S. Serrière

Amyloid load and translocator protein 18 kDa in APPswePS1-dE9 mice: a longitudinal study.

We studied concomitantly the level of neuroinflammation and β-amyloid (Aβ) load in the APPswePS1dE9 transgenic mouse model of Alzheimers disease using positron emission tomography. The translocator protein 18 kDa (TSPO) tracer [(18)F]DPA-714 was used to measure neuroinflammation and [(18)F]AV-45 for Aβ load in mice at 6, 9, 12, 15, and 19 months of age. At 19 months, we also analyzed the neuroinflammatory and neuroanatomic status of mice brains. The main affected brain areas were the cortex and hippocampus, with a concomitant progression of neuroinflammation with increased amyloid burden. At 19 months, no increase in TSPO binding was observed in the cerebellum; immunostaining revealed W0-2-positive plaques, indicating that the amyloid deposits seemed not stimulate inflammation. This finding was in agreement with the observed level of microglia and astrocytes staining. Our findings provide a better understanding of the relationships between neuroinflammation and plaque accumulation in the course of the disease in this mouse model. The monitoring of both processes should be of value to validate potential therapeutic approaches.

L’échographie haute résolution de la souris

Small-animal ultrasound imaging has been made possible using high-resolution imaging devices. The spatial resolution is therefore sufficient to accurately measure anatomical parameters in mice. This paper reviews some of the main applications of high-resolution ultrasound imaging of the mouse and highlights what could be the forthcoming advances.

Assessment of the Protection of Dopaminergic Neurons by an α7 Nicotinic Receptor Agonist, PHA 543613 Using [18F]LBT-999 in a Parkinson’s Disease Rat Model

The inverse association between nicotine intake and Parkinson’s disease (PD) is well established and suggests that this molecule could be neuroprotective through anti-inflammatory action mediated by nicotinic receptors, including the α7-subtype (α7R). The objective of this study was to evaluate the effects of an agonist of α7R, PHA 543613, on striatal dopaminergic neurodegeneration and neuroinflammation in a rat model of PD induced by 6-hydroxydopamine (6-OHDA) lesion. Adult male Wistar rats were lesioned in the right striatum and assigned to either the PHA group (n = 7) or the Sham group (n = 5). PHA 543613 hydrochloride at the concentration of 6 mg/kg (PHA group) or vehicle (Sham group) was intra-peritoneally injected 2 h before 6-OHDA lesioning and then at days 2, 4, and 6 post-lesion. Positron emission tomography (PET) imaging was performed at 7 days post-lesion using [18F]LBT-999 to quantify the striatal dopamine transporter (DAT). After PET imaging, neuroinflammation was evaluated in same animals in vitro through the measurement of the microglial activation marker 18 kDa translocator protein (TSPO) by quantitative autoradiography with [3H]PK-11195. The DAT density reflecting the integrity of dopaminergic neurons was significantly decreased while the intensity of neuroinflammation measured by TSPO density was significantly increased in the lesioned compared to intact striatum in both groups. However, these both modifications were partially reversed in the PHA group compared to Sham. In addition, a significant positive correlation between the degree of lesion and the intensity of neuroinflammation was evidenced. These findings indicate that PHA 543613 exerts neuroprotective effects on the striatal dopaminergic neurons associated with a reduction in microglial activation in this model of PD. This reinforces the hypothesis that an α7R agonist could provide beneficial effects for the treatment of PD.

Techniques et applications de l’échographie haute résolution non invasive

Today manufacturers propose echographic systems with a resolution ranging from 100 microm down to 30 microm. This requires ultrasonic frequencies ranging from 20 to 60 MHz. However, when associated with an increase in the attenuation of the wave in the media this limits the applications to superficial exploration. High frequencies also bring special technological limitations mainly in the fields of transducers, electronics, and acoustic coupling. Although high-resolution echography has long remained marginal and been used for the exploration of the skin or the anterior chamber of the eye, new powerful and easy-to-use devices have recently appeared on the market. With these new products, new applications have also appeared such as the exploration of the oral cavity or small laboratory animals (mice).Resume Aujourd’hui quelques fabricants proposent des appareils d’echographie dont la resolution peut aller de 100 μm a 30 μm. Pour cela ils utilisent des frequences ultrasonores comprises dans une gamme allant de 20 a 60 MHz. Mais cela se traduit par une augmentation de l’attenuation des milieux d’exploration, limitant les applications a l’exploration superficielle, et par l’apparition de nouvelles contraintes technologiques (transducteurs, systeme electronique, couplages acoustiques). Si l’echographie haute resolution est restee longtemps marginale et reservee a l’exploration de la peau ou de la chambre anterieure de l’œil, de nouveaux appareils performants et faciles a utiliser sont recemment apparus sur le marche. Avec ces nouveaux produits sont aussi apparus de nouveaux domaines d’applications comme l’exploration de la cavite buccale ou du petit animal de laboratoire (souris).

Detection of Neuroinflammation in a Rat Model of Subarachnoid Hemorrhage Using [18F]DPA-714 PET Imaging

Subarachnoid hemorrhage (SAH) can lead to delayed cerebral ischemia, which increases the rate of morbidity and mortality. The detection of microglial activation may serve as a biomarker for the identification of patients at risk of this deleterious consequence. We assessed this hypothesis in a rat model of SAH in which the exploration of neuroinflammation related to microglial activation was correlated with the degree of bleeding. We used the rat filament model and evaluated (at 48 hours postsurgery) the intensity of neuroinflammation using positron emission tomography (PET) imaging with the 18-kDa translocator protein (TSPO) tracer [18F]DPA-714, quantitative autoradiography with [3H]PK-11195, and SAH grade by postmortem brain picture. High SAH grades were strongly and positively correlated with in vivo PET imaging of TSPO in the cortex and striatum. In addition, a positive correlation was found in the cortex in TSPO, with densities determined by imaging and autoradiographic approaches. Qualitative immunofluorescence studies indicated that overexpression of TSPO was linked to astrocytic/microglial activation. In this model, PET imaging of TSPO using [18F]DPA-714 appeared to be a relevant index of the degree of bleeding, indicating that this imaging method could be used in human patients to improve the management of patients with SAH.

Ultrasound contrast agents in an in vivo murine melanoma model

The purpose of the study was to test different types of microbubble contrast agents (SonoVue®, Definity® and targeted microbubbles against vascular endothelial growth factor receptors (KDR, antiCD31)) to quantify angiogenesis. After SonoVue® and Definity® injections, a strong, rapid and heterogeneous signal enhancement was detected in all tumors. According to the tumor size, the quantification of the perfused area revealed major inter‐individual variations. Three groups of animals bearing tumors, following SonoVue® administration, were arbitrarily constituted to compare various sonographic parameters such as AUC, mTT, etcœ. The tumoral size increase seemed negatively correlated to a decrease in all quantified parameters. Non linear acoustic signal from microbubbles targeted to the molecular site was determined by an ultrasound‐based destruction‐reperfusion scheme. In tumor‐bearing mice, an increase of the retention time (>10 minutes) was revealed following KDR and antiCD31 targeted microbubbles administra...

Extensive exploration of a novel rat model of Parkinson's disease using partial 6-hydroxydopamine lesion of dopaminergic neurons suggests new therapeutic approaches

Parkinsons disease (PD) is characterized by the degeneration of dopaminergic (DA) neurons constituting the nigrostriatal pathway. Neuroinflammation, related to microglial activation, plays an important role in this process. Exploration of animal models of PD using neuroimaging modalities allows to better understand the pathophysiology of the disease. Here, we fully explored a moderate lesion model in the rat in which 6‐hydroxydopamine was unilaterally delivered in three sites along the striatum. The degenerative process was assessed through in vivo Positron Emission Tomography (PET) imaging and in vitro autoradiographic quantitation of the striatal dopamine transporter (DAT) and immunostaining of tyrosine hydroxylase (TH). The microglial activation was studied through in vitro autoradiographic quantitation of the 18 kDa translocator protein (TSPO) in the striatum and CD11b staining in the SN. In addition, a targeted metabolomics exploration was performed in both these structures using mass spectrometry coupled to HPLC. Our results showed a reproducible decrease in the striatal DAT density associated with a reduction in the number of TH‐positive cells in the SN and striatum, reflecting a robust moderate degeneration of nigrostriatal DA neurons. In addition, we observed strong microglia activation in both the striatum and SN ipsilateral to the lesion, highlighting that this moderate degeneration of DA neurons was associated with a marked neuroinflammation. Our metabolomics studies revealed alterations of specific metabolites and metabolic pathways such as carnitine, arginine/proline, and histidine metabolisms. These results bring new insights in the PD mechanism knowledge and new potential targets for future therapeutic strategies.

Irinotecan delivery by microbubble-assisted ultrasound - A pilot preclinical study

Irinotecan is conventionally used for the treatment of colorectal cancer. However, its administration is associated with severe side effects. Targeted drug delivery using ultrasound (US) combined with microbubbles offers new opportunities to increase the therapeutic effectiveness of antitumor treatment and to reduce toxic exposure to healthy tissues. The objective of this study is to investigate the safety and efficacy of in-vivo delivery of irinotecan by microbubble-assisted US in human glioblastoma model (U-87 MG). In order to validate the potential of this new method in-vivo, subcutaneous tumors were implanted in the flank of nude mouse and treated when they reached a volume of 100 mm3. In the first study, the measured volumes with caliper and anatomic ultrasound imaging were compared for the monitoring and the quantification of tumor growth during 27 days. Ultrasound imaging measurements were positively correlated to caliper measurements. The tumor treatment consisted of an i.v. injection of irinoteca...

Delivery of dopamine transporter tracer (PE2I) through blood brain barrier with ultrasound and microbubbles

The blood-brain barrier plays a major role in controlling the delivery of therapeutic and imaging agents to the brain. The aim of this study was to investigate the use of ultrasound and microbubbles to increase its delivery through the BBB and by determining the optimal experimental conditions that achieve a transient and safe BBB disruption. First, we established the ultrasound conditions that achieved a transient BBB disruption in rats using a non-permeant marker, Evans blue. Hence SonoVue® (450 μL/kg) and Evans blue (100 mg/kg) were intravenously administered. BBB leakage was obtained using ultrasound insonation through the rat skull at 1.6 MPa, PRF 1 Hz, duty cycle 12%, burst 10 ms during 120 sec. BBB disruption was observed in all treated animals (N=4) by histological analysis. The same experimental conditions were applied to enhance brain uptake of PE2I. Biological samples were analyzed using a scintillation counter apparatus. The results showed 50% and 20% increase of 125I-PE2I uptake in the striatum and cerebral cortex, respectively, in the treated rats (N=5) versus control (N=4). Similar enhancements were observed using SonoVue® at half concentration. This innovative method provides a great potential for intracerebral delivery of molecular ligands that could be used for the therapy of brain diseases.The blood-brain barrier plays a major role in controlling the delivery of therapeutic and imaging agents to the brain. The aim of this study was to investigate the use of ultrasound and microbubbles to increase its delivery through the BBB and by determining the optimal experimental conditions that achieve a transient and safe BBB disruption. First, we established the ultrasound conditions that achieved a transient BBB disruption in rats using a non-permeant marker, Evans blue. Hence SonoVue® (450 μL/kg) and Evans blue (100 mg/kg) were intravenously administered. BBB leakage was obtained using ultrasound insonation through the rat skull at 1.6 MPa, PRF 1 Hz, duty cycle 12%, burst 10 ms during 120 sec. BBB disruption was observed in all treated animals (N=4) by histological analysis. The same experimental conditions were applied to enhance brain uptake of PE2I. Biological samples were analyzed using a scintillation counter apparatus. The results showed 50% and 20% increase of 125I-PE2I uptake in the striat...

Appreciation precoce par echographie de contraste de la reponse des carcinomes hepatocellulaires traites par sorafenib

Objectifs Preciser les parametres d’evaluation en echographie de contraste (ECUS) de la reponse locale des carcinomes hepatocellulaires traites par sorafenib. Materiels et methodes Trente patients porteurs d’au minimum 1 lesion focale hepatique de type carcinome hepatocellulaire ont beneficie d’une ECUS pre-therapeutique puis a J30, J60 en sus du bilan habituel incluant la TDM avant et a 3 mois apres consentement eclaire. Les parametres suivants ont ete mesures : pourcentage de tissu viable intra-tumoral (2D et 3D), pic maximal de rehaussement, le temps d’arrivee, temps au pic, pente d’arrivee, aire sous la courbe, temps de transit moyen, indice de perfusion. Resultats En comparaison de J0, alors qu’etait notee une stabilite de taille il apparaissait des J30 une diminution significative des parametres precites y compris le taux de tissu viable intra-tumoral chez les patients presentant une diminution de la taille tumorale superieure a 10 % a J60. Par contre chez les patients non repondeurs, il etait note une stabilite ou augmentation des differents parametres. Ces variations etaient significativement reliees a une augmentation du temps jusqu’a progression et de la survie des patients. Conclusion L’echographie de contraste permet d’apprecier des J30 la reponse tumorale au traitement par sorafenib et ainsi la reponse clinique tardive.