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The endothelial cell cytoskeleton modulates extravascular polymorphonuclear leukocyte accumulations in vivo
I S Paterson1, J M Klausner, G Goldman
1Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Abstract:
Actin microfilaments, key elements in the endothelial cell (EC) cytoskeleton, have been noted in in vitro studies to play a modulating role in the diapedesis of polymorphonuclear leukocytes (PMN). The role of the cytoskeleton in PMN diapedesis in vivo was the subject of this study. Small skin abrasions were produced in rabbits. Cytoskeletal manipulation was accomplished by local application of phalloidin which promotes microfilament assembly or cytochalasin B which causes their disassembly, prior to addition of a chemotaxin. When the initial treatment to the abrasion site was saline, the secondary addition of more saline resulted in PMN accumulations, expressed as PMN/mm3 of 36 +/- 19, while 10(-4) M cytochalasin B led to 91 +/- 32 (P less than 0.05). Secondary addition of chemotaxins or histamine also led to significant PMN accumulations of 169 +/- 54 with 10(-8) M leukotriene (LT) B4, 318 +/- 85 with zymosan-activated plasma (ZAP), and 158 +/- 48 with 10(-4) M histamine. When the initial treatment was 10(-8) M phalloidin, PMN accumulations were reduced to 31 +/- 22 with cytochalasin B (P less than 0.05 relative to saline as initial treatment); 63 +/- 43 with LTB4 (P less than 0.05); 137 +/- 48 with ZAP (P less than 0.05); and 51 +/- 35 with histamine (P less than 0.05). In contrast, initial blister treatment with cytochalasin B rather than saline increased PMN accumulations in response to LTB4, 291 +/- 71 (P less than 0.05), and histamine, 270 +/- 56 (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
This study reveals that manipulating actin microfilaments in endothelial cells affects polymorphonuclear leukocyte diapedesis in vivo. Disrupting actin assembly with cytochalasin B enhances leukocyte migration, while promoting assembly with phalloidin reduces it.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Actin microfilaments are crucial for endothelial cell (EC) cytoskeleton structure and function.
- In vitro studies suggest a role for actin microfilaments in polymorphonuclear leukocyte (PMN) diapedesis.
- The in vivo role of the EC cytoskeleton in PMN diapedesis requires further investigation.
Purpose of the Study:
- To investigate the in vivo role of the endothelial cell cytoskeleton in regulating PMN diapedesis.
- To determine how manipulating actin microfilaments affects PMN accumulation at sites of inflammation.
Main Methods:
- Small skin abrasions were created in rabbits to serve as experimental sites.
- Local application of phalloidin (promotes microfilament assembly) or cytochalasin B (promotes microfilament disassembly) was used for cytoskeletal manipulation.
- Chemotaxins, histamine, or saline were added secondarily to assess PMN accumulation.
Main Results:
- Cytochalasin B treatment significantly increased PMN accumulation compared to saline control.
- Phalloidin treatment significantly reduced PMN accumulation in response to various chemoattractants (LTB4, ZAP, histamine).
- Initial cytochalasin B treatment of blisters enhanced PMN accumulation in response to LTB4 and histamine.
Conclusions:
- Actin microfilament dynamics play a critical role in regulating PMN diapedesis in vivo.
- Disassembly of actin filaments enhances PMN migration, while assembly inhibits it.
- Targeting the EC cytoskeleton may offer therapeutic strategies for inflammatory conditions.