Effects of sildenafil on rat irritable bowel syndrome

The trace aminergic system: a gender-sensitive therapeutic target for IBS?

Due to a lack of specific or sensitive biomarkers, drug discovery advances have been limited for individuals suffering from irritable bowel syndrome (IBS). While current therapies provide symptomatic relief, inflammation itself is relatively neglected, despite the presence of chronic immune activation and innate immune system dysfunction. Moreover, considering the microgenderome concept, gender is a significant aetiological risk factor. We believe that we have pinpointed a "missing link" that connects gender, dysbiosis, diet, and inflammation in the context of IBS, which may be manipulated as therapeutic target. The trace aminergic system is conveniently positioned at the interface of the gut microbiome, dietary nutrients and by-products, and mucosal immunity. Almost all leukocyte populations express trace amine associated receptors and significant amounts of trace amines originate from both food and the gut microbiota. Additionally, although IBS-specific data are sparse, existing data supports an interpretation in favour of a gender dependence in trace aminergic signalling. As such, trace aminergic signalling may be altered by fluctuations of especially female reproductive hormones. Utilizing a multidisciplinary approach, this review discusses potential mechanisms of actions, which include hyperreactivity of the immune system and aberrant serotonin signalling, and links outcomes to the symptomology clinically prevalent in IBS. Taken together, it is feasible that the additional level of regulation by the trace aminergic system in IBS has been overlooked, until now. As such, we suggest that components of the trace aminergic system be considered targets for future therapeutic action, with the specific focus of reducing oxidative stress and inflammation.

Irritable Bowel Syndrome between Molecular Approach and Clinical Expertise-Searching for Gap Fillers in the Oxidative Stress Way of Thinking

Irritable bowel syndrome (IBS) remains to date an intriguing functional gastrointestinal disorder. Recent studies described a multitude of exogenous factors that work together in IBS, gradually impairing intestinal lining cellular metabolism, including oxidative status balance, with or without a genetic background. Although the current biomarkers support the differentiation between IBS subtypes and other functional gastrointestinal disorder, they are mostly non-specific, referring to clinical, biochemical, and inflammatory imbalances. Since IBS could be also the result of deficient signaling pathways involving both gastrointestinal secretion and neuro-vegetative stimulation, IBS makes no exception from the oxidative hypothesis in the pathological mechanisms. Regarding the oxidative stress implication in IBS, the previous research efforts showed controversial results, with some animal models and patient studies reporting clear oxidative imbalance both on systemic and local levels, but still with no concrete evidence to point to a direct correlation between oxidative stress and IBS. Additionally, it seems that a major role could be also attributed to gut microbiota and their ability to shape our bodies and behaviors. Moreover, the genetic features study in IBS patients showed that several genetic similarities point to a possible correlation of IBS with affective spectrum disorders. Thus, we focus here the discussion on the assumption that IBS could in fact be more likely a stress-related disorder rather than a gastrointestinal one.

Preliminary Biochemical Description of Brain Oxidative Stress Status in Irritable Bowel Syndrome Contention-Stress Rat Model

Background and objectives: Oxidative stress and inflammation have been implicated in the etiology of irritable bowel syndrome (IBS), a common gastrointestinal functional disease. This study aimed to further characterize the contention-stress rat model by exploring a possible correlation between oxidative stress markers measured in brain tissues with behavioral components of the aforementioned model. Thus, it is hereby proposed a possible IBS animal model relevant to pharmacological and complementary medicine studies. Materials and Methods: Wild-type male Wistar rats (n = 5/group) were chronically exposed to 6-hour/day contention, consisting of isolating the animals in small, vital space-granting plastic devices, for seven consecutive days. Following contention exposure, temporal lobes were extracted and subjected to biochemical analyses to assess oxidative stress-status parameters. Results: Our results show increased brain oxidative stress in contention-stress rat model: decreased superoxide dismutase and glutathione peroxidase activities and increased malondialdehyde production in the IBS group, as compared to the control group. Furthermore, the biochemical ratios which are used to evaluate the effectiveness of an antioxidant system on oxidative stress could be described in this model. Conclusions: The correlations between the behavioral patterns and biochemical oxidative stress features could suggest that this may be a complex model, which can successfully mimic IBS symptomatology further providing evidence of a strong connection between the digestive system, enteric nervous system, and the central nervous system.

Black tea extract and its thearubigins relieve the sildenafil-induced delayed gut motility in mice: a possible role of nitric oxide

In this study we hypothesize that a standardized black tea aqueous extract (BTE) and thearubigins, its main polyphenolic pigments, will improve sildenafil-induced delay in gastric emptying (GE) and small intestinal transit (SIT) in mice. Twenty groups of mice (n = 8) were given a phenol red meal, and three sets of experiments were performed. In the first and second sets, effects of different concentrations of BTE, thearubigins (TRs), and sildenafil (SLD), alone and in combinations, on GE and SIT were measured. In the third set, influence of nω -Nitro-l-arginine methyl ester hydrochloride (l-NAME) pretreatment on effects of these treatments was tested. Black tea extract (3% and 4.5%) and thearubigins (50 and 60 mg/kg) dose-dependently increased GE and SIT, whereas BTE 6% and thearubigins 70 mg/kg did not affect them. Sildenafil dose-dependently reduced both GE and SIT. Combination of metoclopramide, BTE 4.5%, thearubigins 60, or l-NAME with sildenafil (5 mg/kg) reversed its motility-delaying effects. Pretreatment with l-NAME followed by BTE 4.5%, thearubigins 60, BTE 4.5% + sildenafil 5, or thearubigins 60 + sildenafil 5 only partially affected the accelerating effects of BTE 4.5% and thearubigins 60. In conclusion, a standardized BTE and its thearubigins improve the sildenafil-induced delayed gut motility in mice. This improvement was partially blocked by l-NAME suggesting a possible role of nitric oxide. Thus, BTE 4.5% or TRs 60 mg/kg solution could be considered a reliever therapy for the sildenafil-induced dyspepsia.

Dual effect of cAMP agonist on ameliorative function of PKA inhibitor in morphine-dependent mice

The present study shows interactive effects of bucladesine (db-cAMP) as a cyclic adenosine monophosphate (cAMP) agonist and H-89 as a protein kinase A (PKA) inhibitor on naloxone-induced withdrawal signs in morphine-dependent mice. Animals were treated subcutaneously with morphine thrice daily with doses progressively increased from 50 to 125 mg/kg. A last dose of morphine (50 mg/kg) was administered on the 4th day. Several withdrawal signs were precipitated by intraperitoneal (i.p.) administration of naloxone (5 mg/kg). Different doses of bucladesine (50, 100, 200 nm/mouse) and H-89 (0.05, 0.5, 1, 5 mg/kg) were administered (i.p.) 60 min before naloxone injection. In combination groups, bucladesine was injected 15 min before H-89 injection. Single administration of H-89 (0.5, 1, 5 mg/kg) and bucladesine (50, 100 nm/mouse) significantly attenuated prominent behavioral signs of morphine withdrawal. Lower doses of bucladesine (50, 100 nm/mouse) in combination with H-89 (0.05 mg/kg) increased the inhibitory effects of H-89 on withdrawal signs while in high dose (200 nm/mouse) decreased the ameliorative function of H-89 (0.05 mg/kg) in morphine-dependent animals. It is concluded that H-89 and bucladesine could affect morphine withdrawal syndrome via possible interaction with cyclic nucleotide messengering systems, protein kinase A signaling pathways, and modified related neurotransmitters.

Benefit of Aloe vera and Matricaria recutita mixture in rat irritable bowel syndrome: Combination of antioxidant and spasmolytic effects

OBJECTIVE: To evaluate the beneficial effects of a mixture of Aloe vera (AV) and Matricaria recutita (German chamomile, GC) in an experimental model of irritable bowel syndrome (IBS). METHODS: IBS was induced by a 5-day restraint stress in rats including the groups of control (water), GC (300 mg/kg), loperamide (10 mg/kg), mixed AV and GC (50: 50 at doses of 150, 300 or 450 mg/kg assigned as Mix-150, Mix-300 and Mix-450, respectively) and the sham group which did not receive any restraint stress and was fed with saline. All medications were administered intragastrically by gavage for 7 days, 2 days as pre-treatment followed by 5 days during induction of IBS every day before restraining. RESULTS: The increased tumor necrosis factor alpha (TNF-α), myeloperoxidase (MPO) activity, and lipid peroxidation (LPO) in colonic cells in the control group were significantly decreased in the treatment groups. GC inhibited only small bowel transit while the AV/GC mixture delayed gastric emptying at the doses of 150 and 300 mg/kg. The AV/GC mixture also reduced colonic transit and small bowel transit at the dose of 150 mg/kg. CONCLUSIONS: The severity of stress-induced IBS was diminished by the AV/GC mixture at all doses used but not dose-dependently, via inhibiting colonic MPO activity and improving oxidative stress status. The effect of the mixture was more effective than GC alone. The present results support effectiveness of the AV and GC combination in IBS.

Beneficial effect of phosphodiesterase-5 inhibitor in experimental inflammatory bowel disease; molecular evidence for involvement of oxidative stress

ABSTRACT Inflammatory bowel disease (IBD) is a common and chronic gastrointestinal disorder characterized by intestinal inflammation and mucosal tissue damage. Reactive oxygen metabolites (ROMs) play a pathogenic role in IBD. We aimed to examine the protective effect of sildenafil, a cGMP phosphodiesterase inhibitor, in the experimental mouse model of IBD. Intrarectal instillation of acetic acid was used to induce IBD. Prednisolone was used as the standard drug for comparison. Sildenafil was used at doses of 0.75, 1.5, and 3 mg/kg. Biochemicals and macroscopic and microscopic examinations of colonic tissue were performed. Results indicated that activity of myeloperoxidase (MPO) and lipid peroxidation product (TBARS) markers of oxidative stress are increased in acetic acid-treated groups and are recovered by sildenafil pretreatment and prednisolone. Sildenafil- (1.5 and 3 mg/kg) and prednisolone-treated groups showed significantly lower score values of macroscopic and microscopic characters when compared to the acetic acid-treated group. The beneficial effect of sildenafil (3 mg/kg) was comparable to that of prednisolone. It is concluded that sildenafil is helpful in the management of IBD, which is presumably related to its strong antioxidative stress potential mediated through enhanced cGMP. Results of proper clinical trials will determine the possible efficacy of phosphodiesterase-5 inhibitors in human IBD.

Biochemical and histopathological evidences for beneficial effects of satureja khuzestanica jamzad essential oil on the mouse model of inflammatory bowel diseases

The essential oil from Satureja Khuzestanica Jamzad (SKEO), an endemic plant from Iran, was evaluated for its activity against inflammatory bowel disease (IBD). SKEO was examined on the experimental mouse model of inflammatory bowel disease, which is acetic acid-induced colitis. Prednisolone was used as the standard drug for comparison. Biochemical, macroscopic, and microscopic examinations of colon were performed. Lipid peroxidation significantly increased in acetic acid-treated mice in comparison to the normal group (4.88 vs. 3.02 mumol/g) and was significantly restored by SKEO (500, 1000, 1500 ppm) and prednisolone treatment. The mean percentage of decreases of lipid peroxidation in SKEO (500, 1000, 1500 ppm)- and prednisolone-treated groups were 10.5, 28.5, 42.85, and 33.33 of control, respectively. The myeloperoxidase activity significantly increased in acetic acid-treated mice in comparison to the normal group (4.1 vs. 0.8 U/g) and significantly restored in SKEO (1000 and 1500 ppm)- and prednisolone-treated groups. The mean percentage of decreases of myeloperoxidase activity in SKEO (1000 and 1500 ppm)- and prednisolone-treated groups were 24.56, 50, and 52.63 of control, respectively. SKEO (1000 and 1500 ppm)- and prednisolone-treated groups showed significantly lower score values of macroscopic and microscopic characters when compared to the acetic acid-treated group. The beneficial effect of SKEO (1500 ppm) was comparable to that of prednisolone. Known antioxidant, antimicrobial, antiinflammatory, and antispasmodic potentials of Satureja Khuzestanica may be the mechanisms by which this plant protects animals against experimentally induced IBD. Proper clinical investigation should be carried out to confirm the activity in human disease.

Systematic review of modulators of benzodiazepine receptors in irritable bowel syndrome: Is there hope?

Several drugs are used in the treatment of irritable bowel syndrome (IBS) but all have side effects and variable efficacy. Considering the role of the gut-brain axis, immune, neural, and endocrine pathways in the pathogenesis of IBS and possible beneficial effects of benzodiazepines (BZD) in this axis, the present systematic review focuses on the efficacy of BZD receptor modulators in human IBS. For the years 1966 to February 2011, all literature was searched for any articles on the use of BZD receptor modulators and IBS. After thorough evaluation and omission of duplicate data, 10 out of 69 articles were included. BZD receptor modulators can be helpful, especially in the diarrhea-dominant form of IBS, by affecting the inflammatory, neural, and psychologic pathways, however, controversies still exist. Recently, a new BZD receptor modulator, dextofisopam was synthesized and studied in human subjects, but the studies are limited to phase IIb clinical trials. None of the existing trials considered the neuroimmunomodulatory effect of BZDs in IBS, but bearing in mind the concentration-dependent effect of BZDs on cytokines and cell proliferation, future studies using pharmacodynamic and pharmacokinetic approaches are highly recommended.

Improvement of inflammatory and toxic stress biomarkers by silymarin in a murine model of type one diabetes mellitus

Type 1 diabetes mellitus (T1DM) is characterized by an impairment of the insulin-secreting beta cells with an immunologic base. Inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and free radicals are believed to play key roles in destruction of pancreatic β cells. The present study was designed to investigate the effect of Silybum marianum seed extract (silymarin), a combination of several flavonolignans with immunomodulatory, anti-oxidant, and anti-inflammatory potential on streptozotocin (STZ)-induced T1DM in mouse. Experimental T1DM was induced in male albino mice by IV injection of multiplelow- doses of STZ for 5 days. Seventy-two male mice in separate groups received various doses of silymarin (20, 40, and 80 mg/kg) concomitant or after induction of diabetes for 21 days. Blood glucose and pancreatic biomarkers of inflammation and toxic stress (IL-1β, TNF-α, myeloperoxidase, lipid peroxidation, protein oxidation, thiol molecules, and total antioxidant capacity) were determined. Silymarin treatment reduced levels of inflammatory cytokines such as TNF-α and IL-1β and oxidative stress mediators like myeloperoxidase activity, lipid peroxidation, carbonyl and thiol content of pancreatic tissue in an almost dose dependent manner. No marked difference between the prevention of T1DM and the reversion of this disease by silymarin was found. Use of silymarin seems to be helpful in T1DM when used as pretreatment or treatment. Benefit of silymarin in human T1DM remains to be elucidated by clinical trials.

Benefit of Satureja khuzestanica in subchronically rat model of cyclophosphamide-induced hemorrhagic cystitis

Cyclophosphamide (CP) as a widely used antineoplastic drug causes hemorrhagic cystitis (HC) mainly via induction of oxidative stress. Regarding established antioxidant potential of Satureja khuzestanica (Lamiaceae) essential oil (SKEO), we aimed to investigate its protective effects in a subchronic rat model of CP-induced HC. CP (6mg/kg/day) and SKEO (225mg/kg/day) were administered alone or in combination by gavage for 28 days. Histopathological changes were investigated by light microscopy. Plasma samples were assayed for lipid peroxidation and total antioxidant power as biomarkers of toxic stress. In the CP-treated animals, irregular mucus layer, severe hemorrhage and edema, infiltration of inflammatory cells, and accumulation of mast cells were observed. In the CP+SKEO group, a relatively normal urothelial topography with decreased number of mucosal mast cells and inflammatory cells were observed. Increased lipid peroxidation along with decreased total antioxidant capacity resulting from CP treatment was significantly recovered by SKEO co-treatment. It is concluded that SKEO protects rats from CP-induced HC by reduction of free radical-induced toxic stress. It is strongly recommended to examine SKEO in the clinic to approve its benefit in patients undertaking CP.

Efficacy of probiotics in irritable bowel syndrome: a meta-analysis of randomized, controlled trials

PURPOSE

This study was designed to evaluate whether probiotics improve symptoms in patients with irritable bowel syndrome.

METHODS

PubMed, Embase, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials were searched for studies that investigated the efficacy of probiotics in the management of irritable bowel syndrome. Clinical improvement was the key outcome of interest. Data were searched within the time period of 1966 through September 2007.

RESULTS

Eight randomized, placebo-controlled, clinical trials met our criteria and were included in the analysis. Pooling of eight trials for the outcome of clinical improvement yielded a significant relative risk of 1.22 (95 percent confidence interval, 1.07-1.4; P = 0.0042).

CONCLUSIONS

Probiotics may improve symptoms of irritable bowel syndrome and can be used as supplement to standard therapy.

Molecular evidences on the benefit of N-acetylcysteine in experimental colitis

Inflammatory bowel disease (IBD) is a chronic recurrent disease of the digestive tract with an unknown etiology. The aim of this study was to examine the possible protective effects of N-acetylcysteine (NAC) in the mouse model of IBD by measuring specific biomarkers in the colon cells. Colitis was induced by administration of dextran sodium sulfate (DSS) in drinking water (3%) for 7 days. Three doses of NAC (106, 160, and 240 mg/kg) were given after induction of colitis (4 days post DSS) for 4 days by gavage. Lipid peroxides (LP), total antioxidant power (TAP), total thiol molecules (TTM), tumor necrosis factor-α (TNF-α), nitric oxide (NO), superoxide dismutase (SOD), and catalase (CAT) were measured in the colon homogenate of the treated animals. NAC (160 and 240 mg/kg) significantly decreased LP, TNF-α, NO and increased TTM, SOD, and CAT. The TAP was also increased by NAC (240 mg/kg). It is concluded that moderate to high doses of NAC improves cellular biomarkers of IBD in mice. Further studies should be trialled in humans suffering from two common inflammatory bowel disease called ulcerative colitis and Crohn’s disease.

Efficacy and tolerability of alosetron for the treatment of irritable bowel syndrome in women and men: a meta-analysis of eight randomized, placebo-controlled, 12-week trials

BACKGROUND

Stimulated 5-hydroxytryptamine-3 (5-HT(3)) receptors promote intestinal motility, secretion, and sensation, effects that are related to the known pathophysiology of irritable bowel syndrome (IBS). A previous meta-analysis of 6 randomized controlled trials of the 5-HT(3)-receptor antagonist alosetron found that this agent was associated with global improvement in symptoms, pain, and discomfort in patients with IBS.

OBJECTIVE

This was a meta-analysis of randomized, placebo-controlled trials that evaluated the efficacy and tolerability of alosetron for the management of IBS. It updated and expanded on the previous meta-analysis.

METHODS

PubMed, EMBASE, SCOPUS, Web of Science, and the cochrane central Register of controlled Trials were searched from 1966 through September 2007 for placebo-controlled trials that examined the efficacy and tolerability of alosetron in the management of IBS. The search terms were alosetron, 5-HT, irritable bowel, functional bowel diseases, and irritable colon. No language restriction was applied. The data were analyzed in terms of 2 main outcomes: global improvement in IBS symptoms and adequate relief of IBS pain and discomfort.

RESULTS

Eight multicenter, randomized, placebo-controlled, 12-week clinical trials met the criteria for inclusion in the meta-analysis. The studies included 4,170 patients with IBS (80% female) who were randomized to receive either alosetron or placebo. All patients met the Rome criteria for IBS, and all subtypes of IBS were represented. Most patients had diarrhea-predominant IBS; only 2.6% of patients had constipation-predominant IBS. In the 3 trials included in the analysis of global improvement in symptoms, alosetron was significantly more effective than placebo (relative risk [RR] = 1.60; 95% CI, 1.44-1.76; P <0.001). In the 6 trials included in the analysis of adequate relief of IBS pain and discomfort, there was also a significant difference in favor of alosetron (RR = 1.31; 95% CI, 1.20-1.43; P < 0.001). Analysis of adequate relief of IBS pain and discomfort by sex also indicated significant differences between alosetron and placebo in both sexes (female: RR = 1.34 [95% cI, 1.21-1.48]; male: RR = 1.23 [95% CI, 1.02-1.47]). The analysis of tolerability, which was based on data from 7 studies, found a significant difference between alosetron and placebo (RR = 1.19; 95% cI, 1.07-1.31; P<0.001). The only adverse events that occurred with a significantly higher incidence in those treated with alosetron compared with placebo were constipation in 8 trials (RR = 4.35; 95% CI, 3.01-6.26; P < 0.001) and abdominal pain and discomfort in 5 trials (RR = 1.96; 95% CI, 1.46-2.64; P < 0.001). In the alosetron group, there were 4 cases of ischemic colitis (0.16%) and 2 cases of serious complications of constipation (0.08%); neither of these was reported in the placebo group. Alosetron was not associated with any deaths.

CONCLUSIONS

Alosetron was effective in these men and women with IBS. constipation was the most frequently reported adverse event associated with alosetron therapy. Ischemic colitis and serious complications of constipation were reported in a small number of patients treated with alosetron.

Protection by Ziziphora clinopoides of acetic acid-induced toxic bowel inflammation through reduction of cellular lipid peroxidation and myeloperoxidase activity

Inflammatory bowel disease (IBD) is a chronic condition of the intestine with unknown etiology involving multiple immune, genetic and environmental factors. We were interested in examining the effect of a total extract from Ziziphora clinopoides, an Iranian folk herbal medicine, in the prevention and control of experimental mouse IBD. Z. clinopoides was administered (75, 150, 300 mg/kg) through drinking water to mice, which dispensed a toxic dose of acetic acid intrarectally. Prednisolone was used as the standard drug for comparison. Biochemical, macroscopic and microscopic examinations of the colon were performed. Biochemical evaluation of the inflamed colon was carried out using assays of myeloperoxidase (MPO) activity and thiobarbituric acid reacting substances (TBARS) as indicators of free radical activity and cellular lipid peroxidation. Results indicated that the activity of MPO and lipid peroxidation products (TBARS) increased in acetic acid-treated groups, while recovered by pretreatment of animals with Z. clinopoides (75-300 mg/kg) and prednisolone. All doses of Z. clinopoides and prednisolone-treated groups showed significant lower score values of macroscopic and microscopic characters when compared to the acetic acid-treated group. The beneficial effect of Z. clinopoides (300 mg/kg) was comparable to that of prednisolone. It is concluded that Z. clinopoides inhibits acetic acid toxic reactions in the mouse bowel through inhibition of cellular oxidative stress. Proper clinical investigation should be carried out to confirm the same activity in human.