Calcium-sensing receptor activator cinacalcet for treatment of cyclic nucleotide-mediated secretory diarrheas.

Cyclic nucleotide elevation in intestinal epithelial cells is the key pathology causing intestinal fluid loss in secretory diarrheas such as cholera. Current secretory diarrhea treatment is primarily supportive, and oral rehydration solution is the mainstay of cholera treatment. There is an unmet need for safe, simple and effective diarrhea treatments. By promoting cAMP hydrolysis, extracellular calcium-sensing receptor (CaSR) is a regulator of intestinal fluid transport. We studied the antidiarrheal mechanisms of FDA-approved CaSR activator cinacalcet and tested its efficacy in clinically relevant human cell, mouse and intestinal organoid models of secretory diarrhea. By using selective inhibitors, we found that cAMP agonists-induced secretory short-circuit currents (Isc) in human intestinal T84 cells are mediated by collective actions of apical membrane cystic fibrosis transmembrane conductance regulator (CFTR) and Clc-2 Cl- channels, and basolateral membrane K+ channels. 30 µM cinacalcet pretreatment inhibited all 3 components of forskolin and cholera toxin-induced secretory Isc by ∼75%. In mouse jejunal mucosa, cinacalcet inhibited forskolin-induced secretory Isc by ∼60% in wild type mice, with no antisecretory effect in intestinal epithelia-specific Casr knockout mice (Casr-flox; Vil1-cre). In suckling mouse model of cholera induced by oral cholera toxin, single dose (30 mg/kg) oral cinacalcet treatment reduced intestinal fluid accumulation by ∼55% at 20 hours. Lastly, cinacalcet inhibited forskolin-induced secretory Isc by ∼75% in human colonic and ileal organoids. Our findings suggest that CaSR activator cinacalcet has antidiarrheal efficacy in distinct human cell, organoid and mouse models of secretory diarrhea. Considering its excellent clinical safety profile, cinacalcet can be repurposed as a treatment for cyclic nucleotide-mediated secretory diarrheas including cholera.

Evaluation of Various Solvent Extracts of Tetrastigma leucostaphylum (Dennst.) Alston Leaves, a Bangladeshi Traditional Medicine Used for the Treatment of Diarrhea.

Tetrastigma leucostaphylum (TL) is an important ethnic medicine of Bangladesh used to treat diarrhea and dysentery. Hence, current study has been designed to characterize the antidiarrheal (in vivo) and cytotoxic (in vitro) effects of T. leucostaphylum. A crude extract was prepared with methanol (MTL) and further partitioned into n-hexane (NTL), dichloromethane (DTL), and n-butanol (BTL) fractions. Antidiarrheal activity was investigated using castor oil induced diarrhea, enteropooling, and gastrointestinal transit models, while cytotoxicity was evaluated using the brine shrimp lethality bioassay. In antidiarrheal experiments, all doses (100, 200, and 400 mg/kg) of the DTL extract significantly reduced diarrheal stool frequency, volume and weight of intestinal contents, and gastrointestinal motility in mice. Similarly, in the cytotoxicity assay, all extracts exhibited activity, with the DTL extract the most potent (LC50 67.23 µg/mL). GC-MS analysis of the DTL extract identified 10 compounds, which showed good binding affinity toward M3 muscarinic acetylcholine, 5-HT3, Gut inhibitory phosphodiesterase, DNA polymerase III subunit alpha, and UDP-N-acetylglucosamine-1 carboxyvinyltransferase enzyme targets upon molecular docking analysis. Although ADME/T analyses predicted the drug-likeness and likely safety upon consumption of these bioactive compounds, significant toxicity concerns are evident due to the presence of the known phytotoxin, 2,4-di-tert-butylphenol. In summary, T. leucostaphylum showed promising activity, helping to rationalize the ethnomedicinal use and importance of this plant, its safety profile following both acute and chronic exposure warrants further investigation.

Preparation, characterization and in vivo studies of amorphous solid dispersion of berberine with hydrogenated phosphatidylcholine.

Berberine, a pure crystalline quaternary ammonium salt with the basic structure of isoquinoline alkaloid, has multiple pharmacological bioactivities. But the poor bioavailability of berberine limited its wide clinical applications. In the present study, we aimed to develop an amorphous solid dispersion of berberine with hydrogenated phosphatidylcholine (HPC) in order to improve its bioavailability. The physical characterization studies such as differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier transform infrared spectrophotometry (FT-IR) and scanning electron microscopy (SEM) were conducted to characterize the formation of amorphous berberine HPC solid dispersion (BHPC-SD). The everted intestinal sac and single-pass intestinal perfusion study proved that permeability and intestinal absorption of amorphous BHPC-SD was improved compared with that of pure crystalline berberine, and the pharmacokinetic study results demonstrated that the extent of bioavailability was significantly increased as well. However, the dissolution study indicated that the aqueous cumulative dissolution percentages of berberine remained unchanged or even lower by means of preparation into solid dispersion with HPC. Therefore, according to the previous mechanistic studies, the present results supported that it is the enhanced molecularly dissolved concentration (supersaturation) of berberine by transformation from crystalline structure into amorphous solid dispersions that triggers the enhanced permeability, and consequently results in the improved intestinal absorption and bioavailability.

Determination of loperamide in human plasma and saliva by liquid chromatography-tandem mass spectrometry.

A simple and sensitive liquid chromatography-tandem mass spectrometric method for quantification of loperamide in human plasma and saliva was developed and validated, and then successfully applied in pharmacokinetic clinical study to investigate and correlate bioavailability of Imodium(®) 2mg quartet tablet dose in both human plasma and saliva. Loperamide with labeled internal standard was extracted from its biological matrix by methanol as protein direct precipitant in single extraction step. Adequate chromatographic separation for analytes from plasma and saliva matrices was achieved using ACE C18 (50mm×2.1mm, 5µm) column, eluted by water/methanol/formic acid (30:70:0.1%, v/v), delivered isocratically at constant flow rate of 0.75ml/min. The method validation intends to investigate specificity, sensitivity, linearity, precision, accuracy, recovery, matrix effect and stability according to European guideline, and partial validation was applied on saliva, specificity, matrix effect, recovery, sensitivity, within and between day precision and accuracy. The calibration curve was linear through the range of 20-3000pg/ml in both plasma and saliva using a 50µl sample volume. The partial validation sections outcome in saliva was so close to those in plasma. The within- and between-day precisions were all below 8.7% for plasma and below 11.4% for saliva. Accuracies ranged from 94 to 105% for both matrices. In this study, 26 healthy volunteers participated in the clinical study, and 6 of gave their saliva samples in addition to plasma at the same time schedule. The pharmacokinetic parameters of Cmax, AUC0-t and AUC0-∞, Tmax and T1/2 in both plasma and saliva were calculated and correlated.

Chrysin abrogates cisplatin-induced oxidative stress, p53 expression, goblet cell disintegration and apoptotic responses in the jejunum of Wistar rats.

Cisplatin (cis-diamminedichloroplatinum (II) (CDDP)) is a commonly used chemotherapeutic drug for the treatment of numerous forms of cancer, but it has pronounced adverse effects, namely nephrotoxicity, ototoxicity, neurotoxicity, hepatotoxicity, diarrhoea and nausea. CDDP-induced emesis and diarrhoea are also marked toxicities that may be due to intestinal injury. Chrysin (5,7-dihydroxyflavone), a natural flavone commonly found in many plants, possesses multiple biological activities, such as antioxidant and anti-inflammatory properties. In the present study, we investigated the protective effect of chrysin against CDDP-induced jejunal toxicity. The plausible mechanism of CDDP-induced jejunal toxicity includes oxidative stress, p53 and apoptosis via up-regulating the expression of caspase-6 and -3. Chrysin was administered to Wistar rats orally in maize oil. A single intraperitoneal injection of CDDP was given and the animals were killed after 24 h of CDDP injection. Chrysin ameliorated CDDP-induced lipid peroxidation, increase in xanthine oxidase activity, glutathione depletion, decrease in antioxidant (catalase, glutathione reductase, glutathione peroxidase and glucose-6-phosphate dehydrogenase) and phase-II detoxifying (glutathione-S-transferase and quinone reductase) enzyme activities. Chrysin attenuated CDDP-induced goblet cell disintegration, enhanced expression of p53 and apoptotic tissue damage. Histological findings further substantiated the protective effects of chrysin against CDDP-induced damage in the jejunum. The results of the present study demonstrate that oxidative stress and apoptosis are closely associated with CDDP-induced toxicity and chrysin shows the protective efficacy against CDDP-induced jejunum toxicity possibly via attenuating the oxidative stress and apoptotic tissue damage.

Determination of loperamide in mdr1a/1b knock-out mouse brain tissue using matrix-assisted laser desorption/ionization mass spectrometry and comparison with quantitative electrospray-triple quadrupole mass spectrometry analysis.

Recently matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) imaging has been used to analyze small molecule pharmaceutical compounds directly on tissue sections to determine spatial distribution within target tissue and organs. The data presented to date usually indicate relative amounts of drug within the tissue. The determination of absolute amounts is still done using tissue homogenization followed by traditional liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this study, the quantitative determination of loperamide, an antidiarrheal agent and a P-glycoprotein substrate, in mdr1a/1b (-/-) mouse brain tissue sections using MALDI MS on a quadrupole time-of-flight mass spectrometry is described. 5 mg/mL α-cyano-4-hydroxycinnamic acid in 50% acetonitrile with 0.1% trifluoroacetic acid and 0.5 µM reserpine was used as the MALDI matrix. The calibration curve constructed by the peak intensities of standard samples from MALDI MS was linear from 0.025 to 0.5 µM with r² = 0.9989. The accuracy of calibration curve standards was 78.3-105.9% and the percent deviation was less than 25%. Comparison between direct MALDI tissue analysis and conventional tissue analysis using homogenization followed by electrospray LC-MS/MS was also explored.

Synthesis and biological evaluation of novel peripherally active morphiceptin analogs.

Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)), a tetrapeptide present in the enzymatic digest of bovine beta-casein, is a selective ligand of the mu-opioid receptor. In the present study, we describe the synthesis of a series of novel morphiceptin analogs modified in positions 1-3. Two of the obtained analogs, [Dmt(1), D-Ala(2), D-1-Nal(3)]morphiceptin and [Dmt(1), D-NMeAla(2), D-1-Nal(3)]morphiceptin (Dmt-2',6'-dimethyltyrosine and d-1-Nal-3-(1-naphthyl)-D-alanine)) displayed very high mu-receptor affinity, resistance to enzymatic degradation, and remarkable supraspinally mediated analgesia, as shown in the hot-plate test after intracerebroventricular but not intravenous administration, which indicated that they could not cross the blood-brain barrier. Therefore, these two analogs were further tested in vitro and in vivo towards their possible peripheral analgesic activity and inhibitory effect on gastrointestinal (GI) motility. We report that both peptides showed strong antinociceptive effect in the writhing test after intraperitoneal administration, inhibited smooth muscle contractility in vitro and GI motility in vivo. Taken together, these findings indicate that the novel morphiceptin analogs which induce peripheral, but not central antinociception, inhibit GI transit, and possess exceptional metabolic stability, may provide an interesting approach to the development of peripherally restricted agents for the treatment of GI motility disorders, such as diarrhea or diarrhea-predominant irritable bowel syndrome.

Geochemical and mineralogical characteristics of elephant geophagic soils in Udawalawe National Park, Sri Lanka.

Geophagy or deliberate ingestion of soils was observed among Asian elephants (Elephas maximus) in the Udawalwe National Park, Sri Lanka, for several years. The geochemical and mineralogical composition of the clayey soil layers which are purposefully selected and eaten by elephants in the park were studied, in order to identify the possible reasons for elephant geophagy. The concentrations of major and trace elements were determined by means of X-ray fluorescence spectrometry in 21 soil samples from eight geophagic sites and six soil samples collected from four non-geophagic sites. The mineralogical composition of selected soil samples was investigated using X-ray diffractometry (XRD). These geochemical analyses revealed that geophagic soils in the study areas are deeply weathered and that most of the elements are leached from the soil layers under extreme weathering conditions. The XRD data showed that the soils of the area consisted mainly quartz, feldspar, and the clay minerals kaolinite, Fe-rich illite, and smectite. Although no significant geochemical differences were identified between geophagic and non-geophagic soils, a clear difference was observed in their clay mineralogical content. Soils eaten by elephants are richer in kaolinite and illite than non-geophagic soils, which contain a higher amount of smectite. It is suggested that elephants in Udawalawe National Park ingest soils mainly not to supplement the mineral contents of their forage but to detoxify unpalatable compounds in their diet.

Effect of pectin charge density on formation of multilayer films with chitosan.

The effect of pectin charge density on the formation of multilayer films with chitosan (PEC/CHI) is studied by means of electro-optics. Pectins of low (21%) and high (71%) degrees of esterification, which are inversely proportional to the pectin charge density, are used to form films on colloidal beta-FeOOH particles at pH 4.0 when the CHI is fully ionized. We find that, after deposition of the first 3-4 layers, the film thickness increases linearly with the number of adsorbed layers. However, the increase in the film thickness is larger when the film is terminated with CHI. Irregular increase of the film thickness is more marked for the PEC with higher density of charge. Oscillation in the electrical polarizability of the film-coated particles with the number of deposited layers is also registered in the PEC/CHI films. The charge balance of the multilayers, calculated from electrical polarizability of the film-coated particles, is positive, with larger excess of positive charge within the film constructed from CHI and less charged PEC. This is attributed to the ability of CHI to diffuse into the film at each deposition step. Despite the CHI diffusion, the film thickness increases linearly due to the dissolution of unstable PEC/CHI complexes from the film surface.

Adsorption of irinotecan onto oral adsorbent AST-120 (Kremezin) for preventing delayed diarrhea.

PURPOSE: One of the significant dose-limiting toxicities of irinotecan hydrochloride (CPT-11) is severe diarrhea due to impairment of the intestinal membrane induced by the excreted CPT-11 and its metabolites. AST-120 (Kremezin) is a prominent oral adsorbent that consists of porous spherical carbonic particles. To evaluate whether Kremezin can prevent the diarrhea induced by CPT-11, we investigated the adsorption characteristics of CPT-11 and its metabolites onto Kremezin in vitro and in vivo. METHODS: For in vitro studies, Kremezin was added to each solution containing one of the camptothecin drugs (CPT-11, SN-38, and SN-38-glucuronide), and adsorption activities were determined under various conditions. For in vivo studies, CPT-11 was consecutively administered, and the occurrence of diarrhea was compared between Kremezin-treated and non-treated rats. RESULTS: Kremezin drastically adsorbed the camptothecin drugs in vitro, and the adsorption percentages of the camptothecin drugs for 60 min were more than 85%. In addition, the frequency of diarrhea in Kremezin-treated rats decreased by approximately half of that in the non-treated rats. CONCLUSION: Kremezin showed potent adsorption capacities for the camptothecin drugs and mitigated the symptoms of diarrhea in rats. These results suggest that Kremezin is useful to prevent the diarrhea in clinical CPT-11 chemotherapy.

Identification of an N-methyl-4-phenylpyridinium-like metabolite of the antidiarrheal agent loperamide in human liver microsomes: underlying reason(s) for the lack of neurotoxicity despite the bioactivation event.

In contrast with the Parkinson's-like effects associated with the mitochondrial neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and the neuroleptic agent haloperidol, there exist no reports on adverse central nervous system (CNS) effects with the structurally related N-substituted-4-arylpiperidin-4-ol derivative and antidiarrheal agent loperamide. Although this difference can be attributed to loperamide's P-glycoprotein substrate properties that prevent it from accessing the brain, an alternative possibility is that loperamide metabolism in humans is different from that of MPTP and haloperidol and does not involve bioactivation to a neurotoxic pyridinium species. In the current study, loperamide bioactivation was examined with particular focus on identification of pyridinium metabolites. A NADPH-dependent disappearance of loperamide was observed in both rat and human liver microsomes (human t(1/2) = 13 min; rat t(1/2) = 22 min). Loperamide metabolism was similar in human and rat and involved N-dealkylation to N-desmethylloperamide (M3) as the principal metabolic fate. Other routes of loperamide biotransformation included N- and C-hydroxylation to the loperamide-N-oxide (M4) and carbinolamide (M2) metabolites, respectively. Furthermore, the formation of an additional metabolite (M5) was also discernible in human and rat liver microsomes. The structure of M5 was assigned to the pyridinium species (LPP(+)) based on comparison of the liquid chromatography/tandem mass spectrometry characteristics to the pyridinium obtained from loperamide via a chemical reaction. Loperamide metabolism in human microsomes was sensitive to ketoconazole and bupropion treatment, suggesting P4503A4 and -2B6 involvement. Recombinant P4503A4 catalyzed all of the loperamide biotransformation pathways in human liver microsomes, whereas P4502B6 was only responsible for N-dealkylation and N-oxidation routes. The wide safety margin of loperamide (compared with MPTP and haloperidol) despite metabolism to a potentially neurotoxic pyridinium species likely stems from a combination of factors that include a therapeutic regimen normally restricted to a few days and the fact that loperamide and perhaps LPP(+) are P-glycoprotein substrates and are denied entry into the CNS. The differences in safety profile of haloperidol and loperamide despite a common bioactivation event supports the notion that not all compounds undergoing bioactivation in vitro will necessarily elicit a toxicological response in vivo.

Antisecretory factor expression is regulated by inflammatory mediators and influences the severity of experimental autoimmune encephalomyelitis.

Antisecretory factor (ASF) was originally identified as a potent inhibitor of intestinal fluid secretion induced by a number of enterotoxins. In addition to its involvement in intestinal fluid secretion, ASF modulates the proliferation of memory/effector T cells and is expressed by cells of the immune system. This report describes the role of ASF in modulating immune responses and assesses the regulation of ASF during an in vivo immunological reaction. ASF expression was redistributed during adoptively transferred experimental autoimmune encephalomyelitis (EAE), and in response to other inflammatory stimuli. Administration of the anti-ASF antibody TLD-1A8A increased the clinical severity and duration of the disease. Consistent with these findings, addition of TLD-1A8A to T cell proliferation assays resulted in up-regulation of the proinflammatory cytokines IL-18 and IL-6 and in down-regulation of IL-10. Furthermore, we identified cytokines that regulated the expression of ASF at both the mRNA and protein level. ASF, therefore, appears to play a previously unappreciated and potentially important role in the regulation of immune responses.

pH dependent uptake of loperamide across the gastrointestinal tract: an in vitro study.

UNLABELLED: Loperamide is a peripherally acting antidiarrheal opioid with some affinity for P-glycoprotein (P-gp). One of the main reasons for its lack of central nervous system (CNS) activity is a combination first-pass metabolism and P-gp-mediated efflux preventing brain penetration. It was assumed that P-gp would also have a similar effect at the intestinal tract, limiting loperamide systemic absorption. However, previous in vitro studies had not determined loperamide flux using pH gradients present in the intestinal tract. Hence, our aim was to determine the influence of pH gradient conditions on the gastrointestinal uptake of loperamide, including any changes to its P-gp-mediated efflux. METHODS: Cellular uptake and transcellular transport were determined after exposure to various concentrations of loperamide (2-50 microM) with and without the presence of active efflux protein inhibitors. Loperamide was detected at 214 nm using high-performance liquid chromatography (HPLC) protocols. RESULTS: Bidirectional transport studies of 10 microM loperamide with a pH 6.0/7.4 apical (Ap)-to-basolateral (Bas) gradient showed efflux to be 17-fold higher than influx (10 ng/cm2/min Bas-->Ap compared to 0.6 for Ap-->Bas). This differential was much greater than when examined at pH 7.4/7.4 (only two-fold higher). The potent P-gp inhibitor, PSC-833, had only a moderate effect at blocking loperamide efflux under pH gradient conditions, yet could equilibrate bidirectional transport at pH 7.4. This suggested the presence of significant P-gp independent mechanisms, preventing loperamide access to the basolateral chamber. Amiloride and 5-(N-ethyl-N-isopropyl) amiloride had some effect on reducing efflux, hence the Na(+)--H(+) antiporter may have some involvement. Accumulation of loperamide into Caco-2 cells reduced almost 70% at pH 6.0 compared to pH 7.4, yet P-gp was always able to approximately double the equilibrium concentration in the cells within a defined pH study. This showed that P-gp was not affected by pH conditions. CONCLUSIONS: P-gp-mediated efflux of loperamide is supplemented under pH gradient conditions. Hence, drugs used to decrease acid secretion in the stomach could result in higher plasma loperamide levels based on our in vitro system reflecting the in vivo environment. The addition of a P-gp inhibitor could potentially further increase the gastrointestinal absorption of loperamide.

Interaction of morphine, fentanyl, sufentanil, alfentanil, and loperamide with the efflux drug transporter P-glycoprotein.

BACKGROUND: The efflux transporter P-glycoprotein, a member of the adenosine triphosphate-binding cassette superfamily, is a major determinant of the pharmacokinetics and pharmacodynamics of the opioid loperamide, a well-recognized antidiarrheal agent. Animal studies indicate that P-glycoprotein limits morphine entry into the brain. In this study, the authors examined whether other opioids of importance to anesthesiologists such as fentanyl, sufentanil, and alfentanil, and also morphine-6-glucuronide and morphine-3-glucuronide, are P-glycoprotein substrates and whether, in turn, these opioids act also as P-glycoprotein inhibitors. METHODS: The transcellular movement of the various opioids, including loperamide and morphine, was assessed in L-MDR1 (expressing P-glycoprotein) and LLC-PK1 cell monolayers (P-glycoprotein expression absent). A preferential basal-to-apical versus apical-to-basal transport in the L-MDR cells but not the LLC-PK1 cells is seen for P-glycoprotein substrates. In addition, the effect of the various opioids on the transcellular movement of the prototypical P-glycoprotein substrate digoxin was examined in Caco-2 cell monolayers. IC50 values were calculated according to the Hill equation. RESULTS: Loperamide was a substrate showing high dependence on P-glycoprotein in that basal-apical transport was nearly 10-fold greater than in the apical-basal direction in L-MDRI cells. Morphine also showed a basal-to-apical gradient in the L-MDR1 cell monolayer, indicating that it too is a P-glycoprotein substrate, but with less dependence than loperamide in that only 1.5-fold greater basal-apical directional transport was observed. Fentanyl, sufentanil, and alfentanil did not behave as P-glycoprotein substrates, whereas the morphine glucuronides did not cross the cell monolayers at all, whether P-glycoprotein was present or not. Loperamide, sufentanil, fentanyl, and alfentanil inhibited P-glycoprotein-mediated digoxin transport in Caco-2 cells with IC50 values of 2.5, 4.5, 6.5, and 112 microm, respectively. Morphine and its glucuronides (20 microm) did not inhibit digoxin (5 microm) transport in Caco-2 cells, and therefore IC50 values were not determined. CONCLUSIONS: Opioids have a wide spectrum of P-glycoprotein activity, acting as both substrates and inhibitors, which might contribute to their varying central nervous system-related effects.

Identification of three sulfate-conjugated metabolites of berberine chloride in healthy volunteers' urine after oral administration.

AIM: To identify the structure of unknown metabolites of berberine (Ber) in human urine after oral administration. METHODS: Urine samples were obtained from 5 volunteers after they orally took Ber chloride 0.9 g per day for three days. Metabolites in urine samples were isolated and purified by polyporous resin column chromatography. The individual metabolites were identified mainly using electrospray ionization mass spectroscopy (ESI-MS) and proton nuclear magnetic resonance (1H NMR) spectroscopy. RESULTS: Three unknown metabolites (M1, M2, and M3) were isolated. They were susceptible to arylsufatase. ESI-MS measurements of M1, M2, and M3 produced quasimolecular ions [M+H]+, m/z 17.9, 404.0, and 402.0 respectively. Especially, each of them produced a characteristic protonated ion [M-80+H]+, which can be ascribed as quasimolecular ions lost a SO3 fragment. 1H NMR spectra of the metabolites were also obtained and each of 1H signals was assigned. CONCLUSION: Structures of M1, M2, and M3 were firmly identified as jatrorrhizine-3-sulfate, demethyleneberberine-2-sulfate, and thalifendine-10-sulfate, and the major metabolite was M2.

The antisecretory factor: synthesis, anatomical and cellular distribution, and biological action in experimental and clinical studies.

The antisecretory factor (AF) is a 41-kDa protein that provides protection against diarrheal diseases and intestinal inflammation. Its cDNA has been cloned and sequenced. AF is highly potent, with 10(-12) mol of recombinant AF being sufficient to counteract experimentally induced diarrhea in rat. The antisecretory activity is exerted by a peptide located between positions 35 and 50 of the AF sequence. Synthetic peptides based on this sequence are promising candidates for drugs to counteract intestinal hypersecretion, as well as imbalances of fluid transport in other body compartments. AF probably exerts its effects via nerves; AF immediately and potently inhibits ion transport across isolated nerve membranes from Deiters' cells. Immunocytochemistry has shown that AF is present in most tissues in the body, and in situ nucleic acid hybridization has shown that cells that store AF are also capable of AF synthesis. The endogenous plasma level of AF is increased by enterotoxins and by certain food constituents such as hydrothermally processed cereals. These cereals significantly improve clinical performance in patients suffering from inflammatory bowel diseases. AF-enhancing food also protects domestic animals against diarrheal diseases, and such feed has been used successfully in Swedish swine farming for the past 10 years. Increased understanding of AF action might result in expanded clinical applications and confirm that AF is an important regulator of homeostasis.

Increased drug delivery to the brain by P-glycoprotein inhibition.

BACKGROUND: Although the antidiarrheal loperamide is a potent opiate, it does not produce opioid central nervous system effects at usual doses in patients. On the basis of in vitro studies demonstrating that loperamide is a substrate for the adenosine triphosphate-dependent efflux membrane transporter P-glycoprotein, we postulated that inhibition of P-glycoprotein with quinidine would increase entry of loperamide into the central nervous system with resultant respiratory depression. METHODS: To test this hypothesis, a 16-mg dose of loperamide was administered to eight healthy male volunteers in the presence of either 600 mg quinidine, a known inhibitor of P-glycoprotein, or placebo. Central nervous system effects were measured by evaluation of the respiratory response to carbon dioxide rebreathing as a measure of opiate-induced respiratory depression. RESULTS: Loperamide produced no respiratory depression when administered alone, but respiratory depression occurred when loperamide (16 mg) was given with quinidine at a dose of 600 mg (P < .001). These changes were not explained by increased plasma loperamide concentrations. CONCLUSION: This study therefore demonstrates first the potential for important drug interactions to occur by a new mechanism, namely, inhibition of P-glycoprotein, and second that the lack of respiratory depression produced by loperamide, which allows it to be safely used therapeutically, can be reversed by a drug causing P-glycoprotein inhibition, resulting in serious toxic and abuse potential.

Food induced stimulation of the antisecretory factor can improve symptoms in human inflammatory bowel disease: a study of a concept.

BACKGROUND: Antisecretory factor (AF), a 41 kDa cloned and sequenced protein, suppresses intestinal inflammation and hypersecretion in animals. Endogenous AF production can be induced by dietary modifications in several animal species, and this feed has been shown to reduce the incidence of diarrhoeal disease in weaning piglets. The role of AF in intestinal disease in humans is not known. AIMS: To study the effects of hydrothermally processed cereals, optimised for AF induction in animals, added to the diet of patients with longstanding symptoms of inflammatory bowel disease (IBD). PATIENTS: Fifty three patients with IBD (ulcerative colitis and Crohn's disease) were entered into the study, and 50 completed follow up. The experimental group consisted of 16 females (mean age 50 (SEM 5) years) and 10 males (41 (4) years) and the placebo group of 12 women (41 (4) years old) and 12 men (51 (5) years). METHODS: Patients were randomised to receive either hydrothermally processed cereals (active treatment) or the same amount of ordinary cereals (placebo treatment) for four weeks in a double blind study design. Baseline diet and medications remained unchanged. Bowel symptoms, plasma levels of AF, and colonic biopsies were evaluated before and after treatment. RESULTS: The active treatment significantly improved subjective ratings of clinical symptoms and increased plasma AF levels compared with placebo. Plasma lipid levels were unaffected. CONCLUSION: Hydrothermally processed cereals can induce AF production in human IBD. This increase in endogenous AF activity is associated with clinical improvement. Further studies are warranted to clarify the exact role of AF in human intestinal disease.