Increased apoptosis in the alveolar microenvironment of the healthy human lung.
BACKGROUND
Apoptosis represents a physiological clearance mechanism in human tissues. The role of apoptosis has not been examined in normal lung cell populations, such as alveolar macrophages and polymorphonuclear cells. What is the percentage, as well as the role, of apoptosis in the alveolar microenvironment of the healthy human lung?


METHODS
Bronchoalveolar lavage was obtained from 21 volunteers without lung disease. The specimens were analyzed using: Annexin V binding, DNA laddering, light microscopy and immunohistochemistry for bcl-2 expression.


RESULTS
Apoptosis of the total bronchoalveolar lavage cell population was 51.2%. Both alveolar macrophages and polymorphonuclear cells had a high apoptotic rate (62.1% and 48.3%, respectively) as determined by Annexin V binding. These findings were further confirmed using morphological criteria for apoptosis and gel electrophoresis for DNA fragmentation. In the majority of the individuals examined, (8 out of 21), the bcl-2 gene was expressed in the lymphocyte population mainly.


CONCLUSIONS
The percentage of apoptosis in lung cells of healthy humans is high. Apoptosis plays a key role in normal lung cell death. It appears to be the mechanism that opposes cell proliferation by eliminating, aged or damaged cells thus facilitating the process of lung remodeling.
Liacos
Christine
C
First Department of Propaedeutic Surgery, Laboratory of Surgical Research, Athens University Medical School, Athens, Greece.
Konstadoulakis
Manousos M
MM
Economou
Venetia
V
Katsaragakis
Stylianos
S
Chatzigianni
Emmy
E
Georgiadis
George G
GG
Prekates
Athanasios
A
Karampinis
Andreas
A
Bramis
John
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology*; D053938:DNA Fragmentation; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology* / Q000378:metabolism
D017304:Annexin A5; D019253:Proto-Oncogene Proteins c-bcl-2