Agata Mulak

Stress and visceral pain: from animal models to clinical therapies

Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.

Brain-gut-microbiota axis in Parkinson's disease

Parkinsons disease (PD) is characterized by alpha-synucleinopathy that affects all levels of the brain-gut axis including the central, autonomic, and enteric nervous systems. Recently, it has been recognized that the brain-gut axis interactions are significantly modulated by the gut microbiota via immunological, neuroendocrine, and direct neural mechanisms. Dysregulation of the brain-gut-microbiota axis in PD may be associated with gastrointestinal manifestations frequently preceding motor symptoms, as well as with the pathogenesis of PD itself, supporting the hypothesis that the pathological process is spread from the gut to the brain. Excessive stimulation of the innate immune system resulting from gut dysbiosis and/or small intestinal bacterial overgrowth and increased intestinal permeability may induce systemic inflammation, while activation of enteric neurons and enteric glial cells may contribute to the initiation of alpha-synuclein misfolding. Additionally, the adaptive immune system may be disturbed by bacterial proteins cross-reacting with human antigens. A better understanding of the brain-gut-microbiota axis interactions should bring a new insight in the pathophysiology of PD and permit an earlier diagnosis with a focus on peripheral biomarkers within the enteric nervous system. Novel therapeutic options aimed at modifying the gut microbiota composition and enhancing the intestinal epithelial barrier integrity in PD patients could influence the initial step of the following cascade of neurodegeneration in PD.

Activation of Corticotropin-Releasing Factor Receptor 2 Mediates the Colonic Motor Coping Response to Acute Stress in Rodents

BACKGROUND & AIMS Corticotropin-releasing factor receptor-1 (CRF(1)) mediates the stress-induced colonic motor activity. Less is known about the role of CRF(2) in the colonic response to stress. METHODS We studied colonic contractile activity in rats and CRF(2)-/-, CRF-overexpressing, and wild-type mice using still manometry; we analyzed defecation induced by acute partial-restraint stress (PRS), and/or intraperitoneal injection of CRF ligands. In rats, we monitored activation of the colonic longitudinal muscle myenteric plexus (LMMP) neurons and localization of CRF(1) and CRF(2) using immunohistochemical and immunoblot analyses. We measured phosphorylation of extracellular signal-regulated kinase 1/2 by CRF ligands in primary cultures of LMMP neurons (PC-LMMPn) and cyclic adenosine monophosphate (cAMP) production in human embryonic kidney-293 cells transfected with CRF(1) and/or CRF(2). RESULTS In rats, a selective agonist of CRF(2) (urocortin 2) reduced CRF-induced defecation (>50%), colonic contractile activity, and Fos expression in the colonic LMMP. A selective antagonist of CRF(2) (astressin(2)-B) increased these responses. Urocortin 2 reduced PRS-induced colonic contractile activity in wild-type and CRF-overexpressing mice, whereas disruption of CRF(2) increased PRS-induced colonic contractile activity and CRF-induced defecation. CRF(2) colocalized with CRF(1) and neuronal nitric oxide synthase in the rat colon, LMMP, and PC-LMMPn. CRF-induced phosphorylation of extracellular signal-regulated kinase in PC-LMMPn; this was inhibited or increased by a selective antagonist of CRF(1) (NBI35965) or astressin(2)-B, respectively. The half maximal effective concentration, EC(50), for the CRF-induced cAMP response was 8.6 nmol/L in human embryonic kidney-293 cells that express only CRF(1); this response was suppressed 10-fold in cells that express CRF(1) and CRF(2). CONCLUSIONS In colon tissues of rodents, CRF(2) activation inhibits CRF(1) signaling in myenteric neurons and the stress-induced colonic motor responses. Disruption of CRF(2) function impairs colonic coping responses to stress.

Visceral analgesia induced by acute and repeated water avoidance stress in rats: sex difference in opioid involvement

Background  Chronic psychological stress‐induced alterations in visceral sensitivity have been predominantly assessed in male rodents. We investigated the effect of acute and repeated water avoidance stress (WAS) on the visceromotor response (VMR) to colorectal distension (CRD) and the role of opioids in male and cycling female Wistar rats using a novel non‐invasive manometric technique.

The Lifetime Prevalence of Anxiety Disorders Among Patients with Irritable Bowel Syndrome

BACKGROUND The prevalence of irritable bowel syndrome (IBS), the most common functional gastrointestinal disorder, ranges from 10% to 20% in the general population. It is estimated that from 40% to 90% of persons with a diagnosis of IBS suffer from mental disorders, mainly anxiety and depressive disorders. OBJECTIVES The aim of the study was to assess the lifetime prevalence of anxiety disorders in IBS patients and to compare it with the prevalence of these disorders in a control group of patients with gastroesophageal reflux disease (GERD). MATERIAL AND METHODS The study included 106 patients with IBS and 53 patients with GERD. IBS was diagnosed according to the Rome II criteria after a basic evaluation to exclude an organic disease. Anxiety disorders were diagnosed using the Composite International Diagnostic Interview (CIDI) in accordance with ICD-10 diagnostic criteria. RESULTS Anxiety disorders during the patients lifetime were diagnosed in 50 IBS patients (47%). Specific phobias occurred in 23.5% of them, social phobias in 10.4%, generalized anxiety disorder in 10.4%, panic disorder in 3.8% and agoraphobia in 8.5%. In the control group with GERD, anxiety disorders during the subjects lifetime were diagnosed in 30% of the group. The difference in the prevalence of anxiety disorders between patients with IBS and GERD was statistically significant (p<0.05). CONCLUSIONS The lifetime prevalence of anxiety disorders in IBS patients was higher than in the control group with GERD (47% vs. 30%). The prevalence rate of anxiety disorders in the control group with GERD was similar to the prevalence rate in the general population.

Anorectal function and visceral hypersensitivity in celiac disease.

Objective To evaluate anorectal function and rectal sensitivity thresholds in patients with celiac disease (CD). Methods In 25 unselected patients with CD (16 female, 9 male; mean age 45, range 24 to 75 y) and 20 controls (12 female, 8 male; mean age 41, range 20 to 65 y) anorectal manometry and rectal balloon distension test were conducted using a 4 lumen water perfused catheter with a polyethylene balloon (Zinectics Manometric Catheter, Medtronic). Results In celiac patients the maximal anal resting pressure, reflecting the internal anal sphincter function, was significantly higher than that in the controls: 87.8±21.7 mm Hg versus 66.7±15.2 mm Hg (P<0.001). There were no considerable differences between both the groups neither in the maximal anal squeeze nor in the cough pressures. Celiac patients had significantly lower first sensation threshold: 25.6±10.8 mL versus 37.5±12.5 mL (P<0.05). Visceral hypersensitivity (rectal pain/discomfort threshold ≤100 mL) was observed in 36% of celiac patients and in none of the controls (P<0.01). Conclusions The increased anal resting pressure and rectal hypersensitivity are observed in CD. Disturbances in gastrointestinal motility and visceral perception in the course of CD may occur at different levels of the brain-gut axis including direct changes in the enteric nervous system.

Selective agonists of somatostatin receptor subtype 1 or 2 injected peripherally induce antihyperalgesic effect in two models of visceral hypersensitivity in mice

Somatostatin interacts with five G-protein-coupled receptor (sst1-5). Octreotide, a stable sst2≫3≥5 agonist, exerts a visceral anti-hyperalgesic effect in experimental and clinical studies. Little is known on the receptor subtypes involved. We investigated the influence of the stable sst1-5 agonist, ODT8-SST and selective receptor subtype peptide agonists (3 or 10μg/mouse) injected intraperitoneally (ip) on visceral hypersensitivity in mice induced by repeated noxious colorectal distensions (four sets of three CRD, each at 55mmHg) or corticotropin-releasing factor receptor 1 agonist, cortagine given between two sets of graded CRD (15, 30, 45, and 60mmHg, three times each pressure). The mean visceromotor response (VMR) was assessed using a non-invasive manometry method and values were expressed as percentage of the VMR to the 1st set of CRD baseline or to the 60mmHg CRD, respectively. ODT8-SST (10μg) and the sst2 agonist, S-346-011 (3 and 10μg) prevented mechanically induced visceral hypersensitivity in the three sets of CRD, the sst1 agonist (10μg) blocked only the 2nd set and showed a trend at 3μg while the sst4 agonist had no effect. The selective sst2 antagonist, S-406-028 blocked the sst2 agonist but not the sst1 agonist effect. The sst1 agonist (3 and 10μg) prevented cortagine-induced hypersensitivity to CRD at each pressure while the sst2 agonist at 10μg reduced it. These data indicate that in addition to sst2, the sst1 agonist may provide a novel promising target to alleviate visceral hypersensitivity induced by mechanoreceptor sensitization and more prominently, stress-related visceral nociceptive sensitization.

A 'cocoon immunization strategy' among patients with inflammatory bowel disease.

Background and aims A ‘cocoon strategy’ is defined as the strategy of protecting vulnerable patients from infectious diseases by vaccinating those in close contact with them. In our study, we evaluate the vaccination status among children living with patients with inflammatory bowel disease (IBD) to determine the realization of the cocoon strategy and to identify characteristics associated with pediatric vaccine refusal. Patients and methods A self-completed survey was conducted on 136 hospitalized patients with IBD. The survey comprised questions about household child vaccination coverage, the reasons for vaccine refusal, and the history of infectious diseases among the patients. Results Fifty-six patients reported living with children. Forty percent of children were vaccinated with at least one of the recommended vaccines. Most frequently, children received pneumococcal (26%) and rotaviruses (22%) vaccines. The most common reason for nonimmunization was patients’ opinion that immunizations are not necessary for them (52%). There was a statistically significant association between the nonreimbursed vaccines coverage and the educational level of the patients (P<0.0001). Despite the fact that 28% of the patients could not definitively recall varicella infection, none of them and none of the children in their household had been vaccinated against chickenpox. Conclusion The use of nonmandatory vaccines recommended in family members of patients with IBD is insufficient. Further vaccine promotion and education of patients as well as their healthcare providers is required. A particular concern is associated with the pneumococcal, influenza, rotaviruses, and varicella infections. Nonimmunized and varicella-zoster virus-seronegative patients should be vaccinated, and in case of immunosuppression, vaccination of children in the household is required.

Psychological Stress Induces Visceral Analgesic or Hyperalgesic Response in Rodents: A Role of Preconditions

A dual action of stress on pain modulation has been well characterized in the somatic pain studies, while much less is known in the visceral field. In the context of clinical observations that stress plays a critical role in the pathophysiology, symptoms presentation and clinical outcome of functional gastrointestinal disorders such as irritable bowel syndrome (IBS), a number of acute and chronic stress models have been developed in rodents. Recent data have demonstrated that the state of the animal tested (naïve vs. exposed to surgery), its social environment (group housing vs. single housing), the methods used to record visceromotor responses (EMG requiring surgery and antibiotic after surgery vs. manometry not requiring surgery/antibiotic) can significantly affect the analgesic response to exteroceptive stressors. Growing body of evidence indicates that a new noninvasive solid-state manometric method to monitor viscero motor response is valuable to unravel both analgesia and hyperalgesia without confounding factors. This is of critical importance regarding the recently recognized role of a compromised engagement of the inhibitory descending pain pathways in IBS patients. Better understanding of mechanisms of stress-related modulation of visceral pain leading to analgesia and hyperalgesia, along with the role of sex-dependent factors and complex interactions of the brain-gut-enteric microbiota axis may lead to new therapeutic targets in IBS.

Mo2040 Association of Polymorphisms in 5-HT2A and 5-HT2C Receptors Genes With Depressive and Anxiety Disorders in Patients With Irritable Bowel Syndrome

BACKGROUND: Subgroups of patients with irritable bowel syndrome (IBS) may have low grade mucosal immune activity. Fecal calprotectin (f-calprotectin) levels are considered a marker for mucosal neutrophil inflammation and may be used as a biomarker for disease activity in inflammatory diseases. IBS patients are reported to have normal levels of calprotectin, but the levels may vary within the patient group, and it is not known whether this variation within or slightly above the normal range may reflect pathology or symptoms of the patients. AIM: To determine if levels of f-calprotectin may reflect the clinical and pathophysiological phenotype of IBS patients. METHODS: Analyses of f-calprotectin in stool samples of 98 IBS patients and 35 healthy controls were performed with Buhlmann ELISA (lower detection limit 10 ug/g). All IBS subjects completed the Bristol stool form (BSF) scale and the IBS symptom severity scale (IBS-SSS) questionnaire to assess gastrointestinal symptom severity. Patients also underwent a rectal barostat test with ballon distentions and colonic transit time measurement with ingestion of radiopaque rings. RESULTS: IBS patients had comparable levels of f-calprotectin to controls (17.5 (10-47.0) vs. 11(10-44.0) (median (2575%) percentiles) ug/g; p=0.21)). Among IBS patients, 13 subjects (13.2%) had f-calprotectin levels above the 90th percentile in the controls (98.8ug/g). There was no difference in IBS subgroup according to Rome III (IBS-C, IBS-D, IBS-M, IBS-U) in patients with high as compared to normal f-calprotectin. Also the disease duration was comparable in the two groups (9.5 (2-15) vs. 10 (5-15.3) years; p=0.46). There was no difference between IBS patients with high vs. normal levels of f-calprotectin regarding intensity or frequency of pain, bloating severity, bowel habit dissatisfaction, or daily life as estimated by IBS-SSS (Table 1). Also, total IBS-SSS score was comparable in the two groups (Table 1). The average stool form according to BSF (3.7 (2.9-4.4) vs. 4.1 (3.3-4.9); p=0.2) and stool frequency (1.5 (0.75-1.9) vs. 1.6 (1.2-2.3); p=0.29) were also similar in patients with high respective normal calprotectin levels. The pain threshold in rectal barostat test was comparable in IBS patients with high respective normal levels of f-calprotectin (24 (24-28) vs. 24 (20-32) mmHg; p=0.65). Moreover, oroanal transit time (OATT) was comparable in the two groups (1.5 (0.5-1.9) vs. 1.2(0.7-1.9) days; p=0.95) CONCLUSION: Fecal calprotectin within the normal range is not associated with the severity of IBS symptoms or key pathophysiological factors. Our data do not support that mucosal neutrophil inflammation is of major importance for symptom generation in IBS. Table 1. Symptom severity assessed by -IBS-SSS in IBS patients with high respective normal levels of fecal calprotectin.