Antiandrogenic Effects of a Polyphenol in Carex kobomugi through Inhibition of Androgen Synthetic Pathway and Downregulation of Androgen Receptor in Prostate Cancer Cell Lines.

Prostate cancer (PC) represents the most common cancer disease in men. Since high levels of androgens increase the risk of PC, androgen deprivation therapy is the primary treatment; however this leads to castration-resistant PC (CRPC) with a poor prognosis. The progression to CRPC involves ectopic androgen production in the adrenal glands and abnormal activation of androgen signaling due to mutations and/or amplification of the androgen receptor (AR) as well as activation of androgen-independent proliferative pathways. Recent studies have shown that adrenal-derived 11-oxygenated androgens (11-ketotestosterone and 11-ketodihydrotestosterone) with potencies equivalent to those of traditional androgens (testosterone and dihydrotestosterone) are biomarkers of CRPC. Additionally, dehydrogenase/reductase SDR family member 11 (DHRS11) has been reported to be a 17ß-hydroxysteroid dehydrogenase that catalyzes the production of the 11-oxygenated and traditional androgens. This study was conducted to evaluate the pathophysiological roles of DHRS11 in PC using three LNCaP, C4-2 and 22Rv1 cell lines. DHRS11 silencing and inhibition resulted in suppression of the androgen-induced expression of AR downstream genes and decreases in the expression of nuclear AR and the proliferation marker Ki67, suggesting that DHRS11 is involved in androgen-dependent PC cell proliferation. We found that 5,7-dihydroxy-8-methyl-2-[2-(4-hydroxyphenyl)ethenyl]-4H-1-benzopyran-4-one (Kobochromone A, KC-A), an ingredient in the flowers of Carex kobomugi, is a novel potent DHRS11 inhibitor (IC50 = 0.35 µM). Additionally, KC-A itself decreased the AR expression in PC cells. Therefore, KC-A suppresses the androgen signaling in PC cells through both DHRS11 inhibition and AR downregulation. Furthermore, KC-A enhanced the anticancer activity of abiraterone, a CRPC drug, suggesting that it may be a potential candidate for the development of drugs for the prevention and treatment of CRPC.

Identification and immunohistochemical characterization of G-quadruplexes in mouse brain.

Guanine-rich DNA and RNA can form a four-stranded structure, termed G-quadruplexes (G4s) in vitro as well as in cells. The formation of G4 is implicated in many physiological events, such as gene transcription, translation, and epigenetics. However, the presence of G4 has not been revealed in the brain. Here, we demonstrate the localization of G4 in the mouse brain by immunohistochemical analysis. In cultured mouse forebrain neurons, numerous punctate G4 foci were observed in nuclei as well as in cytoplasmic areas, including axons, dendrites, and postsynapses. Interestingly, the G4 foci in nuclei show more marked co-localizations with the bright spots of DAPI-positive heterochromatin clusters in mature neurons compared to immature ones. In slices from adult mouse brain, the G4 foci were distributed throughout the brain but were particularly prominent in the hippocampus, olfactory bulb, and cerebellum. In the hippocampus, G4 foci were strongly expressed in neurons and weakly in astrocytes. Consistent with the results in cultured neurons, the nuclear G4 foci were co-localized with heterochromatin in calbindin-positive mature granule cells but less in doublecortin-positive neuronal progenitor cells in the dentate gyrus. Electron microscopic immunolabeling revealed G4 foci on nucleolus-associated chromosomal domains (NADs) and cytoplasm in the adult mouse hippocampal CA1 region. These observations suggest potentially critical roles of G4 in neuronal developmental stages through regulating chromatin structures and cytoplasmic metabolism of RNA.

Perspectives for Applying G-Quadruplex Structures in Neurobiology and Neuropharmacology.

The most common form of DNA is a right-handed helix or the B-form DNA. DNA can also adopt a variety of alternative conformations, non-B-form DNA secondary structures, including the DNA G-quadruplex (DNA-G4). Furthermore, besides stem-loops that yield A-form double-stranded RNA, non-canonical RNA G-quadruplex (RNA-G4) secondary structures are also observed. Recent bioinformatics analysis of the whole-genome and transcriptome obtained using G-quadruplex-specific antibodies and ligands, revealed genomic positions of G-quadruplexes. In addition, accumulating evidence pointed to the existence of these structures under physiologically- and pathologically-relevant conditions, with functional roles in vivo. In this review, we focused on DNA-G4 and RNA-G4, which may have important roles in neuronal function, and reveal mechanisms underlying neurological disorders related to synaptic dysfunction. In addition, we mention the potential of G-quadruplexes as therapeutic targets for neurological diseases.

Flavonol glycosides of Rosa multiflora regulates intestinal barrier function through inhibiting claudin expression in differentiated Caco-2 cells.

Eijitsu, the fruits of Rosa multiflora Thunberg, is a traditional Japanese natural medicine and used as purgatives. The active constituents were identified as flavonol glycosides, multiflorin A (MF), and multinoside A (MSA), but mechanism of the purgative action is still unknown. We hypothesized that the flavonol glycosides 1 and 2 may exhibit the purgative actions through modulating intestinal epithelial barrier function. Then, this study aimed to investigate their effects on intestinal epithelial barrier function and possible molecular mechanisms in human intestinal Caco-2 cells. MF and MSA decreased transepithelial electrical resistance and increased paracellular permeability of Caco-2 cell monolayers. Expression of claudins (CLDNs) involved in paracellular permeability of ions and low-molecular substances was significantly decreased by the treatment with MF or MSA. The compounds increased the ratio of N-cadherin/E-cadherin, expression of transforming growth factor-ß and Slug, and phosphorylation level of Smad3, suggesting epithelial-mesenchymal transition activation, and epithelial-mesenchymal transition inhibition by transforming growth factor-ß receptor kinase inhibitors completely recovered the decreased CLDNs expression caused by MF and MSA. Moreover, the increased paracellular permeability and the decreased CLDNs expression by the treatment with MF or MSA for 24 hours recovered to the same extent as the untreated group with the compounds by continuous culture in the growth medium alone for 48 hours. These results suggest that Eijitsu may be effective in preventing or relieving constipation symptoms, unless used chronically.