Convenient Application of a Compact-Type Magnetic Resonance Imager with Blood Pool Contrast Agent Gadolinium-Conjugated Dextran to Assess Vascular Abnormalities in Experimental Animals.

Vascular lesions are symptomatic of lifestyle-related diseases and include blood clots, coarctations, aneurysms, and apoplexy. Furthermore, increased blood vessel permeability is usually observed in tumors. To develop therapeutic drugs treating vascular lesions and tumors, methods with which the vascular abnormalities can be readily assessed in experimental animals are necessary. In this paper, a laboratory-size magnetic resonance imaging (MRI) system with permanent magnets, a compact-type MRI, was used to assess vascular abnormalities. Blood vessels in the head of a mouse were clearly visualized with the compact-type MRI in combination with gadolinium-diethylenetriamine-N,N,N',N″,N″-pentaacetic acid chelate (Gd-DTPA)-linked dextran (Gd-Dex) as blood pool contrast agents. The rat middle cerebral artery was imaged, and artery occlusion was identified. The difference between normal and occluded rats became more apparent upon intravenous injection of sodium nitroprusside, a nitric oxide (NO) donor. The system also visualized poor circulation in a rat saphenous artery by femoral artery occlusion. In a tumor-bearing mouse, a compact-type MRI visualized accumulation of Gd-Dex similar to that of small molecular Gd-DTPA, in the rim of tumor. Gd-Dex accumulation was more consistent than that of Gd-DTPA. Tumor vasculature was characterized by estimating the plasma-to-tumor interstitial tissue transfer constant, Ktrans, of Gd-Dex and fractional plasma volume, Vp, using image data. These results demonstrate the efficacy of a compact-type MRI in combination with Gd-Dex for vascular abnormality assessment in both mice and rats.

Protective effects of 2-aminoethylthiosulfuric acid and structurally analogous organosulfur compounds against ionizing radiation.

High efficacy and minimal toxicity radioprotectors are desirable options for the hazards posed by nuclear medical and energy technologies and the dangers presented by nuclear weapons in an unstable global situation. Although cysteamine is an effective radioprotector, it has considerable toxicity. In this study, the protective effects of the less toxic organosulfur compounds 2-aminoethylthiosulfate (AETS), thiotaurine (TTAU), and hypotaurine (HTAU) against X-ray damage in mice were compared with that of cysteamine. Intraperitoneal injection of either AETS or cysteamine (2.2 mmol/kg body weight) 30 min before X-ray irradiation (7.0 Gy) provided 100% survival for 30 days, limited the decrease in erythrocytes and neutrophils over 9 days, and reduced damage to bone marrow and spleen over 9 days. Neither TTAU nor HTAU provided any protection. In mice, 30 min after AETS administration, non-protein thiol content increased in the spleen, indicating cysteamine generation by AETS hydrolysis, the active protective species of AETS. All examined compounds scavenged •OH under diffusion control in aqueous solution, which is inconsistent with the difference in the protective effects among the compounds. The results indicate that AETS protects animals from ionizing radiation by several mechanisms, including scavenging •OH as cysteamine.

Synthesis of Fluorescent Probes Targeting Tumor-Suppressor Protein FHIT and Identification of Apoptosis-Inducing FHIT Inhibitors.

For the early diagnosis of cancer, leading to a better chance of full recovery, marker genes whose expression is already altered in precancerous lesions are desirable, and the tumor-suppressor gene FHIT is one candidate. The gene product, FHIT protein, has a unique dinucleoside triphosphate hydrolase (AP3Aase) activity, and in this study, we designed and synthesized a series of FHIT fluorescent probes utilizing this activity. We optimized the probe structure for high and specific reactivity with FHIT and applied the optimized probe in a screening assay for FHIT inhibitors. Screening of a compound library with this assay identified several hits. Structural development of a hit compound afforded potent FHIT inhibitors. These inhibitors induce apoptosis in FHIT-expressing cancers via caspase activation. Our results support the idea that FHIT binders, no matter whether inhibitors or agonists of AP3Aase activity, might be promising anticancer agents.

Synthesis of artificial substrate based on inhibitor for detecting LSD1 activity.

Lysine methylation is one of the most important modification, which is regulated by histone lysine methyltransferases and histone lysine demethylases. Lysine-specific demethylase 1 (LSD1) specifically demethylates mono- and dimethyl-lysine on histone H3 (H3K4Me/Me2, H3K9Me/Me2) to control chromatin structure, resulting in transcriptional repression or activation of target genes. Furthermore, LSD1 is overexpressed in various cancers. Therefore, LSD1 inhibitors would be not only potential therapeutic agents for cancers but also chemical tools to research biological significance of LSD1 in physiological and pathological events. However, known assay methods to date have some inherent drawbacks. The development of simple method in detecting LSD1 activity has been indispensable to identify useful inhibitors. In this study, we designed and synthesized artificial substrates based on inhibitors of LSD1 to examine LSD1 activity by an absorption increment.

Ratiometric assay of CARM1 activity using a FRET-based fluorescent probe.

One of the regulatory mechanisms of epigenetic gene expression is the post-translational methylation of arginine residues, which is catalyzed by protein arginine methyltransferases (PRMTs). Abnormal expression of PRMT4/CARM1, one of the PRMTs, is associated with various diseases, including cancers. Here, we designed and synthesized a Förster resonance energy transfer (FRET)-based probe, FRC, which contains coumarin and fluorescein fluorophores at the N-terminus and C-terminus of a peptide containing an arginine residue within an appropriate amino acid sequence to serve as a substrate of CARM1; the two fluorophores act as a FRET donor and a FRET acceptor, respectively. Since trypsin specifically hydrolyzes the arginine residue, but not a monomethylarginine or dimethylarginine residue, CARM1 activity can be evaluated from the change of the coumarin/fluorescein fluorescence ratio of FRC in the presence of trypsin.