Agonist Activity Research Articles

Two-point immobilization of M3 muscarinic receptor: a method for recognizing receptor antagonists in natural products

In the investigation of active ingredients from natural products, current technologies relying on drug–target affinity recognition analysis face significant challenges. This is primarily due to their limited specificity and inability to provide downstream pharmacodynamic information, such as agonistic or antagonistic activity. In this study, a two-point method was developed by immobilizing M3 acetylcholine receptor (M3R) through the combination of the conformation-specific peptide BJ-PRO-13a and the HaloTag trap system. We systematically assessed the specificity of the immobilized M3R using known M3R antagonists (pirenzepine and atropine) and agonists (cevimeline and pilocarpine). By frontal analysis and nonlinear chromatography, the performance of immobilized M3R was evaluated in terms of binding kinetics and thermodynamics of four drugs to the immobilized M3R. Additionally, we successfully identified two M3R antagonists within an extract from Daturae Flos (DF), specifically hyoscyamine and scopolamine. Our findings demonstrate that this immobilization method effectively captures receptor-ligand binding interactions and can discern receptor agonists from antagonists. This innovation enhances the efficiency of receptor chromatography to determine binding-affinity in the development of new drugs, offering promise for the screening and characterization of active compounds, particularly within complex natural products.

Abstract PO4-24-07: The Impact of GPER Modulation on Cancer Associated Fibroblasts on Extracellular Matrix Formation in Breast Cancer

Abstract Background: The G-protein coupled estrogen receptor (GPER) is a noncanonical estrogen receptor (ER) that is estimated to be present in roughly 50-60% of all breast cancer (BC) subtypes. Previous studies have suggested that the presence of GPER during primary disease aids in disease progression, metastasis, as well as chemotherapy resistance due to the agonistic activity of traditional chemotherapies for ER+ BC, tamoxifen and fulvestrant. It is also well established that the extracellular matrix (ECM), specifically collagen, contributes to the overall risk and progression of BC in patients. Importantly, fibroblasts are one of the primary cell types responsible for ECM deposition in the tumor microenvironment. We hypothesize that the modulation of cancer-associated fibroblasts (CAFs) via estrogen signaling through GPER regulates the deposition and structure of key ECM proteins, such as collagen, to aid in disease progression. Methods: CAFs, isolated from human BC surgical resections, were plated at 100% confluency, and incubated with either 10nM β-estradiol (E2), 50nM G1 (a GPER specific agonist) or a vehicle control and 50ug/mL ascorbic acid daily for 14 days to induce matrix deposition. Phenol-free, high glucose DMEM with 10% charcoal stripped FBS was used as media to reduce FBS sourced estrogen. Following the 14-day incubation, cell proliferation was quantified prior to extracting the cells to isolate the CAF-derived matrix (CDM). The organization and composition of ECM was analyzed in CDMs through immunofluorescence (IF) or western blot, respectively. An unpaired t-test was conducted on biological triplicates and between vehicle control and either G1 or E2. Significance was determined as p< 0.05. Results: Culturing CAFs with E2 resulted in a 10% increase in cell proliferation (n=3, p< 0.05) and a 1.6-fold (n=3, p< 0.05) increase in total ECM deposition by western blot. Key ECM proteins such as collagen, fibronectin, and periostin had a 1.8, 1.3, and 1.3-fold increase, respectively (n=3, p< 0.05), in protein deposition with E2 treatment when normalized to cell number. Collagen fiber analysis of IF stained CDM for collagen resulted in a coefficient of alignment with E2 of 0.76 compared to 0.51 without (n=3 for E2 and n=6 for vehicle, p< 0.05). To confirm E2 was acting through GPER, CDMs were subsequently generated with exposure to 50nM G1, a specific GPER agonist. Collagen fiber analysis of the G1 exposed CDMs resulted in a coefficient of alignment with G1 of 0.71 compared to 0.51 without (n=3 for G1 and n=6 for vehicle, p< 0.05). Conclusions: This study demonstrates that estrogen signaling through GPER modulates the deposition of fibronectin, periostin, and collagen as well as the organization of collagen architecture. These results highlight the need to further investigate how the interplay between the ECM, GPER activity, and fibroblasts impacts breast cancer progression. Citation Format: Shelby Fertal, Brian Burkel, Fern Murdoch, Kathy O'Leary, Linda Schuler, Suzanne Ponik. The Impact of GPER Modulation on Cancer Associated Fibroblasts on Extracellular Matrix Formation in Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-24-07.

Periodontal ligament fibroblasts utilize isoprenoid intermediate farnesyl diphosphate for maintaining osteo/cementogenic differentiation abilities

Background/purposePeroxisome proliferator-activated receptor γ (PPARγ) is a major transcription factor of energy metabolism-associated genes, and three PPARγ isoforms have been identified in periodontal tissues and cells. When energy metabolism homeostasis is affected by PPARγ downregulation in periodontal ligament fibroblasts (PDLFs), osteo/cementogenic abilities are markedly lost. Herein, we investigated whether PPARγ agonists promote periodontal tissue regeneration, and which PPARγ isoforms and metabolic pathways are indispensable for osteo/cementogenic abilities. Materials and methodsA PPARγ agonist was locally administered to regenerate murine periodontal tissue. The distinct functions of the PPARγ isoforms in PDLFs were assessed using an overexpression strategy. Candidate metabolic processes were searched using gene ontology analysis of PPARγ-knockdown PDLFs. In vitro differentiation assays were performed to evaluate the effects of farnesyl diphosphate (FPP) and geranylgeranyl diphosphate (GGPP), two major isoprenoid intermediates. ResultsPPARγ agonists accelerated periodontal tissue regeneration. Full-length PPARγ overexpression specifically enhanced the osteo/cementogenic differentiation of PPARγ agonist–induced PDLFs. The isoprenoid metabolic process was the top-ranked downregulated metabolism-associated pathway following PPARγ knockdown; FPP and GGPP enhanced and suppressed PDLFs' differentiation, respectively. Gene expression analysis of human clinical periodontal tissues revealed that osteocalcin correlated with farnesyl pyrophosphate synthetase (FDPS), which catalyzes FPP production, but not with two FPP conversion enzymes: geranylgeranyl diphosphate synthase 1 (GGPS1) or farnesyl diphosphate farnesyltransferase 1 (FDFT1). ConclusionPreferable PPARγ agonistic actions depend on the full-length PPARγ isoform. FPP increased PDLFs' osteo/cementogenic abilities. Therefore, administering FPP and precisely controlling FDPS, GGPS1, and FDFT1 activities could be a novel strategy for accelerating periodontal tissue regeneration.

Synthesis and In vitro and In silico Anti-inflammatory Activity of New Thiazolidinedione-quinoline Derivatives.

Inflammation is a series of complex defense-related reactions. The inflammation cascade produces various pro-inflammatory mediators. Unregulated production of these pro-inflammatory mediators can lead to a wide range of diseases, including rheumatoid arthritis, sepsis, and inflammatory bowel disease. In the literature, the anti-inflammatory action of quinoline and thiazolidinedione nuclei are well established, alone, and associated with other nuclei. The synthesis of hybrid molecules is a strategy for obtaining more efficient molecules due to the union of pharmacophoric nuclei known to be related to pharmacological activity. Based on this, this work presents the synthesis of thiazolidinedione-quinoline molecular hybrids and their involvement in the modulation of cytokines involved in the inflammatory reaction cascade. After synthesis and characterization, the compounds were submitted to cell viability test (MTT), ELISA IFN-γ and TNF-α, adipogenic differentiation, and molecular docking assay with PPARy and COX-2 targets. LPSF/ZKD2 and LPSF/ZKD7 showed a significant decrease in the concentration of IFN- γ and TNF-α, with a dose-dependent behavior. LPSF/ZKD4 at a concentration of 50 μM significantly reduced IL-6 expression. LPSF/ZKD4 demonstrates lipid accumulation with significant differences between the untreated and negative control groups, indicating a relevant agonist action on the PPARγ receptor. Molecular docking showed that all synthesized compounds have good affinity with PPARγ e COX-2, with binding energy close to -10,000 Kcal/mol. These results demonstrate that the synthesis of quinoline-thiazolidinedione hybrids may be a useful strategy for obtaining promising candidates for new anti-inflammatory agents.

FIRST COMPREHENSIVE ECHOCARDIOGRAPHIC ASSESSMENT IN PATIENTS WITH VASCULAR EHLERS-DANLOS SYNDROME WITH OR WITHOUT CELIPROLOL THERAPY AT THE MAXIMUM RECOMMENDED DOSE

Objective: Vascular Ehlers-Danlos syndrome (vEDS) is an inherited connective tissue disorder characterized by arterial fragility. Celiprolol is a beta1-adrenoceptor antagonist with partial beta2 agonist activity that has been shown to reduce rates of vascular events in this setting, though the underlying mechanisms are not yet fully understood. Moreover, few data on echocardiographic assessment are available in patients with vEDS. Design and method: Twenty patients with genetically confirmed diagnosis of vEDS followed at our Institution were divided into two groups (10 patients each) according to whether or not they were on celiprolol therapy at the maximum recommended dose (400 mg daily) for at least 12 months. Both groups were compared to 10 healthy individuals matched for sex, age, body mass index (BMI), and office blood pressure values. Each participant underwent transthoracic echocardiography with tissue Doppler analysis for a comprehensive evaluation of cardiac structure and function. Results: Mean age was 35 years and mean BMI was 21.6 kg/m2. Female sex was prevalent (60%). Left ventricular (LV) internal diameter values tended to be lower in patients with untreated vEDS than in healthy controls, though this difference was not statistically significant (4.33 vs 4.74 cm, respectively; p=0.053). Similar data were observed for LV mass index (56.9 vs 68.6 g/m2; p=0.093), stroke volume (56.6 vs 71.6 mL; p=0.068), and E/A ratio (1.26 vs 1.66; p=0.082), whereas an opposite trend was observed for e’ lateral (13.2 vs 12.2; p=0.096). No statistically significant difference was found between groups in terms of other parameters of LV mass, systolic and diastolic function. A normal LV geometry was found in all the cases. Indices of mechano-energetic efficiency and ventricular-arterial coupling were also similar between groups. No patient presented with aortic root dilation, mitral valve prolapse, valve insufficiency of more than mild degree, or valve stenosis of any degree. Conclusions: Our study suggests that patients with vEDS have normal cardiac mass and geometry, as well as normal systolic and diastolic function. Celiprolol therapy does not seem to significantly influence such aspects. Future studies on larger cohort of patients should confirm these aspects.

A novel fatty acid mimetic with pan-PPAR partial agonist activity inhibits diet-induced obesity and metabolic dysfunction-associated steatotic liver disease

ObjectiveThe prevalence of metabolic diseases is increasing globally at an alarming rate; thus, it is essential that effective, accessible, low-cost therapeutics are developed. Peroxisome proliferator-activated receptors (PPARs) are transcription factors that tightly regulate glucose homeostasis and lipid metabolism and are important drug targets for the treatment of type 2 diabetes and dyslipidemia. We previously identified LDT409, a fatty acid-like compound derived from cashew nut shell liquid, as a novel pan-active PPARα/γ/δ compound. Herein, we aimed to assess the efficacy of LDT409 in vivo and investigate the molecular mechanisms governing the actions of the fatty acid mimetic LDT409 in diet-induced obese mice. MethodsC57Bl/6 mice (6–11-month-old) were fed a chow or high fat diet (HFD) for 4 weeks; mice thereafter received once daily intraperitoneal injections of vehicle, 10 mg/kg Rosiglitazone, 40 mg/kg WY14643, or 40 mg/kg LDT409 for 18 days while continuing the HFD. During treatments, body weight, food intake, glucose and insulin tolerance, energy expenditure, and intestinal lipid absorption were measured. On day 18 of treatment, tissues and plasma were collected for histological, molecular, and biochemical analysis. ResultsWe found that treatment with LDT409 was effective at reversing HFD-induced obesity and associated metabolic abnormalities in mice. LDT409 lowered food intake and hyperlipidemia, while improving insulin tolerance. Despite being a substrate of both PPARα and PPARγ, LDT409 was crucial for promoting hepatic fatty acid oxidation and reducing hepatic steatosis in HFD-fed mice. We also highlighted a role for LDT409 in white and brown adipocytes in vitro and in vivo where it decreased fat accumulation, increased lipolysis, induced browning of WAT, and upregulated thermogenic gene Ucp1. Remarkably, LDT409 reversed HFD-induced weight gain back to chow-fed control levels. We determined that the LDT409-induced weight-loss was associated with a combination of increased energy expenditure (detectable before weight loss was apparent), decreased food intake, increased systemic fat utilization, and increased fecal lipid excretion in HFD-fed mice. ConclusionsCollectively, LDT409 represents a fatty acid mimetic that generates a uniquely favorable metabolic response for the treatment of multiple abnormalities including obesity, dyslipidemia, metabolic dysfunction-associated steatotic liver disease, and diabetes. LDT409 is derived from a highly abundant natural product-based starting material and its development could be pursued as a therapeutic solution to the global metabolic health crisis.

Cholecystokinin 1 Receptor Is Activated Permanently in Photodynamic Action

In contrast to agonist activation that is reversed after washout of agonist, we have found that cholecystokinin 1 receptor (CCK1R) is activated permanently by singlet oxygen in type II photodynamic action, the G Protein Coupled Receptor (GPCR) Activated By Singlet Oxygen is named GPCR-ABSO. CCK1R ectopically expressed in cell lines is activated in photodynamic action with photosensitizer sulphonated aluminum phthalocyanine (SALPC) or with genetically encoded protein photosensitizers (such as miniSOG, KillerRed) to trigger persistent calcium oscillations which are not washed out. Such permanent photodynamic CCK1R activation is seen also in freshly isolated pancreatic acini, which is inhibited by CCK1R antagonist. Photodynamic CCK1R activation is physiological in intensity, triggering calcium oscillations similar in frequencies to those induced by physiological CCK concentrations (10 - 100 pM). The molecular mechanisms for such permanent photodynamic activation of CCK1R at the physiological level are three-fold. When membrane proteins prepared from isolated rat pancreatic acini are subject to Western blot, CCK1R is found to be present as both dimers and monomers. After photodynamic action with SALPC at an intensity that would trigger persistent calcium oscillations in live cells, the resting receptor dimer is converted quantitatively to monomer, similar to agonist stimulated CCK1R monomerization revealed by bioluminescence resonance energy transfer (BRET) method in rat CCK1R-expressing COS cells, suggesting that photodynamic CCK1R activation we have demonstrated is likely quite physiological. Whilst CCK1R is activated by singlet oxygen in photodynamic action, the M3 acetylcholine receptor is not affected. However, when TM3 of CCK1R is transplanted to M3R to replace TM3 of M3R, the chimeric receptor M3R-TM3CCK1R becomes activatable in photodynamic action, after tagging with miniSOG. The calculated extent of miniSOG photodynamic activation of M3R, chimeric M3R-TM3CCK1R, and CCK1R are 0%, 65%, 100% respectively. Comparative studies with pancreatic acini isolated from the rat, mouse and Peking duck found that sensitivity for photodynamic CCK1R activation is, in descending order: mouse > rat > Peking duck, the same order of the size of structure-free region of intracellular loop 3 (ICL3). Other than CCK1R, CCK2R is photodynamically activated also, after tagging with protein photosensitizer miniSOG. CCK1R and CCK2R are known to be involved in vital physiological functions: pancreatic secretion, satiety sensation, sinoatrial node pace-making, memory formation and storage, and others. Our work implies that all these and other physiological functions might be modulated in vivo by photodynamic CCK1R activation. The fact that such property of permanent photodynamic activation could be transplanted from CCK1R to other GPCR such as M3R suggests that photodynamic activation of GPCR could be used to tease apart the roles and functions of vast numbers of GPCR. Other functional proteins such as NAD(P)H oxidase 2, BK/Slo channel, CaMKII, riboflavin transporter (SLC52A1/RFVT1), might also be photodynamically activated permanently. This work was supported by The Natural Science Foundation of China (NSFC, Grant Nos. 31971170 and 32271278). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Incretin-Based Weight Loss Pharmacotherapy: Can Resistance Exercise Optimize Changes in Body Composition?

This narrative review highlights the degree to which new antiobesity medications based on gut-derived nutrient-stimulated hormones (incretins) cause loss of lean mass, and the importance of resistance exercise to preserve muscle. Glucagon-like peptide 1 receptor agonists (GLP-1RA) induce substantial weight loss in randomized trials, effects that may be enhanced in combination with glucose-dependent insulinotropic polypeptide (GIP) receptor agonists. Liraglutide and semaglutide (GLP-1RA), tirzepatide (GLP-1 and GIP receptor dual agonist), and retatrutide (GLP-1, GIP, and glucagon receptor triple agonist) are peptides with incretin agonist activity that induce ∼15-24% weight loss in adults with overweight and obesity, alongside beneficial impacts on blood pressure, cholesterol, blood glucose, and insulin. However, these agents also cause rapid and significant loss of lean mass (∼10% or ∼6 kg), comparable to a decade or more of aging. Maintaining muscle mass and function as humans age is crucial to avoiding sarcopenia and frailty, which are strongly linked to morbidity and mortality. Studies indicate that supervised resistance exercise training interventions with a duration >10 weeks can elicit large increases in lean mass (∼3 kg) and strength (∼25%) in men and women. After a low-calorie diet, combining aerobic exercise with liraglutide improved weight loss maintenance compared with either alone. Retaining lean mass during incretin therapy could blunt body weight (and fat) regain on cessation of weight loss pharmacotherapy. We propose that tailored resistance exercise training be recommended as an adjunct to incretin therapy to optimize changes in body composition by preserving lean mass while achieving fat loss.

The online conversion framework: Understanding antagonism, planning theory, and social media

Digital technology is reshaping participatory planning, including conflict and antagonism in the planning process. Yet planning theory has largely failed to engage with emerging digital mechanisms that could stimulate antagonism in online environments. This paper seeks to explore different ways of framing conflict and antagonism in planning and the degree to which they reflect an increasingly digital approach to public participation. We introduce an Online Conversion Framework to delineate the process of conversion for antagonistic to agonistic action on social media, using X (formerly Twitter) as an example.

Structural Insights into Partial Activation of the Prototypic G Protein-Coupled Adenosine A2A Receptor.

The adenosine A2A receptor (A2AAR) belongs to the rhodopsin-like G protein-coupled receptor (GPCR) family, which constitutes the largest class of GPCRs. Partial agonists show reduced efficacy as compared to physiological agonists and can even act as antagonists in the presence of a full agonist. Here, we determined an X-ray crystal structure of the partial A2AAR agonist 2-amino-6-[(1H-imidazol-2-ylmethyl)sulfanyl]-4-p-hydroxyphenyl-3,5-pyridinedicarbonitrile (LUF5834) in complex with the A2AAR construct A2A-PSB2-bRIL, stabilized in its inactive conformation and being devoid of any mutations in the ligand binding pocket. The determined high-resolution structure (2.43 Å) resolved water networks and crucial binding pocket interactions. A direct hydrogen bond of the p-hydroxy group of LUF5834 with T883.36 was observed, an amino acid that was mutated to alanine in the most frequently used A2AAR crystallization constructs thus preventing the discovery of its interactions in most of the previous A2AAR co-crystal structures. G protein dissociation studies confirmed partial agonistic activity of LUF5834 as compared to that of the full agonist N-ethylcarboxamidoadenosine (NECA). In contrast to NECA, the partial agonist was still able to bind to the receptor construct locked in its inactive conformation by an S913.39K mutation, although with an affinity lower than that at the native receptor. This could explain the compound's partial agonistic activity: while full A2AAR agonists bind exclusively to the active conformation, likely following conformational selection, partial agonists bind to active as well as inactive conformations, showing higher affinity for the active conformation. This might be a general mechanism of partial agonism also applicable to other GPCRs.

Developing insulin-like peptide 5-based antagonists for the G protein-coupled receptor, RXFP4

Human insulin-like peptide 5 (INSL5) is a gut hormone produced by colonic L-cells, and its biological functions are mediated by Relaxin Family Peptide Receptor 4 (RXFP4). Our preliminary data indicated that RXFP4 agonists are potential drug leads for the treatment of constipation. More recently, we designed and developed a novel RXFP4 antagonist, A13-nR that was shown to block agonist-induced activity in cells and animal models. We showed that A13-nR was able to block agonist-induced increases in colon motility in mice of both genders that express the receptor, RXFP4. Our data also showed that colorectal propulsion induced by intracolonic administration of short-chain fatty acids was antagonized by A13-nR. Therefore, A13-nR is an important research tool and potential drug lead for the treatment of colon motility disorders, such as bacterial diarrhea. However, A13-nR acted as a partial agonist at high concentrations in vitro and demonstrated modest antagonist potency (∼35 nM). Consequently, the primary objective of this study is to pinpoint novel modifications to A13-nR that eliminate partial agonist effects while preserving or augmenting antagonist potency. In this work, we detail the creation of a series of A13-nR-modified analogues, among which analogues 3, 4, and 6 demonstrated significantly improved RXFP4 affinity (∼3 nM) with reduced partial agonist activity, enhanced antagonist potency (∼10 nM) and maximum agonist inhibition (∼80 %) when compared with A13-nR. These compounds have potential as candidates for further preclinical evaluations, marking a significant stride toward innovative therapeutics for colon motility disorders.

Synthesis of a new 2-prenylated quinoline as potential drug for metabolic syndrome with pan-PPAR activity and anti-inflammatory effects

We have previously reported the total synthesis and structure–activity relationships (SAR) of 2-prenylated benzopyrans with PPAR agonist activity. Herein, we have described the synthesis and PPAR activity of 2-prenylated benzopyrans and 2-prenylated quinolines. The benzopyran nucleus was generated via enamine-catalyzed Kabbe condensation, and the quinoline nucleus via Friedländer condensation. Results demonstrated that both benzopyran (5a) and quinoline (4b) derivatives bearing a γ,δ-unsaturated ester displayed a pan-PPAR agonism. They were full PPARα agonists, but showed different preferences for PPARγ and PPARβ/δ activation. It was noteworthy that quinoline 4b displayed full hPPARα activation (2-fold than WY-14,643), weak PPARβ/δ and partial PPARγ activation. In addition, quinoline 4b showed anti-inflammatory effects on macrophages by reducing LPS-induced expression of both MCP-1 and IL-6. Therefore, 4b emerges as a first-in-class promising hit compound for the development of potential therapeutics aimed at treating metabolic syndrome, metabolic dysfunction-associated fatty liver disease (MAFLD), and its associated cardiovascular comorbidities.

Characterization of a Trispecific PD-L1 Blocking Antibody That Exhibits EGFR-Conditional 4-1BB Agonist Activity.

Immune checkpoint blockade has changed the treatment paradigm for advanced solid tumors, but the overall response rates are still limited. The combination of checkpoint blockade with anti-4-1BB antibodies to stimulate tumor-infiltrating T cells has shown anti-tumor activity in human trials. However, the further clinical development of these antibodies has been hampered by significant off-tumor toxicities. Here, we generated an anti-4-1BB/EGFR/PD-L1 trispecific antibody consisting of a triple-targeting tandem trimerbody (TT) fused to an engineered silent Fc region. This antibody (IgTT-4E1-S) was designed to combine the blockade of the PD-L1/PD-1 axis with conditional 4-1BB costimulation specifically confined to the tumor microenvironment (TME). The antibody demonstrated simultaneous binding to purified EGFR, PD-L1, and 4-1BB in solution, effective blockade of the PD-L1/PD1 interaction, and potent 4-1BB-mediated costimulation, but only in the presence of EGFR-expressing cells. These results demonstrate the feasibility of IgTT-4E1-S specifically blocking the PD-L1/PD-1 axis and inducing EGFR-conditional 4-1BB agonist activity.

Functional Activity of Enantiomeric Oximes and Diastereomeric Amines and Cyano Substituents at C9 in 3-Hydroxy-N-phenethyl-5-phenylmorphans.

The synthesis of stereochemically pure oximes, amines, saturated and unsaturated cyanomethyl compounds, and methylaminomethyl compounds at the C9 position in 3-hydroxy-N-phenethyl-5-phenylmorphans provided μ-opioid receptor (MOR) agonists with varied efficacy and potency. One of the most interesting compounds, (2-((1S,5R,9R)-5-(3-hydroxyphenyl)-2-phenethyl-2-azabicyclo[3.3.1]nonan-9-yl)acetonitrile), was found to be a potent partial MOR agonist (EC50 = 2.5 nM, %Emax = 89.6%), as determined in the forskolin-induced cAMP accumulation assay. Others ranged in potency and efficacy at the MOR, from nanomolar potency with a C9 cyanomethyl compound (EC50 = 0.85 nM) to its totally inactive diastereomer, and three compounds exhibited weak MOR antagonist activity (the primary amine 3, the secondary amine 8, and the cyanomethyl compound 41). Many of the compounds were fully efficacious; their efficacy and potency were affected by both the stereochemistry of the molecule and the specific C9 substituent. Most of the MOR agonists were selective in their receptor interactions, and only a few had δ-opioid receptor (DOR) or κ-opioid receptor (KOR) agonist activity. Only one compound, a C9-methylaminomethyl-substituted phenylmorphan, was moderately potent and fully efficacious as a KOR agonist (KOR EC50 = 18 nM (% Emax = 103%)).

Facile generation of biepitopic antibodies with intrinsic agonism for activating tumor necrosis factor receptors

Agonist antibodies are being pursued for therapeutic applications ranging from neurodegenerative diseases to cancer. For the tumor necrosis factor (TNF) receptor superfamily, higher-order clustering of three or more receptors is key to their activation, which can be achieved using antibodies that recognize two unique epitopes. However, the generation of biepitopic (i.e., biparatopic) antibodies typically requires animal immunization and is laborious and unpredictable. Here, we report a simple method for identifying biepitopic antibodies that potently activate TNF receptors without the need for additional animal immunization. Our approach uses existing, receptor-specific IgGs, which lack intrinsic agonist activity, to block their corresponding epitopes, then selects single-chain antibodies that bind accessible epitopes. The selected antibodies are fused to the light chains of IgGs to generate human tetravalent antibodies. We highlight the broad utility of this approach by converting several clinical-stage antibodies against OX40 and CD137 (4-1BB) into biepitopic antibodies with potent agonist activity.

Discovery of an Ortho-Substituted N-Cyclopropylmethyl-7α-phenyl-6,14-endoethano-tetrahydronorthebaine Derivative as a Selective and Potent Kappa Opioid Receptor Agonist with Subsided Sedative Effect.

Research into kappa opioid receptor (KOR) agonists with attenuated central-nervous-system side effects is a critical focus for developing productive and safe analgesics. Herein, a series of ortho-substituted N-cyclopropylmethyl-7α-phenyl-6,14-endoethano-tetrahydronorthebaines were designed, synthesized, and subjected to bioassays. Compound 7a exhibited high subtype selectivity and potent agonistic activity toward KOR (KOR, Ki = 3.9 nM, MOR/KOR = 270, DOR/KOR = 1075; [35S]GTPγS binding, EC50 = 3.4 nM). Additionally, this compound exhibited robust and persistent antinociceptive effects in rodent models with different animal strains (hot plate test, ED50 = 0.20-0.30 mg/kg, i.p.; abdominal constriction test, ED50 = 0.20-0.60 mg/kg, i.p.), with its KOR-mediated mechanism for antinociception firmly established. Notably, compound 7a, unlike conventional KOR agonists, displayed minimal sedation and aversion at the antinociceptive ED50 dose. This feature addresses a crucial limitation in existing KOR agonists, positioning compound 7a as a promising novel therapeutic agent.

Discovery and Structure-Activity Relationships of 2,5-Dimethoxyphenylpiperidines as Selective Serotonin 5-HT2A Receptor Agonists.

Classical psychedelics such as psilocybin, lysergic acid diethylamide (LSD), and N,N-dimethyltryptamine (DMT) are showing promising results in clinical trials for a range of psychiatric indications, including depression, anxiety, and substance abuse disorder. These compounds are characterized by broad pharmacological activity profiles, and while the acute mind-altering effects can be ascribed to their shared agonist activity at the serotonin 2A receptor (5-HT2AR), their apparent persistent therapeutic effects are yet to be decidedly linked to activity at this receptor. We report herein the discovery of 2,5-dimethoxyphenylpiperidines as a novel class of selective 5-HT2AR agonists and detail the structure-activity investigations leading to the identification of LPH-5 [analogue (S)-11] as a selective 5-HT2AR agonist with desirable drug-like properties.

Effect-directed analysis of androgenic compounds from sewage sludges in China

The safety of municipal sewage sludge has raised great concerns because of the accumulation of large-scale endocrine disrupting chemicals in the sludge during wastewater treatment. The presence of contaminants in sludge can cause secondary pollution owing to inappropriate disposal mechanisms, posing potential risks to the environment and human health. Effect-directed analysis (EDA), involving an androgen receptor (AR) reporter gene bioassay, fractionation, and suspect and nontarget chemical analysis, were applied to identify causal AR agonists in sludge; 20 of the 30 sludge extracts exhibited significant androgenic activity. Among these, the extracts from Yinchuan, Kunming, and Shijiazhuang, which held the most polluted AR agonistic activities were prepared for extensive EDA, with the dihydrotestosterone (DHT)-equivalency of 2.5 – 4.5 ng DHT/g of sludge. Seven androgens, namely boldione, androstenedione, testosterone, megestrol, progesterone, and testosterone isocaproate, were identified in these strongest sludges together, along with testosterone cypionate, first reported in sludge media. These identified androgens together accounted for 55 %, 87 %, and 52 % of the effects on the sludge from Yinchuan, Shijiazhuang, and Kunming, respectively. This study elucidates the causative androgenic compounds in sewage sludge and provides a valuable reference for monitoring and managing androgens in wastewater treatment.

Structural insights into the unexpected agonism of tetracyclic antidepressants at serotonin receptors 5-HT1eR and 5-HT1FR.

Serotonin [5-hydroxytryptamine (5-HT)] acts via 13 different receptors in humans. Of these receptor subtypes, all but 5-HT1eR have confirmed roles in native tissue and are validated drug targets. Despite 5-HT1eR's therapeutic potential and plausible druggability, the mechanisms of its activation remain elusive. To illuminate 5-HT1eR's pharmacology in relation to the highly homologous 5-HT1FR, we screened a library of aminergic receptor ligands at both receptors and observe 5-HT1eR/5-HT1FR agonism by multicyclic drugs described as pan-antagonists at 5-HT receptors. Potent agonism by tetracyclic antidepressants mianserin, setiptiline, and mirtazapine suggests a mechanism for their clinically observed antimigraine properties. Using cryo-EM and mutagenesis studies, we uncover and characterize unique agonist-like binding poses of mianserin and setiptiline at 5-HT1eR distinct from similar drug scaffolds in inactive-state 5-HTR structures. Together with computational studies, our data suggest that these binding poses alongside receptor-specific allosteric coupling in 5-HT1eR and 5-HT1FR contribute to the agonist activity of these antidepressants.

Structure-activity relationship studies of tetrahydroquinolone derivatives as GPR41 modulators

GPR41, a G protein-coupled receptor, serves as a sensor for short-chain fatty acids and plays a crucial role in regulating multiple physiological processes such as the maintenance of metabolic and immune homeostasis. Therefore, the modulation of GPR41 has garnered attention as a potential strategy for the treatment of various disorders. We conducted a structure–activity relationship study on a lead tetrahydroquinolone derivative bearing a 2-(trifluoromethoxy)benzene group that displayed antagonistic activity toward GPR41. Modification of the aryl group attached to the furan moiety revealed that derivatives containing di- or trifluorobenzene, instead of 2-(trifluoromethoxy)benzene, exhibited agonistic activity toward GPR41, comparable with the reported agonistic modulator AR420626. These results suggest that the aryl group plays a pivotal role in regulating the activity of compounds toward GPR41, providing valuable insights for the design of GPR41 modulators.