SummaryLigand-directed signal bias offers opportunities for sculpting molecular events, with the promise of better, safer therapeutics. Critical to the exploitation of signal bias is an understanding of the molecular events coupling ligand binding to intracellular signaling. Activation of class B G protein-coupled receptors is driven by interaction of the peptide N terminus with the receptor core. To understand how this drives signaling, we have used advanced analytical methods that enable separation of effects on pathway-specific signaling from those that modify agonist affinity and mapped the functional consequence of receptor modification onto three-dimensional models of a receptor-ligand complex. This yields molecular insights into the initiation of receptor activation and the mechanistic basis for biased agonism. Our data reveal that peptide agonists can engage different elements of the receptor extracellular face to achieve effector coupling and biased signaling providing a foundation for rational design of biased agonists.

BackgroundGalectin-3 is a 32 kDa protein secreted by macrophages involved in processes such as cell activation, chemotaxis and phagocytosis. Galectin-3 has previously been shown to improve the ability of airway macrophages to ingest apoptotic cells (efferocytosis) in chronic obstructive pulmonary disease (COPD) and may be of interest in non-eosinophilic asthma (NEA) which is also characterised by impaired efferocytosis. It was hypothesised that the addition of exogenous galectin-3 to monocyte-derived macrophages (MDMs) derived from donors with NEA would enhance their ability to engulf apoptotic granulocytes.MethodsEligible non-smoking adults with asthma (n = 19), including 7 with NEA and healthy controls (n = 10) underwent a clinical assessment, venepuncture and sputum induction. MDMs were co-cultured with apoptotic granulocytes isolated from healthy donors with or without exogenous recombinant galectin-3 (50 μg/mL) and efferocytosis was assessed by flow cytometry. Galectin-3 expression and localisation in MDMs was visualised by immunofluorescence staining and fluorescence microscopy. Galectin-3, interleukin (IL)-6 and CXCL8 secretion were measured in cell culture supernatants by ELISA and cytometric bead array.ResultsBaseline efferocytosis (mean (±standard deviation)) was lower in participants with asthma (33.2 (±17.7)%) compared with healthy controls (45.3 (±15.9)%; p = 0.081). Efferocytosis did not differ between the participants with eosinophilic asthma (EA) (31.4 (±19.2)%) and NEA (28.7 (±21.5)%; p = 0.748). Addition of galectin-3 significantly improved efferocytosis in asthma, particularly in NEA (37.8 (±18.1)%) compared with baseline (30.4 (±19.7)%; p = 0.012). Efferocytosis was not associated with any of the clinical outcomes but was negatively correlated with sputum macrophage numbers (Spearman r = − 0.671; p = 0.017). Galectin-3 was diffusely distributed in most MDMs but formed punctate structures in 5% of MDMs. MDM galectin-3 secretion was lower in asthma (9.99 (2.67, 15.48) ng/mL) compared with the healthy controls (20.72 (11.28, 27.89) ng/mL; p = 0.044) while IL-6 and CXCL8 levels were similar.ConclusionsGalectin-3 modulates macrophage function in asthma, indicating a potential role for galectin-3 to reverse impaired efferocytosis in NEA.Electronic supplementary materialThe online version of this article (10.1186/s12931-018-0967-9) contains supplementary material, which is available to authorized users.

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The incidence of type 2 diabetes in developed countries is increasing yearly with a significant negative impact on patient quality of life and an enormous burden on the healthcare system. Current biguanide and thiazolidinedione treatments for type 2 diabetes have a number of clinical limitations, the most serious long-term limitation being the eventual need for insulin replacement therapy (Table 1). Since 2007, drugs targeting the glucagon-like peptide-1 (GLP-1) receptor have been marketed for the treatment of type 2 diabetes. These drugs have enjoyed a great deal of success even though our underlying understanding of the mechanisms for their pleiotropic effects remain poorly characterized even while major pharmaceutical companies actively pursue small molecule alternatives. Coupling of the GLP-1 receptor to more than one signalling pathway (pleiotropic signalling) can result in ligand-dependent signalling bias and for a peptide receptor such as the GLP-1 receptor this can be exaggerated with the use of small molecule agonists. Better consideration of receptor signalling pleiotropy will be necessary for future drug development. This is particularly important given the recent failure of taspoglutide, the report of increased risk of pancreatitis associated with GLP-1 mimetics and the observed clinical differences between liraglutide, exenatide and the newly developed long-acting exenatide long acting release, albiglutide and dulaglutide. LINKED ARTICLESThis article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://dx.doi. org/10.1111/bph.2014.171.issue-5 Abbreviations ADP, adenosine diphosphate; ANS, autonomic nervous system; ATP, adenosine triphosphate; Bad, Bcl-2-associated death promoter; cAMP, cyclic adenosine monophosphate; CREB, cAMP response element binding protein; DPPIV, dipeptidyl peptidase IV; EGF-R1, epidermal growth factor receptor; Epac2, exchange protein directly activated by cAMP 2; GCGR, glucagon receptor; GIP, gastric inhibitory polypeptide; GLP-1, glucagon-like peptide-1; GLP-1R, glucagon-like peptide-1 receptor; GLP-2, glucagon-like peptide-2; GPCR, G protein-coupled receptor; GRK, G protein-coupled receptor kinase; GSIS, glucose stimulated insulin secretion; ICV, introcerebroventricular; KATP, ATP sensitive potassium channel (potassium inwardly-rectifying channel, subfamily J); MAPK, mitogen activated protein kinase; NFAT, nuclear factor of activated T-cells; PACAP, pituitary adenylate cyclase activating polypeptide; PDX-1, pancreatic-duodenum homeobox-1; PI3K, phosphoinositide 3-kinase; PKA, protein kinase A; Rab3A, Ras-associated protein 3A; Rap1, Ras-proximate-1; Rim2, regulating synaptic membrane exocytosis 2; SNAP25, synaptosomal-associated protein 25; T2DM, type 2 diabetes mellitus; VDCC, voltage-dependant calcium channel; VIP, vasoactive intestinal peptide The incretin effectThe observation that oral glucose administration results in significantly higher pancreatic insulin secretion compared with intravenous dosing...

Type 2 diabetes is a major global health problem and there is ongoing research for new treatments to manage the disease. The GLP-1R (glucagon-like peptide-1 receptor) controls the physiological response to the incretin peptide, GLP-1, and is currently a major target for the development of therapeutics owing to the broad range of potential beneficial effects in Type 2 diabetes. These include promotion of glucose-dependent insulin secretion, increased insulin biosynthesis, preservation of β-cell mass, improved peripheral insulin sensitivity and promotion of weight loss. Despite this, our understanding of GLP-1R function is still limited, with the desired spectrum of GLP-1R-mediated signalling yet to be determined. We review the current understanding of GLP-1R function, in particular, highlighting recent contributions in the field on allosteric modulation, probe-dependence and ligand-directed signal bias and how these behaviours may influence future drug development.

Piceatannol (PIC) is known to have anticancer activity, which has been attributed to its ability to block the proliferation of cancer cells via suppression of the NF-kB signaling pathway. However, its effect on hypoxia-inducible factor (HIF) is not well known in cancer. In this study, PIC was loaded into bovine serum albumin (BSA) by desolvation method as PIC–BSA nanoparticles (NPs). These PIC–BSA nanoparticles were assessed for in vitro cytotoxicity, migration, invasion, and colony formation studies and levels of p65 and HIF-1α. Our results indicate that PIC–BSA NPs were more effective in downregulating the expression of nuclear p65 and HIF-1α in colon cancer cells as compared to free PIC. We also observed a significant reduction in inflammation induced by chemical colitis in mice by PIC–BSA NPs. Furthermore, a significant reduction in tumor size and number of colon tumors was also observed in the murine model of colitis-associated colorectal cancer, when treated with PIC–BSA NPs as compared to free PIC. The overall results indicate that PIC, when formulated as PIC–BSA NPs, enhances its therapeutic potential. Our work could prompt further research in using natural anticancer agents as nanoparticels with possible human clinical trails. This could lead to the development of a new line of safe and effective therapeutics for cancer patients.

The present study is aimed at improving the solubility of a poorly water-soluble drug, norfloxacin by incorporating solubilizing additives such as ascorbic acid and citric acid into the beta-cyclodextrin complexes. Norfloxacin, being amphoteric in nature, exhibits a higher solubility at pH below 4 and above 8. Addition of substances like ascorbic acid and citric acid in beta-cyclodextrin complexes reduces the pH of the immediate microenvironment of the drug below pH 4. In the present work, beta-cyclodextrin complexes of norfloxacin were prepared along with solubilizing additives such as citric acid and ascorbic acid in various proportion and the dissolution profile was performed in both HCl buffer, pH 1.2 and phosphate buffer, pH 7.4. The results have shown an enhanced dissolution rate in both media. DSC and IR spectral studies performed on the solid complexes have shown that there is no interaction of the drug with the additives and beta-cyclodextrin. Disc diffusion studies have shown larger diameters of zone of inhibition indicating a greater diffusivity of the drug into the agar medium.

The objective of the present investigation was to study the effect of β-cyclodextrin (β-CD) on the in vitro dissolution of aceclofenac (AF) from molecular inclusion complexes. Aceclofenac molecular inclusion complexes in 1:1 and 1:2 M ratio were prepared using a kneading method. The in vitro dissolution of pure drug, physical mixtures, and cyclodextrin inclusion complexes was carried out. Molecular inclusion complexes of AF with β-CD showed a considerable increase in the dissolution rate in comparison with the physical mixture and pure drug in 0.1 N HCl, pH 1.2, and phosphate buffer, pH 7.4. Inclusion complexes with a 1:2 M ratio showed the maximum dissolution rate in comparison to other ratios. Fourier transform infrared spectroscopy and differential scanning calorimetry studies indicated no interaction between AF and β-CD in complexes in solid state. Molecular modeling results indicated the relative energetic stability of the β-CD dimer-AF complex as compared to β-CD monomer-AF. Dissolution enhancement was attributed to the formation of water soluble inclusion complexes with β-CD. The in vitro release from all the formulations was best described by first-order kinetics (R2 = 0.9826 and 0.9938 in 0.1 N HCl and phosphate buffer, respectively) followed by the Higuchi release model (R2 = 0.9542 and 0.9686 in 0.1 N HCl and phosphate buffer, respectively). In conclusion, the dissolution of AF can be enhanced by the use of a hydrophilic carrier like β-CD.