Preliminary studies on induction of apoptosis by abamectin in Spodoptera frugiperda (Sf9) cell line

Avermectins are a series 16-membered macrocyclic lactone derivatives derived from the actinomycete Streptomyces avermectinius, which has been applied worldwide in veterinary, human medicine and agriculture. Abamectin is a mixture of avermectins containing ⩾80% avermectin B1a and ⩽20% avermectin B1b. In this paper, the apoptotic induction effect of abamectin on Spodoptera frugiperda (Sf9) cells was detected by using various techniques including cell proliferation assay, flow cytometry, morphology analysis with inverted phase contrast microscope, scanning electron microscope, transmission electron microscopy, enzyme activity assay and Western blot. The results revealed that within the concentrations of 5–15 μg/mL, abamectin inhibited the growth of the Sf9 cells and induced apoptotic cell death in a time- and dose-dependent manner. The proliferation inhibition rates of Sf9 cells were 6.45 ± 0.47%, 11.51 ± 0.20% and 12.97 ± 0.46% after 12 h of treatment with avermectin at the concentrations of 5, 10 and 15 μg/mL, which increased to 30.74 ± 0.57%, 36.14 ± 0.25% and 39.27 ± 0.63% after 72 h of the same treatments, respectively. The maximum apoptosis rate of each concentration was 24.13 ± 0.43%, 24.69 ± 0.38% and 27.285 ± 0.84%, respectively. Treated cells showed typical apoptosis morphological changes including cell swelling, chromatin condensation, apoptotic bodies, swollen mitochondria and high content of phagosome. Both mitochondrial events including mitochondrial membrane potential (Δψm) loss as well as cytochrome-c release into cytosol and significant activation of caspase-3 occurred during apoptosis. These data confirmed the apoptosis inducing effects of abamectin on S. frugiperda (Sf9) cell line, and provide preliminary studies on its mechanism.

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► Loss of mitochondrial membrane potential.
► Cytochrome-c release from mitochondria to cytosol.
► Activation of caspase-3.