5-HT2C Receptor Structures Reveal the Structural Basis of GPCR Polypharmacology.

Drugs frequently require interactions with multiple targets-via a process known as polypharmacology-to achieve their therapeutic actions. Currently, drugs targeting several serotonin receptors, including the 5-HT2C receptor, are useful for treating obesity, drug abuse, and schizophrenia. The competing challenges of developing selective 5-HT2C receptor ligands or creating drugs with a defined polypharmacological profile, especially aimed at G protein-coupled receptors (GPCRs), remain extremely difficult. Here, we solved two structures of the 5-HT2C receptor in complex with the highly promiscuous agonist ergotamine and the 5-HT2A-C receptor-selective inverse agonist ritanserin at resolutions of 3.0 Å and 2.7 Å, respectively. We analyzed their respective binding poses to provide mechanistic insights into their receptor recognition and opposing pharmacological actions. This study investigates the structural basis of polypharmacology at canonical GPCRs and illustrates how understanding characteristic patterns of ligand-receptor interaction and activation may ultimately facilitate drug design at multiple GPCRs.

Optimal staffing for a good quality inpatient diabetes service.

INTRODUCTION: Increasing numbers of people admitted to hospital have diabetes and need specialist support. To date, there is no mechanism which can help teams estimate the number of health care professionals they need to provide optimal care for people with diabetes in hospitals. METHODS: The Joint British Diabetes Societies (JBDS) for Inpatient Care Group organised a survey of specialist inpatient diabetes teams in the UK for current staffing and the perception of optimal staffing using mailing lists available through their representative organisations. The results were verified and confirmed by one-to-one conversations with individual respondents and discussed in multiple expert-group meetings to agree on the results. RESULTS: Responses were received from 17 Trusts covering 30 hospital sites. Current diabetes specialist staffing level per 100 people with diabetes in hospital (Median, IQR) for consultants was 0.24 (0.22-0.37), diabetes inpatient specialist nurses was 1.94 (1.22-2.6), dieticians was 0.00 (0.00-0.00), podiatrists was 0.19 (0.00-0.62), pharmacists was 0.00 (0.00-0.37), psychologists was 0.00 (0.00-0.00). The teams also reported that for optimal care the total staff needed for each group (Median, IQR) was much higher; consultants 0.65 (0.50-0.88), specialist nurses 3.38 (2.78-4.59), dieticians 0.48 (0.33-0.72), podiatrists, 0.93 (0.65-1.24), pharmacists, 0.65 (0.40-0.79) and psychologists 0.33 (0.27-0.58). Based on the results of the survey, the JBDS expert group produced an Excel calculator to estimate staffing needs of any hospital site in question just by populating a few of the cells. CONCLUSION: Current inpatient diabetes staffing is much lower than needed in most Trusts who responded to the survey. The JBDS calculator can provide an estimate of the staffing needs of any hospital.

Subchronic and developmental toxicity of aromatic extracts.

Aromatic extracts (AEs; distillate AEs [DAEs] and residual AEs [RAEs]) are complex, highly viscous liquid petroleum streams with variable compositions derived by extraction of aromatic compounds from distillate and residual petroleum fractions from a vacuum distillation tower, respectively. The DAEs generally contain significant amounts of polycyclic aromatic compounds (PACs) and are carcinogenic. The RAEs typically contain lower concentrations of biologically active PACs. The PACs in refinery streams can cause effects in repeated-dose and developmental toxicity studies. In a 13-week dermal study, light paraffinic DAE had several dose-related effects involving multiple organs; no-observed-effect level was <5 mg/kg/d, with no overt toxicity. Predicted dose-responses at 10% (PDR10s), modeled doses causing a 10% effect on sensitive end points based on PAC content, ranged from 25 to 78 mg/kg/d for untested paraffinic DAEs. The no observed adverse effect level (NOAEL) for developmental toxicity for light paraffinic DAE was 5 mg/kg/d. Statistically significant developmental effects at higher doses were associated with maternal effects. The PDR10s for developmental toxicity of paraffinic DAEs ranged from 7 to >2000 mg/kg/d, reflecting differences due to variation in PACs. The NOAELs for RAEs were 500 mg/kg for 90-day studies and 2000 mg/kg for developmental toxicity. Reproductive toxicity is not considered to be a sensitive end point for AEs based on the toxicity tests with DAEs, RAEs, and other PAC-containing petroleum substances. In vivo micronucleus tests on heavy paraffinic DAE, RAEs, and a range of other petroleum substances have been negative. The exception to this general trend was a marginally positive response with light paraffinic DAE. Most DAEs are considered unlikely to produce chromosomal effects in vivo.

Acute, subchronic, and developmental toxicological properties of lubricating oil base stocks.

Lubricating oil base stocks (LOBs) are substances used in the manufacture of finished lubricants and greases. They are produced from residue remaining after atmospheric distillation of crude oil that is subsequently fractionated by vacuum distillation and additional refining steps. Initial LOB streams that have been produced by vacuum distillation but not further refined may contain polycyclic aromatic compounds (PACs) and may present carcinogenic hazards. In modern refineries, LOBs are further refined by multistep processes including solvent extraction and/or hydrogen treatment to reduce the levels of PACs and other undesirable constituents. Thus, mildly (insufficiently) refined LOBs are potentially more hazardous than more severely (sufficiently) refined LOBs. This article discusses the evaluation of LOBs using statistical models based on content of PACs; these models indicate that insufficiently refined LOBs (potentially carcinogenic LOBs) can also produce systemic and developmental effects with repeated dermal exposure. Experimental data were also obtained in ten 13-week dermal studies in rats, eight 4-week dermal studies in rabbits, and seven dermal developmental toxicity studies with sufficiently refined LOBs (noncarcinogenic and commonly marketed) in which no observed adverse effect levels for systemic toxicity and developmental toxicity were 1000 to 2000 mg/kg/d with dermal exposures, typically the highest dose tested. Results in both oral and inhalation developmental toxicity studies were similar. This absence of toxicologically relevant findings was consistent with lower PAC content of sufficiently refined LOBs. Based on data on reproductive organs with repeated dosing and parameters in developmental toxicity studies, sufficiently refined LOBs are likely to have little, if any, effect on reproductive parameters.

Venom-inspired somatostatin receptor 4 (SSTR4) agonists as new drug leads for peripheral pain conditions.

Persistent pain affects one in five people worldwide, often with severely debilitating consequences. Current treatment options, which can be effective for mild or acute pain, are ill-suited for moderate-to-severe persistent pain, resulting in an urgent need for new therapeutics. In recent years, the somatostatin receptor 4 (SSTR 4 ), which is expressed in sensory neurons of the peripheral nervous system, has emerged as a promising target for pain relief. However, the presence of several closely related receptors with similar ligand-binding surfaces complicates the design of receptor-specific agonists. In this study, we report the discovery of a potent and selective SSTR 4 peptide, consomatin Fj1, derived from extensive venom gene datasets from marine cone snails. Consomatin Fj1 is a mimetic of the endogenous hormone somatostatin and contains a minimized binding motif that provides stability and drives peptide selectivity. Peripheral administration of synthetic consomatin Fj1 provided analgesia in mouse models of postoperative and neuropathic pain. Using structure-activity studies, we designed and functionally evaluated several Fj1 analogs, resulting in compounds with improved potency and selectivity. Our findings present a novel avenue for addressing persistent pain through the design of venom-inspired SSTR 4 -selective pain therapeutics. One Sentence Summary: Venom peptides from predatory marine mollusks provide new leads for treating peripheral pain conditions through a non-opioid target.

Fish-hunting cone snail disrupts prey's glucose homeostasis with weaponized mimetics of somatostatin and insulin.

Venomous animals have evolved diverse molecular mechanisms to incapacitate prey and defend against predators. Most venom components disrupt nervous, locomotor, and cardiovascular systems or cause tissue damage. The discovery that certain fish-hunting cone snails use weaponized insulins to induce hypoglycemic shock in prey highlights a unique example of toxins targeting glucose homeostasis. Here, we show that, in addition to insulins, the deadly fish hunter, Conus geographus, uses a selective somatostatin receptor 2 (SSTR2) agonist that blocks the release of the insulin-counteracting hormone glucagon, thereby exacerbating insulin-induced hypoglycemia in prey. The native toxin, Consomatin nG1, exists in several proteoforms with a minimized vertebrate somatostatin-like core motif connected to a heavily glycosylated N-terminal region. We demonstrate that the toxin's N-terminal tail closely mimics a glycosylated somatostatin from fish pancreas and is crucial for activating the fish SSTR2. Collectively, these findings provide a stunning example of chemical mimicry, highlight the combinatorial nature of venom components, and establish glucose homeostasis as an effective target for prey capture.

Determining in-patient diabetes treatment satisfaction in the UK--the DIPSat study.

AIMS: To measure in-patient diabetes treatment satisfaction and its relationship to in-patient diabetes care. METHODS: In a cross-sectional study, diabetes in-patient specialist nurses at 58 UK hospitals asked insulin-treated in-patients with diabetes to complete the recently updated Diabetes Treatment Satisfaction Questionnaire for In-patients and a general questionnaire; 1319 in-patients completed these questionnaires. RESULTS: Satisfaction with the general diabetes treatment items in the Diabetes Treatment Satisfaction Questionnaire for In-patients was high, but there were high levels of extreme dissatisfaction with meal choices, meal quality and lack of similarity of hospital meals to normal domestic choices--23% would never or rarely have made similar meal choices at home. Hyperglycaemia or hypoglycaemia was reported for much of the in-patient stay (20% and 7%, respectively) and 26% reported at least one severe hypoglycaemic episode; these groups had lower satisfaction with the timing of medication in relation to meals (P < 0.003). More frequent in-patient hyperglycaemia or hypoglycaemia were associated with significantly poorer overall satisfaction scores and negative well-being scores (both P < 0.0001). Previous experience of a multiple daily insulin injection regimen was associated with more dissatisfaction than other regimens (P < 0.01). Multiple regression models explained 36% of variability in overall treatment satisfaction, with most (22.4%) accounted for by satisfaction with time spent with a diabetes in-patient specialist nurse (P < 0.0001). Self-administration of insulin was independently associated with higher treatment satisfaction (P < 0.006) in this model. CONCLUSIONS: The DIPSat programme describes the complex relationships between diabetes in-patient treatment satisfaction and in-patient diabetes care.

Ligand selectivity hotspots in serotonin GPCRs.

Serotonin is a neurotransmitter regulating numerous physiological processes also modulated by drugs, for example, schizophrenia, depression, migraine, and obesity. However, these drugs typically have adverse effects caused by promiscuous binding across 12 serotonin and more than 20 homologous receptors. Recently, structures of the entire serotonin receptor family uncovered molecular ligand recognition. Here, we present a map of 19 'selectivity hotspots', that is, nonconserved binding site residues governing selectivity via favorable target interactions or repulsive 'off-target' contacts. Furthermore, we review functional rationale from observed ligand-binding affinities and mutagenesis effects. Unifying knowledge underlying specific probes and drugs is critical toward the functional characterization of different receptors and alleviation of adverse effects.

(S)-2-Mercaptohistidine: A First Selective Orthosteric GluK3 Antagonist.

The development of tool compounds for the ionotropic glutamate receptors (iGluRs) remains an important research objective, as these are essential for the study and understanding of the roles of these receptors in health and disease. Herein, we report on the pharmacological characterization of (S)-2-hydroxyhistidine (2a) and (S)-2-mercaptohistidine (2b) as mediators of glutamatergic neurotransmission. While 2a displayed negligible binding affinity or activity at all glutamate receptors and transporters investigated, 2b displayed selectivity for homomeric GluK3 with binding affinities in the low micromolar range (Ki = 6.42 ± 0.74 µM). The iGluR subtype selectivity ratio for 2b was calculated at ∼30-fold for GluK1/GluK3, GluA3/GluK3, and GluA4/GluK3 and >100-fold for GluK2/GluK3, GluA1/GluK3, and GluA2/GluK3. Unexpectedly, functional characterization of 2b revealed that the compound is an antagonist (Kb = 7.6 µM) at homomeric GluK3 receptors while exhibiting only weak agonist activity at GluA2 (EC50 = 3.25 ± 0.55 mM). The functional properties of 2b were explored further in electrophysiological recordings of mouse hippocampal neurons.

Somatostatin venom analogs evolved by fish-hunting cone snails: From prey capture behavior to identifying drug leads.

Somatostatin (SS) is a peptide hormone with diverse physiological roles. By investigating a deep-water clade of fish-hunting cone snails, we show that predator-prey evolution has generated a diverse set of SS analogs, each optimized to elicit specific systemic physiological effects in prey. The increased metabolic stability, distinct SS receptor activation profiles, and chemical diversity of the venom analogs make them suitable leads for therapeutic application, including pain, cancer, and endocrine disorders. Our findings not only establish the existence of SS-like peptides in animal venoms but also serve as a model for the synergy gained from combining molecular phylogenetics and behavioral observations to optimize the discovery of natural products with biomedical potential.

Curses or Cures: A Review of the Numerous Benefits Versus the Biosecurity Concerns of Conotoxin Research.

Conotoxins form a diverse group of peptide toxins found in the venom of predatory marine cone snails. Decades of conotoxin research have provided numerous measurable scientific and societal benefits. These include their use as a drug, diagnostic agent, drug leads, and research tools in neuroscience, pharmacology, biochemistry, structural biology, and molecular evolution. Human envenomations by cone snails are rare but can be fatal. Death by envenomation is likely caused by a small set of toxins that induce muscle paralysis of the diaphragm, resulting in respiratory arrest. The potency of these toxins led to concerns regarding the potential development and use of conotoxins as biological weapons. To address this, various regulatory measures have been introduced that limit the use and access of conotoxins within the research community. Some of these regulations apply to all of the ≈200,000 conotoxins predicted to exist in nature of which less than 0.05% are estimated to have any significant toxicity in humans. In this review we provide an overview of the many benefits of conotoxin research, and contrast these to the perceived biosecurity concerns of conotoxins and research thereof.

Psychometric validation and use of a novel diabetes in-patient treatment satisfaction questionnaire.

AIMS: To develop the first psychometrically validated Diabetes Treatment Satisfaction Questionnaire for in-patients (DTSQ-IP) and examine determinants of in-patient diabetes treatment satisfaction. METHODS: We studied 366 in-patients with insulin-treated diabetes at a single UK centre. We developed a 19-item DTSQ-IP to assess in-patient diabetes treatment satisfaction, and collected data on in-patient length of stay (LOS) and in-patient care at the same time. RESULTS: Psychometric analyses including Principal Components Analysis and Cronbach's alpha reliability coefficient showed that a single satisfaction score (excluding two items scored individually) can be computed for the entire DTSQ-IP, indicating very good internal consistency reliability (0.92). The DTSQ-IP detected considerable dissatisfaction with meal choice and timing (13.7% of in-patients would never have chosen similar meals at home), and with in-patient hypoglycaemia (35.3% felt that their blood glucose was too low most of the time). In-patients on surgical wards, women, and those long established on insulin were significantly more dissatisfied, particularly with competence of hospital staff. Patients who administered their own insulin were not significantly less dissatisfied overall, but were so with the choice of meals (P = 0.005). Multiple regression analysis produced a model accounting for 8.2% of variability in DTSQ-IP (r = 0.29; P = 0.0058) and 21.7% of variability in LOS (r = 0.46; P = 0.0001). CONCLUSIONS: The DTSQ-IP is a novel, psychometrically validated and sensitive tool that adds to the DTSQ portfolio. The DTSQ-IP facilitates efforts to assess and improve treatment satisfaction in in-patients with diabetes.

Identification and Structure-Activity Relationship Study of Imidazo[1,2-a]pyridine-3-amines as First Selective Inhibitors of Excitatory Amino Acid Transporter Subtype 3 (EAAT3).

In the present study, screening of a library of 49,087 compounds at the excitatory amino acid transporter subtype 3 (EAAT3) led to the identification of 2-(furan-2-yl)-8-methyl-N-(o-tolyl)imidazo[1,2-a]pyridin-3-amine (3a) which showed a >20-fold preference for inhibition of EAAT3 (IC50 = 13 µM) over EAAT1,2,4 (EAAT1: IC50 ∼ 250 µM; EAAT2,4: IC50 > 250 µM). It was shown that a small lipophilic substituent (methyl or bromine) at the 7- and/or 8-position was essential for activity. Furthermore, the substitution pattern of the o-tolyl group (compound 5b) and the chemical nature of the substituent in the 2-position (compound 7b) were shown to be essential for the selectivity toward EAAT3 over EAAT1,2. The most prominent analogues to come out of this study are 3a and 3e that display ∼35-fold selectivity for EAAT3 (IC50 = 7.2 µM) over EAAT1,2,4 (IC50 ∼ 250 µM).

Design and Synthesis of 2,3- trans-Proline Analogues as Ligands for Ionotropic Glutamate Receptors and Excitatory Amino Acid Transporters.

Development of pharmacological tools for the ionotropic glutamate receptors (iGluRs) is imperative for the study and understanding of the role and function of these receptors in the central nervous system. We report the synthesis of 18 analogues of (2 S,3 R)-2-carboxy-3-pyrrolidine acetic acid (3a), which explores the effect of introducing a substituent on the ε-carbon (3c-q). A new synthetic method was developed for the efficient synthesis of racemic 3a and applied to give expedited access to 13 racemic analogues of 3a. Pharmacological characterization was carried out at native iGluRs, cloned homomeric kainate receptors (GluK1-3), NMDA receptors (GluN1/GluN2A-D), and excitatory amino acid transporters (EAAT1-3). From the structure-activity relationship studies, several new ligands emerged, exemplified by triazole 3p-d1, GluK3-preferring (GluK1/GluK3 Ki ratio of 15), and the structurally closely related tetrazole 3q-s3-4 that displayed 4.4-100-fold preference as an antagonist for the GluN1/GluN2A receptor ( Ki = 0.61 µM) over GluN1/GluN2B-D ( Ki = 2.7-62 µM).

The importance of the excitatory amino acid transporter 3 (EAAT3).

The neuronal excitatory amino acid transporter 3 (EAAT3) is fairly ubiquitously expressed in the brain, though it does not necessarily maintain the same function everywhere. It is important in maintaining low local concentrations of glutamate, where its predominant post-synaptic localization can buffer nearby glutamate receptors and modulate excitatory neurotransmission and synaptic plasticity. It is also the main neuronal cysteine uptake system acting as the rate-limiting factor for the synthesis of glutathione, a potent antioxidant, in EAAT3 expressing neurons, while on GABAergic neurons, it is important in supplying glutamate as a precursor for GABA synthesis. Several diseases implicate EAAT3, and modulation of this transporter could prove a useful therapeutic approach. Regulation of EAAT3 could be targeted at several points for functional modulation, including the level of transcription, trafficking and direct pharmacological modulation, and indeed, compounds and experimental treatments have been identified that regulate EAAT3 function at different stages, which together with observations of EAAT3 regulation in patients is giving us insight into the endogenous function of this transporter, as well as the consequences of altered function. This review summarizes work done on elucidating the role and regulation of EAAT3.

ß-Sulfonamido Functionalized Aspartate Analogues as Excitatory Amino Acid Transporter Inhibitors: Distinct Subtype Selectivity Profiles Arising from Subtle Structural Differences.

In this study inspired by previous work on 3-substituted Asp analogues, we designed and synthesized a total of 32 ß-sulfonamide Asp analogues and characterized their pharmacological properties at the excitatory amino acid transporter subtypes EAAT1, EAAT2, and EAAT3. In addition to several potent EAAT inhibitors displaying IC50 values ∼1 µM at all three subtypes, this elaborate structure-activity relationship also identified analogues exhibiting distinct preferences or selectivities for specific transporter subtypes. Introduction of two fluorine atoms on the phenyl ring yielded analogue 4y that displayed an IC50 of 0.8 µM at EAAT1 with a 14- and 9-fold preference over EAAT2 and EAAT3, respectively. Conversely, the m-CF3-phenyl analogue 4r was a potent selective EAAT2-inhibitor (IC50 = 2.8 µM) exhibiting 30- and 50-fold selectivity over EAAT1 and EAAT3, respectively. In conclusion, even small structural differences in these ß-sulfonamide Asp analogues provide analogues with diverse EAAT subtype selectivity profiles.

Identification of a New Class of Selective Excitatory Amino Acid Transporter Subtype 1 (EAAT1) Inhibitors Followed by a Structure-Activity Relationship Study.

Screening of a small compound library at the three excitatory amino acid transporter subtypes 1-3 (EAAT1-3) resulted in the identification of compound (Z)-4-chloro-3-(5-((3-(2-ethoxy-2-oxoethyl)-2,4-dioxothiazolidin-5-ylidene)methyl)furan-2-yl)benzoic acid (1a) that exhibited a distinct preference as an inhibitor at EAAT1 (IC50 20 µM) compared to EAAT2 and EAAT3 (IC50 > 300 µM). This prompted us to subject 1a to an elaborate structure-activity relationship study through the purchase and synthesis and subsequent pharmacological characterization of a total of 36 analogues. Although this effort did not result in analogues with substantially improved inhibitory potencies at EAAT1 compared to that displayed by the hit, it provided a detailed insight into structural requirements for EAAT1 activity of this scaffold. The discovery of this new class of EAAT1-selective inhibitors not only supplements the currently available pharmacological tools in the EAAT field but also substantiates the notion that EAAT ligands not derived from α-amino acids hold considerable potential in terms of subtype-selective modulation of the transporters.

New 4-Functionalized Glutamate Analogues Are Selective Agonists at Metabotropic Glutamate Receptor Subtype 2 or Selective Agonists at Metabotropic Glutamate Receptor Group III.

The metabotropic glutamate (Glu) receptors (mGluRs) play key roles in modulating excitatory neurotransmission in the brain. In all, eight subtypes have been identified and divided into three groups, group I (mGlu1,5), group II (mGlu2,3), and group III (mGlu4,6-8). In this article, we present a L-2,4-syn-substituted Glu analogue, 1d, which displays selective agonist activity at mGlu2 over the remaining mGluR subtypes. A modeling study and redesign of the core scaffold led to the stereoselective synthesis of four new conformationally restricted Glu analogues, 2a-d. Most interestingly, 2a retained a selective agonist activity profile at mGlu2 (EC50 in the micromolar range), whereas 2c/2d were both selective agonists at group III, subtypes mGlu4,6,8. In general, 2d was 20-fold more potent than 2c and potently activated mGlu4,6,8 in the low-mid nanomolar range.

New Insight into the Structure-Activity Relationships of the Selective Excitatory Amino Acid Transporter Subtype†1 (EAAT1) Inhibitors UCPH-101 and UCPH-102.

In the present study, we made further investigations on the structure-activity requirements of the selective excitatory amino acid transporter 1 (EAAT1) inhibitor, 2-amino-4-(4-methoxyphenyl)-7-(naphthalen-1-yl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (UCPH-101), by exploring 15 different substituents (R(1) ) at the 7-position in combination with eight different substituents (R(2) ) at the 4-position. Among the 63 new analogues synthesized, we identified a number of compounds that unexpectedly displayed inhibitory activities at EAAT1 in light of understanding the structure-activity relationship (SAR) of this inhibitor class extracted from previous studies. Moreover, the nature of the R(1) and R(2) substituents were observed to contribute to the functional properties of the various analogues in additive and non-additive ways. Finally, separation of the four stereoisomers of analogue 14 g (2-amino-4-([1,1'-biphenyl]-4-yl)-3-cyano-7-isopropyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene) was carried out, and in agreement with a study of a related scaffold, the R configuration at C4 was found to be mandatory for inhibitory activity, while both the C7 diastereomers were found to be active as EAAT1 inhibitors. A study of the stereochemical stability of the four pure stereoisomers 14 g-A-D showed that epimerization takes places at C7 via a ring-opening, C-C bond rotation, ring-closing mechanism.