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GPR40 (FFAR1 or FFA1) is a G protein-coupled receptor, primarily expressed in pancreatic islet β-cells and intestinal enteroendocrine cells. When activated by fatty acids, GPR40 elicits increased insulin secretion from islet β-cells only in the presence of elevated glucose levels. Towards this end, studies were undertaken towards discovering a novel GPR40 Agonist whose mode of action is via Positive Allosteric Modulation of the GPR40 receptor (AgoPAM). Efforts were made to identify a suitable GPR40 AgoPAM tool molecule to investigate mechanism of action and de-risk liver toxicity of GPR40 AgoPAMs due to reactive acyl-glucuronide (AG) metabolites.

G protein-coupled receptor 40 (GPR40) partial agonists lower glucose through the potentiation of glucose-stimulated insulin secretion, which is believed to provide significant glucose lowering without the weight gain or hypoglycemic risk associated with exogenous insulin or glucose-independent insulin secretagogues. The class of small-molecule GPR40 modulators, known as AgoPAMs (agonist also capable of acting as positive allosteric modulators), differentiate from partial agonists, binding to a distinct site and functioning as full agonists to stimulate the secretion of both insulin and glucagon-like peptide-1 (GLP-1). Here we show that GPR40 AgoPAMs significantly increase active GLP-1 levels and reduce acute and chronic food intake and body weight in diet-induced obese (DIO) mice. These effects of AgoPAM treatment on food intake are novel and required both GPR40 and GLP-1 receptor signaling pathways, as demonstrated in GPR40 and GLP-1 receptor-null mice. Furthermore, weight loss associated with GPR40 AgoPAMs was accompanied by a significant reduction in gastric motility in these DIO mice. Chronic treatment with a GPR40 AgoPAM, in combination with a dipeptidyl peptidase IV inhibitor, synergistically decreased food intake and body weight in the mouse. The effect of GPR40 AgoPAMs on GLP-1 secretion was recapitulated in lean, healthy rhesus macaque demonstrating that the putative mechanism mediating weight loss translates to higher species. Together, our data indicate effects of AgoPAMs that go beyond glucose lowering previously observed with GPR40 partial agonist treatment with additional potential for weight loss.

GPR40 is a G-protein-coupled receptor expressed primarily in pancreatic islets and intestinal L-cells that has been a target of significant recent therapeutic interest for type II diabetes. Activation of GPR40 by partial agonists elicits insulin secretion only in the presence of elevated blood glucose levels, minimizing the risk of hypoglycemia. GPR40 agoPAMs have shown superior efficacy to partial agonists as assessed in a glucose tolerability test (GTT). Herein, we report the discovery and optimization of a series of potent, selective GPR40 agoPAMs. Compound 24 demonstrated sustained glucose lowering in a chronic study of Goto Kakizaki rats, showing no signs of tachyphylaxis for this mechanism.

Structure-guided optimization of a series of C-5 alkyl substituents led to the discovery of a potent nicotinic acid receptor agonist SCH 900271 (33) with an EC50 of 2 nM in the hu-GPR109a assay. Compound 33 demonstrated good oral bioavailability in all species. Compound 33 exhibited dose-dependent inhibition of plasma free fatty acid (FFA) with 50% FFA reduction at 1.0 mg/kg in fasted male beagle dogs. Compound 33 had no overt signs of flushing at doses up to 10 mg/kg with an improved therapeutic window to flushing as compared to nicotinic acid. Compound 33 was evaluated in human clinical trials.

In this study, we present the identification and characterization of hamster and guinea pig nicotinic acid receptors. The hamster receptor shares approximately 80-90% identity with the nucleotide and amino acid sequences of human, mouse, and rat receptors. The guinea pig receptor shares 76-80% identity with the nucleotide and amino acid sequences of these other species. [(3)H]nicotinic acid binding affinity at guinea pig and hamster receptors is similar to that in human (dissociation constant = 121 nM for guinea pig, 72 nM for hamster, and 74 nM for human), as are potencies of nicotinic acid analogs in competition binding studies. Inhibition of forskolin-stimulated cAMP production by nicotinic acid and related analogs is also similar to the activity in the human receptor. Analysis of mRNA tissue distribution for the hamster and guinea pig nicotinic acid receptors shows expression across a number of tissues, with higher expression in adipose, lung, skeletal muscle, spleen, testis, and ovary.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic cause of familial and sporadic Parkinson's disease (PD). That the most prevalent mutation, G2019S, leads to increased kinase activity has led to a concerted effort to identify LRRK2 kinase inhibitors as a potential disease-modifying therapy for PD. An internal medicinal chemistry effort identified several potent and highly selective compounds with favorable drug-like properties. Here, we characterize the pharmacological properties of cis-2,6-dimethyl-4-(6-(5-(1-methylcyclopropoxy)-1H-indazol-3-yl)pyrimidin-4-yl)morpholine (MLi-2), a structurally novel, highly potent, and selective LRRK2 kinase inhibitor with central nervous system activity. MLi-2 exhibits exceptional potency in a purified LRRK2 kinase assay in vitro (IC50 = 0.76 nM), a cellular assay monitoring dephosphorylation of LRRK2 pSer935 LRRK2 (IC50 = 1.4 nM), and a radioligand competition binding assay (IC50 = 3.4 nM). MLi-2 has greater than 295-fold selectivity for over 300 kinases in addition to a diverse panel of receptors and ion channels. Acute oral and subchronic dosing in MLi-2 mice resulted in dose-dependent central and peripheral target inhibition over a 24-hour period as measured by dephosphorylation of pSer935 LRRK2. Treatment of MitoPark mice with MLi-2 was well tolerated over a 15-week period at brain and plasma exposures >100× the in vivo plasma IC50 for LRRK2 kinase inhibition as measured by pSer935 dephosphorylation. Morphologic changes in the lung, consistent with enlarged type II pneumocytes, were observed in MLi-2-treated MitoPark mice. These data demonstrate the suitability of MLi-2 as a compound to explore LRRK2 biology in cellular and animal models.

The P2X7 channel is a member of the P2X family of ligand-gated ion channels which respond to ATP as the endogenous agonist. Studies suggest that P2X7 has a potentially pivotal role in inflammatory responses largely stemming from its role in mediating the release of IL-1beta in response to ATP. We report the identification of seven variants of human P2X7 which result from alternative splicing. Two of these variants (one lacking the first transmembrane domain, the second lacking the entire cytoplasmic tail) were compared to the full-length channel. Real-time PCR analysis demonstrated that both variants were expressed in various tissues and that the cytoplasmic tail deleted variant is highly expressed. Deletion of the first transmembrane domain resulted in a non-functional channel. Deletion of the cytoplasmic tail did not affect ion movement but severely affected the ability to form a large pore and to induce activation of caspases.

GPR40 agonists are effective antidiabetic agents believed to lower glucose through direct effects on the beta cell to increase glucose stimulated insulin secretion. However, not all GPR40 agonists are the same. Partial agonists lower glucose through direct effects on the pancreas, whereas GPR40 AgoPAMs may incorporate additional therapeutic effects through increases in insulinotrophic incretins secreted by the gut. Here we describe how GPR40 AgoPAMs stimulate both insulin and incretin secretion in vivo over time in diabetic GK rats. We also describe effects of AgoPAMs in vivo to lower glucose and body weight beyond what is seen with partial GPR40 agonists in both the acute and chronic setting. Further comparisons of the glucose lowering profile of AgoPAMs suggest these compounds may possess greater glucose control even in the presence of elevated glucagon secretion, an unexpected feature observed with both acute and chronic treatment with AgoPAMs. Together these studies highlight the complexity of GPR40 pharmacology and the potential additional benefits AgoPAMs may possess above partial agonists for the diabetic patient.

Several small molecule non-peptide antagonists of the NK-1 and NK-2 receptors have been developed. Mutational analysis of the receptor protein sequence has led to the conclusion that the binding site for these non-peptide antagonists lies within the bundle created by transmembrane domains IV-VII of the receptor and differs from the binding sites of peptide agonists and antagonists. The current investigation uses site-directed mutagenesis of the NK-1 and NK-2 receptors to elucidate the amino acids that are important for binding and functional activity of the first potent dual NK-1/NK-2 antagonist MDL103,392. The amino acids found to be important for MDL103,392 binding to the NK-1 receptor are Gln-165, His-197, Leu-203, Ile-204, Phe-264, His-265 and Tyr-272. The amino acids found to be important for MDL103,392 binding to the NK-2 receptor are Gln-166, His-198, Tyr-266 and Tyr-289. While residues in transmembrane (TM) domains IV and V are important in both receptors (Gln-165/166 and His-197/198), residues in TM V and VI are more important for the NK-1 receptor and residues in TM VII play a more important role in the NK-2 receptor. These data are the first report of the analysis of the binding site of a dual tachykinin receptor antagonist and indicate that a single compound (MDL103,392) binds to each receptor in a different manner despite there being a high degree of homology in the transmembrane bundles. In addition, this is the first report in which a model for the binding of a non-peptide antagonist to the NK-2 receptor is proposed.

High affinity receptor for IL-5 (IL-5R), a predominant eosinophil maturation factor, is composed of an IL-5-binding α-chain (IL-5Rα) and a signal-transducing β-chain that is shared by IL-3 and granulocyte-macrophage CSF (GM-CSF) receptors (IL-3R and GM-CSFR). By Northern blot analysis of mRNAs obtained from normal human blood eosinophils, we show in this report that the hematopoietic cytokines IL-5, IL-3, and GM-CSF down-regulate IL-5Rα mRNA while up-regulating α-chain mRNAs for both IL-3R and GM-CSFR as well as the β-chain mRNA. More detailed characterization reveals that the down-regulation of IL-5Rα mRNA is specific to IL-3, IL-5, and GM-CSF; occurs very rapidly (reaching maximum inhibition within 2 h); is cytokine dose dependent; and does not require protein synthesis. Nuclear run-on and mRNA stability experiments demonstrate that cytokine-induced inhibition of IL-5Rα mRNA accumulation occurs at the level of IL-5Rα gene transcription, whereas enhanced accumulation of mRNAs for IL-3Rα and the β-chain results from reduced mRNA degradation. We suggest from these experiments that in human blood eosinophils, IL-5Rα gene transcription and IL-5Rα mRNA metabolism can be regulated by mechanisms that are distinct from those used for IL-3Rα and GM-CSFRα.

When cytochalasin B-treated neutrophils were stimulated with fMet-Leu-Phe (fMLP) in the presence of Ca2+, phospholipase C (PLC) activity, as measured by inositol-1,4,5-trisphosphate (IP3) formation, preceded phospholipase D (PLD)-catalyzed breakdown of choline- containing phosphoglycerides to form choline and dirady 1-sn -glycero-3-phosphate (phosphatidic acid), suggesting a possible link between PLC and PLD. However, in the absence of cytochalasin B or extracellular Ca2+, PLC was fully activated by fMLP with minimal activation of PLD, indicating that PLC activation alone is not sufficient for PLD activation. Full activation of PLD by fMLP required the simultaneous presence of both Ca2+ and cytochalasin B, a condition that caused no further enhancement of PLC. This result suggests that PLD products are not involved in the regulation of PLC activation. Furthermore, under conditions of complete inhibition of PLC by phorbol 12-myristate 13-acetate (PMA), there was no inhibition of PLD, showing that fMLP can activate PLD in the absence of PLC. Treatment of intact neutrophils with pertussis toxin inhibited both PLC and PLD, with PLC inhibition occurring at lower concentrations than PLD inhibition. These differential effects of pertussis toxin and the observed lack of inhibition of fMLP-stimulated PLD by PMA, which is believed to inactivate G-proteins involved in PLC activation, imply that PLC and PLD are linked to fMLP receptors through distinct G-proteins. Taken together, these observations suggests that, in fMLP-stimulated neutrophils, PLC and PLD are activated through independent mechanisms. J. Leukoc. Biol. 53: 630–635; 1993.

Nicotinic acid has been used clinically for decades to control serum lipoproteins. Nicotinic acid lowers very low-density lipoprotein (VLDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, and lipoprotein-a (LPa), and it is also effective in raising high-density lipoprotein (HDL)-cholesterol. However, nicotinic acid has several side effects in clinical use. The most notable is intense cutaneous vasodilation “flushing” on the upper body and face. We discovered a pyranopyrimidinedione series to be nicotinic acid receptor agonists. A potent nicotinic acid receptor agonist from this series {5-(3-cyclopropylpropyl)-2-(difluoromethyl)-3H-pyrano[2,3-d]pyrimidine-4,7-dione}with reduced flushing side effect in dogs was identified.

Young female random-bred Wistar rats were immunized with homologous renal brush border membranes. The immunized animals exhibited all the clinical and immunopathological characteristics of chronic autologous immune complex glomerulonephritis (Heymann nephritis) closely resembling the idiopathic membranous glomerulonephritis in humans. The animals were subsequently mated. Congenital malformations and fetal growth retardation were observed in the offspring of the nephritic mothers; high incidence of embryonic/fetal resorptions was also observed. The types of anomalies were microphthalmia, cataractic lens, abnormal retina, micrognathia, cleft palate, lordosis, fetal edema, variable hemorrhage, omphalocele, syndactaly and cryptochidism. The most frequently observed anomaly was associated with the eye. Immunofluorescent studies indicated that no rat IgG was detected in the extraembryonic membranes, embryo or fetuses. Rat complement C 3 was also absent around the conceptuses. The pathophysiolgic mechanism leading to such deleterious embryonic/fetal effect is not clear.

Mast cells are the central mediating cells of allergic reactions. Binding of allergen specific IgE to high affinity IgE receptor (Fcepsilon RI) and subsequent binding of allergen by the IgE causes receptor cross-linking and activation. In a study examining the differential gene expression in human cord blood-derived mast cells (CBMCs) mediated by activation of Fcepsilon RI both with IgE and IgE followed by cross-linking with alpha-IgE, the chemokine I-309 was found to be upregulated. I-309 is the ligand for the CCR8 receptor and is responsible for chemoattraction of TH2 type T-cells. Interestingly, I-309 RNA and protein levels were elevated not only in response to IgE/alpha-IgE activation but also by IgE alone. In addition, the I-309 levels were augmented by growth of the CBMCs in the presence of the proinflammatory cytokine IL-4. GM-CSF and MIP-1alpha secretion was also induced by IgE. These results suggest that IgE, through the production and release of cytokines such as I-309, GM-CSF and MIP-1alpha could promote an inflammatory reaction in the absence of antigen stimulation of mast cells.

The neuropeptide substance P binds to the G protein-coupled neurokinin-1 (NK-1) receptor and elicits cellular responses thought to be involved in pain, neurogenic inflammation, vasodilatation, and plasma exudation. Several small molecule nonpeptide antagonists of the substance P/NK-1 receptor interaction have been developed. Mutational analysis of the receptor protein sequence has led to the conclusion that the binding site for these nonpeptide antagonists lies within the bundle created by transmembrane domains IV-VII of the receptor. This current investigation employs site directed mutagenesis of the NK-1 receptor to compare the binding site of CP-96,345 with that of a related compound CP-99,994. The data demonstrate that while both compounds appear to bind within the transmembrane domain bundle, the contribution of individual amino acid residues to the binding of each compound differs.

Although four members (A, B, C, and D) of the cAMP-specific phosphodiesterase (PDE4) family have been cloned by different groups, no study comparing the characteristics of purified human PDE4 subtypes has been published. In this study, we have expressed human PDE4 A, B, C, and D in insect (SF9) cells by using the baculovirus expression system, purified the expressed proteins, and compared their characteristics. The recombinant PDE4 subtypes all showed catalytic activity for cAMP with a K(m) of 1-5 microM. V(max) values differed significantly among these subtypes with the following order: C > B > A > D. PDE4 A, B, C, and D showed a very similar Mg2+ dependence profile. PDE4 B and C showed similar pH profiles with the optimal pH being 8.0. The pH profiles of PDE4 A and D were very different from each other and from those of B and C, with the optimal pH being 6.5 and 7.5, respectively. Furthermore, although PDE4 A, B, C, and D were all inhibited by the standard PDE4 inhibitors rolipram, Ro20-1724, and etazolate, the inhibitory potency varied. Thus, by several criteria including kinetics, pH dependency, and inhibitor sensitivity, various PDE4 subtypes differ significantly from one another.

Slices of renal cortices were homogenized in Trisolv (Bioteck Laboratories, Houston,Tex., USA) at an approximate ratio of 1 g tissue/10 ml. RNA was precipitated with isopro-panol and washed twice with 75% ethanol. The electrophoresis of RNA was performed in1% agarose-formaldehyde gel, with 20 lg of RNA sample in each lane. After the electrophor-esis, RNA was transferred to a nylon membrane (maximum strength Nytran; Schleicher &Schuell, Keene, N.H., USA) with vacuum blotting. The membrane was prehybridized for2 h with 4¶standard saline citrate (SSC), 5¶Denhart’s solution, 40% formamide, 2.5% SDS,1¶blocking reagent (Bioteck Laboratories), 5% dextran, 0.05 mg/ml sheared salmon sperm,0.1 mg/ml Poly C, 0.05 mg/ml Torula yeast RNA and 20 m

Primary cultures of visceral yolk-sac (VYS) endodermal cells were used to assess the effects of teratogenic and nonteratogenic antibodies. When assessed by cytotoxicity assay, teratogenic antibodies appeared to be lethal to the cultured cells at high concentrations (1.25-5 mg of antibodies per ml of culture medium). At a nonlethal dosage, the teratogenic antibodies induced morphological changes, including retraction and rounding up of living cells. The cytotoxic effect as well as the effect on cell morphology appeared to be dose-dependent and specific to VYS endodermal cells. The mechanisms of cell killing were not the same as those attributed to complement-mediated cell lysis. The nonteratogenic antibodies did not have any cytotoxic effect nor did they cause any cell morphological alterations. The results of this investigation, when interpreted by correlating the dose-dependent effects of the teratogenic antibodies on cultured endodermal cells with the in vivo teratogenic effect, suggest that teratogenic antibodies when given at a teratogenic dose cause congenital abnormalities without killing the VYS endodermal cells.

Previous work from our laboratory has demonstrated that specific rabbit immunoglobulins G (IgG) against a glycoprotein antigen of rat kidney proximal tubule or a cross-reacting visceral yolk-sac endodermal cell antigen will induce abnormal embry- onic development when they are injected into pregnant rats during the period of organogenesis. It has been proposed that these antibodies may induce embryopa- thy by interfering with functions of the visceral yolk- sac placenta, an important organ providing nutrients to the embryo at this stage of development. In order to gain some insight into the underlying pathogenic mech- anism(s) in which specific teratogenic I& may inter- fere with visceral yolk-sac functions, we examined the uptake of these teratogenic IgG by the visceral yolk-sac endodermal cells at the electron microscopic level. microscopic level. The results demonstrated that teratogenic rabbit IgG specifically localized on the fuzzy coat of the external apical cell membrane of the visceral yolk-sac endoderm at the intermicrovillous region. Within 5 min, the IgG were rapidly internalized via coated pits and micropi- nocytic vesicles. Within 30 min, an increasing propor- tion of gold particles appeared within uncoated vesicles or vacuoles of various sizes; most of the gold particles were in close proximity to the inner membranous lining of the vesicles. Similar findings were observed after 1- or 2-hr incubation. After 24- to 48-hr culture, however, the gold particles appeared to have dissociated from the inner surface of the vesicle membrane. For all the time points studied, gold particles were not observed in close association with the basal or lateral plasmalemma of the endodermal cells or in the connective tissue spaces and blood vessels of the visceral yolk-sac placenta. We interpret the results as follows: 1) the teratogenic rabbit IgGs interacted with their antigen on the apical plasma membrane of the visceral yolk-sac endodermal cells; 2) the teratogenic IgGs (coupled to their antigen) were internalized by endocytosis via coated pits; 3) the IgGs were later either hydrolyzed or dissociated from their antigen in uncoated vesicles or vacuoles; and 4) there was little or no evidence to indicate that the IgGs were transported between or across the endodermal cells to reach the embryo. It is postulated that the responsible antigen may be a receptor which plays an important role in transporting nutrient($ to the embryo. Specific polyclonal terato- genic

It has been well established that heterologous antibodies against certain tissue components may cause congenital abnormalities when injected into pregnant rats during the critical period of organogenesis. A glycoprotein antigen (gp340) of rat renal proximal tubules was isolated (C.C.K. Leung: (J. Exp. Med., 156:372–384, 1982); antibodies against gp340 were teratogenic. Indirect colloidal gold immunocytochemical method was utilized to study the ultrastructural localization of gp340. For comparative studies, both preembedding and postembedding immunostaining procedures were used. The results indicate that gp340 is a resident of coated pits and possibly also of coated vesicles of the rat renal proximal tubules and visceral yolk-sac (VYS) endodermal cells. It appears that gp340 may also be associated with the microvilli and some as-yet-unidentified cytoplasmic structures of the same tissues. However, gp340 is absent on the epithelium of the small intestine. It is hypothesized that the teratogenic antibodies may interact with gp340 on the coated pits and interfere with receptor-mediated endocytosis, causing yolk-sac placenta dysfunction which in turn causes abnormal embryonic development.

Passive Heymann nephritis (PHN) is an animal model of immune-complex-induced renal dis- ease resembling human membranous glomerulonephri- tis. It was induced in rats by injecting rabbit antiserum directed against glycoprotein antigens isolated from rat embryonic visceral yolk-sac microvilli (VYS-MV). The glycoprotein antigens were isolated by extracting the VYS-MV with detergent Nonidet P-40 followed by gel filtration in Sephacryl S-300 and finally by lectin affin- ity chromatography with Ricinus communis agglutinin I. In uitro immunofluorescent localization studies dem- onstrated that the nephritogenic antibodies were local- ized along the apical region of the visceral yolk-sac endodermal cells and the brush border of the proximal tubular cells of the kidney. Rats injected with a single dose of the antiserum manifested proteinuria. Indirect immunofluorescent studies showed that the injected rabbit IgG was localized in uiuo along the capillary walls of the glomerulus in a granular fashion. Electron microscopic examination of the same kidney glomeruli revealed numerous electron-dense deposits along the lamina rara externa of the glomerular basement mem- brane. Fusion of the epithelial foot processes was also present. These findings represent the typical immuno- pathological characteristics of Heymann nephritis. Furthermore, with the aid of Ouchterlony analysis, the antiserum against the isolated VYS antigens exhibited an immunoprecipitin band which was in common with that formed by the antiserum against the homogeneous nephritogenic antigen (gp330) of renal brush border or- igin. Thus, the nephritogenic antigens which have been found to be associated with the brush border of the renal proximal tubules may also be present or cross- reacted in the microvilli of the rat embryonic visceral yolk-sac.