Impact of Novel Antidepressants on Cardiac Metaiodobenzylguanidine (mIBG) Uptake: Experimental Studies in SK-N-SH Cells and Healthy Rabbits

Background: $^{123}$I-metaiodobenzylguanidine (mIBG) provides independent prognostic value for risk stratification among heart failure patients, but the use of concomitant medication should not impact its quantitative information. We aimed to evaluate the four most-prescribed antidepressants currently used as a first‑line treatment for patients with major depressive disorder (MDD) and their potential on altering mIBG imaging results. Methods: The inhibition effect of four different types of antidepressants (desipramine, escitalopram, venlafaxine and bupropion) for MDD treatment on $^{131}$I-mIBG uptake was assessed by in-vitro cell uptake assays using human neuroblastoma SK-N-SH cells. The half maximal inhibitory concentration (IC50) of tracer uptake was determined from dose-response curves. To evaluate the effects of IV pretreatment with desipramine (1.5 mg/kg) and escitalopram (2.5, 15 mg/kg) on mIBG cardiac uptake, in-vivo planar 123I-mIBG scans in healthy New Zealand White Rabbits were conducted. Results: The IC50 values of desipramine, escitalopram, venlafaxine and bupropion on $^{131}$I-mIBG cellular uptake were 11.9 nM, 7.5 μM, 4.92 μM, and 12.9 μM, respectively. At the maximum serum concentration (Cmax, as derived by previous clinical trials), the inhibition rates of 131I-mIBG uptake were 90.6 % for desipramine, 25.5 % for venlafaxine, 11.7 % for bupropion and 0.72 % for escitalopram. A low inhibition rate for escitalopram in the cell uptake study triggered investigation of an in-vivo rabbit model: with dosage considerably higher than clinical practice, the non-inhibitory effect of escitalopram was confirmed. Furthermore, pretreatment with desipramine led to a marked reduction of cardiac 123I-mIBG uptake. Conclusions: In the present in-vitro binding assay and in-vivo rabbit study, the selective-serotonin reuptake inhibitor escitalopram had no major impact on neuronal cardiac mIBG uptake within therapeutic dose ranges, while other types of first-line antidepressants for MDD treatment led to a significant decrease. These preliminary results warrant further confirmatory clinical trials regarding the reliability of cardiac mIBG imaging, in particular, if the patient’s neuropsychiatric status would not tolerate withdrawal of a potentially norepinephrine interfering antidepressant

Cryo-EM structure of cell-free synthesized human histamine 2 receptor/Gs complex in nanodisc environment

Abstract Here we describe the cryo-electron microscopy structure of the human histamine 2 receptor (H2R) in an active conformation with bound histamine and in complex with Gs heterotrimeric protein at an overall resolution of 3.4 Å. The complex was generated by cotranslational insertion of the receptor into preformed nanodisc membranes using cell-free synthesis in E. coli lysates. Structural comparison with the inactive conformation of H2R and the inactive and Gq-coupled active state of H1R together with structure-guided functional experiments reveal molecular insights into the specificity of ligand binding and G protein coupling for this receptor family. We demonstrate lipid-modulated folding of cell-free synthesized H2R, its agonist-dependent internalization and its interaction with endogenously synthesized H1R and H2R in HEK293 cells by applying a recently developed nanotransfer technique

Electroneutral Polymer Nanodiscs Enable Interference‐Free Probing of Membrane Proteins in a Lipid‐Bilayer Environment

Membrane proteins can be examined in near-native lipid-bilayer environments with the advent of polymer-encapsulated nanodiscs. These nanodiscs self-assemble directly from cellular membranes, allowing in vitro probing of membrane proteins with techniques that have previously been restricted to soluble or detergent-solubilized proteins. Often, however, the high charge densities of existing polymers obstruct bioanalytical and preparative techniques. Thus, the authors aim to fabricate electroneutral—yet water-soluble—polymer nanodiscs. By attaching a sulfobetaine group to the commercial polymers DIBMA and SMA(2:1), these polyanionic polymers are converted to the electroneutral maleimide derivatives, Sulfo-DIBMA and Sulfo-SMA(2:1). Sulfo-DIBMA and Sulfo-SMA(2:1) readily extract proteins and phospholipids from artificial and cellular membranes to form nanodiscs. Crucially, the electroneutral nanodiscs avert unspecific interactions, thereby enabling new insights into protein–lipid interactions through lab-on-a-chip detection and in vitro translation of membrane proteins. Finally, the authors create a library comprising thousands of human membrane proteins and use proteome profiling by mass spectrometry to show that protein complexes are preserved in electroneutral nanodiscs

Cryo-EM structure of a cell-free synthesized human histamine 2 receptor/ Gs complex in nanodisc environment

We describe the cryo-electron microscopy structure of the human histamine 2 receptor (H2R) in an active conformation with bound histamine and in complex with Gs heterotrimeric protein at an overall resolution of 3.4 Å. The complex was generated by cotranslational insertion into preformed nanodisc membranes using cell-free synthesis in E. coli lysates. It is the first structure obtained by this detergent-free strategy and the first GPCR/Gs complex structure in lipid environment. Structural comparison with the inactive conformation of H2R and the inactive and Gq-coupled active state of H1R together with structure-guided functional experiments reveal molecular insights into the specificity of ligand binding and G protein coupling for this receptor family. We demonstrate lipid-modulated folding of cell-free synthesized H2R, its agonist-dependent internalization and its interaction with endogenously synthesized H1R and H2R in HEK293 cells by applying a recently developed nanotransfer technique

Evidence for the charge asymmetry in (Formula presented.) production at √s = 13 TeV with the ATLAS detector

Inclusive and differential measurements of the top–antitop (Formula presented.) charge asymmetry (Formula presented.) and the leptonic asymmetry (Formula presented.) are presented in proton–proton collisions at s = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb−1, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive (Formula presented.) charge asymmetry is measured to be (Formula presented.), which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the (Formula presented.) system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients. [Figure not available: see fulltext.]