Objective: To study the effect of tumor necrosis factor-alpha (TNF-alpha) on the proliferation and apoptosis of type II lung alveolar epithelial cells and the regulation of retinoic acid (RA) to this effect.
Methods: Human type II lung alveolar epithelial cells of the line A569 were cultured and divided into 2 groups: control group (cultured in culture fluid only), TNF-group (cultured in the culture fluid with TNF-alpha 10 micromol/L for 24 or 46 h respectively), RA group (cultured in culture fluid without RA 1 microg/L), and TNF-alpha plus RA group (cultured in culture fluid with TNF-alpha 10 micromol/L + RA 1 microg/L). MTT method was used to test the proliferation of the A549 cells. The cell apoptosis was detected by flow cytometric assay.
Results: The proliferation rates of A549 cells treated with TNF-alpha of the concentrations of 0, 0.1, 1, 5, and 10 microg/L were 95.0%, 90.0%, 79.6%, 72.4%, and 59.6% after 24 h (F = 18.04, P < 0.001), and were 93.2%, 82.7%, 61.5%, 50.3%, and 44.7% after 48 h (F = 40.61, P < 0.0001). The inhibition effect on the proliferation of A549 cells treated with 10 microg/L TNF-alpha for 24 h could be reversed, however, the inhibition effect on the proliferation of A549 cells treated with 10 microg/L TNF-a for 48h could not be reversed. RA alone did not significantly promote the proliferation of the A549 cells, but weakened the inhibitory effect of TNF-alpha on the proliferation of the A549 cells. The apoptotic rate of the A549 cells treated with TNF-alpha for 12 h, 24 h and 48 h respectively were 14.3% +/- 3.2%, 18.6% +/- 2.9%, and 43.4% +/- 3.5% respectively, all significantly higher than those of the control group (6.3% +/- 1.2%, 8.2% +/- 1.3%, and 26.1% +/- 2.5% respectively, all P < 0.01), and the apoptotic rate of the A549 cells treated with both TNF-alpha and RA for 12 h, 24 h, and 48h were 4.8% +/- 1.1%, 5.2% +/- 1.3%, and 16.4% +/- 2.3% respectively, all significantly lower than those of the TNF-alpha group (all P < 0.01), and the apoptotic rates of the A549 cells treated with both TNF-alpha and RA for 24 h and 48 h respectively were both significantly lower than those of the control group (both P < 0.05).
Conclusion: RA relieves the injury of alveolar epithelial cells and protects the pulmonary surfactant by inhibiting the destruction of TNF-alpha to type II lung alveolar epithelial cells.