Biology subjects

Haider, A.

Publications and source records attributed to Haider, A..

18 recordsLinked to original sources

bioRxiv2026

Highly diverged non-vertebrate Ki-67 proteins with conserved biophysical and functional properties

The Ki-67 protein is a widely used marker of mammalian cell proliferation that plays critical roles in heterochromatin organisation and mitotic perichromosomal layer formation. Thus, its apparent restriction to vertebrates is puzzling. However, sequences with limited homology to subdomains of Ki-67 are present in genomes from some non-vertebrate species. Here, using structural modelling, biophysical and functional analysis, we identify Ki-67-like proteins across diverse non-vertebrate eukaryotes, including tunicates, sponges, molluscs, insects and fungi. Despite extremely low sequence homology, the disordered domains of Ki-67 homologues have generally conserved biophysical and molecular properties. This is further reflected by comparison of cellular localisation, dynamics and effects on chromatin organisation of human, Ciona and Drosophila Ki-67 homologues. These results reinforce the emerging paradigm that functions may be encoded by general biophysical features in highly diverged intrinsically disordered domains. Our approach provides a blueprint for comparative biology of disordered proteins and a foundation for future studies exploring functions of Ki-67 homologues across eukaryotes.

Cell Biology↗

bioRxiv2026

Radiosynthesis and Evaluation of Novel Cholesterol 24-Hydroxylase Positron Emission Tomography Tracers

Cholesterol 24-hydroxylase (CH24H or CYP46A1) is a pivotal enzyme in brain cholesterol metabolism and has emerged as a therapeutic and imaging target in neurodegenerative disorders. Although [18F]Cholestify ([18F]CHL-2205) has shown promise as a positron emission tomography (PET) tracer for imaging of CYP46A1, the impact of cyclopropyl moiety conformation on binding and imaging performance remains unexplored. Here, we report the rational design and preliminary evaluation of novel CYP46A1 PET tracers, in which the left-side cyclopropyl group was modified into bridged, spirocyclic, and fused bicyclic architectures to probe steric and conformational effects. All compounds 9-11 exhibited high CYP46A1 affinity (IC50 = 0.19-0.28 nM). Radiosynthesis of [18F]9-11 was achieved via copper-mediated [18F]fluorination, providing practical non-decay-corrected radiochemical yields of 10-34% with excellent radiochemical purity (>98%). In vitro autoradiography in rat brain sections demonstrated specific and regionally selective binding, comparable to that observed for [18F]CHL-2205. These cyclopropyl-derived scaffolds establish a scaffold-driven strategy for PET tracer development, providing a robust framework for further structure-activity relationship studies and the rational optimization of CYP46A1 PET tracers.

pharmacology and toxicology↗

bioRxiv2025

Longitudinal multi-omic evaluation of biomarkers of health and ageing over smoking cessation intervention

Smoking is one of the single most important preventable risk factors for cancer and other adverse health outcomes 1,2. Smoking cessation represents a key public health intervention with the potential to reduce its negative health outcomes 2-4. While epidemiological, cross-sectional, and individual longitudinal omic or biomarker studies have evaluated the impact of smoking cessation, no study to date has systematically profiled molecular and clinical changes in several organ systems or tissues longitudinally over the course of smoking cessation that could allow for more detailed assessment of response biomarkers and the identification of interindividual differences in the recovery of physiological functions. Here, we report the first human longitudinal multi-omic study of smoking cessation, evaluating 2,501 unique single or composite features from 1,094 longitudinal samples. Our comprehensive analysis, leveraging over half a million longitudinal data points, revealed a profound effect of smoking cessation on epigenetic biomarkers and microbiome features across multiple organ systems within 6 months of smoking cessation, alongside shifts in the immune and blood oxygenation system. Moreover, our multi-omic analysis provided unprecedented granularity that allows for identification of new cross-ome associations for mechanistic discovery. We anticipate that data and an interactive app from the Tyrol Lifestyle Atlas (eutops.github.io/lifestyle-atlas), comprising the current study and a parallel study arm evaluating the impact of diet on biomarkers of health and disease, will provide the basis for future discovery, biomarker benchmarking in their responsiveness to health-promoting interventions, and study of individualised response group, representing a major advance for personalised health monitoring using biomarkers.

systems biology↗

bioRxiv2025

Systemic multi-omic remodelling underlies health benefits of intermittent fasting

While intermittent fasting (IF) promotes longevity in animal models, its systemic effects in humans remain poorly understood. Here, we present a six-month longitudinal IF intervention in 114 women (BMI 25-35) with deep clinical, molecular, and microbiome profiling across >3,400 biospecimens from six tissues. Analyses spanning >2,200 multi-omic features and 11,000 microbial function predictions demonstrate coordinated clinical benefits, including improvements in body composition and cardiorespiratory fitness, and reveal coordinated molecular responses across tissues. Iron metabolism emerged as a central axis: transferrin increased while ferritin, haemoglobin, and erythrocytes decreased, changes that opposed ageing trajectories yet remained within physiological limits. Epithelial DNA methylation biomarkers (cervical, buccal) of cancer risk reduced, while blood clocks were largely unresponsive, underscoring tissue-specificity of the epigenome. Immune profiling uncovered dynamic, partially reversible shifts. Notably, we derived a new immunophenotyping-based ImmuneAge score that increased during fasting and tracked with inflammatory function, while the pro-inflammatory cytokine IL-17A declined selectively in postmenopausal women. Oral microbiota showed rapid restructuring, whereas gut microbiota shifted more subtly toward enhanced metabolic capacity. Together, these data provide unprecedented insight into the systemic and tissue-specific responses to IF in humans and identify iron homeostasis and immune remodelling as candidate mechanisms. Our findings are available through the Lifestyle Atlas (https://eutops.github.io/lifestyle-atlas). HighlightsO_LIIntermittent fasting remodels iron metabolism, opposing age-associated trajectories C_LIO_LIEpithelial but not blood methylation biomarkers respond to fasting C_LIO_LIFasting transiently elevates ImmuneAge and TNF-producing cytotoxic T cells C_LIO_LIOral microbiota restructure rapidly, while gut microbiota show subtler functional shifts C_LIO_LIIntegrative networks link iron, immunity, adiposity, and epithelial barrier function C_LI

systems biology↗

bioRxiv2025

FAVABEAN and FALAPhyl: Open-Source Pipelines for Scalable 16s rRNA Microbiome Data Processing and Visualization

Reproducible and scalable analysis of 16S rRNA amplicon sequencing data remains a persistent challenge in microbiome research due to the complexity of available tools, incompatibilities between platforms, and the need for extensive bioinformatics expertise. We developed two containerized workflows--FAVABEAN (Fast Amplicon Variant Annotation, Binning, Error-correction And ANalysis) and FALAPhyl (Forays into Automating Laborious Analyses of Phylogeny)--to address these challenges. FAVABEAN and FALAPhyl are Snakemake-based pipelines designed for flexible execution across local, cluster, and cloud environments. FAVABEAN automates preprocessing, ASV inference, and taxonomic assignment using DADA2 and FIGARO, including primer averaging when samples are sequenced with multiple primers. FALAPhyl supports downstream analysis including alpha/beta diversity, network analysis, and differential abundance testing, with integrated provenance tracking. We validated both pipelines using three case studies involving oral microbiome datasets. In Case Study 1, we compared oral microbiota across family members and niches, showing primer-dependent variability in ASV-based similarity and minimal reseeding from familial sources after prophylaxis. Case Study 2 analyzed dental aerosol samples, revealing no significant microbial differences between pre-, intra-, and post-procedure air. Case Study 3, a randomized trial of a nitrate mouthrinse, demonstrated no significant microbiome shifts, highlighting oral microbial stability. FALAPhyls integration of DAtest enabled empirical evaluation of multiple statistical tests, aiding robust differential abundance inference. FAVABEAN and FALAPhyl offer a reproducible, automated solution for 16S rRNA amplicon data analysis. Their modular design, containerization, and provenance tracking enhance accessibility and scientific rigor in microbiome research.

bioinformatics↗

bioRxiv2025

SARM1 base-exchange inhibitors induce SARM1 activation and neurodegeneration at low doses

SARM1 has emerged as a promising therapeutic target in neurology due to its central role in axonal degeneration and its amenability to different modes of small molecule inhibition. One chemical approach to modulate SARM1 involves orthosteric inhibition via a SARM1-mediated base-exchange reaction between a small molecule and nicotinamide adenine dinucleotide (NAD+), the substrate of SARM1, to generate the active inhibitor. Here, we report that subinhibitory concentrations of SARM1 base-exchange inhibitors (BEIs) paradoxically increase SARM1 activity and worsen SARM1-induced cell death and neuronal damage in vitro. Low dose administration of RO-7529, a SARM1 BEI, exacerbated experimental autoimmune encephalomyelitis (EAE)-induced neurodegeneration in vivo. Our data highlight a unique pharmacological feature of SARM1 BEIs that may limit their therapeutic application in disorders associated with SARM1 activation and axonal degeneration.

neuroscience↗

bioRxiv2025

Preclinical Evaluation of P4B-2412 as Phosphodiesterase 4B Radioligand for Positron Emission Tomography Imaging

Phosphodiesterase 4B (PDE4B) plays a critical role in cAMP hydrolysis and is highly expressed in brain regions associated with neuroinflammation and neurodegenerative disorders. Selective PDE4B radioligands hold significant potential for elucidating disease mechanisms and enabling target occupancy measurements. In this study, we developed [18F]P4B-2412, a novel PDE4B-selective radioligand, and evaluated its utility for PET imaging. [18F]P4B-2412 was synthesized with high radiochemical yield (27.2%), excellent radiochemical purity (99%), and favorable molar activity (66.2 {+/-} 2.5 GBq/mol). In vitro autoradiography revealed high PDE4B binding, while dynamic PET imaging demonstrated high in vivo specificity for PDE4B in rodent brain regions. Notably, [18F]P4B-2412 exhibited excellent metabolic stability in vitro and in vivo. These findings establish [18F]P4B-2412 as a promising PET probe for imaging PDE4B in vivo, offering a valuable tool for investigating neuroinflammation and advancing CNS drug development.

neuroscience↗

bioRxiv2024

GenomeDelta: detecting recent transposable element invasions without repeat library

To evade repression by the host defense, transposable elements (TEs) are occasionally horizontally transferred (HT) to naive species. TE invasions triggered by HT may be much more abundant than previously thought. For example, previous studies in Drosophila melanogaster found 11 TE invasions over 200 the past years. A major limitation of current approaches for detecting recent invasions is the necessity for a repeat-library, which is notoriously difficult to generate. To address this, we developed GenomeDelta, a novel approach for identifying sample-specific sequences, such as recently invading TEs, without prior knowledge of the sequence. It can thus be used with model and non-model organisms. As input, GenomeDelta requires a long-read assembly and short-read data. It will find sequences in the assembly that are not represented in the short read data. Beyond identifying recent TE invasions, GenomeDelta can detect sequences with spatially heterogeneous distributions, recent insertions of viral elements and recent lateral gene transfers. We thoroughly validated GenomeDelta with simulated and real data from extant and historical specimens. Finally, we demonstrate that GenomeDelta can reveal novel biological insights: we discovered the three most recent TE invasions in Drosophila melanogaster and a novel TE with a geographically heterogeneous distribution in Zymoseptoria tritici.

bioinformatics↗

bioRxiv2024

Unveiling the complete invasion history of D. melanogaster: three horizontal transfers of transposable elements in the last 30 years

Transposable elements (TEs) are repetitive sequences capable of mobilizing within genomes, exerting significant influence on evolution throughout the tree of life. Using a novel approach that does not require prior knowledge about the sequence of repeats, we identified three novel TE invasions in D. melanogaster : MLE spread between 1990-2000, Souslik between 2009-2012, and Transib1 between 2013-2016. We recapitulate prior findings, revealing that a total of 11 TEs invaded D. melanogaster over the past two centuries. Leveraging data from over 1400 arthropod genomes, we provide evidence that the TE invasions were triggered by horizontal transfers, with D. simulans and species of the D. willistoni group acting as putative donors. Through analysis of[~] 600 short-read datasets spanning diverse geographic regions, we reveal the rapidity of TE invasions: Transib1 swiftly multiplied from three isolated epicenters in 2014 to all investigated populations within just two years. Our findings suggest that anthropogenic activities, facilitating habitat and population expansions of D. melanogaster, might have accelerated the rate of horizontal transposon transfer as well the spread of the TEs into the worldwide population. Given the significant impact of TEs in genomes and the potential involvement of humans in their dispersal, our research has crucial implications for both evolution and ecology.

genomics↗

bioRxiv2022

Loss of Mfn1 but not Mfn2 enhances adipogenesis

ObjectiveA biallelic missense mutation in mitofusin 2 (MFN2) causes multiple symmetric lipomatosis and partial lipodystrophy, implicating disruption of mitochondrial fusion or interaction with other organelles in adipocyte differentiation, growth and/or survival. In this study, we aimed to document the impact of loss of mitofusin 1 (Mfn1) or 2 (Mfn2) on adipogenesis in cultured cells. MethodsWe characterised adipocyte differentiation of wildtype (WT), Mfn1-/- and Mfn2-/- mouse embryonic fibroblasts (MEFs) and 3T3-L1 preadipocytes in which Mfn1 or 2 levels were reduced using siRNA. ResultsMfn1-/- MEFs displayed striking fragmentation of the mitochondrial network, with surprisingly enhanced propensity to differentiate into adipocytes, as assessed by lipid accumulation, expression of adipocyte markers (Plin1, Fabp4, Glut4, Adipoq), and insulin-stimulated glucose uptake. RNA sequencing revealed a corresponding pro-adipogenic transcriptional profile including Pparg upregulation. Mfn2-/- MEFs also had a disrupted mitochondrial morphology, but in contrast to Mfn1-/- MEFs they showed reduced expression of adipocyte markers and no increase in insulin-stimulated glucose uptake. Mfn1 and Mfn2 siRNA mediated knockdown studies in 3T3-L1 adipocytes generally replicated these findings. ConclusionsLoss of Mfn1 but not Mfn2 in cultured pre-adipocyte models is pro-adipogenic. This suggests distinct, non-redundant roles for the two mitofusin orthologues in adipocyte differentiation.

cell biology↗

bioRxiv2022

A mouse model of human mitofusin 2-related lipodystrophy exhibits adipose-specific mitochondrial stress and reduced leptin secretion

Mitochondrial dysfunction has been reported in obesity and insulin resistance, but primary genetic mitochondrial dysfunction is generally not associated with these, arguing against a straightforward causal relationship. A rare exception, recently identified in humans, is a syndrome of lower body adipose loss, leptin-deficient severe upper body adipose overgrowth, and insulin resistance caused by the p.Arg707Trp mutation in MFN2, encoding mitofusin-2. How this selective perturbation of mitochondrial function leads to tissue- and adipose depot-specific growth abnormalities and systemic biochemical perturbation is unknown. To address this, Mfn2R707W/R707W knock-in mice were generated and phenotyped on chow and high fat diets. Electron microscopy revealed adipose-specific mitochondrial morphological abnormalities. Oxidative phosphorylation by isolated mitochondria was unperturbed, but the cellular integrated stress response was activated in adipose tissue. Fat mass and distribution, body weight, and systemic glucose and lipid metabolism were unchanged, however serum leptin and adiponectin concentrations, and their secretion from adipose explants were reduced. Pharmacological induction of the integrated stress response in wild-type adipocytes also reduced secretion of leptin and adiponectin, suggesting an explanation for the in vivo findings. These data suggest that the p.Arg707Trp MFN2 mutation perturbs mitochondrial morphology and activates the integrated stress response selectively in adipose tissue. In mice, this does not disrupt most adipocyte functions or systemic metabolism, whereas in humans it is associated with pathological adipose remodelling and metabolic disease. In both species, disproportionate effects on leptin secretion may relate to cell autonomous induction of the integrated stress response.

cell biology↗

bioRxiv2022

Evaluation of CB2R expression and pyridine-based radiotracers in brains from a mouse model of Alzheimer's disease

Neuroinflammation plays an important role in the pathophysiology of Alzheimers disease. The cannabinoid type 2 receptor (CB2R) is an emerging target for neuroinflammation and therapeutics of Alzheimers disease. Here, we aimed to assess the alterations in brain CB2R levels and evaluate novel CB2R imaging tracers in the arcA{beta} mouse model of Alzheimers disease amyloidosis. Immunohistochemical staining for A{beta} deposits (6E10), microgliosis (anti-Iba1 and anti-CD68 antibodies), astrocytes (GFAP) and the anti-CB2R antibody was performed on brain slices from arcA{beta} mice 17 months of age. Autoradiography using the CB2R imaging probes [18F]RoSMA-18-d6, [11C]RSR-056 and [11C]RS-028 and mRNA analysis were performed in brain tissue from arcA{beta} and nontransgenic littermate (NTL) mice at 6, 17, and 24 months of age. Specific increased CB2R immunofluorescence intensities on the increased number of GFAP-positive astrocytes and Iba1-positive microglia were detected in the hippocampus and cortex of 17-month-old arcA{beta} mice compared to NTL mice. CB2R immunofluorescence was higher in the glial cells inside 6E10-positive amyloid-{beta} deposits than peri-plaque with a low background. Ex vivo autoradiography showed that the binding of [18F]RoSMA-18-d6 and [11C]RSR-056 was comparable in arcA{beta} and NTL mice at 6, 17 and 24 months. The level of Cnr2 mRNA expression in the brain was not significantly different between arcA{beta} and NTL mice at 6, 17 or 24 months. In conclusion, we demonstrated pronounced specific increases in microglial and astroglial CB2R expression levels in a model of AD-related cerebral amyloidosis/AD mouse model, emphasizing CB2R as a suitable target for imaging neuroinflammation.

neuroscience↗

bioRxiv2022

Endogenous GDF15 and FGF21 additively alleviate hepatic steatosis and insulin resistance in obese mice.

Obesity in mice and humans is associated with elevated levels of at least two hormones responsive to cellular stress, namely GDF15 and FGF21. Over-expression of each of these is associated with weight loss and beneficial metabolic changes but where they are secreted from and what they are required for physiologically in the context of overfeeding remains unclear. Here we used tissue selective knockout mouse models to establish that, like FGF21, circulating GDF15 is primarily derived from the liver, rather than adipose tissue, muscle or macrophages in high fat fed mice. Combined whole body deletion of FGF21 and GDF15 does not result in any additional weight gain in high fat fed mice but is associated with significantly greater hepatic steatosis and insulin resistance. Collectively the data suggest that activation of the integrated stress response in hepatocytes is a major driver for GDF15 and FGF21 secretion in the context of overfeeding, and that they both act to alleviate this metabolic stress.

physiology↗

bioRxiv2021

Transcriptional adaptation of sensory neurons to GPCR identity and activity

Sensory adaptation is critical to extract information from a changing world. Taking advantage of the extensive parallel coding lines present in the olfactory system, we explored the potential variations of neuronal identities before and after olfactory experience. We found that at rest, the transcriptomic profiles of olfactory sensory neuron populations are already highly divergent, specific to the olfactory receptor they express, and are surprisingly associated with the sequence of these latter. These divergent profiles further evolve in response to the environment, as odorant exposure leads to massive reprogramming via the modulation of transcription. Adenylyl cyclase 3, but not other main elements of the olfactory transduction cascade, plays a critical role in this activity-induced transcriptional adaptation. These findings highlight a broad range of sensory neuron identities that are present at rest and that adapt to the experience of the individual, thus providing a novel layer of complexity to sensory coding.

neuroscience↗

bioRxiv2021

Rest/Stress Myocardial Perfusion Imaging by Positron Emission Tomography with 18F-Flurpiridaz: A Feasibility Study in Mice

BackgroundMyocardial perfusion imaging by positron emission tomography (PET-MPI) is the current gold standard for quantification of myocardial blood flow. 18F-flurpiridaz was recently introduced as a valid alternative to currently used PET-MPI probes. Nonetheless, optimum scan duration and time interval for image analysis are currently unknown. Further, it is unclear whether rest/stress PET-MPI with 18F-flurpiridaz is feasible in mice. MethodsRest/stress PET-MPI was performed with 18F-flurpiridaz (0.6-3.0 MBq) in 29 mice aged 7-8 months. Regadenoson (0.1 g/g) was used for induction of vasodilator stress. Kinetic modeling was performed using a metabolite-corrected arterial input function. Image-derived myocardial 18F-flurpiridaz uptake was assessed for different time intervals by placing a volume of interest in the left ventricular myocardium. ResultsTracer kinetics were best described by a two-tissue compartment model. K1 ranged from 6.7-20.0 mL/cm3/min, while myocardial volumes of distribution (VT) were between 34.6 and 83.6 mL/cm3. Of note, myocardial 18F-flurpiridaz uptake (%ID/g) was significantly correlated with K1 at rest and following pharmacological stress testing for all time intervals assessed. However, while Spearmans coefficients (rs) ranged between 0.478 and 0.672, R2 values were generally low. In contrast, an excellent correlation of myocardial 18F-flurpiridaz uptake with VT was obtained, particularly when employing the averaged myocardial uptake from 20-40 min post tracer injection (R2 [≥]0.98). Notably, K1 and VT were similarly sensitive to pharmacological stress induction. Further, mean stress-to-rest ratios of K1, VT, and %ID/g 18F-flurpiridaz were virtually identical, suggesting that %ID/g 18F-flurpiridaz can be used to estimate CFR in mice. ConclusionOur findings suggest that a simplified assessment of relative myocardial perfusion and coronary flow reserve (CFR), based on image-derived tracer uptake, is feasible with 18F-flurpiridaz in mice, enabling high-throughput mechanistic CFR studies in rodents.

physiology↗

bioRxiv2021

Radiosynthesis and preclinical evaluation of a carbon-11 labeled PDE7 inhibitor for PET neuroimaging

BackgroundDysfunction of cyclic nucleotide phosphodiesterase 7 (PDE7) has been associated with excess intracellular cAMP concentrations, fueling pathogenic processes that are implicated in neurodegenerative disorders. The aim of this study was to develop a suitable PDE7-targeted positron emission tomography (PET) probe that allows non-invasive mapping of PDE7 in the mammalian brain. MethodsBased on a spiro cyclohexane-1,4-quinazolinone scaffold with known inhibitory properties towards PDE7, we designed and synthesized a methoxy analog that was suitable for carbon-11 labeling. Radiosynthesis was conducted with the respective desmethyl precursor using [11C]MeI. The resulting PET probe, codenamed [11C]26, was evaluated by cell uptake studies, ex vivo biodistribution and radiometabolite studies, as well as in vivo PET experiments in rodents and nonhuman primates (NHP). ResultsTarget compound 26 and the corresponding phenolic precursor were synthesized in 2-3 steps with overall yields of 49.5% and 12.4%, respectively. An inhibitory constant (IC50) of 31 nM towards PDE7 was obtained and no significant interaction with other PDE isoforms were observed. [11C]26 was synthesized in high molar activities (170 - 220 GBq/{micro}mol) with radiochemical yields of 34{+/-}7%. In vitro cell uptake of [11C]26 was 6-7 folds higher in PDE7 overexpressing cells, as compared to the controls, whereas an in vitro specificity of up to 90% was measured. Ex vivo metabolite studies revealed a high fraction of intact parent in the rat brain (98% at 5 min and 75% at 30 min post injection). Considerable brain penetration was further corroborated by ex vivo biodistribution and PET imaging studies - the latter showing heterogenic brain uptake. While marginal specific binding was observed by PET studies in rodents, a moderate, but dose-dependent, blockade was observed in the NHP brain following pretreatment with non-radioactive 26. ConclusionIn this work, we report on the preclinical evaluation of [11C]26 (codename [11C]P7-2104), a PDE7-targeted PET ligand that is based on a spiroquinazolinone scaffold. [11C]26 displayed promising in vitro performance characteristics, a moderate degree of specific binding in PET studies with NHP. Accordingly, [11C]26 will serve as a valuable lead compound for the development of a new arsenal of PDE7-targeted probes with potentially improved in vivo specificity.

neuroscience↗

bioRxiv2021

In vivo imaging of cannabinoid type 2 receptors, functional and structural alterations in mouse model of cerebral ischemia by PET and MRI

Background and purposeBrain ischemia is one of the most important pathologies of the central nervous system. Non-invasive molecular imaging methods have the potential to provide critical insights into the temporal dynamics and follow alterations of receptor expression and metabolism in ischemic stroke. The aim of this study was to assess the cannabinoid type 2 receptors (CB2R) levels in transient middle cerebral artery occlusion (tMCAO) mouse models at subacute stage using positron emission tomography (PET) with our novel tracer [18F]RoSMA-18-d6, and structural imaging by magnetic resonance imaging (MRI). MethodsOur recently developed CB2R PET tracer [18F]RoSMA-18-d6 was used for imaging the neuroinflammation at 24 h after reperfusion in tMCAO mice. The RNA expression levels of CB2R and other inflammatory markers were analyzed by quantitative real-time polymerase chain reaction using brain tissues from tMCAO (1 h occlusion) and sham-operated mice. [18F]fluorodeoxyglucose (FDG) was included for evaluation of the cerebral metabolic rate of glucose (CMRglc). In addition, diffusion-weighted imaging and T2-weighted imaging were performed for anatomical reference and delineating the lesion in tMCAO mice. ResultsmRNA expressions of inflammatory markers TNF-, Iba1, MMP9 and GFAP, CNR2 were increased at 24 h after reperfusion in the ipsilateral compared to contralateral hemisphere of tMCAO mice, while mRNA expression of the neuronal marker MAP-2 was markedly reduced. Reduced [18F]FDG uptake was observed in the ischemic striatum of tMCAO mouse brain at 24 h after reperfusion. Although higher activity of [18F]RoSMA-18-d6 in ex-vivo biodistribution studies and higher standard uptake value ratio (SUVR) were detected in the ischemic ipsilateral compared to contralateral striatum in tMCAO mice, the in-vivo specificity of [18F]RoSMA-18-d6 was confirmed only in the CB2R-rich spleen. ConclusionsThis study revealed an increased [18F]RoSMA-18-d6 measure of CB2R and a reduced [18F]FDG measure of CMRglc in ischemic striatum of tMCAO mice at subacute stage. [18F]RoSMA-18-d6 might be a promising PET tracer for detecting CB2R alterations in animal models of neuroinflammation without neuronal loss.

neuroscience↗

bioRxiv2021

Development of a Triazolobenzodiazepine-Based PET Probe for Subtype-Selective Vasopressin 1A Receptor Imaging

ObjectivesTo enable non-invasive real-time quantification of vasopressin 1A (V1A) receptors in peripheral organs, we sought to develop a suitable PET probe that would allow specific and selective V1A receptor imaging in vitro and in vivo. MethodsWe synthesized a high-affinity and -selectivity ligand, designated compound 17. The target structure was labeled with carbon-11 and tested for its utility as a V1A-targeted PET tracer by cell uptake studies, autoradiography, in vivo PET imaging and ex vivo biodistribution experiments. ResultsCompound 17 (PF-184563) and the respective precursor for radiolabeling were synthesized in an overall yield of 49% (over 7 steps) and 40% (over 8 steps), respectively. An inhibitory constant of 0.9 nM towards the V1A receptor was measured, while excellent selectivity over the related V1B, V2 and OT receptor (IC50 >10,000 nM) were obtained. Cell uptake studies revealed considerable V1A binding, which was significantly reduced in the presence of V1A antagonists. Conversely, there was no significant blockade in the presence of V1B and V2 antagonists. In vitro autoradiography and PET imaging studies in rodents indicated specific tracer binding mainly in the liver. Further, the pancreas, spleen and the heart exhibited specific binding of [11C]17 ([11C]PF-184563) by ex vivo biodistribution experiments. ConclusionWe have developed the first V1A-targeted PET ligand that is suitable for subtype-selective receptor imaging in peripheral organs including the liver, heart, pancreas and spleen. Our findings suggest that [11C]PF-184563 can be a valuable tool to study the role of V1A receptors in liver diseases, as well as in cardiovascular pathologies.

pharmacology and toxicology↗