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[Changes of L-selectin expression on polymorphonuclear leukocytes and its role during polymorphonuclear leukocytes
Objective:
To explore the changes of L-selectin protein expression on peripheral blood polymorphonuclear leukocytes (PMN) and their role during PMN sequestration in the lungs of rats with acute lung injury (ALI).
Methods:
The model of ALI in rat was established by intravenous injection of E. Coli endotoxin (ET). The protein expression of L-selectin on peripheral blood PMNs was measured by immunofluorescence and flow cytometry. Myeloperoxidase (MPO) enzyme analysis and histology were employed to estimate the quantity of PMN sequestration in lungs of rats during ALI.
Results:
(1) The protein expression of L-selectin on PMN after injection of ET (7.8 +/- 1.6) was all significantly lower than that in control group (10.5 +/- 2.1, P < 0.05). (2) MPO activity increased significantly after injection of ET in comparison with the control group [0.069 +/- 0.011) U/mg lung tissue, P < 0.01]. The difference was not significant between the fucodin treated 5 min group [(0.391 +/- 0.071) U/mg lung tissue] and ET-treated 5 min group [(0.359 +/- 0.074) U/mg lung tissue]. But MPO activity was significantly lower in fucodin-treated 15 min group [(0.396 +/- 0.061) U/mg lung tissue] than that in ET-treated group at same time point [(0.490 +/- 0.069) U/mg lung tissue, P < 0.05].
Conclusions:
(1) In physiological state, L-selectin are consistently expressed on the surface of PMN membrane. The protein expression of L-selectin on PMNs reduces rapidly after injection of ET and is the lowest at 15 min, then gradually increases. (2) The early stage of PMN sequestration in lungs is not dependent on L-selectin, but L-selectin is still important for maintaining a continual PMN sequestration in lungs of rats with ALI.
Insights
L-selectin protein expression on polymorphonuclear leukocytes (PMN) decreases after endotoxin injection in acute lung injury (ALI) rats. While early lung PMN sequestration is L-selectin independent, it
Area of Science:
- Immunology and Inflammation Research
- Pulmonary Medicine and Critical Care
Background:
- Polymorphonuclear leukocytes (PMN) play a critical role in acute lung injury (ALI).
- L-selectin is a cell adhesion molecule expressed on leukocytes, involved in cell trafficking.
- Understanding PMN sequestration in the lungs during ALI is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the dynamic changes in L-selectin protein expression on peripheral blood PMNs in a rat model of ALI.
- To elucidate the role of L-selectin in PMN sequestration within the lungs during the development of ALI.
Main Methods:
- Acute lung injury (ALI) was induced in rats via intravenous injection of E. coli endotoxin (ET).
- L-selectin protein expression on peripheral blood PMNs was quantified using immunofluorescence and flow cytometry.
- PMN sequestration in lung tissue was assessed by measuring myeloperoxidase (MPO) activity and performing histology.
Main Results:
- ET injection significantly reduced L-selectin expression on PMNs compared to controls (7.8 ± 1.6 vs. 10.5 ± 2.1, P < 0.05).
- MPO activity, an indicator of PMN sequestration, significantly increased in the lungs after ET administration (P < 0.01).
- While early PMN sequestration (5 min) was not significantly affected by fucodin treatment, later sequestration (15 min) was reduced in fucodin-treated rats compared to ET-treated rats (P < 0.05).
Conclusions:
- L-selectin expression on PMNs decreases rapidly following endotoxin challenge in ALI, reaching its lowest point at 15 minutes.
- The initial phase of PMN sequestration in the lungs during ALI is not dependent on L-selectin.
- L-selectin plays a significant role in sustaining PMN sequestration in the lungs throughout the course of ALI.
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