Introduction The accumulation of neurofibrillary tangles, composed of aggregated hyperphosphorylated tau protein, starts spreading early in specific regions in the course of Alzheimer's disease (AD), ...correlating with the progression of memory dysfunction. The non-invasive imaging of tau could therefore facilitate the early diagnosis of AD, differentiate it from other dementing disorders and allow evaluation of tau immunization therapy outcomes. In this study we characterized the in vitro binding properties of THK5117, a tentative radiotracer for positron emission tomography (PET) imaging of tau brain deposits. Results Saturation and competition binding studies of .sup.3H-THK5117 in post-mortem AD brain tissue showed the presence of multiple binding sites. THK5117 binding was significantly higher in hippocampal (p 0.001) and temporal (p 0.01) tissue homogenates in AD compared to controls. Autoradiography studies with .sup.3H-THK5117 was performed on large frozen brain sections from three AD cases who had been followed clinically and earlier undergone in vivo.sup.18F-FDG PET investigations. The three AD cases showed distinct differences in regional THK5117 binding that were also observed in tau immunohistopathology as well as in clinical presentation. A negative correlation between in vivo.sup.18F-FDG PET and in vitro.sup.3H-THK5117 autoradiography was observed in two of the three AD cases. Conclusions This study supports that new tau PET tracers will provide further understanding on the role of tau pathology in the diversity of the clinical presentation in AD. Keywords: Alzheimer's disease, Tau pathology, THK5117, Imaging biomarker, Autopsy brain, Autoradiography
Imidazoquinoline compounds, such as resiquimod (R-848), are well known topically active immune modifiers that bind to toll-like receptor 7 (TLR7). The aim of this study was to characterize the R-848 ...induced inflammatory response in mice and to validate the response using methyl-prednisolone and anti-TNF antibody.
Intra-colonic application of R-848 to BALB/c mice induced a systemic transient elevation of TNF, CXCL1, IL-6, and IL-12p40 and a colonic elevation of cytokines/chemokines and iNOS, without infiltration of immune cells or epithelial destruction. Treatment with methyl-prednisolone or anti-TNF antibody attenuated the systemic (TNF, IL-6, IL-12p40, and CXCL1) and local (colonic TNF and iNOS mRNA expression) response induced by R-848.
In summary, intra-colonic administration of R-848 induces an acute systemic and local inflammatory response, which can be attenuated by steroids or anti-TNF antibody. We suggest that the R-848 inflammatory model can be useful in future validation of new drugs for gastrointestinal inflammatory conditions.
Tolterodine is a new muscarinic receptor antagonist intended for the treatment of urinary urge incontinence and other symptoms related to an overactive bladder. The aim of the present study was to ...compare the antimuscarinic properties of tolterodine with those of oxybutynin, in vitro and in vivo. Tolterodine effectively inhibited carbachol-induced contractions of isolated strips of urinary bladder from guinea pigs (
K
B 3.0 nM; pA
2 8.6; Schild slope 0.97) and humans (
K
B 4.0 nM; pA
2 8.4; Schild slope 1.04) in a concentration-dependent, competitive manner. The affinity of tolterodine was similar to that derived for oxybutynin (
K
B 4.4 nM; pA
2 8.5; Schild slope 0.89) in the guinea-pig bladder. Tolterodine (21–2103 nmol/kg (0.01–1 mg/kg); intravenous infusion) was significantly more potent in inhibiting acetylcholine-induced urinary bladder contraction than electrically-induced salivation in the anaesthetised cat. In contrast, oxybutynin displayed the opposite tissue selectivity. Radioligand binding data showed that tolterodine bound with high affinity to muscarinic receptors in urinary bladder (
K
i 2.7 nM), heart (
K
i 1.6 nM), cerebral cortex (
K
i 0.75 nM) and parotid gland (
K
i 4.8 nM) from guinea pigs and in urinary bladder from humans (
K
i 3.3 nM). Tolterodine and oxybutynin were equipotent, except in the parotid gland, where oxybutynin bound with 8-times higher affinity (
K
i 0.62 nM). Binding data on human muscarinic m1–m5 receptors expressed in Chinese hamster ovary cells showed that oxybutynin, in contrast to tolterodine, exhibits selectivity (10-fold) for muscarinic m3 over m2 receptors. The
K
B value determined for oxybutynin (4.4 nM) in functional studies on guinea-pig bladder correlated better with the binding affinity at muscarinic M
2/m2 receptors (
K
i 2.8 and 6.7 nM) than at muscarinic M
3/m3 receptors (
K
i 0.62 and 0.67 nM). The tissue selectivity demonstrated for tolterodine in vivo cannot be attributed to selectivity for a single muscarinic receptor subtype. However, the combined in vitro and in vivo data on tolterodine and oxybutynin may indicate either that muscarinic M
3/m3 receptors in glands are more sensitive to blockade than those in bladder smooth muscle, or that muscarinic M
2/m2 receptors contribute to bladder contraction.
Abstract
Background
The pathological features in Alzheimer’s disease (AD) brain include the accumulation and deposition of β-amyloid (Aβ), activation of astrocytes and microglia and disruption of ...cholinergic neurotransmission. Since the topographical characteristics of these different pathological processes in AD brain and how these relate to each other is not clear, this motivated further exploration using binding studies in postmortem brain with molecular imaging tracers. This information could aid the development of specific biomarkers to accurately chart disease progression.
Results
In vitro
binding assays demonstrated increased
3
H-PIB (fibrillar Aβ) and
3
H-PK11195 (activated microglia) binding in the frontal cortex (FC) and hippocampus (HIP), as well as increased binding of
3
H-
l
-deprenyl (activated astrocytes) in the HIP, but a decreased
3
H-nicotine (α4β2 nicotinic acetylcholine receptor (nAChR)) binding in the FC of AD cases compared to age-matched controls. Quantitative autoradiography binding studies were also performed to investigate the regional laminar distributions of
3
H-
l
-deprenyl,
3
H-PIB as well as
125
I-α-bungarotoxin (α7 nAChRs) and
3
H-nicotine in hemisphere brain of a typical AD case. A clear lamination pattern was observed with high
3
H-PIB binding in all layers and
3
H-deprenyl in superficial layers of the FC. In contrast,
3
H-PIB showed low binding to fibrillar Aβ, but
3
H-deprenyl high binding to activated astrocytes throughout the HIP. The
3
H-PIB binding was also low and the
3
H-deprenyl binding high in all layers of the medial temporal gyrus and insular cortex in comparison to the frontal cortex. Low
3
H-nicotine binding was observed in all layers of the frontal cortex in comparison to layers in the medial temporal gyrus, insular cortex and hippocampus. Immunohistochemical detection in the AD case revealed abundant glial fibrillary acidic protein positive (GFAP
+
) reactive astrocytes and α7 nAChR expressing GFAP
+
astrocytes both in the vicinity and surrounding Aβ neuritic plaques in the FC and HIP. Although fewer Aβ plaques were observed in the HIP, some hippocampal GFAP
+
astrocytes contained Aβ-positive (6 F/3D) granules within their somata.
Conclusions
Astrocytosis shows a distinct regional pattern in AD brain compared to fibrillar Aβ, suggesting that different types of astrocytes may be associated with the pathophysiological processes in AD.
Background
The 4R tauopathies corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are described as dementias with parkinsonian syndrome. Even if they are proven to represent ...clinically different entities, their complex neuropathology and common hallmarks often make the differential clinical diagnosis of CBD and PSP challenging. The highly entangled astrocytic and tau pathologies observed in these diseases are however displaying unique disparities which might unravel specific neuropathological profiles for each disease. The multi‐PET tracer approach applied in the present study in postmortem brain tissue might provide new mechanistic insights. We recently demonstrated that the second‐generation tau PET tracer, 3H‐PI2620 had a discriminative potential in CBD, PSP, and Alzheimer’s disease (AD) brains (Malarte et al. Mol. Psychiatry. 2022). To further understand the interaction between tau spatial distribution and its potential effects on astrocytic reactivity, we conducted a comparative multi‐tracer investigation in CBD, PSP, AD, and control brains using novel tau and astrocytic tracers. To gain a deeper insight into the relationship between tau, astrogliosis, and concomitant motor impairments, we also studied the interaction with the dopaminergic system.
Method
We performed autoradiography studies on large frozen hemispherical brain tissue of CBD, PSP, AD, and control cases using the tau PET tracer 3H‐PI2620, in comparison to astrocytic tracers (3H‐BU99008 and 3H‐Deprenyl) and dopaminergic tracers (3H‐Raclopride and 3H‐FE‐PE2I). We also analyzed the regional distribution of these tracers in small adjacent frozen brain sections of pathologically specific brain regions (globus pallidus, putamen, caudate, frontal cortex, medulla oblongata). We also performed saturation studies with 3H‐BU99008 and 3H‐Deprenyl on CBD and PSP brain homogenates
Result
Our preliminary results are promising and suggest high astrogliosis measured by 3H‐BU99008 and 3H‐Deprenyl in large frozen autoradiography in CBD and PSP brains, and with different binding intensities in different brain regions comparable with regional 3H‐PI2620 binding. 3H‐BU99008 and 3H‐Deprenyl both highlighted two binding sites in the putamen of CBD cases, but only one site in PSP.
Conclusion
Ongoing multi‐PET tracer studies targeting different pathological hallmarks of CBD and PSP tauopathies will improve differentiation and provide new knowledge regarding the spatial distribution of tau and its correlation with astrogliosis and the dopaminergic system in primary tauopathies.
Background
The 4R tauopathies corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are described as dementias with parkinsonian syndrome. Even if they are proven to represent ...clinically different entities, their complex neuropathology and common hallmarks often make the differential clinical diagnosis of CBD and PSP challenging. The highly entangled astrocytic and tau pathologies observed in these diseases are however displaying unique disparities which might unravel specific neuropathological profiles for each disease. The multi‐PET tracer approach applied in the present study in postmortem brain tissue might provide new mechanistic insights. We recently demonstrated that the second‐generation tau PET tracer, 3H‐PI2620 had a discriminative potential in CBD, PSP, and Alzheimer’s disease (AD) brains (Malarte et al. Mol. Psychiatry. 2022). To further understand the interaction between tau spatial distribution and its potential effects on astrocytic reactivity, we conducted a comparative multi‐tracer investigation in CBD, PSP, AD, and control brains using novel tau and astrocytic tracers. To gain a deeper insight into the relationship between tau, astrogliosis, and concomitant motor impairments, we also studied the interaction with the dopaminergic system.
Method
We performed autoradiography studies on large frozen hemispherical brain tissue of CBD, PSP, AD, and control cases using the tau PET tracer 3H‐PI2620, in comparison to astrocytic tracers (3H‐BU99008 and 3H‐Deprenyl) and dopaminergic tracers (3H‐Raclopride and 3H‐FE‐PE2I). We also analyzed the regional distribution of these tracers in small adjacent frozen brain sections of pathologically specific brain regions (globus pallidus, putamen, caudate, frontal cortex, medulla oblongata). We also performed saturation studies with 3H‐BU99008 and 3H‐Deprenyl on CBD and PSP brain homogenates
Result
Our preliminary results are promising and suggest high astrogliosis measured by 3H‐BU99008 and 3H‐Deprenyl in large frozen autoradiography in CBD and PSP brains, and with different binding intensities in different brain regions comparable with regional 3H‐PI2620 binding. 3H‐BU99008 and 3H‐Deprenyl both highlighted two binding sites in the putamen of CBD cases, but only one site in PSP.
Conclusion
Ongoing multi‐PET tracer studies targeting different pathological hallmarks of CBD and PSP tauopathies will improve differentiation and provide new knowledge regarding the spatial distribution of tau and its correlation with astrogliosis and the dopaminergic system in primary tauopathies.
Objective. To simultaneously study gastric accommodation and peristaltic motility in the whole stomach of conscious rats by measuring intragastric pressure (IGP) during test-meal infusion. Material ...and methods.After an overnight fast, a test-meal infusion system and a catheter to measure IGP were connected to a chronically implanted gastric fistula. IGP was measured during infusion of an X-ray-opaque, non-nutritious viscous test meal (0.25-2 ml min−1); gastric motility and emptying were assessed by X-ray fluoroscopy. Peristaltic motility-induced IGP waves were quantified as a motility index (wave amplitude divided by wavelength). Experiments were performed in Sprague-Dawley (SD) rats and in the high-anxiety Wistar Kyoto (WKY) rats. Moreover, the effects of 30 mg kg−1 NG-nitro-L-arginine methyl ester (L-NAME), 1 mg kg−1 atropine or 20 mg kg−1 molsidomine were tested in SD rats. Results. Compared with SD rats, IGP increased significantly faster during stomach distension in WKY rats, indicating impaired accommodation in the latter strain. Motility indices did not differ between the two strains. L-NAME significantly increased IGP during stomach distension, indicating decreased gastric accommodation. However, no change in motility indices was observed with L-NAME. Treatment with atropine significantly increased IGP and decreased motility indices, indicating decreased gastric accommodation and motility. Molsidomine significantly decreased IGP during stomach distension but did not affect motility. The results correspond to X-ray observations, and confirm literature data. Conclusions. We conclude that IGP measurement during test-meal infusion represents an efficient and novel method to compare gastric accommodation and peristaltic motility in the whole stomach of conscious rats.
The aim of this study was to investigate if a rapid magnetic resonance imaging (MRI) screening protocol (<5
min/mouse) could characterize colonic inflammation in a chronic experimental colitis model. ...No respiratory triggering or spasmolytic agent was used during MRI-acquisition. Biomarkers assessed
in vivo were colon wall thickness and T2w signal intensity (reflecting oedema) and
ex vivo inflammatory score, colon weight, and plasma haptoglobin. The inflammation was characterised by significantly higher local and systemic inflammatory markers in the colitic mice compared to healthy mice. MRI-colon wall thickness and T2w signal intensity correlated well with inflammatory score (
r
=
0.95 and 0.94), colon weight (
r
=
0.92 and 0.93) and plasma haptoglobin (
r
=
0.89 and 0.95). Thus, the data showed that
in vivo MRI screening could be used to assess colon wall inflammation, suggesting that high-throughput MRI can be used to follow the potential efficacy of new IBD therapies in individual animal in longitudinal studies.
Background
The Alzheimer’s disease (AD) biomarker field is moving rapidly. Creating a platform where multi‐PET tracer approaches and various fluid biomarkers with discriminative power in the early ...pathological stages could provide deeper insight into the role of reactive astrogliosis in the AD continuum. Accumulating data indicates that reactive astrogliosis may play a critical role in the early stages and, perhaps, precedes other pathological hallmarks of AD. Different PET tracers for imaging reactive astrogliosis are now available along with plasma GFAP showing a direct correlation with increased brain amyloid‐PET. We also propose that alpha‐7‐nicotinic acetylcholine receptors (α7nAChRs) might be early modulators of reactive astrogliosis and Aβ‐pathology in AD. New α7nAChRs‐PET‐tracers might be promising future new biomarkers of reactive astrogliosis with potential early diagnostic properties.
Method
Translational molecular imaging studies including in vivo multimodal PET investigations (11C‐deprenyl, 11C‐PIB, 18F‐Flutemematol, 18F‐FDG, 18F‐RO‐948), MRI, plasma GFAP analyses in control, presymptomatic ADAD, MCI to AD dementia and in vitro PET tracer binding studies (deprenyl, SMBT‐1, and BU99008) in postmortem brains using small/large section‐autoradiography and tissue‐homogenates.
Result
We hypothesize from our in vivo PET/in vitro brain imaging translational/clinical studies a ‘first and second wave of reactive astrogliosis’ with distinct close‐loop relationships with other pathological biomarkers across AD continuum. Validation of newly developed PET‐tracers BU99008 and SMBT‐1 for mapping and visualizing reactive astrogliosis in the brain demonstrated multiple binding properties in AD brain and highlighted the crucial need of multi‐PET tracer approach for understanding the complexity of reactive astrogliosis in AD. We have observed a significant positive correlation between plasma GFAP levels and 18F‐flutemetamol binding in patients undergoing memory assessment. In presymtomatic ADAD patients, high 11C deprenyl binding is observed earlier in the disease evolution than increase in plasma GFAP levels following a divergent direction. This clearly suggests plasma GFAP as a later biomarker than 11C‐deprenyl in AD trajectory, possibly reflecting different types of reactive astrocytes at different stages of AD.
Conclusion
It’s an exciting time for the AD field with several new biomarkers/PET‐tracers for reactive astrogliosis, which will improve our understanding of underlying astrocytic complexity and add power to the existing diagnostic criteria in AD.
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