Taraxerol Induces Cell Apoptosis through A Mitochondria-Mediated Pathway in HeLa Cells.

OBJECTIVES: Taraxerol acetate has potent anti-cancer effects via the induction of apoptosis, autophagy, cell cycle arrest, and inhibition of cell migration. However, whether taraxerol induced apoptosis and its underlying mechanisms of action is not clear. In the present study, we assess the effects of taraxerol on the mitochondrial apoptotic pathway and determine the release of cytochrome c to the cytosol and activation of caspases. MATERIALS AND METHODS: In this experimental study, we mainly investigated the effect of taraxerol on HeLa cells. We tested cell viability by the MTT assay and morphologic changes, analyzed apoptosis by DAPI staining and flow cytometry. We also determined reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) using a Microplate Reader. In addition, the apoptotic proteins were tested by Western blot. RESULTS: Taraxerol enhanced ROS levels and attenuated the MMP (Δψm) in HeLa cells. Taraxerol induced apoptosis mainly via the mitochondrial pathway including the release of cytochrome c to the cytosol and activation of caspases 9 and 3, and anti-poly (ADPribose) polymerase (PARP). Taraxerol could induce the down-regulation of the anti-apoptotic protein Bcl-2 and up-regulation of pro-apoptotic protein Bax. It suppressed the PI3K/ Akt signaling pathway. CONCLUSIONS: These results demonstrated that taraxerol induced cell apoptosis through a mitochondria-mediated pathway in HeLa cells. Thus, taraxerol might be a potential anticervical cancer candidate.

Solanesol induces the expression of heme oxygenase-1 via p38 and Akt and suppresses the production of proinflammatory cytokines in RAW264.7 cells.

The aim of the present study was to examine the anti-inflammatory effect of solanesol and to elucidate the underlying mechanisms. Heme oxygenase-1 (HO-1) plays an important role in cytoprotection against oxidative stress and inflammation. Solanesol induced HO-1 expression both at the level of mRNA and proteins, resulting in increased HO-1 activity. Solanesol treatment enhanced the level of the phosphorylated form, nuclear translocation, ARE-binding, and transcriptional activity of Nrf2. p38 and Akt contributed to ARE-driven HO-1 expression. Solanesol activated both p38 and Akt, and treatments with SB203580 (a p38 kinase inhibitor), LY294002 (an Akt inhibitor), specific p38 siRNA and Akt siRNA suppressed the solanesol-induced activation of Nrf2, resulting in a decrease in HO-1 expression. Solanesol also elevated the autophagic protein LC3B-II level. SnPP (a HO-1 inhibitor) and HO-1 siRNA markedly abolished the anti-inflammatory effect of solanesol against LPS-induced cell damage. Likewise, SB203580, LY294002, 3-MA and Baf-A1 inhibited the solanesol-induced anti-inflammatory effect. These studies demonstrate that solanesol attenuates inflammation by HO-1 induction via p38 and Akt signaling. Thus, it is quite plausible that HO-1 induction by solanesol could trigger anti-inflammatory pathways including limiting LPS-stimulated cytokine production through autophagic signaling via p38 and Akt.

Solanesol protects human hepatic L02 cells from ethanol-induced oxidative injury via upregulation of HO-1 and Hsp70.

In present study, we showed that the mRNA and protein levels of HO-1 and Hsp70 in solanesol-treated L02 cells were significantly increased. The induction of the HO-1 by solanesol is majorly achieved via enhancing the nuclear translocation and transactivity of Nrf2 through enhancement of Hsp90-Keap1 interaction, while solanesol-elevated Hsp70 is related with promoting the nuclear translocation of HSF1 through the involvement of chaperones interaction. Furthermore, the induction of HO-1 and Hsp70 by solanesol could protect against ethanol-induced liver injury, including significantly suppressing the elevation of the activities of LDH and AST, attenuating ethanol-induced increase of the MDA, ROS level and decrease of the GSH level. Moreover, solanesol also suppressed ethanol-induced apoptosis of L02 cells by inhibition of nuclear morphological damage, procaspase 3 and cleavage of caspase 3 and PARP, suggesting solanesol may be beneficial against ALD. Solanesol also promoted tBHQ-mediated protective effects. However, treatment cells with SnPP or PES markedly abrogated the protective effects of solanesol on ethanol-induced cell injury. These results strongly suggested that solanesol could protect ethanol-induced L02 cell damage, which might be attributed to the activation of HO-1 and Hsp70.

Taraxerol inhibits LPS-induced inflammatory responses through suppression of TAK1 and Akt activation.

Taraxerol, a triterpenoid compound, has potent anti-inflammatory effects. However, the molecular mechanisms are not clear. In the study, taraxerol concentration dependently inhibited nitric-oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein and mRNA levels and these inhibitions decreased the production of nitric oxide (NO), prostaglandin 2 (PGE2), tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1ß induced by LPS. Furthermore, we found that taraxerol suppressed translocation of nuclear factor-κB (NF-κB), phosphorylation of IκBα, blocked the IκBα degradation as well as IKK and mitogen-activated protein kinase (MAPK) activation by inactivation of TGF-ß-activated kinase-1 (TAK1) and Akt. In addition, taraxerol significantly inhibited the formation of TAK1/TAK-binding protein1 (TAB1), which was accompanied by inducing degradation of TAK1, decreasing LPS-induced polyubiquitination of TAK1 as well as TAK1 phosphorylation. Taken together, our data suggest that taraxerol downregulates the expression of proinflammatory mediators in macrophages by interfering with the activation of TAK1 and Akt, thus preventing NF-κB activation.

Inhibition of the JAK-STAT3 signaling pathway by ganoderic acid A enhances chemosensitivity of HepG2 cells to cisplatin.

Ganoderic acid A is a lanostane triterpene isolated from Ganoderma lucidum. It has been reported to exhibit antitumor activity, which is mainly mediated through its inhibitory effect on nuclear transcription factor-kappaB and activator protein-1. But the role of ganoderic acid A in JAK-STAT3 signaling pathways is still unclear. In the present study, we investigated the effect of ganoderic acid A on the signal transducer and activator of the transcription 3 pathway and evaluated whether suppression of the signal transducer and activator of transcription 3 activity by ganoderic acid A could sensitize HepG2 cells to cisplatin. Our results show that ganoderic acid A significantly suppressed both the constitutively activated and IL-6-induced signal transducer and activator of transcription 3 phosphorylation in HepG2 cells. Inhibition of the signal transducer and activator of transcription 3 tyrosine phosphorylation was found to be achieved through suppression of JAK1 and JAK2. Furthermore, ganoderic acid A promoted cisplatin-induced cell death by enhancing the sensitivity of HepG2 cells to cisplatin mainly via the signal transducer and activator of transcription 3 suppression. These observations suggest a potential therapeutic strategy of using ganoderic acid A in combination with chemotherapeutic agents for cancer treatment.

Arctigenin promotes degradation of inducible nitric oxide synthase through CHIP-associated proteasome pathway and suppresses its enzyme activity.

Arctigenin, a natural dibenzylbutyrolactone lignan compound, has been reported to possess anti-inflammatory properties. Previous works showed that arctigenin decreased lipopolysaccharide (LPS)-induced iNOS at transcription level. However, whether arctigenin could regulate iNOS at the post-translational level is still unclear. In the present study, we demonstrated that arctigenin promoted the degradation of iNOS which is expressed under LPS stimulation in murine macrophage-like RAW 264.7 cells. Such degradation of iNOS protein is due to CHIP-associated ubiquitination and proteasome-dependency. Furthermore, arctigenin decreased iNOS phosphorylation through inhibiting ERK and Src activation, subsequently suppressed iNOS enzyme activity. In conclusion, our research displays a new finding that arctigenin can promote the ubiqitination and degradation of iNOS after LPS stimulation. iNOS activity regulated by arctigenin is likely to involve a multitude of crosstalking mechanisms.