Inhibition of intestinal adenoma formation in APC(Min/+) mice by Riccardin D, a natural product derived from liverwort plant Dumortiera hirsuta.

BACKGROUND: Mutation of tumor suppressor gene, adenomatous polyposis coli (APC), is the primary molecular event in the development of most intestinal carcinomas. Animal model with APC gene mutation is an effective tool for study of preventive approaches against intestinal carcinomas. We aimed to evaluate the effect of Riccardin D, a macrocyclic bisbibenzyl compound, as a chemopreventive agent against intestinal adenoma formation in APC(Min/+) mice. METHODS: APC(Min/+) mice were given Riccardin D by p.o. gavage for 7 weeks. Mice were sacrificed, and the number, size and histopathology of intestinal polyps were examined under a microscope. We performed immunohistochemical staining, western blotting, reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) in intestinal polyps to investigate the mechanism of chemopreventive effect of Riccardin D. RESULTS: Riccardin D treatment resulted in a significant inhibition of intestinal adenoma formation, showing a reduction of polyp number by 41.7%, 31.1% and 44.4%, respectively, in proximal, middle and distal portions of small intestine. The activity of Riccardin D against polyp formation was more profound in colon, wherein Riccardin D decreased polyp number by 79.3%. Size distribution analysis revealed a significant reduction in large-size polyps (2-3 mm) by 40.0%, 42.5% and 33.3%, respectively, in proximal, middle and distal portions of small intestine, and 77.8% in colon. Histopathological analysis of the intestinal polyps revealed mostly hyperplastic morphology without obvious dysplasia in Riccardin D-treated mice. Molecular analyses of the polyps suggested that the inhibitory effect of Riccardin D on intestinal adenoma formation was associated with its abilities of reduction in cell proliferation, induction of apoptosis, antiangiogenesis, inhibition of the Wnt signaling pathway and suppression of inflammatory mediators in polyps. CONCLUSIONS: Our results suggested that Riccardin D exerts its chemopreventive effect against intestinal adenoma formation through multiple mechanisms including anti-proliferative, apoptotic, anti-angiogenic and anti-inflammatory activity.

Inhibitory effect of riccardin D on growth of human non-small cell lung cancer: in vitro and in vivo studies.

Riccardin D is a macrocyclic bisbibenzyl compound extracted from liverwort plant Dumortiera hirsuta. Our previous study showed that riccardin D induced apoptosis of human leukemia cells by targeting DNA topoisomerase II (topo II). Riccardin D has been considered as a novel DNA topo II inhibitor and potential chemotherapeutic agent for treatment of cancers. In this study, we evaluated the inhibitory effects of riccardin D on growth of human non-small cell lung cancer (NSCLC) both in vitro and in vivo. Riccardin D effectively inhibited the proliferation of NSCLC cells as estimated by the MTT assay. Further examination showed that the ability of invasion and migration of NSCLC cells was suppressed on exposure to riccardin D as estimated by the assays of scratch and transwell chamber. The anticancer activity of riccardin D was verified in mice bearing human NSCLC H460 xenografts. Riccardin D injection produced a 44.5% inhibition of cancer growth without apparent signs of toxicity to animals. Further, riccardin D induced apoptosis of NSCLC cells as evidenced by the increases of cells with externalization of phosphatidylserine and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive in H460 xenografts. The analysis of apoptotic proteins showed that riccardin D activated the caspases cascade signaling pathway as demonstrated by the increases of cleaved caspase-3 and cleaved PARP in NSCLC cells in vitro and in H460 xenografts in mice. The pBR322 DNA relaxation assay indicated that riccardin D inhibited the activity of DNA topo II in H460 and A549 cells, suggesting the mechanism of riccardin D in induction of NSCLC apoptosis. In addition, we studied the activity and expression of matrix metalloproteinases (MMPs) in NSCLC cells. The activities of MMP-2 and MMP-9 in supernatants of NSCLC cells were suppressed on exposure to riccardin D as estimated by gelatin zymography assay. The inhibitory effects of riccardin D on expressions of MMP-2 and MMP-9 were verified in H460 xenografts in mice and the decreases of vascular endothelial growth factor (VEGF) and Erk1/2 might associate with the inhibition of MMPs and NSCLC growth. Together, our results suggest that riccardin D has a high inhibitory effect on human NSCLC growth through induction of apoptosis.

Sphingosine 1-phosphate antagonizes the effect of all-trans retinoic acid (ATRA) in a human colon cancer cell line by modulation of RARß expression.

All-trans retinoic acid (ATRA) is a promising therapeutic agent, but exhibits low efficacy against human cancers. We investigated the effect of sphingosine-1-phosphate (S1P) on ATRA activity in human colon cancer HT-29 cells. S1P antagonized ATRA activity on HT-29 cell proliferation and retinoic acid receptor beta (RARß) expression. S1P treatment or transient co-transfection with SphK2 expression vector antagonized ATRA-induced RARß promoter activity. Proteasome inhibition prevented S1P-induced modulation of ATRA activity. Overall, S1P antagonized ATRA's inhibitory effects by down-regulating RARß expression, likely via the proteasome-dependent pathway. Decreasing S1P production or inhibiting SphK2 activity could enhance the efficacy of retinoids in cancer treatments.

[Ecological distribution and antimicrobial effects of soil actinomycetes in artificial vegetation systems in Shazhuyu of Qinghai, China].

In order to probe into the effects of artificial vegetation rehabilitation on soil actinomycetes, dilution plate and agar block methods were used to investigate the ecological distribution and antimicrobial effects of actinomycetes in sandy soil in Shazhuyu area of Qinghai after artificial vegetation restoration. The results showed that with the vegetation rehabilitation and the improvement of vegetation coverage on alpine sandy dry land, the quantity of soil actinomycetes increased significantly, being 145.4% higher in the grassland transferred from farmland than in sandy land. The quantity of soil Micromonospora in grassland transferred from farmland was about six times as much as that in sandy land. The average selection rate of antimicrobial actinomycetes was increased greatly, with the antimicrobial actinomycetes in the soil of grassland transferred from farmland, the antibacterial actinomycetes in the soil of natural grassland, and the pathogenic fungus resistant aetinomycetes in the soil of forestland being approximately 2, 3.2 and 1.5 times as much as those in the soil of sandy land, respectively. Vegetation coverage and soil nutrients had great influences on the quantities of actinomycetes and antimicrobial actinomycetes. The contents of soil organic matter and alkali-hydrolyzable nitrogen and the yield of fresh grasses had significant correlations with the quantities of actinomycetes (P < 0.01), and the content of soil organic matter and the yield of fresh grasses significantly correlated with the strain numbers of antimicrobial actinomycetes (P < 0.01). Furthermore, vegetation coverage and the contents of soil total nitrogen, total phosphorous, total potassium, total salt, and available potassium had significant correlations with the total quantities of actinomycetes, Streptomycetes, and Micromonospora (P < 0.05).

Hypericum sampsonii induces apoptosis and nuclear export of retinoid X receptor-alpha.

Natural products derived from plants provide a rich source for development of new anticancer drugs. Recent studies suggest that modulation of subcellular localization of retinoid X receptor-alpha (RXRalpha) represents a potential approach for inducing cancer cell apoptosis. In this study, we screened a herbal library for inducing translocation of RXRalpha from the nucleus to the cytoplasm. Our results revealed that the extract of Hypericum sampsonii, a member of the genus Hypericum, had remarkable effect on RXRalpha subcellular localization in various cancer cells. Treatment of NIH-H460 human lung cancer cells with H. sampsonii extract resulted in relocalization of RXRalpha from the nucleus to the cytoplasm. Cytoplasmic RXRalpha induced by H. sampsonii was associated with mitochondria, accompanied with cytochrome c release and apoptosis. H. sampsonii extract effectively inhibited the growth of various cancer cell lines, including NIH-H460 lung cancer, MGC-803 stomach cancer and SMMC7721 liver cancer cells. The growth inhibitory effect of H. sampsonii extract depended on levels of RXRalpha, as it failed to inhibit the growth of CV-1 cells lacking detectable RXRalpha, whereas transfection of RXRalpha into CV-1 cells restored its apoptotic response to H. sampsonii. Furthermore, the apoptotic effect of H. sampsonii was significantly enhanced when RXRalpha was overexpressed in NIH-H460 cells. Together, our results demonstrate that H. sampsonii contains ingredient(s) that induce apoptosis of cancer cells by modulating subcellular localization of RXRalpha.