[The second stage larvae of Ascaris lumbricoides].

Objective: To induce the apoptosis of human alveolar epithelial cells (A549) by the extraction of the second stage larvae of Ascaris lumbricoides and investigate the extraction concentration and inducing time related to the apoptosis.

Methods: Following to the results of Microculture Tetrazolium Test (MTT), five concentrations of the extraction of the second stage larvae were chosen to induce the apoptosis of A549 cells. Meanwhile, control groups without the inducement were set up. For each group, observation was made at five time points since the start of inducement, to assess the existence of apoptosis and percentage of cells showing characteristics of apoptosis. HE stain and diphenylamine reaction methods were used to assess the cell apoptosis. Agarose gel electrophoresis of DNA and flow cytometry were also employed to confirm the apoptosis for some groups.

Results: Observations indicated that the apoptosis ratio of A549 cells induced by the extraction at different concentrations were significantly higher than that of the control cells (P < 0.05). At most time points of observation, the apoptosis ratio increased with the increase of concentration, indicating a positive correlation between them. For each concentration group, the apoptosis ratio increased as the inducing time prolonged until a peak appeared at 5 h of the inducement.

Conclusion: The extraction of the second stage larvae of Ascaris lumbricoides can induce apoptosis of human alveolar epithelial cells in vitro with a concentration-dependent pattern. With regard to the relationship of apoptosis to the time of inducement, two trends were revealed and the relationship also influenced by the concentration of the larvae extraction.