RESUMEN

This study demonstrated the tracking of ulcerative colitis, which is considered a stressful immune disease. Although there are many ways to test for this disease including dependence on gases, dyes, and painful anal endoscopy, these treatment modalities have many disadvantages. Hence, it is the utmost need of time to discover new methods to detect this chronic immune disease and to avoid the defects of traditional methodologies. Sulfasalazine (SSD) was labeled with iodine-131 (half-life: 8 days, Energy: 971 keV) under optimum reaction conditions including the amount of reducing agent, pH factor, chloramine-T (Ch-T) amount, and incubation period. Characterization was performed using 1 H/ 13 C-NMR, ESI-MS, and HPLC (UV/ Radio) techniques. The biodistribution study was performed in normal and ulcerative mice models, and in silico molecular docking study was performed to evaluate the possible mechanism of action to target peroxisome proliferator-activated receptor gamma (PPARγ). The high radiolabeling yield of [131 I]-sulfasalazine ([131 I]-SSD) was achieved ≥90% through the direct labeling method with radioactive iodine-131 in the presence of chloramine-T (100 µg). The radiotracer [131 I]-SSD was observed to be stable in normal saline and freshly eluted serum up to 12 hr at ambient temperature (37℃ ± 2℃). The radiotracer [131 I]-SSD showed the highest uptake in the targeted organ (i.e., ulcerative colon) which was observed to be ≥75% injected dose per gram (% ID/g) organ for 24 hr postinjection (p.i). Furthermore, in silico data collected from molecular modeling analysis of SSD and [131 I]-SSD with antimicrobial protein (PDB code: 3KEG) and peroxisome proliferator-activated receptor gamma (PPARγ) (PDB code: 4XTA) showed azoreductase activity and high binding potential for PPAR-γ site, respectively. The results of biological studies obtained in this study enlighten the usefulness of radiotracer [131 I]-SSD as a potential imaging agent for ulcerative colitis.

Asunto(s)

Colitis Ulcerosa/radioterapia , Isótopos de Yodo/química , Sulfasalazina/química , Animales , Cloraminas/química , Defensinas/química , Modelos Animales de Enfermedad , Humanos , Concentración de Iones de Hidrógeno , Isótopos de Yodo/farmacología , Cinética , Masculino , Ratones , Simulación del Acoplamiento Molecular , Nitrorreductasas/química , Oxidación-Reducción , PPAR gamma/metabolismo , Proteínas de Plantas/química , Tomografía de Emisión de Positrones , Unión Proteica , Conformación Proteica , Coloración y Etiquetado , Distribución Tisular

RESUMEN

High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope (125)I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual (125)I atoms into (125)Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic (125)I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies.

Asunto(s)

Partículas beta , Electrones , Oro/química , Membranas Artificiales , Isótopos de Yodo/química

RESUMEN

In this study, nanosuspension of stable iodine ((127)I) was prepared by nanoprecipitation process in microfluidic devices. Then, size of particles was optimized using artificial neural networks (ANNs) modeling. The size of prepared particles was evaluated by dynamic light scattering. The response surfaces obtained from ANNs model illustrated the determining effect of input variables (solvent and antisolvent flow rate, surfactant concentration, and solvent temperature) on the output variable (nanoparticle size). Comparing the 3D graphs revealed that solvent and antisolvent flow rate had reverse relation with size of nanoparticles. Also, those graphs indicated that the solvent temperature at low values had an indirect relation with size of stable iodine ((127)I) nanoparticles, while at the high values, a direct relation was observed. In addition, it was found that the effect of surfactant concentration on particle size in the nanosuspension of stable iodine ((127)I) was depended on the solvent temperature. Nanoprecipitation process of stable iodine (127I) and optimization of particle size using ANNs modeling.

Asunto(s)

Isótopos de Yodo/química , Técnicas Analíticas Microfluídicas , Modelos Químicos , Nanopartículas , Nanotecnología/métodos , Redes Neurales de la Computación , Tecnología Farmacéutica/métodos , Precipitación Química , Dispersión Dinámica de Luz , Dispositivos Laboratorio en un Chip , Técnicas Analíticas Microfluídicas/instrumentación , Nanotecnología/instrumentación , Tamaño de la Partícula , Solventes/química , Tensoactivos/química , Tecnología Farmacéutica/instrumentación , Temperatura

RESUMEN

Although antigen-binding fragments (Fabs) of antibodies constitute established tracers for in vivo radiodiagnostics, their functionality is hampered by a very short circulation half-life. PASylation, the genetic fusion with a long, conformationally disordered amino acid chain comprising Pro, Ala and Ser, provides a convenient way to expand protein size and, consequently, retard renal filtration. Humanized αHER2 and αCD20 Fabs were systematically fused with 100 to 600 PAS residues and produced in E. coli. Cytofluorimetric titration analysis on tumor cell lines confirmed that antigen-binding activities of the parental antibodies were retained. The radio-iodinated PASylated Fabs were studied by positron emission tomography (PET) imaging and biodistribution analysis in mouse tumor xenograft models. While the unmodified αHER2 and αCD20 Fabs showed weak tumor uptake (0.8% and 0.2% ID/g, respectively; 24 h p.i.) tumor-associated radioactivity was boosted with increasing PAS length (up to 9 and 26-fold, respectively), approaching an optimum for Fab-PAS400. Remarkably, 6- and 5-fold higher tumor-to-blood ratios compared with the unmodified Fabs were measured in the biodistribution analysis (48 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200, respectively. These findings were confirmed by PET studies, showing high imaging contrast in line with tumor-to-blood ratios of 12.2 and 5.7 (24 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200. Even stronger tumor signals were obtained with the corresponding αCD20 Fabs, both in PET imaging and biodistribution analysis, with an uptake of 2.8% ID/g for Fab-PAS100 vs. 0.24% ID/g for the unmodified Fab. Hence, by engineering Fabs via PASylation, plasma half-life can be tailored to significantly improve tracer uptake and tumor contrast, thus optimally matching reagent/target interactions.

Asunto(s)

Anticuerpos Antineoplásicos , Antígenos CD20 , Fragmentos Fab de Inmunoglobulinas , Marcaje Isotópico , Neoplasias Experimentales , Tomografía de Emisión de Positrones , Receptor ErbB-2 , Animales , Anticuerpos Antineoplásicos/química , Anticuerpos Antineoplásicos/farmacología , Línea Celular Tumoral , Femenino , Xenoinjertos , Humanos , Fragmentos Fab de Inmunoglobulinas/química , Fragmentos Fab de Inmunoglobulinas/genética , Fragmentos Fab de Inmunoglobulinas/farmacología , Isótopos de Yodo/química , Isótopos de Yodo/farmacocinética , Isótopos de Yodo/farmacología , Ratones , Trasplante de Neoplasias , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/metabolismo , Neoplasias Experimentales/patología

RESUMEN

The radionuclides released from the Fukushima Daiichi nuclear power plant in 2011 pose a health risk. In this study, we estimated the 1st-year average doses resulting from the intake of iodine 131 (131I) and cesium 134 and 137 (134Cs and 137Cs) in drinking water and food ingested by citizens of Fukushima City (∼50 km from the nuclear power plant; outside the evacuation zone), Tokyo (∼230 km), and Osaka (∼580 km) after the accident. For citizens in Fukushima City, we considered two scenarios: Case 1, citizens consumed vegetables bought from markets; Case 2, citizens consumed vegetables grown locally (conservative scenario). The estimated effective doses of 134Cs and 137Cs agreed well with those estimated through market basket and food-duplicate surveys. The average thyroid equivalent doses due to ingestion of 131I for adults were 840 µSv (Case 1) and 2700 µSv (Case 2) in Fukushima City, 370 µSv in Tokyo, and 16 µSv in Osaka. The average effective doses due to 134Cs and 137Cs were 19, 120, 6.1, and 1.9 µSv, respectively. The doses estimated in this study were much lower than values reported by the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiation, whose assessments lacked validation and full consideration of regional trade in foods, highlighting the importance of including regional trade. The 95th percentile effective doses were 2-3 times the average values. Lifetime attributable risks (LARs) of thyroid cancers due to ingestion were 1.7-37×10-6 (Case 1) and5.6-79×10-6 (Case 2) in Fukushima City, 0.73-13×10-6 in Tokyo, and 0.04-0.49×10- 6 in Osaka. The contributions of LARs of thyroid cancers due to ingestion were 5.4%-11% of all exposure (Case 1) and 11%-25% (Case 2) in Fukushima City [corrected].

Asunto(s)

Isótopos de Yodo/química , Radioisótopos/química , Glándula Tiroides/efectos de la radiación , Verduras/química , Adolescente , Adulto , Radioisótopos de Cesio/química , Niño , Preescolar , Agua Potable/análisis , Femenino , Alimentos , Accidente Nuclear de Fukushima , Humanos , Lactante , Masculino , Plantas de Energía Nuclear , Embarazo , Dosis de Radiación , Monitoreo de Radiación/métodos , Liberación de Radiactividad Peligrosa , Riesgo , Tokio , Adulto Joven

RESUMEN

Cancers are often with spontaneous or therapeutic necrosis that could be utilized as a generic target for developing new treatments. The purpose of this study was to investigate the biodistribution and pharmacokinetics of radioiodinated hypericin (Hyp), a naturally occurring compound, after intravenous (i.v.) injection in a rat model of liver and muscle necrosis (n = 42), and evaluate its necrosis affinity. Hyp was labeled with (131)I with labeling efficiency >99%. After incubating in solution/rat plasma for 8 days, radiochemical purity of (131)I-Hyp remained 98.1 and 97.1%, respectively, indicating good in vitro stability. SPECT-CT images at 24 h after i.v. injection of (131)I-Hyp in rats with induced liver and muscle necrosis showed obvious tracer absorption in necrotic tissues. Biodistribution studies revealed that the percentage of the injected dose per gram of tissue (%ID/g) evolved from 1.9 %ID/g at 6 h, through a maximum 3.0 %ID/g at 12 h, to 1.0 %ID/g at 192 h in necrotic liver. Pharmacokinetics studies revealed that the terminal elimination half-life, total body clearance and area under the curve of (131)I-Hyp were 32.7 h, 9.2 L/h/kg and 1.6 MBq/L*h, respectively. These results demonstrated that (131)I-Hyp features a long blood circulation in animals and persistent retention in necrotic tissues. Therefore, (131)I-labeled Hyp could be a broad-spectrum anti-tumor agent with a cost much cheaper relative to the biological agents such as monoclonal antibodies.

Asunto(s)

Isótopos de Yodo/administración & dosificación , Isótopos de Yodo/química , Necrosis/tratamiento farmacológico , Perileno/análogos & derivados , Animales , Antracenos , Área Bajo la Curva , Semivida , Marcaje Isotópico/métodos , Masculino , Necrosis/metabolismo , Perileno/química , Perileno/farmacocinética , Perileno/farmacología , Radiofármacos/química , Radiofármacos/farmacocinética , Radiofármacos/farmacología , Ratas , Ratas Wistar , Distribución Tisular

RESUMEN

In research and development sufficiently high and constant plasma levels of drug candidates are often requested, but simple solutions of hydrophobic drugs delivered from the commonly used micro-osmotic pumps cannot meet these demands. Nanosuspensions released from implanted osmotic devices can be a strategy to overcome this challenge but little is known about their pharmacokinetic behavior after subcutaneous application. In the current study, four different nanosuspension formulations containing iodinated fenofibrate were prepared, physicochemically characterized and investigated concerning their in-vitro release kinetics from osmotic pumps. One nanosuspension of lower viscosity exhibited thereby an unexpectedly first order release kinetics, whereas the higher viscous counterpart was released in the expected zero-order manner. To assess the relation of the in-vitro release kinetics to the in-vivo fate of nanosuspensions, various [(131)I] iodinated fenofibrate formulations were subcutaneously applied to mice. The biodistribution was followed by means of γ-scintigraphy and γ-scintillation. Two different nanosuspensions released from osmotic pumps were compared to bolus injections of a nanosuspension and an organic drug solution. The distribution and elimination of the bolus injected drug solution were almost completed within 48h. In contrast, a long lasting (>1week) depot at the injection site was formed by the bolus injected nanosuspension. Ex vivo examination of the organs showed a sustained, but exponential decrease of the radiolabel concentration. More constant drug levels in the organs were achieved within the nanosuspensions released from osmotic pumps. The organ levels of [(131)I] labeled fenofibrate were found to be more constant in case of the pump with the higher viscous nanosuspension in contrast to the lower viscous counterpart. However, the very different release profiles of the lower and higher viscous nanosuspension observed in-vitro were not observed in-vivo, as both pumps showed zero order release. In conclusion, nanosuspensions of poorly soluble compounds released from subcutaneously implanted osmotic pumps can be a suitable approach in pharmacokinetic studies. Although the in-vivo release of nanosuspensions differed in the expected release profile from the in-vitro test results, these in-vitro release tests present a valuable tool for the pre-selection of suitable nanosuspension candidates.

Asunto(s)

Fenofibrato/administración & dosificación , Bombas de Infusión Implantables , Animales , Sistemas de Liberación de Medicamentos , Femenino , Fenofibrato/química , Fenofibrato/farmacocinética , Isótopos de Yodo/química , Ratones , Nanoestructuras , Suspensiones , Distribución Tisular

RESUMEN

BACKGROUND: Microdosing is a technique for studying the behavior of compounds in vivo at 1/100th of the dose of a test substance calculated, based on animal data, to yield a pharmacologic effect. In microdosing, use is made of accelerator MS (AMS). In this study, we investigated whether (129)I-labeling of proteins with subsequent AMS measurements is a suitable method to perform microdose studies with therapeutic proteins. We used erythropoietin (EPO) as a case study. RESULTS: In an animal study with (129)I-labeled EPO in Han-Wistar rats, an increase of (129)I-EPO is observed after dose administration. The half-life was found to be 2 and 5.5 h for two different EPOs. These results are in accordance with expected values. CONCLUSION: Although further research is required, (129)I-labeling of proteins seems a feasible method for AMS microdose studies with peptide and protein drugs, such as biosimilars.

Asunto(s)

Descubrimiento de Drogas/métodos , Eritropoyetina/sangre , Espectrometría de Masas , Aceleración , Animales , Cromatografía Liquida , Relación Dosis-Respuesta a Droga , Eritropoyetina/administración & dosificación , Eritropoyetina/química , Eritropoyetina/farmacocinética , Estudios de Factibilidad , Semivida , Humanos , Isótopos de Yodo/sangre , Isótopos de Yodo/química , Masculino , Ratas , Ratas Wistar , Resonancia por Plasmón de Superficie

RESUMEN

PURPOSE: Avidin-coupled monoclonal antibody MX35 (avidin-MX35) and astatine-211-labeled, biotinylated, succinylated poly-l-lysine ((211)At-B-PL(suc)) were administered in mice to assess potential efficacy as an intraperitoneal (i.p.) therapy for microscopic tumors. We aimed to establish a timeline for pretargeted radioimmunotherapy using these substances, and estimate the maximum tolerable activity. METHODS: (125)I-avidin-MX35 and (211)At-B-PL(suc) were administered i.p. in nude mice. Tissue distributions were studied at various time points and mean absorbed doses were estimated from organ uptake of (211)At-B-PL(suc). Studies of myelotoxicity were performed after administration of different activities of (211)At-B-PL(suc). RESULTS: We observed low blood content of both (125)I-avidin-MX35 and (211)At-B-PL(suc), indicating fast clearance. After sodium perchlorate blocking, the highest (211)At uptake was found in kidneys. Red bone marrow (RBM) accumulated some (211)At activity. Mean absorbed doses of special interest were 2.3 Gy/MBq for kidneys, 0.4 Gy/MBq for blood, and 0.9 Gy/MBq for RBM. An absorbed dose of 0.9 Gy to the RBM was found to be safe. These values suggested that RBM would be the key dose-limiting organ in the proposed pretargeting scheme, and that blood data alone was not sufficient for predicting its absorbed dose. CONCLUSIONS: To attain a favorable distribution of activity and avoid major toxicities, at least 1.0 MBq of (211)At-B-PL(suc) can be administered 24 hours after an i.p. injection of avidin-MX35. These results provide a basis for future i.p. therapy studies in mice of microscopic ovarian cancer.

Asunto(s)

Anticuerpos Monoclonales/farmacocinética , Astato/farmacocinética , Avidina/farmacocinética , Lisina/farmacocinética , Radioinmunoterapia/métodos , Animales , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/química , Astato/administración & dosificación , Astato/química , Avidina/administración & dosificación , Avidina/química , Biotinilación/métodos , Médula Ósea/efectos de los fármacos , Femenino , Isótopos de Yodo/administración & dosificación , Isótopos de Yodo/química , Isótopos de Yodo/farmacocinética , Marcaje Isotópico/métodos , Riñón/efectos de los fármacos , Lisina/administración & dosificación , Lisina/química , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/radioterapia , Polímeros/administración & dosificación , Polímeros/química , Polímeros/farmacocinética , Distribución Tisular

RESUMEN

Despite the common incorporation of iodine in the biological cycle and occurrence of huge contamination of the radioactive isotope (129)I in the Baltic Proper, Skagerrak and Kattegat, there is no data on chemical speciation of iodine in these waters. We here present first time data on iodine isotopes (129)I and (127)I species as iodide and iodate in surface seawater samples collected from 16 locations in August 2006 and 19 locations in April 2007 in the Baltic Proper, Skagerrak and Kattegat. After extensive separation methods, the isotopes concentrations were determined using accelerator mass spectrometry (AMS) technique for the (129)I and inductively coupled plasma mass spectroscopy (ICP-MS) for (127)I. High concentrations of both isotopes species were found in the Skagerrak-Kattegat basins, whereas the values in the Baltic Proper are low for both species. The ratios of (129)I(-)/(129)IO(3)(-) and (127)I(-)/(127)IO(3)(-) significantly increase from south to central Baltic Sea, and iodide (both isotopes) appears as the predominant inorganic iodine species along the Baltic Sea. The results show insignificant change in (129)I and (127)I speciation and suggest that reduction of iodate and oxidation of iodide in Skagerrak and Kattegat may be a slow process. Additionally, the positive correlation between salinity and iodide and iodate (both isotopes) may reflect effective control of Skagerrak water mass on iodine distribution in surface water of the Baltic Sea.

Asunto(s)

Monitoreo del Ambiente/métodos , Yodatos/análisis , Yoduros/análisis , Isótopos de Yodo/análisis , Agua de Mar/química , Europa (Continente) , Yodatos/química , Yoduros/química , Isótopos de Yodo/química , Espectrometría de Masas , Océanos y Mares , Oxidación-Reducción , Salinidad , Estaciones del Año , Agua de Mar/análisis

RESUMEN

Natural organic matter, such as humic and fulvic acids and humin, plays a key role in determining the fate and mobility of radioiodine in soil and sediments. The radioisotope ¹²9I is continuously produced and released from nuclear fuel reprocessing plants, and as a biophilic element, its environmental mobility is strongly linked to organic matter. Due to its long half-life (15.7 million years), ¹²9I builds up in the environment and can be traced since the beginning of the nuclear era in reservoirs such as soils and marine sediments. Nevertheless, partition of the isotope between the different types of organic matter in soil and sediment is rarely explored. Here we present a sequential extraction of ¹²9I and ¹²7I chemical forms encountered in a Danish soil, a soil reference material (IAEA-375), an anoxic marine sediment from Southern Norway and an oxic sediment from the Barents Sea. The different forms of iodine are related to water soluble, exchangeable, carbonates, oxides as well as iodine bound to humic acid, fulvic acid and to humin and minerals. This is the first study to identify ¹²9I in humic and fulvic acid and humin. The results show that 30-56% of the total ¹²7I and 42-60% of the total ¹²9I are associated with organic matter in soil and sediment samples. At a soil/sediment pH below 5.0-5.5, (¹²7I and ¹²9I in the organic fraction associate primarily with the humic acid while at soil/sediment pH > 6 ¹²9I was mostly found to be bound to fulvic acid. Anoxic conditions seem to increase the mobility and availability of iodine compared to oxic, while subaerial conditions (soils) reduces the availability of water soluble fraction compared to subaqueous (marine) conditions.

Asunto(s)

Sedimentos Geológicos/química , Isótopos de Yodo/análisis , Radioisótopos de Yodo/análisis , Monitoreo de Radiación , Suelo/química , Dinamarca , Semivida , Isótopos de Yodo/química , Radioisótopos de Yodo/química , Noruega

RESUMEN

In order to quantify changes in iodine speciation and to assess factors controlling the distribution and mobility of iodine at an iodine-129 ((129)I) contaminated site located at the U.S. Department of Energy's Savannah River Site (SRS), spatial distributions and transformation of (129)I and stable iodine ((127)I) species in groundwater were investigated along a gradient in redox potential (654 to 360 mV), organic carbon concentration (5 to 60 µmol L(-1)), and pH (pH 3.2 to 6.8). Total (129)I concentration in groundwater was 8.6±2.8 Bq L(-1) immediately downstream of a former waste seepage basin (well FSB-95DR), and decreased with distance from the seepage basin. (127)I concentration decreased similarly to that of (129)I. Elevated concentrations of (127)I or (129)I were not detected in groundwater collected from wells located outside of the mixed waste plume of this area. At FSB-95DR, the majority (55-86%) of iodine existed as iodide for both (127)I and (129)I. Then, as the iodide move down gradient, some of it transformed into iodate and organo-iodine. Considering that iodate has a higher K(d) value than iodide, we hypothesize that the production of iodate in groundwater resulted in the removal of iodine from the groundwater and consequently decreased concentrations of (127)I and (129)I in downstream areas. Significant amounts of organo-iodine species (30-82% of the total iodine) were also observed at upstream wells, including those outside the mixed waste plume. Concentrations of groundwater iodide decreased at a faster rate than organo-iodine along the transect from the seepage basin. We concluded that removal of iodine from the groundwater through the formation of high molecular weight organo-iodine species is complicated by the release of other more mobile organo-iodine species in the groundwater.

Asunto(s)

Agua Subterránea/química , Isótopos de Yodo/química , Radioisótopos de Yodo/química , Ríos/química , Monitoreo del Ambiente , Concentración de Iones de Hidrógeno , Isótopos de Yodo/análisis , Radioisótopos de Yodo/análisis , Oxidación-Reducción , Estados Unidos , United States Government Agencies , Movimientos del Agua

RESUMEN

BACKGROUND AND AIM: In internal radiotherapy, the variable distribution of target receptors within the tumoral tissue, and the variable ranges of electrons may be responsible for a heterogeneous dose distribution at the cellular level. The aim of the present study was to use Monte Carlo simulations to assess (131)I electron dose in a model of heterogeneous tumor containing multiple clusters of cancer cells, targeted by (131)I-labeled molecules. METHODS: The model consisted of 150-µm-diameter spherical tumor cell clusters, in which (131)I was homogeneously distributed. Clusters were placed 24 µm apart, separated by septa of nonradioactive connective tissue. The electron dose distribution to tumor cells in a single cluster was first assessed. Then was assessed the dose increase to these targets after adding multiple layers of neighboring clusters (total number of clusters = 15,624). RESULTS: Dose distribution within a single isolated cluster follows a decreasing gradient, the dose for the outermost cell layer being about half that at the center. When radioactive neighbors were added, the dose to the central cluster increased. The most important contribution was given by the nearest neighbors, whereas the contribution from neighbors beyond a distance of 1 mm was only for 5% of the final dose. If the central cluster was unlabeled, the absorbed dose to the outermost cell layer of this cluster was reduced by 27%, and that at the center by 45%. CONCLUSIONS: The electron cross-dose of (131)I falls rapidly as a function of distance and becomes negligible after just 1 mm. Small clusters of tumor cells that are not radiolabeled may receive a very small dose. Therefore, in internal radiotherapy it is important to aim at targeting tumor cells as homogeneously as possible, rather than relying on the cross-dose to achieve a therapeutic effect.

Asunto(s)

Isótopos de Yodo/farmacología , Modelos Biológicos , Neoplasias/radioterapia , Simulación por Computador , Electrones , Isótopos de Yodo/química , Método de Montecarlo , Neoplasias/patología , Radiometría/métodos , Dosificación Radioterapéutica

RESUMEN

Pituitary adenylate cyclase-activating polypeptide (PACAP) exerts many crucial biological functions through the interaction with its specific PAC1 receptor (PAC1-R), a class B G protein-coupled receptor (GPCR). To identify the binding sites of PACAP in the PAC1-R, three peptide derivatives containing a photoreactive p-benzoyl-phenylalanine (Bpa) residue were developed. These photosensitive PACAP analogs were fully biologically active and competent to displace radiolabeled Ac-PACAP27 from the PAC1-R. Subsequently, the (125)I-labeled photoprobes were used to anchor the PAC1-R expressed in Chinese hamster ovary cells. Photolabeling led to the formation of two protein complexes of 76 and 67 kDa, representing different glycosylated forms of the receptor. Proteinase and chemical cleavages of the peptide-receptor complexes revealed that (125)I[Bpa(0), Nle(17)]PACAP27, (125)I[Bpa(6), Nle(17)]PACAP27 and (125)I[Nle(17), Bpa(22)]PACAP27 covalently labeled the Ser(98) - Met(111) segment, the Ser(124) - Glu(125) dipeptide and the Ser(141) - Met(172) fragment, respectively. Taking into account the topology of the PAC1-R, these segments are mainly located within the extracellular N-terminal domain, indicating that this PAC1-R domain is the major binding site of PACAP27. The present study constitutes the first characterization of the binding domains of PACAP to its specific receptor and suggests heterogeneity within the binding mode of peptide ligands to class B GPCRs.

Asunto(s)

Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/metabolismo , Receptores del Polipéptido Activador de la Adenilato-Ciclasa Hipofisaria/metabolismo , Secuencia de Aminoácidos , Animales , Benzofenonas/análisis , Sitios de Unión , Células CHO , Cricetinae , Cricetulus , Glicosilación , Humanos , Isótopos de Yodo/química , Datos de Secuencia Molecular , Fenilalanina/análogos & derivados , Fenilalanina/análisis , Etiquetas de Fotoafinidad/química , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/análisis , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/química , Unión Proteica/genética , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Receptores del Polipéptido Activador de la Adenilato-Ciclasa Hipofisaria/química , Receptores del Polipéptido Activador de la Adenilato-Ciclasa Hipofisaria/genética

RESUMEN

Central-transition (127)I solid-state nuclear magnetic resonance (SSNMR) spectra are presented for several anhydrous group 2 metal iodides (MgI(2), CaI(2), SrI(2), and BaI(2)), hydrates (BaI(2)·2H(2)O and SrI(2)·6H(2)O), and CdI(2) (4H polytype). Variable offset cumulative spectrum data acquisition coupled with echo pulse sequences and an 'ultrahigh' applied field of 21.1 T were usually suitable to acquire high-quality spectra. Spectral analysis revealed iodine-127 nuclear quadrupole coupling constants (C(Q)((127)I)) ranging in magnitude from 43.5 (CaI(2)) to 214 MHz (one site in SrI(2)). For very large C(Q), analytical second-order perturbation theory could not be used to reliably extract chemical shifts and a treatment which includes quadrupolar effects exactly was required (Bain, A. D. Mol. Phys. 2003, 101, 3163). Differences between second-order and exact modeling allowed us to observe 'higher-order' quadrupole-induced effects for the first time. This finding will have implications for the interpretation of SSNMR spectra of quadrupolar nuclei with large quadrupole moments. In favorable situations (i.e., C(Q)((127)I) < 120 MHz), measurements were also performed at 11.75 T which when combined with the 21.1 T data allowed us to measure iodine chemical shift (CS) tensor spans in the range from 60 (BaI(2)·2H(2)O) to 300 ppm (one site in BaI(2)). These measurements represent the first complete characterizations (i.e., electric field gradient and CS tensors as well as their relative orientation) of noncubic iodide sites using (127)I SSNMR. In select cases, the SSNMR data are supported with (127)I NQR measurements. We also summarize a variety of trends in the halogen SSNMR parameters for group 2 metal halides. Gauge-including projector-augmented wave DFT computations are employed to complement the experimental observations, to predict potential structures for the two hydrates, and to highlight the sensitivity of C(Q)((127)I) to minute structural changes, which has potential applications in NMR crystallography.

Asunto(s)

Isótopos de Yodo/química , Espectroscopía de Resonancia Magnética/métodos , Simulación por Computador , Metales Alcalinotérreos/química , Modelos Químicos , Estructura Molecular

Asunto(s)

Medios de Contraste/efectos adversos , Isótopos de Yodo/efectos adversos , Enfermedades Renales/inducido químicamente , Sesgo , Medios de Contraste/química , Creatinina/sangre , Humanos , Isótopos de Yodo/química , Concentración Osmolar , Proyectos de Investigación/normas , Literatura de Revisión como Asunto

RESUMEN

The validity of using tyrosine iodination chemistry for the absolute and generic quantification of peptides by capillary high-performance liquid chromatography (capHPLC) coupled to inductively coupled plasma mass spectrometry (ICPMS) is investigated in detail. In this approach, two iodine atoms are specifically bioconjugated to the meta positions of the aromatic ring of every tyrosine residue. Characterization studies by capHPLC with parallel ICPMS and electrospray ionization tandem mass spectrometry (ESIMS/MS) detection clearly showed that such labeling iodination reaction affords one to obtain most accurate peptide determinations (after translation of the picomoles of iodine, quantified by ICPMS in each chromatographic peak, into picomoles of the corresponding labeled peptide). It is demonstrated that only, but every, tyrosine residue present in the peptide is completely diiodinated. The excellent detection limits for iodine using ICPMS allowed robust and highly sensitive tyrosine-containing peptide quantification (480 pM, 480 amol absolute). Derivatization is easily accomplished in a water/acetonitrile solution in only 2 min. Moreover, since the signal in ICPMS is completely independent from the chemical species containing the detected element, any iodine-containing standard (e.g., iodobenzoic acid) could be used as internal standard for the absolute quantification of every iodine-labeled tyrosine-containing peptide separated and detected along the gradient. The approach was optimized for tyrosine labeling and then validated by application to the absolute quantification of the three standard peptides present in the only reference material for peptide quantity (NIST 8327) commercially available. Identification of the species quantified by ICPMS was carried out by parallel capHPLC-ESI quadrupole time-of-flight (Q/TOF) analysis and corresponded, as expected, to the diiodinated peptides. The collision-induced dissociation (CID) spectra obtained demonstrated unequivocally the specific and complete derivatization of the tyrosine residues. The obtained quantitative results closely matched the reference values reported by the National Institute of Standards and Technology (NIST). In terms of precision, the relative standard deviation was as low as 3% RSD. Finally the approach was tested for the absolute quantification of proteins using a model standard protein (beta-casein). Results agreed again with the value specified showing that this labeling reaction is compatible with tryptic digestion.

Asunto(s)

Cromatografía Líquida de Alta Presión/métodos , Isótopos de Yodo/química , Péptidos/análisis , Espectrometría de Masa por Ionización de Electrospray/métodos , Tirosina/química , Secuencia de Aminoácidos , Caseínas/análisis , Caseínas/química , Marcaje Isotópico , Datos de Secuencia Molecular , Péptidos/química , Estándares de Referencia , Espectrometría de Masa por Ionización de Electrospray/normas

RESUMEN

A facile synthesis of six 4-iodophenyl tagged sphingosine (SP) derivatives bearing alkyl chain lengths from 6 to 13 is described. The key steps for the assembly of these molecules, 5a-f, are Suzuki-Miyaura cross-coupling and cross-metathesis reactions. The feasibility of radiolabeling was demonstrated by synthesizing two (125)I labeled compounds, [(125)I]5c and [(125)I]5e. In vitro enzyme assays indicated that the molecules, 5c-e, are potent inhibitors. Thus, they deserve further evaluation as potential radioactive probes for tumor imaging.

Asunto(s)

Isótopos de Yodo/química , Fosfotransferasas (Aceptor de Grupo Alcohol)/antagonistas & inhibidores , Radiofármacos/síntesis química , Esfingosina/análogos & derivados , Humanos , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo , Radiofármacos/química , Radiofármacos/farmacología , Esfingosina/síntesis química , Esfingosina/química , Esfingosina/farmacología

RESUMEN

Amiodarone interferes with the endocytic pathway, inhibits proteolysis, and causes the formation of vacuoles, but uptake and intracellular distribution of the drug, origin of vacuoles, and functional consequences of amiodarone accumulation remain unclear. Our objective was to study amiodarone uptake, clarify the origin of vacuoles, and investigate the effect of amiodarone on the life cycle of the coronavirus responsible for the Severe Acute Respiratory Syndrome (SARS), which, to enter cells, relies on the proteolytic cleavage of a viral spike protein by the endosomal proteinase cathepsin L. Using alveolar macrophages, we studied uptake of (125)I-amiodarone and (125)I-B2, an analog lacking the lateral group diethylamino-beta-ethoxy, and analyzed the effects of amiodarone on the distribution of endosomal markers and on the uptake of an acidotropic dye. Furthermore, using Vero cells, we tested the impact of amiodarone on the in vitro spreading of the SARS coronavirus. We found that (1) amiodarone associates with different cell membranes and accumulates in acidic organelles; (2) the diethylamino-beta-ethoxy group is an important determinant of uptake; (3) vacuoles forming upon exposure to amiodarone are enlarged late endosomes; (4) amiodarone inhibits the spreading in vitro of SARS coronavirus; and (5) trypsin cleavage of the viral spike protein before infection, which permits virus entry through the plasma membrane, does not impair amiodarone antiviral activity. We conclude that amiodarone alters late compartments of the endocytic pathway and inhibits SARS coronavirus infection by acting after the transit of the virus through endosomes.

Asunto(s)

Amiodarona/farmacología , Antivirales/farmacología , Endosomas/metabolismo , Macrófagos Alveolares/metabolismo , Síndrome Respiratorio Agudo Grave/metabolismo , Coronavirus Relacionado al Síndrome Respiratorio Agudo Severo/efectos de los fármacos , Amiodarona/farmacocinética , Animales , Antivirales/farmacocinética , Catepsina L , Catepsinas/metabolismo , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Chlorocebus aethiops , Cisteína Endopeptidasas/metabolismo , Citoplasma/efectos de los fármacos , Citoplasma/metabolismo , Endosomas/efectos de los fármacos , Humanos , Isótopos de Yodo/química , Macrófagos Alveolares/efectos de los fármacos , Macrófagos Alveolares/virología , Glicoproteínas de Membrana/metabolismo , Coronavirus Relacionado al Síndrome Respiratorio Agudo Severo/fisiología , Síndrome Respiratorio Agudo Grave/tratamiento farmacológico , Síndrome Respiratorio Agudo Grave/virología , Glicoproteína de la Espiga del Coronavirus , Vacuolas/efectos de los fármacos , Vacuolas/metabolismo , Células Vero , Proteínas del Envoltorio Viral/metabolismo

RESUMEN

Iodine is a biophilic element, with several short-lived isotopes (e.g. (131)I, t(1/2)=8 days), one long-lived isotope, (129)I (t(1/2)=15.6 million years) and one stable isotope, (127)I. The inventory of (129)I in surface environments has been overwhelmed by anthropogenic releases over the past 50 years. Iodine and its isotopes are important for a number of reasons: (1) The largest fraction of the short-term and long-term dose from accidental releases and fallout from atomic bomb tests was from iodine isotopes. (2) (129)I is one of the two long-lived nuclides with highest mobility in stored radioactive waste. (3) (129)I could provide the scientific community with a new geochemical tracer and new geochronological applications in environmental science. (4) A better assessment of iodine deficiency disorders, mineralization in exploration geochemistry, and the transfer of volatile organic greenhouse-active and ozone-destroying iodine species from the oceans to the atmosphere is needed. One of the most promising future applications for the (129)I/(127)I ratio is not only as a new geochronometer, but also as a new source tracer for terrestrial organic matter with ages of 50 years or less. This is especially attractive, since radiocarbon can be, at times, an ambiguous chronometer for the 50-year time-scale, whereas (129)I concentrations during this time are overwhelming previous levels by orders of magnitude. Iodine is to a significant extent involved in the cycle of organic matter in all surface environments. Its biophilic nature is demonstrated by a relative enrichment of iodine in seaweed and dissolved macromolecular organic matter. Because of the close coupling of iodine and organic carbon cycles, our understanding of the underlying molecular mechanisms of the processes regulating iodination reactions in aquatic systems is still limited. The binding of iodine by organic matter has the potential to modify the transport, bioavailability and transfer of iodine isotopes to man. Equilibration times for (129)I in many reservoirs are likely long enough that (129)I could be used as a new source tracer for organic matter of terrestrial origin, and as a geochronometer. Current tracer applications of (129)I are limited by our knowledge of the effects of UV-radiation, microbial activity and geochemical redox conditions on organo-I compounds and overall iodine speciation. The biogeochemical behavior of iodine and its isotopes appears to be different in North America and European waters, possibly due to climatic, source and speciation differences.

Asunto(s)

Monitoreo del Ambiente/métodos , Contaminantes Ambientales/análisis , Isótopos de Yodo/química , Radioisótopos de Yodo/química , Europa (Continente) , Cinética , Trazadores Radiactivos , Estados Unidos