Yu Su Shin

Anti-influenza effect of Cordyceps militaris through immunomodulation in a DBA/2 mouse model

The immune-modulatory as well as anti-influenza effects of Cordyceps extract were investigated using a DBA/2 mouse model. Three different concentrations of Cordyceps extract, red ginseng extract, or drinking water were orally administered to mice for seven days, and then the mice were intranasally infected with 2009 pandemic influenza H1N1 virus. Body weight changes and survival rate were measured daily post-infection. Plasma IL-12, TNF-α, and the frequency of natural killer (NK) cells were measured on day 4 post-infection. The DBA/2 strain was highly susceptible to H1N1 virus infection. We also found that Cordyceps extract had an antiinfluenza effect that was associated with stable body weight and reduced mortality. The anti-viral effect of Cordyceps extract on influenza infection was mediated presumably by increased IL-12 expression and greater number of NK cells. However, high TNF-α expression after infection of H1N1 virus in mice not receiving treatment with Cordyceps extract suggested a two-sided effect of the extract on host immune regulation.

DNA hypermethylation induced by Epstein-Barr virus in the development of Epstein-Barr virus-associated gastric carcinoma.

Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) is a recently recognized disease entity defined by the presence of EBV in gastric carcinoma cells. EBV infection causes major epigenetic alterations in the EBV genome and its cellular host genome, suggesting that EBV acts as a direct epigenetic driver for EBVaGC. One of the major epigenetic events in the viral and cellular genomes to control transcription is DNA hypo- or hyper-methylation. Particularly, local and global hypermethylation have been reported in EBVaGC. It is therefore important to understand the molecular mechanisms of DNA hypermethylation during EBVaGC carcinogenesis. To understand the functional roles of DNA methylation and suggest therapeutic target candidates for EBVaGC, we reviewed recent literature reporting DNA hypermethylation in EBVaGC. We summarized the identified candidate genes that are markedly hypermethylated in EBVaGC, which can potentially be targets for chemotherapies with demethylating agents.

Anti-Cancer Effect of Quercetin in Xenograft Models with EBV-Associated Human Gastric Carcinoma

Licorice extracts have been widely used in herbal and folk medications. Glycyrrhiza contains diverse range of biological compounds including triterpenes (glycyrrhizin, glycyrrhizic acid) and flavonoids (quercetin, liquiritin, liquiritigenin, glabridin, licoricidin, isoliquiritigenin). The flavonoids in licorice are known to have strong anti-cancer activities. Quercetin, the most abundant flavonoid, has been shown to have anti-ulcer, anti-cancer, antioxidant, and anti-inflammatory properties. Latent Epstein-Barr virus (EBV) infection can lead to serious malignancies, such as, Burkitt’s lymphoma, Hodgkin’s disease and gastric carcinoma(GC), and (Epstein-Barr virus associated gastric carcinoma) EBVaGC is one of the most common EBV-associated cancers. In this study, the authors first examined the anti-cancer effects of quercetin and isoliquiritigenin in vivo xenograft animal models implanted with EBV(+) human gastric carcinoma (SNU719) or EBV(−) human gastric carcinoma (MKN74), and then explored the molecular mechanisms responsible for their anti-cancer activities. The results obtained showed that anti-cancer effect of quercetin was greater than isoliquiritigenin in mice injected with EBV(+) human gastric carcinoma (SNU719) cells. On the other hand, quercetin and isoliquiritigenin had similar anti-cancer effects in mice injected with EBV(−) human gastric carcinoma (MKN74) cells. Interestingly, quercetin inhibited EBV viral protein expressions, including EBNA-1 and LMP-2 proteins in tumor tissues from mice injected with EBV(+) human gastric carcinoma. Quercetin more effectively induced p53-dependent apoptosis than isoliquiritigenin in EBV(+) human gastric carcinoma, and this induction was correlated with increased expressions of the cleaved forms of caspase-3, -9, and Parp. In EBV(−)human gastric carcinoma (MKN74), both quercetin and isoliquiritigenin induced the expressions of p53, Bax, and Puma and the cleaved forms of caspase-3 and -9 and Parp at similar levels.

Dysregulation of KSHV Replication by Extracts from Carthamus tinctorius L.

Carthamus tinctorius L. (CT) is traditionally used to reduce ailments from diseases of the musculoskeletal system and connective tissue and diseases of blood circulation and the cardiovascular system. Flower extracts from CT are known to have antibacterial activity, anti-inflammatory activity, and to inhibit tumor promotion in mouse skin carcinogenesis. In order to discover new antiviral agents from CT extracts, we tested whether CT extracts contain antiviral activity against gammaherpesvirus infection. This study demonstrated that treatment with CT extracts disrupted KSHV latency in the viral-infected host cells, iSLK-BAC16. n-Hexane and EtOH fractions of CT extracts critically affected at least two stages of the KHSV life-cycle by abnormally inducing KSHV lytic reactivation and by severely preventing KSHV virion release from the viral host cells. In addition to the effects on KSHV itself, CT extract treatments induced cellular modifications by dysregulating cell-cycle and producing strong cytotoxicity. This study demonstrated for the first time that CT extracts have antiviral activities that could be applied to development of new anti-gammaherpesviral agents.

Genipin Enhances Kaposi’s Sarcoma-Associated Herpesvirus Genome Maintenance

Kaposis sarcoma-associated herpesvirus (KSHV) is a Gammaherpesvirus that causes acute infection and establishes life-long latency. KSHV causes several human cancers, including Kaposis sarcoma, an acquired immune deficiency syndrome (AIDS)-related form of non-Hodgkin lymphoma. Genipin, an aglycone derived from geniposide found in Gardenia jasminoides, is known to be an excellent natural cross-linker, strong apoptosis inducer, and antiviral agent. Although evidence suggests antiviral activity of genipin in several in vitro viral infection systems, no inhibitory effect of genipin on KSHV infection has been reported. Thus, our aim was to determine, using the iSLK-BAC16 KSHV infection system, whether genipin has inhibitory effects on KSHV infection. For this purpose, we evaluated biological effects of genipin on KSHV infection and finally determined the underlying mechanisms responsible for the bioactive effects of genipin. A cytotoxicity assay revealed that genipin caused 50% cytotoxicity at 49.5 μM in iSLK-puro (KSHV-negative) cells and at 72.5 μM in iSLK-BAC16 (KSHV-positive) cells. Caspase 3/7 activities were slightly suppressed by genipin treatment in iSLK-BAC16 cells while significantly induced in iSLK-puro cells. Production of the KSHV latency-associated nuclear antigen (LANA), but not that of the R-transactivator (RTA) protein, was significantly induced by genipin treatment at lower concentration. Consistent with the LANA upregulation, KSHV LANA transcripts, but not RTA transcripts, were expressed at a higher level. Furthermore, KSHV intracellular copy numbers were slightly increased at lower concentration of genipin, while KSHV extracellular copy numbers were significantly increased at higher concentration of genipin. Interestingly, genipin treatment at a lower concentration did induce the expression of DNA (cytosine-5)-methyltransferase 1 (DNMT1); however, a co-immunoprecipitation assay showed that the DNMT1 and LANA induced by genipin did not co-precipitate from iSLK-BAC16 cells. Moreover, a chromatin immunoprecipitation assay demonstrated that genipin treatment enhanced the binding of CCCTC-binding factor (CTCF) to the CTCF-binding site in the KSHV latency control region but suppressed the binding of structural maintenance of chromosomes protein 3 (SMC3) to this site. Genipin treatment also led to the recruitment of additional RNA polymerase to the majority of binding sites of some interesting proteins in the KSHV latency control region, which might be related to the extension of S phase in iSLK-BAC16 cells by genipin treatment. Finally, genipin treatment at lower concentration could promote the KSHV latent replication. In contrast, the treatment at higher concentration could induce the KSHV lytic replication. In conclusion, genipin was shown to be an interesting reagent, which we used to manipulate KSHV life cycle in KSHV latently infected cells.

Correction: Genipin Enhances Kaposi's Sarcoma-Associated Herpesvirus Genome Maintenance.

[This corrects the article DOI: 10.1371/journal.pone.0163693.].