The Mitochondria-Mediate Apoptosis of Lepidopteran Cells Induced by Azadirachtin

Abstract

Mitochondria have been shown to play an important role in apoptosis using mammalian cell lines. However, this seems not to be the case in Drosophila, an insect model organism; thus more in-depth studies of insect cell apoptosis are necessary. In the present study, mitochondrial involvement during azadirachtin- and camptothecin-induced apoptosis in Spodoptera frugiperda Sf9 cells (isolated from Spodoptera frugiperda pupal ovarian tissue) was investigated. The results showed that both azadirachtin and camptothecin could induce apoptosis in Sf9 cells. Reactive oxygen species (ROS) generation, activation of mitochondrial permeability transition pores (MPTPs) and loss of mitochondrial membrane potential (MMP) were observed very early during apoptosis and were followed subsequently by the release of cytochrome-c from the mitochondria. Furthermore, the results also revealed that the opening of MPTPs and the loss of MMP induced by azadirachtin could be significantly inhibited by the permeability transition pore (PTP) inhibitor cyclosporin A (CsA), which was used to identify the key role of mitochondria in the apoptosis of Sf9 cells. However, in camptothecin-treated Sf9 cells, CsA could not suppress the opening of MPTPs and the loss of MMP when apoptosis was induced. The data from caspase-3 and caspase-9 activity assays and detection of apoptosis by morphological observation and flow cytometry also uncovered the different effect of CsA on the two botanical apoptosis inducers. Although different mechanisms of apoptosis induction exist, our study revealed that mitochondria play a crucial role in insect cell line apoptosis.

Fipronil induces apoptosis through caspase-dependent mitochondrial pathways in Drosophila S2 cells

“…The apoptotic signals affect the mitochondrial membrane potential and Cyt c release and disrupt electron transport, which results in an increased generation of reactive oxygen species (ROS) [17]. ROS largely originate from mitochondria, mainly in the complexes I and III of the respiratory chain [17,36].…”

“…Mitochondria have been reported to play a significant role in the intrinsic pathway [17,19]. Using fluorescent microscopy, we determined that exposure of S2 cells to 20, 30, 40 and 50 μg/mL fipronil for 24 h resulted in a decrease in red fluorescence in the mitochondria and an increase in green fluorescence in the cytoplasm (Fig.…”

“…However, whether Cytochrome c plays an essential role in the apoptotic process in Drosophila is controversial and may depend on cell type [17][18][19]. Overexpression of rpr or treatment with cycloheximide or staurosporine in Drosophila SL2 cells, causes the release of Cytochrome c into the cytosol in the apoptosis process [20].…”

Redox imbalance mediates entomotoxic effects of the conifer Araucaria angustifolia in Anticarsia gemmatalis velvetbean caterpillar

“…Superoxide anion and hydrogen peroxide are thought to be byproducts of aerobic respiration generated by electron transport chain of the mitochondria (Bae, Oh, Rhee, & Yoo, 2011). Though mitochondria are traditionally known for producing energy for cellular survival, they also play an important role in regulating other cellular mechanisms such as apoptosis, an essential dynamic process that maintains the stability of the internal environment and controls the development of multicellular organisms, including insects (Huang, Lv, Hu, & Zhong, 2013). Taking into account the link between redox imbalance and apoptosis, our results suggests that AAE-induced ROS generation, mainly by O ⋅− 2 formation observed in this study, may be responsible for the reduction in insect viability, leading to cell death possibly via mitochondrial regulation of apoptosis signaling.…”

Azadirachtin blocks the calcium channel and modulates the cholinergic miniature synaptic current in the central nervous system of Drosophila

“…In recent study, the induction of apoptosis by AZ was investigated. AZ can induce apoptosis in a Spodoptera frugiperda cell by exciting the mitochondrial permeability transition pores and reducing the mitochondrial membrane potential . However, the effect of AZ on the central nervous system (CNS) , especially in the cholinergic transmission, is rarely reported.…”