Effects of tea constituents on cell cycle progression of human leukemia U937 cells

The Effects of Green Tea Catechins in Hematological Malignancies

Green tea catechins are bioactive polyphenol compounds which have attracted significant attention for their diverse biological activities and potential health benefits. Notably, epigallocatechin-3-gallate (EGCG) has emerged as a potent apoptosis inducer through mechanisms involving caspase activation, modulation of Bcl-2 family proteins, disruption of survival signaling pathways and by regulating the redox balance, inducing oxidative stress. Furthermore, emerging evidence suggests that green tea catechins can modulate epigenetic alterations, including DNA methylation and histone modifications. In addition to their apoptotic actions, ROS signaling effects and reversal of epigenetic alterations, green tea catechins have shown promising results in promoting the differentiation of leukemia cells. This review highlights the comprehensive actions of green tea catechins and provides valuable insights from clinical trials investigating the therapeutic potential of green tea catechins in leukemia treatment. Understanding these multifaceted mechanisms and the outcomes of clinical trials may pave the way for the development of innovative strategies and the integration of green tea catechins into clinical practice for improving leukemia patient outcomes.

Effect of Andrographis paniculata polysaccharide on human retinoblastoma Y79 cell proliferation and apoptosis

AIM

To explore the effect of the Andrographis paniculata (A. paniculata) polysaccharide on the proliferation and apoptosis of human retinoblastoma (RB) Y79 cells and its mechanism.

METHODS

The refined A. paniculata polysaccharide was obtained using techniques such as water extraction, ethanol precipitation, and decompression concentration. The inhibition effect of the A. paniculata polysaccharide on the proliferation of Y79 cells was detected by cell proliferation assay. Flow cytometry was used for the detection of cell apoptosis rate and cycle change. Real-time qunatitative polymerase chain reaction (RT qPCR)and Western blotting were used to detect the expression of cell apoptosis signal pathway-related factors (caspase-3, caspase-8, and caspase-9) and cell cycle signal pathway-related factors (CDK1 and cyclinB1) at the transcriptional and translational levels.

RESULTS

Infrared and ultraviolet spectrum scanning showed that the extracted drug was a polysaccharide with high purity. After being treated with different concentrations of A. paniculata polysaccharide for different periods of time, the Y79 cells showed different degrees of proliferation inhibition. Flow cytometric observations showed that the cell apoptosis rate and the proportion of cells blocked in the G2/M phase were significantly increased after A. paniculata polysaccharide treatment. Further analysis revealed that the mRNA and protein expression of caspase-3, caspase-8, and caspase-9 in the A. paniculata polysaccharide treatment groups increased significantly compared with that in the control groups, while the expression of CDK1 and cyclinB1 decreased significantly.

CONCLUSION

The A. paniculata polysaccharide could inhibit the proliferation and induce apoptosis of Y79 cells. Its possible mechanism is via the upregulation of caspase-3, caspase-8, and caspase-9 expression in the cell apoptotic signaling pathway and the downregulation of CDK1 and cyclinB1 expression in the cell cycle signaling pathway.

Docking Characterization and in vitro Inhibitory Activity of Flavan-3-ols and Dimeric Proanthocyanidins Against the Main Protease Activity of SARS-Cov-2

We report to use the main protease (M^pro) of SARS-Cov-2 to screen plant flavan-3-ols and proanthocyanidins. Twelve compounds, (-)-afzelechin (AF), (-)-epiafzelechin (EAF), (+)-catechin (CA), (-)-epicatechin (EC), (+)-gallocatechin (GC), (-)-epigallocatechin (EGC), (+)-catechin-3-O-gallate (CAG), (-)-epicatechin-3-O-gallate (ECG), (-)-gallocatechin-3-O-gallate (GCG), (-)-epigallocatechin-3-O-gallate (EGCG), procyanidin A2 (PA2), and procyanidin B2 (PB2), were selected for docking simulation. The resulting data predicted that all 12 metabolites could bind to M^pro. The affinity scores of PA2 and PB2 were predicted to be -9.2, followed by ECG, GCG, EGCG, and CAG, -8.3 to -8.7, and then six flavan-3-ol aglycones, -7.0 to -7.7. Docking characterization predicted that these compounds bound to three or four subsites (S1, S1', S2, and S4) in the binding pocket of M^pro via different spatial ways and various formation of one to four hydrogen bonds. In vitro analysis with 10 available compounds showed that CAG, ECG, GCG, EGCG, and PB2 inhibited the M^pro activity with an IC₅₀ value, 2.98 ± 0.21, 5.21 ± 0.5, 6.38 ± 0.5, 7.51 ± 0.21, and 75.3 ± 1.29 μM, respectively, while CA, EC, EGC, GC, and PA2 did not have inhibitory activities. To further substantiate the inhibitory activities, extracts prepared from green tea (GT), two muscadine grapes (MG), cacao, and dark chocolate (DC), which are rich in CAG, ECG, GAG, EGCG, or/and PB2, were used for inhibitory assay. The resulting data showed that GT, two MG, cacao, and DC extracts inhibited the M^pro activity with an IC₅₀ value, 2.84 ± 0.25, 29.54 ± 0.41, 29.93 ± 0.83, 153.3 ± 47.3, and 256.39 ± 66.3 μg/ml, respectively. These findings indicate that on the one hand, the structural features of flavan-3-ols are closely associated with the affinity scores; on the other hand, the galloylation and oligomeric types of flavan-3-ols are critical in creating the inhibitory activity against the M^pro activity.

Antitumor activities of Quercetin and Green Tea in xenografts of human leukemia HL60 cells

Quercetin is one of the most abundant flavonoids, present in fruits and vegetables and has been shown to have multiple properties capable of reducing cell growth in cancer cells. Green tea is a widely consumed beverage, known for a potential source of free radical scavenging and anti-cancer activities. Herein, we investigate the in vivo antitumor efficacy of quercetin and green tea in human leukemia. Human tumors were xenografted into NOD/SCID mice. Quercetin and green tea reduced tumor growth in HL-60 xenografts accompanied by decreased expression of anti-apoptotic proteins, BCL-2, BCL-XL and MCL-1 and increased expression of BAX, a pro-apoptotic protein. Moreover, caspase-3 was activated to a greater extent after quercetin and green tea treatment. Quercetin and green tea also mediated G1 phase cell cycle arrest in HL-60 xenografts. Treatment with quercetin and green tea induced conversion of LC3-I to LC3-II as well as activation of autophagy proteins, suggesting that quercetin and green tea initiate the autophagic progression. We have provided evidence that quercetin and green tea induces signaling at the level of apoptosis, cell cycle and autophagy which converge to antigrowth effects in HL-60 xenograft mice suggesting that these compounds may be a compelling ally in cancer treatment.

Established Human Cell Lines as Models to Study Anti-leukemic Effects of Flavonoids

Despite the extensive work on pathological mechanisms and some recent advances in the treatment of different hematological malignancies, leukemia continues to present a significant challenge being frequently considered as incurable disease. Therefore, the development of novel therapeutic agents with high efficacy and low toxicity is urgently needed to improve the overall survival rate of patients. In this comprehensive review article, the current knowledge about the anticancer activities of flavonoids as plant secondary polyphenolic metabolites in the most commonly used human established leukemia cell lines (HL-60, NB4, KG1a, U937, THP-1, K562, Jurkat, CCRF- CEM, MOLT-3, and MOLT-4) is compiled, revealing clear anti-proliferative, pro-apoptotic, cell cycle arresting, and differentiation inducing effects for certain compounds. Considering the low toxicity of these substances in normal blood cells, the presented data show a great potential of flavonoids to be developed into novel anti-leukemia agents applicable also in the malignant cells resistant to the current conventional chemotherapeutic drugs.

Piper and Vismia species from Colombian Amazonia differentially affect cell proliferation of hepatocarcinoma cells

There is an increasing interest to identify plant-derived natural products with antitumor activities. In this work, we have studied the effects of aqueous leaf extracts from Amazonian Vismia and Piper species on human hepatocarcinoma cell toxicity. Results showed that, depending on the cell type, the plants displayed differential effects; thus, Vismia baccifera induced the selective killing of HepG2, while increasing cell growth of PLC-PRF and SK-HEP-1. In contrast, these two last cell lines were sensitive to the toxicity by Piper krukoffii and Piper putumayoense, while the Piperaceae did not affect HepG2 growth. All the extracts induced cytotoxicity to rat hepatoma McA-RH7777, but were innocuous (V. baccifera at concentrations < 75 µg/mL) or even protected cells from basal death (P. putumayoense) in primary cultures of rat hepatocytes. In every case, cytotoxicity was accompanied by an intracellular accumulation of reactive oxygen species (ROS). These results provide evidence for the anticancer activities of the studied plants on specific cell lines and suggest that cell killing could be mediated by ROS, thus involving mechanisms independent of the plants free radical scavenging activities. Results also support the use of these extracts of the Vismia and Piper genera with opposite effects as a model system to study the mechanisms of the antitumoral activity against different types of hepatocarcinoma.

Antioxidant and pro-apoptotic effects of marine-derived, multi-mineral aquamin supplemented with a pine bark extract, Enzogenol, and a green tea extract, Sunphenon

A high dietary intake of polyphenols has been associated with a decreased risk of cardiovascular disease and cancer, attributed in part to their antioxidant activity and pro-apoptotic effects. Aquamin is a multi-mineral algal extract that enhances bone mineralization, relieves osteoarthritis, and aids digestion; however, Aquamin has not demonstrated antioxidant activity. In the present study, Aquamin was supplemented with 8% Enzogenol, a pine bark extract with a high phenolic content, and 2% Sunphenon, a green tea extract that also has a high phenolic content to produce a mixed product (A:E:S). The antioxidant activity of A:E:S was compared with that of its constituent compounds and also with catechin and epigallocatechin by measuring total phenol content, ferric-reducing antioxidant potential, and 2,2-diphenyl-2-picrylhydrazyl hydrate. The cytotoxic and apoptotic effects of the compounds were also measured in the U937, human monocytic blood cell line. A:E:S demonstrated an antioxidant activity that was equal to that of the compounds used in its preparation. Aquamin was not cytotoxic in the U937 cell line; however, A:E:S was cytotoxic and the primary mechanism of cell death was apoptosis. The biological effects of Aquamin were enhanced by supplementation with Enzogenol and Sunphenon to include antioxidant effects and the ability to induce apoptosis in U937 cells.

Health-promoting effects of green tea

Green tea is manufactured from the leaves of the plant Camellia sinensis Theaceae and has been regarded to possess anti-cancer, anti-obesity, anti-atherosclerotic, anti-diabetic, anti-bacterial, and anti-viral effects. Many of the beneficial effects of green tea are related to the activities of (-)-epigallocatechin gallate (EGCG), a major component of green tea catechins. For about 20 years, we have engaged in studies to reveal the biological activities and action mechanisms of green tea and EGCG. This review summarizes several lines of evidence to indicate the health-promoting properties of green tea mainly based on our own experimental findings.

Theaflavin-3,3'-digallate, a component of black tea: an inducer of oxidative stress and apoptosis

Treatment of human oral squamous carcinoma HSC-2 cells and normal GN46 fibroblasts with theaflavin-3,3'-digallate (TF-3), a polyphenol in black tea, showed a concentration and time dependent inhibition of growth, with the tumor cells more sensitive than the fibroblasts. In buffer and in cell culture medium, TF-3 generated reactive oxygen species, with lower levels detected in buffer amended with catalase and superoxide dismutase, indicating the generation of hydrogen peroxide and superoxide, respectively, and suggesting that TF-3 may be an inducer of oxidative stress. The toxicity of TF-3 was decreased in the presence of catalase, pyruvate, and divalent cobalt, all scavengers of reactive oxygen species, but was potentiated in the presence of diethyldithiocarbamate, an inhibitor of superoxide dismutase. The intracellular level of glutathione in HSC-2 cells was lessened after a 4-h exposure to 250 and 500 microM TF-3. However, for GN46 fibroblasts, a 4-h exposure to 250 microM TF-3 stimulated, but to 500 microM TF-3 lessened, intracellular glutathione. Treatment of the cells with the glutathione depleters, 1,3-bis(2-chloroethyl)-N-nitrosourea, 1-chloro-2,4-dinitrobenzene, and d,l-buthionine-[S,R]-sulfoximine potentiated the toxicity of TF-3. Induction of apoptotic cell death in HSC-2 cells treated with TF-3 was noted by apoptotic cell morphologies, by TUNEL staining, by PARP cleavage, and by elevated activity of caspase-3. Apoptosis was not noted in GN46 fibroblasts treated with TF-3.

DNA microarray analysis of changes in gene expression induced by 1,25-dihydroxyvitamin D3 in human promyelocytic leukemia HL-60 cells

Using a DNA microarray, we analyzed about 16,600 genes for changes in expression associated with the differentiation of human promyelocytic leukemia HL-60 cells induced by 1alpha,25-dihydroxyvitamin D3 (DVD). Many of the up-regulated genes could be correlated to differentiation-associated changes toward a monocyte/macrophage lineage, and many down-regulated genes could be correlated to repressed cell growth. The present study revealed the down-regulated gene expression of importins and exportins 1, 5, 7, and exportin-tRNA. Thus, the present results confirmed our previous findings of down-regulation of exportin 1 and exportin-tRNA by DVD. Gene expression of exportin 6 is suggested to be regulated differently from that of exportins 1, 5, 7, and exportin-tRNA. The down-regulation of nuclear transport factors may be deeply associated with the differentiation of HL-60 cells induced by DVD.

1,25-Dihydroxyvitamin D3 suppresses gene expression of eukaryotic translation initiation factor 2 in human promyelocytic leukemia HL-60 cells

The physiologically active metabolite of vitamin D(3), 1alpha,25-dihydroxyvitamin D(3) (DVD), is a potent inducer of cell differentiation in human myeloid leukemia cells. In the present study, we examined changes in gene expression during DVD-induced cell differentiation of promyelocytic HL-60 cells employing a DNA microarray technique. The results identified 7 up-regulated and 9 down-regulated genes with a change greater than 1.5-fold after the DVD-treatment for both 2 and 6 days. Seven of these genes were further examined by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that findings obtained from the DNA microarray analysis and RT-PCR are generally comparable with each other. Gene expression of the subunits of eukaryotic translation initiation factor 2 was then examined by methods including RT-PCR and real-time PCR. The results indicated the suppression of these genes, suggesting a linkage to differentiation-associated growth inhibition of these cells.

Intakes of selected food groups and beverages and adult acute myeloid leukemia

Few studies have explored the association between diet and adult acute myeloid leukemia (AML). In a hospital-based case-control study among 111 cases and 439 controls, AML risk was negatively associated with milk intake among women (OR 0.25, 95% CI 0.08-0.73) and tea (OR 0.50, 95% CI 0.23-1.09), and positively associated among women with beer (OR 2.48, 95% CI 1.05-5.85), wine (OR 2.32, 95% CI 1.05-5.09), and beef (OR 4.78, 95% CI 1.35-16.94). Our findings support a role of diet in adult AML; however, further research is needed to explore gender differences in risk.

1,25-Dihydroxyvitamin D3 suppresses exportin expression in human promyelocytic leukemia HL-60 cells

The active form of vitamin D3, 1alpha,25-dihydroxyvitamin D3 (DVD), is a potent inducer of cell differentiation and inhibits proliferation of cells such as human promyelocytic leukemia HL-60 cells. In the present study, we examined the effects of DVD on the expression of exportin-1 and exportin-t, which play essential roles in the transport of mRNA and tRNA, respectively. The results of reverse transcription-polymerase chain reaction and quantitative real-time polymerase chain reaction indicated that DVD down-regulated the gene expression of these exportins. Western blotting revealed the decreased production of these proteins in DVD-treated cells. Thus, the present findings of decreased expression of exportin-1 and exportin-t induced by DVD can be correlated to inhibition of the proliferation of HL-60 cells.

Green tea with a high catechin content suppresses inflammatory cytokine expression in the galactosamine-injured rat liver

Galactosamine is known to induce hepatic injury in rats and the galactosamine-induced hepatitis is believed to be similar to viral hepatitis both morphologically and functionally. In the present study, we examined how drinking green tea affects the gene expression of inflammatory cytokines which may be up-regulated in galactosamine-induced hepatitis. As has been reported, galactosamine caused hepatic injury in rats as evidenced by an increase in serum transaminase activities and histological observations of the liver. The results of the reverse transcription and polymerase chain reaction indicated an increased gene expression of inflammatory cytokines, tumor necrosis factor-alpha and interleukin-1beta, in the injured liver and the enzyme linked immunoassay showed an increase in the serum levels of these cytokines. Oral administration of green tea rich in catechins (Healthya green tea) restored these biomarkers in the galacotsamine-treated rats to near the control levels. These results suggest that the drinking of green tea with a high catechin content may help to prevent and/or attenuate the development of a certain type of hepatitis.