Paraquat (PQ), as a highly effective and nonselective herbicide, induces cell apoptosis through generation of superoxide anions which forms reactive oxygen species (ROS). Mitochondria, as regulators for cellular redox signaling, have been proved to play an important role in PQ-induced cell apoptosis. This study aimed to evaluate whether and how mitochondrial fission interacts with oxidative stress in PQ-induced apoptosis in mouse alveolar type II (AT-II) cells. Firstly, we demonstrated that PQ promoted apoptosis and release of cytochrome-c (Cyt-c). Furthermore, we showed that PQ broke down mitochondrial network, enhanced the expression of fission-related proteins, increased Drp1 mitochondrial translocation while decreased the expression of fusion-related proteins in AT-II cells. Besides, inhibiting mitochondrial fission using mdivi-1, a selective inhibitor of Drp1, markedly attenuated PQ-induced apoptosis, release of Cyt-c and the generation of ROS. These results indicate that mitochondrial fission involves in PQ-induced apoptosis. Further study demonstrated that antioxidant ascorbic acid inhibited Drp1 mitochondrial translocation, mitochondrial fission and attenuated PQ-induced apoptosis. Overall, our findings suggest that mitochondrial fission interplays with ROS in PQ-induced apoptosis in mouse AT-II cells and mitochondrial fission could serve as a potential therapeutic target in PQ poisoning.

Therapeutic agents used to treat sepsis-induced cardiac dysfunction are designed to suppress tumor necrosis factor (TNF)-α release and inhibit cell apoptosis. Exogenous administration of growth arrest-specific 6 (Gas6) exerts several biological and pharmacological effects; however, the role of Gas6 in sepsis-induced myocardial dysfunction remains unclear. In this study, H9C2 cardiomyocytes were stimulated with LPS (10 µ g/ml) to mimic septic cardiac dysfunction and Gas6 (100 ng/ml) was applied exogenously. Subsequently, mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB activation, TNF-α expression, and apoptosis in the presence or absence of TP-0903 (15 nM) and Wortmannin (3 nM) were evaluated. The morphological alterations of H9C2 cells were visualized by phase-contrast microscopy. Cell viability was determined using the Cell Counting kit 8 assay and lactate dehydrogenase release, and TNF-α release was analyzed by ELISA analysis. Cell apoptosis was analyzed by flow cytometry and TUNEL assay. Nuclear morphological alterations were detected by Hoechst staining and caspase-3 activity was measured using biochemical methods. The expression levels of Bax and Bcl-2, and the phosphorylation and expression levels of Axl, Akt, IκB-α, p65, c-Jun N-terminal protein kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 were determined by western blotting. Furthermore, immunofluorescence analysis was performed to visualize translocation of NF-κB p65. The results demonstrated that Gas6 suppressed TNF-α release and inhibited cell apoptosis, and attenuated nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) activation via the Axl/PI3K/Akt pathway. Furthermore, the cardioprotective properties of Gas6 on the suppression of LPS-induced TNF-α release and apoptosis were abolished by treatment with TP-0903 (an Axl inhibitor) and Wortmannin (a PI3K inhibitor). Pretreatment with TP-0903 and Wortmannin abrogated the effects of Gas6 on phosphorylated-IκB-α, IκB-α, NF-κB, ERK1/2, JNK and p38 MAPK. These findings suggested that activation of Axl/PI3K/Akt signaling by Gas6 may inhibit LPS-induced TNF-α expression and apoptosis, as well as MAPK and NF-κB activation.

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