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Silibinin induces apoptosis via calpain-dependent AIF nuclear translocation in U87MG human glioma cell death.

Jeong JC, Shin WY, Kim TH, Kwon CH, Kim JH, Kim YK, Kim KH - J. Exp. Clin. Cancer Res. (2011)

Bottom Line: Silibinin caused ROS generation and its effect was inhibited by calpain inhibitor, the general PKC inhibitor GF 109203X, the specific PKCδ inhibitor rottlerin, and catalase.Silibinin induced AIF nuclear translocation and its effect was prevented by calpain inhibitor.Transfection of vector expressing microRNA of AIF prevented the silibinin-induced cell death.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oriental Medicine, Dongguk University, Kyung Ju, 780-714, Korea.

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Role of AIF nuclear translocation in silibinin-induced cell death. (A) Cells were exposed to with 30 μM silibinin for various times and cytosolic and nuclear fractions were prepared. AIF expression was estimated by Western blot using antibodies specific against AIF. (B) Cells were exposed to 30 μM silibinin for 36 h in the presence or absence of 0.5 μM calpain inhibitor (CHO). AIF nuclear translocation was estimated by immunofluorescence using antibody specific against AIF. Nuclei were counterstained with propidium iodide (PI). Images were captured by confocal microscope and presented. Arrows indicate AIF nuclear localization. (C) Cells were transfected with mipcDNA vector for LacZ or AIF micro-RNA (mi-AIF). The expression levels of AIF were determined by Western blotting. (D) Cells transfected with LacZ or mi-AIF were exposed to 30 μM silibinin for 36 h and cell viability was estimated by MTT assay. Data are mean ± SEM of four independent experiments performed in duplicate. *p < 0.05 compared with LacZ control; #p < 0.05 compared with LacZ silibinin.
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Figure 5: Role of AIF nuclear translocation in silibinin-induced cell death. (A) Cells were exposed to with 30 μM silibinin for various times and cytosolic and nuclear fractions were prepared. AIF expression was estimated by Western blot using antibodies specific against AIF. (B) Cells were exposed to 30 μM silibinin for 36 h in the presence or absence of 0.5 μM calpain inhibitor (CHO). AIF nuclear translocation was estimated by immunofluorescence using antibody specific against AIF. Nuclei were counterstained with propidium iodide (PI). Images were captured by confocal microscope and presented. Arrows indicate AIF nuclear localization. (C) Cells were transfected with mipcDNA vector for LacZ or AIF micro-RNA (mi-AIF). The expression levels of AIF were determined by Western blotting. (D) Cells transfected with LacZ or mi-AIF were exposed to 30 μM silibinin for 36 h and cell viability was estimated by MTT assay. Data are mean ± SEM of four independent experiments performed in duplicate. *p < 0.05 compared with LacZ control; #p < 0.05 compared with LacZ silibinin.

Mentions: The mitochondrial apoptotic pathway is initiated by the cytosolic release of mitochondrial intermembrane space proteins that can trigger either caspase-activation or caspase-independent apoptotic pathways [25,26]. Mitochondrial proteins that cause caspase-dependent cell death include cytochrome c which triggers caspase-9 activation through Apaf-1. The activated caspase-9 then activates the downstream caspase-3 [26-28]. Mitochondria have also been reported to contain AIF, which can cleave directly DNA and intracellular substrates when released into the cytosol. During apoptosis, AIF translocates into the nucleus where it causes oligonucleosomal DNA fragmentation [29,30]. The present study showed that silibinin causes AIF nuclear translocation, which was inhibited by the calpain inhibitor (Figure 5A and 5B). To determine if silibinin induced cell death through AIF nuclear translocation, effect of silibinin on the cell death in cells transfected with AIF mi-RNA was measured. Transfection of AIF mi-RNA was decreased AIF protein levels (Figure 5C) and effectively prevented the silibinin-induced cell death (Figure 5D). These data suggest that calpain activation induces AIF-dependent cell death in silibinin-treated cells. This is the first report showing involvement of calpain-dependent AIF nuclear translocation in the silibinin-induced glioma cell death.


Silibinin induces apoptosis via calpain-dependent AIF nuclear translocation in U87MG human glioma cell death.

Jeong JC, Shin WY, Kim TH, Kwon CH, Kim JH, Kim YK, Kim KH - J. Exp. Clin. Cancer Res. (2011)

Role of AIF nuclear translocation in silibinin-induced cell death. (A) Cells were exposed to with 30 μM silibinin for various times and cytosolic and nuclear fractions were prepared. AIF expression was estimated by Western blot using antibodies specific against AIF. (B) Cells were exposed to 30 μM silibinin for 36 h in the presence or absence of 0.5 μM calpain inhibitor (CHO). AIF nuclear translocation was estimated by immunofluorescence using antibody specific against AIF. Nuclei were counterstained with propidium iodide (PI). Images were captured by confocal microscope and presented. Arrows indicate AIF nuclear localization. (C) Cells were transfected with mipcDNA vector for LacZ or AIF micro-RNA (mi-AIF). The expression levels of AIF were determined by Western blotting. (D) Cells transfected with LacZ or mi-AIF were exposed to 30 μM silibinin for 36 h and cell viability was estimated by MTT assay. Data are mean ± SEM of four independent experiments performed in duplicate. *p < 0.05 compared with LacZ control; #p < 0.05 compared with LacZ silibinin.
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Related In: Results  -  Collection

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Figure 5: Role of AIF nuclear translocation in silibinin-induced cell death. (A) Cells were exposed to with 30 μM silibinin for various times and cytosolic and nuclear fractions were prepared. AIF expression was estimated by Western blot using antibodies specific against AIF. (B) Cells were exposed to 30 μM silibinin for 36 h in the presence or absence of 0.5 μM calpain inhibitor (CHO). AIF nuclear translocation was estimated by immunofluorescence using antibody specific against AIF. Nuclei were counterstained with propidium iodide (PI). Images were captured by confocal microscope and presented. Arrows indicate AIF nuclear localization. (C) Cells were transfected with mipcDNA vector for LacZ or AIF micro-RNA (mi-AIF). The expression levels of AIF were determined by Western blotting. (D) Cells transfected with LacZ or mi-AIF were exposed to 30 μM silibinin for 36 h and cell viability was estimated by MTT assay. Data are mean ± SEM of four independent experiments performed in duplicate. *p < 0.05 compared with LacZ control; #p < 0.05 compared with LacZ silibinin.
Mentions: The mitochondrial apoptotic pathway is initiated by the cytosolic release of mitochondrial intermembrane space proteins that can trigger either caspase-activation or caspase-independent apoptotic pathways [25,26]. Mitochondrial proteins that cause caspase-dependent cell death include cytochrome c which triggers caspase-9 activation through Apaf-1. The activated caspase-9 then activates the downstream caspase-3 [26-28]. Mitochondria have also been reported to contain AIF, which can cleave directly DNA and intracellular substrates when released into the cytosol. During apoptosis, AIF translocates into the nucleus where it causes oligonucleosomal DNA fragmentation [29,30]. The present study showed that silibinin causes AIF nuclear translocation, which was inhibited by the calpain inhibitor (Figure 5A and 5B). To determine if silibinin induced cell death through AIF nuclear translocation, effect of silibinin on the cell death in cells transfected with AIF mi-RNA was measured. Transfection of AIF mi-RNA was decreased AIF protein levels (Figure 5C) and effectively prevented the silibinin-induced cell death (Figure 5D). These data suggest that calpain activation induces AIF-dependent cell death in silibinin-treated cells. This is the first report showing involvement of calpain-dependent AIF nuclear translocation in the silibinin-induced glioma cell death.

Bottom Line: Silibinin caused ROS generation and its effect was inhibited by calpain inhibitor, the general PKC inhibitor GF 109203X, the specific PKCδ inhibitor rottlerin, and catalase.Silibinin induced AIF nuclear translocation and its effect was prevented by calpain inhibitor.Transfection of vector expressing microRNA of AIF prevented the silibinin-induced cell death.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oriental Medicine, Dongguk University, Kyung Ju, 780-714, Korea.

Show MeSH
Related in: MedlinePlus