Design, Synthesis, and Structure-Activity Relationships of Novel Peptide Derivatives of the Severe Acute Respiratory Syndrome-Coronavirus-2 Spike-Protein that Potently Inhibit Nicotinic Acetylcholine Receptors.

The spike-protein of SARS-CoV-2 has a distinctive amino-acid sequence (682RRARS686) that forms a cleavage site for the enzyme furin. Strikingly, the structure of the spike-protein loop containing the furin cleavage site bears substantial similarity to neurotoxin peptides found in the venoms of certain snakes and marine cone snails. Leveraging this relationship, we designed and synthesized disulfide-constrained peptides with amino-acid sequences corresponding to the furin cleavage-sites of wild-type (B.1 variant) SARS-CoV-2 or the Alpha, Delta, and Omicron variants. Remarkably, some of these peptides potently inhibited α7 and α9α10 nicotinic acetylcholine receptors (nAChR) with nM affinity and showed SARS-CoV-2 variant and nAChR subtype-dependent potencies. Nuclear magnetic resonance spectroscopy and molecular dynamics were used to rationalize structure-activity relationships between peptides and their cognate receptors. These findings delineate nAChR subtypes that can serve as high-affinity spike-protein targets in tissues central to COVID-19 pathophysiology and identify ligands and target receptors to inform the development of novel SARS-CoV-2 therapeutics.

Aspartic acid mutagenesis of αO-Conotoxin GeXIVA isomers reveals arginine residues crucial for inhibition of the α9α10 nicotinic acetylcholine receptor.

The two most active disulfide bond isomers of the analgesic αO-conotoxin GeXIVA, namely GeXIVA[1, 2] and GeXIVA[1, 4], were subjected to Asp-scanning mutagenesis to determine the key amino acid residues for activity at the rat α9α10 nicotinic acetylcholine receptor (nAChR). These studies revealed the key role of arginine residues for the activity of GeXIVA isomers towards the α9α10 nAChR. Based on these results, additional analogues with 2-4 mutations were designed and tested. The analogues [T1A,D14A,V28K]GeXIVA[1, 2] and [D14A,I23A,V28K]GeXIVA[1, 4] were developed and showed sub-nanomolar activity for the α9α10 nAChR with IC50 values of 0.79 and 0.38 nM. The latter analogue had exceptional selectivity for the α9α10 receptor subtype over other nAChR subtypes and can be considered as a drug candidate for further development. Molecular dynamics of receptor-ligand complexes allowed us to make deductions about the possible causes of increases in the affinity of key GeXIVA[1, 4] mutants for the α9α10 nAChR.

Catharanthine Modulates Mesolimbic Dopamine Transmission and Nicotine Psychomotor Effects via Inhibition of α6-Nicotinic Receptors and Dopamine Transporters.

Iboga alkaloids, also known as coronaridine congeners, have shown promise in the treatment of alcohol and opioid use disorders. The objective of this study was to evaluate the effects of catharanthine and 18-methoxycoronaridine (18-MC) on dopamine (DA) transmission and cholinergic interneurons in the mesolimbic DA system, nicotine-induced locomotor activity, and nicotine-taking behavior. Utilizing ex vivo fast-scan cyclic voltammetry (FSCV) in the nucleus accumbens core of male mice, we found that catharanthine or 18-MC differentially inhibited evoked DA release. Catharanthine inhibition of evoked DA release was significantly reduced by both α4 and α6 nicotinic acetylcholine receptors (nAChRs) antagonists. Additionally, catharanthine substantially increased DA release more than vehicle during high-frequency stimulation, although less potently than an α4 nAChR antagonist, which confirms previous work with nAChR antagonists. Interestingly, while catharanthine slowed DA reuptake measured via FSCV ex vivo, it also increased extracellular DA in striatal dialysate from anesthetized mice in vivo in a dose-dependent manner. Superfusion of catharanthine or 18-MC inhibited the firing rate of striatal cholinergic interneurons in a concentration dependent manner, which are known to potently modulate presynaptic DA release. Catharanthine or 18-MC suppressed acetylcholine currents in oocytes expressing recombinant rat α6/α3ß2ß3 or α6/α3ß4 nAChRs. In behavioral experiments using male Sprague-Dawley rats, systemic administration of catharanthine or 18-MC blocked nicotine enhancement of locomotor activity. Importantly, catharanthine attenuated nicotine self-administration in a dose-dependent manner while having no effect on food reinforcement. Lastly, administration of catharanthine and nicotine together greatly increased head twitch responses, indicating a potential synergistic hallucinogenic effect. These findings demonstrate that catharanthine and 18-MC have similar, but not identical effects on striatal DA dynamics, striatal cholinergic interneuron activity and nicotine psychomotor effects.

Continuous endosomes form functional subdomains and orchestrate rapid membrane trafficking in trypanosomes.

Endocytosis is a common process observed in most eukaryotic cells, although its complexity varies among different organisms. In Trypanosoma brucei, the endocytic machinery is under special selective pressure because rapid membrane recycling is essential for immune evasion. This unicellular parasite effectively removes host antibodies from its cell surface through hydrodynamic drag and fast endocytic internalization. The entire process of membrane recycling occurs exclusively through the flagellar pocket, an extracellular organelle situated at the posterior pole of the spindle-shaped cell. The high-speed dynamics of membrane flux in trypanosomes do not seem compatible with the conventional concept of distinct compartments for early endosomes (EE), late endosomes (LE), and recycling endosomes (RE). To investigate the underlying structural basis for the remarkably fast membrane traffic in trypanosomes, we employed advanced techniques in light and electron microscopy to examine the three-dimensional architecture of the endosomal system. Our findings reveal that the endosomal system in trypanosomes exhibits a remarkably intricate structure. Instead of being compartmentalized, it constitutes a continuous membrane system, with specific functions of the endosome segregated into membrane subdomains enriched with classical markers for EE, LE, and RE. These membrane subdomains can partly overlap or are interspersed with areas that are negative for endosomal markers. This continuous endosome allows fast membrane flux by facilitated diffusion that is not slowed by multiple fission and fusion events.

Using Constellation Pharmacology to Characterize a Novel α-Conotoxin from Conus ateralbus.

The venom of cone snails has been proven to be a rich source of bioactive peptides that target a variety of ion channels and receptors. α-Conotoxins (αCtx) interact with nicotinic acetylcholine receptors (nAChRs) and are powerful tools for investigating the structure and function of the various nAChR subtypes. By studying how conotoxins interact with nAChRs, we can improve our understanding of these receptors, leading to new insights into neurological diseases associated with nAChRs. Here, we describe the discovery and characterization of a novel conotoxin from Conus ateralbus, αCtx-AtIA, which has an amino acid sequence homologous to the well-described αCtx-PeIA, but with a different selectivity profile towards nAChRs. We tested the synthetic αCtx-AtIA using the calcium imaging-based Constellation Pharmacology assay on mouse DRG neurons and found that αCtx-AtIA significantly inhibited ACh-induced calcium influx in the presence of an α7 positive allosteric modulator, PNU-120596 (PNU). However, αCtx-AtIA did not display any activity in the absence of PNU. These findings were further validated using two-electrode voltage clamp electrophysiology performed on oocytes overexpressing mouse α3ß4, α6/α3ß4 and α7 nAChRs subtypes. We observed that αCtx-AtIA displayed no or low potency in blocking α3ß4 and α6/α3ß4 receptors, respectively, but improved potency and selectivity to block α7 nAChRs when compared with αCtx-PeIA. Through the synthesis of two additional analogs of αCtx-AtIA and subsequent characterization using Constellation Pharmacology, we were able to identify residue Trp18 as a major contributor to the activity of the peptide.

αO-Conotoxin GeXIVA[1,2] Reduced Neuropathic Pain and Changed Gene Expression in Chronic Oxaliplatin-Induced Neuropathy Mice Model.

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting painful neuropathy that occurs commonly during cancer management, which often leads to the discontinuation of medication. Previous studies suggest that the α9α10 nicotinic acetylcholine receptor (nAChR)-specific antagonist αO-conotoxin GeXIVA[1,2] is effective in CIPN models; however, the related mechanisms remain unclear. Here, we analyzed the preventive effect of GeXIVA[1,2] on neuropathic pain in the long-term oxaliplatin injection-induced CIPN model. At the end of treatment, lumbar (L4-L6) spinal cord was extracted, and RNA sequencing and bioinformatic analysis were performed to investigate the potential genes and pathways related to CIPN and GeXIVA[1,2]. GeXIVA[1,2] inhibited the development of mechanical allodynia induced by chronic oxaliplatin treatment. Repeated injections of GeXIVA[1,2] for 3 weeks had no effect on the mice's normal pain threshold or locomotor activity and anxiety-like behavior, as evaluated in the open field test (OFT) and elevated plus maze (EPM). Our RNA sequencing results identified 209 differentially expressed genes (DEGs) in the CIPN model, and simultaneously injecting GeXIVA[1,2] with oxaliplatin altered 53 of the identified DEGs. These reverted genes were significantly enriched in immune-related pathways represented by the cytokine-cytokine receptor interaction pathway. Our findings suggest that GeXIVA[1,2] could be a potential therapeutic compound for chronic oxaliplatin-induced CIPN management.

Analogs of α-conotoxin PnIC selectively inhibit α7ß2- over α7-only subtype nicotinic acetylcholine receptors via a novel allosteric mechanism.

This study was undertaken to identify and characterize the first ligands capable of selectively identifying nicotinic acetylcholine receptors containing α7 and ß2 subunits (α7ß2-nAChR subtype). Basal forebrain cholinergic neurons express α7ß2-nAChR. Here, they appear to mediate neuronal dysfunction induced by the elevated levels of oligomeric amyloid-ß associated with early Alzheimer's disease. Additional work indicates that α7ß2-nAChR are expressed across several further critically important cholinergic and GABAergic neuronal circuits within the central nervous system. Further studies, however, are significantly hindered by the inability of currently available ligands to distinguish heteromeric α7ß2-nAChR from the closely related and more widespread homomeric α7-only-nAChR subtype. Functional screening using two-electrode voltage-clamp electrophysiology identified a family of α7ß2-nAChR-selective analogs of α-conotoxin PnIC (α-CtxPnIC). A combined electrophysiology, functional kinetics, site-directed mutagenesis, and molecular dynamics approach was used to further characterize the α7ß2-nAChR selectivity and site of action of these α-CtxPnIC analogs. We determined that α7ß2-nAChR selectivity of α-CtxPnIC analogs arises from interactions at a site distinct from the orthosteric agonist-binding site shared between α7ß2- and α7-only-nAChR. As numerous previously identified α-Ctx ligands are competitive antagonists of orthosteric agonist-binding sites, this study profoundly expands the scope of use of α-Ctx ligands (which have already provided important nAChR research and translational breakthroughs). More immediately, analogs of α-CtxPnIC promise to enable, for the first time, both comprehensive mapping of the distribution of α7ß2-nAChR and detailed investigations of their physiological roles.

Computational Design of α-Conotoxins to Target Specific Nicotinic Acetylcholine Receptor Subtypes.

Nicotinic acetylcholine receptors (nAChRs) are drug targets for neurological diseases and disorders, but selective targeting of the large number of nAChR subtypes is challenging. Marine cone snail α-conotoxins are potent blockers of nAChRs and some have been engineered to achieve subtype selectivity. This engineering effort would benefit from rapid computational methods able to predict mutational energies, but current approaches typically require high-resolution experimental structures, which are not widely available for α-conotoxin complexes. Herein, five mutational energy prediction methods were benchmarked using crystallographic and mutational data on two acetylcholine binding protein/α-conotoxin systems. Molecular models were developed for six nAChR subtypes in complex with five α-conotoxins that were studied through 150 substitutions. The best method was a combination of FoldX and molecular dynamics simulations, resulting in a predictive Matthews Correlation Coefficient (MCC) of 0.68 (85 % accuracy). Novel α-conotoxin mutants designed using this method were successfully validated by experimental assay with improved pharmaceutical properties. This work paves the way for the rapid design of subtype-specific nAChR ligands and potentially accelerated drug development.

Differential tyrosine and serine/threonine phosphorylation/dephosphorylation pathways regulate the expression of α7 versus α3ß4 nicotinic receptor subtypes in mouse hippocampal neurons.

We have recently reported that α7 and α3ß4 nicotinic acetylcholine receptor (nAChR) subtypes are expressed in human chromaffin cells in the plasma membrane where they colocalize and physically interact. The present study was designed to evaluate whether those receptor subtypes also colocalize at the central nervous system to mutually interact, and whether their expression and colocalization are regulated by phosphorylation/dephosphorylation processes, as they are in human chromaffin cells. We have here found that in isolated and maintained in culture mouse hippocampal neurons, nAChR expression and colocalization of α7, but not α3ß4, nAChR subtypes decreased by tyrosine (Tyr)- and serine/threonine (Ser/Thr)-phosphatase inhibition. However, Tyr-kinase inhibition or protein-phosphatase 2A (PP2A) activation increased α3ß4 nAChR expression, diminishing receptor subtypes colocalization. Furthermore, colocalization is not recovered if the inhibitors of Tyr-phosphatase and kinases, or the inhibitor of Ser/Thr-phosphatases and the activator of PP2A are applied together. Therefore, regulation of α7 and α3ß4 nAChR subtypes expression by Tyr- and Ser/Thr kinases and phosphatases exhibit differential mechanisms in mouse hippocampal neurons. Colocalization of nAChR subtypes, however, is altered by any maneuver that affects these kinases or phosphatases, which might have consequences in the functional activity of nAChR subtypes.

Distinct regions of the kinesin-5 C-terminal tail are essential for mitotic spindle midzone localization and sliding force.

Kinesin-5 motor proteins play essential roles during mitosis in most organisms. Their tetrameric structure and plus-end-directed motility allow them to bind to and move along antiparallel microtubules, thereby pushing spindle poles apart to assemble a bipolar spindle. Recent work has shown that the C-terminal tail is particularly important to kinesin-5 function: The tail affects motor domain structure, ATP hydrolysis, motility, clustering, and sliding force measured for purified motors, as well as motility, clustering, and spindle assembly in cells. Because previous work has focused on presence or absence of the entire tail, the functionally important regions of the tail remain to be identified. We have therefore characterized a series of kinesin-5/Cut7 tail truncation alleles in fission yeast. Partial truncation causes mitotic defects and temperature-sensitive growth, while further truncation that removes the conserved BimC motif is lethal. We compared the sliding force generated by cut7 mutants using a kinesin-14 mutant background in which some microtubules detach from the spindle poles and are pushed into the nuclear envelope. These Cut7-driven protrusions decreased as more of the tail was truncated, and the most severe truncations produced no observable protrusions. Our observations suggest that the C-terminal tail of Cut7p contributes to both sliding force and midzone localization. In the context of sequential tail truncation, the BimC motif and adjacent C-terminal amino acids are particularly important for sliding force. In addition, moderate tail truncation increases midzone localization, but further truncation of residues N-terminal to the BimC motif decreases midzone localization.

DM506 (3-Methyl-1,2,3,4,5,6-hexahydroazepino[4,5-b]indole fumarate), a Novel Derivative of Ibogamine, Inhibits α7 and α9α10 Nicotinic Acetylcholine Receptors by Different Allosteric Mechanisms.

The main objective of this study was to determine the pharmacological activity and molecular mechanism of action of DM506 (3-methyl-1,2,3,4,5,6-hexahydroazepino[4,5-b]indole fumarate), a novel ibogamine derivative, at different nicotinic acetylcholine receptor (nAChR) subtypes. The functional results showed that DM506 neither activates nor potentiates but inhibits ACh-evoked currents at each rat nAChR subtype in a non-competitive manner. The receptor selectivity for DM506 inhibition follows the sequence: α9α10 (IC50 = 5.1 ± 0.3 µM) ≅ α7ß2 (5.6 ± 0.2 µM) ∼ α7 (6.4 ± 0.5 µM) > α6/α3ß2ß3 (25 ± 1 µM) > α4ß2 (62 ± 4 µM) ≅ α3ß4 (70 ± 5 µM). No significance differences in DM506 potency were observed between rat and human α7 and α9α10 nAChRs. These results also indicated that the ß2 subunit is not involved or is less relevant in the activity of DM506 at the α7ß2 nAChR. DM506 inhibits the α7 and α9α10 nAChRs in a voltage-dependent and voltage-independent manner, respectively. Molecular docking and molecular dynamics studies showed that DM506 forms stable interactions with a putative site located in the α7 cytoplasmic domain and with two intersubunit sites in the extracellular-transmembrane junction of the α9α10 nAChR, one located in the α10(+)/α10(─) interface and another in the α10(+)/α9(─) interface. This study shows for the first time that DM506 inhibits both α9α10 and α7 nAChR subtypes by novel allosteric mechanisms likely involving modulation of the extracellular-transmembrane domain junction and cytoplasmic domain, respectively, but not by direct competitive antagonism or open channel block.

Nicotinic acetylcholine receptors: Therapeutic targets for novel ligands to treat pain and inflammation.

Nicotinic acetylcholine receptors (nAChRs) have been historically defined as ligand-gated ion channels and function as such in the central and peripheral nervous systems. Recently, however, non-ionic signaling mechanisms via nAChRs have been demonstrated in immune cells. Furthermore, the signaling pathways where nAChRs are expressed can be activated by endogenous ligands other than the canonical agonists acetylcholine and choline. In this review, we discuss the involvement of a subset of nAChRs containing α7, α9, and/or α10 subunits in the modulation of pain and inflammation via the cholinergic anti-inflammatory pathway. Additionally, we review the most recent advances in the development of novel ligands and their potential as therapeutics.

Role of α6-Nicotinic Receptors in Alcohol-Induced GABAergic Synaptic Transmission and Plasticity to Cholinergic Interneurons in the Nucleus Accumbens.

The prevailing view is that enhancement of dopamine (DA) transmission in the mesolimbic system, consisting of DA neurons in the ventral tegmental area (VTA) that project to the nucleus accumbens (NAc), underlies the reward properties of ethanol (EtOH) and nicotine (NIC). We have shown previously that EtOH and NIC modulation of DA release in the NAc is mediated by α6-containing nicotinic acetylcholine receptors (α6*-nAChRs), that α6*-nAChRs mediate low-dose EtOH effects on VTA GABA neurons and EtOH preference, and that α6*-nAChRs may be a molecular target for low-dose EtOH. However, the most sensitive target for reward-relevant EtOH modulation of mesolimbic DA transmission and the involvement of α6*-nAChRs in the mesolimbic DA reward system remains to be elucidated. The aim of this study was to evaluate EtOH effects on GABAergic modulation of VTA GABA neurons and VTA GABAergic input to cholinergic interneurons (CINs) in the NAc. Low-dose EtOH enhanced GABAergic input to VTA GABA neurons that was blocked by knockdown of α6*-nAChRs. Knockdown was achieved either by α6-miRNA injected into the VTA of VGAT-Cre/GAD67-GFP mice or by superfusion of the α-conotoxin MII[H9A;L15A] (MII). Superfusion of MII blocked EtOH inhibition of mIPSCs in NAc CINs. Concomitantly, EtOH enhanced CIN firing rate, which was blocked by knockdown of α6*-nAChRs with α6-miRNA injected into the VTA of VGAT-Cre/GAD67-GFP mice. The firing rate of CINs was not enhanced by EtOH in EtOH-dependent mice, and low-frequency stimulation (LFS; 1 Hz, 240 pulses) caused inhibitory long-term depression at this synapse (VTA-NAc CIN-iLTD) which was blocked by knockdown of α6*-nAChR and MII. Ethanol inhibition of CIN-mediated evoked DA release in the NAc was blocked by MII. Taken together, these findings suggest that α6*-nAChRs in the VTA-NAc pathway are sensitive to low-dose EtOH and play a role in plasticity associated with chronic EtOH.

Conus regius-Derived Conotoxins: Novel Therapeutic Opportunities from a Marine Organism.

Conus regius is a marine venomous mollusk of the Conus genus that captures its prey by injecting a rich cocktail of bioactive disulfide bond rich peptides called conotoxins. These peptides selectively target a broad range of ion channels, membrane receptors, transporters, and enzymes, making them valuable pharmacological tools and potential drug leads. C. regius-derived conotoxins are particularly attractive due to their marked potency and selectivity against specific nicotinic acetylcholine receptor subtypes, whose signalling is involved in pain, cognitive disorders, drug addiction, and cancer. However, the species-specific differences in sensitivity and the low stability and bioavailability of these conotoxins limit their clinical development as novel therapeutic agents for these disorders. Here, we give an overview of the main pharmacological features of the C. regius-derived conotoxins described so far, focusing on the molecular mechanisms underlying their potential therapeutic effects. Additionally, we describe adoptable chemical engineering solutions to improve their pharmacological properties for future potential clinical translation.

RgIA4 Prevention of Acute Oxaliplatin-Induced Cold Allodynia Requires α9-Containing Nicotinic Acetylcholine Receptors and CD3+ T-Cells.

Chemotherapy-induced neuropathic pain is a debilitating and dose-limiting side effect. Oxaliplatin is a third-generation platinum and antineoplastic compound that is commonly used to treat colorectal cancer and commonly yields neuropathic side effects. Available drugs such as duloxetine provide only modest benefits against oxaliplatin-induced neuropathy. A particularly disruptive symptom of oxaliplatin is painful cold sensitivity, known as cold allodynia. Previous studies of the Conus regius peptide, RgIA, and its analogs have demonstrated relief from oxaliplatin-induced cold allodynia, yielding improvement that persists even after treatment cessation. Moreover, underlying inflammatory and neuronal protection were shown at the cellular level in chronic constriction nerve injury models, consistent with disease-modifying effects. Despite these promising preclinical outcomes, the underlying molecular mechanism of action of RgIA4 remains an area of active investigation. This study aimed to determine the necessity of the α9 nAChR subunit and potential T-cell mechanisms in RgIA4 efficacy against acute oxaliplatin-induced cold allodynia. A single dose of oxaliplatin (10 mg/kg) was utilized followed by four daily doses of RgIA4. Subcutaneous administration of RgIA4 (40 µg/kg) prevented cold allodynia in wildtype mice but not in mice lacking the α9 nAChR-encoding gene, chrna9. RgIA4 also failed to reverse allodynia in mice depleted of CD3+ T-cells. In wildtype mice treated with oxaliplatin, quantitated circulating T-cells remained unaffected by RgIA4. Together, these results show that RgIA4 requires both chrna9 and CD3+ T-cells to exert its protective effects against acute cold-allodynia produced by oxaliplatin.

Alkaloid ligands enable function of homomeric human α10 nicotinic acetylcholine receptors.

In the nervous system, nicotinic acetylcholine receptors (nAChRs) rapidly transduce a chemical signal into one that is electrical via ligand-gated ion flux through the central channel of the receptor. However, some nAChR subunits are expressed by non-excitable cells where signal transduction apparently occurs through non-ionic mechanisms. One such nAChR subunit, α10, is present in a discreet subset of immune cells and has been implicated in pathologies including cancer, neuropathic pain, and chronic inflammation. Longstanding convention holds that human α10 subunits require co-assembly with α9 subunits for function. Here we assessed whether cholinergic ligands can enable or uncover ionic functions from homomeric α10 nAChRs. Xenopus laevis oocytes expressing human α10 subunits were exposed to a panel of ligands and examined for receptor activation using voltage-clamp electrophysiology. Functional expression of human α10 nAChRs was achieved by exposing the oocytes to the alkaloids strychnine, brucine, or methyllycaconitine. Furthermore, acute exposure to the alkaloid ligands significantly enhanced ionic responses. Acetylcholine-gated currents mediated by α10 nAChRs were potently inhibited by the snake toxins α-bungarotoxin and α-cobratoxin but not by α-conotoxins that target α9 and α9α10 nAChRs. Our findings indicate that human α10 homomers are expressed in oocytes and exposure to certain ligands can enable ionic functions. To our knowledge, this is the first demonstration that human α10 subunits can assemble as functional homomeric nAChRs. These findings have potential implications for receptor regulatory-mechanisms and will enable structural, functional, and further pharmacological characterization of human α10 nAChRs.

Comparison of the Anti-inflammatory Properties of Two Nicotinic Acetylcholine Receptor Ligands, Phosphocholine and pCF3-diEPP.

Activation of nicotinic acetylcholine receptors (nAChRs) expressed by innate immune cells can attenuate pro-inflammatory responses. Silent nAChR agonists, which down-modulate inflammation but have little or no ionotropic activity, are of outstanding clinical interest for the prevention and therapy of numerous inflammatory diseases. Here, we compare two silent nAChR agonists, phosphocholine, which is known to interact with nAChR subunits α7, α9, and α10, and pCF3-N,N-diethyl-N'-phenyl-piperazine (pCF3-diEPP), a previously identified α7 nAChR silent agonist, regarding their anti-inflammatory properties and their effects on ionotropic nAChR functions. The lipopolysaccharide (LPS)-induced release of interleukin (IL)-6 by primary murine macrophages was inhibited by pCF3-diEPP, while phosphocholine was ineffective presumably because of instability. In human whole blood cultures pCF3-diEPP inhibited the LPS-induced secretion of IL-6, TNF-α and IL-1ß. The ATP-mediated release of IL-1ß by LPS-primed human peripheral blood mononuclear leukocytes, monocytic THP-1 cells and THP-1-derived M1-like macrophages was reduced by both phosphocholine and femtomolar concentrations of pCF3-diEPP. These effects were sensitive to mecamylamine and to conopeptides RgIA4 and [V11L; V16D]ArIB, suggesting the involvement of nAChR subunits α7, α9 and/or α10. In two-electrode voltage-clamp measurements pCF3-diEPP functioned as a partial agonist and a strong desensitizer of classical human α9 and α9α10 nAChRs. Interestingly, pCF3-diEPP was more effective as an ionotropic agonist at these nAChRs than at α7 nAChR. In conclusion, phosphocholine and pCF3-diEPP are potent agonists at unconventional nAChRs expressed by monocytic and macrophage-like cells. pCF3-diEPP inhibits the LPS-induced release of pro-inflammatory cytokines, while phosphocholine is ineffective. However, both agonists signal via nAChR subunits α7, α9 and/or α10 to efficiently down-modulate the ATP-induced release of IL-1ß. Compared to phosphocholine, pCF3-diEPP is expected to have better pharmacological properties. Thus, low concentrations of pCF3-diEPP may be a therapeutic option for the treatment of inflammatory diseases including trauma-induced sterile inflammation.

Cross Talk between α7 and α3ß4 Nicotinic Receptors Prevents Their Desensitization in Human Chromaffin Cells.

The physical interaction and functional cross talk among the different subtypes of neuronal nicotinic acetylcholine receptors (nAChRs) expressed in the various tissues is unknown. Here, we have investigated this issue between the only two nAChRs subtypes expressed, the α7 and α3ß4 subtypes, in a human native neuroendocrine cell (the chromaffin cell) using electrophysiological patch-clamp, fluorescence, and Förster resonance energy transfer (FRET) techniques. Our data show that α7 and α3ß4 receptor subtypes require their mutual and maximal efficacy of activation to increase their expression, to avoid their desensitization, and therefore, to increase their activity. In this way, after repetitive stimulation with acetylcholine (ACh), α7 and α3ß4 receptor subtypes do not desensitize, but they do with choline. The nicotinic current increase associated with the α3ß4 subtype is dependent on Ca2+ In addition, both receptor subtypes physically interact. Interaction and expression of both subtypes are reversibly reduced by tyrosine and serine/threonine phosphatases inhibition, not by Ca2+ In addition, expression is greater in human chromaffin cells from men compared to women, but FRET efficiency is not affected. Together, our findings indicate that human α7 and α3ß4 subtypes mutually modulate their expression and activity, providing a promising line of research to pharmacologically regulate their activity.SIGNIFICANCE STATEMENT Desensitization of nicotinic receptors is accepted to occur with repetitive agonist stimulation. However, here we show that human native α3ß4 and α7 nicotinic acetylcholine receptor (nAChR) subtypes do not desensitize, and instead, increase their activity when they are activated by the physiological agonist acetylcholine (ACh). An indispensable requirement is the activation of the other receptor subtype with maximal efficacy, and the presence of Ca2+ to cooperate in the case of the α3ß4 current increase. Because choline is an α3ß4 partial agonist, it will act as a limiting factor of nicotinic currents enhancement in the absence of ACh, but in its presence, it will further potentiate α7 currents.

From adolescence to parenthood: a multi-decade study of preconception mental health problems and postpartum parent-infant bonds.

PURPOSE: To examine associations between anxiety and depressive symptoms across adolescence and young adulthood with subsequent maternal- and paternal-infant bonding at 1 year postpartum. METHODS: The data were from a prospective, intergenerational cohort study. Participants (381 mothers of 648 infants; 277 fathers of 421 infants) self-reported depression and anxiety at three adolescent waves (ages 13, 15 and 17 years) and three young adult waves (ages 19, 23 and 27 years). Subsequent parent-infant bonds with infants were reported at 1 year postpartum (parent age 29-35 years). Generalised estimating equations (GEE) separately assessed associations for mothers and fathers. RESULTS: Mean postpartum bonding scores were approximately half a standard deviation lower in parents with a history of persistent adolescent and young adult depressive symptoms (maternal ßadj = - 0.45, 95% CI - 0.69, - 0.21; paternal ßadj = - 0.55, 95% CI - 0.90, 0.20) or anxiety (maternal ßadj = - 0.42, 95% CI - 0.66, - 0.18; paternal ßadj = - 0.49, 95% CI - 0.95, 0.03). Associations were still mostly evident, but attenuated after further adjustment for postpartum mental health concurrent with measurement of bonding. CONCLUSIONS: Persistent symptoms of depression or anxiety spanning adolescence and young adulthood predict poorer emotional bonding with infants 1-year postbirth for both mothers and fathers.

Application of alpha1-antitrypsin in a rat model of veno-arterial extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is a life-saving intervention for patients suffering from respiratory or cardiac failure. The ECMO-associated morbidity and mortality depends to a large extent on the underlying disease and is often related to systemic inflammation, consecutive immune paralysis and sepsis. Here we tested the hypothesis that human α1-antitrypsin (SERPINA1) due to its anti-protease and anti-inflammatory functions may attenuate ECMO-induced inflammation. We specifically aimed to test whether intravenous treatment with α1-antitrypsin reduces the release of cytokines in response to 2 h of experimental ECMO. Adult rats were intravenously infused with α1-antitrypsin immediately before starting veno-arterial ECMO. We measured selected pro- and anti-inflammatory cytokines and found, that systemic levels of tumor necrosis factor-α, interleukin-6 and interleukin-10 increase during experimental ECMO. As tachycardia and hypertension developed in response to α1-antitrypsin, a single additional bolus of fentanyl and midazolam was given. Treatment with α1-antitrypsin and higher sedative doses reduced all cytokine levels investigated. We suggest that α1-antitrypsin might have the potential to protect against both ECMO-induced systemic inflammation and immune paralysis. More studies are needed to corroborate our findings, to clarify the mechanisms by which α1-antitrypsin inhibits cytokine release in vivo and to explore the potential application of α1-antitrypsin in clinical ECMO.