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beta1 integrins are critically involved in neutrophil locomotion in extravascular tissue In vivo
1Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Abstract:
Recruitment of leukocytes from blood to tissue in inflammation requires the function of specific cell surface adhesion molecules. The objective of this study was to identify adhesion molecules that are involved in polymorphonuclear leukocyte (PMN) locomotion in extravascular tissue in vivo. Extravasation and interstitial tissue migration of PMNs was induced in the rat mesentery by chemotactic stimulation with platelet-activating factor (PAF; 10(-7) M). Intravital time-lapse videomicroscopy was used to analyze migration velocity of the activated PMNs, and the modulatory influence on locomotion of locally administered antibodies or peptides recognizing various integrin molecules was examined. Immunofluorescence flow cytometry revealed increased expression of alpha4, beta1, and beta2 integrins on extravasated PMNs compared with blood PMNs. Median migration velocity in response to PAF stimulation was 15.5 +/- 4.5 micron/min (mean +/- SD). Marked reduction (67 +/- 7%) in motility was observed after treatment with mAb blocking beta1 integrin function (VLA integrins), whereas there was little, although significant, reduction (22 +/- 13%) with beta2 integrin mAb. Antibodies or integrin-binding peptides recognizing alpha4beta1, alpha5beta1, or alphavbeta3 were ineffective in modulating migration velocity. Our data demonstrate that cell surface expression of beta1 integrins, although limited on blood PMNs, is induced in extravasated PMNs, and that members of the beta1 integrin family other than alpha4beta1 and alpha5beta1 are critically involved in the chemokinetic movement of PMNs in rat extravascular tissue in vivo.
Insights
Beta1 integrins are crucial for polymorphonuclear leukocyte (PMN) movement in tissues during inflammation. Blocking beta1 integrin function significantly reduced PMN motility in vivo.
Area of Science:
- Immunology
- Cell Biology
- Physiology
Background:
- Leukocyte recruitment to inflamed tissues relies on cell surface adhesion molecules.
- Understanding these molecules is key to controlling inflammatory responses.
Purpose of the Study:
- To identify specific adhesion molecules involved in polymorphonuclear leukocyte (PMN) locomotion within extravascular tissue.
- To investigate the role of integrins in PMN migration in vivo.
Main Methods:
- Induced PMN extravasation and migration in rat mesentery using platelet-activating factor (PAF).
- Utilized intravital time-lapse videomicroscopy to assess PMN migration velocity.
- Examined the effect of blocking antibodies against various integrins on PMN motility.
Main Results:
- Increased expression of alpha4, beta1, and beta2 integrins was observed on extravasated PMNs.
- Blocking beta1 integrin function reduced PMN motility by 67%, while beta2 integrin blockade reduced it by 22%.
- Specific integrins like alpha4beta1, alpha5beta1, and alphavbeta3 did not significantly affect migration velocity.
Conclusions:
- Beta1 integrins are upregulated on extravasated PMNs and are critical for their chemokinetic movement in tissues.
- Beta1 integrin family members, excluding alpha4beta1 and alpha5beta1, play a significant role in PMN extravascular migration.
- Targeting specific beta1 integrins may offer therapeutic strategies for inflammatory conditions.