Repurposing of Loperamide as a New Drug With Anticancer Activity for Human Osteosarcoma

BACKGROUND/AIM

Osteosarcoma is an aggressive malignant bone tumor, with unfavorable outcomes in patients with metastatic and recurrent disease. To improve patient survival new treatment options are needed. By using the drug repurposing approach, which takes advantage of already approved drugs with non-oncology primary use, we investigated the activity of loperamide, a peripheral opiate receptor agonist, a drug widely used in clinical practice to treat acute non-specific and chronic diarrhea, on human osteosarcoma.

MATERIALS AND METHODS

Human osteosarcoma cell lines (143B, Saos-2, HOS and MG-63) and multidrug-resistant MG-63DXR30 cells were treated with loperamide. Proliferation and cell viability were determined by viable cell count and acid phosphatase assay. Loperamide activity on cell cycle and apoptosis induction were evaluated by flow cytometry and a luminescence assay testing caspase 3/7 activity, respectively.

RESULTS

Loperamide significantly inhibited cell proliferation, through alteration of cell cycle profile at G0/G1 phase and apoptotic death in human osteosarcoma cells. Furthermore, loperamide significantly inhibited the growth of multidrug-resistant osteosarcoma cells.

CONCLUSION

Our findings provide new perspectives for loperamide and its therapeutic repositioning for the treatment of osteosarcoma.

Croton tiglium L. seeds ameliorate loperamide-induced constipation via regulating gastrointestinal hormones and gut microbiota before and after processing

ETHNOPHARMACOLOGICAL RELEVANCE

Crotonis Fructus (CF), the seeds of Croton tiglium L., have been commonly used in the treatment of constipation for more than two thousand years in traditional Chinese medicine (TCM). CF needs to be processed before clinical use and Crotonis Semen Pulveratum (CP) is the processed cream of CF, which could reduce the drastic purgative action and gastrointestinal damages. However, the mechanism of CF and CP in the treatment of constipation is still unclear.

AIM OF THE STUDY

This study was to evaluate the effects of CF and CP on loperamide-induced constipation and the underlying mechanism.

MATERIALS AND METHODS

The chemical compositions of CF and CP were analyzed by UPLC-Q-TOF-MS. Constipated mouse model was established by loperamide (9.6 mg/kg, b.w., i.g.) for two weeks. After successful modeling, the mice were treated with CF or CP (45.5 and 136.5 mg/kg, b.w., i.g.) once a day for seven days. The physiological status, defecation indices, defecation time, and intestinal propulsion rate in mice were measured. Histopathologic examination and serum biochemical parameters were further estimated. 16S rDNA gene sequencing was carried out to characterize the effects of CF and CP on intestinal microbiome structure. Spearman correlation analysis was also performed to explore the association between gut microbiotic abundance and serum indices.

RESULTS

The results verified the therapeutic effects of CF and CP on loperamide-induced constipation. CF and CP could significantly ameliorate the reduction of fecal number, fecal weight, fecal water content, and intestinal propulsion rate in mice with constipation, and the first stool defecation time was also obviously reduced. Moreover, CF and CP could regulate the secretion of gastrointestinal hormones and inflammatory factors induced by constipation. Histopathologic examination showed that CP was superior to CF in relieving pathological injury and inflammatory cell infiltration. According to 16S rDNA sequencing, CF and CP treatment could improve gut microbiota disturbance in mice with constipation and the abundance of opportunistic pathogens such as Parabacteroides, Parasutterella and Bacillus remarkably declined, while the levels of beneficial bacterial such as Candidatus_Arthromitus significantly increased. Besides, CP may play a better role in correcting the intestinal flora disorder than CF, which was more obvious in the high-dose group. In addition, phytochemical analysis revealed the presence of diterpenoids and alkaloids in CF and CP.

CONCLUSIONS

CF and CP could ameliorate loperamide-induced constipation by regulating gastrointestinal hormones secretion, reducing the levels of inflammatory cytokines and improving the disturbance of gut microbiota. Moreover, CP was superior to CF in the enrichment of beneficial bacteria and reduction of harmful bacteria and histopathological damage induced by constipation, which may be related to the changes in the species and content of diterpenoids after processing. The study provides new evidence for the processing mechanism and clinical application of CF and CP.

Loperamide induces protective autophagy and apoptosis through the ROS/JNK signaling pathway in bladder cancer

Bladder cancer is one of the most common carcinomas in the human urinary system worldwide. Loperamide, known as an antidiarrheal drug, exerts anti-tumor activities against various cancers. However, the effect of loperamide on bladder cancer cells remains unclear. Our study aimed to investigate the effect of loperamide on bladder cancer and explore the underlying mechanisms. We found that loperamide suppressed the proliferation of 5637 and T24 cells in a dose-dependent manner. Loperamide treatment showed both pro-apoptotic and pro-autophagic effects on bladder cancer cells. Moreover, it was revealed that loperamide induced reactive oxygen species (ROS) accumulation, leading to the activation of c-Jun N-terminal kinase (JNK) signaling pathway. Notably, ROS scavenger N-acetyl-L-cysteine (NAC) and JNK inhibitor SP600125 effectively attenuated the induction of autophagy and apoptosis triggered by loperamide. Finally, blocking autophagy with CQ could significantly enhance the anti-cancer effect of loperamide both in vitro and in vivo. Overall, these findings demonstrated that loperamide induced autophagy and apoptosis through the ROS-mediated JNK pathway in bladder cancer cells. Our results suggest that the strategy of combining loperamide with autophagy inhibitor CQ may provide a therapeutic option for the treatment of bladder cancer.

Loperamide, a peripheral Mu-Opioid receptor agonist, attenuates chemotherapy-induced neuropathic pain in rats

Opioids are employed in the management of chemotherapy-induced neuropathic pain (CINP) when other pain management approaches have failed and proven ineffective. However, their use in CINP is generally considered as a second-line or adjunctive therapy owing to their central side effects and development of tolerance with their long-term usage. Targeting peripheral sites may offer several advantages over the conventional CNS-based approaches as peripheral targets modulate pain signals at their source, thereby relieving pain with higher specificity, efficacy and minimizing adverse effects associated with off-site CNS actions. Therefore, present study was designed with an aim to investigate the effect of loperamide, a peripherally acting mu-opioid receptor agonist, on paclitaxel-induced neuropathic pain in rats and elucidate its underlying mechanism. Loperamide treatment significantly attenuated mechanical, and cold hypersensitivity and produced significant place preference behaviour in neuropathic rats indicating its potential to treat both evoked and spontaneous pain. More importantly, loperamide treatment in naïve rats did not produce place preference to drug-paired chamber pointing towards its non-addictive analgesic potential. Further, molecular investigations revealed increased expression of ion channels such as TRPA1, TRPM8; voltage-gated sodium channels (VGSCs) and neuroinflammatory markers in the dorsal root ganglion (DRG) and lumbar (L4-L5) spinal cord of neuropathic rats, which was significantly downregulated upon loperamide treatment. These findings collectively suggest that activation of peripheral mu-opioid receptors contributes to the amelioration of both evoked and spontaneous pain in neuropathic rats by downregulating TRP channels and VGSCs along with suppression of oxido-nitrosative stress and neuroinflammatory cascade.

Proteasome inhibition protects blood-brain barrier P-glycoprotein and lowers Aβ brain levels in an Alzheimer's disease model

BACKGROUND

Loss of P-glycoprotein (P-gp) at the blood-brain barrier contributes to amyloid-β (Aβ) brain accumulation in Alzheimer's disease (AD). Using transgenic human amyloid precursor protein (hAPP)-overexpressing mice (Tg2576), we previously showed that Aβ triggers P-gp loss by activating the ubiquitin-proteasome pathway, which leads to P-gp degradation. Furthermore, we showed that inhibiting the ubiquitin-activating enzyme (E1) prevents P-gp loss and lowers Aβ accumulation in the brain of hAPP mice. Based on these data, we hypothesized that repurposing the FDA-approved proteasome inhibitor, bortezomib (Velcade®; BTZ), protects blood-brain barrier P-gp from degradation in hAPP mice in vivo.

METHODS

We treated hAPP mice with the proteasome inhibitor BTZ or a combination of BTZ with the P-gp inhibitor cyclosporin A (CSA) for 2 weeks. Vehicle-treated wild-type (WT) mice were used as a reference for normal P-gp protein expression and transport activity. In addition, we used the opioid receptor agonist loperamide as a P-gp substrate in tail flick assays to indirectly assess P-gp transport activity at the blood-brain barrier in vivo. We also determined P-gp protein expression by Western blotting, measured P-gp transport activity levels in isolated brain capillaries with live cell confocal imaging and assessed Aβ plasma and brain levels with ELISA.

RESULTS

We found that 2-week BTZ treatment of hAPP mice restored P-gp protein expression and transport activity in brain capillaries to levels found in WT mice. We also observed that hAPP mice displayed significant loperamide-induced central antinociception compared to WT mice indicating impaired P-gp transport activity at the blood-brain barrier of hAPP mice in vivo. Furthermore, BTZ treatment prevented loperamide-induced antinociception suggesting BTZ protected P-gp loss in hAPP mice. Further, BTZ-treated hAPP mice had lower Aβ40 and Aβ42 brain levels compared to vehicle-treated hAPP mice.

CONCLUSIONS

Our data indicate that BTZ protects P-gp from proteasomal degradation in hAPP mice, which helps to reduce Aβ brain levels. Our data suggest that the proteasome system could be exploited for a novel therapeutic strategy in AD, particularly since increasing Aβ transport across the blood-brain barrier may prove an effective treatment for patients.

Chinese patent medicine shouhui tongbian capsule attenuated loperamide-induced constipation through modulating the gut microbiota in rat

ETHNOPHARMACOLOGICAL RELEVANCE

Shouhui tongbian capsule (SHTC) is a commercial Chinese patent medicine used in the treatment of constipation. However, its mechanism of action remains unclear.

AIM OF THE STUDY

The present study was undertaken to assess SHTC relieved effects on the clinical symptoms of loperamide (LOP) induced constipation in Sprague Dawley (SD) rat model and to clarify the relationship between the protective effect of SHTC on constipation and the gut microbiota.

MATERIALS AND METHODS

Constipation male SD rats models were induced with solution of LOP (1.5 mg/kg bw), and rats were treated with an oral dose of SHTC (35, 70 mg/kg bw) three times a day after successful modeling. All rats were assessed weekly by change in body weight, gastric emptying rate, fecal moisture content and wet/dry weight. Hematoxylin and eosin (H&E) were used to observe parts of the rats small intestine. The gut microbiota in colonic contents was analyzed using 16SrRNA gene sequencing. Contents of short-chain fatty acids (SCFAs) were analyzed by gas chromatography-mass spectrometer (GCMS).

RESULTS

The results confirmed the therapeutic effects of SHTC on constipation. Specifically, SHTC could alleviate the decrease in body weight, gastric emptying rate and fecal moisture content caused by LOP-induced constipation. The pathological damage of small intestine was significantly improved by H&E staining. Notably, SHTC increased the relative abundances of Lactobacillus and the ratio of Firmicutes to Bacteroides (F/B). In addition, the content of acetic acid and propionic acid was significantly increased in constipated rats fed with SHTC.

CONCLUSION

SHTC could ameliorate the development of LOP-induced constipation in rats by remodeling the structure of gut microbial community and regulating production of intestinal metabolites.

Cucumis sativus extract elicits chloride secretion by stimulation of the intestinal TMEM16A ion channel

CONTEXT

Cucumber (Cucumis sativus Linn. [Cucurbitaceae]) is widely known for its purgative, antidiabetic, antioxidant, and anticancer therapeutic potential. However, its effect on gastrointestinal (GI) disease is unrecognised.

OBJECTIVE

This study investigated the effect of C. sativus fruit extract (CCE) on intestinal chloride secretion, motility, and motor function, and the role of TMEM16A chloride channels.

MATERIALS AND METHODS

CCE extracts were obtained from commercially available cucumber. Active fractions were then purified by HPLC and analysed by high resolution mass spectrometry. The effect of CCE on intestinal chloride secretion was investigated in human colonic T84 cells, ex vivo mouse intestinal tissue using an Ussing chamber, and the two-electrode voltage-clamp technique to record calcium sensitive TMEM16A chloride currents in Xenopus laevis oocytes. In vivo, intestinal motility was investigated using the loperamide-induced C57BL/6 constipation mouse model. Ex vivo contractility of mouse colonic smooth muscles was assessed by isometric force measurements.

RESULTS

CCE increased the short-circuit current (ΔIsc 34.47 ± µA/cm²) and apical membrane chloride conductance (ΔI_Cl 95 ± 8.1 µA/cm²) in intestinal epithelial cells. The effect was dose-dependent, with an EC₅₀ value of 0.06 µg/mL. CCE stimulated the endogenous TMEM16A-induced Cl^- current in Xenopus laevis oocytes. Moreover, CCE increased the contractility of smooth muscle in mouse colonic tissue and enhanced small bowel transit in CCE treated mice compared to loperamide controls. Mass spectrometry suggested a cucurbitacin-like analogue with a mass of 512.07 g/mol underlying the bioactivity of CCE.

CONCLUSION

A cucurbitacin-like analog present in CCE activates TMEM16A channels, which may have therapeutic potential in cystic fibrosis and intestinal hypodynamic disorders.

Autophagy activation, lipotoxicity and lysosomal membrane permeabilization synergize to promote pimozide- and loperamide-induced glioma cell death

Increasing evidence suggests that induction of lethal macroautophagy/autophagy carries potential significance for the treatment of glioblastoma (GBM). In continuation of previous work, we demonstrate that pimozide and loperamide trigger an ATG5- and ATG7 (autophagy related 5 and 7)-dependent type of cell death that is significantly reduced with cathepsin inhibitors and the lipid reactive oxygen species (ROS) scavenger α-tocopherol in MZ-54 GBM cells. Global proteomic analysis after treatment with both drugs also revealed an increase of proteins related to lipid and cholesterol metabolic processes. These changes were accompanied by a massive accumulation of cholesterol and other lipids in the lysosomal compartment, indicative of impaired lipid transport/degradation. In line with these observations, pimozide and loperamide treatment were associated with a pronounced increase of bioactive sphingolipids including ceramides, glucosylceramides and sphingoid bases measured by targeted lipidomic analysis. Furthermore, pimozide and loperamide inhibited the activity of SMPD1/ASM (sphingomyelin phosphodiesterase 1) and promoted induction of lysosomal membrane permeabilization (LMP), as well as release of CTSB (cathepsin B) into the cytosol in MZ-54 wild-type (WT) cells. Whereas LMP and cell death were significantly attenuated in ATG5 and ATG7 knockout (KO) cells, both events were enhanced by depletion of the lysophagy receptor VCP (valosin containing protein), supporting a pro-survival function of lysophagy under these conditions. Collectively, our data suggest that pimozide and loperamide-driven autophagy and lipotoxicity synergize to induce LMP and cell death. The results also support the notion that simultaneous overactivation of autophagy and induction of LMP represents a promising approach for the treatment of GBM.Abbreviations: ACD: autophagic cell death; AKT1: AKT serine/threonine kinase 1; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG14: autophagy related 14; CERS1: ceramide synthase 1; CTSB: cathepsin B; CYBB/NOX2: cytochrome b-245 beta chain; ER: endoplasmatic reticulum; FBS: fetal bovine serum; GBM: glioblastoma; GO: gene ontology; HTR7/5-HT7: 5-hydroxytryptamine receptor 7; KD: knockdown; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LAP: LC3-associated phagocytosis; LMP: lysosomal membrane permeabilization; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; RB1CC1: RB1 inducible coiled-coil 1; ROS: reactive oxygen species; RPS6: ribosomal protein S6; SMPD1/ASM: sphingomyelin phosphodiesterase 1; VCP/p97: valosin containing protein; WT: wild-type.

Loperamide Inhibits Replication of Severe Fever with Thrombocytopenia Syndrome Virus

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease caused by the SFTS virus (SFTSV). SFTS is mainly prevalent in East Asia. It has a mortality rate of up to 30%, and there is no approved treatment against the disease. In this study, we evaluated the effect of loperamide, an antidiarrheal and antihyperalgesic agent, on the propagation of SFTSV in a cell culture system.

METHODS

SFTSV-infected human cell lines were exposed to loperamide, and viral titers were evaluated. To clarify the mode of action of loperamide, several chemical compounds having shared targets with loperamide were used. Calcium imaging was also performed to understand whether loperamide treatment affected calcium influx.

RESULTS

Loperamide inhibited SFTSV propagation in several cell lines. It inhibited SFTSV in the post-entry step and restricted calcium influx into the cell. Furthermore, nifedipine, a calcium channel inhibitor, also blocked post-entry step of SFTSV infection.

CONCLUSIONS

Loperamide inhibits SFTSV propagation mainly by restraining calcium influx into the cytoplasm. This indicates that loperamide, a Food and Drug Administration (FDA)-approved drug, has the potential for being used as a treatment option against SFTS.

Assessment of pharmacological activities of Lygodium microphyllum Cav. leaves in the management of pain, inflammation, pyrexia, diarrhea, and helminths: In vivo, in vitro and in silico approaches

Lygodium microphyllum Cav. (Family: Lygodiaceae) is a perennial, snake fern and an invasive weed in Florida and also known as old world climbing fern. This study is intended to evaluate the antipyretic, analgesic, anti-inflammatory, antidiarrheal and anthelmintic activity of methanol extract of Lygodium microphyllum Cav. leaves (MELM) by in vivo, in vitro and in silico approaches. In addition, Biovia, PyRx autoDock Vina, UCSF Chimera have been applied to investigate the docking study in order to evaluate the binding interaction and an online tool was used to explore the ADME/T properties of selected bioactive compounds. In acetic acid induced writhing study, MELM inhibited 44.28% and 56.61% of writhes at 200 and 400 (mg/kg) respectively compared to standard drug Diclofenac-Na (10 mg/kg) (74.42% inhibition). In anti-inflammatory experiment by formalin triggered licking method, MELM caused significant (p < 0.05) inhibition of licking in both early phase (42.97%, 63.30%) and late phase (43.35%, 63.03%) at the doses of 200 and 400 mg/kg respectively, whereas reference drug Ibuprofen inhibited paw licking 77.18% in early phase and 76.86% in late phase. MELM also showed promising antipyretic potential where the maximum reduction of fever was produced by MELM 400 mg/kg whose fever lowering capacity is close to the prescribe drug Indomethacin 4 mg/kg, i.p. In Castor oil triggered diarrhea method, MELM delayed the onset time of diarrhea, continuous persistence of wet feces, and decreased the weight of wet feces remarkably. Defection inhibition was achieved 27.56% and 51.72%, for MELM 200 and at 400 (mg/kg) respectively while loperamide 2 (mg/kg) yields 55.17% inhibition of the diarrheal defecation. In anthelmintic bioassay, MELM took 5.83 ± 0.83 and 41.67 ± 1.78 min respectively for paralyzing and death compared to standard drug albendazole; (paralysis time 4.00 ± 0.73 min and death time 31,00 ± 1.71 min). Isoeleutherol, isoquercetin and quercetin were found prominent in molecular docking study and ADME/T analysis verified their drug likeliness. The research validates the moderate analgesic, anti-inflammatory, and remarkable antipyretic, antidiarrheal, anthelmintic activities of the plant extract which can be used an alternative source of novel therapeutics.

Mechanisms of antidiarrhoeal activity of methanol leaf extract of Combretum hypopilinum diels (combretaceae): Involvement of opioidergic and (α1 and β)-adrenergic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

The plant Combretum hypopilinum Diels (Combretaceae) is used in traditional medicine for the treatment of diarrhoea and other diseases in Africa. Previously, the antidiarrhoeal activity of its methanol leaf extract was reported. However, the mechanism(s) responsible for this activity is yet to be evaluated.

AIM OF THE STUDY

This study aimed to elucidate the possible mechanism(s) of antidiarrhoeal activity of methanol leaf extract of Combretum hypopilinum (MECH) in mice.

MATERIALS AND METHODS

Phytochemical screening and acute toxicity study were conducted according to standard methods. Adult mice were orally (p.o) administered distilled water (10 ml/kg), MECH (1000 mg/kg) and loperamide (5 mg/kg). The probable mechanisms of antidiarrhoeal activity of MECH were investigated following pretreatment with naloxone (2 mg/kg, subcutaneously), prazosin (1 mg/kg, s.c), yohimbine (2 mg/kg, intraperitoneally), propranolol (1 mg/kg, i.p), pilocarpine (1 mg/kg, s.c) and isosorbide dinitrate (150 mg/kg, p.o) 30 min before administration of MECH (1000 mg/kg). The mice were then subjected to castor oil-induced intestinal motility test.

RESULTS

The oral median lethal dose (LD₅₀) of MECH was found to be higher than 5000 mg/kg. There were significant (p < 0.05) decrease in the charcoal movement in the mice treated with the MECH (1000 mg/kg) and loperamide (5 mg/kg). The pretreatment of the mice with naloxone, prazosin and propranolol each significantly (p<0.05) reversed the antidiarrhoeal activity produced by MECH.

CONCLUSION

The results obtained in this study suggest the probable involvement of opioidergic and (α₁ and β)-adrenergic systems in the antidiarrhoeal activity of the methanol leaf extract of Combretum hypopilinum.

Antidiarrheal and antinociceptive activities of ethanol extract and its chloroform and pet ether fraction of Phrynium imbricatum (Roxb.) leaves in mice

BACKGROUND

The objective of the study was to evaluate the antidiarrheal and antinociceptive activities of ethanol extract and its chloroform and pet ether fraction of Phrynium imbricatum (Roxb.) leaves in mice.

METHODS

In the present study, the dried leaves of P. imbricatum were subjected to extraction with ethanol, and then it was fractioned by chloroform and pet ether solvent. Antidiarrheal effects were tested by using castor oil-induced diarrhea, castor oil-induced enteropooling, and gastrointestinal transit test. Antinociceptive activity was evaluated by using the acetic acid-induced writhing test and formalin-induced paw licking test.

RESULTS

The standard drug loperamide (5 mg/kg) showed significant (p<0.001) inhibitory activity against castor oil-induced diarrhea, in which all the examined treatments decreased the frequency of defecation and were found to possess an anti-castor oil-induced enteropooling effect in mice by reducing both weight and volume of intestinal content significantly, and reducing the propulsive movement in castor oil-induced gastrointestinal transit using charcoal meal in mice. The results showed that the ethanol extract of P. imbricatum leaves has significant dose-dependent antinociceptive activity, and among its two different fractions, the pet ether fraction significantly inhibited the abdominal writhing induced by acetic acid and the licking times in formalin test at both phases.

CONCLUSIONS

These findings suggest that the plant may be a potential source for the development of a new antinociceptive drug and slightly suitable for diarrhea, as it exhibited lower activity. Our observations resemble previously published data on P. imbricatum leaves.

Freeze dried extracts of Bidens biternata (Lour.) Merr. and Sheriff. show significant antidiarrheal activity in in-vivo models of diarrhea

ETHNOPHARMACOLOGICAL RELEVANCE OF THE STUDY

Diarrhea remains one of the main killers of children aged below five years. Traditional antidiarrheal remedies form a potentially viable source of novel low cost efficacious treatments in low resource settings. There is therefore a pressing need to scientifically evaluate these remedies.

AIM OF THE STUDY

This study aimed to investigate the in vivo and in vitro antidiarrheal activity of freeze dried Bidens biternata, a herb used in traditional Ayurvedic medicine in the management of diarrhea.

MATERIALS AND METHODS

In the castor oil test, twenty (20) adult Sprague-Dawley rats were randomized to a negative control (normal saline, n=5), a positive control (5mg/kg loperamide, n=5), and two test groups. The low dose test group received 200mg/kg Bidens biternata extract (n=5) while the high dose test group received 400mg/kg B. biternata extract (n=5). Castor oil (4ml/kg) was then administered to the animals one hour after administration of the respective treatments after which the total mass of fecal output excreted after four (4) hours was determined. In the charcoal meal test fifteen (15) Sprague Dawley rats were randomized to a control group (normal saline 5ml/kg orally, n=5), a positive control group (atropine sulfate 0.1mg/kg i.p., n=5) and a test group (400mg/kg B. biternata extract, n=5). Charcoal meal was then administered via oral gavage to each rat thirty (30) minutes after the administration of the various treatments. The distance covered by the charcoal meal from the pylorus was then determined after sacrifice of the animals thirty minutes after the meal. In the enteropooling test twenty (20) Sprague-Dawley rats were randomized to a control group (5% v/v ethanol in normal saline, n=5), a positive control group (5mg/kg loperamide, n=5) and a test group (400mg/kg B. biternata extract, n=5). For each group prostaglandin E2 (PGE2) (100μg/kg) was administered immediately after the treatments. The animals were then sacrificed half an hour later and the volume of the small intestine contents determined. The effects of different concentrations of B. biternata extract (0.5. 1.0, 2.0, 3.0 and 5.0mg/ml) on jejunal contraction were investigated and a dose-response curve constructed using the experimental data after which The ED50 dose was determined. The effect of tamsulosin (α1 adrenergic blocker), yohimbine (α2 adrenergic blocker), propranolol (β adrenergic blocker) and naloxone (μ opioid blocker) on the contractile activity of the extract were also investigated. The experimental data were expressed as mean±standard error of mean (SEM) and then analyzed using one-way ANOVA followed by Tukey's post hoc test in cases of significance (set at p<0.05).

RESULTS

The freeze dried extracts of B. biternata had significant antidiarrheal effects in the castor oil induced diarrhea model (p<0.01) with the highest activity being observed at the 400mg/kg dosage level (1.66±0.81g vs. 4.54±0.51g control, p=0.01). B. biternata extract had significant effects on intestinal motility in the charcoal meal test compared to the control group (43.61±4.42% vs. 60.54±3.33%: p<0.05). B. biternata extract had a significant effect on PGE2 induced enteropooling (3.06±0.07ml vs. 4.74±0.10ml; p<0.001). The freeze dried extracts of B. biternata had a significant negative effect on the contractility of the isolated rabbit jejunum (p<0.001). The effects of the extract were significantly attenuated by tamsulosin (53.94±4.20% vs. 80.57±4.09%; p<0.01) and naloxone (53.94±4.20% vs. 73.89±7.26%; p<0.05). Yohimbine (p>0.05) and propranolol (p>0.05) however did not have any significant effect on the contractile activity of the extract.

CONCLUSIONS

The freeze dried extract of B. biternata possess significant antidiarrheal activity in both in vitro and in vivo models which appears to be mediated by modulating both the intestinal motility as well as the secretory activity. The results of this study also validate its traditional use as an antidiarrheal remedy.

The effect of methanol rhizome extract of Nymphaea lotus Linn. (Nymphaeaceae) in animal models of diarrhoea

ETHNOPHARMACOLOGICAL RELEVANCE

Nymphaea lotus, which is widely distributed throughout tropical Africa, enjoys a number of ethnomedical uses in Nigeria. Traditionally, the rhizomes of N. lotus are used to cure diarrhoea.

AIM OF STUDY

This study aims to evaluate the antidiarrhoeal activity of the methanol rhizome extract of N. lotus plant in laboratory animals.

MATERIALS AND METHODS

The extract was screened for activity against castor oil-induced diarrhoea and magnesium sulphate-induced diarrhoea as well as effect on gastric transit time in mice. The effect of methanol rhizome extract of Nymphaea lotus on the perfused isolated tissue preparation was also determined.

RESULTS

For castor oil-induced diarrhoea, the extract at doses of 200, 400 and 800mg/kg produced significant reduction in the frequency of diarrhoea (at p<0.001, p<0.001 and p<0.01 respectively). The extract at 800mg/kg produced a significant delay in onset of diarrhoea (p<0.05) comparable to loperamide (3mg/kg). The frequency of magnesium sulphate-induced diarrhoea was also significantly reduced in the groups treated with 200, 400 and 800mg/kg of the extract at p<0.001, p<0.001 and p<0.01 respectively. At doses of 200mg/kg and 400mg/kg, the protection produced was comparable to loperamide, 3mg/kg. All treated groups produced significant reduction in the transit of charcoal meal along the intestinal tract at p<0.001. The extract at low concentration (4×10(-4)-6.4×10(-2)mg/ml) had contractile effect on the tone of contraction of the rabbit jejunum while at higher concentrations (8×10(-2)-512×10(-2)mg/ml) produced significant reduction in the tone and rate of spontaneous contraction of rabbit jejunum. The extract at lower concentrations (4×10(-4)-2×10(-2)mg/ml) has no effect on contraction of the guinea pig ileum while higher concentrations (4×10(-2)-512×10(-2)mg/ml) produced significant relaxant activity on guinea pig ileum.

CONCLUSION

This study has shown that the methanol rhizome extract of N. lotus has antidiarrhoeal properties thus justifying its use by the local population for this purpose.

Distribution and trafficking of the μ-opioid receptor in enteric neurons of the guinea pig

The μ-opioid receptor (MOR) is a major regulator of gastrointestinal motility and secretion and mediates opiate-induced bowel dysfunction. Although MOR is of physiological and therapeutic importance to gut function, the cellular and subcellular distribution and regulation of MOR within the enteric nervous system are largely undefined. Herein, we defined the neurochemical coding of MOR-expressing neurons in the guinea pig gut and examined the effects of opioids on MOR trafficking and regulation. MOR expression was restricted to subsets of enteric neurons. In the stomach MOR was mainly localized to nitrergic neurons (∼88%), with some overlap with neuropeptide Y (NPY) and no expression by cholinergic neurons. These neurons are likely to have inhibitory motor and secretomotor functions. MOR was restricted to noncholinergic secretomotor neurons (VIP-positive) of the ileum and distal colon submucosal plexus. MOR was mainly detected in nitrergic neurons of the colon (nitric oxide synthase positive, 87%), with some overlap with choline acetyltransferase (ChAT). No expression of MOR by intrinsic sensory neurons was detected. [d-Ala(2), MePhe(4), Gly(ol)(5)]enkephalin (DAMGO), morphiceptin, and loperamide induced MOR endocytosis in myenteric neurons. After stimulation with DAMGO and morphiceptin, MOR recycled, whereas MOR was retained within endosomes following loperamide treatment. Herkinorin or the δ-opioid receptor agonist [d-Ala(2), d-Leu(5)]enkephalin (DADLE) did not evoke MOR endocytosis. In summary, we have identified the neurochemical coding of MOR-positive enteric neurons and have demonstrated differential trafficking of MOR in these neurons in response to established and putative MOR agonists.

Experimental assessment of antidiarrheal and antisecretory activity of 80% methanolic leaf extract of Zehneria scabra in mice

BACKGROUND

The leaf of Zehneria scabra is traditionally used for the management of diarrhea in Ethiopia. Its use, however, has not been scientifically validated for safety and efficacy. The aim of this study was to investigate antidiarrheal and antisecretory effects of hydroalcolic leaf extract of Z. scabra in mice models.

METHODS

For each of antidiarrheal, gastrointestinal motility and antisecretory activity study Swiss albino mice were divided in to five groups. Group I was treated as control group and received 10 ml/kg of 2% Tween-80 orally; Group II served as a positive control and took standard drug in each of the experiments orally; Group III, IV and V were test groups which received the methanolic extract orally at 100, 200 and 400 mg/kg, respectively. Depending on the model total weight of fecal output, total weight of wet feces, total number of fecal output, number of wet faeces, length of intestinal transit and intestinal weight were collected. Finally, data were analyzed using one-way ANOVA followed by Tukey's post test.

RESULT

In castor oil induced diarrhea model, the extract dose produced a significant reduction in mean stool score (1.94 ± 0.102) at 200 mg/kg. Moreover, the 100, 200, and 400 mg/kg doses inhibited stool frequency by 40, 45 and 55%, respectively. All test doses of extract and loperamide (3mg/kg) reduced fecal fluid content significantly (p<0.01). The 100 mg/kg dose of extract produced 25.74% reduction of fluid content (p<0.001) while both 200 and 400 mg/kg showed 29.70 % (p<0.001) compared to negative control group.

CONCLUSION

The extract of Zehineria scabra showed antidiarrheal and antisecretory activity in mice model. Moreover, the extract found to be safe at dose of 2000mg/kg in mice model. The findings suggest the validity of the acclaimed effect of Zehineria scabra as antidiarrheal agent in Ethiopian traditional herbal medicine.

Cytotoxic effects of loperamide hydrochloride on canine cancer cells

Loperamide is a peripheral opiate agonist that can cause apoptosis and G2/M arrest in human cancer cell lines and may sensitize cells to chemotherapy. The objectives of this study were to investigate the effects of loperamide on viability, apoptosis and cell cycle kinetics in canine cancer cells and to establish whether the drug sensitizes cells to doxorubicin. Cell viability was assessed using Alamar Blue. Cell death and cell cycle were studied using flow cytometry with 7-Aminoactinomycin-D (7-AAD) and propidium iodide (PI), respectively. Loperamide decreased cell viability in a dose-dependent fashion and was most effective against canine osteosarcoma cells. In all cell lines, it induced a dose and time dependent apoptosis and resulted in accumulation in G0/G1. When co-incubated with doxorubicin, loperamide induced a synergistic cell kill in canine carcinoma cells. Investigation is warranted into the role of loperamide in the treatment of canine cancer.

Molecular characterization of eluxadoline as a potential ligand targeting mu-delta opioid receptor heteromers

Eluxadoline, an orally active mixed μ opioid receptor (μOR) agonist δ opioid receptor (δOR) antagonist developed for the treatment of diarrhea-predominant irritable bowel syndrome, normalizes gastrointestinal (GI) transit and defecation under conditions of novel environment stress or post-inflammatory altered GI function. Furthermore, compared to loperamide, which is used to treat non-specific diarrhea, the effects of eluxadoline on GI transit occur over a wider dosage range. However, the mechanisms of action of eluxadoline are unclear. In this study, we compared the ability of eluxadoline and loperamide to activate G-protein- and β-arrestin-mediated signaling at μOR homomers or μOR-δOR heteromers in heterologous cells. We also examined the ability of both compounds to reduce castor oil induced diarrhea in wild type (WT) and mice lacking δOR. We find that eluxadoline is more potent than loperamide in eliciting G-protein activity and β-arrestin recruitment in μOR expressing cells. However, in cells expressing μOR-δOR heteromers, the potency of eluxadoline is higher, but its maximal effect is lower than that of loperamide. Moreover, in these cells the signaling mediated by eluxadoline but not loperamide is reduced by μOR-δOR heteromer-selective antibodies. We find that in castor oil-induced diarrhea eluxadoline is more efficacious compared to loperamide in WT mice, and δOR appears to play a role in this process. Taken together these results indicate that eluxadoline behaves as a potent μOR agonist in the absence of δOR, while in the presence of δOR eluxadoline's effects are mediated through the μOR-δOR heteromer.

Safety and antidiarrheal activity of Priva adhaerens aqueous leaf extract in a murine model

ETHNOPHARMACOLOGICAL RELEVANCE

Priva adhaerens (Forssk.) Chiov., a wildly growing plant, is reported in central Uganda to be an effective traditional remedy for diarrhea. The objective of this study was to provide a scientific basis for the ethnopharmacological utility of this plant whose aqueous leaf and shoot extract was evaluated for acute toxicity and antidiarrheal activity using a murine model.

MATERIALS AND METHODS

Acute toxicity of the aqueous leaf and shoot extract was assessed after determining the major phytochemicals present in the extract. The aqueous leaf and shoot extract was assayed against castor oil-induced diarrhea, transit time, and enteropooling, in comparison to loperamide, a standard drug.

RESULTS

The oral LD50 value obtained for Priva adhaerens aqueous extract was greater than 5000mg/kg in rats; the aqueous leaf and shoot extract possessed several important phytochemicals. Furthermore, the aqueous extract significantly, and dose-dependently, reduced frequency of stooling in castor oil-induced diarrhea, intestinal motility, and castor oil-induced enteropooling in rats.

CONCLUSION

This murine model shows that it is relatively safe to orally use the aqueous leaf and shoot extract of Priva adhaerens. The aqueous extract contains phytochemicals that are active for the treatment of diarrhea in a rat model.

Case study 6. Transporter case studies: in vitro solutions for translatable outcomes

Assessing the interactions of a new drug candidate with transporters, either as a substrate or as an inhibitor, is no simple matter. There are many clinically relevant transporters, as many as nine to be evaluated for an FDA submission and up to eleven for the EMA as of 2013. Additionally, it is likely that if a compound is a substrate or inhibitor of one transporter, it will be so for other transporters as well. There are practically no specific substrates or inhibitors, presumably because the specificities of drug transporters are so broad and overlapping, and even fewer clinically relevant probes that can be used to evaluate transporter function in humans. In the case of some transporters, it is advisable to evaluate an NCE with more than one test system and/or more than one probe substrate in order to convince oneself (and regulatory authorities) that a clinical drug interaction study is not warranted. Finally, each test system has its own unique set of advantages and disadvantages. One has to really appreciate the nuances of the available tools (test systems, probe substrates, etc.) to select the best tools for the job and design the optimal in vitro experiment. In this chapter, several examples are used to illustrate the successful interpretation of in vitro data for both efflux and uptake transporters. Some data presented in this chapter is unpublished at the time of compilation of this book. It has been incorporated in this chapter to provide a sense of complexities in transporter kinetics to the reader.

Antidiarrheal and antioxidant activities of chamomile (Matricaria recutita L.) decoction extract in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Matricaria recutita L. (Chamomile) has been widely used in the Tunisian traditional medicine for the treatment of digestive system disorders. The present work aims to investigate the protective effects of chamomile decoction extract (CDE) against castor oil-induced diarrhea and oxidative stress in rats.

METHODS

The antidiarrheal activity was evaluated using castor oil-induced diarrhea method. In this respect, rats were divided into six groups: Control, Castor oil, Castor oil+Loperamide (LOP) and Castor oil+various doses of CDE. Animals were per orally (p.o.) pre-treated with CDE during 1h and intoxicated for 2 or 4h by acute oral administration of castor oil.

RESULTS

Our results showed that CDE produced a significant dose-dependent protection against castor oil-induced diarrhea and intestinal fluid accumulation. On the other hand, we showed that diarrhea was accompagned by an oxidative stress status assessed by an increase of malondialdehyde (MDA) level and depletion of antioxidant enzyme activities as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Castor oil also increased gastric and intestinal mucosa hydrogen peroxide (H2O2) and free iron levels. Importantly, we showed that chamomile pre-treatment abrogated all these biochemical alterations.

CONCLUSION

These findings suggested that chamomile extract had a potent antidiarrheal and antioxidant properties in rats confirming their use in traditional medicine.

Urethane dimethacrylate induces cytotoxicity and regulates cyclooxygenase-2, hemeoxygenase and carboxylesterase expression in human dental pulp cells

The toxic effect of urethane dimethacrylate (UDMA), a major dental resin monomer, on human dental pulp is not fully clear. In this study, we investigated the influence of UDMA on the cytotoxicity, cell cycle distribution, apoptosis and related gene expression of dental pulp cells. The role of reactive oxygen species, hemeoxygenase-1 (HO-1) and carboxylesterase (CES) in UDMA cytotoxicity, was evaluated. UDMA induced morphological changes of pulp cells and decreased cell viability by 29-49% at concentrations of 0.1-0.35 mM. UDMA induced G0/G1, G2/M cell cycle arrest and apoptosis. The expression of cdc2, cyclinB1 and cdc25C was inhibited by UDMA. Moreover, UDMA stimulated COX-2, HO-1 and CES2 mRNA expression of pulp cells. The cytotoxicity of UDMA was attenuated by N-acetyl-l-cysteine, catalase and esterase, but was enhanced by Zn-protoporphyrin (HO-1 inhibitor), BNPP (CES inhibitor) and loperamide (CES2 inhibitor). Exposure of UDMA may potentially induce the inflammation and toxicity of dental pulp. These findings are important for understanding the clinical response of human pulp to resin monomers after operative restoration and pulp capping, and also provide clues for improvement of dental materials.

Antidiarrhoeal and antimicrobial activity of Calpurnia aurea leaf extract

BACKGROUND

In Ethiopia, Calpurnia aurea is used for the treatment of syphilis, malaria, rabies, diabetes, hypertension, diarrhoea, leishmaniasis, trachoma, elephantiasis, fungal diseases and different swellings. However, despite its traditional usage as an antidiarrhoeal and antimicrobial agent, there is limited or no information regarding its effectiveness and mode of action in diarrhoea which may be caused by Shigella flexneri, Staphylococcus aureus, Escherichia coli and Salmonella typhi. Hence, we evaluated the 80% methanol (MeOH) extract of dried and powdered leaves of C. aurea for its antidiarrhoeal and antimicrobial activities.

METHODS

Swiss albino mice of either sex were divided into five groups (five/group): Group I served as control and received vehicle (1% Tween 80) at a dose of 10 ml/kg orally; Group II served as standard and received loperamide at the dose of 3 mg/kg orally; Groups III, IV and V served as test groups and received the 80% MeOH leaf extract of C. aurea at doses of 100, 200 and 400 mg/kg orally, respectively. Diarrhoea was induced by oral administration of 0.5 ml castor oil to each mouse, 1 h after the above treatments. During an observation period of 4 h, time of onset of diarrhea, total number of faecal output (frequency of defecation) and weight of faeces excreted by the animals were recorded. Data were analyzed using one way analysis of variance followed by Tukey post test. Antimicrobial activity test was conducted using agar well diffusion assay. Clinical isolates tested were Salmonella typhi, Salmonella paratyphi, Salmonella typhimurium, Shigella species, Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli.

RESULTS

In castor oil induced diarrhea model, the 80% methanol leaf extract of C. aurea at 100, 200 and 400 mg/kg and the standard drug loperamide (3 mg/kg) significantly reduced the time of onset of diarrhea, the frequency of defecation (total number of faecal output) and weight of faeces. C. aurea leaf extract also showed good antimicrobial activity against all tested organisms.

CONCLUSIONS

C. aurea possesses good antidiarrhoeal and antimicrobial activity which support the traditional use of the plant in the treatment of diarrhea in Ethiopia.

P-glycoprotein, multidrug-resistance associated protein 2, Cyp3a, and carboxylesterase affect the oral availability and metabolism of vinorelbine

We investigated the interactions of the anticancer drug vinorelbine with drug efflux transporters and cytochrome P450 3A drug-metabolizing enzymes. Vinorelbine was transported by human multidrug-resistance associated protein (MRP) 2, and Mrp2 knockout mice displayed increased vinorelbine plasma exposure after oral administration, suggesting that Mrp2 limits the intestinal uptake of vinorelbine. Using P-glycoprotein (P-gp), Cyp3a-, and P-gp/Cyp3a knockout mice, we found that the absence of P-gp or Cyp3a resulted in increased vinorelbine plasma exposure, both after oral and intravenous administration. Surprisingly, P-gp/Cyp3a knockout mice displayed markedly lower vinorelbine plasma concentrations than wild-type mice upon intravenous administration but higher concentrations upon oral administration. This could be explained by highly increased formation of 4'-O-deacetylvinorelbine, an active vinorelbine metabolite, especially in P-gp/Cyp3a knockout plasma. Using wild-type and Cyp3a knockout liver microsomes, we found that 4'-O-deacetylvinorelbine formation was 4-fold increased in Cyp3a knockout liver and was not mediated by Cyp3a or other cytochrome P450 enzymes. In vitro incubation of vinorelbine with plasma revealed that vinorelbine deacetylation in Cyp3a and especially in P-gp/Cyp3a knockout mice but not in P-gp-deficient mice was strongly up-regulated. Metabolite formation in microsomes and plasma could be completely inhibited with the nonspecific carboxylesterase (CES) inhibitor bis(4-nitrophenyl) phosphate and partly with the CES2-specific inhibitor loperamide, indicating that carboxylesterase Ces2a, which was appropriately up-regulated in Cyp3a and especially in P-gp/Cyp3a knockout liver was responsible for the 4'O-deacetylvinorelbine formation. Such compensatory up-regulation can complicate the interpretation of knockout mouse data. Nonetheless, P-gp, Mrp2, Cyp3a, and Ces2a clearly restricted vinorelbine availability in mice. Variation in activity of their human homologs may also affect vinorelbine pharmacokinetics in patients.

Local loperamide injection reduces mechanosensitivity of rat cutaneous, nociceptive C-fibers

Loperamide reverses signs of mechanical hypersensitivity in an animal model of neuropathic pain suggesting that peripheral opioid receptors may be suitable targets for the treatment of neuropathic pain. Since little is known about loperamide effects on the responsiveness of primary afferent nerve fibers, in vivo electrophysiological recordings from unmyelinated afferents innervating the glabrous skin of the hind paw were performed in rats with an L5 spinal nerve lesion or sham surgery. Mechanical threshold and responsiveness to suprathreshold stimulation were tested before and after loperamide (1.25, 2.5 and 5 µg in 10 µl) or vehicle injection into the cutaneous receptive field. Loperamide dose-dependently decreased mechanosensitivity in unmyelinated afferents of nerve-injured and sham animals, and this effect was not blocked by naloxone pretreatment. We then investigated loperamide effects on nerve conduction by recording compound action potentials in vitro during incubation of the sciatic nerve with increasing loperamide concentrations. Loperamide dose-dependently decreased compound action potentials of myelinated and unmyelinated fibers (ED50 = 8 and 4 µg/10 µl, respectively). This blockade was not prevented by pre-incubation with naloxone. These results suggest that loperamide reversal of behavioral signs of neuropathic pain may be mediated, at least in part, by mechanisms independent of opioid receptors, most probably by local anesthetic actions.

Garcinia buchananii bark extract is an effective anti-diarrheal remedy for lactose-induced diarrhea

ETHNOPHARMACOLOGICAL RELEVANCE

The extract from the stem bark of Garcinia buchananii trees is used as an anti-diarrhea remedy in sub-Saharan Africa. We tested the hypothesis that G. buchananii bark extract and its anti-motility fractions are effective treatments against lactose-induced diarrhea.

MATERIALS AND METHODS

A high-lactose (35%) diet was used to induce diarrhea in Wistar rats, which were then treated with either G. buchananii bark extract (0.1, 0.5, 1.0 and 5.0 g bark powder), and its anti-motility fractions isolated using preparative thin layer chromatography; termed PTLC1 (15 mg) and PTLC5 (3.8 mg) or loperamide (8.4 mg). Drug preparations were dissolved in 1L except PTCL1 and PTLC5 that were dissolved in 100mL tap water. Numerous parameters were measured in each condition including consistency, fluid and mucus content of feces, body weight, water and food consumption, urine production and bloating.

RESULTS

Diarrheic rats produced watery or loose, mucuoid, sticky, feces. Fluids constituted 86% of stool mass compared with only 42% for control rats fed standard chow. Compared with controls, diarrheic rats produced more urine, lost weight and had bloated ceca and colons. All doses of the extract, its anti-motility fractions and loperamide individually stopped diarrhea within 6-24 h of administration, whilst significantly reducing mucus and fecal fluid content, urine production and intestinal bloating. Rats treated with 0.1g extract, PTLC1 and PTLC5 gained weight, whilst PTLC5 also increased water intake.

CONCLUSIONS

Garcinia buchananii extract and its anti-motility fractions are effective remedies against lactose-induced diarrhea. The extract contains compounds that reverse weight loss, promote food and water intake, supporting the notion that characterization of the compounds could lead to new therapies against diarrheal diseases.

Antidiarrhoeal activity of an ethanol extract of the stem bark of Piliostigma reticulatum (Caesalpiniaceae) in rats

Piliostigma reticulatum (Caesalpiniaceae) is used in Africa as a traditional medicine for the treatment of many diseases, such as malaria, tuberculosis and diarrhoea. We investigated the antidiarrhoeal properties of a crude ethanol extract from the stem bark of Piliostigma reticulatum (EEPR) in Wistar albino rats to substantiate its traditional use and to determine its phytochemical constituents. The antidiarrhoeal activity of the plant extract was evaluated in a castor oil-induced diarrhoea model in rats and compared with loperamide. The effect of the extract on gastrointestinal motility was also determined by the oral administration of charcoal meal and castor oil-induced intestinal fluid accumulation (enteropooling). EEPR showed remarkable dose-dependent antidiarrhoeal activity evidenced by a reduction of defecation frequency and change in consistency. Extracts at 250, 500 and 1000 mg/kg body weight significantly reduced diarrhoeal faeces. EEPR also significantly inhibited gastrointestinal motility and castor oil-induced enteropooling at 500 and 1000 mg/kg, similar to the inhibition obtained in control rats treated by atropine. Phytochemical screening revealed the presence of tannins, flavonoids, polyphenols and reducing sugars in the stem bark of P. reticulatum. No mortality or visible signs of general weakness were observed in the rats following administration of the crude extract in doses up to 6000 mg/kg body weight in an acute toxicity study. Our results show that the stem bark of P. reticulatum possesses antidiarrhoeal activity and strongly suggest that its use in traditional medicine practice could be justified.

NPY Y2 receptor agonist PYY(3-36) inhibits diarrhea by reducing intestinal fluid secretion and slowing colonic transit in mice

Peptide YY (PYY)(3-36), a neuropeptide Y (NPY) Y2 receptor agonist, is a powerful inhibitor of intestinal secretion. Based on this anti-secretory effect, NPY Y2 receptor agonists may be useful as novel anti-diarrheal agents, but anti-diarrheal efficacy has yet to be determined. We therefore examined the anti-diarrheal efficacy of PYY(3-36) and a selective Y2 receptor agonist, N-acetyl-[Leu28, Leu31]-NPY(24-36), in experimental mouse models of diarrhea. Intraperitoneal administration of PYY(3-36) (0.01-1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) significantly inhibited diarrhea (increase in wet fecal weight and diarrhea score) induced by dimethyl-prostaglandin E2, 5-hydroxytryptamine, and castor oil. Anti-diarrheal activities of PYY(3-36) and N-acetyl-[Leu28, Leu31]-NPY(24-36) were comparable to the effects of loperamide (1mg/kg), a widely used anti-diarrheal drug. To clarify the anti-diarrheal mechanisms of NPY Y2 receptor agonists, we investigated the effects of PYY(3-36) and N-acetyl-[Leu28, Leu31]-NPY(24-36) on intestinal fluid secretion and colonic transit. PYY(3-36) (1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) significantly reduced dimethyl-prostaglandin E2-induced intestinal fluid accumulation in conscious mice, suggesting that NPY Y2 receptor agonists inhibit diarrhea, at least in part, by reducing intestinal secretion. In addition, PYY(3-36) (0.01-1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) potently inhibited normal fecal output, suggesting that NPY Y2 receptor activation inhibits colonic motor function and NPY Y2 receptor agonists inhibit diarrhea partly by slowing colonic transit. These results indicate that NPY Y2 receptor agonists inhibit diarrhea in mice by not only reducing intestinal fluid secretion, but also slowing colonic transit, and illustrate the therapeutic potential of NPY Y2 receptor agonists as effective treatments for diarrhea.

Loperamide modifies the tissue disposition kinetics of ivermectin in rats

Ivermectin (IVM) is a broad-spectrum antiparasitic drug extensively used in human and veterinary medicine that is largely excreted in bile and faeces. Loperamide (LPM) is an opioid derivative that reduces gastrointestinal secretions and motility. Both IVM and LPM have been reported to act as P-glycoprotein substrates (P-GP). The goal of the present work was to study the LPM-induced modifications to the pattern of tissue distribution for IVM. Thirty-six Wistar male rats were randomly allocated to two groups (n = 18) and treated subcutaneously with IVM alone or co-administered with LPM. Rats were killed at different times post-treatment and samples (blood and tissues) were collected and analyzed by HPLC. The presence of LPM induced a marked enhancement in the IVM plasma concentrations, resulting in a significantly higher area under concentration time curve (AUC) value (P &lt; 0.01) than that obtained after the administration of IVM alone. Significantly higher IVM availabilities in the liver tissue and small intestine wall (P &lt; 0.05) were obtained in the presence of LPM. There were no statistically significant differences in drug availability in the large intestinal wall after both treatments. However, LPM induced a marked decrease in the amount of IVM recovered in the large intestinal lumen content. The ratio between IVM concentrations in the large intestinal luminal content and plasma at day 1 post-treatment was 4.64-fold higher in the absence of LPM. The delayed intestinal transit time caused by LPM accounting for an extended plasma–intestine recycling time, and a potential competition between IVM and LPM for the P-GP-mediated bile–intestinal secretion processes, may account for the enhanced IVM systemic availability reported in the current study.

Intrasperm Ca2+ modulation and human ejaculated sperm viability: influence of miconazole, clotrimazole and loperamide

Elevation of intrasperm Ca2+ is reported to influence viability of ejaculated spermatozoa. Human spermatozoa possess inositol triphosphate (IP3)-sensitive Ca2+ stores, which can be targeted for increasing intrasperm Ca2+ level. The influence of agents affecting Ca2+ homeostasis has been investigated. Miconazole nitrate, clotrimazole and loperamide hydrochloride produced a dose- and time-dependent decrease in viability, each requiring respectively 0.5, 1.0 and 1.0 mM for producing death of all sperm cells immediately upon addition to ejaculated human semen samples. The reduction in sperm viability was accompanied by elevation of intrasperm Ca2+ and was not affected by presence or absence of extracellular Ca2+. Significantly (P &lt; 0.05) less time was required for producing complete loss of sperm viability and increasing intrasperm Ca2+ when any of these drugs was added to sperm cells previously treated with selected agents affecting Ca2+ homeostasis. This enhanced spermicidal activity of miconazole, clotrimazole and loperamide appeared to be due to further mobilization of Ca2+ from partially depleted intrasperm Ca2+ stores. Synergism of spermicidal activity and intrasperm Ca2+ elevation by miconazole or clotrimazole was observed when Ca2+ efflux from sperm cells was simultaneously inhibited by 2′,4′-dichlorobenzamil hydrochloride, a Na+-Ca2+ exchange inhibitor. The spermicidal activity of miconazole, clotrimazole or loperamide due to elevation of intrasperm Ca2+ and its synergism, therefore, has great potential for exploitation of these drugs as contact spermicides.

Loperamide inhibits the biliary excretion of irinotecan (CPT-11) in the rat isolated perfused liver

Patients treated with irinotecan (CPT-11) occasionally suffer from severe diarrhoea and aggressive treatment with loperamide at the first signs of loose stools is recommended. We have examined the effect of loperamide on the hepatic metabolism and biliary excretion of CPT-11 in the isolated perfused rat liver (IPRL). CPT-11 (0.5 μmol) was injected as a bolus into the IPRL reservoir, and perfusate and bile samples were collected over 3h. Experiments were conducted using loperamide-free perfusate (n = 5) or perfusate containing 10 μm loperamide (n = 6). Perfusate and bile concentrations of total CPT-11 and the major metabolites SN-38 (7-ethyl-10-hydroxy-camptothecin), SN-38G (7-ethyl-10-hydroxy-camptothecin glucuronide) and APC (7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidine] carbonyloxycamptothecin) were determined by HPLC. The unchanged parent drug was the predominant species in bile, with approximately 4% of the dose recovered over 180 min as compared with only 1% for the metabolites. Loperamide significantly reduced the biliary excretion of CPT-11 by approximately 50% (2.0 ± 0.9% dose compared with 3.8 ± 1.0% in the control group, P = 0.019) over the same period. In contrast, the biliary excretion of SN-38, SN-38G and APC was not significantly affected by loperamide (P &gt; 0.05). Furthermore, bile flow rate was not affected by loperamide. Loperamide appeared to selectively inhibit the biliary excretion of CPT-11, although the extent to which loperamide altered the disposition of CPT-11 in the clinical setting remains to be determined.

Antidiarrheal activity of aqueous extract of Hermannia incana Cav. leaves in Wistar rats

Hermannia incana Cav. is a prostrate herb used to treat diarrhea, stomach ache, nausea and vomiting, by the people of Eastern Cape Province, South Africa. The phytochemical screening as well as the antidiarrheal activity of H. incana leaf extract at 200, 400 and 600 mg/kg body weight was evaluated in rats. Phytochemical screening revealed the presence of bioactive agents such as alkaloids, tannins, saponins, phenolics, triterpenes, cardiac glycosides, flavonoids, cardenolides and dienolides. The extract significantly prolonged the time of induction of diarrhea, reduced the frequency of diarrheal episodes and water content of the feces, and inhibited castor oil-induced enteropooling. The extract also suppressed intestinal propulsive movement of a charcoal meal through the gastrointestinal tract. These results demonstrate the antidiarrheal properties of the extract, thereby supporting the folkloric use of the plant as an antidiarrheal agent in the Eastern Cape of South Africa.

Spinal antinociceptive action of loperamide is mediated by opioid receptors in the formalin test in rats

Opioids like morphine produce antinociception after intrathecal administration. Being hydrophilic in nature, morphine also spreads rostrally which leads to respiratory depression. Loperamide has been reported to produce antinociception after both intracisternal and intrathecal administration. It is also hydrophobic, which could restrict its diffusion in the spinal canal. However, the mechanism of its antinociceptive action after intrathecal administration is not definitely known. In the present study, the antinociceptive effect of loperamide was evaluated by the formalin test. It significantly inhibited Phase II flinching behavior. This antinociceptive effect was reversed by pre-administration of naloxone indicating that it was predominantly due to activation of opioid receptors.

Limited effects of beta-endorphin compared to loperamide or fentanyl in a neuroendocrine biomarker assay in non-human primates

The in vivo pharmacodynamics of the opioid neuropeptide beta-endorphin (a major endogenous agonist at the mu-opioid receptor) is difficult to determine in non-human primate models with translational value, or in humans. The present studies therefore employed a neuroendocrine biomarker assay, prolactin release, to systematically compare the in vivo profile of i.v. beta-endorphin (0.01-0.32 mg/kg; i.v.) in gonadally intact male rhesus monkeys (n=4) to that of the peripherally selective mu-agonist loperamide (0.01-0.32 mg/kg; i.v.) and the centrally penetrating mu-agonist fentanyl (0.0056-0.018 mg/kg; i.v.). Studies utilized a standardized time course design (measuring prolactin levels 5-120 min after agonist administration). Beta-endorphin displayed only limited effectiveness in causing prolactin release when tested over this 30-fold dose range, compared to loperamide or fentanyl. Furthermore, two of the four subjects were only minimally responsive to beta-endorphin. This differential responsiveness was not due to the presence of a previously described single nucleotide polymorphism at the OPRM1 gene (C77G), known to affect beta-endorphin pharmacodynamics in vitro. In vivo biotransformation studies with MALDI-mass spectrometry determined that full-length beta-endorphin was detectable in all subjects up to at least 5 min after i.v. administration. Thus, the relative ineffectiveness of i.v. beta-endorphin in this assay does not appear to be principally due to rapid generation of non-opioid fragments of this neuropeptide.

The role of loperamide in gastrointestinal disorders

Loperamide is an effective therapy for a variety of diarrheal syndromes, including acute, nonspecific (infectious) diarrhea; traveler's diarrhea; and chemotherapy-related and protease inhibitor?associated diarrhea. Loperamide is effective for the "gut-directed" symptom of diarrhea in patients with painless diarrhea or diarrhea-predominant irritable bowel syndrome. Loperamide and diphenoxylate are commonly used to treat diarrhea in numerous settings of inflammatory bowel disease. Loperamide has also been observed to increase anal sphincter tone, which may lead to improvement of fecal continence in patients with and without diarrhea. Loperamide is generally well tolerated at recommended nonprescription doses, with the most common side effects related to the impact on bowel motility (abdominal pain, distention, bloating, nausea, vomiting, and constipation).

Evaluation of the pharmacological profile of ramosetron, a novel therapeutic agent for irritable bowel syndrome

We examined the pharmacological profile of ramosetron, a 5-HT(3)-receptor antagonist for irritable bowel syndrome with diarrhea, comparing it with those of other 5-HT(3)-receptor antagonists, alosetron and cilansetron, and the anti-diarrheal agent loperamide. Ramosetron showed high affinity for cloned human and rat 5-HT(3) receptors, with K(i) values of 0.091 +/- 0.014 and 0.22 +/- 0.051 nmol/L, respectively, while its affinities for other receptors, transporters, ion channels, and enzymes were negligible. Dissociation of ramosetron from the human 5-HT(3) receptor was extremely slow (t(1/2) = 560 min), while alosetron (t(1/2) = 180 min) and cilansetron (t(1/2) = 88 min) dissociated relatively rapidly. Ramosetron competitively inhibited 5-HT-induced contraction of isolated guinea-pig colon, with pA(2) values of 8.6 (8.5 - 9.0). Ramosetron given orally also dose-dependently inhibited the von Bezold-Jarisch reflex in rats, with an ED(50) value of 1.2 (0.93 - 1.6) microg/kg. In addition, oral ramosetron dose-dependently inhibited restraint stress-induced defecation in rats, with an ED(50) value of 0.62 (0.17 - 1.2) microg/kg. In all of these experiments, the potencies of ramosetron were greater than those of alosetron, cilansetron, or loperamide. These results indicate that ramosetron is a highly potent and selective 5-HT(3)-receptor antagonist, with beneficial effects against stress-induced abnormal defecation in rats.

Inhibition of Phosphodiesterase Type 4 Decreases Stress-Induced Defecation in Rats and Mice

BACKGROUND/AIMS

Phosphodiesterase type 4 (PDE4) has been previously shown to regulate colonic contractile activity in vitro. In this study, the effects of PDE4 inhibition were assessed in a model of stress-induced defecation previously demonstrated to be due to increased colonic transit/evacuation.

METHODS

Rats were individually placed in a mild restraint cage and placed into a 12 degrees C environment (cold-restraint stress) for 60 min. Mice received restraint (only) stress at room temperature for 30 min. Loperamide (positive control compound) or two different PDE4 inhibitors (rolipram and roflumilast) were administered orally at several doses to the rodents 1 h before stress began. Vehicle alone was administered for comparison. The number of fecal pellets expelled during stress (fecal pellet output), total fecal pellet wet weight and total fecal water content were measured.

RESULTS

Loperamide produced a dose-related decrease (ID(50)s in mg/kg) in fecal pellet output (rat = 7.4, mouse = 0.7) and significantly decreased fecal wet weight (72.9%) and decreased fecal percent water content (9.4%). The two PDE4 inhibitors produced a similar dose-related inhibition of fecal pellet output. Rolipram exhibited ID(50)s in rat and mouse of 14.1 and 27.1, respectively. Rolipram significantly decreased fecal wet weight (58.8%) but increased fecal percent water content (15.0%). For roflumilast, ID(50)s were 24.2 mg/kg and 12.4 in the rat and mouse, respectively. Although roflumilast also significantly (p < 0.05) decreased fecal wet weight (47.2%), it did not significantly increase fecal percent water content.

CONCLUSIONS

These data indicate that PDE4 inhibition is effective in reducing rodent stress-induced defecation, provides the first functional data on a potential role for PDE4 activity in the colonic evacuation response to stress, and indicates the potential utility of PDE4 inhibitors in functional bowel disease such as irritable bowel syndrome requires further evaluation.

Specificity of procaine and ester hydrolysis by human, minipig, and rat skin and liver

The capacity of human, minipig, and rat skin and liver subcellular fractions to hydrolyze the anesthetic ester procaine was compared with carboxylesterase substrates 4-methylumbelliferyl-acetate, phenylvalerate, and para-nitrophenylacetate and the arylesterase substrate phenylacetate. Rates of procaine hydrolysis by minipig and human skin microsomal and cytosolic fractions were similar, with rat displaying higher activity. Loperamide inhibited procaine hydrolysis by human skin, suggesting involvement of human carboxylesterase hCE2. The esterase activity and inhibition profiles in the skin were similar for minipig and human, whereas rat had a higher capacity to metabolize esters and a different inhibition profile. Minipig and human liver and skin esterase activity was inhibited principally by paraoxon and bis-nitrophenyl phosphate, classical carboxylesterase inhibitors. Rat skin and liver esterase activity was inhibited additionally by phenylmethylsulfonyl fluoride and the arylesterase inhibitor mercuric chloride, indicating a different esterase profile. These results have highlighted the potential of skin to hydrolyze procaine following topical application, which possibly limits its pharmacological effect. Skin from minipig used as an animal model for assessing transdermal drug preparations had similar capacity to hydrolyze esters to human skin.

Effect of ramosetron on conditioned emotional stress-induced colonic dysfunction as a model of irritable bowel syndrome in rats

The aim of this study was to establish a pathophysiologic model of irritable bowel syndrome, and then to evaluate the pharmaceutical efficacy of ramosetron, a potent serotonin 3 (5-HT(3)) receptor antagonist, and other anti-irritable bowel syndrome agents in this model. Rats stressed by a conditioned stress procedure exhibited marked prolongation of freezing time, an index of fear level, and an increase in the frequency of defecation (P<0.01). A corticotropin-releasing factor (CRF) antagonist, alpha-helical CRF, inhibited both defecation and freezing behavior, while the antidiarrheal loperamide inhibited defecation only. The 5-HT(3) receptor antagonists ramosetron, cilansetron and alosetron also inhibited defecation (ED(50) values: 0.012, 0.094, 0.078 mg/kg p.o., respectively) without affecting freezing behavior. Ramosetron showed longer-lasting effect on defecation than cilansetron. Stress also resulted in increases in both proximal and distal colonic transit rates. Ramosetron and other 5-HT(3) receptor antagonists at doses inhibiting stress-induced defecation also ameliorated both stress-stimulated colonic transit rates. These results suggest that ramosetron, as well as agents used for the treatment of irritable bowel syndrome with diarrhea, has beneficial effects against emotional stress-induced colonic dysfunction. Furthermore, this emotional stress model may be useful in evaluation of drugs to treat irritable bowel syndrome presenting with diarrhea.

Control of Mycosphaerella graminicola on wheat seedlings by medical drugs known to modulate the activity of ATP-binding cassette transporters

Medical drugs known to modulate the activity of human ATP-binding cassette (ABC) transporter proteins (modulators) were tested for the ability to potentiate the activity of the azole fungicide cyproconazole against in vitro growth of Mycosphaerella graminicola and to control disease development due to this pathogen on wheat seedlings. In vitro modulation of cyproconazole activity could be demonstrated in paper disk bioassays. Some of the active modulators (amitriptyline, flavanone, and phenothiazines) increased the accumulation of cyproconazole in M. graminicola, suggesting that they reversed cyproconazole efflux. However, synergism between cyproconazole and modulators against M. graminicola on wheat seedlings could not be shown. Despite their low in vitro toxicity to M. graminicola, some modulators (amitriptyline, loperamide, and promazine) did show significant intrinsic disease control activity in preventive and curative foliar spray tests with wheat seedlings. The results suggest that these compounds have indirect disease control activity based on modulation of fungal ABC transporters essential for virulence and constitute a new class of disease control agents.

Direct Inhibition of Ih by Analgesic Loperamide in Rat DRG Neurons

Hyperpolarization-activated cyclic nucleotide–gated (HCN) channels are responsible for the functional hyperpolarization-activated current ( Ih) in dorsal root ganglion (DRG) neurons, playing an important role in pain processing. We found that the known analgesic loperamide inhibited Ih channels in rat DRG neurons. Loperamide blocked Ih in a concentration-dependent manner, with an IC50 = 4.9 ± 0.6 and 11.0 ± 0.5 μM for large- and small-diameter neurons, respectively. Loperamide-induced Ih inhibition was unrelated to the activation of opioid receptors and was reversible, voltage-dependent, use-independent, and was associated with a negative shift of V1/2 for Ih steady-state activation. Loperamide block of Ih was voltage-dependent, gradually decreasing at more hyperpolarized membrane voltages from 89% at –60 mV to 4% at –120 mV in the presence of 3.7 μM loperamide. The voltage sensitivity of block can be explained by a loperamide-induced shift in the steady-state activation of Ih. Inclusion of 10 μM loperamide into the recording pipette did not affect Ih voltage for half-maximal activation, activation kinetics, and the peak current amplitude, whereas concurrent application of equimolar external loperamide produced a rapid, reversible Ih inhibition. The observed loperamide-induced Ih inhibition was not caused by the activation of peripheral opioid receptors because the broad-spectrum opioid receptor antagonist naloxone did not reverse Ih inhibition. Therefore we suggest that loperamide inhibits Ih by direct binding to the extracellular region of the channel. Because Ih channels are involved in pain processing, loperamide-induced inhibition of Ih channels could provide an additional molecular mechanism for its analgesic action.

Pharmacological modulation of gut mucosal and large vessel blood flow

BACKGROUND

Constipation, diminished gut blood flow, ischaemic colitis and drug therapy may be associated.

AIM

To study the effect of constipating medication on, and the regulation of, gut blood flow.

METHODS

24 healthy females (mean age 30) received, in a double-blind, three-way crossover study: (i) placebo, (ii) ipratropium 40 microg by inhalation (positive control known to reduce rectal mucosal blood flow) and (iii) oral loperamide 4 mg. Mucosal blood flow was measured at the splenic flexure and rectum using laser Doppler flowmetry. Blood flow in the superior and inferior mesenteric arteries was measured by trans-abdominal Doppler ultrasound.

RESULTS

Ipratropium decreased rectal mucosal blood flow by 16% (P=0.009) and splenic flexure mucosal blood flow by 8% (P=0.075). Loperamide caused no change in rectal (P=0.40) or splenic flexure mucosal blood flow (P=0.73). Neither treatment changed superior or inferior mesenteric artery blood flow. Splenic flexure mucosal blood flow showed a positive correlation with rectal mucosal blood flow (r=0.69; P<0.0001).

CONCLUSIONS

Vasoactive agents may reduce gut mucosal blood flow in the absence of reduced large vessel flow. Constipating drugs do not necessarily reduce gut blood flow. Rectal mucosal blood flow correlates with splenic flexure mucosal flow, and potentially may be used as a more convenient surrogate for studying splenic flexure blood flow.

Activation of μ-opioid receptors improves insulin sensitivity in obese Zucker rats

In the current study we investigated the effect of mu-opioid receptor activation on insulin sensitivity. In obese Zucker rats, an intravenous injection of loperamide (18 microg/kg, three times daily for 3 days) decreased plasma glucose levels and the glucose-insulin index. Both effects of loperamide were subsequently inhibited by the administration of 10 microg/kg of naloxone or 10 microg/kg of naloxonazine, doses sufficient to block mu-opioid receptors. Other metabolic defects characteristic of obese Zucker rats, such as defects in insulin signaling, the decreased expression of insulin receptor substrate (IRS)-1, the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3 kinase), and the glucose transporter subtype 4 (GLUT 4), and the reduction of phosphorylation in IRS-1 or Akt serine, were also studied. These defects were all reversed by loperamide treatment in a dose which overcame mu-opioid receptor blockade. Moreover, loss of tolbutamide-induced plasma glucose lowering action (10 mg/kg) in wild-type mice given a fructose-rich diet was markedly delayed by repeated treatment with loperamide; however, this delay induced by loperamide did not occur in mu-opioid receptor knockout mice. These results indicate an important role of peripheral mu-opioid receptors in the loperamide-induced improvement of insulin sensitivity. Our results suggest that activation of peripheral mu-opioid receptors can ameliorate insulin resistance in animals, and provide a new target for therapy of insulin resistance.

Covalent attachment of apolipoprotein A-I and apolipoprotein B-100 to albumin nanoparticles enables drug transport into the brain

Apolipoprotein E3, A-I as well as B-100 were covalently attached to human serum albumin nanoparticles via the NHS-PEG-Mal 3400 linker. Loperamide as a model drug was bound to these nanoparticles, and the antinociceptive reaction of these preparations was recorded after intravenous injection in mice by the tail-flick test. After 15 min, all three nanoparticle preparations with the coupled apolipoproteins E3, A-I, and B-100 yielded considerable antinociceptive effects, which lasted over 1 h. The maximally possible effects [MPE] of these preparations amounted to 95%, 65%, and 50%, respectively, and were statistically different from the controls (p<0.02), whereas the loperamide solution achieved no effect. This result demonstrates that more than one mechanism is involved in the interaction of nanoparticles with the brain endothelial cells and the resulting delivery of drugs to the central nervous system.

Loperamide: a pharmacological review

Loperamide is an antidiarrheal medication approved for the control of diarrhea symptoms and is available without a prescription. Loperamide works by a number of different mechanisms of action that decrease peristalsis and fluid secretion, resulting in longer gastrointestinal transit time and increased absorption of fluids and electrolytes from the gastrointestinal tract. It is a phenylpiperidine derivative with a chemical structure similar to opiate receptor agonists such as diphenoxylate and haloperidol. It was designed to maintain the antidiarrheal activity of these drugs, but minimize the negative aspects associated with their effects on the opiate receptor. Because of loperamides's low oral absorption and inability to cross the blood-brain barrier, it has minimal central nervous system effects. It also has a longer duration of action than diphenoxylate. However, it has no clinically significant analgesic activity and does not decrease the pain associated with some forms of irritable bowel syndrome and diarrhea. Loperamide is metabolized by the cytochrome P450 (CYP) system and is a substrate for the CYP3A4 isoenzyme. Concurrent administration with CYP3A4 inhibitors may elevate loperamide concentrations. Common adverse reactions to loperamide include cramps and nausea. Loperamide is an effective treatment for patients with painless diarrhea and is considered to be free of abuse potential.

Investigation on the relationship between cannabinoid CB1 and opioid receptors in gastrointestinal motility in mice

1. This study investigated whether (a) cannabinoid CB(1) receptor knockout (CB(1)(-/-)) mice displayed altered gastrointestinal transit and (b) cannabinoid CB(1) and opioid receptors functionally interact in the regulation of gastrointestinal transit. 2. Gastrointestinal transit was assessed by the Whole Gastrointestinal Transit, measuring the excretion time of an intragastrically administered marker (whole intestine), and the Upper Gastrointestinal Transit, measuring the distance covered by the marker in the small intestine. 3. CB(1)(-/-) and homozygous CB(1)(+/+) (CB(1)(+/+)) mice did not differ in both whole gut and small intestine transit. CB(1)(-/-) and CB(1)(+/+) mice were equally responsive to the inhibitory effect of morphine (10 mg kg(-1)) and loperamide (3 mg kg(-1)) on whole gut transit.4. Additionally, in CD1 mice the cannabinoid CB(1) receptor antagonist, rimonabant (0-0.5 mg kg(-1)), failed to block the inhibitory effect of morphine (0-1.25 mg kg(-1)) and loperamide (0-0.5 mg kg(-1)) on transit in small and whole intestine. Similarly, the opioid receptor antagonists, naloxone (0-1 mg kg(-1)) and naltrexone (0-10 mg kg(-1)), failed to block the inhibitory effect of the cannabinoid WIN 55,212-2 (0-3 mg kg(-1)) on transit in small and whole intestine.5. These results suggest that (a) compensatory mechanisms likely developed in CB(1)(-/-) mice to overcome the lack of inhibitory function of endocannabinoid system; (b) cannabinoid and opioid receptor systems did not interact in regulating gastrointestinal transit in mice.

Adaptive immunity-dependent intestinal hypermotility contributes to host defense against Giardia spp

Humans infected with Giardia exhibit intestinal hypermotility, but the underlying mechanisms and functional significance are uncertain. Here we show in murine models of giardiasis that small-intestinal hypermotility occurs in a delayed fashion relative to peak parasite burden, is dependent on adaptive immune defenses, and contributes to giardial clearance.