Capillin, a major constituent of Artemisia capillaris Thunb. flower essential oil, induces apoptosis through the mitochondrial pathway in human leukemia HL-60 cells.

BACKGROUND: Natural products are one of the most important sources of drugs used in pharmaceutical therapeutics. Screening of several natural products in the search for novel anticancer agents against human leukemia HL-60 cells led us to identify potent apoptosis-inducing activity in the essential oil fraction from Artemisia capillaris Thunb. flower. METHODS: The cytotoxic effects of extracts were assessed on human leukemia HL-60 cells by XTT assay. Induction of apoptosis was assessed by analysis of DNA fragmentation and nuclear morphological change. The plant name was checked with the plant list website (http://www.theplantlist.org). RESULTS: A purified compound from the essential oil fraction from Artemisia capillaris Thunb. flower that potently inhibited cell growth in human leukemia HL-60 cells was identified as capillin. The cytotoxic effect of capillin in cells was associated with apoptosis. When HL-60 cells were treated with 10(-6) M capillin for 6 h, characteristic features of apoptosis such as DNA fragmentation and nuclear fragmentation were observed. Moreover, activation of c-Jun N-terminal kinase (JNK) was detected after treatment with capillin preceding the appearance of characteristic properties of apoptosis. Release of cytochrome c from mitochondria was also observed in HL-60 cells that had been treated with capillin. CONCLUSION: Capillin induces apoptosis in HL-60 cells via the mitochondrial apoptotic pathway, which might be controlled through JNK signaling. Our results indicate that capillin may be a potentially useful anticancer drug that could enhance therapeutic efficacy.

Hinesol, a compound isolated from the essential oils of Atractylodes lancea rhizome, inhibits cell growth and induces apoptosis in human leukemia HL-60 cells.

Hinesol is a unique sesquiterpenoid isolated from the Chinese traditional medicine, Atractylodes lancea rhizome. In a previous study, we screened various natural products in human leukemia HL-60 cells and identified an essential oil fraction from A. lancea rhizome that exhibited apoptosis-inducing activity in these cells; hinesol was subsequently shown to be the compound responsible for this apoptosis-inducing activity. In this study, we describe the cytotoxic effects and molecular mechanisms of hinesol in HL-60 cells. The antitumor effect of hinesol was associated with apoptosis. When HL-60 cells were treated with hinesol, characteristic features of apoptosis, such as nuclear fragmentation and DNA fragmentation, were observed. These growth-inhibitory and apoptosis-inducing activities of hinesol in leukemia cells were much stronger than those of ß-eudesmol, another compound isolated from the essential oil fraction. Furthermore, hinesol induced activation of c-Jun N-terminal kinase (JNK), but not p38, prior to the onset of apoptosis. These results suggested that hinesol induced apoptosis through the JNK signaling pathway in HL-60 cells. Therefore, hinesol may represent a novel medicinal drug having indications in the treatment of various cancers, including leukemia.

Sp1 is an essential transcription factor for LPS-induced tissue factor expression in THP-1 monocytic cells, and nobiletin represses the expression through inhibition of NF-kappaB, AP-1, and Sp1 activation.

Nobiletin is a citrus polymethoxylated flavonoid extracted from Citrus depressa, and has several reported biological effects. In this study, we investigated the effect of nobiletin on bacterial lipopolysaccharide (LPS)-induced expression of tissue factor (TF), a trigger protein for the blood coagulation cascade, and studied the possible mechanism of TF transcriptional regulation. THP-1 monocytic cells stimulated with LPS showed an increased expression of both TF protein and mRNA levels. However, pretreatment with nobiletin resulted in inhibition of LPS-induced expression of both TF protein and mRNA in a dose-dependent manner. Electrophoretic mobility shift assays revealed that binding of nuclear proteins from LPS-stimulated THP-1 cells to the NF-kappaB or AP-1 binding motif was increased as compared to non-stimulated control cells. Such increased binding activities were significantly reduced by pretreatment with nobiletin. Binding activity of nuclear proteins to the Sp1 binding motif was observed irrespective of LPS stimulation, but Sp1 activation was inhibited by nobiletin treatment of the cells. Treatment of THP-1 cells with Sp1-specific small interfering RNA (Sp1 siRNA) abolished the ability of LPS to induce TF activity. A similar reduction in the level of TF mRNA was also observed upon treatment of cells with Sp1 siRNA. These studies reveal that constitutive Sp1 activation is an essential event for transcriptional activation of TF, and nobiletin prevents LPS-induced TF expression by inhibiting NF-kappaB, AP-1, and Sp1 activation.

Involvement of tumor necrosis factor receptor-associated protein 1 (TRAP1) in apoptosis induced by beta-hydroxyisovalerylshikonin.

beta-Hydroxyisovalerylshikonin (beta-HIVS), a compound isolated from the traditional oriental medicinal herb Lithospermum radix, is an ATP non-competitive inhibitor of protein-tyrosine kinases, such as v-Src and EGFR, and it induces apoptosis in various lines of human tumor cells. However, the way in which beta-HIVS induces apoptosis remains to be clarified. In this study, we performed cDNA array analysis and found that beta-HIVS suppressed the expression of the gene for tumor necrosis factor receptor-associated protein 1 (TRAP1), which is a member of the heat-shock family of proteins. When human leukemia HL60 cells and human lung cancer DMS114 cells were treated with beta-HIVS, the amount of TRAP1 in mitochondria decreased in a time-dependent manner during apoptosis. A similar reduction in the level of TRAP1 was also observed upon exposure of cells to VP16. Treatment of DMS114 cells with TRAP1-specific siRNA sensitized the cells to beta-HIVS-induced apoptosis. Moreover, the reduction in the level of expression of TRAP1 by TRAP1-specific siRNA enhanced the release of cytochrome c from mitochondria when DMS114 cells were treated with either beta-HIVS or VP16. The suppression of the level of TRAP1 by either beta-HIVS or VP16 was blocked by N-acetyl-cysteine, indicating the involvement of reactive oxygen species (ROS) in the regulation of the expression of TRAP1. These results suggest that suppression of the expression of TRAP1 in mitochondria might play an important role in the induction of apoptosis caused via formation of ROS.

Sophoranone, extracted from a traditional Chinese medicine Shan Dou Gen, induces apoptosis in human leukemia U937 cells via formation of reactive oxygen species and opening of mitochondrial permeability transition pores.

Screening of various natural products in a search for novel inducers of apoptosis in human leukemia cells led us to identify the strong apoptosis-inducing activity in a fraction extracted with methanol from the roots of Sophora subprostrata Chun et T. Chen. We purified the compound that induced apoptosis in human leukemia cells and identified it as sophoranone. Sophoranone inhibited cell growth and induced apoptosis in various lines of cells from human solid tumors, with 50% inhibition of growth of human stomach cancer MKN7 cells at 1.2 +/- 0.3 microM. The growth-inhibitory and apoptosis-inducing activities of sophoranone for leukemia U937 cells were very much stronger than those of other flavonoids, such as daidzein, genistein and quercetin. At the early stages of treatment of U937 cells with sophoranone, reactive oxygen species were formed, mitochondrial permeability pores were opened and cytochrome c was released from mitochondria. Cytochrome c was also released upon treatment of isolated mitochondria with sophoranone. Inhibitors of complexes III and IV, but not complexes I and II, of the mitochondrial respiratory chain prevented the release of cytochrome c from isolated mitochondria by sophoranone, as well as the induction of apoptosis in U937 cells in response to sophoranone. Our results indicate that sophoranone might be a unique apoptosis-inducing anticancer agent that targets mitochondria.