Ken-ichi Nishijima

Myocardial beta-Adrenergic Receptor Density Assessed by 11C-CGP12177 PET Predicts Improvement of Cardiac Function After Carvedilol Treatment in Patients with Idiopathic Dilated Cardiomyopathy

We evaluated whether myocardial β-adrenergic receptor (β-AR) density, as determined by 11C-CGP12177 PET, could predict improvement of cardiac function by β-blocker carvedilol treatment in patients with idiopathic dilated cardiomyopathy (IDC). Methods: Ten patients with IDC (left ventricular ejection fraction [LVEF] < 45%) were studied. Myocardial β-AR density was estimated using 11C-CGP12177 PET before treatment with carvedilol. Changes of LVEF in response to dobutamine infusion (ΔLVEF-dobutamine) were also measured by echocardiography. Changes of LVEF (ΔLVEF-carvedilol) were evaluated after 20 mo of carvedilol treatment. Results: Baseline myocardial β-AR density significantly correlated with ΔLVEF-carvedilol (r = −0.88, P < 0.001). In contrast, ΔLVEF-dobutamine did not correlate with ΔLVEF-carvedilol (P = 0.65). Myocardial β-AR density was the significant multivariate independent predictor of ΔLVEF-carvedilol (β = −0.88, P < 0.001) among univariate predictors, including functional class (r = 0.76, P < 0.05), plasma norepinephrine (r = 0.85, P < 0.01), LVEF (r = −0.64, P < 0.05), and age as confounding factors. Furthermore, myocardial β-AR density was significantly correlated with plasma norepinephrine (r = −0.79, P < 0.01) and LVEF (r = 0.70, P < 0.05). Conclusion: Myocardial β-AR density is more tightly related to improvement of LVEF-carvedilol than is cardiac contractile reserve in patients with IDC. Patients with decreased myocardial β-AR have higher resting adrenergic drive, as reflected by plasma norepinephrine, and may receive greater benefit from being treated by antiadrenergic drugs.

Decreased Myocardial β-Adrenergic Receptor Density in Relation to Increased Sympathetic Tone in Patients with Nonischemic Cardiomyopathy

Cardiac sympathetic function plays an important role in the regulation of left ventricular (LV) function and the pathophysiology of LV dysfunction. 11C-CGP-12177 (11C-CGP) has been used to assess myocardial β-adrenergic receptor (β-AR) density in vivo using PET. The aim of this study is to measure myocardial β-AR density in patients with nonischemic cardiomyopathy and to compare the measurements with various standard parameters of heart failure (HF), particularly with presynaptic function assessed by 123I- metaiodobenzylguanidine (123I-MIBG) imaging. Methods: 11C-CGP PET was performed on 16 patients with nonischemic cardiomyopathy and 8 age-matched healthy volunteers using a double injection method. A 11C-CGP dynamic scan for 75 min was performed after the injection of 11C-CGP with a high specific activity. After 30 min, 11C-CGP with a low specific activity was injected. The β-AR density of the whole LV was calculated on the basis of the graphical analysis method. Additionally, β-AR density was compared with LV ejection fraction (LVEF), sympathetic presynaptic function assessed using 123I-MIBG kinetics, and neurohormonal parameters. Results: The β-AR density of patients was significantly lower than that of healthy volunteers (3.80 ± 0.96 vs. 7.70 ± 1.92 pmol/mL; P < 0.0001). In the patients, β-AR density correlated significantly with LVEF (r = 0.62, P < 0.05). Furthermore, β-AR density correlated significantly with the 123I-MIBG washout rate (r = −0.68, P < 0.01) and delayed heart-to-mediastinum ratio (H/M ratio) (r = 0.61, P < 0.05). On the other hand, the correlation between β-AR density and early H/M ratio was not significant (r = 0.40, P = 0.13). The β-AR density of patients with severe HF (New York Heart Association functional [NYHA] class III) was significantly lower than that of those with NYHA functional class I or class II HF (3.24 ± 0.96 vs. 4.24 ± 0.73 pmol/mL; P < 0.05). Conclusion: A reduction in β-AR density measured by 11C-CGP PET was observed in patients with nonischemic cardiomyopathy. This downregulation may be due to the increased presynaptic sympathetic tone as assessed by 123I-MIBG imaging.

A simplified and improved synthesis of [11C]phosgene with iron and iron (III) oxide.

[11C]Phosgene ([11C]COCl2), a useful precursor for labeling several radiopharmaceuticals, is generally produced by catalytic oxidation of [11C]carbon tetrachloride over Fe granules, although in low yields or with poor reproducibility. In order to develop am improved synthesis of [11C]phosgene, two oxidizing agents, Fe2O3 and CuO, were examined. The yield of [11C]phosgene was significantly increased using Fe2O3 powder mixed with Fe granules, while the use of CuO alone, or CuO powder mixed with Fe granules resulted in an insignificant yield. The yield and specific activity of S- (-) [11C]CGP-12177 synthesized using Fe2O3 powder mixed with Fe granules were markedly higher than those synthesized by the previous methods using Fe granules alone or Fe granules mixed with Fe powder. Thus, in the present study, we developed a simple and practical method for the synthesis of [11C]phosgene, which provided an improved yield of S- (-) [11C]CGP-12177.

Evaluation of changes in the tumor microenvironment after sorafenib therapy by sequential histology and 18F-fluoromisonidazole hypoxia imaging in renal cell carcinoma

The mechanistic dissociation of ‘tumor starvation’ versus ‘vascular normalization’ following anti-angiogenic therapy is a subject of intense controversy in the field of experimental research. In addition, accurately evaluating changes of the tumor microenvironment after anti-angiogenic therapy is important for optimizing treatment strategy. Sorafenib has considerable anti-angiogenic effects that lead to tumor starvation and induce tumor hypoxia in the highly vascularized renal cell carcinoma (RCC) xenografts. 18F-fluoromisonidazole (18F-FMISO) is a proven hypoxia imaging probe. Thus, to clarify early changes in the tumor microenvironment following anti-angiogenic therapy and whether 18F-FMISO imaging can detect those changes, we evaluated early changes in the tumor microenvironment after sorafenib treatment in an RCC xenograft by sequential histological analysis and 18F-FMISO autoradiography (ARG). A human RCC xenograft (A498) was established in nude mice, for histological studies and ARG, and further assigned to the control and sorafenib-treated groups (80 mg/kg, per os). Mice were sacrificed on Days 1, 2, 3 and 7 in the histological study, and on Days 3 and 7 in ARG after sorafenib treatment. Tumor volume was measured every day. 18F-FMISO and pimonidazole were injected intravenously 4 and 2 h before sacrifice, respectively. Tumor sections were stained with hematoxylin and eosin and immunohistochemically with pimonidazole and CD31. Intratumoral 18F-FMISO distribution was quantified in ARG. Tumor volume did not significantly change on Day 7 after sorafenib treatment. In the histological study, hypoxic fraction significantly increased on Day 2, mean vessel density significantly decreased on Day 1 and necrosis area significantly increased on Day 2 after sorafenib treatment. Intratumoral 18F-FMISO distribution significantly increased on Days 3 (10.2-fold, p<0.01) and 7 (4.1-fold, p<0.01) after sorafenib treatment. The sequential histological evaluation of the tumor microenvironment clarified tumor starvation in A498 xenografts treated with sorafenib. 18F-FMISO hypoxia imaging confirmed the tumor starvation. 18F-FMISO PET may contribute to determine an optimum treatment protocol after anti-angiogenic therapy.

The accumulation mechanism of the hypoxia imaging probe "FMISO" by imaging mass spectrometry: possible involvement of low-molecular metabolites.

18F-fluoromisonidazole (FMISO) has been widely used as a hypoxia imaging probe for diagnostic positron emission tomography (PET). FMISO is believed to accumulate in hypoxic cells via covalent binding with macromolecules after reduction of its nitro group. However, its detailed accumulation mechanism remains unknown. Therefore, we investigated the chemical forms of FMISO and their distributions in tumours using imaging mass spectrometry (IMS), which visualises spatial distribution of chemical compositions based on molecular masses in tissue sections. Our radiochemical analysis revealed that most of the radioactivity in tumours existed as low-molecular-weight compounds with unknown chemical formulas, unlike observations made with conventional views, suggesting that the radioactivity distribution primarily reflected that of these unknown substances. The IMS analysis indicated that FMISO and its reductive metabolites were nonspecifically distributed in the tumour in patterns not corresponding to the radioactivity distribution. Our IMS search found an unknown low-molecular-weight metabolite whose distribution pattern corresponded to that of both the radioactivity and the hypoxia marker pimonidazole. This metabolite was identified as the glutathione conjugate of amino-FMISO. We showed that the glutathione conjugate of amino-FMISO is involved in FMISO accumulation in hypoxic tumour tissues, in addition to the conventional mechanism of FMISO covalent binding to macromolecules.

Biological characteristics of intratumoral [F-18]‑fluoromisonidazole distribution in a rodent model of glioma

Accurate imaging to identify hypoxic regions in tumors is key for radiotherapy planning. [F-18]-fluoromisonidazole ([F-18]-FMISO) is widely used for tumor hypoxia imaging and has the potential to optimize radio-therapy planning. However, the biological characteristics of intratumoral [F-18]-FMISO distribution have not yet been fully investigated. In hypoxic cells, the hypoxia-inducible factor-1 (HIF-1) target proteins that induce cellular prolif-HIF-1) target proteins that induce cellular proliferation and glucose metabolism, glucose transporter-1 (Glut-1) and hexokinase-II (HK-II), are upregulated. In this study, we determined the intratumoral distribution of [F-18]-FMISO by autoradiography (ARG) and compared it with pimonidazole uptake, expression of Glut-1, tumor proliferative activity (Ki-67 index) and glucose metabolism ([C-14]2-fluoro-2-deoxy-D-glucose uptake; [C-14]-FDG) in a glioma rat model. Five C6 glioma-bearing rats were injected with [F-18]-FMISO and [C-14]-FDG. After 90 min, the rats were injected with pimonidazole and 60 min later, the rats were sacrificed and tumor tissues were sectioned into slices. The adjacent slices were used for ARG and immunohistochemical (IHC) analyses of pimonidazole, Glut-1 and Ki-67. [F-18]-FMISO ARG images were divided into regions of high [F-18]-FMISO uptake (FMISO+) and low [F-18]-FMISO uptake (FMISO−). Pimonidazole and Glut-1 expression levels, Ki-67 index and [C-14]-FDG distribution were evaluated in the regions of interest (ROIs) placed on FMISO+ and FMISO−. [F-18]-FMISO distribution was generally consistent with pimonidazole distribution. The percentage of positively stained areas (% positive) of Glut-1 in FMISO+ was significantly higher compared to FMISO (24±8% in FMISO+ and 9±4% in FMISO−; P<0.05). There were no significant differences in Ki-67 index and [C-14]-FDG uptake between FMISO+ and FMISO− (for Ki-67, 10±5% in FMISO+ and 12±5% in FMISO−, P = ns; for [C-14]-FDG, 1.4±0.3% ID/g/kg in FMISO+ and 1.3±0.3% ID/g/kg in FMISO−, P = ns). Intratumoral [F-18]-FMISO distribution reflected tumor hypoxia and expression of the hypoxia-related gene product Glut-1; it did not, however, reflect tumor proliferation or glucose metabolism. Our findings help elucidate the biological characteristics of intratumoral [F-18]-FMISO distribution that are relevant to radiotherapy planning.

Stereoselective synthesis of 4a-fluoro-5,10-ethenobenzo[f]quinazolines via photo-Diels–Alder reaction of 5-fluoro-1,3-dimethyluracil with naphthalenes

UV-irradiation of a solution of 5-fluoro-1,3-dimethyluracil (5-FDMU) in aprotic media effected a stereoselective 1,4-cycloaddition reaction to give a barrelene derivative in high yield. In direct contrast, irradiation of a solution of 5-FDMU and naphthalene in a protic medium afforded 5-(1-naphthyl)uracil as the major product.

Increased [18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) yield with recycled target [18O]water: factors affecting the [18F]FDG yield

The reuse of [18O] water after being purified by distillation has been reported to give lower [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) yields, probably due to the presence of organic impurities. In our routine production of [18F]FDG, however, we observed increased [18F]FDG yields with recycled [18O]water. Thus, factors affecting [18F]FDG yield were examined using as-purchased (virgin) and recycled (by photochemical combustion and distillation) [18O]water. [18F]FDG was synthesized by nucleophilic 18F-fluorination on a quaternary 4-aminopyridinium resin. The recycled [18O]water gave an [18F]FDG yield significantly higher than did the virgin water, without any significant difference in the [18F]fluoride yield. Levels of several ionic impurities including Cl- and Ca2+ were significantly higher in the virgin [18O]water than in the recycled water, while significantly larger amounts of organic impurities were detected in the former. Hence, trace amounts of organic impurities were not responsible for the lower [18F]FDG yield. Chloride anion in the [18O]water may compete with [18F]fluoride to lower the [18F]FDG yield.

Chemical impurities in [18F]FDG preparations produced by solid-phase 18F-fluorination

[18F]FDG was produced by solid-phase 18F-fluorination (resin method) and chemical impurities were determined in the [18F]FDG preparations by ion chromatography. The major chemical impurities were D-glucose (90.5 +/- 6.4 microg/mL), 2-chloro-2-deoxy-D-glucose (11.8 +/- 2.7 microg/mL), and D-mannose (1.7 +/- 0.7 microg/mL), which were expected to be present by considering the synthetic routes. An FDG mass (0.5 +/- 0.2 microg/mL) was also detected in the preparations. No notable radiochemical impurities, including 2-[18F]fluoro-2-deoxy-D-mannose, were detected in the [18F]FDG preparations. Thus, the levels of several chemical impurities were determined in the [18F]FDG preparations produced by solid-phase 18F-fluorination.

Characterization of the role of sphingomyelin synthase 2 in glucose metabolism in whole-body and peripheral tissues in mice.

Sphingomyelin synthase 2 (SMS2) is a proposed potential therapeutic target for obesity and insulin resistance. However, the contributions of SMS2 to glucose metabolism in tissues and its possible therapeutic mechanisms remain unclear. Thus, to determine whole-body glucose utilization and the contributions of each insulin-targeted tissue to glucose uptake, we performed a glucose kinetics study, using the radiolabeled glucose analog (18)F-2-fluoro-2-deoxy-D-glucose ((18)F-FDG), in wild-type (WT) and SMS2 knockout (KO) mice. Insulin signaling was enhanced in the liver, white adipose tissue and skeletal muscle of SMS2 KO mice compared with those of WT mice. In addition, compared with in WT mice, blood clearance of (18)F-FDG was accelerated in SMS2 KO mice when they were fed either a normal or a high fat diet. (18)F-FDG uptake was also increased in insulin-targeted tissues such as skeletal muscle in the SMS2 KO mice. Whereas skeletal muscle sphingolipid content was not clearly affected, plasma levels of very long-chain fatty acid (VLCFA)-containing ceramides were markedly increased in SMS2 KO mice, compared with in WT mice. We also generated liver-conditional SMS2 KO mice and performed glucose and insulin tolerance tests on mice with a high fat diet. However, no significant effect was observed. Thus, our study provided evidence that genetic inhibition of SMS2 elevated glucose clearance through activation of glucose uptake into insulin-targeted tissues such as skeletal muscle by a mechanism independent of hepatic SMS2. Our findings further indicate that this occurs, at least in part, via indirect mechanisms such as elevation of VLCFA-containing ceramides.