutes of hypoxia, but its role shifted to a second messenger at 120 minutes.
- Adhesion involved ICAM-1 on HUVEC and CD18/CD11b on neutrophils; GMP-140 was involved at 90 minutes.
Conclusions:
- Hypoxia-induced endothelial cell activation and subsequent neutrophil recruitment are significantly mediated by PAF.
- The findings highlight the involvement of specific adhesion molecules in this process, offering insights into inflammatory mechanisms in ischemia.