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Lipoxygenase products induce neutrophil activation and increase endothelial permeability after thrombin-induced
M B Perlman1, A Johnson, W Jubiz
1Department of Pediatrics, Albany Medical College, Union University, New York.
Abstract:
We examined the mechanism of the neutrophil (PMN)-dependent increase in pulmonary vascular permeability to protein after thrombin-induced pulmonary microembolism. Humoral factors that activate PMNs after thrombin-induced pulmonary microembolism were characterized in pulmonary lymph obtained from unanesthetized sheep challenged with intravenous infusion of alpha-thrombin. Time-dependent increases in PMN migration, aggregation, and superoxide anion (O2-) generation were induced by the pulmonary lymph obtained within 20 minutes after thrombin infusion. The pulmonary lymph neutrophil activating factors present in ether extracts of lymph had retention times of leukotriene B4 (LTB4) and monohydroxyeicosatetraenoic acids (HETEs) by high-performance liquid chromatography. The postthrombin lymph samples containing the LTB4 and HETEs increased PMN O2- generation and endothelial monolayer permeability to 125I-albumin in the presence of PMNs layered on the endothelial monolayers. Control lymph samples replete with LTB4, 5-HETE, and 15-HETE induced increases in PMN O2- generation and endothelial monolayer permeability to 125I-albumin in the presence of PMNs layered on the endothelial monolayers. Maximal increases in PMN O2- production and endothelial permeability occurred when LTB4, 5-HETE, and 15-HETE were coincubated with PMNs, indicating a synergistic action of these mediators in inducing PMN activation. Endothelial monolayer permeability to 125I-albumin did not increase with postthrombin lymph samples obtained after pretreatment with the 5-lipoxygenase inhibitor, L-651,392. The results indicate that lipoxygenase products generated in the lungs after thrombin-induced microembolism contribute to increased endothelial permeability secondary to PMN activation.
Insights
Thrombin-induced microembolism increases lung vascular permeability via neutrophil activation. Lipoxygenase products like leukotriene B4 and HETEs are key mediators, enhancing neutrophil superoxide generation and endothelial permeability.
Area of Science:
- Pulmonary vascular physiology
- Inflammation and immunology
Background:
- Thrombin-induced pulmonary microembolism increases vascular permeability.
- Neutrophils (PMNs) play a crucial role in this process.
Purpose of the Study:
- To investigate the mechanism of neutrophil-dependent increase in pulmonary vascular permeability.
- To characterize humoral factors activating PMNs after thrombin challenge.
Main Methods:
- Sheep model of thrombin-induced pulmonary microembolism.
- Collection and analysis of pulmonary lymph.
- High-performance liquid chromatography (HPLC) to identify lipid mediators.
- Assays for PMN migration, aggregation, and superoxide anion (O2-) generation.
- Endothelial monolayer permeability studies using 125I-albumin.
Main Results:
- Pulmonary lymph from sheep challenged with thrombin induced PMN activation (migration, aggregation, O2- generation).
- Ether extracts of lymph contained leukotriene B4 (LTB4) and monohydroxyeicosatetraenoic acids (HETEs).
- LTB4 and HETEs synergistically increased PMN O2- generation and endothelial permeability to albumin in the presence of PMNs.
- Inhibition of 5-lipoxygenase pathway with L-651,392 blocked the increase in endothelial permeability.
Conclusions:
- Lipoxygenase products, including LTB4 and HETEs, are critical mediators of increased pulmonary endothelial permeability following thrombin-induced microembolism.
- These mediators contribute to increased permeability through PMN activation.