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[¹⁸F]PBR146 and [¹⁸F]DPA-714 in vivo Imaging of Neuroinflammation in Chronic Hepatic Encephalopathy Rats.

ABSTRACT: Neuroinflammation is an important pathogenesis of hepatic encephalopathy (HE). The upregulation of translocator protein (TSPO) during neuroinflammation provides an imaging molecular target to evaluate the severity of neuroinflammation in chronic HE rats. [18F]DPA-714 and [18F]PBR146 targeting TSPO are often used for neuroinflammation imaging. This study performed bile duct ligation (BDL) in rats to simulate chronic HE model, tested the behavioral experiments, and conducted [18F]PBR146 and [18F]DPA-714 micro-PET/CT scans followed analyzing the average %ID/g values of the whole brain, brain regions and main organs of subjects. After sacrifice the rats, the blood plasma samples were taken for blood biochemical indexes and plasma inflammatory factor levels examination, the liver and brain specimens were obtained for pathological analysis. The BDL rats showed chronic liver failure with defects in cognition, motor coordination ability and mental state. [18F]PBR146 and [18F]DPA-714 micro-PET/CT imaging results were similar in whole brain of BDL group and Sham group. Besides, some regional brain areas in BDL rats were found abnormal uptakes mainly located in basal ganglia area, auditory cortex, motor cortex, cingulate gyrus, somatosensory cortex, hippocampus, thalamus, midbrain, and medulla oblongata, and these regions also correlated with behavioral alterations. In conclusion, both [18F]PBR146 and [18F]DPA-714 had the similar imaging effects in hepatic encephalopathy models could quantitatively evaluate neuroinflammation load and distribution. The difference brain regions with higher uptake values of radiotracers in BDL rats were correlated with behavioral alterations.

SUBMITTER: Kong X

PROVIDER: S-EPMC8415356 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Hypothyroidism is closely related to mental disorders, mainly depression, through an as-yet-unknown mechanism. The cerebral inflammatory immune process has been implied to play a pivotal role in the onset of affective symptoms in several conditions. In order to gain insight into the mechanism underlying the depressive behaviors in hypothyroid rats, brain microglial activation was evaluated using micro positron emission tomography imaging with a translocator protein (TSPO) radioligand. Hypothyroidism was induced in adult male Wistar rats by administration of 0.05% propylthiouracil in drinking water for five weeks. Open field, forced swimming and tail suspension tests were employed to evaluate the depressive behavior in hypothyroid rats, and the relationship between the behavioral changes and brain microglial activation was evaluated using [18F] DPA-714 micro positron emission tomography imaging. The open field test revealed significantly reduced first-minute activity and rearing behavior in the hypothyroid group, as well as significantly increased immobility in the forced swimming test and the tail suspension test. Hypothyroidism induced significantly increased microglial activation in the hippocampus. The radioligand uptake in the hippocampus correlated negatively with first-minute activity in the open field test (p < 0.05), and the radioligand uptake in the hippocampus correlated positively with changes in the immobility time in the forced swimming test and the tail suspension test (p < 0.05). Immunohistochemistry also confirmed the activation of microglia and inflammatory bodies in hypothyroid rats. The results indicate that hypothyroidism can induce depressive behavior in adult Wistar rats, microglial activation in the hippocampus plays an important role in the depressive behavior in hypothyroid rats and the inflammatory immune mechanism may underlie the behavioral abnormalities in thyroid dysfunction. Furthermore, the findings in the present study suggest there might be a common mechanism underlying depressive behavior in adult-onset hypothyroidism and depression.

Project description:BACKGROUND:Cerebral stroke is a severe and frequent condition that requires rapid and reliable diagnosis. If administered shortly after the first symptoms manifest themselves, IV thrombolysis has been shown to increase the functional prognosis by restoring brain reperfusion. However, a better understanding of the pathophysiology of stroke should help to identify potential new therapeutic targets. Stroke is known to induce an inflammatory brain reaction that involves overexpression of the 18-kDa translocator protein (TSPO) in glial cells and infiltrated leukocytes, which can be visualised by positron emission tomography (PET). We aimed to evaluate post-stroke neuroinflammation using the PET TSPO radioligand (18)?F-DPA-714. METHODS:Nine patients underwent (18)?F-DPA-714 PET and magnetic resonance imaging (MRI) between 8 and 18 days after the ictus. Co-registration of MRI and PET images was used to define three volumes of interest (VOIs): core infarction, contralateral region, and cerebellum ipsilateral to the stroke lesion. Time activity curves were obtained from each VOI, and ratios of mean and maximum activities between the VOIs were calculated. RESULTS:We observed an increased uptake of (18)?F-DPA-714 co-localised with the infarct tissue and extension beyond the region corresponding to the damage in the blood brain barrier. No correlation was identified between (18)?F-DPA-714 uptake and infarct volume. (18)?F-DPA-714 uptake in ischemic lesion (mainly associated with TSPO expression in the infarct area and in the surrounding neighbourhood) slowly decreased from 10 min pi to the end of the PET acquisition, remaining higher than that in both contralateral region and ipsilateral cerebellum. CONCLUSION:Our results show that (18)?F-DPA-714 uptake after acute ischemia is mainly associated with TSPO expression in the infarct area and in the surrounding neighbourhood. We also demonstrated that the kinetics of (18)?F-DPA-714 differs in injured tissue compared to normal tissue. Therefore, (18)?F-DPA-714 may be useful in assessing the extent of neuroinflammation associated with acute stroke and could also help to predict clinical outcomes and functional recovery, as well as to assess therapeutic strategies, such as the use of neuroprotective/anti-inflammatory drugs.

Project description:Background: Activation and dysregulation of innate, adaptive and resident immune cells in response to damage determine the pathophysiology of demyelinating disorders. Among the plethora of involved cells, microglia/macrophages and astrocytes play an important role in the pathogenesis of demyelinating disorders. The in-depth investigation of the spatio-temporal profile of these cell types in vivo may inform about the exact disease state and localization as well as may allow to monitor therapeutic modulation of the components of the neuroinflammatory response during the course of multiple sclerosis (MS). In this study, we aimed to non-invasively decipher the degree and temporal profile of neuroinflammation (TSPO - [18F]DPA-714 PET) in relation to selected magnetic resonance imaging (MRI) parameters (T2 maps) in the cuprizone (CPZ)-induced model of demyelination. Methods: C57Bl6 (n=30) mice were fed with a standard chow mixed with 0.2% (w/w) CPZ for 4 (n=10; demyelination) and 6 weeks (n=10; spontaneous remyelination). The degree of neuroinflammation at de- and remyelination was assessed by [18F]DPA-714 PET, multi-echo T2 MRI, autoradiography and immunohistochemistry. Results: CPZ-induced brain alterations were confirmed by increase of T2 relaxation times in both white and grey matter after 3 and 5 weeks of CPZ. Peak [18F]DPA-714 was found in the corpus callosum (CC, white matter), the hippocampus (HC, grey matter) and thalamus (grey matter) after 4 weeks of CPZ treatment and declined after 6 weeks of CPZ. Ex vivo autoradiography and dedicated immunofluorescence showed demyelination/remyelination with corresponding increased/decreased TSPO levels in the CC and hippocampus, confirming the spatial distribution of [18F]DPA-714 in vivo. The expression of TSPO microglia and astrocytes is time-dependent in this model. Microglia predominantly express TSPO at demyelination, while the majority of astrocytes express TSPO during remyelination. The combination of PET- and MRI-based imaging biomarkers demonstrated the regional and temporal development of the CPZ model-associated neuroinflammatory response in grey and white matter regions. Conclusions: The combination of [18F]DPA-714 PET and T2 mapping may allow to further elucidate the regional and temporal profile of inflammatory signals depending on the myelination status, although the underlying inflammatory microenvironment changes. A combination of the described imaging biomarkers may facilitate the development of patient-tailored strategies for immunomodulatory and neuro-restorative therapies in MS.

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[¹⁸F]PBR146 and [¹⁸F]DPA-714 in vivo Imaging of Neuroinflammation in Chronic Hepatic Encephalopathy Rats.

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[18F]PBR146 and [18F]DPA-714 in vivo Imaging of Neuroinflammation in Chronic Hepatic Encephalopathy Rats.

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OmicsDI is part of the ELIXIR infrastructure

Tweets

[¹⁸F]PBR146 and [¹⁸F]DPA-714 in vivo Imaging of Neuroinflammation in Chronic Hepatic Encephalopathy Rats.