PMID: 

Nutrients. 2019 Apr 2 ;11(4). Epub 2019 Apr 2. PMID: 30987009

Abstract Title: 

Luteolin Shifts Oxaliplatin-Induced Cell Cycle Arrest at G₀/G₁ to Apoptosis in HCT116 Human Colorectal Carcinoma Cells.

Abstract: 

Certain antioxidative flavonoids are known to activate nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates cellular antioxidants and detoxifying response and is reportedly highly activated in many types of cancers. Few studies on the potential undesired effects of flavonoid intake during chemotherapy have been conducted, yet Nrf2 activators could favor cancer cell survival by attenuating chemotherapeutic efficiency. This study aimed to examine if luteolin, an Nrf2 activator, hinders chemotherapeutic activity of oxaliplatin, a potent anticancer agent for colorectal cancer, in HCT116 cells. Luteolin treatment strongly increased the transcriptional activity of the antioxidant response element in HCT116 cells and induced the protein expression of heme oxygenase-1, which were indicative of its Nrf2-inducing potential. Intriguingly, 25μM luteolin reduced cell viability through apoptotic induction, which was intensified in p53-expressing cells while 1 μM oxaliplatin caused cell cycle arrest at G₀/G₁-phase via the p53/p21-dependent mechanism. Moreover, luteolin treatment was found to reduce oxaliplatin-treated p53-null cell viability and colony counts further, thereby demonstrating an additional effect of luteolin in the killing of human colorectal tumor HCT116 cells not expressing functional p53 protein. The findings suggest that luteolin can induce p53-mediated apoptosis regardless of oxaliplatin treatment and may eliminate oxaliplatin-resistant p53-null colorectal cells.

read more

PMID: 

Exp Mol Med. 2019 Apr 15 ;51(4):40. Epub 2019 Apr 15. PMID: 30988303

Abstract Title: 

Luteolin promotes apoptotic cell death via upregulation of Nrf2 expression by DNA demethylase and the interaction of Nrf2 with p53 in human colon cancer cells.

Abstract: 

Luteolin, a dietary flavone, modulates various signaling pathways involved in carcinogenesis. In this study, we investigated the molecular mechanism that underlies the apoptotic effects of luteolin mediated by DNA demethylation of the nuclear factor erythroid 2-related factor 2 (Nrf2) promoter and the interaction of Nrf2 and p53, a tumor suppressor, in human colon cancer cells. Luteolin increased the expression of apoptosis-related proteins and antioxidant enzymes. In DNA methylation, luteolin inhibited the expression of DNA methyltransferases, a transcription repressor, and increased the expression and activity of ten-eleven translocation (TET) DNA demethylases, a transcription activator. Methyl-specific polymerase chain reaction and bisulfite genomic sequencing indicated that luteolin decreased the methylation of the Nrf2 promoter region, which corresponded to the increased mRNA expression of Nrf2. In addition, luteolin increased TET1 binding to the Nrf2 promoter, as determined using a chromatin immunoprecipitation (ChIP) assay. TET1 knockdown decreased the percentages of luteolin-treated cells in sub-Gphase and cells with fragmented nuclei. Furthermore, complex formation between p53 and Nrf2 was involved in the apoptotic effects of luteolin. These results provide insight into the mechanism that underlies the anticancer effects of luteolin on colon cancer, which involve the upregulation of Nrf2 and its interaction with the tumor suppressor.

read more

PMID: 

Onco Targets Ther. 2019 ;12:2383-2396. Epub 2019 Mar 28. PMID: 30992674

Abstract Title: 

Luteolin suppresses tumor proliferation through inducing apoptosis and autophagy via MAPK activation in glioma.

Abstract: 

Purpose: Glioma is a malignant tumor that originates in the brain and spine and is difficult to be completely removed. Though glioma patients receive active treatment, the survival rate is still poor. Therefore, it is urgent to discover a new medicine to treat glioma patients in order to improve the survival rate. In this study, we explored the anticancer effect and the potential mechanism of luteolin on glioma in vitro.Materials and methods: Cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. Fluorescent microscopy and flow cytometry analysis were used to determine the cellular apoptosis. Western blot analysis was performed to explore the changes in protein expression. Quantitative reverse transcription-PCR (qRT-PCR) analysis was utilized to evaluate the expression level of the tumor suppressor miR-124-3p.Results: CCK-8 assays indicated that luteolin significantly inhibited glioma cell proliferation in a time- and dose-dependent manner. Fluorescent microscopy and flow cytometry analysis confirmed that luteolin induced glioma cell apoptosis. Western blot analysis showed that luteolin induced cellular apoptosis in glioma cells via MAPK activation (JNK, ERK, and p38). Luteolin stimulated the death receptor (FADD) to regulate the apoptosis proteins (Caspase-8, Caspase-3, and PARP). Luteolin increased the expression levels of LC3B II/I and downregulated the level of p62 that promotes cell autophagy. Finally, qRT-PCR confirmed that luteolin upregulated the expression levels of miR-124-3p.Conclusion: These findings illustrate that luteolin may be a potential drug for glioma treatment.

read more

PMID: 

Phytomedicine. 2019 Jun ;59:152774. Epub 2018 Nov 28. PMID: 31009852

Abstract Title: 

Luteolin protects against diabetic cardiomyopathy by inhibiting NF-κB-mediated inflammation and activating the Nrf2-mediated antioxidant responses.

Abstract: 

BACKGROUND: Diabetes mellitus is a well-known risk factor for the development of heart failure. Inflammation and oxidative stress play a key role in the development of diabetic cardiomyopathy (DCM), and this nexus represents an attractive target to combat this disease. Naturally occurring flavonoid luteolin exhibits both anti-inflammatory and antioxidant activities in various systems.HYPOTHESIS/PURPOSE: In this study, we aimed to investigate potential cardioprotective effects of luteolin in cultured cardiomyocytes and in mice with type 1 diabetes.METHODS: C57BL/6 mice were intraperitoneal injection of streptozotocin (STZ) to induce DCM. High glucose (HG) was used to induce H9C2 cells injury in vitro. Cardiac fibrosis, hypertrophy, inflammation and oxidative stress were studied both in vitro and in vivo.RESULTS: Our studies show that luteolin significantly reduces HG-induced inflammatory phenotype and oxidative stress in H9C2 cardiomyocytes. We found that the mechanisms involved inhibition of nuclear factor-kappa B (NF-κB) pathway and the activation of antioxidant nuclear factor-erythroid 2 related factor 2 (Nrf2) signaling pathway. Modulation of these pathways resulted in reduced expression of matrix proteins and cellular hypertrophy. Luteolin also prevented cardiac fibrosis, hypertrophy, and dysfunction in STZ-induced diabetic mice. These readouts were also associated with reduced levels of inflammatory cytokines and oxidative stress biomarkers.CONCLUSION: Our results indicate that luteolin protects heart tissues in STZ-induced diabetic mice through modulating Nrf2-mediated oxidative stress and NF-κB-mediated inflammatory responses. These findings suggest that luteolin may be a potential therapeutic agent for DCM.

read more

PMID: 

J Periodontol. 2019 May 22. Epub 2019 May 22. PMID: 31115905

Abstract Title: 

The effect of luteolin in prevention of periodontal disease in Wistar rats.

Abstract: 

BACKGROUND: Periodontal disease is the chronic infectious disease of the periodontium. Because of irreversibility, prevention of disease is one of the most important goals of periodontal treatment. The aim of this study was to evaluate the effect of luteolin, a powerful anti-inflammatory agent, on the prevention of experimental periodontitis by determining morphological and histological tissue alterations.METHODS: This study consisted of 28 rats and four experimental groups: healthy control group (C, n = 6); periodontitis group (P, n = 6); periodontitis and 50 mg/kg luteolin administered group (L-50, n = 8); and periodontitis and 100 mg/kg luteolin administered group (L-100, n = 8). Experimental periodontitis was induced via ligature method around lower right first molar teeth. All rats were euthanized 11 days after. The severity of periodontal destruction was determined by measuring alveolar bone loss under a stereomicroscope. Osteoblast and inflammatory cell counts were counted on hematoxylin-eosin-stained slides and osteoclasts were counted on tartrate-resistant acid phosphatase-stained slides. The levels of inducible nitric oxide synthase (iNOS), bone morphogenetic protein (BMP)-2, matrix metalloproteinase (MMP)-8, tissue inhibitor of MMP (TIMP)-1, receptor activator of nuclear factorκB ligand (RANKL), and osteoprotegerin (OPG) were determined by immunohistochemistry.RESULTS: The highest alveolar bone loss was observed in the periodontitis group and the luteolin administration decreased bone loss in both groups. Osteoblast cell number was higher and osteoclast and inflammatory cell numbers were lower in the P group compared to C, L-50, and L-100 groups. Luteolin, dose-dependently increased osteoblast cell counts. Luteolin attenuated periodontal inflammation in both L-50 and L-100 groups. Like osteoblast cell numbers, BMP-2 expressions were also elevated in luteolin groups. Both doses of luteolin significantly increased TIMP-1 and BMP-2 expressions and decreased MMP-8 levels. iNOS expressions increased in P group and L-100 significantly decreased iNOS levels. RANKL increased and OPG decreased in P group and 100 mg/kg luteolin increased OPG and decreased RANKL levels significantly.CONCLUSIONS: Within the limits of present experimental study, luteolin successfully improved periodontal health in a ligature-induced experimental periodontitis model in Wistar rats. The decrease in inflammation, osteoclastic and collagenase activity and increase in osteoblastic activity are possibly involved in this process.

read more

PMID: 

Biomed Pharmacother. 2019 Aug ;116:109004. Epub 2019 May 22. PMID: 31128404

Abstract Title: 

Flavonoids showed anticancer effects on the ovarian cancer cells: Involvement of reactive oxygen species, apoptosis, cell cycle and invasion.

Abstract: 

Flavonoids have been recently identified as a potential anticancer agent against various human epithelial cancers. In this study, the elucidation of mechanisms underlying the anticancer effects of the apigenin, luteolin and myricetin will be new knowledge about preventive strategies against epithelial ovarian cancer in which the effect of flavonoids is still unclear. The cytotoxic effect of flavonoids was assessed by MTT analysis of the ovarian cancer cells (A2780, OVCAR-3 and SKOV-3) in comparison to the ovarian epithelial cells (OSE). The intracellular reactive oxygen species (ROS) generation, malondialdehyde (MDA) and protein carbonyl levels, caspase-3 and -9 activities were evaluated using fluorescence spectrometry. Apoptosis and cell cycle arrest, and cell invasion were measured by flow cytometry and Boyden chamber assay, respectively. MTT analysis showed that flavonoids selectively decreased the cell viability of cancer cells. Furthermore, the intracellular ROS generation was induced or scavenged by flavonoids depending on the structural differences. The flavonoids increased MDA levels due to the disruption of the membrane. Caspase activities indicated that flavonoids activated the extrinsic apoptotic pathway when ROS was scavenged. In contrast, the induced intracellular ROS generation resulted in the activation of the intrinsic apoptotic pathway. In addition, the cell cycle was arrested in different cell cycle phases and cell invasion on the collagen was disrupted by flavonoids. The anticancer activities of apigenin, luteolin and myricetin were attributed to the alterations of ROS signaling, and as well as the induction of apoptosis, cell cycle arrest and abrogation of the invasion. The present study may uncover new strategies for ovarian cancer therapy.

read more

PMID: 

IUBMB Life. 2019 Sep ;71(9):1401-1408. Epub 2019 Jun 11. PMID: 31185137

Abstract Title: 

The modulatory effects of luteolin on cyclic AMP/Ciliary neurotrophic factor signaling pathway in experimentally induced autoimmune encephalomyelitis.

Abstract: 

Multiple sclerosis (MS) is considered to be an autoimmune disorder of the central nervous system (CNS) manifested by chronic inflammation. Although its etiology is not completely understood, inflammation and apoptosis are known to be major players involved in its pathogenesis. Luteolin, the naturally occurring flavonoid, is known by strong antioxidant and anti-inflammatory properties, yet research studies about its therapeutic role in MS are still lacking. The study aimed to provide insight into effects of luteolin in experimental autoimmune encephalomyelitis (EAE) by monitoring inflammatory, apoptotic, and antioxidant biochemical parameters in addition to histological examination findings. The study included 45 adult female Wistar rats allocated to three equal groups: (a) group I: control group, (b) group II: EAE group, EAE was induced by single intradermal injection of 0.2 mL inoculum comprising 20-μg recombinant rat myelin oligodendrocyte glycoprotein (MOG), and (c) group III: luteolin-treated EAE group, luteolin was given in a dose of 10 mg/kg/day, i.p. All groups were subjected to assessment of brain ciliary neurotropic factor (CNTF) mRNA gene expression and measurement of cleaved caspase3, nuclear factor kappa B (NF-κB), cyclic AMP (cAMP), and macrophage inflammatory protein 1 alpha (MIP-1α) by the ELISA technique, total antioxidant capacity (TAC) level is assessed spectrophotometrically. Compared with the EAE group, luteolin-treated EAE group showed upregulation of CNTF expression and significant increase in cAMP and TAC levels, while it showed significant decrease in cleaved caspase 3, NF-κB, and MIP-1α levels. Based on our data herein, luteolin may provide a promising preclinical therapeutic line in MS being anti-inflammatory, antiapoptotic, and neurotrophic agent. ©2019 IUBMB Life, 71(9):1401-1408, 2019.

read more

PMID: 

Phytother Res. 2018 Sep ;32(9):1795-1802. Epub 2018 May 11. PMID: 29748995

Abstract Title: 

Apigenin inhibits growth of the Plasmodium berghei and disrupts some metabolic pathways in mice.

Abstract: 

Due to the challenges in the control, prevention, and eradication of parasitic diseases like malaria, there is an urgent need to discover new therapeutic agents. Plant-derived medicines may open new ways in the field of antiplasmodial therapy. This study is aimed to investigate the toxicity and in vivo antiplasmodial activity of apigenin, a dietary flavonoid. Apigenin cytotoxicity was investigated on Huh7 cell line, brine shrimp (Artemia salina) larva, and human red blood cells. In vivo toxicity of apigenin was assessed by metabolomics approaches. Apigenin exhibited significant suppression of parasitemia in a dose-dependent manner; it suppressed Plasmodium berghei growth by 69.74%, 50.3%, and 49.23% at concentrations of 70, 35, and 15 mg/kg/day, respectively. The ICvalue for apigenin after 24 hr exposure to Huh7 cells was 225 μg/ml. Apigenin did not show noticeable toxicity on A. salina and also on the membrane integrity of red blood cells. After 24 hr exposure of mice to apigenin, alterations were seen in the metabolism of glucocorticoids and mineralocorticoids, bile acid metabolism (alternative pathway), sulfur metabolism, bile acid metabolism, metabolism of estrogens and androgens, cholesterol catabolism, and biosynthesis of cholesterol. These findings indicate that apigenin has potential in vivo antiplasmodial activity against P. berghei infected mice with high selectivity against malaria, but it can disrupt some metabolic pathways in mice.

read more

PMID: 

J Pharm Pharmacol. 2018 Sep ;70(9):1253-1261. Epub 2018 Jun 25. PMID: 29943490

Abstract Title: 

Co-administrating apigenin in a high-cholesterol diet prevents hypercholesterolaemia in golden hamsters.

Abstract: 

OBJECTIVES: Hypercholesterolaemia is a major risk factor for developing atherosclerosis. Increased consumption of fruits and vegetables is recommended to hypercholesterolaemic patients. In this study, the hypocholesterolaemic effect of apigenin and luteolin was evaluated in a hamster model.METHODS: Hamsters were put on a high-cholesterol diet for 9 weeks, and apigenin or luteolin was administered in the diet at 60 and 300 ppm.KEY FINDINGS: Both apigenin and luteolin supplementations could attenuate the aorta plaque formation by 30% and 20%, respectively. Apigenin-fed hamsters at both dosages displayed a 1.5-fold increase in hepatic Ldlr expression and a 40% reduction in non-HDL cholesterol level as compared with those in the control fed a high-cholesterol (HC) diet. Besides, faecal elimination of cholesterol was facilitated by 20% in the hamsters with high apigenin consumption. Suppressing the expression of the cholesterol transporter ncp1l1 in the intestinal mucosa could block the cholesterol absorption and promote its elimination. The differential regulations of ncp1l1 and Ldlr appeared to be the underlying hypocholesterolaemic mechanism of apigenin in this model system. Luteolin supplementation, on the other hand, had no effect on the blood cholesterol.CONCLUSIONS: This study illustrated that dietary administration of apigenin attenuated HC feeding-induced hypercholesterolemia in hamsters.

read more

PMID: 

Biomed Pharmacother. 2018 Sep ;105:1283-1290. Epub 2018 Jun 22. PMID: 30021365

Abstract Title: 

Apigenin prevents metabolic syndrome in high-fructose diet-fed mice by Keap1-Nrf2 pathway.

Abstract: 

Chronic dietary high fructose leads to various kinds of undesirable metabolic effects. Apigenin, a naturally occurring plant flavone, is plentiful in fruits and vegetables. The aim of this study was to identify the protective effects of apigenin on metabolic syndrome and elucidate potential underlying mechanisms. The animal model was established by 4-weeks high fructose feeding. Insulin resistance was estimated by oral glucose tolerance test and homeostasis model assessment-insulin resistance index. Liver function was evaluated by serum AST and ALT, hepatic histopathological alternation, and lipid accumulation in the liver. The alterations of lipid profile was evaluated by TG, TC, LDL-C and HDL-C levels in serum. Administration of apigenin exerted beneficial effects through improving insulin resistance, alleviating liver injury, and inhibiting the alterations of lipid profile in high fructose-fed mice. In addition, apigenin potently facilitated the accumulation of Nrf2 nuclear translocation and accompanied by increasing HO-1 and NQO1 protein expressions, which are responsible for attenuating oxidative stress. Molecular docking results demonstrated that potential interaction of apigenin with the Nrf2-binding site in the Keap1 protein. In summary, we demonstrated that apigenin prevented high fructose-induced metabolic syndrome probably by inhibiting binding of Keap1 to Nrf2, and thus Nrf2 nuclear translocation, subsequently resulting in increased the expressions of anti-oxidative genes including HO-1 and NQO1.

read more