The nociceptin receptors (NOPs) are expressed in the gastrointestinal (GI) tract on muscle cell membranes and neurons, as well as the immune cells that infiltrate the mucosa. The involvement of NOPs in the pathophysiology of GI inflammation has been suggested, but due to the lack of selective NOP agonists, it never fully elucidated. Our aim was to characterize the anti-inflammatory and antinociceptive effect of the NOP agonist, SCH 221510 [3-endo-8-[bis(2-methylphenyl)methyl]-3-phenyl-8-azabicyclo [3.2.1]octan-3-ol], as a potential therapeutic strategy in the treatment of inflammatory bowel diseases (IBD). The anti-inflammatory action of SCH 221510 was determined after intraperitoneal, oral, and intracolonic administration of SCH 221510 (0.1–3.0 mg/kg once or twice daily) in mice treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). Antinociceptive action of SCH 221510 was evaluated in the mouse model of mustard oil (MO)-induced abdominal pain. Relative NOP mRNA expression was assessed in patients with IBD using real-time reverse transcriptase-polymerase chain reaction. We found that the expression of NOP mRNA was significantly decreased in patients with IBD. The administration (0.1 and 1.0 mg/kg i.p. twice daily and 3 mg/kg p.o. twice daily) of SCH 221510 attenuated TNBS colitis in mice. This effect was blocked by a selective NOP antagonist [J-113397 [(±)-1-[(3R*,4R*)-1-(cyclooctylmethyl)-3-(hydroxymethyl)-4-piperidinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one]]. The intracolonic injections of SCH 221510 did not improve colitis in mice. The antinociceptive effect of SCH 221510 was observed after oral administration of SCH 221510 in MO-induced pain tests in mice with acute colitis. In conclusion, our results show a potent anti-inflammatory and antinociceptive effect upon selective activation of NOP receptors and suggest that the NOP agonist SCH 221510 is a promising drug candidate for future treatment of IBD.
Inflammatory bowel diseases (IBD) constitute a large group of severe and chronic gastrointestinal (GI) disorders, in which inflammation occurs constantly or transitorily. Crohn’s disease (CD) and ulcerative colitis (UC) are the most common disorders among IBD, and the first reports on these ailments date back to the beginning of the 20th century (Loftus, 2004). The inflammation in UC is restricted to the large intestine (continuous inflammation), and the inflammation in CD may occur anywhere in the GI tract (discontinuous inflammation). The major symptoms of IBD are altered bowel movements, abdominal pain, and chronic inflammation of the gut wall (Brandhorst et al., 2013). IBD is also associated with weight loss, malnutrition, fever, and lack of appetite (Castaneda et al., 2013). In several cases, the symptoms are not restricted to the GI tract; the parenteral IBD symptoms include aphthosis, erythema nodosum, pyoderma gangrenosum, endophthalmitis, and arthritis (Korzenik and Podolsky, 2006).
The etiology of IBD remains unknown. A leading hypothesis associates IBD with the dysregulation and constant activation of the immune system function. This results in local influx of immune cells, such as neutrophils, monocytes, macrophages, and mast cells, to the large intestine. The immune cells infiltrating the mucosa (Fries et al., 2013) produce tumor necrosis factor–α and other proinflammatory molecules, including interleukin-1 and interleukin-6, which play primary roles in mediating IBD (Guindi and Riddell, 2004).
Many genetic, environmental, and microbiological factors may influence the development of IBD, but they are still not well defined, and therefore, there is no effective therapy. The major goal in anti-IBD therapy involves reduction of abdominal pain and control of immune response (Sandborn, 2012). Current anti-IBD treatments are based on pharmacological (e.g., antibiotics, biologic drugs, aminosalicylates, immunosuppressants, and steroids) or surgical intervention, which only act symptomatically (Danese et al. 2013). Therefore, novel therapies and—even more importantly—novel pharmacological targets for anti-IBD treatments are urgently needed.
The nociceptin system is composed of an endogenous ligand nociceptin/orphanin and the nociceptin receptor (NOP) (Meunier et al., 1995). Nociceptin is a heptapeptide, which is a product of an enzymatic degradation of a larger precursor prepro-nociceptin (Reinscheid et al., 1995). Nociceptin and NOP receptors are widely distributed in the central nervous system (CNS) and the peripheral nervous system, as well as in the GI tract (Mollereau and Mouledous, 2000) where they play an important role in its physiology (Broccardo et al., 2004; Osinski and Brown, 2000; unpublished observations). It was shown that nociceptin is involved in the regulation of pain signaling and modulation of hormone and neurotransmitter release, attenuation of stress response, and reversal of stress-induced analgesia (Darland et al., 1998). The effect of nociceptin on physiologic processes strongly depends on multiple factors, such as the route of administration, the dose distribution, the animal species, and the pain model used in the study (Hara et al., 1997; Minami et al., 2000).
There are some lines of evidence showing that NOP may be involved in the pathophysiology of inflammatory GI disorders; this suggests a possible clinical application for targeting the nociceptin system in the GI tract (Gavioli and Romao, 2011). Here, our aim was to characterize the anti-inflammatory and antinociceptive effect of the synthetic NOP agonist SCH 221510 in the treatment of IBD using an animal model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. SCH 221510 is a potent and selective NOP agonist with nonpeptide structure, which displays 217-fold binding selectivity and 57-fold functional selectivity for the NOP site, compared with the opioid receptors (Varty et al., 2008).
Materials and Methods
Male balbC mice (Animal Facility of the University of Lodz, Poland), weighing 22–24 g, were used for all experiments. Mice were maintained under a 12-hour light/dark cycle and housed at a constant temperature (22°C to 23°C) in sawdust-lined plastic cages with free access to chow and water ad libitum.
The study was carried out in accordance with the recommendations described in the Guide for the Care and Use of Laboratory Animals of the Medical University of Lodz, Poland. All experiments on animals were approved by the Local Ethics Committee for Animal Experiments (Protocol 589).
The TNBS-induced mouse model of colitis is a well-established acute animal model of CD, as described earlier (Fichna et al., 2012a). On day 0, mice (5–8 per treatment group) were lightly anesthetized using 1% isoflurane (Aerrane; Baxter Healthcare Corp., Deerfield, IL), and TNBS (4 mg in 0.1 ml of 30% EtOH in 0.9% NaCl) was administered into the distal colon using a catheter (silicone pusher). On days 0–2, animals received treatment as described below. On day 3, mice were killed by cervical dislocation, and the colon with the cecum was removed to assess macroscopic parameters, including ulcer area, colonic shortening, wall thickening, and the presence of hemorrhage, fecal blood, and diarrhea. All parameters constituted the macroscopic damage score. Moreover, the colonic samples were collected to assess myeloperoxidase (MPO) activity and for histologic analysis.
Determination of MPO Activity.
The MPO activity within inflamed tissue increases with the infiltration by immune cells. Here, to quantify the MPO activity, the sections of the distal colon in the inflamed area were isolated and homogenized in hexadecyltrimethylammonium bromide buffer (0.5% hexadecyltrimethylammonium bromide in 50 mM potassium phosphate buffer, pH 6.0; 50 mg of tissue/ml) using the homogenizer Ika Ultra Turrax Disperser T25 Digital 2 (Sigma-Aldrich, St. Louis, MO). The homogenates were centrifuged (15 minutes, 13,200g, 4°C), and the supernatants were transferred into new test tubes. Seven microliters of supernatant was pipetted on a 96-well plate, in triplicates, and 200 µl of 50 mM potassium phosphate buffer (pH 6.0) containing 0.167 mg/ml O-dianisidine hydrochloride and 0.05 µl of 1% hydrogen peroxide was added. The absorbance was measured at 450 nm after 30 and 60 seconds (iMARK Microplate Reader; Bio-Rad, Hercules, CA). The obtained results were expressed in milliunits per gram of wet tissue. A unit of MPO activity was defined as that converting 1 μmol of hydrogen peroxide to water in 1 minute at room temperature.
Sections of the distal colon were stapled flat, mucosal side up, onto cardboard strips and fixed in Zamboni’s fixative (20 g of paraformaldehyde mixed with 150 ml of picric acid, heated gently for 2 hours, clarified by 2.52 g of sodium hydroxide in 100 ml of water, and added phosphate-buffered saline to 500 ml). Specimens then were dehydrated, embedded in paraffin, sectioned at 5 µm, and mounted onto slides. The fragments of colon were stained with hematoxylin and eosin and examined using a Motic AE31 microscope (Motic AE31 microscope; Ted Pella, Vendelső, Sweden). The photographs were taken using a digital imaging system consisting of a digital camera (Moticam 2300; Ted Pella) and image analysis software (Motic Images Plus 2.0; Motic Microscopes, Wetzlar, Germany).
A microscopic total damage score was based on the following parameters: the goblet cell depletion and the crypt abscesses (presence = 1 or absence = 0) and the damage of mucosa, thickness of muscle layer, and immune cell infiltration (1–3; 1 = normal, 2 = moderate, 3 = extensive).
Behavioral Response to Pain.
To assess the antinociceptive action of SCH 221510 in the inflamed mice, colitis was induced by instillation of TNBS on day 0, as described above. The development of inflammation was monitored on days 0–3, and mice with acute colitis were used in the tests. On day 3, animals were treated with SCH 221510. and 15 minutes later, behavioral response to pain, induced by the intracolonic instillation of 1% mustard oil (MO, allyl isothiocyanate) in 70% EtOH in saline (Fichna et al., 2013), was measured. In brief, mice were separated into clear plastic boxes (20 × 20 × 15 cm) and allowed a 5-minute recovery after MO administration. Spontaneous behaviors were then observed and counted for 20 minutes. The behavioral pain responses included licking of the abdomen, stretching the abdomen, squashing of lower abdomen against the floor, and abdominal retraction. Each behavioral pain response was counted as 1.
The relative expression of human NOP was evaluated in forceps biopsy samples containing the intestinal mucosa and submucosa. In total, 44 samples prepared from the human colon biopsies were used. The study population consisted of 15 patients with UC, 15 with CD, and 14 healthy, unrelated controls recruited from January 2011 to July 2012. There were 13 females and 17 males, ages 23–71, mean age 30 ± 10, among patients with IBD, and seven females and seven males, ages 18–82, mean age 64 ± 8, among control subjects. The diagnosis of IBD was assessed according to established clinical criteria using endoscopic, radiologic, and histopathologic criteria. The severity of the disease was graded according to Montreal classification: among patients with UC, there were four with S0, four with S1, three with S2, and four with the S3 category; in patients with CD, there were 12 with B1 and three with the B2 category. In patients with IBD, colonic samples were collected from the inflamed area.
Human studies were approved by the Ethics Committee of the Medical University of Lodz (Poland). All participating subjects gave written, informed consent prior to genetic analysis.
Real-Time Reverse Transcriptase-Polymerase Chain Reaction and Quantification of NOP Expression.
The biopsy specimens were frozen directly after isolation and stored at −70°C until processing. RNA was isolated using the PureLink RNA Mini kit (Life Technologies, Carlsbad, CA), as described previously (Fichna et al., 2012b). In brief, the biopsy specimens were homogenized and supplemented with 1% 2-mercaptoethanol. Homogenate then was centrifuged and loaded onto columns and washed. Finally, the purified total RNA sample was eluted into collection tubes. The purity and quantity of isolated RNA was measured using a dedicated spectrophotometer (BioPhotometer; Eppendorf, Hamburg, Germany). Total RNA (1 μg) was used for cDNA synthesis using a first-strand cDNA synthesis kit (Fermentas; Burlington, ON, Canada). Quantitative analysis was performed using fluorescently labeled TaqMan probes Hs00173471_ml and Hs01003267_ml for human NOP and hypoxanthine-guanine phosphoribosyltransferase (HPRT, endogenous control), respectively (Life Technologies) on Mastercycler S Realplex 4 apparatus (Eppendorf). All experiments were performed in triplicates. The relative amount of mRNA copies was calculated using 2^-ΔCt method. For presentation, relative copy number values were recalculated to number of copies of each studied gene per 1000 copies of HPRT. The mean Ct values for the housekeeping gene (HPRT) in samples from all patients did not alter regardless of the studied group.
All reagents, unless otherwise stated, were purchased from Sigma-Aldrich. SCH 221510 [3-endo-8-[bis(2-methylphenyl)methyl]-3-phenyl-8-azabicyclo [3.2.1]octan-3-ol] and J-113397 [(±)-1-[(3R*,4R*)-1-(cyclooctylmethyl)-3-(hydroxymethyl)-4-piperidinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one] were purchased from Tocris Bioscience (Ellisville, MO).
SCH 221510 and J-113397 were dissolved in dimethyl sulfoxide (DMSO) and further diluted with saline to the final DMSO concentration of 5%. The solution of 5% DMSO in saline alone constituted a vehicle for control groups and had no influence on observed parameters.
SCH 221510 was administered at doses of 0.1 and 1 mg/kg i.p. (twice daily), 3 mg/kg p.o. (twice daily), or 3 mg/kg i.c. (once daily). The NOP antagonist J-113397 was injected at the dose of 12 mg/kg i.p. twice daily 15 minutes before the administration of SCH 221510. J-113397 given alone had no effect on observed parameters.
The results are expressed as mean ± S.E.M. Statistical analysis was performed using Prism 5.0 (GraphPad Software Inc., La Jolla, CA). Analysis of variance followed by Newman-Keuls post-hoc testing was used. P values < 0.05 were considered statistically significant. The Student’s t test with Welch’s correction was applied for comparison of relative NOP mRNA expression levels between control, UC, and CD samples.
SCH 221510 Attenuates TNBS-Induced Colitis after Intraperitoneal Administration.
The intracolonic administration of TNBS in mice induced acute colitis, as shown by increased total macroscopic score and decreased colon length, and ulceration of the intestinal wall (Fig. 1) compared with control animals. The intraperitoneal injection of SCH 221510 at the doses of 0.1 and 1 mg/kg improved macroscopic scores (4.75 ± 0.72 and 3.3 ± 0.72, respectively) in comparison with TNBS-treated mice (6.55 ± 0.76) (Fig. 1A). The MPO activity was comparable in samples collected from all experimental groups, suggesting that SCH 221510 had no influence on MPO activity (Fig. 1B). The ulceration was improved after SCH 221510 treatment, but the observed change was not statistically significant (Fig. 1C). The colon length was shortened in TNBS-treated mice (7.55 ± 0.22 cm) in comparison with control group (9.93 ± 0.11 cm), and SCH 221510 did not influence this parameter (Fig. 1D). Likewise, the thickness of the colon wall was not reduced after SCH 221510 treatment in comparison with TNBS-treated mice (0.77 ± 0.05 versus 0.82 ± 0.08 mm) (data not shown).
SCH 221510 Alleviates TNBS-Induced Colitis after Oral Administration.
The oral administration of SCH 221510 (3 mg/kg twice daily) alleviated TNBS-induced colitis in mice, as shown by significant improvement of the following parameters: the macroscopic score (Fig. 2A), MPO activity (Fig. 2B), and the ulcer score (Fig. 2C), in addition to a nonsignificant change in colon length (Fig. 2D) versus TNBS-treated animals. The thickness of the colon wall was reduced in mice treated with SCH 221510 (0.73 ± 0.06 versus 0.84 ± 0.06 mm for TNBS-treated animals).
Anti-Inflammatory Effect of SCH 221510 Is Blocked by the NOP Antagonist J-113397.
To characterize the role of NOP in the anti-inflammatory effect of SCH 221510, a nonpeptide selective NOP antagonist J-113397 was used in coadministration experiments.
The effect of SCH 221510 (3 mg/kg p.o. twice daily) was blocked by J-113397 (12 mg/kg i.p.), as shown by significantly increased macroscopic scores (Fig. 3A) and MPO activity (Fig. 3B) compared with animals treated with SCH 221510 alone. Colon length (Fig. 3C), ulcer score (Fig. 3D), and colon thickness (1.21 ± 0.11, 0.63 ± 0.03, and 0.92 ± 0.06 mm for TNBS, SCH 221510 + TNBS, and J-113397 + SCH 221510 + TNBS, respectively) were also worsened by coadministration of SCH 221510 with J-113397.
Orally Administered SCH 221510 Decreases Microscopic Damage in the Colon.
The sections of the distal colon, stained with hematoxylin and eosin, were used to establish microscopic inflammation score. In the control group, intact epithelium, regular muscle architecture, and absence of edema were observed (Fig. 4A). The colons of TNBS-treated mice were characterized by loss of mucosal architecture, thickening of muscle layer, infiltration of immune cells, and presence of crypt abscesses (Fig. 4B). Oral administration of SCH 221510 (3 mg/kg twice daily) significantly improved microscopic scores (Fig. 4C); this effect was blocked by the NOP antagonist J-113397 (12 mg/kg i.p.; Fig. 4D).
The microscopic score was then calculated for all samples analyzed. The total microscopic score was increased in sections of the colon collected from TNBS-treated mice compared with control group (8.00 ± 0.35 versus 3.75 ± 0.48, respectively). The oral administration of SCH 221510 (3 mg/kg twice daily) significantly decreased the total microscopic score (5.30 ± 0.25) versus TNBS-treated mice. The blockage of NOP receptors by J-113397 worsened the microscopic score (9.10 ± 0.29) compared with SCH 221510-treated mice.
SCH 221510 Has No Anti-Inflammatory Effect after Intracolonic Administration.
SCH 221510 injected intracolonically at a dose of 3 mg/kg once daily had no anti-inflammatory effect in TNBS-treated mice, as shown by the macroscopic damage score (5.49 ± 0.71 and 4.67 ± 0.92 for SCH 221510 and TNBS-treated mice, respectively, Fig. 5A), MPO activity (7.46 ± 1.04 and 8.43 ± 1.23, respectively, Fig. 5B), and the ulcer score (1.75 ± 0.14 and 1.67 ± 0.17, respectively, Fig. 5C). The colon wall was thicker in TNBS-treated mice versus control animals (1.16 ± 0.09 versus 0.6 ± 0.07 mm, respectively) and was not improved after SCH 221510 administration (1.12 ± 0.03 mm). Similarly, the colon length after SCH 221510 treatment did not change compared with TNBS-treated mice (Fig. 5D).
Orally Administered SCH 221510 Has Potent Antinociceptive Action.
To assess the antinociceptive effect of SCH 221510 during inflammation, the behavioral pain response test was performed in mice on day 3 after TNBS instillation. Oral administration of SCH 221510 (3 mg/kg) significantly decreased the number of abdominal pain responses induced by intracolonic administration of MO in TNBS-treated mice (22.75 ± 2.87 versus 55.00 ± 1.29, for SCH 221510 versus vehicle-treated mice, respectively; Fig. 6), indicating a potent antinociceptive action of SCH 221510 during an acute inflammation.
Relative NOP mRNA Expression in Patients with IBD.
Real-time reverse transcriptase-polymerase chain reaction analysis of colon samples collected from patients with UC and CD and from healthy volunteers showed that NOP mRNA expression was decreased in patients with IBD compared with control subjects (29.47 ± 8.42 for UC and 6.31 ± 2.10 for patients with CD versus 35.79 ± 14.38 relative units in healthy controls; Fig. 7). NOP were expressed in 71% of control samples, 38% of patients with UC, and 21% of patients with CD.
In the present study, we showed that a selective nonpeptide NOP agonist SCH 221510, administered intraperitoneally and orally, produced a potent anti-inflammatory effect in the well-established animal model of IBD induced by intracolonic administration of TNBS. Moreover, our data suggest that this effect was mediated exclusively by NOP, as it was completely reversed by a selective NOP antagonist J-113397. Finally, SCH 221510 produced analgesia in TNBS-treated mice, which displayed symptoms of acute colitis.
The components of the endogenous nociceptin system are widely distributed in the central and peripheral nervous systems and in peripheral tissues (Osinski et al., 1999). The role of nociceptin and NOP receptors is multidirectional; they participate in a broad range of physiologic and behavioral functions, including locomotion, learning, stress, anxiety, and pain processing (Reinscheid et al., 2000; Lambert, 2008). In the GI tract, nociceptin and NOP receptors are localized in nervous, muscle, and immune cells, and therefore, they seem indispensable for maintaining homeostasis (Calò et al., 2000). However, the precise description of the nociceptin and NOP function in the GI tract has not been provided so far (Sobczak et al., 2013).
In our study, we observed a decreased level of the relative NOP mRNA expression in biopsies collected from the patients with IBD in comparison with healthy subjects. Moreover, we found that NOP expression was significantly reduced in patients with CD, and there was only a nonsignificant decrease in NOP mRNA level in patients with UC versus control subjects, which likely points to different roles of NOP in the course of these two diseases and possibly differential association with Th1- and Th2-dependent pathways, which are selectively activated depending on the disease type. Our observation also indicates that dysregulation of the nociceptin system may be crucial in the development of IBD and gives a translational basis for a more detailed characterization.
Our demonstration is in line with the study of Fiset et al. (2003), who first suggested a cross-talk between the immune system and the nociceptin system in human tissues. They showed that the endogenous nociceptin levels were elevated in human polymorphonuclear neutrophils isolated from synovial fluids of patients with arthritis (rheumatoid arthritis, osteoarthritis, gouty arthritis). Furthermore, freshly isolated polymorphonuclear neutrophils expressed and secreted nociceptin following degranulation, suggesting that preformed nociceptin molecules were stored in granules, rather than synthesized de novo. The data obtained by Fiset et al. (2003) suggested that nociceptin and NOP may directly participate in immunomodulation and may constitute a good alternative in the treatment of diseases with inflammatory and nociceptive components in which pain is the major symptom, such as IBD.
In our experiments in the mouse model of TNBS-induced colitis, we applied a wide range of doses of SCH 221510 (0.1–3.0 mg/kg twice daily) and observed an anti-inflammatory action of the NOP agonist at all doses tested after intraperitoneal and oral administration. Recently, Petrella et al. (2013) characterized the peripheral effect of nociceptin in low and high doses and its influence on TNBS-induced colitis. The low doses of nociceptin (0.02 and 0.2 nmol/kg i.p. twice daily) improved colitis in rats, and the effect was completely reversed by the selective NOP antagonist N-(Bn)Gly-Gly-Gly-Phe-Thr-Gly-Ala-Arg-Lys-Ser-Ala-Arg-Lys-Arg-Lys-Asn-Gln-NH2 (UFP-101). Moreover, the MPO activity and interleukin-1β levels were significantly lower in nociceptin-treated rats versus TNBS alone–treated animals. Surprisingly, the higher doses (100–1000-fold) of nociceptin significantly worsened colitis, but this atypical, dual mechanism action has not been further refined. However, it has been suggested that nociceptin given exogenously has an additional effect, mediated not only by NOP receptors but also by other molecular targets and/or pathways. This is in contrast to the potent anti-inflammatory action of SCH 221510, which is mediated exclusively by NOP receptors. Taken together, these observations suggest that the involvement of the nociceptin system may be critical for IBD therapy, and the ligands that selectively bind to NOP receptors, such as SCH 221510, may become promising templates for novel anti-IBD therapies. However, further studies may be necessary to elucidate whether the CNS, GI tract, and/or immune system are the likely sites of action for nociceptin in colitis.
The major symptom of IBD is abdominal pain, which is described as a cramping sensation, varying in intensity and with exacerbations (Srinath et al., 2012). There are two types of abdominal pain: somatic, which is musculoskeletal; and visceral, caused by stretching of the viscera by obstruction or widely affected inflammation. Nociceptin has a potent antinociceptive effect in the abdomen, as shown in the acetic acid–induced abdominal pain model in mice (Himukashi et al., 2006). This suggests that the activation of NOP receptors is crucial for abdominal nociceptive signaling and that the NOP ligands may alleviate GI tract–related pain (Himukashi et al., 2006). Recently, Agostini et al. (2009) confirmed the antinociceptive action of nociceptin, characterized by the changes in the visceromotor response to colorectal distension in the rat model of TNBS-induced colitis. Of note, the antinociception produced by nociceptin was not mediated by NOP localized in the CNS. Furthermore, in the rat model of colitis induced by acute stress, activation of the endogenous nociceptin system was not observed after nociceptin administration, but the decreased visceromotor response to colorectal distension was present, indicating the complexity of nociceptin system action.
In our study, the oral administration of SCH 221510 at a dose 3 mg/kg decreased the number of pain responses in a well-established animal model of abdominal pain, induced by intracolonic instillation of MO solution. Importantly, the antinociceptive action of SCH 221510 was observed in mice with acute inflammation, suggesting a dual, anti-inflammatory and antinociceptive effect of SCH 221510 in colitis and further confirming its possible application for anti-IBD treatment.
In conclusion, based on the results obtained in our study, we suggest that the nociceptin system is involved in the etiology of IBD in humans and propose the NOP receptors to be a promising target for the IBD treatment. Furthermore, based on animal models of colitis and abdominal pain, we prove that a selective nonpeptide NOP agonist, SCH 221510, is a valuable drug candidate for the anti-IBD therapy.
Participated in research design: Fichna, Storr, Kordek, Malecka-Panas.
Conducted experiments: Sobczak, Mokrowiecka, Cygankiewicz, Zakrzewski, Sałaga, Fichna.
Performed data analysis: Sobczak, Mokrowiecka, Cygankiewicz, Zakrzewski, Sałaga, Fichna.
Wrote or contributed to the writing of the manuscript: Sobczak, Krajewska, Fichna.
- Received September 20, 2013.
- Accepted December 16, 2013.
This work was supported by the Iuventus Plus program of the Polish Ministry of Science and Higher Education [Grants 0119/IP1/2011/71 and IP2012 010772] (to J.F.) and the Medical University of Lodz [Grant 502-03/1-156-02/502-14-141] (to M.So.).
- Crohn’s disease
- central nervous system
- dimethyl sulfoxide
- hypoxanthine-guanine phosphoribosyltransferase
- inflammatory bowel diseases
- mustard oil (allyl isothiocyanate)
- nociceptin receptor
- SCH 221510
- 3-endo-8-[bis(2-methylphenyl)methyl]-3-phenyl-8-azabicyclo [3.2.1]octan-3-ol
- 2,4,6-trinitrobenzenesulfonic acid
- ulcerative colitis
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics