Related Experiment Videos
Glucocorticoid-induced, caspase-dependent organ apoptosis early after burn injury
K Fukuzuka1, C K Edwards, M Clare-Salzler
1Department of Surgery, University of Florida College of Medicine, Gainesville, Florida 32610, USA.
Abstract:
Immune suppression and increased apoptotic loss of circulating lymphocytes have been reported after burn injury. However, little is known about the underlying mechanisms responsible for the increased apoptosis of lymphoid and parenchymal cells in solid organs and the role played by inflammatory mediators, such as tumor necrosis factor-alpha (TNF-alpha) and Fas ligand (FasL), as well as by glucocorticoids. To evaluate the role of endogenously produced glucocorticoids and FasL, mice subjected to a 20% steam burn were pretreated with a glucocorticoid receptor antagonist (mifepristone) or a neutralizing murine Fas fusion protein. Three and twenty-four hours after burn injury, histological analysis, caspase-3 activity, and in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and phenotyping of lymphocyte populations for apoptosis were evaluated. Burn injury increased the number of apoptotic cells and caspase-3 activity in thymus and spleen, but not in other solid organs. Increased apoptosis was seen in several T and B cell populations from both thymus and spleen. Mifepristone pretreatment significantly reduced the apoptosis and caspase-3 activity after burn injury, whereas blocking FasL activity had only minimal effects. We conclude that corticosteroids, and not FasL, are primarily responsible for the increased caspase-3 activity and apoptosis in thymus and spleen cell populations early after burn injury.
Insights
Burn injury increases lymphocyte apoptosis in the thymus and spleen. Endogenous corticosteroids, not Fas ligand, are the primary cause of this cell death, highlighting a key mechanism in post-burn immune suppression.
Area of Science:
- Immunology
- Cell Biology
- Burn Injury Research
Background:
- Burn injury is known to cause immune suppression and lymphocyte apoptosis.
- Mechanisms driving apoptosis in lymphoid and parenchymal cells post-burn, particularly involving inflammatory mediators like tumor necrosis factor-alpha (TNF-alpha) and Fas ligand (FasL), and glucocorticoids, remain unclear.
Purpose of the Study:
- To investigate the roles of endogenously produced glucocorticoids and Fas ligand (FasL) in mediating apoptosis of lymphoid cells following burn injury.
- To elucidate the specific mechanisms contributing to increased cell death in solid organs after thermal trauma.
Main Methods:
- Mice were subjected to a 20% steam burn and pretreated with either a glucocorticoid receptor antagonist (mifepristone) or a neutralizing Fas fusion protein.
- Histological analysis, caspase-3 activity assays, in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNL) staining, and lymphocyte phenotyping for apoptosis were performed at 3 and 24 hours post-burn.
Main Results:
- Burn injury significantly increased apoptotic cells and caspase-3 activity in the thymus and spleen.
- Apoptosis was elevated in various T and B cell populations within the thymus and spleen.
- Mifepristone pretreatment markedly reduced burn-induced apoptosis and caspase-3 activity.
- Blocking FasL activity demonstrated only minimal effects on apoptosis.
Conclusions:
- Endogenously produced corticosteroids are the primary mediators of increased caspase-3 activity and apoptosis in thymus and spleen cell populations shortly after burn injury.
- Fas ligand plays a minimal role in the early apoptotic response of lymphoid tissues to burn trauma.