Luteolin induces apoptosis via death receptor 5 upregulation in human malignant tumour cells

Mano Horinaka, Tatsushi Yoshida, Takumi Shiraishi, Susumu Nakat, et al. Oncogene (2005) 24, 7180–7189. doi:10.1038/sj.onc.1208874; published online 11 July 2005

Luteolin, a naturally occurring flavonoid, induces apoptosis in various cancer cells. Little is known however concerning the underlying molecular mechanisms responsible for this activity. In this report, we reveal a novel mechanism by which luteolin-induced apoptosis occurs, and show for the first time that the apoptosis by luteolin is mediated through death receptor 5 (DR5) upregulation. Luteolin markedly induced the expression of DR5, along with Bcl-2-interacting domain cleavage and the activation of caspase-8, -10, -9 and -3. In addition, suppression of DR5 expression with siRNA efficiently reduced luteolin-induced caspase activation and apoptosis. Human recombinant DR5/Fc also inhibited luteolin-induced apoptosis. On the other hand, luteolin induced neither DR5 protein expression nor apoptosis in normal human peripheral blood mononuclear cells. These results suggest that DR5 induced by luteolin plays a role in luteolin-induced apoptosis, and raises the possibility that treatment with luteolin might be promising as a new therapy against cancer.


Fang Su, Shu-Qin Liu, Ying Chen, Fang-Xia Chen, Hui-Ping Wang and Qiang Xia. FASEB Journal. 597.9

Aim: To investigate the effects of luteolin on cardiac functions and mitochondrial oxidative stress in streptozotocin (STZ)-induced diabetic rats.

Methods: Male Sprague-Dawley rats were randomly divided into a normal control group, a luteolin control group, a diabetic group, and diabetic groups orally administered with a low dose (10 mg/kg/d) or a high dose of luteolin (100 mg/kg/d) for eight weeks. The body weight, blood glucose, cardiac functions, left ventricular weight, myocardial collagen, and reactive oxygen species (ROS) levels were assayed. The cardiac mitochondrial ROS level, superoxide dismutase (SOD) activity and the mitochondrial swelling were measured.

Results: Treatment with luteolin had no effect on the blood glucose but reduced the losing of body weight in diabetic rats. High dose of luteolin markedly reduced the ratio of ventricular weight and body weight, increased the left ventricular develop pressure, and decreased the left ventricular end diastolic pressure in diabetic rats. The myocardial levels of ROS and collagen, the cardiac mitochondrial ROS level, and the mitochondrial swelling in diabetic rats were all markedly reduced by high dose of luteolin. Furthermore, high dose of luteolin significantly increased the mitochondrial SOD activity in diabetic rat hearts.

Conclusion: Treatment with luteolin for 8 weeks markedly improves the cardiac function, which may be related to reducing mitochondrial oxidative stress and mitochondrial swelling, in diabetic rats.

Luteolin Inhibits an Endotoxin-Stimulated Phosphorylation Cascade and Pro-inflammatory Cytokine Production in Macrophages.
Angeliki Xagorari, Andreas Papapetropoulos, Antonis Mauromatis, Michalis Economou, Theodore Fotsis and Charis Roussos. JPET January 1, 2001 vol. 296 no. 1 181-187
Flavonoids are naturally occurring polyphenolic compounds with a wide distribution throughout the plant kingdom. In the present study, we compared the ability of several flavonoids to modulate the production of proinflammatory molecules from lipopolysaccharide (LPS)-stimulated macrophages and investigated their mechanism(s) of action. Pretreatment of RAW 264.7 with luteolin, luteolin-7-glucoside, quercetin, and the isoflavonoid genistein inhibited both the LPS-stimulated TNF-α and interleukin-6 release, whereas eriodictyol and hesperetin only inhibited TNF-α release. From the compounds tested luteolin and quercetin were the most potent in inhibiting cytokine production with an IC50 of less than 1 and 5 μM for TNF-α release, respectively. To determine the mechanisms by which flavonoids inhibit LPS signaling, we used luteolin and determined its ability to interfere with total protein tyrosine phosphorylation as well as Akt phosphorylation and nuclear factor-κB activation. Pretreatment of the cells with luteolin attenuated LPS-induced tyrosine phosphorylation of many discrete proteins. Moreover, luteolin inhibited LPS-induced phosphorylation of Akt. Treatment of macrophages with LPS resulted in increased IκB-α phosphorylation and reduced the levels of IκB-α. Pretreatment of cells with luteolin abolished the effects of LPS on IκB-α. To determine the functional relevance of the phosphorylation events observed with IκB-α, macrophages were transfected either with a control vector or a vector coding for the luciferase reporter gene under the control of κBcis-acting elements. Incubation of transfected RAW 264.7 cells with LPS increased luciferase activity in a luteolin-sensitive manner. We conclude that luteolin inhibits protein tyrosine phosphorylation, nuclear factor-κB-mediated gene expression and proinflammatory cytokine production in murine macrophages.

Luteolin reduces IL-6 production in microglia by inhibiting JNK phosphorylation and activation of AP-1
Saebyeol Jang, Keith W. Kelley, and Rodney W. Johnson. PNAS May 27, 2008 vol. 105 no. 21 7534-7539
Luteolin, a flavonoid found in high concentrations in celery and green pepper, has been shown to reduce production of proinflammatory mediators in LPS-stimulated macrophages, fibroblasts, and intestinal epithelial cells. Because excessive production of proinflammatory cytokines by activated brain microglia can cause behavioral pathology and neurodegeneration, we sought to determine whether luteolin also regulates microglial cell production of a prototypic inflammatory cytokine, IL-6. Pretreatment of primary murine microlgia and BV-2 microglial cells with luteolin inhibited LPS-stimulated IL-6 production at both the mRNA and protein levels. To determine how luteolin inhibited IL-6 production in microglia, EMSAs were performed to establish the effects of luteolin on LPS-induced binding of transcription factors to the NF-κB and activator protein-1 (AP-1) sites on the IL-6 promoter. Whereas luteolin had no effect on the LPS-induced increase in NF-κB DNA binding activity, it markedly reduced AP-1 transcription factor binding activity. Consistent with this finding, luteolin did not inhibit LPS-induced degradation of IκB-α but inhibited JNK phosphorylation. To determine whether luteolin might have similar effects in vivo, mice were provided drinking water supplemented with luteolin for 21 days and then they were injected i.p. with LPS. Luteolin consumption reduced LPS-induced IL-6 in plasma 4 h after injection. Furthermore, luteolin decreased the induction of IL-6 mRNA by LPS in hippocampus but not in the cortex or cerebellum. Taken together, these data suggest luteolin inhibits LPS-induced IL-6 production in the brain by inhibiting the JNK signaling pathway and activation of AP-1 in microglia. Thus, luteolin may be useful for mitigating neuroinflammation.

Mast Cells, T Cells, and Inhibition by Luteolin: Implications for the Pathogenesis and Treatment of Multiple Sclerosis.
Theoharis C. Theoharides, Duraisamy Kempuraj and Betina P. Iliopoulou. Advances in Experimental Medicine and Biology, 2007, Volume 601, Part 8, 423-430, DOI: 10.1007/978-0-387-72005-0_45
Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) mainly mediated by Th1, but recent evidence indicates that Th2 T cells, mostly associated with allergic reactions, are also involved. Mast cells are involved in allergic and inflammatory reactions because they are located perivascularly and secrete numerous pro-inflammatory cytokines. Brain mast cells are critically placed around the blood–brain barrier (BBB) and can disrupt it, a finding preceding any clinical or pathological signs of MS. Moreover, mast cells are often found close to MS plaques, and the main MS antigen, myelin basic protein (MBP), can activate human cultured mast cells to release IL-8, TNF-α , tryptase, and histamine. Mast cells could also contribute to T cell activation since addition of mast cells to anti-CD3/anti-CD28 activated T cells increases T cell activation over 30-fold. This effect requires cell-to-cell contact and TNF, but not histamine or tryptase. Pretreatment with the flavone luteolin totally blocks mast cell stimulation and T cell activation. Mast cells could constitute a new unique therapeutic target for MS.

Induction of cell cycle arrest and apoptosis in HT-29 human colon cancer cells by the dietary compound luteolin.
Do Y. Lim, Yoonhwa Jeong, Angela L. Tyner, and Jung H. Y. Park. Am J Physiol Gastrointest Liver Physiol 292: G66-G75, 2007. First published August 10, 2006; doi:10.1152/ajpgi.00248.2006
Luteolin is 3',4',5,7-tetrahydroxyflavone found in celery, green pepper, and perilla leaf that inhibits tumorigenesis in animal models. We examined luteolin-mediated regulation of cell cycle progression and apoptosis in the HT-29 human colon cancer cell line. Luteolin decreased DNA synthesis and viable HT-29 cell numbers in a concentration-dependent manner. It inhibited cyclin-dependent kinase (CDK)4 and CDK2 activity, resulting in G1 arrest with a concomitant decrease of phosphorylation of retinoblastoma protein. Activities of CDK4 and CDK2 decreased within 2 h after luteolin treatment, with a 38% decrease in CDK2 activity (P < 0.05) observed in cells treated with 40 µmol/l luteolin. Luteolin inhibited CDK2 activity in a cell-free system, suggesting that it directly inhibits CDK2. Cyclin D1 levels decreased after luteolin treatment, although no changes in expression of cyclin A, cyclin E, CDK4, or CDK2 were detected. Luteolin also promoted G2/M arrest at 24 h posttreatment by downregulating cyclin B1 expression and inhibiting cell division cycle (CDC)2 activity. Luteolin promoted apoptosis with increased activation of caspases 3, 7, and 9 and enhanced poly(ADP-ribose) polymerase cleavage and decreased expression of p21CIP1/WAF1, survivin, Mcl-1, Bcl-xL, and Mdm-2. Decreased expression of these key antiapoptotic proteins could contribute to the increase in p53-independent apoptosis that was observed in HT-29 cells. We demonstrate that luteolin promotes both cell cycle arrest and apoptosis in the HT-29 colon cancer cell line, providing insight about the mechanisms underlying its antitumorigenic activities.

Effects of luteolin on inflammation and immune function
CHEN Min-zhu, JIN Wen-zhen, DAI Li-min, XU Shu-yun. Chinese Journal of Pharmacology and Toxicology 1986-01. DOI:CNKI:SUN:YLBS.0.1986-01-010
Luteolin (Lut) is an effective chemical component of Prunella vulgaris L. In this paper, the anti-inflammatory and immunostimu-latory effects of Lut was described. Lut possesses significant antiinflam-matory activity in well established models of acute and chronic inflammation, such as xylene-induced ear oedema in mice (ED50= 107 mg/ kg), carrageenin-induced swellingof the ankle, acetic acid-induced pleurisy and croton oil-induced gaseous pouch granuloma in rats. Lut had a marked inhibitory effect on the inflammatory exudation, but did not affect the number of leucocyte. The Schultz-Dale response of the isolated guinea pig's ileum was inhibited by Lut. The action of such allergic mediators as SRS-A and histamine was also directly antagonized, Lut possesses significant immunosti-mulatory activity in some of immu-nological models,such as the production of hemolysin in mice, experimental allergic encephalomyelitis in guinea pigs and the proliferative response of mouse splenic lymphocytes in vitro.Its combined immunostimulatory and antiinflammatory activity, and inhibitory effect upon immediate hypersensitive response provide the pharmacologic bases for the beneficial effects of Lut in the treatment of chronic bronchitis.

Luteolin suppresses inflammation-associated gene expression by blocking NF-κB and AP-1 activation pathway in mouse alveolar macrophages
Chiu-Yuan Chen, Wen-Huang Peng, Kuen-Daw Tsai and Shih-Lan Hsu. Life Sciences. Volume 81, Issues 23-24, 30 November 2007, Pages 1602-1614. doi:10.1016/j.lfs.2007.09.028
Luteolin, a plant flavonoid, has potent anti-inflammatory properties both in vitro and in vivo. However, the molecular mechanism of luteolin-mediated immune modulation has not been fully understood. In this study, we examined the effects of luteolin on the production of nitric oxide (NO) and prostaglandin E2 (PGE2), as well as the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in mouse alveolar macrophage MH-S and peripheral macrophage RAW 264.7 cells. Luteolin dose-dependently inhibited the expression and production of these inflammatory genes and mediators in macrophages stimulated with lipopolysaccharide (LPS). Semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) assay further confirmed the suppression of LPS-induced TNF- α, IL-6, iNOS and COX-2 gene expression by luteolin at a transcriptional level. Luteolin also reduced the DNA binding activity of nuclear factor-kappa B (NF-κB) in LPS-activated macrophages. Moreover, luteolin blocked the degradation of IκB-α and nuclear translocation of NF-κB p65 subunit. In addition, luteolin significantly inhibited the LPS-induced DNA binding activity of activating protein-1 (AP-1). We also found that luteolin attenuated the LPS-mediated protein kinase B (Akt) and IKK phosphorylation, as well as reactive oxygen species (ROS) production. In sum, these data suggest that, by blocking NF-κB and AP-1 activation, luteolin acts to suppress the LPS-elicited inflammatory events in mouse alveolar macrophages, and this effect was mediated, at least in part, by inhibiting the generation of reactive oxygen species. Our observations suggest a possible therapeutic application of this agent for treating inflammatory disorders in lung.

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