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The expression of genes modulating programmed cell death in normal human polymorphonuclear neutrophils
S C Hsieh1, M H Huang, C Y Tsai
1Department of Medicine, Veterans General Hospital, Taipei, Taiwan, Republic of China.
Abstract:
Normal human polymorphonuclear neutrophils (PMN) have a short life and die in progression via apoptosis. In order to understand the molecular basis of PMN apoptosis, the expression of apoptosis-related (Fas, Fas-ligand, p53, and c-myc) and survival-related (bcl-2) genes was detected by flow cytometry, Western blot and reverse transcription-assisted polymerase chain reaction (RT-PCR). We found that Fas and Fas-ligand (FasL) were expressed on the surface of most of the cells. However, the disappearance of FasL was much faster than Fas after 24 h incubation. p53 and bcl-2 were also expressed in the cytoplasm of most of the cells. In contrast, the expression of c-myc was negligible in PMN. The addition of monoclonal anti-human Fas antibody (25 micrograms/ml) to PMN suspension enhanced whereas anti-FasL antibody (25 micrograms/ml) suppressed PMN apoptosis in 48 h incubation. These results suggest that the activation of Fas pathway induced by Fas-FasL interaction among PMNs is one of the mechanisms for spontaneous PMN apoptosis. Lack of proto-oncoprotein c-myc expression in PMN is responsible for their non-proliferative property and may aggravate the spontaneous apoptosis of the cells.
Insights
Polymorphonuclear neutrophils (PMN) undergo apoptosis. Fas-FasL interactions promote PMN apoptosis, while low c-myc expression contributes to their short lifespan and apoptosis.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Normal human polymorphonuclear neutrophils (PMN) have a limited lifespan and undergo programmed cell death (apoptosis).
- Understanding the molecular mechanisms regulating PMN apoptosis is crucial for immune system regulation.
Purpose of the Study:
- To investigate the molecular basis of spontaneous polymorphonuclear neutrophil apoptosis.
- To determine the expression patterns of key apoptosis-related and survival-related genes in PMNs.
Main Methods:
- Gene expression analysis using flow cytometry, Western blot, and reverse transcription-assisted polymerase chain reaction (RT-PCR).
- Functional assays involving monoclonal antibodies against Fas and Fas-ligand (FasL).
Main Results:
- Fas and FasL were expressed on PMN surfaces, with FasL diminishing faster than Fas.
- p53 and bcl-2 were detected in the cytoplasm, while c-myc expression was negligible.
- Anti-Fas antibody enhanced PMN apoptosis, whereas anti-FasL antibody suppressed it.
Conclusions:
- Fas-FasL pathway activation is a key mechanism driving spontaneous PMN apoptosis.
- The absence of c-myc expression contributes to PMN non-proliferative nature and may enhance apoptosis.