title: Soluble mediators in plasma from irritable bowel syndrome patients excite rat submucosal neurons.
abstract: BACKGROUND
  Episodic bouts of abdominal pain and altered bowel habit are characteristic of irritable bowel syndrome (IBS). Although a comprehensive understanding of IBS pathophysiology remains elusive, support is growing for a primary role for immune activation in disease severity as evidenced by altered cytokine profiles in IBS plasma. Additionally, aberrant stimulation of the stress axis is likely to result in altered plasma constituents.
  
  
  METHODS
  Whole-mount preparations of submucosal plexus from adult male Sprague Dawley rats were exposed to plasma from IBS patients and healthy controls. Ratiometric calcium imaging recordings were used to measure changes in intracellular calcium ([Ca(2+)]i) as a marker of neuronal excitability.
  
  
  RESULTS
  IBS plasma stimulated a robust increase in [Ca(2+)]i (0.09 ± 0.02) whereas plasma from healthy volunteers had little effect (-0.02 ± 0.02, n=24, p<0.001). The neuromodulatory actions of IBS plasma were reduced by pre-neutralisation with anti-interleukin (IL)-6 (p<0.01) but not IL-8, immunoglobulin G or C-reactive protein. Moreover, IBS plasma-evoked responses (0.22 ± 0.06) were inhibited by the corticotrophin releasing factor receptor (CRFR) 1 antagonist, antalarmin (1μM, 0.015 ± 0.02, n=14, p<0.05), but not the CRFR2 antagonist, astressin 2B. Neuronal activation was mediated by ERK/MAPK signalling.
  
  
  CONCLUSIONS
  These data provide evidence that factors present in IBS plasma modulate neuronal activity in the submucosal plexus and that this is likely to involve CRFR1 activation and IL-6 signalling. These neuromodulatory actions of stress and immune factors indicate a potential mechanism by which immune activation during periods of stress may lead to symptom flares in IBS.
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Physiology, University College Cork, Cork, Ireland. Electronic address: d.omalley@ucc.ie.
authors.forename: Dervla
authors.initials: D
authors.lastname: O'Malley
authors.affiliation: Department of Physiology, University College Cork, Cork, Ireland.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Buckley
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
authors.forename: Declan P
authors.initials: DP
authors.lastname: McKernan
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Medicine, University College Cork, Cork, Ireland.
authors.forename: Eamonn M M
authors.initials: EM
authors.lastname: Quigley
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Anatomy & Neuroscience, University College Cork, Cork, Ireland.
authors.forename: John F
authors.initials: JF
authors.lastname: Cryan
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; Department of Psychiatry, University College Cork, Cork, Ireland.
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Dinan
mesh_terms: D000328:Adult; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D043183:Irritable Bowel Syndrome / Q000097:blood*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D010949:Plasma / Q000737:chemistry; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D013368:Submucous Plexus / Q000378:metabolism*
chemical_list: D015850:Interleukin-6; D016760:Proto-Oncogene Proteins c-fos; D018019:Receptors, Corticotropin-Releasing Hormone; D019947:Receptors, Interleukin-6; D002118:Calcium
keywords: Corticotropin-releasing factor; Enteric nervous system; Interleukin-6; Irritable bowel syndrome