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Phorbol myristate acetate-treated endothelium stimulates polymorphonuclear leukocyte adhesion and superoxide
P W Gudewicz1, M B Weaver, P J Del Vecchio
1Department of Physiology, Albany Medical College, NY 12208.
Abstract:
The adherence of polymorphonuclear leukocytes (PMNLs) to the pulmonary vascular endothelium may contribute to acute lung injury. We studied the mechanism whereby treatment of bovine pulmonary artery endothelial cells with the potent inflammatory agent phorbol myristate acetate (PMA) stimulated the adherence and secretion of superoxide anion by human PMNLs. Treatment of endothelial cell monolayers with 100 ng/ml PMA resulted in a time-dependent increase in PMNL adherence to the endothelial cells. Treatment of endothelial cells with PMA or the less-lipophilic active phorbol ester 4-beta-phorbol 12,13-dibutyrate stimulated PMNL adherence in a dose-dependent manner, but the inactive phorbol ester 4-alpha-12,13 dideconoate had no effect on PMNL adherence. When formalin-fixed endothelial cells were treated with PMA, the increase in PMNL adherence was similar to that observed with unfixed endothelial cells. Treatment of fixed endothelial cells with 4-beta-phorbol 12,13 dibutyrate did not promote adherence. PMA-induced stimulation of PMNL adherence to endothelial cells was not eliminated by washing the PMA-treated endothelial cells, and the 4-hour conditioned medium obtained from PMA-treated endothelial cells also stimulated PMNL adherence to untreated endothelial cell monolayers PMNL adherence induced by PMA also stimulated the secretion of superoxide anion. Thus, PMA bound to the vascular endothelium will promote both PMNL adhesion and the secretion of reactive oxygen intermediates. Furthermore bound PMA rereleased from the endothelium can also stimulate PMNL adherence and superoxide anion secretion at a distant site.
Insights
Phorbol myristate acetate (PMA) enhances polymorphonuclear leukocyte (PMNL) adherence to pulmonary endothelium, promoting superoxide anion secretion. Bound PMA can re-release, further stimulating PMNLs and contributing to acute lung injury.
Area of Science:
- Pulmonary vascular biology
- Inflammation and immunology
- Cellular adhesion mechanisms
Background:
- Polymorphonuclear leukocyte (PMNL) adherence to pulmonary endothelium is implicated in acute lung injury.
- Understanding the molecular mechanisms of PMNL-endothelial interactions is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the mechanism by which phorbol myristate acetate (PMA) stimulates PMNL adherence and superoxide anion secretion by pulmonary artery endothelial cells.
- To determine the role of endothelial cell fixation and PMA release in PMNL adhesion.
Main Methods:
- Bovine pulmonary artery endothelial cells were treated with PMA, and PMNL adherence was quantified.
- Dose- and time-dependent effects of PMA and its analogs on PMNL adherence were assessed.
- Experiments were conducted using both fixed and unfixed endothelial cells, and conditioned media were analyzed.
Main Results:
- PMA treatment significantly increased PMNL adherence to endothelial cells in a time- and dose-dependent manner.
- Active phorbol esters stimulated adherence, while inactive ones did not.
- PMA-induced adherence was observed with fixed endothelial cells and was mediated by factors released from treated cells.
- PMA also stimulated superoxide anion secretion by adhered PMNLs.
Conclusions:
- PMA bound to vascular endothelium promotes PMNL adhesion and secretion of reactive oxygen intermediates.
- Released PMA can act at distant sites to stimulate PMNL adherence and superoxide anion secretion.
- These findings elucidate a mechanism contributing to acute lung injury involving PMNL-endothelial cell interactions.