Proglumide Reverses Nonalcoholic Steatohepatitis by Interaction with the Farnesoid X Receptor and Altering the Microbiome.

Nonalcoholic steatohepatitis (NASH) is associated with obesity, metabolic syndrome, and dysbiosis of the gut microbiome. Cholecystokinin (CCK) is released by saturated fats and plays an important role in bile acid secretion. CCK receptors are expressed on cholangiocytes, and CCK-B receptor expression increases in the livers of mice with NASH. The farnesoid X receptor (FXR) is involved in bile acid transport and is a target for novel therapeutics for NASH. The aim of this study was to examine the role of proglumide, a CCK receptor inhibitor, in a murine model of NASH and its interaction at FXR. Mice were fed a choline deficient ethionine (CDE) diet to induce NASH. Some CDE-fed mice received proglumide-treated drinking water. Blood was collected and liver tissues were examined histologically. Proglumide's interaction at FXR was evaluated by computer modeling, a luciferase reporter assay, and tissue FXR expression. Stool microbiome was analyzed by RNA-Sequencing. CDE-fed mice developed NASH and the effect was prevented by proglumide. Computer modeling demonstrated specific binding of proglumide to FXR. Proglumide binding in the reporter assay was consistent with a partial agonist at the FXR with a mean binding affinity of 215 nM. FXR expression was significantly decreased in livers of CDE-fed mice compared to control livers, and proglumide restored FXR expression to normal levels. Proglumide therapy altered the microbiome signature by increasing beneficial and decreasing harmful bacteria. These data highlight the potential novel mechanisms by which proglumide therapy may improve NASH through interaction with the FXR and consequent alteration of the gut microbiome.

Investigation of cholecystokinin receptors in the human lower esophageal sphincter.

AIM: To compare the binding of cholecystokinin (CCK)-8 to CCK receptors in sling and clasp fibers of the human lower esophageal sphincter. METHODS: Esophageal sling and clasp fibers were isolated from eight esophagectomy specimens, resected for squamous cell carcinoma in the upper two thirds of the esophagus, which had been maintained in oxygenated Kreb's solution. Western blot was used to measure CCK-A and CCK-B receptor subtypes in the two muscles. A radioligand binding assay was used to determine the binding parameters of (3)H-CCK-8S to the CCK receptor subtypes. The specificity of binding was determined by the addition of proglumide, which blocks the binding of CCK to both receptor subtypes. RESULTS: There was no significant difference between the sling and clasp fibers of the human lower esophageal sphincter in the amount of CCK-A [integrated optical density (IOD) value: 22.65 ± 0.642 vs 22.328 ± 1.042, P = 0.806] or CCK-B receptor protein (IOD value: 13.20 ± 0.423 vs 12.45 ± 0.294, P = 0.224) as measured by Western blot. The maximum binding of radio-labeled CCK-8S was higher in the sling fibers than in the clasp fibers (595.75 ± 3.231 cpm vs 500.000 ± 10.087 cpm, P < 0.001) and dissociation constant was lower (K(d): 1.437 ± 0.024 nmol/L vs 1.671 ± 0.024 nmol/L, P < 0.001). The IC50 of the receptor specific antagonists were lower for the CCK-A receptors than for the CCK-B (P < 0.01). CONCLUSION: CCK binding modulates the contractile function of the lower esophageal sphincter through differential binding to the CCK-A receptor on the sling and clasp fibers.

Potential of the gastric motility drug lorglumide in prostate cancer imaging.

The use of tissue-specific receptor ligands is a promising approach for cancer diagnostics and therapy. Lorglumide, a highly effective competitive ligand for the cholecystokinine-A receptor (CCKRA) was conjugated to a fluorescent dye and a magnetic resonance imaging (MRI) contrast agent to obtain a bifunctional marker for tissue with high CCKRA expression. An intermediate conjugate containing only lorglumide and a fluorescent dye was also produced. By performing CCKRA mRNA expression analysis on carcinoma cell lines we found that CCKRA is highly expressed in PC3 prostate carcinoma cells compared to U373 glioma and U2OS osteosarcoma cells. Uptake, specificity and detection sensitivity of both lorglumide conjugates was evaluated by confocal laser scanning microscopy, fluorescence activated cell sorting (FACS) and magnetic resonance relaxometry. While the conjugate containing only lorglumide and rhodamine isothiocyanate as fluorescent dye showed clearly higher uptake than the bifunctional conjugate in FACS analysis, both conjugates clearly showed preferential staining of the PC3 prostate carcinoma cells. Magnetic resonance relaxometry experiments with the bifunctional conjugate containing the MRI contrast agent gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid confirmed the higher PC3-affinity of the lorglumide ligand. Confocal laser scanning microscopy images of PC3/U2OS mixed cell cultures incubated with the bifunctional conjugate also clearly showed PC3 preference and cytoplasmic dot-like staining concurring with uptake by receptor binding and subsequent receptor internalization. Considering these results, CCKRA ligands like lorglumide could play a role in the future design of prostate-cancer-specific markers.

Anthranilic acid based CCK1 receptor antagonists and CCK-8 have a common step in their "receptor desmodynamic processes".

The interaction between the 1-47 N-terminus of the CCK(1)-R and the anthranilic acid based antagonists has been investigated by fluorescence spectroscopy. These antagonists interact with W39 of the N-terminal domain of the CCK(1)-R like that of the endogenous ligand CCK-8. This specific interaction was not found in other nonpeptide ligands of the CCK(1)-R. Conformational studies, using NMR and energy minimization procedures, have allowed formulation of a new hypothesis on the CCK(1)-R binding mode of the anthranilic antagonists.

Use of a hepta-Tyr antibiotic modified silica stationary phase for the enantiomeric resolution of D,L-loxiglumide by electrochromatography and nano-liquid chromatography.

Hepta-Tyr antibiotic modified silica stationary phase was used for the chiral resolution of D,L-loxiglumide, a new drug under investigation proposed for the treatment of gastrointestinal diseases. The chiral stationary phase was packed into fused silica capillaries of 75 microm i.d. for a length of only 7 cm and used for both capillary electrochromatography (CEC) and nano-liquid chromatography (nano-LC) running the experiments with the same instrumentation; in order to increase the electroosmotic flow (EOF) the antibiotic stationary phase was mixed with amino-silica particles (3:1, w/w) generating a relatively high reversed EOF. The enantiomeric resolution of loxiglumide by CEC was strongly influenced by several experimental parameters such as applied electric field, mobile phase composition, capillary temperature, etc. Optimum experimental conditions were found applying 15 kV at 20 degrees C and eluting with acetonitrile-sodium phosphate buffer at pH 6 (1:1, v/v). The same capillary was tested for nano-LC experiments. Good chiral separation of loxiglumide was achieved selecting the appropriate mobile phase considering the type and concentration of organic modifier. The nano-LC optimised method was therefore validated and applied to the analysis of a pharmaceutical formulation declared to contain only D-loxiglumide.

Sensitive SPE-HPLC method to determine a novel angiotensin-AT1 antagonist in biological samples.

A high-performance liquid chromatography (HPLC)-method after solid-phase extraction (SPE) has been developed in order to determine a new angiotensin-AT1 antagonist, i.e. CR 3210 (C27H24N8; MW = 460.54), 4-[4-[(2-ethyl-5,7-dimethylimidazo[4,5-b]pyridin-3-yl)methyl]phenyl]-3-(2H-tetrazol-5-yl)quinoline in rat plasma and urine after oral administration to Sprague-Dawley rats. CR 3210 and the internal standard (IS) CR 1505 (loxiglumide), i.e. 4-[(3,4-dichlorobenzoyl)amino]-5-[(3-methoxypropyl)pentylamino]-5-oxopentanoic acid, were isolated from rat urine and plasma by solid-phase extraction. The procedure was optimized regarding the sorbent extraction material, the pH in the conditioning solution, the washing step, the dry time and the type of elution solvent. The separation was performed by reversed-phase high-performance liquid chromatography with ultraviolet detection. The samples were injected onto the analytical column (Tracer Extrasil ODS1) and detected at 238 nm, giving a capacity factor of 1.87 for CR 3210 and 1.10 for the internal standard. The selectivity of the method was satisfactory. The mean recovery of CR 3210 from spiked rat plasma was 68.5 at 75 ng/ml and 80.9 at 3000 ng/ml; the mean recovery of CR 3210 from spiked rat urine was 69.9 at 75 ng/ml and 78.6 at 3000 ng/ml. The lower limit of detection (LOD) was 14 ng/ml in plasma and 22 ng/ml in urine samples. The lower limit of quantification (LOQ) was taken as 30 ng/ml, the lowest calibration standard using 500 microl rat plasma and urine. The procedures were validated according to international standards with a good reproducibility and linear response from 30 to 3000 ng/ml, for either plasma or urine. The sensitivity of the method allowed for its application to pharmacokinetic studies.

Resolution of (RS)-proglumide using lipase from Candida cylindraceae.

Proglumide is used in the treatment of neuropathic pain. It acts by inhibiting peptide cholecystokinin (CCK). Neural injury produces an elevation in plasma CCK. Proglumide has been also shown to augment the analgesic effect of sustained release morphine in neuropathic pain. Currently proglumide is administered as a racemic mixture. In the present study, an attempt is made to separate the racemic mixture of the drug using lipase obtained from Candida cylindracea by stereoselective esterification. Enzymatic stereoselective esterification was carried out in organic solvents. The resolution was studied using a chromatographic column with a chiral support and mass spectrometry. The reaction conditions for stereoselective esterification including amount of substrate, amount of enzyme, alcohol, solvent and temperature were optimised during the present investigation. Butanol and hexanol were found to be suitable for formation of S and R esters, respectively. Hexane was the best solvent for esterification and the optimum temperature was found to be 30 degreesC.

Synthesis, molecular modeling and QSAR studies in chiral 2,3-disubstituted-1,2,3,4-tetrahydro-9H-pyrido(3,4-b)indoles as potential modulators of opioid antinociception.

In view of coexistence of opioid and cholecystokinin (CCK) in the brain areas concerned with pain processing, some semirigid racemic and chiral analogues of a potent CCK receptor antagonist (benzotript) have been synthesized and tested for their modulatory role on opioid antinociception, which may be mediated by CCK-B receptor. Some of these compounds, 3e, 3g, 3h, 4a, 4b and 4h, exhibited antinociceptive potentiation comparable to benzotript and proglumide. In order to identify the essential chemical structural features important for this potentiation, molecular modeling and quantitative structure activity relationship (QSAR) studies have been carried out in the S and R enantiomers of some of these semi-rigid compounds. The 3D-biophore models, common to all molecules of the training set have been derived. These models with superimposition (match value >0.25) depicted three biophoric sites one each for, pi/hydrophobic interactions, hydrogen bonding and ionic interactions among the phenyl/pyrrole ring, indole nitrogen, amidic oxygen, pyridyl nitrogen and lone pair of amidic oxygen. The total hydrophobicity and S absolute stereochemistry are found to positively contribute to potentiation of antinociception induced by morphine and the resulting quantitative pharmacophoric model with good correlation is found to well describe the observed activity.

Recent advances in the chemistry of cholecystokinin receptor ligands (agonists and antagonists).

During the last few years, cholecystokinin (CCK) has emerged as an important hormone. This polypeptide has been located either in peripheral tissues such as the gastro-intestinal tract and the pancreas as well as in the central nervous system. High affinity CCK receptors are divided in two main subtypes: the CCK-A (A for (A for "alimentary") and the CCK-B (B for "brain") receptors. The latters are currently associated with the gastrin receptors. Since CCK is involved in many different biological processes such as gut function, digestive processes, control of feeding behaviour and neurotransmitter release, the therapeutical potential of cholecystokinin receptor ligands seems to be extremely broad and promising. Several families of CCK receptor ligands (peptides, peptidomimetics, peptoids or non-peptides) were prepared during the last twenty years. The main goal of these researches was to improve agonistic or antagonistic potency but also to find selective compounds for a specific CCK receptor subtype. This review presents the recent developments (since 1995) in the chemistry of CCK receptor ligands.