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Science review: apoptosis in acute lung injury
Gustavo Matute-Bello1, Thomas R Martin
1Medical Research Service of the Veterans Affairs Puget Sound Health Care System, Seattle, Washington, USA.
Abstract:
Apoptosis is a process of controlled cellular death whereby the activation of specific death-signaling pathways leads to deletion of cells from tissue. The importance of apoptosis resides in the fact that several steps involved in the modulation of apoptosis are susceptible to therapeutic intervention. In the present review we examine two important hypotheses that link apoptosis with the pathogenesis of acute lung injury in humans. The first of these, namely the 'neutrophilic hypothesis', suggests that during acute inflammation the cytokines granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor prolong the survival of neutrophils, and thus enhance neutrophilic inflammation. The second hypothesis, the 'epithelial hypothesis', suggests that epithelial injury in acute lung injury is associated with apoptotic death of alveolar epithelial cells triggered by soluble mediators such as soluble Fas ligand. We also review recent studies that suggest that the rate of clearance of apoptotic neutrophils may be associated with resolution of neutrophilic inflammation in the lungs, and data showing that phagocytosis of apoptotic neutrophils can induce an anti-inflammatory phenotype in activated alveolar macrophages.
Insights
Apoptosis, or programmed cell death, plays a key role in acute lung injury. Understanding apoptosis pathways offers therapeutic targets for treating this condition.
Area of Science:
- Cellular Biology
- Immunology
- Pathophysiology
Background:
- Apoptosis is a critical process of programmed cell death essential for tissue homeostasis.
- Dysregulation of apoptosis is implicated in various human diseases, including acute lung injury (ALI).
- Therapeutic strategies targeting apoptosis modulation are actively being explored.
Purpose of the Study:
- To review the role of apoptosis in the pathogenesis of acute lung injury (ALI).
- To examine the 'neutrophilic hypothesis' and 'epithelial hypothesis' linking apoptosis to ALI.
- To discuss the implications of apoptotic cell clearance in resolving lung inflammation.
Main Methods:
- Review of existing scientific literature and studies on apoptosis in ALI.
- Analysis of hypotheses concerning the involvement of neutrophils and alveolar epithelial cells in ALI pathogenesis.
- Examination of data on the clearance of apoptotic cells and its anti-inflammatory effects.
Main Results:
- The 'neutrophilic hypothesis' posits that cytokines prolong neutrophil survival, exacerbating inflammation in ALI.
- The 'epithelial hypothesis' suggests that soluble mediators induce apoptotic death of alveolar epithelial cells in ALI.
- Efficient clearance of apoptotic neutrophils is linked to the resolution of lung inflammation.
- Phagocytosis of apoptotic neutrophils by macrophages can induce an anti-inflammatory state.
Conclusions:
- Apoptosis is a central mechanism in the development and resolution of acute lung injury.
- Targeting apoptosis pathways, particularly involving neutrophils and epithelial cells, holds therapeutic potential for ALI.
- Effective clearance of apoptotic cells is crucial for mitigating inflammation in ALI.