Biology subjects

Zhang, H. J.

Publications and source records attributed to Zhang, H. J..

3 recordsLinked to original sources

bioRxiv2022

Evaluation of an image-derived input function for kinetic modeling of nicotinic acetylcholine receptor-binding PET ligands

Development of positron emission tomography (PET) radiotracers that bind with high-affinity to 4{beta}2-type nicotinic receptors (4{beta}2Rs) allows for in vivo investigations of the mechanisms underlying nicotine addiction and smoking cessation. One challenge associated with preclinical PET imaging involves the lack of true tissue reference regions free of specific tracer binding in the rodent brain, impeding accurate quantification of the tracer binding potential. Here, we investigate the use of an image-derived arterial input function for kinetic analysis of radiotracer binding in male and female mice. Two radiotracers were explored in this study: 2-[18F]FA85380 (2-FA), which displays similar pKa and binding affinity to the smoking cessation drug varenicline (Chantix), and [18F]Nifene, which displays similar pKa and binding affinity to nicotine. For both radiotracers, time-activity curves of the left ventricle of the heart displayed similar standardized uptake values (SUVs) across wild type mice, mice lacking the {beta}2 subunit for tracer binding, and acute nicotine-treated mice, whereas typical reference tissue SUVs displayed high variation between groups. Binding potential values estimated from a two-tissue compartment model (2TCM) fit of the data with the image-derived input function were significantly higher than estimates from reference tissue-based estimations. Rate constants of radiotracer dissociation were very slow for 2-FA and very fast for Nifene, similar to the in vitro dissociation rates reported for varenicline and nicotine, respectively. We conclude that use of an image-derived input function for kinetic modeling of nicotinic PET ligands improves quantification compared to reference tissue-based methods, and that the chemical properties of 2-FA and Nifene are suitable to study receptor response to nicotine addiction and smoking cessation therapies.

neuroscience↗

bioRxiv2022

Drug-like small molecules that inhibit expression of the oncogenic microRNA-21

We report the discovery of a series of drug-like small molecules which bind specifically to the precursor of the oncogenic and pro-fibrotic microRNA-21 with mid-nanomolar affinity. These molecules are highly ligand-efficient (MW<330) and display specific biochemical and cellular activity by suppressing maturation of miR-21, thereby providing an avenue towards therapeutic intervention in multiple diseases where miR-21 is abnormally expressed. The small molecules target a local structure at the Dicer cleavage site and induce distinctive structural changes in the RNA which correlate with specific inhibition of miRNA processing. Structurally conservative single nucleotide substitutions eliminate the conformational change, which is not observed in other miRNA precursors. The most potent of these compounds reduces cellular proliferation and miR-21 levels in cancer cell lines without inhibiting kinases or classical receptors, while closely related compounds without this specific binding activity are inactive in cells.

biochemistry↗

bioRxiv2020

Assessment of Brain Glucose Metabolism Following Cardiac Arrest by FDG Positron Emission Tomography

BackgroundCardiac arrest (CA) patients who survived by cardiopulmonary resuscitation (CPR) can present different levels of neurological deficits ranging from minor cognitive impairments to persistent vegetative state and brain death. The pathophysiology of the resulting brain injury is poorly understood and whether changes in post-CA brain metabolism contribute to the injury are unknown. Here we utilized [18F]FDG-PET to study in vivo cerebral glucose metabolism 72 hours following CA in a murine cardiac arrest model. MethodsAnesthetized and ventilated adult C57BL/6 mice underwent 12-minute KCl-induced CA followed by CPR. Seventy-two hours following cardiac arrest, surviving mice were intraperitoneally injected with [18F]FDG (~186 Ci/200 L) and imaged on Molecubes preclinical micro PET/CT imaging systems after a 30-minute awake uptake period. Brain [18F]FDG uptake was determined by the VivoQuant software on fused PET/CT images with the 3D brain atlas. Upon completion of PET imaging, remaining [18F]FDG radioactivity in the brain, heart, and liver was determined using a gamma counter. ResultsGlobal increases in brain [18F]FDG uptake in post-CA mice were observed compared to shams and controls. The median standardized uptake value (SUV) of [18F]FDG for CA animals was 1.79 vs. sham 1.25 (p<0.05) and control animals 0.78 (p<0.01). This increased uptake was consistent throughout the 60-minute imaging period and across all brain regions reaching statistical significance in the midbrain, pons, and medulla. Biodistribution analyses of various key organs yielded similar observations that the median [18F]FDG uptake for brain were 7.04%ID/g tissue for CA mice vs 5.537%ID/g tissue for sham animals, p<0.05). ConclusionsThis study has successfully applied [18F]FDG-PET/CT to measure changes in brain metabolism in a murine model of asystolic CA. Our results demonstrate increased [18F]FDG uptake in the brain 72 hours following CA, suggesting increased metabolic demand in the case of severe neurological injury. Further study is warranted to determine the etiology of these changes.

neuroscience↗