Shingo Kasamatsu

Intra-tumoral distribution of 64Cu-ATSM: A comparison study with FDG

(64)Cu-labeled diacetyl-bis(N(4)-methylthiosemicarbazone) ((64)Cu-ATSM) is a promising agent for internal radiation therapy and imaging of hypoxic tissues. In the present study, the intra-tumoral distribution of (64)Cu-ATSM was investigated by comparing it to that of [(18)F]FDG and histological findings. VX2 tumors were implanted into Japanese white rabbits subcutaneously. (64)Cu-ATSM and [(18)F]FDG were co-injected intravenously and the tumor was dissected and cut into 1 mm thick slices 1 h after the injection. The uptake of (64)Cu-ATSM and [(18)F]FDG was measured using a dual-tracer autoradiographic technique. Histological cell biology was estimated from the optical microscopy of tumor sections. The major accumulation of (64)Cu-ATSM was observed around the outer rim of the tumor masses which consisted mainly of active cells and expected to be hypoxic. [(18)F]FDG was distributed more widely with highest levels in the inner regions where pre-necrotic cells were mainly observed. (64)Cu-ATSM appears to be useful for the detection of hypoxic but active tumor cell regions in vivo.

Cysteinyl-tRNA synthetase governs cysteine polysulfidation and mitochondrial bioenergetics

Cysteine hydropersulfide (CysSSH) occurs in abundant quantities in various organisms, yet little is known about its biosynthesis and physiological functions. Extensive persulfide formation is apparent in cysteine-containing proteins in Escherichia coli and mammalian cells and is believed to result from post-translational processes involving hydrogen sulfide-related chemistry. Here we demonstrate effective CysSSH synthesis from the substrate l-cysteine, a reaction catalyzed by prokaryotic and mammalian cysteinyl-tRNA synthetases (CARSs). Targeted disruption of the genes encoding mitochondrial CARSs in mice and human cells shows that CARSs have a crucial role in endogenous CysSSH production and suggests that these enzymes serve as the principal cysteine persulfide synthases in vivo. CARSs also catalyze co-translational cysteine polysulfidation and are involved in the regulation of mitochondrial biogenesis and bioenergetics. Investigating CARS-dependent persulfide production may thus clarify aberrant redox signaling in physiological and pathophysiological conditions, and suggest therapeutic targets based on oxidative stress and mitochondrial dysfunction.Cysteine hydropersulfides (CysSSH) are believed to have a cellular redox protective role. Here the authors show that these species can be produced from L-cysteine by cysteinyl-tRNA synthetases and that these enzymes are also involved in mitochondrial biogenesis and bioenergetics regulation.

Development of microwave-based automated nucleophilic [18F]fluorination system and its application to the production of [18F]flumazenil

INTRODUCTION This study presents the development of an automated radiosynthesis system integrating a microwave reactor and its subsequent application in the synthesis of [(18)F]flumazenil, a potentially useful compound in the evaluation of central benzodiazepine receptor density. METHODS Preparation of dry [K/K(222)](+18)F(-) complex and radiofluorination of the nitro-flumazenil precursor were achieved using the developed microwave-based radiosynthesis system. The crude product was prepurified in a C18 cartridge followed by reversed-phase preparative high-performance liquid chromatography. The isolated [(18)F]flumazenil was evaporated in vacuo and reconstituted in an ethanol-free solution. RESULTS Optimum incorporation of (18)F(-) in the nitro-precursor was achieved in 5 min time utilizing 2 mg of precursor in N,N-dimethylformamide reacted at 160 degrees C which gave an incorporation yield of 40+/-5%. The radiochemical yield obtained at the end of synthesis was 26+/-4% (EOB) with a radiochemical purity of >99% and a total synthesis time of about 55-60 min. The produced [(18)F]flumazenil was observed to be stable for at least 8 h. CONCLUSION The developed [(18)F]flumazenil radiosynthesis system offers shorter reaction time, simplicity in operation and applicability for use in routine clinical practice.

Vonoprazan is superior to proton pump inhibitors in healing artificial ulcers of the stomach post-endoscopic submucosal dissection: A propensity score-matching analysis.

Proton pump inhibitors (PPI) are effective at healing artificial ulcers after endoscopic submucosal dissection (ESD) for gastric neoplasms; however, the efficacy of vonoprazan is not completely understood. The aim of the present study was to determine the healing effect of vonoprazan on artificial ulcers post‐gastric ESD relative to PPI.

Redox Signaling Regulated by Cysteine Persulfide and Protein Polysulfidation

For decades, reactive persulfide species including cysteine persulfide (CysSSH) have been known to exist endogenously in organisms. However, the physiological significance of endogenous persulfides remains poorly understood. That cystathionine β-synthase and cystathionine γ-lyase produced CysSSH from cystine was recently demonstrated. An endogenous sulfur transfer system involving CysSSH evidently generates glutathione persulfide (GSSH) that exists at concentrations greater than 100 μM in vivo. Because reactive persulfide species such as CysSSH and GSSH have higher nucleophilicity than parental cysteine (Cys) and glutathione do, these reactive species exhibit strong scavenging activities against oxidants, e.g., hydrogen peroxide, and electrophiles, which contributes to redox signaling regulation. Also, several papers indicated that various proteins and enzymes have Cys polysulfides including CysSSH at their specific Cys residues, which is called protein polysulfidation. Apart from the redox signaling regulatory mechanism, another plausible function of protein polysulfidation is providing protection for protein thiol residues against irreversible chemical modification caused by oxidants and electrophiles. Elucidation of the redox signaling regulatory mechanism of reactive persulfide species including small thiol molecules and thiol-containing proteins should lead to the development of new therapeutic strategies and drug discoveries for oxidative and electrophilic stress-related diseases.

Protein polysulfidation-dependent persulfide dioxygenase activity of ethylmalonic encephalopathy protein 1

Reactive persulfide species such as glutathione persulfide (GSSH) are highly abundant biomolecules. Persulfide dioxygenase (also called ethylmalonic encephalopathy protein 1, ETHE1) reportedly metabolizes GSSH to GSH with simultaneous oxygen consumption. How ETHE1 activity is regulated is still unclear, however. In this study, we describe the possible role of protein polysulfidation in the catalytic activity of ETHE1. We first found that ETHE1 catalyzed the persulfide dioxygenase reaction mostly for glutathione polysulfides, GS-(S)n-H, as well as for GSSH, but not for other endogenous persulfides such as cysteine and homocysteine persulfides/polysulfides. We then developed a novel method to detect protein polysulfidation and named it the polyethylene glycol-conjugated maleimide-labeling gel shift assay (PMSA). PMSA analysis indicated that most cysteine residues in ETHE1 were polysulfidated. Site-directed mutagenesis of cysteine residues in ETHE1 combined with liquid chromatography tandem mass spectrometry for polysulfidation determination surprisingly indicated that the Cys247 residue was important for polysulfidation of other Cys residues and that the C247S mutant possessed no persulfide dioxygenase activity. These results suggested that ETHE1 is a major enzyme regulating endogenous GSSH/GS-(S)n-H and that its activity is controlled by polysulfidation of the Cys247 residue.

Redox regulation of electrophilic signaling by reactive persulfides in cardiac cells

ABSTRACT Maintaining a redox balance by means of precisely controlled systems that regulate production, and elimination, and metabolism of electrophilic substances (electrophiles) is essential for normal cardiovascular function. Electrophilic signaling is mainly regulated by endogenous electrophiles that are generated from reactive oxygen species, nitric oxide, and the derivative reactive species of nitric oxide during stress responses, as well as by exogenous electrophiles including compounds in foods and environmental pollutants. Among electrophiles formed endogenously, 8‐nitroguanosine 3′,5′‐cyclic monophosphate (8‐nitro‐cGMP) has unique cell signaling functions, and pathways for its biosynthesis, signaling mechanism, and metabolism in cells have been clarified. Reactive persulfide species such as cysteine persulfides and polysulfides that are endogenously produced in cells are likely to be involved in 8‐nitro‐cGMP metabolism. These new aspects of redox biology may stimulate innovative and multidisciplinary research in cardiovascular physiology and pathophysiology. In our review, we focus on the redox‐dependent regulation of electrophilic signaling via reduction and metabolism of electrophiles by reactive persulfides in cardiac cells, and we include suggestions for a new therapeutic strategy for cardiovascular disease. Graphical abstract Figure. No caption available. HighlightsCardiovascular electrophilic signaling is controlled by reactive persulfides.Electrophilic signaling by 8‐nitro‐cGMP is regulated by reactive persulfides.Long‐term exposure to electrophiles may increase the risk for cardiovascular diseases.Reactive persulfides suppress 8‐nitro‐cGMP‐mediated cardiac early senescence.Excessive activation of Nrf2 antioxidant response may cause reductive stress in heart.

Heparin-bridging therapy is associated with a high risk of post-polypectomy bleeding regardless of polyp size.

Evidence regarding safety and efficacy of heparin‐bridging therapy for colonoscopic polypectomy remains scarce. The aim of the present study was to evaluate the risk of post‐polypectomy bleeding (PPB) in patients receiving heparin‐bridging therapy.

Endoscopy-Guided Evaluation of Duodenal Mucosal Permeability in Functional Dyspepsia

OBJECTIVES: The pathophysiology of functional dyspepsia (FD) is not fully understood. Impaired duodenal mucosal integrity characterized by increased mucosal permeability and/or low‐grade inflammation was reported as potentially important etiologies. We aimed to determine the utility of a recently developed simple catheterization method to measure mucosal admittance (MA), the inverse of mucosal impedance, for evaluation of duodenal mucosal permeability in patients with FD. METHODS: We conducted two prospective studies. In the first study, duodenal MA of 23 subjects was determined by catheterization during upper endoscopy, and transepithelial electrical resistance (TEER) of duodenal biopsy samples in Ussing chambers was measured to assess the correlation between MA and TEER. In the second study, duodenal MA of 21 patients with FD fulfilling the Rome III criteria was compared with that of 23 healthy subjects. RESULTS: The mean MA and TEER values were 367.5±134.7 and 24.5±3.7 Ω cm2, respectively. There was a significant negative correlation between MA and TEER (r=−0.67, P=0.0004, Pearsons correlation coefficient). The mean MA in patients with FD was significantly higher than that in healthy subjects (455.7±137.3 vs. 352.1±66.9, P=0.002, unpaired t‐test). No procedure‐related complications were present. CONCLUSIONS: We demonstrated the presence of increased duodenal mucosal permeability in patients with FD by MA measurement using a simple catheterization method during upper endoscopy.

Cold polypectomy for duodenal adenomas: a prospective clinical trial

Background and study aims Endoscopic resection is effective in treating nonampullary duodenal adenomas but has a high incidence of complications. Cold polypectomy, including cold forceps polypectomy (CFP) and cold snare polypectomy (CSP), is safe and effective in treating colorectal polyps. However, its utility in sporadic nonampullary duodenal adenomas has not been investigated. The purpose of this prospective study was to examine the safety and efficacy of cold polypectomy for sporadic nonampullary duodenal adenomas. Patients and methods Between March 2015 and June 2016, patients who were endoscopically diagnosed with sporadic nonampullary duodenal adenomas up to 6 mm underwent cold polypectomy. Patients with pathologically confirmed adenomas underwent endoscopic biopsy 3 months after resection. The main outcomes of interest were incomplete resection and complications. Results Overall, 39 lesions in 30 patients were removed via cold polypectomy (CFP, 9 lesions in 8 patients; CSP, 30 lesions in 22 patients). Seven of 9 (77.8 %) and 29 of 30 (96.7 %) lesions were removed en bloc via CFP and CSP, respectively. Pathologically, 34 of the 39 lesions (87.2 %) were confirmed as adenomas, and their mean size was 3.9 ± 1.2 mm (range 2 - 6 mm). Of the 34 adenomas, 20 (58.8 %) were R0 resection lesions, of which 3 of 9 (33.3 %) and 17 of 25 (68.0 %) had undergone CFP and CSP, respectively. No delayed bleeding or intraprocedural/delayed perforation was observed. All 30 patients with the 34 pathologically confirmed adenomas underwent upper gastrointestinal endoscopy 3 months after cold polypectomy, and no morphological or pathological recurrence was identified. Conclusions In this small study, cold polypectomy appeared to be safe and effective in treating diminutive and small sporadic nonampullary duodenal adenomas.(Clinical trial registration number: UMIN000016829).