Targeted nanocarriers based on iodinated-cyanine dyes as immunomodulators for synergistic phototherapy.

Photodynamic therapy (PDT), as one of the most powerful photo-therapeutic strategies for cancer treatment with minimum invasiveness, can effectively damage local tumor cells and significantly induce systemic antitumor immunity. However, current nanotechnology-assisted PDT-immunomodulators have either poor penetration for deep tumors or low singlet oxygen generation. Herein, we construct a novel theranostic nanocarrier (HA-PEG-CyI, HPC) by inducing the self-assembly of PEGylated CyI and attaching the ligand HA to its surface. The prepared HPC can be used as an ideal PDT-immunomodulator for synergistic cancer therapy. CyI is an iodinated-cyanine dye with enhanced singlet oxygen generation ability as well as excellent photo-to-photothermal and near-infrared fluorescence imaging properties. Under 808 nm laser irradiation, the prepared HPC can generate both reactive oxygen species (ROS) and elevate temperature which can subsequently result in apoptosis and necrosis at tumor sites. Moreover, the HPC-induced cell death can generate a series of acute inflammatory reactions, leading to systemic immunity induction and secondary death of tumor cells, which further results in reducing tumor recurrence. In vitro and in vivo results show that HPC can enhance the tumor targeting efficacy, generate ROS efficiently and exhibit a high temperature response under NIR irradiation, which working together can activate immune responses for synergistic phototherapy on tumor cells. Accordingly, the proposed multi-functional HPC nanocarriers represent an important advance in PDT and can be used as a superior cancer treatment strategy with great promise for clinical applications.

Iodinated Cyanine Dyes for Fast Near-Infrared-Guided Deep Tissue Synergistic Phototherapy.

Phototheranostics, which combines deep tissue imaging and phototherapy [photodynamic therapy (PDT) and/or photothermal therapy (PTT)] via light irradiation, is a promising strategy to treat tumors. Near-infrared (NIR) cyanine dyes are researched as potential phototheranostics reagents for their excellent photophysical properties. However, the low singlet oxygen generation efficiency of cyanine dyes often leads to inadequate therapeutic efficacy for tumors. Herein, we modified an indocyanine green derivative Cy7 with heavy atom iodine to form a novel NIR dye CyI to improve the reactive oxygen species (ROS) production and heat generation while, at the same time, maintain their fluorescence characteristics for in vivo noninvasive imaging. More importantly, in vitro and in vivo therapeutic results illustrated that CyI could quickly and simultaneously generate enhanced ROS and heat to induce more cancer cell apoptosis and higher inhibition rates in deep HepG2 tumors than other noniodinated NIR dyes upon NIR irradiation. Besides, low toxicity of the resulted iodinated NIR dyes was confirmed by in vivo biodistribution and acute toxicity. Results indicate that this low toxic NIR dye could be an ideal phototheranostics agent for deep tumor treatments. Our study presents a novel approach to achieve the fast-synergistic PDT/PTT treatment in deep tissues.

Synthesis and evaluation of PET probes for the imaging of I2 imidazoline receptors in peripheral tissues.

INTRODUCTION: To explore the possible use of positron emission tomography (PET) probes for imaging of I(2)-imidazoline receptors (I(2)Rs) in peripheral tissues, we labeled two new I(2)R ligands, 2-[2-(o-tolyl)vinyl]-4,5-dihydro-1H-imidazole (K(i) for I(2)Rs, 3.7 nM) and 2-[2-(o-tolyl)ethyl]-4,5-dihydro-1H-imidazole (K(i) for I(2)Rs, 1.7 nM) with (11)C ([(11)C]metrazoline and [(11)C]TEIMD), respectively, and evaluated these ligands and the recently developed I(2)R ligand 2-[3-fluoro-[4-(11)C]tolyl]-4,5-dihydro-1H-imidazole ([(11)C]FTIMD) by in vivo studies. METHODS: [(11)C]Metrazoline and [(11)C]TEIMD were prepared by a palladium-promoted cross-coupling reaction of the tributylstannyl precursor and [(11)C]methyl iodide. Their biodistribution in mice was investigated by tissue dissection. In addition, PET scans and metabolite analysis were performed. RESULTS: [(11)C]Metrazoline and [(11)C]TEIMD were successfully synthesized with a suitable radioactivity for injection. In the liver and pancreas expressing I(2)Rs, coinjection with the high-affinity I(2)R ligand, BU224, induced a reduction in the radioactivity level at 30 min after injection of [(11)C]metrazoline and [(11)C]FTIMD. However, the radioactivity level after injection of [(11)C]TEIMD was unchanged. In the PET study, coinjection with BU224 induced a decrease in the radioactivity level in the liver and pancreas after more than 15 min of injection of [(11)C]metrazoline and [(11)C]FTIMD as compared with the results obtained for controls. In metabolite analysis, coinjection with BU224 induced a significant reduction in the percentage of unchanged [(11)C]metrazoline at 30 min after injection as compared with that in the control, although no significant difference was observed in the percentage of unchanged [(11)C]FTIMD. CONCLUSION: [(11)C]Metrazoline may be a more useful PET probe than [(11)C]FTIMD for imaging of I(2)Rs in peripheral tissues.

Sleep deprivation differentially affects dopamine receptor subtypes in mouse striatum.

The effects of sleep deprivation on dopaminergic systems remain elusive, in part due to the lack of selective ligands for dopamine receptor subtypes. We examined D1, D2, and D3 receptor density in the mouse brain after sleep deprivation by receptor autoradiography using [H]SCH 23390 for D1R, [H]raclopride for D2R, and [H]WC-10 for D3R (a novel D3R-selective compound developed in our laboratory, not previously reported in mouse). Sleep-deprived mice showed a significant decrease in D1R, no change in D2R, and a significant increase in D3R binding in striatum. This pattern of dopamine receptor changes was not seen in mice subjected to restraint stress, suggesting specificity to sleep. These data provide evidence that brain dopaminergic circuits are remodeled after sleep deprivation.

Development of a physiologically based pharmacokinetic (PBPK) model for methyl iodide in rats, rabbits, and humans.

Methyl iodide (MeI) has been proposed as an alternative to methyl bromide as a pre-plant soil fumigant that does not deplete stratospheric ozone. In inhalation toxicity studies performed in animals as part of the registration process, three effects have been identified that warrant consideration in developing toxicity reference values for human risk assessment: nasal lesions (rat), acute neurotoxicity (rat), and fetal loss (rabbit). Uncertainties in the risk assessment can be reduced by using an internal measure of target tissue dose that is linked to the likely mode of action (MOA) for the toxicity of MeI, rather than the external exposure concentration. Physiologically based pharmacokinetic (PBPK) models have been developed for MeI and used to reduce uncertainties in the risk assessment extrapolations (e.g. interspecies, high to low dose, exposure scenario). PBPK model-derived human equivalent concentrations comparable to the animal study NOAELs (no observed adverse effect levels) for the endpoints of interest were developed for a 1-day, 24-hr exposure of bystanders or 8 hr/day exposure of workers. Variability analyses of the PBPK models support application of uncertainty factors (UF) of approximately 2 for intrahuman pharmacokinetic variability for the nasal effects and acute neurotoxicity.

Iodomethane human health risk characterization.

Iodomethane is a new pre-plant soil fumigant approved in the United States. Human exposure may occur via inhalation due to the high vapor pressure of iodomethane. A quantitative human health risk assessment was conducted for inhalation exposure. The critical effects of acute duration iodomethane exposure are: (1) fetal losses in rabbits, (2) lesions in rat nasal epithelium, and (3) transient neurotoxicity in rats. Chronic exposure of rats resulted in increased thyroid follicular cell tumors from sustained perturbation of thyroid hormone homeostasis. A physiologically based pharmacokinetic (PBPK) model for iodomethane was developed to characterize potential human health effects from iodomethane exposure. The model enabled calculation of human equivalent concentrations (HECs) to the animal no-observed-adverse-effect levels (NOAELs) using chemical-specific parameters to determine the internal dose instead of default assumptions. Iodomethane HECs for workers and bystanders were derived using the PBPK model and NOAELs for acute exposure endpoints of concern. The developmental endpoint NOAEL was 10 ppm and corresponding bystander HEC was 7.4 ppm. The nasal endpoint NOAEL was 21 ppm and the HEC was 4.5 ppm. The transient neurotoxicity endpoint NOAEL was 27 ppm and the HEC was10 ppm. Data demonstrated that humans are less sensitive to the effect that causes developmental toxicity in rabbits and the PBPK model incorporated this information, resulting in a higher HEC for the developmental endpoint than for the nasal endpoint. Nasal olfactory degeneration is the primary endpoint for risk assessment of acute exposure to iodomethane.

Studies supporting the development of a physiologically based pharmacokinetic (PBPK) model for methyl iodide: pharmacokinetics of sodium iodide (NaI) in pregnant rabbits.

Methyl iodide (MeI) is a water soluble monohalomethane that is metabolized in vivo to release iodide (I-). A physiologically based pharmacokinetic (PBPK) model exists for iodide in adult rats, pregnant rats and fetuses, and lactating rats and neonates, but not for pregnant rabbits and fetuses, which have been used extensively for toxicity testing with MeI. Thus, this study was conducted to determine the blood and tissue distribution kinetics of radioiodide in pregnant rabbits and fetuses. Timed-pregnant New Zealand White rabbits received a single intravenous injection of the sodium salt of iodine-131 (Na131I) at either a high (10 mg/kg body weight) or low (0.75 mg/kg body weight) dose on gestation day 25. At various intervals ranging from 0.5 to 24h post- injection, blood and tissues (thyroid, stomach contents, and skin) were collected from each doe, and blood, stomach contents, thyroid, trachea, and amniotic fluid were collected from a random sampling of three fetuses per doe per time point. Radioiodide accumulated as expected in the thyroid of maternal animals, where concentrations were the highest of any maternal tissues measured in both dose groups. Radioiodide also accumulated in fetal blood and tissues; levels were consistently higher than maternal levels and, unlike maternal tissues, showed no evidence of clearance over the 24-h sampling period. In contrast to observations in the maternal animals, fetal stomach contents showed the highest accumulation of radioiodide for both dose groups by 1-2h after dosing, followed by the trachea and thyroid tissues, with the lowest concentrations of radioiodide in the amniotic fluid and blood. There was no evidence for preferential accumulation of radioiodide in fetal thyroid tissues.

Synthesis of two potential NK1-receptor ligands using [1-11C]ethyl iodide and [1-11C]propyl iodide and initial PET-imaging.

BACKGROUND: The previously validated NK1-receptor ligand [O-methyl-11C]GR205171 binds with a high affinity to the NK1-receptor and displays a slow dissociation from the receptor. Hence, it cannot be used in vivo for detecting concentration changes in substance P, the endogenous ligand for the NK1-receptor. A radioligand used for monitoring these changes has to enable displacement by the endogenous ligand and thus bind reversibly to the receptor. Small changes in the structure of a receptor ligand can lead to changes in binding characteristics and also in the ability to penetrate the blood-brain barrier. The aim of this study was to use carbon-11 labelled ethyl and propyl iodide with high specific radioactivity in the synthesis of two new and potentially reversible NK1-receptor ligands with chemical structures based on [O-methyl-11C]GR205171. METHODS: [1-11C]Ethyl and [1-11C]propyl iodide with specific radioactivities of 90 GBq/mumol and 270 GBq/mumol, respectively, were used in the synthesis of [O-methyl-11C]GR205171 analogues by alkylation of O-desmethyl GR205171. The brain uptake of the obtained (2S,3S)-N-(1-(2- [1-11C]ethoxy-5-(3-(trifluoromethyl)-4H-1,2,4-triazol-4-yl)phenyl)ethyl)-2-phenylpiperidin-3-amine (I) and (2S,3S)-2-phenyl-N-(1-(2- [1-11C]propoxy-5-(3-(trifluoromethyl)-4H-1,2,4-triazol-4-yl)phenyl)ethyl)piperidin-3-amine (II) was studied with PET in guinea pigs and rhesus monkeys and compared to the uptake of [O-methyl-11C]GR205171. RESULTS: All ligands had similar uptake distribution in the guinea pig brain. The PET-studies in rhesus monkeys showed that (II) had no specific binding in striatum. Ligand (I) had moderate specific binding compared to the [O-methyl-11C]GR205171. The ethyl analogue (I) displayed reversible binding characteristics contrary to the slow dissociation rate shown by [O-methyl-11C]GR205171. CONCLUSION: The propyl-analogue (II) cannot be used for detecting changes in NK1-ligand levels, while further studies should be performed with the ethyl-analogue (I).

The deposition and translocation of methyl iodide by crops.

Organic forms of radioactive iodine are released during routine and accidental releases from the nuclear industry. Methyl iodide is often the predominant species in these releases. This paper describes the results of a study to determine the deposition, allocation, and loss of radioiodine after crops of bean, carrot, and cabbage were exposed to CH3 125I. The deposition velocity ranged from 0.14-7.10 x 10(-4) cm s(-1), which is in line with previous studies. Translocation of radioiodine away from the leaves to other crop components was observed post exposure. The partition of radioiodine was to those crop components growing most actively at the time of exposure. This finding contradicts some previous studies and will have implications for dose assessments. Losses of radioiodine were only observed as a consequence of leaf fall. The consequences of these findings for the modeling the movement of radioiodine in crops following the deposition of methyl iodide are discussed.

3-Pyridyl ethers as SPECT radioligands for imaging nicotinic acetylcholine receptors.

To develop a suitable single photon emission computed tomography (SPECT) radioligand for neuronal nicotinic acetylcholine receptors (nAChRs) that displays faster in vivo kinetics than 5-[123I]iodo-A-85380, we synthesised the radioiodinated analogue of A-84543. 5-[123I]Iodo-A-84543 was prepared by electrophilic iododestannylation in a modest yield of 23%. In the baboon brain, 5-[123I]iodo-A-85380 displayed a profile consistent with the known distribution of nAChRs, however, 5-[123I]iodo-A-84543 displayed a homogenous uptake with no preferential localisation in regions known to contain nAChRs. To examine the effect of halogen substitution on the 3-pyridyl ether, A-84543, the 5-chloro, 5-bromo and 5-iodo analogues were synthesised and evaluated with respect to nAChR binding. In vitro binding data revealed that halogen substitution at the 5-position of A-84543 was not well tolerated with an increase in halogen size resulting in lower binding towards nAChRs. The 5-chloro analogue 4 displayed highest affinity, Ki =1.3 nM, compared to the 5-bromo and 5-iodo compounds, 5 Ki =3.3 nM and 3 Ki =40.8 nM, respectively. Taken together, these results clearly indicate that 5-[123I]iodo-A-84543 is not suitable for the study of nAChRs in vivo using SPECT.

Synthesis of iodinated 3beta-aryltropanes with selective binding to either the dopamine or serotonin transporters.

Iodinated 3beta-aryltropanes functionalized appropriately at the 2beta-, 8- and aryl positions display selective binding to either the dopamine or serotonin transporters.

[Consciousness disturbance caused by iodoform absorption in a patient with decubitus ulcer topically treated with iodoform-gauze].

A 76-year-old man with supranuclear palsy, developed consciousness disturbance followed by the treatment of decubitus ulcer in the sacral region using iodoform-gauze. He was semicoma and tachycardia. His pupils were miotic and light reflexes were absent. EEG demonstrated diffuse and random slow activities. Plasma concentration of free iodine was high (151 micrograms/dl), but the other laboratory findings including thyroid functions were normal. He was diagnosed as suffering from iodoform poisoning. The symptoms and laboratory abnormalities of the patient recovered soon after the removal of iodoform-gauze. Although iodoform has been widely used for the treatment of wounds, there are few case reports of its side effects, such as consciousness disturbance, delirium, headache and tachycardia.

Experimental models, protocols, and reference values for evaluation of iodinated analogues of glucose.

For an iodinated analogue of glucose to be useful for evaluating glucose uptake using single-photon emission computed tomography (SPECT), it must enter the cell via the same transporter as glucose and accumulate within the cell without being degraded. The biological behavior of the iodinated tracer must therefore be similar to that of 2-deoxy-D(-)[1-14C]-glucose (2-DG). In the present study, four experimental models (biodistribution in mouse, isolated rat heart, human erythrocytes in suspension and cultured neonatal rat cardiomyocytes) have been chosen and protocols have been set up which allow for the examination of small quantities of iodinated analogues of glucose. The uptakes of 2-DG and of L(-)[1-14C]-glucose have been measured in these models to establish reference values which will be compared with uptake values for iodinated analogues of glucose.

DNA binding of methyl iodide in male and female F344 rats.

The genotoxic potency of methyl iodide was investigated in a DNA binding study. Male and female F344 rats were exposed to 14C-labelled methyl iodide orally or by inhalation in a closed exposure system. DNA adducts were detected in the liver, lung, stomach and forestomach of the exposed animals. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine could be identified by a combination of three different methods of hydrolysing DNA and subsequent HPLC or GC/MS analysis. The highest values of methylated guanines were determined in the stomach and forestomach of the animals following both oral and inhalative exposure. These results demonstrate a systemic genotoxic effect of methyl iodide.

Interspecies pharmacokinetic scaling of some iodinated organic acids.

We have investigated the possibility of interspecies scaling of relationships between the structure and total plasma clearance in a group of nine organic acids (iododerivatives of benzoic, phenylacetic and hippuric acids) in rabbits, rats and mice. The intercompound comparison established the dependence of total plasma clearance predominantly on the molecular structure in all the animals under study, but the dependence on drug lipophilicity was also meaningful. For interspecies scaling of total plasma clearance, the use of a biological clock with an effective renal plasma flow as the unit seemed most suitable and is probably connected with the principal role of the kidney in the elimination of the compounds under study.