Optimizing the Performance of 68Ga Labeled FSHR Ligand in Prostate Cancer Model by Means of Aprotinin

Purpose: Radiolabeled FSH1 peptides are potential specific probes for FSHR imaging. However, moderate uptakes and fast washout from the tumors may limit its widespread use. In this study, 68Ga labeled modified FSH1 analogs was prepared and the imaging properties were determined in the prostate cancer model with or without aprotinin.Methods: NOTA-MAL-FSH4 was synthesized and labeled with 68Ga. The pharmacokinetic profile of the peptide after co-administration with aprotinin was determined through metabolism analyses and microPET imaging.Results: 68Ga-NOTA-MAL-FSH4 was successfully prepared. The IC50 value of displacement 68Ga-NOTA-MAL-FSH4 with FSH1 was 139.4±1.16 nM. The PC-3 prostate tumor was visible after administration of the 68Ga labeled tracer. In vitro RP-HPLC analysis revealed that the average percentage of intact peptide in the plasma, liver and tumor was 8.30, 9.57 and 7.06 % respectively. In presence of aprotinin, the amounts of intact peptide increased to 34.32%, 20.63 % and 15.39 % in the counterparts respectively. MicroPET imaging showed that the uptakes of PC-3 tumors at 60mins after co-administration of 100μg, 200μg or 400μg enzyme inhibitors were 2.91±0.21%ID/g, 3.89±0.16%ID/g and 9.21±0.22%ID/g respectively.Conclusion: With the aid of a serine protease inhibitor, the performance of the 68Ga labeled peptide was optimized, which may benefit further clinical application.

Antidepressant-Like Effects of Chronic Guanosine in the Olfactory Bulbectomy Mouse Model

Major depressive disorder (MDD) leads to pervasive changes in the health of afflicted patients. Despite advances in the understanding of MDD and its treatment, profound innovation is needed to develop fast-onset antidepressants with higher effectiveness. When acutely administered, the endogenous nucleoside guanosine (GUO) shows fast-onset antidepressant-like effects in several mouse models, including the olfactory bulbectomy (OBX) rodent model. OBX is advocated to possess translational value and be suitable to assess the time course of depressive-like behavior in rodents. This study aimed at investigating the long-term behavioral and neurochemical effects of GUO in a mouse model of depression induced by bilateral bulbectomy (OBX). Mice were submitted to OBX and, after 14 days of recovery, received daily (ip) administration of 7.5 mg/kg GUO or 40 mg/kg imipramine (IMI) for 45 days. GUO and IMI reversed the OBX-induced hyperlocomotion and recognition memory impairment, hippocampal BDNF increase, and redox imbalance (ROS, NO, and GSH levels). GUO also mitigated the OBX-induced hippocampal neuroinflammation (IL-1, IL-6, TNF-α, INF-γ, and IL-10). Brain microPET imaging ([18F]FDG) shows that GUO also prevented the OBX-induced increase in hippocampal FDG metabolism. These results provide additional evidence for GUO antidepressant-like effects, associated with beneficial neurochemical outcomes relevant to counteract depression.

JAK2/STAT3 Signaling Pathway Plays a Key Role in Nicotine Mediated Neuroinflammation Suppression in an Ischemic Rat Model

BackgroundTo explore the mechanism of nicotine mediated improvement of cognitive impairment in an established ischemic rat model. MethodsEndothelin-1 (ET-1) was injected into the left thalamic region in adult male Sprague-Dawley (SD) rats to establish ischemia model. 6 groups of rats (6 rats in each group) were then treated with nicotine, nicotine+DHβE, DHβE, AG490, nicotine +AG490 and saline respectively via intraperitoneal injection for 9 days. Another sham operation group was treated with saline as above. Morris Water Maze (MWM) test was performed for 6 consecutive days starting on the 4th day after operation to detect the cognitive function of rats in each group. 2-[18F]-A-85380 microPET imaging was performed on day 10 to evaluate the changes of α4β2 nAChRs in different brain regions of rats. Real-time PCR and Western blot were used to detect the amount of α4β2 nAChRs, JAK2, STAT3 and inflammatory factors in thalamus of rats in each group. ResultsThe results of MWM test showed the spatial learning and memory abilities of rats in the nicotine and sham operation groups were significantly better than the saline treating group in this ischemic rat model (p<0.05). There was no significant difference in other groups (p>0.05). MicroPET imaging showed more uptake of 2-[18F]-A-85380 in the nicotine, nicotine+AG490 and sham operation groups than in saline treating group, while there was no significant difference found in other groups (p>0.05). The expression of α4- and β2-nAChR in nicotine, nicotine+AG490 and sham operation groups was significantly higher than the saline treating group (p<0.05). In the nicotine group, the expression of p-JAK2 and p-STAT3 in left thalamus of rats was significantly higher than the saline treating group (p<0.05), and the expression of IL-1β and IL-6 protein was found to be lower than the saline treating group (p<0.05). While the expression of p-JAK2, p-STAT3 and inflammatory factors was not significantly different in all the other groups (p>0.05). ConclusionThe study suggests nicotine inhibits the expression of inflammatory factors by activating α4β2 nAChRs through the activation of JAK2-STAT3 signaling pathway to improve cognitive impairment in ischemic rats.

Synthesis and Preliminary Evaluation of a Novel 18F-Labeled 2-Nitroimidazole Derivative for Hypoxia Imaging

ObjectiveHypoxia is prevalent in tumors and plays a pivotal role in resistance to chemoradiotherapy. 18F-MISO (18F-labeled fluoromisonidazole) is currently the preferred choice of PET hypoxia tracers in clinical practice, but has severe disadvantages involving complex labeling methods and low efficient imaging due to lipophilicity. We aimed to design a novel nitroimidazole derivative labeled by 18F via a chelation technique to detect hypoxic regions and provide a basis for planning radiotherapy.Materials and MethodsFirst, we synthesized a 2-nitroimidazole precursor, 2-[4-(carboxymethyl)-7-[2-(2-(2-nitro-1H-imidazol-1-yl)acetamido)ethyl]-1,4,7-triazanonan-1-yl]acetic acid (NOTA-NI). For 18F-labeling, a 18F solution was reacted with a mixture of AlCl3 and NOTA-NI at pH 3.5 and 100°C for 20 min, and the radiochemical purity and stability were evaluated. Biological behaviors of Al18F-NOTA-NI were analyzed by an uptake study in ECA109 normoxic and hypoxic cells, and a biodistribution study and microPET imaging in ECA109 xenografted mice.ResultsAl18F-NOTA-NI required a straightforward and efficient labeling procedure compared with 18F-MISO. The uptake values were distinctly higher in hypoxic tumor cells. Animal studies revealed that the imaging agent was principally excreted via the kidneys. Due to hydrophilicity, the radioactivities in blood and muscle were decreased, and we could clearly distinguish xenografted tumors from para-carcinoma tissue by PET imaging.ConclusionsThe nitroimidazole tracer Al18F-NOTA-NI steadily accumulated in hypoxic areas in tumors and was rapidly eliminated from normal tissue. It appears to be a promising candidate for hypoxia imaging with high sensitivity and resolution.

Application of a new 68Ga-labeled cNGR dimer peptide to microPET imaging of ovarian cancer

Introduction: Peptides containing the asparagine-glycine-arginine (NGR) sequence have been found to specifically bind to cluster of differentiation 13 (CD13) (aminopeptidase N), a tumor neovascular biomarker that is overexpressed on the surface of angiogenic blood vessels and various tumor cells and plays an important role in angiogenesis and tumor progression. The aim of this study was to evaluate the efficacy of a gallium-68 ( 68 Ga)-labeled dimeric cyclic NGR (cNGR) peptide as a new molecular probe that binds to CD13 in vitro and in vivo .Materials and Methods: A dimeric cNGR peptide conjugated with 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) and DOTA-c(NGR) 2 was synthesized and labeled with 68 Ga. In vitro uptake and binding analysis was performed in two ovarian tumor cell lines, ES2 and SKOV3, each of which have different expression levels of CD13. An in vivo biodistribution study was performed in normal mice, and micro positron emission tomography (PET) imaging was performed in nude mice xenografts with ES2 and SKOV3 tumors. Results : 68 Ga-DOTA-c(NGR) 2 with high radiochemical purity (>95%) was obtained and found to be stable at room temperature and when incubated with bovine serum at 37°C for 3 h. In vitro studies showed that uptake of 68 Ga-DOTA-c(NGR) 2 in ES2 cells increased over time, was higher than that in SKOV3 cells at all time points, and could be blocked by cold DOTA-c(NGR) 2 . Biodistribution studies demonstrated that 68 Ga-DOTA-c(NGR) 2 was mainly excreted from the kidney and rapidly cleared from blood. MicroPET imaging of ES2 tumor xenografts showed that focal uptake in tumors was distinctly observed from 1 to 1.5 h post-injection of 68 Ga-DOTA-c(NGR) 2 . Clear and high-contrast tumor visualization occurred at 1 h, which corresponded to the highest tumor/background ratio of 10.30±0.26. Moreover, accumulation of the probe in ES2 tumors apparently declined with pretreatment of unlabeled peptide, which further proved the specificity of 68 Ga-DOTA-c(NGR) 2 . In SKOV3 tumor models, the tumor was not obviously displayed under the same imaging protocols. Conclusion : We conclude that 68 Ga-DOTA-c(NGR) 2 might be a potential molecular probe for evaluating the expression levels of CD13 in different tumors, thereby providing a basis for targeting angiogenesis in cancer therapy.

Synthesis and evaluation of novel F-18-labeled pyrimidine derivatives: potential FAK inhibitors and PET imaging agents for cancer detection

Compound [18F]-8a exhibited good in vivo biodistribution data in mice bearing S180 tumor. And the microPET imaging study of [18F]-8a in S180 tumor-bearing mice was also preformed, which illustrated that the uptake in S180 tumor at 60 min post-injection of [18F]-8a was obvious.