Abstract: Both destruxin A and destruxin B are bioactive molecules. In the present study, the effects of the two destruxins (destruxin A and destruxin B ) on Spodoptera litura SL-1 cells were compared with MTT assay, inverted phase contrast microscope (IPCM), fluorescence microscopy (FM) and flow cytometry (FCM) technologies. The results showed that both destruxins had an apparent effect on inhibition of cellular proliferation, and they had a positive relationship of time-concentration-efficacy. The IC₅₀ values were 7.80 and 20.73 μg/mL at 48 h after treatment with destruxin A and destruxin B, respectively. With inverted phase contrast microscopy observation, we found that both destruxins could cause cell rounded, celluar membrane shrunk, and apoptotic bodies formed. Most of cells were suspended and dead as vacuoles appeared and cytoplasm leaked out with extension of the treatment time. However, under the same concentrations tested, destruxin A showed stronger effect than destruxin B. With fluorescence microscopy observation after AO/EB staining, a relative higher fluorescent intensity of the cells induced by destruxin A was found as compared with destruxin B. Observations by flow cytometer showed that destruxin A and destruxin B could induce apoptosis in SL-1 cells, and the total apoptotic rates reached 78.88%±0.97% and 72.23%±2.29% at 48 h after treatment with 10 μg/mL destruxin A and destruxin B, respectively. This research demonstrated that destruxins possess a preferable activity for cell proliferation and apoptosis at the cellular level, and provided some theoretical support for their potential application in pest control.

Key words:  Spodoptera litura, destruxin A, destruxin B, SL-1 cell, cellular proliferation, apoptosis