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Proceedings of the National Academy of... Jan 2023Spinal muscular atrophy (SMA) is a severe autosomal recessive neuromuscular disease affecting children and young adults, caused by mutations of the survival motor neuron...
Spinal muscular atrophy (SMA) is a severe autosomal recessive neuromuscular disease affecting children and young adults, caused by mutations of the survival motor neuron 1 gene (). SMA is characterized by the degeneration of spinal alpha motor neurons (αMNs), associated with muscle paralysis and atrophy, as well as other peripheral alterations. Both growth hormone-releasing hormone (GHRH) and its potent agonistic analog, MR-409, exert protective effects on muscle atrophy, cardiomyopathies, ischemic stroke, and inflammation. In this study, we aimed to assess the protective role of MR-409 in SMNΔ7 mice, a widely used model of SMA. Daily subcutaneous treatment with MR-409 (1 or 2 mg/kg), from postnatal day 2 (P2) to euthanization (P12), increased body weight and improved motor behavior in SMA mice, particularly at the highest dose tested. In addition, MR-409 reduced atrophy and ameliorated trophism in quadriceps and gastrocnemius muscles, as determined by an increase in fiber size, as well as upregulation of myogenic genes and inhibition of proteolytic pathways. MR-409 also promoted the maturation of neuromuscular junctions, by reducing multi-innervated endplates and increasing those mono-innervated. Finally, treatment with MR-409 delayed αMN death and blunted neuroinflammation in the spinal cord of SMA mice. In conclusion, the present study demonstrates that MR-409 has protective effects in SMNΔ7 mice, suggesting that GHRH agonists are promising agents for the treatment of SMA, possibly in combination with SMN-dependent strategies.
Topics: Animals; Mice; Atrophy; Disease Models, Animal; Growth Hormone-Releasing Hormone; Motor Neurons; Muscular Atrophy, Spinal; Spinal Cord; Survival of Motor Neuron 1 Protein
PubMed: 36603028
DOI: 10.1073/pnas.2216814120 -
Journal of the American Chemical Society Jun 2023Class B1 G protein-coupled receptors (GPCRs), collectively, respond to a diverse repertoire of extracellular polypeptide agonists and transmit the encoded messages to...
Class B1 G protein-coupled receptors (GPCRs), collectively, respond to a diverse repertoire of extracellular polypeptide agonists and transmit the encoded messages to cytosolic partners. To fulfill these tasks, these highly mobile receptors must interconvert among conformational states in response to agonists. We recently showed that conformational mobility in polypeptide agonists themselves plays a role in activation of one class B1 GPCR, the receptor for glucagon-like peptide-1 (GLP-1). Exchange between helical and nonhelical conformations near the N-termini of agonists bound to the GLP-1R was revealed to be critical for receptor activation. Here, we ask whether agonist conformational mobility plays a role in the activation of a related receptor, the GLP-2R. Using variants of the hormone GLP-2 and the designed clinical agonist glepaglutide (GLE), we find that the GLP-2R is quite tolerant of variations in α-helical propensity near the agonist N-terminus, which contrasts with signaling at the GLP-1R. A fully α-helical conformation of the bound agonist may be sufficient for GLP-2R signal transduction. GLE is a GLP-2R/GLP-1R dual agonist, and the GLE system therefore enables direct comparison of the responses of these two GPCRs to a single set of agonist variants. This comparison supports the conclusion that the GLP-1R and GLP-2R differ in their response to variations in helical propensity near the agonist N-terminus. The data offer a basis for development of new hormone analogues with distinctive and potentially useful activity profiles; for example, one of the GLE analogues is a potent agonist of the GLP-2R but also a potent antagonist of the GLP-1R, a novel form of polypharmacology.
Topics: Glucagon-Like Peptide 1; Glucagon-Like Peptide-2 Receptor; Peptides; Receptors, G-Protein-Coupled; Signal Transduction; Glucagon-Like Peptide-1 Receptor
PubMed: 37235770
DOI: 10.1021/jacs.3c01628 -
Immunologic Research Aug 2021Toll-like receptors 3 (TLR3) have been broadly studied among all TLRs over the last few decades together with its agonists due to their contribution to cancer... (Comparative Study)
Comparative Study Review
Toll-like receptors 3 (TLR3) have been broadly studied among all TLRs over the last few decades together with its agonists due to their contribution to cancer regression. These agonists undeniably have some shared characteristics such as mimicking dsRNA but pathways through which they exhibit antitumor properties are relatively diverse. In this review, three widely studied agonists RGC100, ARNAX, and poly-IC are discussed along with their structural and physiochemical differences including the signaling cascades through which they exert their actions. Comparison has been made to identify the finest agonist with maximum effectivity and the least side effect profile.
Topics: Adjuvants, Immunologic; Animals; Humans; Poly I-C; RNA; Toll-Like Receptor 3
PubMed: 34145551
DOI: 10.1007/s12026-021-09203-6 -
The Journal of Pharmacology and... Mar 2021Pharmacodynamic efficacy of drugs to activate their receptors is a key determinant of drug effects, and intermediate-efficacy agonists are often useful clinically...
Pharmacodynamic efficacy of drugs to activate their receptors is a key determinant of drug effects, and intermediate-efficacy agonists are often useful clinically because they retain sufficient efficacy to produce therapeutically desirable effects while minimizing undesirable effects. Molecular mechanisms of efficacy are not well understood, so rational drug design to control efficacy is not yet possible; however, receptor theory predicts that fixed-proportion mixtures of an agonist and antagonist for a given receptor can be adjusted to precisely control net efficacy of the mixture in activating that receptor. Moreover, the agonist proportion required to produce different effects provides a quantitative scale for comparing efficacy requirements across those effects. To test this hypothesis, the present study evaluated effectiveness of fixed-proportion agonist/antagonist mixtures to produce in vitro and in vivo effects mediated by -opioid receptors (MOR) and cannabinoid type 1 receptors (CBR). Mixtures of 1) the MOR agonist fentanyl and antagonist naltrexone and 2) the CBR agonist CP55,940 and antagonist/inverse agonist rimonabant were evaluated in an in vitro assay of ligand-stimulated guanosine 5'--(3-[S]thio)triphosphate binding and an in vivo assay of thermal nociception in mice. For both agonist/antagonist pairs in both assays, increasing agonist proportions produced graded increases in maximal mixture effects, and lower agonist proportions were sufficient to produce in vivo than in vitro effects. These findings support the utility of agonist-antagonist mixtures as a strategy to control net efficacy of receptor activation and to quantify and compare efficacy requirements across a range of in vitro and in vivo endpoints. SIGNIFICANCE STATEMENT: Manipulation of agonist proportion in agonist/antagonist mixtures governs net mixture efficacy at the target receptor. Parameters of agonist/antagonist mixture effects can provide a quantitative metric for comparison of efficacy requirements across a wide range of conditions.
Topics: Analgesics, Opioid; Animals; CHO Cells; Cannabinoids; Cricetulus; Dose-Response Relationship, Drug; Drug Interactions; Male; Mice; Receptor, Cannabinoid, CB1; Receptors, Opioid, mu
PubMed: 33443077
DOI: 10.1124/jpet.120.000349 -
Frontiers in Immunology 2020In recent years, the success of immunotherapy targeting immunoregulatory receptors (immune checkpoints) in cancer have generated enthusiastic support to target these... (Review)
Review
In recent years, the success of immunotherapy targeting immunoregulatory receptors (immune checkpoints) in cancer have generated enthusiastic support to target these receptors in a wide range of other immune related diseases. While the overwhelming focus has been on blockade of these inhibitory pathways to augment immunity, agonistic triggering these receptors offers the promise of dampening pathogenic inflammatory responses. V-domain Ig suppressor of T cell activation (VISTA) has emerged as an immunoregulatory receptor with constitutive expression on both the T cell and myeloid compartments, and whose agonistic targeting has proven a unique avenue relative to other checkpoint pathways to suppress pathologies mediated by the innate arm of the immune system. VISTA agonistic targeting profoundly changes the phenotype of human monocytes towards an anti-inflammatory cell state, as highlighted by striking suppression of the canonical markers CD14 and Fcγr3a (CD16), and the almost complete suppression of both the interferon I (IFN-I) and antigen presentation pathways. The insights from these very recent studies highlight the impact of VISTA agonistic targeting of myeloid cells, and its potential therapeutic implications in the settings of hyperinflammatory responses such as cytokine storms, driven by dysregulated immune responses to viral infections (with a focus on COVID-19) and autoimmune diseases. Collectively, these findings suggest that the VISTA pathway plays a conserved, non-redundant role in myeloid cell function.
Topics: Animals; Antigen Presentation; B7 Antigens; CD4-Positive T-Lymphocytes; COVID-19; Cytokine Release Syndrome; GPI-Linked Proteins; Humans; Immunotherapy; Interferon Type I; Lipopolysaccharide Receptors; Lymphocyte Activation; Mice; Myeloid Cells; Receptors, IgG; SARS-CoV-2
PubMed: 33643285
DOI: 10.3389/fimmu.2020.595950 -
Cancer Cell Apr 2018Most tumors are unresponsive to immune checkpoint blockade, especially if deep immunosuppression in the tumor develops prior to and prevents T cell immunosurveillance.... (Review)
Review
Most tumors are unresponsive to immune checkpoint blockade, especially if deep immunosuppression in the tumor develops prior to and prevents T cell immunosurveillance. Failed or frustrated T cell priming often needs repair before successful sensitization to PD-1/PD-L1 blockade. CD40 activation plays a critical role in generating T cell immunity, by activating dendritic cells, and converting cold tumors to hot. In preclinical studies, agonistic CD40 antibodies demonstrate T cell-dependent anti-tumor activity, especially in combination with chemotherapy, checkpoint inhibitory antibodies, and other immune modulators. With the advent of multiple CD40 agonists with acceptable single-agent toxicity, clinical evaluation of CD40 combinations has accelerated.
Topics: Animals; Antibodies, Blocking; B7-H1 Antigen; CD40 Antigens; Humans; Immunotherapy; Neoplasms; T-Lymphocytes; Tumor Microenvironment
PubMed: 29634944
DOI: 10.1016/j.ccell.2018.03.008 -
Scientific Reports Nov 2019Agonists of β adrenergic receptors (βAR) and glucocorticoid receptors (GR) are prescribed to treat pulmonary diseases. Since ozone effects are mediated through the...
Agonists of β adrenergic receptors (βAR) and glucocorticoid receptors (GR) are prescribed to treat pulmonary diseases. Since ozone effects are mediated through the activation of AR and GR, we hypothesized that the treatment of rats with relevant therapeutic doses of long acting βAR agonist (LABA; clenbuterol; CLEN) and/or GR agonist (dexamethasone; DEX) would exacerbate ozone-induced pulmonary and systemic changes. In the first study, male 12-week-old Wistar-Kyoto rats were injected intraperitoneally with vehicle (saline), CLEN (0.004 or 0.02 mg/kg), or DEX (0.02 or 0.1 mg/kg). Since dual therapy is commonly used, in the second study, rats received either saline or combined CLEN + DEX (each at 0.005 or 0.02 mg/kg) one day prior to and on both days of exposure (air or 0.8ppm ozone, 4 hr/day x 2-days). In air-exposed rats CLEN, DEX or CLEN + DEX did not induce lung injury or inflammation, however DEX and CLEN + DEX decreased circulating lymphocytes, spleen and thymus weights, increased free fatty acids (FFA) and produced hyperglycemia and glucose intolerance. Ozone exposure of vehicle-treated rats increased bronchoalveolar lavage fluid protein, albumin, neutrophils, IL-6 and TNF-α. Ozone decreased circulating lymphocytes, increased FFA, and induced hypeerglycemia and glucose intolerance. Drug treatment did not reverse ozone-induced ventillatory changes, however, lung effects (protein and albumin leakage, inflammation, and IL-6 increase) were exacerbated by CLEN and CLEN + DEX pre-treatment in a dose-dependent manner (CLEN > CLEN + DEX). Systemic effects induced by DEX and CLEN + DEX but not CLEN in air-exposed rats were analogous to and more pronounced than those induced by ozone. These data suggest that adverse air pollution effects might be exacerbated in people receiving LABA or LABA plus glucocorticoids.
Topics: Adrenergic beta-2 Receptor Agonists; Animals; Clenbuterol; Dexamethasone; Drug Interactions; Fatty Acids; Glucocorticoids; Glucose; Interleukin-6; Lung; Lymphocytes; Male; Ozone; Rats; Rats, Wistar; Spleen; Thymus Gland; Tumor Necrosis Factor-alpha
PubMed: 31784596
DOI: 10.1038/s41598-019-54269-w -
Biophysical Journal May 2021Agonists are evaluated by a concentration-response curve (CRC), with a midpoint (EC) that indicates potency, a high-concentration asymptote that indicates efficacy, and...
Agonists are evaluated by a concentration-response curve (CRC), with a midpoint (EC) that indicates potency, a high-concentration asymptote that indicates efficacy, and a low-concentration asymptote that indicates constitutive activity. A third agonist attribute, efficiency (η), is the fraction of binding energy that is applied to the conformational change that activates the receptor. We show that η can be calculated from EC and the asymptotes of a CRC derived from either single-channel or whole-cell responses. For 20 agonists of skeletal muscle nicotinic receptors, the distribution of η-values is bimodal with population means at 51% (including acetylcholine, nornicotine, and dimethylphenylpiperazinium) and 40% (including epibatidine, varenicline, and cytisine). The value of η is related inversely to the size of the agonist's headgroup, with high- versus low-efficiency ligands having an average volume of 70 vs. 102 Å. Most binding site mutations have only a small effect on acetylcholine efficiency, except for αY190A (35%), αW149A (60%), and those at αG153 (42%). If η is known, the EC and high-concentration asymptote can be calculated from each other. Hence, an entire CRC can be estimated from the response to a single agonist concentration, and efficacy can be estimated from EC of a CRC that has been normalized to 1. Given η, the level of constitutive activity can be estimated from a single CRC.
Topics: Binding Sites; Nicotinic Agonists; Receptors, Nicotinic
PubMed: 33675765
DOI: 10.1016/j.bpj.2021.02.034 -
Journal of Controlled Release :... May 2023Stimulator of interferon genes (STING) pathway is the key innate immune pathway involving in cancer immunity. Emerging new molecules and drug delivery systems have made...
Stimulator of interferon genes (STING) pathway is the key innate immune pathway involving in cancer immunity. Emerging new molecules and drug delivery systems have made systemic STING agonist immunotherapy possible and demonstrated efficient tumor eradication in preclinical studies. In this perspective, we will discuss the potential mechanisms of STING agonism as a multifaceted anti-cancer therapy and the pharmacological challenges associated with systemic delivery of STING agonists on the level of organs, tissues, cells, and intracellular compartments. We will present and discuss drug delivery strategies to address these challenges. New advances in the field can unlock the promise of systemic STING agonist as effective and safe cancer immunotherapy.
Topics: Humans; Immunotherapy; Membrane Proteins; Neoplasms; Signal Transduction
PubMed: 37001564
DOI: 10.1016/j.jconrel.2023.03.047 -
Toxicological Sciences : An Official... Oct 2020Concentration/dose addition is widely used for compounds that act by similar mechanisms. But it cannot make predictions for mixtures of full and partial agonists for...
Concentration/dose addition is widely used for compounds that act by similar mechanisms. But it cannot make predictions for mixtures of full and partial agonists for effect levels above that of the least efficacious component. As partial agonists are common, we developed generalized concentration addition, which has been successfully applied to systems in which ligands compete for a single binding site. Here, we applied a pharmacodynamic model for a homodimer receptor system with 2 binding sites, the androgen receptor, that acts according to the classic homodimer activation model: Each cytoplasmic monomer protein binds ligand, undergoes a conformational change that relieves inhibition of dimerization, and binds to DNA response elements as a dimer. We generated individual dose-response data for full (dihydroxytestosterone, BMS564929) and partial (TFM-4AS-1) agonists and a competitive antagonist (MDV3100) using reporter data generated in the MDA-kb2 cell line. We used the Schild method to estimate the binding affinity of MDV3100. Data for individual compounds fit the homodimer pharmacodynamic model well. In the presence of a full agonist, the partial agonist had agonistic effects at low effect levels and antagonistic effects at high levels, as predicted by pharmacological theory. The generalized concentration addition model fits the empirical mixtures data-full/full agonist, full/partial agonist, and full agonist/antagonist-as well or better than relative potency factors or effect summation. The ability of generalized concentration addition to predict the activity of mixtures of different types of androgen receptor ligands is important as a number of environmental compounds act as partial androgen receptor agonists or antagonists.
Topics: Androgens; Binding Sites; Ligands; Receptors, Androgen
PubMed: 32726424
DOI: 10.1093/toxsci/kfaa108