Chikungunya virus (CHIKV) is the causative agent of the human disease chikungunya fever, characterized by debilitating acute and chronic arthralgia. No licensed vaccines or antivirals are currently ...available for CHIKV. Therefore, the prevention of attachment of viral particles to host cells is a potential intervention strategy. As an arbovirus, CHIKV infects a wide variety of cells in both its mammalian and mosquito host. This broad cell tropism might stem from CHIKV's ability to bind to a variety of entry factors in the host cell including phosphatidylserine receptors (PSRs), glycosaminoglycans (GAGs), and the proteinaceous receptor Mxra8, among others. In this study, we aimed to determine the relevance of each attachment factor during CHIKV entry into a panel of mammalian and mosquito cells. Our data suggest that the importance of particular binding factors during CHIKV infection is highly cell line dependent. Entry into mammalian Vero cells was mediated through attachment to PSRs, mainly T-cell immunoglobulin mucin domain-1 (TIM-1). Conversely, CHIKV infection into HAP1 and NIH3T3 was predominantly mediated by heparan sulfate (HS) and Mxra8, respectively. Entry into mosquito cells was independent of PSRs, HS, and Mxra8. Although entry into mosquito cells remains unclear, our data denotes the importance of careful evaluation of reagents used to identify receptor use in invertebrate cells. While PSRs, GAGs, and Mxra8 all enhance entry in a cell line dependent manner, none of these factors are necessary for CHIKV entry, suggesting additional host factors are involved.
Purpose
Hypoxia-inducible factor 1α (HIF-1α) activity is one of the major players in hypoxia-mediated glioma progression and resistance to therapies, and therefore the focus of this study was the ...evaluation of HIF-1α modulation in relation to tumour response with the purpose of identifying imaging biomarkers able to document tumour response to treatment in a murine glioma model.
Methods
U251-HRE-mCherry cells expressing Luciferase under the control of a hypoxia responsive element (HRE) and mCherry under the control of a constitutive promoter were used to assess HIF-1α activity and cell survival after treatment, both in vitro and in vivo, by optical, MRI and positron emission tomography imaging.
Results
This cell model can be used to monitor HIF-1α activity after treatment with different drugs modulating transduction pathways involved in its regulation. After temozolomide (TMZ) treatment, HIF-1α activity is early reduced, preceding cell cytotoxicity. Optical imaging allowed monitoring of this process in vivo, and carbonic anhydrase IX (CAIX) expression was identified as a translatable non-invasive biomarker with potential clinical significance. A preliminary in vitro evaluation showed that reduction of HIF-1α activity after TMZ treatment was comparable to the effect of an Hsp90 inhibitor, opening the way for further elucidation of its mechanism of action.
Conclusion
The results of this study suggest that the U251-HRE-mCherry cell model can be used for the monitoring of HIF-1α activity through luciferase and CAIX expression. These cells can become a useful tool for the assessment and improvement of new targeted tracers for potential theranostic procedures.
Purpose
The aim of this study was to characterize a cell-based model for the molecular study of hypoxia-inducible factor (HIF)-1α activity, in the context of hypoxia, by means of different imaging ...techniques.
Procedures
Engineered U251-HRE glioma cells were used to analyze the molecular mechanisms underlying HIF-1α activity
in vitro
in relation to luciferase expression. The same cells were orthotopically implanted in mice to evaluate tumor progression and hypoxia induction by bioluminescence imaging, fluorescence imaging, positron emission tomography (PET), and magnetic resonance imaging (MRI).
Results
In vitro
analyses highlighted the relationship between HIF-1α and luciferase activity in hypoxic conditions and after pharmacological treatments in U251-HRE cells. Through
in vivo
studies, it was possible to assess hypoxia establishment in relation to tumor growth by optical imaging, PET and MRI.
Conclusions
The findings of this study indicate that the U251-HRE orthotopic murine model can be used to reliably evaluate processes modulating HIF-1α activity, using both molecular and preclinical non-invasive imaging techniques.
The aim of this study was to evaluate the suitability of 11CSCH442416 for the in vivo imaging of adenosine A2A receptors.
In rats and Macaca nemestrina, we evaluated the time course of the cerebral ...distribution of 11CSCH442416. Furthermore, in rats we investigated the rate of metabolic degradation, the inhibitory effects of different drugs acting on adenosine or dopamine receptors and the modification induced by the intrastriatal administration of quinolinic acid (QA).
The rate of metabolic degradation of 11CSCH442416 in rats was slow; 60 min after tracer injection, more than 40% of total plasma activity was due to unmetabolised 11CSCH442416. At the time of maximum uptake, radioactive metabolites represented only 6% of total extractable activity in the cerebellum and less than 1% in the striatum. In the striatum, the region with the highest expression of A2A receptors, the in vivo uptake of 11CSCH442416 was significantly reduced only by drugs acting on A2A receptors or by QA, a neurotoxin that selectively reduces the number of intrastriatal GABAergic neurons. Position emission tomography (PET) studies in monkeys indicated that the tracer rapidly accumulates in brain, reaching maximum uptake between 5 and 10 min. Twenty minutes after the injection, radioactivity concentration in the striatum was two times that in the cerebellum.
The specificity of binding, the rank order of regional distribution in the brain of rats and M. nemestrina, the good signal to noise ratios and the low amount of radioactive metabolites in brain and periphery indicate that 11CSCH442416 is a promising tracer for the in vivo imaging of A2A adenosine receptors using PET.
A preclinical insert for small animal simultaneous SPECT and MR imaging, in particular for imaging mouse brains, is presented. It consists of ten static magnetic resonance imaging (MRI)-compatible ...gamma cameras based on tiles of silicon photomultipliers readout by a multichannel ASIC and coupled to 5 cm × 5 cm CsI(Tl) scintillators and to an MRI-compatible multipinhole collimator. Calibration and image reconstruction algorithm are illustrated. Mutual compatibility is demonstrated along with imaging performance that is comparable with other non-MR micro-SPECT systems: 0.9 mm tomographic spatial resolution across a transverse field of view of 15.6 mm, 12% energy resolution (at 140 keV), and 1105 cps/MBq sensitivity. Experimental results with phantoms (glass capillaries of 290 μm diameter and a mini Derenzo) are presented.
The peripheral-type benzodiazepine receptors (PBRs) are only minimally expressed in normal brain parenchyma, where they are primarily localized in glial cells. Their basal expression rises in ...different neurodegenerative disorders, due to the presence of infiltrating inflammatory cells and activated microglia.
11
C
PK11195, a selective PBR antagonist, has been used for the in vivo PET monitoring of neurodegeneration in clinical observations. We recently developed and labeled with carbon-11 three new carboxamide derivatives:
11
C
VC193M,
11
C
VC195 and
11
C
VC198M. Aim of this study was to evaluate these ligands for the in vivo measuring of PBRs expression in neurodegenerations and compare their kinetic behavior with that of the reference tracer
11
C
PK11195. Radioligands were evaluated in a preclinical model of Huntington’s disease consisting in the monolateral striatal injection of quinolinic acid (QA). Activated microglia and astrocytic gliosis was present only within the affected striatum. A concomitant increase in radioactivity accumulation was observed for all the tracers examined (
P<0.01). Among the new compounds,
11
C
VC195 showed higher levels of lesioned/unlesioned striatum ratios (3.28±0.44), in comparison with
11
C
VC193M and
11
C
VC198M (2.69±0.53 and 1.52±0.36, respectively), but slightly inferior to that observed for
11
C
PK11195 (3.76±1.41).
In conclusion, the results of the study indicate that
11
C
VC195 is a promising candidate for in vivo PET monitoring of neurodegenerative processes but its in vivo behavior overlap that of
11
C
PK11195.
The DRAGO gamma camera Fiorini, C; Gola, A; Peloso, R ...
Review of scientific instruments,
04/2010, Letnik:
81, Številka:
4
Journal Article
Recenzirano
In this work, we present the results of the experimental characterization of the DRAGO (DRift detector Array-based Gamma camera for Oncology), a detection system developed for high-spatial resolution ...gamma-ray imaging. This camera is based on a monolithic array of 77 silicon drift detectors (SDDs), with a total active area of 6.7 cm(2), coupled to a single 5-mm-thick CsI(Tl) scintillator crystal. The use of an array of SDDs provides a high quantum efficiency for the detection of the scintillation light together with a very low electronics noise. A very compact detection module based on the use of integrated readout circuits was developed. The performances achieved in gamma-ray imaging using this camera are reported here. When imaging a 0.2 mm collimated (57)Co source (122 keV) over different points of the active area, a spatial resolution ranging from 0.25 to 0.5 mm was measured. The depth-of-interaction capability of the detector, thanks to the use of a Maximum Likelihood reconstruction algorithm, was also investigated by imaging a collimated beam tilted to an angle of 45 degrees with respect to the scintillator surface. Finally, the imager was characterized with in vivo measurements on mice, in a real preclinical environment.
Purpose
Huntington’s disease (HD) is a progressive neurodegenerative disorder, which is characterised by prominent neuronal cell loss in the basal ganglia with motor and cognitive disturbances. One ...of the most well-studied pharmacological models of HD is produced by local injection in the rat brain striatum of the excitotoxin quinolinic acid (QA), which produces many of the distinctive features of this human neurodegenerative disorder. Here, we report a detailed analysis, obtained both in vivo and in vitro of this pharmacological model of HD.
Materials and methods
By combining emission tomography (PET) with autoradiographic and immunocytochemical confocal laser techniques, we quantified in the QA-injected striatum the temporal behavior (from 1 to 60 days from the excitotoxic insult) of neuronal cell density and receptor availability (adenosine A
2A
and dopamine D
2
receptors) together with the degree of microglia activation.
Results
Both approaches showed a loss of adenosine A
2A
and dopamine D
2
receptors paralleled by an increase of microglial activation.
Conclusion
This combined longitudinal analysis of the disease progression, which suggested an impairment of neurotransmission, neuronal integrity and a reversible activation of brain inflammatory processes, might represent a more quantitative approach to compare the differential effects of treatments in slowing down or reversing HD in rodent models with potential applications to human patients.
We investigated the tissue-specific effects of dichlorodyphenyltrichloroethane (DDT) isomers in adult and suckling newborn mice, using a novel mouse line engineered to express a reporter of estrogen ...receptor transcriptional activity (ERE-tkLUC mouse). The DDT isomers p,p’-DDT 1,1,1-trichloro2,2-bis(p-chlorophenyl) ethane and o,p’-DDT 1,1,1-trichloro-2(p-chlorophenyl)-2-(o-chlorophenyl) ethane were specifically selected as a weak and a strong estrogen, respectively. In adult male mice, p,p’-DDT induced luciferase activity in liver, brain, thymus, and prostate but not in heart and lung. The effect of p,p’-DDT was dose-dependent, maximal at 16 h after sc treatment, and completely blocked by the estrogen receptor antagonist ICI-182,780. In all the organs analyzed, except the liver, administration of o,p’-DDT showed a pattern of luciferase induction superimposable to that of its isomer p,p’-DDT. In liver, o,p’-DDT significantly decreased basal luciferase activity and blocked the reporter induction by 17β-estradiol. These data lead us to hypothesize that a modulation of ER activity may be involved in the toxic effects of DDT demonstrated by epidemiological and experimental studies.
Luciferase activity was also studied in 4-d-old mice lactating from a mother injected with either p,p’-DDT or o,p’-DDT. Both isomers induced a 2-fold increase in the newborn brain. An opposite effect was observed in liver, where p,p’-DDT increased and o,p’-DDT decreased luciferase, thus indicating that these compounds modulate ER activity in adult and newborn tissues by use of a similar mechanism.
The ERE-tkLUC mouse proves to be a suitable tool to functionally assess the tissue specificity of estrogenic/antiestrogenic compounds in adult (as well as in suckling) mice.
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