Association of brain serotonin transporter availability and brain-derived neurotrophic factor in models of serotonin transporter genotypes in healthy subjects.

The S-allele of functional polymorphisms of the serotonin transporter (SERT) gene has been demonstrated to have lower transcriptional activity compared with the L-allele, which shows low expression of SERT in the brain. However, this finding cannot be consistently replicated in vivo. The aim of this study was to determine the availability of SERT based on SERT genotype. We also examined the relationship between brain-derived neurotrophic factor (BDNF) and the availability of SERT. Sixty-two healthy subjects were recruited. Each subject underwent single-photon emission computed tomography with I-ADAM (I-labeled 2-([2-({dimethylamino}methyl)phenyl]thio)-5-iodophenylamine) for imaging SERT in the brain. The specific uptake ratio was measured, and venous blood was drawn when the subject underwent single-photon emission computed tomography to evaluate BDNF levels and SERT genotype. All subjects expressed SERT genotypes that were consistent with a biallelic model, and 26 subjects had SERT genotypes that were consistent with a triallelic model. No differences in specific uptake ratio were detected in the midbrain, putamen, caudate, and thalamus based on the SERT genotype using the biallelic and triallelic models. Interestingly, The Pearson correlation coefficient revealed a positive correlation between BDNF and SERT availability. In particular, this relationship was observed in homozygous S-allele expression and a genotype with low functional expression (SaSa/SaLg) in the biallelic and triallelic models of SERT genotypes, respectively. This finding might explain why the SS genotype of SERT did not increase the risk of major depressive disorder in Asian populations and implicate an important role of BDNF in the patients, who has the SS genotype of the SERT gene.

Development of acute and subacute toxicity with the serotonin transporter radiopharmaceutical, ADAM.

It is predicted that depression will become the most common neurological disease in the new millennium. Its incidence is currently about 3% of diseases worldwide. Serotonin is an essential neurotransmitter for the central and peripheral nervous systems and plays a crucial role in neuropsychiatric disorders. (123)I-labeled ADAM was developed to facilitate an early diagnosis of serotonin transporter (SERT) abnormalities in the brain. Many studies have confirmed that the binding of this radiotracer to SERTs is associated with depression. The aim of this study was to evaluate the acute and subacute toxicity of ADAM and to determine its no observed adverse effect level (NOAEL) by administering it via intravenous injection to Sprague-Dawley rats for 14 consecutive days. None of the animals died, and no treatment-related clinical signs were observed. Urinalysis, hematology, and clinical chemistry analysis revealed that daily administration of ADAM (2-2-dimethylaminomethylphenylthio-5-iodophenylamine) for 2 weeks had no toxicological effects. It is concluded that ADAM exerts no adverse toxic effects on this animal model. The NOAEL was 155 microg/kg/day.

Association of novelty seeking scores and striatal dopamine D2/D3 receptor availability of healthy volunteers: single photon emission computed tomography with ¹²³i-iodobenzamide.

It has been speculated that novelty seeking (NS) behavior is related to the dopaminergic system. Fifty-two subjects completed the Tridimensional Personality Questionnaire and underwent single photon emission computed tomography with (123)I-iodobenzamide. A marginally positive correlation was noted between NS and striatal dopamine D(2)/D(3) receptor availability (r = 0.25, p =0.07). A positive association was noted between the NS scores and left striatal D(2)/D(3) receptor availability (r= 0.29, p =0.04). The results suggest that a relationship might exist between NS score and dopaminergic activity.

Imaging the serotonin transporter using (123)I-ADAM in the human brain.

The aim of this study was to examine the feasibility of (123)I-ADAM to image the serotonin transporter (SERT) in Asian (Taiwanese) subjects. Single photon emission computed tomography (SPECT) scans were performed on nine healthy volunteers who were s-allele carriers at the polymorphism within the serotonin transporter promoter region (SERTPR) after intravenous bolus injection of (123)I-ADAM. Quantification of (123)I-ADAM binding was performed using the ratio equilibrium method (REM) with specific uptake ratio (SUR) and a simplified reference tissue model (SRTM). Curve-fitting techniques were used to obtain the peak equilibrium point from 241 to 301 min (average 264+/-20 min) after injection of (123)I-ADAM for the midbrain and from 215 to 270 min (average 235+/-18 min) after injection of (123)I-ADAM for the striatum. Two sets of SUR were obtained by either curve fitting (estimated values) or integrated period from 240 to 270 min (observed values). The estimated values of SUR were 2.11+/-0.51 for the midbrain and 1.50+/-0.44 for the striatum, whereas the observed values were 2.11+/-0.83 for the midbrain and 1.24+/-0.31 for the striatum. The SRTM showed that the binding potential (BP) was 2.10+/-0.66 for the midbrain and 1.35+/-0.25 for the striatum. There was a good correlation between estimated SUR, observed SUR and SRTM in the midbrain but not in the striatum. The optimal scanning duration for both the midbrain and the striatum should be 220 to 280 min similar to that suggested by previous studies in Caucasians. However, due to the low signal-to-noise ratio in the striatum, (123)I-ADAM could be an ideal tracer for imaging SERT in the midbrain but not in the striatum.

Acute toxicity of two Alzheimer's disease radiopharmaceuticals: FDDNP and IMPY.

Alzheimer's disease (AD) is a neurodegenerative disorder that results in memory deficits. The effect of AD is the leading cause of dementia in the United States and constitutes a burgeoning public health problem. AD is characterized by the presence of two aberrant structures, senile plaques, and neurofibrillary tangles, present in the brain of the patients. [(18)F]FDDNP and [(123)I]IMPY were developed for the early diagnosis of AD by Dr. J. Barrios and Dr. H. Kung, respectively. These two radiotracers could bind with the amyloid location site in the AD patient brain. The aim of this study was to analyze the acute single toxic effects dose of two nonradiochemical labeled compounds in rats. Animals were injected from the tail vein with nonlabeled-FDDNP (0- 5 mg/kg) and nonlabeled-IMPY (0-300 microg/kg), respectively, and observed for 2 weeks. These doses provide safety margins of 35,000- to 140-fold and 1,000- to 100-fold over the maximal recommend human dose (0.1 mg/70 kg) and (20 microg/60 kg) (by FDDNP and IMPY), respectively. With IMPY, there were no changes in mortality, clinical situation, and gross necropsy. With FDDNP, the high dose (5 mg/kg) produced mortality in 2 of 5 and 1 of 5 in male and female rats, respectively. The high dose of FDDNP showed liver damage in dying animals. No other adverse toxic effects at dose levels up to 1.0 mg/kg of FDDNP were noted. FDDNP exerted no adverse toxic effects in rats given doses up to 1 mg/kg and IMPY at the dose levels up to 300 microg/kg.

Imaging the availability of serotonin transporter in rat brain with 123I-ADAM and small-animal SPECT.

BACKGROUND: Imaging serotonin transporters during antidepressant treatment in small animals is a useful tool for preclinical study during drug development. In this work, we aimed to demonstrate the feasibility of using 123I-ADAM and small-animal SPECT to monitor serotonin transporter availabilities in rat brains prior to and after administration of a selective serotonin re-uptake inhibitor. METHODS: Male Sprague-Dawley rats with and without administration of citalopram (4 mg x kg body weight) were examined in this study. During the process rat brains were scanned using a double-headed microSPECT system equipped with pinhole collimators. SPECT tomographic images and X-ray computed tomography (CT) were acquired after introducing 123I-ADAM via the tail vein. The 123I-ADAM specific binding was assessed by SPECT/CT fused image to draw regions of interest in the midbrain and cerebellum. Ex-vivo autoradiography was carried out as a parallel investigation to validate the SPECT technique. RESULTS: SPECT images displayed specific binding ratio in midbrain to be 0.91+/-0.30 averaged from three rats. Drug occupancies (95.47+/-1.56)% were shown after administration of citalopram in a dosage of 4 mg x kg. CONCLUSION: This study demonstrated that the serotonin transporter availability during antidepressant treatment in small animals can be assessed semi-quantitatively by using 123I-ADAM and SPECT.

The association between heroin expenditure and dopamine transporter availability--a single-photon emission computed tomography study.

One of the consequences of heroin dependency is a huge expenditure on drugs. This underlying economic expense may be a grave burden for heroin users and may lead to criminal behavior, which is a huge cost to society. The neuropsychological mechanism related to heroin purchase remains unclear. Based on recent findings and the established dopamine hypothesis of addiction, we speculated that expenditure on heroin and central dopamine activity may be associated. A total of 21 heroin users were enrolled in this study. The annual expenditure on heroin was assessed, and the availability of the dopamine transporter (DAT) was assessed by single-photon emission computed tomography (SPECT) using [(99m)TC]TRODAT-1. Parametric and nonparametric correlation analyses indicated that annual expenditure on heroin was significantly and negatively correlated with the availability of striatal DAT. After adjustment for potential confounders, the predictive power of DAT availability was significant. Striatal dopamine function may be associated with opioid purchasing behavior among heroin users, and the cycle of spiraling dysfunction in the dopamine reward system could play a role in this association.

Microautoradiography of [123I]ADAM in mice treated with fluoxetine and serotonin reuptake inhibitors.

A radiopharmaceutical, (123)I-labeled 2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine ([(123)I]ADAM), has been developed recently for evaluation of how serotonin transporters (SERT) function in the brain. However, the detailed biodistribution and specific binding in certain brain areas are not well investigated. In this study, both phosphor plate imaging and microautoradiography were applied to explore the binding characteristics of [(123)I]ADAM in SERT neurons. The effect of two psychotropics and one narcotic on the binding of [(123)I]ADAM to SERT was also studied. Fluoxetine and desipramine, both are psychotropics and specific SERT ligands and decreased the affinity of [(123)I]ADAM, while p-chloroamphetamine (PCA), a narcotic, destroyed most of serotonergic neurons, as well as reducing the concentration of serotonin and the number of SERT in the brain as shown by the biodistribution of [(123)I]ADAM. Significant and selective accumulation of [(123)I]ADAM in the areas from midbrain to brain stem in normal mice with maximum target-to-background ratio was found at 90 minutes postinjection. A rapid clearance of [(131)I]ADAM at 120 minutes postinjection was found in the CA1, CA3 and ThN brain areas. In addition, the inhibition effect on binding ability of [(123)I]ADAM to SERT by the psychotropics and the narcotic was found to have the order of: PCA > fluoxetine > desipramine.

The study of the sterilization effect of gamma ray irradiation of immobilized collagen polypropylene nonwoven fabric surfaces.

Exposure to gamma ray irradiation is a frequent, clean, and superior method used to prevent bacterial contamination of sterilized biomedical end products. However, the potential damage induced by gamma ray irradiation of collagen is of concern because of the decay of bioactivity, which correlates with considerable structural alterations. In this experiment, antenna-coupling microwave plasma was utilized to activate nonwoven polypropylene (PP) fabric, and then the sample was grafted to acrylic acid (AAc). Type III collagen was immobilized by using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a coupling agent. The collagen-immobilized samples, with temperatures of under 4 degrees C, were exposed to gamma ray irradiation at different dose intervals. Gamma ray irradiation was applied to evaluate the bioactivity on the collagen-immobilized nonwoven polypropylene and to determine the results of sterilization. Five kinds of sterilization index bacteria, all subject to Good Manufacturing Practice (GMP) criteria, were applied as a standard plate-count sterilization test. Our experimental results demonstrate that in human plasma incubated with various intervals of gamma ray irradiation, fibrinogen concentration decreases while platelet and red blood cell adhesion increase. However, the dose required for thrombination demonstrated a significant change in gamma ray irradiation exposure of fewer than 10 KGy (p = 0.05). The decay of bioactivity of the gamma-ray-irradiated collagen-bonded surfaces was evaluated and indicated that the decrease of R-CONHR', the degradation of amides ([broken bond]C[bond]N bonds of collagen and formation of the ROCNH(2) and O[double bond]CR' bonds), and the increase of C[bond]O, C[double bond]O bonds gradually may damage collagen by increasing the intervals of gamma ray irradiation. These effects considerably influence the bioactivity of the collagen-bonded fabric. It is clear that gamma ray irradiation exposure of approximately 10 KGy has the potential of moderating the bioactivities of collagen and therefore likely is a vital factor in the acceleration of biodegradation. The dose required for thrombination and sterilization reaches significance at 7.5 KGy.

Serotonin transporter availability in the midbrain and perceived social support in healthy volunteers.

OBJECTIVE: Serotonin modulates human behavior and emotion. Recent evidence implies that a higher level of serotonergic activity could be associated with a higher level of perceived social support. This study aimed to examine the correlation between serotonin transporter (SERT) availability and perceived social support scores in healthy volunteers. METHODS: 111 healthy participants, 50 males and 61 females, were enrolled from the community and completed the Measurement of Support Function questionnaire. Single photon emission computed tomography (SPECT) with [(123)I] ADAM was performed to examine SERT availability. RESULTS: Perceived social support was positively correlated with SERT availability (Spearman's ρ=0.29, p<0.01; χ(2)=7.57, p<0.01), particularly in males (Spearman's ρ=0.37, p<0 .01; χ(2)=11.77, p<0.01). Censored regressions indicated that these associations are not influenced by a ceiling effect and remained significant after controlling the effect of age. CONCLUSIONS: This result confirmed the correlation between perceived social support and central serotonergic activity. However, this correlation was present only in males.

[123I]Epidepride neuroimaging of dopamine D2/D3 receptor in chronic MK-801-induced rat schizophrenia model.

PURPOSE: [(123)I]Epidepride is a radio-tracer with very high affinity for dopamine D(2)/D(3) receptors in brain. The importance of alteration in dopamine D(2)/D(3) receptor binding condition has been wildly verified in schizophrenia. In the present study we set up a rat schizophrenia model by chronic injection of a non-competitive NMDA receptor antagonist, MK-801, to examine if [(123)I]epidepride could be used to evaluate the alterations of dopamine D(2)/D(3) receptor binding condition in specific brain regions. METHOD: Rats were given repeated injection of MK-801 (dissolved in saline, 0.3mg/kg) or saline for 1month. Afterwards, total distance traveled (cm) and social interaction changes were recorded. Radiochemical purity of [(123)I]epidepride was analyzed by Radio-Thin-Layer Chromatography (chloroform: methanol, 9:1, v/v) and [(123)I]epidepride neuroimages were obtained by ex vivo autoradiography and small animal SPECT/CT. Data obtained were then analyzed to determine the changes of specific binding ratio. RESULT: Chronic MK-801 treatment for a month caused significantly increased local motor activity and induced an inhibition of social interaction. As shown in [(123)I]epidepride ex vivo autoradiographs, MK-801 induced a decrease of specific binding ratio in the striatum (24.01%), hypothalamus (35.43%), midbrain (41.73%) and substantia nigra (37.93%). In addition, [(123)I]epidepride small animal SPECT/CT neuroimaging was performed in the striatum and midbrain. There were statistically significant decreases in specific binding ratio in both the striatum (P<.01) and midbrain (P<.05) between the saline and MK-801 group. CONCLUSION: These results suggest that [(123)I]epidepride is a useful radio-tracer to reveal the alterations of dopamine D(2)/D(3) receptor binding in a rat schizophrenia model and is also helpful to evaluate therapeutic effects of schizophrenia in the future.

Mirtazapine inhibits tumor growth via immune response and serotonergic system.

To study the tumor inhibition effect of mirtazapine, a drug for patients with depression, CT26/luc colon carcinoma-bearing animal model was used. BALB/c mice were randomly divided into six groups: two groups without tumors, i.e. wild-type (no drug) and drug (mirtazapine), and four groups with tumors, i.e. never (no drug), always (pre-drug, i.e. drug treatment before tumor inoculation and throughout the experiment), concurrent (simultaneously tumor inoculation and drug treatment throughout the experiment), and after (post-drug, i.e. drug treatment after tumor inoculation and throughout the experiment). The "psychiatric" conditions of mice were observed from the immobility time with tail suspension and spontaneous motor activity post tumor inoculation. Significant increase of serum interleukin-12 (sIL-12) and the inhibition of tumor growth were found in mirtazapine-treated mice (always, concurrent, and after) as compared with that of never. In addition, interferon-γ level and immunocompetent infiltrating CD4+/CD8+ T cells in the tumors of mirtazapine-treated, tumor-bearing mice were significantly higher as compared with that of never. Tumor necrosis factor-α (TNF-α) expressions, on the contrary, are decreased in the mirtazapine-treated, tumor-bearing mice as compared with that of never. Ex vivo autoradiography with [(123)I]ADAM, a radiopharmaceutical for serotonin transporter, also confirms the similar results. Notably, better survival rates and intervals were also found in mirtazapine-treated mice. These findings, however, were not observed in the immunodeficient mice. Our results suggest that tumor growth inhibition by mirtazapine in CT26/luc colon carcinoma-bearing mice may be due to the alteration of the tumor microenvironment, which involves the activation of the immune response and the recovery of serotonin level.

Involvement of SHP2 in focal adhesion, migration and differentiation of neural stem cells.

OBJECTIVES: SHP2 (Src-homology-2 domain-containing protein tyrosine phosphatase) plays an important role in cell adhesion, migration and cell signaling. However, its role in focal adhesion, differentiation and migration of neural stem cells is still unclear. METHODS: In this study, rat neurospheres were cultured in suspension and differentiated neural stem cells were cultured on collagen-coated surfaces. RESULTS: The results showed that p-SHP2 co-localized with focal adhesion kinase (FAK) and paxillin in neurospheres and in differentiated neural precursor cells, astrocytes, neurons, and oligodendrocytes. Suppression of SHP2 activity by PTP4 or siRNA-mediated SHP2 silencing caused reduction in the cell migration and neurite outgrowth, and thinning of glial cell processes. Differentiation-induced activation of FAK, Src, paxillin, ERK1/2, and RhoA was decreased by SHP2 inactivation. CONCLUSIONS: These results indicate that SHP2 is recruited in focal adhesions of neural stem cells and regulates focal adhesion formation. SHP2-mediated regulation of neural differentiation and migration may be related to formation of focal adhesions and RhoA and ERK1/2 activation.

A study on radiation technological degradation of organic chloride wastewater--exemplified by TCE and PCE.

This paper describes the potential of using gamma radiation technology to degrade trichloroethylene (TCE) and perchloroethylene (PCE) wastewater. The experimental method is divided into two parts: (1) using the gamma-ray to irradiate the TCE and PCE solution, the dose-rate is 10Gy/minute, the irradiation dosage is 0-2.5kGy and (2) self-making the UV irradiation system, the tube specification is 254nm and 6W, and turning on 8 tubes at the same time to make the irradiation. The efficiency of degradation ratio for gamma-ray is better than UV in the range of 0.1-250ppm; for example, as for the concentration of 0.1ppm, when TCE is degraded to D(90) and T(90), the gamma-ray only needed 46.7Gy and took about 4.67 minutes, but UV needed to take about 28.1 minutes. The dose-concentration equations of TCE and PCE are: TCE: y=44.58+8.832x, R(2)=0.999; and PCE: y=81.33+12.81x, R(2)=0.997. We verified that the radiation technology is able to effectively degrade the organic chlorine wastewater without yielding the secondary pollution, and the TCE and PCE that degraded by using gamma-ray will be reached US-EPA and Taiwan Effluent Standard (5ppb).

Dual-isotope single-photon emission computed tomography for dopamine and serotonin transporters in normal and Parkinsonian monkey brains.

INTRODUCTION: Parkinson's disease (PD) affects both dopaminergic and serotonergic systems. In this study, we simultaneously evaluated dopamine and serotonin transporters in primates using dual-isotope single-photon emission computed tomography (SPECT) imaging and compared the results with traditional single-isotope imaging. METHODS: Four healthy and one 6-OHDA-induced PD monkeys were used for this study. SPECT was performed over 4 h after individual or simultaneous injection of [(99m)Tc]TRODAT-1 (a dopamine transporter imaging agent) and [(123)I]ADAM (a serotonin transporter imaging agent). RESULTS: The results showed that the image quality and uptake ratios in different brain regions were comparable between single- and dual-isotope studies. The striatal [(99m)Tc]TRODAT-1 uptake in the PD monkey was markedly lower than that in normal monkeys. The uptake of [(123)I]ADAM in the midbrain of the PD monkey was comparable to that in the normal monkeys, but there were decreased uptakes in the thalamus and striatum of the PD monkey. CONCLUSIONS: Our results suggest that dual-isotope SPECT using [(99m)Tc]TRODAT-1 and [(123)I]ADAM can simultaneously evaluate changes in dopaminergic and serotonergic systems in a PD model.

Imaging of regional metabolic activity by (18)F-FDG/PET in rats with transient cerebral ischemia.

Changes in regional metabolic activities induced by middle cerebral artery occlusion (MCAO) can influence patient outcome. Our aim was to demonstrate in a rat model that (18)F-FDG with positron emission tomography (PET) imaging is a quantitative, reproducible approach for identifying acute and sub-acute metabolic variations in infarct regions. We found that imaging with (18)F-FDG/PET enabled detection and quantification of ischemia-induced metabolic deficits and provided a sensitive and reliable means of assessing cerebral ischemic lesions compared with conventional neurological scoring systems in rodents.

Effects of interleukin-15 on neuronal differentiation of neural stem cells.

Interleukin-15 (IL-15) signaling has pleiotropic actions in many cell types during development and has been best studied in cells of immune system lineage, where IL-15 stimulates proliferation of cytotoxic T cells and induces maturation of natural killer cells. A few reports have indicated that IL-15 and the IL-15 receptor are expressed in central nervous system tissues and neuronal cell lines. Because this aspect of IL-15 action is poorly studied, we used cultured rat neural stem cells (NSCs) to study IL-15 signal transduction and activity. Primary cultures of rat NSCs in culture will form neurospheres and will differentiate into neuron, astrocyte, and oligodendrocyte progenitors under permissive conditions. We found by immunofluorescence that the IL-15Ralpha subunit of the IL-15 receptor was expressed in NSCs and differentiating neurons, but not astrocyte or oligodendrocyte progenitors. We also showed that IL-15 treatment reduced MAP-2 protein levels in neurons and could reduce neurite outgrowth in differentiating neurons but did not affect NSC proliferation, and cell proportions and viability of the corresponding lineage cells. In the presence of a STAT3 inhibitor, Stattic, IL-15 no longer reduced MAP-2 protein levels. IL-15 treatment caused STAT3 phosphorylation. Furthermore, using anti-IL-15Ralpha antibody to block IL-15 signaling completely inhibited IL-15-induced phosphorylation of STAT3 and prevented IL-15 from decreasing neurite outgrowth. In conclusion, IL-15 may influence neural cell differentiation through a signal transduction pathway involving IL-15Ralpha and STAT3. This signal transduction modifies MAP-2 protein levels and, consequently, the differentiation of neurons from NSCs, as evidenced by reduced neurite outgrowth.

Simultaneous [99mTc]TRODAT-1 and [123I]ADAM brain SPECT in nonhuman primates.

PURPOSE: This study examined the feasibility of simultaneous dopamine and serotonin transporter imaging using [(123)I]ADAM and [(99m)Tc]TRODAT-1 single photon emission computed tomography (SPECT). PROCEDURES: Simultaneous [(123)I]ADAM (185 MBq) and [(99m)Tc]TRODAT-1 (740 MBq) SPECT was performed in three age-matched female Formosan rock monkeys. An asymmetric energy window was used for dual, and symmetric energy windows were used for single-isotope imaging. Oral fluoxetine (20 mg) and intravenous methylphenidate HCl (1 mg/kg) were given 24 h and 10 min, respectively, before dual-isotope SPECT to test imaging specificities of [(123)I]ADAM and [(99m)Tc]TRODAT-1. RESULTS: Comparable image quality and uptake ratios between dual- and single-isotope SPECT scans were found. Dual-isotope SPECT in fluoxetine-pretreated monkeys showed decreased uptake of [(123)I]-ADAM, but not of [(99m)Tc]TRODAT-1. Dual-isotope SPECT in methylphenidate-pretreated monkeys showed decreased [(99m)Tc]TRODAT-1 uptake without affecting [(123)I]-ADAM uptake. CONCLUSION: Simultaneous [(123)I]-ADAM and [(99m)Tc]TRODAT-1 SPECT appears promising in nonhuman primates and may provide a suitable preclinical model with further clinical implications.