Vanilloid receptor-1 containing primary sensory neurones mediate dextran sulphate sodium induced colitis in rats

Involvement of the cannabimimetic compound, N-palmitoyl-ethanolamine, in inflammatory and neuropathic conditions: review of the available pre-clinical data, and first human studies

The endogenous cannabimimetic compound, and anandamide analogue, N-palmitoyl-ethanolamine (PEA), was shown to exert potent anti-inflammatory and analgesic effects in experimental models of visceral, neuropathic and inflammatory pain by acting via several possible mechanisms. However, only scant data have been reported on the regulation of PEA levels during pathological conditions in animals or, particularly, humans. We review the current literature on PEA and report the results of three separate studies indicating that its concentrations are significantly increased during three different inflammatory and neuropathic conditions, two of which have been assessed in humans, and one in a mouse model. In patients affected with chronic low back pain, blood PEA levels were not significantly different from those of healthy volunteers, but were significantly and differentially increased (1.6-fold, P<0.01, N=10 per group) 30 min following an osteopathic manipulative treatment. In the second study, the paw skin levels of PEA in mice with streptozotocin-induced diabetic neuropathic pain were found to be significantly higher (1.5-fold, P<0.005, N=5) than those of control mice. In the third study, colonic PEA levels in biopsies from patients with ulcerative colitis were found to be 1.8-fold higher (P<0.05, N=8-10) than those in healthy subjects. These heterogeneous data, together with previous findings reviewed here, substantiate the hypothesis that PEA is an endogenous mediator whose levels are increased following neuroinflammatory or neuropathic conditions in both animals and humans, possibly to exert a local anti-inflammatory and analgesic action.

HCl-activated neural and epithelial vanilloid receptors (TRPV1) in cat esophageal mucosa

To test whether transient receptor potential channel vanilloid subfamily member-1 (TRPV1) mediates acid-induced inflammation in the esophagus, a tubular segment of esophageal mucosa was tied at both ends, forming a sac. The sac was filled with 0.01 N HCl (or Krebs buffer for control) and kept in oxygenated Krebs buffer at 37 degrees C. The medium around the sac (supernatant) was collected after 3 h. Supernatant of the HCl-filled sac abolished contraction of esophageal circular muscle strips in response to electric field stimulation. Contraction was similarly abolished by supernatant of mucosal sac filled with the TRPV1 agonist capsaicin (10(-6) M). These effects were reversed by the selective TRPV1 antagonist 5'-iodoresiniferatoxin (IRTX) and by the platelet-activating factor (PAF) receptor antagonist CV9388. Substance P and CGRP levels in mucosa and in supernatant increased in response to HCl, and these increases were abolished by IRTX and by tetrodotoxin (TTX) but not affected by CV9388, indicating that substance P and CGRP are neurally released and PAF independent. In contrast, the increase in PAF was blocked by IRTX but not by TTX. Presence of TRPV1 receptor was confirmed by RT-PCR and by Western blot analysis in whole mucosa and in esophageal epithelial cells enzymatically isolated and sorted by flow cytometry or immunoprecipitated with cytokeratin antibodies. In epithelial cells PAF increased in response to HCl, and the increase was abolished by IRTX. We conclude that HCl-induced activation of TRPV1 receptors in esophageal mucosa causes release of substance P and CGRP from neurons and release of PAF from epithelial cells.

Balsalazine decreases intestinal mucosal permeability of dextran sulfate sodium-induced colitis in mice

AIM

To investigate the effect of balsalazine treatment on intestinal mucosal permeability in dextran sulfate sodium (DSS)-induced colitis and to determine the mechanism of the balsalazine-induced changes.

METHODS

Experimental colitis was induced in C57BL/6J mice by the administration of 5% DSS. Balsalazine was administered intragastrically at doses of 42, 141, and 423 mg/kg. The disease activity index (DAI) score was evaluated and colon tissue was collected for the assessment of histological changes. The amount of malondialdehyde (MDA) in the colon was determined, along with the activity of myeloperoxidase (MPO), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Mucosa from the small intestine was collected to determine the levels of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. The mucosa was ultrastructurally examined with transmission electron microscopy and intestinal permeability was assayed using Evans blue.

RESULTS

Balsalazine was found to reduce the DAI score and the histological index (HI) score, decrease the MDA content and the activity of MPO, and increase the activity of SOD and GSH-Px in colitis mice. At the same time, balsalazine ameliorated microvillus and tight junction structure, resulting in a decrease in the amount of Evans blue permeating into the intestinal wall and the levels of TNF-alpha and IFN-gamma in colitis mice.

CONCLUSION

In colitis mice, the anti-colitis effect of balsalazine results in a decrease in intestinal mucosal permeability. The mechanism of this effect is partly associated with balsalazine's antioxidative and anti-inflammatory effects.Acta Pharmacologica Sinica (2009) 30: 987-993; doi: 10.1038/aps.2009.77.

The pharmacological challenge to tame the transient receptor potential vanilloid-1 (TRPV1) nocisensor

The transient receptor potential vanilloid-1 (TRPV1) cation channel is a receptor that is activated by heat (>42 degrees C), acidosis (pH<6) and a variety of chemicals among which capsaicin is the best known. With these properties, TRPV1 has emerged as a polymodal nocisensor of nociceptive afferent neurones, although some non-neuronal cells and neurones in the brain also express TRPV1. The activity of TRPV1 is controlled by a multitude of regulatory mechanisms that either cause sensitization or desensitization of the channel. As many proalgesic pathways converge on TRPV1 and this nocisensor is upregulated and sensitized by inflammation and injury, TRPV1 is thought to be a central transducer of hyperalgesia and a prime target for the pharmacological control of pain. As a consequence, TRPV1 agonists causing defunctionalization of sensory neurones and a large number of TRPV1 blockers have been developed, some of which are in clinical trials. A major drawback of many TRPV1 antagonists is their potential to cause hyperthermia, and their long-term use may carry further risks because TRPV1 has important physiological functions in the peripheral and central nervous system. The challenge, therefore, is to pharmacologically differentiate between the physiological and pathological implications of TRPV1. There are several possibilities to focus therapy specifically on those TRPV1 channels that contribute to disease processes. These approaches include (i) site-specific TRPV1 antagonists, (ii) modality-specific TRPV1 antagonists, (iii) uncompetitive TRPV1 (open channel) blockers, (iv) drugs interfering with TRPV1 sensitization, (v) drugs interfering with intracellular trafficking of TRPV1 and (vi) TRPV1 agonists for local administration.

Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain

OBJECTIVE

The capsaicin receptor TRPV1 (transient receptor potential vanilloid type-1) may play an important role in visceral pain and hypersensitivity states. In irritable bowel syndrome (IBS), abdominal pain is a common and distressing symptom where the pathophysiology is still not clearly defined. TRPV1-immunoreactive nerve fibres were investigated in colonic biopsies from patients with IBS, and this was related to abdominal pain.

METHODS

Rectosigmoid biopsies were collected from 23 IBS patients fulfilling Rome II criteria, and from 22 controls. Abdominal pain scores were recorded using a validated questionnaire. TRPV1-, substance P- and neuronal marker protein gene product (PGP) 9.5-expressing nerve fibres, mast cells (c-kit) and lymphocytes (CD3 and CD4) were quantified, following immunohistochemistry with specific antibodies. The biopsy findings were related to the abdominal pain scores.

RESULTS

A significant 3.5-fold increase in median numbers of TRPV1-immunoreactive fibres was found in biopsies from IBS patients compared with controls (p<0.0001). Substance P-immunoreactive fibres (p = 0.01), total nerve fibres (PGP9.5) (p = 0.002), mast cells (c-kit) (p = 0.02) and lymphocytes (CD3) (p = 0.03) were also significantly increased in the IBS group. In multivariate regression analysis, only TRPV1-immuno-reactive fibres (p = 0.005) and mast cells (p = 0.008) were significantly related to the abdominal pain score.

CONCLUSIONS

Increased TRPV1 nerve fibres are observed in IBS, together with a low-grade inflammatory response. The increased TRPV1 nerve fibres may contribute to visceral hypersensitivity and pain in IBS, and provide a novel therapeutic target.

Neuromuscular changes in a rat model of colitis

Intracolonic administration of Trichinella spiralis larvae in rats causes colitis with features similar to ulcerative colitis, notably with inflammation predominantly limited to the colonic mucosa. Our aim was to characterize the functional and neurochemical changes occurring within the myenteric (MP) and submucosal plexuses (SMP) during T. spiralis-induced colitis. Infected rats had decreased body weight, altered stool consistency and elevated myeloperoxidase activity, 6 and 14 days post-infection (PI). Responses to acetylcholine and KCl in circular muscle strips were reduced in infected tissues, demonstrating an impairment of contractility. In addition, there was a decrease in spontaneous motor activity and reduced sensitivity to the nitric oxide synthase (NOS) inhibitor L-NOArg, corresponding with a significant reduction in NOS immunoreactive neurons in the MP of infected animals. T. spiralis did not alter the total number of myenteric or submucosal neurons. Substance P innervation of submucosal blood vessels was reduced after infection, as were submucosal calretinin and calbindin immunoreactive neurons. No changes in choline acetyltransferase and calcitonin gene-related peptide immunoreactivity were observed. T. spiralis-induced colitis causes profound neuromuscular adaptations. The reduction in NOS neurons appears to underlie changes in motility.

Protective roles of alpha-calcitonin and beta-calcitonin gene-related peptide in spontaneous and experimentally induced colitis

Calcitonin gene-related peptide (CGRP) is thought to be involved in the regulation of gastric and mesenteric blood flow, in the control of gastric acid secretion and in the modulation of intestinal motility, yet the precise physiological roles of CGRP remain to be elucidated. To further examine the role(s) of CGRP in gastrointestinal function, we examined mutant mice lacking alphaCGRP or betaCGRP expression. Mutant mice did not demonstrate any overt phenotypic changes, yet exhibited a spontaneous, adult-onset colitis and increased colonic damage using a dextran sulfate sodium model of experimental colitis. Surprisingly, mice lacking betaCGRP show no obvious alterations in CGRP immunoreactivity in the gut, accompanied by an increase in alphaCGRP messenger RNA expression, suggesting an adaptive mechanism to compensate for the lack of betaCGRP. These data demonstrate that both alphaCGRP and betaCGRP play a protective role in the generation of spontaneous colitis, supporting a role for both extrinsic and intrinsic CGRP-containing neurons.

Acute colitis enhances responsiveness of lumbosacral spinal neurons to colorectal distension in rats

Aim of this study was to examine excitability and responsiveness of lumbosacral spinal neurons to colorectal distension (CRD) in rats with colitis induced by dextran sulphate sodium (DSS). Extracellular potentials of single L6-S2 spinal neurons were recorded in pentobarbital anesthetized and paralyzed rats. Results showed that 40/154 (26%) and 53/156 (34%) neurons responded to noxious CRD (80 mmHg, 20 s) in DSS-treated and control animals, respectively. Neurons with long-lasting and low-threshold excitatory responses to CRD were more frequently encountered in DSS-treated than in control groups (P < 0.05). The mean maximal excitatory responses of neurons to noxious CRD in DSS-treated animals were significantly greater and the duration of responses was longer than those in control animals (P < 0.05). It was suggested that lumbosacral spinal neurons with colorectal input had increased excitability and responsiveness following colitis, which might play an important role in development of colonic hypersensitivity and viscerosomatic referred pain.

The role of transient receptor potential vanilloid 1 in mechanical and chemical visceral hyperalgesia following experimental colitis

The transient receptor potential vanilloid 1 receptor (TRPV1) is an important nociceptor involved in neurogenic inflammation. We aimed to examine the role of TRPV1 in experimental colitis and in the development of visceral hypersensitivity to mechanical and chemical stimulation. Male Sprague-Dawley rats received a single dose of trinitrobenzenesulfonic acid (TNBS) in the distal colon. In the preemptive group, rats received the TRPV1 receptor antagonist JYL1421 (10 mumol/kg, i.v.) or vehicle 15 min prior to TNBS followed by daily doses for 7 days. In the post-inflammation group, rats received JYL1421 daily for 7 days starting on day 7 following TNBS. The visceromotor response (VMR) to colorectal distension (CRD), intraluminal capsaicin, capsaicin vehicle (pH 6.7) or acidic saline (pH 5.0) was assessed in all groups and compared with controls and naïve rats. Colon inflammation was evaluated with H&E staining and myeloperoxidase (MPO) activity. TRPV1 immunoreactivity was assessed in the thoraco-lumbar (TL) and lumbo-sacral (LS) dorsal root ganglia (DRG) neurons. In the preemptive vehicle group, TNBS resulted in a significant increase in the VMR to CRD, intraluminal capsaicin and acidic saline compared the JYL1421-treated group (P<0.05). Absence of microscopic colitis and significantly reduced MPO activity was also evident compared with vehicle-treated rats (P<0.05). TRPV1 immunoreactivity in the TL (69.1+/-4.6%) and LS (66.4+/-4.2%) DRG in vehicle-treated rats was increased following TNBS but significantly lower in the preemptive JYL1421-treated group (28.6+/-3.9 and 32.3+/-2.3 respectively, P<0.05). JYL1421 in the post-inflammation group improved microscopic colitis and significantly decreased the VMR to CRD compared with vehicle (P<0.05, >/=30 mm Hg) but had no effect on the VMR to chemical stimulation. TRPV1 immunoreactivity in the TL and LS DRG was no different from vehicle or naïve controls. These results suggest an important role for TRPV1 channel in the development of inflammation and subsequent mechanical and chemical visceral hyperalgesia.

TRPV1 in colitis: is it a good or a bad receptor?--a viewpoint

The role of the transient receptor potential vanilloid-1 (TRPV1) has been repeatedly investigated in animal models of inflammation. The present issue of Neurogastroenterology and Motility includes another report on this issue and, not unexpectedly, many questions on the precise role of TRPV1 receptors in inflammation remain unanswered. This Editorial Viewpoint discusses the present knowledge on TRPV1 receptor involvement in intestinal inflammation and discusses the question whether the TRPV1 has to be regarded as the good or the bad receptor in this context. Since TRPV1 activation turns out being a valuable approach, translation of this knowledge to human disease is highly recommended.

A potential role for the vanilloid receptor TRPV1 in the therapeutic effect of curcumin in dinitrobenzene sulphonic acid-induced colitis in mice

A protective role of the transient potential vanilloid receptor 1 (TRPV1) in intestinal inflammation induced by dinitrobenzene sulphonic acid (DNBS) has been recently demonstrated. Curcumin, the major active component of turmeric, is also able to prevent and ameliorate the severity of the damage in DNBS-induced colitis. We evaluated the possibility that curcumin (45 mg kg(-1) day p.o. for 2 days before and 5 days after the induction of colitis) was able to reduce DNBS-induced colitis in mice, by acting as a TRPV1 agonist. Macroscopic damage score, histological damage score and colonic myeloperoxidase (MPO) activity were significantly lower (by 71%, 65% and 73%, respectively; P < 0.01), in animals treated with curcumin compared with untreated animals. Capsazepine (30 mg kg(-1), i.p.), a TRPV1 receptor antagonist, completely abolished the protective effects of curcumin. To extend these data in vitro, Xenopus oocytes expressing rat TRPV1 were examined. Capsaicin-evoked currents (3.3 micromol L(-1)) disappeared subsequent either to removal of the agonist or subsequent to the addition of capsazepine. However, curcumin (30 micromol L(-1)) was ineffective both as regard direct modification of cell membrane currents and as regard interference with capsaicin-mediated effects. As sensitization of the TRPV1 receptor by mediators of inflammation in damaged tissues has been shown previously, our results suggest that in inflamed, but not in normal tissue, curcumin can interact with the TRPV1 receptor to mediate its protective action in DNBS-induced colitis.

Stimulation of neuronal receptors, neuropeptides and cytokines during experimental oil of mustard colitis

Oil of mustard (OM), administered intracolonically, produces severe colitis in mice that is maximized within 3 days. The purpose of this study was to characterize the cytokine response, and to establish expression patterns of enteric neuronal mediators and neuronal receptors affected during active colitis. We measured the changes in the mRNA levels for neuronal receptors and mediators by real-time PCR, and cytokine and chemokine protein levels in the affected tissue. Significant increases in neuronal receptors, such as transient receptor potential A1 (TRPA1), cannabinoid type 1 receptor, neurokinin 1 receptor (NK1R) and delta-opioid receptor; prokineticin-1 receptor; and soluble mediators, such as prodynorphin, proenkephalin1, NK1, prokineticin-1 and secretory leukocyte protease inhibitor, occurred. Significant increases in cytokines, such as interleukin (IL)-1beta, IL-6 and granulocyte macrophage colony stimulating factor (GM-CSF), and in chemokines, such as macrophage chemotactic protein 1 (MCP-1), macrophage inflammatory protein 1 (MIP-1alpha) and Kupffer cell derived chemokine (KC), were detected, with no changes in T-cell-derived cytokines. Furthermore, immunodeficient C57Bl/6 RAG2(-/-) mice exhibited OM colitis of equal severity as seen in wt C57Bl/6 and CD-1 mice. The results demonstrate rapidly increased levels of mRNA for neuronal receptors and soluble mediators associated with pain and inflammation, and increases in cytokines associated with macrophage and neutrophil activation and recruitment. Collectively, the data support a neurogenic component in OM colitis coupled with a myeloid cell-related, T- and B-cell-independent inflammatory component.

Therapeutic treatment of experimental colitis with regulatory dendritic cells generated with vasoactive intestinal peptide

BACKGROUND & AIMS

Crohn's disease is a chronic debilitating disease characterized by severe T helper cell (Th)1-driven inflammation of the colon partially caused by a loss of immune tolerance against mucosal antigens. The use of regulatory dendritic cells (DCs) with the capacity to induce regulatory T cells has been proposed recently for the treatment of Crohn's disease in a strategy to restore immune tolerance. Vasoactive intestinal peptide is an immunomodulatory neuropeptide that induces regulatory DCs. The aim of this study was to investigate the therapeutic effect of vasoactive intestinal peptide-induced regulatory DCs (DC(VIP)) in a murine model of colitis.

METHODS

We examined the therapeutic action of DC(VIP) in the colitis induced by intracolonic administration of trinitrobenzene sulfonic acid, evaluating diverse clinical signs of the disease including weight loss, diarrhea, colitis, and histopathology. We also investigated the mechanisms involved in the potential therapeutic effect of DC(VIP), such as inflammatory cytokines and chemokines, Th1-type response, and the generation of regulatory T cells.

RESULTS

DC(VIP) injection significantly ameliorated the clinical and histopathologic severity of colitis, abrogating body weight loss, diarrhea, and inflammation, and increasing survival. The therapeutic effect was associated with down-regulation of both inflammatory and Th1-driven autoimmune response, by regulating a wide spectrum of inflammatory mediators directly through activated macrophages, and by generating interleukin-10-secreting regulatory T cells with suppressive capacity on autoreactive T cells.

CONCLUSIONS

The possibility to generate/expand ex vivo regulatory DC(VIP) opens new therapeutic perspectives for the treatment of Crohn's disease in human beings, and may minimize the dependence on nonspecific immunosuppressive drugs used currently for autoimmune disorders.

Endocannabinoid overactivity and intestinal inflammation

Cannabinoid receptors of type 1 and 2 (CB(1) and CB(2)), endogenous ligands that activate them (endocannabinoids), and mechanisms for endocannabinoid biosynthesis and inactivation have been identified in the gastrointestinal system. Activation of CB(1 )receptors by endocannabinoids produces relaxation of the lower oesophageal sphincter and inhibition of gastric acid secretion, intestinal motility, and fluid stimulated secretion. However, stimulation of cannabinoid receptors impacts on gastrointestinal functions in several other ways. Recent data indicate that the endocannabinoid system in the small intestine and colon becomes over stimulated during inflammation in both animal models and human inflammatory disorders. The pathological significance of this "endocannabinoid overactivity" and its possible exploitation for therapeutic purposes are discussed here.

Agonists of cannabinoid receptor 1 and 2 inhibit experimental colitis induced by oil of mustard and by dextran sulfate sodium

Oil of mustard (OM) is a potent neuronal activator that is known to elicit visceral hyperalgesia when given intracolonically, but the full extent to which OM is also proinflammatory in the gastrointestinal tract is not known. We have previously shown that male CD-1 mice given a single administration of 0.5% OM develop a severe colitis that is maximum at day 3 and that gradually lessens until essentially absent by day 14. OM-induced neuronal stimulation is reported to be reduced by cannabinoid agonists, and cannabinoid receptor 1 (CB1R)-/- mice have exacerbated experimental colitis. Therefore, we examined the role of cannabinoids in this OM-induced 3-day model of colitis in CD-1 mice and in a 7-day dextran sulfate sodium (DSS) colitis model in BALB/c mice. In OM colitis, the CB1R-selective agonist ACEA and the CB2R-selective agonist JWH-133 reduced (P < 0.05) colon weight gain (means +/- SE; 82 +/- 13% and 47 +/- 15% inhibition, respectively), colon shrinkage (98 +/- 24% and 42 +/- 12%, respectively), colon inflammatory damage score (49 +/- 11% and 40 +/- 12%, respectively), and diarrhea (58 +/- 12% and 43 +/- 11%, respectively). Histological damage was similarly reduced by these treatments. Likewise, CBR agonists attenuated DSS colitis, albeit at higher doses; ACEA at 10 mg/kg, twice daily, inhibited (P < 0.05) macroscopic and microscopic scores (46 +/- 9% and 63 +/- 7%, respectively); whereas 20 mg/kg, twice daily, of JWH-133 was required to diminish (P < 0.05) macroscopic and microscopic scores (29 +/- 7% and 43 +/- 5%, respectively). CB1R and CB2R immunostaining of colon sections revealed that CB1R in enteric neurons was more intense in colitic vs. control mice; however, CB1R was also increased in the endothelial layer in OM colitis only. CB2R immunostaining was more marked in infiltrated immune cells in OM colitis. These findings validate the OM colitis model with respect to the DSS model and provide strong support to the emerging idea that cannabinoid receptor activation mediates protective mechanisms in experimental colitis. The demonstration of CB1R agonist effects in colitis support the neurogenic nature of the OM-induced colitis model and reinforce the importance of neuronal activation in intestinal inflammation.

Therapeutic effect of urocortin and adrenomedullin in a murine model of Crohn's disease

BACKGROUND AND AIMS

Urocortin 1 (UCN) and adrenomedullin (AM) are two recently discovered neuropeptides that, due to their distribution and binding to receptors in immune cells, have emerged as potential endogenous anti-inflammatory factors. Crohn's disease is a chronic debilitating disease characterised by a Th1 driven severe inflammation of the gastrointestinal tract. This study investigated the therapeutic effect of UCN and AM in a murine model of colitis.

METHODS AND RESULTS

Treatment with UCN or AM ameliorated significantly the clinical and histopathological severity of the inflammatory colitis, abrogating body weight loss, diarrhoea, and inflammation, and increased the survival rate of colitic mice. The therapeutic effect was associated with downregulation of both inflammatory and Th1 driven autoimmune responses, including regulation of a wide spectrum of inflammatory mediators. In addition, partial involvement of interleukin 10 secreting regulatory cells in this therapeutic effect was demonstrated. Importantly, UCN or AM treatments were therapeutically effective in established colitis and avoided recurrence of the disease.

CONCLUSIONS

This work identifies UCN and AM as two potent anti-inflammatory factors with the capacity to deactivate the intestinal inflammatory response and restore mucosal immune tolerance at multiple levels. Consequently, both peptides represent novel multistep therapeutic approaches for the treatment of Crohn's disease and other Th1 mediated inflammatory diseases.

Therapeutic action of ghrelin in a mouse model of colitis

BACKGROUND & AIMS

Ghrelin is a novel growth hormone-releasing peptide with potential endogenous anti-inflammatory activities ameliorating some pathologic inflammatory conditions. Crohn's disease is a chronic debilitating disease characterized by severe T helper cell (Th)1-driven inflammation of the colon. The aim of this study was to investigate the therapeutic effect of ghrelin in a murine model of colitis.

METHODS

We examined the anti-inflammatory action of ghrelin in the colitis induced by intracolonic administration of trinitrobenzene sulfonic acid. Diverse clinical signs of the disease were evaluated, including weight loss, diarrhea, colitis, and histopathology. We also investigated the mechanisms involved in the potential therapeutic effect of ghrelin, such as inflammatory cytokines and chemokines, Th1-type response, and regulatory factors.

RESULTS

Ghrelin ameliorated significantly the clinical and histopathologic severity of the trinitrobenzene sulfonic acid-induced colitis; abrogating body weight loss, diarrhea, and inflammation; and increasing survival. The therapeutic effect was associated with down-regulation of both inflammatory and Th1-driven autoimmune response through the regulation of a wide spectrum of inflammatory mediators. In addition, a partial involvement of interluekin-10/transforming growth factor-beta1-secreting regulatory T cells in this therapeutic effect was demonstrated. Importantly, the ghrelin treatment was therapeutically effective in established colitis and avoided the recurrence of the disease.

CONCLUSIONS

Our data demonstrate novel anti-inflammatory actions for ghrelin in the gastrointestinal tract, ie, the capacity to deactivate the intestinal inflammatory response and to restore mucosal immune tolerance at multiple levels. Consequently, ghrelin administration represents a novel possible therapeutic approach for the treatment of Crohn's disease and other Th1-mediated inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis.

Transient receptor potential vanilloid 1-immunopositive neurons in the mouse are more prevalent within colon afferents compared to skin and muscle afferents

Previous studies in our laboratories found that isolectin B(4)(IB(4))-positive polymodal nociceptors in the mouse do not express transient receptor potential vanilloid 1 (TRPV1), nor does deletion of TRPV1 compromise the ability of these afferents to detect thermal stimuli. Considering that IB(4)-positive afferents account for over 70% of cutaneous nociceptors and that 30-50% of all mouse primary afferents express TRPV1, it is highly likely that many TRPV1-positive fibers project to non-cutaneous structures. To investigate this issue, Alexa Fluor-conjugated wheat germ agglutinin (WGA) or IB(4) was injected into the nerves innervating quadriceps muscle (femoral) or hindlimb skin (saphenous) of male C57Bl/6 mice. Similarly, Alexa Fluor-conjugated cholera toxin-beta was injected subserosally into the distal colon. Spinal ganglia at the appropriate level (L2-3 for saphenous and femoral nerves; L6 for colon) were processed for TRPV1, calcitonin gene-related peptide (CGRP), neurofilament heavy chain (NHF) and IB(4) visualization and examined on a confocal microscope. Colon afferents contained the highest percentage of both TRPV1- and CGRP-positive neurons, followed by femoral (WGA) and saphenous afferents (WGA and IB(4)). In contrast, NHF staining was more prevalent among femoral afferents, followed by saphenous (WGA) and colon afferents. IB(4) binding was observed in very few colon or saphenous (WGA) afferents, with no femoral afferents binding or transporting IB(4). Considering that the largest percentages of TRPV1-positive neurons observed in this study were within visceral and muscle afferent populations (neurons that typically are not subject to noxious temperatures), these results suggest that TRPV1 may not function primarily as a temperature sensor but rather as a detector of protons, vanilloid compounds or through interactions with other membrane proteins.

Cortistatin, an antiinflammatory peptide with therapeutic action in inflammatory bowel disease

Cortistatin is a recently discovered cyclic neuropeptide related to somatostatin that has emerged as a potential endogenous antiinflammatory factor based on its production by, and binding to, immune cells. Crohn's disease is a chronic debilitating disease characterized by severe T helper 1 (Th1)-driven inflammation of the gastrointestinal tract. The aim of this study is to investigate the therapeutic effect of cortistatin in a murine model of colitis. Cortistatin treatment significantly ameliorated the clinical and histopathologic severity of the inflammatory colitis, abrogating body weight loss, diarrhea, and inflammation and increased the survival rate of the colitic mice. The therapeutic effect was associated with down-regulation of inflammatory and Th1-driven autoimmune response, including the regulation of a wide spectrum of inflammatory mediators. In addition, a partial involvement of regulatory IL-10-secreting T cells in this therapeutic effect was demonstrated. Importantly, cortistatin treatment was therapeutically effective in established colitis and avoided the recurrence of the disease. This work identifies cortistatin as an antiinflammatory factor with the capacity to deactivate the intestinal inflammatory response and restore mucosal immune tolerance at multiple levels. Consequently, cortistatin represents a multistep therapeutic approach for the treatment of Crohn's disease and other Th1-mediated inflammatory diseases.

Noradrenergic and cholinergic neural pathways mediate stress-induced reactivation of colitis in the rat

Evidence to date suggests that stress-induced exacerbation or relapse of intestinal inflammation in inflammatory bowel disease requires both activation of the autonomic nervous system and the activation of the immune system by the presence of previously encountered luminal antigens. The aim of the present study was to further explore these associations and to determine the role of the autonomic nervous in modulating the intestinal inflammatory response to stress. Rats healed from an initial dinitrobenzene sulfonic acid-induced colitis were given a non-colitic dose of dinitrobenzene sulfonic acid (dissolved in saline) or 0.9% saline intra-rectally and then subjected to restraint stress. Cardiac sympathovagal balance was assessed by power spectral analysis of heart rate variability data collected from telemetric electrocardiogram recordings before, during and post stress. Only rats that were stressed and received dinitrobenzene sulfonic acid showed an inflammatory relapse characterized by significant macroscopic damage and elevated myeloperoxidase activity associated with a significant infiltration of mucosal and submucosal T lymphocytes. No difference in inflammatory markers was observed in animals that received intra-rectal saline and restraint stress. Rats subjected to stress and intra-rectal dinitrobenzene sulfonic acid demonstrated an increase in sympathetic activity with a nearly four fold increase in LF:HF ratio during stress and a significant increase in heart rate. Shortly after cessation of stress, the LF:HF ratio decreased significantly, returning to baseline levels, however the heart rate remained significantly elevated over baseline levels following stress, but decreased to a level that was significantly lower than during stress. The stress/dinitrobenzene sulfonic acid-induced relapses were preventable by pre-treating rats with hexamethonium (a nicotinic cholinergic ganglion blocking agent) or the co-administration of atropine (a muscarinic cholinoceptor antagonist) and bretylium (a noradrenergic ganglion blocking agent), but was not prevented when either atropine or bretylium were administered alone. This study utilizes an established model of chemically induced colitis that when integrated with stress results in relapsing inflammatory bowel disease. Moreover, this study demonstrates that noradrenergic and cholinergic neural pathways mediate the stress response critical for the relapse of colitis.

Effects of exopolysaccharide-producing probiotic strains on experimental colitis in rats

PURPOSE

Inflammatory bowel disease is suggested to result from a dysregulated immune response toward intestinal microflora, which may be restored by probiotic therapy based on the concept of healthy microflora. Ideal probiotic bacteria may be beneficial in inflammatory bowel disease; however, the mechanism of action and the clinical efficacy of probiotic usage are still unclear. In the present study, the effect of exopolysaccharide producing probiotics was evaluated on an experimental colitis model in rats.

METHODS

Colitis was induced by intracolonic administration of acetic acid. Then, rats were treated daily with two probiotic strains, Lactobacillus delbrueckii subsp. bulgaricus B3 strain (exopolysaccharide of 211 mg/l: high-EPS group) or Lactobacillus delbrueckii subsp. bulgaricus A13 strain (EPS of 27 mg/l: low-EPS group), which were given into the stomach. The non-colitis-fed control group was only treated with high-exopolysaccharide strain. The model-control and control groups were treated only with tap water. Rats were killed after a seven-day treatment period. Disease activity was quantified by use of histologic scores and colonic myeloperoxidase activity, which is a marker of neutrophil infiltration during inflammation.

RESULTS

The enhanced inflammatory response was accompanied by a higher level of myeloperoxidase activity in the colitis group. Histologic scores of colonic damage and myeloperoxidase activity were lower in both probiotic-treated groups compared with those of the colitis control group (P<0.001), although the mentioned scores improved significantly more in the high-EPS group than in the low-EPS group (P<0.001).

CONCLUSIONS

Exopolysaccharide-producing probiotics significantly attenuate experimental colitis, which may be mediated by exopolysaccharide in a dose-dependent manner. Therefore, exopolysaccharide-producing probiotics may be a promising therapeutic role in inflammatory bowel disease.

Gastrointestinal pain in functional bowel disorders: sensory neurons as novel drug targets

Functional bowel disorders (FBDs) are defined by symptoms of gastrointestinal (GI) dysfunction, discomfort and pain in the absence of a demonstrable organic cause. Since the prevalence of FBDs, particularly functional dyspepsia and irritable bowel syndrome, can be as high as 20%, FBDs represent a significant burden in terms of direct healthcare and productivity costs. There is emerging evidence that the discomfort and pain experienced by many FBD patients is due to persistent hypersensitivity of primary afferent neurons, which may develop in response to infection, inflammation or other insults. This concept identifies vagal and spinal sensory neurons as important targets for novel therapies of GI hyperalgesia. Sensory neuron-specific targets can be grouped into three categories: receptors and sensors at the peripheral nerve terminals, ion channels relevant to nerve excitability and conduction and transmitter receptors. Particular therapeutic potential is attributed to targets that are selectively expressed by afferent neurons, such as the transient receptor potential channel TRPV1, acid-sensing ion channels and tetrodotoxin-resistant Na + channels.

Up-regulation of anandamide levels as an endogenous mechanism and a pharmacological strategy to limit colon inflammation

Direct stimulation of cannabinoid CB1 receptors exerts a protective function in animal models of inflammatory bowel diseases (IBDs). However, it is not known whether endocannabinoids are up-regulated during IBDs in animals or humans, nor whether pharmacological elevation of endocannabinoid levels can be exploited therapeutically in these disorders. In this study we addressed these questions. Colon inflammation was induced in mice and rats with 2,4-dinitrobenzene- and 2,4,6-trinitrobenzene sulfonic acids (DNBS and TNBS), respectively. DNBS-treated mice were treated chronically (for 3 or 7 days) with inhibitors of anandamide enzymatic hydrolysis (N-arachidonoyl-serotonin, AA-5-HT) or reuptake (VDM11), 10 or 5 mg/kg, s.c., or with 5-amino-salicilic acid (5-ASA, 1.4 mg/kg, i.r.). Endocannabinoids (anandamide and 2-arachidonoylglycerol, 2-AG) were quantified in mouse colon, or in rat colon mucosa and submucosa, and in bioptic samples from the colon of patients with untreated ulcerative colitis, by liquid chromatography-mass spectrometry. A strong elevation of anandamide, but not 2-AG, levels was found in the colon of DNBS-treated mice, in the colon submucosa of TNBS-treated rats, and in the biopsies of patients with ulcerative colitis. VDM-11 significantly elevated anandamide levels in the colon of DNBS-treated mice and concomitantly abolished inflammation, whereas AA-5-HT did not affect endocannabinoid levels and was significantly less efficacious at attenuating colitis. 5-ASA also increased anandamide levels and abolished colitis. Thus, anandamide is elevated in the inflamed colon of patients with ulcerative colitis, as well as in animal models of IBDs, to control inflammation, and elevation of its levels with inhibitors of its cellular reuptake might be used in the treatment of IBDs.

Unilateral Severe Chronic Periodontitis Associated With Ipsilateral Surgical Resection of Cranial Nerves V, VI, and VII

BACKGROUND

The central and peripheral nervous systems participate in several local physiological and pathological processes. There is experimental evidence that the inflammatory, local immune, and wound healing responses of a tissue can be modulated by its innervation. The aim of this clinical report is to present a case of unilateral severe periodontitis associated with ipsilateral surgical resection of the fifth, sixth, and seventh cranial nerves and to discuss the possible contribution of the nervous system to periodontal pathogenesis.

METHODS

A 39-year-old female patient with a history of a cerebrovascular accident caused by a right pontine arteriovenous malformation and destruction of the right fifth, sixth, and seventh cranial nerves was diagnosed with severe chronic periodontitis affecting only the right maxillary and mandibular quadrants. The patient's oral hygiene was similar for right and left sides of the mouth. Percentages of tooth surfaces carrying dental plaque were 41% and 36% for right and left sides, respectively. Non-surgical and surgical periodontal therapy was performed, and the patient was placed on a regular periodontal maintenance schedule.

RESULTS

Healing following initial periodontal therapy and osseous periodontal surgery occurred without complications. Follow-up clinical findings at 1 year revealed stable periodontal health.

CONCLUSIONS

This case report suggests that periodontal innervation may contribute to the regulation of local processes involved in periodontitis pathogenesis. It also suggests that periodontal therapy can be performed successfully at sites and in patients affected by paralysis.

Attenuation of acid induced oesophagitis in VR-1 deficient mice

BACKGROUND AND AIMS

Activation of the vanilloid receptor subtype 1 (VR-1) results in release of proinflammatory peptides which initiate an inflammatory cascade known as neurogenic inflammation. We investigated its role in an acute model of surgically induced oesophagitis.

METHODS

Oesophagitis was induced by pyloric ligation in wild-type and VR-1 deficient mice. A subset of animals were administered the VR-1 antagonist capsazepine, famotidine, or omeprazole one hour before surgery. Five hours after surgery, myeloperoxidase activity (MPO), histological damage scores, intragastric pH, and immunocytochemical analysis of substance P (SP) receptor endocytosis were determined.

RESULTS

Oesophagitis induced knockout mice exhibited significantly lower levels of MPO activity, histological damage scores, and SP receptor endocytosis than wild-type mice. Inflammatory parameters were significantly reduced by acid inhibition and capsazepine in wild-type mice.

CONCLUSIONS

We conclude that acute acid induced oesophagitis is reduced in animals lacking VR-1. This suggests that acid induced oesophagitis may act through VR-1 and that inhibition of the receptor may reduce inflammation.

Vanilloid receptor (TRPV1)-deficient mice show increased susceptibility to dinitrobenzene sulfonic acid induced colitis

In the human colon, vanilloid receptor TRPV1 is overexpressed both in afferent nerve terminals and in epithelial cells during inflammation. In the past years, pharmacological experiments using TRPV1 agonists and antagonists revealed that TRPV1 receptors may play proinflammatory and protective roles in the gastrointestinal tract. Here, we applied a genetic approach to define the role of TRPV1 and analyzed the effects of dinitrobenzene sulfonic acid (DNBS)-induced colitis in TRPV1-deficient (TRPV1-/-) mice. Intrarectal infusion of DNBS induced increased inflammation in TRPV1-/- mice compared to wild-type littermates (TRPV1+/+) as evaluated by macroscopic scoring and myeloperoxidase assays. This finding indicates that TRPV1 receptors are required for the protection within sensory pathways that regulate the response following the initiation of colonic inflammation. Electrophysiological recordings from circular smooth-muscle cells, performed 8 and 24 h after DNBS treatment, revealed strong spontaneous oscillatory action potentials in TRPV1-/- but not in TRPV1+/+ colons, indicating an early TRPV1-mediated control of inflammation-induced irritation of smooth-muscle activities. These unexpected results suggest that TRPV1 receptors mediate endogenous protection against experimentally induced colonic inflammation.

The Distribution of Sensory Fibers Immunoreactive for the TRPV1 (Capsaicin) Receptor in the Human Prostate

OBJECTIVES

To determine the distribution of sensory fibers immunoreactive to the pain receptor TRPV1 in the human prostate.

METHODS

Eight prostates were harvested from cadaver transplant donors and immediately immersion fixed. Longitudinal and transverse 20 microm sections were cut on a cryostat and immunoreacted with two anti-human TPRV1 antibodies.

RESULTS

TRPV1-immunoreactive nerve fibers were distributed throughout the prostatic urethral mucosa, verumontanum, ejaculatory ducts and periurethral prostatic acini. In the urethral mucosa, TRPV1-immunoreactive fibers penetrated the epithelial layer up to its surface. In the transitional and peripheral zones of the gland no TRPV1-immunoreactive nerve fibers were detected.

CONCLUSIONS

The existence of a rich TRPV1 sensory innervation in the human prostate may open new therapeutic perspectives for the treatment of pain in patients with chronic prostatitis (Chronic Pelvic Pain Syndrome).

Rectal instillation of butyrate provides a novel clinically relevant model of noninflammatory colonic hypersensitivity in rats

BACKGROUND & AIMS

The treatment of irritable bowel syndrome (IBS), characterized by abdominal pain and bloating, is empirical and often poorly efficient. Research lacks suitable models for studying the pathophysiologic mechanisms of the colonic hypersensitivity and new pharmacologic targets. The present study aimed to develop a novel model of colonic hypersensitivity possessing several of the characteristics encountered in patients with IBS.

METHODS

Rats received enemas of a butyrate solution (8-1000 mmol/L) twice daily for 3 days. A time course was determined for colonic hypersensitivity (colorectal distention test) and referred cutaneous lumbar hyperalgesia (von Frey hairs). Macroscopic and histologic analyses were performed on colonic mucosa. The efficacy of morphine, U50488H (a kappa opioid agonist), and trimebutine on the 2 pain parameters was determined. Finally, the involvement of peptidergic C-fibers was evaluated using capsaicin-pretreated animals and treatments with calcitonin gene-related peptide (CGRP) and neurokinin 1 receptor antagonists.

RESULTS

Butyrate enemas induced a sustained, concentration-dependent colonic hypersensitivity and, to a lesser extent, a referred cutaneous mechanical hyperalgesia, particularly in female rats, but no macroscopic and histologic modifications of the colonic mucosa, as observed in patients with IBS. Both pain parameters were sensitive to morphine, U50488H, trimebutine, neonatal capsaicin treatment, and the CGRP receptor antagonist but not to the neurokinin 1 receptor antagonist.

CONCLUSIONS

These results present our noninflammatory model of chronic colonic hypersensitivity as a useful novel tool for studying IBS. The CGRP receptor antagonist-induced reduction of colonic hypersensitivity suggests that CGRP receptors may provide a promising target for treatment of IBS.

Transient receptor potential vanilloid (TRPV-1) promotes neurogenic inflammation in the pancreas via activation of the neurokinin-1 receptor (NK-1R)

OBJECTIVES

The transient receptor potential vanilloid 1 (TRPV-1) is an ion channel found on primary sensory afferent neurons. Activation of TRPV-1 leads to the release of the proinflammatory neuropeptide substance P (SP). SP then binds to the neurokinin-1 receptor (NK1-R) on endothelial cells and promotes extravasation of plasma and proteins into the interstitial tissue and neutrophil infiltration, a process called neurogenic inflammation. We tested 2 hypotheses: (1) activation of TRPV-1 in the pancreas leads to interstitial edema and neutrophil infiltration and (2) TRPV-1-induced plasma extravasation is mediated by the release of SP and activation of the NK1-R in the rat.

METHODS

We measured extravasation of the intravascular tracer Evans blue as an index of plasma extravasation and quantified pancreas tissue myeloperoxidase activity (MPO) as a marker of neutrophil infiltration. The severity of inflammation following intravenous infusion of the secretagogue cerulein (10 microg/kg/h x 4 hours) was assessed using a histologic scoring system.

RESULTS

Intravenous injection of the TRPV-1 agonist capsaicin induced a dose-dependent increase in Evans blue accumulation in the rat pancreas (P < 0.05 vs. vehicle control). This effect was blocked by pretreatment with the TRPV-1 antagonist capsazepine (1.8 mg/kg), or the NK1-R antagonist CP 96,345 (1 mg/kg). Capsazepine also reduced cerulein-induced Evans blue, MPO, and histologic severity of inflammation in the pancreas but had no effect on serum amylase.

CONCLUSION

Activation of TRPV-1 induces SP-mediated plasma extravasation in the rat pancreas via activation of the NK1-R. TRPV-1 mediates neurogenic inflammation in cerulein-induced pancreatitis in the rat.

Attenuation of acute experimental colitis by preventing NPY Y1 receptor signaling

Neuropeptide Y (NPY), a 36-amino acid peptide, is widely expressed in the central and peripheral nervous system. NPY is involved in the regulation of several physiological processes, including energy balance, food intake, and nociception. Recently, we showed that activation of the NPY Y1 receptor is required for cutaneous neurogenic inflammation. Because neurogenic inflammation could participate in colitis, the aim of this study was to investigate the role of the NPY Y1 receptor in acute colitis using mice genetically deficient of NPY Y1 receptor. In addition, the Y1 receptor antagonist H409/22, was also investigated. Animals received 5% dextran sulfate sodium (DSS) in drinking water for 7 days. One group of animals also received the Y1 receptor antagonist, administered intraperitoneally twice daily. Disease activity was assessed daily for 7 days in all groups. DSS induced colitis in all animals resulting in weight loss, diarrhea, epithelial damage, crypt shortening, and inflammatory infiltration. However, clinical manifestation of the disease was markedly attenuated in Y1 null mutant mice as well as in mice receiving the Y1 antagonist. Histological analysis showed that tissue damage and ulceration were less severe in Y1-deficient animals. Consistent with the clinical and histological data, capsaicin-induced plasma extravasation was significantly reduced in the gut of Y1 null mutant animals compared with treated wild-type animals. These data indicate that NPY and Y1 receptor are involved in intestinal inflammation and suggest that inhibition of NPY Y1 receptor signaling may provide a novel therapeutic approach in the treatment of colonic inflammation.

Therapeutic potential of follistatin for colonic inflammation in mice

BACKGROUND AND AIMS

Activins belong to the transforming growth factor-beta superfamily. Recent studies have shown that activin and its natural antagonist, follistatin, are involved in tissue repair and inflammatory processes. The aim of this study was to determine whether neutralization of activins with follistatin would have an in vivo anti-inflammatory effect in several murine models of colitis.

METHODS

We assessed activin levels in the colitis induced by intracolonic administration of trinitrobenzene sulfonic acid (TNBS). We subsequently tested the effects of an intraperitoneal injection of follistatin before or after induction of TNBS colitis. We also examined the established colitis induced by oral dextran sulfate sodium (DSS) as well as the spontaneous colitis that develops in interleukin (IL)-10 gene-deficient (IL-10 -/- ) mice.

RESULTS

Levels of activin transcripts in the colon during the acute phase of TNBS colitis were up-regulated. Epithelial cells, infiltrating macrophages (Mvarphi), and endothelial cells produced excess activin betaA. Pretreatment with follistatin increased the survival rate of mice with TNBS colitis from 33% to 82% and decreased the plasma levels of IL-6 and amyloid A. Administration of follistatin also reduced the histologic score and tissue myeloperoxidase activity in established TNBS and DSS colitis and reduced the severity of the colitis in IL-10 -/- mice. Based on results obtained from 3 mouse models and from in vitro experiments, follistatin promoted the proliferation of colonic epithelial cells.

CONCLUSIONS

Neutralization of activins by follistatin promoted epithelial cell division and tissue repair, clearly suggesting a treatment modality for intestinal inflammation.

Vanilloid receptor 1 antagonists attenuate disease severity in dextran sulphate sodium-induced colitis in mice

Neurogenic mechanisms have been implicated in the induction of inflammatory bowel disease (IBD). Vanilloid receptor type 1 (TRPV1) has been visualized on nerve terminals of intrinsic and extrinsic afferent neurones innervating the gastrointestinal tract and local administration of a TRPV1 antagonist, capsazepine, reduces the severity of dextran sulphate sodium (DSS)-induced colitis in rats (Gut 2003; 52: 713-9(1)). Our aim was to test whether systemically or orally administered TRPV1 antagonists attenuate experimental colitis induced by 5% DSS in Balb/c mice. Intraperitoneal capsazepine (2.5 mg kg(-1), bid), significantly reduced the overall macroscopic damage severity compared with vehicle-treated animals (80% inhibition, P < 0.05); however, there was no effect on myeloperoxidase (MPO) levels. An experimental TRPV1 antagonist given orally was tested against DSS-induced colitis, and shown to reverse the macroscopic damage score at doses of 0.5 and 5.0 mg kg(-1). Epithelial damage assessed microscopically was significantly reduced. MPO levels were attenuated by approximately 50%, and diarrhoea scores were reduced by as much as 70%. These results suggest that pharmacological modulation of TRPV1 attenuates indices of experimental colitis in mice, and that development of orally active TRPV1 antagonists might have therapeutic potential for the treatment of IBD.

Inhibition of the vanilloid receptor subtype-1 attenuates TNBS-colitis

Primary sensory neurons are important in regard to the initiation and propagation of intestinal inflammation. The vanilloid receptor subtype-1 (VR-1) is a cation channel located on the sensory nerves that, when stimulated, release proinflammatory peptides. Previous reports have indicated that inhibition of VR-1 with capsazepine (CPZ), a VR-1 antagonist, attenuates dextran sodium sulfate (DSS) colitis in rats. DSS-induced colitis resembles ulcerative colitis with regard to its pathologic features. In this study, we examined the effect of CPZ on trinitrobenzene sulfonic acid (TNBS)-induced colitis, an experimental model of intestinal inflammation that most closely resembles the histologic and microscopic features of Crohn's disease. Colitis was induced by administering a single enema of 100 mg/kg TNBS in 50% ethanol via catheter to lightly anesthetized rats. Subsets of rats were treated with either 1 micromol/kg/ml of CPZ or CPZ-vehicle via enema for 6 days. Seven days after TNBS administration, rats were sacrificed and inflammation was assessed using a validated macroscopic damage score (MDS) and by measuring myeloperoxidase (MPO) activity. In addition, histologic examination was performed. TNBS administration resulted in reproducible chronic erosive lesions extending into the muscularis propria and extensive recruitment of neutrophils in the distal colon. MDS and MPO scores were considerably elevated in the TNBS colons when compared with the TNBS vehicle animals. TNBS rats treated with CPZ enemas exhibited a substantial reduction in MDS and MPO scores and demonstrated dramatically improved pathologic findings. Topical CPZ resulted in considerable attenuation of TNBS-induced colitis. These results support the role of VR-1 and sensory neurons with regard to intestinal inflammation.

Combined determination with functional and morphological studies of origin of nerve fibers expressing transient receptor potential vanilloid 1 in the myenteric plexus of the rat jejunum

The aim of this study was to determine the action of capsaicin in isolated rat intestine and the origin of nerve fibers expressing transient receptor potential vanilloid 1 (TRPV1: capsaicin receptor) in the rat jejunum by combination of functional and immunohistochemical experiments. Capsaicin (1 microM) produced a prolonged relaxation response (52. +/-15.3% of the relaxation response to papaverine, mean +/- S.D., n=27) of the isolated jejunum in the presence of atropine and guanethidine. Pretreatment with the TRPV1 antagonist, capsazepine (10 microM) and ruthenium red (3 microM) significantly reduced the relaxation response to capsaicin by 78% (P<0.01) and 38% (P<0.05), respectively. Tetrodotoxin and calcitonin gene-related peptide (CGRP)-desensitization significantly reduced the response to capsaicin by 72% (P<0.01) and 42% (P<0.01), respectively. Therefore, we investigated the distribution of TRPV1-immunoreactivity (IR) in the myenteric plexus of the rat jejunum. Using antisera raised against either the N-terminal or C-terminal domains of rat TRPV1, TRPV1-IR was present in the nerve fibers, but not in the cell bodies of myenteric neurons. These TRPV1-immunoreactive nerve fibers were running in myenteric ganglia and their interconnecting strands. Most TRPV1-immunoreactive nerve fibers showed CGRP-IR, whereas few VR1-immunoreactive nerve fibers showed substance P-IR. After chronic denervation of the extrinsic nerve supply to the jejunum, both the relaxation response to capsaicin and TRPV1-immunoreactive nerve fibers completely disappeared. These findings indicate that these TRPV1-immunoreactive nerve fibers in the rat jejunum derive from extrinsic neurons and that activation of TRPV1 produces the relaxation response in the rat jejunum, at least in part, through the release of CGRP from nerve fibers expressing TRPV1.

TRPV1 and the gut: from a tasty receptor for a painful vanilloid to a key player in hyperalgesia

Capsaicin, the pungent ingredient in red pepper, has been used since ancient times as a spice, despite the burning sensation associated with its intake. More than 50 years ago, Nikolaus Jancso discovered that capsaicin can selectively stimulate nociceptive primary afferent neurons. The ensuing research established that the neuropharmacological properties of capsaicin are due to its activation of the transient receptor potential ion channel of the vanilloid type 1 (TRPV1). Expressed by primary afferent neurons innervating the gut and other organs, TRPV1 is gated not only by vanilloids such as capsaicin, but also by noxious heat, acidosis and intracellular lipid mediators such as anandamide and lipoxygenase products. Importantly, TRPV1 can be sensitized by acidosis and activation of various pro-algesic pathways. Upregulation of TRPV1 in inflammatory bowel disease and the beneficial effect of TRPV1 downregulation in functional dyspepsia and irritable bladder make this polymodal nociceptor an attractive target of novel therapies for chronic abdominal pain.