Related Experiment Videos
Leukocyte contribution to parenchymal cell death in an experimental model of inflammation
D K Tung1, L M Bjursten, B W Zweifach
1Department of Bioengineering, University of California, San Diego, La Jolla 92093-0412, USA.
Abstract:
The relationship between leukocyte migration and parenchymal cell death in vivo remains poorly documented. Accordingly, cell killing in the rat mesentery, as recorded by propidium iodide staining, was investigated with an intravital approach. Superfusion of platelet-activating factor (PAF, 10(-8) M) or N-formyl-methionyl-leucyl-phenylalanine (fMLP, 10(-8) M) led to extensive leukocyte extravasation but no significant cell death. In contrast, pretreatment with 10(-8) M PAF or fMLP for 1 h, followed by superfusion of PAF in combination with fMLP (both at 10(-8) M) led to an increase in cell death. Mesenteric parenchymal cells but no endothelial cells were killed. Some of the dead cells were identified as granulocytes/monocytes that were already in the tissue at the start of the experiment. The incidence of cell death was lower but not eliminated when leukocyte migration was blocked with a monoclonal antibody against CD18. A xanthine oxidase inhibitor, BOF-4272, failed to diminish cell death, whereas a hydroxyl radical scavenger, dimethylthiourea, attenuated cell killing without an effect on the number of adhering and migrating leukocytes. These observations demonstrate that leukocytes serve as a factor in the killing of extravascular cells only after the development of a level of stimulation that differs from that required to induce a migratory stimulus into the extravascular space.
Insights
Leukocyte migration alone does not cause cell death. However, prolonged stimulation leads to leukocyte-induced parenchymal cell death, involving reactive oxygen species but not xanthine oxidase.
Area of Science:
- Immunology
- Cell Biology
- Physiology
Background:
- Leukocyte migration into tissues is crucial for immune responses.
- The direct role of leukocyte migration in causing parenchymal cell death in vivo is not well understood.
Purpose of the Study:
- To investigate the relationship between leukocyte migration and parenchymal cell death in the rat mesentery.
- To determine the conditions under which leukocyte migration leads to cell killing.
Main Methods:
- Intravital microscopy of the rat mesentery.
- Propidium iodide staining to assess cell death.
- Stimulation with platelet-activating factor (PAF) and N-formyl-methionyl-leucyl-phenylalanine (fMLP).
- Inhibition of leukocyte migration (anti-CD18 antibody) and reactive oxygen species (dimethylthiourea).
Main Results:
- Extensive leukocyte extravasation occurred with PAF or fMLP alone, but without significant cell death.
- Combined and prolonged PAF/fMLP stimulation increased parenchymal cell death, including resident granulocytes/monocytes.
- Cell death was reduced, but not abolished, by blocking leukocyte migration.
- A hydroxyl radical scavenger attenuated cell killing, while a xanthine oxidase inhibitor did not.
Conclusions:
- Leukocyte migration alone does not induce parenchymal cell death.
- A specific level of leukocyte stimulation, distinct from that inducing migration, is required for cell killing.
- Hydroxyl radicals, not xanthine oxidase, appear to mediate leukocyte-induced cell death in this model.