QiQi Zhou

Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome

ABSTRACT Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which the underlying pathophysiology is poorly understood; however, increased intestinal permeability in diarrhea‐predominant IBS patients has been reported. Here we demonstrate that diarrhea‐predominant IBS (D‐IBS) patients display increased intestinal permeability. We have also found that increased intestinal membrane permeability is associated with visceral and thermal hypersensitivity in this subset of D‐IBS patients. We evaluated 54 D‐IBS patients and 22 controls for intestinal membrane permeability using the lactulose/mannitol method. All subjects ingested 5 g of lactulose and 2 g of mannitol in 100 ml of water after which their urine was collected. We also evaluated the mean mechanical visual analogue scale (M‐VAS) pain rating to nociceptive thermal and visceral stimulation in all subjects. All study participants also completed the FBDSI scale. Approximately 39% of diarrhea‐predominant IBS patients had increased intestinal membrane permeability as measured by the lactulose/mannitol ratio. These IBS patients also demonstrated higher M‐VAS pain intensity reading scale. Interestingly, the IBS patients with hypersensitivity and increased intestinal permeability had a higher FBDSI score (100.8 ± 5.4) than IBS patients with normal membrane permeability and sensitivity (51.6 ± 12.7) and controls (6.1 ± 5.6) (p < 0.001). A subset of D‐IBS patients had increased intestinal membrane permeability that was associated with an increased FBDSI score and increased hypersensitivity to visceral and thermal nociceptive pain stimuli. Thus, increased intestinal membrane permeability in D‐IBS patients may lead to more severe IBS symptoms and hypersensitivity to somatic and visceral stimuli.

MicroRNA-29a Regulates Intestinal Membrane Permeability in Patients with Irritable Bowel Syndrome

Background The molecular mechanisms underlying the pathophysiology of irritable bowel syndrome (IBS) are poorly understood. One mechanism may involve increased intestinal permeability that is reversed with glutamine supplementation. Our goal was to evaluate the expression of glutamine synthetase and its complementary miRNA in blood microvesicles and gut tissues of IBS patients with increased intestinal membrane permeability. Methods We evaluated 19 diarrhoea-predominant IBS patients and 10 controls for intestinal membrane permeability using the lactulose/mannitol method. miRNA expression was evaluated in blood microvesicles and gut tissue. To further confirm the relationship between miRNA and glutamine synthetase expression, cell culture experiments were conducted. Glutamine synthetase was also evaluated in the gut tissues of patients. Results A subset of patients with IBS (8/19, 42%) had increased intestinal membrane permeability and decreased glutamine synthetase expression compared to patients with IBS normal membrane permeability, and to controls. Expression of miR-29a was increased in blood microvesicles, small bowel and colon tissues of IBS patients with increased intestinal membrane permeability. Increased intestinal permeability was modulated by miR-29a which has a complementary site in the 3′-UTR of the GLUL gene. Conclusions The results support the conclusion that GLUL regulates intestinal membrane permeability and miR-29a regulates both GLUL and intestinal membrane permeability. The data suggests that miR-29a effects on intestinal membrane permeability may be due to its regulation of GLUL. Targeting this signalling pathway could lead to a new therapeutic approach to the treatment of patients with IBS, especially because small molecules that mimic or inhibit miRNA-based mechanisms are readily available.

Central and peripheral hypersensitivity in the irritable bowel syndrome

&NA; Previous investigations of somatic hypersensitivity in IBS patients have typically involved only a single stimulus modality, and little information exists regarding whether patterns of somatic pain perception vary across stimulus modalities within a group of patients with IBS. Therefore, the current study was designed to characterize differences in perceptual responses to a battery of noxious somatic stimuli in IBS patients compared to controls. A total of 78 diarrhea‐predominant and 57 controls participated in the study. We evaluated pain threshold and tolerance and sensory and affective ratings of contact thermal, mechanical pressure, ischemic stimuli, and cold pressor stimuli. In addition to assessing perceptual responses, we also evaluated differences in neuroendocrine and cardiovascular responses to these experimental somatic pain stimuli. A subset of IBS patients demonstrated the presence of somatic hypersensitivity to thermal, ischemic, and cold pressor nociceptive stimuli. The somatic hypersensitivity in IBS patients was somatotopically organized in that the lower extremities that share viscerosomatic convergence with the colon demonstrate the greatest hypersensitivity. There were also changes in ACTH, cortisol, and systolic blood pressure in response to the ischemic pain testing in IBS patients when compared to controls. The results of this study suggest that a more widespread alteration in central pain processing in a subset of IBS patients may be present as they display hypersensitivity to heat, ischemic, and cold pressor stimuli.

New insights into visceral hypersensitivity--clinical implications in IBS.

A subset of patients with IBS have visceral hypersensitivity and/or somatic hypersensitivity. Visceral hypersensitivity might have use as a clinical marker of IBS and could account for symptoms of urgency for bowel movements, bloating and abdominal pain. The mechanisms that lead to chronic visceral hypersensitivity in patients who have IBS are unclear. However, several working models may be considered, including: nociceptive input from the colon that leads to hypersensitivity; increased intestinal permeability that induces a visceral nociceptive drive; and alterations in the expression of microRNAs in gastrointestinal tissue that might be delivered via blood microvesicles to other target organs, such as the peripheral and/or central nervous system. As such, the chronic visceral hypersensitivity that is present in a subset of patients with IBS might be maintained by both peripheral and central phenomena. The theories underlying the development of chronic visceral hypersensitivity in patients with IBS are supported by findings from new animal models in which hypersensitivity follows transient inflammation of the colon. The presence of somatic hypersensitivity and an alteration in the neuroendocrine system in some patients who have IBS suggests that multisystemic factors are involved in the overall disorder. Thus, IBS is similar to other chronic pain disorders, such as fibromyalgia, chronic regional pain disorder and temporomandibular joint disorder, as chronic nociceptive mechanisms are activated in all of these disorders.

MicroRNA 29 targets nuclear factor-κB-repressing factor and Claudin 1 to increase intestinal permeability.

BACKGROUND & AIMS Some patients with irritable bowel syndrome with diarrhea (IBS-D) have intestinal hyperpermeability, which contributes to their diarrhea and abdominal pain. MicroRNA 29 (MIR29) regulates intestinal permeability in patients with IBS-D. We investigated and searched for targets of MIR29 and investigated the effects of disrupting Mir29 in mice. METHODS We investigated expression MIR29A and B in intestinal biopsies collected during endoscopy from patients with IBS (n = 183) and without IBS (controls) (n = 36). Levels were correlated with disease phenotype. We also generated and studied Mir29(-/-) mice, in which expression of Mir29a and b, but not c, is lost. Colitis was induced by administration of 2,4,6-trinitrobenzenesulfonic acid; intestinal tissues were collected and permeability was assessed. Microarray analysis was performed using tissues from Mir29(-/-) mice. Changes in levels of target genes were measured in human colonic epithelial cells and small intestinal epithelial cells after knockdown of MIR29 with anti-MIRs. RESULTS Intestinal tissues from patients with IBS-D (but not IBS with constipation or controls) had increased levels of MIR29A and B, but reduced levels of Claudin-1 (CLDN1) and nuclear factor-κB-repressing factor (NKRF). Induction of colitis and water avoidance stress increased levels of Mir29a and Mir29b and intestinal permeability in wild-type mice; these increased intestinal permeability in colons of far fewer Mir29(-/-) mice. In microarray and knockdown experiments, MIR29A and B were found to reduce levels of NKRF and CLDN1 messenger RNA, and alter levels of other messenger RNAs that regulate intestinal permeability. CONCLUSIONS Based on experiments in knockout mice and analyses of intestinal tissue samples from patients with IBS-D, MIR29 targets and reduces expression of CLDN1 and NKRF to increase intestinal permeability. Strategies to block MIR29 might be developed to restore intestinal permeability in patients with IBS-D.

Visceral and somatic hypersensitivity in a subset of rats following TNBS-induced colitis.

Background. Chronic abdominal pain is one of the most common gastrointestinal symptoms experienced by patients. Visceral hypersensitivity has been shown to be a biological marker in many patients with chronic visceral pain. We have previously shown that IBS patients with visceral hypersensitivity also have evidence of thermal hyperalgesia of the hand/foot. Objective. The objective of the current study was to develop an animal model of chronic visceral and somatic hypersensitivity in rats treated with intracolonic trinitrobenzene sulfonic acid. Design. Male Sprague–Dawley rats (200–250 g) were treated with either 20 mg/rat trinitrobenzene sulfonic acid (TNBS, Sigma Chemical Co.) in 50% ethanol (n = 75), an equivalent volume of 50% ethanol (n = 20) or an equivalent volume of saline (n = 20). The agents were delivered with a 24‐gauge catheter inserted into the lumen of the colon. Mechanical and thermal behavioral tests were performed using an automated von Frey and Hargreaves device to evaluate somatic hyperalgesia. Colonic distension was performed using an automated distension device to evaluate visceral pain thresholds. All animals were tested 16 weeks after TNBS treatment following complete resolution of the colitis. Results. At 16 weeks, 24% of the treated rats (18/75 rats) still exhibited evidence of visceral as well as somatic hypersensitivity compared to saline‐ and ethanol‐treated rats. Conclusion. Transient colonic inflammation leads to chronic visceral and somatic hypersensitivity in a subset of rats. These findings are similar to the subset of patients who develop chronic gastrointestinal symptoms following enteric infection.

Central sensitisation in visceral pain disorders

The concepts of visceral hyperalgesia and visceral hypersensitivity have been examined in a variety of functional gastrointestinal disorders (FGIDs). Although the pathophysiological mechanisms of pain and hypersensitivity in these disorders are still not well understood, exciting new developments in research have been made in the study of the brain-gut interactions involved in the FGIDs

Effects of the N-methyl-D-aspartate receptor on temporal summation of second pain (wind-up) in irritable bowel syndrome.

UNLABELLED Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which the pathophysiological mechanisms of the pain and hypersensitivity are not well understood. IBS patients frequently complain of pain in body regions somatotopically distinct from the gut, suggesting that central hyperalgesic mechanisms may be involved. In the current study, during the wind-up testing session, a series of 6 heat pulses were presented with an interstimulus interval (ISI) of 3 seconds. Following the 1st, 3rd, and 6th thermal stimuli, subjects were asked to rate the late thermal sensation or second pain. IBS patients who demonstrated temporal summation of pain (TSSP) then received dextromethorphan and placebo in a randomized, double-blind, fashion to block wind-up. The results showed: 1) a subset of IBS patients, but not controls, showed TSSP in response to a series of noxious heat pulses; and 2) TSSP was blocked by administration of dextromethorphan, an NMDA receptor antagonist. In summary, these findings further elucidate mechanisms of somatic hypersensitivity in a subset of IBS patients. Our results also support an etiologic basis for abnormal NMDA receptor mechanisms in some IBS patients. Future studies are needed to determine if NMDA receptor antagonists may be used to treat IBS patients. PERSPECTIVE This study evaluates temporal summation of second pain in a subset of IBS patients that is blocked by Dextromethorphan, an NMDA receptor antagonist. Theses results could lead to the use of an NMDA receptor antagonist in the treatment of pain in a subset of IBS patients.

Reversal of visceral and somatic hypersensitivity in a subset of hypersensitive rats by intracolonic lidocaine

Abstract Chronic abdominal pain is a common gastrointestinal symptom experienced by patients. We have previously shown that IBS patients with visceral hypersensitivity also have evidence of thermal hypersensitivity of the hand and foot that is reversed by rectal lidocaine jelly. We have also recently developed an animal model of chronic visceral and somatic hypersensitivity in rats treated with intracolonic trinitrobenzene sulfonic acid (TNBS). The objective of the current study was to determine the effects of intracolonic lidocaine on visceral/somatic hypersensitivity in TNBS‐treated rats. A total of 20 hypersensitive rats received either 20 mg intracolonic lidocaine (n = 10) or saline jelly (n = 10). In comparison to saline jelly, intracolonic lidocaine jelly reduced responses to nociceptive visceral/somatic stimuli in hypersensitive rats. The effects were present within 5–30 min after administration of lidocaine and lasted for 6 h. Lidocaine had no effects on recovered rats or control rats that had originally been treated with intracolonic saline instead of TNBS. Local anesthetic blockade of peripheral impulse input from the colon reduces both visceral and somatic hypersensitivity in TNBS‐treated rats, similar to results in IBS patients. The results provide further evidence that visceral and secondary somatic hypersensitivity in a subset of TNBS‐treated rats reflect central sensitization mechanisms maintained by tonic impulse input from the colon. This study evaluates the reversal of visceral/somatic hypersensitivity in a subset of TNBS‐treated rats with intracolonic lidocaine. This animal model may be used in the future to study the mechanisms of local anesthetic agents applied to the gut to reduce visceral pain.

Spinal NMDA NR1 subunit expression following transient TNBS colitis

BACKGROUND N-methyl-D-aspartic acid (NMDA) receptors play an important role in the development of hypersensitivity to visceral and somatic stimuli following inflammation or tissue injury. Our objective was to investigate the role of NMDA NR1 receptors in the spinal cord (T10-L1; L4-S1) of a subset of rats that remain hypersensitive following the histological resolution of TNBS-induced colitis compared to saline treated rats and rats that had recovered both behaviorally and histologically. We hypothesized that NMDA NR1 subunit expression mediates hypersensitivity following transient TNBS colitis. METHODS Male Sprague-Dawley rats (150 g-250 g) received 20 mg/rat intracolonic trinitrobenzene sulfonic acid (TNBS) in 50% ethanol or saline. Animals underwent nociceptive visceral/somatic pain testing 16 weeks after resolution of TNBS colitis. Animals were sacrificed and their spinal cords (T10-L1; L4-S1) were retrieved and 2-dimensional polyacrylamide gel electrophoresis and immunohistocytochemistry techniques were used to investigate spinal-NMDA receptor expression. RESULTS NR1(001) was the only NMDA NR1 receptor subunit that was expressed in recovered and control rats, whereas hypersensitive animals expressed NR1(011) and NR1(111) as well as NR1(001) subunits. Immunohistochemistry analysis demonstrated increased expression of NMDA NR1-N1, C1, and C2-plus expression in laminae I and II of the spinal cord (T10-L1; L4-S1) in hypersensitive rats but not in recovered/control rats. CONCLUSIONS Selective increases in the expression of the NMDA NR1 splice variants occur in hypersensitive rats following resolution of TNBS colitis. This suggests that the NMDA NR1 receptor plays an important role in the development of neuronal plasticity and central sensitization. The recombination of NR1 splice variants may serve as a key functional protein that maintains hypersensitivity following resolution of TNBS colitis.