Takafumi Okabe

Tumor-selective cytotoxicity of benzo[c]phenanthridine derivatives from Toddalia asiatica Lam.

PurposeTo develop a novel anti-cancer drug of low side effect against lung adenocarcinoma, the authors screened the bioresources of Okinawa Island, Japan. The medicinal plant Toddalia asiatica Lam. contained three benzo[c]phenanthridine derivatives: dihydronitidine (DHN), nitidine (NTD) and demethylnitidine (DMN). Of the three derivatives, DHN had been shown to selectively inhibit the growth of cancer cells in our previous study. Because of similar molecular topology of NTD or DMN to DHN, it can be expected that NTD and DMN also show selective cytotoxicity. The aim of the present study was therefore to examine the selective cytotoxicity of these two compounds in vitro and in vivo.MethodsBenzo[c]phenanthridine derivatives were isolated from T. asiatica Lam., and their chemical structures were identified by interpretation of NMR and MS spectrum. Of the isolated compounds, NTD and DMN were evaluated for cytotoxicity in vitro or in vivo.ResultsNTD as well as DHN selectively reduced the growth of murine and human lung adenocarcinoma in vitro with selective intracellular accumulation. NTD has also been proven to be highly effective in vivo to inhibit the growth of both murine and human lung adenocarcinoma in a subcutaneous xenograft model without any deteriorating side effect. In contrast, DMN had no selective cytotoxicity suggesting that 8-methoxy group of NTD is the critical structural feature for the selective cytotoxicity.ConclusionsThis study thus proves the effectiveness of benzo[c]phenanthridine derivatives as anti-cancer agent in vivo for the first time, and discusses the mechanisms responsible for the selective cytotoxicity.

Peucedanum japonicum Thunb Inhibits High‐fat Diet Induced Obesity in Mice

This study examined the antiobese activity of Peucedanum japonicum Thunb (PJT) in mice. In the first experiment, 4‐week‐old C57BL/6 mice were fed seven different diets containing 15% corn oil and 0–20% PJT powder for 4 weeks. Feeding the 10% and 20% PJT diet suppressed the body weight gain and the accumulation of abdominal and subcutaneous fats. PJT reduced serum and liver levels of triglyceride and serum levels of leptin in a dose‐dependent manner. PJT intake decreased the proportion of saturated fatty acids and increased polyunsaturated and n‐3 fatty acids in the liver. To obtain more insight into the antiobese activity of PJT, its effect on lipid absorption and enzyme activities related to lipid metabolism was studied in the second experiment. There was an increased faecal excretion of triglyceride in mice fed 5% and 10% PJT diets. Fatty acid synthase activity was decreased while carnitine palmitoyltransferase activity was increased by 10% PJT intake. These findings pointed to the usefulness of PJT for the development of a safe natural agent to reduce obesity or body weight for the first time. The rationale for the lipid lowering mechanism of PJT and the candidate compound responsible for the observations have also been discussed. Copyright

Tumor specific cytotoxicity of β-glucosylceramide: structure–cytotoxicity relationship and anti-tumor activity in vivo

This study describes the structure–cytotoxicity relationship of β-glucosylceramide (β-GluCer) and its antitumor activity in vivo. Unglycosylated ceramide had no selective cytotoxicity which demonstrated that the sugar moiety plays a critical role for the expression of selective cytotoxicity by β-GluCer. β-Galactosylceramide also showed tumor specific cytotoxicity suggesting that the chemical structure of sugar group is not a factor for the selective toxicity. Similarly, unglycosylated ceramides of short acyl chain also selectively inhibited the growth of cancer cells. These findings in concert point to the importance of the hydrophilicity of the ceramide molecule rather than the chemical structure for the cyto-selectivity. Treatment of the cells with β-GluCer increased the concentration of reactive oxygen species leading to cell cycle arrest and necrosis. Intraperitoneal administration of β-GluCer significantly suppressed the growth of tumor implanted to the back of mice. β-GluCer also induced antitumor immunity via the activation of NKT cells in vivo, and decreased the tumor metastasis of lymphoma cells. The present study thus demonstrated the antitumor activity of β-GluCer in vivo, and discussed the mechanisms responsible for the growth inhibition.

Antiatherosclerotic function of Kokuto, Okinawan noncentrifugal cane sugar.

In the present study, we investigated the effect of phenolic compounds (PCs) and policosanol of Kokuto, Okinawan noncentrifugal cane sugar, on the development of atherosclerosis. A total of 67 male Japanese quail were divided into eight dietary groups in trial 1. The dietary groups were fed the atherosclerotic diet (AD) containing 5% corn oil, 2% cholesterol, and 30% sucrose or seven different types of Kokuto. Dietary intakes of Kokuto notably prevented the development of atherosclerosis. Furthermore, there was a significant negative correlation between the serum radical scavenging activity and the degree of atherosclerosis in the dietary groups. In trial 2, a total of 63 Japanese quail were fed AD with sucrose, Kokuto, PC extracts from Kokuto, wax extracts from sugar cane, octacosanol, vitamin C, and vitamin E. As a result, the supplementation of the diet with Kokuto and PCs significantly reduced the development of atherosclerosis as compared with the ingestion of AD with sucrose. In conclusion, these findings suggest that, among various components of Kokuto, PCs play a central role for the prevention of experimental atherosclerosis in Japanese quail.

Down-regulation of lipids transporter ABCA1 increases the cytotoxicity of Nitidine

PurposeNitidine (NTD) cytotoxicity is highly specific for A549 human lung adenocarcinoma cells. We hypothesized that this cytotoxicity involved the accumulation of NTD in intracellular organelles. However, there have been no reports of NTD transporting factors. In this study, we screened for an NTD transporter and evaluated its association with NTD cytotoxicity.MethodsGene expression analyses were done for A549 and human fetal lung normal diploid fibroblast (WI-38) cells. We screened for ABC transporter, multi-drug resistance-associated genes. Gene expressions of ATP-binding cassette transporter A1 (ABCA1) were confirmed in 8 cell lines by quantitative PCR. The involvement of ABCA1 in NTD cytotoxicity was evaluated using siRNA-mediated ABCA1 gene silencing.ResultsGene expression analysis indicated that A549 cells expressed higher levels of ABCC1, ABCC2, ABCC3, and ABCG2 and a lower level of ABCA1 compared to WI-38 cells. NTD resistant cell lines uniformly showed higher ABCA1 expression levels. Gene silencing experiments showed that the down-regulation of ABCA1 resulted in increased sensitivity to NTD.ConclusionsThese results indicated that NTD efflux is controlled by ABCA1 activity, suggesting that ABCA1 transports molecules other than lipids. Thus, there is a possibility that ABCA1 acts as a drug resistance transporter involved in the cytotoxicity of NTD derivatives. This also suggested that the expression level of the ABCA1 gene may be an indicator for the efficiency of NTD treatment.

Anti-obesity Activity of Peucedanum japonicum Thunb Extract in Obese Diabetic Animal Model C57BL/6J Ham Slc-ob/ob Mice

Aim of the study is to evaluate the anti-diabetic activity of PJT. This study examined its anti-obesity activity in obese-diabetic animal model of C57BL/6J Ham Slc-ob/ob mice. By dividing animals into control and ethanol extract of PJT groups, body weight gain, tissue weight, biochemical parameters in serum, liver, fecal lipid concentrations and gene expression in the tissues were compared between control and PJT extract groups after been fed with the basal low-fat diet supplemented with or without PJT extract for four weeks. The results show that supplementation of the diet with ethanol extract of PJT significantly reduced white adipose tissue (WAT), serum triglyceride (TG), total cholesterol (TC) and adipocyte size. The ethanol extracts also significantly increase insulin sensitivity, fecal excretion of TG, TC, and decreased that of bile acid. The ethanol extract of PJT modulated the obesity related genes in liver, adipose tissues of ob/ob mice: upregulation of PBEF1, PPARα, and downregulation of FAS genes in the liver; upregulation of RORC, DGAT1, FXRα, PPARγ genes in the adipose tissue; increased expression of CPT1α, UCP2 and GLUT4 genes in muscle. In conclusion, it is suggested that ethanol extract of PJT exerted anti-diabetic activity through the modulation of obesity-related lipid parameters in obese-diabetic animal model.