木犀草素通过调节凝血活性物质及凝血因子含量维持机体血液循环功能的稳定

目的 探讨木犀草素通过调节凝血活性物质及凝血因子含量维持机体血液循环功能的作用机制。 方法 采用试剂盒和试管法测定木犀草素作用后的凝血酶原时间和血浆复钙时间;采用酶联免疫吸附法检测木犀草素对血液凝血活性物质血栓素(TXB2)、纤维酶原激活物抑制剂(PAI 1)、促红细胞生成素(EPO)和凝血因子Ⅶ(FⅦ)、凝血因子Ⅸ(FⅨ)含量的影响;采用PCR法测定木犀草素对凝血因子Ⅶ、Ⅸ的基因表达情况。 结果 木犀草素能缩短凝血酶原时间和血浆复钙时间,与对照组相比,40 mg/kg的木犀草素使凝血酶原时间和血浆复钙时间分别降低62.89%和64.05%(t=8.713 6、6.218 1,均P结论 木犀草素具有维持机体血液循环功能稳定的作用,其作用机制是通过提高凝血活性物质的含量,调节凝血因子的基因表达量,提高凝血因子的含量,以及抑制纤维酶原的激活和增加血液的黏度等多方面综合作用来实现的。     

Luteolin attenuates TGF-β1-induced epithelial–mesenchymal transition of lung cancer cells by interfering in the PI3K/Akt–NF-κB–Snail pathway

Aims

Luteolin is a natural flavonoid that possesses a variety of pharmacological activities, such as anti-inflammatory and anti-cancer abilities. Whether luteolin regulates the transformation ability of lung cancer cells remains unclear. The current study aims to uncover the effects and underlying mechanisms of luteolin in regulation of and epithelial–mesenchymal transition of lung cancer cells.

Main methods

The lung adenocarcinoma A549 cells were used in this experiment; the cells were pretreated with luteolin followed by administration with TGF-β1. The expression levels of various cadherin and related upstream regulatory modules were examined.

Key findings

Pretreatment of luteolin prevented the morphological change and downregulation of E-cadherin of A549 cells induced by TGF-β1. In addition, the activation of PI3K–Akt–IκBa–NF-κB–Snail pathway which leads to the decline of E-cadherin induced by TGF-β1 was also attenuated under the pretreatment of luteolin.

Significance

We provide the mechanisms about how luteolin attenuated the epithelial–mesenchymal transition of A549 lung cancer cells induced by TGF-β1. This finding will strengthen the anti-cancer effects of flavonoid compounds via the regulation of migration/invasion and EMT ability of various cancer cells.     

Leishmania donovani: dyskinetoplastid cells survive and proliferate in the presence of pyruvate and uridine but do not undergo apoptosis after treatment with camptothecin

We have shown that treatment with luteolin in leishmanial cells causes loss of mt-DNA and induces apoptosis through mitochondria dependent pathway [Sen, N., Das, B.B., Ganguly, A., Banerjee, B., Sen, T., Majumder, H.K., 2006. Leishmania donovani: intracellular ATP level regulates apoptosis-like death in luteolin induced dyskinetoplastid cells. Experimental Parasitology, in press]. Here, we report that mitochondrial DNA depleted leishmanial cells require exogenous sources of pyruvate and uridine to survive and proliferate. The presence of pyruvate and uridine in a growing media help them to produce sufficient amount of glycolytic ATP to maintain the mitochondrial membrane potential in the absence of their functional ETC. Treatment of wild type cells with CPT causes generation of ROS that leads to apoptosis. But unlike the normal cells ROS was not generated in these mt-DNA depleted cells after treatment with CPT. Taken together we have shown for the first time that dyskinetoplastid cells are auxotrophic for pyruvate and uridine and apoptosis cannot be induced in these cells in the presence of CPT. Therefore, the presence of mitochondrial DNA is absolutely necessary for the cytotoxicity of CPT in kinetoplastid parasites.     

Luteolin from Flos Chrysanthemi and its derivatives: New small molecule Bcl-2 protein inhibitors

Over-expression of the Bcl-2 anti-apoptotic proteins is closely related to tumorigenesis and associated with drug resistance. Here we report that luteolin, a main substance found in Flos Chrysanthemi, directly binds to and shows inhibitory activity against the Bcl-2 protein. We studied the binding mode of luteolin and its derivatives with target proteins, their structure-activity relationship, and their effect on the human leukemia cell line HL-60. The results suggest that luteolin and its derivatives with a benzyl group introduced to the B ring, are new small molecule Bcl-2 protein inhibitors, and their anti-tumor activity is likely related to their effect on the Bcl-2 protein.     

Study of thiol consumption by yeast lees

A plant flavone, luteolin is a well-known inducer of nod genes in the Rhizobium meliloti. Its poor aqueous solubility was greatly enhanced by the complexation with a family of cyclosophoraoses synthesized in R .meliloti. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the chemical shifts of the aromatic ring moieties of the luteolin were changed greatly by the complexation with cyclosophoraoses. Fourier transform infrared (FTIR) spectroscopic analysis also showed a restricted vibrational pattern in carbonyl stretching region of the luteolin due to the complexation. This effective complex formation of cyclosophoraoses with a plant flavone, luteolin, suggests that rhizobial cyclosophoraoses play an important role as a solubility enhancer of the hydrophobic legume-derived flavonoids. This revised version was published online in August 2006 with corrections to the Cover Date.     

Experimental evidence that flavonoid metal complexes may act as mimics of superoxide dismutase

Radical scavenging activities of flavonoids rutin, taxifolin, (-)-epicatechin, luteolin, and their complexes with transition metal (Fe2+, Fe3+, and Cu2+) towards superoxide were determined using illumination of riboflavin as source and NBT as detector of O*2-. The scavenger potencies of flavonoid metal complexes were significantly higher than those of the parent flavonoids. To elucidate the mechanism of this phenomenon, the rates of superoxide-dependent oxidation of flavonoids and their metal complexes in photochemical system with riboflavin were examined. It was found for the first time that flavonoids bound to metal ions were much less subjected to oxidation compared with those of free compounds. The findings directly demonstrate superoxide scavenging activity of metal ions in complexes with flavonoids and support earlier suggestions that flavonoid metal complexes may exhibit superoxide dismuting activity.     

Leishmania donovani: intracellular ATP level regulates apoptosis-like death in luteolin induced dyskinetoplastid cells

Leishmaniasis presents a spectrum of diseases ranging from benign cutaneous lesions to the often-fatal visceralizing form. Luteolin, a dietary flavone induces apoptosis-like death in both promastigote and amastigote forms of Leishmania, the causative agent of the diseases. Here, we have elucidated the mechanism of action of luteolin by analyzing the mitochondrial and cytosolic changes associated with apoptosis-like death of leishmanial cells. In Leishmania donovani, treatment with luteolin induces the loss of both maxicircles and minicircles which resulted in the formation of dyskinetoplastid cells. The loss of mitochondrial DNA causes reduction in the activities of complex I, II, III, and IV of electron transport chain. However, the mitochondrial ATPase activity of complex V remains almost unaltered during treatment with luteolin but the sensitivity to oligomycin is lost. The inactivation of ETC complex is associated with decrease in mitochondrial as well as glycolytic ATP production, which is responsible for depolarization of Deltapsi(m) and alteration in mitochondrial structure. This event is followed by the release of cytochrome c from mitochondria in mt-DNA depleted leishmanial cells and causes an activation of caspase like proteases. Collectively our results provide the first insight into the mechanistic pathway of apoptosis-like death where inhibition of glycolytic ATP production is an essential event responsible for depolarization of Deltapsi(m) in mt-DNA depleted cells to propagate apoptosis-like death in leishmanial cells.     

Selective synthesis of 7-O-substituted luteolin derivatives and their melanonenesis and proliferation inhibitory activity in B16 melanoma cells

In our previous study, the isolation of ugonin J, K, and L, which are luteolin derivatives, from the roots of Helminthostachys zeylanica and their identification as potent melanogenesis inhibitors, was described. The structure activity relationship (SAR) investigation in that study revealed that the catechol moiety in the B-ring of the flavone skeleton of ugonin K was important for its melanogenesis inhibitory activity, and the presence of the low polarity substituents at the C-7 position enhanced this activity. In order to further investigate the SAR of the C-7-substituent in the luteolin derivatives, different groups were selectively introduced at the C-7 position of luteolin after borax protection of the catechol hydroxyl group and the C-5 hydroxyl group. NMR and MS analysis of the borax protected derivatives revealed that the borax protects not only hydroxyl groups of catechol on the B ring but also the 5-hydroxyl group on the A ring. Eight luteolin derivatives were synthesized and evaluated for melanogenesis inhibitory effect in B16 melanoma cells. Two bulky groups and six alkoxyl groups were introduced at the C-7 position. The resulting luteolin derivatives showed improved melanogenesis and cell proliferation inhibitory activities. From among these derivatives, 7-O-hexylluteolin (7) showed the highest activity and inhibited the melanogenesis to 14% at 6.25?μM. The present study also revealed that the length of the carbon chain rather than the bulky substituent was more important for the melanogenesis inhibitory activity.     

Luteolin inhibits inflammatory response and improves insulin sensitivity in the endothelium

Endothelial insulin resistance is tightly associated with diabetic cardiovascular complication, and it is well known that inflammation plays an important role in the development of insulin resistance. Luteolin, a flavonoid abundant in some medical and eatable plants, is a potent inhibitor of inflammation. It is also reported that luteolin exhibited some chemoprotection capability to the endothelial integrity. This study aims to clarify whether the anti-inflammatory potency of luteolin contributes to amelioration of insulin resistance in the endothelium. Palmitate (PA) stimulation markedly reduced insulin-mediated endothelium-dependent relaxation in rat aorta, while luteolin pretreatment effectively reversed the effects of palmitate in a concentration-dependent manner. PA stimulation also evoked inflammatory response in endothelial cells. When the cells were pretreated with luteolin, IKKβ phosphorylation were reduced, which, in turn, blocked the NF-κB activation through attenuating P65 phosphorylation. At the same time, it was also found that the gene over-expressions for TNF-α and IL-6 were also reduced by luteolin pretreatment. When endothelial cells were stimulated with PA, the insulin signaling cascades were impaired with reduced insulin-dependent production of NO. Again, pretreatment of luteolin could effectively reverse the effects of PA. Luteolin modulated the Ser/Thr phosphorylation of insulin receptor substrates-1 and restored downstream Akt/eNOS activation, resulting in increased NO production in the presence of insulin. In conclusion, these results suggested that luteolin ameliorated inflammation related endothelial insulin resistance in an IKKβ/IRS-1/Akt/eNOS-dependent pathway.