Multidrug resistance reversal effect of DMC derived from buds of Cleistocalyx operculatus in human hepatocellular tumor xenograft model.

BACKGROUND: Multidrug resistance (MDR) is a major obstacle in the chemotherapeutic treatment of many human cancers. 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC) isolated from the buds of Cleistocalyx operculatus (Roxb.) Merr. et Perry (Myrtaceae), was investigated for its reversal effects on cancer cell MDR. RESULTS: A human hepatocellular tumor xenograft model was established with the BEL-7402/5-FU cell line. Combined 5-fluorouracil (5-FU) and DMC (40 mg kg(-1) ) treatment significantly elevated tumor inhibition rate to 72.2%. DMC could also increase 5-FU concentrations in tumor tissues and increase caspase-3 activity. Also, combined therapy resulted in enhanced tumor apoptotic and reduced proliferative activities relative to 5-FU alone. Examining body weight and other signs of unwanted toxicity of the different treatment groups revealed no significant signs of adverse effects. CONCLUSION: All results suggested that DMC reverses 5-FU resistance, with a benign side effects profile.

Reversal effect of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone on multi-drug resistance in resistant human hepatocellular carcinoma cell line BEL-7402/5-FU.

Multi drug resistance (MDR) is a major obstacle in the chemotherapeutic treatment of many human cancers. 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a chalcone, isolated from the buds of Cleistocalyx operculatus, has been shown to have antitumor effects on human carcinoma SMMC-7721 cells in vitro and in vivo. In this paper, we studied the reversal effect and the mechanism of DMC on human hepatocellular carcinoma drug-resistant cells BEL-7402/5-FU in vitro. Administration of DMC reversed the multi-drug resistance of human hepatocellular carcinoma BEL-7402/5-FU cells significantly. DMC enhanced the sensitivity of BEL-7402/5-FU cells to 5-fluorouracil (5-FU) and doxorubicin (DOX). Staining with Hoechst 33258 and flow cytometric analysis showed that DMC has apoptosis-inducing effect on BEL-7402/5-FU cells. It could also increase the concentration of 5-FU in the resistant multi-drug-resistant cells. We also observed that over-expression of the multi-drug resistance-associated protein (MRP1) and of the glutathione S-transferase π (GST-π) contributed to MDR in BEL-7402/5-FU cells. The mRNA expressions of MRP1 and GST-π and the protein expression of MRP1 were decreased by DMC. These data demonstrated that DMC could effectively reverse MDR in BEL-7402/5-FU cells.

Protective effects of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone to PC12 cells against cytotoxicity induced by hydrogen peroxide.

Oxidative stress has been considered as a major cause of cellular injuries in various clinical abnormalities. One of the possible ways to prevent reactive oxygen species (ROS)-mediated cellular injury is dietary or pharmaceutical therapies to augment the endogenous antioxidant defense capacity. The present study found that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a chalcone isolated from the buds of Cleistocalyx operculatus, possessed cytoprotective activity in PC12 cells treated with H(2)O(2). The results showed that DMC could effectively increase cell viability [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) reduction], decrease the cell apoptotic percentage [annexin V/propidium iodide (AV/PI) assay], prevent the membrane from damage [lactate dehydrogenase (LDH) release], scavenge ROS formation, reduce caspase-3 activity, and attenuate the decrease of mitochondrial membrane potential (MMP) in PC12 cells treated with H(2)O(2). Meanwhile, DMC increased the catalytic activity of superoxide dismutase (SOD) and the cellular amount of glutathione (GSH), decreased the cellular amount of malondialdehyde (MDA), and decreased the production of lipid peroxidation in PC12 cells treated with H(2)O(2).

Protective effects of the citrus flavanones to PC12 cells against cytotoxicity induced by hydrogen peroxide.

Oxidative stress has been considered as a major cause of cellular injuries in a variety of clinical abnormalities. One of the plausible ways to prevent the reactive oxygen species (ROS)-mediated cellular injury is dietary or pharmaceutical augmentation of endogenous antioxidant defense capacity. In this study, we investigated the protective actions of citrus flavanones naringin and nobiletin against the cytotoxicity induced by exposure to hydrogen peroxide (H(2)O(2)) (150µM, 3h) in PC12 cells. The results showed that naringin and nobiletin inhibited the decrease of cell viability (MTT reduction), prevented membrane damage (LDH release), scavenged ROS formation, reduced caspase-3 activity, and attenuated the decrease of mitochondrial membrane potential (MMP), respectively, in H(2)O(2)-induced PC12 cells. Meanwhile, naringin and nobiletin increased superoxide dismutase (SOD) and glutathione (GSH) activity, while decreased malondialdehyde (MDA), the production of lipid peroxidation, in H(2)O(2)-induced PC12 cells. In addition, the percentage of cells undergoing H(2)O(2)-induced apoptosis was decreased in the presence of naringin and nobiletin. These results first demonstrate that naringin and nobiletin, even at physiological concentrations, have neuroprotective effects against H(2)O(2)-induced cytotoxicity in PC12 cells. All the above results suggest that these dietary antioxidants are potential candidates for use in the intervention for neurodegenerative diseases.